bluuebunny/crossref_metadata_2025 huggingface dataset:
Stents for the Treatment of Aortic Aneurysms
Authors: Ebert D. , Langer M. , Uhrmeister P.
Published: March 2018

The endovascular treatment of abdominal aortic aneurysms has generated a great deal of interest since the early 1990s, and many different devices are currently available. The procedure of endovascular repair has been evaluated in many institutions and the different devices are compared. The first results were encouraging, but complications like endoleak, dislocation or thrombosis of the graft occurred. By the available devices the stent application is only promising, if the known exclusion criteria are strictly respected. Therefore a careful preinterventional assessment of the patient by different imaging modalities is necessary. As the available results up to now are preliminary and the durability of the devices has to be controlled, multicenter studies are required to improve the devices and observe their long- term success in the exclusion of abdominal aortic aneurysms.
Coagulation Factor XIII and Cardiovascular Disease in UK Asian Patients Undergoing Coronary Angiography
Authors: Mansfield Michael , Grant Peter , Warner Darren
Published: March 2018

Possession of the coagulation factor XIII Val34Leu (FXIIIVal34Leu) polymorphism is associated with protection against myocardial infarction (MI) in Caucasians, in the absence of features of insulin resistance. The role of this polymorphism in the UK Asian population, with its high prevalence of insulin resistance and ischaemic heart disease, is unknown. We investigated the frequency of genotypes at this polymorphism, and measures of circulating FXIII in a group of UK Asians attending for coronary angiography. Genotype at the FXIIIVal34Leu polymorphism was not associated with MI. FXIII B-subunit levels correlated with waist: hip ratio (r = 0.19, p 0.005), HbA1c (r = 0.18, p 0.05), fasting triglycerides (r = 0.21, p 0.005), total cholesterol (r = 0.29, p 0.0005) and PAI-1 antigen (r = 0.24, p 0.005). An association between FXIIIVal34Leu and FXIII cross-linking activity was confirmed in these subjects (one-way ANOVA p 0.0005). This evidence does not support the hypothesis that FXIIIVal34Leu is protective against MI in the UK Asian population. FXIII B-subunit levels are strongly linked to risk factors for cardiovascular disease, suggesting an underlying association with insulin resistance.
Hypofibrinogenemia due to Novel 316 Asp → Tyr Substitution in the Fibrinogen Bβ Chain
Authors: Wyatt Jane , May Stephen , De Caigney Susan , George Peter , Brennan Stephen
Published: March 2018

We investigated the molecular basis of hypofibrinogenemia in a woman with a plasma fibrinogen of 1.0 mg/mL. After sequencing the coding region and intronic boundaries of all three fibrinogen genes a single heterozygous GACTAC mutation was identified at codon 316 of the B gene. This AspTyr substitution segregated with the hypofibrinogenemia in the only other affected family member. Examination by SDS-PAGE, isoelectric focussing, reverse phase chromatography and electrospray ionisation (ESI) mass spectrometery, failed to detect expression of the new B chain in purified plasma fibrinogen. The absence of the variant chain was confirmed by ESI tryptic mapping; while the [M + 1 H] and [M + 2 H] ions of the affected peptide (MGPTELLIEMEDWK) were clearly visible at 1,692 and 847 m/z, there were no new signals (1741 or 871 m/z) that would at indicate expression of the variant in plasma. Asp 316 and itschain homologue (Asp 252) are conserved in all known species and this is the first report of a mutation at either of these. The residue appears to be critical in maintaining the structure of the five stranded sheet that forms the dominant structural feature of the D domains.
The Role of Catalytic Cleft and Exosite Residues of Factor VIIa for Complex Formation with Tissue Factor Pathway Inhibitor
Authors: Iakhiaev Alexei , Ruf Wolfram , Rao Vijaya Mohan
Published: March 2018

The extrinsic coagulation pathway is initiated by the binding of plasma factor VIIa (VIIa) to the cell surface receptor tissue factor (TF). Formation of the TF-VIIa complex results in allosteric activation of VIIa as well as the creation of an extended macromolecular substrate binding exosite that greatly enhances proteolytic activation of substrate factor X. The catalytic function of the TF-VIIa complex is regulated by a specific Kunitz-type inhibitor, tissue factor pathway inhibitor (TFPI). TFPI inhibition of the TF-VIIa complex was enhanced by the presence of Xa. This study investigates the relative contribution of catalytic cleft and exosite residues in VIIa for inhibitory complex formation with TFPI. VIIa protease domain residues Q176, T239 and E296 are involved in the formation of stable inhibitor complex with free TFPI. Kinetic analysis further demonstrated a predominant role of the S2’ subsite residue Q176 for the initial complex formation with TFPI. In contrast, no significant reductions in inhibition by TFPI-Xa were found for each of the mutants in complex with phospholipid reconstituted TF. However, reduced rates of inhibition of the VIIa Gla-domain (R36) and Q176 mutant by TFPI-Xa were evident when TF was solubilized by detergent micelles. These data demonstrate docking of the TFPI-Xa complex with the macromolecular substrate exosite and the catalytic cleft, in particular the S2’ subsite. The masking of the mutational effect by the presence of phospholipid shows a critical importance of Xa Gla-domain interactions in stabilizing the quaternary TF-VIIa-Xa-TFPI complex.
Novel Design of Peptides to Reverse the Anticoagulant Activities of Heparin and other Glycosaminoglycans
Authors: Gradowski Joel , San Antonio James , Martinez Jose , Schick Barbara
Published: March 2018

