scholarly journals Ion channel activity in lobster skeletal muscle membrane

1993 ◽  
Vol 182 (1) ◽  
pp. 113-130
Author(s):  
M. K. Worden ◽  
R. Rahamimoff ◽  
E. A. Kravitz
Keyword(s):  
Ion Channel ◽  
Single Channel ◽  
Muscle Fibers ◽  
Muscle Membrane ◽  
Channel Activity ◽  
Experimental Conditions ◽  
Sarcolemmal Membrane ◽  
Excised Patches ◽  
Current Flows

Ion channel activity in the sarcolemmal membrane of muscle fibers is critical for regulating the excitability, and therefore the contractility, of muscle. To begin the characterization of the biophysical properties of the sarcolemmal membrane of lobster exoskeletal muscle fibers, recordings were made from excised patches of membrane from enzymatically induced muscle fiber blebs. Blebs formed as evaginations of the muscle sarcolemmal membrane and were sufficiently free of extracellular debris to allow the formation of gigaohm seals. Under simple experimental conditions using bi-ionic symmetrical recording solutions and maintained holding potentials, a variety of single channel types with conductances in the range 32–380 pS were detected. Two of these ion channel species are described in detail, both are cation channels selective for potassium. They can be distinguished from each other on the basis of their single-channel conductance and gating properties. The results suggest that current flows through a large number of ion channels that open spontaneously in bleb membranes in the absence of exogenous metabolites or hormones.

scholarly journals Neuromuscular junction-specific genes screening by deep RNA-seq analysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tiankun Hui ◽  
Hongyang Jing ◽  
Xinsheng Lai
Keyword(s):  
Ion Channel ◽  
Neuromuscular Junctions ◽  
Gene Set Enrichment Analysis ◽  
Differentially Expressed ◽  
Muscle Membrane ◽  
Receptor Interaction ◽  
Specific Gene ◽  
Rna Seq ◽  
Channel Activity ◽  
Ppi Networks

Abstract Background Neuromuscular junctions (NMJs) are chemical synapses formed between motor neurons and skeletal muscle fibers and are essential for controlling muscle contraction. NMJ dysfunction causes motor disorders, muscle wasting, and even breathing difficulties. Increasing evidence suggests that many NMJ disorders are closely related to alterations in specific gene products that are highly concentrated in the synaptic region of the muscle. However, many of these proteins are still undiscovered. Thus, screening for NMJ-specific proteins is essential for studying NMJ and the pathogenesis of NMJ diseases. Results In this study, synaptic regions (SRs) and nonsynaptic regions (NSRs) of diaphragm samples from newborn (P0) and adult (3-month-old) mice were used for RNA-seq. A total of 92 and 182 genes were identified as differentially expressed between the SR and NSR in newborn and adult mice, respectively. Meanwhile, a total of 1563 genes were identified as differentially expressed between the newborn SR and adult SR. Gene Ontology (GO) enrichment analyses, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and gene set enrichment analysis (GSEA) of the DEGs were performed. Protein–protein interaction (PPI) networks were constructed using STRING and Cytoscape. Further analysis identified some novel proteins and pathways that may be important for NMJ development, maintenance and maturation. Specifically, Sv2b, Ptgir, Gabrb3, P2rx3, Dlgap1 and Rims1 may play roles in NMJ development. Hcn1 may localize to the muscle membrane to regulate NMJ maintenance. Trim63, Fbxo32 and several Asb family proteins may regulate muscle developmental-related processes. Conclusion Here, we present a complete dataset describing the spatiotemporal transcriptome changes in synaptic genes and important synaptic pathways. The neuronal projection-related pathway, ion channel activity and neuroactive ligand-receptor interaction pathway are important for NMJ development. The myelination and voltage-gated ion channel activity pathway may be important for NMJ maintenance. These data will facilitate the understanding of the molecular mechanisms underlying the development and maintenance of NMJ and the pathogenesis of NMJ disorders.

scholarly journals TOK Homologue in Neurospora crassa: First Cloning and Functional Characterization of an Ion Channel in a Filamentous Fungus

2003 ◽  
Vol 2 (1) ◽  
pp. 181-190 ◽  
Author(s):  
Stephen K. Roberts
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Neurospora Crassa ◽  
Filamentous Fungus ◽  
Single Channel ◽  
Functional Characterization ◽  
Reversal Potential ◽  
Channel Activity ◽  
Biophysical Properties ◽  
Patch Clamp Technique

ABSTRACT In contrast to animal and plant cells, very little is known of ion channel function in fungal physiology. The life cycle of most fungi depends on the “filamentous” polarized growth of hyphal cells; however, no ion channels have been cloned from filamentous fungi and comparatively few preliminary recordings of ion channel activity have been made. In an attempt to gain an insight into the role of ion channels in fungal hyphal physiology, a homolog of the yeast K+ channel (ScTOK1) was cloned from the filamentous fungus, Neurospora crassa. The patch clamp technique was used to investigate the biophysical properties of the N. crassa K+ channel (NcTOKA) after heterologous expression of NcTOKA in yeast. NcTOKA mediated mainly time-dependent outward whole-cell currents, and the reversal potential of these currents indicated that it conducted K+ efflux. NcTOKA channel gating was sensitive to extracellular K+ such that channel activation was dependent on the reversal potential for K+. However, expression of NcTOKA was able to overcome the K+ auxotrophy of a yeast mutant missing the K+ uptake transporters TRK1 and TRK2, suggesting that NcTOKA also mediated K+ influx. Consistent with this, close inspection of NcTOKA-mediated currents revealed small inward K+ currents at potentials negative of EK. NcTOKA single-channel activity was characterized by rapid flickering between the open and closed states with a unitary conductance of 16 pS. NcTOKA was effectively blocked by extracellular Ca2+, verapamil, quinine, and TEA+ but was insensitive to Cs+, 4-aminopyridine, and glibenclamide. The physiological significance of NcTOKA is discussed in the context of its biophysical properties.

