Ames test

Ames test

The Ames test is a biological assay to assess the mutagenic potential of chemical compounds. A positive test indicates that the chemical might act as a carcinogen (although a number of false-positives and false-negatives are known). ["Ames Test." Encyclopedia of Public Health. Ed. Lester Breslow. Gale Cengage, 2002. eNotes.com. 2006. as of 29 Aug, 2008 ] As cancer is often linked to DNA damage, the test also serves as a quick assay to estimate the carcinogenic potential of a compound since it is difficult to ascertain whether standard carcinogen assays on rodents were successful. The procedure is described in a series of papers from the early 1970s by Bruce Ames and his group at the University of California, Berkeley.

General procedure

The test uses several strains of the bacterium "Salmonella typhimurium" that carry mutations in genes involved in histidine synthesis, so that they require histidine for growth. The variable being tested is the mutagen's ability to cause a reversion to growth on a histidine-free medium. The tester strains are specially constructed to have both frameshift and point mutations in the genes required to synthesize histidine, which allows for the detection of mutagens acting via different mechanisms. Some compounds are quite specific, causing reversions in just one or two strains. [cite journal | author= Bruce N. Ames, E. G. Gurney, James A. Miller, and H. Bartsch | title= Carcinogens as Frameshift Mutagens: Metabolites and Derivatives of 2-acetylaminofluorene and other Aromatic Amine Carcinogens | journal= PNAS | year= 1972 | volume= 69| pages= 3128–2132 | url = http://www.pnas.org/cgi/content/full/69/11/3128 | doi= 10.1073/pnas.69.11.3128 | pmid= 4564203] The tester strains also carry mutations in the genes responsible for lipopolysaccharide synthesis, making the cell wall of the bacteria more permeable, [cite journal | author= Bruce N. Ames, Frank D. Lee, and William E. Durston | title= An Improved Bacterial Test System for the Detection and Classification of Mutagens and Carcinogens | journal= PNAS | year= 1973 | volume= 70 | pages= 782–6 | url = http://www.pnas.org/cgi/content/full/70/3/782 | doi= 10.1073/pnas.70.3.782 | pmid= 4577135] and in the excision repair system to make the test more sensitive. [cite journal | author= Joyce McCann, Neil E. Spingarn, Joan Kobori, and Bruce N. Ames | title= Detection of Carcinogens as Mutagens: Bacterial Tester Strains with R Factor Plasmids | journal= PNAS | year= 1975 | volume= 72 | pages= 979–83 | url = http://www.pnas.org/cgi/content/full/72/3/979 | doi= 10.1073/pnas.72.3.979 | pmid= 165497] Rat liver extract is added to simulate the effect of metabolism, as some compounds, like benzopyrene, are not mutagenic themselves but their metabolic products are. [cite journal | author= Bruce N. Ames, William E. Durston, Edith Yamasaki, and Frank D. Lee | title= Carcinogens are Mutagens: A Simple Test System Combining Liver Homogenates for Activation and Bacteria for Detection | journal= PNAS | year= 1973 | volume= 70 | pages= 2281–5 | url = http://www.pnas.org/cgi/content/full/70/8/2281 | doi= 10.1073/pnas.70.8.2281 | pmid= 4151811]

The bacteria are spread on an agar plate with a small amount of histidine. This small amount of histidine in the growth medium allows the bacteria to grow for an initial time and have the opportunity to mutate.When the histidine is depleted only bacteria that have mutated to gain the ability to produce its own histidine will survive. The plate is incubated for 48 hours. The mutagenicity of a substance is proportional to the number of colonies observed.

Problems

As Salmonella is a prokaryote, it is not a perfect model for humans. An adapted "in vitro" model has been made for eukaryotic cells, for example yeast structure.

References


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Look at other dictionaries:

  • Ames-Test — [ eɪmz ; nach dem amer. Biochemiker B. N. Ames (*1928)]: zum Nachweis von Mutagenen, Carcinogenen u. Teratogenen entwickelter Test mit Hilfe von Defektmutanten. * * * Ames Test   [ eɪmz ], von dem amerikanischen Biochemiker Bruce Nathan Ames (*… …   Universal-Lexikon

  • Ames test — āmz n a test for identifying potential carcinogens by studying the frequency with which they cause histidine producing genetic mutants in bacterial colonies of the genus Salmonella (S. typhimurium) initially lacking the ability to synthesize… …   Medical dictionary

  • Ames test — Ames′ test [[t]eɪmz[/t]] n. med pha a test that exposes a strain of bacteria to a chemical compound in order to determine the potential of the compound for causing cancer • Etymology: 1975–80; after Bruce N. Ames (born 1928), U.S. biochemist, who …   From formal English to slang

  • Ames-Test — [e̱ims...; nach dem zeitgenössischen amer. Biochemiker B.Ames TestN. Ames]: Schnelltest zur Prüfung chemischer Substanzen auf Mutagenität mit Hilfe des Bakteriums Salmonella typhimurium …   Das Wörterbuch medizinischer Fachausdrücke

  • Ames Test — ☆ Ames Test [āmz ] n. [after B. Ames (1928 ), U.S. biochemist who developed it] a laboratory test for the carcinogenic potential of a substance, in which bacteria are exposed to the substance to determine whether it will cause mutations …   English World dictionary

  • Ames test — Ames test. См. тест Эймса. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Ames-Test — Der Ames Test ist ein Testverfahren, um (chemische) Mutagene zu identifizieren. Das Verfahren wurde von Bruce Ames (University of California, Berkeley, USA) entwickelt. Inhaltsverzeichnis 1 Das Prinzip 2 Anwendung 3 Literatur 4 …   Deutsch Wikipedia

  • Ames test — Test d Ames Pour les articles homonymes, voir Ames (homonymie). Le test d Ames est un test biologique permettant de déterminer le potentiel mutagène d un composé chimique. Les cancers étant souvent liés à des dommages causés dans l ADN, ce test… …   Wikipédia en Français

  • Ames test — a test that exposes a strain of bacteria to a chemical compound in order to determine the mutagenic potential of the compound. [1975 80; after U.S. biochemist Bruce N. Ames (born 1928), who developed the test] * * * …   Universalium

  • Ames test — noun Etymology: Bruce N. Ames b1928 American biochemist Date: 1976 a test for identifying potential carcinogens by studying their mutagenic effect on bacteria …   New Collegiate Dictionary


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