Cerebellar capillaries. Qualitative and quantitative observations in young and senile rats.

Ultrastructural changes including reduced electron density, reduction in polysomes and cisternae of rough endoplasmic reticulum occur in tthe cytoplasm of endothelial cells and pericytes in the cerebellar cortex of senile virgin female Han: WIST-rats in comparison to 3-month old virgin rats. processes of pericytes cover less of the capillary surface in the cerebellar cortex of senile rats; moreover, arithmetic and harmonic mean thickness of the endothelium and relative volume of mitochondria in endothelial cells and pericytes are reduced, whereas he luminal diameter of the capillaries, harmonic and arithmetic mean thickness of pericytes and their processes and of the basal laminae between endothelial cells and astrocytes (abbreviated BAL 1), pericytes and astrocytes (BAL 2) and endothelial cells and pericytes (BAL 3) increase. The increase in harmonic mean thickness of the basal laminae is statistically significant (alpha less than or equal to 0.05) and compensates for a decrease in thickness of capillary endothelium. Consequently, the total barrier mass and thickness of cerebellar cortical capillaries in senile animals is higher than in young individuals.