Membrane potential and threshold of single muscle fibers

1953 ◽  
Vol 42 (1) ◽  
pp. 79-102 ◽  
Author(s):  
H. P. Jenerick ◽  
R. W. Gerard
Keyword(s):  
Membrane Potential ◽  
Muscle Fibers ◽  
Single Muscle

scholarly journals Graded Activation in Frog Muscle Fibers

1973 ◽  
Vol 61 (4) ◽  
pp. 424-443 ◽  
Author(s):  
L. L. Costantin ◽  
S. R. Taylor
Keyword(s):  
Membrane Potential ◽  
Voltage Clamp ◽  
Cross Section ◽  
Muscle Fibers ◽  
Frog Muscle ◽  
Single Muscle ◽  
Fiber Cross Section ◽  
Striation Spacing ◽  
Velocity Of Shortening ◽  
Electrode Voltage

The membrane potential of frog single muscle fibers in solutions containing tetrodotoxin was controlled with a two-electrode voltage clamp. Local contractions elicited by 100-ms square steps of depolarization were observed microscopically and recorded on cinefilm. The absence of myofibrillar folding with shortening to striation spacings below 1.95 µm served as a criterion for activation of the entire fiber cross section. With depolarizing steps of increasing magnitude, shortening occurred first in the most superficial myofibrils and spread inward to involve axial myofibrils as the depolarization was increased. In contractions in which the entire fiber cross section shortened actively, both the extent of shortening and the velocity of shortening at a given striation spacing could be graded by varying the magnitude of the depolarization step. The results provide evidence that the degree of activation of individual myofibrils can be graded with membrane depolarization.

Kinetics of L-glutamate influx in single barnacle muscle fibers under 0-trans conditions

1992 ◽  
Vol 262 (6) ◽  
pp. C1485-C1490
Author(s):  
L. W. Horn
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Binding Site ◽  
Kinetic Models ◽  
Glutamate Uptake ◽  
Muscle Fibers ◽  
Single Muscle ◽  
Constant Flux ◽  
Kinetics Of ◽  
Barnacle Muscle Fibers

The dependence of L-glutamate influx on extracellular Na and L-glutamate concentrations was determined using internally dialyzed single muscle fibers of Balanus nubilus. Internal Na and glutamate concentrations were held at zero, and the cell membrane potential was constant. Flux activation curves for external glutamate were measured for five different external Na concentrations, and flux activation curves for external Na were measured independently for three different external glutamate concentrations. An analysis of alternative kinetic models for the transporter mechanism was made and led to the conclusions that under 0-trans conditions the Na:glutamate stoichiometry is 1:1, that glutamate first binding to the external transporter binding site is the preferred order under most extracellular conditions, and that the Na:glutamate coupling is too tight to permit measurable Na-independent glutamate uptake by the transporter.

scholarly journals Length-dependent electromechanical coupling in single muscle fibers.

1976 ◽  
Vol 68 (6) ◽  
pp. 653-669 ◽  
Author(s):  
A M Gordon ◽  
E B Ridgway
Keyword(s):  
Membrane Potential ◽  
Calcium Release ◽  
Muscle Fibers ◽  
Membrane Properties ◽  
Constant Current ◽  
Equilibrium Potential ◽  
Muscle Membrane ◽  
Single Muscle ◽  
Fiber Membrane ◽  
Length Dependence

In single muscle fibers from the giant barnacle, a small decrease in muscle length decreases both the calcium activation and the peak isometric tension produced by a constant current stimulus. The effect is most pronounced if the length change immediately precedes the stimulation. In some cases, the decrease in tension with shortening can be accounted for almost entirely by a decrease in calcium release rather than changes in mechanical factors such as filament geometry. During the constant current stimulation the muscle membrane becomes more depolarized at longer muscle lengths than at the shorter muscle lengths. Under voltage clamp conditions, when the membrane potential is kept constant during stimulation, there is little length dependence of calcium release. Thus, the effect of length on calcium release is mediated through a change in membrane properties, rather than an effect on a subsequent step in excitation-contraction coupling. Stretch causes the unstimulated fiber membrane to depolarize by about l mV while release causes the fiber membrane to hyperpolarize by about the same amount. The process causing this change in potential has an equilibrium potential nearly 10 mV hyperpolarized from the resting level. This change in resting membrane potential with length may account for the length dependence of calcium release.

scholarly journals Relation between Membrane Potential Changes and Tension in Barnacle Muscle Fibers

1964 ◽  
Vol 48 (2) ◽  
pp. 225-234 ◽  
Author(s):  
Charles Edwards ◽  
Shiko Chichibu ◽  
Susumu Hagiwara
Keyword(s):  
Membrane Potential ◽  
Muscle Fibers ◽  
State Level ◽  
Metal Electrode ◽  
Constant Current ◽  
Single Muscle ◽  
Membrane Potential Change ◽  
Mechanical Factors ◽  
Set Up ◽  
Barnacle Muscle Fibers

