scholarly journals Factors Affecting the Factor X Activator Activity of Human Platelets

1977 ◽  
Author(s):  
J. Vermylen ◽  
N. Semeraro
Keyword(s):  
Factor Viii ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Activate Factor ◽  
Factor Viii Inhibitor ◽  
Factor X ◽  
Factors Affecting ◽  
Coagulant Activity ◽  
Viii Inhibitor

Several recent studies have indicated that patients with a thrombotic tendency have enhanced platelet coagulant activity. It therefore is of importance to attempt to identify factors which modify platelet coagulant activities. Recent work in our laboratory has provided evidence that human platelets possess the capacity to directly activate factor X.Adenosine-5'-diphosphate, collagen, acetylsalicylic acid and prostaglandin E1 do not modify this activity. All endotoxins studied however clearly enhanced this activity.Furthermore, infusion of ‘activated’ prothrombin concentrates in haemophiliacs with or without factor VIII inhibitor enhanced the activity of this platelet activator of factor X. The hypothesis has been put forward that this may be the mechanism through which ‘activated’ prothrombin concentrates ‘bypass’ factor VIII of IX inhibitors. Platelet isolated from platelet-rich plasma to which the ‘activated’ prothrombin concentrate had been added at a concentration approaching the maximal concentration achieved following in vivo infusion, also showed an increase in platelet coagulant activity. Work is in progress to identify the component in ‘activated’ prothrombin concentrates which enhances platelet coagulant activity.

Acquired Haemophilia: Functional Study of Antibodies to Factor VIII

1981 ◽  
Vol 45 (03) ◽  
pp. 285-289 ◽  
Author(s):  
J P Allain ◽  
A Gaillandre ◽  
D Frommel
Keyword(s):  
Factor Viii ◽  
Functional Study ◽  
Factor Viii Inhibitor ◽  
Acquired Haemophilia ◽  
Viii Inhibitor ◽  
Kinetics Of ◽  
Antibody Function ◽  
Native Plasma

SummaryFactor VIII complex and its interaction with antibodies to factor VIII have been studied in 17 non-haemophilic patients with factor VIII inhibitor. Low VIII:C and high VIIIR.Ag levels were found in all patients. VIII:WF levels were 50% of those of VTIIRrAg, possibly related to an increase of poorly aggregated and electrophoretically fast moving VIIIR:Ag oligomers.Antibody function has been characterized by kinetics of VIII :C inactivation, saturability by normal plasma and the slope of the affinity curve. Two major patterns were observed:1) Antibodies from 6 patients behaved similarly to those from haemophiliacs by showing second order inhibition kinetics, easy saturability and steep affinity slope (> 1).2) Antibodies from other patients, usually with lower titres, inactivated VIII :C according to complex order kinetics, were not saturable, and had a less steep affinity slope (< 0.7). In native plasma, or after mixing with factor VIII concentrate, antibodies of the second group did not form immune complexes with the whole factor VIII molecular complex. However, dissociation procedures did release some antibodies from apparently low molecular weight complexes formed in vivo or in vitro. For appropriate management of non-haemophilic patients with factor VIII inhibitor, it is important to determine the functional properties of their antibodies to factor VIII.

Factor-VIII Inhibitor in Less Severely Affected Haemophilic Patients

1975 ◽  
Author(s):  
E. G. D. Tuddenham ◽  
A. L. Bloom ◽  
J. C. Giddings ◽  
C. A. Barrett
Keyword(s):  
Factor Viii ◽  
Factor Viii Inhibitor ◽  
Factor Viii Level ◽  
Replacement Treatment ◽  
Viii Level ◽  
Viii Inhibitor ◽  
In Vivo Recovery ◽  
Better Than

