Ultrastructural heterogeneity in cerebral amyloid of Alzheimer's disease.

Cerebral amyloid deposits from five patients with presenile or senile cerebral disease of the Alzheimer type were stained with uranyl acetate and lead citrate or with periodic acid-thiocarbohydrazide-silver proteinate, and examined with traditional high-resolution electron microscopy and with a goniometer tilting stage. In addition to a carbohydrate-rich matrix, we also consistently found local cell-derived vesicles within plaque and dyshoric amyloid. The most likely source for these vesicles appeared to be degenerate neurites. Amyloid fibrils were intimately associated with plasmalemmata, particularly those of degenerate neurites, which supported a neuronal origin for the amyloid fibril of Alzheimer's disease.