Widespread environmental contamination by bisphenol A (BPA) has created the need to fully define its potential toxic mechanisms of action (MOA) to properly assess human health and ecological risks ...from exposure. Although long recognized as an estrogen receptor (ER) agonist, some data suggest that BPA may also behave as an androgen receptor (AR) antagonist. However, direct evidence of this activity is deficient. To address this knowledge gap, we employed a metabolomic approach using in vivo exposures of fathead minnows (FHM; Pimephales promelas ) to BPA either alone or in a binary mixture with 17β-trenbolone (TB), a strong AR agonist. Changes in liver metabolite profiles in female FHM in response to these exposures were determined using high resolution (1)H NMR spectroscopy and multivariate and univariate statistics. Using this approach, we observed clear evidence of the ability of BPA to mitigate the impact of TB, consistent with an antiandrogenic MOA. In addition, a transcriptional activation assay with the FHM AR was used to confirm the AR antagonistic activity of BPA in vitro. The results of these in vivo and in vitro analyses provide strong and direct evidence for ascribing an antiandrogenic MOA to BPA in vertebrates.
We have developed an alteration strength index (ASI) equation to address the effect of hydrothermal alteration on mechanical rock properties. This equation can be used to estimate a range of rock ...strengths, comparable to uniaxial compressive strength (UCS), based on rapid analysis of mineralogy and microstructure. We used rock samples from three geothermal fields in the Taupo Volcanic Zone (TVZ) to represent a range of alteration types. These are sedimentary, intrusive and extrusive rocks, typical of geothermal systems, from shallow and deep boreholes (72 measured Depth (mD) to 3280mD). The parameters used in ASI were selected based on literature relating these aspects of mineralogy and microstructure to rock strength. The parameters in ASI define the geological characteristics of the rock, such as proportions of primary and secondary mineralogy, individual mineral hardness, porosity and fracture number. We calibrated the ASI against measured UCS for our samples from the TVZ to produce a strong correlation (R2 of 0.86), and from this correlation we were able to derive an equation to convert ASI to UCS. Because the ASI–UCS relationship is based on an empirical fit, the UCS value that is obtained from conversion of the ASI includes an error of 7MPa for the 50th percentile and 25MPa for the 90th percentile with a mean error of 11MPa. A sensitivity analysis showed that the mineralogy parameter is the dominant characteristic in this equation, and the ASI equation using only mineralogy can be used to provide an estimated UCS range, although the error (or uncertainty) becomes greater. This provides the ability to estimate strength even when either fracture or porosity information are not available, for example in the case of logging drill cuttings. This research has also allowed us to provide ranges of rock strengths based solely on the alteration zones, mineralogy, and depth of lithologies found in a typical geothermal field that can be used to update conceptual models of geothermal fields.
•ASI equation developed to estimate strength of hydrothermally altered rocks•Mineralogy is key factor for strength of hydrothermally altered rocks.•Pre-existing fractures and porosity also factors for strength.•mASI can be used for rapid strength estimation using drill cuttings.•Strength can add value to conceptual models for geothermal reservoir operation.
•The drilling parameters in a 800m long well were held nearly constant, providing the opportunity to use rate of penetration as an analog for rock strength.•We compared two drillability equations ...from the oil and gas industry to mASI, which was developed for use in hydrothermally altered rocks.•The strengths predicted by mASI correlate to rate of penetration better than those based on conventional oil and gas equations.•mASI provides a realistic range of rock strength estimates, can be based on thin sections (ASI) or drill cuttings (mASI), and does not require drilling parameters to estimate rock strength.•ASI used in conjunction with a predictive geologic model will aid with drilling optimization through drill bit selection.
Many methods for estimating rock strength for drilling rate optimization were developed for the oil and gas industry, some of which are being used in geothermal fields. We have developed a methodology for using estimated rock strength for drillability assessment in the hydrothermally altered lithologies encountered in the geothermal industry. The Modified Alteration Strength Index (mASI) provides rock strength estimates using simple intact rock properties observable in drill cuttings, such as mineralogy and fractures. We show that rock strengths for hydrothermally altered rock estimated using mASI correlate better to drillability indicators than convetional methods from the oil and gas industry.
