bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the Hirudin Carboxy-Terminal Peptide 54-65 on the Interaction of Thrombin with Platelets
Authors: Jandrot-Perrus Martine , Huisse Marie-Geneviève , Krstenansky John L , Bezeaud Annie , Guillin Marie-Claude 
Published: July 2018

SummaryThe carboxy-terminal region of hirudin (residues 54-65) has previously been shown to inhibit thrombin clotting activity without binding to the catalytic site of the enzyme. In the present study, the effect of hirudin 54-65 on thrombin interaction with specified platelet proteins has been investigated. Hirudin 54-65 was found to inhibit thrombin-induced platelet aggregation and secretion in a dose-dependent manner. Substitution of either Phe56, Glu57, Ile59, Pro60 or Leu64 showed that these residues were critical for inhibition of thrombin-induced platelet activation whereas sulfation of Tyr63 increased the inhibitory potency of the peptide. Hydrolysis of glycoprotein V, a platelet membrane substrate for thrombin, was only partially inhibited by hirudin 54-65. Although hirudin 54-65 did not decrease the amount of thrombin bound to platelets during cross-linking experiments, it was found to inhibit the specific binding of thrombin to platelet glycoprotein Ib. Since the carboxy-terminal region of hirudin has previously been reported to bind near the trypsin-catalyzed β cleavage site, we have analyzed the consequences of a to β-thrombin conversion on both thrombin-hirudin 54-65 interaction and thrombin activity toward platelets. The β cleavage induced a decrease in the affinity of thrombin for both glycoprotein Ib and hirudin 54-65. Altogether, our results indicate that thrombin recognition sites for hirudin 54-65 and platelet membrane glycoprotein Ib share common structures located near the β cleavage site at Arg 73 on the thrombin B chain.
Rapid Aequorin Loading into Platelets in the Presence of DMSO - Characteristics of the Responses (Changes in Light Transmission and in Calcium) to Various Agonists
Authors: Potevin F , Lecompte T , Favier R , Samama M 
Published: July 2018

SummaryWe have looked at different parameters which could modify platelet behaviour during and after aequorin loading in the presence of DMSO. There is a decreased platelet reactivity in response to ADP, PAF and A-23,187 which appears to be mainly due to the exposure to EGTA during washing and loading and the 1 ml volume of the test suspension. All the studied agonists (including PMA) which elicit aggregation are able to induce an intracellular Ca2+ change detected with the aequorin probe. By contrast, epinephrine alone induces neither aggregation nor Ca2+ rise, but potentiates the responses to ADP. Different consecutive phases in Ca2+ changes after stimulation with ADP, PMA and A-23,187 can be evidenced. In the presence of external Ca2+, the second component of the Ca2+ change evoked with ADP is dependent on aggregation and the subsequent TXA2 synthesis. When the external medium is Ca2+ depleted, the two Ca2+ peaks induced by ADP disappear whereas a Ca2+ rise persists (endogenous mobilization) with the other agonists, being independent of TXA2 and ADP release. Ca2+ mobilization parallels activation with A-23,187 but not with low concentrations of thrombin.
Platelet Survival in Patients with Dilated Cardiomyopathy
Authors: Weidinger Franz , Glogar Dietmar , Sochor Heinz , Sinzinger Helmut 
Published: July 2018

