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- Aquatic toxicology (7)
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- Rainbow trout (5)
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- Neurotoxicity (3)
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- Daphnia magna (2)
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- Medaka (2)
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- Phenols (2)
- Pyrethroid insecticides (2)
- QSAR (2)
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- Redox cycling (2)
- Respiratory-cardiovascular responses (2)
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Articles 1 - 30 of 52
Full-Text Articles in Life Sciences
The North American Carbon Program Multi-Scale Synthesis And Terrestrial Model Intercomparison Project – Part 2: Environmental Driver Data, Y. Wei, S. Liu, D. N. Huntzinger, A. M. Michalak, N. Viovy, W. M. Post, C. R. Schwalm, K. Schaefer, A. R. Jacobson, Chaoqun (Crystal) Lu, Hanqin Tian, D. M. Ricciuto, R. B. Cook, J. Mao, X. Shi
The North American Carbon Program Multi-Scale Synthesis And Terrestrial Model Intercomparison Project – Part 2: Environmental Driver Data, Y. Wei, S. Liu, D. N. Huntzinger, A. M. Michalak, N. Viovy, W. M. Post, C. R. Schwalm, K. Schaefer, A. R. Jacobson, Chaoqun (Crystal) Lu, Hanqin Tian, D. M. Ricciuto, R. B. Cook, J. Mao, X. Shi
Chaoqun (Crystal) Lu
Ecosystems are important and dynamic components of the global carbon cycle, and terrestrial biospheric models (TBMs) are crucial tools in further understanding of how terrestrial carbon is stored and exchanged with the atmosphere across a variety of spatial and temporal scales. Improving TBM skills, and quantifying and reducing their estimation uncertainties, pose significant challenges. The Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP) is a formal multi-scale and multi-model intercomparison effort set up to tackle these challenges. The MsTMIP protocol prescribes standardized environmental driver data that are shared among model teams to facilitate model–model and model–observation comparisons. This paper describes …
Evaluation Of Trophic Niche Overlap Between Native Fishes And Young-Of-The-Year Common Carp, Michael J. Weber, Jessica M. Howell, Michael L. Rown
Evaluation Of Trophic Niche Overlap Between Native Fishes And Young-Of-The-Year Common Carp, Michael J. Weber, Jessica M. Howell, Michael L. Rown
Michael J Weber Dr
Common carp Cyprinus carpio is a ubiquitous invasive species that commonly imposes negative effects on aquatic ecosystems. However, research evaluating the effects of carp on native fishes is limited. Carp are highly fecund and larvae and juveniles can be abundant. If age-0 carp use similar prey resources as native fishes, they may compete if food becomes limited. We used traditional diet analysis for samples during Jul. and Aug. 2008 in Brant Lake. Stable sotopes were used for samples collected during Aug. and Sep. 2009 in Brant Lake and Lake Sinai to examine prey resource use by age-0 carp and four …
Continuous, Pulsed And Disrupted Nutrient Subsidy Effects On Ecosystem Productivity, Stability, And Energy Flow, Michael J. Weber, Michael L. Brown
Continuous, Pulsed And Disrupted Nutrient Subsidy Effects On Ecosystem Productivity, Stability, And Energy Flow, Michael J. Weber, Michael L. Brown
Michael J Weber Dr
Resource pulses and subsidies can supply ecosystems with an important source of nutrients that supports additional productivity at multiple trophic levels. Common carp Cyprinus carpio provide ecosystems with a continuous nutrient subsidy through bioturbation and excretion but may also initiate a nutrient pulse through carcass decomposition. We examined how continuous (common carp foraging and excretion), pulsed (carcass decomposition) and disrupted (carp introduced and then removed) nutrient subsidies differed in their ability to alter nutrient availability, ecosystem productivity and stability and energy flow. Nitrogen and phosphorus availability and primary production were highest in pulsed, intermediate in continuous and lowest for disrupted …
Application Of The Tissue Residue Approach In Ecological Risk Assessment, Steven P. Bradbury, Keith G. Sappington, Todd S. Bridges, Russell J. Erickson, A. Jan Hendriks, Roman P. Lanno, James P. Meador, David R. Mount, Mike H. Salazar, Doug J. Spry
