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

Oxidative damage to DNA is shown to be extensive and could be a major cause of the physiological changes associated with aging and the degenerative diseases related to aging such as cancer. The oxidized nucleoside, 8-hydroxy-2'-deoxyguanosine (oh8dG), one of the approximately 20 known oxidative DNA damage products, has been measured in DNA isolated from various organs of Fischer 344 rats of different ages. oh8dG was present in the DNA isolated from all the organs studied: liver, brain, kidney, intestine, and testes. Steady-state levels of oh8dG ranged from 8 to 73 residues per 10(6) deoxyguanosine residues or 0.2-2.0 x 10(5) residues per cell. Levels of oh8dG in DNA increased with age in liver, kidney, and intestine but remained unchanged in brain and testes. The urinary excretion of oh8dG, which presumably reflects its repair from DNA by nuclease activity, decreased with age from 481 to 165 pmol per kg of body weight per day for urine obtained from 2-month- and 25-month-old rats, respectively. 8-Hydroxyguanine, the proposed repair product of a glycosylase activity, was also assayed in the urine. We estimate approximately 9 x 10(4) oxidative hits to DNA per cell per day in the rat. The results suggest that the age-dependent accumulation of oh8dG residues observed in DNA from liver, kidney, and intestine is principally due to the slow loss of DNA nuclease activity; however, an increase in the rate of oxidative DNA damage cannot be ruled out.

https://www.pnas.org/content/pnas/87/12/4533.full.pdf

Oxidative damage to DNA during aging: 8-hydroxy-2'-deoxyguanosine in rat organ DNA and urine.

https://www.cell.com/cell/pdf/S0092-8674(85)80056-8.pdf

Positive Control of a Regulon for Defenses against Oxidative Stress and Some Heat-Shock Proteins in Salmonella typhimurium

We described previously a simple test on petri plates for detecting chemical carcinogens as mutagens, using an especially sensitive set of bacterial strains to detect mutagenic acitivty and a mammalian liver extract for carcinogen activity. We now extend the utility of the method by introducing two new bacterial strains which can detect with great sensitivity many carcinogens which we did not detect before or detected with less sensitivity. Among these carcinogens are aflatoxin B-1, sterigmatocystin, benzyl chloride, benzo[a]-pyrene, 7,12-dimethylbenzanthracene, 1'-acetoxysafrole, and the nitrofuran food additive furylfuramide (AF-2). The new strains TA100 and TA98 contain an R factor plasmid, pKM101, in our standard tester strains TA1535 and TA1538. The R factor increases mutagenesis with certain mutagens, but not others. We present evidence that the mutagens that become more effective work through an error-prone recombinational repair.

https://www.pnas.org/content/pnas/72/3/979.full.pdf

Detection of carcinogens as mutagens: bacterial tester strains with R factor plasmids.

Oxidative Decay of DNA

The oxyR gene positively regulates genes induced by oxidative stress in Salmonella typhimurium and Escherichia coli. Purification of the OxyR protein showed that oxidized but not reduced OxyR activates transcription of oxidative stress-inducible genes in vitro. Conversion between the two forms of OxyR is rapid and reversible. Both the oxidized and the reduced forms of the OxyR protein are capable of binding to three diverse sequences upstream of OxyR-regulated promoters, but the interactions of the two forms of OxyR with the promoter regions are different. The results suggest that direct oxidation of the OxyR protein brings about a conformational change by which OxyR transduces an oxidative stress signal to RNA polymerase.

https://science.sciencemag.org/content/sci/248/4952/189.full.pdf

Bruce N. Ames

Papers

Oxidative damage to DNA during aging: 8-hydroxy-2'-deoxyguanosine in rat organ DNA and urine.

Positive Control of a Regulon for Defenses against Oxidative Stress and Some Heat-Shock Proteins in Salmonella typhimurium

Detection of carcinogens as mutagens: bacterial tester strains with R factor plasmids.

Oxidative Decay of DNA

Transcriptional regulator of oxidative stress-inducible genes: direct activation by oxidation