[Cell composition and ultrastructure of the thymus in offspring during changes in the hormonal background in the...

Micro- and ultrastructure has been studied in newborn rats, developed under conditions of an altered hormonal background in the functional system mother--fetus (FSMF), when hydrocortisone acetate is injected on the 17th-18th days of pregnancy, and at bilateral adrenalectomy of pregnant females. A number of similar changes in the offspring thymus are revealed under both procedure: the portion of mitotically dividing and blast forms of cells decreases, there is a certain tendency to increasing destructively altered cells and intensity of the processes in differentiation of cellular elements and subcellular structures, that is, evidently, depended on increasing contents of corticosteroids in the developing organism. When hydrocortisone acetate is injected to the pregnant rats, some amount of the drug can penetrate across the placenta and a superfluous concentration of glucocorticoids is created in the fetus blood. When adrenalectomy is performed in the pregnant rats, the main cause of elevated secretion of corticosteroids in the fetuses is, evidently, stimulation of the adrenals with their own ACTH, that is produced as a response to a decreased concentration of corticosteroids in FSMF. Nevertheless, in the fetal thymus reaction to the effects mentioned there are some differences. In the experiments with adrenalectomy in the pregnant rats, in the offspring thymus signs of degradation of lymphocytes and reticuloepitheliocytes are manifested more distinctly; that can be connected with a high concentration of endogenic corticosteroids in the fetus blood and with a qualitative composition of the hormones.