| aggregation | Massing of materials together as in clumping. (18 Nov 1997) |
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| receptor aggregation | Chemically stimulated aggregation of cell surface receptors, which potentiates the action of the effector cell. (12 Dec 1998) |
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| cell aggregation | The phenomenon by which dissociated cells intermixed in vitro tend to group themselves with cells of their own type. (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) |
| erythrocyte aggregation | Aggregation of erythrocytes probably resulting from changes in the negative surface charge (zeta potential) of the cells caused by the dielectric effect of proteins in the surrounding plasma, especially asymmetric macromolecules like fibrinogen and gamma-globulin. (12 Dec 1998) |
| erythrocyte aggregation, intravascular | The massing or clumping of erythrocytes in intact blood vessels in response to injury or in certain diseases, interfering with adequate blood flow. It is also called sludging of blood and intravascular agglutination. (12 Dec 1998) |
| familial aggregation | <genetics> The occurrence of a trait in more members of a family than can be readily accounted for by chance; presumptive but not cogent evidence of the operation of genetic factors. (05 Mar 2000) |