bluuebunny/crossref_metadata_2025 huggingface dataset:
Proteolysis, Cell Adhesion, Chemotaxis, and Invasiveness Are Regulated by the u-PA-u-PAR-PAI-1 System
Authors: Blasi Francesco
Published: March 2018

Introduction

High levels of urokinase-type plasminogen activator (u-PA), of its inhibitor (plasminogen activator inhibitor (PAI)-1), or of its receptor (u-PAR, CD87) are strong prognostic indicators of relapse in human cancers. In addition, many in vitro data show that u-PA, PAI-1, and u-PAR have a profound influence on cell migration. This set of molecules regulates surface proteolysis, cell adhesion, and chemotaxis through different mechanisms. Binding to u-PAR strongly stimulates the activation of pro-u-PA and, hence, of plasminogen, resulting in localized production of the broad-spectrum serine protease, plasmin, which can digest extracellular matrix proteins or activate latent motogenic factors. Chemotaxis is induced through an u-PA-dependent conformational change in u-PAR, which uncovers a very potent chemotactic epitope(s) that acts through a pertussis toxin-sensitive step and activates intracellular tyrosine kinases. In addition, cell adhesion is affected by an u-PA-dependent exposure of u-PAR epitope(s), which interact with vitronectin (VN), integrins, and caveolin, thus modifying the substrate specificity. Thus, u-PA binding can transform u-PAR from a simple receptor for u-PA into a pleiotropic ligand for other surface molecules.

All of these processes are regulated by the u-PA inhibitor, PAI-1. Inhibition of cell adhesion and migration by PAI-1 on VN occurs because the same region of VN is required for interaction with PAI-1, u-PAR, and integrins. PAI-1, however, also affects u-PAR occupancy by triggering the internalization of the u-PA-u-PAR complex, the degradation of u-PA, and the recycling of free u-PAR. Available data suggest that cells respond to a “stop” signal, due to the PAI-1-dependent internalization and degradation of u-PA. Cells also respond to a “go” signal through the stimulation of surface-proteolysis, exposure of chemotactic epitopes, and recycling of u-PAR to novel surface positions. Finally, cells respond to a “pause” signal through transient u-PAR-dependent adhesion stages, thus shifting the cells between an “adhesion-mode” and a “migration-mode.”
Structure and Function of von Willebrand Factor
Authors: Ruggeri Zaverio
Published: March 2018

Introduction

The reader will find here a concise summary of established notions on the structure and function of von Willebrand factor (vWF), followed by a brief discussion of selected recent advances that illustrate how this molecule supports platelet function in hemostasis and thrombosis. A comprehensive review of the topic is beyond the scope of this chapter and may be found elsewhere.1-3
Von Willebrand Factor in Thrombotic Thrombocytopenic Purpura
Authors: Lämmle Bernhard , Furlan Miha
Published: March 2018

Introduction

Thrombotic thrombocytopenic purpura (TTP), a disseminated form of thrombotic microangiopathy, was initially described by Moschcowitz in 1924.1 TTP is defined by a pentad of findings, including severe thrombocytopenia, intravascular hemolysis with erythrocyte fragmentation, neurologic deficit, renal dysfunction, and fever.2–4 The thrombocytopenia occurs in the presence of normal or even increased numbers of megakaryocytes in the bone marrow, suggesting increased consumption. Platelet aggregates, found in the microcirculation, contain little if any fibrin polymers, indicating that activation of coagulation and fibrin formation may be secondary and limited in extent.

About one-third of patients experience recurrent acute episodes at irregular and unpredictable intervals, whereas the majority of patients who recover from an acute TTP event experience no relapse and no persistent organ failure. TTP is usually classified as relapsing if complete remissions occurred between acute events and as chronic if complete recovery did not occur between bouts.

Genetic predisposition to TTP has been shown in several siblings suffering from recurrent TTP.5 Thus, cases of TTP can be further divided according to whether the disease has a familial or genetic component or is not heritable. Acute episodes of TTP may be triggered by viral or bacterial infection, autoimmune disorders, bone marrow transplantation, drug therapy, cancer, chemotherapy, and pregnancy.3,4 The incidence of TTP is estimated to be two to eight cases per million people per year.3,6 Until four decades ago, the mortality rate was virtually 100% but has since decreased to less than 20% after introduction of plasma therapy. Still, there were more than 4,500 TTP-associated deaths recorded in the United States between 1968 and 1991.6
Risk Factors for Venous Thrombotic Disease
Authors: Rosendaal F.R.
Published: March 2018

Introduction

Venous thrombosis occurs in about 1 per 1,000 individuals per year.1,2 It usually affects the deep veins of the leg, but may occur in other sites, such as the upper extremities, cerebral sinus, liver and portal veins, or retinal veins. It also may occur in the superficial veins, usually in the leg. The predilection of thrombosis occurring in the leg is the result of the upright position of man, with the resulting slow antigravitational flow of blood in the veins of the leg. Embolization occurs when parts of the clot dislodge and are transported by the blood flow, usually through the heart to the vasculature of the lungs.3

Thrombosis is a serious disorder. It may be fatal by pulmonary embolism, although this is rare (case fatality rate of venous thrombosis is estimated at 1% to 2%). A common, and often disabling, consequence of deep vein thrombosis is postthrombotic syndrome, with symptoms ranging from discoloration to pain and ulceration.4 Because thrombosis is not very rare and often has serious consequences, prophylactic treatment is focussed on preventing first events and recurrences through adequate knowledge about risks and risk factors.5
APTT Revisited: Detecting Dysfunction in the Hemostatic System Through Waveform Analysis
Authors: Toh Cheng Hock
Published: March 2018

