ABSTRACT
This chapter describes some of the cytoskeletal changes which do also occur spontaneously during aging, albeit at a much lower frequency than in pathological states. The neuronal cytoskeleton, like that of most mammalian cells, is composed of three biochemically, morphologically, and functionally distinct systems: microfilaments, intermediate filaments, and microtubules. Aging is of particular interest to neurobiologists because neurons are postmitotic cells and cannot be replaced if they degenerate. The neurofibrillary tangle is the hallmark alteration of Alzheimer's disease. The mirano body is an eosinophilic, usually rod-shaped inclusion originally described in Parkinson-dementia complex of Guam. The Lewy body is the hallmark lesion of Parkinson's disease. Again, as for the Alzheimer neurofibrillary tangles, Lewy bodies can also be found in old patients without neurological disturbances, although in smaller numbers than in neurological diseases. Variety of other filamentous inclusions has been observed sporadically in aging. They appear as "tangles" of normal neurofilaments, which can be very tightly packed and arranged in a paracrystal.
