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The adaptation to weightlessness of two postural muscles, the slow soleus (SOL) and the fast gastrocnemius lateralis (GL), and a fast muscle used in movements, the extensor digitorum longus (EDL), was studied on five adult Wistar rats. The animals exposed to 14-day spaceflight aboard COSMOS 2044, designated as flight (F), were compared with synchronous (S)(More)
The effects of ryanodine, a neutral alkaloid, on crab muscle fibers were investigated under voltage clamp conditions using the double sucrose-gap technique. In the presence of ryanodine, contracture develops without any membrane depolarization and the Ca-conductance variables are shifted in a hyperpolarizing direction. As a result, the Ca channels are(More)
The neural message is known to play a key role in muscle development and function. We analyzed the specific role of the afferent message on the functional regulation of two subcellular muscle components involved in the contractile mechanism: the contractile proteins and the sarcoplasmic reticulum (SR). Rats were submitted to bilateral deafferentation (DEAF(More)
Inactivation of Ca channels was examined in crab muscle fibres using the voltage-clamp method. A satisfactory suppression of outward currents was attempted by the use of K+ blocking agents: TEA, 4AP and Cs ions instead of K+ ions applied extracellularly. The inactivation of Ca current appeared as a bi-exponential process. The faster component had a mean(More)
The functional capacity of skeletal muscle sarcoplasmic reticulum (SR) was examined in the slow soleus of rats submitted to 15 days of disuse produced by hindlimb suspension (HS). By using caffeine-induced contractions of single skinned fibers, Ca2+ uptake, Ca2+ release, and passive Ca2+ leakage through the SR membrane were investigated. In the SR of(More)
Membrane currents are investigated under voltage-clamp conditions in crab muscle fibre. 2. Step depolarizations elicit an initial composite current followed by a late outward current. 3. One of the components of the initial current is inward. It is sensitive to the external calcium concentration and inhibited by manganese ions, it can be carried also by(More)
This study was undertaken to correlate some of the functional characteristics with the myofibrillar composition in myosin heavy chain isoforms on newborn and adult rat soleus muscles. The following postnatal ages were chosen in order to determine the role of innervation in the establishment of the mature muscle phenotype: before (postnatal day 6), when(More)
Chemically skinned fibres from soleus and plantaris rat muscles were used to compare the contractile properties of slow and fast muscles. The maximal isometric tension appeared larger in plantaris than in soleus fibres. The apparent Ca2+ threshold for activation was lower in slow than in fast fibres while Ca2+ concentrations required to obtain either the(More)
Morphological, contractile properties and myosin heavy chain (MHC) composition of rat soleus muscles were studied after 2 weeks of unloading (HS) and after 2 weeks of HS associated with selective deafferentation (HS + DEAF) at the level L4 and L5. The same significant reductions in muscle mass and tetanic tension were found after HS and HS + DEAF. However,(More)
AIMS Although modifications of the survival motor neurone gene are responsible for most spinal muscular atrophy (SMA) cases, the molecular pathophysiology and the muscular target proteins involved are still unknown. The aim of this study was to compare the expression of contractile and regulatory protein isoforms in quadriceps muscles from SMA children with(More)