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PubMed1995

Developmental hemostasis: relevance to hemostatic problems during childhood.

Congenital and acquired hemostatic disorders present during childhood. An accurate diagnosis is critically important in order to implement optimal therapy. Over the last century, several investigators have measured plasma concentrations of hemostatic components in newborns and compared the results to adult values. Clinically significant differences exist for many hemostatic components. Recently, three large studies in more than 400 healthy children have provided reference ranges for hemostatic components throughout childhood. Together, these studies provide insight into the regulation of coagulation and fibrinolysis in children in physiologic and pathologic states. Some examples of the influence of age on hemostasis are: (1) the diagnosis of some congenital factor deficiencies, based on plasma levels, can be difficult due to physiologically low values; (2) despite very low levels of many inhibitors of hemostasis, thrombotic complications are rare; (3) the interaction of anti-coagulants and thrombolytic agents is profoundly influenced by the relative immaturity of hemostasis at birth; and (4) in contrast to the risk of thrombosis, healthy infants are at risk for vitamin K deficiency bleeding due to poor transport of vitamin K across the placenta and plasma concentrations of the vitamin K dependent proteins of less than 50% of adults values. The following review discusses the age dependency of hemostasis during childhood and the effect of the physiologically immature system on the diagnosis and treatment of hemostatic disorders.

Age Factors↗
PubMed1988

Antithrombin III, protein C, and protein S. Naturally occurring anticoagulant proteins.

Protein C, protein S, and antithrombin III are naturally occurring anticoagulant proteins. Activated protein C and protein S act by inhibiting the action of the cofactors factor Va and factor VIIIa. Antithrombin III inhibits the serine proteases (factors II, IX, X, XI, and XII); its anticoagulant action is dramatically enhanced by heparin. Deficiencies of these proteins are associated with thromboembolic disease. Antigen and activity assays practical for the clinical laboratory are available for protein C and antithrombin III. Protein S antigen assays are also available. Diagnosis of an anticoagulant protein deficiency has serious implications for a patient and his kindred, and should therefore only be made on the basis of repeated abnormal determinations of a single protein in an individual patient, or documentation of the same protein deficiency in other family members.

Antithrombin III↗
PubMed1990

[Ischemic occlusion of the central retinal vein and protein C deficiency].

We present a case of a 52-year-old woman suffering from an ischemic central retinal vein thrombosis with neovascular glaucoma of her left eye. Protein C activity was found to be reduced (32%). This supports the hypothesis that protein C may play a role in the pathogenesis of ocular vaso-occlusive disease, as protein C is an important inhibitor of hemostasis. Thus, we suggest to measure protein C in patients with preceding thromboembolic diseases or assumed disorders of coagulation.

Female↗
PubMed1987

Hemophilia B (factor IXSeattle 2) due to a single nucleotide deletion in the gene for factor IX.

To understand the molecular basis for hemophilia B in patients with little or no circulating Factor IX antigen, a patient who had less than 0.2% circulating Factor IX antigen (Factor IXSeattle 2) was selected for analysis of his Factor IX gene. Genomic DNA fragments from the abnormal gene were cloned into bacteriophage lambda vectors and recombinant phage were identified using radiolabeled genomic probes obtained from the normal Factor IX gene. The exons and flanking regions of the abnormal gene were sequenced by the dideoxy chain-termination method and this sequence was compared with that of the normal gene. Only one significant difference was observed, the deletion of a single adenine nucleotide in exon V. This resulted in a frameshift that converted an aspartic acid at position 85 in the protein to a valine and the formation of a stop signal at position 86. These data indicate that the gene for Factor IXSeattle 2 codes for an 85 residue polypeptide that terminates after the first epidermal growth factor domain. Thus, the putative Factor IXSeattle 2 polypeptide lacks the second epidermal growth factor domain, the activation peptide, and the catalytic domain present in the normal protein. This provides an explanation for the coagulation disorder in this patient and represents the first report of a single nucleotide deletion and frameshift resulting in hemophilia B.

Adenine↗
PubMed1990

[Possibilities of prenatal diagnosis in hemophilia A based on DNA analysis].

