Guide for the Care and Use of Laboratory Animals

https://zenodo.org/record/1253874/files/article.pdf

A simple technique for quantitation of low levels of DNA damage in individual cells

At high concentrations, free radicals and radical-derived, nonradical reactive species are hazardous for living organisms and damage all major cellular constituents. At moderate concentrations, how...

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Free Radicals in the Physiological Control of Cell Function

Living in an oxygenated environment has required the evolution of effective cellular strategies to detect and detoxify metabolites of molecular oxygen known as reactive oxygen species. Here we review evidence that the appropriate and inappropriate production of oxidants, together with the ability of organisms to respond to oxidative stress, is intricately connected to ageing and life span.

Oxidants, oxidative stress and the biology of ageing.

Mutations in the evolutionarily conserved codons of the p53 tumor suppressor gene are common in diverse types of human cancer. The p53 mutational spectrum differs among cancers of the colon, lung, esophagus, breast, liver, brain, reticuloendothelial tissues, and hemopoietic tissues. Analysis of these mutations can provide clues to the etiology of these diverse tumors and to the function of specific regions of p53. Transitions predominate in colon, brain, and lymphoid malignancies, whereas G:C to T:A transversions are the most frequent substitutions observed in cancers of the lung and liver. Mutations at A:T base pairs are seen more frequently in esophageal carcinomas than in other solid tumors. Most transitions in colorectal carcinomas, brain tumors, leukemias, and lymphomas are at CpG dinucleotide mutational hot spots. G to T transversions in lung, breast, and esophageal carcinomas are dispersed among numerous codons. In liver tumors in persons from geographic areas in which both aflatoxin B1 and hepatitis B virus are cancer risk factors, most mutations are at one nucleotide pair of codon 249. These differences may reflect the etiological contributions of both exogenous and endogenous factors to human carcinogenesis.

https://zenodo.org/record/1230948/files/article.pdf

p53 mutations in human cancers

The Histidine Operon

The scientific understanding of cancer and degenerative disease is being aided by new methodologies which are now used to approach the problem of environmental and occupational carcinogens and anticarcinogens. This paper reviews these powerful new tools and relates them to "natural" mutagens and carcinogens in food. It also discusses the use of oxygen radicals as a cause of degenerative disease associated with aging. Since no human diet can be totally free of carcinogens or mutagens, it is necessary to consider the risks of alternative courses of actions and to quantitate the magnitude of the risks through the "quantification" of these risks. Since carcinogens and anticarcinogens differ in their potency in animals over one million fold, the extrapolation of risks from rodents to humans is difficult but it is a first step. Despite better understanding of all of these risks, it is important to realize that the overall trend in life expectancy in the United States is continuing steadily to improve.

Dietary carcinogens and anti-carcinogens.

A transgenic mouse strain that expresses the hepatitis B virus (HBV) large envelope protein in the liver was used to determine the extent of oxidative DNA damage that occurs during chronic HBV infection. This mouse strain develops a chronic necroinflammatory liver disease that mimics the inflammation, cellular hyperplasia, and increased risk for cancer that is evident in human chronic active hepatitis. When perfused in situ with nitroblue tetrazolium, an indicator for superoxide formation, the liver of transgenic mice displayed intense formazan deposition in Kupffer cells, indicating oxygen radical production, and S-phase hepatocytes were commonly seen adjacent to the stained Kupffer cells. Similar changes were not observed in nontransgenic control livers. To determine whether these events were associated with oxidative DNA damage, genomic DNA from the livers of transgenic mice and nontransgenic controls was isolated and examined for 8-oxo-2'-deoxyguanosine, an oxidatively modified adduct of deoxyguanosine. Results showed a significant, sustained accumulation in steady-state 8-oxo-2'-deoxyguanosine that started early in life exclusively in the transgenic mice and increased progressively with advancing disease. The most pronounced increase occurred in livers exhibiting microscopic nodular hyperplasia, adenomas, and hepatocellular carcinoma. Thus, HBV transgenic mice with chronic active hepatitis display greatly increased hepatic oxidative DNA damage. Moreover, the DNA damage occurs in the presence of heightened hepatocellular proliferation, increasing the probability of fixation of the attendant genetic and chromosomal abnormalities and the development of hepatocellular carcinoma.

https://www.pnas.org/content/pnas/91/26/12808.full.pdf

Extensive oxidative DNA damage in hepatocytes of transgenic mice with chronic active hepatitis destined to develop hepatocellular carcinoma

AppppA and related adenylylated nucleotides are synthesized as a consequence of oxidation stress

A method has been devised for the rapid identification of nonsense mutations (UAG, UAA, UGA codons) in Salmonella. The mutations to be tested are reverted, and the revertants are replica-printed onto lactose plates spread with lawns of tester strains. These tester strains contain F' lac episomes with nonsense mutations in the episomal Z gene. The revertants are infected with the episome from the tester strain lawn. Because S. typhimurium is unable to ferment lactose, only those revertants which have nonsense suppressors are able to grow on lactose. If colonies appear on the lactose plate, it may be concluded that the original strain carries a nonsense mutation, since nonsense suppressors suppress the mutant phenotype.

Bruce N. Ames

Papers

The Histidine Operon

Dietary carcinogens and anti-carcinogens.

Extensive oxidative DNA damage in hepatocytes of transgenic mice with chronic active hepatitis destined to develop hepatocellular carcinoma

AppppA and related adenylylated nucleotides are synthesized as a consequence of oxidation stress

Procedure for identifying nonsense mutations