Alternatives to animal testing
Scientists are trying to reduce the use of mammalian species that have traditionally served for toxicity testing, especially monkeys, dogs, cats, and rabbits. In the second part of a three-part series on animal testing, Sklarew (p. 288) describes some of the lower vertebrate and invertebrate animal species that are substitutes for testing, the use of cell and tissue cultures and single-cell microorganisms in testing, and at-tempts to use mathematical modeling as a surrogate for biological testing. The advantages and limitations of each test system are presented. The dilemma is that, currently, physiological responses can only be measured in whole animals; no other adequate substitutes exist. Next month the final part of the series will address the use of animal data in risk assessment.
Investigating the connection between electricity and cancer
Some of us can remember paying a penny to hold an iron ball with one hand while turning a dial with the other, just to prove we could stand more electric shock than our buddies. Now fears about electromagnetic fields are aroused by everything from overhead power lines to electric blankets and include diverse sources such as micro-wave ovens, cellular phones, computer screens, radar guns, and clock radios. In the second of this issue's Focus articles (p. 292), Pinholster discusses the current debate on EMF: scientists cannot agree about the potential cancer risks incurred from EMF exposure.
The world of transgenic mice
Transgenic mice have changed the face of biomedical research. Eddy (p. 298) reviews the history of transgenic mouse models, methods of creating transgenic mice, and their use in environmental health research. Continuing improvements in technology are allowing researchers to introduce subtle changes in genes. The combination of improved technology and the identification of genes paves the way for significant advancements in understanding interactions between genes and environmental agents.
Nondestructive tissue analyses using PIXE
Lowe et al. (p. 302) exposed slices of cultured rabbit kidney tissue to mercury, cadmium, chromium, or arsenic, alone or in a mixture. Analysis of about 5 mg of tissue using proton-induced X-ray emission (PIXE) yielded concentrations of these and 20-30 other elements with detection limits of 1-5 ppm dry weight. PIXE is unique in its ability to measure uptake of multiple metals and other elements without damaging tissue.
Benzene metabolism in mice
The toxicity of benzene is generally be-lieved to be mediated by metabolites formed in the liver. Kline et al. (p. 310) showed that benzene metabolism in CD-1 mice proceeds through
trans,trans
-mucon-aldehyde to
trans,trans
-muconic acid, which is eliminated in the urine, along with a newly identified ring-opened compound. This new compound was confirmed by HPLC and diode-array spectral analysis to be 6-hydroxy-
trans,trans
-2,4-hexadienoic acid. The identification of this metabolite may have important implications for biological markers of benzene exposure.
Passive smoke and coal heating in China
About 1000 young, nonsmoking Chinese women working in textile mills were surveyed for five respiratory symptoms. Pope and Xu (p. 314) report that the incidence of all of the symptoms except one were significantly elevated in women living in homes with smokers and coal heating. The response to passive smoke and coal fumes was additive, suggesting a dose- response relationship between indoor air pollution and respiratory distress.
Ozone exposure at home and at play
The traditional method of using static measurements for ozone may not be ap-propriate. Spatial variation was shown to occur between urban and rural areas and inside and outside homes, probably as a consequence of population density, furnishings, traffic patterns, and other variables. Liu et al. (p. 318) used passive ozone samplers in a preliminary study to collect time-activity data for 23 children. They present evidence that fixed-site ambient measurements may not be representative of indoor microenvironments for personal ozone concentrations.
Lung membrane as a barrier to cancer
Sekhon et al. (p. 326) used an excised rat lung preparation to evaluate the toxic effects of cigarette smoke on mesothelial cells. The mesothelial cells are a component of the external pleural connective tissue covering the lungs. The data showed that external smoke injures the mesothelial cells, as does hydrogen peroxide, but that internal smoke is unable to penetrate the pleural barrier and damage these cells. These findings suggest that one reason smoking causes lung cancer but not meso-thelial cancer is that smoke cannot penetrate the pleural barrier.
Predicting chemical carcinogenicity using computers
Malacarne et al. (p. 332) designed a computer software program to analyze chemical structures for predicting carcinogenicity. The program uses graph theory to represent chemical structures by associating the atoms with vertices and bonds with the edges of the molecules. Malacarne and co-workers used 826 chemicals for the analysis that had been previously tested and designated as carcinogens or noncarcinogens. Eight computer runs were performed, yielding an average level of accuracy for the prediction of carcinogenicity of 67.5%. The authors state that results of such analyses should be regarded as a set of biological indicators but cannot be used to replace in-depth analyses of carcinogenesis data.
Last Update: August 26, 1997
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