Patients undergoing anticoagulation with unfractionated heparin, low molecular weight heparin, or danaparoid may experience excess bleeding which requires reversal of the anticoagulant agent. Protamine is at present the only agent available for reversal of unfractionated heparin. Protamine is not effective in patients who have received low molecular weight heparin or danaparoid. We have developed a series of peptides based on consensus heparin binding sequences (Verrecchio et al., J Biol Chem 2000; 275: 7701-7707) that are capable of neutralizing the anti-thrombin activity of unfractionated heparin in vitro, the antifactor Xa activity of unfractionated heparin, Enoxaparin (Lovenox) and danaparoid (Orgaran) in vitro and the anti-Factor Xa activity of Enoxaparin in vivo in rats. These peptides may serve as alternatives for Protamine reversal of UFH and may be useful for neutralization of enoxaparin and danaparoid in humans.
Antithrombotic Effects of Ionic and Non-ionic Contrast Media in Nonhuman Primates
Authors: Markou Christos , Chronos Nicolas , Hanson Stephen
Published: March 2018

Thromboembolic complications have been attributed to the use of radiographic contrast media (CM) during interventional procedures for arterial revascularization. However, due to the low frequency of adverse events, comparisons between different CM have been difficult to perform, although it has been suggested that ionic (vs. non-ionic) CM may be associated with fewer thrombotic events. The present study was undertaken using well-characterized baboon thrombosis models in order to compare different CM under physiologically relevant and controlled conditions of blood flow, exposure time, and CM concentration. Three CM were studied: ioxaglate, iohexol, and iodixanol. CM were locally infused into the proximal segment of femoral arteriovenous shunts. Palmaz-Schatz stents (4 mm i.d.) and expanded tubular segments (9 mm i.d.), which exhibited venous-type flow recirculation and stasis, were deployed into the shunts distally. Saline was infused in identical control studies. Blood flow was maintained at 100 ml/min. Thrombosis was measured over a blood exposure period of 2 hours by gamma camera imaging of 111In-platelets and by gamma counting of deposited 125I-fibrin. CM concentrations within the flowfield were predicted using computational fluid dynamics. At infusion rates of 0.1 and 0.3 ml/min, the low-osmolar ionic CM ioxaglate reduced both platelet and fibrin deposition on the stents by 75-80% (p <0.005), while both iohexol and iodixanol reduced platelet deposition by 30-50% (p <0.05). In the regions of low shear flow, ioxaglate (0.3 ml/min) also reduced platelet deposition significantly (by 52% vs. control results; p <0.05). Thus the three agents evaluated – ioxaglate, iohexol, and iodixanol – all produced anticoagulant and antiplatelet effects and were inherently antithrombotic in vivo. The most striking effects were seen with the low osmolarity, ionic contrast agent ioxaglate.
Region of Factor IXa Protease Domain that Interacts with Factor VIIIa: Analysis of Select Hemophilia B Mutants
Authors: Bajaj S. Paul
Published: March 2018

Introduction

The identification of coagulation factor IX as a substance required for blood coagulation was first established by Pavlovsky, who reported that a mixture of blood from two hemophiliacs clotted normally.1 Based on this discovery and subsequent observations,2 hemophilia was divided into two conditions-hemophilia A or factor VIII deficiency, the most prevalent condition, and hemophilia B or factor IX deficiency, a less common condition. Since then, much has been learned about the molecular and structural biology of factor IX. It is a vitamin K-dependent protein that participates in the middle phase of the intrinsic as well as the extrinsic coagulation cascade.3 The gene for factor IX consists of eight exons and seven introns, is approximately 34 kb long, and located on the long arm of the X-chromosome at band Xq27.1.4,5 The positions of the introns in the factor IX gene are essentially identical to those of the other three homologous proteins, namely, factor VII, factor X, and protein C;3 the genes for the latter three proteins, however, are not located on the X-chromosome.
The Plasminogen (Fibrinolytic) System
Authors: Collen Désiré
Published: March 2018

Introduction

The plasminogen (fibrinolytic) system (Fig. 1) comprises an inactive proenzyme, plasminogen, that can be converted to the active enzyme, plasmin. Plasmin degrades fibrin and activates matrix metalloproteinases (MMPs) that, in turn, degrade the extracellular matrix (ECM).1-3 Two physiological plasminogen activators (PAs) have been identified: tissue-type PA (t-PA) and urokinase-type PA (u-PA), which binds to a cellular u-PA receptor (u-PAR). Inhibition of the plasminogen/MMP system occurs at the level of the PA, by specific PA inhibitors (PAIs), at the level of plasmin, primarily by α2-antiplasmin, or at the level of MMPs, by tissue inhibitors of MMPs (TIMPs).

The dual roles of the plasminogen system are presently well established. The t-PA-mediated pathway is primarily involved in fibrin homeostasis, and the u-PA-mediated pathway is primarily involved in phenomena, such as cell migration and tissue remodeling. Consequently, the terminology “fibrinolytic system” has become inadequate and, therefore, will be replaced by “plasminogen system” in the present review.

