bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Independent Factor XI Activation by Thrombin in the Presence of High Molecular Weight Kininogen
Authors: von dem Borne Peter A Kr , Koppelman Stefan J , Bouma Bonno N , Meijers Joost C M 
Published: July 2018

SummaryA deficiency of one of the proteins of the contact system of blood coagulation does not result in a bleeding disorder. For this reason activation of blood coagulation via this system is believed to be an in vitro artefact. However, patients deficient in factor XI do suffer from variable bleeding abnormalities. Recently, an alternative pathway for factor XI activation has been described. Factor XI was found to be activated by thrombin in the presence of dextran sulfate as a surface. However, high molecular weight kininogen (HK), to which factor XI is bound in plasma, and fibrinogen were shown to block this activation suggesting it to be an in vitro phenomenon. We investigated the thrombin-mediated factor XI activation using an amplified detection system consisting of factors IX, VIII and X, which was shown to be very sensitive for factor XIa activity. This assay is approximately 4 to 5 orders of magnitude more sensitive than the normal factor XIa activity assay using a chromogenic substrate. With this assay we found that factor XI activation by thrombin could take place in the absence of dextran sulfate. The initial activation rate was approximately 0.3 pM/min (using 25 nM factor XI and 10 nM thrombin). The presence of dextran sulfate enhanced this rate about 8500-fold. A very rapid and complete factor X activation was observed in the presence of dextran sulfate. Although only minute amounts of factor XIa were formed in the absence of dextran sulfate, significant activation of factor X was detected in the amplification assay within a few minutes. HK inhibited the activation of factor XI by thrombin strongly in the presence, yet only slightly in the absence of dextran sulfate (26 and 1.2 times, respectively). Despite the strong inhibition of HK on the activation of factor XI by thrombin in the presence of dextran sulfate, HK had only a minor effect on the factor Xa generation.We conclude that activation of factor XI by thrombin can take place regardless of the presence of a surface or HK. This activation might therefore be physiologically relevant. The inhibitory effect of HK on the thrombin-mediated factor XI activation is largely dextran sulfate dependent. Due to the amplification in the intrinsic system, trace amounts of factor XIa might generate physiological sufficient amounts of factor Xa for an adequate haemostatic response.
A Pilot Study of Pro-Urokinase in the Treatment of Deep Vein Thrombosis
Authors: Mola Marco , Mannucci Pier Mannuccio , Pini Marlo , Prandoni Paolo , Gurewich Victor 
Published: July 2018

SummarySafety and efficacy of the thrombolytic agent pro-urokinase (pro-UK) in the treatment of deep vein thrombosis of the lower limbs (DVT) have been investigated in an open, uncontrolled, pilot study. Fifteen patients were infused with 800.000 IU (5 mg)/h of pro-UK over 24 h (120 mg), together with unfractionated heparin adjusted to maintain the activated partial thromboplastin time between 1.5 and 2.5 times the basal value. Efficacy was assessed comparing venographic changes in the 11 evaluable limbs before and after pro-UK infusion. The Marder score decreased from a median pre-thrombolysis value of 28 (range 4-40) to 16 (3-38) (p <0.05). One major hemorrhagic event (retroperitoneal bleeding 4 days after the end of the pro-UK infusion) occurred. Fibrinogen, alpha2-antiplasmin and plasminogen significantly decreased from baseline values after 12 and 24 h, fibrin(ogen) degradation products significantly increased. Changes in hemostasis parameters were unrelated to thrombolytic efficacy. The results of this pilot study indicate that pro-UK is thrombolytic in DVT and that it can be administered simultaneously with conventional heparin treatment.
A Standard Nomenclature for Factor VIII and Factor IX Gene Mutations and Associated Amino Acid Alterations
Authors: Peake Ian , Tuddenham Edward 
Published: July 2018

AbstractThe exponential increase in reported mutations within the factor VIII and IX genes in patients with haemophilia A and B has resulted in the use of several different systems for reporting such mutations. The Factor VIII/IX Subcommittee believe that a standardised reporting system will be beneficial to all interested in the field of haemophilia genetics. This article contains proposals for a mutation nomenclature based on general working practices and standardised to the present state of our knowledge of the sequence and structure of the factor VIII and IX genes.
The Presence of Glycogen Synthase in Preparations of Platelet Plasma Membranes
Authors: Greenberg J. H , Fletcher A. P , Jamieson G. A 
Published: July 2018

