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O'Brien TE, Silcox JW. Nonlinear Regression Modelling: A Primer with Applications and Caveats. Bull Math Biol 2024; 86:40. [PMID: 38489047 PMCID: PMC10943168 DOI: 10.1007/s11538-024-01274-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 02/21/2024] [Indexed: 03/17/2024]
Abstract
Use of nonlinear statistical methods and models are ubiquitous in scientific research. However, these methods may not be fully understood, and as demonstrated here, commonly-reported parameter p-values and confidence intervals may be inaccurate. The gentle introduction to nonlinear regression modelling and comprehensive illustrations given here provides applied researchers with the needed overview and tools to appreciate the nuances and breadth of these important methods. Since these methods build upon topics covered in first and second courses in applied statistics and predictive modelling, the target audience includes practitioners and students alike. To guide practitioners, we summarize, illustrate, develop, and extend nonlinear modelling methods, and underscore caveats of Wald statistics using basic illustrations and give key reasons for preferring likelihood methods. Parameter profiling in multiparameter models and exact or near-exact versus approximate likelihood methods are discussed and curvature measures are connected with the failure of the Wald approximations regularly used in statistical software. The discussion in the main paper has been kept at an introductory level and it can be covered on a first reading; additional details given in the Appendices can be worked through upon further study. The associated online Supplementary Information also provides the data and R computer code which can be easily adapted to aid researchers to fit nonlinear models to their data.
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Affiliation(s)
- Timothy E O'Brien
- Department of Mathematics and Statistics, Loyola University Chicago, Chicago, IL, USA.
| | - Jack W Silcox
- Department of Psychology, University of Utah, Salt Lake City, UT, USA
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2
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Wang P, Ma Y, Xu S, Wang YX, Zhang Y, Lou X, Li M, Wu B, Gao G, Yin P, Liu N. MOVER-R and Penalized MOVER-R Confidence Intervals for the Ratio of Two Quantities. AM STAT 2023; 77:381-389. [PMID: 38188694 PMCID: PMC10769102 DOI: 10.1080/00031305.2023.2173294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 01/08/2023] [Indexed: 02/02/2023]
Abstract
Developing a confidence interval for the ratio of two quantities is an important task in statistics because of its omnipresence in real world applications. For such a problem, the MOVER-R (method of variance recovery for the ratio) technique, which is based on the recovery of variance estimates from confidence limits of the numerator and the denominator separately, was proposed as a useful and efficient approach. However, this method implicitly assumes that the confidence interval for the denominator never includes zero, which might be violated in practice. In this article, we first use a new framework to derive the MOVER-R confidence interval, which does not require the above assumption and covers the whole parameter space. We find that MOVER-R can produce an unbounded confidence interval, just like the well-known Fieller method. To overcome this issue, we further propose the penalized MOVER-R. We prove that the new method differs from MOVER-R only at the second order. It, however, always gives a bounded and analytic confidence interval. Through simulation studies and a real data application, we show that the penalized MOVER-R generally provides a better confidence interval than MOVER-R in terms of controlling the coverage probability and the median width.
