Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The factor VIII complex consists of two noncovalently linked proteins: von Willebrand factor (VWF) and factor VIII (FVIII). VWF plays an important role in primary hemostasis by mediating the adherence of blood platelets to the damaged vessel wall. A review of the literature on VWF is given with regard to its physicochemical properties and mode of action. FVIII acts as a cofactor in the factor Xa-generating enzyme complex of the intrinsic coagulation cascade. Starting with the recently published primary structure of FVIII, the literature is reviewed for structural information on FVIII. Also, an effort is made to characterize the interaction of FVIII with VWF and to discuss the possible physiological significance of FVIII-VWF complex formation. Interaction of FVIII with the clotting factors of the intrinsic pathway of coagulation is described in detail. Hemophilia and von Willebrand's disease (VWD) are both congenital bleeding disorders affecting a great many people. The different variants of these diseases are described with some reference to therapy and detection.
...
PMID:The physiology and pathophysiology of the factor VIII complex. 309 83

A bleeding disorder (von Willebrand's disease) was diagnosed in a 9-year-old male Himalayan cat examined because of persistent oral bleeding after routine dental extraction. Bleeding subsided after empirical treatment, which included prednisolone, vitamin K1, and transfusion of fresh blood, but recurred spontaneously after 8 months of apparent good health. Pertinent results of routine laboratory testing included an inconstant prolongation of the activated partial thromboplastin time and recurring iron-deficiency anemia. Assays of specific coagulation factors revealed low factor VIII coagulant activity and undetectable factor VIII-related antigen, a pattern considered to be diagnostic of von Willebrand's disease. This condition, not previously reported in a cat, should be included in the differential diagnosis when cats are examined because of abnormal bleeding.
...
PMID:A bleeding disorder (von Willebrand's disease) in a Himalayan cat. 310 51

Ageing does not bring with it any major changes in the coagulation or fibrinolytic proteins or platelets. It does bring a greater burden of disease, with less reserves, and so when haemorrhage occurs in the elderly it has more serious consequences. The cause of a bleeding diathesis can usually be determined after a careful history, and examination of the patient followed by simple tests--the platelet count, blood film, bleeding time, prothrombin time, partial thromboplastin time, thrombin time, fibrin degradation products and the euglobulin clot lysis time. Other confirmatory tests, assays and inhibitor titres, will seal the diagnosis. Treatment is mainly directed at removing the underlying cause, if possible, and remedying the defect, with platelet transfusion, fresh frozen plasma or factor concentrates. These treatments will not be effective where there is an inhibitor or antibody present; steroids, splenectomy (for ITP), plasma exchange or immunosuppression are needed. Two major advances have occurred in the early 1980s. One has been the introduction of high-dose intravenous immunoglobulin in the management of ITP, although worries remain about thrombotic events in elderly patients. The other is the spreading use of DDAVP, originally introduced for von Willebrand's disease and mild haemophilia, and now finding a role in uraemia and with cardiopulmonary bypass. Drugs are a significant and potentially preventable cause of bleeding in the elderly. The most frequent problems arise with anticoagulants. The risk of interactions increase with the number of other medications which are prescribed.
...
PMID:Bleeding and coagulation disorders in the elderly. 332 49

The incidence of abnormal results of coagulation tests and the risks for postoperative hemorrhage were assessed in 235 patients with congenital heart disease. Preoperatively, the prothrombin time, partial thromboplastin time, activated partial thromboplastin time, thrombin time, or platelet count was abnormal in 45 of the 235 patients (19%), a significantly higher incidence than that expected in a normal population (P less than 0.002). Prolonged values for the prothrombin time or the partial thromboplastin time or activated partial thromboplastin time were seen most frequently. Further evaluation in eight of the patients with prolonged prothrombin time or partial thromboplastin or activated partial thromboplastin time showed decreased levels of either factor VII or IX in six of them, suggesting that impaired vitamin K-dependent carboxylation is commonly present. Normal results of preoperative coagulation tests do not exclude the presence of a major bleeding diathesis (von Willebrand's disease was later diagnosed in a patient with such findings). The use of blood products during subsequent cardiac operations was not significantly different in patients with normal or abnormal test results. Two of the three patients who required reoperation and were found to have a nonsurgical cause of bleeding had abnormalities in two or more of the preoperative coagulation tests. This finding suggests that abnormal results of preoperative coagulation tests may be predictive of defective hemostasis in the postoperative period.
...
PMID:Preoperative evaluation of hemostasis in patients with congenital heart disease. 357 26

