Thinning of capillary walls and declining numbers of endothelial mitochondria in the cerebral cortex of the aging primate, Macaca nemestrina.

Samples were obtained from the frontal and occipital cortex of Macaque monkeys at 4, 10 and 20 years of age. Electron microscopic studies revealed attenuation of capillary walls and declining numbers of endothelial mitochondria per capillary profile with increasing age. The basal lamina surrounding the capillary increased in thickness between 4 and 10 years of age; however, it did not undergo further change between 10 and 20 years. These results corroborate morphological and biochemical studies indicative of declining numbers of mitochondria, and decreasing mitochondrial ATP synthesis and ATPase activity in other tissues during aging.