[A study on causative factors of newborn intraventricular hemorrhages. An ultrastructural investigation on changes in the subependymal layer of the rat fetus].

To investigate the causes of the onset of newborn intraventricular hemorrhages , perplacental ischemic loads were applied and ultrastructural changes in the subependymal layer, which is assumed to be one of the most predominant site of hemorrhages were observed in rat fetuses at 17 , 19 and 21 days of gestation. The following results were obtained : 1) The subependymal layer of the rat fetus was not well devoloped and scanty fibrous compo nent was discernible. Junctional complexes between the cells were incomplete and structural maturation was not well comfirmed. 2) With respect to intracellular organelles, the cells of the subependymal layers at 17 days of gestation cotained mainly ribosomes and were undifferentiated. However, in the cells of the subepen dymal layer at 19 and 21 days of gestation, the number of organelles such as Golgi complexes , mitochondria and rough-surfaced endoplasmic reticulum was increased and the increase of filament was observed, suggesting differentiation and maturity had far progressed . 3) The perplacental ischemic loads caused dilatation of the intercellular space , elongation of the cellular processes and destruction of the cytoplasm in the subependymal layer at 17 days of gestation . In the subependymal layer at 19 and 21 days of gestation , the intercellular space had dilated mainly in the pericapillary space. From the above mentioned findings, it was suggested that the increased capillary permeability and subsequent intercellular edema may play an important role as one of the initial pathological causative factors of the newborn intraventricular hemorrhages . It was also suggested that the structural immaturity as well as the poor development of the cell constituents , might participate in the causation of the hemorrhages.