bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneity of Lupus Anticoagulant (LA) Antibodies: LA Activity in Dilute Russell’s Viper Venom Time and Dilute Kaolin Clotting Time Detect Different Populations of Antibodies in Patients with the “Antiphospholipid” Syndrome
Authors: Kandiah David , Krilis Steven 
Published: March 2018

Summary“Antiphospholipid” (aPL) antibodies comprise two main groups of antibodies, lupus anticoagulant (LA) antibodies and “anticardiolipin” (aCL) antibodies which can be separated by certain chromatographic techniques. In this study we analysed the plasma of 10 patients with aPL antibodies, and were able to demonstrate that in four patients with both clotting test reactivities, the dilute Russell’s Viper Venom Time (dRVVT) activity can be separated from the dilute Kaolin Clotting Time (dKCT) reactivity by using a polyacrylamide-immobilised phosphatidylserine column but not with phospholipid liposomes. The differential reactivity of the autoantibodies in this patient population is not due to binding to β2GPI, prothrombin or protein C in solid-phase immunoassays. Hence LA antibodies detected in different phospholipid-dependent clotting tests detect different populations of antibodies in some APS patients and the routine detection of LA antibodies should be performed with at least two clotting tests looking at different coagulation reactions.
The Prothrombin 20210A Allele Is the Most Prevalent Genetic Risk Factor for Venous Thromboembolism in the Spanish Population
Authors: Coll Inma , Llobet Dolors , Río Elisabeth del , Oliver Arturo , Mateo José , Borrell Montserrat , Fontcuberta Jordi , Souto Juan Carlos 
Published: March 2018

SummaryWe investigated the prevalence of the new recently reported mutation in the prothrombin gene (20210 A) in a sample of 116 unrelated patients with venous thromboembolism. We found 20 heterozygous carriers (17.2%, CI 95% 10.4-21.1). In comparison, we observed 13 carriers among 201 healthy unmatched controls (6.5%, CI 3.5-10.8). The 20210 A mutation seems to increase the risk of venous thrombosis 3-fold (odds ratio 3.1, 95% CI 1.4-6.6). Considering only patients with a first event (n = 62) the OR was 2.0 (p = 0.18, NS) while those with recurrent events (n = 54) showed an OR of 5.9 (95% CI 2.5-14.4). A majority of heterozygous patients (55%) presented a second thrombophilic factor and 60% of affected females had their first event before 30 years of age, while on oral contraceptive treatment. The prevalence found in this study for healthy people is the highest reported to date. The 20210 A variant appears to be the most prevalent genetic risk factor among patients with thrombosis in our geographical area.
The Effects of Standard and Low Molecular Weight Heparin on Bone Nodule Formation In Vitro
Authors: Bhandari Mohit , Hirsh Jack , Weitz Jeffrey , Young Edward , Venner Thomas , Shaughnessy Stephen 
Published: March 2018

SummaryPreviously, we demonstrated in a rat model of heparin-induced osteoporosis that low molecular weight heparin (LMWH) produces less bone loss than unfractionated heparin, and that only heparin increases osteoclast number and activity. In contrast, both heparin and LMWH were found to decrease osteoblast function to a similar extent, possibly because at the doses tested both agents produced maximal inhibition. To examine the relative effects of heparin and LMWH on osteoblast function more closely we used an in vitro bone nodule assay, together with measurements of alkaline phosphatase (ALP) activity. Both agents inhibited bone nodule formation and ALP activity in a concentration-dependent manner, but 6 to 8-fold higher concentrations of LMWH were required to achieve equivalent effects. The effect of heparin on osteoblast function was both chain-length and negative charge-dependent because the ability of defined heparin fragments to inhibit nodule formation correlated with their molecular weight (r = 0.98), and N-desulfated heparin was less inhibitory than heparin. In contrast, the effect of heparin on osteoblast function was pentasaccharide-independent because heparin with low affinity for antithrombin had similar activity to heparin with high antithrombin activity. These findings help to explain mounting clinical evidence that the risk of osteoporosis is lower with LMWH than with heparin.
Ristocetin- and Thrombin-induced Platelet Aggregation at Physiological Shear Rates: Differential Roles for GPIb and GPIIb-IIIa Receptor
Authors: Kasirer-Friede A. , Frojmovic M. M. 
Published: March 2018

