Deep venous thrombosis of the arm: a study of coagulation and fibrinolysis.

Sixty consecutive patients with phlebographically verified deep venous thrombosis of the upper arm were studied for disorders of coagulation and fibrinolysis. No appreciable increase in abnormalities of the factor VIII complex, antithrombin III, or inhibitors of activators of fibrinolysis were found. A decreased fibrinolytic defence mechanism, evident either as a deficient release capacity of fibrinolytic activators from the vein during stasis or as decreased fibrinolytic activity in the vein wall as determined histochemically, was found in 26 out of 53 patients studied (49%). It is concluded that deep venous thrombosis of the upper arm is a multifactorial disease. An impaired fibrinolytic defence mechanism is one of the factors that may be of pathogenetic importance.     

Liver Transplantation in Man—IV,Haemorrhage and Thrombosis

Blood coagulation and fibrinolytic factors have been measured in 13 patients treated by liver transplantation. During operation intravascular coagulation and fibrinolysis were increased, but seldom to a degree which would cause abnormal bleeding. Measurement of the catabolism of radioactive fibrinogen showed that increased intravascular coagulation continued for long periods after the operation. Despite secondarily increased fibrinolysis, there was a high incidence of thrombosis. Treatment with anticoagulants or with fibrinolysis inhibitors may be valuable in these patients.     

Effect of heparin and ASA on changes of haemostasis induced by venous occlusion (author's transl)

The influence of venous occlusion on plasmatic coagulation, on platelets, and on fibrinolysis was examined. After occlusion, activated factors XI and X could be demonstrated. Simultaneously, platelet aggregation induced by both collagen and epinephrine was increased. Fibrinolysis was found to be moderately enhanced. In patients taking acetylsalicylic acid (ASA), platelet functions were not altered by occlusion but the activation of plasmatic clotting factors was not influenced. Low dose heparin inhibited plasmatic activation but had no influence on the increase of platelet activities. By simultaneous administration of both substances, an additive effect was observed resulting in inhibition of plasmatic and platelet activation due to venous occlusion.     

Snake venom proteins acting on hemostasis

The venoms of Viperidae and Crotalidae snakes are a rich source of proteins with activity against various factors involved in coagulation and fibrinolysis. These proteins are very specific for their molecular targets, resistant to physiological inhibitors and stable in vitro and in vivo. They have therefore proved to be useful for diagnostic tests. Based on sequence similarities, these snake venom proteins have been classified into various families, such as serine proteinases, metalloproteinases, C-type lectins, disintegrins and phospholipases A(2). The various members of a given family, although structurally similar, act selectively on different blood coagulation factors. This opens up the possibility of characterizing the structural elements involved in target molecule recognition. Thus, snake venom proteins provide excellent models for studies of structure-function relationships.     

Anti-hemostatic effects of a serpin from the saliva of the tick Ixodes ricinus

Serpins (serine protease inhibitors) are a large family of structurally related proteins found in a wide variety of organisms, including hematophagous arthropods. Protein analyses revealed that Iris, previously described as an immunomodulator secreted in the tick saliva, is related to the leukocyte elastase inhibitor and possesses serpin motifs, including the reactive center loop (RCL), which is involved in the interaction between serpins and serine proteases. Only serine proteases were inhibited by purified recombinant Iris (rIris), whereas mutants L339A and A332P were found devoid of any protease inhibitory activity. The highest Ka was observed with human leukocyte-elastase, suggesting that elastase-like proteases are the natural targets of Iris. In addition, mutation M340R completely changed both Iris substrate specificity and affinity. This likely identified Met-340 as amino acid P1 in the RCL. The effects of rIris and its mutants were also tested on primary hemostasis, blood clotting, and fibrinolysis. rIris increased platelet adhesion, the contact phase-activated pathway of coagulation, and fibrinolysis times in a dose-dependent manner, whereas rIris mutant L339A affected only platelet adhesion. Taken together, these results indicate that Iris disrupts coagulation and fibrinolysis via the anti-proteolytic RCL domain. One or more other domains could be responsible for primary hemostasis inhibition. To our knowledge, this is the first ectoparasite serpin that interferes with both hemostasis and the immune response.     

