| Type | Journal Article |
|---|---|
| Author | Carol S. Surowy |
| Author | Torben R. Neelands |
| Author | Bruce R. Bianchi |
| Author | Steve McGaraughty |
| Author | Rachid El Kouhen |
| Author | Ping Han |
| Author | Katharine L. Chu |
| Author | Heath A. McDonald |
| Author | Melissa Vos |
| Author | Wende Niforatos |
| Author | Erol K. Bayburt |
| Author | Arthur Gomtsyan |
| Author | Chih-Hung Lee |
| Author | Prisca Honore |
| Author | James P. Sullivan |
| Author | Michael F. Jarvis |
| Author | Connie R. Faltynek |
| Abstract | The transient receptor potential vanilloid (TRPV) 1 receptor, a nonselective cation channel expressed on peripheral sensory neurons and in the central nervous system, plays a key role in pain. TRPV1 receptor antagonism is a promising approach for pain management. In this report, we describe the pharmacological and functional characteristics of a structurally novel TRPV1 antagonist, (R)-(5-tert-butyl-2,3-dihydro-1H-inden-1-yl)-3-(1H-indazol-4-yl)-urea (ABT-102), which has entered clinical trials. At the recombinant human TRPV1 receptor ABT-102 potently (IC50 = 5–7 nM) inhibits agonist (capsaicin, N-arachidonyl dopamine, anandamide, and proton)-evoked increases in intracellular Ca2+ levels. ABT-102 also potently (IC50 = 1–16 nM) inhibits capsaicin-evoked currents in rat dorsal root ganglion (DRG) neurons and currents evoked through activation of recombinant rat TRPV1 currents by capsaicin, protons, or heat. ABT-102 is a competitive antagonist (pA2 = 8.344) of capsaicin-evoked increased intracellular Ca2+ and shows high selectivity for blocking TRPV1 receptors over other TRP receptors and a range of other receptors, ion channels, and transporters. In functional studies, ABT-102 blocks capsaicin-evoked calcitonin gene-related peptide release from rat DRG neurons. Intraplantar administration of ABT-102 blocks heat-evoked firing of wide dynamic range and nociceptive-specific neurons in the spinal cord dorsal horn of the rat. This effect is enhanced in a rat model of inflammatory pain induced by administration of complete Freund's adjuvant. Therefore, ABT-102 potently blocks multiple modes of TRPV1 receptor activation and effectively attenuates downstream consequences of receptor activity. ABT-102 is a novel and selective TRPV1 antagonist with pharmacological and functional properties that support its advancement into clinical studies. |
| Publication | Journal of Pharmacology and Experimental Therapeutics |
| Volume | 326 |
| Issue | 3 |
| Pages | 879 -888 |
| Date | 2008 |
| DOI | 10.1124/jpet.108.138511 |
| URL | http://jpet.aspetjournals.org/content/326/3/879.abstract |
| Accessed | Wednesday, November 17, 2010 6:24:23 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:24:23 PM |
| Modified | Wednesday, November 17, 2010 6:24:23 PM |
| Type | Journal Article |
|---|---|
| Author | Bruce R. Bianchi |
| Author | Rachid El Kouhen |
| Author | Torben R. Neelands |
| Author | Chih-Hung Lee |
| Author | Arthur Gomtsyan |
| Author | Shirish N. Raja |
| Author | Sriajan N. Vaidyanathan |
| Author | Bruce Surber |
| Author | Heath A. McDonald |
| Author | Carol S. Surowy |
| Author | Connie R. Faltynek |
| Author | Robert B. Moreland |
| Author | Michael F. Jarvis |
| Author | Pamela S. Puttfarcken |
| Abstract | 1-((R)-5-tert-Butyl-indan-1-yl)-3-isoquinolin-5-yl-urea (A-778317) is a novel, stereoselective, competitive antagonist that potently blocks transient receptor potential vanilloid-1 (TRPV1) receptor-mediated changes in intracellular calcium concentrations (pIC50 = 8.31 ± 0.13). The (S)-stereoisomer, 1-((S)-5-tert-butyl-indan-1-yl)-3-isoquinolin-5-yl-urea (A-778316), is 6.8-fold less potent (pIC50 = 7.47 ± 0.07). A-778317 also potently blocks capsaicin and acid activation of native rat TRPV1 receptors in dorsal root ganglion neurons. A-778317 was tritiated ([3H]A-778317; 29.3 Ci/mmol) and used to study recombinant human TRPV1 (hTRPV1) receptors expressed in Chinese ovary cells (CHO) cells. [3H]A-778317 labeled a single class of binding sites in hTRPV1-expressing CHO cell membranes with high affinity (KD = 3.4 nM; Bmax = 4.0 pmol/mg protein). Specific binding of 2 nM [3H]A-778317 to hTRPV1-expressing CHO cell membranes was reversible. The rank-order potency of TRPV1 receptor antagonists to inhibit binding of 2 nM [3H]A-778317 correlated well with their functional potencies in blocking TRPV1 receptor activation. The present data demonstrate that A-778317 blocks polymodal activation of the TRPV1 receptor by binding to a single high-affinity binding site and that [3H]A-778317 possesses favorable binding properties to facilitate further studies of hTRPV1 receptor pharmacology. |
| Publication | Journal of Pharmacology and Experimental Therapeutics |
| Volume | 323 |
| Issue | 1 |
| Pages | 285 -293 |
| Date | October 01 , 2007 |
| DOI | 10.1124/jpet.107.124305 |
| Short Title | [3H]A-778317 [1-((R)-5-tert-Butyl-indan-1-yl)-3-isoquinolin-5-yl-urea] |
| URL | http://jpet.aspetjournals.org/content/323/1/285.abstract |
| Accessed | Wednesday, November 17, 2010 4:51:06 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 4:51:06 PM |
| Modified | Wednesday, November 17, 2010 4:51:06 PM |
| Type | Journal Article |
|---|---|
| Author | P.M. Heyward |
| Publication | Journal of Microscopy |
| Volume | 240 |
| Issue | 3 |
| Pages | 207-215 |
| Date | 12/2010 |
| DOI | 10.1111/j.1365-2818.2010.03382.x |
| ISSN | 00222720 |
| URL | http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.2010.03382.x/abstract |
| Accessed | Wednesday, November 17, 2010 6:15:29 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:15:29 PM |
| Modified | Wednesday, November 17, 2010 6:15:29 PM |
| Type | Journal Article |
|---|---|
| Author | Pasqualina Castaldo |
| Author | Patrizia Stefanoni |
| Author | Francesco Miceli |
| Author | Giangennaro Coppola |
| Author | Emanuele Miraglia del Giudice |
| Author | Giulia Bellini |
| Author | Antonio Pascotto |
| Author | James R. Trudell |
| Author | Neil L. Harrison |
| Author | Lucio Annunziato |
| Author | Maurizio Taglialatela |
| Abstract | In this study, we have compared the functional consequences of three mutations (R218Q, V260M, and Q266H) in the α1 subunit of the glycine receptor (GlyRA1) causing hyperekplexia, an inherited neurological channelopathy. In HEK-293 cells, the agonist EC50s for glycine-activated Cl- currents were increased from 26 μm in wtGlyRA1, to 5747, 135, and 129 μm in R218Q, V260M, and Q266H GlyRA1 channels, respectively. Cl- currents elicited by β-alanine and taurine, which behave as agonists at wtGlyRA1, were decreased in V260M and Q266H mutant receptors and virtually abolished in GlyRA1 R218Q receptors. Gly-gated Cl- currents were similarly antagonized by low concentrations of strychnine in both wild-type (wt) and R218Q GlyRA1 channels, suggesting that the Arg-218 residue plays a crucial role in GlyRA1 channel gating, with only minor effects on the agonist/antagonist binding site, a hypothesis supported by our molecular model of the GlyRA1 subunit. The R218Q mutation, but not the V260M or the Q266H mutation, caused a marked decrease of receptor subunit expression both in total cell lysates and in isolated plasma membrane proteins. This decreased expression does not seem to explain the reduced agonist sensitivity of GlyRA1 R218Q channels since no difference in the apparent sensitivity to glycine or taurine was observed when wtGlyRA1 receptors were expressed at levels comparable with those of R218Q mutant receptors. In conclusion, multiple mechanisms may explain the dramatic decrease in GlyR function caused by the R218Q mutation, possibly providing the molecular basis for its association with a more severe clinical phenotype. |
| Publication | Journal of Biological Chemistry |
| Volume | 279 |
| Issue | 24 |
| Pages | 25598 -25604 |
| Date | June 11 , 2004 |
| DOI | 10.1074/jbc.M311021200 |
| URL | http://www.jbc.org/content/279/24/25598.abstract |
| Accessed | Wednesday, November 17, 2010 4:39:57 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 4:39:57 PM |
| Modified | Wednesday, November 17, 2010 4:39:57 PM |
| Type | Journal Article |
|---|---|
| Author | Mo Yang |
| Author | Xin Zhang |
| Abstract | Cardiac hypertrophy is the heart's response to a variety of extrinsic and intrinsic stimuli that impose increased biomechanical stress that may be regulated by growth factor such as Endothelin-1 (ET-1). The majority of existing techniques to monitor hypertrophy in vitro are based on florescence probes designed to show morphological and biochemical alterations indicative of cardiomyocyte hypertrophy. In this work, a new cardiomyocyte-based impedance sensing system with the assistance of dielectrophoresis (DEP) cell concentration is developed to monitor the dynamics process of ET-1 induced cardiomyocyte hypertrophy. This device can increase the sensitivity of the impedance system and also has the potential to reduce the time for detection by a significant factor. |
| Publication | Sensors and Actuators A: Physical |
| Volume | 136 |
| Issue | 2 |
| Pages | 504-509 |
| Date | May 16, 2007 |
| DOI | 10.1016/j.sna.2006.09.014 |
| ISSN | 0924-4247 |
| URL | http://www.sciencedirect.com/science/article/B6THG-4M6SBD7-2/2/3c700065a0604f08327213803505948f |
| Accessed | Wednesday, November 17, 2010 4:59:01 PM |
| Library Catalog | ScienceDirect |
| Date Added | Wednesday, November 17, 2010 4:59:01 PM |
| Modified | Wednesday, November 17, 2010 4:59:01 PM |
| Type | Journal Article |
|---|---|
| Author | Rachid El Kouhen |
| Author | Carol S. Surowy |
| Author | Bruce R. Bianchi |
| Author | Torben R. Neelands |
| Author | Heath A. McDonald |
| Author | Wende Niforatos |
| Author | Arthur Gomtsyan |
| Author | Chih-Hung Lee |
| Author | Prisca Honore |
| Author | James P. Sullivan |
| Author | Michael F. Jarvis |
| Author | Connie R. Faltynek |
| Abstract | The vanilloid receptor transient receptor potential type V1 (TRPV1) integrates responses to multiple stimuli, such as capsaicin, acid, heat, and endovanilloids and plays an important role in the transmission of inflammatory pain. Here, we report the identification and in vitro characterization of A-425619 [1-isoquinolin-5-yl-3-(4-trifluoromethyl-benzyl)-urea], a novel, potent, and selective TRPV1 antagonist. A-425619 was found to potently block capsaicin-evoked increases in intracellular calcium concentrations in HEK293 cells expressing recombinant human TRPV1 receptors (IC50 = 5 nM). A-425619 showed similar potency (IC50 = 3–4 nM) to block TRPV1 receptor activation by anandamide and N-arachidonoyl-dopamine. Electrophysiological experiments showed that A-425619 also potently blocked the activation of native TRPV1 channels in rat dorsal root ganglion neurons (IC50 = 9 nM). When compared with other known TRPV1 antagonists, A-425619 exhibited superior potency in blocking both naive and phorbol estersensitized TRPV1 receptors. Like capsazepine, A-425619 demonstrated competitive antagonism (pA2 = 2.5 nM) of capsaicinevoked calcium flux. Moreover, A-425619 was 25- to 50-fold more potent than capsazepine in blocking TRPV1 activation. A-425619 showed no significant interaction with a wide range of receptors, enzymes, and ion channels, indicating a high degree of selectivity for TRPV1 receptors. These data show that A-425619 is a structurally novel, potent, and selective TRPV1 antagonist. |
| Publication | Journal of Pharmacology and Experimental Therapeutics |
| Volume | 314 |
| Issue | 1 |
| Pages | 400 -409 |
| Date | July 01 , 2005 |
| DOI | 10.1124/jpet.105.084103 |
| URL | http://jpet.aspetjournals.org/content/314/1/400.abstract |
| Accessed | Wednesday, November 17, 2010 6:45:21 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:45:21 PM |
| Modified | Wednesday, November 17, 2010 6:45:21 PM |
| Type | Journal Article |
|---|---|
| Author | X Wan |
| Author | S Chen |
| Author | A Sadeghpour |
| Author | Q Wang |
| Author | G E Kirsch |
| Abstract | Idiopathic ventricular fibrillation (IVF) can cause sudden death in both adults and children. One form of IVF (Brugada syndrome), characterized by S-T segment elevation (STE) in the electrocardiogram, has been linked to mutations of SCN5A, the gene encoding the voltage-gated cardiac Na(+) channel. A missense mutation of SCN5A that substitutes glutamine for leucine at codon 567 (L567Q, in the cytoplasmic linker between domains I and II) is identified with sudden infant death and Brugada syndrome in one family. However, neither the functional effect of the L567Q mutation nor the molecular mechanism underlying the pathogenicity of the mutation is known. Patch-clamp analysis of L567Q channels expressed in human embryonic kidney cells revealed a marked acceleration and a negative shift in the voltage dependence of inactivation. Unlike other Brugada mutations, this phenotype was expressed independently of temperature or auxiliary beta(1)-subunits. These results support a proposed linkage between Brugada syndrome and some instances of sudden infant death and the hypothesis that reduced Na(+) conductance is the primary cause of IVF with STE. |
| Publication | American Journal of Physiology. Heart and Circulatory Physiology |
| Volume | 280 |
| Issue | 1 |
| Pages | H354-360 |
| Date | Jan 2001 |
| Journal Abbr | Am. J. Physiol. Heart Circ. Physiol |
| ISSN | 0363-6135 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/11123251 |
| Accessed | Wednesday, November 17, 2010 12:52:23 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 11123251 |
| Date Added | Wednesday, November 17, 2010 12:52:23 PM |
| Modified | Wednesday, November 17, 2010 12:52:23 PM |
| Type | Journal Article |
|---|---|
| Author | Torben R Neelands |
| Author | Michael F Jarvis |
| Author | Ping Han |
| Author | Connie R Faltynek |
| Author | Carol S Surowy |
| Abstract | TRPV1 (vanilloid receptor 1) receptors are activated by a variety of ligands such as capsaicin, as well as by acidic conditions and temperatures above 42°C. These activators can enhance the potency of one another, shifting the activation curve for TRPV1 to the left. In this study, for example, we observed an approximately 10-fold shift in the capsaicin EC50 (640 nM to 45 nM) for rat TRPV1 receptors expressed in HEK-293 cells when the pH was lowered from 7.4 to 5.5. To investigate potential causes for this shift in capsaicin potency, the rates of current activation and deactivation of whole-cell currents were measured in individual cells exposed to treatments of pH 5.5, 1 μM capsaicin or in combination. Acidic pH was found to both increase the activation rate and decrease the deactivation rate of capsaicin-activated currents providing a possible mechanism for the enhanced potency of capsaicin under acidic conditions. Utilizing a paired-pulse protocol, acidic pH slowed the capsaicin deactivation rate and was readily reversible. Moreover, the effect could occur under modestly acidic conditions (pH 6.5) that did not directly activate TRPV1. When TRPV1 was maximally activated by capsaicin and acidic pH, the apparent affinity of the novel and selective capsaicin-site competitive TRPV1 antagonist, A-425619, was reduced ~35 fold. This shift was overcome by reducing the capsaicin concentration co-applied with acidic pH. Since inflammation is associated with tissue acidosis, these findings enhance understanding of TRPV1 receptor responses in inflammatory pain where tissue acidosis is prevalent. |
| Publication | Molecular Pain |
| Volume | 1 |
| Pages | 28-28 |
| Journal Abbr | Mol Pain |
| DOI | 10.1186/1744-8069-1-28 |
| Library Catalog | PubMed Central |
| Extra | PMID: 16191202 PMCID: 1266034 |
| Date Added | Wednesday, November 17, 2010 4:43:45 PM |
| Modified | Wednesday, November 17, 2010 4:43:45 PM |
| Type | Journal Article |
|---|---|
| Author | A. F Soleng |
| Author | A Baginskas |
| Author | P Andersen |
| Author | M Raastad |
| Abstract | The membrane potential changes following action potentials in thin unmyelinated cortical axons with en passant boutons may be important for synaptic release and conduction abilities of such axons. In the lack of intra-axonal recording techniques we have used extracellular excitability testing as an indirect measure of the after-potentials. We recorded from individual CA3 soma in hippocampal slices and activated the axon with a range of stimulus intensities. When conditioning and test stimuli were given to the same site the excitability changes were partly masked by local effects of the stimulating electrode at intervals < 5 ms. Therefore, we elicited the conditioning action potential from one axonal branch and tested the excitability of another branch. We found that a single action potential reduced the axonal excitability for 15 ms followed by an increased excitability for ∼200 ms at 24°C. Using field recordings of axonal action potentials we show that raising the temperature to 34°C reduced the magnitude and duration of the initial depression. However, the duration of the increased excitability was very similar (time constant 135 ± 20 ms) at 24 and 34°C, and with 2.0 and 0.5 mm Ca2+ in the bath. At stimulus rates > 1 Hz, a condition that activates a hyperpolarization-activated current (Ih) in these axons, the decay was faster than at lower stimulation rates. This effect was reduced by the Ih blocker ZD7288. These data suggest that the decay time course of the action potential-induced hyperexcitability is determined by the membrane time constant. |
| Publication | The Journal of Physiology |
| Volume | 560 |
| Issue | 2 |
| Pages | 491 -503 |
| Date | October 15 , 2004 |
| DOI | 10.1113/jphysiol.2004.071225 |
| URL | http://jp.physoc.org/content/560/2/491.abstract |
| Accessed | Wednesday, November 17, 2010 1:58:06 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 1:58:06 PM |
| Modified | Wednesday, November 17, 2010 1:58:06 PM |
| Type | Journal Article |
|---|---|
| Author | B Venegas |
| Publication | Biophysical Journal |
| Volume | 85 |
| Issue | 4 |
| Pages | 2323-2332 |
| Date | 10/2003 |
| Journal Abbr | Biophysical Journal |
| DOI | 10.1016/S0006-3495(03)74656-6 |
| ISSN | 00063495 |
| Short Title | Amphotericin B Channels in the Bacterial Membrane |
| URL | http://www.cell.com/biophysj/abstract/S0006-3495(03)74656-6 |
| Accessed | Wednesday, November 17, 2010 1:02:25 AM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 1:02:25 AM |
| Modified | Wednesday, November 17, 2010 1:02:25 AM |
| Type | Journal Article |
|---|---|
| Author | Abdallah Hayar |
| Author | Chunping Gu |
| Author | Elie D. Al-Chaer |
| Abstract | The properties of dorsal root ganglion (DRG) neurons have been mostly investigated in culture of dissociated cells, and it is uncertain whether these cells maintain the electrophysiological properties of the intact DRG neurons. Few attempts have been made to record from DRG neurons in the intact ganglion using the patch clamp technique. In this study, rat DRGs were dissected and incubated for at least 1 hour at 37°C in collagenase (10 mg/ml). We used oblique epi-illumination to visualize DRG neurons and perform patch clamp recordings. All DRG neurons exhibited strong delayed rectifier potassium current and a high threshold for spike generation (−15 mV) that rendered the cells very weakly excitable, generating only one action potential upon strong current injection (>300 pA). It is therefore possible that cultured DRG neurons, commonly used in studies of pain processing, may be hyperexcitable because they acquired "neuropathic" properties due to the injury induced by their dissociation. Electrical stimulation of the attached root produced an antidromic spike in the soma that could be blocked by intracellular hyperpolarization or high frequency stimulation. Imaging intracellular calcium concentration with Oregon Green BAPTA-1 indicates that antidromic stimulation caused a long-lasting increase in intracellular calcium concentration mostly near the cell membrane. This study describes a simple approach to examine the electrophysiological and pharmacological properties and intracellular calcium signaling in DRG neurons in the intact ganglion where the effects of somatic spike invasion can be studied as well. |
| Publication | Journal of neuroscience methods |
| Volume | 173 |
| Issue | 1 |
| Pages | 74-82 |
| Date | 2008-8-15 |
| Journal Abbr | J Neurosci Methods |
| DOI | 10.1016/j.jneumeth.2008.05.023 |
| ISSN | 0165-0270 |
| Library Catalog | PubMed Central |
| Extra | PMID: 18588915 PMCID: 2590941 |
| Date Added | Wednesday, November 17, 2010 6:22:19 PM |
| Modified | Wednesday, November 17, 2010 6:22:19 PM |
| Type | Journal Article |
|---|---|
| Author | M Lynne McAnelly |
| Author | Harold H Zakon |
| Abstract | Weakly electric fish such as Sternopygus macrurus utilize a unique signal production system, the electric organ (EO), to navigate within their environment and to communicate with conspecifics. The electric organ discharge (EOD) generated by the Sternopygus electric organ is quasi-sinusoidal and sexually dimorphic; sexually mature males produce long duration EOD pulses at low frequencies, whereas mature females produce short duration EOD pulses at high frequencies. EOD frequency is set by a medullary pacemaker nucleus, while EOD pulse duration is determined by the kinetics of Na+ and K+ currents in the electric organ. The inactivation of the Na+ current and the activation of the delayed rectifying K+ current of the electric organ covary with EOD frequency such that the kinetics of both currents are faster in fish with high (female) EOD frequency than those with low (male) EOD frequencies. Dihydrotestosterone (DHT) implants masculinize the EOD centrally by decreasing frequency at the pacemaker nucleus (PMN). DHT also acts at the electric organ, broadening the EO pulse, which is at least partly due to a slowing of the inactivation kinetics of the Na+ current. Here, we show that chronic DHT treatment also slows the activation and deactivation kinetics of the electric organ's delayed rectifying K+ current. Thus, androgens coregulate the time-varying kinetics of two distinct ion currents in the EO to shape a sexually dimorphic communication signal. |
| Publication | Developmental Neurobiology |
| Volume | 67 |
| Issue | 12 |
| Pages | 1589-1597 |
| Date | Oct 2007 |
| Journal Abbr | Dev Neurobiol |
| DOI | 10.1002/dneu.20530 |
| ISSN | 1932-8451 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17562532 |
| Accessed | Wednesday, November 17, 2010 5:22:04 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17562532 |
| Date Added | Wednesday, November 17, 2010 5:22:04 PM |
| Modified | Wednesday, November 17, 2010 5:22:04 PM |
| Type | Journal Article |
|---|---|
| Author | Gentaro Iribe |
| Author | Peter Kohl |
| Abstract | Cardiac cellular calcium (Ca2+) handling is the well-investigated mediator of excitation-contraction coupling, the process that translates cardiac electrical activation into mechanical events. The reverse--effects of mechanical stimulation on cardiomyocyte Ca2+ handling--are much less well understood, in particular during the inter-beat period, called 'diastole'. We have investigated the effects of diastolic length changes, applied axially using a pair of carbon fibres attached to opposite ends of Guinea pig isolated ventricular myocytes, on the availability of Ca2+ in the main cellular stores (the sarcoplasmic reticulum; SR), by studying the rest-decay of SR Ca2+ content [Ca2+]SR, and the reloading of the SR after prior depletion of Ca2+ from the cell. Cells were loaded with Fura-2 AM (an indicator of the cytosolic 'free' Ca2+ concentration, [Ca2+]i), and pre-conditioned by field-stimulation (2 Hz) at 37 degrees C, while [Ca2+]i transients and sarcomere length (SL) were recorded simultaneously. After reaching a steady state in the behaviour of observed parameters, stimulation was interrupted for between 5 and 60s, while cells were either held at resting length, or stretched (controlled to cause a 10% increase in SL, to aid inter-individual comparison). Thereafter, each cell was returned to its original resting length, followed by swift administration of 10mM of caffeine (in Na+/Ca2+-free solution), which causes the release of Ca2+ from the SR (caffeine), but largely prevents extrusion of Ca2+ from the cytosol to the cell exterior (Na+/Ca2+-free solution). By comparing the [Ca2+]i in cells exposed/not exposed to diastolic stretch of different duration, we assessed the rest-decay dynamics of [Ca2+]SR. To assess SR reloading after initial Ca2+ depletion, the same stretch protocol was implemented after prior emptying of the cell by application of 10mM of caffeine in normal Tyrode solution (which causes Ca2+ to be released from the SR and extruded from the cell via the Na+/Ca2+ exchanger; NCX). Axial stretch enhanced the rate of both rest-decay and reloading of [Ca2+]SR. Application of 40 microM streptomycin, a blocker of stretch-activated ion channels, did not affect the stretch-induced increase in SR reloading. This behaviour was reproduced in a computer simulation study, using a modified version of the 2006 Iribe-Kohl-Noble model of single cardiac myocyte Ca2+ handling, suggesting that stretch increases both Ca2+ leak from the SR and Ca2+ influx via the sarcolemma. This may have important implications for the mobilisation of Ca2+ in stretched cells, and could contribute to the regional 'matching' of individual cardiomyocyte contractility to dynamic, and regionally varying, changes in mechanical loads, such as diastolic pre-load, of cardiac tissue. |
