Developmental change in the second half of life--strategies for modification of selected compartments of aging.

Age-related changes of different individuals multicentric and polymorphic. We have approached this problem of age-related changes by examining (1) membrane densities of receptors of various ligands in different organs, and (2) changes in different classes of T cells and of antibody response. Three strategies have been developed to modify progression of age-related changes to different extents in different compartments in which age-related changes occur. The first is based on administration of hormones, the second on administration of purine analogues and the third on administration of diets which differ in fatty acid content. Details of this last approach are reviewed in this paper. Lifespan of different species is a component of the evolution of each species. The variables which are decisive in the evolutionary processes which affect lifespans of different species are not necessarily variables which play a decisive role in the different health span of different individuals of the same species. For each individual of a given species, relative health span represents variations within the limits of the evolved lifespan of the species and depends on alleles of many different genes.