[Early development and cell differentiation of the parasympathetic vagus-glossopharyngeal nucleus in cattle. Light...

The early development, differentiation of the cell and cell migration of the nucleus parasympathicus nervi vagi et glossopharyngei were examined by light microscope in 32 bovine embryos with crown-rump-lengths (CRL) ranging from 1 cm to 53 cm. During this period the nucleus is being enlarged 6 to 7 times and the size of the cell increases to 35-40 microns. The ultrastructure during the differentiation of the cell is shown electron microscopically in embryos with CRL of 2.5 cm and 3.6 cm. Several layers of matrix cells arise from the neuroepithelium of the neural tube by mitosis. They migrate in the shape of dark nucleated cells into the parasympathetic cell column. With advancing age of the embryos the number of cells with light nucleus increases. They represent the presumptive neurons. In embryos of 2.5 cm CRL their cytoplasm surrounds the nucleus on three sides in the shape of a narrow rim while on the fourth side it is enlarged into an outgrowing process. In this process a smaller number of organelles and their preliminary stages appears. Their number is significantly increased in embryos of 3.6 cm CRL and they can be seen throughout the growing process. In the following stages of maturity cytological development proceeds. In embryos of 53 cm CRL topographical and cytological data are comparable to those in adult animals.