Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study was carried out to extend an earlier observation from this laboratory that mean plasma factor X levels fell by about 15% after the injection into rabbits of a formed factor Xa/phospholipid complex that caused only minimal intravascular coagulation. We have now injected rabbits with formulations of factor Xa/phospholipid that caused considerable intravascular coagulation, as documented by substantial falls in fibrinogen, factor V, and factor VIII and a fall in plasma prothrombin activity of about 15% to 20% of the initial level. Mean plasma factor X activity fell by about 30% of the initial level. Factors participating in the intrinsic coagulation pathway--XII, XI, and IX--all fell by about 50% after injection of a complex made with 16.3 pmol factor Xa and 80 nmol phospholipid per 1 kg body wt and by about 35% after injection of a complex made with 32.6 pmol factor Xa and 40 nmol phospholipid per 1 kg body wt. In contrast, total plasma factor VII activity did not change, and specific plasma factor VIIa levels, which were lower than those measured in human plasma, did not rise after injection of factor Xa/phospholipid. The data are compatible with the hypothesis that factor Xa/phospholipid-induced generation of thrombin in vivo leads to factor XII-dependent activation of the intrinsic pathway of coagulation that results in significant activation of factor X. Further testing of this hypothesis appears warranted.
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PMID:Evidence suggestive of activation of the intrinsic pathway of blood coagulation after injection of factor Xa/phospholipid into rabbits. 774 9

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.
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PMID:Resistance to activated protein C: evaluation of three functional assays. 781 60

Direct potential-mediated and time-controlled activation of purified human factor XII (FXII) immobilized on carbon has been demonstrated. Initial experiments were required to find a procedure for characterizing the immobilization of FXII and its activated form, factor XIIa (FXIIa). After achieving saturation of the carbon surface with FXII, surface catalytic activities could be generated under negative potential conditions. Activities depended on the duration and amplitude of the polarization applied to the immobilized FXII. The activities thus electrochemically induced in the surface-bound FXII molecules were tested biologically in the presence of normal human plasma and FXII-deficient plasma. The shortening of the activated partial thromboplastin time test suggested identity of the catalytic activities with that of activated FXII molecules. The electrochemical activation mechanism was consistently analysed according to first-order kinetics. The apparent rate constants increased in the presence of zinc ions.
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PMID:Potential-mediated and time-controlled first order activation of factor XII (Hageman factor) adsorbed to carbon surfaces. 784 13

Amyloid precursor protein forms that contain Kunitz protease inhibitor domains are released from activated platelets, T-lymphocytes, and leukocytes and inhibit trypsin, plasmin, and activated factor XI. We investigated the effects of amyloid precursor protein isoforms on activated Hageman factor (factor XII), activated factor X (Stuart factor), and thrombin. Recombinant amyloid precursor proteins with or without the Kunitz domain, 770 and 695 amino acids, respectively, were produced in insect cells by Baculovirus expression (BAC770 and BAC695). Neither BAC695 nor BAC770 inhibited human alpha-thrombin or activated factor X. The partial thromboplastin time was prolonged by both amyloid precursor proteins, only one of which, BAC770, contains the Kunitz protease inhibitor domain. Both forms of amyloid precursor proteins inhibited ellagic acid-induced activation of Hageman factor but did not inhibit activated Hageman factor. Bismuth subgallate, which is an insoluble analog of ellagic acid, lost its ability to activate Hageman factor on being exposed to BAC770. Inhibition of ellagic acid-induced activation of Hageman factor by both forms of amyloid precursor protein was enhanced by heparin. These findings suggested that the heparin-binding domain of amyloid precursor proteins is not in the Kunitz domain. This heparin-binding domain may block the activation of Hageman factor by negatively charged agents. Thus, amyloid precursor proteins may be involved in the control of hemostasis, properties not all dependent on the Kunitz domain.
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PMID:Inhibitory action of amyloid precursor protein against human Hageman factor (factor XII). 784 73

A patient without a history of bleeding or thromboembolism presented with an activated partial thromboplastin time (aPTT) of 55.1 s (normal 24-38 s). Incubation of the patient plasma with an equal volume of normal plasma failed to correct the aPTT, suggesting the presence of an inhibitor. The MRVVT (modified Russell Viper venom time) was normal, and the anti-cardiolipin antibody titres were not elevated, indicating that the presence of a lupus anticoagulant was unlikely. Plasma prekallikrein (PK) measured by a coagulant assay (2 U/dl) was very low, but PK was in the low normal range (approximately 65%) when measured by an enzymatic assay (amidolytic) or by an antigenic assay (ELISA). The purified patient IgG reacted with purified PK, the heavy chain, and the 28 kD fragment of the heavy chain, indicating that it contained an autoantibody to PK. The purified IgG did not directly inhibit the amidolytic activity of kallikrein, but it did inhibit the activation of PK to kallikrein by activated factor XII. Activation of the contact system by dextran sulphate, as reflected by the cleavage of HK on a Western blot, was inhibited when the patient IgG was added to pooled normal plasma. The antibody appears to be oligoclonal with IgG1 being most abundant, followed by IgG4. This report appears to be the first of a spontaneously occurring antibody to prekallikrein.
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PMID:An autoantibody to human plasma prekallikrein blocks activation of the contact system. 794 59

Three Streptoverticillium anticoagulants, SAC I, II, and III, which strongly inhibit human intrinsic blood coagulation, were each isolated in a homogeneous form from a culture fluid of Streptoverticillium cinnamoneum subsp. cinnamoneum IFO 12852. SAC I, II, and III are simple proteins with molecular weights of around 12,000, and with isoelectric points of 9.7, 9.7, and 9.9, respectively. Their amino acid compositions are similar and each SAC possesses two disulfide bonds. The COOH-terminal residue of each of these proteins is phenylalanine. Together with the similarity of their protein chemical properties, the results of NH2-terminal amino acid sequence analysis of these SAC proteins strongly suggested that the deletion of Ser-Leu and Ser-Leu-Tyr from the NH2-terminus of SAC I (Ser-Leu-Tyr-Ala-Pro-...) results in the generation of SAC II and III, respectively. The amount of each SAC necessary to double the partial thromboplastin time was around 5 micrograms/ml. SAC I inhibited activated human factor XII and human plasma kallikrein. It also inhibited, but to a lesser extent, activated factor X. The inhibition constants (Ki) of SAC I toward activated factor XII and plasma kallikrein were 5.3 x 10(-8) and 7.2 x 10(-9) M, respectively. The SACs also inhibited some microbial serine proteases such as subtilisin Carlsberg and, to a lesser extent, mammalian serine proteases including bovine trypsin and alpha-chymotrypsin. Of these three inhibitors, only SAC I inhibited metalloproteases such as thermolysin in addition to these serine proteases.
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PMID:Isolation and characterization of Streptoverticillium anticoagulant (SAC), a novel protein inhibitor of blood coagulation produced by Streptoverticillium cinnamoneum subsp. cinnamoneum. 808 92

A rare case of blood coagulation disorder, congenital factor XII deficiency, detected in a patient with mandibular osteomyelitis is presented. Routine laboratory tests showed prolonged clotting and activated partial thromboplastin time. Detailed investigations for the intrinsic and extrinsic pathways of coagulation, fibrinolytic system, kinin-kallikrein system, and complement system were performed because factor XII is known as an activator of these systems. No hemorrhagic or thromboembolic complication occurred during and after surgery. Substitution therapy with fresh frozen plasma was not necessary. Magnetic resonance imaging and electrocardiography were used to examine the possible occurrence of postoperative cerebral hemorrhage or myocardial infarction.
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PMID:Surgical management in the patient with congenital factor XII deficiency. Report of a case. 810 88

Using an optimized test, reference ranges were established for the activity of the coagulation factors VIII:C (72-124%), IX (81-130%), XI (69-134%) and XII (51-142%) in the cat (n = 58 cats, 2.5-97.5% quantile). Compared to a reference curve prepared by using a cat-pool plasma (n = 50), the factor VIII:C activity in humans (commercial human reference plasma) was 7.6%, i.e. the factor VIII:C activity in cats was 13 fold higher than in humans. The values for the factors IX, XI and XII depended distinctly on the dilution step of the human plasma. The activity of the cat in relation to humans was approximately 90% (factor IX), 170% (factor XI) and 135% (factor XII). Two clinically healthy cats who were conspicuous pre-operative because of a distinctly prolonged, activated partial thromboplastin time showed a decreased factor XII activity.
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PMID:[Measurements of the activity of the coagulation factors VIII:C, IX,XI, and XII in cats]. 859 97

During acute exercise both coagulant and fibrinolytic potential increase. Since strenuous exertion is associated with an enhanced risk for cardiac events, especially in untrained individuals, it is important to determine whether the initial haemostatic balance is maintained during exercise. Twenty-nine sedentary males (20-30 years) were subjected to a standardized cycle ergometer test. Blood samples were obtained at two exercise levels, 70% VO2max (submaximal), 100% VO2max (maximal) and during 25 min recovery. Both during submaximal and maximal performance, tissue type plasminogen activator antigen, urokinase plasminogen activator antigen and tissue type plasminogen activator activity were increased. A concomitant enhancement of clotting activity of factors VII, VIII, IX, XII and fibrinogen resulted in a shortening of clotting times. Following correction for changes in plasma volume, the results for factor VII:c were reversed, and factor XII:c and fibrinogen no longer demonstrated exercise-related changes. Increases in coagulant (activated partial thromboplastin time) and fibrinolytic (tissue type plasminogen activator activity) potential proceeded in parallel during exercise. However, during recovery while there was a sustained increase in coagulant potential, fibrinolytic potential demonstrated a sharp fall. We conclude that during physical activity, while parallel changes in coagulant and fibrinolytic activity occur, this haemostatic balance is not maintained during recovery. This phenomenon could constitute an enhanced risk for coronary artery thrombosis which may contribute to exercise-related cardiovascular events.
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PMID:Unbalanced haemostatic changes following strenuous physical exercise. A study in young sedentary males. 868 38

Intraglomerular coagulation, initiated by the local activation of contact coagulation factors, has been suggested as one possible factor causing glomerular injury in IgA nephritis. The plasma activity of factor XII, prekallikrein and high molecular weight (HMW) kininogen were measured in 24 patients with biopsy-proven IgA nephritis and in 123 normal controls, using an activated partial thromboplastin time assay with the appropriate factor-deficient plasma as substrate. IgA patients had significantly lower plasma activity of factor XII (45.5% +/- 28.3% against 80.7% +/- 31.8%; mean +/- standard deviation, P < 0.001), prekallikrein (37.7% +/- 24.5% against 119.8% +/- 37.7%; P < 0.001) and HMW kininogen (72.8% +/- 37.8% against 119.1% +/- 42.8%; P < 0.001) when compared with controls. In the IgA patients, there was no significant correlation between factor XII, prekallikrein and HMW kininogen activity and 24-hour total urinary protein excretion, suggesting that the reduced plasma activity was not due to increased urinary loss of the coagulation factors. One possible explanation for these results is that the intrinsic coagulation pathway is activated in patients with IgA nephritis.
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PMID:Plasma activity of contact coagulation factors in patients with IgA nephritis. 879 9


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