Unbalanced Growth and Death 



83 



esis as a working basis in attempting the improvement of antitumor 

 agents. One type of such improvement has been suggested in connec- 

 tion with the use of the antileukemia agent Amethopterin. Perhaps 

 thymidine analogs will also fulfill an important role in tumor therapy, 

 since the nucleoside rather than the free pyrimidine appears to be 

 utilized in higher organisms. 



3 6 



5 — 



Unirradiated + 

 thymine. 



Unirradiated 

 no thymine 



Irradiated 

 no thymine 







20 



40 



80 



100 



120 



60 

 Minutes 

 Fig. 1. The numbers of viable cells in cultures of E. coli 15,, 



Control of ir- 



radiated cultures were incubated at 37° in a glucose-NH 4 + medium in the pres- 

 ence or absence of thymine. 



I have described only that type of unbalanced growth which is 

 characterized by inadequate nuclear synthesis. What would happen 

 to a cell in which cytoplasmic synthesis was inhibited while nuclear 

 or chromosome multiplication continued unabated? Such a situation 

 might occur if the synthesis of cytosine riboside were specifically in- 

 hibited. This could result in the accumulation of DNA-containing 

 bodies, each of which might also contain a structure preventing the 

 synthesis or utilization of cytosine riboside. Such a DNA body might 

 be liberated when multiplication led an increase of osmotic pressure 



