[ATPase activity and the contractile capacity of the muscle tissue in chick embryos during development]

The value of ATPase activity of the myofibril preparations and the value and duration of actomyosin superprecipitation were estimated for different muscles during the chick embryonic development. The ATPase level increases during embryogenesis 4.5-fold, in the leg muscle this change takes place distinctly earlier than in the leg muscle. The value and rate of actomyosin superprecipitation also markedly increase, to a lesser extent for m. soleus than for m. pectoralis. It is suggested that these changes and differences are mainly due to the delay in synthesis of certain types of the embryonic myosin light chains.