Nishiyama residents exposed to fallout from the Nagasaki atomic bomb were selected by their location and duration in the fallout area and were studied for any retained radionuclide activity and any harmful effects by whole-body counting, physical and laboratory examinations, and chromosome studies. Soil, reservoir sediments, and crops from Nishiyama and comparison areas were assessed by scintillation counting for 137Cs content. Whole-body counting and radiochemical uninalysis showed a significantly greater concentration of 137Cs among the Nishiyama subjects than the nonexposed, but no physical or laboratory abnormalities were detected among the index subjects of this study. Results demonstrated that the internally deposited material is maintained at a relatively high level by the ingestion of food stuffs containing 137Cs.
Preliminary results of studies in Drosophila melanogaster led to the conclusion that there is a linear relation between mutation rates and radiation dose down to 8 r. Sexlinked recessive lethal mutations were used as indicators of mutation induction. No evidence was seen of a threshold dose in genetic effect for doses of x radiation down to 8 r. (C.H.)
The problem of genetic effects from low dose level radiation is a very important one. We have tested the linear relationship between dose and mutation rates of Drosophila at doses as low as 8 r. The material used was the wild Canton-S strain which were isogenized every four months. Wild males were stocked for one week after their emergence, and irradiated with X-rays. Sex-linked recessive lethals were detected by M-5 method, and about 530, 000 X-chromosomes including the control were examined. The straignt line obtained at the high dose level was in good accord with that obtained by Spencer and Stern (1948). And the curve obtained at high dose level was found to be applicable at the low dose level as well. Among the 26, 897 males treated, there were 25 cases which produced two to fifteen lethals. How to treat the simultaneous occurence of two or more lethals in a set of twenty tested chromosomes originated from one treated male is an important and troublesome problem. However, sufficient evidence is available to conclude that the linear relationship between mutation rates and radiation dose can be applied to low doses down to 8r, by using the sex-linked recessive lethal mutaions in Drosophila, one of the most reliable indicators of mutation induction.
Abstract To estimate the absorbed dose of N‐ethyl‐N‐nitrosourea (ENU) ingested in Drosophila melanogaster , males were fed with sucrose solutions containing various concentrations of ENU plus 3 H‐labeled sucrose for 24 hr. Flies showed decreasing intakes with increase in ENU concentration when monitored by intake 3 H radioactivity. Absorbed dose, D , per male can be estimated by the following formula: D = v μ C , where v is intake volume per male of sucrose solution at concentration C. Estimating the v value for each ENU solution from 3 H radioactivities in male flies, and using the above formula, we reached the conclusion that average absorbed doses of ENU were 0.064, 0.221, and 0.302 nmol, respectively, for the ENU concentrations of 0.03, 0.3, and 1.0 mM. Sex‐linked recessive lethals were measured for males exposed to these sucrose solutions at three different ENU concentrations. Their frequencies increased nonlinearly with increasing exposure doses—ie, ENU concentration C —but linearly with increasing absorbed doses estimated in the above‐mentioned way.
