[Characteristics of the human masseter muscle during hypokinesia].

Bioptates of the m. masseter from 20 male persons at the age of 21-30 years have been studied 3, 6, 12 and 24 days after immobilization of the mandible in connection with its fracture. Succinate dehydrogenase (SDG) activity and cross section area of muscle fibers have been determined. Relative volume (Vv) of submicroscopic structures of myons have been found stereologically. In the muscle tissue reactive-destructive changes are revealed; they depend on hypokinesia duration: decreasing SDG activity, cross section area of the fibers and contents of pinocytic vesicles in the endothelial cells of the capillaries. Vv of mitochondria and tubular formations in the sarcoplasmic reticulum change. Certain stageness of structural rearrangements in the muscles are noted, they are considered as a result of the influence of the restricted function and some disturbances occurring between the blood vessels and the muscle fibers.