Application Of The Tissue Residue Approach In Ecological Risk Assessment, Steven P. Bradbury, Keith G. Sappington, Todd S. Bridges, Russell J. Erickson, A. Jan Hendriks, Roman P. Lanno, James P. Meador, David R. Mount, Mike H. Salazar, Doug J. Spry
Steven P. Bradbury
The objective of this work is to present a critical review of the application of the tissue residue approach (TRA) in ecological risk and/or impact assessment (ERA) of chemical stressors and environmental criteria development. A secondary goal is to develop a framework for integrating the TRA into ecological assessments along with traditional, exposure concentration-based assessment approaches. Although widely recognized for its toxicological appeal, the utility of the TRA in specific applications will depend on numerous factors, such as chemical properties, exposure characteristics, assessment type, availability of tissue residue-response data, and ability to quantify chemical exposure. Therefore, the decision to use …
Meeting The Common Needs Of A More Effective And Efficient Testing And Assessment Paradigm For Chemical Risk Management, Steven P. Bradbury, Vicki Dellarco, Tala Henry, Phil Sayre, Jennifer Seed
Meeting The Common Needs Of A More Effective And Efficient Testing And Assessment Paradigm For Chemical Risk Management, Steven P. Bradbury, Vicki Dellarco, Tala Henry, Phil Sayre, Jennifer Seed
Steven P. Bradbury
Significant advances have been made in human health and ecological risk assessment over the last decade. Substantial challenges, however, remain in providing credible scientific information in a timely and efficient manner to support chemical risk assessment and management decisions. A major challenge confronting risk managers is the need for critical information to address risk uncertainties in large chemical inventories such as high- and medium-production-volume industrial chemicals or pesticide inert ingredients. From a strategic and tactical viewpoint, an integrated approach that relies on all existing knowledge and uses a range of methods, including those from emerging and novel technologies, is needed …
Application Of Genomics To Regulatory Ecological Risk Assessments For Pesticides, Steven P. Bradbury, Sigmund J. Degitz, Robert A. Hoke, Richard Brennan, Lee Ferguson, Rebecca Klaper, Laszlo Orban, David Spurgeon, Susan Tilton
Application Of Genomics To Regulatory Ecological Risk Assessments For Pesticides, Steven P. Bradbury, Sigmund J. Degitz, Robert A. Hoke, Richard Brennan, Lee Ferguson, Rebecca Klaper, Laszlo Orban, David Spurgeon, Susan Tilton
Steven P. Bradbury
Substantial advances in human health and ecological risk assessment have been achieved by the risk assessment community; however, challenges remain, such as providing credible scientific information on a timely, efficient basis to support decisions for industrial chemicals and pesticides. Current risk assessment data generation requirements-including animal welfare concerns and the volume, appropriateness, and cost of required data-and the large number of chemicals requiring evaluation are a challenge confronting the chemical industry, national and international regulatory agencies, and associated stakeholders (Bradbury et al. 2004). The lack of hazard data for many chemicals and the need to improve the efficiency and quality …
Toxic Responses Of The Fish Nervous System, Steven P. Bradbury, Richard W. Carlson, Tala R. Henry, Stephanie Padilla, John Cowden
Toxic Responses Of The Fish Nervous System, Steven P. Bradbury, Richard W. Carlson, Tala R. Henry, Stephanie Padilla, John Cowden
Steven P. Bradbury
Few of the approximately 70,000 chemicals on the Toxic Substances Control Act inventory or the 1000 to 1600 new chemicals introduced each year in the United States have been tested for neurotoxicity to support risk assessments (NRC, 1992), even though it is estimated that 5 to 10% of them are likely to be neurotoxic. Neurotoxicity has been defined as adverse effects of physical, biological, or chemical agents on the structure or function of the nervous system in developing or adult organisms (Philbert et al., 2000). From a human health risk assessment perspective, the potential for neurotoxic effects associated with synthetic …
