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PubMed1985

Deficiency of the contact phase of intrinsic coagulation in a horse.

A 16-year-old gelding was examined because of weight loss, inappetence, and intermittent fever of 2 months' duration. Preliminary laboratory findings revealed anemia, hypoproteinemia, thrombocytopenia, and prolongation of the activated partial thromboplastin time. A deficiency or inhibition of coagulation factor XI, factor XII, or high molecular weight kininogen was diagnosed. This defect was not associated with a bleeding diathesis, but should be considered as a cause of prolongation of the activated partial thromboplastin time.

Animals↗
PubMed1996

Coagulation-dependent inhibition of fibrinolysis: role of carboxypeptidase-U and the premature lysis of clots from hemophilic plasma.

Coagulation is initiated by the binding of factor VIIa to tissue factor, with resultant limited factor IX and X activation and thrombin production. Owing to the feedback inhibition of the factor VIIa/tissue factor complex by tissue factor pathway inhibitor (TFPI), additional factor X activation and thrombin generation must proceed through a pathway involving factors VIII, IX, and XI. Experiments designed to elucidate the requirement for amplified factor Xa and thrombin generation in normal hemostasis show that the resistance of plasma clots to tissue plasminogen activator (tPA)- and urokinase-induced fibrinolysis is related to the extent of thrombin generation. Inhibition of fibrinolysis is mediated in part by plasma carboxypeptidase-U ([CPU] carboxypeptidase-R, procarboxypeptidase-B, thrombin-activatable fibrinolysis inhibitor), a proenzyme that is proteolytically activated by thrombin in a process enhanced dramatically by the cofactor thrombomodulin. A clot induced in factor IX-deficient plasma with limited amounts of tissue factor in the presence of urokinase (100 U/mL) lyses prematurely, and this defect is corrected by supplementation of the deficient plasma with factor IX (5 micrograms/mL) or thrombomodulin (20 ng/mL). These additions enhance the rate and extent of CPU activation: in the case of factor IX, presumably by permitting amplified generation of factor Xa and thrombin, and in the case of thrombomodulin, presumably by increasing the degree of CPU activation produced by the low levels of thrombin generated in the absence of factor IX. Pretreatment of the factor IX-deficient plasma with specific anti-CPU antibodies prevents the increased resistance to fibrinolysis produced by addition of factor IX and thrombomodulin. Likewise, when coagulation is induced by thrombin (2 U/mL) in the presence of tPA (60 U/mL), clots formed from plasmas deficient in factors VIII, IX, X, or XI lyse prematurely unless the missing factor is replaced or thrombomodulin (20 ng/mL) is added.

Animals↗
PubMed1991

Functional characterization of an abnormal factor XII molecule (F XII Bern).

An 18-year-old healthy woman was found to have cross-reacting material (CRM)-positive factor XII (F XII) deficiency, F XII clotting activity was less than 0.01 U/mL, whereas F XII antigen was 0.11 U/mL. An F XII inhibitor was excluded. To partially characterize the molecular defect of the abnormal F XII, immunologic and functional studies were performed on the proposita's plasma. The abnormal F XII was a single chain molecule with the same molecular weight (80 Kd) and the same isoelectric points (pl, 5.9 to 6.8) as normal F XII. Dextran sulfate activation of the proposita's plasma showed no proteolytic cleavage of F XII even after 120 minutes, whereas F XII in pooled normal plasma, diluted 1:10 with CRM-negative F XII-deficient plasma, was completely cleaved after 40 minutes. Adsorption to kaolin was identical for both abnormal and normal F XII. In the presence of dextran sulfate and exogenous plasma kallikrein, the abnormal F XII was cleaved with the same rate as normal F XII. However, kallikrein-cleaved abnormal F XII was not able to cleave factor XI and plasma prekallikrein, in contrast to activated normal F XII. Thus, these studies show that the functional defect of this abnormal F XII, denoted as F XII Bern, is due to the lack of protease activity of the kallikrein-cleaved molecule. Therefore, the structural defect is likely to be located in the light chain region of F XII, containing the enzymatic active site.

