scholarly journals Hypotonic stimulation of the Na+ active transport in frog skeletal muscle: role of the cytoskeleton

2003 ◽  
Vol 548 (2) ◽  
pp. 451-459 ◽  
Author(s):  
R A Venosa
Keyword(s):  
Skeletal Muscle ◽  
Active Transport ◽  
Frog Skeletal Muscle ◽  
Stimulation Of

Hg2+-induced contracture in mechanically skinned fibers of frog skeletal muscle

1985 ◽  
Vol 63 (9) ◽  
pp. 1070-1074 ◽  
Author(s):  
Takako Aoki ◽  
Toshiharu Oba ◽  
Ken Hotta
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Sulfhydryl Groups ◽  
Skinned Fibers ◽  
Frog Skeletal Muscle ◽  
Semitendinosus Muscle ◽  
Skinned Fiber ◽  
Brij 58 ◽  
Develop Tension

In mechanically skinned fibers of the semitendinosus muscle of bullfrogs, we examined the role of membrane sulfhydryl groups on Ca2+ release from the sarcoplasmic reticulum (SR). Hg2+, a sulfhydryl reagent (20–100 μM), induced a repetitive contracture of skinned fibers, and this contracture did not occur in skinned fibers in which the SR had been disrupted by treatment with a detergent (Brij 58). Procaine (10 mM), Mg2+ (5 mM), or dithiothreitol (1 mM) blocked the Hg2+-induced contracture. Ag+ or p-chloromercuribenzenesulfonic acid produced similar contractures to that induced by Hg2+. We conclude that Hg2+ releases Ca2+ from SR of a skinned fiber by modifying sulfhydryl groups on the SR membrane, and suggest that the Ca2+ released by Hg2+ may trigger a greater release of Ca2+ from SR to develop tension.

Ca(2+)- and pH-dependent halothane stimulation of Ca2+ release in sarcoplasmic reticulum from frog muscle

1996 ◽  
Vol 271 (2) ◽  
pp. C540-C546 ◽  
Author(s):  
M. Beltran ◽  
R. Bull ◽  
P. Donoso ◽  
C. Hidalgo
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Release Kinetics ◽  
Frog Muscle ◽  
Time Range ◽  
Frog Skeletal Muscle ◽  
Open Probability ◽  
Filtration System ◽  
Stimulation Of

The effect of halothane on calcium release kinetics was studied in triad-enriched sarcoplasmic reticulum vesicles from frog skeletal muscle. Release from vesicles passively equilibrated with 3 mM 45CaCl2 was measured in the millisecond time range by use of a fast-filtration system. Halothane (400 microM) increased release rate constants at pH 7.1 and 7.4 as a function of extravesicular pCa. In contrast, halothane at pH 6.8 produced the same stimulation of release from pCa 7.0 to 3.0; no release took place in these conditions in the absence of halothane. Halothane shifted the calcium activation curve at pH 7.1, but not at pH 7.4, to the left and increased channel open probability at pH 7.1 in the cis pCa range of 7.0 to 5.0. These results indicate that cytosolic pCa and pH modulate the stimulatory effects of halothane on calcium release. Furthermore, halothane stimulated release in frog skeletal muscle at low pH and resting calcium concentration, indicating that in frog muscle halothane can override the closing of the release channels produced by these conditions, as it does in malignant hyperthermia-susceptible porcine muscle.

scholarly journals The Changes in Ca2+ Sparks Associated with Measured Modifications of Intra-store Ca2+ Concentration in Skeletal Muscle

2006 ◽  
Vol 128 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Bradley S. Launikonis ◽  
Jingsong Zhou ◽  
Demetrio Santiago ◽  
Gustavo Brum ◽  
Eduardo Ríos
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Confocal Imaging ◽  
Frog Skeletal Muscle ◽  
Average Increase ◽  
Global Level ◽  
Event Frequency ◽  
Average Change ◽  
Contractile Activation

