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PubMed1993

Quantitation of activated factor VII levels in plasma using a tissue factor mutant selectively deficient in promoting factor VII activation.

Although the majority of factor VII (FVII) circulates in the zymogen form, low levels of activated factor VII (FVIIa) have been postulated to exist in plasma and to serve a priming function for triggering of the clotting cascade. However, direct measurement of plasma FVIIa has not previously been possible. We have quantified plasma FVIIa levels using a novel, highly sensitive assay that is free from interference by FVII. Specificity of this clot-based assay results from the use of a mutant tissue factor that is selectively deficient in promoting FVII activation, but retains FVIIa cofactor function. In normal adults, FVIIa was found to be present in plasma (mean: 3.6 ng/mL) with considerable variation between individuals (range: 0.5 to 8.4 ng/mL). FVIIa levels were only loosely correlated with FVII coagulant activity, but were elevated in pregnancy and reduced with oral anticoagulant therapy. Incubation of plasma on ice in glass containers (cold activation) resulted in substantial FVIIa generation. Measurement of plasma forms of factor VII is of potential clinical importance because elevated FVII coagulant activity has been implicated as a significant risk predictor for ischemic heart disease. Clinically, this new assay will now permit direct assessment of the role of plasma FVIIa in thrombotic disorders.

Adult↗
PubMed2003

Four factor deficiency.

Four factor deficiency is variably associated with mild to fatal bleeding. We describe a 3-month-old boy, born of consanguineous parents, who presented with a right subdural haematoma and a clotting screen showing a prothrombin time (PT) > 100 s, an activated partial thromboplastin time (aPTT) > 150 s, a fibrinogen of 0.4 g/l, and fibrinogen degradation products < 1 microg/ml. He was given 300 U of factor IX concentrate (containing factors II and X) and 1 mg of vitamin K intravenously. Forty-five minutes later, clotting tests showed a PT of 24 s, an aPTT of 31 s and a fibrinogen of 2.6 g/l. The patient was found to be deficient in all the vitamin K-dependent factors: factors II, VII, IX and X, protein C and protein S. A 14-base deletion was found in intron 1 (bases 1056-1069) of the gamma-carboxylase gene. The patient and his elder sister were homozygous for this deletion, whereas both parents were heterozygous. The deletion destroys a reverse palindromic sequence (TTGAGGCAA) of the type often associated with cis-acting elements. Our results suggest that this element may be involved in the regulation of gamma-carboxylase expression. Expression studies are being completed so that this region can be definitively ascribed as a cis-acting element involved in gene regulation.

Blood Coagulation Factors↗
PubMed1986

Combined deficiency of coagulation factors II, VII, IX, and X: a case of probable congenital origin.

Combined deficiency of coagulant activity of the vitamin K-dependent factors was found in a 14-year-old boy suffering from severe hemorrhages. Immunoassays revealed the presence of acarboxyprothrombin. The bleedings could be controlled, but the coagulation defects persisted during more than 2 years' follow-up and could not be corrected by oral or parenteral vitamin K. No intoxication or underlying disease was found. The abnormality was considered a congenital disorder of the carboxylation of prothrombin.

Adolescent↗
PubMed1994

Protracted treatment with phorbol ester modulates J-7 human hepatoma-cell-induced aggregation and coagulation of human platelet-rich plasma.

In heparinized human platelet-rich plasma (PRP), J-7 human hepatoma cells initially induced platelet aggregation; then a clot formed. ADP-scavenger systems, apyrase and creatine phosphate/creatine phosphokinase did not inhibit this tumor-cell-induced platelet aggregation (TCIPA), whereas hirudin and concanavalin A completely blocked it. J-7 cells also shortened the recalcification time of normal and of Factor-VIII- and IX-deficient human plasma, although it was inactive in shortening the recalcification time of Factor-VII-deficient plasma. After treatment with phorbol 12,13-dibutyrate (PDBu) for 5 to 90 min, the aggregation and coagulation abilities of J-7 cells were unaffected. Prolonged treatment of J-7 cells with PDBu but not with alpha-PDBu for 24 and 72 hr resulted in gradual loss of aggregation and coagulation. Staurosporine antagonized the effect of PDBu and restored aggregation and coagulation in J-7 cells. Protracted treatment with PDBu (24 or 72 hr) did not affect adherence of J-7 cells to the extracellular-matrix proteins (i.e., fibrinogen, fibronectin, laminin, vitronectin and collagen types I and IV) or to the surface of plastic culture dishes. The treatment also did not affect J-7 cell detachment from plastic culture dishes. These in vitro results demonstrate that protracted phorbol ester treatment diminishes TCIPA and blood coagulation of tumor cells.

Alkaloids↗
PubMed2000

Recombinant coagulation factor VIIa: from the concept to clinical application in hemophilia treatment in 2000.