Introduction

Despite extensive investigations in both experimental and clinical disseminated intravascular coagulation (DIC), much remains to be learned about this condition of hemostatic dysfunction. Although the technological armory available to the clinical investigator has expanded enormously since the early 1980s, particularly with regard to immunologically-based testing, the sobering fact is that prognosis has remained dismally unchanged.1 Although some of the new laboratory approaches can identify DIC at an early enough stage to allow for useful clinical intervention, most require a level of stringency in performance that is not attainable in the routine clinical setting.2 The pace of acute DIC precludes many of these specific tests, and reliance is still based on traditional screening assays, such as the prothrombin time (PT), activated partial thromboplastin time (APTT) and platelet count (Plt). These tests lack specificity on an individual basis and are only useful in DIC if there is further determination of fibrinogen (Fgn) and fibrin breakdown products (fdp)/D-Dimers.3 However, changes in these battery of tests seldom occur together. As a result, the realization of DIC is often only made after serial testing, with the inevitable delay and consequent jeopardization of patient critical care.4 The numerous failures of new therapies in sepsis and DIC testifies to this problem of a lack of early definition in the disease process to forewarn the clinician of more timely intervention.5 The gold standard must, therefore, be a single, rather than multiple, assay system that is both sensitive and specific for early DIC and simple and rapid to perform. It is therefore, not too surprising that such a test has remained elusive for such a considerable length of time.

In the context of complex scenarios, the simplest of approaches can often be the most rewarding. Such an axiom could fit with the description of APTT transmittance waveform analysis as a useful test in DIC that could also potentially lead to an improved understanding of the condition.
New Discoveries with Mice Mutant in Endothelial and Platelet Selectins
Authors: Hartwell Daqing , Wagner Denisa
Published: March 2018

Introduction

The selectin family of adhesion receptors consists of three members: P-, E-, and L-selectin. P-selectin is constitutively present in the α-granules of platelets and Weibel-Palade bodies of endothelial cells and is rapidly translocated to the cell surface upon activation. E-selectin is synthesized and expressed by activated endothelial cells, whereas L-selectin is constitutively expressed by leukocytes. All three selectins support the rolling of leukocytes on endothelium, which is a prerequisite to firm adhesion and extravasation of leukocytes mediated by integrins and members of the immunoglobulin superfamily.1,2 More recently, it has been demonstrated that P- and E-selectin also support platelet rolling in venules, which will be discussed below. In addition, P-selectin expressed on the surface of activated platelets also mediates platelet-leukocyte adhesion.3,4

Since the discovery of the selectins, considerable efforts have been devoted to uncover the functions of these molecules. The development of genetically engineered animals deficient in one or more of the adhesion receptors has provided a unique opportunity and an alternative approach to antibody-blocking experiments for defining the contribution of each of the molecules in normal physiology and pathological conditions. At this time, mice deficient in a single selectin, all combinations of two of the selectins, and all three selectins have been produced by gene targeting.5-10 In this chapter, we will discuss some of the recent findings obtained using mice deficient in P-selectin alone (P-/-), both P- and E-selectin (P/E-/-), and mice expressing Pselectin with a deleted cytoplasmic domain (ΔCT).
Prophylaxis of Venous Thromboembolism Following Orthopedic Surgery: Mechanical and Pharmacological Approaches and the Need for Extended Prophylaxis
Authors: Hull R.D. , Pineo G.F
Published: March 2018

Introduction

Major orthopedic surgery, particularly total joint replacement or hip fracture, represents a high risk of future development of postoperative venous thromboembolism and warrants the routine use of prophylaxis with either mechanical devices or pharmacological agents. The aim of prophylaxis is to prevent fatal pulmonary embolism (PE) and the morbidity of deep vein thrombosis (DVT), particularly the development of post-thrombotic syndrome. Patterns of clinical practice, with respect to the prevention of venous thromboembolism and the appropriate use of anticoagulants for the treatment of thrombotic disease, have been strongly influenced by recent consensus conferences.1,2 Rules of evidence for assessing the literature have been applied to all recommendations regarding the prevention and treatment of thrombotic disease. These results were extrapolated using evidence gleaned from major clinical disorders and are based only on nonrandomized clinical trials or case series.1-3 Data from a large number of Level I clinical trials in patients undergoing orthopedic surgery have provided answers to many of the questions regarding prophylaxis of venous thromboembolism. In this review, we will discuss the prevention of venous thromboembolism following orthopedic surgery and discuss some of the controversial issues where further studies are required.
Prevention of Venous Thromboembolism After Neurosurgery
Authors: Agnelli Giancarlo
Published: March 2018

Introduction

The optimal strategy for the prevention of venous thromboembolism in patients undergoing neurosurgery has been a matter of debate for many years,1 and it is currently under review because of the results of recent clinical trials. This issue is, indeed, of particular clinical interest because of the neurosurgeons’ fear of bleeding complications, potentially associated with the use of anticoagulants, and the high incidence of venous thromboembolism. Preventing venous thromboembolism is of crucial importance in neurosurgery patients for reasons that go beyond its high incidence. The management of patients who develop venous thromboembolism immediately after neurosurgery is rather complicated, due to the risks connected with the administration of therapeutic doses of heparin and warfarin. In addition, the insertion of a vena caval filter, which is frequently required, is rather expensive and not without risk. Thus, in neurosurgery, even more than in other clinical settings, the optimal strategy for the management of venous thromboembolism is its prevention.

The purpose of this paper is to review the epidemiology of venous thromboembolism in neurosurgery, its biological risk factors, and the results of clinical trials that have studied the prevention of venous thromboembolism in this clinical setting.
Thrombolysis in Acute Cerebrovascular Disease: Indications and Limitations
Authors: Ringleb Peter , Stingele Robert , Hacke Werner
Published: March 2018

Introduction

Large-scale trials have shown that thrombolytic therapy reduces mortality and preserves left ventricular function in patients with acute myocardial infarction (AMI). As most ischemic strokes are thromboembolic in origin,1 there appears to be a rationale for the use of thrombolytic agents in the management of ischemic stroke.