In cardiac muscle and amphibian skeletal muscle, the intracellular Ca2+ release that signals contractile activation proceeds by discrete local packets, which result in Ca2+ sparks. The remarkably stereotyped duration of these release events requires a robustly timed termination mechanism. In cardiac muscle the mechanism of spark termination appears to crucially involve depletion of Ca2+ in the lumen of the sarcoplasmic reticulum (SR), but in skeletal muscle, the mechanism is unknown. We used SEER (shifted excitation and emission ratioing of fluorescence) of SR-trapped mag-indo-1 and confocal imaging of fluorescence of cytosolic rhod-2 to image Ca2+ sparks while reversibly changing and measuring [Ca2+] in the SR ([Ca2+]SR) of membrane-permeabilized frog skeletal muscle cells. Sparks were collected in cells immersed in a solution promoting production of events at moderate frequency. Just after permeabilization, event frequency was zero, and in 10 minutes it reached close to a steady value. Controlled interventions modified [Ca2+]SR reversibly between a low value (299 μM on average in 10 experiments) and a high value (433 μM, a 45% average increase). This change increased sparks frequency by 93%, spatial width by 7%, rise time by 10%, and peak amplitude by 38% (provided that it was calculated in absolute terms, rather than normalized by resting fluorescence). The changes in event frequency and amplitude were statistically significant. The “strength” of the effect of [Ca2+]SR on frequency, quantified by decomposition of variance, was <6%. While the average change in [Ca2+]SR was limited, it reached up to 200% in individual fibers, without causing massive Ca2+ release or an increase of >3.5-fold in event frequency. Taken together with existing evidence that depletion is modest during Ca2+ sparks or release elicited by an action potential, the mild effects of [Ca2+]SR reported here do not support a major role of depletion in either the termination of sparks or the strong inactivation that terminates Ca2+ release at the global level in frog skeletal muscle.

Role of eIF4E in stimulation of protein synthesis by IGF-I in perfused rat skeletal muscle

2000 ◽  
Vol 278 (1) ◽  
pp. E58-E64 ◽  
Author(s):  
Thomas C. Vary ◽  
Leonard S. Jefferson ◽  
Scot R. Kimball
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Initiation Factor ◽  
Translational Efficiency ◽  
Rat Skeletal Muscle ◽  
Phosphorylation State ◽  
Factor I ◽  
Igf I ◽  
Stimulation Of

Insulin-like growth factor I (IGF-I) promotes anabolism by stimulating protein synthesis in skeletal muscle. In the present study, we have examined mechanisms by which IGF-I stimulates protein synthesis in skeletal muscle with a perfused rat hindlimb preparation. IGF-I (10 nM) stimulated protein synthesis over 2.7-fold. Total RNA content was unaffected, but translational efficiency was increased by IGF-I. We next examined the effect of IGF-I on eukaryotic initiation factor (eIF) 4E as a mechanism regulating translation initiation. IGF-I did not alter either the amount of eIF4E associated with the eIF4E binding protein 4E-BP1 or the phosphorylation state of 4E-BP1. Likewise, the phosphorylation state of eIF4E was unaltered by IGF-I. In contrast, the amount of eIF4E bound to eIF4G was increased threefold by IGF-I. We conclude that IGF-I regulates protein synthesis in skeletal muscle by enhancing formation of the active eIF4E ⋅ eIF4G complex.

A forty-year memoir of research on the regulation of glucose transport into muscle

2003 ◽  
Vol 284 (3) ◽  
pp. E453-E467 ◽  
Author(s):  
John O. Holloszy
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Transport ◽  
Historical Review ◽  
Additive Effects ◽  
Glut4 Translocation ◽  
Glut4 Expression ◽  
Exercise Muscle ◽  
Stimulation Of

This historical review describes the research on the regulation of glucose transport in skeletal muscle conducted in my laboratory and in collaboration with a number of colleagues in other laboratories. This research includes studies of stimulation of glucose transport, GLUT4 translocation, and GLUT4 expression by exercise/muscle contractions, the role of Ca2+ in these processes, and the interactions between the effects of exercise and insulin. Among the last are the additive effects of insulin and contractions on glucose transport and GLUT4 translocation and the increases in muscle insulin sensitivity and responsiveness induced by exercise.

Role of Parvalbumin in Skeletal Muscle Relaxation

Physiology ◽  
1996 ◽  
Vol 11 (6) ◽  
pp. 249-255 ◽  
Author(s):  
JA Rall
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Muscle Relaxation ◽  
Calcium Pump ◽  
Frog Skeletal Muscle ◽  
Animal Kingdom ◽  
Calcium Buffer ◽  
High Concentrations ◽  
Sarcoplasmic Reticulum Calcium

Parvalbumin, a soluble intracellular calcium buffer, is present in high concentrations in fast-contracting skeletal muscles across the animal kingdom. In frog skeletal muscle, pharmacological or low-temperature inhibition of the sarcoplasmic reticulum calcium pump reveals that parvalbumin sequesters calcium and promotes relaxation at a rate determined by magnesium dissociation from parvalbumin.

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