Adsorption↗
PubMed1977

Plasma thromboplastin antecedent (PTA, factor XI): a specific and sensitive radioimmunoassay.

A specific, sensitive, and reproducible radioimmunoassay for human plasma thromboplastin antecedent (PTA, factor XI) has been developed with purified PTA and monospecific rabbit antiserum. Precise measurements of PTA antigen were possible for concentrations as low as 0.3% of that in normal pooled plasma. Normal plasma contained approximately 6 microgram PTA/ml. A good correlation (correlation coefficient 0.68) existed between the PTA procoagulant assays and radioimmunoassays among 50 normal adults (25 males and 25 females). PTA antigen was markedly reduced in plasma of 13 patients with congenital homozygous PTA deficiency (range less than 0.003-0.128 U/ml) and 9 patients with hepatic cirrhosis (0.35+/-0.17 U/ml), but was normal in those of 9 patients under treatment with warfarin, 8 patients with disseminated intravascular coagulation and 16 patients with other congenital clotting factor abnormalities, including prekallikrein deficiency (Fletcher trait) and high molecular weight kininogen deficiency (Fitzgerald trait).

Adult↗
PubMed1978

Apparent antihaemophilic activity of basic amphoteric polyelectrolytes.

Amphoteric polyelectrolytes with alkaline isoelectric points (for example Ampholine 9-11) intended for use in isoelectric focussing were found to shorten the prolonged partial thrombosplastin clotting time with kaolin (PTTK) of plasma deficient in factor VIII. The response of this PTTK to Ampholine 9-11 was linear when plotted on double log paper with a slope slightly greater than that of factor VIII itself. Ampholine 9-11 at 2% concentration had factor VIII and factor IX activity equal to that of normal plasma as well as somewhat less activity as factor XI. It had no significant correcting effect on the clotting of plasmas deficient in factors V, VII, X, II OR XII. Ampholine 9-11 inhibited low concentrations of contact activators and its effect in correcting factor VIII deficient plasma was found to be related to the degree of contact activation.

Amino Acids↗
PubMed1979

Factor-XII congenital deficiency. A new family study.

This report describes two people in a family with Hageman trait (homozygotes) (Factor XII = 0.06%). In addition eight family members were studied to evaluate the inheritance of this congenital deficiency. A study of the Kallikrein-Kininogen system induced by the fragments of Factor XII was carried out. It is concluded that the inheritance is as described by Veltkamp and that the Kallikrein release from the prekallikreinogen (Fletcher factor) "in vitro" is related to the amount of Factor XII procoagulant protein.

Adult↗
PubMed2005

Thrombophilia, clinical factors, and recurrent venous thrombotic events.

