Additional Mechanisms of Coagulation

This equation is called the continuous general dynamic equation for aerosols (Gelbard and Seinfeld 1979). Its initial and boundary conditions are 

In the absence of nucleation (Jq(v) = 0), sources (S(v) = 0), sinks (R(v) = 0), and growth [/( ) = 0], we have the continuous coagulation equation (13.61). If particle concentrations are sufficiently small, coagulation can be neglected. If there are no sources or sinks of particles then the general dynamic equation is simplified to the condensation equation (13.7). 

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APPENDIX 13.1 ADDITIONAL MECHANISMS OF COAGULATION 13.A. 1 Coagulation in Laminar Shear Flow... 

Besides cholesterol efflux from arterial wall and its role in RCT, additional properties of HDL have been proposed for its protective anti-atherogenic activities. HDL protects vascular function by a number of potential alternative mechanisms, including inhibition of LDL oxidation [8,9], platelet aggregation and coagulation [10], and endothelial monocyte adhesion [11], as well as promotion of endothelial nitric oxide synthase (eNOS) [12], and prostacyclin synthesis [13-15]. The proposed alternate protective mechanisms for HDL are attractive but many of them lack validation under in vivo conditions. 

Therapeutic irradiation is known to have multiple interactions with the vasculature of the irradiated tissue (12). Radiation has direct cytotoxic effects on the vascular endothelium, likely due to induction of oxidative injury. Radiation-induced injury stimulates inflammation and influx of inflammatory cells in addition to creating aprocoagulant state in the vascular space by the transcriptional induction of tissue factor with the subsequent activation of coagulation factors as well as von Willebrand factor and platelets. Experimental evidence suggests that the mechanism by which radiation initiates these responses is in part through the induction of cell-adhesion molecules including ICAM-1, E-selectin, and P-selectin and in part through local cytokine production and release (13). 

Dr. David Calverley is a hematologist with a research interest in the molecular mechanisms of platelet adhesion and activation. His clinical interest lies in the area ofplatelet and hemostatic disorders. In addition to research, clinical, and teaching activities, he is Associate Director of the University of Southern Califomia/Nonis Cancer Hospital Qinical Coagulation Laboratoiy. Dr. Gerald Roth is a hematologist with interests in both research and clinical aspects of platelets. He has studied molecular aspects of aspirin s effect on platelets and observed the acetylation reaction between aspirin and platelet cyclo-oxygenase. 

The accepted mechanism for vitamin K is to function as a cofactor in the posttranslational synthesis of y ar-boxyl-glutamic acid (Glu) from glutamic acid residues. The discovery of Gla in 1974 - clarified the mechanism of vitamin K and led to the identification of additional vitamin K-dependent proteins. The only known function of vitamin K in mammals is to maintain adequate levels of vitamin K-dependent proteins involved in coagulation. The.se include prothrombin (factor II). factor VII (proconvertin), factor IX (autoprothrombin II). factor X (Stuart-Prower factor), and proteins C. S. and Z. Prothrombin and factors VII. IX. and X promote coagulation, while proteins C and S have anticoagulant activity. The function of protein Z is not known. 

None of the models satisfy all of the above requirements for micelle structure. However, a discussion of the mechanism of milk coagulation in terms of some of the models may prove illuminating (2). A number of models for micelle structure have been proposed four models requiring various clotting mechanisms are discussed here. Since any mechanism of milk clotting must be predicated on the correct micelle model, it will become evident from the ensuing discussion that much additional research is necessary to fully understand the clotting process. 

If a polystyrene latex that is stabilized solely by an electrostatic mechanism is coagulated by the addition of electrolyte, that coagulation is usually irreversible to subsequent dilution. In contrast, sterically stabilized dispersions can usually be flocculated by the addition to the dispersion medium of a nonsolvent for the stabilizing moieties mere dilution of the concentration of the nonsolvent to a suitably low value is often sufficient to induce the particles to redisperse spontaneously. 

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