Endocrine disruption is considered a highly relevant hazard for environmental risk assessment of chemicals, plant protection products, biocides and pharmaceuticals. Therefore, screening tests with a ...focus on interference with estrogen, androgen, and thyroid hormone pathways in fish and amphibians have been developed. However, they use a large number of animals and short-term alternatives to animal tests would be advantageous. Therefore, the status of alternative assays for endocrine disruption in fish and frogs was assessed by a detailed literature analysis. The aim was to (i) determine the strengths and limitations of alternative assays and (ii) present conclusions regarding chemical specificity, sensitivity, and correlation with in vivo data. Data from 1995 to present were collected related to the detection/testing of estrogen-, androgen-, and thyroid-active chemicals in the following test systems: cell lines, primary cells, fish/frog embryos, yeast and cell-free systems. The review shows that the majority of alternative assays measure effects directly mediated by receptor binding or resulting from interference with hormone synthesis. Other mechanisms were rarely analysed. A database was established and used for a quantitative and comparative analysis. For example, a high correlation was observed between cell-free ligand binding and cell-based reporter cell assays, between fish and frog estrogenic data and between fish embryo tests and in vivo reproductive effects. It was concluded that there is a need for a more systematic study of the predictive capacity of alternative tests and ways to reduce inter- and intra-assay variability.
A field-based metabolomic study was conducted during a shutdown of a pulp and paper mill (PPM) to assess the impacts of treated PPM effluent on endogenous polar metabolites in fathead minnow (FHM; ...Pimephales promelas) livers. Caged male and female FHMs were deployed at a Great Lakes area of concern during multiple periods (pre-, during, and post-shutdown) near the outflow for a wastewater treatment plant. Influent to this plant is typically 40% PPM effluent by volume. Additional FHMs were exposed to reference lake water under laboratory conditions. A bioassay using T47D-KBluc cells showed that estrogenic activity of receiving water near the outflow declined by 46% during the shutdown. We then used (1)H NMR spectroscopy and principal component analysis to profile abundances of hepatic endogenous metabolites for FHMs. Profiles for males deployed pre-shutdown in receiving water were significantly different from those for laboratory-control males. Profiles were not significantly different for males deployed during the shutdown, but they were significant again for those deployed post-shutdown. Impacts of treated effluent from this PPM were sex-specific, as differences among profiles of females were largely nonsignificant. Thus, we demonstrate the potential utility of field-based metabolomics for performing biologically based exposure monitoring and evaluating remediation efforts occurring throughout the Great Lakes and other ecosystems.
This paper reviews the roles of the fathead minnow (
Pimephales promelas) as a small fish model in the field of aquatic toxicology. The species has been (and is) extensively used both for regulatory ...testing and research, especially in North America. For example, tests with the fathead minnow, ranging from 48-h lethality through partial and full life-cycle assays, are routinely used for regulatory programs aimed at assessing potential risks of new chemicals such as high-production volume materials and pesticides, as well as impacts of complex mixtures like effluents. The species also has been used for a wide variety of research applications focused on topics like the development of quantitative structure–activity relationship models, mixture toxicity, extrapolation of the effects of chemicals across species, and understanding the results of laboratory assays relative to impacts in the field. Attributes of the fathead minnow also make it an excellent model for addressing new challenges in aquatic toxicology, including identification of sensitive life-stages/endpoints for chemicals with differing modes/mechanisms of action, predicting population-level effects based on data collected from lower levels of biological organization, and exploring/understanding the emerging role of genomics in research and regulation.
