Claude Léoty

Learn More
The effect of cyclopiazonic acid, an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase, was investigated on force generation by the contractile apparatus in Triton-skinned fibres from extensor digitorum longus and soleus. Concentrations of cyclopiazonic acid lower than 10 microM were without effect on Ca(2+)-activated tension in both types of muscles. In(More)
PURPOSE We studied the effects of high doses of an anabolic-androgenic steroid, exercise training, and a combination of steroid and training on mammalian fast- and slow-twitch skeletal muscles at the cellular level. METHODS Thirty-two male rats were divided into sedentary and treadmill-trained groups (increased speed and time: 18 m.min-1, 0.5 h.d-1, 5(More)
This investigation was designed to examine whether short-term administration of anabolic-androgenic steroids (AAS) (nandrolone decanoate) could produce changes in contractile responses of untrained rat fast- (edl) and slow- (soleus) twitch skeletal muscle. Twenty male rats were divided into two groups, one group received weekly (for 6 weeks) an(More)
In frog atrial fibres, cyclopiazonic acid as well as thapsigargin, which are inhibitors of sarcoplasmic reticulum Ca(2+)-ATPase, induced a significant increase in the twitch amplitude without detectable changes in its kinetics. The measurements performed on chemically skinned fibres show that cyclopiazonic acid has no effect on the properties of contractile(More)
We have investigated the influence of the sarcoplasmic reticulum (SR) Ca2+ content on the retrograde control of skeletal muscle L-type Ca2+ channels activity by ryanodine receptors (RyR). The effects of cyclopiazonic acid (CPA) and thapsigargin (TG), two structurally unrelated inhibitors of SR Ca(2+)-adenosine triphosphatase (ATPase), were examined on the(More)
The purpose of the present work was to see whether changes in rat soleus characteristics due to 3 wk of hindlimb suspension could be modified by ciliary neurotrophic factor (CNTF) treatment. Throughout the tail suspension period, the cytokine was delivered by means of an osmotic pump (flow rate 16 microg. kg(-1). h(-1)) implanted under the hindlimb skin. In(More)
When mammals are constrained to hypogravity, their neuromuscular apparatus undergoes modifications which rend difficult postural maintenance and muscular activity upon the return to normal gravitational conditions. Muscle atrophy and differetial gene expression are particularly evident in slow-twitch antigravity muscles such as the soleus. During(More)
The properties of the contractile system at different times of the year in the ferret extensor digitorum longus (EDL), soleus and cremaster muscles were examined by using chemically skinned (Triton X-100) preparations. The results show clear differences in calcium sensitivity between these skeletal muscles. The apparent calcium threshold for activation was(More)
The purpose of this study was to determine whether 4-chloro-m-cresol (4-CmC) could generate caffeine-like responses in ferret cardiac muscle. The concentration dependence of 4-CmC-mediated release of Ca(2+) from the sarcoplasmic reticulum was studied in intact cardiac trabeculae and saponin-skinned fibers in which the sarcoplasmic reticulum was loaded with(More)
The effects of cyclopiazonic acid (CPA) were investigated on isolated skeletal muscle fibers of frog semitendinosus muscle. CPA (0.5-10 microM) enhanced isometric twitch but produced little change in resting tension. At higher concentrations (10-50 microM), CPA depressed twitch and induced sustained contracture without affecting resting and action(More)