bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Carotid Stenosis and Endothelial Injury in the Rabbit: An In Vivo Model to Study Intravascular Platelet Aggregation
Authors: Golino Paolo , Ambrosio Giuseppe , Pascucci Immacolata , Ragni Massimo , Russolillo Enrico , Chiariello Massimo 
Published: July 2018

SummaryPrevious studies have shown that experimental canine coronary artery stenosis associated with endothelial injury results in a typical pattern of coronary flow characterized by gradual decreases in coronary flow to almost zero values followed by restorations of flow to normal values. This pattern of flow, called cyclic flow reductions (CFRs), is the consequence of recurrent platelet aggregation at the site of the stenosis and endothelial injury and subsequent dislodgement of the thrombus. In the present study, platelet activation and aggregation in vivo was induced by placing an external constrictor around carotid arteries with endothelial injury in anesthetized rabbits. Carotid blood flow velocity was measured continuously with a Doppler flow probe positioned proximally to the constrictor. After placement of the constrictor, CFRs developed in 14 of 14 rabbits with a mean frequency of 16.5 ± 2.3 cycles/h. CFRs were observed for 30 min, and the animals were treated with either an i.v. bolus of aspirin (10 mg/kg) or R 68070 (20 mg/kg), a drug with simultaneous TxA2 synthase and TxA2/PGH2 receptor blocking properties. Aspirin completely inhibited CFRs in 4 of 7 rabbits, whereas R 68070 eliminated CFRs in 7 of 7 animals. In the 3 animals that did not respond to aspirin, administration of ketanserin (0.25 mg/ kg i.v.), a selective serotonin S2 receptor antagonist, completely abolished CFRs. Both aspirin and R 68070 resulted in a marked reduction in serum TxB2 formation and in a complete inhibition of ex vivo platelet aggregation in response to arachidonic acid, whereas aggregation in response to U46619, a TxA2 mimetic, was inhibited only in R 68070-treated rabbits. We conclude that 1) CFRs develop in rabbit carotid arteries at sites of experimental stenosis and endothelial injury; 2) this model can be usefully employed to study platelet aggregation and platelet-vessel wall interaction in vivo and to test the efficacy of antiplatelet interventions.
Absence of the Largest Platelet-von Willebrand Multimers in a Patient with Lactoferrin Deficiency and a Bleeding Tendency
Authors: Parker Robert I , McKeown Laurie P , Gallin John I , Gralnick Harvey R 
Published: July 2018

SummaryWe have studied a young male with lactoferrin deficiency and a bleeding tendency responsive to cryoprecipitate. This child has had increased bleeding following surgical procedures and a variably prolonged template bleeding time. The patient has a normal platelet count, normal in vitro platelet ATP secretion and aggregation in response to a variety of agonists, and normal concentration of plasma-von Willebrand factor ristocetin cofactor activity and antigen. Analysis of plasma-vWf multimers by agarose gel electrophoresis consistently demonstrated a subtle decrease in the largest vWf multimers. In contrast, analysis of the patient’s platelet-vWf revealed normal vWf:Ag, decreased vWf ristocetin cofactor activity, and a striking absence of the high and intermediate size molecular weight vWf multimers. Analysis of surface bound platelet-vWf demonstrated normal amounts on the surface of unstimulated platelets, but after thrombin stimulation the platelet-vWf surface expression did not increase. This lack of increased platelet-vWf surface expression resulted from decreased binding of secreted platelet-vWf to be surface of stimulated platelets. These data suggest that the patient’s bleeding tendency may be related to a defect in his platelet-vWf structure and/or mobilization. This case represents a unique demonstration of an abnormality of platelet-vWf in the presence of normal plasma-vWf, and supports the data indicating an important role for platelet-vWf in primary hemostasis.
Hypofibrinolysis in Patients with a History of Idiopathic Deep Vein Thrombosis and/or Pulmonary Embolism
Authors: Grimaudo Vito , Bachmann Fedor , Hauert Jacques , Christe Maria-Adele , Kruithof Egbert K O 
Published: July 2018

SummaryAn impaired fibrinolytic activity after a venous occlusion test is the most common abnormality associated with thomboembolic disease. To better characterize the causes of abnormal responses we have measured different fibrinolytic parameters, before and after 10 and 20 min of venous occlusion, in 77 patients with a history of idiopathic deep vein thrombosis and/or pulmonary embolism and in 38 healthy volunteers.The patients had a lower mean fibrinolytic response to venous occlusion than the controls and higher antigen levels of tissue-type plasminogen activator (t-PA: Ag) and plasminogen activator inhibitor type 1 (PAI-1:Ag). Before venous occlusion, PAI-1 levels were at a molar excess over those of t-PA in all patients and controls. After 20 min of venous occlusion, the release of t-PA from the vascular endothelium resulted in a molar excess of t-PA over PAI-1 in the majority of controls (72%) but only in a minority of patients (39%).To identify patients with fibrinolytic abnormalities, reference intervals (RI) for fibrinolytic activity, t-PA:Ag and PAI-1:Ag were established in healthy controls. None of the patients had low levels of t-PA:Ag, but 17 (22%) had elevated PAI-1:Ag levels before venous occlusion and 12 (16%) exhibited low fibrinolytic activity after 20 min of venous occlusion. Ten of these were among the 17 subjects with high PAI-1: Ag levels before venous occlusion. Thus, the measurement of PAI-1:Ag levels before venous occlusion (i.e. in samples taken without any stimulation) is a sensitive (83%) and specific (89%) assay for the detection of patients with an impaired fibrinolytic response to venous occlusion.
Platelet and Fibrinogen Survival in Calves Implanted with Artificial Heart and Ventricular Assist Device -Correlation with Autopsy Findings
Authors: Al-Mondhiry Hamid , Pae Walter E , Miller Cynthia A , Pierce William S 
Published: July 2018

SummaryThe two main ingredients of blood clots formed on artificial surface are platelets and fibrinogen. In this study, we measured platelet and fibrinogen survival in calves implanted with total artificial heart (TAH) and left ventricular assist device (LVAD), and correlate these data with autopsy findings. Platelet survival with autologous 111In-labeled platelets was performed on nine calves implanted with TAH and five with LVAD. Fibrinogen survival with 131I-labeled homologous fibrinogen was performed on six calves with TAH and three with LVAD. Platelet survival was significantly shortened in both groups of animals: 5.89 ± 0.52 days, control 6.46 ± 0.31 days, p = 0.0013; fibrinogen survival was normal: 8.79 ± 1.20 days, control 8.64 ± 1.16 days. At autopsy two calves with TAH had multiorgan thromboembolism. Two other animals with TAH and four with LVAD had focal renal infarcts. Most animals had minor clot formation within the prosthetic device. Major septic complications occurred in four calves with TAH and one with LVAD. Continuous platelet activation by artificial surface probably explains the shortened platelet survival and thromboembolic complications.
Inhibition by Glaucocalyxin A of Aggregation of Rabbit Platelets Induced by ADP, Arachidonic Acid and Platelet-Activating Factor, and Inhibition of [3H]-PAF Binding
Authors: Bin Zhang , Kun Long 
Published: July 2018

SummaryGlaucocalyxin A is a new diterpenoid isolated from the ethereal extract of the leaves of Rabdosia japonica (Burm f) Hara var glaucocalyx (Maxim) Hara (Labiatae) collected in the northeastern China. When it was incubated with washed rabbit platelets, glaucocalyxin A inhibited ADP- or arachidonic acid-induced platelet aggregation with IC50 values of 4.4 μmol/1, 14.1 μmol/1 respectively. Glaucocalyxin A also inhibited PAF-induced aggregation of rabbit platelets which were refractory to ADP and arachidonic acid with an IC50 value of 13.7 μmol/1. Analysis of [3H]-PAF binding showed that glaucocalyxin A prevented [3H]-PAF binding to intact washed rabbit platelets with an IC50 value of 8.16 μmol/1, which was consistent with its inhibition of PAF-induced platelet aggregation.
Human Vascular Endothelial Cells Catabolise Exogenous Glycosaminoglycans by a Novel Route
Authors: Dawes Joan , Pepper Duncan S 
Published: July 2018

