DEHYDROGENASE 



96 



DESOXYRIBONUCLEIC ACID 



pensive, inflammable and quickly takes 

 up water from the air. Wtiether it is 

 injurious when breathed remains to 

 be determined. On the whole it ap- 

 pears that little is to be gained by such 

 substitutes. However, Cyclohexanone 

 deserves further trial. If alcohol must 

 be avoided it is always possible to fix 

 in formalin and to use frozen sections. 

 By the Altmann-Gersh technique the 

 tissues are dehydrated in vacuo while 

 still frozen. 



Dehydrogenase — Written by E. W. Demp- 

 sey, Dept. of Anatomy, Washington 

 University, St. Louis. February 26, 

 1951 — Sometimes used synonomously 

 with Oxidase, since it is an enzyme 

 which catalyzes the transfer of hydro- 

 gen from one substance to another, and 

 therefore operates to reduce one ma- 

 terial and simultaneously to oxidise 

 another. A variety of dehydrogenases 

 are recognized, depending upon the sub- 

 strate which acts as the hydrogen 

 donor (e.g. succinic, malic, lactic 

 dehydrogenase). Dehydrogenases have 

 been measured in slices or homogenates 

 of tissues, particularly with reference 

 to malignancy (Greenstein, J. P., Bio- 

 chemistry of Cancer, New York: Aca- 

 demic Press, 1947, 389 pp. ) and to changes 

 in the reproductive cycle, a review of 

 which is presented in Chapter 4 of 

 The Enzymes, New York: Academic 

 Press, 1950, Vol. 1, Part 1, 724 pp. 



Methylene blue and other dyes have 

 been used as hydrogen acceptors in 

 the dehydrogenase systems. The rate 

 of decolorization of the dye serves 

 as an index of activity. Recently, tet- 

 razolium salts, which form colorless 

 solutions but which upon reduction 

 are converted into colored, insoluble 

 formazans, have been used to localize 

 the enzymes in tissue sections or blocks. 

 Rutenberg, A. M., R. Gofstein and 

 A. M. Seligman, Cancer Research, 1950, 

 10, 113-121 present a review of the 

 use of tetrazolium salts and methods 

 for studying both non-specific and spe- 

 cific dehydrogenase systems in living 

 tissue and in frozen sections. These 

 methods are still somewhat lacking in 

 histological precision, but are provid- 

 ing interesting data showing altered 

 concentrations of the enzyme in states 

 of different physiological activity 

 (Zweifach, B. W.,'M. M. Black and E. 

 Shorr, Proc. Soc. Exp. Biol, and Med., 

 1950, 74, 848-854). See Succinic De- 

 hydrogenase and Triphenyltetrazolium 

 Chloride. 



Dehydropyridines. Warburg noted a marked 

 whitish fluorescence in ultraviolet light. 

 Blaschko and Jacobson (Bourne, p. 196) 

 report that the pyridines do not show 



this fluorescence and that the small gran- 

 ules that exhibit it in sections of living 

 liver tissue may well be dehydropyri- 

 dines. Their brilliant white fluores- 

 cence quickly fades. 



Delafield's Alum Hematoxylin. To 400 cc. 

 sat. aq. ammonia alum add 4 gms. 

 hematoxylin dissolved in 25 cc. 95% 

 ale. Leave exposed to air and light 4 

 days. Add 100 cc. methyl ale. and 10 

 cc. glycerin; filter. Filtrate will slowly 

 ripen. To hasten ripening add 10 cc. 

 hydrogen peroxide. 



Delta Dye Indicator, see Nitrazine. 



Dempsey, see Phosphatases, Esterases, En- 

 zymes, Dehydrogenase, Nucleases. 



Dempster, see Shaddow Casting. 



Density Determinations. Technique de- 

 scribed for amebae is by use Starch 

 Density Gradient (L0vtrup, S., C. rend. 

 Lab. Carlsberg, S6r. Chim., 1950, 27, 

 137-144). 



Dental Enamel, see Enamel. 



Dentin. Can be studied in ground sections 

 of undecalcified teeth as well as in 

 paraffin and celloidin sections of de- 

 calcified ones (see Teeth). For the 

 latter Hematoxylin and Eosin, Mal- 

 lory's Connective Tissue stain and 

 many others can be applied as in the 

 case of decalcified bone. Hanazawa's 

 (Dent. Cosmos, 1917, 59, 125) methods 

 for the minute structure of dentin are 

 given in detail by Wellings, A. W., 

 Practical Microscopy of the Teeth and 

 Associated Parts, London: John Bale, 

 Sons & Curnow. Ltd., 1938, 281 pp. 

 Dentin can be advantageously ex- 

 amined after vital staining with Alizarin 

 Red S. Its pH can be estimated 

 (Grossman, L. I., J. Dent. Res., 1940, 

 19, 171-172). For determination of 

 rate of mineral replacement see Radio- 

 active Phosphorus; for Korff's fibers, 

 see Teeth, Developing; and for nerve 

 endings, see Teeth, Innervation. 



Desmoglycogen, see Glycogen. 



Desoxyribonuclease is an enzyme for de- 

 grading desoxyribonucleic acid. It has 

 been used for histochemical observa- 

 tions (Catheside, D. G., and Holmes 

 B., Symp. Soc. Exp. Biol., No. 1, 

 Nucleic Acids, 1947, 225-231, Cambridge 

 University Press) to remove this type 

 of nucleic acid from cells. 



Desoxyribonucleic acid. Method for deter- 

 mination in Isolated Hepatic Nuclei — 

 Written by Joseph A. Falzone, Dept. 

 of Anatomy, Washington University, 

 St. Louis 10, Mo. October 26, 1951— 

 This technique may be applied, with 

 slight modifications to a wide variety of 

 tissues and organisms, but is here de- 

 scribed for use with rat liver. In prin- 

 ciple, the nuclei of a tissue homogenate 

 are isolated and washed by centrifu- 



