Chapter 2, also merit support. Some of these important research directions are as follows:
the study of the repair and regeneration of postmitotic nondividing cells, including neurons and cardiac and skeletal muscle cells, as well as conditionally proliferating cells, such as hepatocytes;
the study of the major integrative systems of physiology, including the effects of aging on the immune and endocrine-neuroendocrine systems, the effect of dietary restriction on lifespan, and the regulation of reproductive and developmental physiology;
the study of the varying rates of aging among different cells, tissues, and organs for individual differences within species and for species differences that will provide information about genetic influences;
the study of the biomarkers of aging, their relationship to overall functional state, and the role of functional capacity as a marker of senescence;
the study of the general question of gene expression in aging (especially as applied to the abnormal proteins associated with Alzheimer's disease or the inactivation of enzymes with age), selective changes in gene activity, and the effects of environmental influences on aging (e.g., free radicals, radiation, and various toxins); and
the use of comparative genetics and development of new model systems to study aging and the lifespan.
The committee emphasizes that additional resources to support research on aging should supplement, not supplant, existing support for current basic research, either in aging or in other areas of biological investigation.
First in importance, increase the funding of NIA—and other NIH—approved investigator-originated research proposals on aging from the present level of one in four to one in two.
Increase the availability of animal models (including primates and other long-lived animals that more closely resemble humans) and laboratory animal models with contrasting maximal lifespans.
Improve access to cell lines and tissue samples, especially cryopreserved cells and tissues, and cell and tissue types from different human populations that crosscut age, sex, and stages of disease (e.g., different stages of diabetes mellitus or Alzheimer's disease).
Expand existing human longitudinal studies, making available