Heparin biological reactions

While a biologically active surface performs well based on the specific biological reaction, it is a highly perturbable surface tailored for the specific reaction that could, in principle, cause other biological reactions. For instance, a heparinized surface seems to increase hemolysis (breakdown of red blood cells). When the biologically active agents wear out, the surface of the treated material returns to the untreated surface, which required the surface modification to be blood compatible in the first place. 

Other surface modification reactions that are relevant to biological studies include the binding of the blood anticoagulent, heparin,189 and of dopamine190 to polyphosp-hazene surfaces. The heparin immobilization brought about a five-fold increase in the coagulation time of blood, and the immobilized dopamine generated the same response in rat pituitary cells as did free dopamine. 

In order that the heparin remain biologically active after fixation to a polymer substrate, the covalent bond must be achieved via functional groups on the heparin molecule, which are non-essential for its biological activity. Further, the binding reaction should be performed under reaction conditions which themselves do not cause loss of the antithrombogenic character of the heparin. 

I. Bjork, S. T. Olson, and J. D. Shore, Molecular mechanisms of the accelerating effect of heparin on the reactions between antithrombin and clotting proteinases, in Heparin, Chemical and Biological Properties, Clinical Applications (D. A. Lane and U. Lindahl, eds.), Edward Arnold, London, 1989, pp. 229-255. 

The subject of the present review stems from the discoveries of A. Fischer and E. Jorpes. Fischer demonstrated that heparin binds or complexes with proteins and other bases and so modifies their biological activity. As a result, heparin is able to release or activate enzymes such as lipoprotein lipase -, to inhibit hormones such as cortisone and aldosterone , to detoxify toxic agents, and to bind histamine in body cells . Jorpes discovered that heparin is a highly sulphated polysaccharide and that it gives a specific colour reaction with dyes the metachromatic reaction. This resulted in (i) the association of heparin with the naturally occurring mucopolysaccharides ... 

One of the critical factors in our research has been the adaptation and use of multiple assays to follow heparinase activity. Particularly important were assays (e.g., Azure A) used in monitoring the fermentation and early stages of purification. By utilizing three different approaches for assaying heparin (disappearance of heparin, appearance of reaction products, and disappearance of heparin s biological activity), the occurrence of any arti-... 

Whatever the mechanism, a pharmaceutical incompatibility between sodium heparin and chlorpromazine hydrochloride solutions is confirmed. The clinical significance of an interaction between the two drugs after administration has not been demonstrated. The type of electrode reaction demonstrated in the model in vitro system may occur in vivo, because a biological membrane has been shown to be capable of acting as an electrode and it known that heparin is taken up by cell membranes. Binding of chlorpromazine to other mucopolysaccharides may be of significance in the pharmacokinetic disposition of the drug. 

While ECPs are, at few exceptions [395], usually not used for reduction reactions, on the other hand a few compounds of biological interest have been oxidized on modified conducting polymers, among which, ascorbic acid [396] and of course glucose (see Section 18.4.3.1). A PPy-heparin composite has been appUed to the separation of thrombin [397]. 

A model [22] of how heparin acts specifically in many biological systems in modifying activities of complex ions may be provided by the metachromatic effect on dyes referred to earlier. The dye. Azure A, shows maximum light absorption at 610 nm. This is decreased when heparin is added, and a new absorption band at 505 mu develops. Heparins and heparinoids are able to produce this color change at very low concentrations and under conditions unfavorable to other metachromatic inducing substances. However, little attention has been paid to the numerous experimental observations reported on metachromasia with heparin and heparinoids, of practical importance to those using this color reaction in studies on heparin and mast cells. In... 

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