SummaryHeparin and other anticoagulant glycosaminoglycans were radiolabelled with 125I and their catabolism by human vascular endothelial cells in culture was studied. Heparin, heparan sulphate and pentosan polysulphate were associated with the cellular fraction and incorporated into the subendothelial matrix, but dermatan sulphate was not found in either fraction. High molecular weight, fully desulphated carbohydrate chains were major catabolic products of all those glycosaminoglycans which were taken up by the cells. Pentosan polysulphate was not degraded further, but the catabolism of heparan sulphate, and to a lesser extent that of heparin, also yielded small oligosaccharides. Thus the first step in catabolism of exogenous glycosaminoglycans by human vascular endothelial cells appears to be complete desul-phation, which destroys their biological activity, followed by depolymerisation of the carbohydrate chain. This alternative to the sequential action of lysosomal exoenzymes is dependent upon binding to the cell; thus dermatan sulphate, which is not associated with the cellular fraction, is not catabolised.
Autoantibodies to Thrombomodulin: Development of an Enzyme Immunoassay and a Survey of their Frequency in Patients with the Lupus Anticoagulant
Authors: Gibson John , Nelson Margaret , Brown Ross , Salem Hatem , Kronenberg Harry 
Published: July 2018

SummaryIn order to investigate the possibility that autoantibodies to thrombomodulin (TM) may exist in patients with the lupus anticoagulant (LA) and perhaps be implicated in the pathogenesis of recurrent thrombosis seen in such patients, we developed an enzyme-immunoassay to screen serum samples for anti-human TM activity. The major technical problem encountered in developing this assay was to reduce the non-specific binding of serum components from both the LA positive and the negative population. Considerable reduction of non-specific binding was achieved by use of a phosphate/citrate buffer at pH 8.0 and the use of an optimal sample dilution of 1/40. In addition, samples were always tested in parallel in blank wells and results are expressed as an OD ratio. Samples from 113 patients with the LA were assayed and compared to 78 patients referred for LA testing but found to be negative. The mean OD values for the LA positive patients (± SD) was 1.36 (0.44) with a range of 0.78-2.57. This was virtually identical to the values for the LA negative population (1.38 ± 0.40, range 0.76-2.77). The results of this study indicate that there is no evidence for the presence of a significant autoantibody activity to TM in patients with the LA when compared to LA negative patients. If such autoantibodies do exist their frequency must be quite low.
The Use of the D-Dimer Test in Combination with Non-Invasive Testing Versus Serial Non-Invasive Testing Alone for the Diagnosis of Deep-Vein Thrombosis
Authors: Heijboer Harriët , Ginsberg Jeffrey S , Büller Harry R , Lensing Anthonie W A , Colly Louisa P , ten Cate Jan Wouter 
Published: July 2018

SummaryWe studied the usefulness of the determination of plasma D-dimer levels (using an ELISA) in combination with non-invasive testing with impedance plethysmography (IPG) or real-time ultrasonography (US) for the diagnosis of deep-vein thrombosis (DVT), in outpatients with clinically suspected DVT This combined approach was compared to serial non-invasive testing alone in these patients. The sensitivity of a positive D-dimer test (>300 μg/1) for the presence of DVT was 100% (70/70 patients; 95% C. I.: 95-100%), whereas the specificity was 29% (69/ 239 patients; 95% C. I.: 23-34%). The proportion of patients in which a definitive decision about the presence or absence of DVT could be made on the day of referral, was calculated for both approaches. When applying the combined approach, in 42% of all referred patients the diagnosis of DVT could either be established or refuted on entry, as opposed to only 19% of patients using serial non-invasive testing alone.Also, the costs per DVT diagnosed were calculated for the two diagnostic approaches. For the diagnosis of DVT the costs using serial IPG were comparable to the costs using the combination of IPG and the D-dimer test. The same conclusion holds for the comparison of serial US with the combination of US and D-dimer testing.We conclude that for the diagnosis of DVT in symptomatic outpatients the combination of non-invasive testing with the D-dimer test might be preferred over serial non-invasive testing alone, although the safety of such an approach remains to be established in future management studies.
Venous Thrombosis during Pregnancy: Leg and Trimester of Presentation
Authors: Ginsberg J S , Brill-Edwards P , Burrows R F , Bona R , Prandoni P , Büller H R , Lensing A 
Published: July 2018