Haemophilia-A is the most common bleeding disorder in man, resulting from a deficiency of the coagulant protein, factor VIII. The factor VIII gene is located at Xq28 and the disease is inherited as an X-linked recessive disorder. There is a possibility using DNA probes closely linked to the gene factor VIII to determine the genotype. The availability of factor VIII DNA probes has led to the detection of carrier females and first trimester prenatal diagnosis of haemophilia-A. The authors give a short account on their experiences with four DNA probes. Their studies were carried out in nine families who have affected individuals and plan another pregnancies in the near future. DNA analysis can allow first trimester prenatal diagnosis from chorionic villi taken at 8-10th weeks of gestation. In the case of a male fetus it is possible to determine whether the mutant gene is inherited or not. Till now seven prenatal diagnoses have been performed based on the chorionic DNA.

Chorionic Villi Sampling↗
PubMed1996

An autosomal dominant, qualitative platelet disorder associated with multimerin deficiency, abnormalities in platelet factor V, thrombospondin, von Willebrand factor, and fibrinogen and an epinephrine aggregation defect.

Multimerin is a massive soluble, multimeric protein found in platelets and endothelial cells. Recent studies identified multimerin as a specific coagulation factor V binding protein, complexed with platelet, but not plasma, factor V. These findings led us to investigate individuals with inherited factor V deficiencies for possible multimerin abnormalities. Platelet proteins were evaluated using immunoassays, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, immunoprecipitation, and direct binding studies. Patients with factor V Quebec, a disorder with abnormal platelet factor V, had a quantitative deficiency in multimerin (n = 11 tested; mean, 12.5%; range, 5% to 27% of the normal pool; normal range, 45% to 214%) with a normal multimer pattern. Quantitative and qualitative abnormalities were detected in their platelet factor V. An unrelated patient who was deficient in platelet and plasma factor V had normal platelet multimerin. The levels of platelet beta-thromboglobulin, von Willebrand factor, thrombospondin, and fibrinogen antigen were normal in the factor V Quebec patients. However, proteins with abnormal mobility were detected in their platelet lysate and releasate, and their platelet thrombospondin, von Willebrand factor, and fibrinogen showed evidence of proteolytic degradation. Platelet counts of the factor V Quebec patients ranged from mildly thrombocytopenic to low normal (mean, 159 x 10(9)/L; range, 104 to 198 x 10(9)/L). In addition, their platelets failed to aggregate in response to 6 to 10 micromol/L epinephrine despite normal numbers of platelet alpha 2-adrenergic receptors. These data indicate that patients with factor V Quebec have an inherited bleeding disorder distinct from other platelet disorders and associated with multiple abnormalities, including multimerin deficiency, abnormal platelet factor V, thrombospondin, von Willebrand factor, and fibrinogen, and an epinephrine aggregation defect.

Afibrinogenemia↗
PubMed1994

Automation and quality control in the coagulation laboratory.

Hemostasis is a balance between complex interactions of directly opposing systems (coagulation and fibrinolysis) with seemingly unrelated systems at both the enzymatic and cellular levels (platelets, endothelium, leukocytes). It should not be surprising that coagulation disorders often accompany many different disease states. Because the function of each protein involved in coagulation is now better defined, newer methodologies have been developed to assay them. In this regard, the hemostasis laboratory can take a two-step approach to diagnosis: global screening and targeted analysis. Several new global test systems provide more detailed, quantitative, and more physiologically relevant evaluations than earlier assays allowed. In addition, individual enzymes, inhibitors, cellular release products, and low molecular weight products of activation reactions (molecular markers) can now be measured in sensitive, specific assays. With this new perspective, genetic predisposition to pathologic hemostatic conditions can be identified through molecular biology and can be identified during the early stages of disease (i.e., at subclinical stages before major pathologic complications are established), and more specifically targeted prophylactic, as well as therapeutic drug interventions, can be administered. The molecular markers of hemostatic activation that can be assessed by various immunochemical methods provide very early evidence of thrombotic, fibrinolytic, or platelet-involved aberrations. Technological advances in methodology and instrumentation have changed the scope of all clinical laboratories but, in particular, that of the coagulation laboratory. The dramatic growth and development have resulted from the influences of clinical chemistry, clinical immunology, pharmacology, biochemistry, and biotechnology. Analytical instruments for use in hemostatic testing go beyond plasma or whole blood clot-based readers, platelet aggregometers, and microscopes to a range of automated, discrete, chemistrylike analyzers, spectrophotometers, microliter ELISA systems, RIA systems, and multiprobe instruments designed to measure simultaneously the different assay end-points of colorimetric and clotting assays and flow cytometers. Instruments are designed for batch processing of single tests on multiple samples or multiple test panels on a single sample. Versatility ranges from instruments that measure only the final reaction solution, by end-point or kinetic analysis, to instruments that automatically pipet reagents and sample, incubate, and analyze the reaction for truly walk-away assay performance. Typically, a wider range of assays are available in automated laboratories as opposed to laboratories performing manual assays.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1994

