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1. A comparison of the delayed outward current of isolated fibres from rat soleus and iliacus muscle has been made using a double sucrose-gap voltage-clamp method. 2. The fast and slow components of the outward current were separated using time constants of the tail currents. The results indicate that in both iliacus and soleus fibres there is a shift in(More)
1. The ionic currents in slow fibres isolated from rat soleus muscle have been studied under voltage-clamp conditions with a double sucrose-gap method and the results are compared to those obtained from fast fibres isolated from the iliacus muscle. 2. The mean value of the resting potential in slow fibres is -70 mV. a value 8 mV more positive that the mean(More)
Slow-twitch and fast-twitch muscle fibres have specific contractile properties to respond to specific needs. Since sodium current density is higher in fast-twitch than in slow-twitch fibres, sodium channels contribute to the phenotypic feature of myofibres. Phenotype determination is not irreversible: after periods of rat hindlimb unloading (HU), a model of(More)
Disuse of postural slow-twitch muscles, as it occurs in hypogravity, induces a slow-to-fast myofibre type transition. Nothing is known about the effects of weightlessness on the resting membrane chloride conductance (gCl), which controls sarcolemma excitability and influences fibre type transition during development and adult life. Using the current-clamp(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)
1. The double sucrose-gap technique has been applied to rat skeletal muscle fibres to study the ionic currents under voltage-clamp conditions. 2. The iliacus muscle was found to be of 'fast' type according to the characteristics of the twitch generated by an action potential. 3. Micro-electrode measurements have shown that the intracellular potential is(More)
The present study was designed to examine whether changes in Ca(2+) release by inositol-1,4,5-trisphosphate (IP(3)) in 8-, 15-, and 30-day-old rat skeletal muscles could be associated with the expression of IP(3) receptors. Experiments were conducted in slow-twitch muscle in which both IP(3)-induced Ca(2+) release and IP(3)-receptor (IP(3)R) expression have(More)
Contractile responses associated with depolarization caused by an increase in [K]0 or by voltage-clamp steps were compared for fast and slow mammalian twitch muscles. The contractions and contractures of isolated mammalian muscle fibres cut into 0.5-1.0 cm lengths are similar to those obtained from intact cells. The slope of the relationship between the(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)