To see the other types of publications on this topic, follow the link: Prothrombine time.
Journal articles on the topic 'Prothrombine time'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Prothrombine time.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Nelly, Nelly, Mansyur Arief, and Ilham Jaya Patellongi. "ANALISIS NILAI CLOTHING TIME, PROTHROMBINE TIME DAN ACTIVATED PARTIAL THROMBOPLASTINE TIME PADA REMAJA OBES." MAGNA MEDICA: Berkala Ilmiah Kedokteran dan Kesehatan 1, no. 5 (March 18, 2019): 36. http://dx.doi.org/10.26714/magnamed.1.5.2018.36-43.
Full textAbstract:
Berdasarkan estimasi WHO, obesitas menjadi masalah kesehatan di dunia. Selain karena insidennya meningkat,juga karena obesitas menimbulkan berbagai komplikasi penyakit metabolik dan vaskuler seperti sindrom metabolik, penyakit jantung, stroke dan gangguan pembekuan darah. Mengingat insiden obesitas pada saat ini telah mengalami pergeseran dari dewasa ke usia anak dan remaja serta berbagai komplikasi yang ditimbulkan oleh obesitas itu sendiri maka dianggap perlu dilakukan deteksi dini adanya gangguan hemostasispada obesitas usia anak dan remaja untuk mencegah komorbiditas obesitas dikemudian hari. Desain penelitian ini adalah cross sectional study yang dilakukan di SMA Katolik Rajawali Makassar dengan menggunakan sampel siswa yang berumur sekitar 10-18 tahun. Dilakukan pemeriksaan antropometrik dan pemeriksaan nilai Clothing Time (TT), Prothrombine Time (PT) dan Activated Partial Thromboplastine Time(aPTT). Obesitas dinyatakan berdasarkan Kategori IMT yang ditentukan berdasarkan ambang batas Z-Score sedangkan kategorilingkar pinggang ditentukan berdasarkan Waist Circumfrence for Hong Kong Chinese Children (2008). Data dianalisis dengan independent t-test untuk menilai perbedaan nilai CT, PT dan aPTT pada remaja obes dan berat badan normal sedangkan uji korelasi pearson digunakan untuk melihat adanya hubungan antara IMT dan LP dengan nilai CT, PT dan aPTT pada remaja obes. Subyek adalah siswa siswi SMA Katolik Rajawali Makassar dengan rerata umur 15 tahun terdiri dari 33 orang laki-laki (22 obesitas,11 normal) dan 16 perempuan (5 obesitas,11 normal). Didapatkan perbedaan bermakna antara nilai CT, PT dan aPTT pada remaja obes dan berat badan normal. Nilai rata-rata CT, PT dan pada kelompok normal adalah masing-masing aPTT 11±1,23; 13,86 ± 0,63 detik ; 32,90 + 1,77 detik dan pada kelompok obes adalah nilai CT,PT dan aPTT adalah 9 ±1,7; 13,11 + 0,59 detik dan 31,92+3,82 detik. Selain itu, terdapat korelasi negatif antara nilai CT,PT dan LP pada remaja obes namun tidak ditemukan adanya korelasi antara IMT dan LP dengan nilai aPTT pada remaja obes. Nilai CT, PT dan aPTT pada remaja obes cenderung memendek dibandingkan dengan berat badan normal.Semakin tinggi nilai IMT dan LP, maka nilai CT, PT dan aPTT semakin memendek. Keywords : obesitas, remaja CT,PT,aPTT
2
Petkovska, L., Z. Pereska, Dz Naumovski, C. Bozinovska, D. Petrovski, F. Licoska, and A. Babulovska. "252 Prothrombine time-usefull prognostic marker in amanita phalloides poisoning." Toxicology Letters 144 (September 2003): s70—s71. http://dx.doi.org/10.1016/s0378-4274(03)90251-7.
Full text
3
Villa, P., M. Martinez, J. Aznar, A. Gilsanz, and A. Romar. "Hyper coagulability study of automatized modified prothrombine time kinetic (PTm)." Thrombosis Research 65 (January 1992): S203. http://dx.doi.org/10.1016/0049-3848(92)90718-p.
Full text
4
Limijadi, Edward Kurnia Setiawan, Lisyani Budi Suromo, and Imam Budiwiyono. "Prothrombine and activated partial thromboplastin time are prolonged in hepatic cirrhosis." Universa Medicina 35, no. 1 (May 9, 2016): 26. http://dx.doi.org/10.18051/univmed.2016.v35.26-32.
Full textAbstract:
<p><strong>Background</strong></p><p>Chronic hepatitis and hepatic cirrhosis are chronic liver diseases that cause disorders of liver function, such as the formation of platelets and coagulation factors (prothrombin time/PT and activated partial thromboplastin time/APTT). Chronic hepatitis in the long term can develop into hepatic cirrhosis. The aim of this study was to determine platelet count, PT, and APTT as indicators in the progression of chronic hepatitis towards hepatic cirrhosis.</p><p><strong> </strong></p><p><strong>Metho</strong><strong>d</strong><strong>s</strong></p><p>A cross-sectional study was conducted on 50 patients with chronic hepatitis and hepatic cirrhosis in Semarang City Regional General Hospital, Telogorejo Hospital and Kariadi General Hospital. The platelet count was measured with a Sysmex XP-100, while PT and APTT was measured with a Sysmex CA-1500 coagulometer. The Mann Whitney test was applied to analyze the difference in platelet count, PT, and APTT between chronic hepatitis and hepatic cirrhosis.</p><p> </p><p><strong>Results </strong><strong></strong></p><p>Median, minimum, and maximum values of platelet count, PT and APTT in chronic hepatitis were 284.000/µl, 210.000/µl, 390.000/µl; 10.6 sec, 9.5 sec, 13.6 sec; and 30.5 sec, 24.2 sec, 46.4 sec, respectively, and in hepatic cirrhosis they were 96.300/µl, 48.200/µl, 133.800/µl; 27.5 sec, 11.9 sec, 44.7 sec; and 55.6 sec, 31.3 sec, 72.0 sec, respectively. There was a significant difference the reduction of platelet count, and the prolongation of PT and APTT in chronic hepatitis compared to hepatic cirrhosis (p=0.000).</p><p> </p><p><strong>Conclusion</strong><strong>s</strong></p>Prothrombine time and APTT were prolonged and platelet count was decreased in hepatic cirrhosis subjects. The three parameters may be used to evaluate the progression of chronic hepatitis towards hepatic cirrhosis.
5
Wu, Yueh-Wern, Kuan-Dee Chen, and Wen-Chuan Lin. "Effect ofGanoderma tsugaeon Chronically Carbon Tetrachloride-Intoxicated Rats." American Journal of Chinese Medicine 32, no. 06 (January 2004): 841–50. http://dx.doi.org/10.1142/s0192415x04002454.
Full textAbstract:
The purpose of this study was to evaluate the hepatoprotective and anti-fibrotic actions of crude extracts of Ganoderma tsugae (GTE) on chronic liver injury induced by carbon tetrachloride ( CCl4) in rats. CCl4(20%, 0.5 ml/rat) was given twice a week for 8 weeks, and animals received GTE through the whole experimental period. GTE showed obvious reducing actions on the elevated levels of glutamate-oxalate-transaminase (GOT) and glutamate-pyruvate-transaminase (GPT) caused by CCl4at weeks 3, 6 and 8. Liver fibrosis in rats induced by CCl4led to the drop of serum albumin and hepatic protein concentrations, while GTE increased serum albumin and hepatic protein concentrations. The CCl4-induced liver fibrosis may prolong the prothrombine time and increase albumin/globulin (A/G) ratio. GTE significantly decreased the prothrombine time and A/G ratio. Liver fibrosis induced by CCl4markedly increased the weight of the spleen, hepatic water and hydroxyproline contents in rats, while GTE decreased the rat's spleen weights, hepatic water and hydroxyproline contents. All these results clearly demonstrated that GTE has hepatoprotective and anti-fibrotic activities.
6
Ivkin, Dmitriy Yuryevich, Anna Veniaminovna Buryakina, Irina Leonidovna Stepanova, and A. S. Ivkina. "Usage of warfarin as a reference drugin experiments on rats." Reviews on Clinical Pharmacology and Drug Therapy 11, no. 1 (March 15, 2013): 46–49. http://dx.doi.org/10.17816/rcf11146-49.
Full textAbstract:
The possibility of using indirect anticoagulant warfarin as a reference drug in sсreening researches on rats was considered in the article. The dose of warfarin leading to true increase of prothrombine time without any internal gemorrhagias in animals has been defined. The optimal terms of administration for warfarin were defined. The dose-dependent regularity of warfarin effect from its duration of administration to rats was revealed.
7
Limantara, V. Lily, Sudaryat S., I. B. Mudita, W. Retayasa, and M. Kardana. "Effect of oral vitamin K prophylaxis on prothrombine time and activated partial thromboplastin time: a randomized controlled comparison with an intramuscular vitamin K in infants." Paediatrica Indonesiana 47, no. 3 (July 1, 2007): 109. http://dx.doi.org/10.14238/pi47.3.2007.109-14.
Full textAbstract:
Background Low plasma concentration of vitamin K in thenewborn accounts for serious bleeding in the neonatal period andearly infancy. The aim of prophylactic vitamin K is to preventbleeding. Oral prophylaxis is preferable to intramuscular (IM)administration because oral administration is less expensive andless traumatic.Objective To compare oral vs. intramuscular vitamin K onprothrombine time (PT) and activated partial thromboplastin time(APTT) during the first 60 days of life.Methods We randomized newborn infants to either receive oralvitamin K 2 mg at birth and repeated at 7 and 30 days of life orthe 1 mg intramuscular vitamin K. PT and APTT were monitoredat 0, 15, and 45 days of age. Independent t-test, repeatedmeasurement, and regression analysis were used for statisticalanalyses and comparison of the results.Results Fifty infants were assigned into the oral group and 50 tothe IM group. All participants completed 60 days of study. BothPT and APTT decreased after administration of oral or IM vitaminK, and the values did not differ significantly at any time pointand through the period of investigation. Using regression analysisit was shown that only vitamin K administration was correlatedwith PT and APTT with P value were 0.044 and 0.036,respectively. During 60 days of study, there was no hemorrhagicdiathesis in both groups.Conclusions Through the first 60 days of life, 3 doses of oralvitamin K maintain hemostasis by decreasing PT and APTT ininfants at values equal to those achieved by the intramuscularpreparation. Diathesis hemorrhagic event did not occur in bothgroups.
