[Development of intramural ganglia of the gastrointestinal tract in embryo rabbits under conditions of thyroidin loading of the mother's body].

Ganglia of myenteric plexus in 13-, 15.5-, 16.5-, 19.5-, 25-, 27- and 29-day-old rabbit embryos, as well as in newborn rabbits delivered under experimentally induced thyrotoxicosis in the maternal organism during gestation were studied and compared with those of control animals at the same age. Different methods of silver impregnation, hematoxylin--eosin staining and Nissl's method were used. Total amount of nervous cells and differentiated neurons were counted; numerical data were statistically treated. At early stages of embryogenesis, there were no differences in migration processes, in laying and differentiation of nervous elements in the intramural ganglia of the intestinal tubes of the test and control embryos, that is in accordance with literature data on the placental barrier nonpermeability for the thyroid hormones at that time. Thyroidin stimulates the intramural ganglia development, growth of their neurons, stipulated by cytoplasmic protein synthesis. The experimental results were seen in increasing amount of highly differentiated multipolar neurons in the embryos before birth and in the newborn animals in comparison with the control. In lower vertebrates, thyroxine was stated by Coujard (1950) to influence the earliest stages of the intramural ganglia laying as a result of stimulation effect on the migrational movements of neuroblasts.