| Publication | Progress in Biophysics and Molecular Biology |
| Volume | 97 |
| Issue | 2-3 |
| Pages | 298-311 |
| Date | 2008 Jun-Jul |
| Journal Abbr | Prog. Biophys. Mol. Biol |
| DOI | 10.1016/j.pbiomolbio.2008.02.012 |
| ISSN | 0079-6107 |
| Short Title | Axial stretch enhances sarcoplasmic reticulum Ca2+ leak and cellular Ca2+ reuptake in guinea pig ventricular myocytes |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/18395247 |
| Accessed | Wednesday, November 17, 2010 1:01:55 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 18395247 |
| Date Added | Wednesday, November 17, 2010 1:01:55 PM |
| Modified | Wednesday, November 17, 2010 1:01:55 PM |
| Type | Journal Article |
|---|---|
| Author | Ulrich Schotten |
| Author | Sunniva de Haan |
| Author | Sander Verheule |
| Author | Erik G.A. Harks |
| Author | Dirk Frechen |
| Author | Eva Bodewig |
| Author | Maura Greiser |
| Author | Rashmi Ram |
| Author | Jos Maessen |
| Author | Malte Kelm |
| Author | Maurits Allessie |
| Author | David R. Van Wagoner |
| Abstract | Background: AVE0118 (2′-{[2-(4-Methoxy-phenyl)-acetylamino]-methyl}-biphenyl-2-carboxylic acid (2-pyridin-3-yl-ethyl)-amide) blocks atrial ultrarapid delayed rectifier currents (IKur) and prolongs the atrial action potential (AP) plateau without affecting ventricular repolarisation. In patients with atrial contractile dysfunction due to atrial tachyarrhythmias, this response might increase atrial contractility without risk of ventricular proarrhythmia. This study was designed to evaluate the inotropic mechanisms of AVE0118.Methods and results: In isometrically contracting atrial trabeculae, AVE0118 increased contractile force by 55.4% in sinus rhythm patients (n=9) and by 107.4% in patients with atrial fibrillation (n=8). In freshly isolated canine atrial myocytes studied under perforated patch current clamp (37 °C), AVE0118 increased myocyte fractional shortening from 3.8±0.6 to 9.6±0.8% and prolonged action potential duration at 30% repolarisation from 9±2 to 102±11 ms. Clamping cells to an AP waveform recorded during exposure to AVE0118 produced the same inotropic response as the drug itself. In action potential clamp, peak Ca2+ inward current (ICaL) current declined from 5.5±1.3 pA/pF during control to 4.1±0.7 pA/pF when an AP recorded in the presence of AVE0118 was used as command waveform. However, ICaL was more sustained with AVE0118 and the time integral did not change (135±37 vs. 173±30 pA/pF*ms, p=ns). Importantly, blockade of reverse mode Na+/Ca2+-exchanger activity with 5 μM KBR7943 or using a Na+-free pipette solution abolished the positive inotropic effect of the AP recorded in the presence of AVE0118. In ventricular myocytes AVE0118 did not elicit a positive inotropic response.Conclusions: Block of IKur by AVE0118 enhances atrial contractility both in patients with sinus rhythm and atrial fibrillation. The positive inotropic effect is atrial-specific and due to the changes of the action potential configuration which enhances Ca2+ entry via reverse mode Na+/Ca2+ exchange. |
| Publication | Cardiovascular Research |
| Volume | 73 |
| Issue | 1 |
| Pages | 37 -47 |
| Date | January 01 , 2007 |
| DOI | 10.1016/j.cardiores.2006.11.024 |
| URL | http://cardiovascres.oxfordjournals.org/content/73/1/37.abstract |
| Accessed | Wednesday, November 17, 2010 6:52:58 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:52:58 PM |
| Modified | Wednesday, November 17, 2010 6:52:58 PM |
| Type | Journal Article |
|---|---|
| Author | Zhi-Hao Zhang |
| Author | John A. Johnson |
| Author | Long Chen |
| Author | Nabil El-Sherif |
| Author | Daria Mochly-Rosen |
| Author | Mohamed Boutjdir |
| Abstract | Abstract We have previously shown that {alpha}1-adrenergic activation inhibited {beta}-adrenergic-stimulated L-type Ca2+ current (ICa). To determine the role of protein kinase C (PKC) in this regulation, the inositol trisphosphate pathway was bypassed by direct activation of PKC with 4{beta}-phorbol 12-myristate 13-acetate (PMA). To minimize Ca2+-induced Ca2+ inactivation, Ba2+ current (IBa) was recorded through Ca2+ channels in adult rat ventricular myocytes. We found that PMA (0.1 {micro}mol/L) consistently inhibited basal IBa by 40.5{+/-}7.4% and isoproterenol (ISO, 0.1 {micro}mol/L)-stimulated IBa by 48.9{+/-}7.8%. These inhibitory effects were not observed with the inactive phorbol ester analogue {alpha}-phorbol 12,13-didecanoate (0.1 {micro}mol/L). To identify the PKC isozymes that mediate these PMA effects, we intracellularly applied peptide inhibitors of a subclass of PKC isozymes, the C2-containing cPKCs. These peptides ({beta}C2-2 and {beta}C2-4) specifically inhibit the translocation and function of C2-containing isozymes ({alpha}-PKC, {beta}I-PKC, and {beta}II-PKC), but not the C2-less isozymes ({delta}-PKC and {epsilon}-PKC). We first used the pseudosubstrate peptide (0.1 {micro}mol/L in the pipette), which inhibits the catalytic activity of all the PKC isozymes, and found that PMA-induced inhibition of ISO-stimulated IBa was reduced to 16.8{+/-}7.4% but was not affected by the scrambled pseudosubstrate peptide. The effects of PMA on basal and ISO-stimulated IBa were then determined in the presence of C2-derived peptides or control peptides. When the pipette contained 0.1 {micro}mol/L of {beta}C2-2 or {beta}C2-4, PMA-induced inhibition of basal IBa was 26.1{+/-}4.5% and 23.6{+/-}2.2%, respectively. Similarly, ISO-stimulated IBa was inhibited by 29.9{+/-}6.6% and 29.3{+/-}7.8% in the presence of {beta}C2-2 and {beta}C2-4, respectively. In contrast, there was no significant change in the effect of PMA in the presence of control peptides, scrambled {beta}C2-4, or pentalysine. Finally, PMA-induced inhibition of basal and ISO-stimulated IBa was almost completely abolished in cells dialyzed with both {beta}C2-2 and {beta}C2-4. Together, these data suggest a role for C2-containing isozymes in mediating PMA-induced inhibition of L-type Ca2+ channel activity. |
| Publication | Circ Res |
| Volume | 80 |
| Issue | 5 |
| Pages | 720-729 |
| Date | May 19, 1997 |
| URL | http://circres.ahajournals.org/cgi/content/abstract/80/5/720 |
| Accessed | Wednesday, November 17, 2010 4:02:20 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 4:02:20 PM |
| Modified | Wednesday, November 17, 2010 4:02:20 PM |
| Type | Journal Article |
|---|---|
| Author | Yuejin Wu |
| Author | Zhan Gao |
| Author | Biyi Chen |
| Author | Olha M. Koval |
| Author | Madhu V. Singh |
| Author | Xiaoqun Guan |
| Author | Thomas J. Hund |
| Author | William Kutschke |
| Author | Satyam Sarma |
| Author | Isabella M. Grumbach |
| Author | Xander H. T. Wehrens |
| Author | Peter J. Mohler |
| Author | Long-Sheng Song |
| Author | Mark E. Anderson |
| Abstract | The best understood “fight or flight” mechanism for increasing heart rate (HR) involves activation of a cyclic nucleotide-gated ion channel (HCN4) by β-adrenergic receptor (βAR) agonist stimulation. HCN4 conducts an inward “pacemaker” current (If) that increases the sinoatrial nodal (SAN) cell membrane diastolic depolarization rate (DDR), leading to faster SAN action potential generation. Surprisingly, HCN4 knockout mice were recently shown to retain physiological HR increases with isoproterenol (ISO), suggesting that other If-independent pathways are critical to SAN fight or flight responses. The multifunctional Ca2+ and calmodulin-dependent protein kinase II (CaMKII) is a downstream signal in the βAR pathway that activates Ca2+ homeostatic proteins in ventricular myocardium. Mice with genetic, myocardial and SAN cell CaMKII inhibition have significantly slower HRs than controls during stress, leading us to hypothesize that CaMKII actions on SAN Ca2+ homeostasis are critical for βAR agonist responses in SAN. Here we show that CaMKII mediates ISO HR increases by targeting SAN cell Ca2+ homeostasis. CaMKII inhibition prevents ISO effects on SAN Ca2+ uptake and release from intracellular sarcoplasmic reticulum (SR) stores that are necessary for increasing DDR. CaMKII inhibition has no effect on the ISO response in SAN cells when SR Ca2+ release is disabled and CaMKII inhibition is only effective at slowing HRs during βAR stimulation. These studies show the tightly coupled, but previously unanticipated, relationship of CaMKII to the βAR pathway in fight or flight physiology and establish CaMKII as a critical signaling molecule for physiological HR responses to catecholamines. |
| Publication | Proceedings of the National Academy of Sciences |
| Volume | 106 |
| Issue | 14 |
| Pages | 5972 -5977 |
| Date | April 07 , 2009 |
| DOI | 10.1073/pnas.0806422106 |
| URL | http://www.pnas.org/content/106/14/5972.abstract |
| Accessed | Wednesday, November 17, 2010 6:18:20 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:18:20 PM |
| Modified | Wednesday, November 17, 2010 6:18:20 PM |
| Type | Journal Article |
|---|---|
| Author | Byung Hee Han |
| Author | Meng-liang Zhou |
| Author | Fadi Abousaleh |
| Author | Robert P. Brendza |
| Author | Hans H. Dietrich |
| Author | Jessica Koenigsknecht-Talboo |
| Author | John R. Cirrito |
| Author | Eric Milner |
| Author | David M. Holtzman |
| Author | Gregory J. Zipfel |
| Abstract | The contributing effect of cerebrovascular pathology in Alzheimer’s Disease (AD) has become increasingly appreciated. Recent evidence suggests that amyloid-β peptide (Aβ) — the same peptide found in neuritic plaques of AD — may play a role via its vasoactive properties. Several studies have examined young Tg2576 mice expressing mutant amyloid precursor protein (APP) and having elevated levels of soluble Aβ but no cerebral amyloid angiopathy (CAA). These studies suggest but don’t prove that soluble Aβ can significantly impair the cerebral circulation. Other studies examining older Tg2576 mice having extensive CAA found even greater cerebrovascular dysfunction, suggesting that CAA is likely to further impair vascular function. Herein, we examined vasodilatory responses in young and older Tg2576 mice to further assess the roles of soluble and insoluble Aβ on vessel function. We found that 1) vascular impairment was present in both young and older Tg2576 mice; 2) a strong correlation between CAA severity and vessel reactivity exists; 3) a surprisingly small amount of CAA led to marked reduction or complete loss of vessel function; 4) CAA-induced vasomotor impairment resulted from dysfunction rather than loss or disruption of vascular smooth muscle cells; and 5) acute depletion of Aβ improved vessel function in young and to a lesser degree older Tg2576 mice. These results strongly suggest that both soluble and insoluble Aβ cause cerebrovascular dysfunction, that mechanisms other than Aβ-induced alteration in vessel integrity are responsible, and that anti-Aβ therapy may have beneficial vascular effects in addition to positive effects on parenchymal amyloid. |
| Publication | The Journal of neuroscience : the official journal of the Society for Neuroscience |
| Volume | 28 |
| Issue | 50 |
| Pages | 13542-13550 |
| Date | 2008-12-10 |
| Journal Abbr | J Neurosci |
| DOI | 10.1523/JNEUROSCI.4686-08.2008 |
| ISSN | 0270-6474 |
| Library Catalog | PubMed Central |
| Extra | PMID: 19074028 PMCID: 2626633 |
| Date Added | Wednesday, November 17, 2010 6:40:41 PM |
| Modified | Wednesday, November 17, 2010 6:40:41 PM |
| Type | Journal Article |
|---|---|
| Author | Arun Sridhar |
| Author | Yoshinori Nishijima |
| Author | Dmitry Terentyev |
| Author | Mahmood Khan |
| Author | Radmila Terentyeva |
| Author | Robert L. Hamlin |
| Author | Tomohiro Nakayama |
| Author | Sandor Gyorke |
| Author | Arturo J. Cardounel |
| Author | Cynthia A. Carnes |
| Abstract | Aims We sought to define the underlying mechanisms for atrial fibrillation (AF) during chronic heart failure (HF).Methods and results Preliminary studies showed that 4 months of HF resulted in irreversible systolic dysfunction (n = 9) and a substrate for sustained inducible AF (>3 months, n = 3). We used a chronic (4-month) canine model of tachypacing-induced HF (n = 10) to assess atrial electrophysiological remodelling, relative to controls (n = 5). Left ventricular fractional shortening was reduced from 37.2 ± 0.83 to 13.44 ± 2.63% (P < 0.05). Left atrial (LA) contractility (fractional area change) was reduced from 34.9 ± 7.9 to 27.9 ± 4.23% (P < 0.05). Action potential durations (APDs) at 50 and 90% repolarization were shortened by ∼60 and 40%, respectively, during HF (P < 0.05). HF-induced atrial remodelling included increased fibrosis, increased Ito, and decreased IK1, IKur, and IKs (P < 0.05). HF induced increases in LA Kv channel interacting protein 2 (P < 0.05), no change in Kv4.3, Kv1.5, or Kir2.3, and reduced Kir2.1 (P < 0.05). When ICa-L was elicited by action potential (AP) clamp, HF APs reduced the integral of ICa in control myocytes, with a larger reduction in HF myocytes (P < 0.05). ICaL measured with standard voltage clamp was unchanged by HF. Incubation of myocytes with N-acetylcysteine (a glutathione precursor) attenuated HF-induced electrophysiological alterations. LA angiotensin-1 receptor expression was increased in HF.Conclusion Chronic HF causes alterations in ion channel expression and ion currents, resulting in attenuation of the APD and atrial contractility and a substrate for persistent AF. |
| Publication | Cardiovascular Research |
| Volume | 84 |
| Issue | 2 |
| Pages | 227 -236 |
| Date | November 01 , 2009 |
| DOI | 10.1093/cvr/cvp216 |
| URL | http://cardiovascres.oxfordjournals.org/content/84/2/227.abstract |
| Accessed | Wednesday, November 17, 2010 6:35:34 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:35:34 PM |
| Modified | Wednesday, November 17, 2010 6:35:34 PM |
| Type | Journal Article |
|---|---|
| Author | Michael R. Markham |
| Author | M. Lynne McAnelly |
| Author | Philip K. Stoddard |
| Author | Harold H. Zakon |
| Abstract | Electric fish strengthen their communication signals nightly and during social encounters by rapidly trafficking ion channels into cell membranes, demonstrating a direct relationship between environmental stimuli, channel trafficking, and behavior. |
| Publication | PLoS Biol |
| Volume | 7 |
| Issue | 9 |
| Pages | e1000203 |
| Date | 2009 |
| Journal Abbr | PLoS Biol |
| DOI | 10.1371/journal.pbio.1000203 |
| URL | http://dx.doi.org/10.1371/journal.pbio.1000203 |
| Accessed | Wednesday, November 17, 2010 6:20:47 PM |
| Library Catalog | PLoS Biol |
| Date Added | Wednesday, November 17, 2010 6:20:47 PM |
| Modified | Wednesday, November 17, 2010 6:20:47 PM |
| Type | Journal Article |
|---|---|
| Author | Sarah S. Garber |
| Author | Mary M. Hoffman |
| Publication | Biol Bull |
| Volume | 203 |
| Issue | 2 |
| Pages | 194-195 |
| Date | October 1, 2002 |
| URL | http://www.biolbull.org |
| Accessed | Wednesday, November 17, 2010 4:43:13 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 4:43:13 PM |
| Modified | Wednesday, November 17, 2010 4:43:13 PM |
| Type | Journal Article |
|---|---|
| Author | P D Thut |
| Author | D Wrigley |
| Author | M S Gold |
| Abstract | Three sub-populations of sensory neurons may be distinguished based on responses to a decrease in temperature: one has a relatively low threshold for activation (cool fibers), a second has a high threshold for activation (cold nociceptors), and the third is unresponsive to a decrease in temperature. Results from several recent studies suggest that the ability to detect a decrease in temperature reflects an intrinsic property(ies) of sensory neurons and therefore may be characterized via the study of the sensory neuron cell body in vitro. However, while three unique ionic mechanisms of cold transduction have recently been identified (i.e. activation of the transient receptor potential channel M8 [TRPM8] or an epithelial Na(+) channel [ENaC] or inhibition of two pore K(+) channel [TREK-1]), the possibility that these "mechanisms" may be differentially distributed among sensory neurons in a manner consistent with predictions based on in vivo observations has not been investigated. To investigate this possibility, we have characterized the influence of cooling on isolated trigeminal ganglion (TG) neurons from adult rats in vitro with Ca(2+) microfluorimetry in combination with a series of pharmacological interventions. We report that neurons responded to a decrease in temperature from approximately 34 degrees C to approximately 12 degrees C in one of two ways: 1) with a low threshold (30.1+/-0.6 degrees C) for activation demonstrating an increase in fluorescence with a minimal decrease in bath temperature (12.3%); 2) with a high threshold for activation (21.5+/-0.6 degrees C), demonstrating an increase in fluorescence only after a substantial decrease in bath temperature (13.3%); 74.4% did not respond to a decrease in temperature with an increase [Ca(2+)](i). These responses also were distinguishable on the basis of their rate of activation and degree of desensitization in response to prolonged application of a cold stimulus: low threshold responses were associated with a rapid (tau=12.0+/-5.7 s) increase in [Ca(2+)](i) and a time constant of desensitization of 85.8+/-20.7 s while high threshold responses were associated with a slow (tau=38.1+/-8.2 s) increase in [Ca(2+)](i) and demonstrated little desensitization over 4 min of stimulation. We refer to low threshold and high threshold cold responsive TG neurons as LT(cool) and HT(cool) neurons, respectively. LT(cool) and HT(cool) neurons were distributed among two distinct subpopulations of TG neurons distinguishable on the basis of cell body size and isolectin B4 staining. Both ENaC and TRPM8 appear to contribute to cold transduction, but neither is sufficient to account for all aspects of cold transduction in either population of TG neurons. Furthermore, inhibition of Ba(2+) and/or Gd(3+) sensitive two-pore K(+) channels (i.e. TREK-1 and TRAAK) was insufficient to account for cold transduction in HT(cool) or LT(cool) neurons. Our results suggest that cold transduction in sensory neurons is a complex process involving the activation and inhibition of several different ion channels. In addition, there appear to be both similarities and differences between mechanisms underlying cold transduction in LT(cool) and HT(cool) neurons. Identification of specific mechanisms underlying cold transduction in LT(cool) and HT(cool) neurons may enable the development of novel therapeutic interventions for the treatment of pathological conditions such as cold allodynia. |
| Publication | Neuroscience |
| Volume | 119 |
| Issue | 4 |
| Pages | 1071-1083 |
| Date | 2003 |
| Journal Abbr | Neuroscience |
| ISSN | 0306-4522 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/12831865 |
| Accessed | Wednesday, November 17, 2010 5:23:36 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 12831865 |
| Date Added | Wednesday, November 17, 2010 5:23:36 PM |
| Modified | Wednesday, November 17, 2010 5:23:36 PM |
| Type | Journal Article |
|---|---|
| Author | Dorothée Ruffieux-Daidié |
| Author | Olivier Poirot |
| Author | Sheerazed Boulkroun |
| Author | François Verrey |
| Author | Stephan Kellenberger |
| Author | Olivier Staub |
| Abstract | The epithelial sodium channel (ENaC) is critical for sodium and BP homeostasis. ENaC is regulated by Nedd4-2–mediated ubiquitylation, which leads to its internalization; this process can be reversed by deubiquitylation, which is regulated by the aldosterone-induced enzyme Usp2-45. In a second regulatory pathway, ENaC can be activated by luminal serine protease–mediated cleavage of its extracellular loops. Whether these two regulatory processes interact, however, is unknown. Here, in HEK293 cells stably transfected with ENaC, Usp2-45 interacted with ENaC, leading to deubiquitylation of the channel and stimulation of ENaC activity >20-fold. This was accompanied by a modest increase in cell surface expression of ENaC and by proteolytic cleavage of αENaC and γENaC at their extracellular loops. When endocytosis was inhibited with dominant negative dynamin (DynK44R), channel density and γENaC cleavage were increased, but αENaC cleavage and ENaC activity were not augmented. When Usp2-45 was coexpressed with DynK44R, both αENaC cleavage and activity were recovered. In summary, these data suggest that Usp2-45 deubiquitylation of ENaC enhances the proteolytic activation of both αENaC and γENaC, possibly by inducing a conformational change and by interfering with endocytosis, respectively. |
| Publication | Journal of the American Society of Nephrology |
| Volume | 19 |
| Issue | 11 |
| Pages | 2170 -2180 |
| Date | November 01 , 2008 |
| DOI | 10.1681/ASN.2007101130 |
| URL | http://jasn.asnjournals.org/content/19/11/2170.abstract |
| Accessed | Wednesday, November 17, 2010 6:23:23 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:23:23 PM |
| Modified | Wednesday, November 17, 2010 6:23:23 PM |
| Type | Journal Article |
|---|---|
| Author | G. Iribe |
| Author | P.J. Cooper |
| Author | M. Lei |
| Author | P. Kohl |
| Publication | J Physiol |
| Volume | 557P |
| Pages | PC13 |
| URL | http://www.physoc.org/custom2/publications/proceedings/archive/article.asp? ID=J%20Physiol%20557PPC13 |
| Accessed | Wednesday, November 17, 2010 1:06:28 PM |
| Date Added | Wednesday, November 17, 2010 1:06:28 PM |
| Modified | Wednesday, November 17, 2010 1:09:31 PM |
| Type | Journal Article |
|---|---|
| Author | Torben R Neelands |
| Author | Xu-Feng Zhang |
| Author | Heath McDonald |
| Author | Pamela Puttfarcken |
| Abstract | Elevated temperature and decreased extracellular pH are hallmarks of inflammatory pain states. Dorsal root ganglia (DRG) neurons are integral in transferring painful stimuli from the periphery to central sites. This study investigated the effect of elevated temperatures on the response of DRG neurons to acute application of acidic solutions. At room temperature (22 degrees C), in response to pH 5.5, there were a variety of kinetic responses consistent with differential expression of TRPV1 and ASIC channels. Increasing the temperature resulted in a significant increase in the peak and total current mediated by TRPV1 in response to an acidic solution. In contrast, the amplitude of a fast activating, rapidly inactivating ASIC1-like current was not affected by increasing the temperature but did result in an increased rate of desensitization that reduced the total current level. This effect on the rate of desensitization was temperature-dependent and could be reversed by returning to 22 degrees C. Likewise, cells exhibiting slowly inactivating ASIC2-like responses also had temperature-dependent increase in the rate of desensitization. The ASIC2-like responses and the TRPV1 responses tended to decrease in amplitude with repetitive application of pH 5.5 even at 22 degrees C. The rate of desensitization of ASIC-like currents activated by less acidic solutions (pH 6.8) was also increased in a temperature-dependent manner. Finally, acidic pH reduced threshold to trigger action potentials, however, the pattern of action potential firing was shaped by the distribution of ASIC and TRPV1 channels. These results indicate that the ambient temperature at which acidosis occurs has a profound effect on the contribution of ASIC and TRPV1 channels, therefore, altering the neuronal excitability. |