8
Rohmah, Martina Kurnia, and Djelang Zainuddin Fickri. "Uji Aktivitas Antiplatelet, Antikoagulan, dan Trombolitik Alkaloid Total Daun Pepaya (Carica papaya L.) secara in Vitro." Jurnal Sains Farmasi & Klinis 7, no. 2 (August 31, 2020): 115. http://dx.doi.org/10.25077/jsfk.7.2.115-125.2020.
Full textAbstract:
Daun pepaya memiliki kandungan beberapa senyawa alkaloid (karpain, pseudokarpain, dehydrokarpain I, dehydrokarpain II, dan emetin). Penelitian ini bertujuan untuk mengetahui aktivitas antiplatelet, antikoagulan, dan trombolitik alkaloid total daun pepaya secara in vitro. Penelitian ini terdiri dari 5 perlakuan: kontrol negatif, kontrol positif, alkaloid total daun pepaya (konsentrasi 0.5, 1.0, dan 2.0 mg/mL) dengan parameter persentasi inhibisi agregasi, persentase inhibisi koagulasi dari nilai Clotting Time (CT), Prothrombine Time (PT), dan Activated Parsial Thromboplastine Time (APTT), dan daya fibrinolitik. Berdasarkan analisis statistik diketahui bahwa terdapat perbedaan yang signifikan antara persentase inhibisi agregasi alkaloid total dibanding kontrol negative, namun tidak berbeda dengan kontrol positif (clopidogrel). Pada uji antikoagulan, alkaloid total daun pepaya secara signifikan dapat memperpanjang CT, PT, dan APTT yang berbeda signifikan dengan kontrol negatif, namun tidak berbeda dengan kontrol positif (heparin). Hasil uji trombolitik menunjukkan bahwa alkaloid total daun pepaya dapat meningkatkan persentase trombolitik yang berbeda dengan kontrol negatif, namun tidak berbeda signifikan dengan kontrol positif (nattokinase).
9
Jajeh, Ahmad. "Management of Major Bleeding Caused By Rivaroxaban and the Use of Desmopressin." Blood 124, no. 21 (December 6, 2014): 5099. http://dx.doi.org/10.1182/blood.v124.21.5099.5099.
Full textAbstract:
Abstract Rivaroxaban is a new anticoagulant that is substituted for Coumadin on a large scale in the treatment and prevention of Deep Vein Thrombosis DVT and Pulmonary Embolism PE. It is an oral agent that inhibits Factor Xa. The most attractive attribute of this new anticogulant is the lack of monitoring PT/INR. However, out of many cases put on Rivaroxaban a few reports of major and threatening bleed that could be fatal. Particularly, the the GI bleeding. Unfortunately, no set standard antidote or management is available when such catastrophic bleeds happen. This abstract present our experience with three major bleeding cases that presented with massive GI bleeding. Two are associated with peptic ulcer upon Upper GI endoscopy. Two males and one female age 60, 71 (males) and 71 (female). The first two patients were treated with Prothrombin complex product. The female patient presented with sever anemia of 4 grams of Hb with hematemesis and bright red blood per rectum. The Prothrombin complex product was not readly available . She was given multipe doses of Fresh Frozen Plasma FFP and multiple units of packed red blood cells. She was also given a product Profilnine which contains Factor II, IX and VII. Patient's coagulation profile of PTT, PT and Thrombin time were corrected. However, she continue to have bright blood per NG suction. Upon receiving D-DAVP Desmopressin 0.3 micrograms per Kg she stopped bleeding and EGD was done later with sclerosing treatment of gastric ulcer and ligation. Patient was given later a small dose of Prothrombine complex when was available since the last dose of Rivaroxaban was given less than 13 hours from her presentation to the hospital. All of the mentioned patients had prolongation of PT/INR/PTT at presentation. Thrombin time was monitored in all of them. All patients had survived the magor GI bleeding. D-DAVP were given to all of them. In conclusion D-DAVP Desmopressin should be considered as an adjuvant drug in patient presentong with major GI bleeding secondary to Rivaroxaban. Disclosures No relevant conflicts of interest to declare.
10
Kwon, Seung Yeon, Jung Woo Han, Sung Chul Won, Jaewoo Song, and Chuhl Joo Lyu. "Analysis of Children with Coagulation Test Abnormality in Pre-Surgical Evaluation." Blood 112, no. 11 (November 16, 2008): 4080. http://dx.doi.org/10.1182/blood.v112.11.4080.4080.
Full textAbstract:
Abstract Prothrombine time (PT) and activated prothrombine time (aPTT) are common tests used for screening of coagulation function before surgical procedures. We analyzed underlying causes of abnormal coagulation test results which were incidentally found during pre-surgical evaluation in healthy patients without definite bleeding history. Total 58 children referred to pediatric hematoloy service for abnormal PT and aPTT results in pre-surgical evaluation between June 2006 and May 2008 were analyzed retrospectively by review of medical records. 50 patients showed aPTT prolongation, 5 patients PT prolongation, 2 patients PT and aPTT prolongation and another three patients showed normal PT and aPTT. Among 55 patients with abnormal results, 25 patients (43%) were recovered spontaneously during their follow up tests, 17 patients (29%) showed lower level of certain coagulation factor than reference range and the other 13 patients were lost during follow up despite of recommendation for further evaluation. Mean value of international normalized ratio (INR) for PT and aPTT of the patients recovered spontaneously were 1.05±0.11, 44.53±5.01seconds(s), and 1.12±0.11, 47.0±5.36s in patients with lower level of coagulation factor, showing significant increase of PTT in patients with lower factor levels (p<0.05). Median time required for spontaneous recovery was four weeks and 18 patients (72%) were recovered within this time. Among 17 patients with lower level of certain coagulation factor then reference level, there were 11 patients with low factor XII level, three patients with low factor VIII level, three patients with low von Willebrand factor, two patients each for low factor VII and factor XI and one patient with low factor V level. Among them three patients with low level in von Willebrand factor, one patient with low factor VII and two patients with low factor XI showed deficient level of coagulation factors requiring factor replacement for the surgical procedures. From this analysis of patients with incidentally found PT or aPTT prolongation, 43% of patients were spontaneously recovered during follow up period within 4 weeks in median. However, we also found that 29% of patients had relatively lower level of coagulation factor than reference range. Even though most of them were factor XII decrease which is not closely related with bleeding tendency, six patients had significant deficiencies of coagulation factors requiring factor replacement during surgical procedures. These results suggest that we should keep following up and undergo adequate evaluation for underlying coagulation factor deficiencies in patients who have sustaining PT and aPTT prolongation abnormalities despite of absence of any bleeding history.
11
Y. Kim, Paul, and Michael E. Nesheim. "Down regulation of prothrombinase by activated protein C during prothrombin activation." Thrombosis and Haemostasis 104, no. 07 (2010): 61–70. http://dx.doi.org/10.1160/th09-09-0650.
Full textAbstract:
SummaryActivated protein C (aPC) proteolytically inactivates factor Va (FVa) and thereby downregulates prothrombinase. Although FVa inactivation by aPC has been studied extensively, the inactivation of prothrombinase during prothrombin activation has not. Therefore, prothrombin activation initiated both without and with aPC (5.0, 7.5 or 10.0 nM) was monitored over time by fluorescence. The experiments were performed with 0.075 nM FVa and 1.0 nM FXa, and with these concentrations reversed. The time courses of the residual prothrombinase activity with aPC, determined from the slopes of fluorescence over time, were pseudo first order with both limiting and excess FVa. With FVa limiting or in excess, the second rate constants for inactivation of prothrombinase were 1.98 ± 0.09 x 105 M-1s-1 and 2.54 ± 0.13 x 105 M-1s-1 , respectively. The former value is 101-fold smaller than that for FVa inactivation by aPC alone. Since with limiting FVa the second order rate constants for prothrombinsase inactivation and FVa inactivation are equal, FVa is protected 101-fold, presumably by both FXa and prothrombin. In contrast, with excess FVa, the calculated rate constant for FVa inactivation exceeds that for prothrombinase inactivation 17.3-fold, which reflects a loss of protection by FXa. Since the protective effects of the two proteins are theoretically multiplicative, FXa protected 17.3-fold and prothrombin protected 5.8-fold. With 150 nM protein S and limiting FVa, prothrombinase inactivation was two-fold faster, yet it was still protected 91-fold. These studies show that FVa is down-regulated by aPC during prothrombin activation, but both FXa and prothrombin protect FVa in a multiplicative way, with or without protein S.
12
Hirbawi, Jamila, and Michael Kalafatis. "Amino Acids Asp695 and Tyr696 of Factor Va Are Essential for Optimal Rate of Prothrombin Activation by Prothrombinase." Blood 114, no. 22 (November 20, 2009): 3163. http://dx.doi.org/10.1182/blood.v114.22.3163.3163.
