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Electrophysiological Properties (electrophysiological + property)
Kinds of Electrophysiological Properties Selected AbstractsRelation of Age and Sex to Atrial Electrophysiological Properties in Patients with No History of Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2003KOICHI SAKABE Although atrial fibrillation is a common arrhythmia, especially in elderly men, little is known about age related changes in atrial electrophysiological properties or gender differences. The aim of this study was to analyze the effects of aging on vulnerability to atrial fibrillation and assessed gender differences in those age related changes. An electrophysiological study was performed on 73 patients with no history of atrial fibrillation, structural heart disease, or conditions with potential effects on cardiac hemodynamic or electrophysiological function, including 25 women (mean age 49 ± 18 years; range 12,84 years). The following atrial excitability parameters were assessed: spontaneous or paced (A1) and extrastimulated (A2) atrial electrogram widths, percent maximum atrial fragmentation(A2/A1 × 100), effective refractory period, wavelength index (effective refractory period/A2), and inducibility of atrial fibrillation. There were no significant differences in percent maximum atrial fragmentation (143 ± 28vs142 ± 35%), effective refractory period (241 ± 39vs238 ± 50 ms), wavelength index (2.9 ± 0.8vs3.1 ± 0.9), induction of atrial fibrillation (10 [21%] vs 7 [28%]), or age (50 ± 17vs 49 ± 20 years) between men and women. Age was not statistically different between those patients with and without induction of atrial fibrillation in men (48 ± 14vs50 ± 18 years) and women (48 ± 18vs49 ± 21 years). Percent maximum atrial fragmentation and effective refractory period were directly correlated with age in men (r = 0.35, P = 0.01; r = 0.46, P < 0.001, respectively) and women (r = 0.42, P = 0.04; r = 0.45, P = 0.02, respectively), though wavelength index did not correlate with age in men (r =,0.04) or women (r =,0.04) with no history of atrial fibrillation. Considering these findings, the authors conclude that the mechanism triggering atrial fibrillation may be different between older and younger patients with atrial fibrillation, because younger patients who have no marked substrate for atrial fibrillation may need many trigger beats to induce atrial fibrillation. (PACE 2003; 26:1238,1244) [source] Effects of Sex and Age on Electrocardiographic and Cardiac Electrophysiological Properties in AdultsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2001TARESH TANEJA TANEJA, T., et al.: Effects of Sex, and Age on Electrocardiographic and Cardiac Electrophysiological Properties in Adults. Although differences in patient sex in heart rate and QT interval have been well characterized, sexual differences in other cardiac electrophysiological properties have not been well defined. The study population consisted of 354 consecutive patients without structural heart disease or preexcitation who underwent clinically indicated electrophysiological testing in the drug-free state. Atrial, AV nodal, and ventricular effective refractory periods (AERP, AVNERP, VERP) were determined at a pacing cycle length of 500 ms using an 8-beat drive train and 3-second intertrain pause. There were 124 men and 230 women with a mean age of 45 ± 19 and 47 ± 18 years, respectively The sinus cycle length (SCL) was longer in men than in women (864 ± 186 and 824 ± 172 ms, respectively, P < 0.05). The QRS duration was significantly longer in men (90 ± 12 ms) than women (86 ± 13 ms) (P < 0.005). The HV interval was 48 ± 9 ms in men and 45 ± 8 ms in women (P < 0.05). The sinus node recovery time (SNRT) was significantly longer in men than in women (1215 ± 297 ms and 1135 ± 214 ms, respectively, P < 0.05). AERP and VERP were similar in both sexes. Aging did not influence sexual differences in cardiac electrophysiological properties, although, it independently prolonged the SCL, PR, and QT intervals, AH and HV intervals, SNRT, AVNERP, and the AV Wenckebach cycle length. The SCL, QRS duration, HV interval, and SNRT were significantly longer in men than in women. Aging prolonged cardiac conduction and increased the SCL but the effects were similar in both sexes. AERP and VERP were unaffected by aging or sex. [source] New Fatty Acid Oxidation Inhibitors with Increased Potency Lacking Adverse Metabolic and Electrophysiological Properties.CHEMINFORM, Issue 16 2004Dmitry O. Koltun Abstract For Abstract see ChemInform Abstract in Full Text. [source] SHORT COMMUNICATION Inhibition of GABAergic neurotransmission in the ventral tegmental area by cannabinoidsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2002Bela Szabo Abstract It was shown recently that ,9-tetrahydrocannabinol, like several other drugs eliciting euphoria, stimulates dopaminergic neurons projecting from the ventral tegmental area (VTA) to the nucleus accumbens. The aim of the present work was to clarify the mechanism of this stimulatory effect. Our hypothesis was that cannabinoids depress the GABAergic inhibition of dopaminergic neurons in the VTA. Electrophysiological properties of VTA neurons in rat coronal midbrain slices were studied with the patch-clamp technique. GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) were evoked by electrical stimulation in the vicinity of the recorded neurons. The amplitude of IPSCs was depressed by the synthetic mixed CB1/CB2 cannabinoid receptor agonist WIN55212-2 (10,6 and 10,5 m). The CB1 cannabinoid receptor antagonist SR141716A (10,6 m) prevented the inhibition produced by WIN55212-2 (10,5 m). Two observations showed that IPSCs were depressed with a presynaptic mechanism. WIN55212-2 (10,5 m) did not change the amplitude of miniature IPSCs recorded in the presence of tetrodotoxin. Currents evoked by pressure ejection of muscimol from a pipette were also not changed by WIN55212-2 (10,5 m). The results indicate that activation of CB1 cannabinoid receptors inhibits GABAergic neurotransmission in the VTA with a presynaptic mechanism. Depression of the GABAergic inhibitory input of dopaminergic neurons would increase their firing rate in vivo. Accordingly, dopamine release in the projection region of VTA neurons, the nucleus accumbens, would also increase. [source] Analysis of neural potential of human umbilical cord blood,derived multipotent mesenchymal stem cells in response to a range of neurogenic stimuliJOURNAL OF NEUROSCIENCE RESEARCH, Issue 9 2008Isabel Zwart Abstract We investigated the neurogenic potential of full-term human umbilical cord blood (hUCB),derived multipotent mesenchymal stem cells (MSCs) in response to neural induction media or coculture with rat neural cells. Phenotypic and functional changes were assessed by immunocytochemistry, RT-PCR, and whole-cell patch-clamp recordings. Naive MSCs expressed both mesodermal and ectodermal markers prior to neural induction. Exposure to retinoic acid, basic fibroblast growth factor, or cyclic adenosine monophosphate (cAMP) did not stimulate neural morphology, whereas exposure to dibutyryl cAMP and 3-isobutyl-1-methylxanthine stimulated a neuron-like morphology but also appeared to be cytotoxic. All protocols stimulated increases in expression of the neural precursor marker nestin, but expression of mature neuronal or glial markers MAP2 and GFAP was not observed. Nestin expression increases were serum level dependent. Electrophysiological properties of MSCs were studied with whole-cell patch-clamp recordings. The MSCs possessed no ionic currents typical of neurons before or after neural induction protocols. Coculture of hUCB-derived MSCs and rat neural cells induced some MSCs to adopt an astrocyte-like morphology and express GFAP protein and mRNA. Our data suggest hUCB-derived MSCs do not transdifferentiate into mature functioning neurons in response to the above neurogenic protocols; however, coculture with rat neural cells led to a minority adopting an astrocyte-like phenotype. © 2008 Wiley-Liss, Inc. [source] Electrophysiological properties of two axonal sodium channels, Nav1.2 and Nav1.6, expressed in mouse spinal sensory neuronesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Anthony M. Rush Sodium channels Nav1.2 and Nav1.6 are both normally expressed along premyelinated and myelinated axons at different stages of maturation and are also expressed in a subset of demyelinated axons, where coexpression of Nav1.6 together with the Na+/Ca2+ exchanger is associated with axonal injury. It has been difficult to distinguish the currents produced by Nav1.2 and Nav1.6 in native neurones, and previous studies have not compared these channels within neuronal expression systems. In this study, we have characterized and directly compared Nav1.2 and Nav1.6 in a mammalian neuronal cell background and demonstrate differences in their properties that may affect neuronal behaviour. The Nav1.2 channel displays more depolarized activation and availability properties that may permit conduction of action potentials, even with depolarization. However, Nav1.2 channels show a greater accumulation of inactivation at higher frequencies of stimulation (20,100 Hz) than Nav1.6 and thus are likely to generate lower frequencies of firing. Nav1.6 channels produce a larger persistent current that may play a role in triggering reverse Na+/Ca2+ exchange, which can injure demyelinated axons where Nav1.6 and the Na+/Ca2+ exchanger are colocalized, while selective expression of Nav1.2 may support action potential electrogenesis, at least at lower frequencies, while producing a smaller persistent current. [source] Electrophysiological properties of BK channels in Xenopus motor nerve terminalsTHE JOURNAL OF PHYSIOLOGY, Issue 1 2004Xiao-Ping Sun Single channel properties of Ca2+ -activated K+ (BK or Maxi-K) channels have been investigated in presynaptic membranes in Xenopus motoneurone,muscle cell cultures. The occurrence and density of BK channels increased with maturation/synaptogenesis and was not uniform: highest at the release face of bouton-like synaptic varicosities in contact with muscle cells, and lowest in varicosities that did not contact muscle cells. The Ca2+ affinity of the channel (Kd= 7.7 ,m at a membrane potential of +20 mV) was lower than those of BK channels that have been characterized in other terminals. Hill coefficients varied between 1.5 and 2.8 at different potentials and open probability increased e-fold per 16 mV change in membrane potential over a range of [Ca2+]i from 1 ,m to 1 mm. The maximal activation rate of ensembled single BK channel currents was in the submillisecond range at ,+20 mV. The activation rate increased ,10-fold in response to a [Ca2+]i increase from 1 to 100 ,m, but increased only ,2-fold with a voltage change from +20 to +130 mV. The fastest activation kinetics of BK channels in cell-attached patches resembled that in inside-out patches with [Ca2+]i of 100 ,m or more, suggesting that many BK channels are located very close to calcium channels. Given the low Ca2+ affinity and rapid Ca2+ binding/unbinding properties, we conclude that BK channels in this preparation are adapted to play an important role in regulation of neurotransmitter release, and they are ideal reporters of local [Ca2+] at the inner membrane surface. [source] Ion channel activity of transmembrane segment 6 of Escherichia coli proton-dependent manganese transporterBIOPOLYMERS, Issue 8 2010uková Abstract Synthetic peptides corresponding to the sixth transmembrane segment (TMS6) of secondary-active transporter MntH (Proton-dependent Manganese Transporter) from Escherichia coli and its two mutations in the functionally important conserved histidine residue were used as a model for structure,function study of MntH. The secondary structure of the peptides was estimated in different environments using circular dichroism spectroscopy. These peptides interacted with and adopted helical conformations in lipid membranes. Electrophysiological experiments demonstrated that TMS6 was able to form multi-state ion channels in model biological membranes. Electrophysiological properties of these weakly cation-selective ion channels were strongly dependent on the surrounding pH. Manganese ion, as a physiological substrate of MntH, enhanced the conductivity of TMS6 channels, influenced the transition between closed and open states, and affected the peptide conformations. Moreover, functional properties of peptides carrying two different mutations of His211 were analogous to in vivo functional characteristics of Nramp/MntH proteins mutated at homologous residues. Hence, a single functionally important TMS can retain some of the functional properties of the full-length protein. These findings could contribute to understanding the structure,function relationship at the molecular level. However it remains unclear to what extent the peptide-specific channel activity represents a functional aspect of the full-length membrane carrier protein. