SummaryThe monoclonal antibody RFF-VIII:R/1 recognises an epitope on von Willebrand factor involved in its interaction with GPIbα. A two-site, solid phase ELISA has been established using RFF-VIII:R/1 as the solid-phase, capture antibody and an enzyme-conjugated, polyclonal antibody to human VWF, which provides an assay for VWF functional activity with a detection limit of 0.5 U/dl VWF and an interassay %CV<10. Plasma from 192 VWD patients (48 studied retrospectively; 144 prospectively) showed VWF levels of <50 U/dl in type 1 patients (n = 156), <25 U/dl in type 2A (n = 26) and <35 U/dl in type 2B (n = 8) which, in type 1 and 2A patients, correlated with RiCoF activity (r >0.82). In plasma from patients with type 1 VWD values of VWF in the Mab-based ELISA were similar to levels of VWF:Ag measured in a polyclonal antibody-based ELISA (r >0.87) but were significantly lower than VWF:Ag in type 2A and 2B plasmas (p <0.0005), allowing discrimination of variant VWD. The Mab-based ELISA has advantages of sensitivity and reproducibility over the RiCoF assay to measure VWF activity and can be used to analyse stored samples. In conjunction with an ELISA for VWF:Ag and VWF multimer analysis, it provides a reliable method, for the laboratory diagnosis of VWD.
Objective To assess the changes in overall coagulation status and define the degree of systemic fibrinolysis occurring in patients undergoing transurethral prostatectomy (TURP).
Patients and methods Thirty patients undergoing TURP, 23 for benign prostatic hyperplasia and seven for prostatic carcinoma, were studied prospectively. Serial venous blood samples were taken using the two‐syringe technique. Samples were taken before, during and at intervals up to 72 h and 10–14 days after surgery. Thrombelastography (TEG) was performed on native whole blood samples. Peri‐operative blood loss was assessed, until the catheter was removed, by photometric estimation of the haemoglobin content of the irrigant fluid and the measurement of clot volume.
Results There was no evidence of fibrinolysis (TEG Percentage Clot Lysis Ly60 >15%) in any patient over the whole peri‐operative period. There was a significant change in the mean TEG variables towards hypercoagulation from 3 h until 10–14 days post‐operatively, compared with the pre‐operative values (P<0.05). There was a significant correlation between blood loss and clot volume.
Conclusion These results question the role of systemic fibrinolysis in primary and secondary haemorrhage following TURP and thus the rationale of using antifibrinolytics in these patients. The persistent hypercoagulable state post‐operatively indicates a possible role of hypercoagulability in clot retention.
A plasmid containing human coagulation factor VII (hFVII) complementary DNA regulated by a cytomegalovirus promoter was microinjected into fertilized eggs of zebrafish, African catfish, and tilapia. The active form of hFVll was detected in the fish embryos by various assays. This positive expression of human therapeutic protein in fish embryos demonstrates the possibility of exploitation of transgenic fish as bioreactors.
The biological chemistry that underlies and regulates the blood coagulation cascade is not fully understood. To begin to understand this, we performed clotting assays under various redox conditions. By varying the amount of oxidant and/or antioxidant in these assays, we observed that both the intrinsic/ tenase complex and the extrinsic pathways were susceptible to shifts in the thiol/redox balance. We established a dichotomy where blood clotting via the intrinsic pathway was sensitive to oxidation whereas the tissue factor or extrinsic pathway was more sensitive to reduction. These differential inhibitory effects present a conceptual mechanism for selective modulation of the activities of clotting factors specific for the respective pathways. These data also suggest that blood clotting may be influenced by unidentified redox or thiol equilibria. ß
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