Full textAbstract:
Abstract Abstract 3163 Poster Board III-101 Blood coagulation is initiated after vascular injury, promoting formation of the fibrin clot. Without the proper regulation of this process, serious life threatening conditions, such as DVT (deep vein thrombosis), can occur. The proteolytic conversion of prothrombin to thrombin is catalyzed by the prothrombinase complex composed of the enzyme, factor Xa (fXa), the cofactor, factor Va (fVa), assembled on a membrane surface in the presence of Ca2+. The incorporation of fVa into the prothrombinase complex results in a 300,000-fold increase in the catalytic efficiency of fXa for thrombin generation. Prothrombinase activates prothrombin through initial cleavage at Arg320 followed by cleavage at Arg271 to yield human alpha-thrombin. This pathway is responsible for the generation of a transient intermediate, meizothrombin, that is enzymatically active with increased chromogenic substrate activity, but yields poor clotting activity. Factor Va is composed of heavy and light chains that play a crucial role during thrombin formation. Portions of the fVa heavy chain have been found to interact with proexosite 1 (pro1) of prothrombin and influence prothrombinase activity. It has been recently demonstrated that deletion of the COOH-terminal region of the factor Va heavy chain causes accumulation of meizothrombin due to delayed cleavage of prothrombin at Arg271. Site-directed mutagenesis was performed to generate recombinant mutant molecules in order to identify the specific amino acids of this COOH-terminal region that regulate cleavage. Mutants with the 695DYDY698→DFDY(fVaDFDY), KFDY(fVaKFDY),DEDE(fVaDEDE),DFDF(fVaDFDF) substitutions were constructed. These recombinant molecules along with wild type factor V (fVWT) were transiently expressed in COS7 cells purified to homogeneity and assessed for their capability to promote prothrombin activation. Prothrombin activation was evaluated by SDS-PAGE and the kinetic parameters of the reactions were determined. SDS-PAGE analyses of prothrombin activation time courses revealed that the overall cleavage of prothrombin by prothrombinase assembled with fVaKFDY and fVaDFDY was delayed, while prothrombinase assembled with fVaDEDE and fVaDFDF had no significant effects when compared to fVaWT. Two- stage clotting assays (PT times) revealed that fVaKFDY and fVaDFDY both had reduced clotting activity when compared to fVaWT, while fVaDEDE and fVaDFDF gave similar clotting results as fVaWT. Determination of kcat values for prothrombinase assembled with the various recombinant molecules revealed that prothrombinase assembled fVaKFDY and fVaDFDY had a 20% increase catalytic efficiency as compared with prothrombinase assembled with fVaWT, while fVaDEDE and fVaDFDF gave values that were comparable to prothrombinase assembled with fVaWT. Comparison of the rate of cleavage of two recombinant prothrombin mutant molecules, rMZ that can't be cleaved at Arg271 and rPII that can't be cleaved at Arg320, by prothrombinase assembled with the mutant fVa molecules resulted in normal cleavage of rMZ by all the mutants. Cleavage of rPII, however, was impaired when fVaKFDY and fVaDFDY were incorporated into prothrombinase. The data presented suggests that the 695DY696 portion of the acidic cluster found in the COOH-terminus of the fVa heavy chain plays a significant role in enzyme-substrate interaction during thrombus formation. Disclosures No relevant conflicts of interest to declare.
13
Speijer, Han, Didier Billy, George Willems, H. Coenraad Hemker, and Theo Lindhout. "Inhibition of Prothrombinase by Antithrombin-Heparin at a Macroscopic Surface." Thrombosis and Haemostasis 73, no. 04 (1995): 648–53. http://dx.doi.org/10.1055/s-0038-1653835.
Full textAbstract:
SummaryThe antithrombin-dependent inhibition of prothrombinase, assembled at a macroscopic surface, was studied under flow conditions utilizing a tubular flow reactor that consists of a phospholipid-coated glass capillary. Prothrombinase activity was determined from steady-state rates of thrombin production upon perfusion with prothrombin and from factor Va-associated factor Xa activity present in the flow reactor. The prothrombinase density was maintained at a low level (0.03 fmol/cm2) to assure that the rate of thrombin production reflected the amount of prothrombinase present in the capillary. Perfusion of the flow reactor with antithrombin resulted in an exponential decrease of prothrombinase activity in time. The second order rate constant (8.5 × 104 M-1min-1) is comparable with the rate of inactivation of free factor Xa. Inhibition was much faster when antithrombin was complexed with heparin. The second order rate constants of inhibition decreased with decreasing heparin chain length: 9.6 × 107, 4.5 × 107 and 0.39 × 107 M-1min-1 for unffactionated heparin, low molecular weight heparin and synthetic pentasaccharide heparin, respectively. In the presence of prothrombin (0.2 μM), however, the heparin-dependent rate of inhibition of prothrombinase was about 50-fold lower. The heparin-independent inhibition of prothrombinase by antithrombin (4 μM) in the presence of prothrombin (0.2 μM) was virtually negligible. At a 70-fold higher surface density of prothrombinase (2 fmol/cm2) prothrombinase activity was much faster inactivated. The rate of thrombin production, however, was not affected. In conclusion, at low prothrombinase densities, prothrombin efficiently protects prothrombinase from inhibition. At high densities, prothrombinase is much less protected but the higher rate of prothrombinase inactivation has no consequences for the thrombin production because of the transport-limited regime.
14
Schoen, P., C. Reutelingsperger, and T. Lindhout. "Activation of prothrombin in the presence of human umbilical-vein endothelial cells." Biochemical Journal 281, no. 3 (February 1, 1992): 661–64. http://dx.doi.org/10.1042/bj2810661.
Full textAbstract:
Addition of Factor Xa, Factor Va and prothrombin to immobilized cultured human umbilical-vein endothelial cells resulted after a time delay in thrombin formation. The prothrombin-converting (prothrombinase) activity, however, was not associated with the cell surface. Rather, perturbation by thrombin, either formed in situ or exogenously added, induced a procoagulant phospholipid surface in the fluid phase, which, in the presence of Factor Xa and Factor Va, enabled the assembly of prothrombinase.
15
Pomowski, Anja, Fatma Isik Ustok, and James A. Huntington. "Homology model of human prothrombinase based on the crystal structure of Pseutarin C." Biological Chemistry 395, no. 10 (October 1, 2014): 1233–41. http://dx.doi.org/10.1515/hsz-2014-0165.
Full textAbstract:
Abstract Thrombin is generated from prothrombin through cleavage at two sites by the prothrombinase complex. Prothrombinase is composed of a protease, factor (f) Xa, and a cofactor, fVa, which interact on negatively charged phospholipid surfaces and cleave prothrombin into thrombin 300 000 times faster than fXa alone. The balance between bleeding and thrombosis depends on the amount of thrombin produced, and this in turn depends on the function of the prothrombinase complex. How fXa and fVa interact and how improved prothrombin processing is conferred are of critical importance for understanding healthy and pathological blood clotting. Until recently, little structural information was available, and molecular models were built on partial structures with assembly guided by biochemical data. Last year our group published a crystal structure of a prothrombinase complex from the venom of the Australian Eastern Brown snake (known as Pseutarin C). Here we use the crystal structure of Pseutarin C as a starting point for homology modelling and assembly of the full human prothrombinase complex. The interface is complementary in shape and charge, and is consistent with much of the published biochemical data. The model of human prothrombinase presented here provides a powerful resource for contextualizing previous data and for designing future experiments.
16
Ofosu, Frederick A., J. C. Lormeau, Sharon Craven, Lori Dewar, and Noorildan Anvari. "Heparin and Low Molecular Weight Heparins Inhibit Prothrombinase Formation but not its Activity in Plasma." Thrombosis and Haemostasis 72, no. 06 (1994): 862–68. http://dx.doi.org/10.1055/s-0038-1648975.
Full textAbstract:
SummaryFactor V activation is a critical step preceding prothrombinase formation. This study determined the contributions of factor Xa and thrombin, which activate purified factor V with similar catalytic efficiency, to plasma factor V activation during coagulation. Prothrombin activation began without a lag phase after a suspension of coagulant phospholipids, CaCl2, and factor Xa was added to factor X-depleted plasma. Hirudin, a potent thrombin inhibitor, abrogated prothrombin activation initiated with 0.5 and 1.0 nM factor Xa, but not with 5 nM factor Xa. In contrast, hirudin did not abrogate prothrombin activation in plasmas pre-incubated with 0.5,1.0 or 5 nM α-thrombin for 10 s followed by the coagulant suspension containing 0.5 nM factor Xa. Thus, thrombin activates plasma factor V more efficiently than factor Xa. At concentrations which doubled the clotting time of contact-activated normal plasma, heparin and three low Mr heparins also abrogated prothrombin activation initiated with 0.5 nM factor Xa, but not with 5 nM factor Xa. If factor V in the factor X-depleted plasma was activated (by pre-incubation with 10 nM a-thrombin for 60 s) before adding 0.5,1.0, or 5 nM factor Xa, neither hirudin nor the heparins altered the rates of prothrombin activation. Thus, none of the five anticoagulants inactivates prothrombinase. When 5 or 10 pM relipidated r-human tissue factor and CaCl2 were added to normal plasma, heparin and the three low Mr heparins delayed the onset of prothrombin activation until the concentration of factor Xa generated exceeded 1 nM, and they subsequently inhibited prothrombin activation to the same extent. Thus, hirudin, heparin and low Mr heparins suppress prothrombin activation solely by inhibiting prothrombinase formation.
17
Samis, John A., Reginald P. Manuel, and Michael E. Nesheim. "The Interaction of Prothrombin and Its Activation Products with Platelets." Blood 108, no. 11 (November 16, 2006): 1514. http://dx.doi.org/10.1182/blood.v108.11.1514.1514.
Full textAbstract:
Abstract The interaction of human 125I-prothrombin and its activation products with unactivated and thrombin-stimulated human platelets was studied. 125I-prothrombin binding to unactivated platelets was found to be a reversible and calcium-dependent process (n=48,000 sites/platelet, Kd=3.0μM). Thrombin stimulation of platelets resulted in increased prothrombin binding both in the presence and absence of calcium (n=84,000 sites/platelet, Kd=6.0μM and n=53,000 sites/platelet, Kd=8.0μM, respectively). Thrombin stimulation of platelets also increased the calcium-independent binding of prethrombin-1 compared with unstimulated cells. Using thrombin-stimulated platelets as a membrane surface for prothrombinase, 125I-prothrombin was converted exclusively to 125I-Fragment 1.2 and 125I-thrombin when the reactions were carried out in the presence of the reversible thrombin inhibitor, 5-dimethylaminonapthalene-1-sulfonylarginine-N-(3-ethyl-1,5-pentanediyl)amide (DAPA). 125I-thrombin was the major prothrombin activation product that remained bound to the thrombin-stimulated platelets (50,000 molecules/platelet). Platelet-bound 125I-thrombin either added directly or generated from 125I-prothrombin by the action of prothrombinase was found to be inacessible to human antithrombin (AT)/heparin-induced inactivation. Utilization of phosphatidylcholine/phosphatidylserine (PCPS) vesicles as a membrane surface for prothrombinase in the presence of DAPA demonstrated that 125I-prothrombin activation proceeded initially through a meizothrombin intermediate that was replaced at later times by Fragment 1.2 and the A and B chains of α-thrombin. 125I-Fragment 1.2 was the main prothrombin activation product that remained bound to the PCPS vesicles after Sephadex G-150 gel filtration chromatography. The above results indicate that human prothrombin binds specifically to unstimulated human platelets via its Fragment 1 domain only in the presence of calcium and thrombin-stimulation results in the exposure of additional calcium-dependent and -independent prothrombin binding sites. In addition, thrombin was the major prothrombin activation product that remains associated with the thrombin-stimulated human platelets and this platelet-bound thrombin is protected from AT/heparin- induced inactivation. During prothrombin activation on platelets, large amounts of thrombin remain bound and Fragment 1.2 is released from the platelet surface. In contrast, Fragment 1.2 was the major prothrombin activation product that binds PCPS vesicles. Therefore, although both thrombin-stimulated human platelets and PCPS vesicles may each serve as an effective membrane component of prothrombinase, they appear to differ both in their prothrombin activation pathway as well as their ability to bind the products of prothrombin activation.
