382 



radiation: hiolooy 



coinpct iii^ t'oi- llic a('ti\"c products produced l)y radiation. In addition, 

 llollacnder and coworkcns liiivc suggested that certain comi^ounds may 

 give protection l)y supplying a metabolic intermediate which has been 

 blocked temporarily by the irradition effect. This possibility would seem 

 to l)e subject to direct test sinrc, in this case, supplying the particular 

 compound after the irradiation should bi' effective. 



10- 



I0--2- 



i io--iJ 



o 



4 

 K 

 b. 



O 



Z 



> 

 > 



^ io--± 



I0=i4 



10- 



18 



-I— 

 30 



~~1 

 42 



TEMPERATURE, 'C 



Fig. 10-6. Survival of E. coU B/r at several X-ray doses as a function of ineubation 

 temperature. Solid circles, 40,000 r; open circles, 60,000 r; triangles, 80,000 r. 

 {Stapleton, Billen, and Hollaender, 1953.) 



Incubation at Suboptimal Temperatures. Latarjet (1943) has reported a 

 partial recovery of yeast cells subjected to X rays of wave length 1.54 A 

 when the irradiated cells were held for varying numbers of days at 5°C. 

 No such recovery was observed with bacterial cells similarly tested. 

 Ultraviolet irradiation with 2537 A wave length was followed by a similar 

 recovery of the yeast cells. Stapleton et al. (1953) have observed more 

 than a hundredfold recovery of E. coli cells subjected to various doses of 

 X rays when incubated after irradiation at sul^optimal temperatures for 

 24 hours before incubation at 37°C. Figure 10-6 shows typical results. 