CONTEXT: Data on the recurrence rate of venous thrombotic events and the effect of several risk factors, including thrombophilia, remain controversial. The potential benefit of screening for thrombophilia with respect to prophylactic strategies and duration of anticoagulant treatment is not yet known. OBJECTIVES: To estimate the recurrence rate of thrombotic events in patients after a first thrombotic event and its determinants, including thrombophilic abnormalities. DESIGN, SETTING, AND PATIENTS: Prospective follow-up study of 474 consecutive patients aged 18 to 70 years without a known malignancy treated for a first objectively confirmed thrombotic event at anticoagulation clinics in the Netherlands. The Leiden Thrombophilia Study (LETS) was conducted from 1988 through 1992 and patients were followed up through 2000. MAIN OUTCOME MEASURES: Recurrent thrombotic event based on thrombophilic risk factors, sex, type of initial thrombotic event (idiopathic or provoked), oral contraceptive use, elevated levels of factors VIII, IX, XI, fibrinogen, homocysteine, and anticoagulant deficiencies. RESULTS: A total of 474 patients were followed up for mean (SD) of 7.3 (2.7) years and complete follow-up was achieved in 447 (94%). Recurrence of thrombotic events occurred in 90 patients during a total of 3477 patient-years. The rate of thrombotic event recurrence was 25.9 per 1000 patient-years (95% confidence interval [CI], 20.8-31.8 per 1000 patient-years). The incidence rate of recurrence was highest during the first 2 years (31.9 per 1000 patient-years; 95% CI, 20.3-43.5 per 1000 patient-years). The risk of thrombotic event recurrence was 2.7 times (95% CI, 1.8-4.2 times) higher in men than in women. Patients whose initial thrombotic event was idiopathic had a higher risk of a thrombotic event recurrence than patients whose initial event was provoked (hazard ratio [HR], 1.9; 95% CI, 1.2-2.9). Women who used oral contraceptives during follow-up had a higher thrombotic event recurrence rate (28.0 per 1000 patient-years; 95% CI, 15.9-49.4 per 1000 patient-years) than those who did not (12.9 per 1000 patient-years; 95% CI, 7.9-21.2 per 1000 patient-years). Recurrence risks of a thrombotic event by laboratory abnormality ranged from an HR of 0.6 (95% CI, 0.3-1.1) in patients with elevated levels of factor XI to an HR of 1.8 (95% CI, 0.9-3.7) for patients with anticoagulant deficiencies. CONCLUSIONS: Prothrombotic abnormalities do not appear to play an important role in the risk of a recurrent thrombotic event. Testing for prothrombotic defects has little consequence with respect to prophylactic strategies. Clinical factors are probably more important than laboratory abnormalities in determining the duration of anticoagulation therapy.

Adult↗
PubMed1992

Functional characterization of a variant factor XII (F XII Locarno) in a cross reacting material positive F XII deficient plasma.

The plasma of a healthy woman was found to contain half normal factor XII (FXII) antigen level (0.46 U/ml) without any FXII clotting activity (less than 0.01 U/ml). The variant FXII in this plasma, denoted as FXII Locarno, was partially characterized by immunological and functional studies on the proposita's plasma. FXII Locarno is a single chain molecule with the same size (Mr = 80 kDa) as normal FXII. Isoelectric focusing suggested an excess of negative charge in the variant FXII as compared to normal FXII. In contrast to FXII in normal plasma, FXII Locarno was not proteolytically cleaved upon prolonged incubation of proposita's plasma with dextran sulfate. Adsorption to kaolin was similar for both, abnormal and normal FXII. Incubation of the proposita's plasma with dextran sulfate and exogenous plasma kallikrein showed normal cleavage of FXII Locarno outside of the tentative disulfide loop Cys340-Cys467, but only partial cleavage within this disulfide loop. Furthermore, plasma kallikrein-cleaved abnormal FXII showed neither amidolytic activity nor proteolytic activity against factor XI and plasma prekallikrein. These results suggest a structural alteration of FXII Locarno, affecting the plasma kallikrein cleavage site Arg353-Val354 and thus formation of activated FXII (alpha-FXIIa).

Amides↗
PubMed2006

Plasma levels of bradykinin are suppressed in factor XII-deficient mice.

A genetically-transmissible factor (F) XII-inactivated allele has been produced in mice by targeted replacement of exons 3-8 of the FXII gene with the neomycin resistance gene. Interbreeding of these mice provided offspring homozygous for two inactivated FXII alleles (FXII(-/-)). Male and female FXII-deficient mice bred normally in all genotypic combinations of the heterozygous and homozygous states, and the offspring survived to adulthood, suggesting that a total FXII deficiency does not affect embryonic development and survival. Neither FXII transcripts nor FXII antigen was found in various tissues of adult FXII(-/-) mice. No obvious unchallenged coagulopathies were present in FXII(-/-) adult mice, despite greatly prolonged activated partial thromboplastin times in this mouse cohort. FXII(-/-) mice were then used to assess the in vivo importance of the plasma FXII/prekallikrein/kininogen pathway in provision of resting plasma bradykinin (BK) levels and in generation of plasma BK stimulated by contact with an artificial surface, using a new and greatly improved plasma BK assay developed during these studies. It was found that approximately 50% of resting BK, and all of the contact-stimulated plasma BK, was provided by this FXII-dependent pathway, without a requirement for FXI. These results provide clear evidence that surface-stimulated BK production, in mice, is dependent on the activation of FXII.

