[Ultrastructural bases for the postnatal development of the capillaries].

The work has been devoted to establishment of main regularities in the process of developmental reconstruction of the ultrastructure of blood capillaries. The objects of the study were the capillaries of the heart, adrenals, exo- and endocrinous portions of the pancreas of Balb white mice of the following age groups: new-borns, 3-, 7-, 14-, 30-, and 90-day old mice. It has been established that the structural organization of capillaries is not completed by birth-time and actively proceeds during early postnatal ontogenesis. Thickening of the endothelium cytoplasm, high activity of the synthesis organells, imperfectness of intercellular contacts etc., registrated against the background of a decreased transport function of the endothelium represent a common rule for capillaries of newly born animals. In the process of differentiation of organs the synthetic potencies of cells were found to decrease and the motor activity of the endothelium to increase; the developmental reconstruction of capillaries had organic specificity and correlated with processes of development of working structures of the organ.