SummaryGlycogen synthase and glycogen (63 ± 35 μg/unit) have been identified in partially-purified preparations of platelet membranes isolated by density-step centrifugation following glycerol-lysis; this combination is responsible for the endogenous (collagen-independent) activity measured during the assay of collagen: glucosyltransferase. Glycogen synthesized in this way may be complexed with protein since it is precip-itable with trichloracetic acid. High and low density membranes prepared by continuous density gradient centrifugation are devoid of glycogen synthase activity.
Effect of Experimental Coronary Thrombosis upon Platelet Kinetics
Authors: Moschos Christos B. , Lahiri Kamalesh , Manskopf Gisbert , Oldewurtel Henry A. , Regan Timothy J. 
Published: July 2018

SummaryA study was designed to determine the effect of experimental coronary thrombosis upon quantitative changes of platelets in the coronary sinus blood and in the systemic circulation. In addition, using 51Cr-labelled platelets, their distribution in the organ primarily affected by the presence of thrombus, namely the heart, and organs known to be involved in platelet kinetics such as liver, spleen and lungs, was also examined. Following coronary occlusion, a consistent pattern of progressive decrease in platelet counts in the effluent of the infarcted area (coronary sinus) as well as in the systemic blood, maintained for at least 18-20 hours following the thrombotic event, was observed. There was a significant increase in platelet sequestration by spleen, liver and lung and presence of platelet thrombi in the microcirculation of the coronary arterial system. The results suggest that a thrombotic process in a medium size artery induces a more generalized involvement of the platelet population through mechanisms which are not clear at this time. The changes in platelet counts, following coronary thrombosis, obtained as described in this study offer diagnostic possibilities in cases where an active thrombotic process is suspected. However, further studies are necessary before the value of this diagnostic approach is established.
Energy Production and Utilization by Human Platelets in the Presence of Some Guanidines and Phenols (Uremic Toxins) that Inhibit Aggregation
Authors: Carroll Hugh J 
Published: July 2018

SummaryPlatelet aggregation induced by ADP can be inhibited by plasma from uremic patients or by toxins isolated from their plasma, e. g. guanidinosuccinic acid, methylguanidine, phenol and hydroxyphenylacetic acids. Since these chemical substances can interfere with energy metabolism in tissues other than platelets and since ATP production is needed for ADP-induced aggregation, alterations in platelet energy metabolism could underlie excessive bleeding in uremic patients. Platelets incubated with idioacetate and deprived of anaerobic glycolysis produced the same quantity of ATP through respiration in the presence of all the uremic toxins studied as in their absence. Similarly, platelets incubated with cyanide and deprived of the oxidative pathway utilized anaerobic glycolysis to produce normal quantities of ATP in the presence of all the uremic toxins. The utilization of ATP, as indicated by active transmembrane potassium transport, was also unaffected by the above listed guanidines and phenols. It is concluded that the in vitro inhibition of ADP-induced platelet aggregation by the guanidines and phenols studied is not due to inhibition of production or utilization of ATP.
A Study of the Use of the Thromboxane A2 Antagonist, Sulotroban, in Combination with Streptokinase for Local Thrombolysis in Patients with Recent Peripheral Arterial Occlusions: Clinical Effects, Platelet Function and Fibrinolytic Parameters
Authors: Lonsdale Robert J , Heptinstall Stan , Westby John C , Berridge David C , Wenham Peter W , Hopkinson Brian R , Makin Geoffrey S 
Published: July 2018

SummaryIn peripheral thrombolysis adjuvant anti-platelet therapy may help to lyse otherwise resistant thrombus, thereby increasing the number of patients successfully treated and reducing the “time to lysis”. If continued after lysis it may help to prevent early rethrombosis. In this pilot study 21 patients undergoing peripheral thrombolysis with streptokinase were randomised to receive the thromboxane receptor antagonist sulotroban or placebo. The dose of sulotroban given was 2 mg/min (four patients), 4 mg/min (five patients) or 8 mg/min (four patients), eight patients received placebo. The clinical and laboratory effects of the treatment were monitored.Thrombolysis was achieved more quickly in patients receiving sulotroban, however, there was no difference between groups in the number of patients in whom recanalisation was achieved (six of eight receiving placebo and eight of 13 receiving sulotroban) or in the number of cases of early rethrombosis. During lysis there was an increase in plasma beta-thromboglobulin with similar levels being found in patients receiving sulotroban and streptokinase and those receiving streptokinase alone. No other major changes in platelet function during lysis were seen in patients receiving streptokinase alone. Sulotroban significantly reduced platelet aggregtion and 14C-5HT release in response to several platelet agonists. With the thromboxane mimetic U46619 the degree of inhibition of aggregation and 14C-5HT release depended on the dose of sulotroban used. High levels of inhibition were associated with an excess of haemorrhagic complications especially in combination with a low plasma fibrinogen level.We conclude that the use of low dose sulotroban in combination with streptokinase merits further study and may have a role in accelerating lysis. However, the combination of high dose sulotroban with streptokinase causes an increased incidence of bleeding. Monitoring platelet function during such therapy may identify patients likely to bleed.
Lack of Association Between Antiphospholipid Antibodies and Migraine
Authors: Tsakiris D A , Kappos L , Reber G , Marbet G A , Le Floch-Rohr J , Roux E , de Moerloose P 
Published: July 2018