| Publication | Brain Research |
| Volume | 1329 |
| Pages | 55-66 |
| Date | May 6, 2010 |
| Journal Abbr | Brain Res |
| DOI | 10.1016/j.brainres.2010.02.064 |
| ISSN | 1872-6240 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/20206612 |
| Accessed | Wednesday, November 17, 2010 6:30:12 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 20206612 |
| Date Added | Wednesday, November 17, 2010 6:30:12 PM |
| Modified | Wednesday, November 17, 2010 6:30:12 PM |
| Type | Journal Article |
|---|---|
| Author | Kathrin Spendier |
| Author | Amanda Carroll-Portillo |
| Author | Keith A Lidke |
| Author | Bridget S Wilson |
| Author | Jerilyn A Timlin |
| Author | James L Thomas |
| Abstract | There is considerable interest in the signaling mechanisms of immunoreceptors, especially when triggered with membrane-bound ligands. We have quantified the spatiotemporal dynamics of the redistribution of immunoglobulin E-loaded receptors (IgE-FcepsilonRI) on rat basophilic leukemia-2H3 mast cells in contact with fluid and gel-phase membranes displaying ligands for immunoglobulin E, using total internal reflection fluorescence microscopy. To clearly separate the kinetics of receptor redistribution from cell spreading, and to precisely define the initial contact time (+/-50 ms), micropipette cell manipulation was used to bring individual cells into contact with surfaces. On ligand-free surfaces, there are micron-scale heterogeneities in fluorescence that likely reflect regions of the cell that are more closely apposed to the substrate. When ligands are present, receptor clusters form with this same size scale. The initial rate of accumulation of receptors into the clusters is consistent with diffusion-limited trapping with D approximately 10(-1) microm2/s. These results support the hypothesis that clusters form by diffusion to cell-surface contact regions. Over longer timescales (>10 s), individual clusters moved with both diffusive and directed motion components. The dynamics of the cluster motion is similar to the dynamics of membrane fluctuations of cells on ligand-free fluid membranes. Thus, the same cellular machinery may be responsible for both processes. |
| Publication | Biophysical Journal |
| Volume | 99 |
| Issue | 2 |
| Pages | 388-397 |
| Date | Jul 21, 2010 |
| Journal Abbr | Biophys. J |
| DOI | 10.1016/j.bpj.2010.04.029 |
| ISSN | 1542-0086 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/20643056 |
| Accessed | Wednesday, November 17, 2010 6:40:01 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 20643056 |
| Date Added | Wednesday, November 17, 2010 6:40:01 PM |
| Modified | Wednesday, November 17, 2010 6:40:01 PM |
| Type | Journal Article |
|---|---|
| Author | Kathrin Spendier |
| Author | Amanda Carroll-Portillo |
| Author | Keith A. Lidke |
| Author | Bridget S. Wilson |
| Author | Jerilyn A. Timlin |
| Author | James L. Thomas |
| Publication | Biophysical Journal |
| Volume | 99 |
| Issue | 2 |
| Pages | 388-397 |
| Date | 07/2010 |
| Journal Abbr | Biophysical Journal |
| DOI | 10.1016/j.bpj.2010.04.029 |
| ISSN | 00063495 |
| URL | http://www.cell.com/biophysj/abstract/S0006-3495(10)00527-8 |
| Accessed | Wednesday, November 17, 2010 6:50:15 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:50:15 PM |
| Modified | Wednesday, November 17, 2010 6:50:15 PM |
| Type | Journal Article |
|---|---|
| Author | Li-Ting Chien |
| Author | H. Criss Hartzell |
| Abstract | Mutations in the human bestrophin-1 (hBest1) gene are responsible for Best vitelliform macular dystrophy, however the mechanisms leading to retinal degeneration have not yet been determined because the function of the bestrophin protein is not fully understood. Bestrophins have been proposed to comprise a new family of Cl− channels that are activated by Ca2+. While the regulation of bestrophin currents has focused on intracellular Ca2+, little is known about other pathways/mechanisms that may also regulate bestrophin currents. Here we show that Cl− currents in Drosophila S2 cells, that we have previously shown are mediated by bestrophins, are dually regulated by Ca2+ and cell volume. The bestrophin Cl− currents were activated in a dose-dependent manner by osmotic pressure differences between the internal and external solutions. The increase in the current was accompanied by cell swelling. The volume-regulated Cl− current was abolished by treating cells with each of four different RNAi constructs that reduced dBest1 expression. The volume-regulated current was rescued by transfecting with dBest1. Furthermore, cells not expressing dBest1 were severely depressed in their ability to regulate their cell volume. Volume regulation and Ca2+ regulation can occur independently of one another: the volume-regulated current was activated in the complete absence of Ca2+ and the Ca2+-activated current was activated independently of alterations in cell volume. These two pathways of bestrophin channel activation can interact; intracellular Ca2+ potentiates the magnitude of the current activated by changes in cell volume. We conclude that in addition to being regulated by intracellular Ca2+, Drosophila bestrophins are also novel members of the volume-regulated anion channel (VRAC) family that are necessary for cell volume homeostasis. |
| Publication | The Journal of General Physiology |
| Volume | 130 |
| Issue | 5 |
| Pages | 513 -524 |
| Date | November 01 , 2007 |
| DOI | 10.1085/jgp.200709795 |
| URL | http://jgp.rupress.org/content/130/5/513.abstract |
| Accessed | Wednesday, November 17, 2010 5:21:31 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 5:21:31 PM |
| Modified | Wednesday, November 17, 2010 5:21:31 PM |
| Type | Journal Article |
|---|---|
| Author | Tanya L. Butler |
| Author | Jonathan R. Egan |
| Author | Fabian G. Graf |
| Author | Carol G. Au |
| Author | Aisling C. McMahon |
| Author | Kathryn N. North |
| Author | David S. Winlaw |
| Publication | The Journal of Thoracic and Cardiovascular Surgery |
| Volume | 138 |
| Issue | 1 |
| Pages | 141-147.e1 |
| Date | 07/2009 |
| Journal Abbr | The Journal of Thoracic and Cardiovascular Surgery |
| DOI | 10.1016/j.jtcvs.2008.12.008 |
| ISSN | 00225223 |
| Short Title | Dysfunction induced by ischemia versus edema |
| URL | http://www.jtcvsonline.org/article/S0022-5223(08)02194-6/abstract |
| Accessed | Wednesday, November 17, 2010 6:54:54 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:54:54 PM |
| Modified | Wednesday, November 17, 2010 6:54:54 PM |
| Type | Journal Article |
|---|---|
| Author | John C Gant |
| Author | Michelle M Sama |
| Author | Philip W Landfield |
| Author | Olivier Thibault |
| Abstract | Age-dependent changes in multiple Ca2+-related electrophysiological processes in the hippocampus appear to be consistent biomarkers of aging, and several also correlate with cognitive decline. These findings have led to the hypothesis that a common mechanism of Ca2+ dyshomeostasis underlies aspects of aging-dependent brain impairment. However, some key predictions of this view remain untested, including that multiple Ca2+-related biomarkers should emerge concurrently during aging and their onset should also precede/coincide with initial signs of cognitive decline. Moreover, blocking a putative common source of dysregulated Ca2+ should eliminate aging differences. Here, we tested these predictions using combined electrophysiological, imaging, and pharmacological approaches in CA1 neurons to determine the ages of onset (across 4-, 10-, 12-, 14-, and 23-month-old F344 rats) of several established biomarkers, including the increases in the slow afterhyperpolarization, spike accommodation, and [Ca2+]i rise during repetitive synaptic stimulation. In addition, we tested the hypothesis that altered Ca2+-induced Ca2+ release (CICR) from ryanodine receptors, which can be triggered by L-type Ca2+ channels, provides a common source of dysregulated Ca2+ in aging. Results showed that multiple aging biomarkers were first detectable at about the same age (12 months of age; approximately midlife), sufficiently early to influence initial cognitive decline. Furthermore, selectively blocking CICR with ryanodine slowed the Ca2+ rise during synaptic stimulation more in aged rat neurons and, notably, reduced or eliminated aging differences in the biomarkers. Thus, this study provides the first evidence that altered CICR plays a role in driving the early and simultaneous emergence in hippocampus of multiple Ca2+-related biomarkers of aging. |
| Publication | The Journal of Neuroscience: The Official Journal of the Society for Neuroscience |
| Volume | 26 |
| Issue | 13 |
| Pages | 3482-3490 |
| Date | Mar 29, 2006 |
| Journal Abbr | J. Neurosci |
| DOI | 10.1523/JNEUROSCI.4171-05.2006 |
| ISSN | 1529-2401 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/16571755 |
| Accessed | Wednesday, November 17, 2010 4:57:08 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 16571755 |
| Date Added | Wednesday, November 17, 2010 4:57:08 PM |
| Modified | Wednesday, November 17, 2010 4:57:08 PM |
| Type | Journal Article |
|---|---|
| Author | Maxime G Blanchard |
| Author | Stephan Kellenberger |
| Abstract | Acid-sensing ion channels (ASICs) are neuronal H(+)-gated cation channels, and the transient receptor potential vanilloid 1 channel (TRPV1) is a multimodal cation channel activated by low pH, noxious heat, capsaicin, and voltage. ASICs and TRPV1 are present in sensory neurons. It has been shown that raising the temperature increases TRPV1 and decreases ASIC H(+)-gated current amplitudes. To understand the underlying mechanisms, we have analyzed ASIC and TRPV1 function in a recombinant expression system and in dorsal root ganglion (DRG) neurons at room and physiological temperature. We show that temperature in the range studied does not affect the pH dependence of ASIC and TRPV1 activation. A temperature increase induces, however, a small alkaline shift of the pH dependence of steady-state inactivation of ASIC1a, ASIC1b, and ASIC2a. The decrease in ASIC peak current amplitudes at higher temperatures is likely in part due to the observed accelerated open channel inactivation kinetics and for some ASIC types to the changed pH dependence of steady-state inactivation. The increase in H(+)-activated TRPV1 current at the higher temperature is at least in part due to a hyperpolarizing shift in its voltage dependence. The contribution of TRPV1 relative to ASICs to H(+)-gated currents in DRG neurons increases with higher temperature and acidity. Still, ASICs remain the principal pH sensors of DRG neurons at 35°C in the pH range ≥6. |
| Publication | Pflugers Archiv: European Journal of Physiology |
| Date | Oct 6, 2010 |
| Journal Abbr | Pflugers Arch |
| DOI | 10.1007/s00424-010-0884-3 |
| ISSN | 1432-2013 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/20924599 |
| Accessed | Wednesday, November 17, 2010 6:55:49 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 20924599 |
| Date Added | Wednesday, November 17, 2010 6:55:49 PM |
| Modified | Wednesday, November 17, 2010 6:55:49 PM |
| Type | Journal Article |
|---|---|
| Author | Cynthia A Carnes |
| Author | Spencer J Dech |
| Abstract | There are well-described sexually dimorphic differences both in the electrocardiogram and in the propensity to develop drug-induced arrhythmias. The QT interval and the risk of ventricular proarrhythmia are reduced in males compared with females. Inward rectifier potassium current (IK(1)) is a primary determinant of the ventricular resting membrane potential, and an important contributor to myocardial excitability.Methods and results: Using the whole-cell patch-clamp technique, we evaluated the effects of dihydrotestosterone (DHT) on IK(1) in ventricular myocytes from castrated rabbits that were treated with either replacement DHT or vehicle-control for 3 weeks. Compared with the DHT-treated group, myocytes from the control animals had a significant reduction in inward IK(1) conductance (p < 0.005) and rectification ratio (RR) (p < 0.04) with no significant change in peak outward current. Acute DHT superfusion of the myocytes increased inward IK(1) conductance from baseline (p < 0.05) and increased the RR (p < 0.05). Testosterone has been reported to increase intracellular ornithine decarboxylase activity in ventricular tissue, which would increase intracellular polyamines, known modulators of IK(1) rectification. We found that inclusion of the intracellular polyamines spermidine and putrescine in the pipette solution caused a decrease in inward IK(1), accompanied by an increase in peak outward current and a reduction in the RR. Conclusion: In summary, DHT modulates IK(1) in a chronic, as well as, an acute fashion. These effects are not because of altered intracellular polyamines. DHT may modulate myocardial excitability through effects on IK(1). |
| Publication | International Journal of Andrology |
| Volume | 25 |
| Issue | 4 |
| Pages | 210-214 |
| Date | Aug 2002 |
| Journal Abbr | Int. J. Androl |
| ISSN | 0105-6263 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/12121570 |
| Accessed | Wednesday, November 17, 2010 2:46:44 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 12121570 |
| Date Added | Wednesday, November 17, 2010 2:46:44 PM |
| Modified | Wednesday, November 17, 2010 2:46:44 PM |
| Type | Journal Article |
|---|---|
| Author | Eric M. Blalock |
| Author | Jeremiah T. Phelps |
| Author | Tristano Pancani |
| Author | James L. Searcy |
| Author | Katie L. Anderson |
| Author | John C. Gant |
| Author | Jelena Popovic |
| Author | Margarita G. Avdiushko |
| Author | Don A. Cohen |
| Author | Kuey-Chu Chen |
| Author | Nada M. Porter |
| Author | Olivier Thibault |
| Abstract | Thiazolidinediones (TZDs) activate peroxisome proliferator-activated receptor gamma (PPARγ) and are used clinically to help restore peripheral insulin sensitivity in Type 2 diabetes (T2DM). Interestingly, long-term treatment of mouse models of Alzheimer's disease (AD) with TZDs also has been shown to reduce several well-established brain biomarkers of AD including inflammation, oxidative stress and Aβ accumulation. While TZD's actions in AD models help to elucidate the mechanisms underlying their potentially beneficial effects in AD patients, little is known about the functional consequences of TZDs in animal models of normal aging. Because aging is a common risk factor for both AD and T2DM, we investigated whether the TZD, pioglitazone could alter brain aging under non-pathological conditions. We used the F344 rat model of aging, and monitored behavioral, electrophysiological, and molecular variables to assess the effects of pioglitazone (PIO-Actos® a TZD) on several peripheral (blood and liver) and central (hippocampal) biomarkers of aging. Starting at 3 months or 17 months of age, male rats were treated for 4–5 months with either a control or a PIO-containing diet (final dose approximately 2.3 mg/kg body weight/day). A significant reduction in the Ca2+-dependent afterhyperpolarization was seen in the aged animals, with no significant change in long-term potentiation maintenance or learning and memory performance. Blood insulin levels were unchanged with age, but significantly reduced by PIO. Finally, a combination of microarray analyses on hippocampal tissue and serum-based multiplex cytokine assays revealed that age-dependent inflammatory increases were not reversed by PIO. While current research efforts continue to identify the underlying processes responsible for the progressive decline in cognitive function seen during normal aging, available medical treatments are still very limited. Because TZDs have been shown to have benefits in age-related conditions such as T2DM and AD, our study was aimed at elucidating PIO's potentially beneficial actions in normal aging. Using a clinically-relevant dose and delivery method, long-term PIO treatment was able to blunt several indices of aging but apparently affected neither age-related cognitive decline nor peripheral/central age-related increases in inflammatory signaling. |
| Publication | PLoS ONE |
| Volume | 5 |
| Issue | 4 |
| Pages | e10405 |
| Date | April 29, 2010 |
| Journal Abbr | PLoS ONE |
| DOI | 10.1371/journal.pone.0010405 |
| URL | http://dx.doi.org/10.1371/journal.pone.0010405 |
| Accessed | Wednesday, November 17, 2010 6:19:48 PM |
| Library Catalog | PLoS ONE |
| Date Added | Wednesday, November 17, 2010 6:19:48 PM |
| Modified | Wednesday, November 17, 2010 6:19:48 PM |
| Type | Journal Article |
|---|---|
| Author | Zhong-Hua Yang |
| Author | Xing-Huan Wang |
| Author | Huai-Peng Wang |
| Author | Li-Quan Hu |
| Publication | Asian Journal of Andrology |
| Volume | 11 |
| Issue | 2 |
| Pages | 157-165 |
| Date | online February 23, 2009 |
| Journal Abbr | Asian Journal of Andrology |
| ISSN | 1008-682X |
| URL | http://dx.doi.org/10.1038/aja.2009.1 |
| Accessed | Wednesday, November 17, 2010 6:37:53 PM |
| Library Catalog | Nature |
| Date Added | Wednesday, November 17, 2010 6:37:53 PM |
| Modified | Wednesday, November 17, 2010 6:37:53 PM |
| Type | Journal Article |
|---|---|
| Author | David L Brody |
| Author | Christine Mac Donald |
| Author | Chad C Kessens |
| Author | Carla Yuede |
| Author | Maia Parsadanian |
| Author | Mike Spinner |
| Author | Eddie Kim |
| Author | Katherine E Schwetye |
| Author | David M Holtzman |
| Author | Philip V Bayly |
| Abstract | Genetically modified mice represent useful tools for traumatic brain injury (TBI) research and attractive preclinical models for the development of novel therapeutics. Experimental methods that minimize the number of mice needed may increase the pace of discovery. With this in mind, we developed and characterized a prototype electromagnetic (EM) controlled cortical impact device along with refined surgical and behavioral testing techniques. By varying the depth of impact between 1.0 and 3.0 mm, we found that the EM device was capable of producing a broad range of injury severities. Histologically, 2.0-mm impact depth injuries produced by the EM device were similar to 1.0-mm impact depth injuries produced by a commercially available pneumatic device. Behaviorally, 2.0-, 2.5-, and 3.0-mm impacts impaired hidden platform and probe trial water maze performance, whereas 1.5-mm impacts did not. Rotorod and visible platform water maze deficits were also found following 2.5- and 3.0-mm impacts. No impairment of conditioned fear performance was detected. No differences were found between sexes of mice. Inter-operator reliability was very good. Behaviorally, we found that we could statistically distinguish between injury depths differing by 0.5 mm using 12 mice per group and between injury depths differing by 1.0 mm with 7-8 mice per group. Thus, the EM impactor and refined surgical and behavioral testing techniques may offer a reliable and convenient framework for preclinical TBI research involving mice. |
| Publication | Journal of Neurotrauma |
| Volume | 24 |
| Issue | 4 |
| Pages | 657-673 |
| Date | Apr 2007 |
| Journal Abbr | J. Neurotrauma |
| DOI | 10.1089/neu.2006.0011 |
| ISSN | 0897-7151 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17439349 |
| Accessed | Wednesday, November 17, 2010 4:51:39 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17439349 |
| Date Added | Wednesday, November 17, 2010 4:51:39 PM |
| Modified | Wednesday, November 17, 2010 4:51:39 PM |
| Type | Journal Article |
|---|---|
| Author | O Thibault |
| Author | R Hadley |
| Author | P W Landfield |
| Abstract | Considerable evidence supports a Ca(2+) dysregulation hypothesis of brain aging and Alzheimer's disease. However, it is still not known whether (1) intracellular [Ca(2+)](i) is altered in aged brain neurons during synaptically activated neuronal activity; (2) altered [Ca(2+)](i) is directly correlated with impaired neuronal plasticity; or (3) the previously observed age-related increase in L-type voltage-sensitive Ca(2+) channel (L-VSCC) density in hippocampal neurons is sufficient to impair synaptic plasticity. Here, we used confocal microscopy to image [Ca(2+)](i) in single CA1 neurons in hippocampal slices of young-adult and aged rats during repetitive synaptic activation. Simultaneously, we recorded intracellular EPSP frequency facilitation (FF), a form of short-term synaptic plasticity that is impaired with aging and inversely correlated with cognitive function. Resting [Ca(2+)](i) did not differ clearly with age. Greater elevation of somatic [Ca(2+)](i) and greater depression of FF developed in aged neurons during 20 sec trains of 7 Hz synaptic activation, but only if the activation triggered repetitive action potentials for several seconds. Elevated [Ca(2+)](i) and FF also were negatively correlated in individual aged neurons. In addition, the selective L-VSCC agonist Bay K8644 increased the afterhyperpolarization and mimicked the depressive effects of aging on FF in young-adult neurons. Thus, during physiologically relevant firing patterns in aging neurons, postsynaptic Ca(2+) elevation is closely associated with altered neuronal plasticity. Moreover, selectively increasing postsynaptic L-VSCC activity, as occurs in aging, negatively regulated a form of short-term plasticity that enhances synaptic throughput. Together, the results elucidate novel processes that may contribute to impaired cognitive function in aging. |
| Publication | The Journal of Neuroscience: The Official Journal of the Society for Neuroscience |
| Volume | 21 |
| Issue | 24 |
| Pages | 9744-9756 |
| Date | Dec 15, 2001 |
| Journal Abbr | J. Neurosci |
| ISSN | 1529-2401 |
| Short Title | Elevated postsynaptic [Ca2+]i and L-type calcium channel activity in aged hippocampal neurons |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/11739583 |
| Accessed | Wednesday, November 17, 2010 4:57:48 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 11739583 |
| Date Added | Wednesday, November 17, 2010 4:57:48 PM |
| Modified | Wednesday, November 17, 2010 4:57:48 PM |
| Type | Journal Article |
|---|---|
| Author | David N. Charo |
| Author | Michael Ho |
| Author | Giovanni Fajardo |
| Author | Masataka Kawana |
| Author | Ramendra K. Kundu |
| Author | Ahmad Y. Sheikh |
| Author | Thomas P. Finsterbach |
| Author | Nicholas J. Leeper |
| Author | Kavita V. Ernst |
| Author | Mary M. Chen |
| Author | Yen Dong Ho |
| Author | Hyung J. Chun |
| Author | Daniel Bernstein |
| Author | Euan A. Ashley |
| Author | Thomas Quertermous |
| Abstract | Studies have shown significant cardiovascular effects of exogenous apelin administration, including the potent activation of cardiac contraction. However, the role of the endogenous apelin-APJ pathway is less clear. To study the loss of endogenous apelin-APJ signaling, we generated mice lacking either the ligand (apelin) or the receptor (APJ). Apelin-deficient mice were viable, fertile, and showed normal development. In contrast, APJ-deficient mice were not born in the expected Mendelian ratio, and many showed cardiovascular developmental defects. Under basal conditions, both apelin and APJ null mice that survived to adulthood manifested modest decrements in contractile function. However, with exercise stress both mutant lines demonstrated consistent and striking decreases in exercise capacity. To explain these findings, we explored the role of autocrine signaling in vitro using field stimulation of isolated left ventricular cardiomyocytes lacking either apelin or APJ. Both groups manifested less sarcomeric shortening and impaired velocity of contraction and relaxation with no difference in calcium transient. Taken together, these results demonstrate that endogenous apelin-APJ signaling plays a modest role in maintaining basal cardiac function in adult mice with a more substantive role during conditions of stress. In addition, an autocrine pathway seems to exist in myocardial cells, the ablation of which reduces cellular contraction without change in calcium transient. Finally, differences in the developmental phenotype between apelin and APJ null mice suggest the possibility of undiscovered APJ ligands or ligand-independent effects of APJ. |
| Publication | Am J Physiol Heart Circ Physiol |
| Volume | 297 |
| Issue | 5 |
| Pages | H1904-1913 |
| Date | November 1, 2009 |
| DOI | 10.1152/ajpheart.00686.2009 |
