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Thrombotic Disease (thrombotic + disease)
Selected AbstractsDevelopment of an inhibitory antibody fragment to human tissue factor using phage display technologyDRUG DEVELOPMENT RESEARCH, Issue 3 2009S.M. Meiring Abstract Tissue factor is involved in the etiology of thrombotic diseases initiating the thrombosis associated with the inflammation that occurs during infection. The prevention of blood coagulation and inflammation is of primary importance in a number of pathological situations. A single-chain variable antibody fragment of molecular weight of 26,kD that inhibits the action of human tissue factor was selected by phage display technology, purified and tested for its tissue factor inhibitory effect, purified on a protein A column, and its purity evaluated on SDS-PAGE. The effects of the antibody fragment on prothrombin times, Factor Xa production, and thrombin generation were assessed with increasing fragment concentrations, using chromogenic and fluorometric substrates. The antibody fragment dose-dependently prolonged the prothrombin time (IC50=0.5,,M) and delayed the lag phase before the thrombin generation burst and the peak thrombin concentration in the thrombin generation assay. The effect on thrombin generation was more pronounced in thrombophilic plasma than in normal plasma. Antibody-based tissue factor inhibitors therefore may provide an effective treatment for thrombotic disease without serious bleeding complications. Drug Dev Res 2009. © 2009 Wiley-Liss, Inc. [source] REVIEW ARTICLE: Hyperglycemia: a prothrombotic factor?JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 8 2010B. A. LEMKES Summary., Diabetes mellitus is characterized by a high risk of atherothrombotic events. What is more, venous thrombosis has also been found to occur more frequently in this patient group. This prothrombotic condition in diabetes is underpinned by laboratory findings of elevated coagulation factors and impaired fibrinolysis. Hyperglycemia plays an important role in the development of these hemostatic abnormalities, as is illustrated by the association with glycemic control and the improvement upon treatment of hyperglycemia. Interestingly, stress induced hyperglycemia, which is often transient, has also been associated with poor outcome in thrombotic disease. Similar laboratory findings suggest a common effect of acute vs. chronic hyperglycemia on the coagulation system. Many mechanisms have been proposed to explain this prothrombotic shift in hyperglycemia, such as a direct effect on gene transcription of coagulation factors caused by hyperglycemia-induced oxidative stress, loss of the endothelial glycocalyx layer, which harbours coagulation factors, and direct glycation of coagulation factors, altering their activity. In addition, both chronic and acute hyperglycemia are often accompanied by hyperinsulinemia, which has been shown to have prothrombotic effects as well. In conclusion, the laboratory evidence of the effects of both chronic and acute hyperglycemia suggests a prothrombotic shift. Additionally, hyperglycemia is associated with poor clinical outcome of thrombotic events. Whether intensive treatment of hyperglycemia can prevent hypercoagulability and improve clinical outcome remains to be investigated. [source] Programmed autologous cleavage of platelet receptorsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2007M. C. BERNDT Summary., Platelet adhesion receptors play a critical role in vascular pathophysiology, and control platelet adhesion, activation and aggregation in hemostasis, thrombotic disease and atherogenesis. One of the key emerging mechanisms for regulating platelet function is the programmed autologous cleavage of platelet receptors. Induced by ligand binding or platelet activation, proteolysis at extracellular (ectodomain shedding) or intracellular (cytoplasmic domain deactivation) sites down-regulates the adheso-signaling function of receptors, thereby controlling not only platelet responsiveness, but in the case of ectodomain shedding, liberating soluble ectodomain fragments into plasma where they constitute potential modulators or markers. This review discusses the underlying mechanisms for dual proteolytic pathways of receptor regulation, and the impact of these pathways on thrombus formation and stability in vivo. [source] Elevated plasma fibrinogen ,, concentration is associated with myocardial infarction: effects of variation in fibrinogen genes and