SummaryWe prospectively studied the prevalence of lupus anticoagulant, anticardiolipin antibodies (aCL) and various haemostatic parameters in 71 patients with migraine and compared the results with a control group of 32 subjects with back pain never having experienced migraine. The patients with migraine were divided into two groups: group I with migraine without (n = 18) and with aura lasting less than 60 min (n = 24) and group II with migraine with prolonged aura or migrainous infarction (complicated migraine, n = 29). The following results were obtained: a) no difference in aCL positivity was noted between migrainous patients and controls and between common migraine and complicated migraine patients and b) no statistically significant difference in haemostatic parameters (except for thrombin-antithrombin III complexes) was found between the two groups of migraine and between aCL positive and negative migrainous patients. These data suggest that anticardiolipin antibodies are not involved in the pathogenesis of migraine complications.
Self-Association of Antithrombin III Relates to Multimer Formation of Thrombin-Antithrombin III Complexes
Authors: Preissner Klaus T 
Published: July 2018

SummaryDuring the reaction of antithrombin III (AT III) with target proteases the inhibitor serves as pseudo-substrate and undergoes profound conformational changes, becomes incorporated into a covalent stoichiometric enzyme-inhibitor complex which is, in contrast to native AT III, recognized by monoclonal antibody 4C9. In the absence of the target enzyme thrombin, incubation of AT III with 1–2 M guanidine, 0.6% deoxycholate, heating to 56° C, or buffer at pH 4 resulted in inactivation of the inhibitor with concomitant exposure of the epitope for 4C9 and formation of AT III multimers (from 3.9S to 7.1–7.4 S). Loss of activity, formation of multimers and exposure of neoepitope(s) of AT III occurred in a concerted fashion and followed second order kinetics with an activation energy of E
a = 31 kcal/mol. AT III-multimerization induced by treatment with 1 M guanidine (mainly AT III-tetramers with M
r of 250,000) and formation of the binary AT III-thrombin complex revealed similar self-association patterns as judged by gel electrophoresis under non-denaturing conditions. In the presence of heparin, even higher multimers of AT III-thrombin complexes were noted. Moreover, self-association products of the ternary vitronectin-thrombin-AT III complex, which is the ultimate reaction product following thrombin inhibition in the circulation, could be recognized and quantitated due to exposure of the 4C9 epitope on AT III, indicating that AT III exists in multimeric forms within binary and ternary complexes. It is proposed that the ability of these complexes to form high M
r association products is at least in part mediated by the propensity of AT III to multimerize and that multimeric forms of AT III may be involved during clearance of AT III-enzyme complexes.
Heparin Binding Assay of von Willebrand Factor (vWF) in Plasma Milieu – Evidence of the Importance of the Multimerization Degree of vWF
Authors: de Romeuf Christophe , Mazurier Claudine 
Published: July 2018

SummaryWe developed a simple and fast method for studying the heparin binding of von Willebrand factor (vWF) in the plasma milieu. Using plasma from patients with von Willebrand disease (vWD) subtype II, we found that the heparin binding was impaired when compared with a normal plasma control. Further experiments performed with purified vWF of various multimeric composition, obtained either by gradual reduction or gel filtration, confirmed that heparin binding is dependent on the multimerization of vWF and that high molecular weight (HMW) multimers of vWF are required for normal heparin binding. After reduction of plasma vWF by 1.5 mM DTT, the vWF monomer still binds to heparin but to a lower extent. Under these conditions, no significant differences were obtained between control and patients showing that the heparin binding domain located on the vWF subunit is not altered in the subtypes IIA, IIB and IIC studied.
Double Strand Conformation Polymorphism (DSCP) Detects Two Point Mutations at Codon 280 (AAC→ATC) and at Codon 431 (TAC→AAC) of the Blood Coagulation Factor VIII Gene
Authors: Pieneman W C , Reitsma P H , Briët E 
Published: July 2018