In 1980, the state of knowledge concerning the plasminogen system was summarized.4 At that time, most of the components of the system (except the PAIs) were identified and biochemically characterized (except t-PA), but thrombolytic therapy was still in its infancy. The pathophysiologic role of the plasminogen system was deduced indirectly from correlations between levels of its components and clinical disease states, whereas its role in vascular biology, matrix remodeling, tumor growth and dissemination, wound healing, and infection was largely unknown. The last 20 years have witnessed a rapidly progressing elucidation of the biochemistry, (patho)physiology, and therapeutic applications of the plasminogen system. This development has been catalyzed by the emergence of powerful molecular biological technologies, including recombinant DNA techniques for the expression of heterologous proteins and targeted gene manipulation in vivo for the elucidation of the (patho)physiological role of their translation products.

The aim of the present review is to summarize the main developments in the plasminogen field since the 1980s. This account will be incomplete, since references to much significant work were omitted due to space limitations. To alleviate this shortcoming, reference is made primarily to review articles, in which more details and citations to original work can be found.
Structural Studies of Fibrinolysis by Electron and Light Microscopy
Authors: Veklich Yuri , Collet Jean-Philippe , Francis Charles , Weisel John W.
Published: March 2018

Introduction

Much is known about the fibrinolytic system that converts fibrin-bound plasminogen to the active protease, plasmin, using plasminogen activators, such as tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator. Plasmin then cleaves fibrin at specific sites and generates soluble fragments, many of which have been characterized, providing the basis for a molecular model of the polypeptide chain degradation.1-3 Soluble degradation products of fibrin have also been characterized by transmission electron microscopy, yielding a model for their structure.4 Moreover, high resolution, three-dimensional structures of certain fibrinogen fragments has provided a wealth of information that may be useful in understanding how various proteins bind to fibrin and the overall process of fibrinolysis (Doolittle, this volume).5,6

Both the rate of fibrinolysis and the structures of soluble derivatives are determined in part by the fibrin network structure itself. Furthermore, the activation of plasminogen by t-PA is accelerated by the conversion of fibrinogen to fibrin, and this reaction is also affected by the structure of the fibrin. For example, clots made of thin fibers have a decreased rate of conversion of plasminogen to plasmin by t-PA, and they generally are lysed more slowly than clots composed of thick fibers.7-9 Under other conditions, however, clots made of thin fibers may be lysed more rapidly.10 In addition, fibrin clots composed of abnormally thin fibers formed from certain dysfibrinogens display decreased plasminogen binding and a lower rate of fibrinolysis.11-13 Therefore, our increasing knowledge of various dysfibrinogenemias will aid our understanding of mechanisms of fibrinolysis (Matsuda, this volume).14,15

To account for these diverse observations and more fully understand the molecular basis of fibrinolysis, more knowledge of the physical changes in the fibrin matrix that precede solubilization is required. In this report, we summarize recent experiments utilizing transmission and scanning electron microscopy and confocal light microscopy to provide information about the structural changes occurring in polymerized fibrin during fibrinolysis. Many of the results of these experiments were unexpected and suggest some aspects of potential molecular mechanisms of fibrinolysis, which will also be described here.
Thrombopoietin-Induced Signal Transduction and Potentiation of Platelet Activation
Authors: Miyakawa Yoshitaka , Druker Brian , Ozaki Katsutoshi , Ohashi Hideya , Kato Takashi , Miyazaki Hiroshi , Handa Makoto , Ikebuchi Kenji , Ikeda Yasuo , Oda Atsushi
Published: March 2018

Introduction

The presence of thrombopoietin, a humoral regulator of megakaryopoiesis and thrombopoiesis, had been suggested for years,1 however, some investigators were skeptical about the existence of such a factor. Modern studies of thrombopoietin begin with the cloning of c-mpl (the cellular counterpart of the v-mpl oncogene) and its cognate ligand genes. Following the cloning of the c-mpl proto-oncogene,2 Methia et al3 found that, in the presence of oligonucleotides antisense to the gene, CD34+ cells developed into megakaryocytic precursors less efficiently. As the development into other lineage was nearly intact, it was reasonably argued that the c-mpl protein may be the receptor for a thrombopoietin-like factor.3 This study inspired numerous investigations, which culminated in the cloning of the thrombopoietin gene in 1994.1, 4-8
On the Role of Calpain and Rho Proteins in Regulating Integrin-induced Signaling
Authors: Fox Joan
Published: March 2018

The integrin family of transmembrane receptors plays an essential role in inducing the adhesion of cells to the extracellular matrix. In some cases, members of this family of receptors can bind soluble ligands or can bind receptors on other cells and, in this way, mediate interactions between cells. In all cases, once an integrin has bound, ligand signals are transmitted across the occupied integrin. These signals culminate in changes in the behavior of the cell appropriate for the adherent state of the cell. For example, in the case of platelets, an end result of the signaling induced by binding of fibrinogen to αIIbβ3 in a platelet aggregate is a reorganization of the cytoskeleton that leads to retraction of externally-bound fibrin by clots.1,2 In the case of neutrophils, cytoskeletal changes following the integrininduced interaction of neutrophils with endothelial cells lead to the migration of neutrophils into a site of injury.3,4 Other examples of the consequences of integrin-induced signaling in adherent cells include the trafficking of lymphocytes and migration of cells during development, angiogenesis, and metastasis.5-7

