The Role of Factor XI in a Dilute Thromboplastin Assay of Extrinsic Coagulation Pathway

2001 ◽  
Vol 85 (06) ◽  
pp. 1055-1059 ◽  
Author(s):  
Shilong Xiong ◽  
Xiaofan He ◽  
Fayi Liu ◽  
Jianzhong Han ◽  
Juncheng Li ◽  
...  
Keyword(s):  
Blood Coagulation ◽  
Platelet Rich Plasma ◽  
Critical Role ◽  
Extrinsic Pathway ◽  
Thrombin Inhibition ◽  
Normal Plasma ◽  
Low Concentrations ◽  
Plasma Depletion ◽  
Coagulation Pathway

SummaryBlood coagulation has been thought to be composed of both intrinsic and extrinsic pathways. Recent evidence strongly supports the critical role of the extrinsic pathway in the initiation of blood coagulation. This investigation established an assay that examines the role of FXI in the thromboplastin-initiated (extrinsic) coagulation based on this new concept. Plasma clotting times were measured at different concentrations of thromboplastin with activated FXII inhibited (FXIIa-inhibited Diluted Thromboplastin Time, FXIIaiDTT). Only at low concentrations of thromboplastin was FXIIaiDTT of FXI-deficient plasma significantly prolonged than that of normal plasma. Depletion of FXI from normal plasma prolonged its FXIIaiDTT and replenishment of FXI shortened it. FXIIaiDTTs of both FVIII-deficient and FIX-deficient plasma were remarkably prolonged, and addition of normal plasma dose-dependently shortened it. Furthermore, earlier α-thrombin inhibition was directly correlated with decreasing FXa generation. The amount of FXa production was: platelet-rich plasma > platelet-poor plasma > FXI-deficient plasma. Therefore, our findings from the FXIIaiDTT assays not only support the critical role of extrinsic pathway in blood coagulation initiation, but also demonstrate the importance of FXI as an amplifier of thrombin generation in thromboplastin-initiated coagulation.

Testosterone Potentiation of Ionophore and ADP Induced Platelet Aggregation : Relationship to Arachidonic Acid Metabolism

1981 ◽  
Vol 46 (02) ◽  
pp. 538-542 ◽  
Author(s):  
R Pilo ◽  
D Aharony ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Unsaturated Fatty Acids ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Arachidonic Acid Metabolism ◽  
Ionophore A23187 ◽  
Low Concentrations ◽  
Induced Aggregation

SummaryThe role of arachidonic acid oxygenated products in human platelet aggregation induced by the ionophore A23187 was investigated. The ionophore produced an increased release of both saturated and unsaturated fatty acids and a concomitant increased formation of TxA2 and other arachidonate products. TxA2 (and possibly other cyclo oxygenase products) appears to have a significant role in ionophore-induced aggregation only when low concentrations (<1 μM) of the ionophore are employed.Testosterone added to rat or human platelet-rich plasma (PRP) was shown previously to potentiate platelet aggregation induced by ADP, adrenaline, collagen and arachidonic acid (1, 2). We show that testosterone also potentiates ionophore induced aggregation in washed platelets and in PRP. This potentiation was dose and time dependent and resulted from increased lipolysis and concomitant generation of TxA2 and other prostaglandin products. The testosterone potentiating effect was abolished by preincubation of the platelets with indomethacin.

THE ROLE OF FACTOR VII IN HAEMOSTASIS: A DETAILED MICROSCOPIC ANALYSIS OF THE MORPHOLOGY OF THE EVOLVING HAEMOSTATIC PLUG IN NORMAL AND VII DEFICIENT DOGS

1987 ◽  
Author(s):  
Alan R Giles ◽  
Peter Vendervelden
Keyword(s):  
Critical Role ◽  
Microscopic Analysis ◽  
Pulse Generation ◽  
Factor Vii ◽  
Extrinsic Pathway ◽  
Morphological Studies ◽  
Significant Difference ◽  
Activation Pathways