SummaryHemophilia A is a hereditary, X-linked, bleeding disorder that is caused by a defect in the factor VIII gene. Here, we report two novel point mutations in the factor VIII gene that result in an aberrant electrophoretic mobility of double strand PCR fragments (double strand conformation polymorphism, DSCP). In exon 9 a TAC→AAC mutation at codon 431, replacing Tyr by Asn, was observed in a family (A211) with moderately severe hemophilia A. A family with mild hemophilia A revealed an A→T mutation in codon 280 (exon 7) that results in the replacement of Asn by Ile. One of these two mutations was not detected in an analysis based on single strand conformation polymorphisms (SSCP).At present we have no explanation for the effect of the nucleotide changes on the electrophoretic mobility of double strand DNA. Although DSCP is not able to detect all mutations the combination of DSCP analysis with SSCP analysis increases the sensitivity in a screening for factor VIII mutations.
Effects of Hybrid Peptide Analogs to Receptor Recognition Domains on α- and γ-Chains of Human Fibrinogen on Fibrinogen Binding to Platelets
Authors: Mohri Hiroshi , Ohkubo Takao 
Published: July 2018

SummaryWe synthesized a series of hybrid peptides that correspond to the γ-chain dodecapeptide (400-411), variable numbers of glycine residues, and the RGDS peptide [Y-HHLGGAK-QAGDV(G)
n
RGDS] to investigate the relationship of these receptor recognition domains of fibrinogen to platelet membrane glycoprotein IIb/IIIa. The tetrapeptide RGDS, the GRGDSPA peptide and the dodecapeptide inhibited binding of fibrinogen to GPIIb/IIIa by 50% (IC50) at concentrations of 17 ± 1.6 μM, 15 ± 2.1 μM, and 87 ± 6.8 μM, respectively. The inhibitory effect of hybrid peptides increased as the number of glycine residues increased, plateauing with 9-11 glycine residues in hybrid peptide analogs, which had an IC50 of 0.68 ± 0.14 μM. These hybrid peptides completely inhibited the binding of fibrinogen to activated platelets when used in sufficient concentrations. The peptide Y-HHLGGAKQAGDV(G)9RGDS blocked ADP-induced aggregation in citrated platelet-rich plasma with IC50 of 3.5 ± 0.6 μM. When the peptide Y-HHLGGAK-QAGDV(G)9RGDS was labeled with 125I to quantify its binding to platelets, maximal binding was observed within 30 min. The binding sites of the hybrid peptide were 43,600 molecules/platelet (K
d = 3.1 ± 0.5 × 10-7 M) to stimulated platelets and 12,500 molecules/platelet (K
d = 1.4 ± 0.2 × 10-7 M) to nonstimulated platelets. The hybrid peptides had the same binding affinity to platelets as fibrinogen and inhibited platelet function. Moreover, anti-GPIIb/IIIa antibody inhibited the binding of the labeled hybrid peptide to stimulated platelets. These results indicate that in the native fibrinogen molecule the presence of both RGD sequence or γ-chain domain at optimal distances increased the binding affinity to GPIIb/IIIa. These domains may be the source of hybrid peptide, expanding a new class of platelet inhibitors that act at membrane receptors for adhesive proteins.
Effects of Antithrombotic Drugs in a Rat Model of Aspirin-Insensitive Arterial Thrombosis
Authors: Schumacher W A , Steinbacher T E , Heran C L , Megill J R , Durham S K 
Published: July 2018

SummaryThese studies describe experimental conditions where aspirin is less effective than other antiplatelet and anticoagulant drugs in inhibiting acute arterial thrombosis. External electrolytic injury of the rat carotid artery was used to induce occlusive thrombi in 97% of vehicle-treated rats. Thrombi were revealed by light and electron microscopy to be comprised primarily of platelets enmeshed in a fibrin network. The thrombin inhibitor D-phenylalanyl-L-prolyl-L-arginyl chloromethy ketone (PPACK; 6 mg/kg, i. v.) decreased thrombus weight by 90%. Aspirin alone (1, 10 and 30 mg/kg, i. v.), dipyridamole alone (5 mg/kg i. v.) and aspirin (1 and 10 mg/kg, i. v.) in combination with dipyridamole (5 mg/kg, i. v.) did not inhibit thrombosis. The platelet-activating factor (PAF) antagonist, WEB 2086, (1 mg/kg i. v.) was also ineffective. Other drugs had intermediate activity. Thrombi were decreased 56% by the thromboxane receptor antagonist, BMS 180,291, either alone (5.8 mg/kg i.v.) or in combination with aspirin (10 mg/kg, i.v.). Heparin (900 U/kg, i.v.), warfarin (0.25 mg/kg, p.o. once daily for 3 days) and ticlopidine (200 mg/ kg, p.o. once daily for 3 days) reduced thrombus weight by 63, 73 and 43% respectively. Reductions in thrombus weight were always associated with improvements in either average blood flow or vessel patency.
Experimental Thrombosis on a Collagen Coated Arterioarterial Shunt in Rats: A Pharmacological Model to Study Antithrombotic Agents inhibiting Thrombin Formation and Platelet Deposition
Authors: Freund Monique , Mantz Françoise , Nicolini Philippe , Gachet Christian , Mulvihill Juliette , Meyer Laurent , Beretz Alain , Cazenave Jean-Pierre 
Published: July 2018

