In elderly people there is a notable reduction in the capacity to produce new blood cells. Yet, unless there is substantial physiological stress, the number of circulating cells remains fairly constant. Quantitative deficiencies are only apparent when stress produces a demand that exceeds reserve proliferative capacity. Such a demand might occur during an acute infection or after cytotoxic chemotherapy. (more…)

Aging theories cover the biochemical, genetic, and physiological properties of a typical organism, and the way these properties change with time. Genetic theories deal with speculations regarding the identity of aging genes, accumulation of errors in the genetic machinery, programmed senescence, and telomeres. Biochemical theories are concerned with energy metabolism, generation of free (more…)