CYTOCHEMICAL TECHNIQUES FOR NUCLEIC ACIDS 



67 



■~.2 



500 600 500 600 



Wavelength 



Fig. 4. Absorption curves of Feulgen dye. Leji: Absorption curves made with 

 microphotometer on single uncut mouse liver interphase nuclei (diameter about 8 m) 

 fi.xed in acetic alcohol, showing change in shape with different hydrolysis times in N 

 HCl at 60°. Right: b. Mouse liver nucleus fixed in Sanfelice; 12 minutes hydrolysis, 

 c. DXA solution (0.35 mg./ml. in 1-cm. cuvet) hydrolj-zed 12 minutes, a. Same solu- 

 tion but adsorbed on 20-m section of heat-denatured acetic alcohol-fixed egg albumen 

 during 12-minute hydrolysis; the section then stained in Feulgen reagent and meas- 

 ured with a microphotometer. 



readily loses SO2 to reform basic fuchsin. For this reason the reagent should 

 be kept tightly stoppered, and if it turns pink may be decolorized again on 

 addition of more SO 2 . Yellow or brown contaminating substances in the 

 reagent may markedly inhibit staining of tissues and should be removed 

 with activated charcoal.''^ On standing, a white precipitate forms in the 

 Schiff reagent, and when this becomes pronounced optimal staining may no 

 longer be obtained. 



2. Specificity 



The Feulgen reaction depends upon the production of aldehydes by a 

 mild acid hydrolysis of the deoxypentose of DNA. Hydrolysis has been 

 performed with hydrochloric, sulfuric, nitric, citric,^^ perchloric,^^ or phos- 

 phoric^^ acid. It is evident that this hydrolysis actually does form aldehyde 



75 L. C. Coleman, Stain Technol. 13, 123 (1938). 

 '6G. Widstrom, Biochem. Z. 199, 298 (1928). 

 " H. S. DiStefano, Stain Technol. 27, 171 (1952). 

 78 S. A. Hashim, Stain Technol. 28, 27 (1953). 