| URL | http://ajpheart.physiology.org/cgi/content/abstract/297/5/H1904 |
| Accessed | Wednesday, November 17, 2010 6:43:58 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:43:58 PM |
| Modified | Wednesday, November 17, 2010 6:43:58 PM |
| Type | Journal Article |
|---|---|
| Author | Khuram W. Chaudhary |
| Author | Janet M. O'Neal |
| Author | Zun-Li Mo |
| Author | Bernard Fermini |
| Author | Robert H. Gallavan |
| Author | Anthony Bahinski |
| Publication | ASSAY and Drug Development Technologies |
| Volume | 4 |
| Issue | 1 |
| Pages | 73-82 |
| Date | 02/2006 |
| Journal Abbr | ASSAY and Drug Development Technologies |
| DOI | 10.1089/adt.2006.4.73 |
| ISSN | 1540-658X |
| URL | http://www.liebertonline.com/doi/abs/10.1089/adt.2006.4.73 |
| Accessed | Wednesday, November 17, 2010 6:53:43 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:53:43 PM |
| Modified | Wednesday, November 17, 2010 6:53:43 PM |
| Type | Journal Article |
|---|---|
| Author | Daniel Sigg |
| Author | Francisco Bezanilla |
| Author | Enrico Stefani |
| Abstract | An early component of the gating current in Shaker K+ channels with a time constant of approximately 12 microsec has been recorded with a high-speed patch-clamp setup. This fast component was found to be part of the gating current associated with the opening and closing of the channel. With regard to an energy-landscape interpretation of protein kinetics, the voltage and temperature dependence of the fast component may be explained by a combination of drift diffusion and barrier jumping in the initial stages of channel activation. The data were modeled by a gating particle undergoing Brownian motion in a one-dimensional diffusion landscape that featured diminishing electrical resistance and entropy in the direction of channel activation. The final open state of the channel was reasoned to be narrow and deep to account for successful subtraction of linear-charge displacements at positive potentials. The overall picture of gating that emerges from these studies is that the channel experiences incremental organization from a relaxed state in the early steps of activation to a rigidly structured open state. |
| Publication | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 100 |
| Issue | 13 |
| Pages | 7611-7615 |
| Date | Jun 24, 2003 |
| Journal Abbr | Proc. Natl. Acad. Sci. U.S.A |
| DOI | 10.1073/pnas.1332409100 |
| ISSN | 0027-8424 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/12805566 |
| Accessed | Wednesday, November 17, 2010 6:07:50 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 12805566 |
| Date Added | Wednesday, November 17, 2010 6:07:50 PM |
| Modified | Wednesday, November 17, 2010 6:07:50 PM |
| Type | Journal Article |
|---|---|
| Author | Guy M. Hagen |
| Author | Wouter Caarls |
| Author | Keith A. Lidke |
| Author | Anthony H.B. De Vries |
| Author | Cornelia Fritsch |
| Author | B. George Barisas |
| Author | Donna J. Arndt-Jovin |
| Author | Thomas M. Jovin |
| Publication | Microscopy Research and Technique |
| Volume | 72 |
| Issue | 6 |
| Pages | 431-440 |
| Date | 06/2009 |
| Journal Abbr | Microsc. Res. Tech. |
| DOI | 10.1002/jemt.20686 |
| ISSN | 1059910X |
| URL | http://onlinelibrary.wiley.com/doi/10.1002/jemt.20686/abstract |
| Accessed | Wednesday, November 17, 2010 6:31:01 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:31:01 PM |
| Modified | Wednesday, November 17, 2010 6:31:01 PM |
| Type | Journal Article |
|---|---|
| Author | Gentaro Iribe |
| Author | Michiel Helmes |
| Author | Peter Kohl |
| Abstract | We developed a dynamic force-length (FL) control system for single intact cardiomyocytes that uses a pair of compliant, computer-controlled, and piezo translator (PZT)-positioned carbon fibers (CF). CF are attached to opposite cell ends to afford dynamic and bidirectional control of the cell's mechanical environment. PZT and CF tip positions, as well as sarcomere length (SL), are simultaneously monitored in real time, and passive/active forces are calculated from CF bending. Cell force and length were dynamically adjusted by corresponding changes in PZT position, to achieve isometric, isotonic, or work-loop style contractions. Functionality of the technique was assessed by studying FL behavior of guinea pig intact cardiomyocytes. End-diastolic and end-systolic FL relations, obtained with varying preload and/or afterloads, were near linear, independent of the mode of contraction, and overlapping for the range of end-diastolic SLs tested (1.85-2.05 {micro}m). Instantaneous elastance curves, obtained from FL relation curves, showed an afterload-dependent decrease in time to peak elastance and slowed relaxation with both increased preload and afterload. The ability of the present system to independently and dynamically control preload, afterload, and transition between end-diastolic and end-systolic FL coordinates provides a valuable extension to the range of tools available for the study of single cardiomyocyte mechanics, to foster its interrelation with whole heart pathophysiology. |
| Publication | Am J Physiol Heart Circ Physiol |
| Volume | 292 |
| Issue | 3 |
| Pages | H1487-1497 |
| Date | March 1, 2007 |
| DOI | 10.1152/ajpheart.00909.2006 |
| URL | http://ajpheart.physiology.org/cgi/content/abstract/292/3/H1487 |
| Accessed | Wednesday, November 17, 2010 4:55:52 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 4:55:52 PM |
| Modified | Wednesday, November 17, 2010 4:55:52 PM |
| Type | Journal Article |
|---|---|
| Author | Nan Jiang |
| Author | Brian Y. Cooper |
| Publication | Bioelectromagnetics |
| Pages | n/a-n/a |
| Date | 2010 |
| Journal Abbr | Bioelectromagnetics |
| DOI | 10.1002/bem.20620 |
| ISSN | 01978462 |
| URL | http://onlinelibrary.wiley.com/doi/10.1002/bem.20620/abstract |
| Accessed | Wednesday, November 17, 2010 6:52:09 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:52:09 PM |
| Modified | Wednesday, November 17, 2010 6:52:09 PM |
| Type | Journal Article |
|---|---|
| Author | Jixin Wang |
| Author | Kimberly Della Penna |
| Author | Hao Wang |
| Author | Jerzy Karczewski |
| Author | Thomas M. Connolly |
| Author | Kenneth S. Koblan |
| Author | Paul B. Bennett |
| Author | Joseph J. Salata |
| Abstract | We established HEK-293 cell lines that stably express functional canine ether-a-go-go-related gene (cERG) K+ channels and examined their biophysical and pharmacological properties with whole cell patch clamp and 35S-labeled MK-499 ([35S]MK-499) binding displacement. Functionally, cERG current had the hallmarks of cardiac delayed rectifier K+ current (IKr). Channel opening was time- and voltage dependent with threshold near [-]40 mV. The half-maximum activation voltage was [-]7.8 {+/-} 2.4 mV at 23{degrees}C, shifting to [-]31.9 {+/-} 1.2 mV at 36{degrees}C. Channels activated with a time constant of 13 {+/-} 1 ms at +20 mV, showed prominent inward rectification at depolarized potentials, were highly K+ selective (Na+-to-K+ permeability ratio = 0.007), and were potently inhibited by IKr blockers. Astemizole, terfenadine, cisapride, and MK-499 inhibited cERG and human ERG (hERG) currents with IC50 values of 1.3, 13, 19, and 15 nM and 1.2, 9, 14, and 21 nM, respectively, and competitively displaced [35S]MK-499 binding from cERG and hERG with IC50 values of 0.4, 12, 35, and 0.6 nM and 0.8, 5, 47, and 0.7 nM, respectively. cERG channels had biophysical properties appropriate for canine action potential repolarization and were pharmacologically sensitive to agents known to prolong QT. A novel MK-499 binding assay provides a new tool to detect agents affecting ERG channels. |
| Publication | Am J Physiol Heart Circ Physiol |
| Volume | 284 |
| Issue | 1 |
| Pages | H256-267 |
| Date | January 1, 2003 |
| DOI | 10.1152/ajpheart.00220.2002 |
| URL | http://ajpheart.physiology.org/cgi/content/abstract/284/1/H256 |
| Accessed | Wednesday, November 17, 2010 6:12:09 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:12:09 PM |
| Modified | Wednesday, November 17, 2010 6:12:09 PM |
| Type | Journal Article |
|---|---|
| Author | Baerbel Rohrer |
| Author | Roman Blanco |
| Author | Robert E Marc |
| Author | Marcia B Lloyd |
| Author | Dean Bok |
| Author | David M Schneeweis |
| Author | Louis F Reichardt |
| Abstract | In the juvenile trkB knockout (trkB-/-) mouse, retina synaptic communication from rods to bipolar cells is severely compromised as evidenced by a complete absence of electroretinogram (ERG) b-wave, even though the inner retina appears anatomically normal (Rohrer et al., 1999). Since it is well known that the b-wave reflects light-dependent synaptic activation of ON bipolar cells via their metabotropic glutamate receptor, mGluR6, we sought to analyze the anatomical and functional integrity of the glutamatergic synapses at these and other bipolar cells in the trkB(-/-) mouse. Although rod bipolar cells from wild-type juvenile mice were determined to be immunopositive for trkB, postsynaptic metabotropic and ionotropic glutamate receptor-mediated pathways in ON and OFF bipolar cells were found to be functionally intact, based on patch electrode recordings, using brief applications ("puffs") of glutamate or its analog, 2-amino-4-phosphonobutyric acid (APB), a selective agonist for mGluR6 receptors. Ionotropic glutamate receptor function was assayed in OFF-cone bipolar and horizontal cells by applying exogenous glutamatergic agonists in the presence of the channel-permeant guanidinium analogue, 1-amino-4-guanidobutane (AGB). Electron-microscopic analysis revealed that the ribbon synapses between rods and postsynaptic rod bipolar and horizontal cells were formed at the appropriate age and appear to be structurally intact, and immunohistochemical analysis did not detect profound defects in the expression of excitatory amino acid transporters involved in glutamate clearance from the synaptic cleft. These data indicate that there does not appear to be evidence for postsynaptic deficits in glutamatergic signaling in the ON and OFF bipolar cells of mice lacking trkB. |
| Publication | Visual Neuroscience |
| Volume | 21 |
| Issue | 5 |
| Pages | 703-713 |
| Date | 2004 Sep-Oct |
| Journal Abbr | Vis. Neurosci |
| DOI | 10.1017/S095252380421505X |
| ISSN | 0952-5238 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/15683558 |
| Accessed | Wednesday, November 17, 2010 4:44:28 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 15683558 |
| Date Added | Wednesday, November 17, 2010 4:44:28 PM |
| Modified | Wednesday, November 17, 2010 4:44:28 PM |
| Type | Journal Article |
|---|---|
| Author | Erika D Eggers |
| Author | Peter D Lukasiewicz |
| Abstract | Rod bipolar cells relay visual signals evoked by dim illumination from the outer to the inner retina. GABAergic and glycinergic amacrine cells contact rod bipolar cell terminals, where they modulate transmitter release and contribute to the receptive field properties of third order neurones. However, it is not known how these distinct inhibitory inputs affect rod bipolar cell output and subsequent retinal processing. To determine whether GABA(A), GABA(C) and glycine receptors made different contributions to light-evoked inhibition, we recorded light-evoked inhibitory postsynaptic currents (L-IPSCs) from rod bipolar cells mediated by each pharmacologically isolated receptor. All three receptors contributed to L-IPSCs, but their relative roles differed; GABA(C) receptors transferred significantly more charge than GABA(A) and glycine receptors. We determined how these distinct inhibitory inputs affected rod bipolar cell output by recording light-evoked excitatory postsynaptic currents (L-EPSCs) from postsynaptic AII and A17 amacrine cells. Consistent with their relative contributions to L-IPSCs, GABA(C) receptor activation most effectively reduced the L-EPSCs, while glycine and GABA(A) receptor activation reduced the L-EPSCs to a lesser extent. We also found that GABAergic L-IPSCs in rod bipolar cells were limited by GABA(A) receptor-mediated inhibition between amacrine cells. We show that GABA(A), GABA(C) and glycine receptors mediate functionally distinct inhibition to rod bipolar cells, which differentially modulated light-evoked rod bipolar cell output. Our findings suggest that modulating the relative proportions of these inhibitory inputs could change the characteristics of rod bipolar cell output. |
| Publication | The Journal of Physiology |
| Volume | 572 |
| Issue | Pt 1 |
| Pages | 215-225 |
| Date | Apr 1, 2006 |
| Journal Abbr | J. Physiol. (Lond.) |
| DOI | 10.1113/jphysiol.2005.103648 |
| ISSN | 0022-3751 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/16439422 |
| Accessed | Wednesday, November 17, 2010 4:52:33 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 16439422 |
| Date Added | Wednesday, November 17, 2010 4:52:33 PM |
| Modified | Wednesday, November 17, 2010 4:52:33 PM |
| Type | Journal Article |
|---|---|
| Author | Eric P. Hornstein |
| Author | Jan Verweij |
| Author | Peter H. Li |
| Author | Julie L. Schnapf |
| Abstract | We investigated gap-junctional coupling of rods and cones in macaque retina. Cone voltage responses evoked by light absorption in neighboring rods were briefer and smaller than responses recorded in the rods themselves. Rod detection thresholds, calculated from noise and response amplitude histograms, closely matched the threshold for an ideal detector limited by quantal fluctuations in the stimulus. Surprisingly, cone thresholds were only approximately two times higher. Amplitude fluctuations in cones could be explained by a Poisson distribution of photoisomerizations within a pool of seven or more coupled rods. Neurobiotin coupling between rods and cones was consistent with our electrical recordings, with approximately six rods labeled per injected cone. The spatial distribution of tracer-coupled rods matched the light-evoked cone receptive field. The gap junction inhibitor carbenoxolone abolished both electrical and tracer coupling. Amplitude fluctuations in most rods were accounted for by the expected rate of light absorption in their outer segments. The fluctuations in some rods, however, were consistent with a summation pool of up to six rods. When single rods were injected with Neurobiotin, up to 10 rods were labeled. Rod-rod and rod-cone electrical coupling is expected to extend the range of scotopic vision by circumventing saturation at the rod to rod-bipolar cell synapse; however, because coupling also renders the rod synapse less effective at separating out photon signals from dark noise, coupling is expected to elevate the absolute threshold of dark-adapted observers. |
| Publication | J. Neurosci. |
| Volume | 25 |
| Issue | 48 |
| Pages | 11201-11209 |
| Date | November 30, 2005 |
| DOI | 10.1523/JNEUROSCI.3416-05.2005 |
| URL | http://www.jneurosci.org/cgi/content/abstract/25/48/11201 |
| Accessed | Wednesday, November 17, 2010 6:54:20 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:54:20 PM |
| Modified | Wednesday, November 17, 2010 6:54:20 PM |
| Type | Journal Article |
|---|---|
| Author | Andriy E Belevych |
| Author | Sunita Warrier |
| Author | Robert D Harvey |
| Abstract | It has been suggested that protein tyrosine kinase (PTK) activity can directly regulate cardiac L-type Ca(2+) channels. This conclusion is based to a large extent on the observation that the PTK inhibitor genistein can inhibit the cardiac L-type Ca(2+) current. The purpose of the present study was to determine whether the ability of genistein to inhibit cardiac L-type Ca(2+) channel activity is due to inhibition of PTK activity. Genistein significantly reduced the magnitude of the L-type Ca(2+) current in guinea pig ventricular myocytes recorded using the whole-cell patch-clamp technique. However, this effect was associated with extracellular, not intracellular, application of the drug. Peroxovanadate (PVN), a potent protein tyrosine phosphatase inhibitor, had no effect on the basal Ca(2+) current. PVN was also ineffective in preventing the inhibitory effect of genistein. Internal perfusion of cells with a pipette solution containing ATPgammaS was used to prevent reversibility of phosphorylation-dependent processes. This treatment did not alter the inhibitory effect of genistein, although it did result in irreversible protein kinase A-dependent regulation of the Ca(2+) current. Bath application of lavendustin A, a PTK inhibitor that is structurally unrelated to genistein, did not affect the Ca(2+) current amplitude. The inhibitory effect of genistein was also associated with a hyperpolarizing shift in the voltage dependence of Ca(2+) channel inactivation. These results are consistent with the conclusion that the cardiac L-type Ca(2+) current is not directly regulated by PTK activity and that the inhibitory effect of genistein is due to direct non-catalytic blockade of the channels. |
| Publication | Molecular Pharmacology |
| Volume | 62 |
| Issue | 3 |
| Pages | 554-565 |
| Date | Sep 2002 |
| Journal Abbr | Mol. Pharmacol |
| ISSN | 0026-895X |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/12181432 |
| Accessed | Wednesday, November 17, 2010 4:42:24 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 12181432 |
| Date Added | Wednesday, November 17, 2010 4:42:24 PM |
| Modified | Wednesday, November 17, 2010 4:42:24 PM |
| Type | Journal Article |
|---|---|
| Author | K K Rau |
| Author | N Jiang |
| Author | R D Johnson |
| Author | B Y Cooper |
| Abstract | Recordings were made from small and medium diameter dorsal root ganglia (DRG) neurons that expressed transient receptor potential (TRP) proteins. Physiologically characterized skin nociceptors expressed either TRPV1 (type 2) or TRPV2 (type 4) in isolation. Other nociceptors co-expressed both TRP proteins and innervated deep tissue sites (gastrocnemius muscle, distal colon; type 5, type 8) and skin (type 8). Subpopulations of myelinated (type 8) and unmyelinated (type 5) nociceptors co-expressed both TRPs. Cells that expressed TRPV1 were excellent transducers of intense heat. Proportional inward currents were obtained from a threshold of approximately 46.5 to approximately 56 degrees C. In contrast, cells expressing TRPV2 alone (52 degrees C threshold) did not reliably transduce the intensity of thermal events. Studies were undertaken to assess the capacity of skin and deep nociceptors to exhibit sensitization to repeated intense thermal stimuli [heat-heat sensitization (HHS)]. Only nociceptors that expressed TRPV2, alone or in combination with TRPV1, exhibited HHS. HHS was shown to be Ca(2+) dependent in either case. Intracellular Ca(2+) dependent pathways to HHS varied with the pattern of TRP protein expression. Cells co-expressing both TRPs modulated heat reactivity through serine/threonine phosphorylation or PLA(2)-dependent pathways. Cells expressing only TRPV2 may have relied on tyrosine kinases for HHS. We conclude that heat sensitization in deep and superficial capsaicin and capsaicin-insensitive C and Adelta nociceptors varies with the distribution of TRPV1 and TRPV2 proteins. The expression pattern of these proteins are specific to subclasses of physiologically identified C and A fiber nociceptors with highly restricted tissue targets. |
| Publication | Journal of Neurophysiology |
| Volume | 97 |
| Issue | 4 |
| Pages | 2651-2662 |
| Date | Apr 2007 |
| Journal Abbr | J. Neurophysiol |
| DOI | 10.1152/jn.00840.2006 |
| ISSN | 0022-3077 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17287441 |
| Accessed | Wednesday, November 17, 2010 6:12:42 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17287441 |
| Date Added | Wednesday, November 17, 2010 6:12:42 PM |
| Modified | Wednesday, November 17, 2010 6:12:42 PM |
| Type | Journal Article |
|---|---|
| Author | Chee Chew Lim |
| Author | Michiel H. B. Helmes |
| Author | Douglas B. Sawyer |
| Author | Mohit Jain |
| Author | Ronglih Liao |
| Abstract | Isolated permeabilized cardiac myocytes have been used in the study of myofilament calcium sensitivity through measurement of the isometric force-pCa curve. Determining this force-pCa relationship in skinned myocytes is relatively expensive and carries a high degree of variability. We therefore attempted to establish an alternative high-throughput method to measure calcium sensitivity in cardiac myocytes. With the use of commercially available software that allows for precise measurement of sarcomere spacing, we measured sarcomere length changes in unloaded skinned cardiac myocytes over a range of calcium concentrations. With the use of this technique, we were able to accurately detect acute increases or decreases in myofilament calcium sensitivity after exposure to 10 mM caffeine or 5 mM 2,3-butanedione monoxime, respectively. This technique allows for the simple and rapid determination of myofilament calcium sensitivity in cardiac myocytes in a reproducible and inexpensive manner and could be used for high-throughput screening of pharmacological agents and/or transgenic mouse models for changes in myofilament calcium sensitivity. |
| Publication | Am J Physiol Heart Circ Physiol |
| Volume | 281 |
| Issue | 2 |
| Pages | H969-974 |
| Date | August 1, 2001 |
| URL | http://ajpheart.physiology.org/cgi/content/abstract/281/2/H969 |
| Accessed | Wednesday, November 17, 2010 2:01:57 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 2:01:57 PM |
| Modified | Wednesday, November 17, 2010 2:01:57 PM |
| Type | Journal Article |
|---|---|
| Author | Giuseppe Ristagno |
| Author | Simona Tantillo |
| Author | Shijie Sun |
| Author | Max Harry Weil |
| Author | Wanchun Tang |
| Publication | Resuscitation |
| Volume | 81 |
| Issue | 7 |
| Pages | 898-903 |
| Date | 07/2010 |
| Journal Abbr | Resuscitation |
| DOI | 10.1016/j.resuscitation.2010.03.016 |
| ISSN | 03009572 |
| URL | http://www.resuscitationjournal.com/article/S0300-9572(10)00172-3/abstract |
| Accessed | Wednesday, November 17, 2010 6:37:18 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:37:18 PM |
| Modified | Wednesday, November 17, 2010 6:37:18 PM |
| Type | Book Section |
|---|---|
| Editor | Juan S. Bonifacino |
| Editor | Mary Dasso |
| Editor | Joe B. Harford |
| Editor | Jennifer Lippincott-Schwartz |
| Editor | Kenneth M. Yamada |
| Author | Diane S. Lidke |
| Author | Peter Nagy |
| Author | Donna J. Arndt-Jovin |
| Book Title | Current Protocols in Cell Biology |
| Place | Hoboken, NJ, USA |
| Publisher | John Wiley & Sons, Inc. |
| Date | 09/2007 |
| ISBN | 0471143030 |
| URL | http://onlinelibrary.wiley.com/doi/10.1002/0471143030.cb2501s36/abstract |
| Accessed | Wednesday, November 17, 2010 6:32:23 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:32:23 PM |
| Modified | Wednesday, November 17, 2010 6:32:23 PM |
| Type | Journal Article |
|---|---|
| Author | Graeme Lowe |
| Abstract | Lowe, Graeme Inhibition of Backpropagating Action Potentials in Mitral Cell Secondary Dendrites. J. Neurophysiol. 88: 64-85, 2002. The mammalian olfactory bulb is a geometrically organized signal-processing array that utilizes lateral inhibitory circuits to transform spatially patterned inputs. A major part of the lateral circuitry consists of extensively radiating secondary dendrites of mitral cells. These dendrites are bidirectional cables: they convey granule cell inhibitory input to the mitral soma, and they conduct backpropagating action potentials that trigger glutamate release at dendrodendritic synapses. This study examined how mitral cell firing is affected by inhibitory inputs at different distances along the secondary dendrite and what happens to backpropagating action potentials when they encounter inhibition. These are key questions for understanding the range and spatial dependence of lateral signaling between mitral cells. Backpropagating action potentials were monitored in vitro by simultaneous somatic and dendritic whole cell recording from individual mitral cells in rat olfactory bulb slices, and inhibition was applied focally to dendrites by laser flash photolysis of caged GABA (2.5-{micro}m spot). Photolysis was calibrated to activate conductances similar in magnitude to GABAA-mediated inhibition from granule cell spines. Under somatic voltage-clamp with CsCl dialysis, uncaging GABA onto the soma, axon initial segment, primary and secondary dendrites evoked bicuculline-sensitive currents (up to [-]1.4 nA at [-]60 mV; reversal at ~0 mV). The currents exhibited a patchy distribution along the axon and dendrites. In current-clamp recordings, repetitive firing driven by somatic current injection was blocked by uncaging GABA on the secondary dendrite ~140 {micro}m from the soma, and the blocking distance decreased with increasing current. In the secondary dendrites, backpropagated action potentials were measured 93-152 {micro}m from the soma, where they were attenuated by a factor of 0.75 {+/-} 0.07 (mean {+/-} SD) and slightly broadened (1.19 {+/-} 0.10), independent of activity (35-107 Hz). Uncaging GABA on the distal dendrite had little effect on somatic spikes but attenuated backpropagating action potentials by a factor of 0.68 {+/-} 0.15 (0.45-0.60 {micro}J flash with 1-mM caged GABA); attenuation was localized to a zone of width 16.3 {+/-} 4.2 {micro}m around the point of GABA release. These results reveal the contrasting actions of inhibition at different locations along the dendrite: proximal inhibition blocks firing by shunting somatic current, whereas distal inhibition can impose spatial patterns of dendrodendritic transmission by locally attenuating backpropagating action potentials. The secondary dendrites are designed with a high safety factor for backpropagation, to facilitate reliable transmission of the outgoing spike-coded data stream, in parallel with the integration of inhibitory inputs. |
