Whch of the following are NOT suitable experimental approaches for studying whet
ID: 51142 • Letter: W
Question
Whch of the following are NOT suitable experimental approaches for studying whether a substance might pose a cancer risk in humans? (may be more than one correct answer)
a. dose response testing in animals
b. randomized trails in humans
c. the ames test
d. prospective studies in humans
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Why does alcohol use synergistically increase th risk of certain epithelial cancers when combined with tobacco use?
a. alcohol is a potent carcinogen that affects the same tissues as tobacco
b. alcohol causes epithelial cell death
c. alcohol increased blood flow to areas affected by tobacco
d. alcohol increases the number of carcinogens in tobacco
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Which of the following is true of the Ames test?
a. it utilizes yeast as a test organism to screen for mutagens
b. it tests whether a compound is mutagenic by whether the compound causes the test organism to be unable to grow on media lacking histidine
c. it utilizes a live extract to mimic normal biochemical mdifications that would occur in the liver
d. compounds that show high mutagenicity in the ames test tend to show low carcinogenicity
Explanation / Answer
Answer 1. Option (a) and Option (d)
(a)Dose response testing- This is the method use for hazard identification. This method is not suitable for identification of carcinogens. The controlled study of dose- response curve of a particular substance on animals shows three endpoints (Endpoint is defined as an effect observed in study of toxicity). Three endpoints are liver damage, developmental toxicity and mortality.
(b) Randomized trials in humans- Randomized trials or intervention studies are most preferable epidemiologic approach for identification of carcinogens.
(c) The Ames test- This test is a short term test which has been used most widely. This test was developed by a molecular biologist, Bruce Ames. This test is like a biological assay to find out the potential of substance to cause carcinogenic mutations.
(d) Prospective studies in humans- Long term prospective studies in humans identify the individuals having high risk of cancer development in response to exposure with carcinogens. It does not identify the cancer causing substance.
Answer 2. Option (a) alcohol is a potent carcinogen that affects the same tissues as tobacco.
Combined use of alcohol and tobacco synergistically increases the risk of oral cancer (both alcohol and tobacco affect same areas of oral cavity). The Alcohol causes dehydration and high permeability of mucosa. This condition makes the effect of alcohol and tobacco carcinogens more severe.
Answer 3. Option (b) it tests whether a compound is mutagenic by whether the compound causes the test organism to be unable to grow on media lacking histidine.
Ames test uses the strains of bacteria ( Salmonella typhimurium) having mutations in genes responsible for histidine production. These mutagenic bacterial strains require histidine for growth but cannot synthesize them thus they are unable to grow on media lacking histidine.
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