Thrombolytic agents differ in their mechanisms of action, but in general, they act by promoting the conversion of plasminogen into plasmin, resulting in fibrin degradation and clot dissolution. Streptokinase and recombinant tissue plasminogen activator (rt-PA) are the agents that have been the most widely investigated in stroke studies. Ancrod, the active agent in the venom of the Malayan pit viper, is primarily considered an anticoagulant, although it does stimulate endogenous t-PA release from the vascular endothelium and may enhance local thrombolysis. Urokinase is used in local, intra-arterial thrombolysis but has not been subjected to large clinical trials since computed tomography (CT) diagnosis became widely available.
A Cell-based Model of Hemostasis
Authors: Monroe Dougald , Hoffman Maureane
Published: March 2018

Based on our work and that of many other workers, we have developed a model of coagulation in vivo. Many workers have demonstrated mechanisms by which cells can influence the coagulation process. Nonetheless, the prevailing view of hemostasis remains that the protein coagulation factors direct and control the process with cells serving primarily to provide a phosphatidylserine containing surface on which the procoagulant complexes are assembled. By contrast, we propose a model in which coagulation is regulated by properties of cell surfaces. This model emphasizes the importance of specific cellular receptors for the coagulation proteins. Thus, cells with similar phosphatidylserine content can play very different roles in hemostasis depending on their complement of surface receptors. We propose that coagulation occurs not as a “cascade”, but in three overlapping stages: 1) initiation, which occurs on a tissue factor bearing cell; 2) amplification, in which platelets and cofactors are activated to set the stage for large scale thrombin generation; and 3) propagation, in which large amounts of thrombin are generated on the platelet surface. This cell based model explains some aspects of hemostasis that a protein-centric model does not.
Adipose Tissue Expression of Gelatinases in Mouse Models of Obesity
Authors: Maquoi E. , Holvoet P. , Mertens A. , Lupu F. , Morange P. , Alessi M. C. , Juhan-Vague I. , Lijnen H. R.
Published: March 2018

Following the observation by Brown et al. (Am J Physiol 1997; 272: C937-49) that primary rat adipocytes in culture secrete gelatinase A (MMP-2), we have evaluated gelatinase expression in adipose tissue with the use of mouse models of obesity. Wild-type mice were kept on a standard fat diet (SFD) or on a high fat diet (42% fat, HFD) and genetically obese db/db mice were kept on SFD; gonadal and subcutaneous fat pads were removed and analysed ex vivo. These studies revealed that: 1) the HFD induced adipocyte hypertrophy; 2) after 32 weeks, significantly higher levels of 70 kDa (p <0.05) and 65 kDa proMMP-2 (p < 0.01) were observed in extracts of gonadal fat pads of mice on HFD; 3) the contribution of active MMP-2 to the total level was comparable in SFD and HFD groups (20 to 30%); and 4) gelatinase B (MMP-9) was not consistently detected. These findings were confirmed by gelatin zymography and by mRNA determination using competitive RT-PCR. The presence of MMP-2 in the adipose tissue was confirmed immunologically and its localization in adipocytes revealed by immunogold electron microscopy. The potential functional role of MMP-2 in adipose tissue remains to be determined.
Factor V Leiden and Factor V R2 Allele: High-throughput Analysis and Association with Venous Thromboembolism
Authors: Benson Jane , Ellingsen Dorothy , El-Jamil Muhydine , Jenkins Meredith , Miller Connie , Dilley Anne , Evatt Bruce , Hooper Craig
Published: March 2018

Thrombophilia is a multigenic disease in which the combination of genetic polymorphisms increases the risk of deep vein thrombosis (DVT). The rapid identification of these genetic combinations requires high-throughput analysis of single nucleotide polymorphisms (SNPs). The TaqMan® fluorogenic 5’→3’ nuclease assay (PE/Applied Bio-systems, Foster City, CA) with custom-designed primers, probes and controls has provided a highly efficient platform for high throughput. This assay was used to rapidly detect two SNPs, FV Leiden (G1691A) and FV A4070G (R2 allele), in a study of 6295 subjects. With one thermal cycler, we completed sample set-up, PCR and analysis on 84 samples in 3 h with an additional 12 wells containing 4 “no template controls” (NTC), 4 “allele-1 controls”, and 4 “allele-2 controls” in a 96-well plate. When additional thermal cyclers were used and more assays were set up while the initial sets of reactions were in the PCR machines, the output could correspondingly be increased. The TaqMan® assay was extremely accurate, avoided contamination by using uracil-N-glycolase (UNG) in a single, closed tube, and offered the possibility for additional automation with robotic equipment to implement the PCR. This TaqMan® assay facilitates high throughput to screen large populations quickly and economically while utilizing a simple protocol that requires minimal expenditure of personnel time. Our results demonstrated a prevalence of the R2 allele of 11.9% in U.S. Caucasians, 5.6% in African-Americans, 13.4% in Asian or Pacific Islanders and 11.3% in Hispanics. No association between venous thromboembolism and the R2 allele was noted, and furthermore no interaction with FV Leiden was observed.
Increased Brain Natriuretic Peptide as a Marker for Right Ventricular Dysfunction in Acute Pulmonary Embolism
Authors: Tulevski Igor , Hirsch Alexander , Sanson Bernd-Jan , Romkes Hans , van der Wall Ernst , van Veldhuisen Dirk , Büller Harry , Mulder Barbara
Published: March 2018

Right ventricular (RV) function is of major prognostic significance in patients with acute pulmonary embolism (PE). The aim of the present study was to evaluate the role of neurohormone plasma brain natriuretic peptide (BNP) in assessing RV function in patients with acute PE.

