Accumulation of aluminium and silicon in lipofuscin granules.

Since lipofuscin granules were concentrated in the high density fraction in subcellular fractionation of autopsy brains of normal aged subjects and of patients with Alzheimer's disease (AD), it was suspected that inorganic materials accumulated in lipofuscin granules. Therefore, elemental analyses of clusters of lipofuscin granules in the high density fraction were attempted by energy dispersive X-ray spectrometry with a scanning electron microscope. It was demonstrated that aluminium (Al) and silicon (Si) accumulated in some lipofuscin granules. Al has been considered as one of risk factors of AD since Al and Si were found in senile plaques (SP) and neurofibrillary tangles (NFT) of the brains with AD, although conflicting results also have been reported. It was also demonstrated in this experiment by fluorescence microscopy of Bodian stained paraffin sections of AD brain that many SP and NFT contained lipofuscin granules, although lipofuscin granules were not always specific to those neuropathological changes. The results of this experiment imply that Al detected in SP and NFT is contained in lipofuscin granules.