SummaryIn order to determine the relative frequencies of left and right leg venous thrombosis during pregnancy and the frequencies of venous thrombosis during the three trimesters, a cohort study of 60 consecutive patients with a first episode of venous thrombosis during pregnancy was performed. Fifty-eight women had isolated left leg thrombosis, two patients had bilateral venous thrombosis and no patient had isolated right leg venous thrombosis. Thirteen patients had venous thrombosis during the first trimester (21.7%), 28 during the second trimester (46.7%) and 19 during the third trimester (31.7%). These findings indicate that patients with symptoms in the right leg rarely have venous thrombosis. Because leg pain and swelling occur most frequently during the third trimester but venous thrombosis is relatively equally distributed during all three trimesters, patients presenting earlier during pregnancy are more likely to have venous thrombosis than patients presenting later during pregnancy.
In Vivo Significance of Kinetic Constants of Tight Binding Reversible Proteinase Inhibitors
Authors: Longstaff Colin 
Published: July 2018

SummaryFor a reaction between an enzyme and inhibitor, rate constants and equilibrium constants are both widely used as measures of inhibitor potency. Which one of these two parameters should be used depends on the mechanism of the reaction. Moreover, for biological studies it is not always the overall effectiveness of an inhibitor that is important, but also the rate at which it acts in conditions that may be encountered in vivo. In vitro investigations may be performed to determine the kinetic and thermodynamic constants in an enzyme inhibitor system and to investigate the influence of various other effector biomolecules. However, in translating these results into physiological conclusions, care must be taken that the in vitro experiments have been properly designed and data analysed correctly. This article is an attempt to indicate some of the problems that can be encountered in this process.
Effect of Leukocyte Proteinases on Tissue Factor Pathway Inhibitor
Authors: Petersen Lars C , Bjørn Søren E , Nordfang Ole 
Published: July 2018

SummaryThe effect of human neutrophil elastase and cathepsin G on recombinant tissue factor pathway inhibitor (TFPI) was investigated. A weak inhibition by TFPI of both elastase (Kx
= 0.4 μM) and cathepsin G (Kx
= 0.1 μM) was observed. Neutrophil elastase rapidly cleaved TFPI at the Thr87-Thr88 bond situated at the link between Kunitz domains I and II. Cleavage of TFPI by cathepsin G was also observed, but the reaction was much slower and resulted in a number of fragments. Proteolytic cleavage by both elastase and cathepsin G resulted in destruction of inhibitor function with respect to TFPI’s inhibition of factor Xa. Cleavage by neutrophil elastase was capable of restoring factor Xa amidoly-tic activity after its initial inhibition by TFPI. Inhibition of cathepsin G by TFPI was strongly augmented by stoichiometric amounts of factor Xa. However, the augmentation was temporary, presumably due to concomitant cleavage of TFPI by cathepsin G. These observations may have implications for the putative effect of neutrophil leukocyte stimulation on the regulation of the tissue factor-mediated coagulation pathway. Conversely, formation of a factor Xa/TFPI complex may reduce or modulate the proteolytic potential of stimulated leukocytes by temporary inhibition of cathepsin G.
Measurement of Markers of Activated Coagulation in Antithrombin III Deficient Subjects
Authors: Demers Christine , Ginsberg Jeffrey S , Henderson Penny , Ofosu Fred A , Weitz Jeffrey I , Blajchman Morris A 
Published: July 2018

SummaryFunctional antithrombin III levels were measured by factor Xa inhibition in 63 members of a large family with type 2 antithrombin III deficiency and individuals were classified as antithrombin III deficient or non-deficient according to the results. FI+2 and TAT complexes were measured using an ELISA and FPA levels were measured by radioimmunoassay.Thirty subjects (48%) were classified as antithrombin III deficient and 33 (52%) as antithrombin III non-deficient. The mean level of FI+2 was significantly higher in the deficient adults (0.87 ± 0.26) compared to both the non-deficient adults (0.70 ± 0.21) (p = 0.03) and the deficient adults receiving warfarin (0.16 ± 0.01) (p <0.001). The differences in the mean values of TAT complexes and FPA between deficient and non-deficient individuals were not statistically significant.These findings suggest that untreated antithrombin III deficient subjects generate more thrombin than their non-deficient family members and that warfarin inhibits this thrombin formation. In this cross-sectional study, it is not possible to correlate the levels of the surrogate makers with future clinical outcome.
Tumor Necrosis Factor Induces von Willebrand Factor Release in Healthy Humans
Authors: van der Poll Tom , van Deventer Sander J H , Pasterkamp Gerard , van Mourik Jan A , Büller Harry R , ten Cate Jan W 
Published: July 2018

