[Ultrastructure of rat skeletal muscle fibers during prolonged static loading].

Ultrastructural characteristics of the rat skeletal muscle fibers was studied under a prolonged static loading. Disruption of the mitochondrial membranes, desintegration and lysis of myofibrils, desorganization of the T-system and Z-bands were revealed. Destructive processes were accompanied with the physiological reparative regeneration evidenced by a large number of polysomes and accumulation of myofibrils at the peripheral zone of the muscle fibre. The satellite cells with poorly developed organells were revealed in cytoplasm. Mitotic figures were present in the satellite cells. Clusters of the satellite cells were revealed in the interstitial connective tissue with their successive differentiation into mature muscle fibres. Possible mechanisms of the skeletal muscle fibre formation were discussed.