194 Microscopic Histochemistry 



For special purposes the method can be modified by 

 changing the pH of the solution or by using other substrates. 

 Above pH 6 the activity of alkaline phosphatase rapidly in- 

 creases, and one may obtain combination pictures of the dis- 

 tributions of acid and alkaline phosphatase. The choice of 

 substrates is rather limited because the lead salts of most 

 phosphoric esters are very insoluble at pH 5 or higher. Res- 

 orcinol phosphate and adenosinetriphosphate are suitable 

 substrates; they give pictures which differ more or less mark- 

 edly from those obtained with glycerophosphate."^^ This may 

 be an indication of the existence of more than one acid phos- 

 phatase in the tissues, but the point will require further in- 

 vestigation. Abolins^^ finds that the pattern of distribution of 

 activity in the anterior pituitary varies with the pH of the 

 substrate solution, and he attributes the differences to the 

 presence of several enzymes. 



Sources of error are the same as in the method for alkaline 

 phosphatase, with the addition of impregnation artifacts of 

 nerve tissue. 



The sensitivity of the method ( Coujard's method ) is about 

 the same as that of the technique for alkaline phosphatase. 



2) The azo dye method. —Seiigman and Manheimer"^^ rec- 

 ommend a-naphthyl phosphate as a substrate, in the pres- 

 ence of diazotized aminoanthraquinone. Sites of activity are 

 shown in a reddish-brown shade. This method is not recom- 

 mended because of unavoidable gross diffusion artifacts. 



Phosphamedase 



An enzyme hydrolyzing phosphamides has been described 

 in animal and plant tissues. "^^ In animals its natural substrates 

 are probably phosphocreatine, phosphoarginine, and pos- 

 sibly some other less-well-known compounds possessing an 

 N-P bond. 



77. Abolins, L.: Nature, 164:455, 1949. 



78. Seligman, A. M., and Manheimer, L. H.: J. Nat. Cancer Inst., 9:427, 

 1949. 



79. Waldschmidt-Leitz, E., and Kohler, F.: Biochem. Ztschr., 258:360, 

 1933; Ichihara, M.: J. Biochem. (Japan), 18:87, 1933; Bredereck, H., and 

 Geyer, E.: Ztschr. f. physiol. Chem., 254:223, 1938. 