Meeting The Scientific Needs Of Ecological Risk Assessment In A Regulatory Context, Steven P. Bradbury, Tom C. Feitel, Cornelis J. Van Leeuwen
Meeting The Scientific Needs Of Ecological Risk Assessment In A Regulatory Context, Steven P. Bradbury, Tom C. Feitel, Cornelis J. Van Leeuwen
Steven P. Bradbury
During the past decade, the field of ecological risk assessment has progressed considerably. Advances have come from such international bodies as the Organisation for Economic Co-operation and Development (OECD), the World Health Organisation (WHO), the European and Mediterranean Plant Protection Organisation (EPPO), and the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) (1–8). Risk assessments have played a critical role in the development of various regulations within the European Commission (EC) as well as in other parts of the world, including the United States, Canada, and Japan (9–17). But scientists and regulators are faced with three significant challenges: streamlining …
Linear And Nonlinear Effects Of Habitat Structure On Composition And Abundance In The Macroinvertebrate Community Of A Large River, Timothy W. Stewart, Tammy L. Shumaker, Thomas A. Radzio
Linear And Nonlinear Effects Of Habitat Structure On Composition And Abundance In The Macroinvertebrate Community Of A Large River, Timothy W. Stewart, Tammy L. Shumaker, Thomas A. Radzio
Timothy W. Stewart
We used an experiment and regression analyses to quantify effects of spatial variation in habitat structure abundance on a riverine macroinvertebrate community under winter conditions. Concrete slabs (0.21 m2; n 5 24) with different numbers of stones (mean individual stone surface area 5 6.44 cm2) attached to upper faces were placed in the James River and retrieved after 28 d. Macroinvertebrate abundance and taxonomic richness on slabs were significantly positively related to stone abundance. Total macroinvertebrate abundance and abundance of oligochaetes (Nais spp.), Asiatic clams (Corbicula fluminea), caddisflies (Leptoceridae), riffle beetles (Elmidae) and stoneflies (Strophopteryx sp.) were linearly related to …
Overview Of Data And Conceptual Approaches For Derivation Of Quantitative Structure-Activity Relationships For Ecotoxicological Effects Of Organic Chemicals, Steven P. Bradbury, Christine L. Russom, Gerald T. Ankley, T. Wayne Schultz, John D. Walker
Overview Of Data And Conceptual Approaches For Derivation Of Quantitative Structure-Activity Relationships For Ecotoxicological Effects Of Organic Chemicals, Steven P. Bradbury, Christine L. Russom, Gerald T. Ankley, T. Wayne Schultz, John D. Walker
Steven P. Bradbury
The use of quantitative structure–activity relationships (QSARs) in assessing potential toxic effects of organic chemicals on aquatic organisms continues to evolve as computational efficiency and toxicological understanding advance. With the everincreasing production of new chemicals, and the need to optimize resources to assess thousands of existing chemicals in commerce, regulatory agencies have turned to QSARs as essential tools to help prioritize tiered risk assessments when empirical data are not available to evaluate toxicological effects. Progress in designing scientifically credible QSARs is intimately associated with the development of empirically derived databases of well-defined and quantified toxicity endpoints, which are based on …
An Overview Of The Use Of Quantitative Structure-Activity Relationships For Ranking And Prioritzing Large Chemical Inventories For Environmental Risk Assessments, Steven P. Bradbury, Christine L. Russom, Roger L. Breton, John D. Walker
An Overview Of The Use Of Quantitative Structure-Activity Relationships For Ranking And Prioritzing Large Chemical Inventories For Environmental Risk Assessments, Steven P. Bradbury, Christine L. Russom, Roger L. Breton, John D. Walker
Steven P. Bradbury
