ETHYL METHANE SULPHONATE 263 



This deduction cannot, however, be extended to other systems and it may- 

 well be that the effect of ionizing radiations on life-span in, for example, 

 insects, may have a genetic origin, especially since the effect only sets in at 

 much higher doses than for mice. In insects cell division only occurs in the 

 brain and testes and massive cell death following irradiation is unlikely. 

 Life-span shortening in insects may therefore only be seen when the dose is 

 sufficiently high for an effect of radiation other than cell death to come into 

 play. 



ACKNOWLEDGMENTS 



We wish to thank our colleagues, Drs. Fahmy, Roberts and Warwick for 

 valuable discussions and for making their unpublished results available to us. 



This investigation was supported by grants to the Chester Beatty 

 Research Institute (Institute of Cancer Research: Royal Cancer Hospital) 

 from the Medical Research Council, the British Empire Cancer Campaign, 

 the Anna Fuller Fund, and the National Cancer Institute of the National 

 Institutes of Health, U.S. Public Health Service. 



REFERENCES 



Alexander, P., and Connell, D. I. (1960). Radiation Res. 12, 38. 



Fahmy, 0. G., and Fahmy, M. J. (1956). J. Genet. 54, 146. 



Fahmy, 0. G., and Fahmy, M. J. (1961). Genetics 46, 1111. 



Haddow, a. (1955). Proc. 1st International Conference on Peaceful Uses of Atomic 



Energy, Geneva 11, 213. 

 Heslot, H., and Ferrary, V. A. (1958). Ann. inst. natl. recherche agron. 44, 133. 

 Loveless, A. (1959). Proc. roy Soc. B150, 497. 

 Loveless, A., and Howarth, S. (1959). Nature, Loud. 184, 1780. 

 Roberts, J. J., and Warwick, G. P. (1958). Biochem. Pharmacol. 1, 60. 

 Westergaard, M. (1957). Experientia 13, 224. 



DISCUSSION 



CURTIS: Is there any information as to whether ethyl methane sulphonate produces 



chromosome breaks? 



ALEXANDER: This substance is not a cytoxic agent, but it does give rise to chromosome 



damage though the ratio of translocation to recessive lethals is smaller than with the 



bifunctional compounds. 



CURTIS: I think it's perhaps a little premature to say that it does or does not support the 



somatic mutation hypothesis if you don't know whether ethyl methane sulphonate 



produces mutations in the animal with which you're dealing. 



ALEXANDER: I agree; but you will appreciate the great difficulty of establishing mutagenic 



action in mammals under these acute insults with large doses of radiation and alkylating 



agents. One of the important factors in life-span shortening is massive cell death soon 



