216 



Arne Forssberg 



case of RNA and proteins. Since the total activity of Land- 

 schiitz ascites cells, labelled with [2-i4C]glycine, is diluted by 

 cell multiplication more than could be expected from increase 

 ill cell mass, Greenlees and LePage (1955), for instance, 

 deduced an exchange (loss) of protein-bound activity amount- 

 ing to about 9 per cent per day. Using the same material. 



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DAYS AFTER INOCULATION 



Fig. 1. Total number of free tumour cells and inverted specific 

 activity of DNA, RNA and proteins as a function of time after 

 inoculation. All values were brought to a common scale (left) 

 by taking the values corresponding to the inoculum as equal to 

 one. Curves are drawn through the geometrical mean of the 

 values from the different series, each value representing a pool 

 of ascites from 4 to 15 mice. The right-hand scale shows the 



number of generations. 



Ledoux and Revell (1955) made the observation that the RNA 

 concentration per cell decreased considerably with the age of 

 the inoculated cell culture. 



Ehrlich tumour cells, with [8-i^C]adenine or [2-'^^C]g[ycme 

 as precursors, were used in our studies on similar stability 

 problems (Revesz, Forssberg and Klein, unpublished). In 

 parallel analyses of specific activity and cell multiplication 

 during the week following inoculation of the cells labelled 

 in vivo, we obtained the results shown in Fig. 1. There is a 



