Evidence for basal secretion in the subcommissural organ of the chicken (Gallus gallus).

The basal region of the subcommissural organ (SCO) was studied in the chicken Gallus gallus. The presence of concentric rough endoplasmic reticulum associated with lipid droplets in the basal processes of the ependymal cells, along with the increase of the lysosomal population, can be interpreted as evident signs of degeneration of the basal processes. The nearly absence of secretory processes ending on the meningeal blood vessels, suggests that the leptomeningeal route is missing. On the contrary, the presence of basal ependymal processes in contact with the hypendymal vessels could indicate that the ependymo-vascular pathway is well developed. In this sense, several structural features suggest a basal secretory mechanism from the SCO-cells: 1) Positive staining with paraldehyde-fuchsin of secretory material in the pericapillar region of hypendymal vessels and in the basal processes which reach the capillary wall; 2) presence of secretory material within the process endfeet in contact with hypendymal capillaries, and 3) existence of labyrinthis of the basal lamina of the capillaries.