The Role Of Factor VIII: C In Fibrinogen - Fibrin Conversion

1981 ◽  
Author(s):  
T J Frost ◽  
R S Lau
Keyword(s):  
Factor Viii ◽  
Hemophilia A ◽  
Formation Rate ◽  
Fibrin Clot ◽  
Test System ◽  
Clot Formation ◽  
Thrombin Time ◽  
Factor X ◽  
Human Fibrinogen

The cascade mechanism for the coagulation pathway has prevailed since its original proposal, and subsequent observations have supported the role of thrombin on coagulation reactions other than in Fibrinogen - Fibrin conversion. In very small quantities, thrombin has been reported as increasing the activity of Factor VIII: C. We report here, observations which support a reverse proposal, namely that Factor VIII: C increases activity of thrombin in Fibrinogen - Fibrin conversion.Thrombin clotting times were performed employing human Fibrinogen solutions, fresh citrated normal platelet - poor human plasma and fresh citrated platelet - poor plasma from severely affected Hemophilia A patients, in whom Factor VIII : C assays were less than 1% in a one stage, activated partial thromboplastin time assay. A platelet aggregometer was used to assess the thrombin time, and the rate of clot formation (fibrin polymerization) was indicated by optical density change in the form of a curve, the tangent of the maximal slope of curve being equated with this clot formation rate.Results indicate that with very small concentrations of thrombin, Factor VIII: C enhances the rate of fibrin clot formation and that Factor VIII: C restores the abnormal rate of clot formation observed in severe Hemophilia A; the test system was known to be calcium-free, which ensured that activation of Factor X did not ensue. The concentration of Fibrinogen remained constant in all experiments. The observed phenomena are confirmed when employing purified fibrinogen solutions, using decreasing amounts of Factor VIII: C.

The role of blood cells in formation of hemocoagulation shifts in essential hypertension

2018 ◽  
pp. 84-92
Author(s):  
Б.И. Кузник ◽  
С.О. Давыдов ◽  
Е.С. Гусева ◽  
Ю.Н. Смоляков ◽  
А.В. Степанов ◽  
...  
Keyword(s):  
Essential Hypertension ◽  
Prothrombin Time ◽  
Blood Cells ◽  
Formation Rate ◽  
Fibrin Clot ◽  
Stage Ii ◽  
Clot Formation ◽  
Thrombin Time ◽  
Healthy Women

