Summary

Fluorescent changes in the brains of 4 aged dogs and one senile human were studied with the electron microscope using a special techique to reembed conventional histological sections in plastic (Rossiet al., 1970). Using this method typical amyloid filaments were found in fluorescent leptomeningeal and cortical vessels and in fluorescent plaques in the cerebral cortex. Leptomeningeal and cortical vessels in aged dogs and senile human disclosed dense intercellular accumulation of amyloid extending throughout the whole vessel wall. Contrary to man, perivascular penetration of amyloid filaments were not seen in the dog. They are, however, indicated by the presence of filaments in the adventitia. Senile plaques in both species are formed by the same elements. The central core of the plaque predominantly contains amyloid, while the periphery discloses various dystrophic changes of the ageing brain.

Alzheimer filaments clearly distinguished from normal neurofilaments and from amyloid were present in the human brain but were absent in the dog brain.