HISTOPATHOLOGICAL STUDIES ON SENILE PLAQU ES AND CEREBRAL AMYLOID ANGIOPATHY IN AGED CYNOMOLGUS MONKEYS

The incidence and morphological characteristics of senile plaque and a myloid angiopathy in the cerebrum of six aged cynomolgus monkeys (Maca ca fascicularis), 20 to 29 years old, were studied histopathologically and immunohistochemically. By periodic acid methenamine silver stain (PAM) and alkaline Congo red stain, senile plaques were detected in 5 out of 6 cases, and 3 of them were positive for amyloid in the wall of capillaries and arterioles in the cerebral cortex. Senile plaques wer e classified into three types. Mature plaques, including classical and primitive types, were more frequently observed than the immature diff use type. Senile plaques were often seen in the cortex of temporal lob e, putamen and head of caudate nucleus. Since mature types of senile p laques were seen frequently around vascular amyloid deposition and no amyloid angiopathy was detected in the areas without senile plaques, t he close relation between senile plaque of the mature type and amyloid angiopathy might be considered. All senile plaques and amyloid angiop athy were positively stained immunohistochemically with antibody again st amyloid beta-protein (A beta P) 1-40 synthetic peptide, but all dif fuse and some primitive plaques were negative for antibody against A b eta P 8-17 synthetic peptide. Neither senile plaque nor amyloid angiop athy was detected;in the cerebrum of 15 young monkeys, 9 to 11 years o ld, examined as controls.