SummaryTumor necrosis factor (TNF) is an important mediator of the host responses to systemic infection. To investigate the effect of TNF on the release of von Willebrand factor (vWF) into the circulation, we performed a controlled study in six healthy men, sequentially measuring the plasma concentrations of vWF antigen after a bolus intravenous injection of recombinant human TNF (50 μg/m2). TNF induced a marked increase in vWF antigen plasma levels, becoming significant after 45 min and peaking after 4 h (percentage increase from base line: 351 ±46; p <0.0001, TNF versus saline). The multimeric organization of circulating vWF was not affected by TNF. We conclude that TNF may be an early mediator of increased vWF secretion in systemic infection.
A Novel Sensitive Assay for Functional Factor XII Based on the Generation of Kallikrein-C1-lnhibitor Complexes in Factor Xll-Deficient Plasma by Glass-Bound Factor XII
Authors: Dors D M , Nuijens J H , Huijbregts C C M , Hack C E 
Published: July 2018

SummaryWe developed a very sensitive assay for functional factor XII. This assay is based on the property of glass-bound factor XII to activate prekallikrein (PK) into kallikrein in factor XH-deficient plasma, which is assessed by measuring the formation of kallikrein- C1 -inhibitor complexes in this plasma by radioimmunoassay.Incubation of varying amounts of factor XII in glass tubes led to a dose-dependent increase in kallikrein-C1-inhibitor complexes in factor XH-deficient plasma with a lower limit of detection of ± 20 pg of factor XII. The specificity of the assay for factor XII was demonstrated by experiments with plasmas deficient for factor XII, PK or high molecular weight kininogen (HK) and by incubation of factor XII with Polybrene or with a monoclonal antibody that inhibits the amidolytic and procoagulant activity of factor XII. The high sensitivity of the assay appeared to be due to the inability of Cl-inhibitor to inhibit factor XII bound to glass, which resulted in a molar ratio of generated kallikrein to glass-bound factor XII of at least 100:1.This assay for factor XII may be a feasible tool in studies on structural and functional aspects of (recombinant) factor XII species synthesized by cultured cells.
Comparison Between a One-Point Dilute Phospholipid APTT and the Dilute Russell Viper Venom Time for Verification of Lupus Anticoagulants
Authors: Alving Barbara M , Barr Charles F , Johansen Lawrence E , Tang Douglas B 
Published: July 2018

SummaryIn the present study, the dilute Russell viper venom time (RVVT) and the dilute phospholipid activated partial thromboplastin time (PL-APTT), which are two assays used for the verification of lupus anticoagulants (LA), were modified to increase standardization. The modified assays were then compared with respect to sensitivity and specificity in detecting LA in plasmas from 72 patients with a prolonged APTT. Modifications included utilizing a single dilution of phospholipid that was either bovine brain thromboplastin (Thrombofax) or liposomes comprised of phosphatidylcholine/phosphatidylserine, and expressing the results as a ratio of the clotting times of the mixture of patient and normal plasma/clotting time of normal plasma. In the RWT, the correlation coefficient between assay results for liposomes and Thrombofax was 0.88 and in the PL-APTT, the correlation was 0.68. A positive test for LA was defined as a ratio of ≥1.3 for the PL-APTT with liposomes and ≥1.2 for the PL-APTT with Thrombofax and the RWT with Thrombofax or liposomes. Regardless of the phospholipid source in the test system, the PL-APTT demonstrated higher sensitivity and the RWT showed greater specificity in detecting patient plasmas that contained antiphospholipid antibodies.