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.

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.

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.

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.

L-glutamate transport in internally dialyzed barnacle muscle fibers

1989 ◽  
Vol 257 (3) ◽  
pp. C442-C450 ◽  
Author(s):  
L. W. Horn
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
General Model ◽  
Muscle Fibers ◽  
Kinetic Mechanism ◽  
Transport Systems ◽  
Single Muscle ◽  
Single System ◽  
Acid Transport ◽  
Barnacle Muscle Fibers

The transport of L-glutamate (Glu) by single muscle fibers of Balanus nubilus was studied by means of internal dialysis in an effort to obtain transport data under well-defined intracellular conditions. It is shown that the method effectively controls the sarcoplasmic amino acid composition and Glu metabolism. It was found that the classic neutral amino acid transport systems are either absent or inactive, while Glu is strongly transported by a single system. Nonsaturable Glu "leak" is small relative to mediated transport. Glu influx under 0-trans conditions obeys simple Michaelis-Menten kinetics and shows simple competition with aspartate. Influx is strictly dependent on external Na. Trans-Na reduces influx, whereas trans-Glu has a small stimulatory effect. The preparation may serve as a general model for muscle Glu transport and can be used for a thorough study of the kinetic mechanism.

Shrinkage-induced activation of Na(+)-H+ exchange in barnacle muscle fibers

1994 ◽  
Vol 266 (6) ◽  
pp. C1744-C1753 ◽  
Author(s):  
B. A. Davis ◽  
E. M. Hogan ◽  
W. F. Boron
Keyword(s):  
Intracellular Ph ◽  
Muscle Fibers ◽  
Single Muscle ◽  
Extrusion Rate ◽  
Barnacle Muscle ◽  
Hypertonic Solutions ◽  
Acid Extrusion ◽  
Ph Microelectrodes ◽  
Barnacle Muscle Fibers ◽  
Exchange Activity

We examined the effect of shrinkage on Na(+)-H+ exchange in single muscle fibers at intracellular pH (pHi) values of 6.8, 7.2, and 7.6 using pH microelectrodes and internal dialysis. Under normotonic conditions (975 mosmol/kgH2O) at pHi 6.8, the amiloride-sensitive acid-extrusion rate (JAmil/s) averaged 17 microM/min. Exposure to hypertonic solutions (1,600 mosmol/kgH2O) increased JAmil/s to 304 microM/min at pHi 6.8. At pHi approximately 7.2 and 7.6, hypertonicity increased JAmil/s from approximately 0 to approximately 172 microM/min (pHi 7.2) and approximately 0 to approximately 90 microM/min (pHi 7.6). Thus, under normotonic conditions, Na(+)-H+ exchange activity is slight at pHi approximately 6.8 and virtually nil at higher pHi values. Shrinkage stimulated Na(+)-H+ exchange, more at low pHi values. We also examined the Cl- dependence of the Na(+)-H+ exchanger's response to shrinkage. Our results indicate that shrinkage-induced activation of Na(+)-H+ exchange requires Cl-, specifically intracellular Cl-. These results establish that shrinkage is both pHi dependent and requires intracellular Cl-.

Muscle fiber capacity in low conductivity solution

1976 ◽  
Vol 54 (2) ◽  
pp. 107-112 ◽  
Author(s):  
D. Loo ◽  
P. C. Vaughan
Keyword(s):  
Membrane Potential ◽  
Muscle Fiber ◽  
Muscle Fibers ◽  
Circuit Theory ◽  
Frog Muscle ◽  
Constant Current ◽  
Effective Capacity ◽  
Injection Technique ◽  
Length Constant ◽  
Per Se

A method is described for computing the effective capacity of muscle fibers, C = Q/V where Q is the charge stored, and V is the membrane potential, using a standard two-microelectrode, constant current injection technique. The method is used to compare physical (or effective) capacity of frog muscle fibers bathed in a low conductivity, 2.5 mM K+ solution, with circuit-theory derived quantities in the same cells and in control fibers. No differences can be discerned and it is concluded that low conductivity of physiological solutions, per se, does not significantly reduce the length constant of frog muscle transverse tubules.

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