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- Aquatic toxicology (7)
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- Estrogen receptor ligands (2)
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- Multiple stressors (2)
- One-electron reduction potential (2)
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Articles 31 - 60 of 84
Full-Text Articles in Physical Sciences and Mathematics
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 …
Derivation Of Wildlife Values For Mercury, Steven P. Bradbury, John Nichols, Jeff Swartout
Derivation Of Wildlife Values For Mercury, Steven P. Bradbury, John Nichols, Jeff Swartout
Steven P. Bradbury
A procedure has been developed to estimate surface water concentrations of toxicants (“wildlife values”) that will protect the viability of wildlife populations associated with aquatic resources. This procedure was designed primarily to protect piscivorous birds and mammals from compounds that bioaccumulate in fish and was used in the Great Lakes Water Quality Initiative (GLI) to calculate wildlife values (WV) for mercury, DDT/DDE, total polychlorinated biphenyls (PCBs), and 2,3,7,8-tetrachlorodibenzodioxin (TCDD). Published in 1995, and expressed as total mercury in unfiltered water, the final wildlife value (WVf) for mercury derived in the GLI was 1300 pg Hg/L. This value was selected as …
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 …
Species Delineation And The Identification Of Evolutionarily Significant Units: Lessons From The Freshwater Mussel Genus Potamilus (Bivalvia: Unionidae), Kevin J. Roe, Charles Lydeard
Species Delineation And The Identification Of Evolutionarily Significant Units: Lessons From The Freshwater Mussel Genus Potamilus (Bivalvia: Unionidae), Kevin J. Roe, Charles Lydeard
Kevin J. Roe
Accurate identification of biological entities is critical to the timely and efficient preservation of biodiversity. Concepts that define segments of biological diversity--species and evolutionarily significant units (ESUs)--should reflect our current knowledge of the biological world. Conflation of different hierarchical definitions of taxa has the potential to obscure distinct biological entities in need of protection. The concept of the ESU has been criticized because it includes within its definition distinct biological entities that otherwise would be recognized as species. Herein we evaluate several versions of the evolutionary significant unit concept and provide as a case study an analysis of geographic variation …
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 …
Identification Of A Fish Host Of The Inflated Heelsplitter Potamilus Inflatus( Bivalvia: Unionidae) With A Description Of Its Glochidium, Kevin J. Roe, Andrew M. Simons, Paul Hartfield
Identification Of A Fish Host Of The Inflated Heelsplitter Potamilus Inflatus( Bivalvia: Unionidae) With A Description Of Its Glochidium, Kevin J. Roe, Andrew M. Simons, Paul Hartfield
Kevin J. Roe
A survey of the fishes of the lack Warrior River was undertaken to determine fish host(s) of the federally threatened inflated heelsplitter, Potamilus inflatus. Seven hundred-twenty individual fishes representing 30 species were examined; mussel glochidia were found on 10 individual fishes representing nine species. Potamilus inflatus glochidia were only found infesting one freshwater drum (Aplodinotus grunniens), which is concordant with previous findings for the genus Potamilus. The morphology of P. inflatus glochidia is described and compared to P. purpuratus.
Processing Small Quantities Of Walnut Logs For Lumber And Craft Items, Douglas D. Stokke, Peter Y. S. Chen, J. W. Van Sambeek
Processing Small Quantities Of Walnut Logs For Lumber And Craft Items, Douglas D. Stokke, Peter Y. S. Chen, J. W. Van Sambeek
Douglas D. Stokke
Many walnut plantation owners and woodworking hobbyists would like to process small quantities of walnut logs into lumber and discs for furniture and craft items. Various options exist for sawing, drying, and processing small diameter or short logs into lumber and cross-sectional discs. Portable band saws are a safe and inexpensive log breakdown option to commercial headsaw mills. Processing using the saw-dry-rip method will yield higher quantities of usable lumber from small diameter logs than the conventional saw-rip-dry method. Small quantities of lumber and discs can be inexpensively air dried under shelters or open sheds followed by approximately 15 to …
The Silviculture-Wood Quality Connection In Eastern Black Walnut, Douglas D. Stokke, Bruce E. Cutter, John E. Phelps
The Silviculture-Wood Quality Connection In Eastern Black Walnut, Douglas D. Stokke, Bruce E. Cutter, John E. Phelps
Douglas D. Stokke
The known effects of silvicultural practices on eastern black walnut (Juglans nigra L.) wood quality are reviewed. Since desirable quality differs from end user to end user, no specific recommendations are made.
