CYTOCHEMICAL TECHNIQUES FOR NUCLEIC ACIDS 



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0.1 0.2 0.3 



Measured 



Fig. 6. Concentration of DNA in individual mouse nuclei, as measured with the 

 Feulgen reaction and as calculated assuming a constant amount of DNA per nucleus. 

 Circles to left, liver parenchymal nuclei; crosses, thymus nuclei; dots, normoblast 

 nuclei from newborn liver. For each nucleus the dye concentration was determined; 

 the expected dye content was calculated from the measured nuclear diameter, and a 

 "standard" amount of dye assumed to be present in each nucleus. This standard 

 was taken from the mean of 10 additional diploid adult liver nuclei from a section 

 on the same slide. Ordinate and abcissa are in units of DNA concentration, 10~' 

 mg./fx^, or g./ml., assuming each diploid nucleus contains 6 X 10~' mg. DNA. 



cannot be adequately compared. Good estimates of the amounts of DNA in 

 nuclei were obtained, however, when nuclei from shad and chicken liver 

 were compared with beef,"^ so that hydrolysis times are apparently similar 

 for these vertebrates. 



There have been a few reports that the Feulgen reaction may be used in 

 conjunction with modifications in technique to distinguish between differ- 

 ent types of deoxyribonucleoprotein. Sharma"^ reported that the hetero- 

 chromatic segments of onion and bean chromosomes could be selectively 

 stained by treatment with 0.25 M trichloroacetic acid at 60° before hy- 

 drolysis in HCl. Lessler"^ found that Feulgen blocking agents acted differ- 

 ently on erythrocytes of several different vertebrates. 



'IS A. K. Sharma, Nature 167, 441 (1951). 



'>' M. A. Lessler, /. Natl. Cancer Inst. 12, 237 (1951). 