| Publication | J Neurophysiol |
| Volume | 88 |
| Issue | 1 |
| Pages | 64-85 |
| Date | July 1, 2002 |
| URL | http://jn.physiology.org/cgi/content/abstract/88/1/64 |
| Accessed | Wednesday, November 17, 2010 1:59:03 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 1:59:03 PM |
| Modified | Wednesday, November 17, 2010 1:59:03 PM |
| Type | Journal Article |
|---|---|
| Author | Jun Yamazaki |
| Author | Joseph R. Hume |
| Abstract | Abstract Recent studies have provided evidence that sulfonylureas, in addition to blocking ATP-sensitive K+ (KATP) channels, also inhibit cystic fibrosis transmembrane regulator (CFTR) Cl- channels in epithelial and cardiac cells. The purpose of this study was to test whether the sulfonylurea glibenclamide might also inhibit other types of cardiac Cl- channels. Whole-cell patch-clamp techniques were used to compare the effects of glibenclamide on CFTR Cl- currents in guinea pig ventricular myocytes, swelling-activated Cl- currents in guinea pig atrial myocytes, and Ca2+-activated Cl- currents in canine ventricular myocytes. Glibenclamide markedly inhibited CFTR Cl- currents in a voltage-independent manner at 22{degrees}C, with estimated IC50 values of 12.5 and 11.0 {micro}mol/L at +50 and -100 mV, respectively. The outwardly rectifying swelling-activated Cl- current in atrial cells was less sensitive to glibenclamide, and the block exhibited voltage dependence. At 22{degrees}C, the estimated IC50 values were 193 and 470 {micro}mol/L at +50 and -100 mV, respectively, and block was enhanced at 35{degrees}C. Macroscopic Cl- currents activated by a rise in intracellular Ca2+, induced by either Ca2+-induced Ca2+ release or by external application of the Ca2+ ionophore A23187, were also markedly inhibited at 22{degrees}C by glibenclamide in a voltage-independent manner. The estimated IC50 values were 61.5 and 69.9 {micro}mol/L at +50 and -100 mV, respectively. These results suggest that glibenclamide, an inhibitor of cardiac CFTR Cl- channels, also inhibits swelling-activated and Ca2+-activated Cl- channels at higher concentrations. The results also suggest that studies attributing the beneficial or deleterious effects of sulfonylurea compounds in the heart solely to blockade of KATP channels should use submicromolar concentrations of these agents to minimize possible secondary interactions with cardiac Cl- channels. |
| Publication | Circ Res |
| Volume | 81 |
| Issue | 1 |
| Pages | 101-109 |
| Date | July 19, 1997 |
| URL | http://circres.ahajournals.org/cgi/content/abstract/81/1/101 |
| Accessed | Wednesday, November 17, 2010 4:05:02 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 4:05:02 PM |
| Modified | Wednesday, November 17, 2010 4:05:02 PM |
| Type | Journal Article |
|---|---|
| Author | Craig S Nunemaker |
| Author | Min Zhang |
| Author | Leslie S Satin |
| Abstract | Recent work suggests that insulin may exert both positive and negative feedback directly on pancreatic beta-cells. To investigate the hypothesis that insulin modulates beta-cell metabolism, mouse islets and beta-cell clusters were loaded with rhodamine 123 to dynamically monitor mitochondrial membrane potential (DeltaPsi(m)). Spontaneous oscillations in DeltaPsi(m) (period: 218 +/- 26 s) were observed in 17 of 30 islets exposed to 11.1 mmol/l glucose. Acute insulin application (100 nmol/l) hyperpolarized DeltaPsi(m), indicating a change in mitochondrial activity. The ATP-sensitive K(+) (K(ATP)) channel opener diazoxide or the l-type calcium channel blocker nifedipine mimicked the effect of insulin, suggesting that insulin activates K(ATP) channels to hyperpolarize DeltaPsi(m) by inhibiting calcium influx. Treatment with forskolin, which increases endogenous insulin secretion, also mimicked the effect of exogenous insulin, suggesting physiological feedback. Pretreatment with nifedipine or the K(ATP) inhibitor glyburide prevented insulin action, further implicating a K(ATP) channel pathway. Together, these data suggest a feedback mechanism whereby insulin receptor activation opens K(ATP) channels to inhibit further secretion. The resulting reduction in beta-cell calcium increases the energy stored in the mitochondrial gradient that drives ATP production. Insulin feedback onto mitochondria may thus help to calibrate the energy needs of the beta-cell on a minute-to-minute basis. |
| Publication | Diabetes |
| Volume | 53 |
| Issue | 7 |
| Pages | 1765-1772 |
| Date | Jul 2004 |
| Journal Abbr | Diabetes |
| ISSN | 0012-1797 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/15220200 |
| Accessed | Wednesday, November 17, 2010 5:22:52 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 15220200 |
| Date Added | Wednesday, November 17, 2010 5:22:52 PM |
| Modified | Wednesday, November 17, 2010 5:22:52 PM |
| Type | Journal Article |
|---|---|
| Author | Matthew K. Lancaster |
| Author | Sandra A. Jones |
| Author | Simon M. Harrison |
| Author | Mark R. Boyett |
| Abstract | Recent studies have proposed that release of calcium from the sarcoplasmic reticulum (SR) modulates the spontaneous activity of the sinoatrial node (SAN). Previously we have shown that several calcium regulatory proteins are expressed at a lower level in the centre of the SAN compared with the periphery. Such differences may produce heterogeneity of intracellular calcium handling and pacemaker activity across the SAN. Selective isolations showed that the centre of the SAN is composed of smaller cells than the periphery. Measurements of cytosolic calcium in spontaneously beating cells showed that diastolic calcium, systolic calcium, the calcium transient amplitude and spontaneous rate were greater in larger (likely to be peripheral) cells compared with smaller (likely to be central) SAN cells. The SR calcium content was greater in larger cells, although SR recruitment was more efficient in smaller cells. The sodium–calcium exchanger and sarcolemmal calcium ATPase had a lower activity and the exchanger was responsible for a larger proportion of sarcolemmal calcium extrusion in smaller cells compared with larger cells. Ryanodine had a greater effect on the spontaneous calcium transient in larger cells compared with smaller cells, and slowed pacemaker activity in larger cells but not smaller cells, thus abolishing the difference in cycle length. This study shows heterogeneity of intracellular calcium regulation within the SAN and this contributes to differences in pacemaker activity between cells from across the SAN. The smallest central cells of the leading pacemaker region of the SAN do not require SR calcium for spontaneous activity nor does disruption of the SR alter pacemaking in these primary pacemaker cells. |
| Publication | The Journal of Physiology |
| Volume | 556 |
| Issue | 2 |
| Pages | 481 -494 |
| Date | April 15 , 2004 |
| DOI | 10.1113/jphysiol.2003.057372 |
| Short Title | Intracellular Ca2+ and pacemaking within the rabbit sinoatrial node |
| URL | http://jp.physoc.org/content/556/2/481.abstract |
| Accessed | Wednesday, November 17, 2010 3:51:19 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 3:51:19 PM |
| Modified | Wednesday, November 17, 2010 3:51:19 PM |
| Type | Journal Article |
|---|---|
| Author | Ayako Takeuchi |
| Author | Shuji Tatsumi |
| Author | Nobuaki Sarai |
| Author | Keisuke Terashima |
| Author | Satoshi Matsuoka |
| Author | Akinori Noma |
| Abstract | Although the Na(+)/K(+) pump is one of the key mechanisms responsible for maintaining cell volume, we have observed experimentally that cell volume remained almost constant during 90 min exposure of guinea pig ventricular myocytes to ouabain. Simulation of this finding using a comprehensive cardiac cell model (Kyoto model incorporating Cl(-) and water fluxes) predicted roles for the plasma membrane Ca(2+)-ATPase (PMCA) and Na(+)/Ca(2+) exchanger, in addition to low membrane permeabilities for Na(+) and Cl(-), in maintaining cell volume. PMCA might help maintain the [Ca(2+)] gradient across the membrane though compromised, and thereby promote reverse Na(+)/Ca(2+) exchange stimulated by the increased [Na(+)](i) as well as the membrane depolarization. Na(+) extrusion via Na(+)/Ca(2+) exchange delayed cell swelling during Na(+)/K(+) pump block. Supporting these model predictions, we observed ventricular cell swelling after blocking Na(+)/Ca(2+) exchange with KB-R7943 or SEA0400 in the presence of ouabain. When Cl(-) conductance via the cystic fibrosis transmembrane conductance regulator (CFTR) was activated with isoproterenol during the ouabain treatment, cells showed an initial shrinkage to 94.2 +/- 0.5%, followed by a marked swelling 52.0 +/- 4.9 min after drug application. Concomitantly with the onset of swelling, a rapid jump of membrane potential was observed. These experimental observations could be reproduced well by the model simulations. Namely, the Cl(-) efflux via CFTR accompanied by a concomitant cation efflux caused the initial volume decrease. Then, the gradual membrane depolarization induced by the Na(+)/K(+) pump block activated the window current of the L-type Ca(2+) current, which increased [Ca(2+)](i). Finally, the activation of Ca(2+)-dependent cation conductance induced the jump of membrane potential, and the rapid accumulation of intracellular Na(+) accompanied by the Cl(-) influx via CFTR, resulting in the cell swelling. The pivotal role of L-type Ca(2+) channels predicted in the simulation was demonstrated in experiments, where blocking Ca(2+) channels resulted in a much delayed cell swelling. |
| Publication | The Journal of General Physiology |
| Volume | 128 |
| Issue | 5 |
| Pages | 495-507 |
| Date | Nov 2006 |
| Journal Abbr | J. Gen. Physiol |
| DOI | 10.1085/jgp.200609646 |
| ISSN | 0022-1295 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17074975 |
| Accessed | Wednesday, November 17, 2010 5:20:38 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17074975 |
| Date Added | Wednesday, November 17, 2010 5:20:38 PM |
| Modified | Wednesday, November 17, 2010 5:20:38 PM |
| Type | Journal Article |
|---|---|
| Author | K. van Acker |
| Author | B. Bautmans |
| Author | G. Bultynck |
| Author | K. Maes |
| Author | A. F. Weidema |
| Author | P. de Smet |
| Author | J. B. Parys |
| Author | H. de Smedt |
| Author | L. Missiaen |
| Author | G. Callewaert |
| Abstract | van Acker, K., B. Bautmans, G. Bultynck, K. Maes, A. F. Weidema, P. de Smet, J. B. Parys, H. de Smedt, L. Missiaen, and G. Callewaert. Mapping of IP3-Mediated Ca2+ Signals in Single Human Neuroblastoma SH-SY5Y Cells: Cell Volume Shaping the Ca2+ Signal. J. Neurophysiol. 83: 1052-1057, 2000. Fast confocal laser-scanning microscopy was used to study spatiotemporal properties of IP3-mediated Ca2+ release signals in human SH-SY5Y neuroblastoma cells. [Ca2+]i increases were not affected by ryanodine (30 {micro}M) or caffeine (10 mM) and largely insensitive to removal of external Ca2+, indicating predominance of IP3-induced Ca2+ release. Ca2+ signals evoked by high concentration (10 {micro}M) of the muscarinic agonist carbachol appeared as self-propagating waves initiating in cell processes. At low carbachol concentrations (500 nM) Ca2+ changes in most cells displayed striking spatiotemporal heterogeneity. The Ca2+ response in the cell body was delayed and had a smaller amplitude and a slower rise time than that in processes. Ca2+ changes in processes either occurred in a homogeneous manner throughout the whole process or were sometimes confined to hot spots. Regional differences in surface-to-volume ratio appear to be critical clues that determine the spatiotemporal pattern of intracellular Ca2+ release signals. |
| Publication | J Neurophysiol |
| Volume | 83 |
| Issue | 2 |
| Pages | 1052-1057 |
| Date | February 1, 2000 |
| Short Title | Mapping of IP3-Mediated Ca2+ Signals in Single Human Neuroblastoma SH-SY5Y Cells |
| URL | http://jn.physiology.org/cgi/content/abstract/83/2/1052 |
| Accessed | Wednesday, November 17, 2010 3:52:29 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 3:52:29 PM |
| Modified | Wednesday, November 17, 2010 3:52:29 PM |
| Type | Journal Article |
|---|---|
| Author | Victor Pikov |
| Author | Xianghong Arakaki |
| Author | Michael Harrington |
| Author | Scott E Fraser |
| Author | Peter H Siegel |
| Publication | Journal of Neural Engineering |
| Volume | 7 |
| Issue | 4 |
| Pages | 045003 |
| Date | 08/2010 |
| Journal Abbr | J. Neural Eng. |
| DOI | 10.1088/1741-2560/7/4/045003 |
| ISSN | 1741-2560 |
| URL | http://iopscience.iop.org/1741-2552/7/4/045003 |
| Accessed | Wednesday, November 17, 2010 6:18:51 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:18:51 PM |
| Modified | Wednesday, November 17, 2010 6:18:51 PM |
| Type | Journal Article |
|---|---|
| Author | Ravi K Sawhney |
| Author | Jonathon Howard |
| Abstract | Motile fibroblasts generate forces that can be expressed as cell migration or as traction, the drawing-in of extracellular matrix. Traction by cultured fibroblasts can induce a rapid concerted reorganization of collagen gel, creating a pattern of collagen alignment similar to that seen in tendons and ligaments. In such fibrous connective tissues, after pattern morphogenesis is complete, ongoing traction may be responsible for the maintenance of proper form and function. The molecules that generate and transmit forces have been catalogued; however, how these nanometer-scale molecules contribute to millimeter-scale patterns has not been directly tested. Here, we placed pairs of explants of human periodontal ligament fibroblasts in collagen gels, where ligament-like straps of anisotropic collagen formed on the axes between them. We scrutinized the traction apparatus using electron microscopy, video microscopy, and computer-based pattern analysis, augmented with pharmacologic inhibitors of cytoskeletal function. Patterning was marked by the co-alignment of collagen, fibroblasts, and their actin cytoskeletons, all parallel to the axis between explants. The pattern was diminished by depolymerizing actin filaments or by blocking myosin activity, but was accentuated by depolymerizing microtubules. The plasma membrane also seems to contribute to the traction force. These molecular components combine to exert a sub-maximal traction force on the matrix, suggesting that the force may be regulated to ensure tissue tensional homeostasis. |
| Publication | Cell Motility and the Cytoskeleton |
| Volume | 58 |
| Issue | 3 |
| Pages | 175-185 |
| Date | Jul 2004 |
| Journal Abbr | Cell Motil. Cytoskeleton |
| DOI | 10.1002/cm.20004 |
| ISSN | 0886-1544 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/15146536 |
| Accessed | Wednesday, November 17, 2010 1:56:53 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 15146536 |
| Date Added | Wednesday, November 17, 2010 1:56:53 PM |
| Modified | Wednesday, November 17, 2010 1:56:53 PM |
| Type | Journal Article |
|---|---|
| Author | Loren C. Denlinger |
| Author | Julie A. Sommer |
| Author | Karen Parker |
| Author | Lalitha Gudipaty |
| Author | Philip L. Fisette |
| Author | Jyoti W. Watters |
| Author | Richard A. Proctor |
| Author | George R. Dubyak |
| Author | Paul J. Bertics |
| Abstract | Activation of the P2X7 receptor by extracellular nucleotides modulates multiple immune functions, including inflammatory mediator production, membrane fusion events, and apoptosis. Previous studies have revealed that the C terminus of this multimeric cation channel possesses a lipid-interaction motif that has been proposed to regulate receptor function. This domain is homologous to the LPS binding region of the LPS binding protein, and we demonstrated that two basic residues (Arg578, Lys579) within this motif are essential for LPS binding to P2X7 in vitro. Because P2X7 can influence LPS action, and because lipid interaction motifs modulate the trafficking of other ion channel-linked receptors, we hypothesized that this motif of P2X7 is critical for receptor function and trafficking. In these studies we mutated Arg578 and Lys579 of P2X7, and the expression profile, channel activity, and pore formation of the mutant were characterized in transfected human embryonic kidney 293 cells. In contrast with the wild-type receptor, the P2X7-R578E/K579E mutant fails to demonstrate surface immunoreactivity despite normal levels of total protein expression. This effect on the mutant receptor is unlikely to result from widespread defects in protein folding, because surface localization, determined using conformation-specific Abs, can be restored by growing the cells at 25{degrees}C, conditions that slow receptor recycling. Despite surface expression at reduced temperatures, at 25{degrees}C the P2X7-R578E/K579E mutant still exhibits greatly reduced sodium, potassium, and calcium channel activity when compared with the wild-type receptor, and cannot induce pore formation. These data suggest that the lipid interaction motif of the P2X7 C terminus controls receptor trafficking and modulates channel activity. |
| Publication | J Immunol |
| Volume | 171 |
| Issue | 3 |
| Pages | 1304-1311 |
| Date | August 1, 2003 |
| URL | http://www.jimmunol.org/cgi/content/abstract/171/3/1304 |
| Accessed | Wednesday, November 17, 2010 4:06:02 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 4:06:02 PM |
| Modified | Wednesday, November 17, 2010 4:06:02 PM |
| Type | Journal Article |
|---|---|
| Author | M. Danilo Boada |
| Author | C. Jeffery Woodbury |
| Abstract | The substantia gelatinosa (SG) of the dorsal horn of the spinal cord is a recipient zone for unmyelinated sensory neurons in adults. Recent studies of the central anatomy of physiologically identified skin sensory neurons in neonatal mice have shown that this region also receives substantial inputs from a variety of myelinated afferents. The present experiments were performed to determine whether these neonatal inputs represent a transient phenotype that retracts from the SG. Studies were conducted in an in vivo spinal cord preparation from adult mice; thoracic levels were targeted to facilitate comparisons with previous in vitro findings. We show that the SG continues to receive substantial projections from myelinated skin sensory neurons throughout life. A large population of myelinated nociceptors conducting in the upper A{delta} and low A{beta} range maintained extensive projections throughout all areas of the SG well into adulthood; the latter gave rise to dorsally recurving "flame"-shaped arbors extending into the marginal layer that were identical to afferents described in neonates and after nerve injury in adult rats. Furthermore, exquisitely sensitive down hair follicle afferents projected throughout the inner half of the SG (i.e., lamina IIi) and sent dense clusters of terminals well into the outer SG (IIo), where they intermingled with those of unmyelinated nociceptors. Arguments are presented that the SG likely plays a predominant role in tactile processing under normal conditions, but that this role switches rapidly to nociceptive-only during environmental exigencies imposed by temperature extremes. |
| Publication | J. Neurosci. |
| Volume | 28 |
| Issue | 9 |
| Pages | 2006-2014 |
| Date | February 27, 2008 |
| DOI | 10.1523/JNEUROSCI.5609-07.2008 |
| URL | http://www.jneurosci.org/cgi/content/abstract/28/9/2006 |
| Accessed | Wednesday, November 17, 2010 6:22:52 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:22:52 PM |
| Modified | Wednesday, November 17, 2010 6:22:52 PM |
| Type | Journal Article |
|---|---|
| Author | Rajarsi Mandal |
| Author | Vijay Kumar Kutala |
| Author | Mahmood Khan |
| Author | Iyyapu K Mohan |
| Author | Saradhadevi Varadharaj |
| Author | Arun Sridhar |
| Author | Cynthia A Carnes |
| Author | Tamás Kálai |
| Author | Kálmán Hideg |
| Author | Periannan Kuppusamy |
| Abstract | Any clinical intervention (e.g., coronary angioplasty, thrombolysis) used to reintroduce blood flow to an ischemic region of the myocardium is accompanied by a complex enzymatic cascade of reactions resulting in severe injury to the heart, termed myocardial ischemia/reperfusion (I/R) injury. In this study, we evaluated the ability of H-3010 (1-hydroxy-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid (2-(3,4-dimethoxyphenyl)-5-([2-(3,4-dimethoxyphenyl)ethyl]-methylamino)-2-isopropylpentyl)-amide), a pyrroline modification of verapamil (2-(3,4-dimethoxyphenyl)-5-[2-(3,4-dimethoxyphenyl)ethylmethyl-amino]-2-(1-methylethyl)pentanenitrile), to protect the heart against I/R-mediated injury. Isolated perfused rat hearts pretreated with verapamil and H-3010 were subjected to 30 min of global no-flow ischemia followed by 45 min of reperfusion. The recovery (expressed as a percentage of preischemic baseline) in contractile function (left ventricular developed pressure) of hearts subjected to I/R was significantly higher in hearts treated with H-3010 at 5 microM (51.0 +/- 6.4%) as well as at 50 microM (75.1 +/- 7.4%) as compared with verapamil at 5 microM (32.2 +/- 3.7%) or untreated control hearts (18.1 +/- 2.8%). Creatine kinase release was significantly attenuated in hearts treated with H-3010 (45.7 +/- 4.5 U/liter) as compared with untreated controls (131.5 +/- 6.4 U/liter). Similar trends were also observed for lactate dehydrogenase release as well. A marked reduction in percent area of infarction was observed in the H-3010 group (11.7 +/- 1.6%) compared with verapamil (25.1 +/- 2.9%) and control (41.3 +/- 1.9%) groups. Additional in vitro studies showed a marked decrease in reactive oxygen species generation with H-3010. In conclusion, our data clearly demonstrated that the verapamil derivative, H-3010, significantly decreased I/R-induced cardiac dysfunction. This can be attributed to the combined benefits of the pyrroline moiety (antioxidant) and the parent verapamil component (antiarrhythmic) in the protection of the heart from I/R-induced injury. |
| Publication | The Journal of Pharmacology and Experimental Therapeutics |
| Volume | 323 |
| Issue | 1 |
| Pages | 119-127 |
| Date | Oct 2007 |
| Journal Abbr | J. Pharmacol. Exp. Ther |
| DOI | 10.1124/jpet.107.127167 |
| ISSN | 0022-3565 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17646427 |
| Accessed | Wednesday, November 17, 2010 4:50:24 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17646427 |
| Date Added | Wednesday, November 17, 2010 4:50:24 PM |
| Modified | Wednesday, November 17, 2010 4:50:24 PM |
| Type | Journal Article |
|---|---|
| Author | M Flourakis |
| Author | V Lehen'kyi |
| Author | B Beck |
| Author | M Raphael |
| Author | M Vandenberghe |
| Author | F V Abeele |
| Author | M Roudbaraki |
| Author | G Lepage |
| Author | B Mauroy |
| Author | C Romanin |
| Author | Y Shuba |
| Author | R Skryma |
| Author | N Prevarskaya |
| Publication | Cell Death and Dis |
| Volume | 1 |
| Pages | e75 |
| Date | online 2010 |
| Journal Abbr | Cell Death and Dis |
| URL | http://dx.doi.org/10.1038/cddis.2010.52 |
| Accessed | Wednesday, November 17, 2010 6:33:11 PM |
