Comparison of apoptosis and terminal differentiation: The mammalian aging process

Apoptosis is the ordered chain of events that lead to cell destruction. Ter minal differentiation (denucleation) is the process in which cells lose the ir nuclei but remain functional. Our group examined cell death in three tis sues using two different fixatives and a postfixation procedure, involving young (5 months) and old (2 years) guinea pigs. The data reveal that B-DNA and Z-DNA content decreases, whereas single-stranded (ss-) DNA increases, i n older tissues undergoing apoptosis (skin and corneal and terminal differe ntiation (ocular lens). We speculate that some of the factors that contribu te to the aging process might also be responsible for the enhanced amount o f damaged DNA in older tissues undergoing cell death.