Influence of Chemicals on Radiosensitivity 129 



salts-glucose medium, (2) basal medium fortified with amino 

 acids, (3) basal medium fortified with purines and pyrimidines, 

 (4) a combination of these, and (5) nutrient broth. 



Table II 



Chemically Defined Recovery Medium 



After irradiation, cells grown on the various media were 

 plated on the media described in Table III, and the following 

 results were obtained: 



Table III 

 Effect of Culture Medium on Radiation Sensitivity 



Surviving fraction of cells, after 85 kr of gamma-rays, plated 



at 37° C on: 



Basal Basal Basal 



medium -{- medium -{- Complete medium + 



Basal guanine -i- caseamino synthetic 20 mg. of 



Culture medium medium uracil acids medium yeast extr. 



Basal 2-2xl0-« 31xl0-« 40x10-6 2-2x10-5 1-3x10-5 

 Basal + guanine + 



uracil l-OxlO"' l-OxlQ-^ 8-0x10-' 30xl0-« 2-6xl0-« 

 Basal + caseamino 



acids 2-3 + 10-' 2-9 + 10-6 2-3x10-5 5-0x10-5 60x10-5 



Nutrient broth 3 0x10-8 5 0xl0-« 8-^x10"' 2-7x10-6 3-5x10-6 



1. Cells harvested from basal medium did not show a 

 striking response to added nutrilites. The survival as a func- 

 tion of dose indicated that they did not require the nutrilites 

 since essentially similar survival was obtained on basal 



RAD. 



