Degeneration and regeneration in denervated tonic and phasic skeletal muscle: morphology and acid phosphatase cytochemistry.

Following denervation, ultrastructural alterations were observed in the tonic, anterior (ALD) and phasic posterior (PLD) latissimus dorsi muscles of the chicken. In the ALD muscle these changes were characteristic of both degeneration and regeneration, while in the PLD muscle, the changes were characteristic only of degeneration. Acid phosphatase positive structures, which included dense bodies in the ALD and PLD as well as T-tubules in the PLD, were observed intact with no evidence of release of enzyme into the sarcoplasm. No evidence of an increase in the number of autophagic vacuoles was found. The morphological evidence presented in this communication does not support the hypothesis that lysosomes are involved in denervation atrophy through autophagy of muscle cell constituents.