scholarly journals Critical sarcomere extension required to recruit a decaying component of extra force during stretch in tetanic contractions of frog skeletal muscle fibers.

1981 ◽  
Vol 78 (4) ◽  
pp. 365-382 ◽  
Author(s):  
K A Edman ◽  
G Elzinga ◽  
M I Noble
Keyword(s):  
Skeletal Muscle ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
Critical Length ◽  
Length Change ◽  
Frog Skeletal Muscle ◽  
Critical Amplitude ◽  
Force Extension ◽  
Skeletal Muscle Fibers ◽  
Force Increase

29 single frog skeletal muscle fibers were stretched during fused tetanic contractions. The force increase during stretch exhibited a breakpoint at a critical length change (average: 16.6 nm per one-half sarcomere) that was independent of velocity of stretch and of sarcomere length between 1.8 and 2.8 microns. After stretch there was an early decaying force component with a force-extension curve similar to that during stretch, which disappeared over approximately 2 s. This component was removed by a small, quick release, leaving a longer-lasting component. The critical amplitude of release required to produce this result was found by clamping the fiber to a load at which there was zero velocity of shortening. This amplitude increased with time up to the angle in the force record during stretch, was constant for the remainder of the stretch, and decreased with time after the end of stretch; it was consistently less than the critical amplitude of stretch required to reach the breakpoint of force enhancement during stretch but was also independent of sarcomere length. The force drop accompanying the critical release showed a small increase up to an optimum magnitude at 2.4--2.7 microns sarcomere length, with a decrease at longer lengths.

scholarly journals Sarcomere lengthening and tension drop in the latent period of isolated frog skeletal muscle fibers.

1976 ◽  
Vol 68 (3) ◽  
pp. 247-265 ◽  
Author(s):  
P Haugen ◽  
O Sten-Knudsen
Keyword(s):  
Skeletal Muscle ◽  
Latent Period ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
Time Interval ◽  
Maximum Elongation ◽  
Frog Skeletal Muscle ◽  
Sharp Maximum ◽  
Skeletal Muscle Fibers ◽  
Length Range

A laser diffraction technique has been developed for registering small changes in sarcomere length. The technique is capable of resolving changes as small as 0.2 A in isolated frog skeletal muscle fibers. The small sarcomere lengthening that accompanies the drop in tension in the latent period of contraction was investigated. We suggest this lengthening be named latency elongation (LE). The LE is present in a completely slack fiber and must, therefore, be caused by a forcible lengthening process. Furthermore, the LE is dependent on the existence of an overlap between thin and tick filaments. The rate of elongation and the time interval between stimulation and maximum elongation may vary along the fiber. The maximum elongation was 3-5 A per sarcomere. At any instant the drop in tension is a product of the sum of sarcomere lengthenings along the fiber and the slope stiffness of the series elasticity. The latency relaxation (LR) could be registered in the sarcomere length range from 2.2 mum to 3.6-3.7 mum. The amplitude went through a sharp maximum at 3.0-3.1 mum. In the sarcomere length range from 2.2 to 2.8 mum the delay from onset to maximum LR was nearly proportional to the distance from the Z-line to the overlap zone. A working hypothesis is presented. It is suggested that the LE is caused by a lengthening of the thin filaments.

Inaction of saxitoxin-oximes on the sodium channel of frog skeletal muscle fibers

Toxicon ◽  
1987 ◽  
Vol 25 (2) ◽  
pp. 159-165 ◽  
Author(s):  
S.L. Hu ◽  
C.Y. Kao ◽  
F.E. Koehn ◽  
H.K. Schnoes
Keyword(s):  
Skeletal Muscle ◽  
Sodium Channel ◽  
Muscle Fibers ◽  
Frog Skeletal Muscle ◽  
Skeletal Muscle Fibers

scholarly journals Anatomical distribution of voltage-dependent membrane capacitance in frog skeletal muscle fibers.