| Library Catalog | Nature |
| Date Added | Wednesday, November 17, 2010 6:33:11 PM |
| Modified | Wednesday, November 17, 2010 6:33:11 PM |
| Type | Web Page |
|---|---|
| Website Type | Text |
| URL | http://cat.inist.fr/? aModele=afficheN&… |
| Accessed | Wednesday, November 17, 2010 6:47:23 PM |
| Date Added | Wednesday, November 17, 2010 6:47:23 PM |
| Modified | Wednesday, November 17, 2010 6:47:23 PM |
| Type | Journal Article |
|---|---|
| Author | Hervé Schaffhauser |
| Author | Blake A. Rowe |
| Author | Sylvia Morales |
| Author | Laura E. Chavez-Noriega |
| Author | Ruoyuan Yin |
| Author | Christine Jachec |
| Author | Sara P. Rao |
| Author | Gretchen Bain |
| Author | Anthony B. Pinkerton |
| Author | Jean-Michel Vernier |
| Author | Linda J. Bristow |
| Author | Mark A. Varney |
| Author | Lorrie P. Daggett |
| Abstract | In the present study, we describe the characterization of a positive allosteric modulator at metabotropic glutamate subtype 2 receptors (mGluR2). N-(4-(2-Methoxyphenoxy)-phenyl-N-(2,2,2-trifluoroethylsulfonyl)-pyrid-3-ylmethylamine (LY487379) is a selective positive allosteric modulator at human mGluR2 and is without activity at human mGluR3. Furthermore, LY487379 has no intrinsic agonist or antagonist activity at hmGluR2, as determined by functional guanosine 5′(γ-[35S]thio)triphosphate ([35S]GTPγS) binding, single-cell Ca2+ imaging, and electrophysiological studies. However, LY487379 markedly potentiated glutamate-stimulated [35S]GTPγS binding in a concentration-dependent manner at hmGluR2, shifting the glutamate dose-response curve leftward by 3-fold and increasing the maximum levels of [35S]GTPγS stimulation. This effect of LY487479 was also observed to a greater extent on the concentration-response curves to selective hmGluR2/3 agonists. In radioligand binding studies to rat cortical membranes, LY487379 increased the affinity of the radiolabeled agonist, [3H]DCG-IV, without affecting the binding affinity of the radiolabeled antagonist, [3H]LY341495. In rat hippocampal slices, coapplication of LY487379 potentiated synaptically evoked mGluR2 responses. Finally, to elucidate the site of action, we systematically exchanged segments and single amino acids between hmGluR2 and hmGluR3. Substitution of Ser688 and/or Gly689 in transmembrane IV along with Asn735 located in transmembrane segment V, with the homologous amino acids of hmGluR3, completely eliminated LY487379 allosteric modulation of hmGluR2. We propose that this allosteric binding site defines a pocket that is different from the orthosteric site located in the amino terminal domain. |
| Publication | Molecular Pharmacology |
| Volume | 64 |
| Issue | 4 |
| Pages | 798 -810 |
| Date | October 01 , 2003 |
| DOI | 10.1124/mol.64.4.798 |
| URL | http://molpharm.aspetjournals.org/content/64/4/798.abstract |
| Accessed | Wednesday, November 17, 2010 3:34:04 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 3:34:04 PM |
| Modified | Wednesday, November 17, 2010 3:34:04 PM |
| Type | Journal Article |
|---|---|
| Author | G Troy Smith |
| Abstract | The neural circuit that controls the electric organ discharge (EOD) of the brown ghost knifefish (Apteronotus leptorhynchus) contains two spontaneous oscillators. Both pacemaker neurons in the medulla and electromotor neurons (EMNs) in the spinal cord fire spontaneously at frequencies of 500-1,000 Hz to control the EOD. These neurons continue to fire in vitro at frequencies that are highly correlated with in vivo EOD frequency. Previous studies used channel blocking drugs to pharmacologically characterize ionic currents that control high-frequency firing in pacemaker neurons. The goal of the present study was to use similar techniques to investigate ionic currents in EMNs, the other type of spontaneously active neuron in the electromotor circuit. As in pacemaker neurons, high-frequency firing of EMNs was regulated primarily by tetrodotoxin-sensitive sodium currents and by potassium currents that were sensitive to 4-aminopyridine and kappaA-conotoxin SIVA, but resistant to tetraethylammonium. EMNs, however, differed from pacemaker neurons in their sensitivity to some channel blocking drugs. Alpha-dendrotoxin, which blocks a subset of Kv1 potassium channels, increased firing rates in EMNs, but not pacemaker neurons; and the sodium channel blocker muO-conotoxin MrVIA, which reduced firing rates of pacemaker neurons, had no effect on EMNs. These results suggest that similar, but not identical, ionic currents regulate high-frequency firing in EMNs and pacemaker neurons. The differences in the ionic currents expressed in pacemaker neurons and EMNs might be related to differences in the morphology, connectivity, or function of these two cell types. |
| Publication | Journal of Neurobiology |
| Volume | 66 |
| Issue | 1 |
| Pages | 1-18 |
| Date | Jan 2006 |
| Journal Abbr | J. Neurobiol |
| DOI | 10.1002/neu.20202 |
| ISSN | 0022-3034 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/16187302 |
| Accessed | Wednesday, November 17, 2010 6:13:18 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 16187302 |
| Date Added | Wednesday, November 17, 2010 6:13:18 PM |
| Modified | Wednesday, November 17, 2010 6:13:18 PM |
| Type | Journal Article |
|---|---|
| Author | Robert S. Decker |
| Author | Amy K. Rines |
| Author | Sakie Nakamura |
| Author | Tejaswitha J. Naik |
| Author | J. Andrew Wassertsrom |
| Author | Hossein Ardehali |
| Publication | Translational Research |
| Volume | 155 |
| Issue | 1 |
| Pages | 27-34 |
| Date | 01/2010 |
| Journal Abbr | Translational Research |
| DOI | 10.1016/j.trsl.2009.09.007 |
| ISSN | 19315244 |
| URL | http://www.translationalres.com/article/S1931-5244(09)00294-1/abstract |
| Accessed | Wednesday, November 17, 2010 6:51:02 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:51:02 PM |
| Modified | Wednesday, November 17, 2010 6:51:02 PM |
| Type | Journal Article |
|---|---|
| Author | K. M. Dibb |
| Author | C. L. Hagarty |
| Author | A. S. I. Loudon |
| Author | A. W. Trafford |
| Abstract | In mammals, changes in photoperiod regulate a diverse array of physiological and behavioral processes, an example of which in the Siberian hamster (Phodopus sungorus) is the expression of bouts of daily torpor following prolonged exposure to a short photoperiod. During torpor, body temperature drops dramatically; however, unlike in nonhibernating or nontorpid species, the myocardium retains the ability to contract and is resistant to the development of arrhythmias. In the present study, we sought to determine whether exposure to a short photoperiod results in alterations to cardiac excitation-contraction coupling, thus potentially enabling the heart to survive periods of low temperature during torpor. Experiments were performed on single ventricular myocytes freshly isolated from the hearts of Siberian hamsters that had been exposed to either 12 wk of short-day lengths (SD) or 12 wk of long-day lengths (LD). In SD-acclimated animals, the amplitude of the systolic Ca2+ transient was increased (e.g., from 142 {+/-} 17 nmol/l in LD to 229 {+/-} 31 nmol/l in SD at 4 Hz; P < 0.001). The increased Ca2+ transient amplitude in the SD-acclimated animals was not associated with any change in the shape or duration of the action potential. However, sarcoplasmic reticulum Ca2+ content measured after current-clamp stimulation was increased in the SD-acclimated animals (at 4 Hz, 110 {+/-} 5 vs. 141 {+/-} 15 {micro}mol/l, P < 0.05). We propose that short photoperiods reprogram the function of the cardiac sarcoplasmic reticulum, resulting in an increased Ca2+ content, and that this may be a necessary precursor for maintenance of cardiac function during winter torpor. |
| Publication | Am J Physiol Regul Integr Comp Physiol |
| Volume | 288 |
| Issue | 3 |
| Pages | R607-614 |
| Date | March 1, 2005 |
| DOI | 10.1152/ajpregu.00612.2004 |
| URL | http://ajpregu.physiology.org/cgi/content/abstract/288/3/R607 |
| Accessed | Wednesday, November 17, 2010 3:35:29 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 3:35:29 PM |
| Modified | Wednesday, November 17, 2010 3:35:29 PM |
| Type | Journal Article |
|---|---|
| Author | M Danilo Boada |
| Author | C Jeffery Woodbury |
| Abstract | Recent combined analyses of the structural, functional, and molecular attributes of individual skin sensory neurons using semi-intact in vitro preparations from mice have provided a wealth of novel insights into nociceptor biology. How these findings translate to more natural conditions nevertheless remains unresolved. Toward this end, intracellular recordings were obtained from 362 physiologically identified dorsal root ganglion (DRG) neurons in a new in vivo mouse preparation developed for combined structure/function analyses of individual skin sensory neurons. Recordings were conducted at thoracic levels in adult decorticate mice for comparison with in vitro findings from the same trunk region. In all, 270 neurons were recorded at DRG temperatures tightly regulated at normal core values to establish a baseline and 137 skin sensory neurons were included in detailed analyses of somal properties for comparisons with similar data obtained under reduced temperatures mirroring in vitro conditions. Recovery of Neurobiotin-labeled central projections was crucial for verifying perceived afferent identity of certain neurons. Further, profound temperature dependency was seen across diverse physiological properties. Indeed, the broad, inflected somal spikes normally viewed as diagnostic of myelinated nociceptors were found to be a product of reduced temperatures and were not present at normal core values. Moreover, greater complexity was observed peripherally in the mechanical and thermal sensitivity profile of nociceptive and nonnociceptive populations than that seen under in vitro conditions. This novel in vivo preparation therefore holds considerable promise for future analyses of nociceptor function and plasticity in normal and transgenic models of pain mechanisms. |
| Publication | Journal of Neurophysiology |
| Volume | 98 |
| Issue | 2 |
| Pages | 668-680 |
| Date | Aug 2007 |
| Journal Abbr | J. Neurophysiol |
| DOI | 10.1152/jn.00264.2007 |
| ISSN | 0022-3077 |
| Short Title | Physiological properties of mouse skin sensory neurons recorded intracellularly in vivo |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17537905 |
| Accessed | Wednesday, November 17, 2010 4:53:17 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17537905 |
| Date Added | Wednesday, November 17, 2010 4:53:17 PM |
| Modified | Wednesday, November 17, 2010 4:53:17 PM |
| Type | Journal Article |
|---|---|
| Author | Erika D. Eggers |
| Author | Maureen A. McCall |
| Author | Peter D. Lukasiewicz |
| Abstract | Diverse retinal outputs are mediated by ganglion cells that receive excitatory input from distinct classes of bipolar cells (BCs). These classes of BCs separate visual signals into rod, ON and OFF cone pathways. Although BC signalling is a major determinant of the ganglion cell-mediated retinal output, it is not fully understood how light-evoked, presynaptic inhibition from amacrine cell inputs shapes BC outputs. To determine whether differences in presynaptic inhibition uniquely modulate BC synaptic output to specific ganglion cells, we assessed the inhibitory contributions of GABAA, GABAC and glycine receptors across the BC pathways. Here we show that different proportions of GABAA and GABAC receptor-mediated inhibition determined the kinetics of GABAergic presynaptic inhibition across different BC classes. Large, slow GABAC and small, fast GABAA receptor-mediated inputs to rod BCs prolonged light-evoked inhibitory postsynaptic currents (L-IPSCs), while smaller GABAC and larger GABAA receptor-mediated contributions produced briefer L-IPSCs in ON and OFF cone BCs. Glycinergic inhibition also varied across BC class. In the rod-dominant conditions studied here, slow glycinergic inputs dominated L-IPSCs in OFF cone BCs, attributable to inputs from the rod pathway via AII amacrine cells, while rod and ON cone BCs received little and no glycinergic input, respectively. As these large glycinergic inputs come from rod signalling pathways, in cone-dominant conditions L-IPSCs in OFF cone bipolar cells will probably be dominated by GABAA receptor-mediated input. Thus, unique presynaptic receptor combinations mediate distinct forms of inhibition to selectively modulate BC outputs, enhancing the distinctions among parallel retinal signals. |
| Publication | The Journal of Physiology |
| Volume | 582 |
| Issue | 2 |
| Pages | 569 -582 |
| Date | July 01 , 2007 |
| DOI | 10.1113/jphysiol.2007.131763 |
| URL | http://jp.physoc.org/content/582/2/569.abstract |
| Accessed | Wednesday, November 17, 2010 4:47:54 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 4:47:54 PM |
| Modified | Wednesday, November 17, 2010 4:47:54 PM |
| Type | Journal Article |
|---|---|
| Author | Rongxue Wu |
| Author | Kirsten M. Smeele |
| Author | Eugene Wyatt |
| Author | Yoshihiko Ichikawa |
| Author | Otto Eerbeek |
| Author | Lin Sun |
| Author | Kusum Chawla |
| Author | Markus W. Hollmann |
| Author | Varun Nagpal |
| Author | Sami Heikkinen |
| Author | Markku Laakso |
| Author | Kentaro Jujo |
| Author | J. Andrew Wasserstrom |
| Author | Coert J. Zuurbier |
| Author | Hossein Ardehali |
| Abstract | Rationale:Cardiomyocytes switch substrate utilization from fatty acid to glucose under ischemic conditions; however, it is unknown how perturbations in glycolytic enzymes affect cardiac response to ischemia/reperfusion (I/R). Hexokinase (HK)II is a HK isoform that is expressed in the heart and can bind to the mitochondrial outer membrane.Objective:We sought to define how HKII and its binding to mitochondria play a role in cardiac response and remodeling after I/R.Methods and Results: We first showed that HKII levels and its binding to mitochondria are reduced 2 days after I/R. We then subjected the hearts of wild-type and heterozygote HKII knockout (HKII+/-) mice to I/R by coronary ligation. At baseline, HKII+/- mice have normal cardiac function; however, they display lower systolic function after I/R compared to wild-type animals. The mechanism appears to be through an increase in cardiomyocyte death and fibrosis and a reduction in angiogenesis; the latter is through a decrease in hypoxia-inducible factor-dependent pathway signaling in cardiomyocytes. HKII mitochondrial binding is also critical for cardiomyocyte survival, because its displacement in tissue culture with a synthetic peptide increases cell death. Our results also suggest that HKII may be important for the remodeling of the viable cardiac tissue because its modulation in vitro alters cellular energy levels, O2 consumption, and contractility.Conclusions:These results suggest that reduction in HKII levels causes altered remodeling of the heart in I/R by increasing cell death and fibrosis and reducing angiogenesis and that mitochondrial binding is needed for protection of cardiomyocytes. |
| Publication | Circ Res |
| Pages | CIRCRESAHA.110.223115 |
| Date | November 11, 2010 |
| DOI | 10.1161/CIRCRESAHA.110.223115 |
| URL | http://circres.ahajournals.org/cgi/content/abstract/CIRCRESAHA.110.223115v1 |
| Accessed | Wednesday, November 17, 2010 6:43:26 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:43:26 PM |
| Modified | Wednesday, November 17, 2010 6:43:26 PM |
| Type | Journal Article |
|---|---|
| Author | Asako Kamada |
| Author | Hisao Nagaya |
| Author | Taku Tamura |
| Author | Masataka Kinjo |
| Author | Hai-Ying Jin |
| Author | Toshiharu Yamashita |
| Author | Kowichi Jimbow |
| Author | Hideo Kanoh |
| Author | Ikuo Wada |
| Abstract | The quality of nascent protein folding in vivo is influenced by the microdynamics of the proteins. Excessive collisions between proteins may lead to terminal misfolding, and the frequency of protein interactions with molecular chaperones determines their folding rates. However, it is unclear how immature protein dynamics are regulated. In this study, we analyzed the diffusion of immature tyrosinase in the endoplasmic reticulum (ER) of non-pigmented cells by taking advantage of the thermal sensitivity of the tyrosinase. The diffusion of tyrosinase tagged with yellow fluorescence protein (YFP) in living cells was directly measured using fluorescent correlation spectroscopy. The diffusion of folded tyrosinase in the ER of cells treated with brefeldin A, as measured by fluorescent correlation spectroscopy, was critically affected by the expression level of tyrosinase-YFP. Under defined conditions in which random diffusional motion of folded protein was allowed, we found that the millisecond-order diffusion rate observed for folded tyrosinase almost disappeared for the misfolded molecules synthesized at a nonpermissive high temperature. This was not because of enhanced aggregation at the high temperature, as terminally misfolded tyrosinase synthesized in the absence of calnexin interactions showed comparable, albeit slightly slower, diffusion. Yet, the thermally misfolded tyrosinase was not immobilized when measured by fluorescence recovery after photobleaching. In contrast, terminally misfolded tyrosinase synthesized in cells in which alpha-glucosidases were inhibited showed extensive immobilization. Hence, we suggest that the ER represses random fluctuations of immature tyrosinase molecules while preventing their immobilization. |
| Publication | The Journal of Biological Chemistry |
| Volume | 279 |
| Issue | 20 |
| Pages | 21533-21542 |
| Date | May 14, 2004 |
| Journal Abbr | J. Biol. Chem |
| DOI | 10.1074/jbc.M401403200 |
| ISSN | 0021-9258 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/14976197 |
| Accessed | Wednesday, November 17, 2010 4:44:58 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 14976197 |
| Date Added | Wednesday, November 17, 2010 4:44:58 PM |
| Modified | Wednesday, November 17, 2010 4:44:58 PM |
| Type | Journal Article |
|---|---|
| Author | Andrei A Aleksandrov |
| Author | Liying Cui |
| Author | John R Riordan |
| Abstract | We have employed rate-equilibrium free energy relationship (REFER) analysis to characterize the dynamic events involved in the allosteric regulation of cystic fibrosis transmembrane conductance regulator (CFTR) function. A wide range of different hydrolysable and poorly hydrolysable nucleoside triphosphates were used to elucidate the role of ATP hydrolysis in CFTR function. The linearity of the REFER plots and Φ values near unity for all ligands tested implies that CFTR channel gating is a reversible thermally driven process with all structural reorganization in the binding site(s) completed prior to channel opening. This is consistent with the requirement for nucleotide binding for channel opening. However, the channel structural transition from the open to the closed state occurs independently of any events in the binding sites. Similar results were obtained on substitution of amino acids at coupling joints between both nucleotide binding domains (NBD) and cytoplasmic loops (CL) in opposite halves of the protein, indicating that any structural reorganization there also had occurred in the channel closed state. The fact that fractional Φ values were not observed in either of these distant sites suggests that there may not be a deterministic ‘lever-arm’ mechanism acting between nucleotide binding sites and the channel gate. These findings favour a stochastic coupling between binding and gating in which all structural transitions are thermally driven processes. We speculate that increase of channel open state probability is due to reduction of the number of the closed state configurations available after physical interaction between ligand bound NBDs and the channel. |
| Volume | 587 |
| Issue | Pt 12 |
| Pages | 2875-2886 |
| Date | 2009-6-15 |
| Journal Abbr | J Physiol |
| DOI | 10.1113/jphysiol.2009.170258 |
| ISSN | 0022-3751 |
| Library Catalog | PubMed Central |
| Extra | PMID: 19403599 PMCID: 2718247 |
| Date Added | Wednesday, November 17, 2010 6:17:03 PM |
| Modified | Wednesday, November 17, 2010 6:17:03 PM |
| Type | Journal Article |
|---|---|
| Author | Arun Sridhar |
| Author | Yoshinori Nishijima |
| Author | Dmitry Terentyev |
| Author | Radmila Terentyeva |
| Author | Rebecca Uelmen |
| Author | Monica Kukielka |
| Author | Ingrid M. Bonilla |
| Author | Gail A. Robertson |
| Author | Sandor Gyorke |
| Author | George E. Billman |
| Author | Cynthia A. Carnes |
| Abstract | Ventricular tachyarrhythmias are the most common cause of sudden cardiac death (SCD); a healed myocardial infarction increases the risk of SCD. We determined the contribution of specific repolarization abnormalities to ventricular tachyarrhythmias in a postinfarction model of SCD. For our methods, we used a postinfarction canine model of SCD, where an exercise and ischemia test was used to stratify animals as either susceptible (VF+) or resistant (VF-) to sustained ventricular tachyarrhythmias. Our results show no changes in global left ventricular contractility or volumes occurred after infarction. At 8-10 wk postmyocardial infarction, myocytes were isolated from the left ventricular midmyocardial wall and studied. In the VF+ animals, myocyte action potential (AP) prolongation occurred at 50 and 90% repolarization (P < 0.05) and was associated with increased variability of AP duration and afterdepolarizations. Multiple repolarizing K+ currents (IKr, Ito) and inward IK1 were also reduced (P < 0.05) in myocytes from VF+ animals compared with control, noninfarcted dogs. In contrast, only Ito was reduced in VF- myocytes compared with controls (P < 0.05). While afterdepolarizations were not elicited at baseline in myocytes from VF- animals, afterdepolarizations were consistently elicited after the addition of an IKr blocker. In conclusion, the loss of repolarization reserve via reductions in multiple repolarizing currents in the VF+ myocytes leads to AP prolongation, repolarization instability, and afterdepolarizations in myocytes from animals susceptible to SCD. These abnormalities may provide a substrate for initiation of postmyocardial infarction ventricular tachyarrhythmias. |
| Publication | Am J Physiol Regul Integr Comp Physiol |
| Volume | 295 |
| Issue | 5 |
| Pages | R1463-1472 |
| Date | November 1, 2008 |
| DOI | 10.1152/ajpregu.90583.2008 |
| URL | http://ajpregu.physiology.org/cgi/content/abstract/295/5/R1463 |
| Accessed | Wednesday, November 17, 2010 6:41:21 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:41:21 PM |
| Modified | Wednesday, November 17, 2010 6:41:21 PM |
| Type | Journal Article |
|---|---|
| Author | S.H. Kang |
| Author | A. Carl |
| Author | J.M. McHugh |
| Author | H.R. Goff |
| Author | J.L. Kenyon |
| Abstract | We recorded Ca2+ current and intracellular Ca2+ ([Ca2+]i) in isolated adult rat dorsal root ganglion (DRG) neurons at 20 and 30 °C. In neurons bathed in tetraethylammonium and dialyzed with cesium, warming reduced resting average [Ca2+]i from 87 to 49 nM and the time constant of the decay of [Ca2+]i transients (τr) from 1.3 s to 0.99 s (Q10 = 1.4). The Buffer Index, the ratio between Ca2+ influx and Δ[Ca2+]i (∫ICa·dt/Δ[Ca2+]i), increased 2- to 3-fold with warming. Neither inhibition of the plasma membrane Ca2+-ATPase by intracellular sodium orthovanadate nor inhibition of Ca2+ uptake by the endoplasmic reticulum by thapsigargin plus ryanodine were necessary for the effects of warming on these parameters. In contrast, inhibition of the mitochondrial Ca2+ uniporter by intracellular ruthenium red largely reversed the effects of warming. Carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (500 nM) increased resting [Ca2+]i at 30 °C. 10 mM intracellular sodium prolonged the recovery of [Ca2+]i transients to 10 – 40 s. This effect was reversed by an inhibitor of mitochondrial Na+/Ca2+-exchange (CGP 37157, 10 μM). Thus, mitochondrial Ca2+-uptake is necessary for the temperature-dependent increase in Ca2+ buffering and mitochondrial Ca2+ fluxes contribute to the control of [Ca2+]i between 50 and 150 nM at 30 °C. |
| Publication | Cell calcium |
| Volume | 43 |
| Issue | 4 |
| Pages | 388-404 |
| Date | 2008-4 |
| Journal Abbr | Cell Calcium |
| DOI | 10.1016/j.ceca.2007.07.001 |
| ISSN | 0143-4160 |
| Library Catalog | PubMed Central |
| Extra | PMID: 17716728 PMCID: 2409216 |