The development of factor VIII and factor IX concentrates markedly improved the management of hemophilia A and B and made home therapy possible. However, treatment of hemophilic patients with acquired inhibitors remained difficult. The preparation of prothrombin complex concentrates, nonactivated or activated, addressed this difficult clinical problem, but their use was associated with serious side effects. Factor VIIa was found to be a safer treatment modality. Factor VIIa per se is inactive and needs tissue factor (TF) to become biologically active. TF serves as the receptor for factor VIIa. TF is expressed from vessel walls only upon injury. Treatment of inhibitor patients with plasma-derived factor VII was found to be successful. This led to the development of recombinant factor VIIa, which was also found to be successful in managing hemophilia patients with inhibitors. Up to this point, large numbers of patients have been treated and few serious side effects have been noted. Because of its unique effects on the hemostasis system, recombinant factor VIIa will be useful for other indications as well, including patients with congenital factor VII deficiency, patients with bleeding and liver function impairment, patients with quantitative and qualitative platelet defects, and individuals who have sustained multiple trauma. The development of recombinant factor VII is reviewed in detail.

Factor VII↗
PubMed1982

Thrombin activation rate constant: one-stage chromogenic assay for the extrinsic system.

Some properties of a one-stage, chromogenic clotting assay using tissue thromboplastin as an activator are described. The chromogenic assay uses S-2238 as substrate and estimates thrombin by the rate of absorbance produced. Under assay conditions, it was observed that the log (thrombin or absorbance/min) is linear with time. The linearity appeared to extend from zero thrombin up to maximum thrombin concentration for all concentrations of each plasma type examined including factor V and factor VII deficient plasmas. Since the linear slope, b, appears to be a measure of the rate of thrombin production, it was called the Thrombin Activation Rate Constant (TARC). For dilutions of normal plasma log (b) appears to be linearly related to log (plasma concentration) and to log (PT) where PT is the standard one stage clotting time. For plasmas deficient in extrinsic clotting factors, b was linearly related to log (factor concentrations). The chromogenic assay was most sensitive to changes in prothrombin; least sensitive to changes in factor VII; and unaffected by changes in concentration of factors VIII and IX. The standard PT was least sensitive to prothrombin and more sensitive to factors X and VII. For oral anticoagulated plasmas log b and log PT were linearly correlated with a regression slope which was more negative than that from normal plasma. From theses results it was concluded that TARC is a chromogenic assay sensitive to all factors in the extrinsic pathway; that TARC might be used as both a screening assay for extrinsic deficiencies and a monitoring assay for anticoagulants; and that TARC may be more sensitive than the standard PT to the defects from oral anticoagulation.

Anticoagulants↗
PubMed1989

Enhanced procoagulatory activity (PCA) of human monocytes/macrophages after in vitro stimulation with chemically modified LDL.

In cultured human monocytes/macrophages, surface expression of procoagulatory activity (PCA) was induced by chemically modified LDL (acetyl-LDL and MDA-LDL) in a dose- and time-dependent manner. Maximum PCA (30-fold increase) was detected after 24 h of culture with modified LDL at doses of 25-750 micrograms protein/ml. Using factor VII deficient human plasma and phospholipase C this PCA was identified as tissue thromboplastin activity (factor III). These results suggest a further atherogenic potential for modified LDL through stimulation of the conversion of fibrinogen to fibrin in the atheromatous lesion.

Blood Coagulation Factors↗
PubMed1979

Reduction of salivary tissue factor (thromboplastin) activity by warfarin therapy.

The coagulant of normal human saliva has been identified as tissue factor (thromboplastin, TF) by virtue of its ability to cause rapid coagulation in plasmas deficient in first-stage coagulation factors and to activate factor x in the presence of factor VII and by virtue of the fact that its activity is expressed only in the presence of factor VII and is inhibited by an antibody to TF. The TF is related to cells and cell fragments in saliva. Salivary TF activity has been found to be significantly reduced in patients taking warfarin. The decline in TF activity during induction of warfarin anticoagulation occurs during the warfarin-induced decline in vitamin-K-dependent clotting factor activity, as judged by the prothrombin time. The decrease in TF activity is not related to a reduction in salivary cell count or total protein content or to a direct effect of warfarin on the assay. It is hypothesized that the mechanism by which warfarin inhibits TF activity may be related to the mechanism by which it inhibits expression of the activity of the vitamin-K-dependent clotting factors. Inhibition of the TF activity may be involved in the antithrombotic effect of warfarin.

Factor VII↗
PubMed1975

Coagulation studies in patients with trisomy 8 syndrome.

Coagulation studies were performed in three patients with trisomy for chromosome No. 8. In contrast to the findings reported by others, all patients were found to have a normal coagulation status without sign of factor VII deficiency.

Adolescent↗
PubMed1995

Determinants of plasma factor VIIa levels in humans.