To evaluate the effect of 1-deamino-8-D-arginine vasopressin (DDAVP) in various bleeding disorders, 10 micrograms/m2 DDAVP was administered to subjects with von Willebrand disease (13), platelet function defects (12), von Willebrand disease and platelet defects together (8), or isolated prolongation of the bleeding time (5). DDAVP shortened the bleeding time similarly in all patient groups. Shortening of the bleeding time was also observed in 2 patients with aspirin-induced platelet defects and in 2 normal subjects. DDAVP administration was associated with falls in the platelet count, mean platelet volume, and partial thromboplastin time, and rises in platelet adhesion, factor VIII coagulant activity, factor VIII related antigen, and von Willebrand factor activity. The basal bleeding time was the only predictor of the magnitude of the bleeding-time correction. Normal haemostatis was achieved with DDAVP plus epsilon-aminocaproic acid and no blood product support during operations in 18 patients with bleeding disorders.
...
PMID:Shortening of bleeding time by 1-deamino-8-D-arginine vasopressin in various bleeding disorders. 614 76

The factor VIII complex is a macromolecule with two distinct components. One is the coagulation factor VIII. The other, known as the Willebrand factor, is a polymer which probably acts as a carrier for serum factor VIII. Hereditary disorders can affect either of these two components. Hemophilia A is a coagulation disorders due to decreased factor VIII coagulant activity. Increase of partial activated thromboplastin time parallels disease severity. Hematomas and hemarthrosis in large joints are the main clinical features. In von Willebrand disease, mucocutaneous bleeding is the main symptom. Diagnosis is established by demonstrating disorders of primary hemostasis: prolonged bleeding time and decreased ristocetin-induced platelet aggregation. Two forms of von Willebrand disease have been described. In the quantitative form, decreased synthesis of von Willebrand factor is often responsible for severe clinical manifestations. The qualitative form probably results from defective polymerization of von Willebrand factor subunits. In both these forms, deficient primary hemostasis is a consequence of decreased platelet adhesion to the vascular wall. Clinical and biological features of hemophilia A and von Willebrand disease, as well as their management, are discussed.
...
PMID:[The factor VIII complex: hemophilia A and von Willebrand disease]. 629 93

Two family members (daughter and mother) with a bleeding disorder showed prolonged bleeding time and activated partial thromboplastin time associated with decreased plasma levels of factor VIII procoagulant activity, factor VIII-related antigen, and factor VIII-ristocetin cofactor activity. The ristocetin-induced platelet agglutination (RIPA) was enhanced, ADP-, collagen- and Ca ionophore-induced platelet aggregation were also increased at low concentrations of these compounds. In the mother, spontaneous platelet aggregation (SPA) was also observed. Contrary to type II B von Willebrand's disease (vWd), pseudo-vWd and platelet-type vWd, the patients did not show any increased binding of factor VIII/vWf to platelets in the presence of ristocetin. The RIPA in normal controls were inhibited by addition of antifactor VIII antiserum to the platelet-rich plasma, but not in cases 1 and 2. In this atypical vWd, therefore, the hyperreactivity of platelet aggregation may be due to an intrinsic abnormality of the platelets, but not to any enhanced interaction between plasma factor VIII and the platelets.
...
PMID:An atypical von Willebrand's disease with hyperreactivity of platelet aggregation. 642 80

