scholarly journals The after-effects of repetitive stimulation on the isometric twitch contraction of rat fast skeletal muscle

1968 ◽  
Vol 197 (2) ◽  
pp. 461-477 ◽  
Author(s):  
R. Close ◽  
J. F. Y. Hoh
Keyword(s):  
Skeletal Muscle ◽  
Repetitive Stimulation ◽  
Fast Skeletal Muscle ◽  
After Effects ◽  
Twitch Contraction ◽  
Isometric Twitch

Length dependence of staircase potentiation: interactions with caffeine and dantrolene sodium

2000 ◽  
Vol 78 (4) ◽  
pp. 350-357 ◽  
Author(s):  
Dilson E Rassier ◽  
Brian R MacIntosh
Keyword(s):  
Skeletal Muscle ◽  
Gastrocnemius Muscle ◽  
Repetitive Stimulation ◽  
Mammalian Skeletal Muscle ◽  
Optimal Length ◽  
Dantrolene Sodium ◽  
Length Dependence ◽  
Before And After ◽  
Isometric Twitch

In skeletal muscle, there is a length dependence of staircase potentiation for which the mechanism is unclear. In this study we tested the hypothesis that abolition of this length dependence by caffeine is effected by a mechanism independent of enhanced Ca2+ release. To test this hypothesis we have used caffeine, which abolishes length dependence of potentiation, and dantrolene sodium, which inhibits Ca2+ release. In situ isometric twitch contractions of rat gastrocnemius muscle before and after 20 s of repetitive stimulation at 5 Hz were analyzed at optimal length (Lo), Lo - 10%, and Lo + 10%. Potentiation was observed to be length dependent, with an increase in developed tension (DT) of 78 ± 12, 51 ± 5, and 34 ± 9% (mean ± SEM), at Lo - 10%, Lo, and Lo + 10%, respectively. Caffeine diminished the length dependence of activation and suppressed the length dependence of staircase potentiation, giving increases in DT of 65±13, 53 ± 11, and 45 ± 12% for Lo - 10%, Lo, and Lo + 10%, respectively. Dantrolene administered after caffeine did not reverse this effect. Dantrolene alone depressed the potentiation response, but did not affect the length dependence of staircase potentiation, with increases in DT of 58 ± 17, 26 ± 8, and 18 ± 7%, respectively. This study confirms that there is a length dependence of staircase potentiation in mammalian skeletal muscle which is suppressed by caffeine. Since dantrolene did not alter this suppression of the length dependence of potentiation by caffeine, it is apparently not directly modulated by Ca2+ availability in the myoplasm.

Structural Basis of Tirasemtiv Activation of Fast Skeletal Muscle

2021 ◽  
Vol 64 (6) ◽  
pp. 3026-3034
Author(s):  
Monica X. Li ◽  
Pascal Mercier ◽  
James J. Hartman ◽  
Brian D. Sykes
Keyword(s):  
Skeletal Muscle ◽  
Structural Basis ◽  
Fast Skeletal Muscle

scholarly journals An opportunistic promoter sharing regulatory sequences with either a muscle-specific or a ubiquitous promoter in the human aldolase A gene.

1993 ◽  
Vol 13 (1) ◽  
pp. 9-17 ◽  
Author(s):  
J P Concordet ◽  
M Salminen ◽  
J Demignon ◽  
C Moch ◽  
P Maire ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Integration Site ◽  
Regulatory Elements ◽  
Regulatory Sequences ◽  
Beta Globin ◽  
Fast Skeletal Muscle ◽  
High Level Expression ◽  
Adult Skeletal Muscle ◽  
High Level ◽  
Aldolase A

The human aldolase A gene is transcribed from three different promoters, pN, pM, and pH, all of which are clustered within a small 1.6-kbp DNA domain. pM, which is highly specific to adult skeletal muscle, lies in between pN and pH, which are ubiquitous but particularly active in heart and skeletal muscle. A ubiquitous enhancer, located just upstream of pH start sites, is necessary for the activity of both pH and pN in transient transfection assays. Using transgenic mice, we studied the sequence controlling the muscle-specific promoter pM and the relations between the three promoters and the ubiquitous enhancer. A 4.3-kbp fragment containing the three promoters and the ubiquitous enhancer showed an expression pattern consistent with that known in humans. In addition, while pH was active in both fast and slow skeletal muscles, pM was active only in fast muscle. pM activity was unaltered by the deletion of a 1.8-kbp region containing the ubiquitous enhancer and the pH promoter, whereas pN remained active only in fast skeletal muscle. These findings suggest that in fast skeletal muscle, a tissue-specific enhancer was acting on both pN and pM, whereas in other tissues, the ubiquitous enhancer was necessary for pN activity. Finally, a 2.6-kbp region containing the ubiquitous enhancer and only the pH promoter was sufficient to bring about high-level expression of pH in cardiac and skeletal muscle. Thus, while pH and pM function independently of each other, pN, remarkably, shares regulatory elements with each of them, depending on the tissue. Importantly, expression of the transgenes was independent of the integration site, as originally described for transgenes containing the beta-globin locus control region.

scholarly journals Fast skeletal muscle-specific expression of a quail troponin I gene in transgenic mice.

1988 ◽  
Vol 8 (12) ◽  
pp. 5072-5079 ◽  
Author(s):  
P L Hallauer ◽  
K E Hastings ◽  
A C Peterson
Keyword(s):  
Skeletal Muscle ◽  
Transgenic Mice ◽  
Troponin I ◽  
Fiber Type ◽  
Regulatory Elements ◽  
Evolutionary Divergence ◽  
Mrna Levels ◽  
Fast Skeletal Muscle ◽  
Specific Expression ◽  
Exon 2

We have produced seven lines of transgenic mice carrying the quail gene encoding the fast skeletal muscle-specific isoform of troponin I (TnIf). The quail DNA included the entire TnIf gene, 530 base pairs of 5'-flanking DNA, and 1.5 kilobase pairs of 3'-flanking DNA. In all seven transgenic lines, normally initiated and processed quail TnIf mRNA was expressed in skeletal muscle, where it accumulated to levels comparable to that in quail muscle. Moreover, in the three lines tested, quail TnIf mRNA levels were manyfold higher in a fast skeletal muscle (gastrocnemius) than in a slow skeletal muscle (soleus). We conclude that the cellular mechanisms directing muscle fiber type-specific TnIf gene expression are mediated by cis-regulatory elements present on the introduced quail DNA fragment and that they control TnIf expression by affecting the accumulation of TnIf mRNA. These elements have been functionally conserved since the evolutionary divergence of birds and mammals, despite the major physiological and morphological differences existing between avian (tonic) and mammalian (twitch) slow muscles. In lines of transgenic mice carrying multiple tandemly repeated copies of the transgene, an aberrant quail TnIf transcript (differing from normal TnIf mRNA upstream of exon 2) also accumulated in certain tissues, particularly lung, brain, spleen, and heart tissues. However, this aberrant transcript was not detected in a transgenic line which carries only a single copy of the quail gene.

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