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Assessing Human Risk
Published in Gary S. Moore, Kathleen A. Bell, Living with the Earth, 2018
Gary S. Moore, Kathleen A. Bell
Cellular studies are used to test chemicals for mutagenicity and carcinogenicity. These tests can be done on bacteria or animal cells. A widely-known bacterial test is the Ames test, which uses Salmonella bacteria lacking the ability to produce histidine, a vital growth chemical. These bacteria are exposed to the chemical in question and assessed after two to three days for signs of growth. Indications of growth suggest a mutation has occurred in the bacteria’s genetic information, conferring the ability to produce histidine. Although relatively inexpensive and quick, cellular studies are not always accurate in identifying carcinogens. This problem relates to the difficulty in using single-celled organisms to predict human response to a substance. Other cellular studies include animal cellular studies, which are used to identify potential carcinogens. In these tests, the test chemical is applied to rodent or hamster cells. After a one-to-three-week period, these cells are assessed for changes in growth. Unlike the Ames test, this type of study is fairly accurate in predicting carcinogenesis.15
Nonclinical Studies
Published in John M. Centanni, Michael J. Roy, Biotechnology Operations, 2016
John M. Centanni, Michael J. Roy
Nonetheless, when properly applied to a nonclinical safety testing program, in vitro screening tests can provide valuable information that can be used to design more complex in vivo studies. Examples of in vitro tests are discussed here, and a longer list is provided in Box 8.2. Mutagenicity testing, exemplified by the Ames tests, screens compounds for mutagenic potential. The Ames test relies on Salmonella bacteria as a substrate and measures alteration in structure of a gene, after application of a test compound. Other eukaryotic or prokaryotic cells may be used in the same manner, as long as there is a reliable read-out for demonstrating mutagenicity. Carcinogenicity testing takes mutagenicity one step further by asking whether the mutagenic or genotoxic potential of a compound also results in the development of carcinogenic potential. Since not all mutagens are carcinogens and because not all carcinogens are mutagens, the mutagenicity and carcinogenicity tests can give distinct answers about product. Although screening tests can be helpful to making early decisions, they are not definitive, and carcinogenicity testing is considered in animals for compounds that might have carcinogenic potential.
Genetic toxicology
Published in Chris Winder, Neill Stacey, Occupational Toxicology, 2004
Substantial evidence indicates that one step in carcinogenesis is damage to or mutation of DNA. The first short-term test was the Ames test, introduced by Bruce Ames and colleagues in the early 1970s (Ames et al. 1973). The test relies on the fact that many carcinogens initiate cancer through damage to DNA (that is, a mutagenic event), and the Ames test sought to measure mutagenicity. The test relies on mutated strains of the bacteria Salmonella typhimurium to back-mutate to a form that will grow on special media. Over the last 30 years, the Ames test has become more sophisticated, with the number of strains being standardised, and with refinement of test conditions.
Pharmacokinetic and toxicological prediction of the chemical constituents of the essential oil of the leaves of Croton heliotropiifolius Kunth
Published in Journal of Toxicology and Environmental Health, Part A, 2023
Rosemarie Brandim Marques, Maria Das Dores Barreto Sousa, Wesley de Sousa Santos, Neirigelson Ferreira de Barros Leite, Esdras Morais Sobreiro Lima, Angélica Lima Soares, Charllyton Luís Sena da Costa, Francisco Artur e Silva Filho, Antônio Luiz Martins Maia Filho, Evandro Paulo Soares Martins, Ricardo Martins Ramos, Antonio de Macedo Filho
Of the 33 chemical constituents of CHO, only 3 did not induce mutagenicity utilizing the Ames test, which constitutes a simple method to test the mutagenicity of a compound (Ames et al. 1973). The Ames test employs several strains of the bacterium Salmonella typhimurium that carry mutations in genes involved in histidine synthesis, which are required for the bacterium to grow. The variable being tested is the ability of the mutations to initiate a reversal to growth in a histidine-free medium (Ames et al. 1973). However, the in vivo results obtained employing the MN test showed an absence of a concentration-dependent change in the number of MN. Our findings demonstrated marked alteration in frequency of MN occurrence indicating a low level of cytotoxicity attributed to CHO exposure. The MN test is a bioindicator of clastogenic or aneugenic effects, indicating genomic instability (Mughal et al. 2010; Iarmarcovai et al. 2008; Lindberg et al. 2007Thierens and Vral 2009). Micronuclei are formed from small fragments of acentric chromosomes that have not been incorporated into the nucleus or by whole chromosomes that have delayed anaphase during cell division, most likely by cellular exposure to mutagenic agents (Ceppi et al. 2010; Fenech 2000; Iarmarcovai et al. 2008; Bonassi et al. 2007; Thierens and Vral 2009; Valentin-Severin et al. 2003).