18
Kentner, Taryn A., Leslie R. Berry, and Anthony K. C. Chan. "Inhibition of Factor Xa in Prothrombinase Is Enhanced by Covalent Linkage of Antithrombin to Heparin." Blood 104, no. 11 (November 16, 2004): 1051. http://dx.doi.org/10.1182/blood.v104.11.1051.1051.
Full textAbstract:
Abstract Prothrombinase is the surface-bound complex in which factor Xa (Xa) converts prothrombin to thrombin in vivo. Studies have shown that Xa within prothrombinase is resistant to inhibition by antithrombin + heparin (AT+H). Previously we found that, unlike AT+H, a covalent conjugate of AT and H (ATH) was able to neutralize fibrin-bound thrombin. In this study, AT+H and ATH were compared in their reaction with Xa in prothrombinase. Mixtures of CaCl2, PCPS vesicles, factor Va (Va) and prothrombin in TSP buffer were combined with either AT+H or ATH. Following addition of Xa, time samples were neutralized with Na2EDTA + polybrene + substrate (S-2222) and residual Xa activity measured. Second order rate constants (k2) were calculated from plots of activity versus time. Results were compared to those in corresponding experiments with Xa alone. Inhibition of Xa in prothrombinase by AT+H had a k2 (x 108 M−1min−1) of 0.688 +/− 0.030. Conversely, free Xa neutralization by AT+H was significantly more rapid (k2 = 1.53 +/− 0.35, p = 0.041). ATH reaction with prothrombinase Xa proceeded at a rate that was insignificantly different from that with Xa alone (2.36 +/− 0.31 and 2.83 +/− 0.83, respectively) and similar to AT+H reaction with free Xa. Varying concentrations of prothrombinase components showed similar effects. We conclude that covalently linked complexes of AT + H undergo unhindered reaction with Xa in prothrombinase, while non-covalently linked AT+H encounters resistance. It is possible that ATH may effectively prevent plasma thrombin generation by neutralization of Xa in prothrombinase and thus may prohibit feedback activation of coagulation.
19
Rand, MD, JB Lock, C. van't Veer, DP Gaffney, and KG Mann. "Blood clotting in minimally altered whole blood." Blood 88, no. 9 (November 1, 1996): 3432–45. http://dx.doi.org/10.1182/blood.v88.9.3432.bloodjournal8893432.
Full textAbstract:
The sequences of events regulating thrombin generation during tissue factor-initiated clotting in whole blood at 37 degrees C in which the contact pathway was suppressed with corn trypsin inhibitor are studied using quantitative Western blotting of factor V, prothrombin, platelet factor 4, antithrombin III, and fibrinogen. In addition, fibrinopeptide A (FPA), thrombin-antithrombin III (TAT) complex formation, and prothrombin fragment 1.2 (F1.2) were measured via commercially available enzyme-linked immunosorbent assays (ELISAs). In a typical experiment initiated with 40 pmol/L recombinant tissue factor, visual clot time (4.5 minutes), was preceded by significant cleavage of factor V resulting in 65% factor Va heavy-chain generation but only 10% light-chain formation. At this point, 50% of the platelet factor 4 is released, suggesting that half (approximately 700 pmol/L) of the platelet prothrombinase sites available have been generated. At clot time, approximately 15 nmol/L thrombin B-chain is present; however, analyses of FPA release demonstrate that only 15% of the thrombin is acting on fibrinogen. This thrombin is produced by the action of 7 pmol/L prothrombinase. The maximum rate of thrombin production is reached well after clot time and is consistent with the presence of approximately 150 pmol/L prothrombinase (at about 7 minutes). These results suggest that factor Xa is the limiting factor for thrombin generation. After 60 minutes, 75% of the initial prothrombin (1.24 mumol/L) is consumed yielding 400 nmol/ L prethrombin 2 and 360 nmol/l thrombin (B-chain) products. The sum of these values (800 nmol/L) is similar to the (corrected) F1.2 concentration determined by ELISA. The incomplete cleavage of prothrombin indicates both the prothrombinase complex and the formation of prothrombinase are inhibited in the reaction. TAT complex measured by ELISA is almost equivalent to B-chain concentration, but sodium dodecyl sulfate stable thrombin-antithrombin III complexes are not observed until well after clot formation and are never equivalent to ELISA-TAT values. At the point of clot formation, 80% of the fibrinogen is depleted from the fluid phase, whereas only 35% to 45% of the FPA is released, suggesting a significant incorporation of uncleaved fibrinogen into the initial clot formed.
20
Dr.Deepak Nayak M, Dr Deepak Nayak M., Dr Chethan Manohar, Saroja Saroja, and Asha Patil. "Comparison of Photo-Optical and Mechanical Methods for Prothrombin Time Test." Indian Journal of Applied Research 3, no. 9 (October 1, 2011): 457–58. http://dx.doi.org/10.15373/2249555x/sept2013/137.
Full text
21
Hirbawi, Jamila, Melissa A. Blum, Michael A. Bukys, Tivadar Orban, and Michael Kalafatis. "Evidence That the COOH-Terminal Region of Factor Va Heavy Chain Is Involved in the Regulation of Prothrombinase Activity." Blood 106, no. 11 (November 16, 2005): 1025. http://dx.doi.org/10.1182/blood.v106.11.1025.1025.
Full textAbstract:
Abstract The proteolytic conversion of prothrombin to thrombin is catalyzed by the prothrombinase complex composed of the enzyme, factor Xa (fXa), the cofactor, factor Va (fVa), assembled on a membrane surface in the presence of divalent metal ions. Incorporation of fVa into the prothrombinase complex results in a 300,000-fold increase in the catalytic efficiency of fXa for thrombin generation. A first cleavage of prothrombin by prothrombinase at Arg320 produces the active intermediate meizothrombin, while the second cleavage at Arg271 produces thrombin. It has been demonstrated that elimination of the carboxyl terminal portion of the heavy chain of fVa by proteolytic enzymes results in a cofactor molecule with decreased clotting activity and slightly increased to normal chromogenic activity. In addition, we have previously shown that the carboxyl terminal portion of the heavy chain of fVa is involved in the interaction of the cofactor with prothrombin. To further ascertain the importance of this region of the molecule for cofactor activity we used PCR based methods to produce recombinant fVa molecules with several portions of the COOH-terminus deleted. Recombinant fV653 has amino acids 653–709 deleted, recombinant fV696 has amino acid residues 680–696 deleted, recombinant fV680 has amino acid residues 653–680 deleted, while recombinant fV709 has amino acid residues 680–709 missing. These recombinant molecules along with wild type fV (fVWT) were transiently expressed in COS7L cells and assessed for their capability to promote prothrombin activation following activation by Russell’s Viper Venom factor V activator (RVV-V activator). Thrombin generation was evaluated by SDS-PAGE and the kinetic parameters of the reactions were determined. While fVa653 and fVa680 were devoid of clotting activity, fVa696 and fVa709 had reduced clotting activities compared to fVaWT and plasma-derived fVa. This level of clotting activity was similar to the clotting activity of a fV molecule that was treated with thrombin and human neutrophil elastase (HNE) resulting in fVaHNE. fVaHNE is cleaved at Ala677/Thr678 resulting in a cofactor with a shorter heavy chain. Further analyses revealed that all mutant recombinant molecules as well as fVaHNE have similar KD values for fXa when compared to plasma fVa and fVaWT. SDS-PAGE analyses of prothrombin activation time courses revealed that the overall cleavage of prothrombin by prothrombinase assembled with fVa696, fVa709, or fVaHNE was slower resulting in accumulation of meizothrombin. This data confirm our previous findings and suggest that this region on the heavy chain of fVa contribute to cofactor function. A logical explanation for these findings is that the COOH-terminus of the heavy chain of fVa participates in the regulation of the rates of appearance/disappearance of meizothrombin. Increased persistence of meizothrombin in the reaction mixture can explain the slower clotting times since it is well known that meizothrombin has poor clotting activity. Thus at a given time point there will be more meizothrombin present in a sample where prothrombinase was assembled with fVa709, or fVa696, or fVaHNE than in a sample where prothrombinase was formed with fVaWT. Overall the data suggests that the COOH-terminal portion of the factor Va heavy chain contributes to the appropriate orientation of prothrombin with respect to the catalytic site of fXa resulting in efficient cleavages at Arg320 /Arg271 and competent thrombin formation.
22
Kretz, Colin, Karl Cuddy, Alan Stafford, James Fredenburgh, Robin Roberts, and Jeffrey Weitz. "HD1, a thrombin- and prothrombin-binding DNA aptamer, inhibits thrombin generation by attenuating prothrombin activation and thrombin feedback reactions." Thrombosis and Haemostasis 103, no. 01 (2010): 83–96. http://dx.doi.org/10.1160/th09-04-0237.
Full textAbstract:
SummaryHD1, a DNA aptamer, binds exosite 1 on thrombin and blocks its clotting activity. Because HD1 also binds prothrombin and inhibits its activation by prothrombinase, we hypothesised that HD1 would be a more potent inhibitor of coagulation than other exosite 1-directed ligands, such as Hir54–65(SO3 -). Supporting this concept, the effect of HD1 on the prothrombin time and activated partial thromboplastin time was twofold greater than that of Hir54–65(SO3 -) even though both agents inhibited thrombin-mediated factor (F) V and FVIII activation to a similar extent. In thrombin generation assays, HD1 (a) delayed the lag time, (b) reduced peak thrombin concentration, and (c) decreased endogenous thrombin potential to a greater extent than Hir54–65(SO3 -). To eliminate thrombin feedback, studies were repeated in FV- and/or FVIII-deficient plasma supplemented with FVa and/or FVIIIa. Only HD1 prolonged the lag time in FV- and FVIII-deficient plasma supplemented with FVa and FVIIIa. In contrast, HD1 and Hir54–65(SO3 -) inhibited the lag time in FVIII-deficient plasma supplemented with FVIIIa and in normal plasma. The more potent anticoagulant properties of HD1, therefore, reflect its capacity to attenuate FV activation by thrombin and inhibit prothrombinase assembly. These findings identify prothrombin as a potential target for new anticoagulants.
