The effects of aging and transformation on the DNA, RNA, protein, and hydroxyproline content of fibroblasts (WI 38) in culture

The study of the aging process is the investigation as to how the passage of time affects cells, organs, and organisms. Aging is a very complex and incompletely understood phenomenon. This is reflected by the number of theories attributing aging to a variety of causative factors such as: (1) the somatic mutations occurring spontaneously or produced by ionizing radiation, which are thought to have some effect on again but are not responsible for the normal process; (2) the alteration of macromolecules as the cells of an organism age forming neoantigens and functioning in the autoimmune reactions; the Cross-linkage theory which maintains that large molecules necessary for life processes, such as deoxyribonucleic acid (DNA) and collagen are progressively immobilized in all cells and tissues by cross-linkage. Aging has also been studied in relation to the self-destructive “programmed death” characteristic of some parts of embryological development. Moreover, senescent changes involve different kinds of cells and tissues in the organism and therefore various mechanisms must occur. For example, the aging of postmitotic cells, such as neurons and cardiac cells probably proceeds by a different mechanism than the proliferating tissues, such as the skin, the gut lining, and the blood forming elements. It is apparent that there is probably no single aging process, but a series of aging processes which natural selection would tend to synchronize even if the causes were physiologically independent