Risk Analysis Of Black Walnut And Red Oak Plantations, Douglas D. Stokke, Stephen H. Kolison Jr., Jianbang Gan
Risk Analysis Of Black Walnut And Red Oak Plantations, Douglas D. Stokke, Stephen H. Kolison Jr., Jianbang Gan
Douglas D. Stokke
Risks and uncertainties are prevalent in timber production due to the nature and length of the production process. This paper examines the volatility of timber prices and the effects of some economic uncertainties and risks such as fluctuations in timber prices and the interest rate on the economic returns of black walnut and red oak plantations. Historical patterns of timber prices for black walnut and oaks are investigated and compared with those of other timber species and stock price. The sensitivity of economic returns from black walnut and red oak plantations to changes in timber prices and the discount rate …
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 …
Variation In Cell Dimensions And Fibril Angle For Two Fertilized Even-Aged Loblolly Pine Plantations, Douglas D. Stokke, Todd F. Shupe, Elvin T. Choong, Mark D. Gibson
Variation In Cell Dimensions And Fibril Angle For Two Fertilized Even-Aged Loblolly Pine Plantations, Douglas D. Stokke, Todd F. Shupe, Elvin T. Choong, Mark D. Gibson
Douglas D. Stokke
Increment core samples were obtained from randomly selected, nine-year-old lohlolly pine (Pinus faeda L.) in two even-aged plantations in Louisiana in order to determine the variation in cell dimensions and fibril angle of the sites. The Homer site is representative of the growing conditions in north Louisiana, and the Bogalusa site is typical of the conditions in southeastern Louisiana. Both sites were subjected to similar site preparation and weed control and were fertilized in the juvenile period. The anatomical properties that were measured include: fiber length, cell-wall thickness, and microfibril angle (MFA). Observations were made in order to compare corewood …
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 …
Variation In Lightness Of White Oak Dimension Stock, Douglas D. Stokke, Anton D. Pugel, John E. Phelps
Variation In Lightness Of White Oak Dimension Stock, Douglas D. Stokke, Anton D. Pugel, John E. Phelps
Douglas D. Stokke
The objectives of this research were to generate a set of sample parameters for the lightness of planed white oak dimension stock, to investigate the effect of grain angle on lightness values, and to determine the level of sampling needed to color match white oak dimension stock on the basis of lightness or darkness as quantified by the parameter L* (psychometric lightness). This information is important when used to determine the feasibility of low-cost portable instruments for evaluating color in an edge-glued hardwood panel production setting. Color measurements were obtained with a portable spectrophotometer interfaced with a notebook computer. The …
Ecological Risk Assessment For Chemical Stressors: Challenges In Predictive Ecotoxicology Research, Steven P. Bradbury
Ecological Risk Assessment For Chemical Stressors: Challenges In Predictive Ecotoxicology Research, Steven P. Bradbury
Steven P. Bradbury
Environmental management decisions are increasingly based on the results of ecological risk assessments that require data and models to establish the likelihood of adverse ecological effects that may occur or are occurring as a result of exposure to one or more stressors .. Research to support ecological risk assessments for chemical stressors must include a predictive capability.. The great number of chemicals, species and habitats (exposure conditions) associated with prospective and retrospective management decisions precludes the use of empirical testing as the sole means to fill data gaps .. Therefore, strategic laboratory and field testing must be undertaken in the …
Sar Models For Futile Metabolism: One-Electron Reduction Of Quinones, Phenols And Nitrobenzenes, Steven P. Bradbury, Ovanes Mekenyan, G. D. Veith, N. Zaharieva
Sar Models For Futile Metabolism: One-Electron Reduction Of Quinones, Phenols And Nitrobenzenes, Steven P. Bradbury, Ovanes Mekenyan, G. D. Veith, N. Zaharieva
Steven P. Bradbury