Several enzymes can activate factor VII in vitro, but the protease responsible for generating factor VIIa in vivo has not been determined. Using recombinant tissue factor that has undergone a COOH-terminal truncation, a sensitive functional assay has been established for measuring plasma factor VIIa levels. To evaluate the mechanism responsible for the generation of factor VIIa in vivo, we measured the levels of this enzyme after administering purified concentrates of factor IX and factor VIII to patients with severe deficiencies of these clotting factors. In patients with hemophilia B, factor VIIa levels were initially reduced to 0.5 +/- 0.1 ng/mL and gradually increased to normal after infusing 100 U/kg of body weight (BW) of factor IX. Despite these increases, there were no significant changes in the generation of factor Xa or thrombin. In patients with hemophilia A, only a slight reduction in factor VIIa levels (2.5 +/- 1.3 ng/mL) was observed as compared with controls (3.3 +/- 1.1 ng/mL) and no significant changes were observed after factor VIII levels were normalized. The administration of recombinant factor VIIa (10 micrograms/kg BW) to patients with factor VII deficiency increased the mean circulating level of the enzyme to 118 ng/mL, but this only resulted in normalization of the levels of the activation peptides of factor IX and factor X. The above data indicate that factor IXa is primarily responsible for the basal levels of free factor VIIa generated in vivo (ie, in the absence of thrombosis or provocative stimuli) and that changes in the plasma concentrations of free factor VIIa in the blood do not necessarily lead to alterations in the extent of factor X activation.

Adolescent↗
PubMed1994

Synovectomy for haemophilic arthropathy: 6-21 years of follow-up in 16 patients.

OBJECTIVES: To assess the efficacy of synovectomy in reducing recurrent haemarthroses and joint pain in patients suffering from haemophilic arthropathy. Moreover, to study whether synovectomy could improve joint mobility or postpone progression of joint destruction. DESIGN: A retrospective study was conducted addressing joint-related symptoms and findings, and the need of orthopaedic surgery during follow-up. SETTING: Oslo Sanitetsforenings Rheumatism Hospital/The National Hospital, the National Centre for Orthopaedic Surgery for approximately 180 Norwegians suffering from severe congenital coagulation deficiencies. SUBJECTS: Twelve patients with haemophilia A, two patients with von Willebrand's disease and two patients with factor VII deficiency in which 21 synovectomies (nine knees, six ankles and six elbows) were performed. MAIN OUTCOME MEASURES: Joint pain, joint mobility, frequency of haemarthroses and radiographic joint scores at follow-up were compared to preoperative figures, and the number of joints in need of total joint replacement or arthrodesis was evaluated. RESULTS: Synovectomy proved efficacious in reducing recurrent haemarthroses and joint pain in all patients. The total range of motion was not improved, but correction of extension deficiency of the knee was accomplished. The progression of arthropathy was not arrested by synovectomy as judged by the radiographic assessment; and in four patients arthroplasty of the knee, and in two patients arthrodesis of the ankle, had been performed. A major wound haemorrhage and subsequent wound rupture was seen in one patient who developed high-titred neutralizing antibodies to factor VIII. CONCLUSIONS: Synovectomy for haemophilic arthropathy is safe and efficacious in reducing recurrent haemarthroses and joint pain. Synovectomy should not be performed to improve joint mobility. The progression of the arthropathy is not arrested, and subsequently many patients will be candidates for arthroplasty or arthrodesis.

Adolescent↗
PubMed1996

Determinants of coagulation activation in humans.

To evaluate the mechanism responsible for the generation of factor VIIa in vivo, we measured the levels of this enzyme after administering purified factor IX concentrates to patients with hemophilia B. Their factor VIIa levels were initially very low and gradually increased to normal, but there were no significant changes in the generation of factor Xa or thrombin. The administration of 10 mu g/kg body weight of recombinant factor VIIa to patients with factor VII deficiency increased the circulating levels 35-fold, but this only resulted in normalization of the activation of factor IX and factor X. Our data indicate that factor IXa is primarily responsible for the basal levels of free factor VIIa in vivo, and that changes in free factor VIIa in the blood do not necessarily lead to alterations in factor X activation.

Factor IX↗
PubMed1988

Monoclonal antibodies to human factor VII: a one step immunoradiometric assay for VII:Ag.

Three mouse monoclonal antibodies (RFF-VII/1, RFF-VII/2, and RFF-VII/3) which bind specifically to different epitopes on human factor VII antigen were raised. Two of the antibodies, RFF-VII/1 and RFF-VII/2, bound strongly to factor VII antigen (VII:Ag), but only RFF-VII/1 and RFF-VII/3 were potent inhibitors of factor VII coagulation activity (VII:C). RFF-VII/1 and RFF-VII/2 were used in a one step, double monoclonal immunoradiometric assay for VII:Ag. This was highly reproducible and detected as little as 0.05U/dl VII:Ag. Values for VII:Ag obtained for plasma samples from normal subjects (n = 20), patients with liver disease (n = 20), patients treated with warfarin (n = 20), and those congenitally deficient in factor VII (n = 7) correlated very well (r = 0.96) with data obtained in a radioimmunoassay using polyclonal rabbit antiserum to factor VII. This simple and sensitive monoclonal antibody based assay offers a convenient method for the detection of VII:Ag in various disease states.

Animals↗