Numerous signaling molecules have been shown to be activated following integrin-ligand interactions.8 Many of these associate in complexes with ligand-occupied integrin and cytoskeletal proteins. However, in general, little is known about the key steps involved regarding integrin-induced changes in the behavior of adherent cells. The present chapter reviews steps involved in integrin-induced signaling, describes the evidence that calpain is one of the signaling molecules involved in this signal transduction, and discusses potential mechanisms by which cleavage of cytoskeletal proteins and signaling molecules by calpain may regulate the integrin-induced changes in cell behavior.
Inherited Abnormalities of Platelets
Authors: Nurden Alan
Published: March 2018

Introduction

Genetic defects of platelets give rise to bleeding syndromes of varying severity. Affected areas of platelet function include the glycoprotein (GP) effectors of adhesion and aggregation, primary receptors for agonists, signaling pathways where messages are transmitted to targets elsewhere in the membrane or within the platelet, dense- and α-granule secretion, ATP production, and the expression of procoagulant activity. Glanzmann thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) are the best-characterized platelet diseases and will have a major place in this review. GT is caused by abnormalities of platelet membrane GP IIb-IIIa (integrin αIIbβ3), resulting in absent platelet aggregation. BSS is caused by abnormalities of the GP Ib-IX-V complex, resulting in a loss of platelet adherence to vessel wall subendothelium. The disorders affecting platelet morphology, which give rise to the so-called giant platelet syndromes, are also considered.

Studies on platelet disorders are significant because the knowledge gained has provided a better understanding of the molecular basis of primary hemostasis and has helped in the development of new drugs for use in antithrombotic therapy. In 1987, this author gave the inaugural State-of-the-Art lecture at an International Society of Thrombosis and Haemostasis meeting.1 At that time, the application of molecular biology procedures to the study of platelet disorders was just beginning. Now, 12 years later, some of these data will be reviewed and the recent advances discussed.
Surveillance for Bloodborne Infections
Authors: Chamberland Mary
Published: March 2018

Introduction

Since blood is a biological product, it is a natural vehicle for transmission of infectious agents, and until an artificial blood substitute is developed, the risk of transfusion-transmitted infections will probably not be eliminated. Three agencies of the Department of Health and Human Services–the Centers for Disease Control and Prevention (CDC), Food and Drug Administration (FDA), and National Institutes of Health (NIH)–have collaborated with partners in local and state public health departments, academia, industry, and consumers to develop prevention strategies addressing emerging infectious disease threats to public health, including the safety of the U.S. blood supply. Four critical components of these prevention strategies are as follows: surveillance and response capabilities; integration of laboratory science and epidemiology (i.e., “applied research”) to optimize public health practice; prevention and control activities to enhance communication of public health information; and a strengthening of local, state, and federal infrastructures to support these activities.1

As highlighted by the Institute of Medicine, in its series of reports about the ongoing threat to health posed by emerging infectious diseases, surveillance is the critical lynchpin for the public health response to both known and unrecognized pathogenic threats.2 Surveillance data can be used to monitor and track temporal and demographic trends of disease, alert us to outbreaks or unexpected alterations in disease frequency or affected populations, serve as a basis for subsequent epidemiologic and laboratory investigations to describe the natural history of a disease or identify risk factors for its occurrence, and evaluate intervention strategies.2,3

This paper will review programs of surveillance in the U.S. to detect established and emerging infectious risks, with an emphasis on those that address blood safety. In addition, recent examples or case studies that illustrate the responsiveness of U.S. surveillance systems to blood safety issues will be presented.
Characterization of Factor VIII B-Cell Inhibitory Epitopes
Authors: Lollar Pete
Published: March 2018

Introduction

Factor VIII contains three epitopes that are the usual targets of clinically significant antibody inhibitors. Two of these epitopes are located in the A2 and C2 domains of factor VIII. The third epitope appears to be in the A3 domain. Ongoing studies continue to provide higher resolution maps of these epitopes and to understand the mechanism by which inhibitors produce a bleeding diathesis. The manipulation of inhibitor epitopes using recombinant DNA technology may lead to improved forms of factor VIII that have lower antigenicity and/or lower immunogenicity.
Prophylactic Infusion Regimens in the Management of Hemophilia
Authors: Ljung Rolf
Published: March 2018

Introduction

The goal of prophylactic treatment of hemophilia is to convert the severe form of the disorder into a milder form by administration of factors VIII or IX. The rationale behind this is that chronic arthropathy, the hallmark of hemophilia after repeated bleedings, is less frequent and less severe in moderate hemophilia (i.e., factor VIII or factor IX concentrations of 1% to 4% of normal) than in severe hemophilia (i.e., factor VIII/factor IX concentrations lower than 1% of normal).1 Keep in mind, however, that prophylactic treatment also provides protection from all other forms of hemorrhage that may occur spontaneously or as a result of trivial trauma in the untreated hemophilic child. Today, prophylactic treatment is available to only a few hemophilia patients in the world, although it is recommended by the World Health Organization (WHO) and the World Federation of Haemophilia (WFH): “Since the main goal is to prevent joint bleeding and its sequelae, prophylaxis should be considered optimal management for persons with severe hemophilia A or B (i.e., with basal factor VIII and/or factor IX levels <1% of normal). Treatment should be started at the age of 1-2 years and be continued indefinitely. Where prophylaxis is not feasible or appropriate, on-demand therapy should be given.”2 In the United States, the Medical and Scientific Advisory Council of the National Hemophilia Foundation has recommended that “prophylaxis should be considered the optimal therapy for children with severe hemophilia A or B.”3 The aim of this chapter is to discuss prophylactic infusion regimens in the management of hemophilia.
P-Selectin-β2-Integrin Cross-Talk: A Molecular Mechanism For Polymorphonuclear Leukocyte Recruitment At The Site Of Vascular Damage
Authors: Evangelista Virgilio , de Gaetano Giovanni , Cerletti Chiara
Published: March 2018

