SOME UNUSUAL RESPONSES OF ASTROCYTES TO GHOST TANGLES IN A LONG-DURATION CASE OF JUVENILE ALZHEIMERS-DISEASE - AN ELECTRON-MICROSCOPIC STUDY

The ghost tangles (GTs) in usual Alzheimer's disease are separated int o small bundles of abnormal straight filaments by many invading astroc ytic processes lacking a basal lamina (BL). An electron microscopic st udy of GTs in the Ammon's horn of a case of juvenile Alzheimer's disea se of 25 years' duration, however, revealed that only a small number o f astrocytic processes had infiltrated the GTs, resulting in the GTs b eing composed of large bundles. Moreover, the majority of glial proces ses that had invaded or apposed GTs possessed an interrupted but still fairly well-developed BL with hemidesmosome-like profiles. Although p ia-arachnoid cells are required for astrocytes to form a continuous BL , astrocytes can have a segmental BL on their surface facing even empt y intercellular spaces within the brain parenchyma. The much greater f requency and better development of the GT-associated BL in our case in dicate that the GT filaments somehow increased the ability of astrocyt es to form a BL. On the other hand, the scarcity of GT-invading astroc ytic processes implies that many of the glial processes that had once penetrated GTs had been withdrawn, with the result that GTs escaped ex pectable endocyto-phagocytosis by astrocytes.