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Neuritic (Senile) Plaques and Filamentous Changes in Aged Rhesus Monkeys

Henryk M. Wiśniewski M.D., Ph.D., Bernardino Ghetti M.D., Robert D. Terry M.D.
DOI: http://dx.doi.org/10.1097/00005072-197310000-00007 566-584 First published online: 1 October 1973


Three rhesus monkeys, whose approximate ages were 16 to 18 years old, and one 22 to 23 years old, were studied for age changes in the nervous system. The brains of all four were slightly shrunken and the meninges were fibrotic. The vessels were stiff and fibrosed, but were not atheromatous. The lateral ventricles were mildly dilated. Bodian preparations of the oldest monkey and of one of the 16− to 18-year-old monkeys revealed the presence of neuritic (senile) plaques. Serial one-micron toluidine blue-stained sections showed that some plaques were closely associated with capillaries. Electron microscopic studies revealed that the plaques were identical to those of human Alzheimer's disease except that the typical twisted tubules were absent. Outside the plaques there were scattered neurites showing degeneration of the type found in the neuritic plaques. Furthermore, two forms of rare pathological fibrillar material were found in 3 animals. One was made up of pairs of helically wound 100 Å filaments with a twist every 500 Å. The other fibrillar structures were made up of bundles of parallel filamentous elements, each about 130 Å thick, with a distinctly granular structure on longitudinal section. A list of other abnormalities includes vascular amyloidosis, lipofuscin accumulation, dark neurons undergoing phagocytosis, myelin remodeling, aggregates of large electron-dense droplets, enlarged mitochondria and mitochondria with paracrystalline inclusions, corpora amylacea, Rosenthal fibers and two types of virus-like particles.