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At least 217 records · Page 12Linked to original sources
PubMed1989

[Polycythemia vera with an inhibitor against factor XII].

A case of polycythemia vera with an inhibitor against factor XII was reported. A 60-year-old female was admitted to Hokkaido University School Hospital because of erythrocytosis and hepatosplenomegaly. The hemoglobin was 22.5 g/dl and white cell count was 9,500/microliters without immature cells. The platelet count was 484,000/microliters. Bone marrow specimens showed marked hypercellularity. Philadelphia chromosome was not found on chromosome analysis. She was diagnosed as polycythemia vera according to the criteria of polycythemia Vera Study Group. Activity of factor XII was found to be decreased on the initial examination, but she had no personal and familial history of bleeding. In order to clarify the cause of decreased activity of factor XII, her plasma was mixed with normal plasma, and then examined PTT using factor XII deficient plasma. Her plasma mixed with equivalent normal plasma did not show the correction of prolonged PTT. It was suggested that an inhibitor of her plasma was included in the IgG fraction using gel chromatography. The patient was treated with phlebotomy and administration of N4-palmitoyl (1- -D-arabinofurasyl) cytosine (derivative of cytosine arabinoside; PLAC) 200 mg/day and Busulfan (1 mg/day). Factor XII was not corrected by phlebotomy, but corrected gradually by administration of PLAC and Busulfan.

Factor XII↗
PubMed1979

Activation of human factor VII in plasma and in purified systems: roles of activated factor IX, kallikrein, and activated factor XII.

Factor VII can be activated, to a molecule giving shorter clotting times with tissue factor, by incubating plasma with kaolin or by clotting plasma. The mechanisms of activation differ. With kaolin, activated Factor XII (XII(a)) was the apparent principal activator. Thus, Factor VII was not activated in Factor XII-deficient plasma, was partially activated in prekallikrein and high-molecular weight kininogen (HMW kininogen)-deficient plasmas, but was activated in other deficient plasmas. After clotting, activated Factor IX (IX(a)) was the apparent principal activator. Thus, Factor VII was not activated in Factor XII-,HMW kininogen-, XI-, and IX-deficient plasmas, but was activated in Factor VIII-, X-, and V-deficient plasmas. In further studies, purified small-fragment Factor XII(a) (beta-XII(a)), kallikrein, and Factor IX(a) were added to partially purified Factor VII and to plasma. High concentrations of beta-XII(a) activated Factor VII in a purified system; much lower concentrations of beta-XII(a) activated Factor VII in normal plasma but not in prekallikrein or HWM kininogen-deficient plasmas. Kallikrein alone failed to activate partially purified Factor VII but did so when purified Factor IX was added. Kallikrein also activated Factor VII in normal, Factor XII-, and Factor IX-deficient plasmas. Purified Factor IX(a) activated partially purified Factor VII and had no additional indirect activating effect in the presence of plasma. These results demonstrate that both Factor XII(a) and Factor IX(a) directly activate human Factor VII, whereas kallikrein, through generation of Factor XII(a) and Factor IX(a), functions as an indirect activator of Factor VII.

Blood Coagulation↗
PubMed1982

Severe Fletcher factor (plasma prekallikrein) deficiency with partial deficiency of Hageman factor (factor XII): report of a case with observation on in vivo and in vitro leukocyte chemotaxis.

