Fibrous astrocytes in Alzheimer's disease and senile dementia of Alzheimer's type.

In four patients with Alzheimer's disease (AD), on patient with senile dementia of Alzheimer's type (SDAT) and five age-matched controls, occipital cortex, frontal cortex, and hippocampus were evaluated for the distribution of fibrous astrocytes (FA), using peroxidase-anti-peroxidase for glial fibrillary acidic protein (GFAP). FA, neuronal cells, neurofibrillary tangles (NFT), and senile plaques (SP) have been quantified in the occipital cortex. In AD and SDAT there was a significant increase in the number of FA in the molecular layer as well as in the other layers of the cortex. No correlation was found between the increase in FA and the number of neurons, NFT or SP. The GFAP positivity was most pronounced around small blood vessels. Electron-microscopic studies of four cortical biopsies of AD revealed dense perivascular gliosis in 48.8% of the capillaries examined as opposed to 17.8% of capillaries in three controls without dementia. The significance of increased perivascular gliosis in AD and SDAT is unknown. It may be related to a defect in the blood-brain barrier.