| cross-linking reagent | <chemistry> Reagents with two reactive groups, usually at opposite ends of the molecule, that are capable of reacting with and thereby forming bridges between side chains of amino acids in proteins; the locations of naturally reactive areas within proteins can thereby be identified; may also be used for other macromolecules, like glycoproteins, nucleic acids, or other. (12 Dec 1998) |
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| cross-matching | 1. A test for incompatibility between donor and recipient blood, carried out prior to transfusion to avoid potentially lethal haemolytic reactions between the donor's red blood cells and antibodies in the recipient's plasma, or the reverse; performed by mixing a sample of red blood cells of the donor with plasma of the recipient (major crossmatch) and the red blood cells of the recipient with the plasma of the donor (minor crossmatch). Incompatibility is indicated by clumping of red blood cells and contraindicates use of the donor's blood. 2. In allotransplantation of solid organs (e.g., kidney), a test for identification of antibody in the serum of potential allograft recipients which reacts directly with the lymphocytes or other cells of a potential allograft donor; presence of these antibodies usually, if not always, contraindicates the performance of the transplantation because virtually all such grafts will be subject to a hyperacute type of rejection. (05 Mar 2000) |
| cross-pollination | <botany> Fertilization of a plant from a plant with a different genetic makeup. (09 Oct 1997) |
| cross-reacting agglutinin | An immune agglutinin specific for a group antigen. Synonym: cross-reacting agglutinin. (05 Mar 2000) |
| cross-reacting antibody | <immunology> Antibody specific for group antigens, i.e., those with identical functional groups, antibody for antigens that have functional groups of closely similar, but not identical, chemical structure. (05 Mar 2000) |
| cross-reacting material | <haematology> A substance sufficiently different from a reference substance (R) to have a perceptibly different function from R but sufficiently similar to R that it reacts with anti-R antibodies; e.g., mutant factor VIII may be defective or even inert in coagulation and yet be immunologically identified as factor VIII. (05 Mar 2000) |
| cross reaction | <haematology, immunology> Serological reactions in which an antiserum against one antigen reacts with a non-identical but closely related antigen. (12 Dec 1998) |
| cross-reactive antibody | <haematology, immunology> Antibodies which don't respond to any one specific antigen, but will respond to a number of them. These antibodies can be responsible for false positive results in antigen-antibody tests. (09 Oct 1997) |
| cross-resistance | <immunology, microbiology> Immunologic resistance to the pathogenic effects of a microorganism because of previous exposure to another species or type having cross reactive antigens. This phenomenon is seen in microbes that acquire resistance to one drug through direct exposure and turn out to have resistance to one or more other drugs to which it has not been exposed. Cross-resistance arises because the mechanism of resistance to several drugs is the same and arises through the identical genetic mutations. (09 Oct 1997) |
| cross-section | <physics> Usually refers to the (apparent) area presented by a target particle to an oncoming particle (or electromagnetic wave). This measures the probability of an interaction occuring. For typical interactions between ions and electrons, or between two nuclei, these cross sections are generally measured in barns. <anatomy> A transverse cut through a structure or tissue. The opposite of a cross-section is a longitudinal section. By analogy, a study may be cross-sectional or longitudinal. (12 Dec 1998) |
| cross-sectional echocardiography | two-dimensional echocardiography |
| cross-sectional method | <epidemiology> The study of the life span involving comparison of groups of individuals at different age levels. Compare: longitudinal method. (05 Mar 2000) |
| cross-sectional study | <epidemiology> A study in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with longitudinal studies which are followed over a period of time. Synonym: horizontal study. (18 Jul 2002) |
| cross-table lateral projection | <radiology> Lateral projection radiography of a supine subject using a horizontal X-ray beam. (05 Mar 2000) |
| cross tolerance | <pharmacology> The resistance to one or several effects of a compound as a result of tolerance developed to a pharmacologically similar compound. (05 Mar 2000) |