| rosette formation | The in vitro formation of clusters consisting of a cell (usually a lymphocyte) surrounded by antigenic cells or antigen-bearing particles (usually erythrocytes, which may or may not be coated with antibody or antibody and complement). The rosette-forming cell may be an antibody-forming cell, a memory cell, a T-cell, a cell bearing surface cytophilic antibodies, or a monocyte possessing fc receptors. Rosette formation can be used to identify specific populations of these cells. (12 Dec 1998) |
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| rosette | <dermatology> A group of organs or other body features, such as leaves or hair, which are clustered and crowned around a common point of attachment. (09 Oct 1997) |
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| rosette-forming cells | T lymphocytes with an affinity for sheep erythrocytes and which, when suspended in serum, bind the uncoated, nonsensitised erythrocytes in a rosette formation. (05 Mar 2000) |
| rosette test | A test for rosette-forming cells (T-lymphocytes) in which these cells and sheep erythrocytes, are incubated and centrifuged lightly, then examined under a microscope for rosette formation or adherence of erythrocytes to T lymphocytes. (05 Mar 2000) |
| chromosome rosette | Right before metaphase, human chromosomes briefly form this single ring structure. (09 Oct 1997) |
| chromosome rosette john jordan | Right before metaphase, human chromosomes briefly form this single ring structure. (09 Oct 1997) |
| EAC rosette | <haematology> Rosettes formed from erythrocytes (E) coated with antibody (A) and complement (C). A test for C3b or C3bi receptors (CR1 or CR3). The rosettes form more easily then E or EA rosettes. See: E rosettes. (16 Mar 2000) |
| EAC rosette assay | <haematology> Rosettes formed from erythrocytes (E) coated with antibody (A) and complement (C). A test for C3b or C3bi receptors (CR1 or CR3). The rosettes form more easily then E or EA rosettes. See: E rosettes. (16 Mar 2000) |
| EA rosette | A test for the presence of Fc receptors. (18 Nov 1997) |
| E rosette | The adherence of erythrocytes to cells. Sheep erythrocytes will adhere spontaneously to human T-cells, forming rosettes. (05 Mar 2000) |
| E-rosette test | A test to identify T lymphocytes by mixing purified blood lymphocytes with serum and sheep erythrocytes; rosettes of erythrocytes form around human T lymphocytes on incubation. (05 Mar 2000) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |
| reaction formation | In psychoanalysis, a postulated defense mechanism in which attitudes and behaviours that are adopted are the opposites of that which the individual would ordinarily be expected to express and actually feel at an unconscious level. (05 Mar 2000) |
| pattern formation | <cell biology> One of the classic problems in developmental biology is the way in which complex patterns are formed from an apparently uniform field of cells. Various hypotheses have been put forward and there is now evidence for the existence of gradients of diffusible substances (morphogens) specifying the differentiative pathway that should be followed according to the concentration of the morphogen around the cell. (18 Nov 1997) |
| reticular formation | <anatomy, neurology> A region extending from the pons & medulla oblongata through the mesencephalon, characterised by a diversity of neurons of various sizes and shapes, arranged in different aggregations and enmeshed in a complicated fibre network. (12 Dec 1998) |
| personality formation | The life history associated with the development of individual patterns and of one's individuality. (05 Mar 2000) |