| 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) |
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| 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) |
| platelet membrane glycoproteins | Surface glycoproteins on platelets which have a key role in haemostasis and thrombosis such as platelet adhesion and aggregation. Many of these are receptors. (12 Dec 1998) |
| platelet storage pool deficiency | A group of disorders characterised by a decrease or lack of platelet dense bodies in which the releasable pool of adenine nucleotides and 5ht are normally stored. (12 Dec 1998) |
| platelet thrombosis | Thrombosis due to an abnormal accumulation of platelets. (05 Mar 2000) |
| platelet tissue factor | <haematology> Traditional name for substance in plasma that converts prothrombin to thrombin. Now known not to be a single substance. (See thrombin). (18 Nov 1997) |
| platelet transfusion | The transfer of blood platelets from a donor to a recipient or reinfusion to the donor. (12 Dec 1998) |
| platelet-activating factor | <cytokine> Potent phospholipid activator and mediator of many leucocyte functions, including platelet aggregation, inflammation, and anaphylaxis. It is produced in response to specific stimuli by a variety of cell types, including neutrophils, basophils, platelets, and endothelial cells. Several molecular species of platelet-activating factor have been identified which vary in the length of the O-alkyl side chain. It is an important mediator of bronchoconstriction. Synonym: platelet-aggregating factor. Acronym: PAF (20 Sep 2002) |
| platelet-aggregating factor | <cytokine> Potent phospholipid activator and mediator of many leucocyte functions, including platelet aggregation, inflammation, and anaphylaxis. It is produced in response to specific stimuli by a variety of cell types, including neutrophils, basophils, platelets, and endothelial cells. Several molecular species of platelet-activating factor have been identified which vary in the length of the O-alkyl side chain. It is an important mediator of bronchoconstriction. Synonym: platelet-aggregating factor. Acronym: PAF (20 Sep 2002) |
| platelet-derived growth factor | <growth factor> The major mitogen in serum for growth in culture of cells of connective tissue origin. It consists of 2 different but homologous polypeptides A and B (~30,000 D) linked by disulphide bonds. Believed to play a role in wound healing. It is carried in the alpha-granules of platelets and is released when platelets adhere to traumatised tissues. Connective tissue cells near the traumatised region respond by initiating the process of replication. The B chain is almost identical in sequence to p28sis, the transforming protein of simian sarcoma virus, that can transform only those cells that express receptors for platelet derived growth factor, suggesting that transformation is caused by autocrine stimulation. The receptor is a tyrosine kinase. Acronym: PDGF (12 Dec 1998) |
| plateletpheresis | The preparation of platelet concentrates with the return of red cells and platelet-poor plasma to the donor. (12 Dec 1998) |
| platelets | A particle found in the bloodstream that binds to fibrinogen at the site of a wound to begin the blood clotting process. Platelets are formed in bone marrow, where they arise from cells called megakaryocytes. (09 Oct 1997) |