Introduction

Platelets activated at the site of vascular damage play a pivotal role in polymorphonuclear (PMN) leukocyte accumulation in a growing thrombus2,3 and may substitute endothelial cells in the recruitment and migration of leukocytes through damaged vessel wall.4 Leukocytes, accumulated in a platelet thrombus, can contribute to further platelet activation5 and to increased fibrin deposition.6 These events, on the one hand, may contribute to the maintenance of vascular and tissue integrity. They may, however, play a pathogenic role in inflammatory and thrombotic disease, providing some biological plausibility to the epidemiological evidence of significant association between leukocyte count and the incidence of coronary heart disease.7,8

We shall focus our attention on the molecular mechanisms involved in the recruitment of PMN leukocytes on activated platelets as it occurs at the site of vascular damage, with particular attention to P-selectin- β2-integrin cross-talk.
Gene Trap, Gene Knockout, Gene Knock-In, and Transgenics in Vascular Development
Authors: Sato Thomas
Published: March 2018

Introduction

The vascular system is one of the first organ systems to develop in our bodies. Normal development and maturation of the physiological functions of almost all of the other organs are critically dependent on the accurate and tightly controlled establishment of the vascular system. Our understanding of the mechanisms underlying the formation of the vascular system during development is still in its infancy. With further understanding of these mechanisms, we may eventually be able to correct the abnormal development and the malfunctioning of many organs by therapeutically modulating the morphology and/or physiological function of the vascular system.

Our further understanding of the vascular development can, in part, be achieved by discovering the molecules that play critical roles in this process. We could also achieve this goal by learning more about the functions of previously identified molecules in the vascular system. Discovery of new processes underlying the development of the vascular system will also contribute to further understanding of these molecular mechanisms.

Recent advances, using the whole genome approach, have resulted in a flood of new information. This trend will continue, and fortunately, a number of molecular reagents will become available. Therefore, the field will likely experience an exponential growth in terms of novel biological insights and discovering the mechanisms of vascular system development.

Occasionally, reductionistic approaches help to systematically address a number of biological problems, including the problems associated with vascular system development. One such approach is to choose an organism that allows us to systematically address these biological questions. The choice of animal models that are well-suited for the study of a particular question has led to a large number of discoveries. To address questions in vascular system development, current research has focused on animal models, including fish, frog, bird, and mouse, and also studies involving humans. It is also worthwhile to note that the branching morphogenesis of the fly trachea system has been utilized to address fundamental questions of vascular morphogenesis.

This chapter will summarize the genomic manipulation of the murine vascular system to address questions regarding vascular development. In addition, the advances that have been made in this field using such methods will be summarized.
The Effect of Unfractionated vs. Low Molecular Weight Heparin on Tissue Factor Pathway Inhibitor Levels in Hospital Inpatients
Authors: Kuter David , Brown Jennifer
Published: March 2018

Although heparin is widely used as an antithrombotic agent, its multiple mechanisms of action are not fully defined. Recent work has suggested that tissue factor pathway inhibitor (TFPI) may contribute to the antithrombotic activity of heparin by inhibiting the extrinsic pathway of coagulation. We have investigated the effect of heparin on TFPI and have found that when unfractionated heparin is given by continuous intravenous infusion to hospitalized inpatients, TFPI levels increase 2.3-fold and remain high as long as heparin is continued, but return to baseline levels soon after the infusion is stopped. In contrast, therapeutic doses of the low molecular weight heparin, dalteparin, resulted in significantly less TFPI induction. Given the increasing number of studies establishing the clinical efficacy of low molecular weight heparins as antithrombotic agents, these results suggest that TFPI may not be a major contributor to the antithrombotic effect of heparin.
Signal Transduction Pathways Underlying the Expression of Tissue Factor and Thrombomodulin in Promyelocytic Cells Induced to Differentiate by Retinoid Acid and Dibutyryl cAMP
Authors: Dobado-Berrios Pablo , Ros Rosa , Torres Antonio , García-Navarro Socorro , Jardí Mercé , Félez Jordi , Velasco Francisco , López-Pedrera Chari
Published: March 2018