The occurrence of factor VIII inhibitor in five mild or moderately affected liaemophilic patients is described. In four patients the inhibitor inactivated endogenous factor VIII an dtemporarily converted them to severely affected haemophiliacs with factor VIII level of 0%. In the fifth patient, a brother of one of the others, the inhibitor although more potent did not inactivate the patient’s own factor VIII and did not completely inactivate normal factor VIII in vitro. This patient responded to treatment with factor-VIII concentrate but the in-vivo recovery was reduced. The patient’s plasma was tested against a panel of normal donors but it inactivated factor VIII in each to a similar extent and no evidence for normal factor-VIII groups was obtained. In the other patients the response to replacement treatment was also better than that usually seen in severely affected haemophilic patients with inhibitor. In the two related patients the inhibitors have so far persisted but in the unrelated patients the inhibitors eventually disappeared and did not always recur with subsequent therapy. The incidence of factor- VIII inhibitor in less severe haemophiliacs (factor VIII > 3% ) in this centre is 6% suggesting that the complication is more frequent in this type of patient than hitherto recognised.

scholarly journals Feiba Immuno: A Preparation with Factor Eight Inhibitor Bypassing Activity

1977 ◽  
Author(s):  
F. Elsinger
Keyword(s):  
Factor Viii ◽  
Factor Xa ◽  
Coagulation Factors ◽  
Active Principle ◽  
Factor Viii Inhibitor ◽  
Factor V ◽  
In Vitro Experiments ◽  
Factor X ◽  
Viii Inhibitor

FEIBA IMMUNO is a preparation in which a new activity is generated capable of bypassing factor VIII. The preparation which is used to treat patients with inhibitors (especially inhibitors to factor VIII) is standardized in FEIBA units, i.e. in terms of its in vitro capacity to shorten the activated PTT of a factor VIII inhibitor plasma.It could be concluded from different in vitro experiments that none of the classic’ activated coagulation factors is responsible for the factor VIII bypassing reaction; FEIB-activity seems to be correlated to a new complex of coagulation factors.To get an answer to the question which coagulation factors are essential for FEIB-activity, we tried to generate this activity from different deficient plasmas; from these experiments the following conclusions could be drawn:, the presence of at least factors VII, IX, and X is essential for the generation of the molecular species responsible for factor VIII as well as factor X bypassing activity, but factor V is not bypassed. This activity is not factor Xa itself. Factors VIII and V are not necessary for the generation of this active principle, but factor V is finally needed for its bypassing action.

scholarly journals Thrombocytin, A Novel Platelet Activating Enzyme from Bothrops Atrox (MARAJOENSIS) Venom

1977 ◽  
Author(s):  
S. Niewiarowski ◽  
E.P. Kirby ◽  
G.J. Stewart ◽  
R. Turna ◽  
M. Wiedeman ◽  
...  
Keyword(s):  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Activate Factor ◽  
Factor X ◽  
Electron Microscopic ◽  
Platelet Factor ◽  
Small Vessels ◽  
Platelet Aggregates ◽  
Bothrops Atrox ◽  
Induced Aggregation

Thrombocytin (TCN) was purified from Bothrops atrox (BA) venom by precipitation with 1.2% Na-salicylate and chromatography on heparin-agarose column using increasing concentrations of lysine as eluent. It was homogeneous on SDS electrophoresis and had an apparent MW of 36,000. Immunoelectrophoresis with polyvalent anti-BA venom serum gave one cathodic arc indicating an isoelectric point higher than pH 8.6.TCN at a concentration of 1 yg/ml caused aggregation of human platelets, release of low affinity platelet factor 4 and serotonin, and stimulated platelets to retract fibrin.TCN was essentially free of fibrinogen clotting and fibrinolytic activities.TCN action on platelets was not mediated by the formation of thrombin since TCN did not activate Factor X or prothrombin and its action was not inhibited by hirudin.TCN is a serine protease since it was inhibited by DFP and it hydrolyzed a synthetic peptide, chromozyme UK (BZ-Val-Gly-Arg-pNA·HCl).TCN-induced aggregation of human platelets was completely inhibited by soy bean trypsin inhibitor, heparin, prostaglandin E1 and apyrase. Washed human platelets were 2-4 times less sensitive to TCN as compared to platelets in freshly prepared platelet rich plasma (PRP); their sensitivity to TCN gradually deteriorated during incubation of PRP at room temperature for 3 hours. Electron microscopic observations revealed formation of platelet aggregates characterized by pseudopod formation, centralization and partial loss of platelet granules. Infusion of TCN (3 yg) into the main artery of bat wing resulted in the formation of platelet aggregates seen on arterial and venous side which occasionally occluded small vessels.