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 718,726, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Scn3b knockout mice exhibit abnormal sino-atrial and cardiac conduction propertiesACTA PHYSIOLOGICA, Issue 1 2010P. Hakim Abstract Aim:, In contrast to extensive reports on the roles of Nav1.5 , -subunits, there have been few studies associating the , -subunits with cardiac arrhythmogenesis. We investigated the sino-atrial and conduction properties in the hearts of Scn3b,/, mice. Methods:, The following properties were compared in the hearts of wild-type (WT) and Scn3b,/, mice: (1) mRNA expression levels of Scn3b, Scn1b and Scn5a in atrial tissue. (2) Expression of the ,3 protein in isolated cardiac myocytes. (3) Electrocardiographic recordings in intact anaesthetized preparations. (4) Bipolar electrogram recordings from the atria of spontaneously beating and electrically stimulated Langendorff-perfused hearts. Results:,Scn3b mRNA was expressed in the atria of WT but not Scn3b,/, hearts. This was in contrast to similar expression levels of Scn1b and Scn5a mRNA. Immunofluorescence experiments confirmed that the ,3 protein was expressed in WT and absent in Scn3b,/, cardiac myocytes. Lead I electrocardiograms from Scn3b,/, mice showed slower heart rates, longer P wave durations and prolonged PR intervals than WT hearts. Spontaneously beating Langendorff-perfused Scn3b,/, hearts demonstrated both abnormal atrial electrophysiological properties and evidence of partial or complete dissociation of atrial and ventricular activity. Atrial burst pacing protocols induced atrial tachycardia and fibrillation in all Scn3b,/, but hardly any WT hearts. Scn3b,/, hearts also demonstrated significantly longer sinus node recovery times than WT hearts. Conclusion:, These findings demonstrate, for the first time, that a deficiency in Scn3b results in significant atrial electrophysiological and intracardiac conduction abnormalities, complementing the changes in ventricular electrophysiology reported on an earlier occasion. [source] Electrophysiological and morphological characterization of dentate astrocytes in the hippocampusDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2005Masako Isokawa Abstract We studied electrophysiological and morphological properties of astrocytes in the dentate gyrus of the rat hippocampus in slices. Intracellular application of Lucifer yellow revealed two types of morphology: one with a long process extruding from the cell body, and the other with numerous short processes surrounding the cell body. Their electrophysiological properties were either passive, that is, no detectable voltage-dependent conductance, or complex, with Na+/K+ currents similar to those reported in the Ammon's horn astrocytes. We did not find any morphological correlate to the types of electrophysiological profile or dye coupling. Chelation of cytoplasmic calcium ([Ca2+]i) by BAPTA increased the incidence of detecting a low Na+ conductance and transient outward K+ currents. However, an inwardly rectifying K+ current (Kir), a hallmark of differentiated CA1/3 astrocytes, was not a representative K+ -current in the complex dentate astrocytes, suggesting that these astrocytes could retain an immature form of K-currents. Dentate astrocytes may possess a distinct current profile that is different from those in CA1/3 Ammon's horn. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [source] Neurochemical identification of stereotypic burst-firing neurons in the rat dorsal raphe nucleus using juxtacellular labelling methodsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2007Mihály Hajós Abstract Recent electrophysiological studies have discovered evidence of heterogeneity of 5-hydroxytryptamine (5-HT) neurons in the mesencephalic raphe nuclei. Of particular interest is a subpopulation of putative 5-HT neurons that display many of the electrophysiological properties of presumed 5-HT-containing neurons (regular and slow firing of single spikes with a broad waveform) but fire spikes in short, stereotyped bursts. In the present study we investigated the chemical identity of these neurons in rats utilizing in vivo juxtacellular labelling methods. Of ten dorsal raphe nucleus (DRN) neurons firing short stereotyped bursts within an otherwise regular firing pattern, all exhibited immunoreactivity for either 5-HT (n = 6) or the 5-HT synthesizing enzyme, tryptophan hydroxylase (TRH; n = 2) or both (n = 2). Supporting pharmacological experiments demonstrated that the burst firing DRN neurons demonstrated equal sensitivity to 5-HT1A agonism and ,1 -adrenoceptor antagonism to single spiking DRN neurons that we have previously identified as 5-HT-containing. Collectively these data provide direct evidence that DRN neurons that exhibit stereotyped burst firing activity are 5-HT containing. The presence of multiple types of electrophysiologically distinct midbrain 5-HT neurons is discussed. [source] Post-lesion transcommissural growth of olivary climbing fibres creates functional synaptic microzonesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Izumi Sugihara Abstract In the adult mammalian central nervous system, reinnervation and recovery from trauma is limited. During development, however, postlesion plasticity may generate alternate paths, providing models to investigate reinnervating axon,target interactions. After unilateral transection of the neonatal rat olivocerebellar path, axons from the ipsilateral inferior olive grow into the denervated hemicerebellum and develop climbing fibre (CF)-like arbors on Purkinje cells (PCs). However, the synaptic function and extent of PC reinnervation remain unknown. In adult rats pedunculotomized on postnatal day 3 the morphological and electrophysiological properties of reinnervating olivocerebellar axons were studied, using axonal reconstruction and patch-clamp PC recording of CF-induced synaptic currents. Reinnervated PCs displayed normal CF currents, and the frequency of PC reinnervation decreased with increasing laterality. Reinnervating CF arbors were predominantly normal but 6% branched within the molecular layer forming smaller secondary arbors. CFs arose from transcommissural olivary axons, which branched extensively near their target PCs to produce on average 36 CFs, which is six times more than normal. Axons terminating in the hemisphere developed more CFs than those terminating in the vermis. However, the precise parasagittal microzone organization was preserved. Transcommissural axons also branched, although to a lesser extent, to the deep cerebellar nuclei and terminated in a distribution indicative of the olivo-cortico-nuclear circuit. These results show that reinnervating olivocerebellar axons are highly plastic in the cerebellum, compensating anatomically and functionally for early postnatal denervation, and that this reparation obeys precise topographic constraints