A case of cross-reacting material-negative Fletcher trait with additional partial deficiency of Hageman factor (HF, Factor XII) is described. Although the patient presented with a recent history of frequent epistaxis, he had no other personal or family history of a tendency toward bleeding or infection. Similar to other cases of Fletcher trait, his plasma showed a markedly prolonged partial thromboplastin time which could be corrected by prolonged incubation with the surface-activator kaolin. Surface-induced fibrinolysis, amidolysis of alpha-N-benzoyl-proline-L-phenylalanine-L-arginine-p-nitroanilide, and cold-promoted enhancement of factor VII activity, reactions requiring the presence in the plasma of fletcher factor (prekallikrein), in addition to Hageman factor and Fitzgerald factor (high-molecular weight kininogen), were also defective. In vivo chemotaxis of polymorphonuclear leukocytes and monocytes (Rebuck's skin window technique) in response to skin abrasions was defective, but was normal when diphtheria-tetanus toxoid was also applied. In vitro leukocyte chemotaxis (Boyden chamber technique) in response to normal or patient's own serum activated with zymosan was normal. Together with previous observations that kallikrein generated chemotactic activity, possibly via activation of C5, the present observations suggest that prekallikrein activation may be important for in vivo leukocyte chemotactic response to skin abrasion. The inheritance of Fletcher trait in this patient is unclear.l Although the father was an apparent heterozygote, the mother was completely normal for Fletcher factor procoagulant activity and antigen. The mild Hageman factor deficiency in the patient did not contribute significantly to the plasma defects described and was likely inherited from the father who had a low HF procoagulant activity.

Blood Coagulation↗
PubMed2003

[Anesthetic management of a patient with deficiency of congenital coagulation factor XII].

A 63-year-old man with deficiency of congenital coagulation factor XII, was referred to our hospital for an operation of the hypopharynx cancer. The day before surgery under general anesthesia, fresh frozen plasma was administered to him with good response of APTT shortening from 397.0 to 36.4 seconds. During operation, bleeding tendency was controlled and fresh frozen plasma was administered. Total blood loss during the operation was 255 ml. During post-operative period, APTT was kept at an adequate level. The post-operative course was uneventful and he was discharged after the radiation and an adjuvant therapy.

Anesthesia, General↗
PubMed1994

Resistance to activated protein C: evaluation of three functional assays.

Resistance to Activated Protein C (APC) was evaluated using 3 different methods: two of them were based on the prolongation of the Activated Partial Thromboplastin Time (APTT) using 2 different APTT reagents in the presence of APC, whereas the third method was based on the prolongation of prothrombin time when APC is added. The three methods were significantly correlated. APTT-based assays were sensitive to factor XII deficiency, whereas thromboplastin-based assay was sensitive to factor VII deficiency (< 0.5 UI/ml), which surestimates the response to APC. In contrast, an increase in factor VIII (F. VIII) level is associated with a decreased response to APC, when APTT-based assays are used, whereas thromboplastin-based assay is unmodified. During pregnancy, a decreased response to APC is observed, which is not only due to the increase in F. VIII, since thromboplastin-based assay is also modified. In Protein S (PS) immuno-depleted plasma, the low response to APC is corrected by addition of free PS: the thromboplastin-based assay was the most sensitive one to PS deficiency. However, in patients with congenital PS deficiency, there was no correlation between APC-resistance and free PS level. In patients with lupus anticoagulant, discrepancies were observed between the 3 methods, but with a high frequency of low response to APC. For the 3 assays, there was a good differentiation and correlation between normal and pathological results, the thromboplastin-based assay being perhaps the most discriminating. However, 3 unrelated thrombophilic patients showed normal results using thromboplastin-based assay, although they were APC-resistant using APTT-based assays. For 2 patients, this discrepancy can be explained by high levels of F. VIII. For the last patient, an abnormal F. VIII, resistant to APC can be suspected.

Adult↗
PubMed2001

Assembly of high molecular weight kininogen and activation of prekallikrein on cell matrix.

Investigations determined if extracellular matrix of endothelial cells (EC) is a platform for HK assembly and PK activation. In buffers containing bovine serum albumin, biotin-HK binding to ECV304 cells or their matrix requires > or = 50 microM added Zn2+. Ortho-phenanthroline or a HK domain 5 peptide blocks HK binding. Binding to umbilical vein EC or matrix, but not ECV304 cells or matrix, is mediated by cytokeratin 1. Biotin-HK binds to ECV304 cells or matrix with a Kd of 15.8 or 9.0 nM and a Bmax of 2.6 x 10(7) or 2.4 x 10(7) sites/cell, respectively. PK activation on ECV304 cells or matrix is blocked by antipain or SBTI and corn trypsin inhibitor partially inhibits kallikrein formation. PK activation occurs on ECV304 cells or matrix prepared without serum or in human factor XII deficient serum, indicating that the PK activator is not factor XIIa. EC matrix promotes plasminogen activation after the assembly of HK, PK and pro-urokinase. These studies indicate that matrix of various EC has the ability to assemble HK allowing for PK activation and subsequent activities.

