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F J Walker

Publications and source records attributed to F J Walker.

41 records · Page 3Linked to original sources
PubMed1979

Interactions between heparin and factor Xa. Inhibition of prothrombin activation.

The effects of heparin on prothrombin activation have been examined. Heparin was found to inhibit the rate of prothrombin activation by Factor Xa, calcium and phospholipid. In the absence of phospholipid, heparin had no effect on the rate of prothrombin activation. In contrast, heparin was found to increase the rate of activation of prethrombin-1 and prethrombin-2. Initial velocity studies indicated that heparin blocks lipid stimulation of prothrombin activation. In accord with this, binding studies demonstrated that heparin could displace Factor Xa, and in separate experiments, prothrombin, from phospholipid vesicles.

Animals↗
PubMedDate not supplied

Protein C deficiency in liver disease.

Protein C is a vitamin K-dependent zymogen of a serine protease that is found in blood plasma. The active form, activated protein C, can inhibit blood coagulation and stimulate fibrinolysis. Protein C is synthesized in the liver as a single chain protein. Its synthesis requires several post-translational modifications including carboxylation of glutamic acid residues, hydroxylation of aspartic acid residues, and glycosylation. Plasma protein C levels are sensitive to liver function. Protein C levels fall more rapidly than other vitamin K-dependent proteins when synthesis is altered by the administration of oral anticoagulants. In addition, low protein C levels are highly indicative of abnormal liver function. In one case, homozygous protein C deficiency has been corrected by liver transplantation. In liver transplantation for end-stage liver failure, plasma protein C levels may be a good indicator of the success of the transplantation.

Liver Diseases↗
PubMedDate not supplied

Protein S and thrombosis.

Thrombosis is a serious problem in the United States. Activated protein C is a vitamin K-dependent serine protease that seems to be an important regulator of the hemostatic process. Protein S is another vitamin K-dependent protein that is essential for the expression of the anticoagulant activity of activated protein C. Evidence suggests that defects in either of these proteins may be related to the development of thrombosis. Therefore, the accurate measurement of these proteins is important in the study and in the treatment of thrombosis. Sixty percent of the protein S found in human plasma is bound to the complement component C4b-binding protein, and when in this complex, protein S is inactive. The remaining 40 percent is the free, functional form of protein S. This paper describes the measurement of both free and total protein S by two types of assays. The first assay involves immunoelectrophoresis, also known as the Laurell Rocket method. The second assay is a capture enzyme linked immunosorbent assay (ELISA). The two assays are compared as to relative ease and cost.

Electrophoresis↗