Fibrinopeptide-A (FPA) Generation by Factor IX Concentrates (F-IX-C) and Feiba (factor VIII inhibitor bypassing activity)

1979 ◽  
Author(s):  
V. Hofmann ◽  
M. Ermanni ◽  
P.M. Straub
Keyword(s):  
Factor Viii ◽  
Factor Ix ◽  
Time Dependent ◽  
Factor Viii Inhibitor ◽  
Fibrinopeptide A ◽  
Coagulant Activity ◽  
At Iii ◽  
Viii Inhibitor

The increase of FPA from 0.4-2.4 to 5.6-80 mg/ml after infusion of F-I-C in 5 hemophiliacs B prompted a study whether thrombin is present or genera ted in F-IX-C and in FEIBA rasp. Purified dialysed fibrinogen served as substrate, FPA-release was measured by RIA and expressed as % of the total FPA in fibrinogen. F-IX-C + fibrinogen produced only traces of FPA. The addition of Ca++ led to a time-dependent increase of FPA-release. 8 batches F-IX-C from 2 sources (Immuno, SwissRedCross) were preincubated with Ca++ for 2 hrs, added to fibrinogen with and without heparin, and FPA measured after 60 s. In absence of heparin 7 F-IX-C produced 5 to 80% FPA, in its presence no FPA was liberated. FEIBA + fibrinogen produced clotting and an 80% FPA-release in 5 min, prevented by prior heparin addition. Preincubation of FEIBA with Ca++ increased FPA-release from 80 to 100%, however, prevention required an ll-fold heparin conc. Hirudin more effectively blocked FPA-release probably due to low AT III in concentrates. Thus, in F-IX-C thrombin is absent or blocked by heparin added by the manufacturer; however, thrombin is rapidly generated in presence of Ca++. The coagulant activity of FEIBA is due to thrombin rather than to a “factor VIII inhibitor bypassing activity”.

scholarly journals Clinical Use of Factor IX Concentrates

1977 ◽  
Author(s):  
D. Ménaché
Keyword(s):  
Beneficial Effect ◽  
Factor Viii ◽  
Radical Change ◽  
Factor Ix ◽  
Severe Bleeding ◽  
Factor Viii Inhibitor ◽  
Anamnestic Response ◽  
Viii Inhibitor ◽  
Factor Ix Deficiency

The clinical efficacy of Factor IX concentrates in the treatment of patients with Factor IX deficiency is well recognized. The availability of such concentrates has brought a radical change in the management of these patients. The basis for treatment is to obtain an effective Factor IX hemostatic level in vivo. In these conditions, concentrates have been used to reduce the incidence of hemorrhagic episodes in patients particularly exposed and more often to control hemorrhagic episodes or to prevent hemorrhage in the post operative period. Although thromboembolic complications have occured in some instances the major indication of Factor IX concentrates still remains replacement therapy in patients with Factor IX deficiency.More recently Factor IX concentrates have been used for the treatment of patients with antibody to Factor VIII. Although the therapeutic principle(s) responsible for the Factor VIII inhibitor bypassing activity has not yet been characterized several beneficial effect of both “activated” and non activated Factor IX concentrates have been observed in such patients experiencing minor or severe bleeding episodes. On the other hand we are aware of some cases without beneficial effect of Factor IX concentrates in patients with Factor VIII inhibitor. The major complication would seem to be an anamnestic response in some patients resulting in either a moderate or a considerable increase of the Factor VIII inhibitor titer when compared to the initial level before Factor IX concentrates therapy. If Factor IX concentrates prove to be efficacious in the treatment of patients with Factor VIII antibody special attention would be required in the manufacturing processing in order to avoid an anamnestic response.

scholarly journals Experimental Studies on Factor VIII Inhibitor Bypassing Activity

1977 ◽  
Author(s):  
H. Vinazzer
Keyword(s):  
Factor Viii ◽  
Calcium Chloride ◽  
Experimental Studies ◽  
Factor Xa ◽  
Factor Viii Inhibitor ◽  
Factor V ◽  
Factor X ◽  
Tissue Thromboplastin ◽  
Viii Inhibitor ◽  
Thrombin Formation

