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A method for the quantitation of the effects on a biological system by its exposure to a substance, as well as the quantitation of the concentration of a substance by some observable effect on a biological system. The biological material in which the effect is measured can range from subcellular components and microorganisms to groups of animals. The substance can be stimulatory, such as an ion increasing taxis behavior in certain protozoans, or inhibitory, such as an antibiotic for bacterial growth. Bioassays are most frequently used when there is a number of steps, usually poorly understood, between the substance and the behavior observed, or when the substance is a complex mixture of materials and it is not clear what the active components are. Bioassays can be replaced, in time, by either a more direct measure of concentration of the active principle, such as an analytical method (for example, mass spectrometry, high-pressure liquid chromatography, radioimmunoassay), or a more direct measurement of the effect, such as binding to a surface receptor in the case of many drugs, as the substance or its mechanism of action is better characterized.

Assays to quantitate the effects of an exposure model the effect of a substance in the real world. Complex biological responses can be estimated by laboratory culture tests, which use, for example, bacteria or cells cultured in a petri dish (usually to model an effect either on the organism of interest, such as bacteria, or on some basic cellular function); by tissue or organ culture, which isolates pieces of tissue or whole organs in a petri dish (usually to model organ function); or in whole animals (usually to model complex organismic relationships).

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.


(analytical chemistry)
A method for quantitatively determining the concentration of a substance by its effect on the growth of a suitable animal, plant, or microorganism under controlled conditions.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The assay answers the question of bioavailability at the cellular level, and was specifically developed to assist the transition of analytical chemistry testing of natural products into biological assays in vitro and in vivo.
Such interaction could not be discovered by the assays available at the start of the studies but development of new biological assays has revealed a stability issue related to certain containers.
Life science applications are supported with a wide array of preprogrammed biological assays to analyse protein and nucleic acid samples and perform cell growth measurements.
Microfluidic Systems was founded in 2001 and is focused on the development of microfluidic systems for automated preparation of biological assays. MFSI personnel have been involved with the development of automated DNA-based pathogen detection systems and microfluidics for the United States Government and commercial markets for over 12 years, including the world's first miniaturized, portable, battery-operated, real-time, PCR-based detection system.
"We screened the varieties again with the biological assays. And that had never been done before, because it is expensive and a lot of work.
More effective, biological assays are used for simulating what happens in vivo without the use of animal models.
The ISB researchers have applied microfluidics--the study of how fluids behave at the nano level--to successfully conduct biological assays on single cells.
The HTS systems will combine ACLARA's microfluidic chip technology with PE Biosystems' experience in separations, biological assays, high-throughput screening, capillary electrophoresis, and fluorescent detection technologies.
Although biological assays have been the cornerstone of endocrinologic measurements, the development of the radioimmunoassay (RIA) completely changed the field of endocrinology (1).
Bruce Evans and Martin Reaney carried out the biological assays in Larry Gusta's laboratory at the University of Saskatchewan.
Both parties will concentrate on screening ChromaDex's natural product libraries against certain biological assays and tumour models with the intent of identifying high value, potentially patentable natural products for specific therapeutic indications.

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