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Affiliation(s)
- Peng Wang
- Department of Epidemiology and Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yilei Ma
- Department of Epidemiology and Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Siqi Xu
- Department of Statistics and Actuarial Science, The University of Hong Kong, Hong Kong, China
| | - Yi-Xin Wang
- Department of Nutrition, Harvard TH Chan School of Public Health, Boston
| | - Yu Zhang
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, Bloomington
| | - Xiangyang Lou
- Department of Biostatistics, College of Public Health and Health Professions and College of Medicine, University of Florida, Gainesville
| | - Ming Li
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, Bloomington
| | - Baolin Wu
- Department of Epidemiology and Biostatistics, Program in Public Health, University of California, Irvine
| | - Guimin Gao
- Department of Public Health Sciences, University of Chicago, Chicago
| | - Ping Yin
- Department of Epidemiology and Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Nianjun Liu
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, Bloomington
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Berfelo T, Doll RJ, Krabbenbos IP, Buitenweg JR. Observing Altered Nociceptive Detection Thresholds in Patients With Persistent Spinal Pain Syndrome Type 2 With a Dorsal Root Ganglion Stimulator. Neuromodulation 2022; 25:1006-1014. [DOI: 10.1016/j.neurom.2021.10.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 10/08/2021] [Accepted: 10/19/2021] [Indexed: 11/25/2022]
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Wang P, Xu S, Wang Y, Wu B, Fung WK, Gao G, Liang Z, Liu N. Penalized Fieller's confidence interval for the ratio of bivariate normal means. Biometrics 2021; 77:1355-1368. [PMID: 32865227 PMCID: PMC7914261 DOI: 10.1111/biom.13363] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 03/30/2020] [Indexed: 11/29/2022]
Abstract
Constructing a confidence interval for the ratio of bivariate normal means is a classical problem in statistics. Several methods have been proposed in the literature. The Fieller method is known as an exact method, but can produce an unbounded confidence interval if the denominator of the ratio is not significantly deviated from 0; while the delta and some numeric methods are all bounded, they are only first-order correct. Motivated by a real-world problem, we propose the penalized Fieller method, which employs the same principle as the Fieller method, but adopts a penalized likelihood approach to estimate the denominator. The proposed method has a simple closed form, and can always produce a bounded confidence interval by selecting a suitable penalty parameter. Moreover, the new method is shown to be second-order correct under the bivariate normality assumption, that is, its coverage probability will converge to the nominal level faster than other bounded methods. Simulation results show that our proposed method generally outperforms the existing methods in terms of controlling the coverage probability and the confidence width and is particularly useful when the denominator does not have adequate power to reject being 0. Finally, we apply the proposed approach to the interval estimation of the median response dose in pharmacology studies to show its practical usefulness.
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Affiliation(s)
- Peng Wang
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, Bloomington, U.S.A
| | - Siqi Xu
- Department of Statistics and Actuarial Science, The University of Hong Kong, Hong Kong, China
| | - Yixin Wang
- Department of Nutrition, Harvard TH Chan School of Public Health, Boston, U.S.A
| | - Baolin Wu
- Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, U.S.A
| | - Wing Kam Fung
- Department of Statistics and Actuarial Science, The University of Hong Kong, Hong Kong, China
| | - Guimin Gao
- Department of Public Health Sciences, University of Chicago, Chicago, U.S.A
| | - Zhijiang Liang
- Department of Public Health, Guangdong Women and Children Hospital, Guangzhou, China
| | - Nianjun Liu
- Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, Bloomington, U.S.A
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Ahmad SF, Gulzar A, Tariq M, Asad MJ. Field Evolved Resistance in Earias vittella (Lepidoptera: Noctuidae) From Punjab, Pakistan Against Commercial Formulations of Bacillus thuringiensis kurstaki. JOURNAL OF ECONOMIC ENTOMOLOGY 2021; 114:2204-2213. [PMID: 34268576 DOI: 10.1093/jee/toab137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Indexed: 06/13/2023]
Abstract
Transgenic commercial cotton expressing Bacillus thuringiensis (Bt) Cry endotoxins or vegetative Vip toxins provide protection to cotton against bollworm attack. Continuous exposure of these targeted pests to cry toxins and to Bt commercial spray formulations has resulted in the development of resistance through natural selection. Spotted bollworm Earias vittella (Noctuidae: Lepidoptera) is considered to be one of the most destructive pests of cotton and okra crops in South Asia including Pakistan and has developed resistance to various synthetic insecticides. In the present study, the level of resistance in field populations of the spotted bollworm E. vittella against Bt Cry toxins has been evaluated for the first time. We collected twelve populations of E. vittella from three districts of Punjab, Pakistan for testing against four commercial Bt formulations containing different strains of B. thuringiensis subspecies kurstaki (Btk) with a range of Cry toxins. Low to high levels of resistance were found in the field populations compared with a laboratory-reared susceptible population of E. vittella (resistance ratios 6 to 111-fold). These results suggest that E. vittella has developed resistance against different Cry toxins after continuous exposure to Bt cotton in field. In order to prevent field control failures, regular insecticide resistance monitoring programs are required together with the use of integrated management approaches, including the use of Bt cotton varieties expressing two or more toxins to delay the development of resistance against Bt toxins in E. vittella.