environmental factorsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 4 2007M. N. MANNILA Summary., Background:, Fibrinogen ,,, a fibrinogen ,-chain variant generated via alternative mRNA processing, has been associated with susceptibility to thrombotic disease. Objective:, The present case,control study searched for potential determinants of the plasma fibrinogen ,, concentration and examined the relationship between this variant and risk of myocardial infarction (MI). Patients and methods:, The Stockholm Coronary Artery Risk Factor study, comprising 387 postinfarction patients and 387 healthy individuals, was employed. The fibrinogen gamma (FGG) 9340T > C [rs1049636], fibrinogen alpha (FGA) 2224G > A [rs2070011] and fibrinogen beta (FGB) 1038G > A [rs1800791] polymorphisms were determined. The plasma fibrinogen ,, concentration was measured by enzyme-linked immunosorbent assay. The multifactor dimensionality reduction method was used for interaction analyses on risk of MI. Results:, The FGG 9340T > C and FGA 2224G > A polymorphisms, total plasma concentrations of fibrinogen, insulin and high-density lipoprotein, and gender appeared to be independent determinants of plasma fibrinogen ,, concentration in patients, and the corresponding determinants in controls included FGG 9340T > C and FGA 2224G > A polymorphisms and plasma fibrinogen concentration. An elevated plasma fibrinogen ,, concentration proved to be an independent predictor of MI [adjusted odds ratio (OR) (95% CI): 1.24 (1.01, 1.52)]. The plasma fibrinogen ,, concentration was involved in a high-order interaction with total plasma fibrinogen and the FGG 9340T > C and FGA 2224G > A polymorphisms, associated with a further increased risk of MI [OR (95% CI): 3.22 (2.35, 4.39)]. Conclusions:, Plasma fibrinogen ,, concentration influences the risk of MI, and this relationship seems to be strengthened by the presence of an elevated total plasma fibrinogen concentration and the FGG 9340T and FGA 2224G alleles. [source] Spontaneous platelet aggregation in Kawasaki disease using the particle counting methodPEDIATRICS INTERNATIONAL, Issue 6 2003Masashi Taki AbstractBackground:,Platelet aggregation is generally measured by the optical density method. This method is not very sensitive in detecting platelet activation because of the poor correlation between the formation of platelet aggregates and light transmission, and inability to detect small platelet aggregates. Recently, a new method was developed that detects small platelet aggregates formed in the early phase of platelet aggregation by means of a particle counting technique using light scattering. Methods:,The present study used the particle counting method to measure spontaneous platelet aggregation (SPA) produced by agitation with a stirrer bar without agonists in patients with Kawasaki disease (KD) and children's thrombotic disease, and compared the results with the conventional optical density method. Results:,Using the particle counting method, significantly higher SPA rates were found before treatment than in healthy adults and at the other stages of treatment. A similar tendency was noted with the optical density method; however, the positive rate of SPA was significantly higher with the particle counting method in each stage except the second stage, which was the period from the start of gamma-globulin therapy to 20 days. Conclusion:,These results indicate that enhanced platelet aggregation is noted at a high frequency before treatment of KD and that the particle counting method is superior to the optical density method in detecting enhanced platelet aggregation. [source] A case of purpura fulminans is caused by homozygous ,8857 mutation (protein C-Nagoya) and successfully treated with activated protein C concentrateBRITISH JOURNAL OF HAEMATOLOGY, Issue 3 2000Takayuki Nakayama We report a Japanese patient who developed purpura fulminans and disseminated intravascular coagulation (DIC) shortly after birth. The patient was diagnosed to be homozygous for protein C deficiency and was treated with an activated protein C (APC) concentrate. Intravenous infusions of APC markedly improved the necrotic skin lesions and the anticoagulation by APC enabled successful DIC control. The identified mutation (,8857) results in impaired intracellular transport and protein maturation and would be the cause of the complete protein C deficiency. This is the seventh case of the mutation that has been exclusively reported in Japan, but is the first