ABSTRACT

The picture that emerges is that while there are changes in the protein constituents of living systems with age, the importance of these changes in the senescence and death of the system and the mechanisms responsible for these changes are unknown. Studies of human beings have established that there are fundamental changes in protein and amino acid metabolism with aging but the specific changes have been difficult to establish definitively. Mammalian cells in culture offer one model system for aging, although the interpretation and application of the data obtained from cells in vitro are the subject of debate. Reticulocytes are readily generated by inducing anemia in laboratory animals and easily fractionated into discrete cell-age groups with buoyant density gradient centrifugation. Phosphoglycerate kinase is another enzyme that has a marked reduction in specific activity in old nematodes. A variety of different insects are used as models for aging as they contain post-mitotic cells in their adult life.