| Date Added | Wednesday, November 17, 2010 6:14:17 PM |
| Modified | Wednesday, November 17, 2010 6:14:17 PM |
| Type | Journal Article |
|---|---|
| Author | Jixin Wang |
| Author | Joseph J Salata |
| Author | Paul B Bennett |
| Abstract | Potassium (K+) channels mediate numerous electrical events in excitable cells, including cellular membrane potential repolarization. The hERG K+ channel plays an important role in myocardial repolarization, and inhibition of these K+ channels is associated with long QT syndromes that can cause fatal cardiac arrhythmias. In this study, we identify saxitoxin (STX) as a hERG channel modifier and investigate the mechanism using heterologous expression of the recombinant channel in HEK293 cells. In the presence of STX, channels opened slower during strong depolarizations, and they closed much faster upon repolarization, suggesting that toxin-bound channels can still open but are modified, and that STX does not simply block the ion conduction pore. STX decreased hERG K+ currents by stabilizing closed channel states visualized as shifts in the voltage dependence of channel opening to more depolarized membrane potentials. The concentration dependence for steady-state modification as well as the kinetics of onset and recovery indicate that multiple STX molecules bind to the channel. Rapid application of STX revealed an apparent "agonist-like" effect in which K+ currents were transiently increased. The mechanism of this effect was found to be an effect on the channel voltage-inactivation relationship. Because the kinetics of inactivation are rapid relative to activation for this channel, the increase in K+ current appeared quickly and could be subverted by a decrease in K+ currents due to the shift in the voltage-activation relationship at some membrane potentials. The results are consistent with a simple model in which STX binds to the hERG K+ channel at multiple sites and alters the energetics of channel gating by shifting both the voltage-inactivation and voltage-activation processes. The results suggest a novel extracellular mechanism for pharmacological manipulation of this channel through allosteric coupling to channel gating. |
| Publication | The Journal of General Physiology |
| Volume | 121 |
| Issue | 6 |
| Pages | 583-598 |
| Date | Jun 2003 |
| Journal Abbr | J. Gen. Physiol |
| DOI | 10.1085/jgp.200308812 |
| ISSN | 0022-1295 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/12771193 |
| Accessed | Wednesday, November 17, 2010 3:36:43 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 12771193 |
| Date Added | Wednesday, November 17, 2010 3:36:43 PM |
| Modified | Wednesday, November 17, 2010 3:36:43 PM |
| Type | Journal Article |
|---|---|
| Author | Zsolt A Nagy |
| Author | László Virág |
| Author | András Tóth |
| Author | Péter Biliczki |
| Author | Károly Acsai |
| Author | Tamás Bányász |
| Author | Péter Nánási |
| Author | Julius Gy Papp |
| Author | András Varró |
| Publication | British Journal of Pharmacology |
| Volume | 143 |
| Issue | 7 |
| Pages | 827-831 |
| URL | http://onlinelibrary.wiley.com/doi/10.1038/sj.bjp.0706026/abstract |
| Accessed | Wednesday, November 17, 2010 1:13:22 PM |
| Date Added | Wednesday, November 17, 2010 1:13:22 PM |
| Modified | Wednesday, November 17, 2010 1:16:58 PM |
| Type | Journal Article |
|---|---|
| Author | Olivier Poirot |
| Author | Marija Vukicevic |
| Author | Anne Boesch |
| Author | Stephan Kellenberger |
| Abstract | Acid-sensing ion channels (ASICs) are neuronal Na+ channels that belong to the epithelial Na+ channel/degenerin family. ASICs are transiently activated by a rapid drop in extracellular pH. Conditions of low extracellular pH, such as ischemia and inflammation in which ASICs are thought to be active, are accompanied by increased protease activity. We show here that serine proteases modulate the function of ASIC1a and ASIC1b but not of ASIC2a and ASIC3. We show that protease exposure shifts the pH dependence of ASIC1a activation and steady-state inactivation to more acidic pH. As a consequence, protease exposure leads to a decrease in current response if ASIC1a is activated by a pH drop from pH 7.4. If, however, acidification occurs from a basal pH of ∼7, protease-exposed ASIC1a shows higher activity than untreated ASIC1a. We provide evidence that this bi-directional regulation of ASIC1a function also occurs in neurons. Thus, we have identified a mechanism that modulates ASIC function and may allow ASIC1a to adapt its gating to situations of persistent extracellular acidification. |
| Publication | Journal of Biological Chemistry |
| Volume | 279 |
| Issue | 37 |
| Pages | 38448 -38457 |
| Date | 2004 |
| DOI | 10.1074/jbc.M407381200 |
| URL | http://www.jbc.org/content/279/37/38448.abstract |
| Accessed | Wednesday, November 17, 2010 1:01:08 AM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 1:01:08 AM |
| Modified | Wednesday, November 17, 2010 1:01:08 AM |
| Type | Journal Article |
|---|---|
| Author | Hans Meves |
| Author | Jürgen R Schwarz |
| Author | Iris Wulfsen |
| Abstract | Differentiated NG108-15 neuroblastoma×glioma hybrid cells were whole-cell voltage-clamped. Hyperpolarizing pulses, superimposed on a depolarized holding potential (−30 or −20 mV), elicited deactivation currents which consisted of two components, distinguishable by fitting with two exponential functions. Linopirdine [DuP 996, 3,3-bis(4-pyridinylmethyl)-1-phenylindolin-2-one), a neurotransmitter-release enhancer known as potent and selective blocker of the M-current of rat sympathetic neurons, in concentrations of 5 or 10 μM selectively inhibited the fast component (IC50=14.7 μM). The slow component was less sensitive to linopirdine (IC50>20 μM). The class III antiarrhythmics [(4-methylsulphonyl)amido]benzenesulphonamide (WAY-123.398) and 1-[2-(6-methyl-2-pyrydinil)ethyl]-4-(4-methylsulphonylaminobenzoyl) piperidine (E-4031), selective inhibitors of the inwardly rectifying ERG (ether-à-go-go-related gene) potassium channel, inhibited predominantly the slow component (IC50=38 nM for E-4031). The time constant of the WAY-123.398-sensitive current resembled the time constant of the slow component in size and voltage dependence. Inwardly rectifying ERG currents, recorded in K+-rich bath at strongly negative pulse potentials, resembled the slow component of the deactivation current in their low sensitivity to linopirdine (28% inhibition at 50 μM). The size of the slow component varied greatly between cells. Accordingly, varied the effect of WAY-123.398 on deactivation current and holding current. RNA transcripts for the following members of the ether-à-go-go gene (EAG) K+ channel family were found in differentiated NG108-15 cells: ERG1, ERG2, EAG1, EAG-like (ELK)1, ELK2; ERG3 was only present in non-differentiated cells. In addition, RNA transcripts for KCNQ2 and KCNQ3 were found in differentiated and non-differentiated cells. We conclude that the fast component of the deactivation current is M-like current and the slow component is deactivating ERG current. The molecular correlates are probably KCNQ2/KCNQ3 and ERG1/ERG2, respectively. |
| Publication | British Journal of Pharmacology |
| Volume | 127 |
| Issue | 5 |
| Pages | 1213-1223 |
| Date | 1999-07 |
| Journal Abbr | Br J Pharmacol |
| DOI | 10.1038/sj.bjp.0702642 |
| ISSN | 0007-1188 |
| Library Catalog | PubMed Central |
| Extra | PMID: 10455268 PMCID: 1566115 |
| Date Added | Wednesday, November 17, 2010 1:12:28 PM |
| Modified | Wednesday, November 17, 2010 1:12:28 PM |
| Type | Journal Article |
|---|---|
| Author | Ravi K. Sawhney |
| Author | Jonathon Howard |
| Abstract | Aclassic model for tissue morphogenesis is the formation of ligament-like straps between explants of fibroblasts placed in collagen gels. The patterns arise from mechanical forces exerted by cells on their substrates (Harris et al., 1981). However, where do such straps come from, and how are slow local movements of cells transduced into dramatic long-distance redistributions of collagen? We embedded primary mouse skin and human periodontal ligament fibroblasts in collagen gels and measured the time course of patterning by using a novel computer algorithm to calculate anisotropy, and by tracking glass beads dispersed in the gel. As fibroblasts began to spread into their immediate environments, a coordinated rearrangement of collagen commenced throughout the gel, producing a strap on a time scale of minutes. Killing of cells afterwards resulted in a partial relaxation of the matrix strain. Surprisingly, relatively small movements of collagen molecules on the tensile axis between two pulling explants induced a much larger concomitant compression of the gel perpendicular to the axis, organizing and aligning fibers into a strap. We propose that this amplification is due to the geometry of the collagen matrix, and that analogous amplified movements may drive morphological changes in other biological meshes, both outside and inside the cell. |
| Publication | The Journal of Cell Biology |
| Volume | 157 |
| Issue | 6 |
| Pages | 1083 -1092 |
| Date | June 10 , 2002 |
| DOI | 10.1083/jcb.200203069 |
| URL | http://jcb.rupress.org/content/157/6/1083.abstract |
| Accessed | Wednesday, November 17, 2010 3:53:24 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 3:53:24 PM |
| Modified | Wednesday, November 17, 2010 3:53:24 PM |
| Type | Journal Article |
|---|---|
| Author | Scott F. Beach |
| Author | A. Wayne Vogl |
| Abstract | In this study, we demonstrate that specialized junction plaques that occur between Sertoli cells and spermatids in the rat testis support microtubule translocation in vitro. During spermatogenesis, Sertoli cells are attached to spermatids by specialized adhesion junctions termed ectoplasmic specializations (ESs). These structures consist of regions of the plasma membrane adherent to the spermatid head, a submembrane layer of tightly packed actin filaments, and an attached cistern of endoplasmic reticulum. It has been proposed that motor proteins on the endoplasmic reticulum interact with adjacent microtubules to translocate the junction plaques, and hence the attached spermatids, within the epithelium. If this hypothesis is true, then isolated junctions should support microtubule transport. To verify this prediction, we have mechanically isolated rat spermatids, together with their attached ESs, and tested them for their ability to transport microtubules in vitro. Most assays were done in the presence of 2 mg/ml testicular cytosol and at room temperature. ESs attached to spermatids supported microtubule translocation. In some cases in which motility events were detected, microtubules moved smoothly over the junction site. In others, the movement was slow but progressive, saltatory and “inch-worm-like.” No motility was detected in the absence of exogenous ATP or in the presence of apyrase (an enzyme that catalyses the breakdown of ATP). Our results are consistent with the microtubule-based motility hypothesis of spermatid translocation. |
| Publication | Biology of Reproduction |
| Volume | 60 |
| Issue | 4 |
| Pages | 1036 -1046 |
| Date | April 01 , 1999 |
| DOI | 10.1095/biolreprod60.4.1036 |
| Short Title | Spermatid Translocation in the Rat Seminiferous Epithelium |
| URL | http://www.biolreprod.org/content/60/4/1036.abstract |
| Accessed | Wednesday, November 17, 2010 3:38:48 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 3:38:48 PM |
| Modified | Wednesday, November 17, 2010 3:38:48 PM |
| Type | Journal Article |
|---|---|
| Author | Chen-Hong Li |
| Author | Qi Zhang |
| Author | Bunyen Teng |
| Author | S. Jamal Mustafa |
| Author | Jian-Ying Huang |
| Author | Han-Gang Yu |
| Abstract | We recently discovered that the constitutively active Src tyrosine kinase can enhance hyperpolarization-activated, cyclic nucleotide-gated (HCN) 4 channel activity by binding to the channel protein. To investigate the mechanism of modulation by Src of HCN channels, we studied the effects of a selective inhibitor of Src tyrosine kinase, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), on HCN4 and its mutant channels expressed in HEK 293 cells by using a whole cell patch-clamp technique. We found that PP2 can inhibit HCN4 currents by negatively shifting the voltage dependence of channel activation, decreasing the whole cell channel conductance, and slowing activation and deactivation kinetics. Screening putative tyrosine residues subject to phosphorylation yielded two candidates: Tyr531 and Tyr554. Substituting HCN4-Tyr531 with phenylalanine largely abolished the effects of PP2 on HCN4 channels. Replacing HCN4-Tyr554 with phenylalanine did not abolish the effects of PP2 on voltage-dependent activation but did eliminate PP2-induced slowing of channel kinetics. The inhibitory effects of HCN channels associated with reduced Src tyrosine activity is confirmed in HL-1 cardiomyocytes. Finally, we found that PP2 can decrease the heart rate in a mouse model. These results demonstrate that Src tyrosine kinase enhances HCN4 currents by shifting their activation to more positive potentials and increasing the whole cell channel conductance as well as speeding the channel kinetics. The tyrosine residue that mediates most of Src's actions on HCN4 channels is Tyr531. |
| Publication | Am J Physiol Cell Physiol |
| Volume | 294 |
| Issue | 1 |
| Pages | C355-362 |
| Date | January 1, 2008 |
| DOI | 10.1152/ajpcell.00236.2007 |
| URL | http://ajpcell.physiology.org/cgi/content/abstract/294/1/C355 |
| Accessed | Wednesday, November 17, 2010 6:46:02 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:46:02 PM |
| Modified | Wednesday, November 17, 2010 6:46:02 PM |
| Type | Journal Article |
|---|---|
| Author | Megan M. McNulty |
| Author | Dorothy A. Hanck |
| Abstract | Mibefradil is a T-type Ca2+ channel antagonist with reported cross-reactivity with other classes of ion channels, including K+, Cl-, and Na+ channels. Using whole-cell voltage clamp, we examined mibefradil block of four Na+ channel isoforms expressed in human embryonic kidney cells: Nav1.5 (cardiac), Nav1.4 (skeletal muscle), Nav1.2 (brain), and Nav1.7 (peripheral nerve). Mibefradil blocked Nav1.5 in a use/frequency-dependent manner, indicating preferential binding to states visited during depolarization. Mibefradil blocked currents of all Na+ channel isoforms with similar affinity and a dependence on holding potential, and drug off-rate was slowed at depolarized potentials (koff was 0.024/s at -130 mV and 0.007/s at -100 mV for Nav1.5). We further probed the interaction of mibefradil with inactivated Nav1.5 channels. Neither the degree nor the time course of block was dependent on the stimulus duration, which dramatically changed the residency time of channels in the fast-inactivated state. In addition, inhibiting the binding of the fast inactivation lid (Nav1.5 ICM + MTSET) did not alter mibefradil block, confirming that the drug does not preferentially interact with the fast-inactivated state. We also tested whether mibefradil interacted with slow-inactivated state(s). When selectively applied to channels after inducing slow inactivation with a 60-s pulse to -10 mV, mibefradil (1 μM) produced 45% fractional block in Nav1.5 and greater block (88%) in an isoform (Nav1.4) that slow-inactivates more completely. Our results suggest that mibefradil blocks Na+ channels in a state-dependent manner that does not depend on fast inactivation but probably involves interaction with one or more slow-inactivated state(s). |
| Publication | Molecular Pharmacology |
| Volume | 66 |
| Issue | 6 |
| Pages | 1652 -1661 |
| Date | December 01 , 2004 |
| DOI | 10.1124/mol.66.6.1652 |
| URL | http://molpharm.aspetjournals.org/content/66/6/1652.abstract |
| Accessed | Wednesday, November 17, 2010 3:58:48 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 3:58:48 PM |
| Modified | Wednesday, November 17, 2010 3:58:48 PM |
| Type | Journal Article |
|---|---|
| Author | C B Eap |
| Author | S Crettol |
| Author | J-S Rougier |
| Author | J Schläpfer |
| Author | L Sintra Grilo |
| Author | J-J Déglon |
| Author | J Besson |
| Author | M Croquette-Krokar |
| Author | P-A Carrupt |
| Author | H Abriel |
| Abstract | Methadone inhibits the cardiac potassium channel hERG and can cause a prolonged QT interval. Methadone is chiral but its therapeutic activity is mainly due to (R)-methadone. Whole-cell patch-clamp experiments using cells expressing hERG showed that (S)-methadone blocked the hERG current 3.5-fold more potently than (R)-methadone (IC50s (half-maximal inhibitory concentrations) at 37 degrees C: 2 and 7 microM). As CYP2B6 slow metabolizer (SM) status results in a reduced ability to metabolize (S)-methadone, electrocardiograms, CYP2B6 genotypes, and (R)- and (S)-methadone plasma concentrations were obtained for 179 patients receiving (R,S)-methadone. The mean heart-rate-corrected QT (QTc) was higher in CYP2B6 SMs (*6/*6 genotype; 439+/-25 ms; n=11) than in extensive metabolizers (non *6/*6; 421+/-25 ms; n=168; P=0.017). CYP2B6 SM status was associated with an increased risk of prolonged QTc (odds ratio=4.5, 95% confidence interval=1.2-17.7; P=0.03). This study reports the first genetic factor implicated in methadone metabolism that may increase the risk of cardiac arrhythmias and sudden death. This risk could be reduced by the administration of (R)-methadone. |
| Publication | Clinical Pharmacology and Therapeutics |
| Volume | 81 |
| Issue | 5 |
| Pages | 719-728 |
| Date | May 2007 |
| Journal Abbr | Clin. Pharmacol. Ther |
| DOI | 10.1038/sj.clpt.6100120 |
| ISSN | 0009-9236 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/17329992 |
| Accessed | Wednesday, November 17, 2010 4:46:52 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 17329992 |
| Date Added | Wednesday, November 17, 2010 4:46:52 PM |
| Modified | Wednesday, November 17, 2010 4:46:52 PM |
| Type | Journal Article |
|---|---|
| Author | Lih Chyuan Ng |
| Author | Alison M. Gurney |
| Abstract | Abstract---- Cation channels activated by Ca2+ store depletion have been proposed to mediate Ca2+ influx in vascular smooth muscle cells. The aim of this study was to determine if store-operated channels have a functional role in pulmonary artery smooth muscle cells (PASMCs). In intact rat pulmonary artery rings, cyclopiazonic acid (CPA) produced a sustained contraction that was resistant to inhibition by nifedipine, but abolished in Ca2+-free solution and 50% blocked in the presence of 6 {micro}mol/L Cd2+, 10 {micro}mol/L Ni2+, 600 {micro}mol/L La3+, and 7 {micro}mol/L SKF96365. In freshly isolated PASMCs loaded with fura-2, CPA increased the intracellular Ca2+ concentration by stimulating dihydropyridine-resistant Ca2+ influx, which was {approx}50% blocked by 10 {micro}mol/L Ni2+ and 7 {micro}mol/L SKF96365. In perforated-patch recordings, CPA activated a sustained inward current at negative membrane potentials, which persisted in cells dialyzed with BAPTA, showed a near linear dependence on membrane potential when Cs+ was the main intracellular cation, and was blocked by Ni2+, Cd2+, and SKF96365 at concentrations preventing contraction. The current showed a bimodal dependence on extracellular Ca2+, being enhanced 2-fold in the absence of Ca2+ and around 10-fold on reducing Ca from 1.8 to 0.2 mmol/L. RT-PCR revealed the expression of Trp1, Trp3, Trp4, Trp5, and Trp6 mRNA, whereas immunostaining identified Trp1, Trp3, Trp4, and Trp6 channel proteins in isolated PASMCs. At least one of these subunits may contribute to cation channels in PASMCs, which are activated by store depletion to bring about Ca2+ influx and contraction. |
| Publication | Circ Res |
| Volume | 89 |
| Issue | 10 |
| Pages | 923-929 |
| Date | November 9, 2001 |
| DOI | 10.1161/hh2201.100315 |
| URL | http://circres.ahajournals.org/cgi/content/abstract/89/10/923 |
| Accessed | Wednesday, November 17, 2010 4:03:41 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 4:03:41 PM |
| Modified | Wednesday, November 17, 2010 4:03:41 PM |
| Type | Journal Article |
|---|---|
| Author | Jamie I. Vandenberg |
| Author | Anthony Varghese |
| Author | Yu Lu |
| Author | Jane A. Bursill |
| Author | Martyn P. Mahaut-Smith |
| Author | Christopher L.-H. Huang |
| Abstract | The function of voltage-gated human ether-a-go-gorelated gene (hERG) K+ channels is critical for both normal cardiac repolarization and suppression of arrhythmias initiated by premature excitation. These important functions are facilitated by their unusual kinetics that combine relatively slow activation and deactivation with rapid and voltage-dependent inactivation and recovery from inactivation. The thermodynamics of these unusual features were examined by exploring the effect of temperature on the activation and inactivation processes of hERG channels expressed in Chinese hamster ovary cells. Increased temperature shifted the voltage dependence of activation in the hyperpolarizing direction but that of inactivation in the depolarizing direction. This increases the relative occupancy of the open state and contributes to the marked temperature sensitivity of hERG current magnitude observed during action potential voltage clamps. The rates of activation and deactivation also increase with higher temperatures, but less markedly than do the rates of inactivation and recovery from inactivation. Our results also emphasize that one cannot extrapolate results obtained at room temperature to 37{degrees}C by using a single temperature scale factor. |
| Publication | Am J Physiol Cell Physiol |
| Volume | 291 |
| Issue | 1 |
| Pages | C165-175 |
| Date | July 1, 2006 |
| DOI | 10.1152/ajpcell.00596.2005 |
| URL | http://ajpcell.physiology.org/cgi/content/abstract/291/1/C165 |
| Accessed | Wednesday, November 17, 2010 6:08:40 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:08:40 PM |
| Modified | Wednesday, November 17, 2010 6:08:40 PM |
| Type | Journal Article |
|---|---|
| Author | C J Mathews |
| Author | J A Tabcharani |
| Author | J W Hanrahan |
| Abstract | The gating cycle of CFTR (Cystic Fibrosis Transmembrane conductance Regulator) chloride channels requires ATP hydrolysis and can be interrupted by exposure to the nonhydrolyzable nucleotide AMP-PNP. To further characterize nucleotide interactions and channel gating, we have studied the effects of AMP-PNP, protein kinase C (PKC) phosphorylation, and temperature on gating kinetics. The rate of channel locking increased from 1.05 x 10(-3) sec-1 to 58.7 x 10(-3) sec-1 when AMP-PNP concentration was raised from 0.5 to 5 mM in the presence of 1 mM MgATP and 180 nM protein kinase A catalytic subunit (PKA). Although rapid locking precluded estimation of Po or opening rate immediately after the addition of AMP-PNP to wild-type channels, analysis of locking rates in the presence of high AMP-PNP concentrations revealed two components. The appearance of a distinct, slow component at high [AMP-PNP] is evidence for AMP-PNP interactions at a second site, where competition with ATP would reduce Po and thereby delay locking. All channels exhibited locking when they were strongly phosphorylated by PKA, but not when exposed to PKC alone. AMP-PNP increased Po at temperatures above 30 degrees C but did not cause locking, evidence that the stabilizing interactions between domains, which have been proposed to maintain CFTR in the open burst state, are relatively weak. The temperature dependence of normal CFTR gating by ATP was strongly asymmetric, with the opening rate being much more temperature sensitive (Q10 = 9.6) than the closing rate (Q10 = 3.6). These results are consistent with a cyclic model for gating of phosphorylated CFTR. |
| Publication | The Journal of Membrane Biology |
| Volume | 163 |
| Issue | 1 |
| Pages | 55-66 |
| Date | May 1, 1998 |
| Journal Abbr | J. Membr. Biol |
| ISSN | 0022-2631 |
| Short Title | The CFTR chloride channel |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/9569250 |
| Accessed | Wednesday, November 17, 2010 4:46:18 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 9569250 |
| Date Added | Wednesday, November 17, 2010 4:46:18 PM |
| Modified | Wednesday, November 17, 2010 4:46:18 PM |
| Type | Journal Article |
|---|---|
| Author | Armantas Baginskas |
| Author | Damodharan Palani |
| Author | Kenneth Chiu |
| Author | Morten Raastad |
| Publication | European Journal of Neuroscience |