SummaryWe recently reported that washed platelets (WP) activated with ADP and expressing surface-bound vWF aggregated in flow through small tubes or in a cylindrical couette device at physiological shear rates of G = 300 s–1-1000 s–1 in the absence of exogenous ligands, with GPIb-vWF partially, and activated GPIIb-IIIa totally required for the aggregation. We have now extended these studies to aggregation of platelets “activated” with ristocetin or thrombin. Washed platelet suspensions with added soluble vWF and ristocetin (0.3-0.75 mg/ml), or activated with thrombin (0.01-0.5 U/ml) but no added ligand, were sheared in a coaxial cylinder device at uniform shear rate, G = 1000 s–1. The collision capture efficiency (αG) with which small aggregates form (= experimental/calculated initial rates of aggregation) was correlated with vWF platelet binding assessed by flow cytometry. The vWF-GPIb interaction was exclusively able to support ristocetin-mediated shear aggregation of metabolically active platelets, with very few vWF monomer equivalents bound per platelet (representing ≤10 molecules of 10 million Da) required to yield high capture efficiencies (αG = 0.38 ± .02; n = 11), suggesting rapid and stable bond formations between vWF and GPIb. However, platelet surface-expressed vWF, generated by addition of thrombin to washed platelets, was found to mediate platelet aggregation with αG = 0.08 ± .01 (n = 6), surprisingly comparable to that previously reported for WP and ADP activation. Blocking the GPIIb-IIIa receptor decreased αG by 95 ± 3% (n = 3), while a monoclonal antibody to the vWF site on GPIb caused a 49 ± 7% (n = 8) decrease in αG. The partial role for GPIb thus appears to reflect a facilitative function for increasing contact time between flowing platelets, and allowing engagement of the GPIIb-IIIa receptor to yield stable attachment.
A Heparin-coated Circuit Maintains Platelet Aggregability in Response to Shear Stress in an In Vitro Model of Cardiopulmonary Bypass
Authors: Hioki I. , Onoda K. , Shimono T. , Shimpo H. , Tanaka K. , Suzuki Y. , Shiku H. , Ikeda Y. , Yada I. , Nishikawa M. 
Published: March 2018

SummaryAlterations in platelet aggregability may play a role in the pathogenesis of qualitative platelet defects associated with cardiopulmonary bypass (CPB). We circulated fresh heparinized whole blood through tubing sets coated with heparin (C group, n = 10) and through non-coated sets (N group, n = 10) as a simulated CPB circuit. Shear stress (108 dyne/cm2)-induced platelet aggregation (hSIPA), plasma von Willebrand factor (vWF) activity and platelet glycoprotein (GP) Ib expression were measured, before, during, and after this in vitro set up of circulation. In the two groups, the extent of hSIPA significantly decreased during circulation and was partially restored after circulation. Decreases in the extent of hSIPA were significantly less with use of heparin-coated circuits. There was an equivalent reduction in plasma vWF activity, in the two groups. Expression of platelet surface GP Ib decreased significantly during circulation and recovered after circulation. Reduction of surface GP Ib expression during circulation was significantly less in the C group than that in the N group. Decrease in surface GP Ib expression correlated (r = 0.88 in either group) with the magnitude of hSIPA, in the two groups. The progressive removal of surface GP Ib was mainly attributed to redistribution of GP Ib from the membrane skeleton into the cytoskeleton. Our observations suggest that use of heparin-coated circuits partly blocks the reduction of hSIPA, as a result of a lesser degree of redistribution of GP Ib.
Analysis of Platelet Glycoprotein Ia (α2 Integrin) Allele Frequencies in Three North American Populations Reveals Genetic Association between Nucleotide 807C/T and Amino Acid 505 Glu/Lys (HPA-5) Dimorphisms
Authors: Aramaki Kaelen , Teramura Gayle , Gaur Lakshmi , Reiner Alexander 
Published: March 2018

SummaryGlycoprotein Ia (α2 integrin) is a subunit of the heterodimeric membrane complex (GPIa/IIa) that mediates platelet adhesion to collagen. Several nucleotide sequence variations of GPIa have been described. A nucleotide 1648 G/A dimorphism that leads to a Glu/Lys substitution at amino acid 505 is responsible for the human platelet antigen system, HPA-5. Recently, two other linked GPIa nucleotide dimorphisms involving codons Phe224 and Thr246 were identified: a C/T substitution at nucleotide 807 and a G/A substitution at nucleotide 873 (1). Using restriction enzyme digestion of amplified GPIa genomic DNA fragments (PCR-RFLP) to distinguish genotypes, we have determined the allele frequencies of the GPIa 807C/T and Glu/Lys505 dimorphisms in three North American populations, and a panel of non-human primates. Our results indicate a genetic relationship between the 807C/T and Glu/Lys505 dimorphisms that leads to an evolutionary model of GPIa isoforms.
Induction of Endothelial Cell Adhesion Molecules by Serum and Immunoglobulins G from a Patient with Vasculitis and Monoclonal Gammapathy: Potential Relevance to Vasculitis
Authors: Herbert Jean-Marc , Giraudeau Véronique , Quere Isabelle , Zini Jean-Marc , Tobelem Gérard , Dupuy Evelyne 
Published: March 2018