Acute promyelocytic leukaemia (APL) may be associated with disseminated intravascular coagulation, as a result of increased tissue factor (TF) expression and reduced thrombomodulin (TM) expression by APL blast cells. During retinoid acid (RA)- and dibutyryl cAMP (dbcAMP)-induced differentiation of the APL cells, there is a marked up-modulation of both the protein kinase A (PKA) and C (PKC) activities. In order to further assess whether these kinases are intimately associated with both the differentiation process and the regulation of TF and TM expression, we have correlated the modulation of their respective pathways with the extent of differentiation and modulation of these cellular receptors. NB4 cells were incubated with all-trans-RA (ATRA) or dbcAMP for up to 48 h. The contribution of phospholipase C (PLC), inositol phosphate (IP), PKC and PKA in the expression of CD11b, TF and TM was studied by the use of specific inhibitors. Myo-inositol uptake and PKC activity increased in cells induced to differentiate by ATRA but the retinoid did not affect cAMP levels or PKA activity. Under treatment with dbcAMP, PKA activity was increased while inositol uptake and PKC activity remained unchanged. Our results show that the effects of ATRA and dbcAMP on promyelocytic cells are closely related, respectively, to the PLC/IP/PKC and the cAMP/PKA pathways. In cells induced to differentiate by ATRA, CD11b expression seems more closely related to inositol uptake than to PKC activity while the expression of TF and TM show the opposite pattern, which suggests cellular events regulated at a different level within a common signal transduction pathway.
The Effect of Platelet PlA Polymorphism on Experimental Thrombus Formation in Man Depends on Blood Flow and Thrombogenic Substrate
Authors: Sakariassen Kjell , Grandjean Hélène , Thalamas Claire , Boneu Bernard , Sié Pierre , Cadroy Yves
Published: March 2018

A number of studies have reported conflicting data on the association of the PlA1/PlA2 polymorphism of the GPIIIa gene and coronary syndromes. We have investigated the effect of this polymorphism on experimental platelet thrombus formation in man. Forty healthy male volunteers were genotyped for the PlA1/PlA2 polymorphism. Thrombus formation was induced ex vivo by exposing a tissue factor (TF) or a collagencoated coverslip in a parallel plate perfusion chamber to native blood for 2 and 4 min. The shear rates at these surfaces were 650 and 2,600 s–1. Platelet and fibrin deposition was quantified by immunoenzymatic methods. The frequencies of PlA1/PlA1 and PlA1/PlA2 genotypes were 52.5% and 47.5%, respectively. Ex vivo deposition of fibrin on TF was not affected by the PlA1/PlA2 polymorphism. However, the ex vivo platelet deposition at 650 s–1 was higher in blood from PlA1/PlA1 individuals than in PlA1/PlA2 individuals (P = 0.008 at 4 min). On collagen, neither fibrin nor platelet deposition was significantly affected by the PlA1/PlA2 polymorphism. Platelet thrombus formation is significantly influenced by genetic variations in the GPIIIa platelet receptor. This effect depends on the blood flow properties and the nature of the thrombogenic stimulus.
Regulated Secretion in Endothelial Cells: Biology and Clinical Implications
Authors: Ewenstein Bruce , Datta Yvonne
Published: March 2018

Regulated secretion provides a means by which endothelial cells (EC) can rapidly and selectively alter the microenvironment of individual vascular beds, and modulate the interrelated processes of coagulation, fibrinolysis, and inflammation. The rapid release of high molecular weight multimers of von Willebrand factor (VWF) and surface expression of P-selectin in response to a wide variety of stimuli have been well documented, and are the result of exocytosis of Weibel-Palade bodies (WPB). The regulated release of other EC secretory proteins, including tissue plasminogen activator (tPA), interleukin-8, endothelin-1, and multimerin, has also been described. New light is being shed on how secretory proteins are selectively targeted to storage granules in EC, and on the molecular and cellular events that comprise regulated secretion. Knowledge of the mechanisms of sorting and secretion from EC storage granules may provide basis for new strategies for treating inflammatory and coagulation disorders.
Protransglutaminase (Factor XIII) Mediated Crosslinking of Fibrinogen and Fibrin*
Authors: Meh David , Mosesson Michael , Siebenlist Kevin
Published: March 2018

Plasma factor XIII (plasma protransglutaminase) circulates as an A2B2 tetramer bound to the γ’ variant chains of fibrinogen “2”. During clotting the A subunits of fXIII are cleaved by thrombin to form fXIIIa (transglutaminase) and in the presence of calcium ions, activated A2* subunits dissociate from the B subunits. When purified plasma fXIII or recombinant cellular factor XIII (A2) was incubated with fibrinogen in the presence of calcium ions (≥50 μM) a non-synerizing gel formed concomitant with formation of γ dimers, followed by A γ polymers, and eventually γ trimers and γ tetramers. As is the case of fXIIIa, the fXIII-mediated crosslinking rate was enhanced in the presence of thiols. After an initial lag period, fXIII catalyzed fibrinogen cross-linking at ~75% of the rate of fXIIIa under typical crosslinking conditions (100 Loewy u/ml, 5 mM CaCl2 & 500 μM DTT). Fibrin was crosslinked about 8 times more rapidly by fXIII than was fibrinogen, and after an initial lag period fXIII crosslinked fibrin at nearly the same rate as fXIIIa. Substituting plasma for purified fXIII as the source for fXIII resulted in robust fibrinogen crosslinking activity. In contrast to the high level of fXIII-mediated crosslinking activity observed with fibrinogen or fibrin as substrates, when transglutamination was measured using cadaverine incorporation into casein, fXIII was 30-fold less active than fXIIIa. Thus, factor XIII displays constitutive enzymatic activity with respect to fibrinogen and fibrin. The results further indicate that uncleaved fXIII in plasma provides a potent source of readily available crosslinking activity in clotting blood. Fibrinogen 2, whose γ’chains bind fXIII B subunits, was crosslinked 3.5 times more slowly by fXIII than was fibrinogen 1 (lacking γ’ chains), suggesting that complex formation between fibrinogen 2 and plasma fXIII plays a significant role in down-regulating potential plasma fXIII-mediated crosslinking activity. Since fibrin is a considerably better substrate for fXIII than is fibrinogen, the rate at which crosslinking takes place in a fibrinogen-containing plasma environment is much lower than it would be if fibrin were present.
Bilinexin, a Snake C-type Lectin from Agkistrodon bilineatus Venom Agglutinates Platelets via GPIb and α2β1
Authors: Du Xiao-Yan , Navdaev Alexey , Clemetson Jeannine , Magnenat Edith , Wells Timothy , Clemetson Kenneth
Published: March 2018

