856 RADIATION BIOLOGY 



viability even in heterozygous condition (see Chap. 7, this volume). It, 

 therefore, appears likely that mutations induced in spermatogonia in 

 mammals may have appreciable dominant deleterious effects which, in 

 man, will prove to be more of a hazard than the recessive effects. 



The mean induced mutation rate for irradiated spermatogonia in the 

 experiment of Russell on specific loci in the mouse is (25.0 + 3.7) X 10 -8 

 per roentgen, per locus. This is considerably higher than the rates found 

 in similar experiments on Drosophila and indicates that estimates of human 

 hazards based on Drosophila mutation rates may have to be revised. 



In the same investigation, the observed rate of mutation was not 

 appreciably dependent on the length of interval between irradiation and 

 fertilization. It, therefore, appears that, as far as mutations induced in 

 spermatogonia are concerned, postponement of procreation would be 

 ineffective in reducing the probability of transmission. 



The discoveries (reviewed by Hollaender, Baker, and Anderson, 1951) 

 that hypoxia and other treatments protect against the induction by 

 radiation of chromosomal damage, and perhaps other genetic changes, 

 has increased the hope that protective agents will be found that will 

 reduce the genetic hazard of radiation in man. The first test of the effect 

 of hypoxia on radiation induction of genetic damage in mammals has, 

 however, proved discouraging. No protection against the X-ray induc- 

 tion of dominant lethals in sperm in mice was found (Russell et at., 1951). 

 It is possible, of course, that hypoxia will prove to afford protection 

 against genetic damage in earlier germ-cell stages, or even against some 

 types of genetic damage in sperm. 



REFERENCES 



(Information regarding availability of government reports indicated by an asterisk 

 may be obtained from the Office of Technical Services, Department of Commerce, 



Washington, D.C.) 



Amoroso, E. C, and A. S. Parkes (1947) Effects on embryonic development of 

 X-irradiation of rabbit spermatozoa in vitro. Proc. Roy. Soc. (London), B134: 

 57-78. 



Bouricius, J. K. (1048) Embryological and cytological studies in rats heterozygous 

 for a probable reciprocal translocation. Genetics, 33: 577-587. 



Brenneke, H. (1937) Strahlenschadigung von Mause- und Rattensperma, beobachtet 

 an der Friihentwicklung der Eier. Strahlentherapie, 60: 214-238. 



Catcheside, D. G. (1047) Genetic effects of radiations. Brit. J. Radiology, Suppl. 

 1, pp. 100-116. 



Charles, D. R. (1050) Radiation-induced mutations in mammals. Radiology, 

 55: 570-581. 



Deringer, M. K., W. E. Heston, and E. Lorenz (1046) Biological effects of long- 

 continued whole body irradiation with gamma rays on mice, guinea pigs, and 

 rabbits. Part IV. Biological action of gamma radiation on the breeding 

 behavior of mice. USAEC Report MDDC-1247,* pp. 1-30. Also National 

 Nuclear Energy Series, Div. IV, Vol. 22B (in press). 