23
Rezaie, Alireza R. "Prothrombin protects factor Xa in the prothrombinase complex from inhibition by the heparin-antithrombin complex." Blood 97, no. 8 (April 15, 2001): 2308–13. http://dx.doi.org/10.1182/blood.v97.8.2308.
Full textAbstract:
Abstract Heparin is a commonly used anticoagulant drug. It functions primarily by accelerating the antithrombin inhibition of coagulation proteinases, among which factor Xa and thrombin are believed to be the most important targets. There are conflicting results as to whether anticoagulant heparins can catalyze the antithrombin inhibition of factor Xa in the prothrombinase complex (factor Va, negatively charged membrane surfaces, and calcium ion), which is the physiologically relevant form of the proteinase responsible for the activation of prothrombin to thrombin during the blood coagulation process. In this study, a novel assay system was developed to compare the catalytic effect of different molecular-weight heparins in the antithrombin inhibition of factor Xa, either in free form or assembled into the prothrombinase complex during the process of prothrombin activation. This assay takes advantage of the unique property of a recombinant mutant antithrombin, which, similar to the wild-type antithrombin, rapidly inhibits factor Xa, but not thrombin, in the presence of heparin. A direct prothrombinase inhibition assay, monitoring thrombin generation under near physiological concentrations of prothrombin and antithrombin in the presence of therapeutic doses of low- and high-molecular-weight heparins, indicates that factor Xa in the prothrombinase complex is protected from inhibition by antithrombin more than 1000 times, independent of the molecular size of heparin.
24
Hirbawi, Jamila, and Michael Kalafatis. "The Regulatory Function of Amino Acid Region 659–663 of Factor Va on Prothrombinase during Thrombin Formation." Blood 112, no. 11 (November 16, 2008): 2012. http://dx.doi.org/10.1182/blood.v112.11.2012.2012.
Full textAbstract:
Abstract Following vascular injury, the process of hemostasis facilitates the generation of thrombin, which in turn allows the formation of a fibrin clot. Without the proper regulation of this process, serious life threatening conditions, such as DVT (deep vein thrombosis), can occur. The proteolytic conversion of prothrombin to thrombin is catalyzed by the prothrombinase complex composed of the enzyme, factor Xa (fXa), the cofactor, factor Va (fVa), assembled on a membrane surface in the presence of divalent metal ions. The incorporation of factor Va (fVa) into the prothrombinase complex results in a 300,000-fold increase in the catalytic efficiency of factor Xa (fXa) for thrombin generation. Factor Va is composed of heavy and light chains. The light chain of the cofactor contains the binding sites of the cofactor to the membrane surface while the heavy chain contains binding sites for the other components of prothrombinase. Portions of the fVa heavy chain have been found to act as fXa binding sites. It has been demonstrated that the COOH-terminal region of factor Va contains cluster of acidic amino acids that are crucial for its cofactor activity. More specifically, amino acid region 695–698 from fVa heavy chain regulates the rate of cleavage of prothrombin at Arg271 by prothrombinase. The COOH-terminal portion of the heavy chain also contains another cluster of acidic amino acids (encompassing residues 659–663). Site-directed mutagenesis was performed to generate a factor V (fV) molecule with region Asp659-Asp663 (fV663) deleted. We have also constructed mutant molecules with regions Lys680-Arg709 and Asp659-Asp663 (fV663+709)) deleted from the COOH-terminal region of the heavy chain. Finally, a mutant molecule containing point mutations in region Asp659-Asp663 where the five amino acids in this sequence are mutated to all lysines (fV5K), was also constructed. These recombinant molecules along with wild type fV (fVWT) were transiently expressed in COS7L cells and assessed for their capability to promote prothrombin activation following activation by thrombin. Prothrombin activation by prothrombinase assembled with the mutant molecules was evaluated by SDS-PAGE and the kinetic parameters of the reactions were determined. SDS-PAGE analyses of prothrombin activation time courses revealed that the overall cleavage of prothrombin by prothrombinase assembled with the recombinant mutant molecules was slower. Two-stage clotting assays revealed that FV663+709, fVa5K, and fVa663 all had reduced clotting activities compared to fVaWT and plasma-derived fVa. Kinetic analyses demonstrated that Kd values for fXa of all the mutants were similar to fVaWT. However, kcat values for the various molecules varied. The kcat values for prothrombinase assembled with fVa5K, and fVa663 were 10-fold reduced when compared to the values obtained with prothrombinase assembled with fVaWT, while prothrombinase assembled with fVa663+709 had a kcat value that was sligtly lower than that of fVaWT. Our data suggest that amino acid region 659–663 from fV plays a crucial role for fVa cofactor acivity and overall the data demonstrate that acidic amino acids from the COOH-terminus of the factor Va heavy chain play a preeminent role in proper prothrombinase complex assembly and function, resulting in competent thrombin formation. These data assign an important regulatory role of the acidic COOH-terminal region of fVa to the activity of factor Xa within prothrombinase. Finally, our data aid in further studies that may lead to the development of small synthetic molecules that could be used as anticoagulants in individuals with thrombotic tendencies.
25
Greene, Lindsey A., Nabil K. Thalji, Harlan Bradford, Sriram Krishnaswamy, and Rodney M. Camire. "Prothrombin Membrane Binding and Gla-Dependent Function Are Not Required for Effective Hemostasis In Vivo." Blood 126, no. 23 (December 3, 2015): 124. http://dx.doi.org/10.1182/blood.v126.23.124.124.
Full textAbstract:
Abstract Prothrombin, like other vitamin K-dependent coagulation factors, undergoes γ-carboxylation of its Gla domain, a posttranslational modification critical for membrane binding. In patients on anticoagulant treatment with warfarin, the INR has historically been correlated with the degree of des-gamma-carboxy-prothrombin (DCP or PIVKA-II). PIVKA-II can be measured readily and used as a marker for vitamin K deficiency or warfarin therapy and is thought to be useful in detecting subclinical disease. Long-standing dogma suggests prothrombin γ-carboxylation is necessary for prothrombin membrane binding facilitating engagement with prothrombinase leading to rapid thrombin generation and effective hemostasis. However, recent studies indicate that despite an inability to bind membranes, uncarboxylated (desGla) full-length prothrombin demonstrated an unexpected modest decrease in the rate of thrombin generation (J Biol Chem 2013, 288:27789-800). Thus, it is possible loss of prothrombin γ-carboxylation, and thereby membrane binding, is far less significant for prothrombin activation than previously appreciated. Instead warfarin's effect on other coagulation factors (FX, FIX, and FVII) may be the primary causative determinant impairing hemostasis in these anticoagulated patients. To test these ideas, we first analyzed thrombin generation using recombinant full-length fully carboxylated and desGla prothrombin in vitro. Human prothrombin deficient plasma (Factor II activity <4%) was reconstituted to normal levels (100 μg/mL) with desGla or carboxylated prothrombin. DesGla prothrombin generated approximately half the amount of thrombin observed in carboxylated prothrombin plasma and normal human plasma controls. We next analyzed full-length desGla prothrombin's in vivo hemostatic function. A prothrombin anti-sense oligonucleotide (ASO) was administered to hemostatically normal mice to knock down endogenous murine prothrombin expression (<0.1-1μg/mL, 0.1-1%) and confirmed by ELISA analysis. Hemostasis was analyzed by the ferric chloride (FeCl3) carotid artery injury model. In mice treated with an ASO control, vessel occlusion occurred at approximately 8 minutes while mice treated with the prothrombin ASO did not clot during the 30-minute post injury observation period. In additional experiments two minutes following injury, prothrombin ASO treated mice were administered either carboxylated or desGla recombinant prothrombin to restore plasma concentrations to the normal range (100 μg/mL). Remarkably, administration of either desGla or carboxylated prothrombin restored vessel occlusion to ASO control findings, with minimal variability observed between desGla and carboxylated prothrombin treated mice (Figure 1). Warfarin treatment results in impaired prothrombin γ-carboxylation. However, if prothrombin γ-carboxylation, is, in fact, not necessary for prothrombin activation, fully carboxylated Factor Xa (FXa) should reverse the effects of warfarin by efficiently activating the un/under-carboxylated prothrombin thereby bypassing the other warfarin-affected factors. To study this, we used a "zymogen-like" factor Xa (FXaI16L) molecule previously developed by our group (Nat. Biotech 2011, 29:1028-33) that has a greater half-life than the wild-type protein. In thrombin generation assays, addition of 1nM FXaI16L to plasma from patients anticoagulated with warfarin, irrespective on INR (2.8, 4,4 7.1), resulted in thrombin generation comparable to that of normal human plasma. Importantly, similar results were obtained in vivo in warfarin-anticoagulated mice (INR 2-3). Administration of 3 mg/kg FXaI16L to 8 out of 8 warfarin mice corrected the time to carotid artery occlusion in the FeCl3 injury model. In two separate in vitro and in vivo model systems, we demonstrated that prothrombin membrane binding is not absolutely required for thrombin generation. Thrombin is unique among the coagulation serine proteases in that it does not have a Gla domain once fully processed by prothrombinase; thus, the absence of a Gla domain in the protease (thrombin) may explain the lack of a requirement for membrane binding by the zymogen (prothrombin) precursor. Our findings may also have clinical relevance, since they suggest that FXa (or a variant) could be used as a novel warfarin bypass strategy to rapidly achieve hemostasis in the setting of warfarin anticoagulation. Figure 1. Figure 1. Disclosures Greene: Baxter: Research Funding. Camire:Spark Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Patents & Royalties, Research Funding; NovoNordisk: Research Funding.
26
Abrams, Simon Timothy, Dunhao Su, Yasmina Sahraoui, Yasir Alhamdi, Guozheng Wang, and Cheng Hock Toh. "Histones Bind Prothrombin to Generate Alternative Prothrombinase Complexes That Can Disseminate Intravascular Coagulation." Blood 132, Supplement 1 (November 29, 2018): 218. http://dx.doi.org/10.1182/blood-2018-99-116117.