SummaryInteractions between endothelial cell adhesion molecules and their β2 integrin adhesive receptors on leukocytes are thought to play a role in the pathogenesis of inflammatory diseases and probably vasculitis. We describe a case in whom leukocytoclastic vasculitis was associated to a monoclonal immunoglobulin G2 kappa (IgG2K). During the vasculitic crisis, the patient’s serum and the isolated IgG from this serum induced the expression of E-selectin, VCAM-1 and ICAM-1 at the HUVEC surface, but not tissue factor activity, whereas normal, control serum and patient serum at remission were without any effect.A close relationship between the vasculitis and the serum level of the monoclonal IgG was observed. We suggest that the monoclonal IgG might induce the vasculitis by increasing the expression of E-selectin, VCAM-1 and ICAM-1 which facilitate the interaction of leukocytes with vascular endothelium.
Hemorrhagic Transformation of Cerebral Infarction – Possible Mechanisms
Authors: del Zoppo Gregory J. , von Kummer Rüdiger , Hamann Gerhard F. 
Published: March 2018

SummaryTo analyse the risk/benefit of cerebral thrombolysis the role of hemorrhagic transformation, either as clinically silent hemorrhagic infarction or disastreous parenchymal hemorrhage, is crucial. Thrombolysis in acute ischemic stroke increases the risk of severe, life-threatening hemorrhagic complications by up to 10 times compared to controls. In this paper, previous proposed concepts for the development of intracerebral hemorrhage and hemorrhagic transformation are presented. The role of the cerebral microvasculature will be emphasized. In experimental focal cerebral ischemia a significant loss of basal lamina components of the cerebral microvessels has been demonstrated. This loss in vessel wall integrity is associated with the development of petechial hemorrhage. The mechanisms for this microvascular damage may include plasmin-generated laminin degradation, matrix metalloproteinases activation, transmigration of leukocytes through the vessel wall, and other processes. We propose that attenuation of the microvascular integrity loss with subsequent reduction in hemorrhage is theoretically possible 1) by an improvement in the definition of an individual time window of therapy (by means of imaging techniques), 2) by a biochemical quantification of the basal lamina damage to avoid dangerous interventions, and 3) by pharmacological strategies to protect the basal lamina during thrombolysis.
Bed Rest in Deep Vein Thrombosis and the Incidence of Scintigraphic Pulmonary Embolism
Authors: Schwarz Thomas , Kropp Joachim , Prescher Yvette , Beuthien-Baumann Bettina , Daniel Werner G. , Schellong Sebastian M. 
Published: March 2018

SummaryIn several countries of central Europe, patients with acute proximal deep vein thrombosis (DVT) are treated not only by anticoagulation and compression therapy but additionally by strict bed rest for 6-8 days. Until now the theoretical assumption that bed rest substantially reduces the incidence of pulmonary embolism has not been subjected to empirical verification. Patients with acute proximal DVT proven by ultrasonography were randomly assigned to strict bed rest for 8 days (treatment group) or to stay mobilised (control group). In both groups, basic treatment consisted in anticoagulation by subcutaneous low molecular weight heparin/vitamin-K-antagonist and compression therapy. The incidence of pulmonary embolism was assessed by serial ventilation/perfusion SPECT on day 1 and days 8-10. Of the 309 patients with proximal DVT considered for inclusion, 180 were excluded according to the study protocol, and 3 did not give informed consent. One hundred and twenty-six patients were randomly assigned to observe bed rest (n = 62) or to keep mobilised (n = 64). Four patients refused follow-up lung scan.A new lung perfusion defect was detected in 10/59 patients in the treatment group compared to 14/63 patients in the control group (one-sided p-value = 0.25; power 0.8). Bed rest as an additional measure in the treatment of DVT is not able to substantially reduce the incidence of scintigraphically detectable pulmonary embolism. The discomfort and costs associated with the prescription of bed rest in DVT are obviously inappropriate.
Conventional Fibrinolytic Assays for the Evaluation of Patients with Venous Thrombosis: Don’t Bother
Authors: Bauer Kenneth 
Published: March 2018

