bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Role of Platelet FcγRIIa Phenotype in Heparin-Induced Thrombocytopenia
Authors: Brandt John T , Isenhart Craig E , Osborne Jeanne M , Ahmed Alaa , Anderson Clark L 
Published: July 2018

SummaryHeparin induced thrombocytopenia (HIT) is characterized by the formation of antibodies that activate normal donor platelets in vitro in the presence of heparin. We asked whether the commonly observed donor-specific variation in the platelet aggregation response to HIT antibodies is influenced by the density of FcγRII on platelets or by the Arg/His 131 allelic polymorphism of platelet FcγRII. We found that platelets with the His/Hisl31 FcγRII phenotype were unresponsive to HIT antibody (0/9) whereas platelets with the Arg/Argl31 phenotype responded well (7/9). His/Hisl31 platelets were largely unresponsive also to a murine IgG1 antiplatelet monoclonal antibody (UR1) known to activate platelets by FcγRII clustering. We then determined the frequency distribution of FcγRIIa Arg/His 131 phenotypes on a series of 200 patients evaluated for HIT and 100 non-thrombocytopenic hospitalized patients. The frequency of the His/Hisl31 phenotype was significantly increased (34.4%) in the 96 thrombocytopenic patients with HIT antibody compared to the 104 thrombocytopenic patients without HIT antibody and the 100 non-thrombocytopenic patients (∼19%). Thus, the FcγRII phenotype regulates the in vitro activation response of normal platelets to HIT antibody and is a risk factor for the thrombocytopenia of HIT
Laboratory Identification of Lupus Anticoagulants: Results of the Second International Workshop for Identification of Lupus Anticoagulants
Authors: Brandt John T , Barna Linda K , Triplett Douglas A 
Published: July 2018

SummaryLupus anticoagulants (LAs) are antibodies that interfere with phospholipid dependent coagulation reactions in vitro. This workshop was designed to provide the participants with an experience in identification of LAs, to evaluate different criteria for mixing studies, to assess the performance of recently introduced confirmatory studies and to assess the performance of two potential surrogate LA control plasmas. The results demonstrate that there continues to be significant variation in the sensitivity and responsiveness of APTT reagents to the presence of LAs, confirming the need for more than one screening assay before the presence of a LA can be ruled out. In this workshop, the best distinction between factor deficiency and inhibitors was obtained using a 1:1 mix of normal plasma with patient plasma and the criterion defining correction as shortening of the APTT to within 5 s of the APTT of pooled normal plasma. A 4:1 mix of patient to normal plasma did not work well in distinguishing factor deficiency from inhibitors. The platelet neutralization procedure, DVVconfirm® and StaClot LA® all gave positive results with the LA samples. False positive platelet neutralization procedures were seen with the samples from patients on oral anticoagulants and a factor V inhibitor. False positive StaClot LA results were obtained with high titer factor VIII inhibitors. Both of the potential surrogate plasmas gave variable results with multiple assays; they can not be recommended for routine use at present.
The 1691 G → A Mutation in the Factor V Gene: Relationship to Activated Protein C (APC) Resistance and Thrombosis in 65 Patients
Authors: Leroy-Matheron Catherine , Levent Martine , Pignon Jean-Michel , Mendonça Caio , Gouault-Heilmann Michèle 
Published: July 2018

SummaryFour hundred fifty subjects were screened for the 1691 G → A mutation in the factor V gene. Two hundred ninety-seven patients were referred to us for unexplained thrombosis, 133 were family members of these patients and 20 were normal subjects. We studied the relationships between the mutation, resistance to APC and thrombosis. Among the 450 subjects tested, 65 belonging to 42 families were found to have the 1691 G → A mutation in one (n = 61) or both alleles (n = 4). The prevalence of the mutation in the thrombotic patients was 13%. Resistance to APC was tested for in 247 subjects not on anticoagulant treatment (4 homozygous and 44 heterozygous for the mutation, and 199 individuals without the mutation). Incomplete cosegregation of heterozygosity for the 1691 G → A mutation with APC resistance (APC-SR <2.4 or n-APC-SR <0.75) was observed, showing that the functional assay alone is insufficient for a firm diagnosis. In patients carrying the mutation, elevated levels of prothrombin fragment 1+2 and D-dimers pointed to increased thrombin generation in vivo. Clinical manifestations in the heterozygous subjects were very similar to those reported in heterozygous PC or PS deficiencies, but the first thrombotic event occurred later than in PC- or PS-deficient patients. Homozygosity for the factor V gene mutation appears to be a far more benign thrombotic disorder than homozygous PC and PS deficiencies.
Safety and Efficacy of Monoclonal Antibody Purified Factor IX Concentrate in Previously Untreated Patients with Hemophilia B
Authors: Shapiro Amy D , Ragni Margaret V , Lusher Jeanne M , Culbert Steven , Koerper Marion A , Bergman Garrett E , Hannan Margaret M 
Published: July 2018