SummaryA rat thrombosis model was developed to assess the efficacity of antithrombotic drugs. It had the following characteristics: controlled hemodynamic and rheological conditions corresponding to arterial flow, a collagen coated surface as a relevant thrombogenic stimulus, a method of measurement allowing dynamic monitoring of thrombus formation and the possibility to assess the thrombus structure. A shunt composed of polyethylene and silicone catheters, including in the middle of the shunt a collagen coated glass capillary, was inserted between the two primitive carotids of the rat. The duration of patency of the shunt was recorded using a thermic probe fixed on its central part. In this model, the patency of the shunt was 539 ± 55 s. Platelet and fibrinogen-fibrin accumulation in successive one centimeter segments along the shunt were measured using 111In labeled platelets and 125I labeled fibrinogen. Platelet accumulation occurred on the collagen coated surface and at the junctions between the different components of the shunt, where flow was disturbed. The effects of four antithrombotic agents were measured: aspirin, clopidogrel, heparin and r-hirudin. Clopidogrel, heparin and hirudin significantly prolonged patency duration of the shunt, whereas aspirin was inactive. Aspirin did not reduce platelet or fibrinogen-fibrin accumulation on the collagen coated surface. Platelet accumulation on the collagen surface was significantly lower in the clopidogrel group (50 mg/kg) than in the group treated with heparin (500 U/kg), demonstrating the direct antiplatelet effect of clopidogrel. Hirudin at doses giving similar values of APTT as heparin (500 U/kg) prolonged the occlusion time to over 2 h while the heparin occlusion time was only 20 min. We conclude that this experimental arterioarterial thrombosis model is sensitive to both antiplatelet and anticoagulant agents, allowing discrimination between antiplatelet and anticoagulant mechanisms of thrombosis prevention. The technique is easily performed in a small animal, fast and reproducible, and thus comparable to primate models for use in the screening of new antithrombotic drugs.
Monitoring Response Of Disease To Heparin Therapy With The Activated Coagulation Time (ACT)
Authors: Hattersley P G , Mitsuoka J C , King J H 
Published: July 2018

Believing that treatment of thromboembolic disease with heparin is treatment of a dangerous group of disorders with a potentially dangerous drug, and that sensitivity to heparin varies greatly, one patient to the next, we attempted to model heparin infusion rates to the specific needs of the patient. We gave initial doses proportionate to body weight, and monitored responses by the ACT. We chose this test because it is a precise bedside procedure which reliably reflects the variable responses of patients.Our protocol: (1) Screen for conditions causing a high risk of bleeding on heparin; (2) Infuse an initial i.v. heparin bolus of about 50 units per kilogram of body weight; (3) Follow with pump-controlled i.v. infusion of 15 to 25 units/kilo/hr.; (4) Subsequently alter the infusion rate as needed to maintain an ACT of 150 to 190 seconds; (5) When the ACT has been established within this range, start appropriate oral doses of warfarin; (6) After 3 days or more, when the prothrombin time is 2 to 2-1/2 times the control, discontinue heparin and maintain patient on oral warfarin.Of 100 patients with proven thromboembolic disease treated at close to this protocol, there were none with progressive thromboembolic disease; 95 patients responded, and were converted to oral warfarin; 5 developed major bleeding necessitating discontinuing heparin. Of these 5, 2 were unrecognized high risk patients who should not have received full dose heparin. The other 3 all had ACT'S well above 190 seconds.Our conclusion: For treatment of patients with deep venous thrombosis and/or pulmonary embolism, this protocol of heparin therapy, if followed carefully is effective and reasonably safe.