Effects of malnutrition on cell genesis and migration in developing brain in rats

Rats were fed a diet containing either 5% (LP) or 25% (HP) casein throughout gestation. The animals, delivered by a cesarean section on the 21st day of gestation, were given a pulse of [ 3H]thymidine and killed 2 h later. No differences were observed in the mitotic index, but the labeling index of the ventricular zone cells of the lateral ventricle was higher in the case of litters of the LP dams. This we atribute to a disproportionate increase of the S phase in relation to the cell cycle in malnutrition. To study the effects of malnutrition on the programming of cell genesis, the dams were given [ 3H]thymidine on the 20th day of gestation, and the litters were killed on the 21st postnatal day. The labeled neurons reached the second layer of the cerebral cortex in both groups, indicating that the programming was not affected by gestational malnutrition. Postnatal undernutrition was induced by doubling the litter size. The cell generation cycle was prolonged in the undernourished animals. Not all phases, however, were evenly affected: S was prolonged, G 2 was not affected, but G 1 was shortened. The external granular layer maintained its proliferative activity in the undernourished animals beyond the stage it had ceased in the controls. The migration of the cerebellar granule neurons was slow. It is proposed that tardiness in the migration of the neurons may interfere with synaptogenesis.