Animals↗
PubMed1988

Enzymes of the contact phase of blood coagulation: kinetics with various chromogenic substrates and a two-substrate assay for the joint estimation of plasma prekallikrein and factor XI.

Kinetic constants (Km and kcat) of kallikrein and factor XIa for the chromogenic substrates H-D-L-prolyl-L-phenylanyl-L-arginine-p-nitroanilide (S-2302) and L-pyroglutamyl-L-propyl-L-arginine-p-nitroanilide (S-2366) were determined. The determined constants allow the use of S-2302 and S-2366 in an assay that leads to the joint estimation of factor XI and prekallikrein in activated plasma. The assay reports approximately 3.1 micrograms/ml factor XIa and 34.5 micrograms/ml kallikrein in kaolin-activated plasma (kaolin content 2 mg/ml). The dual-substrate amidolytic assay shows good correlation with the coagulant assay of both factors (0.92 with the prekallikrein assay and 0.98 with the factor XI assay). It is capable, through the joint estimation of factor XI and prekallikrein levels, of differentiating among plasma samples deficient in components of the contact phase of blood coagulation. Kinetic constants of factor beta-XIIa (factor XII fragment) for these substrates and for N-benzol-L-isoleusyl-L-glutamyl-glycyl-L-arginine-P-nitro ani lide (S-2222) were determined, and they allowed the assessment of the contribution of this factor to this assay and its estimation in the activated phase.

Blood Coagulation↗
PubMed1986

Prekallikrein deficiency in a dog.

A 15-year-old male dog with chronic hematuria was found to have prolonged activated partial thromboplastin time. Results of plasma coagulation assays indicated a deficiency of prekallikrein, a plasma protein that modulates the rate of activation of factors XI and XII in the intrinsic clotting system. Patients with prekallikrein deficiency rarely have manifestations of hemorrhage. The hematuria was the result of a renal transitional cell carcinoma.

Animals↗
PubMed1998

Frequency of inherited bleeding disorders in women with menorrhagia.

BACKGROUND: Although menorrhagia is a common gynaecological symptom, a specific cause is identified in less than 50% of affected women. We investigated the frequency of inherited bleeding disorders in women with menorrhagia. METHODS: Women referred for investigation of menorrhagia whose pelvis was normal on clinical examination and who had an estimated menstrual blood loss of more than 80 mL were studied. A detailed menstrual history and history about other bleeding symptoms was taken. The activated partial thromboplastin time, factor VIII activity, von-Willebrand-factor antigen and activity, and factor XI (FXI) were measured in all patients; further tests were done when results were at or outside the limits of the assays. FINDINGS: 150 women were screened. An inherited bleeding disorder was diagnosed in 26 (17%) patients: the disorders were von Willebrand's disease of mild (15) or moderate severity (three), mild FXI deficiency (four), mild von Willebrand's disease and FXI deficiency (one), combined von Willebrand's disease, FXI deficiency, and factor X deficiency (one), carriage of haemophilia-A gene (one), and platelet dysfunction (one). The frequency of von Willebrand's disease and FXI deficiency were 13% (95% CI 7.9-18.8%) and 4% (1.5-8.5%), respectively. Menorrhagia since menarche was noted in 11 (8.9%) of 123 women without a bleeding disorder compared with 13 (65%) of 20 women with von Willebrand's disease (p=0.001) and four (66.7%) of six women with FXI deficiency (p<0.001). INTERPRETATION: Inherited bleeding disorders are found in a substantial proportion of women with menorrhagia and a normal pelvis examination. We suggest that such patients should be investigated for these disorders-especially von Willebrand's disease-before invasive procedures are done.

