86 



ERNEST POLLARD 



10 



20 



30 40 50 

 Time (min) 



60 



Fig. 7.— The uptake of 3^804 after various doses. The linear uptake can be seen, also 

 the fact that for very high doses there is an initial effect. 



.E u 



0) J) 



1^ o 



o ^ 



g o 



o o 



CC -O 



20 



40 



60 80 



j'-ray dose 



100 kr 



Fig. 8. — The radioactivity observed in the ribosome fraction as a function of dose. The 

 relative amount of ^-P rises slightly and then falls. 



the stage of departure from exponential incorporation, and also in the 

 reduced slo])e. 



INCORPORATION INTO RIBOSOMES 

 In order to attempt to see what mechanism in the cell is damaged in 

 such a way as to cause the delayed effects the incori3oration of 32p and 

 35S into ribosomes was measured. If cells are broken open in the 

 presence of sufficient concentration of Mg++ the ribosomes remain in- 

 tact and can be separated by differential centrifugation. After clearing 



