258 FACTORS INFLUENCING CELL RADIOSENSITIVITY 



Dale : 



The recovery of Ki2 in the presence of catalase may possibly indicate that a 

 highly active, organically bound ion causes of itself some inactivity. 



Lataejet: 

 If catalase is added after the radiation has been done, the factor is controlled. 



Dale: 



It may be possible that, even if added later, catalase brings about some re- 

 covery. 



Barron: 



Latar jet's experiment on oxygen is confirmed by our experiment with ferrocy- 

 tochrome c, in which the inactivation was due to the hydroxyl and HO2 radicals. 

 Catalase does not protect ferrocytochrome c during exposure to x-rays. Ferrocy- 

 tochrome c irradiated in the absence of oxygen shows 37 per cent protection, as 

 compared with the results of radiation in the presence of oxygen. 



