bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early Platelet Activation by Low Density Lipoprotein via p38MAP Kinase
Authors: Hackeng Christian , Relou Ingrid , Pladet Marc , Gorter Gertie , van Rijn Herman , Akkerman Jan-Willem 
Published: March 2018

SummaryLow Density Lipoprotein (LDL) is known to sensitize platelets for physiological agonists. To clarify the basis of this sensitization, we investigated the involvement of p38MAP Kinase (p38MAPK). As dual phosphorylation on Thr180 and Tyr182 of p38MAPK is the trigger for activation of the kinase, p38MAPK-activity was measured with an antibody that recognizes the dual-phosphorylated sequence. LDL induced a rapid and dose dependent activation of p38MAPK. The activation was not inhibited by a wide variety of inhibitors of platelet signalling, including TxA2-formation, Phospholipase C-activation, Ca2+-mobilization and ERK 1/2-activation. Only a slight reduction in p38MAPK-activation was observed when protein kinase C was inhibited. Activation of p38MAPK was strongly inhibited by a rise in cAMP. Thus, p38MAPK-activation was upstream of most signalling pathways and close to the LDL-receptor. A number of platelet receptors was screened with the use of antibodies. Integrins αIIbβ3 and α2β1, as well as the FcγRII-receptor, CD36 (platelet glycoprotein IV), CD68 (gp110) and Low Density Lipoprotein-receptor related protein (LRP) were not implicated in LDL-induced p38MAPK-activation. Inhibition of LDL binding by modification of apo B100 lysines reduced p38MAPK-activation by 80 %. Activation of p38MAPK resulted in an increase in release of arachidonic acid, the precursor for thromboxane A2 synthesis. In conclusion, activation of p38MAPK might be the first step in platelet sensitization by LDL, leading to formation of arachidonate metabolites and increased aggregation and secretion responses to physiological agonists.
Endothelialization of Crosslinked Albumin-heparin Gels
Authors: Bos Gert , Scharenborg Nicole , Poot André , Engbers Gerard , Beugeling Tom , van Aken Willem , Feijen Jan 
Published: March 2018

SummaryCrosslinked gels of albumin as well as heparinized albumin gels, potential sealants of prosthetic vascular grafts, were studied with regard to in vitro stability, binding of basic fibroblast growth factor (bFGF) and cellular interactions. A small percentage of the heparin present in these gels, was released during storage in SDS solution. During storage in cell culture medium at 37° C, heparin release was 21-25 percent. Release of albumin did not occur.Human umbilical vein endothelial cells (HUVECs) rapidly adhered and subsequently spread on (heparinized) albumin gels, but proliferation was only observed if heparin was present in the gel.Binding of 125I-bFGF to heparinized albumin gel was 35 percent higher than to non-heparinized albumin gel. Growth of HUVECs occurred only on heparinized albumin gel loaded with bFGF and not on bFGF-loaded albumin gel.The number of platelets deposited under stationary conditions onto heparinized albumin gel was about twice the number found on nonheparinized albumin gel. Seeding of HUVECs on heparinized albumin gel, significantly reduced the number of platelets adhering to this surface. Moreover, no spreading of platelets was observed on substrates seeded with HUVECs.It can be concluded that crosslinked gels of albumin to which heparin is immobilized, are candidate sealants for prosthetic vascular grafts and suitable substrates for endothelial cell seeding.
Thermolabile Methylenetetrahydrofolate Reductase and Factor V Leiden in the Risk of Deep-Vein Thrombosis
Authors: Kluijtmans Leo , Heijer Martin den , Reitsma Pieter , Heil Sandra , Rosendaal Frits , Blom Henk 
Published: March 2018

SummaryMild hyperhomocysteinemia is an established risk factor for both arteriosclerosis and thrombosis, and may be caused by genetic and environmental factors. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, the cofactor for the methylation of homocysteine to methionine. Individuals with the thermolabile variant of MTHFR have decreased MTHFR activities, resulting in elevated plasma homocysteine concentrations. A homozygous 677C→T transition in the MTHFR gene has recently been identified as the cause of reduced enzyme activity and thermolability of the protein. We studied the frequency of the homozygous mutant (+/+) genotype in 471 patients with deep-vein thrombosis and 474 healthy controls enrolled in The Leiden Thrombophilia Study (LETS), its interaction with factor V Leiden, and assessed the association between the MTHFR genotypes and plasma homocysteine concentration. Homozygosity for the 677C→T polymorphism was observed in 47 (10%) patients, and in 47 (9.9%) controls (OR 1.01 [95% CI: 0.7-1.5]). No modified risk of the (+/+) genotype was observed in carriers of factor V Leiden. Our data suggest that, although the homozygous mutant genotype is associated with elevated plasma homocysteine concentrations, this homozygous mutation itself is not a genetic risk factor for deep-vein thrombosis, irrespective of factor V Leiden genotype.
Replacing Inpatient Care by Outpatient Care in the Treatment of Deep Venous Thrombosis – An Economic Evaluation
Authors: van den Belt Angelique , Prins Martin , Gallus Alexander , Büller Harry , Bossuyt Patrick ,   for the TASMAN Study Group
Published: March 2018