A new snake protein, named bilinexin, has been purified from Agkistrodon bilineatus venom by ion-exchange chromatography and gel filtration chromatography. Under non-reducing conditions it has a mass of 110 kDa protein on SDS-PAGE. On reduction, it can be separated into five subunits with masses in the range 13-25 kDa. The N-terminal sequences of these subunits are very similar to those of convulxin or the alboaggregins, identifying bilinexin as a new member of the snake C-type lectin family, unusual in having multiple subunits. Bilinexin agglutinates fixed platelets, washed platelets and platelet rich plasma (PRP) without obvious activation (shape change) as confirmed by light microscope examination. Both inhibitory and binding studies indicate that antibodies against α2β1 inhibit not only platelet agglutination induced by bilinexin, but also bilinexin binding to platelets. VM16d, a monoclonal anti-GPIbα antibody, completely inhibits platelet agglutination induced by bilinexin, and polyclonal antibodies against GPIbα prevent its binding to platelets. However, neither convulxin, polyclonal anti-GPVI antibodies, nor GPIIb/IIIa inhibitors affect its binding to and agglutination of platelets. Bilinexin neither activates GPIIb/IIIa integrin on platelets nor induces tyrosine phosphorylation of platelet proteins, nor increases intracellular Ca2+ in platelets. Like alboaggregin B, bilinexin agglutinates platelets, which makes it a good tool to investigate the differences in mechanism between snake C-type lectins causing platelet agglutination and those that induce full activation.
Usefulness and Limitations of Animal Models of Venous Thrombosis
Authors: Dörffler-Melly Janine , Johnson Gerhard , Drouet Ludovic , Badimon Lina , Levi Marcel
Published: March 2018

Introduction

To study the pathogenesis of in vivo thrombus formation and to evaluate novel preventive or therapeutic strategies, animal models of venous thrombosis have been in use for more than 50 years. In the past decades numerous animal models of venous thrombosis have been developed and have been applied for a variety of objectives and mostly without certain predictive value for the relevance to human venous thrombosis. The Subcommittee on Animal, Cellular, and Molecular Models of Thrombosis and Haemostasis of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis decided to systematically review the various animal models of venous thrombosis and to analyze the contribution of these models to the study of the pathogenesis and treatment of venous thrombosis. This manuscript summarizes the results of this analysis and it draws some conclusions on the appropriate use of animal models for venous thrombosis.
Diagnostic Accuracy of Compression Ultrasonography for the Detection of Asymptomatic Deep Venous Thrombosis in Medical Patients
Authors: Bressollette Luc , Nonent Michel , Garcia Jean-François , Larroche Pascal , Guias Bruno , Scarabin Pierre-Yves , Mottier Dominique , Oger Emmanuel
Published: March 2018

We assessed the accuracy of venous compression ultrasonography (CUS) for the detection of asymptomatic deep vein thrombosis in 122 consecutive patients, with a mean age of 69 years, who were hospitalised in an internal medicine unit. All included patients had CUS within 48 h of admission. Twelve out of 17 patients with a positive CUS underwent phlebography, as the others withdrew their consent, whereas the remaining 105 patients with a negative serial CUS testing were clinically followed-up at 3 months. We found that CUS had a sensitivity and a specificity of respectively 1 (95% CI, 0.73 to 1) and 1 (95% CI, 0.96 to 1) for the detection of asymptomatic deep vein thrombosis. Kappa-coefficients for intra-observer and inter-observer agreements were respectively 0.88 and 0.56. We concluded that venous compression ultrasonography, performed as described, fulfils requirements of a screening test that could be available for prophylactic clinical trials or epidemiological researches.
A Cross Sectional Study of Antiphospholipid-protein Antibodies in Patients with Venous Thromboembolism
Authors: Amiral Jean , Martin Luc de Saint , Mottier Dominique , Pasquier Elisabeth
Published: March 2018