A case of congenital factor XIII deficiency

The case of a 53 years old woman was described in whom a congenital factor XIII deficiency was suspected because of deforming scars and hemorrhagic diathesis. A thromboelastographic declination of elasticity as well as decreased factor XIII level up to 5% of normal range were only found in all hemostatic examinations. In 2 children factor XIII decreased to half of its normal level, whereas in the youngest daughter that level was 25%. Sporadically the girl had mild diathesis. No changes in thromboelastograms were observed in members of the patient's family. The platelet function was unchanged in all examined cases.     

Genetics of arterial prothrombotic risk states

Coronary artery disease is a leading cause of death worldwide and the largest killer of men and women in the United States. The pathophysiology of myocardial infarction is multifactorial, and numerous physiologic systems converge to dictate the formation of the two fundamental lesions, thrombosis and atherosclerosis. In this review we address genetic aspects of arterial thrombosis and the key thrombotic factors that have been associated with the increased risk for its development. Specifically, we consider components of coagulation, fibrinolysis, and platelet adhesive receptors, and we review the genetic epidemiology and in vitro laboratory data regarding their risk for the acute coronary syndromes. In combination with traditional risk factor assessment, in the near future these inherited markers can be used to manage patients with vascular disease through a better utilization of invasive or expensive diagnostic testing, as well as pharmacologic intervention.     

Effect of ethyl alcohol on selected parameters of the hemostasis system in vitro]

Alcohol produces several disorders in all components of hemostasis system. However, its mechanism of action is not clear. Therefore, an effect of ethyl alcohol on the selected parameters of both platelet and plasma hemostasis has been examined in vitro. Blood aggregation induced by ADP and PAF and platelet-leucocytic aggregates have been determined in vitro in the group of 45 healthy volunteers. Out of plasma parameters the selected factors of blood coagulation and fibrinolysis have been examined. Results suggest that the examined concentrations of ethyl alcohol mainly affect platelet function decreasing platelet aggregation. Alcohol does not affect significantly blood coagulation and fibrinolysis occurring in vitro.     

Exercise prescription and thrombogenesis

Lifestyle habits, such as exercise, may significantly influence risk of major vascular thrombotic events. The risk of primary cardiac arrest has been shown to transiently increase during vigorous exercise, whereas regular moderate-intensity exercise is associated with an overall reduced risk of cardiovascular diseases. What are the mechanisms underlying these paradoxical effects of vigorous exercise versus exercise training on thrombotic modification? This review analyzes research regarding effects and their underlying mechanisms of acute exercise, endurance training, and deconditioning on platelets, coagulation, and fibrinolysis. Evidence suggests that (i) light, acute exercise ( < or = 49% VO(2 max)) does not affect platelet reactivity and coagulation and increases fibrinolytic activity; (ii) moderate, acute exercise (50 to approximately 74% VO(2 max)) suppresses platelet reactivity and enhances fibrinolysis, which remains unchanged in the coagulation system; and, (iii) strenuous, acute exercise ( > or = 75% VO(2 max)) enhances both platelet reactivity and coagulation, simultaneously promoting fibrinolytic activity. Therefore, moderate exercise is likely a safe and effective exercise dosage for minimizing risk of cardiovascular diseases by inducing beneficial anti-thrombotic changes. Moreover, moderate-intensity exercise training reduces platelet reactivity and enhances fibrinolysis at rest, also attenuating enhanced platelet reactivity and augmenting hyper-fibrinolytic activity during strenuous exercise. However, these favorable effects of exercise training on thrombotic modification return to a pre-training state after a period of deconditioning. These findings can aid in determining appropriate exercise regimes to prevent early thrombotic events and further hinder the cardiovascular disease progression.     

Antithrombotic effect of tissue and plasma type angiotensin converting enzyme inhibitors in experimental thrombosis in rats.