Full textAbstract:
Abstract Background: Increased thrombin generation in vivo is pivotal to the development of disseminated intravascular coagulation (DIC). Typically, thrombin is generated when the prothrombinase complex, composed of activated factor X (FXa), activated co-factor V (FVa) and phospholipids, cleaves prothrombin in the presence of calcium. In critical illness, extensive cell death releases histones into the circulation, which can increase thrombin generation. However, the underlying pathophysiological mechanisms remains to be fully elucidated. Methods: In vitro: Isolation of histone-binding proteins with mass spectrometry analysis. Surface plasmon resonance binding studies, prothrombin cleavage and thrombin generation assays. In vivo: histone infusion mouse models (C57BL/6 mice) with or without prothrombin fragment F1+F2 infusion. Clinical: a prospective cohort of 129 adult intensive care unit patients (ICU) with sepsis and analysed for DIC. Results: Histone-conjugated Sepharose beads were used to pull down proteins from human plasma. Histone-binding proteins were subjected to 2D gel electrophoresis and sequenced by liquid chromatography-mass spectrometry. Prothrombin was the only coagulation factor identified. Histones directly bind to prothrombin (H3 [Kd = 6.8 x 107 M] and H4 [Kd = 7.0 x 107 M]), specifically prothrombin fragments F1+F2, to facilitate FXa-induced prothrombin cleavage and thrombin generation (H4 [12.25 ± 1.25 fold] and H3 [8.82 ± 0.67 fold]). FXa levels are the limiting factor of histone-enhanced thrombin generation since this process was inhibited in FX-deficient plasma unless exogenous FXa was added. Specifically, using either heparin or anti-histone antibodies to block histones, histone-prothrombin interactions, prothrombin cleavage and subsequent thrombin generation were significantly reduced. Unlike FVa which requires a phospholipid surface to form functional prothrombinase complexes, histones can substitute for FVa in the absence of phospholipids. The addition of histones to FV-deficient plasma restored thrombin generation, suggesting that histones can bypass FVa to induce thrombin generation. In vivo, infusion of histones into mice caused significant decreases in platelet counts and fibrinogen levels with elevations in thrombin-antithrombin complexes, D-dimer and prothrombin time in a dose-dependent manner. Pathological examination indicated intravascular thrombi with various organs, particularly in within lung tissues. These histone-induced DIC changes were significantly abrogated when prothrombin fragments F1+F2 were infused prior to histones to act as a decoy for binding of histones to circulating prothrombin. Analysis of DIC scores in ICU patients (n=129) with sepsis showed circulating histone levels to strongly correlate with DIC scores (r=0.446, p<0.0001). Conclusions: Histones can replace FVa in prothrombinase and not require phospholipid surfaces. This alternative histone-assembled prothrombinase can explain how thrombin could be generated and amplified away from cell surfaces to cause systemic dissemination of its effects and potentiate DIC. This study also identifies circulating histones as a potential target for therapeutic intervention in reducing DIC development and subsequent multi-organ failure in ICU patients. Disclosures No relevant conflicts of interest to declare.
27
Feryal Hashim Rada. "Platelet reactivity with a third generation thienopyridine drug versus with a second-generation thienopyridine drug." International Journal of Research in Pharmaceutical Sciences 11, no. 3 (July 18, 2020): 3704–9. http://dx.doi.org/10.26452/ijrps.v11i3.2534.
Full textAbstract:
Prasugrel is a third generation thienopyridine drug and Clopidogrel is a second-generation thienopyridine drug. Both drugs used for reducing platelet aggregation in patients with coronary artery diseases.The aim of this study is to investigate the antiplatelet efficacy and safety of Prasugrel 5mg daily as compared to Clopidogrel 75 mg daily for period along to 12 days treatment.Fifty patients, (10 females, 40 males), their ages ranging from (50- 60) years with stable angina were recruited from IbnAlbitar Center for Cardiac Surgery and enrolled in this case study.Of whom 25 patients (group A) received a dose of 75 mg daily of Clopidogrel and other 25 patients (group B) were on a dose of 5 mg daily of Prasugrel for a period of 12 days .Clinical laboratory data of lipid profile, renal function, and prothrombine time obtained at baseline (before treatment). While Platelet aggregation percent measured at the baseline and after 12 days of treatment.The maximal platelet aggregation percent for group A was fell from 78 % ± 6.3 (baseline) to 43.5% ± 5.8 (after 12 days treatment).While patients of group B showed dropping in the maximal platelet aggregation percent from 76 % ± 7.4 (baseline) to 27.3 % ± 5.7 (after 12 days treatment). Analysis of adverse events showed three patients with minor bleeding occurred during Prasugrel treatment, and no bleeding occurred during Clopidogrel treatment. Compared with Clopidogrel 75mg treatment, Prasugrel 5mg treatment for 12 days averted platelets accumulation more quickly and steadily.
28
Hirbawi, Jamila, Paul Y. Kim, Michael E. Nesheim, and Michael Kalafatis. "The Role of Amino Acids 700–701 of the Factor Va Heavy Chain During Prothrombin Activation by Factor Xa." Blood 116, no. 21 (November 19, 2010): 2203. http://dx.doi.org/10.1182/blood.v116.21.2203.2203.
Full textAbstract:
Abstract Abstract 2203 Blood coagulation is initiated after vascular injury, promoting formation of the fibrin plug. The prothrombinase complex plays a crucial role during activation of prothrombin (Pro) to thrombin. The complex is composed of the enzyme, factor Xa (fXa), along with its non-enzymatic cofactor, factor Va (fVa), in the presence of calcium on a phospholipid surface. The incorporation of fVa into the prothrombinase complex results in a 300,000-fold increase in the catalytic efficiency of fXa for thrombin generation. Prothrombinase activates prothrombin through initial cleavage at Arg320 followed by cleavage at Arg271 to yield human alpha-thrombin. This pathway is responsible for the generation of a transient catalytically active intermediate, meizothrombin. Recent data has suggested a differential effect of bovine and human factor Va on prothrombin-1 (Pre-1) activation by prothrombinase. This difference was localized within the last ten amino acids from the carboxyl-terminal region of fVa heavy chain. The only amino acid difference between the two cofactor molecules is localized at position 700–701 where the Asn-Arg dipeptide in the fVa of human origin is replaced by the Asp-Glu sequence in the carboxyl-terminal region of the cofactor of bovine origin. We have therefore constructed a recombinant human mutant fVa molecule with these amino acids mutated to their bovine counterpart. We have created a recombinant fVa molecule with the mutation700NR701 →DE. This recombinant cofactor molecule (fVDE) along with wild type factor V (fVWT) were transiently expressed in COS7 cells, purified to homogeneity, and assessed for their capability to by assembled in prothrombinase and promote Pro activation. Thrombin generation was evaluated by SDS-PAGE in a system using all proteins of human origin and the kinetic parameters of the reactions were determined using a chromogenic substrate to assess for thrombin activity. Kinetic analyses revealed that the Kd of fVaDE for human fXa, as well as the kcat and Km values of prothrombinase assembled with fVaDE for human Pro activation were similar to the values obtained following Pro activation by prothrombinase assembled with fVaWT. Surprisingly, SDS-PAGE analyses of prothrombin activation time courses revealed that the overall rate of cleavage of Pro by prothrombinase assembled with fVaDE was significantly delayed with significant accumulation of the intermediate meizothrombin, and delayed thrombin generation when compared to the rate of activation of Pro by prothrombinase assembled with fVaWT. Two-stage clotting assays (PT times) also revealed that fVaDE had reduced clotting activity when compared to fVaWT. Comparison of the rate of cleavage of two recombinant Pro mutant molecules, rMZ-II a recombinant Pro molecule that cannot be cleaved at Arg271 and rP2-II a recombinant Pro molecule that cannot be cleaved at Arg320, by prothrombinase assembled with fVaDE demonstrated impaired rate of cleavage of both substrates when compared to the rate of cleavage of the mutant recombinant Pro molecules by prothrombinase assembled with fVaWT. These findings were verified by experiments using active-site blocked purified human meizothrombin (FPR-meizo). Prothrombinase assembled with fVaDE was considerably impaired in its ability to cleave FPR-meizo at Arg271 as compared to the ability of prothrombinase assembled with fVaWT for the same cleavage. In fact, gel electrophoresis analyses demonstrated that prothrombinase assembled with fVaDE cleaves FPR-meizo with a rate similar to the cleavage of FPR-meizo by fXa alone. All these data together strongly suggest that the 700NR701 portion of the COOH-terminus of the fVa heavy chain plays a significant role in enzyme-substrate recognition/interaction during Pro activation by prothrombinase and thus regulates the rates of thrombin formation locally at the place of vascular injury. Disclosures: No relevant conflicts of interest to declare.
29
&NA;. "EVALUATING PROTHROMBIN TIME." Nursing 21, no. 11 (November 1991): 29. http://dx.doi.org/10.1097/00152193-199111000-00011.
Full text
30
Hameeuw, L., L. Sierens, and A. Lust. "Prothrombin Time Standardization." Acta Clinica Belgica 42, no. 4 (January 1987): 238–46. http://dx.doi.org/10.1080/22953337.1987.11719232.
Full text
31
&NA;. "Monitoring Prothrombin Time." Journal of Neuroscience Nursing 32, no. 4 (August 2000): 240. http://dx.doi.org/10.1097/01376517-200008000-00013.
Full text
32
Patel, Sanjay, Leslie R. Berry, Lesley Smith, and Anthony Chan. "Inhibition of Factor Xa in Prothrombinase Is Enhanced by Covalent Linkage of Antithrombin to Heparin." Blood 108, no. 11 (November 16, 2006): 1613. http://dx.doi.org/10.1182/blood.v108.11.1613.1613.
Full textAbstract:
Abstract The rate of prothrombin to thrombin conversion by factor Xa (Xa) is enhanced when Xa is incorporated into the surface-bound prothrombinase complex. However, in comparison to the free state, Xa within the prothrombinase complex is afforded protection from antithrombin + heparin (AT+H) inactivation. We have shown that, unlike AT+H, a covalent conjugate of AT and H (ATH) can neutralize fibrin-bound thrombin. In this study, AT+H and ATH were compared in their reaction with Xa +/− prothrombinase complex. Mixtures of CaCl2, phospholipid vesicles, factor Va (Va) and prothrombin in TSP buffer, were combined with Xa. Following addition of either AT+H or ATH, time samples were neutralized with Na2EDTA + polybrene + substrate (S-2222) and residual Xa activity measured. Second order rate constants (k2) were calculated from plots of activity versus time. Results were compared to corresponding experiments with Xa alone. AT+H inactivation of Xa in prothrombinase occurred at a k2 (x 107 M−1min−1) of 2.34 +/− 0.09. In contrast, neutralization of free Xa by AT+H was significantly faster (k2 = 8.34 +/− 0.18, p = 0.03). Reaction with ATH showed no significant rate difference for Xa inhibition in either the complexed or free states (18.5 +/− 3.3 and 16.3 +/− 3.7, respectively). Intriguingly, the rates achieved for ATH inhibition of complexed and free Xa were significantly greater than that for AT+H with free Xa (p=0.03 and p=0.02, respectively). We conclude that covalent complexes of AT and H do not encounter resistance in the inhibition of Xa in prothrombinase, as seen for non-covalent AT+H mixtures. Thus, it is possible for ATH to effectively inhibit the propagation phase of thrombin generation and thus dampen thrombin production via neutralization of Xa in prothrombinase.
