scholarly journals ELECTRICAL PROPERTIES OF THE FROG SKELETAL MUSCLE MEMBRANE IN Cl-FREE SULPHATE-, FERROCYANIDE-, AND GLUTAMATERINGER'S SOLUTIONS

1963 ◽  
Vol 13 (6) ◽  
pp. 641-656 ◽  
Author(s):  
Teruaki SZAIMI ◽  
Tadao TOMITA
1974 ◽  
Vol 52 (4) ◽  
pp. 887-890 ◽  
Author(s):  
L. L. Odette ◽  
H. L. Atwood

The effect of dantrolene sodium, a muscle relaxant effective on vertebrate skeletal muscle, has been studied on the stretcher muscle of a crab (Callinectes sapidus). The drug rapidly and reversibly attenuates the muscle contractile response to direct and indirect stimulation. Neuromuscular transmission is unaffected, as are the electrical properties of the muscle membrane. It is concluded that dantrolene sodium uncouples excitation–contraction mechanisms in crustacean tonic muscle.


1974 ◽  
Vol 52 (6) ◽  
pp. 1126-1135 ◽  
Author(s):  
D. J. Parry ◽  
A. Kover ◽  
G. B. Frank

Exposure of frog toe muscles to 1 mM La3+ results in a decrease in amplitude and rate of tension development of potassium contractures and twitches. At this concentration La3+ also inhibits the uptake of calcium, both in the resting condition and during stimulation. Caffeine contractures are unaffected even after a 5-min pre-exposure to La3+. The depolarization induced by various concentrations of K+ is reduced by about 10 mV as is the amplitude of the action potential. The rate of rise of the action potential is reduced by about 40% after 1 min in La3+ Ringer. Neither the decreased amplitude nor the reduced rate of depolarization is considered to be sufficient to explain the inhibition of tension development. It is suggested that La3+ partially uncouples excitation from contraction by preventing the release of a trigger-Ca2+ fraction from some site on the muscle membrane. This fraction normally plays a role in excitation–contraction coupling, although some tension may still be developed in the absence of a trigger-Ca2+ influx.


1996 ◽  
Vol 271 (4) ◽  
pp. C1367-C1379 ◽  
Author(s):  
R. W. Putnam ◽  
P. B. Douglas ◽  
N. A. Ritucci

The distribution of pH-regulating transporters in surface and transverse (T) tubular membrane (TTM) domains of frog skeletal muscle was studied. 2',7'-Bis(carboxyethyl)-5(6)- carboxyfluorescein-loaded giant sarcolemmal vesicles, containing surface membrane, exhibited reversible Na+/H+ exchange. A microsomal vesicle fraction was shown to be enriched in TTM on the basis of high Na(+)-K(+)-ATPase and Mg(2+)-ATPase activity, high ouabain and nitrendipine binding, and low Ca(2+)-ATPase activity. TTM vesicles were well sealed and oriented inside out. Vesicles were loaded with the pH-sensitive dye pyranine. In response to an inwardly directed Na+ gradient, vesicles displayed virtually no alkalinization unless monensin was present. No pH response to an imposed Na+ gradient was seen regardless of the direction of the pH gradient across the vesicles, after phosphorylation of the vesicles with protein kinase C, or when exposed to guanosine 5'-O-(3-thiotriphosphate). In the presence of CO2, addition of Na+ or Cl- had no effect on vesicle pH. These data indicate that the TTM lacks functional pH-regulating transporters [Na+/H+ and (Na+ + HCO3-)/Cl- exchangers], suggesting that pH-regulating transporters are localized only to the surface membrane domain in frog muscle.


1973 ◽  
Vol 51 (12) ◽  
pp. 966-975
Author(s):  
N. F. Clinch ◽  
V. Tennant

Isometric contractions of frog sartorii in response to paired stimuli (I ms apart) were compared with isometric twitches following single shocks in order to find the time of the first detectable mechanical response to the second shock (ts). For I > 25 ms at 0°, ts = 0.99 I + 13.3 ms; while for I < 25 ms, ts was found to be independent of I. Electrical recording from the muscle surface showed that for I < 25 ms, the second action potential fell within the relative refractory period of the first. The plateau region of the ts–I plot is consistent with the active state theory, but can also be interpreted as (a) a measurement artifact, or (b) revealing electrical properties of the membrane rather than a property of the contractile mechanism itself.


1994 ◽  
Vol 266 (2) ◽  
pp. C462-C466 ◽  
Author(s):  
K. Anderson ◽  
A. H. Cohn ◽  
G. Meissner

In vertebrate skeletal muscle, the voltage-dependent mechanism of sarcoplasmic reticulum (SR) Ca2+ release, commonly referred to as excitation-contraction (E-C) coupling, is mediated by the voltage-sensing dihydropyridine receptor (DHPR), which is believed to affect SR Ca2+ release through a physical interaction with the SR ryanodine receptor (RYR)/Ca2+ release channel. Scatchard analysis of ligand binding of [3H]PN200-110 to the DHPR and [3H]ryanodine to the RYR indicated the presence of high-affinity sites in muscle homogenates, with maximum binding (Bmax) values of 72 +/- 26 and 76 +/- 30 pmol/g wet wt for rabbit skeletal muscle, and 27 +/- 14 and 44 +/- 13 pmol/g wet wt for frog skeletal muscle, respectively. The Bmax values corresponded to a PN200-110-to-ryanodine binding ratio of 0.98 +/- 0.26 and 0.61 +/- 0.24 for rabbit and frog skeletal muscle, respectively, and were found by Student's t test to be significantly different (P < 0.02, n = 7). These results are compared with measurements with isolated rabbit skeletal muscle membrane fractions and discussed in relation to our current understanding of the mechanism of E-C coupling in skeletal muscle.


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