Adult↗
PubMed2025

Self-organization of sinusoidal vessels in pluripotent stem cell-derived human liver bud organoids.

The induction of tissue-specific vessels in in vitro living tissue systems remains challenging. Here, we directly differentiated human pluripotent stem cells into CD32b+ putative liver sinusoidal progenitors by dictating developmental pathways. By devising an inverted multilayered air-liquid interface culture, hepatic endoderm, septum mesenchyme, arterial and sinusoidal quadruple progenitors self-organize to generate and sustain hepatocyte-like cells neighboured by divergent endothelial subsets composed of CD32blowCD31high, LYVE1+STAB1+CD32bhighCD31lowTHBD-vWF- and LYVE1-THBD+vWF+ cells. WNT2 mediates sinusoidal-to-hepatic intercellular crosstalk potentiating hepatocyte differentiation and branched endothelial network formation. Intravital imaging reveals the iPS-cell-derived putative liver sinusoidal endothelial progenitor develops fully perfused human vessels with functional sinusoid-like features. Organoid-derived hepatocyte- and sinusoid-derived coagulation factors enable correction of in vitro clotting time with Factor V-, VIII-, IX- and XI-deficient plasma, and rescues the severe bleeding phenotype in haemophilia A mice on transplantation. Advanced organoid vascularization technology allows for interrogating key insights governing organ-specific vessel development, paving the way for coagulation disorder therapeutics.

Humans↗
PubMed1998

Performance characteristics of a new synthetic APTT reagent.

Performance characteristics of a totally synthetic activated partial thromboplastin time (APTT) reagent, recently available commercially, were evaluated and compared with a rabbit-brain extracted reagent. We found that the synthetic reagent, Synthasil, returned significantly higher normal APTT values than the brain-extracted reagent, Thrombosil. APTT ratios (APTT patients/normal mean APTT), yielded by Synthasil were higher in the majority of patients receiving heparin therapy. Synthasil also returned longer APTT values than did Thrombosil on normal plasma spiked with heparin. On patients with lupus anticoagulants, APTTs assayed with Synthasil were generally longer than with Thrombosil. However, the differences disappeared when APTT values were converted to ratios. Factors XII-, XI-, IX- and VIII-deficient plasmas supplemented with normal plasma to yield activities of 2-50%, generally gave longer APTTs with Synthasil than with Thrombosil. However, this was not always the case on plasmas from haemophilias A and B patients. No reduction in Synthasil activity was noted after the reagent had been left at 24 degrees C for 28 days.

Coagulation Protein Disorders↗
PubMed1991

Bleeding diathesis coincident with chronic myelomonocytic leukaemia.

Two important haematological problems were found in an otherwise healthy 78 year old man: chronic myelomonocytic leukaemia; and a complex, acquired, hyperfibrinolytic bleeding disorder characterized by prolonged coagulation times, deficiency of coagulation factors V, X, and XI, anti-thrombin III and proteins C and S, with high concentrations of circulating tissue plasminogen activator, and low concentrations of plasminogen activator inhibitor. There may be a causal relation between the two conditions, with the peripheral blood monocytes mediating the hyperfibrinolytic process by the abnormal production of tissue plasminogen activator, though no previous description of a similar association has been reported.

Aged↗
PubMed1980

The "contact system" in health and disease.

In the last 10 years, our understanding of the contact system, particularly its biochemistry, has greatly increased. The components of this system and their interactions have been elucidated from in vitro experiments. Although the activation of the contact system have been implicated in various types of human disease, in only a few instances is its role clearly defined. The physiologic role of the contact system is totally unknown at present. Obviously, more studies are needed to bridge a big gap between in vitro observations and in vivo phenomena.

Blood Coagulation↗