33
Hollenbach, Stan, Uma Sinha, Pei-Hua Lin, Kathy Needham, Lisa Frey, Tom Hancock, Arnold Wong, and David Wolf. "A Comparative Study of Prothrombinase and Thrombin Inhibitors in a Novel Rabbit Model of Non-Occlusive Deep Vein Thrombosis." Thrombosis and Haemostasis 71, no. 03 (1994): 357–62. http://dx.doi.org/10.1055/s-0038-1642443.
Full textAbstract:
SummaryA quantitative and non-occlusive deep vein thrombosis model was developed in rabbits. We used this model to test the antithrombotic activity of the prothrombinase complex inhibitors factor rXai and its chemical analog glutamyl-glycyl-arginyl chloromethyl ketone inactivated human factor Xa (EGR-Xai), along with the thrombin inhibitors D-phenylalanyl-prolyl-arginyl chloromethyl ketone (PPACK) and heparin. Dose dependent effects of the inhibitors during constant infusion were monitored. Measurements included thrombus weights, hemostatic parameters and both cuticle and ear bleeding times. In this model, factor rXai and EGR-Xai had comparable in-vivo efficacy, and showed 80%-93% inhibition at plasma levels of 6.5 nM (rXai) and 8 nM (EGR-Xai). Effects on ex-vivo clotting times varied among the inhibitors. At 80-100% thrombus inhibition, factor rXai and EGR-Xai had no statistically significant effect, while PPACK extended thrombin clotting time (TCT) times 2.3-fold, and heparin prolonged both activated partial thromboplastin time (APTT), prothrombin time (PT) and TCT ex-vivo clotting times 6.9-, 1.2-, and 7-fold respectively. At these dosages, cuticle and ear bleeding times were prolonged for all inhibitors and showed increases of 177%-389% (cuticle) and 45%-129% (ear). Our results demonstrate that direct inhibition of prothrombinase complex assembly is effective in arresting venous thrombosis.
34
Patel, Hemaxi, Toral Jivani, and Purvi Patel. "Comparative Study of Prothrombin Time, Activated Partial Thromboplastin Time and Platelet Counts in Type II Diabetes Mellitus and Healthy Individual." Indian Journal of Pathology: Research and Practice 8, no. 5 (2019): 686–89. http://dx.doi.org/10.21088/ijprp.2278.148x.8519.26.
Full text
35
COHEN, MYRON S. "Cefoperazone and Prothrombin Time." Annals of Internal Medicine 106, no. 5 (May 1, 1987): 778. http://dx.doi.org/10.7326/0003-4819-106-5-778_1.
Full text
36
Chazouilléres, Olivier, and Annie Robert. "Normalizing the prothrombin time." Hepatology 32, no. 4 (October 2000): 881. http://dx.doi.org/10.1053/jhep.2000.18710.
Full text
37
Malinchoc, Michael, and Patrick S. Kamath. "Normalizing the prothrombin time." Hepatology 32, no. 4 (October 2000): 881a. http://dx.doi.org/10.1053/jhep.2000.18711.
Full text
38
Talstad, Ingebrigt, and Knut Korsbrekke. "Simplified Prothrombin Time Standardization." Pathophysiology of Haemostasis and Thrombosis 24, no. 1 (1994): 4–13. http://dx.doi.org/10.1159/000217074.
Full text
39
Richards, FrankO, MaryseB Mcneeley, RalphT Bryan, MarkL Eberhard, DavidF Mcneeley, PatrickJ Lammie, HarrisonC Spencer, et al. "IVERMECTIN AND PROTHROMBIN TIME." Lancet 333, no. 8647 (May 1989): 1139–40. http://dx.doi.org/10.1016/s0140-6736(89)92418-5.
Full text
40
Perzborn, Elisabeth, Adrian Tersteegen, Michaela Harwardt, and Uwe Lange. "Different Characteristics of Direct Factor Xa Inhibitors: In Vitro Comparative Studies of Rivaroxaban and Apixaban." Blood 114, no. 22 (November 20, 2009): 4170. http://dx.doi.org/10.1182/blood.v114.22.4170.4170.
Full textAbstract:
Abstract Abstract 4170 Introduction Rivaroxaban and apixaban are selective, reversible but structurally different direct Factor Xa inhibitors that are in late-stage clinical development for the prevention and treatment of venous and arterial thrombosis. Studies in animal models demonstrated antithrombotic efficacy with these new agents (Perzborn E et al. J Thromb Haemost 2005;3:514–521; Wong PC et al. J Thromb Haemost 2008;6:820–829). The objective of this study was to characterize and compare in vitro rivaroxaban and apixaban in functional assays. Methods Factor Xa activity, rate constants (kon/koff), and prothrombinase activity were measured using purified Factor Xa and measuring the cleavage of chromogenic (Factor Xa), fluorogenic substrates (kon/koff), or using prothrombin as a substrate in a reconstituted prothrombinase complex and measuring the activity of the generated thrombin in the presence of a thrombin-specific chromogenic substrate. Clotting times and thrombin generation (TG) were measured using commercially available kits. Tissue factor (TF)-mediated platelet aggregation was measured in defibrinated plasma. Results Rivaroxaban and apixaban showed similar affinity for free Factor Xa (Ki 0.4 and 0.6 nM, respectively), comparable association (kon 1.7 × 107 M–1 s–1 and 0.88 × 107 M–1 s–1, respectively) and dissociation (koff 5 × 10–3 s–1 and 2.4 × 10–3 s–1, respectively) rates, and inhibition of prothrombinase-bound Factor Xa (2.1 nM and 2.7 nM, respectively; Table). However, in human plasma-based systems, the 2 agents showed different potency. Despite the reported comparable plasma protein binding for apixaban and rivaroxaban (87% and 92–95%, respectively), higher concentrations of apixaban were needed to inhibit TG and TF-mediated platelet aggregation, and to prolong clotting time, compared with rivaroxaban. The concentrations needed to double clotting times, such as prothrombin time, activated partial thromboplastin time, clotting times in thromboelastometric measurements triggered either by the extrinsic (ex-TEM®) or intrinsic (in-TEM®) coagulation pathway, and prothrombinase-induced clotting time, were 3- to 8-fold higher for apixaban than for rivaroxaban (Table). The IC50 values for reducing the peak TG and endogenous thrombin potential in the TG assay were 3-fold higher for apixaban (0.20 and 4.96 μM, respectively) compared with rivaroxaban (0.06 and 1.48 μM, respectively; Table). The IC50 values for inhibiting TF-mediated platelet aggregation were 8-fold higher for apixaban (0.51 μM) versus rivaroxaban (0.06 μM; Table). Conclusions These results demonstrate that structurally different Factor Xa inhibitors may differ in their antihemostatic potency in spite of comparable affinity to Factor Xa, and suggest that rivaroxaban may be a more potent anticoagulant and indirect inhibitor of platelet aggregation than apixaban. Disclosures: Perzborn: Bayer Schering Pharma AG: Employment. Tersteegen:Bayer Schering Pharma AG: Employment. Harwardt:Bayer Schering Pharma AG: Employment. Lange:Bayer Schering Pharma AG: Employment.
41
Hackeng, Tilman M., Peter van Doorn, Jan Rosing, Joost Meijers, Saskia Middeldorp, Paolo Simioni, and Elisabetta Castoldi. "A Plasma-Based Assay to Measure the Susceptibility of Factor V(a) to Inhibition By TFPIα." Blood 132, Supplement 1 (November 29, 2018): 1168. http://dx.doi.org/10.1182/blood-2018-99-118767.
Full textAbstract:
Abstract Background: Coagulation factor V (FV) is the precursor of activated FV (FVa), which assembles with factor Xa (FXa) on phospholipid surfaces to form the prothrombinase complex, accelerating prothrombin activation >1000-fold. FV is activated by FXa or thrombin via limited proteolysis at Arg709, Arg1018 and Arg1545. These cleavages progressively expose the FXa-binding site, generating activation intermediates with increasing affinities for FXa. Recently, it has been shown that tissue factor pathway inhibitor α (TFPIα) inhibits both the activation of FV (by interfering with cleavage at Arg1545) and the ability of partially activated FV(a) species to enhance prothrombin activation. These effects are mediated by interactions of the C-terminus of TFPIα with an acidic region in the B-domain of FV as well as with the FV(a) heavy chain. The pathophysiological relevance of these novel anticoagulant activities of TFPIα is still unexplored, but evidence has been provided that prothrombinase complexes assembled with FV(a) Leiden are less susceptible to TFPIα inhibition. Moreover, FV splicing variants (FV-short) with increased affinity for TFPIα have recently been discovered in two unrelated families (from East Texas and Amsterdam, respectively) with bleeding tendencies. Rationale and Aim: The FV present in plasma from different individuals may differ in its sensitivity to inhibition by TFPIα, with potential implications for the risk of venous thrombosis or bleeding. Therefore, the aim of this study was to develop a plasma-based assay that measures the susceptibility of FV(a) to TFPIα inhibition. Methods: FV in 1/1000 diluted plasma was activated for 3 minutes with a suboptimal FXa concentration on 20/60/20 DOPS/DOPC/DOPE lipids in the presence or absence of a peptide mimicking the C-terminus of TFPIα (TFPIα C-term). Purified prothrombin and a chromogenic substrate for thrombin were then added, and the activity of the prothrombinase complex was monitored continuously up to 30 minutes. The parabolic absorbance curves were fitted to second-order polynomial equations and the rate of prothrombin activation was calculated from the coefficient of the x2-term. The assay outcome was expressed as residual prothrombinase ratio (RP-ratio), defined as the ratio between the rates of prothrombin activation obtained in the presence and absence of TFPIα C-term. The assay was validated using plasma from 4 FV Leiden homozygotes and 4 normal controls. In addition, we tested plasma from 3 members of the FV Amsterdam family (2 carriers of the mutation up-regulating FV-short Amsterdam and 1 non-carrier). Results: The rate of prothrombin activation in the absence of peptide was a function of plasma FV level and pre-incubation time, and was inhibited by TFPIα C-term in a dose-dependent manner. A pre-incubation time of 3 minutes and a peptide concentration of 100 nM, yielding an RP-ratio of 0.30 in normal pooled plasma, were chosen. The RP-ratio was independent of the plasma FV level in the 75-150% range. Moreover, control experiments indicated that, at this high dilution, the plasma background did not influence the assay outcome. The intra- and inter-assay coefficients of variation of the RP-ratio were 5.4% and 12%, respectively. FV Leiden homozygotes had higher RP-ratios than normal controls (0.45 ± 0.04 vs. 0.30 ± 0.03, p=0.002), indicating resistance to inhibition by TFPIα C-term. Differently, the 2 carriers of the FV Asterdam mutation, who express high levels of FV-short Amsterdam, had markedly reduced RP-ratios (0.18 and 0.16 vs. 0.29 in the non-carrier), as expected from the high affinity of FV-short Amsterdam for TFPIα. Conclusions: We have developed and validated an assay that measures the susceptibility of plasma FV(a) to inhibition by TFPIα. This assay can be used to test whether TFPIα-mediated inhibition of FV activation and prothrombinase activity differs for (genetically) different FV variants and whether it correlates with the risk of thrombosis or bleeding. Supported by grant 2014-1 from the Dutch Thrombosis Foundation. Disclosures No relevant conflicts of interest to declare.