SummaryTwo clinical trials in patients with acute deep venous thrombosis have indicated that the outpatient management with fixed-dose, subcutaneous low-molecular-weight heparin is at least as effective and safe as inpatient treatment with unfractionated intravenous heparin with respect to recurrent venous thromboembolism and major bleeding. We performed an economic evaluation alongside one of these trials to assess the cost consequences of the outpatient management strategy. Data were collected through case record forms, complemented by a prospective questionnaire in 78 consecutive patients, interviews with health care providers, and hospital data bases. Our study demonstrated that seventy-five percent of patients allocated to low-molecular-weight heparin received treatment either entirely at home or after a brief hospital stay. Fifteen percent of these patients required professional domiciliary care. Within-centre comparisons of resource utilisation in terms of natural units showed that outpatient management with low-molecular-weight heparin reduced the average number of hospital days in the initial treatment period in nine centres by 59 percent (95% CI: 43 to 71 percent) accompanied by a limited increase in outpatient and professional domiciliary care. The average reduction in hospital days at the end of follow up was 40 percent (95% CI: 25 to 54 percent). A cost-minimisation analysis, focusing on resource utilisation directly related to the treatment of deep venous thrombosis and associated costs in one centre demonstrated a cost reduction of 64 percent (95% CI: 56 to 72 percent) with the outpatient management with low-molecular-weight heparin. These data suggest that outpatient management of patients with proximal venous thrombosis using low-molecular-weight heparin reduces resource utilisation and total treatment cost. Implementation should be preceded by a cautious evaluation of a potential cost shifting and organisational prerequisites.
Impaired Haemostasis by Intravenous Administration of a Gelatin-based Plasma Expander in Human Subjects
Authors: Levi M. , Berends F. , Ende A. E. van der , Cate J. W. ten , Stoutenbeek C. P. , Jonge E. de 
Published: March 2018

SummaryThe aim of this study was to investigate the effects of a gelatin-based plasma expander on blood coagulation and haemostasis in human subjects.Six healthy men were studied in a randomised, controlled cross-over study to investigate the effects of a 60 min intravenous infusion of either 1 l gelatin-based plasma substitute (Gelofusine) or 0.9% NaCl (control). The infusion of gelatin resulted in a 1.7 fold increase in bleeding time at 60 min and a 1.4 fold increase at 120 min, while saline had no effect (p <0.05). Aggregation studies revealed a significant impairment of ristocetin-induced platelet aggregation (p <0.05), associated with a substantial decrease of vWF:ag (–32% vs. –5%, p <0.05) and ristocetin co-factor (–29% vs. +1%, p <0.05) and without in vitro impairment of the platelet glycoprotein 1b receptor. Gelatin caused a decrease in thrombin-antithrombin complexes (–45% vs. –4%, p <0.05) and F1+2 (–40% vs. +1%, p <0.05). The decrease in circulating levels of vWF:ag, vWF R:Co, thrombin-antithrombin complexes and F1+ 2 was more than could be expected by the calculated plasma-dilution generated by Gelofusine.Our results demonstrated that the administration of a gelatin-based plasma substitute results in a significant impairment of primary haemostasis and thrombin generation. The defect in primary haemostasis appears to be related to a gelatin-induced reduction in von Willebrand factor, whereas the decreased thrombin generation may be due to the dilution of coagulation factors induced by Gelofusine.
Initiation and Propagation of Blood Coagulation at Artificial Surfaces Studied in a Capillary Flow Reactor
Authors: Blezer Ron , Willems George , Cahalan Patrick , Lindhout Theo 
Published: March 2018

