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BACKGROUND The mechanisms of vascular thrombosis and pregnancy loss in the antiphospholipid-antibody syndrome are unknown. Levels of annexin V, a phospholipid-binding protein with potent anticoagulant activity, are markedly reduced on placental villi from women with this syndrome. Hypercoagulability in such women may therefore be due to the reduction of(More)
Annexin A5 (AnxA5) is a potent anticoagulant protein that crystallizes over phospholipid bilayers (PLBs), blocking their availability for coagulation reactions. Antiphospholipid antibodies disrupt AnxA5 binding, thereby accelerating coagulation reactions. This disruption may contribute to thrombosis and miscarriages in the antiphospholipid syndrome (APS).(More)
OBJECTIVES The mechanism by which antiphospholipid antibodies are associated with pregnancy loss and thromboembolism has not been established. We previously showed that annexin-V, a phospholipid-binding protein with potent anticoagulant activity, is present on the apical membranes of the syncytiotrophoblasts that line placental villi and that this protein(More)
Vascular anticoagulant alpha (VAC alpha, annexin V) is a member of the family of calcium and phospholipid binding proteins, the annexins. The binding properties of VAC alpha to phospholipid bilayers were studied by ellipsometry. Adsorption was calcium-dependent and completely reversible upon calcium depletion. Half-maximal adsorptions to phospholipid(More)
The antiphospholipid syndrome is a thrombophilic condition marked by antibodies that recognize anionic phospholipid-protein cofactor complexes. We recently reported that exposure to IgG fractions from antiphospholipid patients reduces the level of annexin-V, a phospholipid-binding anticoagulant protein, on cultured trophoblasts and endothelial cells and(More)
In 1985 we isolated a new vascular anticoagulant protein VAC alpha, now called annexin V, with a high binding affinity (Kd less than 10(-10) M) for phospholipids. Its anticoagulant effect was attributed to displacement of coagulation factors from the phospholipid membrane. The present study demonstrates that the inhibition of prothrombinase activity by(More)
A technique has been developed to monitor the development of thrombin in freshly collected whole blood in the absence of anticoagulants. It is based on the centrifugal separation of the cellular components from subsamples of blood drawn from non-anticoagulated clotting whole blood which are diluted in buffer containing a chromogenic substrate. It is shown(More)
Although the phospholipid requirement for tissue factor (TF) activity has been well-established, the mechanism by which the surface regulates enzymatic activity remains unclear. We added phospholipid vesicles to already relipidated TF (30/70 PS/PC) and found that added lipid can both enhance and inhibit the rate of factor X (F.X) activation. Using(More)
For many years, the essential role of tissue factor (TF) in coagulation and thrombogenesis has been recognized. The catalytic complex of TF and VIIa (TF:VIIa) is membrane-bound whereas its substrate, factor X (FX), is distributed between a phospholipid-bound fraction and one that is in true solution in 3-dimensional space. This complicates analytical(More)
Ellipsometry indicated that 1-(4-(trimethylammonio)phenyl-6-phenylhexa-1,3,5-triene (TMA-DPH) bound to platelets in a reversible and saturable way. Accordingly, the fluorescence intensity (F) of a suspension of TMA-DPH-labeled platelets was described as a quantity, determined by the amount of TMA-DPH bound to the platelet surface. Most platelet activators(More)