Цель - изучение роли отдельных форменных элементов крови в развитии гемокоагуляционного потенциала у здоровых женщин и, больных гипертонической болезнью (ГБ). Методика. В исследовании приняли участие 102 женщины. Контрольную группу составили 30 относительно здоровых женщин. Больные ГБ были разделены на 2 подгруппы: в одну (ГБ-1) вошли 37 женщин с гипертонической болезнью II стадии, в другую (ГБ-2) - 35 женщин с ГБ II стадии, регулярно проходящих на протяжении 2-3 лет по 3-4 курса кинезитерапии. Определяли число тромбоцитов, активированное частичное тромбопластиновое время (АЧТВ), протромбиновое время (ПВ), тромбиновое время (ТВ), концентрацию фибриногена и пространственный рост фибринового сгустка, включающий время задержки роста сгустка, начальную и стационарную скорость его роста, плотность и размер сгустка. С помощью корреляционного анализа оценивалась роль отдельных форменных элементов крови в развитии гемокоагуляционного потенциала у здоровых и больных ГБ женщин. Результаты. У всех обследованных женщин обнаружено увеличение числа лимфоцитов и эозинофилов, возрастание предрасположенности к тромбообразованию, выявляемое с помощью оценки тромбодинамических свойств сгустка, возрастание скорости формирования и размеры фибринового сгустка. У женщин в группе ГБ-2 эти сдвиги выражены в меньшей степени. У здоровых женщин обнаружены прямые корреляции между числом моноцитов, АЧТВ и тромбиновым временем. и отрицательные - между числом лимфоцитов и АЧТВ. Число эозинофилов у здоровых женщин положительно коррелирует с протромбиновым временем и плотностью сгустка. В ГБ-1 отмечается негативная связь между числом нейтрофилов и скоростью образования сгустка, а также положительная связь между числом моноцитов, скоростью и размером сгустка и между числом базофилов и тромбиновым временем. У больных ГБ-2, принимавших кинезитерапию число эритроцитов отрицательно коррелирует с АЧТВ, количество тромбоцитов обнаруживает положительную корреляцию тромбиновым временем, скоростью и размерами сгустка, а общее число лейкоцитов - с протромбиновым временем и скоростью образования сгустка. Содержание нейтрофилов положительно коррелирует с протромбиновым временем и отрицательно со скоростью образования сгустка. Количество лимфоцитов и эозинофилов отрицательно коррелирует со скоростью образования сгустка, а базофилов - с уровнем фибриногена и скоростью появления сгустка. Заключение. В формировании гемокоагуляционного потенциала у здоровых женщин и больных ГБ ведущая роль принадлежит тромбоцитам и различным популяциям лейкоцитов. Обсуждается положительное влияние кинезитерапии. Aim. To study the role of different blood cells in the development of coagulation potential in healthy women and patients with essential hypertension (EH). Methods. The study included 102 women. The control group consisted of 30 relatively healthy women. Patients with EH were divided into 2 subgroups: the first subgroup (EH-1) included 37 women with stage II arterial hypertension, the second subgroup (EH-2) - 35 women with stage II EH who received 3-4 courses of kinesitherapy for 2-3 years on a regular basis. The following values were determined: platelet count, activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), fibrinogen concentration, and spatial fibrin clot growth, including the delay time of clot lengthening, initial and steady growth rate, and clot density and size. The role of different blood cells in the development of coagulation potential was evaluated in healthy and EH women using the correlation analysis. Results. All women had increased numbers of lymphocytes and eosinophils; showed a predisposition to thrombosis as was evident from thrombodynamic properties of the clot; and increased formation rate and size of the fibrin clot. These changes were less pronounced in the EH-2 group. In healthy women, a direct correlation was observed between the number of monocytes, APTT and the thrombin time. and a negative correlation - between the number of lymphocytes and APTT. In this group, the number of eosinophils positively correlated with the prothrombin time and the clot density. In the EH-1 group, the number of neutrophils inversely correlated with the rate of clot formation; the number of monocytes positively correlated with the clot formation rate and size; and the number of basophils positively correlated with the thrombin time. In EH-2 patients receiving kinesitherapy, the number of red cells inversely correlated with APTT; the number of platelets positively correlated with the thrombin time, the clot formation rate and size; and the total number of leukocytes positively correlated with the prothrombin time and the clot formation rate. The neutrophil count positively correlated with the prothrombin time and negatively - with the rate of clot formation. The number of lymphocytes and eosinophils negatively correlated with the rate of clot formation, and the number of basophils - with the fibrinogen level and the rate of clot emergence. Conclusion. Platelets and leukocyte populations play the main role in the formation of coagulation potential in healthy women and patients with EH. The beneficial effect of kinesitherapy is discussed.

scholarly journals In Hemophilia Α Plasma Treated with Emicizumab, Factor IX Activation By Factor VIIa Drives Thrombin Generation

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 17-17
Author(s):  
Dougald Monroe ◽  
Mirella Ezban ◽  
Maureane Hoffman
Keyword(s):  
Factor Viii ◽  
Tissue Factor ◽  
Plasma Levels ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Factor Viia ◽  
Factor Ix ◽  
Factor X ◽  
Dose Dependent

