On the Ageing of Intermitotic Cells — Investigations on Enterocytes and Hepatocytes

Abstract

At first, we think, it is necessary to define ageing. Ageing in the sense of Max Burger (1) reflects the physiological, morphological, biochemical and biophysical changes, which occur during the life-span of an individual. These changes are arranged into changes during prenatal development, postnatal development, adolescence and senescence. Ageing takes place at different levels; at the level of the organism, organ and tissue, which includes cells and intercellular substance. The ageing changes are underlying changes at the different levels, because the parts of the organism, its organs, tissues and cells, are aging disproportionately. For that reason the cell represents only one level, but a very important one. Many of the hypotheses now being discussed, put the changes of the cell into the center of consideration. Doubtless there is an ageing process of postmitotic cells concerning lipofuscin, mitochondria, lysosomes, molecular arrangements between DNA and histones, contents of RNA and pattern of enzymes. But it is questionable up to now: Is there an ageing process of intermitotic cells too? At first we have to distinguish between ageing processes starting in single cells and such starting in multicellular arrangements on the level of tissues.’ The single cell shows changes during its cell cycle. But it is questionable, if there is a difference in the view of rise, maturation and death of intermitotic cells between young and old individuals.