report of a homozygous case. Our findings propose new therapeutic and diagnostic tools for the management of this fatal thrombotic disease. [source] Cerebral venous thrombosis and Escherichia coli infection in neonatesACTA PAEDIATRICA, Issue 2 2003H Farstad Aim: To present a possible association between cerebral venous thrombosis (CVT) and infection with Escherichia coli. Methods: Four neonates with deep CVT occurring during an E. coli infection are presented. Results: In these patients the thrombotic disease was found by Doppler ultrasonography. The thrombosis involved at least the sagittal sinus and the transverse sinus according to subsequent MRI scans. The E. coli strains did not produce verotoxin or haemolysin. Disseminated intravascular coagulation was not demonstrated. Three patients presented with seizures. At discharge, all of the patients had signs of neurological damage, but two of them have improved significantly since then. None of the patients has had recurrent (venous) thrombosis. Conclusion: E. coli infections in neonates may predispose to CVT, a finding that has clinical implications. [source] MANAGEMENT OF ANTIPLATELET THERAPY FOR ENDOSCOPIC PROCEDURES: OPTIMAL CESSATION PERIOD OF ANTIPLATELET THERAPY FOR JAPANESEDIGESTIVE ENDOSCOPY, Issue 4 2007Yoshiko Tamai Although antiplatelet agents are widely used for the treatment and prevention of thrombotic diseases, only a few studies have reported the validity of the cessation period prior to endoscopic procedures. In 2002, the American Society for Gastrointestinal Endoscopy (ASGE) published a reference on the management of anticoagulation and antiplatelet therapy for endoscopic procedures, but it should be confirmed as appropriate for use in Asian patients. To evaluate the optimal cessation period of antiplatelet agents prior to endoscopic procedures for Japanese, we have studied: (i) the current clinically adopted cessation period of antiplatelet agents prior to invasive endoscopic procedures in Japan; (ii) the relationship between the cessation period of antiplatelet agents and complications around the invasive endoscopic procedures; (iii) colonic mucosal bleeding time after aspirin ingestion; and (iv) the time course of primary hemostasis after cessation of antiplatelet agents. We conclude that 3 days cessation period for aspirin, 5 days cessation for ticlopidine and 7 days cessation for aspirin + ticlopidine administration should be sufficient for Japanese. [source] Development of an inhibitory antibody fragment to human tissue factor using phage display technologyDRUG DEVELOPMENT RESEARCH, Issue 3 2009S.M. Meiring Abstract Tissue factor is involved in the etiology of thrombotic diseases initiating the thrombosis associated with the inflammation that occurs during infection. The prevention of blood coagulation and inflammation is of primary importance in a number of pathological situations. A single-chain variable antibody fragment of molecular weight of 26,kD that inhibits the action of human tissue factor was selected by phage display technology, purified and tested for its tissue factor inhibitory effect, purified on a protein A column, and its purity evaluated on SDS-PAGE. The effects of the antibody fragment on prothrombin times, Factor Xa production, and thrombin generation were assessed with increasing fragment concentrations, using chromogenic and fluorometric substrates. The antibody fragment dose-dependently prolonged the prothrombin time (IC50=0.5,,M) and delayed the lag phase before the thrombin generation burst and the peak thrombin concentration in the thrombin generation assay. The effect on thrombin generation was more pronounced in thrombophilic plasma than in normal plasma. Antibody-based tissue factor inhibitors therefore may provide an effective treatment for thrombotic disease without serious bleeding complications. Drug Dev Res 2009. © 2009 Wiley-Liss, Inc. [source] Blood coagulation and its regulation by anticoagulant pathways: genetic pathogenesis of bleeding and thrombotic diseasesJOURNAL OF INTERNAL MEDICINE, Issue 3 2005BJÖRN DAHLBÄCK Abstract. Platelet-mediated primary haemostasis and blood coagulation have evolved as important defence mechanisms against bleeding. The formation of the platelet plug provides the initial occlusion of the vascular lesion. This is temporally co-ordinated with the activation of the coagulation system, which occurs in response to the rupture of endothelium and the exposure of blood to the extravascular tissue. The reactions