SLU MNSETTERS a ttt RADIATION STANDARDS, INCLUDING FALLOUT Bor that in mice there is definitely a difference in the frequency of mutations induced at high dose rates and at low dose rates. The difference as might already be gathered from the foregoing remarks, is greater in the case of the female germ cells, the oocytes, than it is in the case of the male germ cells, the spermatogonia. In the latter, for which much more extensive data have been accumulated, there are about four times as many mutations induced at a high dose rate as at a low dose rate. The data of Russell and his group are shown in the accompanying figure. The range of dose is from zero to 1,000 roentgens. The curve obtained for the high dose rate runs up to a rate of 30 mutations per } i é i f ‘ ~~ me ™~ SHReee ‘ ‘ 2 F % _ MEAN NUMBER OF MUTATIONS PER LOCUS PER GAMETE x10° $ @¢- ¢= 8 yn8 NYF NOM 4 30 DOSE (r) 1000 Mutation rates of specific loci in the mouse, with 90 per cent confidence intervals. Solid points represent results with acute x-rays (80 to 90 r/min). Open points represent chronic gamma-ray results (triangles and square, 90 r/wk; circle, 10 r/wk.) Square points are mutation rates in females, all other points being mutation rates in males. The point for zero dose represents the sum of ali male controls. Source: Data from W. L. Russell, Liane Brauch Russell, and Elizabeth M. Kelly, 1959. Reproduced by permission of the authors from “Immediate and Low Level Effects of foulzing Radiations,” a special supplement to the International Journal of Radiation ology. sedateAPRONEGUTRAENetle: