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 effect of acute and subchronic experimental aflatoxicosis on blood clotting activity and platelets was evaluated. Male New Zealand White rabbits (weighing 2.4-3.2 kg each) were used. In Experiment 1, 19 rabbits were given orally 0.05 mg of aflatoxin B1 (AFB1)/kg of body weight daily from Day 0 through Day 23. Blood samples were collected before dosing and on Days 2, 5, 9, 12, 16, 19, and 23 of the experimental period. In Experiment 2, 40 rabbits were given a single dose of 0.4 mg of AFB1/kg of body weight. Blood samples were collected before dosing and at 12, 24, 36, and 48 hr after dosing. When compared to baseline and control animal values, one-stage prothrombin times and activated partial thromboplastin times of aflatoxin-dosed rabbits were lengthened, and there was a statistically significant decrease in fibrinogen, Factor IX, VIII, and V activities. Platelet counts were significantly increased in subacutely exposed rabbits, and platelet size was decreased in single high-dose treated groups. Factor deficiencies were attributed to a combination of decreased factor synthesis from hepatic insufficiency and consumptive coagulopathy or primary fibrinolysis.
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PMID:Induced aflatoxicosis in rabbits: blood coagulation defects. 309 75

A procoagulant activity was found in cerebrospinal fluid (CSF) of patients with myelo- or lymphoproliferative diseases on intrathecal therapy with methotrexate, independently of leukaemic CNS involvement. This activity did not correlate with the cell count in CSF and disappeared on storage at -40 degrees C or after filtration with 0.22 nm filters. Dosage of coagulation factors revealed a strong increase in Factor V activity (F. V:C), an increase in Factor VIII procoagulant activity (F. VIII:C) without a correspondent increase in Factor VIII related antigen (F. VIII R:Ag), and an inconstant increase in Factor IX activity (F. IX:C). These activities all disappeared after filtration with 0.22 micron filters but not with 1.2 micron filters. It is concluded that complexes formed by membrane phospholipids and Factor V were responsible for the procoagulant activity lost after storage. The F. VIII and F. IX.-like procoagulant activity was not lost after storage; it was considered unspecific and attributed to thromboplastin-like substances.
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PMID:Spinal fluid procoagulant activity in leukaemic patients treated with intrathecal methotrexate. 311 27

In the present study, human factor X and factor IX were each digested with chymotrypsin, and the Gla-peptide from each protein was purified by QAE-Sephadex chromatography. The effect of each Gla-peptide on the activation of human prothrombin by a complex of factor Xa, phospholipid, and calcium was studied using an amidolytic assay for generated thrombin. Prothrombin activation was half-maximally inhibited by factor X Gla-peptide at a concentration of 0.7 microM. Factor IX Gla-peptide was markedly less inhibitory and inhibited this reaction half-maximally at a concentration of 3.7 microM. Kinetic analyses revealed that the factor X Gla-peptide inhibited this reaction in an apparent competitive manner, whereas the factor IX Gla-peptide yielded an exponential Dixon plot. Heat decarboxylation experiments revealed that 3-4 gamma-carboxyglutamic acid residues are critical for the expression of inhibitory activity in each peptide. These studies indicate that, in spite of their structural homology, the ability of each of these Gla-peptides to act as a prothrombinase inhibitor is markedly different.
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PMID:Inhibition of prothrombin activation by factor X and factor IX Gla-peptides. 337 73

Although the endothelial cell is considered antithrombogenic, endothelium has recently been shown to participate in procoagulant reactions. Factor IX bound to specific endothelial cell sites can be activated by the intrinsic and extrinsic pathways of coagulation. Perturbation of endothelium results in induction of tissue factor which promotes factor VIIa-mediated activation of factors IX and X, thus initiating procoagulant events on the endothelial surface. Cell bound factor IXa, in the presence of factor VIII, promotes activation of factor X. The factor Xa formed can interact with endothelial cell factor V/Va, resulting in prothrombin activation. Thrombin then cleaves fibrinogen and a fibrin clot closely associated with the endothelial cell forms. The perturbed endothelial cell thus provides a focus of localized procoagulant events. This model suggests a simple endothelial-cell-dependent mechanism for initiation of coagulation at the site of an injured or pathological vessel.
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PMID:A pathway of coagulation on endothelial cells. 387 62

