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GENETIC DAMAGE INDICATORS IN FISH EXPOSED TO VARYING STREAM CONDITIONS IN AN AGRICULTURAL WATERSHED
Citation:
Meier, J R., L W. Chang, F B. Daniel, S E. Franson, AND P A. Wernsing. GENETIC DAMAGE INDICATORS IN FISH EXPOSED TO VARYING STREAM CONDITIONS IN AN AGRICULTURAL WATERSHED. Presented at Environmental Mutagen Society, San Diego, CA, March 16-21, 2001.
Impact/Purpose:
The indeterminate condition of exposure indicator research stands to change markedly with the ability to connect molecular biological technologies with cellular or tissue effects and outcomes. Three focal areas of ecological research aim to develop a sequence of approaches where "the earliest recognizable signatures of exposure" (i.e., unique patterns of up- and down-regulated genes and proteins) are identified for numerous stressors, demonstrable in case studies and incorporated into Agency, State and Regional studies supported by EMAP and other programs.
Area 1, Computational Toxicology Research: Exposure assessment has historically been based on use of chemical analysis data to generate exposure models. While biological activity of chemicals has been recognized to be important for exposure risk assessments, measurement of such activity has been limited to whole organism toxicity tests. Use of molecular approaches will:
improve extrapolation between components of source-to-outcome continuum (source , exposure , dose , effect , outcome)
Using a systems modeling approach, gene and protein expression data, in small fish models (fathead minnow and zebrafish), will be integrated with metabolomic and histopathological data. This will assist in prediction of environmental transformation and chemical effects based on structural characteristics, and enhance quantitative risk assessments, including areas of uncertainty such as a basis for extrapolation of effects of endocrine disrupting chemicals, interspecies extrapolation, complex chemical mixtures and dose-response assessment.
Area 2, Ecological Research-Environmental Diagnostics: Development of molecular diagnostic indicators contributes to several of the GPRA Diagnostic Research Goals. Methods will employ DNA microarray technology and expression proteomics, focusing on species of relevance to aquatic ecosystem risk assessment. Significantly, these diagnostic indicators will open the door to understanding subcellular interactions resulting from exposure to complex chemical mixtures.
define relationship between genetic disposition of populations and degree/specificity of stressor-specific gene transcriptional response in aquatic organisms (fish and invertebrates)
identify of chemical mixture induced transcriptional "patterns" using microarrays and hyperspectral scanning - via collaboration with DOE Sandia National Labs
apply molecular indicators to watershed level stressor study, including pilot studies with targeted pesticides and toxins indicators
develop molecular indicators of exposure for invertebrates (Daphnia, Lumbriculus, Chironomus)
Area 3, Exposure Research in Endocrine Disruptors:
Subobjective 1: Develop exposure methods, measurement protocols, and models for assessment of risk management practices of endocrine disrupting compounds. As risk management approaches are identified and developed, there will be a need to identify, adapt and develop bioassay screening tools and other analytical methods to assess their efficacy. Measurements research will be performed to define management needs. This effort will entail cross-lab participation from NRMRL, NERL and NHEERL.
Subobjective 2: Determine extent of environmental and human exposures to EDCs, characterize sources and factors influencing these exposures, develop and evaluate risk management strategies to reduce exposures. In order to develop effective risk management strategies, it is important to understand the extent of exposures to endocrine disrupting compounds and factors influencing source-to-exposure-to-dose relationships.
apply molecular indicators of exposure to estrogenic compounds in selected wastewater treatment plants located in ten USEPA Regions
identify differential gene expression following exposure of fathead minnows to environmental androgens and androgen-like compounds
apply molecular indicators of exposu
Description:
Micronucleus (MN) and single cell gel electrophoresis (SCG) measures of genetic damage in fish erythrocytes were included in an evaluation of a wide range of biological and physical stream condition parameters being developed for use in watershed and regional scale assessments. Bluegill sunfish (BG; Lepomis macrochirus) and white suckers (WS; Catostomus commersoni) were selected as target species because of their abundance in Midwestern streams and their differing exposures to contaminants in the water column and sediment, respectively. Fish were collected by electroshocking from 11 headwater tributaries of the Little Miami River watershed in southwestern Ohio. All streams were set in a predominantly agricultural landscape but showed a range of landcover metrics, water chemistry conditions and in-stream habitat measures. For the SCG assay, the tail length, tail moment and % tail DNA parameters were analyzed by computerized image analysis. For the MN assay, acridine orange-stained blood smears were scored manually for micronuclei in polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE). MN frequencies in BG from all locations were very low (less than 0.1 MN/1,000 PCEs or NCEs) and comparable to values for laboratory maintained fish. Values for WS ranged from 0 to 0.4 MN/1,000 NCEs. The MN levels in WS appeared to correlate with varying rates of erythrocyte turnover (PCE:NCE ratio) in fish collected from different sites. The SCG parameters in BG were also comparable to laboratory control values, and did not vary significantly among sites for either species. Preliminary results indicate that the levels of genetic damage observed were not correlated with the range of conditions (water chemistry, land cover, etc.) observed in these streams.