SummaryWe have made use of a novel flow reactor to study the initiation and propagation of the ex vivo blood coagulation processes at artificial surfaces. The flow reactor consisted of a primary glass or polymer capillary that is connected to a secondary glass capillary, which inner wall was coated with a phospholipid bilayer of 25 mol% dioleoylphosphatidylserine/75 mol% dioleoylphosphatidylcholine (DOPS/DOPC). Citrated platelet free plasma and a CaCl2 solution were delivered by syringe pumps and mixed just before the entrance of the flow reactor. The outflowing plasma was assayed for factor XIa, factor IXa, factor Xa and thrombin activity. Perfusion of recalcified plasma through a bare glass capillary resulted in a transient generation of fluid phase factor XIa. In contrast, factor IXa production increased slowly to attain a stable steady-state level. We established that surface-bound factor XIa was responsible for a continuous production of factor IXa. Factor IXa-induced generation of factor Xa and thrombin was only observed when contact activated plasma was subsequently perfused through a DOPS/DOPC-coated capillary, showing that propagation of the factor IXa trigger requires a procoagulant, phosphatidylserine-containing, phospholipid membrane. The negatively charged inner surface of a heparin-coated polyurethane capillary, generated like the glass capillary significant amounts of factor XIa and factor IXa when perfused with recalcified plasma. No differences were found between unfractionated heparin and heparin devoid of anticoagulant activity. Thus, it is concluded that contact activation and factor IXa generation in flowing plasma is not inhibited by immobilised anticoagulant active heparin. Consequently, factor IXa-dependent thrombin generation at a downstream located phospholipid membrane was similar, regardless the specific anticoagulant activity of immobilised heparin.
Phosphorothioate Oligodeoxyribonucleotides Antisense to PAI-1 mRNA Increase Fibrinolysis and Modify Experimental Thrombosis in Rats
Authors: Pawlowska Zofia , Pluskota Elzbieta , Chabielska Ewa , Buczko Wlodzimierz , Okruszek Andrzej , Stec Wojciech , Cierniewski Czeslaw 
Published: March 2018

SummaryThe effect of systemic inhibition of PAI-1 expression in rats by PS-16R, a phosphorothioate analogue of hexadecadeoxyribonucleotide complementary to a signal peptide coding sequence of rat PAI-1 mRNA, on PAI-1 activity in blood plasma and thrombus formation was studied in rat models for experimental thrombosis. In previous in vitro studies, oligonucleotides of PS-16R family have been shown to inhibit efficiently PAI-1 synthesis in endothelial cells by antisense mechanism. When PS-16R was administered intravenously as a single bolus injection (1 to 5 mg per rat), it produced a significant reduction in PAI-1 activity of blood plasma. This effect was both time- and concentration-dependent. Under the same conditions, three groups of rats were treated with control oligodeoxynucleotides such as PS-16R with double mismatches, with scrambled sequence, and an oligodeoxynucleotide with sense sequence (complementary to PS-16R), respectively. Based on these preliminary experiments, a low dose of 1.5 mg per rat was selected to produce approximately 20-30% reduction of PAI-1 activity in blood plasma and the effect of such a decrease in PAI-1 expression was tested on thrombus formation in two rat models for experimentally induced thrombosis. Such a limited decrease in PAI-1 activity produced a significant antithrombotic effect in the arterial thrombosis model. There was a profound delay in the occlusion time in rats treated with PS-16R when compared to control animals (80 ± 3 and 55 ± 3 h, respec tively), although blood plasma activity of PAI-1 in the same groups of rats differed only by 20%. There was also a tendency to reduce both an incidence of venous thrombosis (58.33 and 68.11%, respectively) and thrombus weight (2.1 ± 0.4 and 2.9 ± 0.9 mg, respectively) in the animals treated with PS-16R. However, this effect was not significant. Thus, low dose of PS-16R through inhibition of PAI-1 synthesis in targeted cells in rats reduced PAI-1 activity in blood plasma and protected against arterial thrombus formation in the rat.
Thrombin Stimulates Smooth Muscle Cell Procollagen Synthesis and mRNA Levels via a PAR-1 Mediated Mechanism
Authors: Laurent G. J. , McAnulty R. J. , Chambers R. C. , Dabbagh K. 
Published: March 2018

SummaryThrombin is a serine protease involved in haemostasis which exerts a number of cellular effects, including stimulating mesenchymal cell migration, proliferation, and has been implicated both in normal wound healing and pathological conditions associated with hyperproliferation of smooth muscle cells such as atherosclerosis and restenosis. We hypothesize that thrombin, in addition to its proliferative effects, may also influence the deposition of matrix proteins at sites of vascular injury by directly stimulating smooth muscle cell procollagen production.10 nM thrombin significantly stimulated rat aortic smooth muscle cell procollagen production by 34 ± 3% compared to media control cells over a 48 h incubation period, and increased steady state α1(I) pro-collagen mRNA levels by up to 104 ± 22%. These effects are mediated via interaction of thrombin with the PAR-1 receptor since TRAP (Thrombin Receptor Activating Peptide) stimulated procollagen production by 23 ± 0.5%. In addition, conditioned medium from thrombin-treated cells stimulated procollagen production by 30 ± 3% suggesting that thrombin is acting via the production and/or release of an autocrine mediator.These data suggest a novel role for thrombin in vascular wound healing and the development of pathological conditions associated with increased connective tissue deposition.
Platelet Activity In Vivo in Hyperlipoproteinemia – Importance of Combined Hyperlipidemia
Authors: Bröijersén Anders , Hamsten Anders , Eriksson Mats , Angelin Bo , Hjemdahl Paul 
Published: March 2018

