Chronological lifespan of stationary phase yeast cells; a model for investigating the factors that might influence the ageing of postmitotic tissues in higher organisms

Budding yeast can be considered to have two distinct lifespans: (a) a repli cative (budding, non-chronological) lifespan, measured as the number of dau ghters produced by each actively dividing mother cell; and (ii) a chronolog ical lifespan, measured as the ability of stationary cultures to maintain v iability over time. In non-dividing cells, essential components that become damaged cannot be diluted out through cell division but must, of necessity , be turned over and renewed. By elevating stress resistances, many of the activities needed for such renewal should be elevated with commensurate red uction in the steady-state levels of damaged cell components. Therefore, ch ronological lifespan in particular might be expected to relate to stress re sistance. For yeast to attain a full chronological lifespan requires the ex pression of the general stress response. It is more important, though, that the cells should be efficiently adapted to respiratory maintenance, since it is cultures grown to stationary phase on respiratory media that usually display the longest chronological lifespans. For this reason, respiration-a dapted cells potentially provide a better model of chronological ageing tha n cultures pre-grown on glucose. Copyright (C) 2001 John Wiley & Sons, Ltd.