Ecological risk assessments for chemical stressors are used to establish linkages between likely exposure concentrations and adverse effects to ecological receptors. At times, it is useful to conduct screening risk assessments to assist in prioritizing or ranking chemicals on the basis of potential hazard and exposure assessment parameters. Ranking of large chemical inventories can provide evidence for focusing research and/or cleanup efforts on specific chemicals of concern. Because of financial and time constraints, data gaps exist, and the risk assessor is left with decisions on which models to use to estimate the parameter of concern. In this review, several methods …
Influence Of Suspended Solids On Acute Toxicity Of Carbofuran To Daphnia Magna: Ii. An Evaluation Of Potential Interactive Mechanisms, Steven P. Bradbury, Carl Herbrandson, Deborah L. Swackhamer
Influence Of Suspended Solids On Acute Toxicity Of Carbofuran To Daphnia Magna: Ii. An Evaluation Of Potential Interactive Mechanisms, Steven P. Bradbury, Carl Herbrandson, Deborah L. Swackhamer
Steven P. Bradbury
It has been demonstrated that simultaneous exposure of Daphnia magna to suspended solids and a carbamate pesticide potentiates the toxic response to the pesticide. The toxicodynamics between these stressors were investigated to determine possible mechanisms of interaction. Three experimental series were conducted with D. magna to determine: the effect of food availability on carbofuran toxicity; the effect of food availability on jointly administered carbofuran and suspended solids; and changes in the magnitude of effects which can occur with suspended solids of different composition. These experiments demonstrated that both carbofuran toxicity and the joint toxicity of carbofuran and suspended solids to …
Quantitative Structure-Activity Relationship Models For Prediction Of Estrogen Receptor Binding Affinity Of Structurally Diverse Chemicals, Steven P. Bradbury, Patricia K. Schmeider, Gerald Ankley, Ovanes Mekenyan, John D. Walker
Quantitative Structure-Activity Relationship Models For Prediction Of Estrogen Receptor Binding Affinity Of Structurally Diverse Chemicals, Steven P. Bradbury, Patricia K. Schmeider, Gerald Ankley, Ovanes Mekenyan, John D. Walker
Steven P. Bradbury
The demonstrated ability of a variety of structurally diverse chemicals to bind to the estrogen receptor has raised the concern that chemicals in the environment may be causing adverse effects through interference with nuclear receptor pathways. Many structure–activity relationship models have been developed to predict chemical binding to the estrogen receptor as an indication of potential estrogenicity. Models based on either two-dimensional or three-dimensional molecular descriptions that have been used to predict potential for binding to the estrogen receptor are the subject of the current review. The utility of such approaches to predict binding potential of diverse chemical structures in …
Narrowing Historical Uncertainty: Probabilistic Classification Of Ambiguously Identified Tree Species In Historical Forest Survey Data, David J. Mladenoff, Sally E. Dahir, Eric V. Nordheim, Lisa A. Schulte, Glenn G. Guntenspergen
Narrowing Historical Uncertainty: Probabilistic Classification Of Ambiguously Identified Tree Species In Historical Forest Survey Data, David J. Mladenoff, Sally E. Dahir, Eric V. Nordheim, Lisa A. Schulte, Glenn G. Guntenspergen
Lisa A. Schulte Moore
Historical data have increasingly become appreciated for insight into the past conditions of ecosystems. Uses of such data include assessing the extent of ecosystem change; deriving ecological baselines for management, restoration, and modeling; and assessing the importance of past conditions on the composition and function of current systems. One historical data set of this type is the Public Land Survey (PLS) of the United States General Land Office, which contains data on multiple tree species, sizes, and distances recorded at each survey point, located at half-mile (0.8-km) intervals on a 1-mi (1.6 km) grid. This survey method was begun in …
New Developments In A Hazard Identification Algorithm For Hormone Receptor Ligands, Steven P. Bradbury, Ovanes Mekenyan, Nina Nikolova, Stoyan Karabunarliev, Gerald T. Ankley, Bjorn Hansen
New Developments In A Hazard Identification Algorithm For Hormone Receptor Ligands, Steven P. Bradbury, Ovanes Mekenyan, Nina Nikolova, Stoyan Karabunarliev, Gerald T. Ankley, Bjorn Hansen
