Muskulatur, Verschiedenes

Abstract

The site of ATPase activity and the conditions under which it can be demonstrated in indirect flight muscles of the blowfly Phormia regina were studied after incubation in a modified Gomori medium. 3 preparations were used: tissue blocks treated shortly with fixing agents, frozen sections and fresh or pretreated isolated myofibrils. The deposition of lead phosphate indicating the hydrolysis of ATP is demonstrated in the contractile apparatus and in the mitochondria. — (1) Myofibrils. In all preparations ATPase activity is found in 2 different parts of the sarcomeres: in the A band and in the Z disc. The same distribution is shown in experiments where calcium is used as precipitating agent instead of lead. The particles precipitated in the A band are frequently arranged in longitudinal rows which correspond to the position of the thick filaments. Under no conditions is lead phosphate found in the H zone. The A band contains apparently 2 regions of different ATPase activity: the center—often divided by the H zone—is densely covered with precipitate while narrow zones bordering the A-I junction contain significantly less lead phosphate. The ATPase of the Z disc is distinctly different from that in the A band, since it can be demonstrated separately under certain conditions. (2) Mitochondria. The splitting of ATP occurs mainly on the cristae mitochondriales. Little or no activity is found associated with the outer membranes. There seem to be different patterns of mitochondrial precipitation. Some mitochondria contain only a few large cristallites while others next to them have the cristae dotted with a great number very small ones.