Pinus wallichiana-synthesized silver nanoparticles as biomedical agents: in-vitro and in-vivo approach
Published in Green Chemistry Letters and Reviews, 2020
Nazish Khan, Ibrar Khan, Akhtar Nadhman, Sadiq Azam, Inam Ullah, Farhan Ahmad, Hamid Ali Khan
Ames test is a bioassay for evaluating the DNA aggregating or mutating potential (carcinogenic) of nanoparticles and other compounds by utilizing various bacterial strains. Li et al. evaluated the AgNP genotoxicity using Salmonella strains and observed that the treatment with the AgNPs does not change mutation frequency (43). Kim et al. assessed the biocompatibility of AgNPs and the effect was concentration dependent in animal models (44). Heshmati et al. examined the mutagenicity and inhibitory effects of nanoparticles and reported that TA100, TA90, and YG1029S were mutated, whereas in other strains the mutation had reduced (45).
Evaluation of DNA and chromosomal damage in two human HaCaT and L02 cells treated with varying triclosan concentrations
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Donglei Sun, Tianhe Zhao, Xinyang Li, Zunzhen Zhang
Four Salmonella typhimurium strains TA97, TA98, TA100, and TA102 were used for the Ames test. Strains were generously provided by Analytical & Testing Center, Sichuan University (Chengdu, China). The immortalized human hepatocyte L02 cell line exhibits the main phenotypic characteristics of human mature hepatocytes and is commonly used to represent a normal liver cell model for testing the genotoxicity of chemicals (Dai et al. 2015; Hu et al. 2013). HaCaT cells are a spontaneously immortalized human keratinocyte line that has been widely used for studies of genotoxicity in human skin (Genc et al. 2018; Wilson 2014). Therefore, in this study, keratinocyte HaCaT cells and hepatic L02 cells were used as our models to examine the genotoxicity of triclosan. The human keratinocyte HaCaT cell line was purchased from KeyGen Bio-technology (Nanjing, China), and human hepatic cell line L02 was obtained from China Center for Type Culture Collection (Wuhan, China). Cells were routinely cultured in Dulbecco’s modified Eagle medium (DMEM, Gibco Life Technologies, Grand Island, NY, USA) supplemented with 10% (v/v) fetal bovine serum (FBS), penicillin (100 unit/ml), and streptomycin (100 μg/ml). Cultures were maintained at 37°C in a water-saturated atmosphere containing 5% CO2 and 95% air. Triclosan was purchased from Meilun Biological Technology Co. Ltd (Dalian, China; purity, ≥97%; lot number, O1004A). Triclosan was first dissolved with DMSO in 10 mM as the stock solution and was diluted with DMEM to achieve ≤ 20 μM in MTT assay and ≤ 10 μM in comet assay, MN assay, and ROS detection. Therefore, final concentrations of DMSO as a solvent were ≤0.2% (v/v) in MTT assay and ≤0.1% (v/v) in the comet and MN assay as well as ROS detection. These concentrations of DMSO were observed to exert no marked effects on cell viability (Li et al. 2018).