This study compared the antithrombotic effect of plasma angiotensin converting enzyme inhibitors (ACE-Is): captopril (CAP), enalapril (ENA) and tissue ACE-Is: perindopril (PER), quinapril (QUIN) in experimental venous and arterial thrombosis. Normotensive Wistar rats were treated p.o. with CAP (75 mg/kg), ENA (20 mg/kg), PER (2 mg/kg) and QUIN (3 mg/kg) for 10 days. The influence of ACE-Is on coagulation and fibrinolytic systems as well as platelet function was evaluated. The hypotensive effect of ACE-Is was equal in all groups. QUIN maintained the final carotid blood flow at the highest value in comparison to PER and plasma ACE-Is. The arterial thrombus weight was reduced in PER and QUIN groups while venous thrombus weight was also reduced after CAP. Tissue and plasma ACE-Is caused the inhibition of platelet adhesion and aggregation. A reduction of fibrin generation, prolongation of prothrombin time (PT), activated partial thromboplastin time (APTT) and shortening of euglobulin clot lysis time (ECLT) were observed after PER and QUIN treatment. In conclusion, given in equipotent hypotensive doses, tissue ACE-Is exerted more pronounced antithrombotic effect than plasma ACE-Is in experimental thrombosis. The differences between tissue and plasma ACE-Is in terms of their more pronounced inhibition of experimental thrombosis may be related to the intensified activation of fibrinolysis and inhibition of coagulation.     

Laboratory evaluation of a bleeding patient.

Most causes of abnormal bleeding can be determined from a complete blood count including platelet count and bleeding, prothrombin, activated partial thromboplastin, and thrombin times. Occasionally, further evaluation is necessary, such as tests of factor XIII function, fibrinolysis, and vascular integrity. Possible diagnoses include disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, vitamin K deficiency, von Willebrand''s disease, heparin-induced thrombocytopenia, acquired inhibitors of factor VIII, lupus anticoagulants, and coagulation disorders related to the acquired immunodeficiency syndrome.     

Antithrombotic therapy in patients with known risk factors for thromboembolism

In about 50% of the cases of spontaneous deep vein thrombosis a congenital deficiency of an inhibitor of coagulation or an insufficient fibrinolytic mechanism can be detected. In arterial thromboembolism a connection with hyperactive platelets or with a diminished availability of tissue plasminogen activator can be found in about 70%. However, in these cases the defect which provokes thrombosis is mostly acquired and is connected with hyperlipidemia and/or with atherosclerotic alterations of the vessel wall. A study on patients with thromboembolic tendency and detectable risk factors was carried out. A total of 470 patients could be observed for 2 years under an adequate antithrombotic prophylaxis. The occurrence of thromboembolic episodes 2 years prior to prophylaxis and 2 years under prophylaxis was compared. In venous cases thrombosis could be controlled almost completely by coumarins when the underlying cause was a deficient plasmatic inhibitor. In patients with diminished fibrinolysis there was only a partial effect of oral anticoagulants. A better result could be obtained when pentosan polysulfate was administered. In arterial thromboembolism the results of prophylaxis were less convincing. The efficacy of ASA in patients with an increased platelet function was only moderate. In addition, ASA hat to be discontinued in about 20% of the patients because of gastrointestinal problems. Pentosan polysulfate in patients with a diminished fibrinolytic capacity had a fairly good effect and resulted in a 60% reduction of thromboembolic manifestations. It is shown that an exact diagnosis of the underlying deficiency which is likely to cause thrombosis can also improve the efficacy and the specificity of prophylaxis.     

Serine proteases and cardiac function

The serine proteases of the trypsin superfamily are versatile enzymes involved in a variety of biological processes. In the cardiovascular system, the importance of these enzymes in blood coagulation, platelet activation, fibrinolysis, and thrombosis has been well established. Recent studies have shown that trypin-like serine proteases are also important in maintaining cardiac function and contribute to heart-related disease processes. In this review, we describe the biological function of corin, tissue kallikrein, chymase and urokinase and discuss their roles in cardiovascular diseases such as hypertension, cardiac hypertrophy, heart failure, and aneurysm.     

Intravascular clotting activation and bleeding in patients with hematologic malignancies

The association between thrombosis, bleeding and neoplastic disease is well recognized. There are distinctive features of the thrombotic and bleeding complications associated with specific hematologic malignancies. A number of procoagulants can initiate intravascular clotting including tissue factor, cancer procoagulant and interleukin-1. The hematologic malignancy most often associated with intravascular clotting and bleeding is acute promyelocytic leukemia. The pathogenesis of the life-threatening bleeding disorder associated with this uncommon subtype of acute myeloid leukemia (AML) is complex and involves disseminated intravascular coagulation, fibrinolysis and proteolysis. Both all-trans retinoic acid and arsenic trioxide result in relatively rapid resolution of the coagulopathy. Intravascular clotting may also be induced by hyperleukocytosis in AML and by the hyperviscosity syndrome observed in multiple myeloma and Waldenstr?m's macroglobulinemia. In the setting of hematologic malignancies, when thromboembolic complications occur, the presence of comorbid thrombophilic conditions should be excluded. Abnormal platelet production and function contribute to the development of thrombosis in patients with myeloproliferative disorders. The Budd-Chiari syndrome may be observed in patients with myeloproliferative disorders. A number of medications have thrombogenic potential, including corticosteroids, thalidomide, L-asparaginase, all-trans retinoic acid and arsenic trioxide.     

