| platelet actomyosin | The contractile protein of platelets, responsible for clot retraction, platelet aggregation, and release of ADP and other biologic amines essential to platelet function. Synonym: thrombosthenin. (05 Mar 2000) |
|---|---|
| platelet adhesiveness | The process whereby platelets adhere to something other than platelets, e.g., collagen, basement membranes, microfibrils, or other "foreign" surfaces. (12 Dec 1998) |
| platelet aggregation | The attachment of platelets to one another. This clumping together can be induced by a number of agents (e.g., thrombin, collagen) and is part of the mechanism leading to the formation of a thrombus. (12 Dec 1998) |
| platelet aggregation inhibitors | Drugs or agents which antagonise or impair any mechanism leading to blood platelet aggregation, whether during the phases of activation and shape change or following the dense-granule release reaction and stimulation of the prostaglandin-thromboxane system. (12 Dec 1998) |
| platelet aggregation test | A test of the ability of platelets to adhere to each other and hence form a haemostatic plug to prevent bleeding; failure to aggregate occurs in several conditions, e.g., thrombasthenia, Von Willebrand's disease, and following administration of aspirin, phenylbutazone, and indomethacin; the test is conducted by quantitating the decrease in turbidity that occurs in platelet-rich plasma following the in vitro addition of one or several platelet-aggregating agents (e.g., ADP, epinephrine, or serotonin). (05 Mar 2000) |
| platelet basic protein | <protein> Protein that is the precursor of connective tissue activating peptide III and _ thromboglobulin. (18 Nov 1997) |
| platelet cofactor I | A coagulation (clotting) factor. Classic haemophilia (haemophilia A) is due to a congenital deficiency in the amount (or activity) of factor VIII. Factor VIII is also known as antihemophiliac factor (AHF) or antihemophiliac globulin (AHG). The gene for factor VIII (that for classic haemophilia) is on the X chromosome so females can be silent carriers without symptoms and males can be haemophiliacs. (12 Dec 1998) |
| platelet cofactor II | <chemical> Storage-stable blood coagulation factor acting in the intrinsic pathway. Its activated form, ixa, forms a complex with factor viii and calcium on platelet factor 3 to activate factor x to xa. Deficiency of factor ix results in christmas disease (haemophilia b). Chemical name: Blood-coagulation factor IX (12 Dec 1998) |
| platelet count | <haematology> The number of platelets per cubic millimetre of blood. The normal range is 150,000-400,000 platelets per cubic mm. Platelet counts under 10,000 per cubic millimetre place the patient at risk for spontaneous haemorrhage. Platelets are produced in the bone marrow in increased quantities in response to stress. (27 Sep 1997) |
| platelet endothelial cell activated protease | <enzyme> Degrades casein and fibrinogen; secreted by endothelial cells and activated in the extracellular medium by platelets; not inhibited by serine protease inhibitors, metalloproteinase inhibitors, or cystein protease inhibitors; pH optimum 7.5 Registry number: EC 3.4.99.- Synonym: pecap (26 Jun 1999) |
| platelet factor 3 | <haematology> Phospholipid associated with the platelet plasma membrane that contributes to the blood clotting cascade by forming a complex (thromboplastin) with other plasma proteins and activating prothrombin. (31 Dec 1997) |
| platelet factor 4 | <haematology> Platelet released protein that promotes blood clotting by neutralising heparin. (31 Dec 1997) |
| platelet function disorders | <haematology> Platelet function can be affected by a number of different disease processes including polycythaemia vera, leukaemia, myelofibrosis, renal failure, multiple myeloma and some medications (for example penicillins, salicylates, phenothiazines). Disturbed blood clotting can be manifested by: easy bruising, bleeding gums, nosebleeds, abnormal vaginal bleeding, rectal bleeding, skin rash, vomiting blood, coughing up blood or blood in the urine. A measure of bleeding time and coagulation profile will be part of the evaluation. (31 Dec 1997) |
| platelet glycoprotein gpib-ix complex | Platelet membrane glycoprotein complex essential for normal platelet adhesion and clot formation at sites of vascular injury. It is composed of three polypeptides, gpib alpha, gpib beta, and gpix. Glycoprotein ib functions as a receptor for von willebrand factor and for thrombin. Congenital deficiency of the gpib-ix complex results in bernard-soulier syndrome. The platelet glycoprotein gpv associates with gpib-ix and is also absent in bernard-soulier syndrome. (12 Dec 1998) |
| platelet glycoprotein gpiib-iiia complex | Platelet membrane glycoprotein complex important for platelet adhesion and aggregation. The complex is an integrin which recognises the arginine-glycine-aspartic acid (rgd) sequence present on several adhesive proteins. As such, it is a receptor for fibrinogen, von willebrand factor, fibronectin, vitronectin, and thrombospondin. A deficiency of gpiib-iiia results in glanzmann's thrombasthenia. (12 Dec 1998) |