Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FACTOR XII”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMedDate not supplied

Monitoring of factor XII activity and granulocyte elastase release during cardiopulmonary bypass.

Monitoring of the influence of cardiopulmonary bypass (CPB) on hematologic parameters is relevant to an improved understanding of the pathophysiology produced, as well as for the development of improved methods. The selection of suitable parameters is highly important. In this study, both contact phase activation and leukocyte response have been studied. Contact activation was determined by a novel assay for the measurement of Factor XII activity (FXIIA), and leukocyte response was measured by the release of granulocyte elastase. Five patients undergoing elective coronary artery surgery using a bubble oxygenator and pulsatile perfusion were studied. A notable feature of this study was the gradual increase of FXIIA during the study period, with granulocyte elastase levels following a similar pattern. Both FXIIA and granulocyte elastase are appropriate parameters for monitoring CPB, and could be useful in studying alternative bypass procedures and antithrombotic agents.

Aged↗
PubMed1993

Transient lupus anticoagulant associated with hypoprothrombinemia and factor XII deficiency following adenovirus infection.

A potent lupus anticoagulant (LA) was detected in four children, 1 week after the clinical onset of an adenovirus infection. The adenovirus infection was documented by direct virus detection in the stool of one patient and serologically in the others. None of the children had elevated titers of IgM- and only one of IgG-anticardiolipin antibodies (ACA). All patients had a marked reduction of prothrombin activity as well as antigen. Prothrombin-antibody complexes were demonstrated in the patients' plasma or mixtures of patient and normal plasma. Factor XII activity was moderately reduced in three of the patients. All coagulation abnormalities returned to normal within 4-12 weeks. Localized bleeding was observed in two cases, but there was no generalized bleeding tendency or evidence of thrombosis.

Adenoviridae Infections↗
PubMed1988

Dose-dependent effects of postmenopausal estrogen and progestin on antithrombin III and factor XII.

The frequent use of estrogen and progestin replacement for treatment in postmenopausal women makes assessment of its effect on the coagulation system of interest. Although the amount of estrogen used to achieve the desired therapeutic effect is lower than the lowest doses in oral contraception, the age and medical condition of this population may amplify any hormone-induced risk. The common impression is that postmenopausal replacement therapy does not increase risk for thromboembolic disease, but no large epidemiologic studies of estrogen replacement have addressed that question. In this randomized prospective study, we examined the effects of varying low doses of an estrogen-progestin preparation on the titers of clotting factors in postmenopausal women. The coagulation factors selected for investigation were among those that have been reported to be significantly altered in the plasma samples of high-dose estrogen users. There were no changes in prothrombin time, factor X, fibrinogen, factor VII, or fibrinopeptide A in any of the hormone-treated groups. Mild but significant shortening of the partial thromboplastin time and elevation of factor XII titer were noted in all treatment groups. The titer of antithrombin III was reduced in the group given 20 micrograms ethinyl estradiol, but not in the groups given 5 or 10 micrograms. The clinical significance of these changes is difficult to determine in postmenopausal women receiving sex hormone replacement. However, we have not noted any thromboembolic episodes in our volunteers after a 1-year follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

An analysis of the activators of single-chain urokinase-type plasminogen activator (scu-PA) in the dextran sulphate euglobulin fraction of normal plasma and of plasmas deficient in factor XII and prekallikrein.

An analysis was made of the various possible activators of single-chain urokinase-type plasminogen activator (scu-PA) in the dextran sulphate euglobulin fraction (DEF) of human plasma. scu-PA activators were detected in an assay system in which the substrate scu-PA, in physiological concentration (50 pM), was immuno-immobilized. After activation of the immobilized scu-PA for a certain period of time the activity of the generated amount of immuno-immobilized two-chain u-PA was determined with plasminogen and the chromogenic substrate S-2251. The scu-PA activator activity (scuPA-AA) in the DEF of plasmas deficient in factor XII or prekallikrein was about half of that in the DEF of normal plasma. Separation of scuPA-AA in the DEF by gel chromatography showed to major peaks, one eluting with an apparent Mr of 500,000 and the other around Mr 100,000. The former peak, which coincided with the activity peak of the kallikrein-kininogen complex, was absent in the DEF of plasma depleted of prekallikrein and therefore was identified as kallikrein. The latter peak was still present in the depleted plasma and most likely represents plasmin, because its scuPA-AA coincided with the activity peak of plasmin and could be fully inhibited by antibodies raised against human plasminogen. It is concluded that plasmin and the contact-activation factor kallikrein each contribute for about 50% to the scuPA-AA in the DEF. Compared on a molar basis, however, plasmin was found to be almost 1,000 times more effective than kallikrein, and we conclude, therefore, that in vivo plasmin is the primary activator of scu-PA and the role of the contact system is of secondary importance.