SummaryPlatelet hyperactivity in vitro is found in patients with isolated hypercholesterolemia. It is, however, less well established if platelet activity in vivo is enhanced, and if there are differences between various types of hyperlipoproteinemia.Platelet function in vivo was studied at rest and during mental stress in men with isolated hypercholesterolemia (phenotype IIa; n = 21) or combined hyperlipidemia (phenotype IIb; n = 29), and age-matched normolipidemic controls (n = 41). The urinary excretion of 11-dehydrothromboxane B2 was elevated in patients compared to controls (IIa, p <0.05; IIb, p <0.001), and higher in type IIb than in IIa patients (p <0.05). Platelet secretion, assessed as plasma β-thromboglobulin levels, was higher in type IIb patients compared to controls (p <0.01) and type IIa patients (p <0.05) during mental stress. The urinary excretion of β-thromboglobulin was also elevated in type IIb patients compared to controls (p <0.05). Platelet aggregability at rest, as measured by filtragometry ex vivo was, however, reduced in both patient groups compared to controls (p <0.05). No correlations were found between plasma lipoprotein levels and markers of platelet function in vivo. Type IIb patients had higher plasma fibrinogen levels and higher leukocyte counts than controls (p <0.05 and p <0.001) and type IIa patients (p <0.05 and p = 0.06). Thromboxane excretion was positively related to fibrinogen levels and leukocyte counts (p <0.01 for both). Preliminary data regarding serum TNF-α also indicated an elevation of this inflammatory cytokine in type IIb patients (p <0.05 vs controls).In conclusion, thromboxane generation and platelet secretion in vivo are enhanced in patients with hypercholesterolemia, and particularly so among patients with concomitant elevation of plasma triglycerides. The mechanism is unknown, but inflammatory mediators may be involved. The present findings are of interest in relation to the role of triglycerides in coronary artery disease.
Identification of a Glucocorticoid Response Element in the Human γ Chain Fibrinogen Promoter
Authors: Asselta Rosanna , Duga Stefano , Modugno Michele , Malcovati Massimo , Tenchini Maria Luisa 
Published: March 2018

SummaryThe effect of the synthetic glucocorticoid hormone dexamethasone on human γ chain fibrinogen gene expression was examined. The whole promoter region of 3.8 kb of this gene and progressive 5’-deletions were inserted into a promoterless expression vector, upstream of the luciferase gene and transiently transfected into the human hepatoma HepG2 cells, in the presence or in the absence of dexamethasone stimulation. Deletion analysis allowed to identify a region located between –1359 and –954 bp upstream from the transcription start site, involved in hormone inducibility. On the basis of a computer-assisted analysis, a putative GRE was found in this region at bases –1116 to –1102. Specific point mutations eliminating this putative GRE led to complete loss of glucocorticoid inducibility, thus indicating its functional role. Binding of the rat glucocorticoid receptor to this site was demonstrated by mobility-shift assays.
On the Mechanism of Plasmin-induced Aggregation of Human Platelets: Implication of Secreted von Willebrand Factor
Authors: Rabhi-Sabile S. , de Romeuf C. , Pidard D. 
Published: March 2018