The role of F.VII in haemostasis remains controversial, both in terms of the functional consequences of the deficiency state and the activation pathways to which it makes its principal contribution In vivo. We have developed a cuticle bleeding time (CBT) model in dogs and used this to investigate the functional consequence of both congenital and acquired F.VII deficiency (SD) (Blood 65:1197, 1985). There was no significant difference between the CBT of these animals when compared to controls. However, the CBT prolonged at a significantly lower Heparin level than that observed in controls. F.VIIa was also infused into F.VIII deficient and normal dogs and FPA measured as an indicator of thrombin generation. Significant change in FPA level occurred in the latter but not the former, suggesting that activation of F.IX rather than F.X was favoured. We have now performed detailed morphological studies of the evolving haemostatic plug (HP) in the injured cuticle of F.VII and normal animals by light (LM) and electron microscopy (EM). Quantification of the EM changes noted were performed by morphometric analysis. The tightness of the intravascular component of the HP was assessed by random measurement of intraplatelet distance. The degree of platelet activation was measured by comparing the area of the open canalicular system (OCS) in comparison to the total platelet area. The appearance of fibrin in the plug was also noted. Qualitative LM revealed little difference between the two sets of animals. The appearance of fibrin at the periphery of HP plug was delayed in SD and was reduced in quantity. However, by morphometry although the pattern was identical in both groups, there was a significant delay in the changes noted in SD. These results suggest that the extrinsic pathway may play an important role in triggering the intrinsic pathway, either by providing for activation of the cofactors V and VIII or pulse generation of F.IXa. This may play a critical role in haemostasis when the vessel injured is larger than those in the nail cuticle of the dog (50 - 150 μm) or when other components of haemostatic mechanism are compromised

Role of exosite binding modulators in the inhibition of Fxa by TFPI

2016 ◽  
Vol 115 (03) ◽  
pp. 580-590 ◽  
Author(s):  
Alexandra Heinzmann ◽  
Tilman M. Hackeng ◽  
Rudolf Hartmann ◽  
Friedrich Scheiflinger ◽  
Michael Dockal ◽  
...  
Keyword(s):  
Plasma Proteins ◽  
Tissue Factor Pathway Inhibitor ◽  
Anticoagulant Activity ◽  
Protein S ◽  
Low Concentrations ◽  
Tissue Factor Pathway ◽  
Coagulation Pathway ◽  
Prothrombin Activation

SummaryTissue factor pathway inhibitor (TFPI) down-regulates the extrinsic coagulation pathway by inhibiting FXa and FVIIa. Both TFPI and FXa interact with several plasma proteins (e. g. prothrombin, FV/FVa, protein S) and non-proteinaceous compounds (e. g. phospholipids, heparin). It was our aim to investigate effects of ligands that bind to FXa and TFPI on FXa inhibition by full-length TFPI (designated TFPI) and truncated TFPI (TFPI1-150). Inhibition of FXa by TFPI and TFPI1-150 and effects of phospholipids, heparin, prothrombin, FV, FVa, and protein S thereon was quantified from progress curves of conversion of the FXa-specific chromogenic substrate CS11-(65). Low concentrations negatively charged phospholipids (~10 μM) already maximally stimulated (up to 5- to 6-fold) FXa inhibition by TFPI. Unfractionated heparin at concentrations (0.2–1 U/ml) enhanced FXa inhibition by TFPI ~8-fold, but impaired inhibition at concentrations > 1 U/ml. Physiological protein S and FV concentrations both enhanced FXa inhibition by TFPI 2- to 3-fold. In contrast, thrombin-activated FV (FVa) impaired the ability of TFPI to inhibit FXa. FXa inhibition by TFPI1–150 was not affected by FV, FVa, protein S, phospholipids and heparin. TFPI potently inhibited FXa-catalysed prothrombin activation in the absence of FVa, but hardly inhibited prothrombin activation in the presence of thrombin-activated FVa. In conclusion, physiological concentrations TFPI (0.25–0.5 nM TFPI) inhibit FXa with a t1/2 between 3–15 minutes. Direct FXa inhibition by TFPI is modulated by physiological concentrations prothrombin, FV, FVa, protein S, phospholipids and heparin indicating the importance of these modulators for the in vivo anticoagulant activity of TFPI.

scholarly journals Protein C Inhibitor Acts as a Procoagulant by Inhibiting the Thrombomodulin-Induced Activation of Protein C in Human Plasma

Blood ◽  
1998 ◽  
Vol 91 (5) ◽  
pp. 1542-1547 ◽  
Author(s):  
Marc G.L.M. Elisen ◽  
Peter A.Kr. von dem Borne ◽  
Bonno N. Bouma ◽  
Joost C.M. Meijers
Keyword(s):  
Tissue Factor ◽  
Protein C ◽  
Activated Protein C ◽  
Anticoagulant Effect ◽  
Clotting Time ◽  
Thrombin Inhibition ◽  
Normal Plasma ◽  
Protein C Inhibitor ◽  
Inhibition Of Thrombin

