Histochemical analysis of senile plaque amyloid and amyloid angiopathy

Histochemical methods were used to obtain information on the chemical constituents of brain amyloid in senile dementia of the Alzheimer type. The staining properties of brain amyloid (senile plaque and amyloid angiopathy) were compared with those of extraneural amyloidosis and endocrine amyloid. We found no histochemical differences between amyloid in senile plaques and in amyloid angiopathy. The content of aromatic amino acids was higher in amyloid of plaques and in amyloid angiopathy than in endocrine amyloid. Furthermore, we found persistent birefringence and affinity of brain amyloid for Congo red after exposure to potassium permanganate, suggesting that AA amyloid is not a major constituent of cerebral amyloid.