SummaryPlasmin triggers a strong metabolic activation in human platelets, leading to shape change and granule exocytosis. However, its capacity to induce cell aggregation remains discussed and, when observed, this aggregation is preceded by a remarkable lag phase. We have thus investigated the effect of plasmin on the adhesive proteins which can be secreted by isolated platelets and mediate cell-to-cell interactions, but are also substrates for the enzyme. Immunoblot analysis of fibrinogen (Fg), thrombospondin-1 (TSP-1), fibronectin (Fn) and von Willebrand factor (vWf) was performed on extracts of platelets exposed under stirring to increasing concentrations of plasmin for up to 10 min at 37° C. Under conditions leading to formation of large aggregates, Fg, Fn and TSP-1 are extensively degraded concomitantly with their secretion, and readily lost from the surface of aggregated cells. Part of the monomers in the platelet vWf are cleaved during secretion into two main fragments with M
r
≈180,000 and ≈145,000. However, multimer distribution analysis shows only a slight decrease in the very high molecular weight multimers, and most of the fragmented as well as intact vWf remains associated with the platelet surface when aggregation is maximal. That indeed vWf largely supports plasmin-induced aggregation is suggested by the observation that platelets from a patient with type 3 von Willebrand’s disease, who totally lacks vWf, show little aggregation in response to the enzyme. Finally, plasmin-induced aggregation can be totally inhibited by antagonists of the αIIbβ3 integrin. The present study thus indicates a major role for secreted vWf in platelet aggregation induced by plasmin, through its likely interaction with the multifunctional receptor αIIbβ3.Presented in part at the European Platelet Group Meeting, Erfurt, Germany, May 1996
The cDNA Cloning and Molecular Characterization of a Snake Venom Platelet Glycoprotein Ib-binding Protein, Mamushigin, from Agkistrodon halys blomhoffii Venom
Authors: Sakurai Yoshihiko , Kokubo Tetsuro , Imamura Kouji , Kawasaki Tomihisa , Handa Makoto , Suzuki Masami , Matsui Taei , Titani Koiti , Yoshioka Akira , Fujimura Yoshihiro 
Published: March 2018

SummaryThe entire cDNA sequences of a novel snake venom platelet glyco-protein (GP) Ib-binding protein (BP) composed of an α/β heterodimeric structure, termed mamushigin, from Agkistrodon halys blomhoffii were determined, that include the leader peptides (21/23 amino acid residues) and mature subunits (136/123 amino acid residues). The mature subunits of mamushigin are 37.5% identical, and showed a high degree of similarity (37.7-67.5% identity) with the respective subunits of group VII C-type lectins (19). The sequences of the leader peptides of the mamusigin subunits showed the highest similarity (α-73.9/ β-82.6%) with those of factor IX/X-BP from Trimeresurus flavoviridis, and the cleavage site residue in both proteins was the same Ala–1.The GPIb-binding specificity of mamushigin is strongly supported by several lines of evidence, but mamushigin can directly aggregate normal platelets, similar to alboaggregin-B (AL-B) (1). This differs from other GPIb-BP’s. In mamushigin-treated platelets, serotonin was not released, and flow cytometric analysis using a monoclonal antibody PAC-1 totally excluded platelet GPIIb/IIIa activation. Mamushigin enhanced platelet aggregation at low-shear stress, and this effect totally disappeared in the presence of GPIb-receptor blockers specific for von Willebrand factor binding, but not by GPIIb/IIIa-receptor blockers. At high-shear stress, mamushigin blocked platelet aggregation in a dose-dependent manner, as seen with other GPIb-BP’s. This paper, therefore, describes the cDNA cloning and molecular characterization of mamushigin which has a different effect on platelet aggregation under different shear stress.
Platelet Activation and Cytokine Production during Hypothermic Cardiopulmonary Bypass – A Possible Correlation?
Authors: Ferroni P. , Speziale G. , Ruvolo G. , Giovannelli A. , Pulcinelli F. M. , Lenti L. , Pignatelli P. , Criniti A. , Tonelli E. , Marino B. , Gazzaniga P. P. 
Published: March 2018

SummaryCardiopulmonary bypass (CPB) is associated with impaired platelet function and a systemic inflammatory response. The present study was designed to evaluate whether any correlation between platelet activation and inflammatory response during CPB exists. The results obtained from 8 patients undergoing hypothermic CPB for cardiac surgery showed the occurrence of a moderate degree of platelet activation during CPB, demonstrated by an increase of platelet CD62P expression in correlation with an increase of β-thromboglobulin levels, with a concomitant decrease of in vitro platelet response. Plasma IL-1β levels significantly increased during CPB, with a peak between 1 and 4 h after CPB. Similarly, IL-6 levels were elevated 30 min from CPB starting, peaked at 4 h, and remained elevated after 24 h. A direct correlation was found between plasma IL-1β and IL-6 levels. A significant correlation between plasma IL-1β and β-thromboglobulin levels was also found. In turn, plasma β-thromboglobulin levels correlated with CD62P expression on activated platelets. An inverse correlation was found between in vitro platelet aggregation and plasma IL-1β or IL-6 levels. From the present results it may be speculated that platelet activation during CPB may contribute, through the release of IL-1β, to activation of endothelial cells and subsequent release of other cytokines with chemotactic and pro-inflammatory properties, thus playing an important role in the inflammatory response associated with CPB.