BNP levels were measured in 16 consecutive patients with acute PE as diagnosed by high probability lung scintigraphy or pulmonary angiography. Twelve healthy age-matched volunteers served as controls. All 16 patients underwent standard echocardiography and blood tests during the first hour of presentation. In the patient group, survival was studied for a period of 30 days. Plasma BNP levels in patients with acute PE were higher than in controls (7.2 [95% CI 0.4 to 144.6] versus 1.4[95% CI 0.4 to 4.6] pmol/L, p = 0.0008). Plasma BNP was significantly higher in 5 patients with RV dysfunction compared to 11 patients with normal RV function (40.2 [95% CI 7.5 to 214.9] versus 3.3 [95% CI 0.4 to 24.9] pmol/L, p = 0.0003). RV systolic pressure was not significantly correlated with BNP (r = 0.42, p = ns).

In conclusion, plasma BNP neurohormone levels might be of clinical importance as a supplementary tool for assessment of RV function in patients with acute PE.
The ATP-Gated P2X1 Ion Channel Acts as a Positive Regulator of Platelet Responses to Collagen
Authors: Toth-Zsamboki Emese , Thys Chantal , Tytgat Jan , Vermylen Jos , Oury Cecile , Hoylaerts Marc
Published: March 2018

ATP is a potent agonist of the P2X1 ion channel, mediating a rapid, quickly desensitized influx of Ca2+. In hirudinized PRP, containing apyrase, the two stable selective P2X1 agonists, α,β-methylene ATP, and L-β, γ-methylene ATP induced extracellular Ca2+-dependent fast and reversible platelet shape change, leading to desensitization of the P2X1 ion channel. Preincubation with HPLC-purified ADP potently antagonized the subsequent α, β-methylene ATP- and L-β, γ-methylene ATP-evoked platelet shape change. Accordingly, upon heterologous expression of P2X1 in Xenopus oocytes, HPLC-purified ADP acted as an antagonist of the ATP-induced current, but was inactive itself. Since ATP and ADP are co-released from dense granules during platelet activation, we investigated whether the P2X1 ion channel is involved in the response of platelets to collagen. We found that platelet shape change and aggregation induced by low concentrations of collagen were strongly inhibited after selective desensitization of P2X1 with its agonists or by pretreating the platelets with a low concentration of ADP (0.5 μM), that antagonizes the P2X1 channel without desensitizing the P2Y1 receptor. Our data suggest that, during collagen-initiated platelet activation, the early secretion of ATP results in the activation of the P2X1 ion channel, which plays a role as a positive regulator of further platelet responses.
Characteristics of Anticoagulant Therapy and Comorbidity Related to Overanticoagulation
Authors: Penning-van Beest Fernie , Meegen Erik van , Rosendaal Frits , Stricker Bruno
Published: March 2018

The risk of hemorrhage when using coumarin anticoagulants sharply increases when the International Normalised Ratio (INR) is ≥6.0. We performed a prospective cohort study with a nested case-control design among 17,056 outpatients of an anticoagulation clinic to determine the incidence of overanticoagulation and to study the association between overanticoagulation and characteristics of anticoagulant therapy and comorbidity. The incidence rate of an INR ≥6.0 was 7.8 per 10,000 treatment days in prevalent users on the starting date and 22.5 per 10,000 treatment days in incident users during the study period. 300 cases with an INR ≥6.0 were compared with 302 randomly selected matched controls with an INR within the target zone. Patients on acenocoumarol had an increased risk of an INR ≥6.0 compared to patients on phenprocoumon. Regarding comorbidity, impaired liver function, congestive heart failure, diarrhea and fever were risk factors for overanticoagulation. Increased monitoring of INR values if risk factors are present or avoidance of risk factors could prevent excess anticoagulation and potential bleeding complications.
Fibrinolysis/Proteolysis Balance in Stable Angina Pectoris in Relation to Angiographic Findings
Authors: Orbe J. , Fernández J. , Páramo J. A.
Published: March 2018

The plasma fibrinolytic/proteolytic balance was assessed in 60 stable angina patients who underwent control coronary catheterization and the results were correlated with angiographic findings and control samples (n = 20). The concentrations of t-PA, PAI-1, collagenase (MMP-1), tissue inhibitor of MMP (TIMP-1), plasmin-antiplasmin (PAP) complexes and α2-macroglobulin (α2-M) were measured in plasma samples. The results showed a significant increase of PAP (p <0.001) and a reduction of α2-M (p <0.001) in the group of patients when compared to controls, indicating a degree of fibrinolysis/proteolysis activation. There was no correlation between the different parameters analyzed and the extent of angiographically proven atherosclerosis (one or more stenotic vessels), while the t-PA levels were significantly elevated (p <0.03) in patients with coronary stenosis ≥75% or occlusion. We conclude that there is a disturbance of the plasma fibrinolysis/ proteolysis in patients with stable angina not related to the extent of atherosclerosis. The t-PA levels may be a good marker for coronary occlusion in these patients.
Serial Determinations of Platelet Counts in Mice by Flow Cytometry
Authors: Alugupalli Kishore , Michelson Alan , Barnard Marc , Leong John
Published: March 2018

Elucidation of the pathophysiological basis of platelet disorders in murine models requires a reliable method for the frequent determinations of platelet counts in individual mice. Here, we present a rapid, reproducible and accurate flow cytometric method for enumeration of platelets that involves fluorescent staining of platelets in whole blood with specific antibody and the addition of known numbers of fluorescent beads for standardization of the sample volume. Analysis of platelets obtained by tail bleeding indicated that this sampling procedure did not activate platelets, and that only five microliters of blood were required for platelet counting. Using this method, we followed platelet counts in mice infected with the relapsing fever spirochete Borrelia turicatae for 26 days, and found that this bacterium induces thrombocytopenia, a common manifestation of human relapsing fever. Therefore, this method can be used to follow the number and the activation state of circulating platelets from individual mice over extended periods of time and is applicable to a wide range of murine models of platelet disorders.
Vascular-Bed-Specific Hemostasis and Hypercoagulable States: Clinical Utility of Activation Peptide Assays in Predicting Thrombotic Events in Different Clinical Populations
Authors: Rosenberg Robert
Published: March 2018