[Inherited thrombophilia].

The prevalence of inherited thrombophilia in the general population (1 in 2,500) is higher than that of hemophilia and related bleeding disorders. Well established causes of thrombophilia include deficiencies of natural coagulation inhibitors: antithrombin III, protein C and protein S. It is likely that other inherited disorders, such as deficiency of the second cofactor for activated protein C, deficiency of heparin cofactor II, hypo- and dysplasminogenemias, dysfibrinogenemias and homocysteinemia, may predispose to thrombosis. This review discusses clinical and laboratory aspects of these disorders and summarizes the management of individuals with inherited thrombophilia.

Anticoagulants↗
PubMed2004

Mutations in VKORC1 cause warfarin resistance and multiple coagulation factor deficiency type 2.

Coumarin derivatives such as warfarin represent the therapy of choice for the long-term treatment and prevention of thromboembolic events. Coumarins target blood coagulation by inhibiting the vitamin K epoxide reductase multiprotein complex (VKOR). This complex recycles vitamin K 2,3-epoxide to vitamin K hydroquinone, a cofactor that is essential for the post-translational gamma-carboxylation of several blood coagulation factors. Despite extensive efforts, the components of the VKOR complex have not been identified. The complex has been proposed to be involved in two heritable human diseases: combined deficiency of vitamin-K-dependent clotting factors type 2 (VKCFD2; Online Mendelian Inheritance in Man (OMIM) 607473), and resistance to coumarin-type anticoagulant drugs (warfarin resistance, WR; OMIM 122700). Here we identify, by using linkage information from three species, the gene vitamin K epoxide reductase complex subunit 1 (VKORC1), which encodes a small transmembrane protein of the endoplasmic reticulum. VKORC1 contains missense mutations in both human disorders and in a warfarin-resistant rat strain. Overexpression of wild-type VKORC1, but not VKORC1 carrying the VKCFD2 mutation, leads to a marked increase in VKOR activity, which is sensitive to warfarin inhibition.

Amino Acid Sequence↗
PubMed2002

Insulin resistance syndrome: interaction with coagulation and fibrinolysis.

Insulin resistance represents a common metabolic abnormality leading to cardiovascular disease, the major cause of morbidity and mortality in most parts of the world. Insulin resistance is also associated with an increased risk of type 2 diabetes which is strongly associated with obesity. The insulin resistance of obese people and subjects with type 2 diabetes is characterised by defects at many levels, affecting insulin receptor concentration, glucose transport mechanisms and the activities of intracellular enzymes. Around 25% of western populations show some features of the insulin resistance syndrome (often referred to as syndrome X or the metabolic syndrome) ie, a clustering of metabolic, atheromatous risk factors, including hypertriglyceridaemia, hyperinsulinaemia, hyper-tension, hypercholesterinaemia and obesity. However, the known metabolic cardiovascular risk factors associated with the insulin resistance syndrome do not sufficiently explain the excess vascular risk attributed to this syndrome. The observation, that increased plasma plasminogen activator inhibitor 1 (PAI-1) levels were associated with insulin resistance and atherothrombosis added for the first time a pathological basis for an association of the insulin resistance syndrome not only with metabolic, atheromatous (atherosclerotic) risk but also with atherothrombotic risk. It is very likely that not only PAI-1, but also other abnormalities in haemostatic variables contribute to this excess vascular risk. Knowledge of how haemostatic variables cluster with classical metabolic risk factors associated with the insulin resistance syndrome could help to better understand the pathogenesis of cardiovascular diseases. Indeed, many coagulation and fibrinolytic proteins have been shown to be associated with features of the insulin resistance syndrome and these associations suggest that some coagulation and fibrinolytic proteins have a role in atherothrombotic disorders, principally through an association with other established metabolic (atheromatous) risk factors in the presence of underlying insulin resistance. Interestingly, new therapeutic approaches in the prevention and treatment of insulin resistance do show some influence on coagulation and fibrinolysis. The newest drugs are the thiazolidinediones, a totally novel class of insulin sensitisers. They have the potential to offer improvements both in glycaemic control and in cardiovascular events.

