170 R. VENDRELY 



3'-methyl-4-dimethylaminoazobenzene. Price and Laird^" and Price et al.'^ 

 could not demonstrate any difference between the nuclei of induced liver 

 tumors and normal liver in the rat. Davidson et aZ."'" found no difference 

 between the DNA content of nuclei of normal and of leukemic bone mar- 

 row cells, but they noticed a significant rise in DNA in pernicious ane- 

 mia. Metais and MandeP* found the same DNA content in human leukemic 

 cell nuclei and normal leucocyte nuclei. 



On the other hand, Mclndoe and Davidson* have found in a fowl sarcoma 

 an amount of DNA per nucleus higher than the amount in the normal fowl 

 nucleus. Klein and Klein''^' "^^ studied different tumors in the mouse and 

 found that some contained the normal amount of DNA per cell whereas 

 others showed higher values. Further investigations by Leuchtenberger et 

 alJ'^ by ultraviolet microspectrophotometry showed that the DNA content 

 per cell in Ehrlich ascites tumor cells is approximately that of tetraploid 

 nuclei; the relative deviations from the mean value do not differ signifi- 

 cantly from those found in normal cells, while the DBA ascites lymphoma 

 nucleus contains the normal diploid amount of DNA. 



To summarize, the DNA content of the nucleus does not seem to be 

 affected by carcinogenic drugs and the neoplastic process ; only a few cases 

 of variations in DNA content have been found in neoplasms and some can 

 be related to polyploidy. We can therefore say that in normal tissues as well 

 as in tissues undergoing drastic physiological and pathological changes, 

 the DNA of resting nuclei is remarkably stable. But it is possible that some 

 individual changes may occur among the population of cells thus studied. 

 The results of photometric analysis on a great number of nuclei cover a 

 certain range of values, and it is sometimes very difficult to decide whether 

 these difTerences are due to errors inherent in the technique or whether they 

 are biologically significant and illustrate real variations in the nucleus. It 

 might well be, for instance, that a degenerative process is at work when the 

 value found is markedly lower than the theoretical value; or a synthesis of 

 DNA in preparation for future mitosis might account for a high value. This 

 possibility needs further investigation. 



A few examples are known, however, where the DNA per nucleus is defi- 

 nitely different from the normal value. 



7« J. M. Price and A. K. Laird, Cancer Research 10, 650 (1950). 



" J. M. Price, E. C. Miller, J. A. Miller, and G. M. Weber. Cancer Research 10, 18 



(1950). 

 " J. N. Davidson, I. Leslie, and J. C. White, Lancet (i), 1287 (1951). 

 " J. N. Davidson, I. Leslie, and J. C. White, /. Pathol. Bacterial. 63, 471 (1951). 

 ''* P. Metais and P. Mandel, Compt. rend. soc. hiol. 144, 277 (1950). 

 " Eva Klein and G. Klein, Nature 166, 832 (1950). 

 '« G. Klein, Expll. Cell Research 2, 518 (1951). 

 " C. Leuchtenberger, G. Klein, and E. Klein, Cancer Research 12, 480, (1952). 



