Aluminium detected in senile plaques and neurofibrillary tangles is contained in lipofuscin granules with silicon, probably as aluminosilicate.

Aluminium and silicon are incidentally found in senile plaques (SP) and neurofibrillary tangles (NFT) of brains with Alzheimer's disease (AD), and have been considered as one of the risk factors for senile dementia. Since lipofuscin granules were concentrated concomitantly with SP and NFT in the high density fraction in subcellular fractionation of autopsied brains and are solid in nature, it was suspected that aluminum and silicon are accumulated in lipofuscin granules. Therefore, elemental analyses of partially purified lipofuscin granules from autopsied brains with AD and those without dementia, were attempted by energy dispersive X-ray spectrometry with a scanning electron microscope. It was demonstrated by a mapping method that aluminum and silicon were accumulated in some lipofuscin granules, probably as aluminosilicate. In addition, it was demonstrated by fluorescence microscopy of Bodian stained paraffin sections, that many SP and NFT contained lipofuscin granules, although lipofuscin granules were not always specific to those neuropathological changes. These results imply that aluminum detected in SP and NFT is due to lipofuscin granules and can explain the cause of discrepancies in the reports on the presence of aluminum in SP and NFT.