Objective: To look for an association between venous thromboembolism (VTE) and antiphospholipid antibodies (aPL) in patients without Systemic Lupus Erythematosus (SLE) when implementing, beside conventional assays, new tests for aPL screening directed towards purified proteic targets. Methods: We conducted a cross-sectional, hospital-based study of consecutive unselected outpatients. We compared VTE+ patients to VTE- among 398 consecutive unselected outpatients referred for clinical suspicion of VTE. To detect aPL, the following ELISAs were performed : 1) a conventional standardized ELISA 2) an improved APA assay, 3) an anti-Beta2GPI ELISA, 4) an anti-Annexin V ELISA, 5) an anti-Prothrombin ELISA. We sought an association between VTE and aPL through a quantitative (t-test) and a qualitative comparison (chi-square test, according to the cut-off values set as the 95th percentile of aPL distribution). First we conducted an analysis of all patients. Then we stratified them into 2 subgroups, with or without a wellknown risk factor for VTE (prolonged immobilization >72h, surgery or trauma within the past three months, current malignancy). Results: 61% of patients were classified as VTE-positive. Before stratification, we did not find any significant association between the VTE status and aPL. However, after stratification, in the subgroup without risk factors for VTE, the frequency of positive values as regards the anti Prothrombin antibodies detection was significantly higher in VTE+ patients (p = 0,04). Conclusion: The presence of anti Prothrombin antibodies might be an independent risk factor of VTE. However systematic screening for aPL in non SLE patients referred for VTE suspicion at the time of the thromboembolic event has little clinical relevance.
Hospitalisation for Upper Gastrointestinal Bleeding Associated with Use of Oral Anticoagulants
Authors: Sørensen Henrik Toft , Mellemkjœr Lene , Blot William , Nielsen Gunnar Lauge , McLaughlin Joseph , Olsen Jørgen , Johnsen Søren
Published: March 2018

The incidence of hospitalisation for upper GI bleeding with use of oral anticoagulants (OA) alone or in combination with other drugs was examined in a cohort of 4,204 users of OA, identified through record linkage between a population-based prescription database and a hospital discharge registry in Denmark, and compared with the incidence in the general population not exposed to OA. The standardised incidence ratio (SIR) was 2.8 (95% CI = 1.6-4.5) for use of OA alone. SIRs tended to be higher for use of OA combined with acetaminophen alone (4.4, 95% CI = 1.2-11.4), non-aspirin NSAIDs alone (8.0, 95% CI = 2.1 to 20.4) or aspirin/corticosteroids alone (3.8, 95% CI = 0.8-11.0), respectively.

These results indicate that use of OA is associated with a significantly increased risk of upper GI bleeding, with still higher risks associated with the concomitant use of other medications including acetaminophen. Further research is needed to clarify the extent to which drugs interacting with oral anticoagulants may cause GI bleeding and the mechanisms through which these associations operate.
Gene Therapy in Hemophilia: Clinical Trials Update
Authors: White Gilbert
Published: March 2018

Disorders caused by inborn genetic errors have been a primary target for treatment by gene transfer. Hemophilia A and B have been considered especially important targets because the genes for factor VIII and IX are well characterized, levels of factor VIII and IX do not require complex regulation, small increases in factor level would have significant clinical benefits, good clinical and laboratory tests of efficacy exist, and excellent animal models of hemophilia are available. Four clinical trials of gene transfer in hemophilia, two in hemophilia A and two in hemophilia B, are currently underway or have been completed and two other trials have been approved. The collective interim results from these trials indicate that the current approaches and doses are safe and that low levels of expression are detected. These studies support the continued development of gene transfer as a potential treatment option for hemophilia.
The Role of ITAM- and ITIM-coupled Receptors in Platelet Activation by Collagen
Authors: Asazuma Naoki , Atkinson Ben , Berlanga Oscar , Best Denise , Bobe Regis , Jarvis Gavin , Marshall Stuart , Snell Daniel , Stafford Margaret , Tulasne David , Wilde Jonathan , Wonerow Peter , Frampton Jon , Watson Steve
Published: March 2018

The major activation-inducing collagen receptor glycoprotein VI (GPVI) has been cloned within the last two years. It is a member of the Ig superfamily of proteins and is constitutively associated with the ITAM-bearing Fc receptor γ-chain (FcR γ-chain). GPVI signals through a pathway that involves several of the proteins used by Fc, B- and T-lymphocyte receptors and which takes place in glycolipid-enriched membrane domains in the plasma membrane known as GEMs. Responses to GPVI are regulated by PECAM-1 (CD31) and possibly other ITIM-bearing receptors. Despite a pivotal role for GPVI, there are important differences between signalling events to collagen and GPVI-specific ligands. This may reflect a role for co-receptors in the response to collagen.
The Emerging Role of the Bone Marrow-Derived Stem Cells in (Therapeutic) Angiogenesis
Authors: Luttun Aernout , Carmeliet Peter
Published: March 2018

Proper formation of blood vessels (angiogenesis) is essential for development, reproduction and wound healing. When derailed, angiogenesis contributes to numerous lifethreatening disorders. While research has generally been focusing on the two main vascular cell types (endothelial and smooth muscle cells), recent evidence indicates that bone marrow may also contribute to this process, both in the embryo and the adult. Novel vascular progenitors, even one common to both endothelial and smooth muscle cells, have been identified in the embryo. An exciting observation is that endothelial precursors have also been identified in the adult bone marrow. Transplantation studies revealed that these precursors as well as other bone marrow-derived cells contribute to the growth of endothelium-lined vessels (angiogenesis) as well as the expansion of pre-existing collaterals (arteriogenesis) in ischemic disease. These findings have raised hopes that bone marrow-derived cells might one day become useful for cell-based angiogenic therapy.