effect (e-fekt´)

The result or consequence of an action. [L. ef-ficio, pp. effectus, to accomplish, fr. facio, to do]
abscopal e. a reaction produced following irradiation but occurring outside the zone of actual radiation absorption.
additive e. an e. wherein two or more substances or actions used in combination produce a total e. the same as the arithmetic sum of the individual e.'s.
after-e. See aftereffect.
Anrep e. a small transient positive inotropic e. of abrupt increases of systolic aortic and left ventricular pressures related to recovery from transient subendocardial ischemia (e.g., cold pressor test).
Arias-Stella e. Arias-Stella phenomenon
autokinetic e. in psychology, the apparent drifting about of a small, fixed, spot of light which is being observed in a dark room.
Bernoulli e. the decrease in fluid pressure that occurs in converting potential to kinetic energy when motion of the fluid is accelerated, in accordance with Bernoulli's law; applied in water aspirators, atomizers, and humidifiers in which a gas is accelerated across the end of a narrow, fluid-filled orifice.
Bohr e. the influence exerted by carbon dioxide on the oxygen dissociation curve of blood, i.e., the curve is shifted to the right, which means a reduction in the affinity of hemoglobin for oxygen. Cf. Haldane e.
Bowditch e. homeometric autoregulation of cardiac function induced by changing heart rate.
Circe e. an e. observed in enzyme catalysis in which accelerated diffusion of the substrate occurs through attractive forces of the enzyme's active site.
clasp-knife e. clasp-knife spasticity
Compton e. in electromagnetic radiations of medium energy, a decrease in energy of the bombarding photon with the dislodgement of an orbital electron, usually from an outer shell.Compton scattering;
Cotton e. the positive and negative displacement from zero of the rotation of plane polarized monochromatic light and the change of monochromatic circularly polarized light into elliptically polarized light in the immediate vicinity of the absorption band of the substance through which the light passes. See also optical rotatory dispersion, circular dichroism.
Crabtree e. inhibition of cellular respiration of isolated systems by high concentrations of glucose; a "reciprocal" of Pasteur's e.; due, in part, to the inhibition of hexokinase by elevated glucose 6-phosphate. Cf. Pasteur's e.
cumulative e. the condition in which repeated administration of a drug may produce e.'s that are more pronounced than those produced by the first dose.cumulative action;
Cushing e. Cushing phenomenon
cytopathic e. degenerative changes in cells (especially in tissue culture) associated with the multiplication of certain viruses; when, in tissue culture, spread of virus is restricted by an overlay of agar (or other suitable substance) the cytopathic e. may lead to formation of plaque.
Doppler e. a change in frequency observed when the sound and observer are in relative motion away from or toward each other. See also Doppler shift.Doppler phenomenon;
electrophonic e. the sensation of hearing produced when an alternating current of suitable frequency and magnitude is passed from an external source through a person.
experimenter e.'s the influence of the experimenter's behavior, personality traits, or expectancies on the results of that person's own research. See double blind study.
Fahraeus-Lindqvist e. 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.sigma e;
Fenn e. the increased liberation of heat in a stimulated muscle when it is allowed to do mechanical work; the amount of heat liberated is increased in proportion to the distance the muscle is allowed to shorten and in proportion to the tension it must develop (e.g., the weight it lifts) during shortening; thus increased chemical energy is consumed both to liberate increased heat and to do increased mechanical work.
founder e. an unusually high frequency of a gene in a particular population derived from a small set of unrepresentative ancestors.
gene dosage e. in codominant alleles, the more or less linear relationship between the phenotypic value and the number of genes of one type substituted by another type.
generation e. variation in health status arising from the different causal factors of disease to which each successive generation born is exposed as it passes through life.
Haldane e. the promotion of carbon dioxide dissociation by oxygenation of hemoglobin.
halo e. 1. the e. (usually beneficial) that the manner, attention, and caring of a provider have on a patient during a medical encounter, regardless of what medical procedure or services the encounter involves; 2. the influence upon an observation of the observer's perception of the characteristics of the individual observed (other than the characteristics under study) or the influence of the observer's recollection or knowledge of findings on a previous occasion.
