and Sakiko IKEGUCHI Mice of NA-2 strain were administered continuously and through generations with 90Sr and 137Cs contained in drinking water. Concentration of the isotopes was divided into three levels; Group I: (90Sr and Group IV (Control) was fed with noncontaminated water. Abnormality of growth, life-span and reproduction in these groups were summed up till 10th generation. Group I showed shortening of lifespan and lost reproductive function already in 2nd generation. Group II showed injury of growth and reproduction and shortening of life-span, but kept proceeding of the generations. In Group III we could not observe such injury as seen in Group I and II, but there appeared increase in reproductive function and lengthening of life-span. It can be concluded that Group I and II were obviously in state of radiation injury, but Group III was in some excited state by 90Sr and 137Cs. Another remarkable character of Group III is that tolerance against whole body irradiation of 700 R was aquired not by genetic mutation or selection but by effect of the isotopes after birth and that the tolerance was more intence in female than in male mice. This tendency was found also in Group II, but the tolerance was weaker. RadiationCenter of Osaka Prefecture

The postulate that 60-Hz electric field-induced bioeffect severity is proportional to induced transmembrane potential [Vmi] magnitude was tested and supported using a plant root model cell system. Statistically significant correlations were obtained upon regression of the relative rates of exposed Vicia faba and Zea mays root segment growth on the average Vmi (calculated) arising in those segments under specified 60 Hz field exposure conditions. The Vmi associated with the apparent threshold for growth inhibition was similar in Zea and Vicia roots (2.5 vs 2.4 mV, respectively). At Vmi greater than this threshold, Zea root growth declined by about 9% per mV, and Vicia root growth by about 19% per mV induced potential.

Induction of membrane-associated responses, a leg-shaking, a knock-down and a killing, by gamma-ray irradiation was investigated in Shaker (Sh) mutants of Drosophila melanogaster in which the gene cords for the A-current K+ channel. Sh mutants were more sensitive in the knock-down response after gamma-ray irradiation than wild types. There were a great amount of sex difference in the knock-down response, males being more sensitive than females, but not in the killing response. The sex difference was larger than gene dosage effect on X chromosome in females. Genetical analysis revealed that the sensitivity of the knock-down response is an incompletely dominant character without maternal effects. The leg-shaking response, which had previously been reported to be induced by ether treatment, was demonstrated in the head-removed flies of Sh mutants. It was found to be the most sensitive among the responses tested, and may involve changes in K+ channel. The knock-down response may be related to expansion of the leg-shaking response. The killing response should have causes different from the leg-shaking and the knock-down responses judging from the lack of correlation with them.

Median effective dose (ED60) of diethyl ether was determined using loss of "avoidance reflex" . The ED50 in an ether-resistant mutant strain, Eth-29, was 2.90 %atm in females and 3.02 %atm in males and that in an ethersensitive strain, bw; st; svn, was 1.69 %atm in females and 1.71 %atm in males. The sensitivity to gamma-irradiation of 60Co was evaluated by knockdown: the ED50 in Eth-29 was 1.20 kGy in females and 1.16 kGy in males, while the ED50 of bw; st; svn was 1.59 kGy in females and 1.50 kGy in males. The Eth-29 was more resistant to ether anesthesia and more sensitive to gamma-irradiation than bw; st; svn. The ether resistance and radiation sensitivity in the F1 progeny of reciprocal crosses between Eth-29 and bw; st; svn, were intermediate between those of their parents. From chromosomal analysis, using synthesizing strains by chromosomal substitution between Eth-29 and bw; st; svn, it was revealed that the major gene(s) of the ether resistance and radiosensitivity were located on the second chromosome and minor gene (s) on the third chromosome. The opposite effects between ether anesthesia and 60Co r-radiation damage in Eth-29 were proved at chromosomal level . Both knock-down and loss of avoidance reflex refer to a state of dyskinesia associated with convulsion and paralysis, and which involves disfunction of the central nervous system, we propose that ether resistance and radiosensitivity in Eth-29 of the central nervous system have developed simultaneously.

Microsatellite linkage analyses, including QTL analysis, determined the location of the ether-resistance gene, Etan1, within a narrow range. Our findings should be helpful for further experiments, such as cloning of the gene governing the sensitivity to ether anesthesia in mice.