SummaryDilated cardiomyopathy is associated with thromboembolic complications, which correlate poorly, however, with a visible left ventricular thrombus. Therefore, this study was performed to assess whether an abnormality of platelet function in vivo can be detected in patients with dilated cardiomyopathy. Platelet survival was measured after autologous labeling with indium-111 oxine in 28 patients with dilated cardiomyopathy and angiographically normal coronary arteries (mean ejection fraction 21 ± 9% [standard deviation], range 4 to 39%) and in nine patients with coronary artery disease and similar left ventricular dysfunction (mean ejection fraction 21 ± 10%). Plasma levels of beta-thromboglobulin and platelet factor 4 were measured in patients with idiopathic cardiomyopathy (n = 15) and platelet scintigraphic images of the heart (n = 24) were obtained in subsets of both patient groups. Platelet survival was significantly and similarly shortened in patients with idiopathic and ischemic cardiomyopathy (67 ± 34 and 55 ± 24 h, respectively) compared to controls (209 ± 9 h, n = 12; p <0.001). Of the two platelet-specific proteins, beta-thromboglobulin was increased in the patients compared with controls (42 ± 17 versus 22 ± 6 ng/ml, p <0.001). Platelet scintigraphy 24 h (n = 24) and/or 48 h (n = 9) after labeling showed a diffuse pattern of enhanced platelet uptake over the heart which varied in intensity among patients, but which was never seen in controls (n = 6). This increased platelet uptake was similar in patients with idiopathic and ischemic cardiomyopathy but did not correlate with either ejection fraction or cardiothoracic ratio. Patients taking Coumadin (n = 9) had lower values of quantitative and qualitative scintigraphic platelet uptake than patients without Coumadin (n = 14; p <0.05).Thus, platelet survival is markedly shortened and cardiac platelet uptake diffusely enhanced in patients with dilated cardiomyopathy of either idiopathic or ischemic origin. Whether enhanced platelet activation per se contributes to the risk of systemic embolization in this patient population requires further investigation.
Are Haemostatic and Fibrinolytic Parameters Predictors of Preeclampsia in Pregnancy-Associated Hypertension?
Authors: Caron C , Goudemand J , Marey A , Beague D , Ducroux G , Drouvin F 
Published: July 2018

SummaryThe plasma levels of several haemostatic and fibrinolytic parameters were measured before and after delivery in 61 hypertensive pregnant women of whom 22 developed preeclampsia, and compared to the results obtained in 42 normal pregnant women. In the two last weeks before delivery (D ≤ –15) tPA antigen, PAI-1 activity, vWF: Ag/FVIII: C ratio, ATIII activity and platelet count were found to be significantly different in the hypertensive pregnant women with and without preeclampsia. Combined all together, an association of three of these five parameters were found to be pathological (i.e.: tPA: Ag ≥19 ng/ml, PAI-1 activity ≥58 IU/ml, vWF: Ag/FVIII: C ratio 5≥2.6, ATIII activity ≤73%) in none of the hypertensive women without preeclampsia and in only 35% of the preeclamptic group. A positive correlation was demonstrated between vWF:Ag/FVIII:C ratio and tPA:antigen levels suggesting that both tPA and vWF: Ag could be considered as early indicators of a possible micro angiopathy occurring in preeclampsia. However, due to the high dispersion of the results, it appears that the investigated haemostatic and/or fibrinolytic criteria give only presumptive arguments before assigning risk for preeclampsia development among hypertensive pregnant women.
A Method for Measuring Activated Factor VIII in Plasma
Authors: Kessels H , Béguin S , Wagenvoord R , Hemker H C 
Published: July 2018

SummaryA method is described which enables a quantitative measurement of the concentration of activated factor VIII (VIIIa) in plasma. Based on the ability of factor VIIIa to accelerate the activation of factor X by factor IXa, phospholipid and calcium ions, the course of factor X activation in time is measured using a chromogenic substrate. Free factor Xa is able to activate non-activated factor VIII present in a plasma sample, which increases the factor X activation velocity, and thus disturbs the measurement of factor VIIIa. Furthermore, factor Xa was found to be inactivated by serine protease inhibitors from the plasma sample. By adding surplus chromogenic substrate these reactions of factor Xa are inhibited and at the same time the rate of substrate conversion is a measure of the amount of factor Xa present. Factor X activation and amidolysis of chromogenic substrate then take place simultaneously. It is shown that under proper conditions the factor X activation velocity is linearly proportional to the factor VIIIa concentration. This causes the optical density to increase as a parabolic function of time. The concentration of factor VIIIa can be obtained from the quadratic coefficient of the equation describing the parabola. The method is specific for factor VIIIa in that the extrinsic factor X activator is shown to have no influence on the measurement of factor VIIIa in thromboplastin activated plasma. We conclude that a sensitive and reliable method for assessing factor VIIIa concentrations in plasma has been developed on the basis of simultaneous inhibition and measurement of factor Xa by a high concentration of chromogenic substrate.
Determination of the Mean Normal Prothrombin Time for Assessment of International Normalized Ratios
Authors: Peters R H M , van den Besselaar A M H P , Olthuis F M F G 
Published: July 2018