Hawthorne e. the e. (usually positive or beneficial) of being under study, upon the persons being studied; their knowledge of the study often influences their behavior. [city in Illinois; site of the Western Electric plant]
healthy worker e. phenomenon observed initially in studies of occupational diseases; workers usually exhibit lower overall death rates than the general population because severely ill and disabled people are excluded from employment.
hyperchromic e. an increase in absorptivity (or extinction) at a particular wavelength of light by a solution or substance due to structural changes in a molecule.
hypochromic e. 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).
Mach e. the appearance of a light or dark line on a radiograph where there is a concave or convex interface in the subject, a physiological optical form of edge enhancement. See also Mach's band.
e. modifier a factor that modifies the e. of a putative causal factor under study; e.g., age is an e. modifier for many conditions.
nuclear Overhauser e. (NOE) an e. seen in nuclear magnetic resonance in which there is a through-space nearest neighbor interaction.
Orbeli e. the fatigue of a muscle stimulated by its nerve (i.e., indirectly) is reduced by concurrent stimulation of sympathetic fibers to the muscle; thought to be caused by norepinephrine diffusing from adrenergic fibers which innervate blood vessels in the muscle.
oxygen e. enhancement of radiosensitivity of cells in a high concentration of oxygen.
Pasteur's e. the inhibition of fermentation by oxygen, first observed by Pasteur; either not observed, or only slightly observed, in malignant tumors. Cf. Crabtree e.
photechic e. the ability of an agent, other than light, to make a developable latent image in a photographic film emulsion.Russell e;
photoelectric e. the loss of electrons from the surface of a metal upon exposure to light; a mode of interaction of radiation with matter in which all of the energy of the incident photon is absorbed, with ejection of a photoelectron and characteristic radiation from filling the vacancy from another shell; since the energy absorption per gram of tissue is proportional to the cube of the atomic number, this mode is important in diagnostic radiography.
piezoelectric e. the property of certain crystalline or ceramic materials to emit electricity when deformed and to deform when an electric current is passed across them, a mechanism of interconverting electrical and acoustic energy; an ultrasound transducer sends and receives acoustic energy using this e.
position e. a change in the phenotypic expression of one or more genes due to a change in its physical location with respect to other genes; may result from change in chromosome structure or from crossing-over.
Purkinje e. Purkinje's phenomenon
Raman e. a change in frequency undergone by monochromatic light scattered in passage through a transparent substance whose characteristics determine the amount of change, yielding a spectrum in which the incident wavelength band is flanked by small satellite bands of greater and lesser wavelengths.
Rivero-Carvallo e. inspiratory increase in the systolic murmur of tricuspid insufficiency; the characteristic distinguishing tricuspid insufficiency from mitral insufficiency.
Russell e. photechic e
second gas e. when a constant concentration of an anesthetic 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.
sigma e. Fahraeus-Lindqvist e
Somogyi e. in diabetes, a rebound phenomenon of reactive hyperglycemia in response to a preceding period of relative hypoglycemia that has increased secretion of hyperglycemic agents (epinephrine, norepinephrine, glucagon, cortisol, and growth hormone); described in diabetic patients given too much insulin who developed unrecognized nocturnal hypoglycemia that made them hyperglycemic (suggesting insufficient insulin) when tested the next morning.
Staub-Traugott e. in normal persons, a drop in blood glucose which follows a second oral dose of glucose given 30 minutes or so after the first.
Stiles-Crawford e. light that enters through the center of the pupil produces a greater visual effect than light that enters obliquely.
synergistic e. synergism
Tyndall e. Tyndall phenomenon
Venturi e. term applied to the operation of a Venturi tube and similar systems.
Wedensky e. a relatively long enhancing e. following application of a maximal shock or stimulus to a neuromuscular preparation during which a subthreshold stimulation, otherwise too small to evoke a response, will produce a response; a relatively prolonged lowered threshold of excitability following a maximal shock.
Wolff-Chaikoff e. Wolff-Chaikoff block
Zeeman e. the splitting of spectral lines into three or more symmetrically placed lines when the light source is subjected to a magnetic field.


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