Hormone replacement therapy and cardiovascular disease

This year's work on hormone replacement therapy (HRT) and cardiovascular disease has been remarkable for the publication of the first randomised controlled trial of HRT use, the Heart Estrogen Replacement Study (HERS). The findings go against not only the trend of previous observational epidemiological studies, but also against findings in the very many studies which have previously shown and continue to show this year a beneficial effect of HRT on a large variety of cardiovascular risk factors, including endothelial function, here reviewed. The aspect of the effect of HRT on clotting variables is clearly crucial given the increased risk of venous thrombosis, and also increased number of cardiac events in the first 4 months of the HERS. Prothrombotic factors increase with age in women, and HRT alters these, particularly fibrinogen, factor VII, and PAI (less change with transdermal HRT) and antithrombin III. In normal women therefore the balance should be towards fibrinolysis rather than coagulation. Work has been presented in abstract for clarifying the effects of HRT on coagulation markers and grasping the problem of differences according to its route of administration. The full publications on this work are expected shortly. We are still awaiting evidence from randomized controlled trials of HRT in primary prevention; one is now recruited but will not report until 2005.     

Synergistic effect of aptamers that inhibit exosites 1 and 2 on thrombin

Thrombin is a multifunctional protease that plays a key role in hemostasis, thrombosis, and inflammation. Most thrombin inhibitors currently used as antithrombotic agents target thrombin''s active site and inhibit all of its myriad of activities. Exosites 1 and 2 are distinct regions on the surface of thrombin that provide specificity to its proteolytic activity by mediating binding to substrates, receptors, and cofactors. Exosite 1 mediates binding and cleavage of fibrinogen, proteolytically activated receptors, and some coagulation factors, while exosite 2 mediates binding to heparin and to platelet receptor GPIb-IX-V. The crystal structures of two nucleic acid ligands bound to thrombin have been solved. Previously Padmanabhan and colleagues solved the structure of a DNA aptamer bound to exosite 1 and we reported the structure of an RNA aptamer bound to exosite 2 on thrombin. Based upon these structural studies we speculated that the two aptamers would not compete for binding to thrombin. We observe that simultaneously blocking both exosites with the aptamers leads to synergistic inhibition of thrombin-dependent platelet activation and procoagulant activity. This combination of exosite 1 and exosite 2 inhibitors may provide a particularly effective antithrombotic approach.     

蜱源抗凝血因子研究进展

蜱是一种人畜共患体表寄生虫,通过叮咬宿主和吸血,将病原体传播给宿主,引发多种疾病。凝血反应是人和动物的重要生理过程,是生理性止血的重要环节。蜱叮咬和吸食宿主血液周期长,在吸血过程中分泌多种抗凝物质,抑制凝血反应,可帮助蜱长时间保持吸血状态。目前,已知的蜱源抗凝物质依据其功能主要包括蛋白酶抑制剂、纤维蛋白(原)溶解剂、血小板聚集抑制剂和血管活性蛋白4大类。这些抗凝血物质可分别作用于凝血级联反应中内源性通路、外源性通路、共同通路中的关键步骤,以及促进纤蛋白溶解和抑制血小板激活,从而抑制宿主血管中的凝血反应。蛋白酶抑制剂主要通过抑制凝血级联反应共同通路中凝血酶和Xa因子活性;纤维蛋白(原)溶解剂引起纤维蛋白原的水解并延迟纤维蛋白凝块的形成;血小板聚集抑制剂通过降解血小板聚集激动剂,并结合血栓素A2(thromboxane A2, TXA2)和血小板上的αIIbβ3整合素抑制血小板聚集;血管活性蛋白抑制宿主血管收缩以及伤口愈合和血管生成。此外,还有一些蜱分泌的其他蛋白分子可通过不同的通路来实现抗凝血作用。本文对迄今为止各类蜱中发现的具有抗凝血活性的蛋白和小分子及其抗凝血作用机制进行总结阐述,将...     

