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The number of cell divisions of the yeast Saccharomyces cerevisiae is limited, referred to as "replicative lifespan" of this organism and believed to be due to aging mechanisms similar to those of mammalian cells. We demonstrate, using three pairs of isogenic yeast strains (standard and a mutant deficient in an antioxidant defense protein) that although the lifespan differs significantly, the final volume attained after the last division is similar within each pair of strains. In a population, cells cease to bud after various number of cell cycles but attaining a similar final volume. These results indicate that the increase in the mother cell volume, intrinsic to the asymmetric cell division in S. cerevisiae, may be the main mechanism limiting the reproductive capacity of in this organism.

Yeast (Saccharomyces cerevisiae) mutants lacking CuZnSOD have been reported to be hypersensitive to hypertonic media and to show increased oxidative damage. This study demonstrates that hypertonic medium (containing 0.8 M NaCl) increases the generation of superoxide and other reactive species in yeast cells. Other sequelae of exposure to hypertonic medium include oxidation of cellular low-molecular weight thiols and decrease in total antioxidant capacity of cellular extracts. deltasod1 mutant is more sensitive than a wild-type strain to colony growth inhibition on a hypertonic medium. Anaerobic conditions, ascorbate, glutathione, cysteine and dithiothreitol are able to ameliorate this growth inhibition but a range of other antioxidants does not protect. The protective ability of the antioxidants does not correlate with the rate of their reactions with superoxide but seems to be conditioned by low redox potential for one-electron oxidation of free radicals of the antioxidants. It suggests that repair of low-redox potential targets rather than prevention of their damage by superoxide is important in the antioxidant protection against oxidative stress induced by hypertonic conditions.

This paper summarizes numerous arguments demonstrating that the hypothesis of accumulation of the senescence factor, which was the basis for introducing yeast to the group of model organisms of gerontology, finds no experimental support. Among several candidates for the role of the causative agents of replicative aging, only one - hypertrophy - always accompanies symptoms of aging, not only in Saccharomyces cerevisiae, but also in Schizosaccharomyces pombe.