Background.Recently a novel bifunctional antibody (emicizumab) that binds both factor IXa (FIXa) and factor X (FX) has been used to treat hemophilia A. Emicizumab has proven remarkably effective as a prophylactic treatment for hemophilia A; however there are patients that still experience bleeding. An approach to safely and effectively treating this bleeding in hemophilia A patients with inhibitors is recombinant factor VIIa (rFVIIa). When given at therapeutic levels, rFVIIa can enhance tissue factor (TF) dependent activation of FX as well as activating FX independently of TF. At therapeutic levels rFVIIa can also activate FIX. The goal of this study was to assess the role of the FIXa activated by rFVIIa when emicizumab is added to hemophilia A plasma. Methods. Thrombin generation assays were done in plasma using 100 µM lipid and 420 µM Z-Gly-Gly-Arg-AMC with or without emicizumab at 55 µg/mL which is the clinical steady state level. The reactions were initiated with low (1 pM) tissue factor (TF). rFVIIa was added at concentrations of 25-100 nM with 25 nM corresponding to the plasma levels achieved by a single clinical dose of 90 µg/mL. To study to the role of factor IX in the absence of factor VIII, it was necessary to create a double deficient plasma (factors VIII and IX deficient). This was done by taking antigen negative hemophilia B plasma and adding a neutralizing antibody to factor VIII (Haematologic Technologies, Essex Junction, VT, USA). Now varying concentrations of factor IX could be reconstituted into the plasma to give hemophilia A plasma. Results. As expected, in the double deficient plasma with low TF there was essentially no thrombin generation. Also as expected from previous studies, addition of rFVIIa to double deficient plasma gave a dose dependent increase in thrombin generation through activation of FX. Interestingly addition of plasma levels of FIX to the rFVIIa did not increase thrombin generation. Starting from double deficient plasma, as expected emicizumab did not increase thrombin generation since no factor IX was present. Also, in double deficient plasma with rFVIIa, emicizumab did not increase thrombin generation. But in double deficient plasma with FIX and rFVIIa, emicizumab significantly increased thrombin generation. The levels of thrombin generation increased in a dose dependent fashion with higher concentrations of rFVIIa giving higher levels of thrombin generation. Conclusion. Since addition of FIX to the double deficient plasma with rFVIIa did not increase thrombin generation, it suggests that rFVIIa activation of FX is the only source of the FXa needed for thrombin generation. So in the absence of factor VIII (or emicizumab) FIX activation does not contribute to thrombin generation. However, in the presence of emicizumab, while rFVIIa can still activate FX, FIXa formed by rFVIIa can complex with emicizumab to provide an additional source of FX activation. Thus rFVIIa activation of FIX explains the synergistic effect in thrombin generation observed when combining rFVIIa with emicizumab. The generation of FIXa at a site of injury is consistent with the safety profile observed in clinical use. Disclosures Monroe: Novo Nordisk:Research Funding.Ezban:Novo Nordisk:Current Employment.Hoffman:Novo Nordisk:Research Funding.

Evidence that a Fat-Rich, Thrombogenic Diet Enhances Facfor X Activating Activity of Rat Platelets.

1979 ◽  
Author(s):  
E. Tremoli ◽  
M. Colucci ◽  
M.B. Donati ◽  
N. Semeraro
Keyword(s):  
Dietary Treatment ◽  
Fold Increase ◽  
Test System ◽  
Thrombin Time ◽  
Factor X ◽  
Platelet Factor ◽  
Activity Factor ◽  
Coagulant Activity ◽  
Paired Control

The mechanism by which certain fat-rich diets are able to induce a marked thrombotic tendency in rats is uncertain. Several abnormalities of platelet function have been reported including increased platelet adhesiveness, enhanced platelet aggregability and increased platelet factor 3 activity. We have studied a recently described platelet coagulant activity (factor X activating activity) in rats fed a fat-rich, thrombogenic diet for 1, 2 and 7 weeks as compared to rats fed normal laboratory chow. Whatever the duration of the special feeding period, a highly significant shortening of the special clotting time, devised for measuring this activity, was observed. When platelet coagulant activity of individual “fat-fed“ rats was quantitated by reference to that of the respective randomly paired control animal, a 2-5 fold increase was found as early as after one week of dietary treatment. Partial thromboplastin time, thrombin time and soluble fibrin monomer complexes did not differ in control and treated animals. It seems that platelet coagulant activity, as measured in our test system, is one of the first laboratory parameters to be modified by fat-rich diets. These findings may be relevant to an understanding of the role of platelet coagulant activities other than platelet factor 3 in thrombotic phenomena. Supported by CNR (Italy).

scholarly journals Combined Effect of By-Pass Agents and a Sequence Identical Analogue of Emicizumab on Fibrin Clot Turbidity and Structure in Factor VIII Deficient Plasma

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2473-2473
Author(s):  
Iva Pruner ◽  
Yanan Zong ◽  
Nida Mahmoud Hourani Soutari ◽  
Roza Chaireti ◽  
Aleksandra Antovic ◽  
...  
Keyword(s):  
Factor Viii ◽  
Board Of Directors ◽  
Research Funding ◽  
Hemophilia A ◽  
Single Agent ◽  
Fibrin Clot ◽  
Fiber Formation ◽  
Factor X ◽  
Advisory Committees ◽  
Normal Plasma