Blood Coagulation↗
PubMed1997

Autoantibodies to phospholipids and to the coagulation proteins in AIDS.

In HIV-1 infection, an increased prevalence of anticardiolipin autoantibodies (aCL) and lupus anticoagulant (LA) has been described. In order to see if these antibodies are isolated or, like in autoimmune diseases, associated with hematological disorders and with antibodies to other phospholipids and to proteins of coagulation, we investigated 3 groups of patients: 1. 342 HIV-1 infected patients, 2. 145 control patients including 61 systemic lupus erythematosus (SLE) patients, 58 patients with a connective tissue disease, 15 patients with stroke, 11 patients with syphilis and 3. 100 blood donors. In HIV-1 infection antiprothrombin (aPrT) antibodies were present in 2% of patients, the prevalence of antiphosphatidylcholine antibodies (aPC) (50%) was almost as high as aCL (64%), and 39% had both antibodies. Absorption on liposomes of the latter revealed an heterogeneous mixture of aCL and aPC or cross-reacting antibodies. In contrast with SLE, anti-beta 2-glycoprotein I (4%), LA (1%), biological false positive test for syphilis (0.3%), thrombosis (p < 0.001) were uncommon. In HIV-1 infection, antiphospholipid antibodies do not associated with features linked to them in SLE or syphilis.

Acquired Immunodeficiency Syndrome↗
PubMed1985

[Immunologic determination of the protein C of coagulation: detection of deficiencies].

Protein C, discovered by Stenflo in 1976, plays a major role in the regulation of thrombogenic processes. Even moderate deficiencies (0.40 to 0.60 U/ml) can be responsible for serious thromboembolic accidents. The authors evaluated the kits for the immunological assay of protein C, produced by Laboratoire Diagnostica Stago: a immuno-enzymatic method (ELISA) and Laurell's method. Despite the very different characteristics in terms of practicability, threshold of sensitivity and precision, the authors obtained an excellent correlation between these two techniques. The concentrations of protein C Ag obtained in 22 normal plasmas were 0.70 to 1.40 U/ml. In 32 patients with recurrent thrombosis with no apparent cause, 5 had a concentration of protein C Ag less than 0.70 U/ml. The identification of a deficiency of protein C Ag (Vitamin K depend protein) is often made difficulty by the fact that the patients are treated with anti-vitamin K drugs. The ratio between the vitamin K depend pro-coagulation factors and Protein C Ag may provide information about a possible deficiency.

4-Hydroxycoumarins↗
PubMed1984

Protein C: a new plasma protein related to postoperative hypercoagulability.

Protein C is a vitamin-K dependent plasma protein, whose activation is catalyzed by alpha-thrombin. Unlike vitamin-K dependent coagulation factors, activated Protein C is an anticoagulant enzyme. Purpose of the present study was to evaluate the pathophysiology of Protein C in patients undergoing minor and major elective surgery. A third group of patients were operated for cancer of the gastrointestinal tract. Protein C levels have significantly decreased in all patients in third postoperative day, while this decrease occurred since the first postoperative day in the case of cancer patients. This suggests that Protein C is consumed after surgery in its anticoagulant and profibrinolytic activity. The acquired Protein C deficiency may be related to postoperative hypercoagulability and increased risk of deep vein thrombosis.

Adolescent↗