Résumé :
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Communication n° 461 Myosin heavy chain (MyHC) is one of the major components of the contractile apparatus of all striated muscles. MyHC is encoded by a multigene family, the members of which are expressed in a tissue-specific and developmental regulated manner. The functional heterogeneity of muscles can be explained by their MyHC isoform content. Several MyHC isoforms have been described in skeletal muscles, including two developmental isoforms (embryonic and neonatal/perinatal/fetal), one slow isoform (MyHC I) and three fast isoforms (MyHC IIA, IIX/IID and IIB). Soleus muscles were removed from anaesthetised mice (C57BL6) at various times after birth or after regeneration, in denervated and non denervated, adult muscles. Muscle regeneration was induced by a direct intramuscular injection of cardiotoxin into the exposed soleus muscle. In the denervated-regenerated group, denervation was carried out by cutting and removing 5mm of the sciatic nerve high in the thigh just before administration of cardiotoxin. Using a high-resolution gel electrophoresis technique, we have characterized the MyHC composition in soleus muscle of the mouse during postnatal development, regeneration and regeneration without innervation. We have also compared this expression with calcineurin activity.
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