SummaryTo report a Prothrombin Time (PT) as International Normalized Ratio in controlling oral anticoagulant therapy, the Mean Normal PT (MNPT) is required. To correct for methodological differences in performing the PT test, each laboratory should determine its own MNPT for each batch of reagent using fresh blood samples from a large number of normal individuals. This would be a laborious procedure. Two models for simplified assessment of MNPT were investigated by two laboratories in a collaborative study. According to the models, the MNPT of a new batch of reagent is calculated, using the PT of a lyophilized control plasma measured with the new batch and a reference batch, as well as the MNPT of the reference batch obtained with fresh samples. Experimental results were obtained with 19 batches of bovine thromboplastin, 4 lyophilized normal control plasmas and fresh blood samples of 40 normal individuals. The PTs of the 4 lyophilized normal control plasmas were not identical to the MNPT of the fresh normal samples and also different from each other. Therefore, the uncorrected PTs of these control plasmas cannot be used as MNPT.In general, there was good agreement between measured and calculated MNPT, although some control plasmas gave better results than others. There were no significant differences between the results obtained by both calculation models.
The Autoactivation of Factor XII in the Presence of Long-Chain Saturated Fatty Acids – A Comparison with the Potency of Sulphatides and Dextran Sulphate
Authors: Mitropoulos K A , Esnouf M P 
Published: July 2018

SummaryThe incubation of purified human factor XII (Hageman factor [HF]) in the presence of long-chain saturated fatty acids (FA) like stearate (C-18) or behenate (C-22) resulted in a time-dependent increase of amidolytic activity. The HF autoactivation progress curves were sigmoidal. The first order rate for the initial period was constant; this was followed by a period of decreasing rate and a plateau of zero rate. These progress curves were similar to those obtained on the incubation of HF in the presence of sulphatide vesicles or dextran sulphate. The initial rate of autoactivation of HF was dependent on the FA concentration of contact surface and increased with increasing concentration of HF. At constant concentration of contact surface and varying concentration of HF, autoactivation rates in the presence of behenate, sulphatide vesicles or dextran sulphate followed Michaelis-Menten kinetics. The Km values for all three contact surfaces were above the physiological plasma concentration of HF whereas the catalytic efficiency in the presence of behenate (0.034 εM-1s-1) was about % of that in the presence of sulphatide vesicles (0.053 εM-1s-1) and considerably higher than that in the presence of dextran sulphate (0.004 εM-1s-1). Long-chain saturated FA bound to human serum albumin at the high- or low-affinity sites are ineffective, whereas the crystalline non-bound stearate or behenate provided a potent contact surface. Since oleic acid or other unsaturated fatty acids did not promote autoactivation it is suggested that the requirement for an effective contact surface is one containing immobile negatively charged groups with a critical charge density such as that found in miscelles composed of FA in the crystalline phase. It is suggested that saturated FA on triglyceride-rich lipoproteins resulting from the action of lipoprotein lipase could provide these requirements.
Inhibition of Extrinsic Pathway Inhibitor Shortens the Coagulation Time of Normal Plasma and of Hemophilia Plasma
Authors: Nordfang Ole , Valentin Sanne , Beck Thomas C , Hedner Ulla 
Published: July 2018

SummaryAn increasing amount of evidence suggests that coagulation factors VIII and IX play a role not only in the intrinsic but also in the extrinsic pathway of coagulation. In this context the influence of the Extrinsic Pathway Inhibitor (EPI) on the coagulation time of hemophilia plasma lacking FVIII or FIX has been investigated. The coagulation time was measured in a dilute thromboplastin assay. Addition of recombinant EPI (rEPI) prolonged the coagulation time of normal plasma while the addition of an inhibitory antibody against EPI shortened the coagulation time. At low concentrations of thromboplastin the coagulation time of hemophilia plasma was prolonged and at all dilutions of thromboplastin, addition of anti-EPI IgG normalized the coagulation time of a hemophilia plasma. Analysis of 10 individual donor plasma samples and 8 individual hemophilia samples showed that addition of anti-EPI IgG shortened the coagulation time more in hemophilia plasma than in normal plasma. This illustrates the importance of a powerful extrinsic FVII dependent pathway to achieve hemostasis in the case of FVIII or FIX deficiency (hemophilia A and B).
Antithrombotic Effect of MCI-9042, a New Antiplatelet Agent on Experimental Thrombosis Models
Authors: Hara H , Kitajima A , Shimada H , Tamao Y 
Published: July 2018

