PHYSIOLOGY AND BIOCHEMISTRY 



completely established. A specific chemical procedure for the deter- 

 mination of histamine would be useful in any subsequent researches. 

 The present methods are not specific because they measure the amount 

 of the imidazole nucleus only. 



It has been reported relatively recently that histamine may act 

 as a hapten when it is conjugated with certain proteins and that it is 

 possible to produce antibodies which are partially specific for the 

 histamine hapten. 



While the histamine-histaminase system is a very useful one 

 for studies in enzyme chemistry, attempts at commercial exploitation 

 of the enzyme are without justification. There is no physiological 

 basis for the claim made by some clinicians that histaminase exerts 

 therapeutic properties. 



Heparin 



The discovery of heparin at Johns Hopkins University in 1918 

 stimulated a new series of researches on blood coagulation. The 

 anticoagulant, isolated in crystalline form in Toronto in 1935, prevents 

 the clotting of one hundred thousand times its own weight of blood. 

 The experimental and clinical demonstration that the pure substance 

 prevents thrombosis without the production of any harmful eff'ects 

 opened the way for its clinical use and aroused anew the interest of 

 physiologists and biochemists. 



Heparin is one of the mucopolysaccharides. These compounds 

 are of considerable importance in physiology, as they are the chief 

 constituents of connective tissues. The variation in the properties 

 of this group of substances apparently permits the change in character- 

 istics of connected tissues. Heparin is the first substance of this group 

 to be crystallized. Its basic unit consists of two glycuronic acid resi- 

 dues, two glucosamine residues, and five sulfuric acid residues. Its 

 high content of sulfuric acid probably makes it the strongest organic 

 acid found in the body. Since no other mucopolysaccharide has any 

 significant anticoagulant activity, this property must depend on some 

 unique configuration of the molecule. Of considerable interest is the 

 fact that, while heparin in any species is identical from tissue to tissue, 

 on comparison of heparin from diff"erent species variations appear. 

 Thus, the relative anticoagulant potencies of the pure heparins from 



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