Abstract Development of inhibitors to Factor VIII is a serious and not uncommon (occurs in about 30% of treated patients) complication of the treatment with factor concentrate in hemophilia A. Treatment of patients with inhibitors is complicated, expensive and not always successful. By-pass agents (rFVIIa and aPCC) have been considered as a treatment of choice for those patients. Very recently bispecific factor IXa- and factor X-directed antibody - Emicizumab has been approved for the treatment of hemophilia A patients with inhibitors. However, there are data from the clinical studies which raise concerns about potential prothrombotic effect of Emicizumab in combination with by-pass agents particularly aPCC. To elucidate a potential mechanism of hypercoagulability we have investigated fibrin clot quality in hemophilic plasma after addition of a sequence identical analogue (SIA) of Emicizumab in combination with by-pass agents. Parameters of fibrin clot turbidity (lag time, Max Abs, Slope, Slope time) were measured in recalcified FVIII-deficient plasma samples, after addition of low thrombin concentration (0.04 NIH/mL) and different concentrations of SIA (200 and 600 nM), rFVIIa (1.75 and 5.25 µg/mL) and aPCC (50 and 500 mU/mL). Pooled normal plasma (PNP) was used as control. After fixation, fibrin clots were analyzed by scanning electron microscopy (SEM) (Carl Zeiss, Oberkochen, Germany) and the thickness of individual fibers was measured using SIS iTEM software (FEI Company, Eindhoven, Netherlands). As previously determined, 50 randomly selected fibers in each sample were measured to obtain stable mean. All parameters of fibrin turbidity and structure were analyzed in triplicate and the results are presented as mean values. Fibrin clot in FVIII deficient plasma was difficult to analyze due to the lack of polymerization of fibrin monomers and absence of fiber formation. This structure is loose and prone to fibrinolysis. Interestingly the similar structure was observed after addition of both concentrations of rFVIIa while after addition of SIA fibrin structure improves. The best effect using single agent was noticed after addition of aPCC in concentration of 500 mU/mL. In combination with SIA (both concentrations of 200 nM and 600 nM) aPCC in concentrations of 500 mU/mL generated clots with highest density formed from very thin fibers and small intrinsic pores. These clots are even tighter than those formed from PNP samples. Parameters of fibrin turbidity obtained with higher concentrations of agents as well as representative SEM scans are presented on the Figure 1. Addition of SIA to by-pass agents additionally improved fibrin quality in FVIII deficient plasma. Combination of therapeutic concentrations of aPCC and SIA may produce clots even less porous than those in normal plasma. Figure 1. Figure 1. Disclosures Chaireti: Shire: Research Funding. Antovic:NovoNordisk: Membership on an entity's Board of Directors or advisory committees; Shire: Honoraria, Research Funding; Sobi: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Werfen: Honoraria; Stago: Honoraria; Siemens: Honoraria; Roche: Honoraria; Sysmex: Honoraria.

Drug-drug interaction of the anti-TFPI aptamer BAX499 and factor VIII: Studies of spatial dynamics of fibrin clot formation in hemophilia A

2014 ◽  
Vol 133 (1) ◽  
pp. 112-119 ◽  
Author(s):  
Leonid A. Parunov ◽  
Natalia P. Soshitova ◽  
Olga A. Fadeeva ◽  
Anna N. Balandina ◽  
Konstantin G. Kopylov ◽  
...  
Keyword(s):  
Drug Interaction ◽  
Factor Viii ◽  
Hemophilia A ◽  
Spatial Dynamics ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Drug Drug Interaction

scholarly journals The role of emicizumab, a bispecific factor IXa- and factor X-directed antibody, for the prevention of bleeding episodes in patients with hemophilia A

2018 ◽  
Vol 9 (10) ◽  
pp. 319-334 ◽  
Author(s):  
Tristan Knight ◽  
Michael U. Callaghan
Keyword(s):  
Factor Viii ◽  
Hemophilia A ◽  
Factor V ◽  
Factor X ◽  
Interim Analyses ◽  
Factor Ixa ◽  
Bleeding Episodes ◽  
Spatial Approximation ◽  
Antigenic Targets

Hemophilia A, characterized by impaired or absent expression of factor VIII, has long been managed via direct factor replacement. Functionally, factor VIII acts as a cofactor for factor IXa and allows activation of factor X, which, in combination with factor V, generates thrombin. Bispecific antibodies such as emicizumab are recombinant, monoclonal antibodies capable of recognizing and binding to two distinct antigenic targets simultaneously; emicizumab binds factors IXa and X, resulting in spatial approximation and activation of factor X, thereby mimicking the actions of factor VIII. Critically, the presence of antifactor VIII antibodies, for example, inhibitors, impacts neither the mechanism nor the efficacy by which emicizumab functions. The results and interim analyses of the emicizumab clinical trials, HAVEN 1, 2, 3, and 4, are additionally reviewed and discussed.

