| factor II | <haematology> A protein which is synthesised by the liver. Fibrinogen is converted to fibrin, in the formation of a blood clot, via the enzymatic action of thrombin. A fibrinogen assay measures the concentration of fibrinogen in the blood and may be used to evaluate abnormal blood clotting. A lack of fibrinogen may be congenital or acquired. A condition known as DIC results in the excessive utilisation and depletion of fibrinogen. Synonym: thrombin. (15 Nov 1997) |
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| factor IIa | <enzyme> Protease (34 kD) generated in blood clotting that acts on fibrinogen to produce fibrin. Consists of two chains, A and B, linked by a disulphide bond. B chain has sequence homology with pancreatic serine proteases: cleaves at Arg Gly. Thrombin is produced from prothrombin by the action either of the extrinsic system (tissue factor + phospholipid) or, more importantly, the intrinsic system (contact of blood with a foreign surface or connective tissue). Both extrinsic and intrinsic systems activate plasma factor X to form factor Xa which then, in conjunction with phospholipid (tissue derived or platelet factor 3) and factor V, catalyses the conversion. (18 Nov 1997) |
| factor II assay | A test used to measure the activity of a blood clotting factor (thrombin). This test may be used to evaluate excessive bleeding. Abnormally low factor II assays may be seen in the following conditions: congenital deficiency of factor II, fat malabsorption, heparin administration, cirrhosis, vitamin K deficiency and warfarin administration. (27 Sep 1997) |
| factor II deficiency | A congenital or acquired disorder of blood clotting where there is a deficiency of factor II (prothrombin), one of 20 necessary plasma proteins for normal blood coagulation. Acquired factor II deficiency may result from vitamin K deficiency, severe liver disease and anticoagulant drugs. Symptoms include abnormal bleeding, nosebleeds, abnormal menstrual bleeding, easy bruising and umbilical cord bleeding at birth. Treatment involves the infusion of fresh frozen plasma. Vitamin K may be administered in select cases. (27 Sep 1997) |
| factor III | In the clotting of blood, tissue factor or thromboplastin; it initiates the extrinsic pathway by reacting with factor VII and calcium to form factor VIIa. See: thromboplastin. (05 Mar 2000) |
| factor Inv | A factor that determines certain of the allotypes of human immunoglobulins; found on the kappa chains of IgG, IgA, IgM, and Bence Jones protein. (05 Mar 2000) |
| factor IV | In the clotting of blood, calcium ions. (05 Mar 2000) |
| factor P | A chemical (postulated by T. Lewis), formed in ischemic skeletal or cardiac muscle, held to be responsible for the pain of intermittent claudication and angina pectoris. (05 Mar 2000) |
| factor, rheumatoid | Rheumatoid factor is an antibody that is measurable in the blood. It is commonly used as a blood test for the diagnosis of rheumatoid arthritis. Rheumatoid factor is present in about 80% of adults (but a much lower proportion of children) with rheumatoid arthritis. It is also present in patients with other connective tissue diseases (such as systemic lupus erythematosus) and in some with infectious diseases (such as infectious hepatitis). (12 Dec 1998) |
| factor v | <chemical> Heat- and storage-labile plasma glycoprotein which accelerates the conversion of prothrombin to thrombin in blood coagulation. Factor v accomplishes this by forming a complex with factor xa, phospholipid, and calcium (prothrombinase complex). Deficiency of factor v leads to owren's disease. Chemical name: Blood-coagulation factor V (12 Dec 1998) |
| factor V1a | The hexa-amide of cobyrinic acid; a part of the vitamin B12 structure. Synonym: cobyrinamide, cobyrinic hexa-amide, factor V1a. (05 Mar 2000) |
| factor va | <chemical> Activated form of factor v. It is an essential cofactor for the activation of prothrombin catalyzed by factor xa. Chemical name: Blood-coagulation factor Va (12 Dec 1998) |
| factor v assay | A test used to measure the activity of a blood clotting factor V. This test may be used to evaluate excessive bleeding. Abnormally low factor V assays may be seen in the following conditions: congenital deficiency of factor V, DIC, heparin administration, cirrhosis and primary fibrinolysis. (27 Sep 1997) |
| factor v deficiency | An inherited disorder that results in abnormal blood clotting due to the deficiency of factor V, one of 20 plasma proteins responsible for the maintenance of normal blood clotting. Symptoms include excessive bleeding, bleeding gums, nosebleeds, easy bruising, excessive menstrual bleeding and bleeding into muscle tissue (haematoma) or a joint space (haemarthrosis). Treatment includes the infusion of fresh frozen plasma to restore deficient factor V. (27 Sep 1997) |
| factor vii | <chemical> Heat- and storage-stable plasma protein that is activated by tissue thromboplastin to form factor viia in the extrinsic pathway of blood coagulation. The activated form then catalyses the activation of factor x to factor xa. Chemical name: Blood-coagulation factor VII (12 Dec 1998) |