Amino Acid Sequence↗
PubMed2003

Hemostyptic effect of oxidized cellulose on blood platelets.

Cellulose is one of the hemostyptic biomaterials, which are able to initiate or accelerate blood coagulation at the site of their application. It belongs to surgical sealants. The mechanism of its action is not clearly understood. We studied the participation of blood platelets in this mechanism. As a marker of platelet activation we used serotonin release reaction. Serotonin release in platelet rich plasma incubated with various concentrations of oxidized cellulose (0.5%-2.0%) started in about 20 min. Washed platelets were not directly activated by oxidized cellulose within one hour. Washed platelets reconstituted in plasma obtained from two patients with coagulation factor XII deficiency were activated by oxidized cellulose with a prolonged lag phase. Our results demonstrate the significant influence of factor XII on blood platelets activation by oxidized cellulose.

Blood Coagulation↗
PubMed1987

Loss of the activity of human coagulation factor XII by a chymotrypsin-like protease activated in rat mast cells during degranulation with compound 48/80.

Mediator release from mast cells is an initial step in the immediate-type hypersensitivity. Thus, the interaction of neutral proteases released from mast cells with plasma kallikrein-kinin system was investigated. Two proteases, chymotrypsin-like (CHY) and trypsin-like (TRY) proteases, were activated in purified rat mast cells after degranulation with compound 48/80. Three fourths of the CHY activity remained in the cell residue, and the activity was inhibited by chymostatin, whereas most of the TRY activity was released in the medium and was inhibited by leupeptin. The incubation of rat or human plasma with degranulated mast cell (DMC) suspension did not cause the activation of plasma prekallikrein, but did cause a loss in the activity of coagulation factor XII, as ascertained by the lack of activation of prekallikrein in either the DMC-treated plasma by glass powder or in the incubation of DMC-treated human plasma with factor XII deficient plasma activated by kaolin. The prekallikrein and high-molecular-weight kininogen levels were sufficient for activation of factor XII.

Animals↗
PubMed1996

In vivo demonstration in humans that large postprandial triglyceride-rich lipoproteins activate coagulation factor VII through the intrinsic coagulation pathway.

In vitro studies in purified plasma systems have suggested that triglyceride-rich lipoproteins such as chylomicrons, very low density lipoproteins, and their remnants promote activation of factor VII through activated factor XII (XIIa) and the intrinsic coagulation pathway. We specifically examined the roles of factors XII, XI, and IX in activation of factor VII during alimentary lipemia in vivo in humans and addressed the issue of whether generation of activated factor VII (VIIa) is accompanied by increased thrombin production. For this purpose XIIa, factor IX activation peptide (IXP), VIIa, prothrombin fragment 1 + 2 (F1 + 2), and thrombin-antithrombin complex (TAT) were determined in plasma samples taken before and 3, 6, and 9 hours after intake of a mixed meal type of oral fat load in 24 healthy men The VIIa response to fat intake was also determined in 7 patients with single coagulation-factor deficiency, of whom 2 were deficient in factor XII, 2 in factor XI, and 3 in factor IX. Postprandial activation of factors IX and VII occurred in the healthy individuals, whereas the plasma levels of XIIa did not change in response to the test meal. Of note, plasma concentrations of F1 + 2 were unaltered during alimentary lipemia, and TAT levels showed a small decrease (P < .05) in the 3-hour sample compared with the fasting level, indicating that thrombin generation is not stimulated in the postprandial state, despite the generation of activated factor IX (IXa) and VIIa. Factor VIIa increased in the postprandial period in the 2 factor XII-deficient patients who underwent the oral fat tolerance test but appeared to remain unchanged in the factor XI- and factor IX-deficient patients. Therefore, the current concept that activation of factor XII plays a pivotal role in initiating the sequence of events linking postprandial lipemia to activation of factor VII is contradicted by the present study. Whether activation of factor XI by triglyceride rich lipoproteins initiates these reactions needs to be demonstrated in future studies.