Chemical Fractionation↗
PubMed1992

Reconstituted collagen is not capable of activating factor XII but causes intrinsic coagulation by activating platelets.

Using a rheological technique to measure the coagulation of plasma in collagen-coated tubes, we studied the intrinsic coagulant activities of different types (I, III, IV and V) and structures of reconstituted collagen. Recalcified, platelet-free plasma (PFP) in contact with the collagen surface did not clot, irrespective of the type and structure of collagen. Coagulation of platelet-rich plasma (PRP) did occur, although the time of onset of coagulation was highly dependent on the type and structure of the collagen used. Coagulation of PRP occurred rapidly on a collagen surface consisting of highly ordered fibrils (banded structure) to which large numbers of aggregated platelets adhered with shape change. In contrast, initiation of coagulation was delayed in PRP after incubation with 5 mM dibutyrylcyclic AMP (DB-cAMP) for 50 min. Coagulation of PRP was completely suppressed after 30 min incubation with colchicine (5.0 mg/ml). This suggested that disruption of platelet microtubules completely suppressed the stimulation of platelets associated with the initiation of intrinsic coagulation on the collagen surface. We conclude that reconstituted collagen is not capable of activating factor XII. Initiation of coagulation of recalcified PRP in contact with the reconstituted collagen surface is caused by the activation of platelets.

Adult↗
PubMed2005

Synergistic platelet integrin signaling and factor XII activation in poly-N-acetyl glucosamine fiber-mediated hemostasis.

The polymer poly-N-acetylglucosamine (pGlcNAc) containing fiber material is becoming increasingly important as a topical agent for hemostasis at wound sites. The pGlcNAc polymeric fiber provides hemostasis through redundant mechanisms that include platelet activation for fibrin network formation. The research presented here better defines the mechanism for the effect of pGlcNAc containing fibers on platelet-mediated processes. Adsorption experiments demonstrated that pGlcNAc fibers tightly bind most major plasma proteins and a specific sub-set of platelet surface proteins, including the integrin beta(3) subunit (CD61) and the von Willebrand receptor GP1b (CD42b). The result of this interaction is a platelet-dependent acceleration of fibrin gel formation. Accelerated fibrin polymerization is sensitive to factor XII inhibition by corn trypsin inhibitor and integrin inactivation with integrilin. Confocal microscopy studies show that when platelet integrins contact plasma protein-saturated pGlcNAc fibers, an increase in intracellular free calcium for platelet activation occurs to drive surface expression of phosphatidyl serine (PS). Thus, a catalytic surface for thrombin generation and accelerated fibrin clot formation results from the interaction of platelets with pGlcNAc. These findings, when considered with the observation that pGlcNAc fibers also induce red blood cell agglutination and vasoconstriction, provides an explanation for the ability of the pGlcNAc material to provide hemostasis in a wide variety of clinical applications.

Acetylglucosamine↗
PubMed2000

[Preliminary study on the effects of coagulation factor XII on fibrinolysis].

OBJECTIVE: To study the effects of FXII on fibrinolysis in patients with cerebral thrombosis. METHODS: Plasma level of FXII:C, FXII:Ag, FXIIa and beta FXIIa and fibrinolysis activities were examined by ELISA. Screening of FXII gene mutation by MOEA. RESULTS: FXII:C in 22 of 107 patients with cerebral thrombosis decreased, which was similar to the feature of FXII cross-reacting material positive (FXII CRM(+)). There were significant increase in plasma levels of PLG:A and alpha(2)AP:A and decrease in D-dimer, moreover, plasma levels of FXIIa and betaFXIIa were lower in patients than in controls. FXII gene mutation was not found in 22 of 107 patients. CONCLUSION: Decrease of FXII:C may play an important role in cerebral thrombosis by reducing activation of plasminogen. The gene mutation of FXII CRM(+)-like abnormal FXII was different from the known FXII gene mutation. Mutations in the regions of FXII Arg (334) and Arg (353) may be more important for the reducing of FXIIa, beta FXIIa levels and fibrinolysis activities. FXII assay should be included in thrombotic disorder screening.

Adult↗
PubMed1992

Formation of an association between factor XII and kallikrein in human plasma--significance of storage of plasma and the functional state of plasma kallikrein.

