The leading role of membranes in the formation of the myofibrillar system at different stages of chick embryo development (on the 8th, 12th, 15th day) was considered. At the early stages the myofibrillar assembly depends mainly on the plasma membrane (myofibrils are located beneath the sarcolemma) and later on it depends on the developing sarcoplasmic reticulum and T-system. It was shown that transverse tubules invaginating from the plasma membrane are the framework for the forming myofibrillar system, and thin filaments are attached to the transverse tubules at the sites of future Z-lines. These results support the idea that Z-lines originate from the membrane. Destruction of the membrane elements provokes disorganization of myofibrillar contractile material.

Animals↗

PubMedDate not supplied

[Ca2+ localization in muscles with double calcium regulation].

Localization of Ca-accumulating structures was studied in scutal depressor muscles of barnacle (Balanus rostratus) by electron microscopy combined with osmium--pyroantimonate technique. In resting fibers the pyroantimonate precipitate was localized mainly in plasma membranes of the cleft system which can be considered as main calcium store. The precipitate was also located in membranes of sarcoplasmic reticulum and mitochondria and I--bonds diffusely. In contracted fibers fixed at the peak of mechanical activity the number of precipitate granules increased in the sarcoplasm and diminished at cleft plasma membranes. In contracted fibres the fine precipitate also appeared along thick filaments at the sites of myosin heads. The latter seems to be the proof of the presence of myosin control in crayfish muscles.

Animals↗

PubMedDate not supplied

[The accelerating action of polystyrene latex on myoblast proliferation in culture].

Latex beads (1800 A) added to chick embryonic muscle cell culture at the moment of plating accelerate and enhance the mitotic activity of myoblasts as soon as by the end of the first day of cultivation. The mitotic index of the induced cultures was several times greater than that characteristic of usual myoblast cultures. The formation of myotubes and the appearance of satellite-like cells was observed during the same period.

Animals↗