INFLUENCE OF OXYGEN ON RADIO-SENSHl\ I IV OF CELLS AM) ILSSUES 



Table 5. Influence of molecular oxygen on radio-sensitivity in the presence of 



enzyme poisons 



Organism 



Poison 



Injluence on 



oxygen (lef)emlenl 



sensitivity 



Mouse tumour 



Fluoride 

 lodoacetate 

 Cyanide 

 Cyanide 



No change 

 No change 

 Increased 

 No change 



Sarcina lutea Cyanide 



Abolished 



Grasshopper 

 embryo 



Cyanide 



Carbon monoxide 80/20 CO/O, and 

 above (including 2-5 hours pre- 

 treatment) 



No change 

 (summation of injuries) 



Tradescantia Carbon monoxide 4 atm (including Increased 



Reference 



a 

 b 

 c 



a. Crabtree, H. G. and Cramer, W. 11th Scientific Report of the Imperial Cancer Research Fund (1934) 75, 90, 104 



b. Hall, B. v., Hamilton, K. and Brues, A. M. Cancer Res. 12 (1952) 268 



c. Laser, H. Nature, Land. 174 (1954) 753 



d. Tahmisian, T. X. and Devine, Rosemarie L. Radiation Res. 3 (1955) 182 



e. KinK. K. D., Schneidennaii, H. A. and Sax, K. Proc. nat. Acad. Sci., Wash. 38 (1952) 34 



f. Mottram, J. C. Bnt. J. Radiol. X.S. 8 (1935) 643 



g. Read, J. 30th Annual Report of the British Empire Cancer Campaign (1952) 297 

 h. Kihlman, B. A. /. biophvs. biochem. Cvtol. 3 (1957) 363, 381 



i. Kihlman, B. A. Exp. Cell Res. 8 (1955) 404 

 j. Kihlman, B. A. Hereditas, Lund. 41 (1955) 384 

 k. Gray, L. H. Acta. radioL, Stockh. 41( 1954) 61 



normal organisms and their mutant forms which are deficient in the enzymes 

 of aerobic respiration. The three organisms were E. coli B., E. coli ALL., 

 and yeast. In the case of the two strains of is. coli it was estimated that the 

 respiratory enzymes were either absent, or present at a concentration of less 

 than 1 /500th of that in the wild type. The X-ray sensitivities of mutant and 

 wild types were, nevertheless, the same both when irradiated in nitrogen and 

 in oxygen, i.e. the influence of oxygen was as marked in the mutant as in the 

 wild type. The 'petite' mutant of yeast was more sensitive than the wild 

 type, but like the bacteria, showed the same ratio of aerobic to anaerobic 

 sensitivity. Howard-Flanders-^ has also observed that the ratio of aerobic to 

 anaerobic sensitivity is the same in wild type yeast as in a cytochrome- 

 deficient mutant. 



As mentioned earlier, the induction of chromosome structural damage 

 by y and X radiation has almost always been found to be positively correlated 

 with oxygen tension at the time of irradiation. The aberrant configurations 

 which are actually observed, or are inferred from genetic analysis, are 



162 