This chapter summarizes the new paradigm for arterial thrombosis. This new paradigm emphasizes the heterogeneity of endothelial cells and the signaling pathways that control endothelial cell gene expression in surrounding tissue. It is suggested that genetic alterations in the signaling pathways are probably responsible for localized thrombosis, as manifested by heart attacks and strokes. A discussion of two clinical studies supporting the new arterial thrombosis paradigm is also included in this chapter. These studies, carried out by genetic engineering in mice, employ activation peptides to help predict the occurrence of thrombotic events in humans.
ADP Receptors of Platelets and their Inhibition
Authors: Gachet Christian
Published: March 2018

ADP plays a crucial role in haemostasis and thrombosis and its receptors are potential targets for antithrombotic drugs. Two G-protein coupled P2 receptors contribute to platelet aggregation: the P2Y1 receptor initiates aggregation through mobilisation of calcium stores, while the more recently identified P2Y12 receptor coupled to adenylyl cyclase inhibition is essential for a full aggregation response to ADP and the stabilisation of aggregates. The latter is defective in certain patients with a selective congenital deficiency of aggregation to ADP. It is also the target of the antithrombotic drug clopidogrel and of ATP analogues and other compounds currently under evaluation. In addition, the P2X1 ionotropic receptor is present in platelets but its role is not yet completely known. Studies in P2Y1 knock-out mice and experimental thrombosis models using selective P2Y1 antagonists have shown that the P2Y1 receptor, like the P2Y12 receptor, is a potential target for new antithrombotic drugs.
All in the Family: Primary Megakaryocytes for Studies of Platelet αIIbβ3 Signaling
Authors: Leavitt Andrew , Shattil Sanford
Published: March 2018

Integrin αIIbβ3 mediates key platelet adhesive responses during hemostasis and thrombosis. Adhesive ligand binding to αIIbβ3 is regulated by “inside-out” signals, while adhesion-dependent cytoskeletal events are regulated by “outside-in” signals from αIIbβ3. Currently, the molecular basis of bidirectional αIIbβ3 signaling is incompletely understood. The functional assessment of integrin signaling pathways in nucleated cells has been facilitated by techniques such as viral transduction which enable expression of dominant-active and dominant-inhibitory gene products. This approach cannot be used with anucleate platelets. However, recent advances in the ability to expand human and murine megakaryocytes from hematopoietic stem cells provide a tractable and genetically manipulatable system for studies of αIIbβ3 signaling. This overview will discuss some of the advantages and limitations of this approach and provide examples of its utility. Thus, in addition to their intrinsic value for understanding hematopoiesis and platelet formation, primary megakaryocytes represent a model system complementary to platelets for unraveling the remaining mysteries of αIIbβ3 signaling.
Protease-activated Receptors in Vascular Biology
Authors: Coughlin Shaun
Published: March 2018

G protein-coupled protease-activated receptors (PARs) provide one answer to the question of how coagulation factors and other proteases regulate cellular behaviors. In concert with the coagulation cascade, these receptors provide an elegant mechanism that links mechanical information in the form of tissue injury or vascular leak to cellular responses. Roles for PARs in hemostasis and thrombosis, inflammation, and perhaps even blood vessel development are beginning to emerge. Our current understanding of the role of PARs in platelet and endothelial cell activation and their potential importance in normal and disease states is discussed.
Tissue Factor – A Receptor Involved in the Control of Cellular Properties, Including Angiogenesis
Authors: Chen Jiang , Bierhaus Angelika , Schiekofer Stephan , Andrassy Martin , Chen Baosheng , Stern David , Nawroth Peter
Published: March 2018

Tissue factor (TF), the major initiator of blood coagulation, serves as a regulator of angiogenesis, tumor growth and metastasis. In several models, TF expression mediates upregulation of the proangiogenic vasular endothelial growth factor (VEGF) that can directly act on endothelial cells to promote vessel formation. This occurs through ligand binding, activation of signaling cascades, signal transduction and alteration of growth factor expression and is mediated by both, coagulation-dependent and -independent pathways. Depending on the cell type and the biological settings, TF seems to affect cellular properties through (i) factor VIIa (FVIIa)-dependent proteolysis of factor Xa (FXa) and thrombin and subsequent activation of proteinase activated receptor (PAR) -1 and PAR-2, (ii) through direct FVIIa signaling and mitogen activated protein (MAP) kinase activation, that is conferred by a not yet identified receptor, (iii) through interaction of FVII(a) proteolytic activity and signaling of the cytoplasmic domain and (iv) through cytoplasmic signaling independent of ligand binding. The role of phosphorylation of the cytoplasmic domain and the pathways controlling phosphorylation of TF remain poorly understood.
Atherosclerosis and Thrombosis: Lessons from Animal Models
Authors: Badimon Lina
Published: March 2018

