| 21. |
- Goudemand, J, et al.
(författare)
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Pharmacokinetic studies on Wilfactin((R)), a von Willebrand factor concentrate with a low factor VIII content treated with three virus-inactivation/removal methods
- 2005
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 3:10, s. 2219-2227
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Tidskriftsartikel (refereegranskat)abstract
- Objective: In order to correct the primary von Willebrand factor (VWF) defect and avoid supra-physiologic plasma levels of factor VIII, a pure VWF concentrate almost devoid of FVIII was developed and used in France since 1989. Methods: The pharmacokinetic (PK) profile of the most recent version of this concentrate (Wilfactin (R); LFB, Les Ulis, France), treated with three virus-inactivation/removal methods (solvent/detergent, 35 nm filtration, dry heat treatment), was investigated in 25 patients. Seventeen patients with various types of clinically severe von Willebrand disease (VWD) were included in a crossover, randomized trial carried out in five European centers and comparing Wilfactin (R) with concentrates containing both FVIII and VWF (FVIII/VWF). Eight type 3 VWD patients were included in another trial carried out in six French centers comparing Wilfactin (R) with its previous version (Facteur Willebrand-LFB (R); LFB) that adopted one virus-inactivation method only. Results: For both the measurements evaluated in this study (VWF antigen, VWF:Ag; and VWF ristocetin co-factor activity, VWF:RCo), Wilfactin (R) had a PK profile similar to that of the FVIII/VWF concentrates and of Facteur Willebrand-LFB (R). VWF:RCo and VWF:Ag recoveries were 2.1 +/- 0.3 and 1.8 +/- 0.3 per IU kg(-1) respectively, and the half-lives were 12.4 +/- 1.8 and 15.9 +/- 1.5 h. The FVIII synthesis rate was 5.8 +/- 1.0 IU dL(-1) h(-1), with a half-life of 15.8 +/- 2.4 h. Conclusion: The PK of VWF and FVIII have not been altered by the three virus-inactivation/removal steps during the manufacturing of Wilfactin (R).
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| 22. |
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| 23. |
- He, S, et al.
(författare)
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The effect of platelets on fibrin gel structure formed in the presence of recombinant factor VIIa in hemophilia plasma and in plasma from a patient with Glanzmann thrombasthenia
- 2005
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 3:2, s. 272-279
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Tidskriftsartikel (refereegranskat)abstract
- Fibrin gel structure has been shown to be dependent on the thrombin concentration as well as the rate of thrombin generation. Accordingly, factor VIII (FVIII)and FIX-deficient plasma (hemophilia A and B) form loose fibrin clots with high permeability constants. By adding rFVIIa in vitro to FVIII-deficient plasma containing platelets (frozen and thawed), the fibrin gel permeability constant normalized, indicating that extra rFVIIa (1.2 mug mL(-1) or higher) induced a tight fibrin structure. Thrombin generation is highly dependent on the number of platelets, and in this study it was demonstrated that the addition of rFVIIa (5 mug mL(-1)) normalizes the fibrin gel permeability in samples containing platelets (frozen-thawed) in numbers of at least down to 20 x 106 mL(-1). The effect of rFVIIa was not observed when unfrozen platelets instead of frozen-thawed platelets were added. Neither was any effect on the fibrin permeability seen, in the presence of annexin V, known to block the effect of phospholipids on the platelet surface. This indicates an important role of platelet phospholipids for the effect of rFVIIa. A similar effect on the fibrin permeability of rFVIIa was observed when added to platelet-rich plasma from a patient with Glanzinarm thrombasthenia. Recombinant FVIIa has been found to induce hemostasis in patients with hemophilia and inhibitors against FVIII/FIX as well as in patients with Glanzmann thrombasthenia, indicating the importance of the formation of a tight fibrin gel structure, more resistant against premature proteolysis, for maintaining hemostasis. In conclusion, the addition of rFVIIa (5 mug mL(-1)) also substantially decreased the permeability constant of fibrin gels formed in FVIII-deficient plasma in the presence of low numbers of frozen-thawed platelets (down to 20 x 10(6) mL(-1)). A similar pattern was obtained in plasma from a Glanzmann patient. No effect was found in the presence of unfrozen instead of frozen-thawed platelets. Annexin V blocked any effect of rFVIIa. A normalization of the overall fibrinolysis potential (OFP) during the same condition supports the effect of rFVIIa on the fibrin permeability in the presence of a limited number of platelets.
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Hillarp, Andreas, et al.