A growing body of evidence suggests that polychlorinated naphthalenes (PCNs) may be fairly widespread environmental contaminants. This may be cause for concern because exposure to PCNs has been ...linked to dioxin-like biological responses in a wide variety of species. This study used three in vitro bioassays to characterize the dioxin-like potency of 18 individual PCN congeners and 1 PCN metabolite. The PLHC-1 fish hepatoma cell bioassay was relatively insensitive to PCNs. At the concentrations tested, only 1, 4 di-CN and 2,4-dichloro-1-napthol caused significant induction of ethoxyresorufin O-deethylase (EROD) activity in the PLHC-1 assay. In vitro EROD and luciferase assays using recombinant H4IIE rat hepatoma cells were more responsive to PCNs. Structure-activity relationships were observed both in terms of the degree of chlorination and the positions of chlorine substitutions. Hexa-chlorinated naphthalenes (CNs), exhibiting relative potencies (REPs) around 10(-3) (relative to TCDD), were the most potent congeners tested. Penta-CNs were also rather potent, yielding REPs between 10(-3) and 10(-7). Tetra-, tri-, di-, and mono-CNs were less active. REPs for the active congeners were similar to those for some PCBs. The relative potency estimates reported here contribute to an emerging body of information that will aid determination of the relative contribution of PCNs to the total dioxin-like activity associated with environmental samples.
Relative potency (REP) estimates are widely used to characterize and compare the potency of a wide variety of samples analyzed using in vitro bioassays. Relative potency estimates are generally ...calculated as a simple ratio: the EC50 of a well‐characterized standard divided by the EC50 of a sample. Such estimates are valid only when the dose‐response curves for the sample and standard are parallel and exhibit the same maximum achievable response (efficacy). These conditions are often either violated or cannot be demonstrated. As a result, there is a need to calculate and present REPs in a manner that addresses the potential uncertainties caused by violation of the assumptions of parallelism and equal efficacy. Multiple point estimates, over the range of responses from EC20 to EC80, can be used to derive relative potency ranges (REP20–80 range). The width of a REP20–80 range is directly proportional to the degree of deviation from parallelism between sample and standard dose‐response curves. Thus, REP20–80 ranges both test the assumption of parallelism and characterize the amount of uncertainty in an REP estimate resulting from deviation from parallelism. Although uncertainties due to unequal efficacy cannot be easily characterized mathematically, a systematic method for evaluating sample efficacy has been developed into a framework to guide the derivation and application of REP estimates based on in vitro bioassay results. Use of the systematic framework and REP20–80 ranges was illustrated using three sample data sets. It is hoped that the framework and discussion presented will facilitate the use of bioassay‐derived REP estimates to characterize samples of both known and unknown composition without ignoring the assumptions underlying REP estimation.
The potential for profiling metabolites in urine from male fathead minnows (
Pimephales promelas) to assess chemical exposures was explored using nuclear magnetic resonance (NMR) spectroscopy. Both ...one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy was used for the assignment of metabolites in urine from unexposed fish. Because fathead minnow urine is dilute, we lyophilized these samples prior to analysis. Furthermore, 1D
1H NMR spectra of unlyophilized urine from unexposed male fathead minnow and Sprague-Dawley rat were acquired to qualitatively compare rat and fish metabolite profiles and to provide an estimate of the total urinary metabolite pool concentration difference. As a small proof-of-concept study, lyophilized urine samples from male fathead minnows exposed to three different concentrations of the antiandrogen vinclozolin were analyzed by 1D
1H NMR to assess exposure-induced changes. Through a combination of principal components analysis (PCA) and measurements of
1H NMR peak intensities, several metabolites were identified as changing with statistical significance in response to exposure. Among those changes occurring in response to exposure to the highest concentration (450
μg/L) of vinclozolin were large increases in taurine, lactate, acetate, and formate. These increases coincided with a marked decrease in hippurate, a combination potentially indicative of hepatotoxicity. The results of these investigations clearly demonstrate the potential utility of an NMR-based approach for assessing chemical exposures in male fathead minnow, using urine collected from individual fish.
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