| clonal | Pertaining to a clone. (05 Mar 2000) |
|---|---|
| clonal aging | The deterioration in successive generations of a clone; thus paramecia and other simple forms, if allowed to reproduce asexually for a number of generations, invariably undergo deterioration, the characters of each group of descendants progressively departing from those of the original sexually produced ancestor. (05 Mar 2000) |
| clonal anergy | Functional inactivation of t- or B-lymphocytes rendering them incapable of eliciting an immune response to antigen. This occurs through different mechanisms in the two kinds of lymphocytes and can contribute to self tolerance. (12 Dec 1998) |
| clonal deletion | The removal of B-cell and T-cell varieties which recognise parts of the organisms body as targets of the immune system. This process naturally occurs early in the organisms development so that the organism will not be autoimmune (having an immune reaction against one's own body tissues) later in life. (09 Oct 1997) |
| clonal deletion theory | The elimination of certain T-cell populations in the thymus that have receptors for self-antigens. See: immunologic tolerance. (05 Mar 2000) |
| clonal expansion | Production of daughter cells all arising originally from a single cell. (05 Mar 2000) |
| clonal selection | <cell biology> The process whereby one or more clones, i.e. Cells expressing a particular gene sequence are selected by naturally occurring processes from a mixed population. Generally the clonal selection is for general expansion by mitosis, particularly with reference to B lymphocytes where selection with subsequent expansion of clones occurs as a result of antigenic stimulation only of those lymphocytes bearing the appropriate receptors. (18 Nov 1997) |
| clonal selection theory | A theory which states that each lymphocyte has membrane bound immunoglobulin receptors specific for a particular antigen and once the receptor is engaged, proliferation of the cell occurs such that a clone of antibody producing cells (plasma cell) is produced. (05 Mar 2000) |
| abortion | 1. <obstetrics> The premature expulsion from the uterus of the products of conception of the embryo or of a nonviable foetus. The four classic symptoms, usually present in each type of abortion, are uterine contractions, uterine haemorrhage, softening and dilatation of the cervix and presentation or expulsion of all or part of the products of conception. The expulsion or removal of an embryo or foetus from the mother prematurely, this can be done as an artificial procedure, but it often happens naturally when the mother's body expels the foetus because it has died, has genetic or developmental defects, or because of infection or illness in the mother. Natural abortions are typically called miscarriages. Medically-induced abortions, which can be completed with surgery or with hormone drugs, are performed because the foetus is unwanted, deformed, not likely to live, or endangers the mother's life or health. 2. The premature stoppage of a natural or a pathological process. Origin: L. Abortio (18 Nov 1997) |
| abortion applicants | Individuals requesting induced abortions. (12 Dec 1998) |
| abortion, criminal | Illegal termination of pregnancy. (12 Dec 1998) |
| abortion, eugenic | Abortion performed because of possible foetal defects. (12 Dec 1998) |
| abortion, habitual | The miscarriage of 3 or more consecutive pregnancies. Recurrent abortion can be identically defined as 3 or more miscarriages (spontaneous abortions) with no intervening pregnancies. Habitual or recurrent abortion is a form of infertility. (12 Dec 1998) |
| abortion, incomplete | Abortion in which not all the products of conception have been expelled. (12 Dec 1998) |
| abortion, induced | Intentional removal of a foetus from the uterus by any of a number of techniques. (popline, 1978) (12 Dec 1998) |