SummaryThe safety and efficacy of a monoclonal antibody purified factor IX concentrate were evaluated in two continuing trials of 32 previously untreated patients with mild, moderate, or severe hemophilia B. Patients were evaluated every 2 weeks for 24 weeks and every 3 months thereafter for at least 1 year. No patients became positive for human immunodeficiency virus antibody or hepatitis C virus antibody during the trial. Two patients developed a false-positive hepatitis B core antibody, one transiently, but neither had elevated levels of alanine aminotransferase (ALT). None of the 25 patients evaluable for non-A, non-B, non-C hepatitis by strict International Society of Thrombosis and Hemostasis criteria developed elevated levels of ALT indicative of posttransfusion infection. Anaphylaxis occurred in one subject who also developed an inhibitor to factor IX (19.3 Bethesda units). Five of the eight adverse events reported (63%) were mild in severity, and the relationship of three of these to therapy was considered remote. Hemostasis with monoclonal antibody purified factor IX concentrate was excellent in all patients.
Effect of Heterologous Factor V Heavy Chain Sequences on the Secretion of Recombinant Human Factor VIII
Authors: Ortel Thomas L , Moore Karen D , Ezban Mirella , Kane William H 
Published: July 2018

SummaryFactor VIII and factor V share a repetitive domain structure of A1-A2-B-A3-C1-C2. To define the region(s) within the factor VIII heavy chain that result in inefficient expression of the recombinant protein, we expressed a series of factor VIH/factor V chimeras that contained heterologous sequences from the A1 and/or A2 domains. Substitution of the factor VIIIA1 domain dramatically reduced secretion of factor V ~ 500-fold, whereas substitution of the factor VIII A2 domain had minimal effect on secretion. Conversely, substitution of the factor V A1 domain increased secretion of factor VIII ~3-fold, whereas substitution of the factor V A2 domain actually reduced secretion ~4-fold. Pulse chase experiments confirmed that reduced expression levels were due to decreased secretion rather than instability of secreted protein. Smaller substitutions did not further localize within the A1 domain the regions responsible for inefficient secretion.
Mutations which Introduce Free Cysteine Residues in the Gla-Domain of Vitamin K Dependent Proteins Result in the Formation of Complexes with α1-Microglobulin
Authors: Wojcik E G C , Simioni P , Berg M v d , Girolami A , Bertina R M 
Published: July 2018

SummaryWe have previously described a genetic factor IX variant (Cys18→Arg) for which we demonstrated that it had formed a heterodimer with armicroglobulin through formation of a disulphide bond with the remaining free cysteine residue of the disrupted disulphide bond in the Gla-domain of factor IX. Recently, we observed a similar high molecular weight complex for a genetic protein C variant (Arg-1→Cys). Both the factor IX and the protein C variants have a defect in the calcium induced conformation. In this study we show that the aminoterminus of this protein C variant is prolonged with one amino acid, cysteine. This protein C variant, as well as protein C variants with Arg9→Cys and Ser12→Cys mutations which also carry a free cysteine residue, are shown to be present in plasma as a complex with α1-microglobulin. A prothrombin variant with a Tyr44→Cys mutation, had not formed such a complex. Furthermore, complexes between normal vitamin K-dependent clotting factors and α1-microglobulin were shown to be present in plasma at low concentrations. The data suggest that the presence of an unpaired cysteine residue in the propeptide or the N-terminal half of the Gla-domain has strongly promoted the formation of a complex with α1-microglobulin in the variants.
Nafamostat Mesilate, a Broad Spectrum Protease Inhibitor, Modulates Platelet, Neutrophil and Contact Activation in Simulated Extracorporeal Circulation
Authors: Sundaram Sumuk , Gikakis Nicolas , Erik Hack C , Niewiarowski Stefan , Edmunds L H , Koneti Rao A , Sun Ling , Cooper S L , Colman Robert W 
Published: July 2018