Simultaneous determination of functional coagulation factors and competitive (PIVKA-) inhibitors based on enzyme kinetics

For a plasma containing the competitive (PIVKA-) inhibitors induced by anticoagulant treatment the coagulation time t is related to the concentrations of functional coagulation factors S (substrates) and competitive inhibitors I by t = tmin + el/S + gamma I/S with tmin being the minimum possible coagulation time and e and gamma the sensitivities of the test procedure towards a change in the concentration of functional coagulation factors and competitive inhibitors, respectively. The calibration of the test procedure can be achieved by performing a series of dilutions on an inhibitor-free plasma (determination of tmin and e) and, after that, on a plasma of known inhibitor content (determination of gamma) in both cases recording the parametrizing straight line which results from multiplying the respective equation by S. The content of functional coagulation factors and competitive inhibitors in the plasmas of anticoagulated patients then can be determined simultaneously by treating the patient's plasma like in the calibration for gamma. The proposed method should allow the complete metrological characterization of thromboplastin time reagents without any need for reference thromboplastins.     

Oxidative stress in haemostasis

The normal hemostatic mechanisms consist of a balance between hemorrhage and thrombosis that is achieved through the interaction of the blood vessels, blood platelets, the coagulation and fibrinolytic factors. The vascular endothelium sustains the balance between prevention and stimulation of platelet activation, thrombogenesis and fibrinolysis and between vasoconstriction and vasodilatation. Endothelial dysfunction associated with different cardiovascular diseases is related to the local formation of reactive oxygen/nitrogen species, mainly peroxynitrite that is produced in a rapid reaction between nitric oxide and superoxide anion. Reactive oxygen/nitrogen species induce changes in the structure and function in hemostatic elements. Proteins and lipids are major initial targets in endothelial cells, blood platelets and plasma. Reaction of reactive oxygen species and nitrogen species, including peroxynitrite, with cellular proteins can lead to nitration of aromatic amino acid residues, oxidation of thiol groups and conversion of some amino acid residues into carbonyl derivative. Oxidative/nitrative modifications of platelet proteins may induce changes of their signaling and haemostatic function (activation). Peroxynitrite also causes oxidation and nitration of fibrinogen--a key protein in coagulation cascade and plasminogen (the main protein of fibrinolysisprocess) changing their hemostatic functions. Oxidative/nitrative modifications of different components of haemostasis system have been observed in several cardiovascular diseases.     

Obesity-related derangements of coagulation and fibrinolysis: a study of obesity-discordant monozygotic twin pairs

Coagulation and fibrinolytic activities are under strong genetic control. We studied the effects of acquired obesity, independent of genetic factors on coagulation and fibrinolysis activities in obesity-discordant healthy monozygotic (MZ) twin pairs. Fourteen obesity-discordant (BMI within-pair difference >3 kg/m(2)) and 10 concordant (BMI difference <2 kg/m(2)) MZ twin pairs were identified from the nationwide FinnTwin16 study. Body composition (dual-energy x-ray absorptiometry), abdominal fat distribution (magnetic resonance imaging), liver fat (magnetic resonance spectroscopy), high sensitivity C-reactive protein, insulin sensitivity (euglycemic hyperinsulinemic clamp), and a panel of different markers of blood coagulation and fibrinolysis in the fasting state were measured. Strong resemblance was observed in most coagulation factors within all twin pairs, with the intraclass correlations ranging from 0.73 to 0.97, P < 0.03. However, the activities of fibrinogen and FIX, FXI, and FXII, and plasminogen activator inhibitor-1 (PAI-1) activities were increased in the obese co-twins (P < 0.05) and strongly correlated with the measures of adiposity, inflammation, and insulin resistance (r = 0.32-0.73, P < 0.05) among the twin individuals. Intrapair differences in fibrinogen and PAI-1 correlated with those in BMI, adiposity, and fasting insulin levels (r = 0.40-0.58, P < 0.05) indicating the independent effect of obesity. Derangements of blood coagulation and fibrinolysis are present already in early adulthood in obese subjects. Acquired obesity, independent of genetic factors, increases the activities of fibrinogen and activities of FIX, FXI, FXII, and PAI-1. This study confirms the mechanisms of simultaneous activities of intrinsic coagulation factors and impaired fibrinolysis predisposing obese subjects to thrombosis.