Permanganate oxidation of senile cerebral amyloid and its relationship to AA protein.

Immunoreactivity for AA protein was rarely detected in briefly fixed amyloid of senile plaques and dyshoric angiopathy, but was not observed in Congophilic angiopathy. Plaque and dyshoric amyloid exhibited variable sensitivity to permanganate oxidation; Congophilic angiopathy was resistant to oxidation. In contrast to systemic amyloid composed of AA protein, the rare immunoreactivity of senile cerebral amyloid was lost with prolonged fixation. This study demonstrates that the fibrillar protein of senile cerebral amyloid differs from that of systemic amyloid of AA type.