SummaryActivation of humoral and cellular participants in inflammation enhances the risk of postoperative bleeding and multiple organ damage in cardiopulmonary bypass (CPB). We now compare the effects of heparin alone in combination with nafamostat mesilate (NM), a protease inhibitor with specificity of trypsin-like enzymes, in an extracorporeal circuit which simulates CPB. NM significantly inhibits the release of platelet (β-thromboglobulin (βTG) at 60 and 120 min. Platelet counts do not differ. ADP-induced aggregation decreases in circuits with NM, which is due to a direct effect of NM on platelet function. NM prevents any significant release of neutrophil elastase; at 120 min, plasma elastase-α1antitrypsin complex is 0.16 μg/ml in the NM group and 1.24 μg/ml in the control group. NM completely inhibits formation of complexes of C1 inhibitor with kallikrein and FXIIa. NM does not alter markers of complement activation (C1-C1-inhibitor complex and C5b-9), or indicators of thrombin formation (F1.2). However, at 120 min, thrombin activity as measured by release of fibrinopeptide A is significantly decreased. The data indicate that complement activation during CPB correlates poorly with neutrophil activation and that either kallikrein or FXIIa or both may be more important agonists. The ability of NM to inhibit two important contact system proteins and platelet and neutrophil release raises the possibility of suppressing the inflammatory response during clinical CPB.
The Importance of Platelets in the Expression of Monocyte Tissue Factor Antigen Measured by a New Whole Blood Flow Cytometric Assay
Authors: Amirkhosravi A , Alexander M , May K , Francis D A , Warnes G , Biggerstaff J , Francis J L 
Published: July 2018

SummaryPrevious methods for the determination of monocyte tissue factor (TF) have been technically complex, difficult to standardize, prone to spuriously elevated results and difficult to implement in a clinical laboratory environment. We report the development of a two-color whole blood cytometric technique that overcomes many of these disadvantages. The assay uses small volumes of citrated blood (1.0 ml), can be performed in under one hour (if endotoxin stimulation is not performed), is reproducible (CV = 5%) and uses methodology commonly available in clinical laboratories. Baseline (mean ± SD) expression of monocyte TF in normal subjects was very low (1.1 ± 0.95%, Mean Fluorescence [Mean FL] 0.20 ± 0.01) making relatively small increases easy to detect. Monocyte TF expression following endotoxin (LPS) stimulation for 1 h was 34.6 ± 11.2% (Mean FL 0.32 ± 0.04). LPS-stimulated activity varied between subjects (21-68%) but was remarkably consistent for individual subjects (CV = 5.4%). Stimulated monocyte TF expression was directly proportional to the platelet count and was reduced by platelet protective anticoagulants and by ingestion of aspirin. Non LPS-stimulated monocyte TF was markedly increased, in a dose-dependent manner, by adding collagen to whole blood. This was apparently associated with platelet-monocyte binding and could be abolished by anti-P-Selectin. We conclude that the whole blood flow cytometric assay of monocyte TF may be a valuable tool for clinical use and a useful model system for evaluating the humoral and cellular factors governing monocyte TF expression in a natural environment.
Promotion of the Crosslinking of Fibrin and α2-antiplasmin by Platelets
Authors: Hevessy Zsuzsa , Haramura Gizella , Boda Zoltán , Udvardy Miklós , Muszbek László 
Published: July 2018

SummaryFactor XIII (FXIII) is of high importance in the regulation of fibrinolysis. It crosslinks α2-antiplasmin (α2AP) and fibrin and by this way protects fibrin from the prompt elimination by plasmin. Although FXIII of platelets has been implicated in this protective mechanism, the role of platelets and platelet FXIII in the crosslinking process is far from being elucidated. As demonstrated by SDS PAGE and by immunoblotting for α2AP, intact normal platelets resuspended in FXIII-free plasma or FXIII-free fibrinogen solution catalyzed the crosslinking of fibrin chains and also the crosslinking of α2AP to fibrin α-chains. With FXIII-deficient platelets no crosslinking reaction could be observed indicating that the crosslinking with normal platelets was, indeed, due to platelet FXIII and not to another, putative platelet transglutaminase. However, the crosslinking of α2AP to fibrin induced by the FXIII of intact platelets resuspended in FXIII-free plasma was considerably less extensive than the crosslinking carried out by the FXIII of normal plasma in the presence of FXIII-free platelets. Furthermore, the replacement of FXIII-free platelets by normal platelets in normal FXIII-containing plasma resulted in little, if any, difference in the crosslinking process. When crosslinking was induced by highly purified plasma FXIII the presence of intact FXIII-free platelets significantly accelerated the formation of α-chain polymers as well as the incorporation of α2AP-fibrin α-chain hetero-dimer into these polymers. The results indicate that, in physiological conditions, platelet FXIII plays only a minor role in the crosslinking of α2AP and fibrin; however, platelets, independently of their FXIII content, promote the crosslinking reaction by providing a catalytic surface on which the formation of highly crosslinked fibrin polymers is accelerated.
Epinephrine Augments Platelet Recruitment to Immobilized Collagen in Flowing Blood - Evidence for a von Willebrand Factor-mediated Mechanism
Authors: Mustonen Pirjo , Lassila Riitta 
Published: July 2018