In a previous study evidence was provided that zymogen FXII might associate with part of the kallikrein generated by acetone treatment of human plasma in the presence of benzamidine (Thromb. Res. 61, 123-133, 1991). Some results also suggested an increase in such a complex formation upon storage of plasma, and two questions were raised in the present study: Does kallikrein activated by acetone-treatment of plasma exist in modifications with different abilities to associate with FXII? And will -70 degrees storage of plasma increase the liability to complex formation? S-2302 amidase assays carried out in mixtures of normal plasma and plasma genetically deficient in prekallikrein (PK) suggested an inhomogeneity of the kallikrein generated. A minor and unstable part of it could be blocked by corn trypsin inhibitor, thus indicating the presence of an association with FXII. In fractions from gel filtration of acetone-activated plasma, kallikrein was assayed as S-2302 amidase, high molecular weight kininogen (HK) was measured in rocket immunoassay, and FXII, PK and HK were studied in PAGE immunoblot experiments. When freshly collected plasma was used, an amidase double peak (mol. wts. 400 and 300 kD) indicated an inhomogeneity of the kallikrein present, HK being observed in both peaks. FXII eluted separately over a gel. mol. wt. range of 90-55 kD. When plasma was stored at -70 degrees for 10 months before use, the more low-molecular part of the kallikrein double-peak had disappeared and was recovered, in a highly unstable state, adsorbed to the column material together with HK and FXII. Accordingly both functional assays and the results of immunoblot experiments indicated an inhomogeneity of the kallikrein present, and also a tendency of the minor part of it to associate with FXII, a tendency increased upon storage of plasma at -70 degrees.

Acetone↗
PubMed1988

Inhibition of the activation of Hageman factor (factor XII) by beta 2-glycoprotein I.

beta 2-Glycoprotein I (apolipoprotein H), a constituent of normal human plasma, has been shown to inhibit the generation of amidolytic activity in plasma that has been exposed to negatively charged agents. Studies with purified Hageman factor (factor XII) demonstrate that this inhibitory property is directed against the activation of Hageman factor. In this study beta 2-glycoprotein I inhibited the kaolin-induced generation of clot-promoting properties in solutions of Hageman factor. This effect was localized to an interaction between beta 2-glycoprotein I and kaolin. In contrast, once Hageman factor was activated by kaolin, its clot-promoting properties were not inhibited by beta 2-glycoprotein I. Further, beta 2-glycoprotein inhibited the generation of amidolytic activity against H-D-prolyl-L-phenylalanyl-L-arginine p-nitroanilide dihydrochloride in mixtures of Hageman factor and ellagic acid. The specificity of the action of beta 2-glycoprotein I was confirmed by its neutralization by immunoglobulin fractions of antiserums directed against this protein.

Adolescent↗
PubMedDate not supplied

[Hereditary deficiency of antithrombin III, protein C, protein S and factor XII in 121 patients with venous or arterial thrombosis].