although axonal plasticity is modified by target (PC or deep nuclear neurons) interactions. [source] Ionic currents underlying rhythmic bursting of ventral mossy cells in the developing mouse dentate gyrusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2003Shozo Jinno Abstract The electrophysiological properties of mossy cells were examined in developing mouse hippocampal slices using whole-cell patch-clamp techniques, with particular reference to the dorsoventral difference. Dorsal mossy cells exhibited a higher spontaneous excitatory postsynaptic potential (EPSP) frequency and larger maximal EPSP amplitude than ventral mossy cells. On the other hand, the blockade of synaptic inputs with glutamatergic and GABAergic antagonists disclosed a remarkable dorsoventral difference in the intrinsic activity: none (0/27) of the dorsal mossy cells showed intrinsic bursting, whereas the majority (35/47) of the ventral mossy cells exhibited intrinsic rhythmic bursting. To characterize the ionic currents underlying the rhythmic bursting of mossy cells, we used somatic voltage-clamp recordings in the subthreshold voltage range. Ventral bursting cells possessed both hyperpolarization-activated current (Ih) and persistent sodium current (INaP), whereas dorsal and ventral nonbursting cells possessed Ih but no INaP. Blockade of Ih with cesium did not affect the intrinsic bursting of ventral mossy cells. In contrast, the blockade of INaP with tetrodotoxin or phenytoin established a stable subthreshold membrane potential in ventral bursting cells. The current,voltage curve of ventral bursting cells showed a region of tetrodotoxin-sensitive negative slope conductance between ,55 mV and a spike threshold (, ,45 mV). On the other hand, no subthreshold calcium conductances played a significant role in the intrinsic bursting of ventral mossy cells. These observations demonstrate the heterogeneous electrophysiological properties of hilar mossy cells, and suggest that the subthreshold INaP plays a major role in the intrinsic rhythmic bursting of ventral mossy cells. [source] Functional characterization of compound heterozygosity for GlyR,1 mutations in the startle disease hyperekplexiaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2002Ruth Rea Abstract The human disease hyperekplexia is characterized by excessive startle reactions to auditory and cutaneous stimuli. In its familial form, hyperekplexia has been associated with both dominant and recessive mutations of the GLRA1 gene encoding the glycine receptor ,1 subunit (GlyR,1), which mediates inhibitory transmission in the spinal cord and brainstem. Here we have examined the functional consequences of two amino acid substitutions found in a compound heterozygous family, R252H and R392H, to investigate the mechanisms determining this inheritance pattern. When expressed in Xenopus laevis oocytes, both mutations were non-functional. Neither mutant affected the electrophysiological properties of wild type GlyR,1 when co-expressed. We introduced a green fluorescent protein tag to mutant subunits and found that both mutant proteins were detectable. Evidence that subcellular localization differed from wild type was significant for one of the mutants. Thus, an effective loss of functional GlyR,1-mediated current underlies hyperekplexia in this family, whereas a partial loss is asymptomatic. [source] The action of high K+ and aglycaemia on the electrical properties and synaptic transmission in rat intracardiac ganglion neurones in vitroEXPERIMENTAL PHYSIOLOGY, Issue 2 2009Jhansi Dyavanapalli We have investigated the action of two elements of acute ischaemia, high potassium and aglycaemia, on the electrophysiological properties and ganglionic transmission of adult rat intracardiac ganglion (ICG) neurones. We used a whole-mount ganglion preparation of the right atrial ganglion plexus and sharp microelectrode recording techniques. Increasing extracellular K+ from its normal value of 4.7 mm to 10 mm decreased membrane potential and action potential after-hyperpolarization amplitude but otherwise had no effect on postganglionic membrane properties. It did, however, reduce the ability of synaptically evoked action potentials to follow high-frequency (100 Hz) repetitive stimulation. A further increase in K+ changed both the passive and the active membrane properties of the postganglionic neurone: time constant, membrane resistance and action potential overshoot were all decreased in high K+ (20 mm). The ICG neurones display a predominantly phasic discharge in response to prolonged depolarizing current pulses. High K+ had no impact on this behaviour but reduced the time-dependent rectification response to hyperpolarizing currents. At 20 mm, K+ practically blocked ganglionic transmission in most neurones at all frequencies tested. Aglycaemia, nominally glucose-free physiological saline solution (PSS), increased the time constant and membrane resistance of ICG neurones but otherwise had no action on their passive or active properties or ganglionic transmission. However, the combination of aglycaemia and 20 mm K+ displayed an improvement in passive properties and ganglionic transmission when compared with 20 mm K+ PSS. These data indicate that the presynaptic terminal is the primary target of high extracellular potassium and that aglycaemia may have protective actions against this challenge. [source] Characterization of Zebrafish Cx43.4 Connexin and its ChannelsEXPERIMENTAL PHYSIOLOGY, Issue 6 2003T. Desplantez Connexins (Cx) form intercellular junctional channels which are responsible for metabolic and electrical coupling. We report here on the biochemical and immunohistochemical characterization of zebrafish connexin zfCx43.4, an orthologue of mammalian and avian Cx45, and the electrophysiological properties of junctional channels formed by this protein. The investigations were performed on transfected COS-7 cells or HeLa cells. Using site-directed antibodies, zfCx43.4 cDNA (GenBank accession no. X96712) was demonstrated to code for a protein with a Mr of 45 000. In transfected cells, zfCx43.4 was localized in cell-cell contact areas as expected for a gap junction protein. zfCx43.4 channels were shown to transfer Lucifer Yellow. The multichannel currents were sensitive to the transjunctional voltage (Vj). Their properties were consistent with a two-state model and yielded the following Boltzmann parameters for negative/positive Vj: Vj,0= -38.4/41.9 mV; gj,min= 0.19/0.18; z = 2.6/2.3. These parameters deviate somewhat from those of zfCx43.4 channels expressed in Xenopus oocytes and from those of Cx45, an orthologue of zfCx43.4, expressed in