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Affiliation(s)
- Syed Faisal Ahmad
- Department of Entomology, PMAS-Arid Agriculture University, Rawalpindi, Pakistan
| | - Asim Gulzar
- Department of Entomology, PMAS-Arid Agriculture University, Rawalpindi, Pakistan
| | - Muhammad Tariq
- Department of Entomology, PMAS-Arid Agriculture University, Rawalpindi, Pakistan
| | - Muhammad Javaid Asad
- University Institute of Biochemistry and Biotechnology (UIBB), PMAS Arid Agriculture University, Rawalpindi, Pakistan
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Peng X, Lei C, Sun X. Comparison of Lethal Doses Calculated Using Logit/Probit-Log(Dose) Regressions With Arbitrary Slopes Using R. JOURNAL OF ECONOMIC ENTOMOLOGY 2021; 114:1345-1352. [PMID: 33909080 DOI: 10.1093/jee/toab044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Indexed: 06/12/2023]
Abstract
The median lethal dose (LD50) is commonly used to indicate acute toxicity of an insecticide to an insect species. Approximate confidence intervals for LD50s are often calculated using the Fieller and delta methods. It is often necessary to compare the relative potencies of several insecticides with a population or of one insecticide with different populations. Comparing the LD50s using probit/logit-log(dose) regressions with parallel slopes can be implemented in many software packages, but for the cases with arbitrary slopes are not generally available. We used the glm function in R to calculate and compare lethal doses without assuming equal slopes. Bioassay datasets from the literature fitted using the logit model gave the 95% confidence limits (95% CLs) for the lethal doses using Fieller's theorem and incorporating a heterogeneity factor identical to the 95% CLs determined using the PoloPlus software. The delta method gave 95% CLs identical to the 95% CLs determined using the R drc package. The same datasets fitted using the probit model gave 95% CLs similar to the 95% CLs determined using PoloPlus and the drc package. The natural response rates for the control group were included using Abbott's equation. When the potency ratio method and the z-test were used to identify differences between two lethal doses, and when the χ2 and log likelihood ratio tests were used to determine whether the regression lines were parallel, the conclusions were the same as those gave by PoloPlus and the drc package.
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Affiliation(s)
- Xiaowei Peng
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, Hubei, China
- College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chengfeng Lei
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, Hubei, China
| | - Xiulian Sun
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, Hubei, China
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Observation of Nociceptive Processing: Effect of Intra-Epidermal Electric Stimulus Properties on Detection Probability and Evoked Potentials. Brain Topogr 2021; 34:139-153. [PMID: 33459925 PMCID: PMC7892744 DOI: 10.1007/s10548-020-00816-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/25/2020] [Indexed: 12/30/2022]
Abstract
Monitoring nociceptive processing is a current challenge due to a lack of objective measures. Recently, we developed a method for simultaneous tracking of psychophysical detection probability and brain evoked potentials in response to intra-epidermal stimulation. An exploratory investigation showed that we could quantify nociceptive system behavior by estimating the effect of stimulus properties on the evoked potential (EP). The goal in this work was to accurately measure nociceptive system behavior using this method in a large group of healthy subjects to identify the locations and latencies of EP components and the effect of single- and double-pulse stimuli with an inter-pulse interval of 10 or 40 ms on these EP components and detection probability. First, we observed the effect of filter settings and channel selection on the EP. Subsequently, we compared statistical models to assess correlation of EP and detection probability with stimulus properties, and quantified the effect of stimulus properties on both outcome measures through linear mixed regression. We observed lateral and central EP components in response to intra-epidermal stimulation. Detection probability and central EP components were positively correlated to the amplitude of each pulse, regardless of the inter-pulse interval, and negatively correlated to the trial number. Both central and lateral EP components also showed strong correlation with detection. These results show that both the observed EP and the detection probability reflect the various steps of processing of a nociceptive stimulus, including peripheral nerve fiber recruitment, central synaptic summation, and habituation to a repeated stimulus.
