[Muscle tissue histogenesis of the lymph hearts of chick embryos]

By means of electron microscope autoradiography, the ultrastructure of muscle fibers, and the capacity if muscle of cell nuclei of 3H-thymidine (3H-T) incorporating of were studed in developing lymph hearts of 0-13 day old chick embryos, rather active sarcomerogenesis developing lymph hearts of 9-13 day old chick embryos, a rather active sarcomerogenesis being observed. Filament of intermediate size microtubules, Golgi complexes, centrioles, and numbers free ribosomes and polysomes were observed in the sarcoplasm. The sarcoplasmic reticulum channels were not numerous, their terminal cisterns often formed "subsarcolemmal cisternae". Between muscle fibers, cell junctions of fasciae adherentes type were observed. Two hours after 3H-T administrations, only mononuclear cells without myofilaments were labeled. If fixation was made 70 hours after 3H-T administration, then the label was found in addition on muscle fiber nuclei. These data evidence that the lymph heart muscle tissue histogenesis undergoes the same patterns of development as does the somatic muscle tissue.