mammalian cells or Xenopus oocytes. Conceivably, the subtle differences may reflect differences in experimental methods and/or in the expression system. The single channel currents yielded two prominent levels attributable to a main conductance state (,j,main= 33.2 ± 1.5 pS) and a residual conductance state (,j,residual= 11.9 ± 0.6 pS). [source] Regulation of L-type Ca++ currents and process morphology in white matter oligodendrocyte precursor cells by golli-myelin proteinsGLIA, Issue 11 2010Daniel Fulton Abstract The golli myelin basic proteins are expressed in oligodendroglial precursor cells (OPCs) where they play a role in regulating Ca2+ homeostasis. During depolarization, they influence process outgrowth and migration through their action on voltage-operated Ca2+ channels (VOCCs). To identify ion channels that are modulated by golli, we examined the electrophysiological properties of VOCCs in OPCs in the white matter of golli knock-out and control mice. OPCs exhibited two distinct Ca2+ channels, which were distinguished by their voltage dependence and pharmacological profiles and which exhibited many of the hallmarks of LVA/T-type and HVA/L-type Ca2+ channels. The density of high-voltage-activated (HVA) currents was reduced in OPCs recorded in golli-KO tissue, while low-voltage-activated (LVA) currents remained unaltered in these cells. These data indicate that golli exerts an exclusive influence on L-type Ca2+ channels in OPCs. Oligodendrocytes (OLs) also displayed LVA and HVA currents, although the density of these currents was much reduced at this developmental stage. These currents were not altered in golli-KO OLs showing the influence of golli on L-type Ca2+ channels is restricted to a specific time-window during the course of oligodendroglial development. The actions of golli on OPC L-type Ca2+ channels were accompanied by changes in process morphology, including a reduction in process complexity and the appearance of enlarged varicosities that decorated these cellular processes. These data on L-type Ca2+ channels and process development provide in situ evidence for the influence of golli on VOCCs, and offer an explanation for the hypomyelination observed in the brains of golli-KO mice. © 2010 Wiley-Liss, Inc. [source] Altered functional properties of satellite glial cells in compressed spinal gangliaGLIA, Issue 15 2009Haijun Zhang Abstract The cell bodies of sensory neurons in the dorsal root ganglion (DRG) are enveloped by satellite glial cells (SGCs). In an animal model of intervertebral foraminal stenosis and low-back pain, a chronic compression of the DRG (CCD) increases the excitability of neuronal cell bodies in the compressed ganglion. The morphological and electrophysiological properties of SGCs were investigated in both CCD and uninjured, control lumbar DRGs. SGCs responded within 12 h of the onset of CCD as indicated by an increased expression of glial fibrillary acidic protein (GFAP) in the compressed DRG but to lesser extent in neighboring or contralateral DRGs. Within 1 week, coupling through gap junctions between SGCs was significantly enhanced in the compressed ganglion. Under whole-cell patch clamp recordings, inward and outward potassium currents, but not sodium currents, were detected in individual SGCs. SGCs enveloping differently sized neurons had similar electrophysiological properties. SGCs in the compressed vs. control DRG exhibited significantly reduced inwardly rectifying potassium currents (Kir), increased input resistances and positively shifted resting membrane potentials. The reduction in Kir was greater for nociceptive medium-sized neurons compared to non-nociceptive neurons. Kir currents of SGCs around spontaneously active neurons were significantly reduced 1 day after compression but recovered by 7 days. These data demonstrate rapid alterations in glial membrane currents and GFAP expression in close temporal association with the development of neuronal hyperexcitability in the CCD model of neuropathic pain. However, these alterations are not fully sustained and suggest other mechanisms for the maintenance of the hyperexcitable state. © 2009 Wiley-Liss, Inc. [source] Comparison of spontaneous and septally driven hippocampal theta field and theta-related cellular activityHIPPOCAMPUS, Issue 1 2004Darren Scarlett Abstract Experiments were carried out for the purpose of comparing the electrophysiological properties of spontaneously occurring hippocampal theta field activity with those of theta-like field activity elicited by 5-Hz and 7-Hz electrical stimulation of the medial septum in urethane-anesthetized rats. Experiment 1 compared the amplitude and phase depth profiles for the three conditions of spontaneously occurring theta, theta elicited by 5-Hz medial septal stimulation, and theta elicited by 7-Hz medial septal stimulation. The results supported the conclusion that septally elicited theta field activity exhibited characteristics similar to those of spontaneously occurring theta field activity. Experiment 2 compared the discharge properties of hippocampal theta-related cellular discharges during spontaneous and septally elicited theta field activity. In contrast to the results of Experiment 1, the findings of Experiment 2 supported the conclusion that electrical stimulation of medial septal nuclei did not produce typical responses of hippocampal theta-related cellular activity. During spontaneously occurring field conditions, HPC theta-ON cells increased their discharge rates during spontaneous theta field activity, relative to LIA, and theta-OFF cells decreased (often to zero) their discharge rates during theta field activity relative to LIA. During septally elicited theta-like activity, phasic and tonic theta-ON cells decreased their discharge rates (some were totally inhibited), and most tonic theta-OFF cells increased their discharge rates (although two were totally inhibited). In addition, the discharges (albeit reduced) of the majority of both phasic and tonic theta-ON cells during septal driving became entrained to the stimulation pulses and thus exhibited rhythmicity and strong phase relations with the field activity. Furthermore, both cell types discharged near the positive peak of the septally elicited theta field activity during 5-Hz stimulation and near the negative peak during 7-Hz stimulation. The discharges of most tonic theta-OFF cells also became entrained to the stimulation pulses and exhibited similar phase relations to theta-ON cells during the 5-Hz and 7-Hz driving frequencies. Thus, based on cellular evidence, electrical stimulation of the medial septum activates the hippocampal neural circuitry involved in the generation of theta field activity in a nonphysiological manner. The findings of the present paper provide an explanation for why electrical stimulation of the medial septum in freely moving rats elicits a theta-like field activity that is dissociated from the normal behavioral correlates, in contrast to those elicited by stimulation of the posterior nucleus of the hypothalamus (Bland and Oddie. 