Constant current pulses have been applied to single muscle fibers of the barnacle, Balanus nubilus Darwin, with an axial metal electrode. The membrane potential change, which took place over a large part of the muscle fiber, was measured with a similar electrode. Depolarizing pulses, if the voltage was greater than threshold, produced tension. The size of the tension was a function of the magnitude and the duration of the depolarizing pulses. The latency between the onset of depolarization and tension can be only in part attributable to mechanical factors. AC stimulation produced tension, but 5 to 10 seconds were required for the steady-state level of the tension to be reached. Muscles were depolarized in elevated K and studied after the contracture had terminated. If not too depolarized, further depolarization produced tension. Termination of hyperpolarizing pulses also produced tension, which decayed quite slowly. Hyperpolarizing pulses reduced, or abolished, any preexisting tension. Thus, it appears that at certain values of the membrane potential tension is set up, but there is also a slow process of accommodation present.

scholarly journals DISSECTION AND ELECTROPHORETIC PROTEIN ANALYSIS OF SINGLE MUSCLE FIBERS FROM HISTOLOGICALLY IDENTIFIED FREEZE-DRIED SECTIONS: APPLICATION TO MUSCLE FIBERS WITH RIMMED VACUOLES

1983 ◽  
Vol 4 (5) ◽  
pp. 459-466 ◽  
Author(s):  
ITARU TOYOSHIMA ◽  
KEIKO TANAKA ◽  
NOBUYOSHI FUKUHARA ◽  
TOSHIHIDE KUMAMOTO ◽  
TADASHI MIYATAKE
Keyword(s):  
Muscle Fibers ◽  
Protein Analysis ◽  
Single Muscle ◽  
Freeze Dried

Effects of calcium on membrane potential and sodium influx in barnacle muscle fibers

1983 ◽  
Vol 244 (3) ◽  
pp. C297-C302 ◽  
Author(s):  
S. S. Sheu ◽  
M. P. Blaustein
Keyword(s):  
Membrane Potential ◽  
Muscle Fibers ◽  
Cation Channels ◽  
Channel Blockers ◽  
Sodium Influx ◽  
Permeable Channel ◽  
Barnacle Muscle ◽  
Nonselective Cation Channels ◽  
Flux Measurements ◽  
Barnacle Muscle Fibers

The influence of internal and external Ca2+ on membrane potential and 22Na influx were tested in internally perfused giant barnacle muscle fibers. The fibers depolarized by about 2-3 mV, and Na+ influx increased when external Ca2+ was removed. These effects were inhibited and reversed by adding 2 mM La3+ externally but not by tetrodotoxin (TTX). Ca2+ channel blockers did not prevent the depolarization. Increasing internal free Ca2+ ([Ca2+]i) from 10(-7) to 10(-5) M also stimulated Na+ influx and depolarized the fibers by a few millivolts. Neither external La3+ nor TTX prevented the effects of raising [Ca2+]i; however, internal tetrabutylammonium ions depolarized the fibers and attenuated the internal Ca2+-dependent effects. These data are consistent with the idea that removal of external Ca2+ activates a La3+-sensitive channel that is permeable to Na+; raising [Ca2+]i activates a La2+-insensitive, Na+-permeable channel that may be similar to the internal Ca2+-activated nonselective cation channels observed in cardiac muscle. The results demonstrate that all Na+ (and Ca2+) fluxes that do not contribute to Na-Ca exchange must be carefully identified before the exchange stoichiometry can be determined from Na+ and Ca2+ flux measurements.

Contraction-induced injury to single muscle fibers: velocity of stretch does not influence the force deficit

1998 ◽  
Vol 275 (6) ◽  
pp. C1548-C1554 ◽  
Author(s):  
Gordon S. Lynch ◽  
John A. Faulkner
Keyword(s):  
Null Hypothesis ◽  
Muscle Injury ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Single Muscle ◽  
Control Value ◽  
Severity Of Injury ◽  
Before And After ◽  
The Difference ◽  
Permeabilized Fibers

We tested the null hypothesis that the severity of injury to single muscle fibers following a single pliometric (lengthening) contraction is not dependent on the velocity of stretch. Each single permeabilized fiber obtained from extensor digitorum longus muscles of rats was maximally activated and then exposed to a single stretch of either 5, 10, or 20% strain [% of fiber length ( L f)] at a velocity of 0.5, 1.0, or 2.0 L f /s. The force deficit, the difference between maximum tetanic isometric force (Po) before and after the stretch expressed as a percentage of the control value for Po before the stretch, provided an estimate of the magnitude of muscle injury. Despite a fourfold range from the lowest to the highest velocities, force deficits were not different among stretches of the same strain. At stretches of 20% strain, even an eightfold range of velocities produced no difference in the force deficit, although 40% of the fibers were torn apart at a velocity of 4 L f /s. We conclude that, within the range of velocities tolerated by single permeabilized fibers, the severity of contraction-induced injury is not related to the velocity of stretch.

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