NEW FIBER FORMATION IN RAT SOLEUS MUSCLE FOLLOWING ADMINISTRATION OF DENERVATED MUSCLE EXTRACT

A study was made of Wistar rat soleus muscle following intraperitoneal administration of denervated muscle extract over 1 and 2 days. Light microscopy revealed the appearance on fiber surfaces of basophilic sat ellite structures whose histochemical behaviour differed from that of the parent fiber. Small fibers showing regenerative characteristics we re also detected, mainly in the extrafascicular spaces. At ultrastruct ural examination, activated satellite cells were visible, and there wa s evidence of splitting in subsarcolemmal regions of apparently hypert rophic muscle fibers. Interstitial cells were occasionally observed, c ontaining structures like myofilaments. The hypothesis is advanced tha t denervated muscle extract contains substances able to stimulate new fiber formation in adult skeletal muscle.