SummaryHypofibrinolysis, as defined by an absent or deficient increase in blood or plasma fibrinolytic activity after an appropriate stimulus, has been known to be present in patients following an episode of deep venous thrombosis for over 30 years. The usual stimulus is 10 min of venous occlusion using a blood pressure cuff inflated to a pressure midway between systolic and diastolic pressures. The early screening fibrinolytic assays were relatively insensitive in detecting fibrinolytic system hypofunction and lacked standardization.Supported in part by the Medical Research Service of the Department of Veterans Affairs.
Open Multicentre Study of the P
2T
Receptor Antagonist AR-C69931MX Assessing Safety, Tolerability and Activity in Patients with Acute Coronary Syndromes
Authors: Oldroyd Keith , Wilcox Robert , Storey Robert ,   the Investigators
Published: March 2018

SummaryPlatelet aggregation is the central process in the pathophysiology of acute coronary syndromes. ADP contributes to thrombosis by activating platelets, and AR-C69931MX is a specific antagonist of this process acting at the P
2T
receptor. At 5 hospitals, 39 patients with unstable angina or non-Q wave myocardial infarction, who were receiving aspirin and heparin, were administered intravenous AR-C69931MX with stepped dose increments over 3 h to a plateau of either 2 μg/kg/min for 21 h (Part 1; n = 12) or up to 69 h (Part 2; n = 13) or 4 μg/kg/min for up to 69 h (Part 3: n = 14). Safety parameters, platelet aggregation (PA) induced by ADP 3 μmol/L (impedance aggregometry), bleeding time (BT) and plasma concentrations of AR-C69931XX were assessed. AR-C69931MX was well tolerated. 33 patients completed the study. There were no deaths at 30 days and no serious adverse events attributed to AR-C69931MX. Trivial bleeding (56%) was common. At 24 h, mean inhibition of PA was 96.0 ± 8.6, 94.9 ± 14.4 and 98.7 ± 2.1% and BT was 9.5 ± 8.4, 14.0 ± 9.7 and 16.0 ± 11.1 min for Parts 1, 2 and 3 respectively. At 1 h post-infusion, mean inhibition of PA was 36.2 ± 39.2, 20.7 ± 25.9 and 40.7 ± 36.7% respectively. 90% patients had a plasma half-life for AR-C69931XX of 9 min. In conclusion, AR-C69931MX is a potent, short-acting platelet ADP receptor antagonist suitable for further studies as an antithrombotic agent.
Oral Anticoagulant Therapy in Patients with Nonrheumatic Atrial Fibrillation and Risk of Bleeding
Authors: Legnani Cristina , Noventa Franco , Palareti Gualtiero , Pengo Vittorio ,   the ISCOAT
Published: March 2018

SummaryOral anticoagulants (OA) are the drug of choice for stroke prevention in patients with non-rheumatic atrial fibrillation (NRAF). This clear benefit/risk ratio comes from several randomized clinical trials (RCT) in which highly selected patients were strictly monitored. The aim of this study was to ascertain whether the safety of OA was also obtained outside the setting of clinical trials in consecutive patients starting treatment and routinely followed at Italian anticoagulation clinics. A total of 433 patients with NRAF were enrolled in the ISCOAT study and followed up for a mean of 1.4 years. Two patients (0.3% per year) suffered from a complete non-fatal ischemic stroke, 8 patients (1.3% per year) died of thrombosis-related vascular death, and 11 patients (11 events, 1.8% per year) suffered from major bleedings (2 fatal). Major bleeding occurred more frequently in patients >75 years of age (6 events, 5.1% per year) than in younger patients (5 events, 1.0% per year).The cumulative incidence of major bleeding in patients over 75 years of age (10.8%; 95% CI, 1.8-19.8) was significantly higher than in younger patients (2.8%; 95% CI, 0.3-5.3, p = 0.006). Major primary bleeding unrelated to organic lesions (7 patients, 1 male and 6 females) occurred in 5 elderly patients (>75 years old) with a cumulative incidence (9.6%; 95% CI 0.8-18.4) significantly higher than in younger patients (1.2%; 95% CI, 0-3.0, p = 0.0003). Univariate analysis revealed a higher frequency of major primary bleeding in females, in diabetic patients and in in those who had suffered a previous thromboembolic event. Multivariate analysis revealed that only age grater than 75 years was independently related to major primary bleedings (RR 6.6; 95% CI 1.2-37, p = 0.032). Minor bleedings (n = 27) were not more frequent in elderly patients (6% vs 4% per year, p = ns). Patients were kept at optimal intensity of treatment for 63% of the time. These data confirm the efficacy of OA but identify elderly patients as a high risk group of major bleeding.
The Amino Acid Sequence in Fibrin Responsible for High Affinity Thrombin Binding
Authors: Siebenlist Kevin , Brennan Stephen , Holyst Trudy , Mosesson Michael , Meh David 
Published: March 2018