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Widespread Evolution of Molecular Resistance to Snake Venom α-Neurotoxins in Vertebrates. Toxins (Basel) 2020; 12:toxins12100638. [PMID: 33023159 PMCID: PMC7601176 DOI: 10.3390/toxins12100638] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 09/19/2020] [Accepted: 09/22/2020] [Indexed: 02/07/2023] Open
Abstract
Venomous snakes are important subjects of study in evolution, ecology, and biomedicine. Many venomous snakes have alpha-neurotoxins (α-neurotoxins) in their venom. These toxins bind the alpha-1 nicotinic acetylcholine receptor (nAChR) at the neuromuscular junction, causing paralysis and asphyxia. Several venomous snakes and their predators have evolved resistance to α-neurotoxins. The resistance is conferred by steric hindrance from N-glycosylated asparagines at amino acids 187 or 189, by an arginine at position 187 that has been hypothesized to either electrostatically repulse positively charged neurotoxins or sterically interfere with α-neurotoxin binding, or proline replacements at positions 194 or 197 of the nAChR ligand-binding domain to inhibit α-neurotoxin binding through structural changes in the receptor. Here, we analyzed this domain in 148 vertebrate species, and assessed its amino acid sequences for resistance-associated mutations. Of these sequences, 89 were sequenced de novo. We find widespread convergent evolution of the N-glycosylation form of resistance in several taxa including venomous snakes and their lizard prey, but not in the snake-eating birds studied. We also document new lineages with the arginine form of inhibition. Using an in vivo assay in four species, we provide further evidence that N-glycosylation mutations reduce the toxicity of cobra venom. The nAChR is of crucial importance for normal neuromuscular function and is highly conserved throughout the vertebrates as a result. Our research shows that the evolution of α-neurotoxins in snakes may well have prompted arms races and mutations to this ancient receptor across a wide range of sympatric vertebrates. These findings underscore the inter-connectedness of the biosphere and the ripple effects that one adaption can have across global ecosystems.
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Carnesecchi E, Svendsen C, Lasagni S, Grech A, Quignot N, Amzal B, Toma C, Tosi S, Rortais A, Cortinas-Abrahantes J, Capri E, Kramer N, Benfenati E, Spurgeon D, Guillot G, Dorne JLCM. Investigating combined toxicity of binary mixtures in bees: Meta-analysis of laboratory tests, modelling, mechanistic basis and implications for risk assessment. ENVIRONMENT INTERNATIONAL 2019; 133:105256. [PMID: 31683157 DOI: 10.1016/j.envint.2019.105256] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 10/03/2019] [Accepted: 10/09/2019] [Indexed: 05/21/2023]
Abstract
Bees are exposed to a wide range of multiple chemicals "chemical mixtures" from anthropogenic (e.g. plant protection products or veterinary products) or natural origin (e.g. mycotoxins, plant toxins). Quantifying the relative impact of multiple chemicals on bee health compared with other environmental stressors (e.g. varroa, viruses, and nutrition) has been identified as a priority to support the development of holistic risk assessment methods. Here, extensive literature searches and data collection of available laboratory studies on combined toxicity data for binary mixtures of pesticides and non-chemical stressors has been performed for honey bees (Apis mellifera), wild bees (Bombus spp.) and solitary bee species (Osmia spp.). From 957 screened publications, 14 publications provided 218 binary mixture toxicity data mostly for acute mortality (lethal dose: LD50) after contact exposure (61%), with fewer studies reporting chronic oral toxicity (20%) and acute oral LC50 values (19%). From the data collection, available dose response data for 92 binary mixtures were modelled using a Toxic Unit (TU) approach and the MIXTOX modelling tool to test assumptions of combined toxicity i.e. concentration addition (CA), and interactions (i.e. synergism, antagonism). The magnitude of interactions was quantified as the Model Deviation