Surface and total tissue factor activity of endothelial cells.

With a technic that was developed by us, we found that normal human umbilical vein endothelial cells (HUVEC) in culture characteristically had very little tissue factor (TF) activity either on the surface or in the cells which had been disrupted. In the presence of endotoxin (E. coli O26:B6), a trigger for thrombosis in septicemic patients, we could not detect an increased TF activity of HUVEC on its surface. However, an increase in TF (total TF) was detected after disruption of the cells. The increase in total TF was dose-dependent. Endotoxin at the concentration of 10 micrograms/ml caused around 5 fold increase in total TF activity compared to that of HUVEC in the absence of endotoxin.

Thai national reference preparation in blood coagulation. IV. Home made reference plasma for von Willebrand's factor assay.

Two lots of home made reference plasma: FVIII R:Ag 30/8/88 and FVIII R:Ag 18/10/88 were prepared by lyophilization of pooled normal human plasma. Modification of J. Cejka's technique was used to determine FVIII R:Ag. This technique was tested for reliability i.e. precision, reproducibility and sensitivity. The concentration of FVIII R:Ag, determined by calibration against the 1st British Standard for FVIII R:Ag, human 66/355, which was established by National Institute for Biological Standard and Control (NIBS & C), London, the WHO International Laboratory for Biological Standard, were respectively 1.058 and 1.023 Ag units/ml for FVIII R:Ag 30/8/88 and FVIII R:Ag 18/10/88, respectively. The precision of the procedure and the accuracy of FVIII R:Ag concentration of both lots were verified by using them as standard curve to determine FVIII R:Ag in 4 unknown plasma samples, supplied by the UK Reference Laboratory for Anticoagulant Reagent & Control; WHO Collaborating Center for Quality Assessment, in Blood Coagulation Testing for International Quality Control Survey in Blood Coagulation. The results were very satisfactory. The coefficient of variation was between 2.22-5.47 per cent when compared with other 29 laboratories around the world. These home made reference preparation are stable at least up to 30 months at -70 degrees C, and can be applied for calibration of unknown sample instead of the 1st British Standard for FVIII R:Ag, human 66/355.