A morphological study of the neostriatum of aged mice with particular reference to neuroglia.

The most prominent feature of the aged mouse neostriatum is the presence of large vacuoles. Careful inspection showed that these are vacuolated myelin sheaths and are invariably found in, or at the periphery of, the nerve fibre bundles which traverse the neostriatum. Oligodendrocytes showed little evidence of ageing but satellite oligodendrocytes contain more lipofuscin than oligodendrocytes associated with myelin sheaths. Most astrocytes contain pigment-prominent lipofuscin granules but a small minority contain numerous large pigment lipofuscin granules, and are packed with microfilaments and glycogen granules. A few astrocytes have circular nuclear inclusions filled with a fine granular material. Microglial cells contain the largest amount and variety of lipofuscin; in most cases, however, the lipofuscin is of the lipid-pigment type.