2001. Behav Brain Res 127:119,136). © 2003 Wiley-Liss, Inc. [source] Efficient generation of mature cerebellar Purkinje cells from mouse embryonic stem cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2010Osamu Tao Abstract Mouse embryonic stem cells (ESCs) can generate cerebellar neurons, including Purkinje cells (PCs) and their precursor cells, in a floating culture system called serum-free culture of embryoid body-like aggregates (SFEB) treated with BMP4, Fgf8b, and Wnt3a. Here we successfully established a coculture system that induced the maturation of PCs in ESC-derived Purkinje cell (EDPC) precursors in SFEB, using as a feeder layer a cerebellum dissociation culture prepared from mice at postnatal day (P) 6,8. PC maturation was incomplete or abnormal when the adherent culture did not include feeder cells or when the feeder layer was from neonatal cerebellum. In contrast, EDPCs exhibited the morphology of mature PCs and synaptogenesis with other cerebellar neurons when grown for 4 weeks in coculture system with the postnatal cerebellar feeder. Furthermore, the electrophysiological properties of these EDPCs were compatible with those of native mature PCs in vitro, such as Na+ or Ca2+ spikes elicited by current injections and excitatory or inhibitory postsynaptic currents, which were assessed by whole-cell patch-clamp recordings. Thus, EDPC precursors in SFEB can mature into PCs whose properties are comparable with those of native PCs in vitro. © 2009 Wiley-Liss, Inc. [source] Electrophysiological characterization of neural stem/progenitor cells during in vitro differentiation: Study with an immortalized neuroectodermal cell lineJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2007M. Jelitai Abstract Despite the accumulating data on the molecular and cell biological characteristics of neural stem/progenitor cells, their electrophysiological properties are not well understood. In the present work, changes in the membrane properties and current profiles were investigated in the course of in vitro-induced neuron formation in NE-4C cells. Induction by retinoic acid resulted in neuronal differentiation of about 50% of cells. Voltage-dependent Na+ currents appeared early in neuronal commitment, often preceding any morphological changes. A-type K+ currents were detected only at the stage of network formation by neuronal processes. Flat, epithelial- like, nestin-expressing progenitors persisted beside differentiated neurons and astrocytes. Stem/progenitor cells were gap junction coupled and displayed large, symmetrical, voltage-independent currents. By the blocking of gap junction communication, voltage-independent conductance was significantly reduced, and delayed-rectifying K+ currents became detectable. Our data indicate that voltage-independent symmetrical currents and gap junction coupling are characteristic physiological features of neural stem and progenitor cells regardless of the developmental state of their cellular environment. © 2007 Wiley-Liss, Inc. [source] Acute Effects of Low Doses of Red Wine on Cardiac Conduction and Repolarization in Young Healthy SubjectsALCOHOLISM, Issue 12 2009Matteo Cameli Background:, Moderate to high blood concentrations of ethanol have been shown to yield acute changes in cardiac electrophysiological properties, but the effect of low concentrations have never been assessed. The role of concomitant changes in clinical variables or cardiac dimensions is also still unknown. This study aimed at exploring the acute effects of low doses of ethanol, administered as Italian red wine, on conduction, depolarization, and repolarization electrocardiographic (ECG) intervals in a population of healthy subjects. Methods:, Forty healthy young volunteers drank a low quantity of red wine (5 ml/kg), and an equal volume of fruit juice in separate experiments. Heart rate, P-wave duration, PR interval, QRS duration, QT interval, corrected QT interval, QT dispersion, and corrected QT dispersion were assessed at baseline and after 60 minutes from challenge. Results:, Mean blood ethanol concentration after drinking was 0.48 ± 0.06 g/l. Compared to the control challenge, significant changes after red wine intake were observed in P-wave duration (from 101 ± 11 to 108 ± 14 milliseconds, p = 0.0006), PR interval (from 153 ± 15 to 167 ± 17 milliseconds, p < 0.0001), QT interval (from 346 ± 28 to 361 ± 24 milliseconds, p < 0.0001), and corrected QT interval (from 388 ± 24 to 402 ± 30 milliseconds, p = 0.0006). None of these changes showed correlations with modifications in clinical or echocardiographic variables. In multivariate analyses aimed at exploring predictors of ECG changes, none of the variables entered the final models. Conclusions:, Low doses of red wine acutely slow cardiac conduction and prolong repolarization in normal individuals. These changes are poorly predictable. The potential arrhythmogenic impact of these effects is worthy of exploration. [source] Characterization of a human fetal spinal cord stem cell line, NSI-566RSC, and its induction to functional motoneuronsJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 3 2010Xiufang Guo Abstract Specific neuronal subtypes, especially motoneurons (MNs), derived from human stem cells provide a significant therapeutic potential for spinal cord diseases, such as amyotrophic lateral sclerosis (ALS) and spinal cord injury. So far, in vitro, MNs have only been successfully induced from embryonic stem cells (hESC) and human fetal cortical progenitors. Although neural progenitors from spinal cord would be a likely source for generating MNs, there has been no study reporting successful in vitro differentiation of MNs from spinal cord progenitors. This study first characterized a polyclonal spinal cord stem cell line isolated from an 8 week-old fetus. Then a paradigm was introduced to successfully induce MNs from this cell line, which was demonstrated by immunostaining using the MN markers HB9, Islet1 and choline acetyl transferase (ChAT). The combination of HB9 and ChAT immunostainings indicated that ,20% of the cells were MNs after this induction protocol. The presence of other cell types in the differentiated culture was also analysed. Finally, the electrophysiological