Ratio (MDR). The CA model applied to 17% of cases while synergism and antagonism were observed for 72% (MDR > 1.25) and 11% (MDR < 0.83) respectively. Most synergistic effects (55%) were observed as interactions between sterol-biosynthesis-inhibiting (SBI) fungicides and insecticide/acaricide. The mechanisms behind such synergistic effects of binary mixtures in bees are known to involve direct cytochrome P450 (CYP) inhibition, resulting in an increase in internal dose and toxicity of the binary mixture. Moreover, bees are known to have the lowest number of CYP copies and other detoxification enzymes in the insect kingdom. In the light of these findings, occurrence of these binary mixtures in relevant crops (frequency and concentrations) would need to be investigated. Addressing this exposure dimension remains critical to characterise the likelihood and plausibility of such interactions to occur under field realistic conditions. Finally, data gaps and further work for the development of risk assessment methods to assess multiple stressors in bees including chemicals and non-chemical stressors in bees are discussed.
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Affiliation(s)
- Edoardo Carnesecchi
- Institute for Risk Assessment Sciences (IRAS), Utrecht University, 3584 Utrecht, the Netherlands; Laboratory of Environmental Chemistry and Toxicology, Department of Environmental Health, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, via Mario Negri, 2, 20156 Milano, Italy
| | - Claus Svendsen
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford OX10 8BB, UK
| | | | | | | | | | - Cosimo Toma
- Laboratory of Environmental Chemistry and Toxicology, Department of Environmental Health, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, via Mario Negri, 2, 20156 Milano, Italy
| | - Simone Tosi
- Epidemiology Unit, European Union Reference Laboratory (EURL) for Honeybee Health, University Paris Est, French Agency for Food, Environmental and Occupational Health and Safety, Paris, France
| | - Agnes Rortais
- European Food Safety Authority (EFSA), Scientific Committee and Emerging Risks Unit, Parma, Italy
| | - Jose Cortinas-Abrahantes
- European Food Safety Authority (EFSA), Scientific Committee and Emerging Risks Unit, Parma, Italy
| | - Ettore Capri
- Università Cattolica del Sacro Cuore, Dipartimento di Scienze e Tecnologie Alimentari per una filiera agro-alimentare Sostenibile (DiSTAS), Piacenza, Italy
| | - Nynke Kramer
- Institute for Risk Assessment Sciences (IRAS), Utrecht University, 3584 Utrecht, the Netherlands
| | - Emilio Benfenati
- Laboratory of Environmental Chemistry and Toxicology, Department of Environmental Health, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, via Mario Negri, 2, 20156 Milano, Italy
| | - David Spurgeon
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford OX10 8BB, UK
| | - Gilles Guillot
- International Prevention Research Institute, Lyon, France
| | - Jean Lou Christian Michel Dorne
- European Food Safety Authority (EFSA), Scientific Committee and Emerging Risks Unit, Parma, Italy; School of Biosciences and Phenome Centre Birmingham, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Morris JM, Brinkman SF, Carney MW, Lipton J. Copper toxicity in Bristol Bay headwaters: Part 1-Acute mortality and ambient water quality criteria in low-hardness water. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2019; 38:190-197. [PMID: 30125979 DOI: 10.1002/etc.4252] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 05/02/2018] [Accepted: 08/09/2018] [Indexed: 06/08/2023]
Abstract
