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Start Over Author "Mitchell, David" Journal photochemistry and photobiology
79 results on '"Mitchell, David"'

32. Impacts of Solar UVR on Aquatic Microorganisms*

Author

BOOTH, C. R., primary, MORROW, J. H., additional, COOHILL, THOMAS P., additional, CULLEN, JOHN J., additional, FREDERICK, JOHN E., additional, HADER, DONAT-P., additional, HOLM-HANSEN, OSMUND, additional, JEFFREY, WADE H., additional, MITCHELL, DAVID L., additional, NEALE, PATRICK J., additional, SOBOLEV, IGOR, additional, LEUN, JAN VAN DER, additional, and WORREST, ROBERT C., additional

Published
1997
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41. lnterspecific Variation in UV Defense Mechanisms Among Temperate Freshwater Fishes

Author

Olson, Mark H. and Mitchell, David L.

Abstract

An important step in predicting the effects of future increases in UV radiation (UVR) is to evaluate the mechanisms that organisms use to prevent and repair DNA damage and determine how those mechanisms influence UVR sensitivity. Damage is prevented to varying degrees through photo‐protection and repaired viatwo main pathways: nucleotide excision repair and photoenzymatic repair. At present, little is known about the generality or similarity of these defenses among temperate freshwater fishes. We used laboratory experiments to compare UVR defense mechanisms among five freshwater fish species representing four families and three orders. Purified DNA, freeze‐killed larvae and live larvae were exposed to UVB radiation for 12 h in the presence or absence of photorepair radiation. After exposure, we quantified frequencies of cyclobutane pyrimidine dimers in each exposure treatment. All five species used photoprotection and proportional decreases in dimer frequency were similar for all species. Evidence of excision repair was also found for all species but proportional decreases in photoproduct frequencies varied among species. Finally, evidence of photoenzymatic repair was found for only two of the five species.

Published
2006
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42. PHOTOREACTIVATION OF CYCLOBUTANE DIMERS AND (6–4) PHOTOPRODUCTS IN THE EPIDERMIS OF THE MARSUPIAL, Monodelphis domestica

Author

MITCHELL, DAVID L., APPLEGATE, LEE A., NAIRN, RODNEY S., and LEY, RONALD D.

Abstract

Radioimmunoassays were used to investigate the repair of cyclobutane pyrimidine dimers and pyrimidine(6–4)pyrimidone photoproducts ([6–4] photoproducts) in the epidermis of the South American opossum, Monodelphis domestica. In the absence of photoreactivating light, both types of photodamage were excised with similar kinetics, 50% of the damage remaining 8 h after UV irradiation in vivo. Exposure of UV‐irradiated skin to photoreactivating light resulted in removal of most of the cyclobutane dimers and an enhanced rate of (6–4) photoproduct repair. Photoenhanced excision repair of non‐dimer damage increases the range of biologically effective lesions removed by in vivophotoreactivation.

Published
1990
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50. Interspecific variation in the repair of UV damaged DNA in the genus Xiphophorus as a factor in the decline of the Rio Grande Platyfish.

Author

Mitchell D, Paniker L, Lin K, and Fernandez A

Subjects
Animals, Cyprinodontiformes classification, DNA Damage, Endangered Species, Gene Expression, Genetic Variation, Geography, Ozone Depletion, Phylogeny, Radiation Dosage, Rivers, Cyprinodontiformes genetics, DNA genetics, DNA Repair radiation effects, DNA Repair Enzymes genetics, Ultraviolet Rays adverse effects
Abstract

The fish genus Xiphophorus consists of 26 species distributed along the eastern slopes of mountain ranges extending from northern Mexico to Belize and Nicaragua. We analyzed light-dependent repair of UV-induced DNA damage in at least two species from each of the four monophyletic Xiphophorus groups. We found that the northern platyfish had significantly reduced photoenzymatic repair compared to the other three groups, including the northern swordtails, southern platyfish and southern swordtails. All of the species of the northern platyfish, including the Marbled (meyeri), Northern (gordoni) and Monterrey Platyfish (couchianus) are the northernmost species in the genus and are the only three species in the genus that are currently found on the IUCN Red List of Threatened Species. Satellite data from the past 30 years (1979-2008) correlate greater increases in shorter wavelength UVB with higher latitudes within the Xiphophorus range. We suggest that, combined with other consequences of human population growth, anthropogenic deozonation resulting in a disproportionate increase in UVB in temperate latitudes may be a contributing factor in the decline and extirpation of the northern platyfish., (© 2014 The American Society of Photobiology.)

Published
2015
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