SummaryThe antithrombotic effect of MCI-9042, (±)-2-(dimethylamino)-1-[[o-(m-methoxyphenethyl)phenoxy] methyl] ethyl hydrogen succinate hydrochloride was investigated in three different experimental thrombosis models in animals. Simultaneous injection of serotonin and collagen into the tail vein in mice induced acute pulmonary thromboembolic death. MCI-9042 reduced the mortality in a dose dependent manner and its ED50 value was 1.9 mg/kg po. Ticlopidine (TCP) which is a positive reference compound as an antithrombotic drug reduced the mortality at doses of 10 mg/kg po and above. Cyproheptadine (CPH) and ketanserin (KTS) which are S2-serotonergic antagonists were also effective on the reduction of mortality. In mesenteric arterial thrombosis induced by electric stimulation in mice, MCI-9042 prolonged the occlusion time resulted from platelet thrombus formation (PD50: 23 mg/kg po). CPH and KTS prolonged the occlusion time as potent as MCI-9042, but TCP prolonged the occlusion time only at the high doses of 100 mg/kg po and above. In experimental arterial thrombosis which generated in implanted polyethylene tubing, MCI-9042 reduced the incidence of thrombus formation in the tubing and its ED50 value was 18 mg/kg po. TCP was also effective in this model with an ED50 of 170 mg/kg po. The present results lead to the consideration that serotonin plays a more important role in thrombus formation than that conjectured formerly, and suggest that MCI-9042 becomes a new kind of antithrombotic drug with S2-serotonergic receptor antagonism.
A Monoclonal Antibody, VM64, Reacts with a 130 kDa Glycoprotein Common to Platelets and Endothelial Cells: Heterogeneity in Antibody Binding to Human Aortic Endothelial Cells
Authors: Mazurov Alexey V , Vinogradov Dimitry V , Kabaeva Naile V , Antonova Galina N , Romanov Yuri A , VIasik Tatjana N , Antonov Alexander S , Smirnov Vladimir N 
Published: July 2018

SummaryA new monoclonal antibody (mAb), VM64, reacts with a common antigen on the surface of human platelets and vascular endothelial cells (EC). Under nonreduced conditions it recognized in immunoblotting a protein of 130 kDa both in platelets and EC. VM64 precipitated the same 130 kDa protein from the lysate of surface radioiodinated platelets. Electrophoretic mobility of this protein was not altered by reduction and differed from the bands precipitated by reference mAb against platelet glycoproteins (GP) Ia–IIa, Ib, IIb–IIIa and GMP130. VM64 binding to platelets and EC was specific and saturable. The number of binding sites on platelets was 9.9 ± 3.5 × 103 per platelet and on the surface of EC monolayer – 2.40 ± 0.32 × 106 per cell. VM64 also binds to platelets from Glanzmann's thrombasthenia patients which lack GPIIb–IIIa. VM64 did not affect platelet aggregation induced by ADP, collagen, thrombin and ristocetin. In the monolayers of EC from umbilical vein and human aorta, VM64 stained the area at the periphery of the cells adjacent to the cell-cell boundaries. In preconfluent cultures preferential staining was observed at the active leading margins of the cells. Unlike EC cultures from umbilical vein, where all cells were positively stained, in aortic EC cultures some unstained or poorly stained cells were constantly present, indicating a heterogeneity of EC population related to the expression of VM64 antigen. The biochemical characteristics of VM64 antigen, its presence both on platelets and EC and typical distribution on the surface of EC suggested that this antigen is identical to PECAM (CD31) protein.
The Relationship of Antiphospholipid Antibodies to Thromboembolic Disease in Systemic Lupus Erythematosus: A Cross-Sectional Study
Authors: Long A A , Ginsberg J S , Brill-Edwards P , Johnston M , Turner C , Denburg J A , Bensen W G , Cividino A , Andrew M , Hirsh J 
Published: July 2018

