| cytopathogenic effect, viral | Visible morphologic changes in cells infected with viruses. It includes shutdown of cellular RNA and protein synthesis, cell fusion, release of lysosomal enzymes, changes in cell membrane permeability, diffuse changes in intracellular structures, presence of viral inclusion bodies, and chromosomal aberrations. It excludes malignant transformation, which is cell transformation, viral. Viral cytopathogenic effects provide a valuable method for identifying and classifying the infecting viruses. (12 Dec 1998) |
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| healthy worker effect | Phenomenon of workers' usually exhibiting overall death rates lower than those of the general population due to the fact that the severely ill and disabled are ordinarily excluded from employment. (12 Dec 1998) |
| second gas effect | When a constant concentration of an anaesthetic like halothane is inspired, the increase in alveolar concentration is accelerated by concomitant administration of nitrous oxide, because alveolar uptake of the latter creates a potential subatmospheric intrapulmonary pressure that leads to increased tracheal inflow. (05 Mar 2000) |
| homotropic effect | An effect where two identical ligands (small molecules) allosterically interact with each other. (09 Oct 1997) |
| Purkinje effect | <ophthalmology> In the light-adapted eye, the region of maximal brightness is in the yellow; in the dark-adapted eye, the region of maximal brightness is in the green. Synonym: Purkinje effect, Purkinje shift. (05 Mar 2000) |
| hydrophobic effect | <chemistry> The tendency for the nonpolar portions of a group of lipid molecules to clump together with one another and exclude water and other polar molecules. The polar portions of the lipid molecules end up facing out. The hydrophobic effect is primarily responsible for the construction of lipid bilayers. (09 Oct 1997) |
| side effect | <pharmacology> A consequence other than the one for which an agent or measure is used, as the adverse effects produced by a drug, especially on a tissue or organ system other than the one sought to be benefited by its administration. For example: hair loss may be a side effect of chemotherapy, fatigue may be a side effect of radiation therapy. (14 Oct 1997) |
| hyperchromic effect | An increase in absorptivity (or extinction) at a particular wavelength of light by a solution or substance due to structural changes in a molecule. (05 Mar 2000) |
| sigma effect | The decrease in apparent viscosity that occurs when a suspension, such as blood, is made to flow through a tube of smaller diameter; observed in tubes less than about 0.3 mm in diameter. Synonym: sigma effect. (05 Mar 2000) |
| hypochromic effect | A phenomenon in which an individual molecule, containing several chromophores, has a certain absorptivity (or optical density) at a given wavelength that is less than the sum of the optical densities of the individual chromophores (at that same wavelength). (05 Mar 2000) |
| Somogyi effect | In diabetes, a rebound phenomenon of reactive hyperglycaemia in response to a preceding period of relative hypoglycaemia that has increased secretion of hyperglycaemic agents (epinephrine, norepinephrine, glucagon, cortisol, and growth hormone); described in diabetic patients given too much insulin who developed unrecognised nocturnal hypoglycaemia that made them hyperglycaemic (suggesting insufficient insulin) when tested the next morning. (05 Mar 2000) |
| stark effect | <radiobiology> The effect an electric field has on the spectral lines emitted from excited atoms. The effect may arise from externally-applied electric fields, from internal fields due to the presence of neighboring ions or atoms (pressure), or from the electric field associated with the Lorentz (v cross B) force (motional stark effect). Spectroscopic measurements of plasmas using the pressure-based and motional Stark effects are useful for diagnostic purposes. (09 Oct 1997) |
| Staub-Traugott effect | In normal persons, a drop in blood glucose which follows a second oral dose of glucose given 30 minutes or so after the first. (05 Mar 2000) |
| Stiles-Crawford effect | Light that enters through the centre of the pupil produces a greater visual effect than light that enters obliquely. (05 Mar 2000) |
| no-observed-adverse-effect level | The highest dosage administered that does not produce toxic effects. The noael will depend on how closely dosages are spaced (lowest-observed-adverse-effect level and no-observed-effect level) and the number of animals examined. The ultimate objective is usually to determine not the "safe" dosage in laboratory animals but the "safe" dosage for humans. Therefore, the extrapolation most often required of toxicologists is from high-dosage studies in laboratory animals to low doses in humans. (casarett and doull's toxicology: the basic science of poisons, 4th ed) (12 Dec 1998) |