ULTRASTRUCTURAL-STUDY OF A SPECIAL TYPE OF EPENDYMAL CELL AT PARAVENTRICULAR LEVEL OF THE GOLDEN-HAMSTER 3RD VENTRICLE

The present paper describes the presence of a special cell located in the ependymal wall at the level of the paraventricular nucleus. At thi s level, ultrastructural observation of these ependymal cells, unlike most other mammalian species, shows the presence of nucleolus-like bod ies in their cytoplasm and occasionally basal processes. These process es appear perpendicular to the ependymal surface and end in contact wi th the basal membrane of hypothalamic capillaries. Mitochondria, endop lasmic reticulum and numerous filaments are present in the basal proce sses. Nucleolus-like bodies or nematosomes consist of round or ovoid u nbound masses of granular appearing material of variable density locat ed in the apical cytoplasm of the cells. Some of their ultrastructural characteristics are similar to other ependymal specialized cells whic h are classically termed tanycytes. These findings point out the possi bility that those special cells may also be implicated in a ventricle- blood vessel communication.