1989 ◽  
Vol 93 (3) ◽  
pp. 565-584 ◽  
Author(s):  
C L Huang ◽  
L D Peachey
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Fiber Surface ◽  
Membrane Capacitance ◽  
Hypertonic Solution ◽  
Charge Movement ◽  
Frog Skeletal Muscle ◽  
Transverse Tubule ◽  
Skeletal Muscle Fibers ◽  
Voltage Dependent

Components of nonlinear capacitance, or charge movement, were localized in the membranes of frog skeletal muscle fibers by studying the effect of 'detubulation' resulting from sudden withdrawal of glycerol from a glycerol-hypertonic solution in which the muscles had been immersed. Linear capacitance was evaluated from the integral of the transient current elicited by imposed voltage clamp steps near the holding potential using bathing solutions that minimized tubular voltage attenuation. The dependence of linear membrane capacitance on fiber diameter in intact fibers was consistent with surface and tubular capacitances and a term attributable to the capacitance of the fiber end. A reduction in this dependence in detubulated fibers suggested that sudden glycerol withdrawal isolated between 75 and 100% of the transverse tubules from the fiber surface. Glycerol withdrawal in two stages did not cause appreciable detubulation. Such glycerol-treated but not detubulated fibers were used as controls. Detubulation reduced delayed (q gamma) charging currents to an extent not explicable simply in terms of tubular conduction delays. Nonlinear membrane capacitance measured at different voltages was expressed normalized to accessible linear fiber membrane capacitance. In control fibers it was strongly voltage dependent. Both the magnitude and steepness of the function were markedly reduced by adding tetracaine, which removed a component in agreement with earlier reports for q gamma charge. In contrast, detubulated fibers had nonlinear capacitances resembling those of q beta charge, and were not affected by adding tetracaine. These findings are discussed in terms of a preferential localization of tetracaine-sensitive (q gamma) charge in transverse tubule membrane, in contrast to a more even distribution of the tetracaine-resistant (q beta) charge in both transverse tubule and surface membranes. These results suggest that q beta and q gamma are due to different molecules and that the movement of q gamma in the transverse tubule membrane is the voltage-sensing step in excitation-contraction coupling.

Determinants of relaxation rate in skinned frog skeletal muscle fibers

1998 ◽  
Vol 274 (6) ◽  
pp. C1608-C1615 ◽  
Author(s):  
Philip A. Wahr ◽  
J. David Johnson ◽  
Jack. A. Rall
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Slow Phase ◽  
Frog Skeletal Muscle ◽  
Force Of Contraction ◽  
Thin Filaments ◽  
Fast Phase ◽  
Skeletal Muscle Fibers ◽  
Kinetics Of ◽  
Overall Kinetics

The influences of sarcomere uniformity and Ca2+ concentration on the kinetics of relaxation were examined in skinned frog skeletal muscle fibers induced to relax by rapid sequestration of Ca2+ by the photolysis of the Ca2+ chelator, diazo-2, at 10°C. Compared with an intact fiber, diazo-2-induced relaxation exhibited a faster and shorter initial slow phase and a fast phase with a longer tail. Stabilization of the sarcomeres by repeated releases and restretches during force development increased the duration of the slow phase and slowed its kinetics. When force of contraction was decreased by lowering the Ca2+concentration, the overall kinetics of relaxation was accelerated, with the slow phase being the most sensitive to Ca2+ concentration. Twitchlike contractions were induced by photorelease of Ca2+ from a caged Ca2+ (DM-Nitrophen), with subsequent Ca2+ sequestration by intact sarcoplasmic reticulum or Ca2+ rebinding to caged Ca2+. These twitchlike responses exhibited relaxation kinetics that were about twofold slower than those observed in intact fibers. Results suggest that the slow phase of relaxation is influenced by the degree of sarcomere homogeneity and rate of Ca2+ dissociation from thin filaments. The fast phase of relaxation is in part determined by the level of Ca2+ activation.

scholarly journals Sarcomere-Length Dependence of the Low Angle X-Ray Pattern from Skeletal Muscle Fibers at Rest and during Isometric Contraction

2012 ◽  
Vol 102 (3) ◽  
pp. 147a-148a
Author(s):  
Gabriella Piazzesi ◽  
Massimo Reconditi ◽  
Elisabetta Brunello ◽  
Luca Fusi ◽  
Marco Linari ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Isometric Contraction ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
X Ray ◽  
Length Dependence ◽  
Skeletal Muscle Fibers
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