[Electron microscopic study of the rat submaxillary gland during development].

Cytological changes in the submaxillary glands of rat embryos of the 14th-21st days of the intrauterine development and of 7-day-old rats were studied electron microscopically. The cytoplasm of the salivary gland primordium cells of the 14-day embryo was found to possess multiple polysomes, the canals of the granular cytoplasmic network (GCN) being solitary. The latter elongated in the process of embryonic development, and later predominant development of GCN was observed in basal portions of the acinar cells. At early stages of the gland development the GCN was often observed to approximate mitochindria. The laminar complex in the course of embryonic development enlarges its size and at later stages it has a well differentiated appearance in the acinar cells. Secretory inclusions make their appearance in the forming cells of acinuses long before birth, the composition of the embryo gland secretion being somewhat different from that of adult animals. Differentiation of acinuses and striated parts of the salivary tubules is well pronounced in the embryonic period while no signs of appearance of granular portions of the salivary tubules are observed both in light and electron microscopy either in embryos or in 1-week-old rats.