Worm Breeder's Gazette 12(3): 96 (June 15, 1992)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Effects of Temperature and Oxygen Concentration on Aging and Development in rad-8

Naoaki Ishii[1], Norio Suzuki[1], Phil Hartman[2], Kenshi Suzuki[1]

[1]Department of Molecular Biology, Tokai University School of Medicine, Kanagawa, Isehara 259-11 (Japan)
[2]Department of Biology, Texas Christian University, Fort Worth, TX 76129

A mutant of rad-8 was originally isolated on the basis of its hypersensitivity to UV radiation (Hartman and Herman, 1982). We have recently conducted experiments which demonstrate that rad-8 larvae are also hypersensitive to high oxygen concentrations as well as to methyl viologen, a superoxide-anion generator. With respect to the former, there was no inactivation of N2 larvae, even at the highest oxygen concentration tested (90%). Conversely, rad-8 larvae were killed by concentrations of 60% and above. Oxygen also retarded development and reduced fecundity of rad-8 but not N2 in a concentration-dependent fashion. For example, the brood sizes of rad-8 were 182, 75 and 27 at oxygen concentrations of 5%, 21% and 50%, respectively. In addition, the mean life span of rad-8 (but not N2 )was progressively shortened when animals were incubated in increasing oxygen concentrations. Specifically, the mean life span of rad-8 was 16.9 days when reared under atmospheric oxygen and 8.9 days when raised under 60% oxygen.

We have also discovered that temperature can modulate development and aging in the

8 mutant differently than in N2 .When reared at 16°C in 5% oxygen, rad-8 and N2 possessed the same life span. Paradoxically however, this same mutant (whose life span was shortened by high oxygen concentrations at 20°C) actually lived longer than N2 when reared at 16°C in atmospheric oxygen, 27 versus 20 days, respectively. Several types of experiments showed that rad-8 'slonger life span was due to both retarded development and extended senescence.

Free radical damage is considered important in cellular and organismal aging. The cross hypersensitivity of rad-8 animals to both W radiation and free radicals provides further evidence that free-radial mediated DNA damage may be important in the aging process. Further study of rad-8 and mev-1 .a second gene whose development is affected by high oxygen concentrations, should illuminate the cellular mechanisms by which protection of oxygen-radical damage contributes to aging and development.