SummaryAlthough elevated plasma epinephrine (epi) levels are associated with clinical atherothrombosis, the role of epi in platelet-vessel wall interaction has not been established. Our aim was to study the effect of high physiological epi (10 nM) in an experimental model which tests the interaction between platelets and immobilized collagen in whole blood. Shear forces and anticoagulation were modulated. Epi significantly enhanced platelet deposition, but only at high shear rate (1,600 s-1)- In PPACK- or LMWH-anticoagulated blood, the increase in platelet deposition was 32 to 85 % (p <0.02-0.05). Furthermore, platelet aggregation was cotriggered with subthreshold concentrations of epi and ristocetin, and monoclonal antibodies against glycoprotein (GP) lb (AN 51 and SZ 2) attenuated epi-induced aggregation. We conclude that epi is capable of augmenting platelet functions, which are dependent on the interaction of vWF with GP lb and GP IIb/IIIa. Via this mechanism epi may promote arterial thrombosis in vivo.
The Antithrombotic Effect of Aurin Tricarboxylic Acid in the Guinea Pig Is not Solely due to Its Interaction with the von Willebrand Factor-GPIb Axis
Authors: Azzam K , Cissé-Thiam M , Drouet L 
Published: July 2018

SummaryCommercial aurin tricarboxylic acid (ATA) has been reported to interfere specifically with von Willebrand factor-glycoprotein lb (vWF-GPIb) axis. This study was designed to explore the antithrombotic effects of AT A by examining its effects on guinea pig platelet function in vitro, in vivo and ex vivo. In vitro, addition of various concentrations of ATA to platelet-rich guinea pig plasma totally inhibited ristocetin-induced platelet aggregation, as expected. Unexpectedly, however, ATA similarly inhibited the aggregation induced by ADP, PAF, collagen, I-BOP (a thromboxane A2/prostaglandin H2 analogue) and arachidonic acid.In vivo, the antithrombotic action of ATA was assessed in a model of acute platelet-dependent guinea pig mesenteric artery thrombosis triggered by laser-induced intimal injury. As the thrombotic response of arteries to such injury is a spontaneous cyclic recurrent process, 5 arteries in each animal were consecutively studied for 15 min each after i.v. bolus injection of 5, 7.5 or 10 mg/kg of ATA, which reduced the number of recurrent thrombi per artery in a dose-dependent manner. The highest dose of 10 mg/kg induced maximal inhibition of thrombus formation (72%, p <0.001) 5 min after injection.Ex vivo, platelet aggregation was assessed in blood samples taken before and after i.v. bolus injection of 10 or 15 mg/kg ATA. Ten mg/kg significantly inhibited collagen-induced aggregation, and 15 mg/kg, the aggregation induced by ristocetin, ADP, PAF, collagen, I-BOP and arachidonic acid.The results of the in vivo studies confirmed that ATA is an effective antithrombotic agent. In the in vitro and ex vivo studies, ristocetin-induced platelet aggregation confirmed that ATA interacts with the vWF-GPIb axis, and suggests that the final common pathway of the aggregation induced by other agents tested consists of fibrinogen binding to the platelet GPIIb/IIIa receptor. We conclude that ATA interferes with vWF binding to GPIb, that it may interact with fibrinogen binding to GPIIb/IIIa, and that it might possess potent antithrombotic properties in platelet-mediated thrombosis.
Increased Cyclin Dependent Kinase in Aortic Tissue of Rats Fed Homocysteine
Authors: Lubec Barbara , Arbeiter Klaus , Hoeger Harald , Lubec Gert 
Published: July 2018

