| Rh null syndrome | <syndrome> A lack of all Rh antigens, compensated haemolytic anaemia, and stomatocytosis. (05 Mar 2000) |
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| null | 1. Something that has no force or meaning. 2. That which has no value; a cipher; zero. <physics> Null method, a zero method. See Zero. Source: Websters Dictionary (01 Mar 1998) |
| null cell | Lymphocytes lacking typical markers of T or B-cells capable of lysing a variety of tumour or virus infected cells without obvious antigenic stimulation, also effect antibody dependent cell cytotoxicity, carry in humans CD16 marker. (18 Nov 1997) |
| null-cell adenoma | <tumour> An adenoma of the hypophysis composed of cells for which there is no overt evidence or hormone production, but which usually produces hypopituitarism and visual disturbances by compression of adjacent structures; approximately one third of these tumours have cells with abundant mitochondria (oncocytes) that are somewhat larger than the monocytic null cells. Synonym: undifferentiated cell adenoma. (05 Mar 2000) |
| null cells | Large granular lymphocytes that lack surface markers/membrane associated proteins of either B or T lymphocytes. (05 Mar 2000) |
| null hypothesis | The assumption that any observed difference between two samples of a statistical population is purely accidental and not due to systematic causes. (05 Dec 1998) |
| null mutation | Change in a gene that leads to nothing, for example to no enzyme or to a nonfunctioning enzyme. (12 Dec 1998) |
| lymphocytes, null | A class of lymphocytes characterised by the lack of surface markers specific for either t or b lymphocytes. (12 Dec 1998) |
| alveolar point | The most anterior point on the maxillary alveolar process in the midline. Synonym: alveolar point, prostheon. Origin: G. Ntr. Of prosthios, foremost (05 Mar 2000) |
| anterior focal point | The point where parallel rays from the retina are focused. (05 Mar 2000) |
| apophysial point | The centre of the root of the anterior nasal spine. Synonym: apophysary point, apophysial point, spinal point. (05 Mar 2000) |
| arrow point tracing | A tracing of mandibular movements made by means of a device attached to the opposing arches; its shape resembles that of an arrowhead or a Gothic arch, and when the instrument's marking point is at the apex of the arch, the jaws are considered to be in centric relation. Synonym: arrow point tracing, Gothic arch tracing, Gothic arch, stylus tracing. (05 Mar 2000) |
| auricular point | A craniometric point at the centre of the opening of the external acoustic meatus; or, in certain cases, the middle of the upper edge of this opening. Synonym: auricular point. Origin: L. Auricularis, pertaining to the ear (05 Mar 2000) |
| axial point | One of two point's in a compound optical system so related that a ray directed toward the first point will appear to have passed through the second point parallel to its original direction. Synonym: axial point. (05 Mar 2000) |
| boiling point | This is the temperature at which the vapor pressure of a given liquid reaches atmospheric pressure (and thus starts to boil). (09 Oct 1997) |