Persistence: a new statistic for characterizing ion-channel activity

1995 ◽  
Vol 350 (1334) ◽  
pp. 353-367 ◽  
Keyword(s):  
Patch Clamp ◽  
Ion Channel ◽  
Single Channel ◽  
Statistical Technique ◽  
Channel Activity ◽  
Patch Clamp Recording ◽  
Conductance Level

We introduce and illustrate by examples a new statistical technique, the persistence function, for characterizing ion-channel activity in a single-channel patch-clamp recording. Persistence is a function of both current and time. It is the probability that the current is at a given level (conditional on it having been at that level at an earlier time). Viewed as a function of current it exhibits the prominent conductance levels present in the recording, and viewed as a function of time for a conductance level it portrays the kinetics at that level.

scholarly journals Characterization of ryanodine receptor type 1 single channel activity using “on-nucleus” patch clamp

Cell Calcium ◽  
2014 ◽  
Vol 56 (2) ◽  
pp. 96-107 ◽  
Author(s):  
Larry E. Wagner ◽  
Linda A. Groom ◽  
Robert T. Dirksen ◽  
David I. Yule
Keyword(s):  
Patch Clamp ◽  
Ryanodine Receptor ◽  
Single Channel ◽  
Receptor Type ◽  
Channel Activity ◽  
Single Channel Activity

A calcium -activated cation-selective channel in rat cultured Schwann cells

1984 ◽  
Vol 222 (1228) ◽  
pp. 349-355 ◽  
Keyword(s):  
Schwann Cells ◽  
Single Channel ◽  
Outward Current ◽  
Channel Activity ◽  
Experimental Conditions ◽  
Cultured Schwann Cells ◽  
Selective Channel ◽  
Inside Out ◽  
Cation Selective Channel ◽  
Sodium And Potassium

Calcium -activated channels, in the plasm a membrane of rat cultured Schwann cells were studied in isolated ‘inside-out’ membrane patches. With identical (150 mM NaCl) solutions on either side of the membrane, a single channel conductance of 32 pS was calculated for inward current; the conductance was somewhat less for outward current. The channel is about equally permeable to sodium and potassium ions, bu t is not detectably permeable to either chloride or calcium. Under our experimental conditions the channel is activated by high (more than 10 -4 m) concentrations of calcium and is sensitive to voltage, channel activity increasing with membrane depolarization.

scholarly journals Adenosine and anoxia reduce N-methyl-D-aspartate receptor open probability in turtle cerebrocortex.

1998 ◽  
Vol 201 (2) ◽  
pp. 289-297 ◽  
Author(s):  
L T Buck ◽  
P E Bickler
Keyword(s):  
Membrane Potential ◽  
Nmda Receptor ◽  
Ion Channel ◽  
Single Channel ◽  
Tissue Injury ◽  
Brain Slices ◽  
Current Amplitude ◽  
Mammalian Brain ◽  
Open Probability ◽  
Experimental Conditions

During normoxia, glutamate and the glutamate family of ion channels play a key role in mediating rapid excitatory synaptic transmission in the central nervous system. However, during hypoxia, intracellular [Ca2+] increases to neurotoxic levels, mediated largely by the N-methyl-D-aspartate (NMDA) subfamily of glutamate receptors. Adenosine has been shown to decrease the magnitude of the hypoxia-induced increase in [Ca2+]i in mammalian brain slices, delaying tissue injury. Turtle brain is remarkably tolerant of anoxia, maintaining a pre-anoxic [Ca2+]i while cerebral adenosine levels increase 12-fold. Employing cell-attached single-channel patch-clamp techniques, we studied the effect of adenosine (200 micromol l-1) and anoxia on NMDA receptor open probability (Popen) and current amplitude. After 60 min of anoxic perfusion, channel Popen decreased by 65 % (from 6.8+/-1.6 to 2.4+/-0.8 %) an effect that could also be achieved with a normoxic perfusion of 200 micromol l-1 adenosine (Popen decreased from 5.8+/-1.1 to 2.3+/-1.2 %). The inclusion of 10 micromol l-1 8-phenyltheophylline, an A1 receptor blocker, prevented the adenosine- and anoxia-induced decrease in Popen. Mean single-channel current amplitude remained at approximately 2.7+/-0.23 pA under all experimental conditions. To determine whether a change in the membrane potential could be part of the mechanism by which Popen decreases, membrane and threshold potential were measured following each experiment. Membrane potential did not change significantly under any condition, ranging from -76.8 to -80.6 mV. Therefore, during anoxia, NMDA receptors cannot be regulated by Mg2+ in a manner dependent on membrane potential. Threshold potentials did decrease significantly following 60 min of anoxic or adenosine perfusion (control -33.3+/-1.9 mV, anoxia -28.4+/-1.5 mV, adenosine -23.4+/-2.8 mV). We conclude that anoxia modulates NMDA receptor activity and that adenosine plays a key role in mediating this change. This is the first direct measurement of ion channel activity in anoxic turtle brain and demonstrates that ion channel regulation is part of the naturally evolved anoxic defence mechanism of this species.

Design, synthesis, and characterization of peptide nanostructures having ion channel activity

2004 ◽  
Vol 12 (6) ◽  
pp. 1279-1290 ◽  
Author(s):  
Eric Biron ◽  
François Otis ◽  
Jean-Christophe Meillon ◽  
Martin Robitaille ◽  
Julie Lamothe ◽  
...  
Keyword(s):  
Ion Channel ◽  
Synthesis And Characterization ◽  
Channel Activity ◽  
Design Synthesis
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