A modified suspension test for estimating the mutagenicity of samples containing free and (or) protein-bound histidine

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Abstract:

The Ames test has not been very effective in estimating the mutagenicity of histidine-containing samples because external free and (or) protein-bound histidine in these samples would allow the histidine auxotrophs in such test samples to grow more compared with the negative controls that were used as the reference. This could give rise to a false positive.n this study, a modified suspension mutagenicity assay (MS assay) was deveopled. The tester strains were incubated in Luria-Bertani (LB) broth containing different concentrations of traditional Chineses medicines (TCMs) until the declining phase, and the test samples were assayed to be mutagenic or not by observing whether statistically significant differences were demonstrated in the relative reversion frequencies (RRFs) between the negative control groups and the test groups. Collectively, using LB broth as the test medium and comparing the RRFs in the declining phase made this assay less influenced by the presence of histidine in the test samples.The mutagenicity of some TCMs was measured with the MS assay. The results in MS assay were consistent with those in the mammalian bone marrow chromosomal aberration test, which indicated that the MS assay was appropriate to estimate the mutagenicity of samples containing free and (or) protein-bound histidine.

Le test de Ames n’est pas très efficace pour estimer la mutagénicité d’échantillons contenant de l’histidine parce que l’histidine libre ou liée à des protéines peut permettre aux auxotrophes à l’histidine de ces échantillons de croître davantage comparativement aux contrôles négatifs utilisés comme références. Ceci peut générer des résultats faux positifs. Dans cette étude, un essai modifié de mutagénicité en suspension (essai MS) a été développé. Les souches à tester ont été incubées dans du milieu Luria-Bertani (LB) contenant différentes concentrations de médicaments traditionnels chinois (MTC) jusqu’à l’atteinte d’une phase de déclin, et la mutagénicité de ces échantillons a été examinée en déterminant si des différences significatives des fréquences de réversion relatives (FRR) pouvaient être observées entre les groupes contrôles et les groupes à tester. Globalement, en utilisant le milieu LB comme milieu test et en comparant les FRR lors de la phase de déclin, cet essai était moins influencé par la présence d’histidine dans les échantillons. La mutagénicité de quelques MTC a été mesurée à l’aide de cet essai MS. Les résultats de l’essai MS concordaient avec ceux de tests d’aberrations chromosomiques sur moelle osseuse de mammifères, ce qui indique que l’essai MS convient pour estimer la mutagénicité d’échantillons contenant de l’histidine libre ou liée à des protéines.

Document Type: Research Article

Publication date: February 1, 2009

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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