Atherothrombosis defines the occurrence of thrombosis on athero-sclerotic lesions. Atherosclerosis is the most prevalent disease of our time and its thrombotic complications are responsible for an exceedingly high number of deaths and disabilities. Over the past few years, experimental investigation and clinical and pathologic observations have led to a better understanding of how a thrombus forms and also of its incidence in acute ischemic syndromes. A thrombus is usually found secondary to atherosclerotic plaque disruption. Mural thrombosis, also at the site of plaque rupture, is an important mechanism in the progression of atherosclerosis even when symptoms are absent. Because atherosclerosis is a silent and asymptomatic disease until complications arise with thrombosis producing clinical symptoms, it is necessary to have models that reproduce the human disease in its early stages. Unfortunately, not all the experimental models of vascular disease have human resemblance and validity. Knowledge of the disease process and of what an experimental animal model can offer is a milestone for a successful investigation. Experimental models of vascular disease have enhanced our understanding of the pathophysiological processes leading to vascular obstruction in both spontaneous and accelerated atherosclerosis and thrombosis. Animal models have provided insight into the role of platelets, lipids, renin-angiotensin system (RAS), cytokines and growth factors in the evolution and progression of atherosclerosis and have suggested potential therapeutic interventions. Significant advances in our understanding of the vascular biology and pathology of atherosclerosis and thrombosis, and of the interactions of blood cells, lipids and proteins with the vascular wall, have allowed us to formulate new experimental hypotheses and to test therapeutic strategies, either pharmacological or surgical.
Haemostatic Genetic Risk Factors in Arterial Thrombosis
Authors: Simmonds Rachel , Hermida José , Rezende Suely , Lane David
Published: March 2018

Haemostasis plays an integral role in arterial thrombotic disease. However, establishing which of the factors are risk factors has proven surprisingly difficult. Because of its technical simplicity and digital nature, the study of haemostatic polymorphisms as risk factors has grown in popularity. Once established as a risk factor, a genetic polymorphism has the potential to aid selective prophylaxis and therapy of disease. Numerous reports have now been published on polymorphisms of coagulation and fibrinolytic factors, of coagulation and fibrinolytic inhibitory proteins, and of platelet membrane glycoprotein receptors. This article describes the polymorphisms and evaluates the results of these studies using the premises of consistency of within-report genotype/phenotype/disease relationships and consistency of outcome between studies. Many studies have been only of association between polymorphisms and disease, a type of study that is prone to error. Furthermore, the collective outcome of these studies has primarily been inconsistent. It is concluded that despite the early promise of polymorphisms as risk factors, fresh approaches differing in scale and design are now required to clarify their possible importance.
Wann muss man an eine chronisch-entzündliche Darmerkrankung bei Kindern und Jugendlichen denken?
Authors: Lentze M. J. , Broekaert I. J.
Published: March 2018

Die Inzidenz der chronisch-entzündlichen Darmerkrankungen (CED), v. a. des Morbus Crohn, im Kindesalter nimmt zu. Zwischen 20 und 30 % der CED-Patienten befinden sich im Kindes- oder Jugendalter.

Typisch für die Colitis ulcerosa ist eine blutige Diarrhö. Beim M. Crohn zeigen sich häufig unspezifische Bauchschmerzen, Diarrhö, Anämie, Fieber, Gewichtsverlust und Wachstumsverzögerung. Wachstumsverzögerungen durch eine verzögerte Diagnose oder unzureichenden Behandlung einer CED sind eine besondere Komplikation im Kindes- und Jugendalter. Weitere extraintestinale Manifestationen sind Müdigkeit, Anorexie sowie Gelenk-, Haut-, Augen-, Leber-, Gallengangs- und Pankreasbeteiligung. Nach dem Ausschluss von gastrointestinalen Infektionen helfen Entzündungsmarker im Blut sowie Calprotectin und Laktoferrin im Stuhl für die Diagnose. Für die endgültige Diagnose und Klassifizierung sind die Ileokoloskopie und Ösophagogastroduodenoskopie notwendig. Weitere Bildgebung (z. B. MRT, Videokapselendoskopie) wird empfohlen.
Erfordernisse, Defizite und Gelingensbedingungen patientenzentrierter Versorgungsforschung bei Seltenen Erkrankungen
Authors: Nowak U. , Reimann A.
Published: March 2018

Als selten werden Erkrankungen mit einer Prävalenz < 5/10 000 bezeichnet. In Deutschland leben ca. 4 Millionen Menschen mit einer der ca. 7 000–9 000 Seltenen Erkrankungen (SE). Patienten brauchen z. T. Jahre bis zur richtigen Diagnose. Es fehlen kompetente und strukturierte Behandlungseinrichtungen, qualitätsgeprüfte Informationen und meist auch kurative therapeutische Optionen. Ca. 80 % der Erkrankungen haben eine genetische Pathogenese, ca. 50 % manifestieren früh oder – aufgrund der hohen Sterblichkeit – sogar ausschließlich im Kindesalter. Die Versorgung verlangt regelhaft einen interdisziplinären, multiprofessionellen und sektorenübergreifenden Ansatz. Das Nationale Aktionsbündnis für Menschen mit Seltenen Erkrankungen (NAMSE) hat die Versorgungsforschung (VF) bei SE als eine wichtige Maßnahme identifiziert. Prioritär sollten allerdings Fragestellungen untersucht werden, die sowohl hochspezifisch für SE als auch von hoher Versorgungsrelevanz sind. Hierzu gehören die Umsetzung des NAMSE-Zentrenmodells und die Anwendung von Orphan Drugs. VF bei SE muss sich mit besonderen komplexen Herausforderungen, u. a. der geringen Zahl von Clustern, auseinandersetzen. Deshalb sind geeignete VF-Ressourcen an Zentren für Seltene Erkrankungen unabdingbar.
Schwerwiegende thrombembolische Ereignisse bei jugendlichen Erstanwenderinnen oraler Kontrazeption
Authors: Petzold-Quinque S. , Hirsch W. , Kiess W. , Siekmeyer M. , Rolle H.
Published: March 2018

Hintergrund: Die Inzidenz einer venösen Thrombembolie (VTE) bei Anwenderinnen von oralen Kontrazeptiva ist mindestens um das Zweifache höher als bei Nichtanwenderinnen. Insgesamt ist das Auftreten einer venösen Thrombembolie als Nebenwirkung der oralen Kontrazeptiva ein seltenes Ereignis. Noch seltener ist ein letaler Ausgang der VTE. Jedoch haben gerade Neuanwenderinnen im ersten Jahr ein erhöhtes Risiko. Dies betrifft zu einem großen Teil junge Mädchen.