Adult↗
PubMed1984

The possible role of platelets in bypassing the contact phase of blood coagulation.

Data presented herein and previously support an active role for platelets in promoting the interaction and activation of the coagulation proteins of the contact phase of intrinsic coagulation. The platelet membrane, activated by ADP collagen or thrombin, can promote the proteolytic activation of factor XII to factor XIIa in the presence of kallikrein and high molecular weight kininogen. The zymogen factor XI associates with high molecular weight kininogen in plasma and becomes bound to a site on the membrane of thrombin or collagen activated platelets. Thereafter, platelet bound factor XI can be proteolytically activated to factor XIa either in the presence of factor XIIa or in the presence of kallikrein. These observations could explain the absence of bleeding complications in patients with factor XII deficiency. In addition, platelets contain a molecule which has a higher molecular weight than plasma factor XI and possibly consists of a tetramer of four identical subunits of 52000 daltons each of which is functionally and immunologically similar to plasma factor XI. Since this molecule is present in the platelets of patients with severe plasma factor XI deficiency and no evidence of bleeding, we postulate that platelet factor XI can substitute for plasma factor XI in hemostasis and possibly account for the considerable variability in clinical severity observed in patients with factor XI deficiency.

Blood Coagulation↗
PubMed1991

Factor XI activation in a revised model of blood coagulation.

Coagulation factor XI is activated in vitro by factor XIIa in the presence of high molecular weight kininogen (HMWK) and a negatively charged surface. Factor XII deficiency is not associated with bleeding, which suggests that another mechanism for factor XI activation exists in vivo. A revised model of coagulation is proposed in which factor XI is activated by thrombin. In the absence of cofactors, thrombin is more effective (kcat/Km = 1.6 x 10(5)) than factor XIIa (1.7 x 10(4)) in activating factor XI. Dextran sulfate enhances activation of factor XI by thrombin 2000-fold; part of this effect is due to autoactivation of factor XI by activated factor XI.

Blood Coagulation↗
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↗
PubMed1990

[Isolated prolongation of the PTT: 2-year retrospective study].

The hemorrhagic risk associated with isolated prolongation of the PTT has been evaluated in a 2-year retrospective study. Of the 60 cases thus found, a hemorrhagic risk was present in 15 patients of whom 7 had hemophilia A, 5 von Willebrand's disease and 3 factor XI deficiency. Among the other etiologies not associated with a bleeding tendency, there were 31 proved or suspected cases with inhibitors of the PTT, most of whom were children, 2 factor XII deficiencies, 2 prekallikrein deficiencies and 4 contact phase activations. Isolated prolongation of the PTT is therefore without specificity and needs further investigation of hemostasis to determine the associated hemorrhagic risk.

Factor XI Deficiency↗
PubMed1982

Cold-induced contact surface activation of the prothrombin time in whole blood.

Studies of the prothrombin time (PT) have revealed that contact with borosilicate or commercial siliconized borosilicate markedly shortens the PT. This shortening is related to the activation of the contact phase of blood coagulation. This shortening of the PT occurs in both normal whole blood and plasma when stored in borosilicate or siliconized borosilicate tubes at 4 degree C and to a lesser degree at room temperature. Studies indicated the importance of several coagulation factors in decreasing the PT. The PT did not change in blood deficient in factor XII or in plasma deficient in Fletcher factor or high molecular weight kininogen, while blood deficient in CI esterase inhibitor (CI INH) had the most profound shortening. Shortening of the PT correlated directly with increased levels of factor VII. When purified CI INH was added to normal blood, it markedly reduced the activation of factor VII and the shortening of the PT in a dose-related manner. These studies indicate the pivotal roles of the contact phase of coagulation in initiating activation of the PT and of CI INH in inhibiting the activation of the coagulation factor(s) responsible for the cold-promoted activation of factor VII.

Blood Coagulation Factors↗