A 28 year old pregnant woman was referred for genetic counselling because of a bleeding tendency and a family history of hemophilia. The hemophilia patients had 0.02 units/ml of factor IX activity and a normal concentration of factor IX antigen. In addition they had a prolonged coagulation time with bovine thromboplastin and were therefore cases of hemophilia BM. At the age of six the patient was hospitalized because of prolonged bleeding after a tooth extraction. At the age of 20 and 24 she gave birth to healthy daughters. The first delivery was complicated by a serious bleeding seven days post partum whereas the second delivery was without complications. Factor IX activity when she was three months pregnant was 0.02-0.03 units/ml and the factor IX antigen concentration was normal. Coagulation time with bovine thromboplastin was prolonged. Delivery was again normal, and she had a daughter with carrier values of factor IX. Her mother also had carrier values whereas her father was normal. The patient's hemophilia BM was probably due to extreme Lyonization in a heterozygote.
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PMID:Hemophilia BM in a female. 398 11

To evaluate the effects of chlormadinone acetate upon the coagulation of blood and fibrinolysin systems, 35 healthy, young women voluntarily using some form of birth control were studied. 10 women who served as controls used intrauterine devices; 25 women took either a progestin-estrogen (1 mg norethindrone acetate and 1 mg mestranol) combination or a synthetic progestational agent (0.5 mg chlormadinone acetate) on a coded, double-blind basis. Platelet counts, thrombelastograms, and plasma assays were performed prior to and after 3 and 6 months of treatment. After 3 months, those taking progestin-estrogen showed a highly significant increase toward hypercoagulability in Quick time, Factors II, VII, and X, and increased levels in the thromboplastin generation time (TGT), Factors V and IX, and plasminogen. At 6 months all levels remained elevated except for TGT. Those on chlormadinone acetate had only a slightly significant change toward hypercoagulability in Quick time and Factor VIII, an increase in Factor IX, and a decrease in Factor X. In the control group only TGT was elevated. The progestin alone induced only minimal changes in comparison to the marked rises accompanied with progestin-estrogen therapy.
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PMID:Progestational agents and blood coagulation. IV. Changes induced by progestogen alone. 411 4

A persistent puzzle in our understanding of hemostasis has been the absence of hemorrhagic symptoms in the majority of patients with Hageman trait, the hereditary deficiency of Hageman factor (factor XII). One proposed hypothesis is that alternative mechanisms exist in blood through which plasma thromboplastin antecedent (PTA, factor XI) can become active in the absence of Hageman factor. In order to test this hypothesis, the effect of several proteolytic enzymes, among them thrombin, plasma kallikrein, and trypsin, was tested upon unactivated PTA. PTA was prepared from normal human plasma by Ca(3)(PO(4))(2) adsorption, ammonium sulfate fractionation, and successive chromatography on QAE-Sephadex (twice). Sephadex-G150, and SP-Sephadex. The partially purified PTA was almost all in its native form, with a specific activity of 45-70 U/mg protein; the yield was about 10%. It contained no measurable amounts of other known clotting factors, plasmin, plasminogen, nor IgG. Incubation of PTA with trypsin generated potent clot-promoting activity that corrected the abnormally long clotting time of plasma deficient in Hageman factor or PTA but not in Christmas factor. This clot-promoting agent behaved like activated PTA on gel filtration (apparent molecular weight: 185,000) and was specifically inhibited by an antiserum directed against activated PTA. These data suggested that PTA can be converted into its active form by trypsin. PTA was not activated by thrombin, chymotrypsin, papain, ficin, plasmin, plasma kallikrein, tissue thromboplastin, or C. Trypsin converted PTA to its active form enzymatically. Whether trypsin serves to activate PTA in vivo is not yet clear.
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PMID:Partial purification of plasma thromboplastin antecedent (factor XI) and its activation by trypsin. 426 22