INTRODUCTION: Hereditary thrombophilia is caused by various inherited disorders which lead to familial tendency to recurrent venous thrombosis usually at an early age and with spontaneous onset. In the studies reported so far, the different prevalence of hereditary thrombophilia among patients with venous thrombosis was found, greatly depending on criteria for selection of patients. Arterial thrombosis is most often the consequence of arteriosclerosis but the prevalence of hereditary thrombophilia among young patients with arterial thrombosis and without recognized risk factors for arteriosclerosis is not known . In this study, the frequency of hereditary deficiencies of antithrombin III (AT III), protein C (PC), protein S (PS), plasminogen (PLMG), factor XII (F XII) and dysfibrinogenaemia was investigated over a 2-year period in 121 patients with venous or arterial thrombosis selected according to the recommendations of the British Committee for Standards in Haematology. PATIENTS AND METHODS: The study included total a of 121 patients (58 males and 63 females) with documented venous or arterial thrombosis. Table 1 shows patient's characteristics regarding gender, age and clinical manifestation of thrombosis. Each patient fulfilled at least one of the following criteria: a) venous thrombosis prior to the age of 45; b) arterial thrombosis prior to the age of 30, without risk factors for arteriosclerosis; c) recurrent thrombosis; d) familial tendency to thrombosis; e) thrombosis of unusual localization. A detailed history was taken from each patient on earlier personal or familial occurrence of thrombosis. For the purpose of this study, thrombophilia was characterized as congenital when the deficient protein was constantly below normal value and when the same deficiency was confirmed in a close family member; acquired when the acquired disorder predisposing to thrombosis was present in absence of constant protein deficiency; and idiopathic when the cause of thrombosis was unknown. All tests were performed in plasma obtained after centrifugation of venous blood anticoagulated with 0.129 mol/1 sodium citrate. Concentrations of fibrinogen, PT, PTT and F XII were measured by standard clotting methods. At III, PC and plasminogen activity were determined by chromogenic methods using commercial reagents (Boehring, Marburg, Germany). AT III, PC and total PS antigen were assayed by Laurell immunoelectrophoresis. The presence of lupus anticoagulant was investigated by recommended tests. RESULTS: A total of 15 patients (12.4%) fulfilled criteria for hereditary thrombophilia. Seven of them (5.8%) had AT III deficiency, five (4.1%) PC deficiency, two (1.6%) PS deficiency, and one patient had F XII deficiency. Secondary thrombophilia was found in 21.5% of patients and the cause of thrombosis in 66.1% of patients was not elucidated. A high frequency of hereditary thrombophilia has been found in patients with arterial thrombosis (40%). Among patients with hereditary thrombophilia thrombosis occurred at significantly younger age (29.9 vs. 42.2 and 40.9 yr.) compared to the patients with secondary and idiopathic thrombophilia, respectively. Patients with hereditary thrombophilia had also a higher occurrence of positive family history related to thrombosis (66.7% vs. 7.7% and 27.5%). DISCUSSION: The prevalence of hereditary thrombophilia in nonselected patients with venous thrombosis is relatively low, and for that reason the selection of patients, according recommended criteria, in whom the screening tests for congenital thrombophilia should be performed, is strongly suggested by many authors. In our study we used the generally accepted recommendations for investigation of patients with venous and arterial thrombosis. The presence of congenital thrombophilia was found in 15 (12.4%) of 121 studied patients, what is in accordance with results of other similarly designed studies. (ABSTRACT TRUNCATED)

Adolescent↗
PubMed2002

Activated factor XII in rheumatoid arthritis.

Rheumatoid arthritis (RA) is associated with premature mortality, with approximately 50% of deaths being due to cardiovascular disease. It has been shown that the increased incidence of cardiovascular disease is independent of traditional risk factors. Previous studies have shown an increased risk of coronary heart disease with increased levels of activated factor XII (FXIIa). The aim of this study was to investigate levels of FXIIa in patients with RA. We studied 32 patients with RA and 30 age- and sex-matched control subjects. We found FXIIa levels significantly increased in the patient group, with 56% of the patients and 6.7% of controls having levels greater than or equal to 2 ng/ml. A previous study has shown that individuals with levels of 2 ng/ml or more have an increased risk of coronary heart disease. Measurement of FXIIa could perhaps help to identify an 'at risk' group of patients, allowing early intervention therapy.

Adult↗
PubMed1994

Activation of human Hageman factor (factor XII) in the presence of zinc and phosphate ions.

Hageman factor (FXII, HF) is a monomeric plasma zymogen that is capable of autoactivation to the serine protease FXIIa in the presence of negatively charged surfaces such as glass, kaolin, ellagic acid and dextran sulfate. FXIIa activates prekallikrein to kallikrein which in turn digests high molecular weight kininogen (HK) to produce the vasoactive peptide bradykinin (BK). Known natural activators of FXII and the contact system include heparin, sulfatides, phospholipids, endotoxin, and urate crystals. We now present evidence that FXII can undergo activation in the presence of phosphate ions (P(i)) and certain divalent metal ions. FXII (1 microgram/ml) and prekallikrein (1 microgram/ml), in HEPES buffered saline, pH 7.4, were incubated with 0-100 mM sodium phosphate, 0-200 microM zinc chloride, and 0.6 mM Chromozym-PK; absorbance at 405 nm was monitored. Graphic analysis of the data indicated reciprocal activation of the two enzymes within 60 min which was dependent upon Zn(II) and P(i). While Ca(II) did not replace Zn(II) as an activator it significantly enhanced Zn(II)- and P(i)-dependent activation of FXII. Maximum activation occurred at 1-10 mM P(i) and approximately 25 microM Zn(II). Co(II), Cu(II) and Ca(II) were negative while Fe(II) was positive in the presence of 1 mM P(i). Cl-, SO4= and CO3=/HCO3- ions were negative when tested in the presence of 50 microM Zn(II). P(i) and Zn(II) ions promoted activation of FXII alone (but not prekallikrein) and the kinetics of this reaction suggested autoactivation. These data therefore suggest that physiological concentrations of P(i) and Zn(II) may be sufficient for a low-level turnover of the contact system in plasma which in turn may be responsible for the background levels of cleaved HK and BK found in normal plasma.

Chlorides↗