(författare)
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Improved performance characteristics of the von Willebrand factor ristocetin cofactor activity assay using a novel automated assay protocol.
- 2010
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 8, s. 2216-2223
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Tidskriftsartikel (refereegranskat)abstract
- Summary Background, objectives and methods: An accurate, sensitive and precise assay for reliable determination of the ristocetin cofactor activity of von Willebrand factor (VWF:RCo) in plasma and von Willebrand Factor (VWF)-containing concentrates has been evaluated. The assay is based on a commercially available automated protocol with modifications including a combination of adding additional ristocetin and the use of two calibration curves for the high and low measuring ranges. Results: Addition of extra ristocetin resulted in improved measurement of VWF recoveries from various VWF-containing concentrates that were underestimated using the standard automated protocol. The modifications resulted in improved assay performance over an extended measuring range (2.00 - 0.03 IU/mL). Accuracy was tested using VWF deficiency plasma spiked with 1(st) international standard for VWF concentrate. Seven dilutions, ranging between 1.80 and 0.05 IU/mL, were analyzed and resulted in measured concentrations between 80% and 100% of the assigned potency of the standard. Linearity was determined from the regression plot of the same concentrate dilutions and resulted in a correlation coefficient of 0.998. The repeatability, expressed as coefficient of variation, was 2% in the normal range (0.90 IU/mL) and 8% at the level of 0.05 IU/mL. The corresponding reproducibility results were 2% and 15% at the normal and low measuring ranges, respectively. Conclusions: Analysis of patients with von Willebrand disease indicates that the modified automated BCS((R)) protocol has a superior discrimination power compared with the standard protocol. This is especially true in samples with low VWF, as in patients with type 3 von Willebrand disease.
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| 28. |
- Högberg, Carl, et al.
(författare)
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Succinate independently stimulates full platelet activation via cAMP and PI3β kinase signaling.
- 2011
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 9:2, s. 361-372
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Tidskriftsartikel (refereegranskat)abstract
- Background: The citric cycle intermediate succinate has recently been identified as ligand for the G-protein coupled receptor (GPCR) SUCNR1. We have previously found that this receptor is one of the most expressed GPCRs in human platelets. Objective: The aim of this study was to investigate the role of SUCNR1 in platelet aggregation and to explore the signalling pathways of this receptor in platelets. Methods and Results: Using RT-PCR, we could demonstrate that SUCNR1 is expressed in human platelets at a level corresponding to that of the P2Y(1) receptor. Light transmission aggregation experiments showed a dose-dependent aggregation induced by succinate reaching a maximum response at 0.5mM. The effect of succinate on platelet aggregation was confirmed with flow cytometry showing increased surface expression of activated GPIIb/IIIa, and P-selectin. Intracellular SUCNR1 signalling was found to result in decreased cAMP levels, Akt phosphorylation mediated by PI3Kβ activation and receptor desensitisation. Further, succinate-induced platelet aggregation was demonstrated to depend on Src, generation of thromboxane A(2) and ATP release. The platelet SUCNR1 is subject to desensitization through both homologous and heterologous mechanisms. In addition, the P2Y(12) receptor inhibitor ticagrelor completely prevented platelet aggregation induced by succinate. Conclusions: Our experiments show that succinate induces full aggregation of human platelets via SUCNR1. Succinate-induced platelet aggregation depends on thromboxane A(2) generation, ATP release and P2Y(12) activation.
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| 29. |
- Kjellberg, Margareta, et al.
(författare)
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An immunochemical method for quantitative determination of latent antithrombin, the reactive center loop-inserted uncleaved form of antithrombin.
- 2007
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 5, s. 127-132
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Tidskriftsartikel (refereegranskat)abstract
- Antithrombin (AT) is a serine protease inhibitor that has thrombin, factors IXa and Xa as target proteases. In addition to active native AT, two other forms have been identified in plasma: the reactive center loop inserted cleaved and latent, uncleaved forms. Both have been shown to be present in normal human blood. Latent AT forms a dimer with native AT in vitro, thus inactivating the native form. Here we describe a mouse monoclonal antibody, 8C8, that is specific for latent AT. The affinity of 8C8 was found to be 500-fold higher for latent than for native AT and 5000-fold higher for latent than for cleaved AT. A sandwich assay was developed to measure the concentration of latent AT in plasma, which was found to be similar to 4.8 mg L-1 in healthy individuals. The K-D of the interaction between native and latent AT was found to be 51 mu M, i.e. far above the plasma concentration of both native and latent AT, indicating a negligible complex formation in blood.
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| 30. |
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