220 



Arne Forssberg 



part at a normal rate. The fact that isotope incorporation 

 into DNA during the same period is somewhat increased as 

 compared with the initial rate, and occasionally also indicates 

 activities higher than those of the controls, still more em- 

 phasizes the discrepancy between total determinations and 

 isotope measurements. Similar indications of an overcom- 

 pensation in the incorporation of isotopes into DNA have 



ACETO ACETIC ACID = • 

 CITRIC " ^ 



LACTIC " o 



^ PYRUVIC • % 



in 180 



CM 



ai6Qj CELLS 



UJ 



^140 



It) - 



^120 



Fig. 3. Changes in the cellular concentration of acetoacetic, citric, 

 lactic and pyruvic acid in Ehrlich ascites cells. Dose 1250 r. The 

 concentration in non-irradiated cells is taken as equal to 100 (left). 

 Corresponding changes in the ascites fluid ("supernatant", right). 

 Determinations during the first two hours after irradiation. 



been reported also when lethal doses were administered (Kelly 

 et al., 1955). 



Protein synthesis in our material is never appreciably 

 influenced by irradiation, although isotope measurements 

 indicate a slight depression of synthesis during the first hours 

 after irradiation, but a slight increase at approximately the 

 same time as the measurements indicates that DNA and RNA 

 activity is high. A period of general recovery is indicated by 

 all these findings. Simultaneously also, the metabolic changes 

 discussed below (Fig. 3) seem to level out. 



When the mitotic activity is brought to a stop, a number of 