Steven P. Bradbury
Recently we described the Common REactivity PAttern (COREPA) technique to screen data sets of diverse structures for their ability to serve as ligands for steroid hormone receptors [1]. The approach identi®es and quanti®es similar global and local stereoelectronic characteristics associated with active ligands through a comparison of energeticallyreasonable conformer distributions for selected descriptors. For each stereoelectronic descriptor selected, discrete conformer distributions from a training set of ligands are evaluated and parameter ranges common for conformers from all the chemicals in the training set are identi®ed. The use of discrete partitions of parameter ranges to de®ne common reactivity patterns can, however, …
Biotransformation Of 4-Methoxyphenol In Rainbow Trout (Oncorhynchus Mykiss) Hepatic Microsomes, Steven P. Bradbury, R. Kolanczyk, P. Schmieder, T. Spizzo
Biotransformation Of 4-Methoxyphenol In Rainbow Trout (Oncorhynchus Mykiss) Hepatic Microsomes, Steven P. Bradbury, R. Kolanczyk, P. Schmieder, T. Spizzo
Steven P. Bradbury
Rainbow trout liver microsomes were used to study the O-demethylation and ring hydroxylation of 4-methoxyphenol (4-MP) (4-hydroxyanisole) at 11 and 25°C by directly measuring the production of the primary metabolite hydroquinone (HQ), 4-methoxycatechol (4-MCAT), and additional metabolites. An HPLC method with integrated ultraviolet (UV) and electrochemical detection (ECD) was developed for metabolite identification and quantification at low concentrations. Sample handling with appropriate buffers, solvents, low temperature and light prevented loss of extremely labile metabolites. Saturation kinetics for the production of HQ via O-demethylation of 4-MP (0.66–40 mM) was never achieved, with substrate solubility being the limiting factor. The linear rate …
Temporal Changes In Purity And Specific Activity Of Tritium-Labeled 2,3,7,8-Tetrachlorodibenzo-Ρ-Dioxin: Radiopurity Model For Toxicology, Steven P. Bradbury, Joseph D. Fernandez, Philip M. Cook, Brian C. Butterworth
Temporal Changes In Purity And Specific Activity Of Tritium-Labeled 2,3,7,8-Tetrachlorodibenzo-Ρ-Dioxin: Radiopurity Model For Toxicology, Steven P. Bradbury, Joseph D. Fernandez, Philip M. Cook, Brian C. Butterworth
Steven P. Bradbury
The specific activity (S) and radiopurity (R) of tritium labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin, [3H]TCDD, were measured by gas chromatography/mass spectrometry (GC/ MS) while attempting to accurately characterize TCDD doses received by invertebrates, fish, and fish embryos during several toxicology studies conducted over a 3 year period. The [3H]TCDD sample was found to consist of six TCDD analogues involving hydrogen, deuterium, and tritium substitution at the 1,6-dibenzo-p-dioxin carbon positions and a complex mixture of impurities (with and without tritium labels). Planar aromatic impurities were identified as tolyl- TCDD adducts and appeared to result from the decay of 3H radiolabels to produce TCDD carbocations …
New Testing Apparatus For Assessing Interactive Effects Of Suspended Solids And Chemical Stressors On Plankton Invertebrates, Steven P. Bradbury, Carl Herbrandson, Deborah L. Swackhamer
New Testing Apparatus For Assessing Interactive Effects Of Suspended Solids And Chemical Stressors On Plankton Invertebrates, Steven P. Bradbury, Carl Herbrandson, Deborah L. Swackhamer
Steven P. Bradbury
To better predict and interpret the responses of aquatic organisms to environmentally relevant chemical exposures, it is necessary to investigate the combined effects of physical (e.g., suspended solids) and chemical stressors. One of the limitations in investigating suspended solids–chemical interactions has been the lack of an appropriate testing system. The specific objective of the current study was to develop and assess a suspended solids testing apparatus (SSTA) for studies on the combined effects of suspended solids and chemicals on aquatic invertebrates. The SSTA was designed to permit the assessment of varying suspended solids concentrations on Daphnia magna at a constant …
A Kinetic Analysis Of The Conformational Flexibility Of Steroid Hormones, Steven P. Bradbury, Julian Ivanov, Ovanes Mekenyan, Gerritt Schüürmann
