Influence of Chemicals on Radiosensitivity 125 



to understand some of the relationships of postirradiation 

 (recovery) systems on the cell level Some of the details of 

 experimentation and results of these experiments belong in 

 this discussion. Two points of view can be taken immediately : 

 (1) the recovery system may prevent the disruption of key 



10--^ 



y RAYS, 80 kr 



10" 



z 

 o 

 t- 

 o 

 < 

 a: 

 u. 



ID 

 2 

 > 

 > 



a: 



10 



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TEXAS 



18 



— r— 



30 



INCUBATION TEMPERATURE {'O 



— 1 

 42 



Fig. 4. Survival of three strains of Esch. coli 



at 80 kr at various temperatures. J^, Crooks ; 



0, B/r; O, Texas. (Stapleton, Billen and 



HoUaender, 1953.) 



biological material or (2) it may allow the cell to replace 

 damaged material by synthesis. Both types of recovery may 

 be demonstrated. 



1. Reduced postirradiation incubation temperature in- 

 creases the survival of several strains of Esch. coli. TheB/r strain 

 shows a true optimum for survival (Fig. 4) at 18° C after 

 X- or gamma-rays (Stapleton, Billen, and HoUaender, 1953). 



