DOPA AND AMINE OXIDASE 93 



Result. Dopa oxidase is indicated by blackening in the sections. 

 Leucocytes and melanoblasts appear grey or black due to their 

 dopa oxidase content. Melanin maintains its natural yellow-brown 

 color, and collagen appears colorless or pale grey. 



AMINE OXIDASE 



Oster and Schlossman ( 1942) developed a histochemical method 

 for the demonstration of amine oxidase based on the detection of 

 the aldehyde formed as the product of amine oxidation. The fuchsin- 

 sulfurous acid reagent of Feulgen was used for the visualization oi 

 the aldehyde (page 65). Naturally occurring aldehydes and "plas- 

 mal" are prevented from interfering with the test by binding them 

 with bisulfite prior to the application of the tyramine substrate 

 solution. The diffusibility of the color produced subjects the locali- 

 zations which may be observed to criticism. 



Oster and Schlossman Method for Amine Oxidase 



SPECIAL REAGENTS 



2% Sodium Bisulfite Solution. 



Substrate Solution. 0.5% tyramine hydrochloride in M/15 phos- 

 phate buffer of pH 7.2. 

 Control Solution. Omit the tyramine in the substrate soln. 

 Feulgen Reagent. See page 67. 



PROCEDURE 



1. Place frozen sections of fresh tissue in 2% bisulfite solution 

 at 37° for 24 hr. Wash thoroughly and test some of the sections 

 with the fuchsin-sulfurous acid reagent — the test should be negative 

 (no color) indicating all free aldehyde has been bound, 



2. Incubate sections in the substrate solution for 24 hr. at 37°. 

 Run parallel controls with the control solution. 



3. Immerse in fuchsin-sulfurous acid reagent. - 



4. Examine sections when the rapidly formed blue color seems 

 to be maximum. 



Result. Regions of enzymatic activity appear blue, offering a 

 distinct contrast to the reddish-purple given by "plasmal" (see 

 page 65). 