| Volume | 29 |
| Issue | 1 |
| Pages | 87-96 |
| Date | 01/2009 |
| DOI | 10.1111/j.1460-9568.2008.06566.x |
| ISSN | 0953816X |
| URL | http://onlinelibrary.wiley.com/doi/10.1111/j.1460-9568.2008.06566.x/full |
| Accessed | Wednesday, November 17, 2010 6:44:24 PM |
| Library Catalog | CrossRef |
| Date Added | Wednesday, November 17, 2010 6:44:24 PM |
| Modified | Wednesday, November 17, 2010 6:44:24 PM |
| Type | Journal Article |
|---|---|
| Author | P Chen |
| Author | T C Hwang |
| Author | K D Gillis |
| Abstract | The mechanism whereby cAMP stimulates Cl(-) flux through CFTR ion channels in secretory epithelia remains controversial. It is generally accepted that phosphorylation by cAMP-dependent protein kinase increases the open probability of the CFTR channel. A more controversial hypothesis is that cAMP triggers the translocation of CFTR from an intracellular pool to the cell surface. We have monitored membrane turnover in Calu-3 cells, a cell line derived from human airway submucosal glands that expresses high levels of CFTR using membrane capacitance and FM1-43 fluorescence measurements. Using a conventional capacitance measurement technique, we observe an apparent increase in membrane capacitance in most cells that exhibit an increase in Cl(-) current. However, after we carefully correct our recordings for changes in membrane conductance, the apparent changes in capacitance are eliminated. Measurements using the fluorescent membrane marker FM1-43 also indicate that no changes in membrane turnover accompany the activation of CFTR. Robust membrane insertion can be triggered with photorelease of caged Ca(2)+ in Calu-3 cells. However, no increase in Cl(-) current accompanies Ca(2)+-evoked membrane fusion. We conclude that neither increases in cAMP or Ca(2)+ lead to transport of CFTR to the plasma membrane in Calu-3 cells. In addition, we conclude that membrane capacitance measurements must be interpreted with caution when large changes in membrane conductance occur. |
| Publication | The Journal of General Physiology |
| Volume | 118 |
| Issue | 2 |
| Pages | 135-144 |
| Date | Aug 2001 |
| Journal Abbr | J. Gen. Physiol |
| ISSN | 0022-1295 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/11479341 |
| Accessed | Wednesday, November 17, 2010 3:59:24 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 11479341 |
| Date Added | Wednesday, November 17, 2010 3:59:24 PM |
| Modified | Wednesday, November 17, 2010 3:59:24 PM |
| Type | Journal Article |
|---|---|
| Author | J. L. Kenyon |
| Abstract | In order to establish the physiological role of the Ca2+-activated Cl- current (ICl(Ca)) of chick primary afferent neurons, I measured the reversal potential of this current using either the amphotericin perforated patch technique (that alters intracellular Cl-) or the gramicidin perforated patch technique (that does not perturb intracellular Cl-). In the amphotericin experiments at 35°C, ICl(Ca) reversed at the Cl- equilibrium potential (ECl=-24 mV) set by the superfusate (147 mM Cl-) and the pipette solution (60 mM Cl-). In contrast, in the gramicidin experiments at 35°C, ICl(Ca) reversed at -42±2 mV, midway between ECl of the solutions and ECl expected if Cl- were passively distributed. Thus the gramicidin perforated patch technique monitors Cl- currents without perturbing intracellular Cl-. Further, the data imply that chick dorsal root ganglia (DRG) neurons actively accumulate Cl-. ICl(Ca) reversed at the same potential (-46±3 mV) at 20°C indicating that the non-equilibrium distribution of Cl- is maintained at the lower temperature. Thus, ICl(Ca) is a depolarizing current that can contribute to the after-depolarization in chick DRG neurons and thereby alter Ca2+ influx. |
| Publication | Neuroscience Letters |
| Volume | 296 |
| Issue | 1 |
| Pages | 9-12 |
| Date | December 15, 2000 |
| DOI | 10.1016/S0304-3940(00)01610-4 |
| ISSN | 0304-3940 |
| URL | http://www.sciencedirect.com/science/article/B6T0G-41SCDR3-3/2/3798e9f70bae7c75e62b111de4098b24 |
| Accessed | Wednesday, November 17, 2010 5:19:58 PM |
| Library Catalog | ScienceDirect |
| Date Added | Wednesday, November 17, 2010 5:19:58 PM |
| Modified | Wednesday, November 17, 2010 5:19:58 PM |
| Type | Journal Article |
|---|---|
| Author | Alexis Bavencoffe |
| Author | Dimitra Gkika |
| Author | Artem Kondratskyi |
| Author | Benjamin Beck |
| Author | Anne-Sophie Borowiec |
| Author | Gabriel Bidaux |
| Author | Jérôme Busserolles |
| Author | Alain Eschalier |
| Author | Yaroslav Shuba |
| Author | Roman Skryma |
| Author | Natalia Prevarskaya |
| Abstract | The transient receptor potential channel melastatin member 8 (TRPM8) is expressed in sensory neurons, where it constitutes the main receptor of environmental innocuous cold (10–25 °C). Among several types of G protein-coupled receptors expressed in sensory neurons, Gi-coupled α2A-adrenoreceptor (α2A-AR), is known to be involved in thermoregulation; however, the underlying molecular mechanisms remain poorly understood. Here we demonstrated that stimulation of α2A-AR inhibited TRPM8 in sensory neurons from rat dorsal root ganglia (DRG). In addition, using specific pharmacological and molecular tools combined with patch-clamp current recordings, we found that in heterologously expressed HEK-293 (human embryonic kidney) cells, TRPM8 channel is inhibited by the Gi protein/adenylate cyclase (AC)/cAMP/protein kinase A (PKA) signaling cascade. We further identified the TRPM8 S9 and T17 as two key PKA phosphorylation sites regulating TRPM8 channel activity. We therefore propose that inhibition of TRPM8 through the α2A-AR signaling cascade could constitute a new mechanism of modulation of thermosensation in both physiological and pathological conditions. |
| Publication | Journal of Biological Chemistry |
| Volume | 285 |
| Issue | 13 |
| Pages | 9410 -9419 |
| Date | March 26 , 2010 |
| DOI | 10.1074/jbc.M109.069377 |
| URL | http://www.jbc.org/content/285/13/9410.abstract |
| Accessed | Wednesday, November 17, 2010 6:34:56 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 6:34:56 PM |
| Modified | Wednesday, November 17, 2010 6:34:56 PM |
| Type | Journal Article |
|---|---|
| Author | Kiyomitsu Shoudai |
| Author | James H. Peters |
| Author | Stuart J. McDougall |
| Author | Jessica A. Fawley |
| Author | Michael C. Andresen |
| Abstract | Central synapses spontaneously release neurotransmitter at low rates. In the brainstem, cranial visceral afferent terminals in caudal solitary tract nucleus (NTS) display pronounced, activity-dependent, asynchronous release of glutamate and this extra release depends on TRPV1 receptors (TRPV1+). Asynchronous release is absent for afferents lacking TRPV1 (TRPV1-) and resting EPSC frequency was greater in TRPV1+. Here, we studied this basal activity difference by assessing thermal sensitivity of spontaneous and miniature synaptic events in TRPV1+ and TRPV1- second-order NTS neurons. The spontaneous EPSC rate decreased when temperature was decreased, increased steeply between 30 and 42{degrees}C only in TRPV1+ neurons, and was calcium-dependent. TRPV1-specific antagonist SB366791, but not TTX, strongly attenuated thermal responses. Temperature changes failed to alter EPSC frequency in TRPV1- neurons. EPSC amplitudes and decay kinetics changed little with temperature. IPSCs in these second-order NTS neurons were unaltered by temperature. Such results suggest that activated, presynaptic TRPV1+ receptors trigger continuous resting release of glutamate vesicles at physiological temperatures only in capsaicin-responsive terminals. In mechanically isolated individual neurons harvested from medial NTS, increases in temperature increased the rate of glutamate release only in TRPV1+ neurons, whereas IPSC rates were unaffected. Cadmium failed to block thermal increases in glutamate release, suggesting that calcium entry through TRPV1 channels may trigger glutamate release independently of voltage-activated calcium channels. Together, our findings indicate a new form of afferent signaling in which TRPV1 channels within central terminals of peripheral afferents tonically generate glutamate release in NTS at 37{degrees}C in the absence of afferent action potentials. |
| Publication | J. Neurosci. |
| Volume | 30 |
| Issue | 43 |
| Pages | 14470-14475 |
| Date | October 27, 2010 |
| DOI | 10.1523/JNEUROSCI.2557-10.2010 |
| URL | http://www.jneurosci.org/cgi/content/abstract/30/43/14470 |
| Accessed | Wednesday, November 17, 2010 6:21:34 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:21:34 PM |
| Modified | Wednesday, November 17, 2010 6:21:34 PM |
| Type | Journal Article |
|---|---|
| Author | Michiel Helmes |
| Author | Chee Chew Lim |
| Author | Ronglih Liao |
| Author | Ajit Bharti |
| Author | Lei Cui |
| Author | Douglas B. Sawyer |
| Abstract | Titin, a giant protein spanning half the sarcomere, is responsible for passive and restoring forces in cardiac myofilaments during sarcomere elongation and compression, respectively. In addition, titin has been implicated in the length-dependent activation that occurs in the stretched sarcomere, during the transition from diastole to systole. The purpose of this study was to investigate the role of titin in the length-dependent deactivation that occurs during early diastole, when the myocyte is shortened below slack length. We developed a novel in vitro assay to assess myocyte restoring force (RF) by measuring the velocity of recoil in Triton-permeabilized, unloaded rat cardiomyocytes after rigor-induced sarcomere length (SL) contractions. We compared rigor-induced SL shortening to that following calcium-induced (pCa) contractions. The RF–SL relationship was linearly correlated, and the SL-pCa curve displayed a characteristic sigmoidal curve. The role of titin was defined by treating myocytes with a low concentration of trypsin, which we show selectively degrades titin using mass spectroscopic analysis. Trypsin treatment reduced myocyte RF as shown by a decrease in the slope of the RF-SL relationship, and this was accompanied by a downward and leftward shift of the SL-pCa curve, indicative of sensitization of the myofilaments to calcium. In addition, trypsin digestion did not alter the relationship between SL and interfilament spacing (assessed by cell width) after calcium activation. These data suggest that as the sarcomere shortens below slack length, titin-based restoring forces act to desensitize the myofilaments. Furthermore, in contrast to length-dependent activation at long SLs, length-dependent deactivation does not depend on interfilament spacing. This study demonstrates for the first time the importance of titin-based restoring force in length-dependent deactivation during the early phase of diastole. |
| Publication | The Journal of General Physiology |
| Volume | 121 |
| Issue | 2 |
| Pages | 97-110 |
| Date | 2003-2 |
| Journal Abbr | J Gen Physiol |
| DOI | 10.1085/jgp.20028652 |
| ISSN | 0022-1295 |
| Library Catalog | PubMed Central |
| Extra | PMID: 12566538 PMCID: 2217323 |
| Date Added | Wednesday, November 17, 2010 4:45:40 PM |
| Modified | Wednesday, November 17, 2010 4:45:40 PM |
| Type | Journal Article |
|---|---|
| Author | Edwin Janssen |
| Author | Jan Kuiper |
| Author | Denice Hodgson |
| Author | Leonid V Zingman |
| Author | Alexey E Alekseev |
| Author | Andre Terzic |
| Author | Bé Wieringa |
| Abstract | Adenylate kinases (AK, EC 2.7.4.3) have been considered important enzymes for energy homeostasis and metabolic signaling. To gain a better understanding of their cell-specific significance we studied the structural and functional aspects of products of one adenylate kinase gene, AK1, in mouse tissues. By combined computer database comparison and Northern analysis of mRNAs, we identified transcripts of 0.7 and 2.0 kilobases with different 5' and 3' non-coding regions which result from alternative use of promoters and polyadenylation sites. These mRNAs specify two distinct proteins, AK1 and a membrane-bound AK1 isoform (AK1beta), which differ in their N-terminal end and are co-expressed in several tissues with high-energy demand, including the brain. Immunohistochemical analysis of brain tissue and primary neurons and astrocytes in culture demonstrated that AK1 isoforms are expressed predominantly in neurons. AK1beta, when tested in transfected COS-1 and N2a neuroblastoma cells, located at the cellular membrane and was able to catalyze phosphorylation of ADP in vitro. In addition, AK1beta mediated AMP-induced activation of recombinant ATP-sensitive potassium channels in the presence of ATP. Thus, two structurally distinct AK1 isoforms co-exist in the mouse brain within distinct cellular locations. These enzymes may function in promoting energy homeostasis in the compartmentalized cytosol and in translating cellular energetic signals to membrane metabolic sensors. |
| Publication | Molecular and Cellular Biochemistry |
| Volume | 256-257 |
| Issue | 1-2 |
| Pages | 59-72 |
| Date | 2004 Jan-Feb |
| Journal Abbr | Mol. Cell. Biochem |
| ISSN | 0300-8177 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/14977170 |
| Accessed | Wednesday, November 17, 2010 12:56:56 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 14977170 |
| Date Added | Wednesday, November 17, 2010 12:56:56 PM |
| Modified | Wednesday, November 17, 2010 12:56:56 PM |
| Type | Journal Article |
|---|---|
| Author | S De Marchis |
| Author | A Fasolo |
| Author | M Shipley |
| Author | A Puche |
| Abstract | Continual neurogenesis in the subventricular zone (SVZ) of postnatal and adult mammalian forebrain has been well documented, but the mechanisms underlying cell migration and differentiation in this region are poorly understood. We have developed novel in vivo and in vitro methods to investigate these processes. Using stereotaxic injections of a variety of tracers/tracker [Cholera Toxin beta subunit (CTb-), Fluorogold (FG), and Cell Tracker Green (CTG)], we could efficiently label SVZ cells. Over several days, labeled cells migrate along the rostral migratory stream (RMS) to their final differentiation site in the olfactory bulb (OB). The compatibility of these tracers/trackers with immunohistochemistry allows for cell labeling with multiple dyes (e.g., CTb and CTG) and/or specific cell antigens. To investigate the dynamics of migration we labeled SVZ progenitor cells with small injections of CTG and monitored the movements of individual cells in fresh parasagittal brain slices over several hours using time-lapse confocal microscopy. Our observations suggest that tangential cell migration along the RMS occurs more rapidly than radial cell migration into the OB granule cell layer. To investigate migration over longer time periods, we developed an in vitro organotypic slice in which labeled SVZ progenitors migrate along the RMS and differentiate within the OB. The phenotypic characteristics of these cells in vitro were equivalent to those observed in vivo. Taken together, these methods provide useful tools investigating cell migration and differentiation in a preparation that maintains the anatomical organization of the RMS. |
| Publication | Journal of Neurobiology |
| Volume | 49 |
| Issue | 4 |
| Pages | 326-338 |
| Date | Dec 2001 |
| Journal Abbr | J. Neurobiol |
| ISSN | 0022-3034 |
| URL | http://www.ncbi.nlm.nih.gov/pubmed/11745668 |
| Accessed | Wednesday, November 17, 2010 4:40:50 PM |
| Library Catalog | NCBI PubMed |
| Extra | PMID: 11745668 |
| Date Added | Wednesday, November 17, 2010 4:40:50 PM |
| Modified | Wednesday, November 17, 2010 4:40:50 PM |
| Type | Journal Article |
|---|---|
| Author | A F Soleng |
| Author | K Chiu |
| Author | M Raastad |
| Abstract | The mammalian cortex is densely populated by extensively branching, thin, unmyelinated axons that form en passant synapses. Some thin axons in the peripheral nervous system hyperpolarize if action potential frequency exceeds 1-5 Hz. To test the hypothesis that cortical axons also show activity-induced hyperpolarization, we recorded extracellularly from individual CA3 pyramidal neurons while activating their axon with trains consisting of 30 electrical stimuli. Synaptic excitation was blocked by kynurenic acid. We observed a positive correlation between stimulation strength and the number of consecutive axonal stimuli that resulted in soma spikes, suggesting that the threshold increased as a function of the number of spikes. During trains without response failures there was always a cumulative increase in the soma response latency. Intermittent failures, however, decreased the latency of the subsequent response. At frequencies of > 1 Hz, the threshold and latency increases were enhanced by blocking the hyperpolarization-activated H current (Ih)by applying the specific Ih blocker ZD7288 (25 μM) or 2 mM Cs+. Under these conditions, response failures occurred after 15–25 stimuli, independent of the stimulation strength. Adding GABA receptor blockers (saclofen and bicuculline) and a blocker of metabotropic glutamate receptors did not change the activity-induced latency increase in recordings of the compound action potential. We interpret these results as an activity-induced hyperpolarization that is partly counteracted by Ih. Such a hyperpolarization may influence transmitter release and the conduction reliability of these axons. |
| Publication | The Journal of Physiology |
| Volume | 552 |
| Issue | 2 |
| Pages | 459 -470 |
| Date | October 15 , 2003 |
| DOI | 10.1113/jphysiol.2003.048058 |
| URL | http://jp.physoc.org/content/552/2/459.abstract |
| Accessed | Wednesday, November 17, 2010 4:41:38 PM |
| Library Catalog | Highwire 2.0 |
| Date Added | Wednesday, November 17, 2010 4:41:38 PM |
| Modified | Wednesday, November 17, 2010 4:41:38 PM |
| Type | Journal Article |
|---|---|
| Author | Alaine L. Pribisko |
| Author | Edward R. Perl |
| Abstract | A skin-nerve preparation is useful for study of heat transduction mechanisms of A- and C-high threshold primary afferents (nociceptors), but the small dimension and liquid environment of the skin organ bath do not readily accommodate conventional noxious heat delivery systems. For these reasons, a 980 nm (near-infrared) diode laser was tested for activation and differentiation of cutaneous afferents. Current to the laser driver was varied. Exposure time and area, angle of approach, and stand-off distance from the bath solution surface were held constant. Seventy-eight fibers were classified by: conduction velocity, mechanical threshold, and responsiveness to laser radiation. A subset of the sampled fibers was also tested for sensitivity to convective heat. Most C (30/43) and a few A (6/25) nociceptors responded to laser irradiation. All low mechanical threshold primary afferents (10/10) were unresponsive to laser irradiation. Laser-sensitive fibers responded to convective heat, whereas laser-insensitive fibers did not. Laser-induced responses were consistent with literature reports of responses to traditional heat stimulation. Laser stimulation proved to be a rapid, unobtrusive method for reproducible heat stimulation of primary afferents of the mouse skin-nerve preparation. It is effective for defining subpopulations of primary afferent fibers and holds promise as a tool for gauging modification of C-fiber activity. |
| Publication | Journal of Neuroscience Methods |
| Volume | In Press, Corrected Proof |
| DOI | 10.1016/j.jneumeth.2010.10.013 |
| ISSN | 0165-0270 |
| URL | http://www.sciencedirect.com/science/article/B6T04-519210W-1/2/639f143ba39815e06ebf7b87a44f6aa9 |
| Accessed | Wednesday, November 17, 2010 6:42:39 PM |
| Library Catalog | ScienceDirect |
| Date Added | Wednesday, November 17, 2010 6:42:39 PM |
| Modified | Wednesday, November 17, 2010 6:42:39 PM |
| Type | Journal Article |
|---|---|
| Author | Sheerazed Boulkroun |
| Author | Dorothee Ruffieux-Daidie |
| Author | Jean-Jacques Vitagliano |
| Author | Olivier Poirot |
| Author | Roch-Philippe Charles |
| Author | Dagmara Lagnaz |
| Author | Dmitri Firsov |
| Author | Stephan Kellenberger |
| Author | Olivier Staub |
| Abstract | Adjustment of Na+ balance in extracellular fluids is achieved by regulated Na+ transport involving the amiloride-sensitive epithelial Na+ channel (ENaC) in the distal nephron. In this context, ENaC is controlled by a number of hormones, including vasopressin, which promotes rapid translocation of water and Na+ channels to the plasma membrane and long-term effects on transcription of vasopressin-induced and -reduced transcripts. We have identified a mRNA encoding the deubiquitylating enzyme ubiquitin-specific protease 10 (Usp10), whose expression is increased by vasopressin at both the mRNA and the protein level. Coexpression of Usp10 in ENaC-transfected HEK-293 cells causes a more than fivefold increase in amiloride-sensitive Na+ currents, as measured by whole cell patch clamping. This is accompanied by a three- to fourfold increase in surface expression of {alpha}- and {gamma}-ENaC, as shown by cell surface biotinylation experiments. Although ENaC is well known to be regulated by its direct ubiquitylation, Usp10 does not affect the ubiquitylation level of ENaC, suggesting an indirect effect. A two-hybrid screen identified sorting nexin 3 (SNX3) as a novel substrate of Usp10. We show that it is a ubiquitylated protein that is degraded by the proteasome; interaction with Usp10 leads to its deubiquitylation and stabilization. When coexpressed with ENaC, SNX3 increases the channel's cell surface expression, similarly to Usp10. In mCCDcl1 cells, vasopressin increases SNX3 protein but not mRNA, supporting the idea that the vasopressin-induced Usp10 deubiquitylates and stabilizes endogenous SNX3 and consequently promotes cell surface expression of ENaC. |
| Publication | Am J Physiol Renal Physiol |
| Volume | 295 |
| Issue | 4 |
| Pages | F889-900 |
| Date | October 1, 2008 |
| DOI | 10.1152/ajprenal.00001.2008 |
| URL | http://ajprenal.physiology.org/cgi/content/abstract/295/4/F889 |
| Accessed | Wednesday, November 17, 2010 6:26:30 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:26:30 PM |
| Modified | Wednesday, November 17, 2010 6:26:30 PM |
| Type | Journal Article |
|---|---|
| Author | Alaron Lewis |
| Author | Philip Williams |
| Author | Owen Lawrence |
| Author | Rachel O. L. Wong |
| Author | Susan E. Brockerhoff |
| Abstract | In many retinal diseases, the malfunction that results in photoreceptor loss occurs only in either rods or cones, but degeneration can progress from the affected cell type to its healthy neighbors. Specifically, in human and mouse models of Retinitis Pigmentosa the loss of rods results in the death of neighboring healthy cones. Significantly less is known about cone-initiated degenerations and their affect on neighboring cells. Sometimes rods remain normal after cone death, whereas other patients experience a loss of scotopic vision over time. The affect of cone death on neighboring cones is unknown. The zebrafish is a cone-rich animal model in which the potential for dying cones to kill neighboring healthy cones can be evaluated. We previously reported that the zebrafish cone phosphodiesterase mutant (pde6cw59) displays a rapid death of cones soon after their formation and a subsequent loss of rods in the central retina. In this study we examine morphological changes associated with cone death in vivo in pde6cw59 fish. We then use blastulae transplantations to create chimeric fish with a photoreceptor layer of mixed wild-type (WT) and pde6cw59 cones. We find that the death of inoperative cones does not cause neighboring WT cone loss. The survival of WT cones is independent of transplant size and location within the retina. Furthermore, transplanted WT cones persist at least several weeks after the initial death of dysfunctional mutant cones. Our results suggest a potential for the therapeutic transplantation of healthy cones into an environment of damaged cones. |
| Publication | J. Neurosci. |
| Volume | 30 |
| Issue | 1 |
| Pages | 382-389 |
| Date | January 6, 2010 |
| DOI | 10.1523/JNEUROSCI.5019-09.2010 |
| URL | http://www.jneurosci.org/cgi/content/abstract/30/1/382 |
| Accessed | Wednesday, November 17, 2010 6:16:26 PM |
| Library Catalog | HighWire |
| Date Added | Wednesday, November 17, 2010 6:16:26 PM |
| Modified | Wednesday, November 17, 2010 6:16:26 PM |