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Claxton, Larry

Larry D Claxton
As seen through the previous reviews, each carbonaceous source of energy is associated with genotoxic and carcinogenic health risks; however, energy use is central to human society and provides many health benefits. These reviews examined the genotoxicity of carbonaceous sources of energy, focusing on the impacts due to the combustion of fuels and biomass. In previous reviews, information and data were used to examine occupational, industrial, household, and general environmental pollution as well as laboratory research...
January 2015: Mutation Research. Reviews in Mutation Research
Larry D Claxton
Much progress has been made in reducing the pollutants emitted from various combustors (including diesel engines and power plants) by the use of alternative fuels; however, much more progress is needed. Not only must researchers improve fuels and combustors, but also there is a need to improve the toxicology testing and analytical chemistry methods associated with these complex mixtures. Emissions from many alternative carbonaceous fuels are mutagenic and carcinogenic. Depending on their source and derivation, alternative carbonaceous fuels before combustion may or may not be genotoxic; however, in order to know their genotoxicity, appropriate chemical analysis and/or bioassay must be performed...
January 2015: Mutation Research. Reviews in Mutation Research
Larry D Claxton
Within this review the genotoxicity of diesel and gasoline fuels and emissions is placed in an historical context. New technologies have changed the composition of transportation methods considerably, reducing emissions of many of the components of health concern. The similarity of modern diesel and gasoline fuels and emissions to other carbonaceous fuels and emissions is striking. Recently an International Agency for Research on Cancer (IARC) Working Group concluded that there was sufficient evidence in humans for the carcinogenicity of diesel exhaust (Group 1)...
January 2015: Mutation Research. Reviews in Mutation Research
Larry D Claxton
The combustion of solid fuels (like wood, animal dung, and coal) usually involves elevated temperatures and altered pressures and genotoxicants (e.g., PAHs) are likely to form. These substances are carcinogenic in experimental animals, and epidemiological studies implicate these fuels (especially their emissions) as carcinogens in man. Globally, ∼50% of all households and ∼90% of all rural households use solid fuels for cooking or heating and these fuels often are burnt in simple stoves with very incomplete combustion...
October 2014: Mutation Research. Reviews in Mutation Research
Larry D Claxton
As research expands the types of energy sources for the future, there is a need to understand the health impacts of fuels and their emissions and to understand what health-research data gaps exist so that in the future proper and informative research and decision-making can be done. In that regard, this series of papers will explore what is known about the history, carcinogenicity, and genotoxicity of fuels and their emission products and attempt to identify major data gaps and areas of interest for future research...
October 2014: Mutation Research. Reviews in Mutation Research
Sarah H Warren, Larry D Claxton, Janet Diliberto, Thomas J Hughes, Adam Swank, Daniel H Kusnierz, Valerie Marshall, David M DeMarini
U.S. Environmental Protection Agency (US EPA) Regional Applied Research Effort (RARE) projects address the effects of environmental pollutants in a particular region on the health of the population in that region. This report is part of a RARE project that addresses this for the Penobscot Indian Nation (PIN), Penobscot Island, Maine, U.S., where the Penobscot River has had fish advisories for many years due to high levels of mercury. We used the Salmonella mutagenicity assay with strains TA100, TA98, YG1041, and YG1042 with and without metabolic activation to assess the mutagenic potencies of organic extracts of the Penobscot River water and sediment, as well as drinking-water samples, all collected by the PIN Department of Natural Resources...
February 2015: Chemosphere
Larry D Claxton, Gisela de A Umbuzeiro, David M DeMarini
OBJECTIVES: According to the 2007 National Research Council report Toxicology for the Twenty-First Century, modern methods (e.g., "omics," in vitro assays, high-throughput testing, computational methods) will lead to the emergence of a new approach to toxicology. The Salmonella mammalian microsome mutagenicity assay has been central to the field of genetic toxicology since the 1970s. Here we document the paradigm shifts engendered by the assay, the validation and applications of the assay, and how the assay is a model for future in vitro toxicology assays...