properties of these differentiated MNs were characterized to confirm their functional integrity. The majority of these MNs fired repetitive action potentials (APs), which is an indicator of functional maturation. The recordings of spontaneous excitatory postsynaptic currents (EPSCs) confirmed the formation of synapses onto these MNs. This study reports the first successful differentiation of MNs from human spinal cord stem cells in vitro, providing a novel approach for obtaining functional MNs when designing the therapeutic strategy for spinal cord diseases or injuries. Copyright © 2009 John Wiley & Sons, Ltd. [source] Atrial Activation Occurring Immediately after Successful Cardioversion of Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2008ARTURO MARTÍN PEŃATO MOLINA M.D. Background and Objective: Electrical defibrillation is very effective in interrupting atrial fibrillation (AF). However, its mechanism is not completely understood. We report our observations in patients subjected to external electriocardioversion (ECV) of atrial fibrillation and contrast them with recent theories about defibrillation mechanism. Methods: In 13 consecutive patients transthoracic electrical cardioversion for AF was performed during an electrophysiological study (11 monophasic -200,360 J- and 9 biphasic shocks -50,150 J-). About 10,16 electrograms were obtained with multipolar catheters recording right atrium, coronary sinus, and right pulmonary artery. AF was defined by interelectrogram intervals and changing sequences among recordings, indicating complete lack of organization. We evaluated the presence of propagated activations immediately (<300 ms) after successful shocks (,1 discrete electrogram in all recordings). In unsuccessful shocks we evaluated changes in electrogram morphology (discrete/fragmented) and interelectrogram intervals before and after defibrillation. Results: About 16/20 shocks terminated AF. In 6/16 one or two cycles of atrial activation were recorded just after the shock and before AF ended. In 10/16 AF was interrupted immediately after the shock. 4/20 shocks did not interrupt the arrhythmia. After these shocks, transient organization of recorded activity with longer interelectrogram cycle length and disappearance of fragmented activity were transiently observed. Conclusion: Our clinical findings in atrial defibrillation in vivo reproduce experimental data that show myocardial activations early after successful direct current shocks. These observations suggest that successful defibrillation depends not only on the immediate effects of the shock, but also on transient effects on electrophysiological properties of the myocardium, capable of interrupting persistent or reinitiated activations. [source] Dissociated Activity and Pulmonary Vein Fibrillation Following Functional Disconnection:PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2003Impact for the Arrhythmogenesis of Focal Atrial Fibrillation The present study sought to investigate the electrophysiological properties of isolated pulmonary veins following successful radiofrequency (RF) catheter ablation in patients with paroxysmal atrial fibrillation (PAF). Overall, 71 pulmonary veins in 37 consecutive patients (age:56 ± 9 years) with recurrent PAF were targeted for RF ablation at the ostial region in order to achieve a complete functional block. Following disconnection, the incidence of dissociated pulmonary vein (PV) activity and its response to orciprenalin were studied. RF ablation abolished conduction in 67 (94%) of 71 potentially arrhythmogenic PVs after a mean of10.7 ± 6.4 RFapplications for each PV. After ablation, spontaneous dissociated automatic activity (9 to 52 beats/min, median 27) was found in 6 out of 67 isolated PVs (left superior:n = 1, left inferior:n = 1, right superior:n = 2, common left PV:n = 2). Slight acceleration (13 to 68 beats/min, median 29) of dissociated PV activity was observed during infusion of orciprenalin. Following isolation, initiation of sustained or nonsustained local fibrillation was recorded in only two cases of the common left sided PV with preceding automatic activity. In one patient PV fibrillation occurred during orciprenalin infusion following a repetitive response to a dissociated automatic rhythm with increasing duration as well as destabilization. In the other patient, PV fibrillation occurred immediately after the occurrence of PV automaticity. Slow dissociated automatic rhythms are detectable within 9% of disconnected PVs. The unique anatomic substrate of common left PVs seem to favor the occurrence of local fibrillation following isolation. The initiation pattern of fibrillation within the isolated PV has pathophysiological implications and underlines the contribution of multiple factors to the onset and sustenance of PAF. (PACE 2003; 26:1363,1370) [source] Relation of Age and Sex to Atrial Electrophysiological Properties in Patients with No History of Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2003KOICHI SAKABE Although atrial fibrillation is a common arrhythmia, especially in elderly men, little is known about age related changes in atrial electrophysiological properties or gender differences. The aim of this study was to analyze the effects of aging on vulnerability to atrial fibrillation and assessed gender differences in those age related changes. An electrophysiological study was performed on 73 patients with no history of atrial fibrillation, structural heart disease, or conditions with potential effects on cardiac hemodynamic or electrophysiological function, including 25 women (mean age 49 ± 18 years; range 12,84 years). The following atrial excitability parameters were assessed: spontaneous or paced (A1) and extrastimulated (A2) atrial electrogram widths, percent maximum atrial fragmentation(A2/A1 × 100), effective refractory period, wavelength index (effective refractory period/A2), and inducibility of atrial fibrillation. There were no significant differences in percent maximum atrial fragmentation (143 ± 28vs142 ± 35%), effective refractory period (241 ± 39vs238 ± 50 ms), wavelength index (2.9 ± 0.8vs3.1 ± 0.9), induction of atrial fibrillation (10 [21%] vs 7 [28%]), or age (50 ± 17vs 49 ± 20 years) between men and women. Age was not statistically different between those patients with and without induction of atrial fibrillation in men (48 ± 14vs50 ± 18 years) and women (48 ± 18vs49 ± 21 years). Percent maximum atrial fragmentation and effective refractory period were directly correlated with age in men (r = 0.35, P = 0.01; r = 0.46, P < 0.001, respectively) and women (r = 0.42, P = 0.04; r = 0.45, P = 