A Kinetic Analysis Of The Conformational Flexibility Of Steroid Hormones, Steven P. Bradbury, Julian Ivanov, Ovanes Mekenyan, Gerritt Schüürmann
Steven P. Bradbury
For a set of 10 androgen steroids and estradiol (E2), the kinetic feasibility of conformation flexibility of the cyclic moieties was studied under the constraint of maintaining the B/C trans and C/D trans ring fusion of the natural and biologically active enantiomer. To this end, the conformational energy surface was quantified using the semiempirical quantum chemical AM1 model. The computational analysis included the location of Conformational transition states with associated barriers, and intrinsic reaction coordinate (IRC) calculations to characterize the trajectories of the rotations and the relationships of the transition states to neighbouring chair and twist conformations. Conformational transformations were …
Neurological Effects On Startle Response And Escape From Predation By Medaka Exposed To Organic Chemicals, Steven P. Bradbury, Richard W. Carlson, Robert A. Drummond, Dean E. Hammermeister
Neurological Effects On Startle Response And Escape From Predation By Medaka Exposed To Organic Chemicals, Steven P. Bradbury, Richard W. Carlson, Robert A. Drummond, Dean E. Hammermeister
Steven P. Bradbury
Simultaneous electrophysiological and behavioral studies were performed on 21–32 day old juvenile medaka (Oryzias latipes) exposed at sublethal concentrations to organic chemicals representing various modes of action. Non-invasive recordings were made of the electrical impulses generated within giant neuronal Mauthner cells, associated interneurons and motoneurons, and axial musculature, all of which initiate the startle or ‘escape’ response in fish. Timing in ms between these electrical sequelae was measured for each fish before and after 24 and 48 h exposure to a chemical. Carbaryl and phenol affected Mauthner cell to motoneuron transmission while chlorpyrifos, carbaryl, phenol and 2,4-dinitrophenol (DNP) showed neuromuscular …
A Comparative Study Of Molecular Similarity, Statistical, And Neural Methods For Predicting Toxic Modes Of Action, Steven P. Bradbury, Subhash C. Basak, Gregory D. Grunwald, George E. Host, Gerald J. Niemi
A Comparative Study Of Molecular Similarity, Statistical, And Neural Methods For Predicting Toxic Modes Of Action, Steven P. Bradbury, Subhash C. Basak, Gregory D. Grunwald, George E. Host, Gerald J. Niemi
Steven P. Bradbury
Quantitative structure–activity relationship (QSAR) models are routinely used in predicting toxicologic and ecotoxicologic effects of untested chemicals. One critical factor in QSAR-based risk assessment is the proper assignment of a chemical to a mode of action and associated QSAR. In this paper, we used molecular similarity, neural networks, and discriminant analysis methods to predict acute toxic modes of action for a set of 283 chemicals. The majority of these molecules had been previously determined through toxicodynamic studies in fish to be narcotics (two classes), electrophiles/proelectrophiles, uncouplers of oxidative phosphorylation, acetylcholinesterase inhibitors, and neurotoxicants. Nonempirical parameters, such as topological indices and …
The Role Of Ligand Flexibility In Predicting Biological Activity: Structure–Activity Relationships For Aryl Hydrocarbon, Estrogen, And Androgen Receptor Binding Affinity, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley
The Role Of Ligand Flexibility In Predicting Biological Activity: Structure–Activity Relationships For Aryl Hydrocarbon, Estrogen, And Androgen Receptor Binding Affinity, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley
Steven P. Bradbury
Recent studies indicate that the potency and agonist or antagonist activity of steroid hormone ligands are dependent, in part, on ligand–receptor binding affinity as well as the conformation of the ligand–receptor complex. The binding of ligands to hormone receptors is thought to involve interactions by which shapes of both the receptor and ligand are modified in the formation of the ligand–receptor complex. As a consequence, it is essential to explore the significance of ligand flexibility in the development of screening-level structure–activity relationships. In this review, examples are provided of techniques used to generate and screen ligand conformers in the development …