Summary
Background. Hyperhomocyst(e)inemia is strongly associated with occlusive arterial disease. Several mechanisms for the development of vascular lesions have been described. A direct effect of homocysteine on proliferation of smooth muscle cells and collagen expression was proposed recently. These observations led us to examine the effect of homocysteine on cyclin dependent kinase, the starter of mitosis and reflecting proliferation.
Methods and results. Thirty Him: OF A rats were divided into three groups. Ten animals were fed for a period of six weeks 50 mg/kg body wt per day homocysteine, ten the same dose of homocysteic acid and ten remained untreated controls. At the end of the experiment we determined aortic cyclin dependent kinase, phosphokinases A and C, aortic homocyst(e)ine and aortic hydroxyproline. Aortic cyclin dependent kinase was significantly (p = 0.0001) elevated in the homocysteine treated group (mean 120 ± 15) compared with the homocysteic acid treated group (mean 71 ± 11) or the untreated group (mean 72 ± 10 fmol/mg aortic tissue). Aortic homocyst(e)ine was significantly higher in homocysteine treated animals (p = 0.0002) strongly correlating with cyclin dependent kinase (r squared = 0.85, p = 0.0001) and with aortic hydroxyproline (r squared = 0.66, p = 0.0001), which in turn was significantly (p = 0.0001) increased in the homocysteine treated group. Phosphokinases A and C determined to rule out nonspecific effects on kinases were not increased by administered homocysteine.
Conclusions. Our findings indicate that homocysteine stimulates aortic cyclin dependent kinase with the possible consequence of proliferation of aortic cells. Aortic collagen accumulation could be explained by either the homocysteine-effect on collagen synthesis described in literature, or secondarily, by increased proliferation of collagen producing aortic cells.
Mutation Spectrum in Patients with Wiskott-Aldrich Syndrome and X-linked Thrombocytopenia: Identification of Twelve Different Mutations in the WASP Gene
Authors: Schwartz Marianne , Békássy Albert , Donnér Mikael , Hertel Thomas , Hreidarson Stefan , Kerndrup Gitte , Stormorken Helge , Stokland Tore , Tranebjcerg Lisbeth , Ørstavik Karen Helene , Skovby Flemming 
Published: July 2018

SummaryTwelve different mutations in the WASP gene were found in twelve unrelated families with Wiskott-Aldrich syndrome (WAS) or X-linked thrombocytopenia (XLT). Four frameshift, one splice, one nonsense mutation, and one 18-base-pair deletion were detected in seven patients with WAS. Only missense mutations were found in five patients diagnosed as having XLT. One of the nucleotide substitutions in exon 2 (codon 86) results in an Arg to Cys replacement. Two other nucleotide substitutions in this codon, R86L and R86H, have been reported previously, both giving rise to typical WAS symptoms, indicating a mutational hot spot in this codon. The finding of mutations in the WASP gene in both WAS and XLT gives further evidence of these syndromes being allelic. The relatively small size of the WASP gene facilitates the detection of mutations and a reliable diagnosis of both carriers and affected fetuses in families with WAS or XLT.
Anticoagulant Response to Agkistrodon Contortrix Venom (ACV test): a New Global Test to Screen for Defects in the Anticoagulant Protein C Pathway
Authors: Robert A , Eschwège V , Hameg H , Drouet L , Aillaud M-F 
Published: July 2018

SummaryAs specific assays used to identify defects in the protein C (PC) anticoagulant pathway are laborious and expensive, we describe here a global test to screen for these defects. This assay is expressed as the ratio of two activated partial thomboplastin times, one in the absence and one in the presence of 0,125 U/ml of the PC activator of Agkistrodon contortrix venom (ACV). Eight of the 168 healthy volunteers of the control group exhibited an ACV ratio below the lower normal limit of 3.37 [6 subjects with the mutation Arg 506 to Gin in their factor V gene (FV R506Q) and one with PS deficiency]. 128 patients who have had at least one episode of deep-vein thrombosis were retrospectively studied. All patients carrying FV Q506R (n = 48), PC deficiency (n = 14) or combined defects, i. e. FV Q506R and PC deficiency (n = 4) or FV Q506R and PS deficiency (n = 3), had ACV ratios < 3.37. PS deficient plasmas (n = 20) exhibited ACV ratios which overlapped normal range. ACV ratios of one out of seven patients with antithrombin deficiency, and 10% of patients without identified defect in the PC anticoagulant pathway (n = 30) were < 3.37. An ACV ratio raised to 3.70 could lead to a test identifying all patients with a defect in the PC anticoagulant pathway.