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501283 occurrences (No.27 in the rank) during 5 years in the PubMed. [no cache] 500 found

469) Studies have shown that these processes may reduce the bioavailable and biologically effective dose of test chemicals in in vitro assays to levels far below their nominal concentration.

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PMID:23978460 DOI:10.1016/j.tox.2013.08.012

2015 Toxicology

* Dose metric considerations in in vitro assays to improve quantitative in vitro-in vivo dose extrapolations.

- Challenges to improve toxicological risk assessment to meet the demands of the EU chemical's legislation, REACH, and the EU 7th Amendment of the Cosmetics Directive have accelerated the development of non-animal based methods. Unfortunately, uncertainties remain surrounding the power of alternative methods such as in vitro assays to predict in vivo dose-response relationships, which impedes their use in regulatory toxicology. One issue reviewed here, is the lack of a well-defined dose metric for use in concentration-effect relationships obtained from in vitro cell assays. Traditionally, the nominal concentration has been used to define in vitro concentration-effect relationships. However, chemicals may differentially and non-specifically bind to medium constituents, well plate plastic and cells. They may also evaporate, degrade or be metabolized over the exposure period at different rates. Studies have shown that these processes may reduce the bioavailable and biologically effective dose of test chemicals in in vitro assays to levels far below their nominal concentration. This subsequently hampers the interpretation of in vitro data to predict and compare the true toxic potency of test chemicals. Therefore, this review discusses a number of dose metrics and their dependency on in vitro assay setup. Recommendations are given on when to consider alternative dose metrics instead of nominal concentrations, in order to reduce effect concentration variability between in vitro assays and between in vitro and in vivo assays in toxicology.

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(1)236 of	(8)5 at	(15)3 using	(22)2 especially
(2)40 null	(9)4 are	(16)3 while	(23)2 induced
(3)38 in	(10)4 by	(17)2 after	(24)2 or
(4)35 were	(11)4 may	(18)2 between	(25)2 to
(5)34 and	(12)4 on	(19)2 compared
(6)6 was	(13)3 did	(20)2 decreased
(7)5 as	(14)3 for	(21)2 during

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--- WordNet output for levels --- Overview of noun level The noun level has 8 senses (first 6 from tagged texts) 1. (69) degree, grade, level -- (a position on a scale of intensity or amount or quality; "a moderate grade of intelligence"; "a high level of care is required"; "it is all a matter of degree") 2. (22) grade, level, tier -- (a relative position or degree of value in a graded group; "lumber of the highest grade") 3. (15) degree, level, stage, point -- (a specific identifiable position in a continuum or series or especially in a process; "a remarkable degree of frankness"; "at what stage are the social sciences?") 4. (5) level -- (height above ground; "the water reached ankle level"; "the pictures were at the same level") 5. (1) level, spirit level -- (indicator that establishes the horizontal when a bubble is centered in a tube of liquid) 6. (1) horizontal surface, level -- (a flat surface at right angles to a plumb line; "park the car on the level") 7. level, layer, stratum -- (an abstract place usually conceived as having depth; "a good actor communicates on several levels"; "a simile has at least two layers of meaning"; "the mind functions on many strata simultaneously") 8. floor, level, storey, story -- (a structure consisting of a room or set of rooms at a single position along a vertical scale; "what level is the office on?") Overview of verb level The verb level has 6 senses (first 3 from tagged texts) 1. (4) level -- (aim at; "level criticism or charges at somebody") 2. (1) level, raze, rase, dismantle, tear down, take down, pull down -- (tear down so as to make flat with the ground; "The building was levelled") 3. (1) flush, level, even out, even -- (make level or straight; "level the ground") 4. charge, level, point -- (direct into a position for use; "point a gun"; "He charged his weapon at me") 5. level -- (talk frankly with; lay it on the line; "I have to level with you") 6. level, level off -- (become level or even; "The ground levelled off") --- WordNet end ---