SECTION TWO 



Results : 



DNA: bluish purple. Cytoplasmic and other proteins may be 

 stained red, especially if they are strongly basic. 



Note: 



The principle of the reaction is that the 2-hydroxy-3-naphthoic 

 acid hydrazide, which replaces Schiff's reagent, not only combines 

 with aldehydes and ketones, but couples with the diazotized 

 o-dianisidine to give a purplish blue dye. Moreover, the hydrazide 

 combines with tissue proteins to form pinkish coloured protein 

 hydrazides. 



Reference: Pearse, A. G. Everson (195 1). 



FONTANA STAIN 

 For argentaffine granules 



Solutions required: 



A. Silver diaminohydroxide (as page 415). 



B. Sodium thiosulphate 5% aqueous. 



Technique: 



1. Tissues are fixed in 10% neutral formalin, washed, dehy- 

 drated in alcohol, cleared in cedarwood oil, and embedded in 

 paraffin wax as usual. 



2. Fix sections to slides, bring down to distilled water and wash 

 thoroughly in two or three changes of neutral, freshly distilled 

 water. 



3. Immerse in the silver oxide (Fontana) solution for twelve 

 to twenty-four hours in the dark in a covered, scrupulously clean 

 vessel. 



4. Wash in neutral, freshly distilled water for one minute. 



5. Immerse for one minute in the sodium thiosulphate. 



6. Immerse in tap water for ten minutes. 



7. Counterstain, if desired in carmalum. 



8. Dehydrate; clear in xylol and mount. 



207 