Factor VIII (antihemophilic factor) is the protein that is deficient or defective in patients with classical hemophilia and Von Willebrand syndrome. Factor VIII in plasma is thought to be associated in a complex with the highest molecular weight multimers of another glycoprotein, Von Willebrand protein. Highly purified human factor VIII appears to have an Mr of between 200,000 and 300,000 and to consist of several polypeptide chains. The concentration of factor VIII in plasma is around 100-200 ng/ml, equivalent to around 1 nM. The purified proteins retain one or more of the known properties of factor VIII, including the acceleration of factor IXa-mediated activation of factor X, ability to be activated by thrombin and factor Xa, inactivation by activated protein C, and by human antibodies to factor VIII. Among the known clotting factors, factors VIII and V are exceptional in not possessing enzymatic activity. Factors IXa and VIII and X appear to form a functional complex, all of which need to be present and active simultaneously for optimal activation of factor X. The mechanism by which factor VIII promotes activation of factor X by factor IXa is not known, but the major effect is to increase the rate of the reaction. Following treatment of factor VIII with thrombin, a new and smaller polypeptide Mr around 70,000 +/- 5,000 is produced. Factors IXa and Xa also have been reported to activate factor VIII. It is not known whether limited proteolytic cleavage is required absolutely for the expression of factor VIII activity or if it only increases an activity already expressed by the uncleaved protein. Factor VIII is inactivated by thrombin and by activated protein C. Thus, factor VIII can be modulated by at least four of the serine proteases in the clotting system. A major goal for future research is to increase our understanding of the role in blood clotting played by factor VIII, and to apply this information to clinical problems which result from inherited abnormalities of factor VIII.
...
PMID:Factor VIII: structure and function in blood clotting. 642 37

Fifty children with suspected non-accidental injury, most of whom had bruising, were investigated to exclude a bleeding disorder. The following investigations were undertaken in each child: full blood count; platelet count, size, and shape; prothrombin time; partial thromboplastin time including mix with normal plasma; fibrinogen; and a bleeding time. The results of these initial investigations were abnormal in eight children (16%). One child had a severe coagulopathy secondary to spontaneously acquired inhibitory activity to coagulation factors which led to spontaneous bruising and noticeable signs of injury after a minor accident. The remaining children had several features supporting a diagnosis of non-accidental injury. Two had associated bleeding disorders in the form of von Willebrand's disease and a platelet aggregation abnormality and a baby had an acquired platelet disorder secondary to salicylates, provoking severe haemorrhage from a minor injury. The remaining four children initially had an abnormal laboratory finding--a prolonged partial thromboplastin time--which resulted in lengthy discussions during subsequent legal proceedings. Evidence of a bleeding disorder is not uncommon in non-accidental injury and the two conditions are not mutually exclusive.
...
PMID:Bleeding disorders and non-accidental injury. 648 63

Thrombokinetograms are graphic depictions of the optical changes occurring in plasma during the clotting process and provide information, not only on the time required for clotting to begin, but also on the way in which the clot forms. We studied thrombokinetic profiles in plasmas from normal dogs, and dogs with varying degrees of factor VIII deficiency. Clotting was induced through intrinsic, extrinsic and common coagulation pathways [activated partial thromboplastin time, prothrombin time and thrombin time, respectively]. The thrombokinetograms for the various clotting tests were qualitatively similar in normal canine plasmas. After activation of the clotting system there was a period in which no change in optical density occurred. This period was represented by the left base line and corresponded to the duration of the clotting time. When fibrin production commenced there was a rapid increase in the rate of optical density change (DeltaOD) to a maximum (V(max)DeltaOD) in time t(1). This was followed by a more gradual reduction in DeltaOD in time t(2). The activated partial thromboplastin time thrombokinetograms for von Willebrand's disease plasmas were characterized by a reduced V(max)DeltaOD and prolonged t(1). In severe hemophilic plasma [factor VIII coagulant (F VIII:C)<1% of normal] there was a very slow increase in DeltaOD following a prolonged left baseline. The V(max)DeltaOD, t(1) and t(2) could not be determined since a peak was not attained in one minute. The prothrombin and thrombin time thrombokinetograms for von Willebrand's disease plasmas were normal. The prothrombin time thrombokinetogram for hemophilic plasma had a 2X normal V(max)DeltaOD possibly related to the relatively high fibrinogen concentration of this plasma compared to the normal. Changes in thrombokinetogram profiles may be of value in studying mild to moderate clotting factor deficiencies particularly where the clotting times are not markedly prolonged.
...
PMID:Thrombokinetic studies in normal and factor VIII-deficient canine plasmas. 660 92


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---