Predicting Modes Of Toxic Action From Chemical Structure: Acute Toxicity In The Fathead Minnow (Pimephales Promelas), Steven P. Bradbury, Christine L. Russom, Steven J. Broderius, Dean E. Hammermeister, Robert A. Drummond
Predicting Modes Of Toxic Action From Chemical Structure: Acute Toxicity In The Fathead Minnow (Pimephales Promelas), Steven P. Bradbury, Christine L. Russom, Steven J. Broderius, Dean E. Hammermeister, Robert A. Drummond
Steven P. Bradbury
In the field of aquatic toxicology, quantitative structure-activity relationships (QSARs) have developed as scientifically credible models for predicting the toxicity of chemicals when little or no empirical data are available. In recent years, there has been an evolution of QSAR development and application from that of a chemical-class perspective to one that is more consistent with assumptions regarding modes of toxic action. The objective of this research was to develop procedures that relate modes of acute toxic action in the fathead minnow (Pimephales promelas) to chemical structures and properties. An empirically derived database for diverse chemical structures of acute toxicity …
Acute Toxicity And Behavioral Effects Of Chlorpyrifos, Permethrin, Phenol, Strychnine, And 2,4-Dinitrophenol To 30-Day-Old Japanese Medaka (Oryzias Latipes), Steven P. Bradbury, Patricia J. Rice, Charles D. Drewes, Theresa M. Klubertanz, Joel R. Coats
Acute Toxicity And Behavioral Effects Of Chlorpyrifos, Permethrin, Phenol, Strychnine, And 2,4-Dinitrophenol To 30-Day-Old Japanese Medaka (Oryzias Latipes), Steven P. Bradbury, Patricia J. Rice, Charles D. Drewes, Theresa M. Klubertanz, Joel R. Coats
Steven P. Bradbury
Five chemicals with different modes of action were evaluated in laboratory studies to determine their acute toxicity (48-h median lethal concentration [LC50]) and behavioral effects on 30-d-old Japanese medaka (Oryzias latipes). The order of toxicity for these xenobiotics was permethrin > chlorpyrifos > 2,4-dinitrophenol (2,4-DNP) > strychnine > phenol. The 48-h LC50s were significantly different and ranged from 0.011 to 24.1 mg/L. In addition, chlorpyrifos and permethrin accumulated in the tissues of juvenile O. latipes. Observations of five behavioral/morphological responses, including changes in equilibrium, general activity, startle response, and morphology (e.g., hemorrhage and deformities) were used as indicators of sublethal toxicity. Each chemical, with …
A Computationally-Based Hazard Identification Algorithm That Incorporates Ligand Flexibility. 1. Identification Of Potential Androgen Receptor Ligands, Steven P. Bradbury, Ovanes Mekenyan, Julian Ivanov, Stoyan Karabunarliev, Gerald T. Ankley, Walter Karcher
A Computationally-Based Hazard Identification Algorithm That Incorporates Ligand Flexibility. 1. Identification Of Potential Androgen Receptor Ligands, Steven P. Bradbury, Ovanes Mekenyan, Julian Ivanov, Stoyan Karabunarliev, Gerald T. Ankley, Walter Karcher
Steven P. Bradbury
To advance techniques for screening large data sets of diverse structures for toxicologically active compounds, an algorithm was developed that is not dependent upon a predetermined and specified toxicophore or an alignment of conformers to a lead compound. Instead, the approach provides the means to identify and quantify specific global and local stereoelectronic characteristics associated with active compounds through a comparison of energeticallyreasonable conformer distributions for specific descriptors. To illustrate the algorithm, the stereoelectronic requirements associated with the binding affinity of 28 steroidal and non-steroidal ligands to the androgen receptor were defined. Common ranges of interatomic distances, atomic charges, and …
Influence Of Geographic Origin And Soil Properties On Color Of Black Walnut Veneer, Douglas D. Stokke, Edward C. Workman Jr., John E. Phelps, Felix Ponder Jr.
Influence Of Geographic Origin And Soil Properties On Color Of Black Walnut Veneer, Douglas D. Stokke, Edward C. Workman Jr., John E. Phelps, Felix Ponder Jr.