The exact action of factor VIII inhibitor bypassing activity (FEIBA) is still unclear. For this reason, a series of experimental studies was carried out. Procoagulant activities were examined by standard one-stage methods while factor Xa and thrombin were measured by chromogenic substrates. Activities of factors II, VII, IX, and X were similar to PPSB fractions. In addition, low factor V activity and a phospholipid were detected. No activated factor X was present in FEIBA but there was a trace amount of 2.1 NIH units of thrombin per 100 FEIBA units. On addition of calcium chloride slow thrombin formation could be observed which however, reached 1100 NIH units of thrombin per 100 FEIBA units within an incubation time of 10 min. The velocity of thrombin formation was greatly enhanced by addition of a PTT reagent and of thromboplastin respectively. Factor Xa on the other hand, was neither formed after addition of calcium chloride nor by a PTT reagent. Tissue thromboplastin however, activated Xa from FEIBA in the same manner as a PTT reagent plus barium sulfate plasma. From these results, the conclusion could be drawn that thrombin could readily be made available from FEIBA while activation of Xa either needed the complete endogenous pathway or the presence of tissue thromboplastin. The procoagulant activity of FEIBA therefore, could be attributed to direct thrombin formation. By this process, an activation of the clotting mechanism in plasmas deficient in endogenous coagulation factors, and a complete independence from the presence or absence of a specific antibody could be explained.

Quantitative Effects of the Reaction between Factor VIII and Factor VIII Inhibitors

1971 ◽  
Vol 26 (01) ◽  
pp. 124-134
Author(s):  
C. W McMillan ◽  
R. C Elston
Keyword(s):  
Factor Viii ◽  
Factor Viii Inhibitor ◽  
Inhibitor Activity ◽  
Viii Inhibitor ◽  
In Vitro Effects ◽  
Logarithmic Relation

SummaryTo study the effects of factor VIII and factor VIII inhibitor on each other an assay was developed in which inhibitor activity could be directly related to units of factor VIII. Inhibitor activity in units per ml is defined as the number of factor VIII units reduced to 0.01 factor VIII unit by 1 ml inhibitor plasma after incubation for 1 h at 37° C. Whereas factor VIII was destroyed by inhibitor in accord with a double-logarithmic relation between initial and 1-h residual factor VIII activities, final inhibitor activity was found to be inversely proportional to the ratio of initial concentrations of factor VIII to inhibitor. The latter process resembles “dilution”, rather than direct neutralization, of inhibitor by factor VIII. These effects were observed both in the system for inhibitor assay and in more concentrated mixtures of factor VIII and inhibitor sources in vitro. Results of infusion of factor VIII into a subject with classic hemophilia and an acquired inhibitor suggested that in vivo and in vitro effects of factor VIII and inhibitor activities on each other are comparable, if not identical.

Prothrombin-Complex Concentrates, Thromboses, and Factor VIII Inhibitors: Evidence for a Coagulant Formed by the Interaction of Factors X and II

1975 ◽  
Author(s):  
G. H. Tishkoff
Keyword(s):  
Factor Viii ◽  
Human Factor ◽  
Factor Xa ◽  
Activated Partial Thromboplastin Time ◽  
Factor Viii Inhibitor ◽  
Factor V ◽  
Prothrombin Complex Concentrates ◽  
Corrective Effect ◽  
Viii Inhibitor

Kurcyznski and Penner have reported on the use of prothrombin concentrates in the management of bleeding in hemophilia patients with Factor VIII inhibitor. Several commercial concentrates showed marked ability to shorten the activated partial thromboplastin time (APTT) of Factor VIII inhibitor plasma after 40 min preincubation. Significantly, purified human Factor Xa and thrombin did not evidence corrective effect. Highly purified human Factors X and II, isolated by affinity chromatography from partially activated prothrombin complex, effectively corrected the APTT when combined, but were inactive when tested separately. Preliminary studies suggest that Factor V is essential. This study indicates that the thrombogenic properties of prothrombin concentrates in vivo may be due in part to a coagulant complex formed by the interaction of X, V, and a prothrombin intermediate.

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