Falldarstellung: In unserer Klinik sahen wir im vergangenen Jahr drei junge Frauen, die aus scheinbar völliger Gesundheit schwerwiegende thrombembolische Ereignisse erlitten. Dieser Artikel soll deren Fälle und Verläufe vorstellen. Anschließend wird in Anbetracht der aktuellen Literaturlage die klinische Brisanz der Fälle diskutiert.

Schlussfolgerung: Die Einnahme oraler Kontrazeptiva kann in Einzelfällen mit der Möglichkeit des Auftretens schwerer thrombembolischer Komplikationen assoziiert sein. Die Symptome dieser Komplikationen müssen umfassend in der Aufklärung vor der Anwendung dieser Medikamente gewürdigt werden.
Das Adrenogenitale Syndrom (AGS) im Kindes- und Jugendalter
Authors: Dörr H. G.
Published: March 2018

Verschiedene autosomal-rezessiv vererbte Enzymdefekte der adrenalen Kortisolbiosynthese werden unter dem Adrenogenitalen Syndrom (AGS) zusammengefasst. In mehr als 90 % der Fälle liegt ein Defekt der 21-Hydroxylase zugrunde, wobei man eine klassische und eine nicht-klassische Form unterscheidet. Bei der klassischen Form des AGS unterscheidet man zwei Verlaufsformen, eine mit Salzverlust und eine ohne Salzverlust. Das AGS wird durch Mutationen im aktiven 21-Hydroxylase-Gen (CYP21A2) auf dem Chromosom 6 verursacht. Beim klassischen AGS ist das äußere Genitale der Mädchen bei Geburt vermännlicht. Bei der Salzverlustform kommt es bei beiden Geschlechtern in den ersten Lebenswochen zu einer Salzverlustkrise. Die Symptome der Patienten mit nichtklassischem AGS sind durch die vermehrte Androgensekretion charakterisiert, wobei das äußere Genitale der Mädchen bei Geburt unauffällig ist. Je nach Enzymdefekt kann die Diagnose durch ein charakteristisches Steroidprofil im Plasma/Serum oder im Harn gesichert werden. Für das klassische AGS mit 21-Hydroxylase-Defekt ist die massive Erhöhung von 17-Hydroxyprogesteron (17OHP) im Serum beweisend. Im Neugeborenenscreening wird daher am 3. Lebenstag im Vollblut 17OHP bestimmt. Die medikamentöse Therapie wird im Kindesalter mit Hydrokortison und beim Salzverlustsyndrom zusätzlich mit einem Mineralokortikoid (9α-Fludrokortison) durchgeführt. Bei Umstellung auf ein anders Glukokortikoid muss die Äquivalenzdosis beachtet werden. Die pränatale Therapie ist nach wie vor eine experimentelle Therapie. Eine enge Zusammenarbeit aller Beteiligten ist notwendig, um die Ziele der Therapie im Kindes- und Jugendalter umzusetzen. Der Übergang in die Erwachsenenmedizin muss klar geregelt sein.
Konzept der unterstützten Sekundärprävention nach Schlaganfall
Authors: Laumeier I. , Audebert H. J.
Published: March 2018

Hintergrund: Patienten mit einem akuten Schlaganfall oder einer transitorischen ischämischen Attacke (TIA) haben ein hohes Risiko für neue vaskuläre Ereignisse. Mehrere evidenzbasierte Strategien zur Sekundärprävention sind verfügbar, vermutlich aber noch nicht ausreichend genutzt. Bislang wurden Unterstützungsprogramme, die auf eine multifaktorielle Modifikation der Risikofaktoren abzielen, zwar bei anderen Erkrankungen wie Diabetes mellitus oder koronarer Herzkrankheit aber noch nicht beim Schlaganfall in prospektiven kontrollierten Studien untersucht. INSPiRE-TMS ist eine multizentrische, randomisierte offene Interventionsstudie für intensivierte Sekundärprävention nach leichtem Schlaganfall und TIA. Methoden: An den teilnehmenden Zentren werden geeignete Patienten mit TIA oder leichtem Schlaganfall rekrutiert und 1:1 in einen Interventions- und einen Kontrollarm randomisiert. 2 082 Patienten sollen eingeschlossen werden. Das Unterstützungsprogramm beinhaltet die Messung der kardiovaskulären Risikofaktoren und Feedback, das Monitoring der Adhärenz, Beratung bezüglich einer Lebensstiländerung und die aktive Einbeziehung der Angehörigen. Standardisiertes „Motivational Interviewing“ soll die Patienten motivieren und in dieser Motivation stärken. Primäres Studienziel ist die Reduktion vaskulärer Ereignisse (Hirninfarkt, Myokardinfarkt, vaskulärer Tod). Die Beobachtungszeit soll für jeden Patienten mindestens zwei Jahre betragen. Diskussion: Aufgrund des hohen Rezidivrisikos nach einem akuten Schlaganfall und zugleich bekannten effektiven sekundärpräventiven Strategien, hat die INSPiRE-TMS-Intervention das Potenzial, zu einer relevanten Reduktion von erneuten vaskulären Ereignissen und einer verlängerten ereignisfreien Überlebenszeit zu führen. Die Studie wird mit zu der Entscheidung beitragen, ob ein Programm zur intensivierten Sekundärprävention nach Schlaganfall in die Regelversorgung übernommen werden sollte. Zusätzlich wird die Kosteneffektivität mitbeurteilt.
Standardisierte Anwendung der tDCS bei Depressionen
Authors: Leitner B. , Kirsch B. , Tschirdewahn J. , Hasan A. , Pfeiffer A. , Wulf L. , Schaub A. , Pogarell O. , Padberg F. , Palm U.
Published: March 2018

