Immunocytochemical and ultrastructural examination of amyloid plaques in the brains with Alzheimer-type dementia.

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This is a detailed immunohistochemical and ultrastructural examination of "amyloid plaques" in the brains of Alzheimer's disease. The amyloid plaque is a distinctive type of senile palques, in which thin glial bundles penetrate into the mass of amyloid fibrils accompanied with very few degenerating axon terminals, first described by Oyanagi (1990) under the electron microscope in certain cases of Alzheimer's disease.Subjects : Seven clinically and pathologically well-documented Alzheimer's disease cases were examinedResults : 1. Histological studies. Numerous amyloid plaques were found in two cases, in which amyloid plaques tended to occurred in the parietal and temporal cortices and in the floor of the gyrus. Only few amyloid plaques were found in the floor of gyri in the parietal and temporal lobes in three cases. No amyloid plaques were found in two cases.2. Immunohistochemical studies. The amyloid core of the amyloid plaques showed positive immunoreaction with all of the anti-beta- … More amyloid antibodies that recognized amino-acid residues of 1-40,1-42, and 8-17. In terms of molecular spices of Abeta-protein, both of Abeta1-40 and Abeta1-42 were identified. Anti-GFAP antibody stained thin glial bundles that penetrated into the amyloid mass. Anti-tau antibodies visualized only few neuronal processes surrounding the amyloid mass.3. Electron microscopic studies. Astrocytic glial bindles were identified in amyloid plaques. A particular form of astrocytic degeneration called "astrocytic glial tangles" were found in 3 cases that had amyloid plaques. The astrocytic glial tangles consisted of abnormal tubular structures that resembled PHFs and straight tubules of neurofibrillary tangles.4. Immuno-electron microscopy and electron microscopic observation of Gallyas-Braak's silver impregnation sections. Abnormal tubules in the astrocytes showed argyrophilia and anti-tau immunoreactivity.Conclusions : The amyloid plaque was a distinctive type of senile plaques in that the former lacked degenerating axon terminals and that the former had intense astrocytic reaction to the amyloid mass. Association between the occurrence of amyloid plaques and the clinical duration was not found. Less