Bacteria Ames test

Mutagenic potential—effects on genetic stability of bacteria (Ames test) of mammalian cells in culture... 

Mutagenic potential Test effects on genetic stability and mutations in bacteria (Ames test) or mammalian cells in culture dominant lethal test and clastogenicity in mice. 

Although most of the compounds produced hy Alternaria are generally nontoxic, altemariol monomethyl ether has been shown to be mutagenic in bacteria (Ames tests) [166]. Tenuazonic acid (TA) is a protein synthesis inhibitor and is capable of chelating metal ions and forming nitrosamines. TA is also produced... 

Gene Mutation Test in Bacteria (Ames Test)... 

The long latent periods involved in development of cancers make correlation of chemical exposures and disease extremely difficult. This can be countered pardy with tests on naturally short-Hved animals. Tests on bacteria, eg, the Ames test, may permit rapid detection of cancer potential, although there is no direct relationship between the results of bacterial tests and the effects of the tested chemicals on humans (56). 

The Ames test involves the reversion from a his— to his+ phenotype in any one of multiple bacterial strains (usually five strains are tested simultaneously). If the addition of test compound to a his— strain of bacteria allows them to grow on histidine deficient media, the obvious conclusion is compound-induced mutagenesis and a high potential hazard for the compound being carcinogenic. This test can also be conducted in the presence or absence of metabolic activation, in order to provide more information on potential risks (i.e., the parent compound may not be mutagenic, but the primary metabolite may present a safety risk). In practice, a positive Ames test almost always leads to discontinuing work on a compound of interest, and so these data are always collected prior to nomination of a compound for development. 

Ecoflex (powder) was tested for its mutagenic potential on the basis of its ability to induce point mutations in several bacterial strains Salmonella typhimurium and Escherichia coll) in a reverse mutation assay (Ames test), according to OECD guideline 471. Results revealed that the polyester is not mutagenic to bacteria. 

There are no general reliable methods to scale up from a mouse to a rat, and to a person nor is there a reliable method to scale down from a 70 kg male adult to an infant. A faster and less expensive toxicity test is the Ames test, performed on bacteria to test potentials for carcinogenesis, but the scale-up to humans is even more imprecise. 

Bruce Ames is the inventor of the Ames Test, which allows scientists to test chemicals to see whether they cause mutations in bacteria and perhaps cancer in humans. His research and testimony led to bans on such synthetic chemicals as Tris, the flame-retardant used in children s pajamas. 

In some areas, the use of in vitro systems has been successful. For example, the use of in vitro tests for the detection of genotoxicity is now well established. These tests include the well-known Ames test, which relies on detecting mutations in bacteria (such as Salmonella typhimurium). These are useful early screens for detecting potential genotoxicity. 

Figure 6.55 Log-log plot of relative carcinogenic potencies for a group of chemicals against mutagenic potency as determined by the Ames test. The potency is the amount of chemical giving tumors in 50% of the animals or 100 mutant colonies (revertants) of Salmonella bacteria. Aflatoxin B, is the most potent and benzidine the least potent. Abbreviations Moca, 4,4,-methylene-b/s-(2-chloroaniline) mms, methylmethane sulfonate. Source From Ref. 16.

The Ames test using Salmonella bacteria is the most commonly used test. 

Figure 1. Ames assay dose-response curves of the mutagenic effects of 25-, 50-, and 100-pL aliquots of nitrosated fru-trp reaction mixture and controls on S. typhimurium strains TA98 (top) and TA100 (bottom). Bacteria and test mixtures were preincubated with and without S-9 mix for 20 min at 37 °C. Background revertant levels were not subtracted from the data points shown.

Some dyes exhibit a mutagenic potential. The Ames test is commonly used as a first screening for the prediction of mutagenicity of a substance. It is a bacterial point mutation test inducing activity, which uses special strains of the bacteria Salmonella typhimurium with growth-dependence on the amino acid histidine. The dose-dependent reversion to histidine-independent growth is the marker for a point mutation. 

Ames test A method of an experiment performed using bacteria as a test system to determine the mutagenic potential of a substance or chemical. 

There was no evidence of genotoxicity in the standard genotoxicity test battery bacteria reverse mutation (Ames) tests, forward gene mutations in mammalian (Chinese hamster ovary AS42) cells, or mouse bone marrow MN test... 

The bacterial reverse mutation test (Ames Test) investigates the ability of chemicals and drags to induce reverse (back) mutations in bacteria, which involves base pair substitutions additions and/or deletions (frameshift mutations) of one or a few DNA base pairs. The bacterial strains used in the test system have mutations in genes coding for enzymes required for the biosynthesis of the amino acids histidine (Salmonella typhimurium) and tryptophan (Escherichia coli). If... 

THC does not appear to be carcinogenic, but there is plenty of evidence that the tar derived from cannabis smoke is. Bacteria exposed to cannabis tar develop mutations in the standard Ames test for carcinogenicity (53), and hamster lung cells in tissue culture develop accelerated malignant transformations within 3-6 months of exposure to tobacco or cannabis smoke (54). 

Amino acids Building blocks of protein by cells there are about 20 amino acids Ames test A method of an experiment performed using bacteria as a test system to determine the mutagenic potential of a substance or chemical Anaerobic Requiring the absence of oxygen Analyte Any chemical substance measured in the laboratory Analytic epidemiologic study A study that evaluates the association between exposure to hazardous chemical substances and disease by testing scientific hypotheses... 

In vitro tests in bacteria, for example the well-known Ames test, and tests in mammahan cells are used to show if a chemical is able to damage DNA and cause a mutation, fn the bacterial tests, extracts from mammalian liver (usually from a rat) have to be added to provide the enzymes that convert chemicals into products that might react with DNA. 

Studies of mutagenicity of RVX in the Ames test revealed no point mutations in the indicative bacteria. However, studies conducted by a micronuclear test have... 

---