42
Cvirn, Gerhard, Wolfgang Muntean, and Siegfried Gallistl. "Recombinant Factor VIIa Does not Induce Hypercoagulability In Vitro." Thrombosis and Haemostasis 81, no. 02 (1999): 245–49. http://dx.doi.org/10.1055/s-0037-1614451.
Full textAbstract:
SummaryRecombinant factor VIIa (rVIIa) has been reported to be clinically effective and safe in haemophilic patients with inhibitor antibodies. Compared to activated prothrombin complex concentrates the risk of thrombotic complications seems to be very low after rVIIa administration. Determination of free thrombin generation has been shown to identify hypercoagulability. Therefore, free thrombin and prothrombinase activity (Xa generation) were assessed after extrinsic activation of rVIIa supplemented factor VIII and factor IX deficient plasma. Free thrombin generation was also determined after supplementation of (activated) prothrombin complex concentrates. Addition of 150 U rVIIa/ml shortened the clotting times markedly in control, factor VIII, and factor IX deficient plasma. In contrast, free thrombin and Xa generation were not different in the absence or presence of 150 U rVIIa/ml. Addition of (activated) prothrombin complex concentrates resulted in a marked increase of free thrombin generation in all investigated plasmas. Although in vitro studies cannot reflect specific clinical circumstances our results support the notion that rVIIa does not induce a hypercoagulable state as sporadically observed after administration of (activated) prothrombin complex concentrates.
43
Oosting, JD, RH Derksen, IW Bobbink, TM Hackeng, BN Bouma, and PG de Groot. "Antiphospholipid antibodies directed against a combination of phospholipids with prothrombin, protein C, or protein S: an explanation for their pathogenic mechanism? [see comments]." Blood 81, no. 10 (May 15, 1993): 2618–25. http://dx.doi.org/10.1182/blood.v81.10.2618.2618.
Full textAbstract:
Abstract Despite many studies on the pathophysiology of antiphospholipid antibodies (aPL), the mechanism by which aPL causes thrombosis has not been established. We have tried to elucidate the paradox between the prolongation of the clotting time of phospholipid-dependent coagulation tests in vitro and the occurrence of thrombosis in vivo. The effect on endothelial cell-mediated prothrombinase activity of 30 IgG fractions, of which 22 prolong the aPTT of normal plasma, was investigated. Only 4 of 22 fractions (18%) inhibited prothrombinase activity when tested on this more physiologic phospholipid surface, indicating that in most patients with aPL the prolongation of clotting tests is predominantly as in vitro phenomenon. It was recently reported that in detection methods for aPL, two plasma proteins, beta 2-glycoprotein I and prothrombin, enhance the binding of aPL to phospholipids. We have studied the specificity of the 4 IgG fractions that inhibit the prothrombinase activity and found that they were directed against a combination of phospholipids and prothrombin. However, the involvement of prothrombin in binding of aPL leading to impaired thrombin generation could still result in both a bleeding and a thrombotic tendency. Therefore, we proposed a new thrombogenic mechanism for aPL in which aPL bind to complexes of phospholipids and coagulation proteins, thereby interfering in different coagulation reactions. We tested this new hypothesis by investigating the effect of IgG from the same 30 patients on the activated protein C (APC)-mediated factor Va inactivation in the absence and presence of protein S. Three IgGs that inhibited APC-mediated factor Va inactivation independent of protein S and 4 additional IgGs that inhibited in the presence of protein S were found. Furthermore, we could specifically adsorb the inhibitory IgG with cardiolipin vesicles to which APC with or without protein S was bound. In conclusion, these results suggest that subpopulations of aPL exist that are directed to complexes of phospholipids and different plasma proteins. The identity of the plasma proteins involved in the binding of aPL might determine which pathogenic mechanism causes thrombosis.
44
Oosting, JD, RH Derksen, IW Bobbink, TM Hackeng, BN Bouma, and PG de Groot. "Antiphospholipid antibodies directed against a combination of phospholipids with prothrombin, protein C, or protein S: an explanation for their pathogenic mechanism? [see comments]." Blood 81, no. 10 (May 15, 1993): 2618–25. http://dx.doi.org/10.1182/blood.v81.10.2618.bloodjournal81102618.
Full textAbstract:
Despite many studies on the pathophysiology of antiphospholipid antibodies (aPL), the mechanism by which aPL causes thrombosis has not been established. We have tried to elucidate the paradox between the prolongation of the clotting time of phospholipid-dependent coagulation tests in vitro and the occurrence of thrombosis in vivo. The effect on endothelial cell-mediated prothrombinase activity of 30 IgG fractions, of which 22 prolong the aPTT of normal plasma, was investigated. Only 4 of 22 fractions (18%) inhibited prothrombinase activity when tested on this more physiologic phospholipid surface, indicating that in most patients with aPL the prolongation of clotting tests is predominantly as in vitro phenomenon. It was recently reported that in detection methods for aPL, two plasma proteins, beta 2-glycoprotein I and prothrombin, enhance the binding of aPL to phospholipids. We have studied the specificity of the 4 IgG fractions that inhibit the prothrombinase activity and found that they were directed against a combination of phospholipids and prothrombin. However, the involvement of prothrombin in binding of aPL leading to impaired thrombin generation could still result in both a bleeding and a thrombotic tendency. Therefore, we proposed a new thrombogenic mechanism for aPL in which aPL bind to complexes of phospholipids and coagulation proteins, thereby interfering in different coagulation reactions. We tested this new hypothesis by investigating the effect of IgG from the same 30 patients on the activated protein C (APC)-mediated factor Va inactivation in the absence and presence of protein S. Three IgGs that inhibited APC-mediated factor Va inactivation independent of protein S and 4 additional IgGs that inhibited in the presence of protein S were found. Furthermore, we could specifically adsorb the inhibitory IgG with cardiolipin vesicles to which APC with or without protein S was bound. In conclusion, these results suggest that subpopulations of aPL exist that are directed to complexes of phospholipids and different plasma proteins. The identity of the plasma proteins involved in the binding of aPL might determine which pathogenic mechanism causes thrombosis.
45
Solano, C., R. G. Cobcroft, and D. C. Scott. "Prediction of Vitamin K Response Using the Echis Time and Echis-Prothrombin Time Ratio." Thrombosis and Haemostasis 64, no. 03 (1990): 353–57. http://dx.doi.org/10.1055/s-0038-1647317.
Full textAbstract:
Summary Echis carinatus venom contains proteases capable of activating both normal and descarboxy prothrombin. We showed this venom (Sigma) principally activates prothrombin with almost no factor X activation. Echis time in combination with prothrombin time can predict vitamin K responsiveness since the Echis time is usually normal in the presence of descarboxy prothrombin associated with vitamin K deficiency.38 patients with abnormal routine prothrombin times (PT) had both coagulant and immunogenic factor II assays along with Echis times done before and after vitamin K. Of 22 patients responding to vitamin K, based on correction of PT, 21 had normal initial Echis times and of 16 not responding, 11 had abnormal Echis times, giving a sensitivity of 95.4% and specificity of 68.8% for vitamin K responsiveness. 90% of patients with a PT/Echis time ratio <1.3 and a prolonged Echis time did not correct their PTs with vitamin K therapy.The 5 non-responders with normal Echis times all showed normal initial coagulant and antigenic prothrombin, but 3 had low F V and/or F VII.
46
Black, J. "Prolonged Prothrombin Time with Warfarin." Journal of the Royal Society of Medicine 83, no. 7 (July 1990): 478. http://dx.doi.org/10.1177/014107689008300732.
Full text
47
Capel, P., E. Bohy, B. Chatelain, A. Defalque, L. Rondelez, and A. Pierard. "Standardization of The Prothrombin Time." Acta Clinica Belgica 40, no. 6 (January 1985): 360–68. http://dx.doi.org/10.1080/22953337.1985.11719108.
Full text
48
Zucker, Marcia L., and Frank M. LaDuca. "Comment: Prothrombin Time Monitoring Devices." Annals of Pharmacotherapy 34, no. 7-8 (July 2000): 956–57. http://dx.doi.org/10.1345/aph.19376.
Full text
49
Hoskison, T. K. "Anticoagulation and prothrombin time ratios." Archives of Internal Medicine 152, no. 8 (August 1, 1992): 1720b—1720. http://dx.doi.org/10.1001/archinte.152.8.1720b.
Full text
50
Hoskison, T. Karl. "Anticoagulation and Prothrombin Time Ratios." Archives of Internal Medicine 152, no. 8 (August 1, 1992): 1720. http://dx.doi.org/10.1001/archinte.1992.00400200144026.
Full text