Hintergrund: Die transkranielle Gleichstromstimulation (tDCS) wird seit 10 Jahren zur Behandlung der Depression beforscht. Eine Reihe doppelblinder und offener Studien konnte überwiegend eine positive Wirkung der tDCS als Zusatzbehandlung zur medikamentösen Therapie nachweisen. Jedoch gibt es keine größeren Studien zur Anwendung der tDCS in naturalistischem Patientengut ohne studienbedingte Vorselektion durch Ein- und Ausschlusskriterien. Methodik: Das vorgestellte Positionspapier bewertet die Erkenntnisse einer Kombinationsbehandlung mit tDCS und Antidepressivum und empfiehlt eine standardisierte klinische Anwendung. Ein Fallbericht einer standardisierten Anwendung zeigte die Möglichkeit einer Anwendung in der klinischen Routine. Resultate: Die Anwendung von tDCS und begleitender antidepressiver Therapie ist in einer Reihe von Studien untersucht worden, wobei sich Stromstärke und Dauer der Anwendung in den letzten Jahren immer weiter erhöhten. In dem berichteten Fall kam es unter Medikation mit Citalopram 20 mg und intensivierter tDCS (20 Behandlungen zu je 30 min) zu einer raschen und nachhaltigen Verbesserung der depressiven Symptomatik, auch wenn eine Remission knapp nicht erreicht wurde. Schlussfolgerung: Die tDCS scheint bei Verwendung intensivierter Stimulationsprotokolle sicher anwendbar und könnte möglicherweise eine schnellere und nachhaltigere antidepressive Wirkung als eine medikamentöse Monotherapie bewirken. Daraus könnte sich eine weitreichende Bedeutung für die Behandlungsdauern der Erkrankung ergeben.
Neues in der Behandlung neurologischer Notfälle
Authors: Schröder K. , Maschke M.
Published: March 2018

Innovationen: Akute neuromuskuläre Erkrankungen: Rituximab führt bei einer therapierefraktären Myasthenie häufig zu einer signifikanten Verbesserung. Studien weisen auf eine mögliche Wirkung von Eculizumab hin. Bei der Behandlung des Guillain-Barré-Syndroms sind Plasmapherese und Immunglobuline gleichwertig, die Immunadsorption eine gute Alternative. Kortikosteroide scheinen die Prognose zu verschlechtern. Ischämische Schlaganfälle: Neuerungen sind positive Studien zur Thrombektomie. Die Destiny-II-Studie wies bei Patienten über dem 70. Lebensjahr mit einem malignen Mediainfarkt eine Senkung der Mortalität durch eine Hemikraniektomie nach. Intrazerebrale Blutungen: Die INTERACT-2-Studie wies keine sichere Überlegenheit einer aggressiven Blutdrucksättigung nach. In der Therapie der intrazerebralen Blutung ist der STICH-II-Trial zur operativen Therapie von Lobärhämatomen abgeschlossen, eine frühe Operation zeigte keinen eindeutigen Vorteil. Die SAIVMs-Studie wies einen Nachteil der operativen Exzision von Kavernomen gegenüber einem konservativen Vorgehen bezüglich des Outcomes nach 5 Jahren nach. Gleiches gilt für unrupturierte arteriovenöse Malformationen. Meningitis und Enzephalitis: Neuere Studien zeigen einen Rückgang der Inzidenz der Meningitis durch Meningokokken und Pneumokokken. Die Dexamethason-Gabe bei bakterieller Meningitis ist nach den aktualisierten DGN-Leitlinien nur noch nach einer nachgewiesenen Pneumokokkenmeningitis empfohlen. Bei anderen bakteriellen Meningitiden sollte jedoch nach mikrobiologischen Resultaten Dexamethason abgesetzt werden. Bezüglich viraler Enzephalitiden ist die zusätzliche Gabe von Valaciclovir nach einer intravenösen Gabe von Aciclovir bei Herpes-simplex-Enzephalitis nicht prognoseverbessernd. In Serbien wurden mehr als 50 Fälle mit einer West-Nil-Virus-Enzephalitis nachgewiesen, ebenso erste Fälle in Österreich, sodass das Virus in die Differenzialdiagnose einbezogen werden muss. Das in Polynesien, Südamerika und in der Karibik endemisch vorkommende Zikah-Virus führt häufig zu einem parainfektiösen Guillain-Barré-Syndrom, seltener zu einer Meningoenzephalitis.
Myasthenie und Thymus
Authors: Zierz S. , Jordan B.
Published: March 2018

Die Thymuspathologie bei der Myasthenia gravis (MG) umfasst sowohl die lymphofollikuläre Hyperplasie (LFH) bei der Frühmanifestation der Azetylcholinrezeptorantikörper (AChR-AK) positiven Form als auch Thymome. Die Diagnostik schließt die Erhebung des Antikörperstatus ein, um die Indikation zur Thymektomie bei der klassischen AChR-Antikörper positiven Form prüfen zu können. Bei radiologischem Verdacht einer mediastinalen Raumforderung kann nuklearmedizinisch die Bindung von Somatostatinrezeptoren (DOTA-TOC-PET) bei Thymomen visualisiert werden. Die Thymektomie mit Thymomresektion ist unter onkologischem Aspekt grundsätzlich indiziert. Die Diagnose der paraneoplastischen MG besitzt somit eine besondere Indikatorfunktion für den weiteren Verlauf der Thymomerkrankung.

Wenngleich die thymomassoziierte MG sich im klinischen Verlauf nicht von der klassischen Myasthenie unterscheidet, bedarf die Betreuung dieser Patienten besonderer Sorgfalt. Meist ist die Fortführung der Immunsuppression erforderlich. Gleichzeitig sind dabei die erhöhte Infektneigung, das erhöhte Risiko eines Zweitmalignoms als auch eines Thymomrezidivs zu beachten.