Effects of certain nitrogen mustards upon the progression of cultured H.Ep. no. 2 cells through the cell cycle.

The Colcemid block method with some modifications has been used to analyze the cell cycle of cultured H.Ep. No. 2 cells and to determine the effects of certain nitrogen mustards upon the progression of cells through the cycle. The results and conclusions are as follows: Analysis of the cell cycle of H.Ep. No. 2 cells under the described experimental conditions yielded the following values: Tc, 26.1 hr; TGl, 14.4 hr; Ts, 6.9 hr; TGi, 3.9 hr; and TM, 0.9 hr. Treatment with 2 ,2'-dichloro-./V-methyldiethylamine did not interfere with the gross fixation of thymidine-methyl-3H into the acid-insoluble residue of cell nuclei, and hence supposedly not with the gross synthesis of DNA, during the concurrent cell cycle. Treatment with low but toxic doses of 2 ,2'-dichloro-