attenuation /at·ten·u·a·tion/ (ah-ten″u-a´shun) the act of thinning or weakening, as (a) the alteration of virulence of a pathogenic microorganism by passage through another host species, decreasing the virulence of the organism for the native host and increasing it for the new host, or (b) the process by which a beam of radiation is reduced in energy when passed through tissue or other material.
attenuation
attenuation,
attenuation (
ten´yōōā´shn),
attenuation
at·ten·u·a·tion ( -t n y -  shn)n. 1. A dilution, thinning, or weakening of a substance, especially a reduction in the virulence of a pathogen through repeated inoculation, growth in a different culture medium, or exposure to heat, light, air, or other weakening agents. 2. The energy loss of an ultrasonic beam as it passes through a material. |
attenuation
[əten′yo̅o̅·ā′shən]
Etymology: L, attenuare, to make thin
the process of reduction, such as the attenuation of an x-ray beam by reducing its intensity, the weakening of the degree of virulence of a disease organism, or culturing under unfavorable conditions. Attenuated bacteria are often used as vaccine agents.
attenuation,
n 1. reduction in concentration.
2. decrease in the ability of a pathogenic organism to cause disease.
2. decrease in the ability of a pathogenic organism to cause disease.
attenuation (
ten´yōōā´shn),n 1. to make thinner, weaker, or less virulent.
2. the process by which a beam of radiation is reduced in energy when passing through some material.
2. the process by which a beam of radiation is reduced in energy when passing through some material.
attenuation
1. the act of thinning or weakening.
2. reduction in the virulence of a pathogenic microorganism induced by passage through another host species, decreasing its virulence for the native host and increasing it for the new host. Some attenuated strains of microorganisms may occur naturally. The possibility now exists of using genetic engineering to attenuate microorganisms in defined ways. Attenuated organisms are used as live vaccines. See also attenuated vaccine.
3. the change in a beam of radiation or sound beam as it passes through matter. The intensity of the electromagnetic radiation decreases as its depth of penetration increases. A sound beam becomes weaker as it travels through tissue.
attenuation
1. A reduction of intensity of a radiation as it passes through an absorbing or scattering medium.
2. Narrowing of a blood vessel.
3. See penalization.
attenuation
A generic term for a reduction or diminution of activity, intensity, power, or virulence of a reaction, effect, or organisms ability to grow and/or multiply Microbiology ↓ virulence of a microorganism–eg, that of
bacillus Calmette-Guerin–BCG, a strain of Mycobacterium bovis that has been weakened by multiple–238–subcultures on a bile-glycerine medium; the resulting bacterium is immunogenic, ie capable of eliciting antibody formation,
but non-virulent; live attenuated organisms are used to produce the poliomyelitis vaccine but these may revert to a wild type Radiation biology A process by which a beam of radiation is ↓ in intensity when passing through material, due to
absorption and scattering processes, leading to a ↓ in flux density of the beam when projected through matter
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