The world-class Alaskan Bristol Bay salmon fishery and vast deposits of copper (Cu) and other metals in the watershed warrant further investigation into the potential toxicity of Cu to salmonids under the low water-hardness conditions that occur in the watershed. Therefore we investigated the acute toxicity of Cu to rainbow trout (Oncorhynchus mykiss) and fathead minnows (Pimephales promelas) in low-hardness water (∼ 30 mg/L as CaCO3 ) formulated in the laboratory and collected from the Bristol Bay watershed. The median lethal concentration (LC50) for rainbow trout exposed to Cu in low-hardness laboratory water was 16 μg Cu/L (95% confidence intervals [CIs]: 12, 21; dissolved Cu, filtered to 0.45 μm). The LC50 values for fathead minnows exposed to Cu in low-hardness laboratory water or site water were 29 and 79 μg Cu/L (95% CIs: 23, 35 and 58, 125; dissolved Cu), respectively. The biotic ligand model (BLM) LC50 estimates for these bioassays were 1.3 to 2.3 times higher than the actual LC50 values. We also calculated and analyzed acute Cu water quality criteria, also known as criterion maximum concentration (CMC), using hardness-based methods and the BLM for water samples collected throughout the Bristol Bay watershed in 2007. Biotic ligand model CMCs ranged from 0.05 to 17.5 μg Cu/L and hardness-based CMCs ranged from 2.3 to 6.1 μg Cu/L for the 65 samples analyzed. Our results show the need for site-specific research and subsequent water quality guidelines in low-hardness aquatic habitats. Environ Toxicol Chem 2019;38:190-197. © 2018 SETAC.
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Landes RD, Lensing SY, Hauer-Jensen M. Interval estimators of relative potency in toxicology and radiation countermeasure studies: comparing methods and experimental designs. J Biopharm Stat 2018; 29:348-358. [PMID: 30352015 DOI: 10.1080/10543406.2018.1535500] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The relative potency of one agent to another is commonly represented by the ratio of two quantal response parameters; for example, the LD50 of animals receiving a treatment to the LD50 of control animals, where LD50 is the dose of toxin that is lethal to 50% of animals. Though others have considered interval estimators of LD50, here, we extend Bayesian, bootstrap, likelihood ratio, Fieller's and Wald's methods to estimate intervals for relative potency in a parallel-line assay context. In addition to comparing their coverage probabilities, we also consider their power in two types of dose designs: one assigning treatment and control the same doses vs. one choosing doses for treatment and control to achieve same lethality targets. We explore these methods in realistic contexts of relative potency of radiation countermeasures. For larger experiments (e.g., ≥100 animals), the methods return similar results regardless of the interval estimation method or experiment design. For smaller experiments (e.g., < 60 animals), Wald's method stands out among the others, producing intervals that hold closely to nominal levels and providing more power than the other methods in statistically efficient designs. Using this simple statistical method within a statistically efficient design, researchers can reduce animal numbers.
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Affiliation(s)
- Reid D Landes
- a Department of Biostatistics , University of Arkansas for Medical Sciences , Little Rock , Arkansas , USA
| | - Shelly Y Lensing
- a Department of Biostatistics , University of Arkansas for Medical Sciences , Little Rock , Arkansas , USA
| | - Martin Hauer-Jensen
- b Division of Radiation Health , University of Arkansas for Medical Sciences, and Central Arkansas Veterans Healthcare System , Little Rock , Arkansas , USA
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O'Shaughnessy KA, Forth H, Takeshita R, Chesney EJ. Toxicity of weathered Deepwater Horizon oil to bay anchovy (Anchoa mitchilli) embryos. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2018; 148:473-479. [PMID: 29112918 DOI: 10.1016/j.ecoenv.2017.10.052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 10/17/2017] [Accepted: 10/24/2017] [Indexed: 06/07/2023]
Abstract