November 2010: Environmental Health Perspectives
Larry D Claxton, Rex Pegram, Kathleen M Schenck, Jane Ellen Simmons, Sarah H Warren
Although chemical disinfection of drinking water is a highly protective public health practice, the disinfection process is known to produce toxic contaminants. Epidemiological studies associate chlorinated drinking water with quantitatively increased risks of rectal, kidney, and bladder cancer. One study found a significant exposure-response association between water mutagenicity and relative risk for bladder and kidney cancer. A number of studies found that several types of disinfection processes increase the level of mutagens detected by the Salmonella assay...
2008: Journal of Toxicology and Environmental Health. Part A
Gisela A Umbuzeiro, Alexandre Franco, Maria Helena Martins, Fábio Kummrow, Lilian Carvalho, Heinz H Schmeiser, Jutta Leykauf, Marie Stiborova, Larry D Claxton
Urban particulate matter (UPM) contributes to lung cancer incidence. Here, we have studied the mutagenic activity and DNA adduct-forming ability of fractionated UPM extractable organic matter (EOM). UPM was collected with a high-volume sampler in June 2004 at two sites, one at street level adjacent to a roadway and the other inside a park within the urban area of the city of São Paulo, Brazil. UPM was extracted using dichloromethane, and the resulting EOM was separated by HPLC to obtain PAH, nitro-PAH, and oxy-PAH fractions which were tested for mutagenicity with the Salmonella strains TA98 and YG1041 with and without S9 metabolic activation...
March 29, 2008: Mutation Research
Larry D Claxton, George M Woodall
Although ambient air was first shown to be carcinogenic in 1947 and mutagenic in 1975, no overarching review of the subsequent literature has been produced. Recently, Claxton et al. [L.D. Claxton, P.P. Matthews, S.H. Warren, The genotoxicity of ambient outdoor air, a review: Salmonella mutagenicity, Mutat. Res./Rev. Mutat. Res. 567 (2004) 347-399] reviewed the literature on the mutagenicity of urban air in the Salmonella mutagenicity assay. Here, we review the literature on the mutagenicity of urban air in other test systems and review the carcinogenicity of urban air in experimental systems...
November 2007: Mutation Research
Danielle P Oliveira, Patrícia A Carneiro, Célia M Rech, Maria Valnice B Zanoni, Larry D Claxton, Gisela A Umbuzeiro
The water produced by the Cristais River Drinking Water Treatment Plant (CR-DWTP) repeatedly produced mutagenic responses that could not be explained by the presence of disinfection byproducts (DBPs) generated by the reaction of humic acids and chlorine. In order to determine the possible role of chlorinated dye products in this mutagenic activity, solutions of a black dye commercial product (BDCP) composed of C.I. Disperse Blue 373, C.I. Disperse Orange 37, C.I. Disperse Violet 93, and chemically reduced BDCP (R-BDCP) were chlorinated in a manner similar to that used by the CR-DWTP...
November 1, 2006: Environmental Science & Technology
Gisela de Aragão Umbuzeiro, Sarah H Warren, Larry D Claxton
Mutation spectra analysis can provide important information about the types of genotoxic compounds that can be present in environmental samples. In this study, we used the TA7000 base-specific Salmonella typhimurium tester strains to characterize water samples from two drinking water treatment plants (DWTPs) in São Paulo, Brazil. Because of the small sample sizes of these environmental samples, the use of the microsuspension protocol was necessary. Acidic extracts of drinking water samples from the two DWTPs gave similar responses in the TA7000 strains and caused primarily CG to AT transversions...
October 10, 2006: Mutation Research
Jin-Seok Bae, Harold S Freeman, Sarah H Warren, Larry D Claxton
As part of a continuing study aimed at establishing structure-activity relationships and heuristic principles useful for the design of non-genotoxic azo dyes, a series of new direct dyes based on two non-mutagenic benzidine analogs, 2,2'-dimethyl-5,5'-dipropoxybenzidine and 3,3'-dipropoxybenzidine, were evaluated for mutagenic activity in Salmonella typhimurium strains TA98 and TA100. These strains are widely used for mutagenicity screening and have been shown to detect the mutagenic activity of benzidine analogs...