of blood coagulation are carefully controlled by several anticoagulant mechanisms and under normal conditions they prevail over the procoagulant forces. Genetic or acquired disturbances of the natural balance between the pro- and anticoagulant systems may result in bleeding or thrombotic diseases. [source] ADAMTS-13 activity in plasma is rapidly measured by a new ELISA method that uses recombinant VWF-A2 domain as substrateJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 3 2004J. L. Whitelock Summary., The metalloprotease ADAMTS-13 cleaves von Willebrand factor (VWF) at the Y842/M843 peptide bond located in the A2 domain. Measurement of ADAMTS-13 activity is a clinical utility for thrombotic diseases, but the current assays used for diagnostic and clinical research are non-physiological and time consuming. We have expressed in bacteria a recombinant VWF-A2 peptide (aa 718,905) that contains both a 6xHis tag at the N-terminal end and a Tag-100 epitope at the C-terminal end. Diluted plasma was mixed with the VWF-A2 peptide and digestion was allowed to proceed in a Ni2+ -coated microtiter well plate for 2 h. The immobilized Ni2+ captures the VWF-A2 peptide by its 6xHis tag and cleavage of the A2 peptide is measured by the removal of the C-terminus fragment of the A2 peptide that contains the Tag-100. The cleavage activity for this assay was defined by the low detection of A2 peptide containing the Tag-100 epitope by the antiTag-100 monoclonal antibody. The assay was completed in <5 h. We then used the assay to analyze ADAMTS-13 activity in plasma from 39 healthy donors and 16 samples from patients diagnosed as thrombotic thrombocytopenic purpura. The average of enzyme activity ±,SEM for normal plasmas diluted 1 : 50 was 40 ± 4.2% while the value obtained for the patients was 2.4 ± 0.7%. These results were validated by a traditional long incubation assay (24 h). Our assay provides significant advantages over currently used assays because it is quicker, reproducible, cost effective and measures ADAMTS-13 activity under physiological and non-denaturing conditions. This assay is clinically useful and significant in measuring ADAMTS-13 activity in plasma. [source] Endogenous Mechanisms of Inhibition of Platelet FunctionMICROCIRCULATION, Issue 3 2005RICHARD C. JIN MA ABSTRACT Platelets play an important role in coagulation, in maintenance of hemostasis, and in the pathophysiology of thrombotic diseases. In response to blood vessel injury, platelets accumulate at the site, recruit other platelets, promote clotting, and form a hemostatic plug to prevent hemorrhage. By contrast, several inhibitory mechanisms modulate platelet function and act in a synergistic manner to prevent pathologic thrombus formation. This review focuses on the principal endogenous inhibitors of platelet function and the central role of the normal endothelium in these inhibitory processes. The main endothelium-derived platelet inhibitors include nitric oxide, prostacyclin, and Ecto-ADPase/CD39/NTPDase. Each of these factors is discussed in turn, and the specific mechanisms by which they inhibit platelet function are reviewed. [source] The role of insulin as an antithrombotic humoral factorBIOESSAYS, Issue 1 2004Kushal Chakraborty Insulin is well known for its essential role in carbohydrate metabolism: insulin deficiency results in the development of diabetes mellitus. It has been known for many years that people with diabetes mellitus are predisposed to develop thrombotic diseases including myocardial infarction. It was thought that the thrombus formation was the consequence of impaired carbohydrate metabolism. In recent years, it has become apparent that insulin is capable of ameliorating several pathophysiological events, leading to the inhibition and dissolution of the formed thrombus in the system. These insulin-induced events include inhibition of platelet aggregation by prompting the synthesis of NO in platelet and prostacyclin in endothelial cells. Furthermore, insulin upregulates prostacyclin receptors and downregulates ,2 adrenergic receptor in platelets, thereby amplifying the inhibition of platelet aggregation. Insulin also releases tissue plasminogen activator, a potent thrombolytic enzyme, from the platelet membrane which dissolves the formed thrombus leading to the resumption of normal blood circulation. In effect, insulin could be an essential tool in the control of thrombotic disorders. BioEssays 26:91,98, 2004. © 2003 Wiley Periodicals, Inc. [source] | ||||||||||