AbstractProtein C inhibitor (PCI), which was originally identified as an inhibitor of activated protein C, also efficiently inhibits coagulation factors such as factor Xa and thrombin. Recently it was found, using purified proteins, that the anticoagulant thrombin-thrombomodulin complex was also inhibited by PCI. The paradoxical inhibitory effect of PCI on both coagulant and anticoagulant proteases raised questions about the role of PCI in plasma. We studied the role of thrombomodulin (TM)-dependent inhibition of thrombin by PCI in a plasma system. Clotting was induced by addition of tissue factor to recalcified plasma in the absence or presence of TM, and clot formation was monitored using turbidimetry. In the absence of TM, PCI-deficient plasma showed a slightly shorter coagulation time compared with normal plasma. Reconstitution with a physiologic amount of PCI gave normal clotting times. Addition of PCI to normal plasma and protein C–deficient plasma resulted in a minor prolongation of the clotting time. This suggested that PCI can act as a weak coagulation inhibitor in the absence of TM. TM caused a strong anticoagulant effect in normal plasma due to thrombin scavenging and activation of the protein C anticoagulant pathway. This effect was less pronounced when protein C–deficient plasma was used, but could be restored by reconstitution with protein C. When PCI was added to protein C–deficient plasma in the presence of TM, a strong anticoagulant effect of PCI was observed. This anticoagulant effect was most likely caused by the TM-dependent thrombin inhibition by PCI. However, when PCI was added to normal plasma containing TM, a strong procoagulant effect of PCI was observed, due to the inhibition of protein C activation. PCI-deficient plasma was less coagulant in the presence of TM. A concentration-dependent increase in clotting time was observed when PCI-deficient plasma was reconstituted with PCI. The combination of these results suggest that the major function of PCI in plasma during coagulation is the inhibition of thrombin. A decreased generation of activated protein C is a procoagulant consequence of the TM-dependent thrombin inhibition by PCI. We conclude that TM alters PCI from an anticoagulant into a procoagulant during tissue factor-induced coagulation.

scholarly journals The Action of a Synthetic Pentasaccharide on Thrombin Generation in Whole Plasma

1989 ◽  
Vol 61 (03) ◽  
pp. 397-401 ◽  
Author(s):  
S Béguin ◽  
J Choay ◽  
H C Hemker
Keyword(s):  
Binding Site ◽  
Blood Coagulation ◽  
Thrombin Generation ◽  
Platelet Rich Plasma ◽  
Factor Xa ◽  
Heparin Binding ◽  
Extrinsic Pathway ◽  
Prothrombinase Complex ◽  
Factor Va ◽  
Prothrombinase Activity

SummaryWe investigated the effect on thrombin generation in plasma of the pentasaccharide that represent the AT II/binding site in heparin. This compound has no effect on the breakdown of thrombin in plasma. It dose-dependently inhibits the formation of thrombin in both the intrinsic and the extrinsic pathway. If coagulation is triggered by the complete prothrombinase complex (phospholipid – factor Va – factor Xa) under conditions in which the large majority of factor Xa is bound to the complex, the inhibition of prothrombinase activity is only minor. If no factor Va is present or if the prothrombinase activity is triggered by adding complete tenase (PL-FVIIIa-FIXa) or incomplete tenase (PLFIXa) to the plasma the inhibition by pentasaccharide is of the same magnitude as that in the intrinsic or extrinsic system.We conclude that the pentasaccharide inhibits blood coagulation by katalysing the inactivation of free factor Xa. In contrast to classical heparin it does inhibit the peak of thrombin formation in platelet rich plasma, probably because it is less subject to inactivation by heparin binding proteins from platelets than classical heparin is.

scholarly journals Role of the Extrinsic Pathway of Blood Coagulation in Hemostasis and Thrombosis

2007 ◽  
Vol 27 (8) ◽  
pp. 1687-1693 ◽  
Author(s):  
Nigel Mackman ◽  
Rachel E. Tilley ◽  
Nigel S. Key
Keyword(s):  
Blood Coagulation ◽  
Extrinsic Pathway

Inhibition of Extrinsic Pathway Inhibitor Shortens the Coagulation Time of Normal Plasma and of Hemophilia Plasma

1991 ◽  
Vol 66 (04) ◽  
pp. 464-467 ◽  
Author(s):  
Ole Nordfang ◽  
Sanne Valentin ◽  
Thomas C Beck ◽  
Ulla Hedner
Keyword(s):  
Coagulation Factors ◽  
Inhibitory Antibody ◽  
Extrinsic Pathway ◽  
Coagulation Time ◽  
Plasma Analysis ◽  
Normal Plasma ◽  
Low Concentrations ◽  
Viii And Ix ◽  
Dependent Pathway ◽  
Individual Donor

SummaryAn increasing amount of evidence suggests that coagulation factors VIII and IX play a role not only in the intrinsic but also in the extrinsic pathway of coagulation. In this context the influence of the Extrinsic Pathway Inhibitor (EPI) on the coagulation time of hemophilia plasma lacking FVIII or FIX has been investigated. The coagulation time was measured in a dilute thromboplastin assay. Addition of recombinant EPI (rEPI) prolonged the coagulation time of normal plasma while the addition of an inhibitory antibody against EPI shortened the coagulation time. At low concentrations of thromboplastin the coagulation time of hemophilia plasma was prolonged and at all dilutions of thromboplastin, addition of anti-EPI IgG normalized the coagulation time of a hemophilia plasma. Analysis of 10 individual donor plasma samples and 8 individual hemophilia samples showed that addition of anti-EPI IgG shortened the coagulation time more in hemophilia plasma than in normal plasma. This illustrates the importance of a powerful extrinsic FVII dependent pathway to achieve hemostasis in the case of FVIII or FIX deficiency (hemophilia A and B).