0.02, respectively), though wavelength index did not correlate with age in men (r =,0.04) or women (r =,0.04) with no history of atrial fibrillation. Considering these findings, the authors conclude that the mechanism triggering atrial fibrillation may be different between older and younger patients with atrial fibrillation, because younger patients who have no marked substrate for atrial fibrillation may need many trigger beats to induce atrial fibrillation. (PACE 2003; 26:1238,1244) [source] Effects of Sex and Age on Electrocardiographic and Cardiac Electrophysiological Properties in AdultsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2001TARESH TANEJA TANEJA, T., et al.: Effects of Sex, and Age on Electrocardiographic and Cardiac Electrophysiological Properties in Adults. Although differences in patient sex in heart rate and QT interval have been well characterized, sexual differences in other cardiac electrophysiological properties have not been well defined. The study population consisted of 354 consecutive patients without structural heart disease or preexcitation who underwent clinically indicated electrophysiological testing in the drug-free state. Atrial, AV nodal, and ventricular effective refractory periods (AERP, AVNERP, VERP) were determined at a pacing cycle length of 500 ms using an 8-beat drive train and 3-second intertrain pause. There were 124 men and 230 women with a mean age of 45 ± 19 and 47 ± 18 years, respectively The sinus cycle length (SCL) was longer in men than in women (864 ± 186 and 824 ± 172 ms, respectively, P < 0.05). The QRS duration was significantly longer in men (90 ± 12 ms) than women (86 ± 13 ms) (P < 0.005). The HV interval was 48 ± 9 ms in men and 45 ± 8 ms in women (P < 0.05). The sinus node recovery time (SNRT) was significantly longer in men than in women (1215 ± 297 ms and 1135 ± 214 ms, respectively, P < 0.05). AERP and VERP were similar in both sexes. Aging did not influence sexual differences in cardiac electrophysiological properties, although, it independently prolonged the SCL, PR, and QT intervals, AH and HV intervals, SNRT, AVNERP, and the AV Wenckebach cycle length. The SCL, QRS duration, HV interval, and SNRT were significantly longer in men than in women. Aging prolonged cardiac conduction and increased the SCL but the effects were similar in both sexes. AERP and VERP were unaffected by aging or sex. [source] Flavonoids from Chinese Viscum coloratum: antiarrhythmic efficacy and ionic mechanismsPHYTOTHERAPY RESEARCH, Issue 12 2006Chu Wen-Feng Abstract Viscum coloratum flavonoids (VCF) have been demonstrated to produce a variety of biological actions. An accumulating line of evidence supported the view that VCF may exert protective effects on the cardiovascular system. The aim of the study was to assess the antiarrhythmic activity as well as the electrophysiological properties of VCF. The antiarrhythmic effects of VCF were observed in a rat model of arrhythmia induced by aconitine. VCF significantly and dose-dependently increased the dosage of aconitine required to induce the arrhythmia indexes. Electrophysiological experiment revealed that VCF shortened APD through inhibition of ICa-L. Copyright © 2006 John Wiley & Sons, Ltd. [source] Spatiotemporal characteristics of astroglial death in the rat hippocampo-entorhinal complex following pilocarpine-induced status epilepticusTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2008Duk-Soo Kim Abstract Recently we reported that astroglial loss and subsequent gliogenesis in the dentate gyrus play a role in epileptogenesis following pilocarpine-induced status epilepticus (SE). In the present study we investigated whether astroglial damages in the hippocampo-entorhinal complex following SE are relevant to pathological or electrophysiological properties of temporal lobe epilepsy. Astroglial loss/damage was observed in the entorhinal cortex and the CA1 region at 4 weeks and 8 weeks after SE, respectively. These astroglial responses in the hippocampo-entorhinal cortex were accompanied by hyperexcitability of the CA1 region (impairment of paired-pulse inhibition and increase in excitability ratio). Unlike the dentate gyrus and the entorhinal cortex, CA1 astroglial damage was protected by conventional anti-epileptic drugs. ,-Aminoadipic acid (a specific astroglial toxin) infusion into the entorhinal cortex induced astroglial damage and changed the electrophysiological properties in the CA1 region. Astroglial regeneration in the dentate gyrus and the stratum oriens of the CA1 region was found to originate from gliogenesis, while that in the entorhinal cortex and stratum radiatum of the CA1 region originated from in situ proliferation. These findings suggest that regional specific astroglial death/regeneration patterns may play an important role in the pathogenesis of temporal lobe epilepsy. J. Comp. Neurol. 511:581,598, 2008. © 2008 Wiley-Liss, Inc. [source] Differences in sodium voltage-gated channel properties according to myosin heavy chain isoform expression in single muscle fibresTHE JOURNAL OF PHYSIOLOGY, Issue 21 2009F. Rannou The myosin heavy chain (MHC) isoform determines the characteristics and shortening velocity of muscle fibres. The functional properties of the muscle fibre are also conditioned by its membrane excitability through the electrophysiological properties of sodium voltage-gated channels. Macropatch-clamp is used to study sodium channels in fibres from peroneus longus (PL) and soleus (Sol) muscles (Wistar rats, n= 8). After patch-clamp recordings, single fibres are identified by SDS-PAGE electrophoresis according to their myosin heavy chain isoform (slow type I and the three fast types IIa, IIx, IIb). Characteristics of sodium currents are compared (Student's t test) between fibres exhibiting only one MHC isoform. Four MHC isoforms are identified in PL and only type I in Sol single fibres. In PL, maximal sodium current (Imax), maximal sodium conductance (gNa,max) and time constants of activation and inactivation (,m and ,h) increase according to the scheme I,IIa,IIx,IIb (P < 0.05). ,m values related to sodium channel type and/or function, are similar in Sol I and PL IIb fibres (P= 0.97) despite different contractile properties. The voltage dependence of activation (Va,1/2) shows a shift towards positive potentials from Sol type I to IIa, IIx and finally IIb fibres from PL (P < 0.05). These data are consistent with the earlier recruitment of slow fibres in a fast-mixed muscle like PL, while slow fibres of postural muscle such as soleus could be recruited in the same ways as IIb fibres in a fast muscle. [source] | ||||||||||||||||||||||||||||