SummaryIn order to determine whether an association exists between antiphospholipid antibodies (APLA) and thromboembolic events in patients with systemic lupus erythematosus (SLE), we performed a cross-sectional study of consecutive unselected SLE patients. The occurrence of previous thromboembolic events was determined by investigators blinded to the APLA status of the patients by critical review of objective tests that had been performed at the time of symptomatic presentation and by performing venous Doppler ultrasound of the legs to elicit venous reflux as an indication of previous venous thrombosis. The presence of APLA was determined by coagulation assays for the lupus anticoagulant (LA) using five tests with well-defined control ranges and by ELISA assay for anticardiolipin antibodies (ACLA). These tests were measured on two separate occasions. The results of the study demonstrate a statistically significant association between persistently abnormal ACLA assays and thromboembolic events and a non-significant trend between persistently abnormal LA and thromboembolic events. Transient abnormalities of LA and ACLA were less strongly associated with thromboembolic events. We conclude that in patients with SLE, there is a significant association between thromboembolism and APLA.
Blood Lead and Platelet Aggregation – Evidence for a Causal Association
Authors: Sharp Dan S , Beswick Andrew , Renaud Serge , Toothill Colin , Elwood Peter C 
Published: July 2018

SummaryAdenosine diphosphate (ADP) and thrombin are agonists of platelet aggregation in which intracellular calcium plays a significant role as a signal transducer. Lead is a well established toxicological agent affecting intracellular mechanisms controlling free ionized calcium concentration in a number of cell lines. This epidemiological study is the first demonstration of a significant relationship between the extent of primary ADP-induced platelet aggregation measured by optical densitometry in platelet rich plasma (PRP) and blood lead concentration. High blood lead levels are associated with decreased aggregation in this population of 2,150 men aged 49-65 years. This is reflected by a negative regression relationship of –0.19% of maximal extent (PRP vs platelet poor plasma) of aggregation per εg of Pb/dl (T = –3.82, p <0.001). In contrast, no relationship is noted between thrombin-induced aggregation and blood lead concentration. Smoking behaviour represents a potential confounder which may be the explanation for the observed relationship. However, because smoking status is simultaneously related to both ADP- and thrombin-induced aggregation, but is simultaneously related to ADP-induced aggregation and blood lead concentration in a different way, the observed relation is likely to be causal. The mechanisms by which ADP and thrombin effect intracellular calcium transduction signals appear to be distinctively different. The findings in this population-based study are not inconsistent with this difference.
Comparison of High Purity Factor IX Concentrates and a Prothrombin Complex Concentrate in a Canine Model of Thrombogenicity
Authors: MacGregor I R , Ferguson J M , McLaughlin L F , Burnouf T , Prowse C V 
Published: July 2018

SummaryA non-stasis canine model of thrombogenicity has been used to evaluate batches of high purity factor IX concentrates from 4 manufacturers and a conventional prothrombin complex concentrate (PCC). Platelets, activated partial thromboplastin time (APTT), fibrinogen, fibrin(ogen) degradation products and fibrinopeptide A (FPA) were monitored before and after infusion of concentrate. Changes in FPA were found to be the most sensitive and reproducible indicator of thrombogenicity after infusion of batches of the PCC at doses of between 60 and 180 IU/kg, with a dose related delayed increase in FPA occurring. Total FPA generated after 100-120 IU/kg of 3 batches of PCC over the 3 h time course was 9-12 times that generated after albumin infusion. In contrast the amounts of FPA generated after 200 IU/kg of the 4 high purity factor IX products were in all cases similar to albumin infusion. It was noted that some batches of high purity concentrates had short NAPTTs indicating that current in vitro tests for potential thrombogenicity may be misleading in predicting the effects of these concentrates in vivo.
Sustained Bleeding after a leech Bite in the Apparent Absence of Hirudin
Authors: Munro R , Hechtel F O P , Sawyer R T 
Published: July 2018

SummaryThe bite of the medicinal leech bleeds for many hours. For decades it has been assumed that the remarkably prolonged bleeding time of a leech bite wound is due to hirudin, a specific anti-thrombin secreted by the leech during feeding. By measuring haematological parameters of blood oozing from a leech bite wound on 15 different occasions in 7 human volunteers, we demonstrate that the hirudin-sensitive coagulation parameters, including thrombin-induced platelet aggregation, are prolonged for only 15 min, after which they return to normal. This suggests that excess hirudin secreted by the leech is washed out during this period. However, bleeding from the leech bite wound persists for a mean of 10 h. Platelets in smears of exuding blood show no evidence of spontaneous aggregation, but in vitro platelet aggregation can be induced by exogenous collagen at any time. In view of sustained bleeding in the apparent absence of hirudin, attention is focussed onto an unsuspected factor or factors which may better explain the prolonged bleeding phenomenon.