MODIFICATION OF LATE EFFECTS OF IONIZING RADIATION 303 



mice). A lower DRF in newborn mice can be explained, if the marrow in these 

 animals is partially anoxic even when the animals are breathing air. Older 

 animals also show a lower DRF with 25 seconds anoxia, but in this case the 

 result may be due to a longer time requirement for the production of the 

 anoxic state. Lindop and Rotblat found a lower DRF for long-term effects 

 than for acute effects. 



Hornsey (1959) using severe hypothermia, also observed less protection 

 for long-term than for acute effects. 



Dr. Lamberts has mentioned at this meeting that the non-cellular 

 effects which he has investigated show no oxygen effect. 



The presence or absence of the oxygen effect might, therefore, be used to 

 distinguish between cellular and non-cellular effects. 



Other protective techniques, such as feeding of alkoxy glycerol esters, 

 hormone treatment, and marrow transplantation have been reviewed by 

 Odell et at. (1960) and will, no doubt, be discussed further at this meeting. 



REFERENCES 



Andervont, H. B. (1943-4). J. nat. Cancer Inst. 4, 579. 



FuRTH, J., Upton, A. C, and Kimball, A. W. (1959). Radiation Res. Suppl. 1, p. 243. 



Harman, D. (1957). J. Gerontol. 12, 257. 



HOLLCROFT, J. W., LORENZ, E. MiLLER, E., CONGDON, C. C, SCHWEISTHAL, R., and 



Uphoff D. (1957). J. nat. Cancer Inst. 18, 615. 

 Hornsey, S. (1959). Gerontologia 3, 128. 



Krebs, J. S., and Bratjer, R. W. (1961). Radiation Res. 15, 814. 

 Lamson, B. G., Bn^LiNGS, M. S., Ewell, L. H., and Bennett, L. R. (1958). A.M.A. 



Arch. Pathol. Q6, 322. 

 Lindop, P. J., and Rotblat, J. (1962). Brit. J. Radiol. 35, 23. 



Maisin, J., ]\Ialdague, p., Dunjic, A., and Maisin, H. (1957). J. Beige Radiol. 40, 346. 

 Mewissen, D. J., and Brucer, M. (1957). Nature, Lond. 179, 201. 

 Odell, T. T., Cosgrove, G. E., and Upton, A. C. (1960). In "Radiation Protection and 



Recovery" (A. HoUaender, ed.), p. 303. Pergamon Press. 

 PmiE, A., and Lajtha, L. G. (1959). Nature, Lond. 184, 1125. 

 Upton, A. C, Doherty, D. G., and Melville, G. S. (1959). Acta Radiol. 51, 379. 

 VON Sallman, L., Mtjnoz, C. M., and Barr, E. (1952). A.M.A. Arch. Ophthal. 47, 305. 



DISCUSSION 



UPTON: I would certainly endorse what Dr. Scott has said about the paucity of evidence on 

 protection-against tumorigenesis by radiochemicals; the data of course, speak for them- 

 selves. We did endeavour to determine the effects of AET with mercaptoethylguanidine 

 (MEG) in the active form in RF mice at two dose levels of 150 r and 300 r whole-body 

 X-irradiation early in life, plottmg the percentage of leukaemia against dose with myeloid 

 leukaemia; the data with 300 r showed that there was a small difference, as I recall there 

 was also the same kind of a difference at 150 r; this wasn't a 1 : 1 dose comparison, the 

 differences were not large enough certainly to be statistically significant. They were in the 