Coagulation studies were carried out on 30 patients with chronic liver disease. The clotting defect was complex and involved factors V, VII, IX (Christmas factor), and prothrombin. Some patients showed a significant depression of factor IX in the presence of a normal one-stage prothrombin time. Thrombotest was found to be a good indicator of factor IX deficiency in this group of patients and may be of use as an additional liver function test. The screening of patients with liver disease for surgery or liver biopsy should assess the coagulation factors involved in both intrinsic and extrinsic thromboplastin generation.
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PMID:Coagulation factors in chronic liver disease. 577 51

Thrombosis and/or disseminated intravascular coagulation (DIC) are complications specifically associated with the use of factor IX complex in some patients. Assuming that these complications might result from zymogen overload, we have produced, using diethylaminoethyl (DEAE)-Sephadex (Pharmacia, Piscataway, NJ) and sulfated dextran chromatography, a factor IX concentrate (coagulation factor IX) that is essentially free of prothrombin, factor VII, and factor X. Factor IX specific activity is at least 5 U/mg protein, a 250-fold purification compared to plasma. Amounts of factors II, VII, and X are less than 5 units each per 100 units of factor IX. The concentrate is essentially free of activated clotting factors and contains no added heparin. In the rabbit stasis model, a dose of 200 factor IX U/kg was less thrombogenic than 100 factor IX U/kg of the DEAE-Sephadex eluate from which the concentrate was derived. Infusion of 200 factor IX U/kg did not induce DIC in the nonstasis rabbit model, whereas 100 factor IX U/kg of the DEAE-Sephadex eluate resulted in DIC in this model. Several factor IX lots were found to have shortened nonactivated partial thromboplastin times (PTTs), but were nonthrombogenic in both animal models. These data indicate that coagulation factor IX concentrate is less thrombogenic than factor IX complex.
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PMID:Coagulation Factor IX concentrate: method of preparation and assessment of potential in vivo thrombogenicity in animal models. 649 36

Previous studies have shown that factor IX and its activated form, factor IXa, bind to cultured vascular endothelial cells and that cell-bound factor IXa retains its procoagulant activity. The present studies provide evidence that factor IX bound to cultured bovine aortic endothelial cells can be activated. Factor IX activation was assessed by finding cleavage of the factor IX molecule on NaDodSO4/polyacrylamide gel electrophoresis and by the generation of procoagulant activity as assessed by thrombin-treated factor VIII-dependent generation of factor Xa activity. Cell-bound factor IX (0.8 micrograms per 4 X 10(8) cells per ml) could be activated by factor XIa (5 micrograms/ml) or by factor VIIa (0.1 micrograms/ml) without exogenous tissue factor when endothelial cells were treated with phorbol ester and acquired tissue factor-like procoagulant activity. Regardless of how factor IX was activated, the cell-bound factor IXa required thrombin-treated factor VIII and calcium, but not exogenous phospholipid, to activate factor X. In further experiments, factor X bound to endothelial cells specifically and reversibly with a dependence on calcium and with a lower affinity (half-maximal at 480 nM) than factor IX. At saturation, 9.1 X 10(6) factor X molecules were bound per cell. After activation of factor X by factor IXa, approximately 50% of the factor Xa formed could be eluted from the cells by 10 mM EDTA, suggesting that the factor Xa was cell associated. These observations indicate that endothelial cells can bind and promote the activation of factors IX and X in the absence of platelets or exogenous phospholipid.
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PMID:Activation of factor IX bound to cultured bovine aortic endothelial cells. 660 5


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