February 28, 2006: Mutation Research
Kirby C Donnelly, Henry J Huebner, Larry D Claxton, James A Calvin, Gordon A Vos, Leslie Cizmas, Ling-Yu He
Exogenous microorganisms often are used to enhance bioremediation. This study compared the capabilities of two exogenous microbial cultures and an indigenous population to detoxify a Weswood silt loam soil amended with a simple chemical mixture. The first three treatments were unamended soils inoculated with either indigenous microorganisms, Pseudomonas aeruginosa, or Phanerochaete sordida. Three additional treatments consisted of soil amended with benzo[a]pyrene, pentachlorophenol, and 2,4,6-trinitrotoluene, which were inoculated with either indigenous microorganisms, P...
November 2005: Environmental Toxicology and Chemistry
King-Thom Chung, Ssu-Ching Chen, Larry D Claxton
We have reviewed the mutagenicity of benzidine analogues (including benzidine-based dyes), with a primary emphasis on evaluating results of the Salmonella/microsome mutagenicity assay. Many of these amines are mutagenic in tester strains TA98 and TA100 but require exogenous mammalian activation (S9) for activity. A few amines with halogen or nitro-groups in the structure are direct-acting mutagens. The addition of a sulfonic acid moiety to the molecule of benzidine reduced the mutagenicity of benzidine; whereas, methoxy, chloro, or methyl group additions did not...
January 2006: Mutation Research
Gisela de Aragão Umbuzeiro, Harold S Freeman, Sarah H Warren, Danielle Palma de Oliveira, Yoshiyasu Terao, Tetsushi Watanabe, Larry D Claxton
To verify whether dyes emitted within the discharge of a dye processing plant were contributing to the mutagenicity repeatedly found in the Cristais River, Sao Paulo, Brazil, we chemically characterized the following mutagenic samples: the treated industrial effluent, raw and treated water, and the sludge produced by a Drinking Water Treatment Plant (DWTP) located approximately 6 km from the industrial discharge. Considering that 20% of the dyes used for coloring activities might be lost to wastewaters and knowing that several dyes have mutagenic activity, we decided to analyze the samples for the presence of dyes...
June 2005: Chemosphere
Larry D Claxton
One challenge for most scientists is avoiding and resolving issues that center around authorship and the publishing of scientific manuscripts. While trying to place the research in proper context, impart new knowledge, follow proper guidelines, and publish in the most appropriate journal, the scientist often must deal with multi-collaborator issues like authorship allocation, trust and dependence, and resolution of publication conflicts. Most guidelines regarding publications, commentaries, and editorials have evolved from the ranks of editors in an effort to diminish the issues that faced them as editors...
January 2005: Mutation Research
Larry D Claxton
The examination of a single scientific manuscript seldom alerts scientists, reviewers, editors, and scientific administrators to the fabrication and falsification of data and information. This review shows that most documented cases of scientific fraud involve falsification (altering truthful information) and fabrication (inventing information where none previously existed). Plagiarism is much less frequent. The review of published accounts also shows that the publication of scientific papers containing recognizable fraudulent material is very low, probably less than 0...
January 2005: Mutation Research
Gisela de Aragão Umbuzeiro, Harold Freeman, Sarah H Warren, Fabio Kummrow, Larry D Claxton
Textile dyes can enter the water ecosystem through wastewater discharges potentially exposing humans through the consumption of water and food. The commercial disperse dye product CI Disperse Blue 291 containing the aminoazobenzene 2-[(2-bromo-4,6-dinitrophenyl)azo]-5-(diethylamino)-4-methoxyacetanilide (CAS registry no. 56548-64-2) was tested for mutagenic activity in the Salmonella assay. We used strains with different levels of nitroreductase and O-acetyltransferase (i.e., TA98DNP6, YG1024, and YG1041) that are relevant enzymes in the activation of nitrocompounds by the intestinal microflora...
January 2005: Food and Chemical Toxicology
Larry D Claxton, Peggy P Matthews, Sarah H Warren
Mutagens in urban air pollution come from anthropogenic sources (especially combustion sources) and are products of airborne chemical reactions. Bacterial mutation tests have been used for large, multi-site, and/or time series studies, for bioassay-directed fractionation studies, for identifying the presence of specific classes of mutagens, and for doing site- or source-comparisons for relative levels of airborne mutagens. Early research recognized that although carcinogenic PAHs were present in air samples they could not account for the majority of the mutagenic activity detected...
November 2004: Mutation Research
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