Properties of Fibrinogen Cleaved by Jararhagin, a Metalloproteinase from the Venom of Bothrops jararaca

1994 ◽  
Vol 72 (02) ◽  
pp. 244-249 ◽  
Author(s):  
Aura S Kamiguti ◽  
Joseph R Slupsky ◽  
Mirko Zuzel ◽  
Charles R M Hay
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Human Fibrinogen ◽  
Activated Platelets ◽  
Bothrops Jararaca ◽  
Platelet Binding ◽  
Fibrin Monomers ◽  
Fibrinogen Molecule

SummaryHaemorrhagic metalloproteinases from Bothrops jararaca and other venoms degrade vessel-wall and plasma proteins involved in platelet plug and fibrin clot formation. These enzymes also cause proteolytic digestion of fibrinogen which has been suggested to cause defective platelet function. Fibrinogen degradation by jararhagin, a metalloproteinase from B. jararaca, and the effect of jararhagin fibrinogenolysis on both platelet aggregation and fibrin clot formation were investigated. Jararhagin was found to cleave human fibrinogen in the C-terminal region of the Aα-chain giving rise to a 285-290 kDa fibrinogen molecule lacking the Aα-chain RGD 572-574 platelet-binding site. Platelet binding and aggregation of ADP-activated platelets is unaffected by this modification. This indicates that the lost site is not essential for platelet aggregation, and that the remaining platelet binding sites located in the N-terminal portion of Aα chains (RGD 95-97) and the C-terminal of γ chains (dodecapeptide 400-411) are unaffected by jararhagin-digestion of fibrinogen. Fibrin clot formation with thrombin of this remnant fibrinogen molecule was defective, with poor polymerization of fibrin monomers but normal release of FPA. The abnormal polymerization could be explained by the loss of one of the two complementary polymerization sites required for side-by-side association of fibrin protofibrils. Jararhagin-induced inhibition of platelet function, an important cause of haemorrhage in envenomed patients, is not caused by proteolysis of fibrinogen, as had been thought, and the mechanism remains to be elucidated.

Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

1976 ◽  
Vol 36 (01) ◽  
pp. 037-048 ◽  
Author(s):  
Eric P. Brass ◽  
Walter B. Forman ◽  
Robert V. Edwards ◽  
Olgierd Lindan
Keyword(s):  
Particle Size ◽  
Induction Period ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Appreciable Amount ◽  
Buffer System ◽  
Homeostatic Mechanism ◽  
Fibrin Formation ◽  
Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

The Haemocompatibility of Biomaterials In Vitro: Investigations on the Mechanism of the Whole-blood Clot Formation Test

1992 ◽  
Vol 20 (3) ◽  
pp. 390-395 ◽  
Author(s):  
Thomas Groth ◽  
Katrin Derdau ◽  
Frank Strietzel ◽  
Frank Foerster ◽  
Hartmut Wolf
Keyword(s):  
Whole Blood ◽  
Blood Clotting ◽  
Blood Clot ◽  
Formation Rate ◽  
Clot Formation ◽  
Coagulation Cascade ◽  
Contact Activation ◽  
Human Fibrinogen ◽  
Static Conditions

Twenty years ago Imai & Nose introduced a whole-blood clotting test for the estimation of haemocompatibility of biomaterials in vitro In our paper a modification of this assay is described and the mechanism of clot formation further elucidated. It was found that neither the inhibition of platelet function nor the removal of platelets from blood significantly changed the clot formation rate on glass and polyvinyl chloride in comparison to the rate tor whole blood. Scanning electron microscopy demonstrated that platelets were not involved in clot formation near the blood/biomaterial interface. Thus, it was concluded that the system of contact activation of the coagulation cascade dominates during clot formation under static conditions. The latter conclusion was supported by the fact that preadsorption of human serum albumin or human fibrinogen onto the glass plates used, decreased the clot formation rate in the same manner.

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