SummaryHuman fibrin has a low affinity thrombin binding site in its E domain and a high affinity binding site in the carboxy-terminal region of its variant ’ chain (’408-427). Comparison of the ’ amino acid sequence (VRPEHPAETEYDSLYPEDDL) with other protein sequences known to bind to thrombin exosites such as those in GPIb , the platelet thrombin receptor, thrombomodulin, and hirudin suggests no homology or consensus sequences, but Glu and Asp enrichment are common to all. Tyrosine sulfation in these sequences enhances thrombin exosite binding, but this has not been uniformly investigated. The fibrinogen ’ chain mass determined by electrospray ionization mass spectrometry, was 50,549 Da, a value 151 Da greater than predicted from its amino acid/carbohydrate sequence. Since each sulfate group increases mass by 80 Da, this indicates that both tyrosines at 418 and 422 are sulfated. A series of overlapping ’ peptides was prepared for evaluation of their inhibition of 125I-labeled PPACK-thrombin binding to fibrin. ’414-427 was as effective an inhibitor as ’408-427 and its binding affinity was dependent on all carboxy-terminal residues. Mono Tyr-sulfated peptides were prepared by substituting non-sulfatable Phe for Tyr at ’ 418 or 422. Sulfation at either Tyr residue increased binding competition compared with non-sulfated peptides, but was less effective than doubly sulfated peptides, which had 4 to 8-fold greater affinity. The reverse ’ peptide or the forward sequence with repositioned Tyr residues did not compete well for thrombin binding, indicating that the positions of charged residues are important for thrombin binding affinity
Targeted Disruption of the Mouse Gz-alpha Gene: A Role for Gz in Platelet Function?
Authors: Matthaei Klaus , Kelleher Kim 
Published: March 2018

SummaryGz is one of nine G proteins identified in platelets and its role in these cells is unknown. Our laboratory has generated a mouse deficient in the Gz-alpha gene in the hope of determining its in vivo function. Bleeding times from the tail tip of Gzα deficient mice was significantly longer than wild type mice. Platelet aggregation and ATP secretion did not differ between wild type and Gzα deficient mice. When mice were presented with a thromboembolism challenge no differences were observed in the survival or mortality of wild type or Gzα deficient mice, however a strain difference was observed. Ignoring the genetic background of a mutant mouse might lead to a misinterpretation of results and thus it is absolutely critical to take the genetic background into account when assessing any aspect of a mutant mouse.
Factor XI Assembly and Activation on Human Umbilical Vein Endothelial Cells in Culture
Authors: Shariat-Madar Zia , Mahdi Fakhri , Schmaier Alvin 
Published: March 2018

SummaryBiotin-FXI optimally bound to HUVEC in the presence of 40 nM high molecular weight kininogen (HK) and ≥ ≥7 μM Zn2+. There was little specific FXI binding in the absence of added HK and at concentrations of Zn2+ <15 μM. FXI and prekallikrein, but not prothrombin, blocked biotin-FXI binding to HUVEC in the presence of HK with an IC50 of 18 nM and 180 nM, respectively. Monoclonal antibody HKL16 and peptide SDD31 also inhibited biotin-XI binding in the presence of HK with an IC50 of 4.7 nM and 50 μM, respectively. Alternatively, peptide T249-F260 of FXI’s apple domain 3 and heparin monosulfate were weak inhibitors of FXI binding to HUVEC. FXI bound to HUVEC with an apparent K
d
of 6.9 ± 3.0 nM and B
max
of 13 ± 2.6106 sites/cell. FXI bound to HK on HUVEC, but not prothrombin, became converted to FXIa. FXI activation on HUVEC resulted from tissue culture media bovine factor XIIa. HUVEC grown in human factor XII-deficient serum did not support FXI activation. FXI binding to HUVEC in culture was mostly mediated by HK and FXI activation on HUVEC is dependent on cell-associated factor XIIa.