Benzoquinones, naphthoquinones and aziridinylbenzoquinones, can be reduced by flavoproteins to semiquinones that react with molecular oxygen to form superoxide anion with the subsequent regeneration of the parent compounds. This redox cycling, a form of futile metabolism, produces reactive oxygen species and depletes the reducing equivalents of cells without concomitant energy production. The ability of a toxicant to redox cycle is related to its one-electron reduction potential, and this study attempted to estimate reduction potential from structure using semi-empirical quantum chemical models for a diverse set of chemicals. The results of this study suggest that one-electron reduction potentials, within structural classes …
Quantitative Structure-Activity Relationships And Ecological Risk Assessment: An Overview Of Predictive Aquatic Toxicology Research, Steven P. Bradbury
Quantitative Structure-Activity Relationships And Ecological Risk Assessment: An Overview Of Predictive Aquatic Toxicology Research, Steven P. Bradbury
Steven P. Bradbury
In the field of aquatic toxicology, quantitative structure-activity relationships (QSARs) have developed as scientifically credible tools for predicting the toxicity of chemicals when little or no empirical data are available. A fundamental understanding of toxicological principles has been considered an important component to the acceptance and application of QSAR approaches as biologically relevant in ecological risk assessments. As a consequence, 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. In this review, techniques to assess modes of toxic action from …
Use Of Knowledge Bases And Qsars To Estimate The Relative Ecological Risk Of Agrichemicals: A Problem Formulation Exercise, Steven P. Bradbury, C. L. Russom, A. R. Carlson
Use Of Knowledge Bases And Qsars To Estimate The Relative Ecological Risk Of Agrichemicals: A Problem Formulation Exercise, Steven P. Bradbury, C. L. Russom, A. R. Carlson
Steven P. Bradbury
Ecological risk assessments can be used to establish the likelihood that an adverse effect will result from exposure to one or more chemicals. When evaluating contaminated sites with many chemicals present, risk assessors must grapple with the problem of quickly identifying the chemicals that are most likely to be of concern, based on effect and exposure assessment information. Many times data gaps exist and the risk assessor is left with decisions on which models to use to estimate the parameter of concern. In the present paper, a procedure is presented for ranking agrichemicals, utilizing the ASTER (ASsessment Tools for the …
Predicting Modes Of Toxic Action From Chemical Structure: An Overview, Steven P. Bradbury
Predicting Modes Of Toxic Action From Chemical Structure: An Overview, Steven P. Bradbury
Steven P. Bradbury
In the field of environmental toxicology, and especially aquatic toxicology, quantitative structure activity relationships (QSARs) have developed as scientifically-credible tools for predicting the toxicity of chemicals when little or no empirical data are available. A basic and fundamental understanding of toxicological principles has been considered crucial to the continued acceptance and application of these techniques as biologically relevant. As a consequence, 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 assessment of a compound’s likely mode of toxic action …
Field Identification Of Birdseye In Sugar Maple (Acer Saccharum Marsh.), Douglas D. Stokke, Don C. Bragg
Field Identification Of Birdseye In Sugar Maple (Acer Saccharum Marsh.), Douglas D. Stokke, Don C. Bragg
Douglas D. Stokke
Birdseye grain distortions in sugar maple must be identified to capture the full value of a timber sale throughout the economic range of birdseye's occurrence. Even when relatively common, birdseye veneer typically makes up less than 1 percent of the harvested volume, but may account for one-half of the value of the sale. With prices recently reaching $50,000 per Mbf for prime logs, omission of birdseye (when present) from cruise data could cause significant economic loss for the forest landowner. But figured wood can sometimes be detected in standing timber (Pillow 1955). Field identification of birdseye sugar maple is critical …