| direct filling resin | An autopolymerizing resin especially designed as a dental restorative material. (05 Mar 2000) |
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| direct fluorescent antibody | The straightforward detection of antigens using fluorescent labelled antigen-specific antibody. Because detection of the antigen in a substrate of patient sample (cellular smear, fluid or patient-inoculated culture medium) is the goal, direct fluorescent antibody is seldom quantitative. (05 Mar 2000) |
| direct fluorescent antibody test | Test for tissue antigen using either a direct method, by conjugation of antibody with fluorescent dye (fluorescent antibody technique, direct) or an indirect method, by formation of antigen-antibody complex which is then labelled with fluorescein-conjugated anti-immunoglobulin antibody (fluorescent antibody technique, indirect). The tissue is then examined by fluorescence microscopy. (12 Dec 1998) |
| direct fracture | A fracture, especially of the skull, occurring at the point of injury. (05 Mar 2000) |
| direct illumination | An illumination in which the rays of light are directed downward, almost perpendicularly onto the upper surface of the object, which reflects the rays upward into the optical system. Synonym: erect illumination, vertical illumination. (05 Mar 2000) |
| direct image | <microscopy> Such as seen in a mirror or through a magnifier. A virtual image has no real existence in space as does a real image from a lens. It does have a definite location, however, caused by the angles of divergence of the rays received by the eye. This can be shown by the common school experiment of placing a pin coincident with its mirror image behind a sheet of glass acting as a partial mirror. Its location can also be placed in design by extrapolating backwards to a focus. If a magnifier is used as it should be, with the object at its focus, the virtual image is at infinity. The same is true for a microscope focused for the relaxed eye. See: distance of virtual image. (05 Aug 1998) |
| direct inguinal hernia | See: inguinal hernia. (05 Mar 2000) |
| direct lead | In electrocardiography, a unipolar lead recorded with the exploring electrode placed directly on the surface of the exposed heart. (05 Mar 2000) |
| direct life cycle | <epidemiology> A life cycle in which a parasite is transmitted directly from one host to the next without an intermediate host or vector of another species. (05 Dec 1998) |
| direct lytic factor of cobra venom | A polypeptide of 62 residues; action on cells is similar to that of melittin in that it promotes disruption of membranes; used as an investigational antirheumatic agent. Synonym: cobra toxin, direct lytic factor of cobra venom. (05 Mar 2000) |
| direct lytic factors | most abundant proteins in cobra (naja of the elapids) venom; basic polypeptides of 57 to 62 amino acids with four disulfide bonds and a molecular weight of less than 7000; causes skeletal and cardiac muscle contracture, interferes with neuromuscular and ganglionic transmission, depolarises nerve, muscle and blood cell membranes, thus causing haemolysis. Synonym: cobramine a; cobramine b; cobra cytotoxin; gamma toxin; membrane-active polypeptide. (12 Dec 1998) |
| direct maternal death | Death resulting from obstetric complications of the gestation, labour, or puerperium, and from interventions, omissions, incorrect treatment, or a chain of events caused by any of the above, indirect maternal death, an obstetric death resulting from previously existing disease or from disease developing during pregnancy, labour, or the puerperium; it is not directly due to obstetric causes, but to conditions aggravated by the physiological effects of pregnancy. (05 Mar 2000) |
| direct method for making inlays | In dentistry, an inlay technique in which the wax pattern is made directly in the prepared cavity in the tooth. Synonym: direct technique. (05 Mar 2000) |
| direct nuclear division | <cell biology> An unusual form of nuclear division, in which the nucleus simply constricts, rather like a cell without chromosome condensation or spindle formation. Partitioning of daughter chromosomes is haphazard. Observed in some Protozoa. (18 Nov 1997) |
| direct ophthalmoscope | <instrument> An instrument designed to visualise the interior of the eye, with the instrument relatively close to the subject's eye and the observer viewing an upright magnified image. (05 Mar 2000) |