Model systems for aging research: syncretic concepts and diversity of mechanisms.

A variety of very different phenomena have been subsumed under the heading of "aging" research. A review of recent experimental data, in several of the best-studied model systems for the investigation of aging, indicates that molecular changes which are putative or demonstrated proximal causes of senescent deterioration are generally not shared by other systems examined. It is thus argued that different aberrant biochemical processes have evolved as the "weakest link" limiting longevity or intermeiotic interval in different systems, although in each case the germ line must be exempted.