The relationship between lipofuscin pigment and ageing in the human nervous system

The cytoplasmic RNA content, nucleolar volume and lipofuscin content of nerve cells of the inferior olivary and dentate nuclei, Purkinje cells and pyramidal cells of the hippocampus has been measured in 82 persons of age range 2--91 years, who were free from overt neurological disease at the time of death. All 4 cell types accumulate lipofuscin in a linear manner throughout life, but to markedly differing extents. Both the RNA content and nucleolar volume of dentate, olivary and hippocampal cells decrease, with advancing age, in a similar way in all of these 3 cell types, despite the widely differing extents of pigment accumulation, with losses of RNA and nucleolar volume at 90 years of age of 15 and 30% respectively. Olivary cells which contain most pigment show a different pattern of change with losses of RNA and nucleolar volume of about 60%. It seems, therefore, that, if there is a causal relationship between lipofuscin accumulation and reductions in RNA and nucleolar volume, it is rather obscure. It cannot simply be a matter of the absolute amounts of pigment present in any one cell type, but rather might be that there is a critical concentration of such material in the cytoplasm.