Some Observations on the Rôle of Hageman Factor in Blood Coagulation

1961 ◽  
Vol 6 (02) ◽  
pp. 261-269 ◽  
Author(s):  
C Haanen ◽  
F Hommes ◽  
Gerdy Morselt
Keyword(s):  
Blood Coagulation ◽  
Clotting Factors ◽  
Sulphated Polysaccharides ◽  
Hageman Factor ◽  
Normal Plasma ◽  
Plasma Factors ◽  
Positively Charged

SummaryThe defective thromboplastin formation in Hageman factor deficient plasma is completely corrected using incubation tubes which have been coated previously with normal plasma. Positively or negatively charged molecules as protamin and sulphated polysaccharides interfere with this correction in a way that gives evidence Hageman factor is a positively charged protein.The defective thromboplastin generation of Hageman factor deficient incubation mixtures is corrected by addition of a purified Hageman factor preparation. Pre-incubation of Hageman factor with HF deficient serum improves the thromboplastin formation further, while pre-incubation of Hageman factor with HF deficient plasma abolishes this correction complete. Possibly here lies the key for the fact that serum clotting factors augment and plasma factors deteriorate during the clotting process.

Critical role of interfaces and agitation on the nucleation of Aβ amyloid fibrils at low concentrations of Aβ monomers

2010 ◽  
Vol 1804 (4) ◽  
pp. 986-995 ◽  
Author(s):  
Akiyoshi Morinaga ◽  
Kazuhiro Hasegawa ◽  
Ryo Nomura ◽  
Tadakazu Ookoshi ◽  
Daisaku Ozawa ◽  
...  
Keyword(s):  
Amyloid Fibrils ◽  
Critical Role ◽  
Low Concentrations ◽  
Aβ Amyloid

INCREASED ADHESIVE PROPERTIES OF THE CARBOHYDRATE-MODIFIED VON WILLEBRAND FACTOR (CHO-VWF): CRITICAL ROLE OF THE MULTIMERIC STRUCTURE AND CORRELATION WITH PLATELET AGGREGATION

1987 ◽  
Author(s):  
A B Federici ◽  
C De Romeuf ◽  
P G De Groot ◽  
P M Mannucci ◽  
B Samor ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Platelet Rich Plasma ◽  
Critical Role ◽  
Freezing And Thawing ◽  
Adhesive Properties ◽  
Spontaneous Aggregation ◽  
Von Willebrand ◽  
Willebrand Factor

We have reexplored the role of the carbohydrate moiety (CHO) on the von Willebrand Factor (vWF) structure and function by critically evaluating its different purification steps and modifications in CHO content by specific enzymes. Structural and functional assays have been evaluated separately in each laboratory (Milano and Lille) and jointly in Utrecht during several organized experiments. Under our conditions, the CHOVWFs obtained were characterized by less than 5% of sialic acid "(Neu)asevWF" and about 45% of D-Galactose "(Neu-Gal)ase-vWF" remaining, by increased electrophoretic mobility without any significant losses of the high molecular weight multimers and by their capacity to induce spontaneous aggregation in normal platelet rich plasma (PRP). Platelet adhesion to these different CHO-vWFs was tested in the flat chamber devised by Sakariassen in the presence of different subendothelial matrices and data expressed as the percentage of the surface covered by platelets. The blood reconstituted with different plasma samples showed the following percentual values of surface coverage (mean ± SD):- Normal plasma = 15 ± 3.8- Severe vWd plasma = 4 ± 1.9- SvWd pl + Native vWF = 14 ± 2.8- SvWd pl + (Neu) ase-vWF = 23 ± 3.5- SvWd pl + (Neu-Gal) ase-vWF = 19 ± 2.9This significantly increased adhesion to the subendothelium of the CHO-vWFs corresponded to the spontaneous aggregation present in normal PRP but it disappeared when the multimeric structure was damaged by in vitro proteolysis and/or by storage conditions (changes in temperature and freezing and thawing). From these results we may conclude that removal of terminal sugars enhances not only platelet-vWF interactions, but also platelet adhesion to the subendothelium.

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