Research Results: Screening and Testing Methods
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A Short-Term in vivo Screening System for Endocrine Disruptors Utilizing Mosquitofishes (Gambusia affinis and G. holbrook)
Robert Angus, University of Alabama, Birmingham
EPA STAR Grant #R826130
- A solid phase (Western blot) immunoassay for vitellogenin (VTG) was developed, which was used to demonstrate that the effect of 17α-ethynylestradiol on VTG synthesis in male G. affinis is both concentration- and time-dependent.
- When coupled with densitometric scanning, the solid phase assay appeared to be specific, quantitative, and sensitive enough to detect VTG down to 10 ug/g in G. affinis blood.
- A quantitative morphological study of gonopodium development in normal males and in females treated with 11-ketotestosterone showed that length and width ratios of anal fins are useful in that they can be determined with high precision and are not restricted to a limited size range.
- Phytosteriods in paper mill effluent tend to accumulate in the sediment, where microbes convert them first into progesterone and then into androstenedione and other bioactive steroids. Also, it was found that unpolluted water bodies with much lower organic matter still contain progesterone, but at substantially lower levels.
- No histological changes in the testes or liver were observed in male mosquitofish near a wastewater treatment plant that would indicate exposure to estrogens and no detectable levels of VTG were found in their blood.
Computational Tools for the Prediction and Classification of Estrogenic Compounds
William J. Welsh - University of Missouri - St Louis
EPA STAR Grant #R826133
- A range of CoMFA-based QSAR models were developed that successfully predicted the estrogen receptor binding activity of a wide range of chemicals.
- A computational technique called Shape Signatures was developed as a rapid a simple approach to summarizing and comparing the shapes and structural features of molecules to each other and to target receptor sites/subsites.
- The Shape Signatures approach will enable rapid shape comparisons of a library of diverse compounds against a target receptor (e.g., estrogen receptors) or against other compounds (e.g., known estrogenic compounds).
- This technology shows promise for the rapid prioritization of potential EDCs for timely and cost-effective biological screening.
Species-Specific Endocrine Disruption: PCB- and PAH- Induced Estrogen Effects
Timothy Zacharewski , Michigan State University
EPA STAR Grant # R826301
- Competitive ligand binding and reporter gene assays identified several compounds that exhibited differential interactions with recombinant estrogen receptors.
- There were substantial differences in relative binding affinities between species.
- There was poor correlation between the in vitro and in vivo activities and striking differences in efficacy and potency between the species examined.
- Results do not preclude the use of a single surrogate species for screening purposes, but the ability to predict in vivo activity based on in vitro data is questionable.