THE EFFECT OF RADIATION ON FROZEN TUMOUR CELLS 



dry ice. A rise in temperature was therefore possible at the time of irradia- 

 tion. Normally, a rise in temperature up to —20° for short periods was 

 found not to have any injurious effects on cell survival, but the possibility 



lOOr 



(fnozenj 



2 3 t 



Time in weeks 



Figure 7. Percentage take of frozen and 

 fresh control grafts. {X-ray experi- 

 ment) 



2 3 



Time in weeki 



Figure 8. Percentage take of irradiated 

 {X-rays) fresh and fresh con- 

 trol grafts 



could not be excluded that the existence of a temperature change may have 

 increased the radiation damage. To settle this point, the experiment was 

 repeated with the modification that the frozen material was kept on dry ice 

 during exposure and that X-rays instead of gamma radiation was used. 



y-raj-s 



(l^nozenj 

 I \ 



100 



Time in weeks 



Figure 9. Percentage take of irradiated 



{X-rays) frozen and frozen 



control grafts 



Figure 10. Comparison of inhibition of 

 tumour takes from irradiated {X-rays) 

 frozen and fresh grafts expressed as the 

 difference from the control percentage take 



Figure 7 gives the percentage take for the second series of fresh and frozen 

 controls which is similar for both types of cells and shows again that viability 

 is unimpaired by freezing alone. Figure 8 shows the percentage takes of 



324 