Douglas D. Stokke
Walnut veneer frorn sites in Missouri, Illinois, and Indiana was analyzed for color attributes and chemical properties. Veneer color also was compared to an industry color standard. Soil chemical and physical properties were measured on selected sites in each state. In general, walnut trees grown on soils with equal proportions of sand, silt, and clay have better veneer color attributes than trees grown on soils with high clay I sand or clay I silt ratios.
Quantitative Structure-Activity Relationships For Polychlorinated Hydroxybiphenyl Estrogen Receptor Binding Affinity: An Assessment Of Conformer Flexibility, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley
Quantitative Structure-Activity Relationships For Polychlorinated Hydroxybiphenyl Estrogen Receptor Binding Affinity: An Assessment Of Conformer Flexibility, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley
Steven P. Bradbury
A diverse group of xenobiotics has a high binding affinity to the estrogen receptor (ER), suggesting that it can accommodate large variability in ligand structure. Relationships between xenobiotic structure, binding affinity, and estrogenic response have been suggested to be dependent on the conformational structures of the ligands. To explore the influence of conformational flexibility on ER binding affinity, a quantitative structure—activity relationship (QSAR) study was undertaken with estradiol, diethylstilbestrol, and a set of polychlorinated hydroxybiphenyls (PCHBs) of environmental concern. Although the low-energy minima of the PCHB congeners suggested that interconversions among conformers were likely, the electronic parameters associated with the …
Estimating One-Electron Reduction Potentials Of Quinones, Steven P. Bradbury, Ovanes G. Mekenyan, V. B. Kamenska
Estimating One-Electron Reduction Potentials Of Quinones, Steven P. Bradbury, Ovanes G. Mekenyan, V. B. Kamenska
Steven P. Bradbury
The one-electron reduction potential ∗ E1 7 of benzo-, naphtho-and anthracenequinones is related to their ability to undergo redox cycling and elicit cytotoxicity through oxidative stress. To evaluate a general approach to estimate the E1 7 of benzo-, naphtho-and anthracenequinones, QSAR approaches based on gas phase and solvation based methods were employed. Stereoelectronic descriptors of ground state quinones, respective intermediates of the redox cycle, and the di erences in parameters for the transition between intermediates were evaluated. The variation of E1 7 was correlated with descriptors of the parent quinones and speci c transition parameters. The energy of the highest …
Presettlement Vegetation Of The Lower Chippewa River Valley, Lisa A. Schulte-Moore, William J. Barnes
Presettlement Vegetation Of The Lower Chippewa River Valley, Lisa A. Schulte-Moore, William J. Barnes
Lisa A. Schulte Moore
The lower Chippewa River of west-central Wisconsin is the portion that flows southwest from the city of Eau Claire to the Mississippi River at Nelson. The river has a gentle gradient of about 0.8 m/km and highly erodible banks of sand and gravel. The river valley occurs between 35 m to 70 m below the surrounding upland, is between 1 and 5 km wide, and was formed primarily by glacial meltwaters. The floodplain is defined by annual high water levels and is generally below the 25 year flood recurrence interval, which on this part of the Chippewa River is >5m …
2,3, 7,8-Tetrachlorodibenzo-P-Dioxin, Steven P. Bradbury
2,3, 7,8-Tetrachlorodibenzo-P-Dioxin, Steven P. Bradbury
Steven P. Bradbury
Since 1985, the United States Environmental Protection Agency (USEPA) has classified 2,3,7,8-tetrachloro-p-dioxin (TCDD) as a probable human carcinogen; subsequently, sources of TCDD in the environment have been regulated on the basis of animal cancer rates extrapolated to doses associated with human exposures. Two major activities have prompted the decision to reassess this approach for evaluating TCDD toxicity and its associated risks. First, an epidemiological study of cancer mortality in U.S. chemical workers by the National Institute of Occupational Safety and Health provided evidence of TCDD-mediated human carcinogenicity (Fingerhut et al. 1991 ). Second, at a 1990 Banbury conference a consensus …