The BP-contracted Deepwater Horizon Macondo well blowout occurred on 20 April 2010 and lasted nearly three months. The well released millions of barrels of crude oil into the northern Gulf of Mexico, causing extensive impacts on pelagic, benthic, and estuarine fish species. The bay anchovy (Anchoa mitchilli) is an important zooplanktivore in the Gulf, serving as an ecological link between lower trophic levels and pelagic predatory fish species. Bay anchovy spawn from May through November in shallow inshore and estuarine waters throughout the Gulf. Because their buoyant embryos are a dominant part of the inshore ichthyoplankton throughout the summer, it is likely bay anchovy embryos encountered oil in coastal estuaries during the summer and fall of 2010. Bay anchovy embryos were exposed to a range of concentrations of two field-collected Deepwater Horizon oils as high-energy and low-energy water accommodated fractions (HEWAFs and LEWAFs, respectively) for 48h. The median lethal concentrations (LC50) were lower in exposures with the more weathered oil (HEWAF, 1.48µg/L TPAH50; LEWAF, 1.58µg/L TPAH50) compared to the less weathered oil (HEWAF, 3.87µg/L TPAH50; LEWAF, 4.28µg/L TPAH50). To measure delayed mortality and life stage sensitivity between embryos and larvae, an additional 24h acute HEWAF exposure using the more weathered oil was run followed by a 24h grow-out period. Here the LC50 was 9.71µg/L TPAH50 after the grow-out phase, suggesting a toxic effect of oil at the embryonic or hatching stage. We also found that exposures prepared with the more weathered Slick B oil produced lower LC50 values compared to the exposures prepared with Slick A oil. Our results demonstrate that even relatively acute environmental exposure times can have a detrimental effect on bay anchovy embryos.
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Affiliation(s)
| | - Heather Forth
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, CO 80302, USA
| | - Ryan Takeshita
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, CO 80302, USA
| | - Edward J Chesney
- Louisiana Universities Marine Consortium, 8124 Hwy 56, Chauvin, LA 70344, USA
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Hanson AA, Menger-Anderson J, Silverstein C, Potter BD, MacRae IV, Hodgson EW, Koch RL. Evidence for Soybean Aphid (Hemiptera: Aphididae) Resistance to Pyrethroid Insecticides in the Upper Midwestern United States. JOURNAL OF ECONOMIC ENTOMOLOGY 2017; 110:2235-2246. [PMID: 28961778 DOI: 10.1093/jee/tox235] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Indexed: 06/07/2023]
Abstract
Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a damaging invasive pest of soybean in the upper Midwest. Threshold-based insecticide applications are the primary control method for soybean aphid, but few insecticide groups are available (i.e., pyrethroids, organophosphates, and neonicotinoids). To quantify current levels of soybean aphid susceptibility to pyrethroids in the upper Midwest and monitor for insecticide resistance, leaf-dip bioassays were performed with λ-cyhalothrin in 2013-2015, and glass-vial bioassays were performed with λ-cyhalothrin and bifenthrin in 2015 and 2016. Soybean aphids were collected from 27 population-years in Minnesota and northern Iowa, and were compared with a susceptible laboratory colony with no known insecticide exposure since discovery of soybean aphid in North America in 2000. Field-collected aphids from some locations in leaf-dip and glass-vial bioassays had significantly lower rates of insecticide-induced mortality compared with the laboratory population, although field population susceptibility varied by year. In response to sublethal concentrations of λ-cyhalothrin, adult aphids from some locations required higher concentrations of insecticide to reduce nymph production compared with the laboratory population. The most resistant field population demonstrated 39-fold decreased mortality compared with the laboratory population. The resistance documented in this study, although relatively low for most field populations, indicates that there has been repeated selection pressure for pyrethroid resistance in some soybean aphid populations. Integrated pest management and insecticide resistance management should be practiced to slow further development of soybean aphid resistance to pyrethroids.
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Affiliation(s)
- Anthony A Hanson
- Department of Entomology, University of Minnesota, St. Paul, MN 55108
| | | | - Celia Silverstein
- Department of Entomology, University of Minnesota, St. Paul, MN 55108
| | - Bruce D Potter
- University of Minnesota Extension, Southwest Research and Outreach Center, University of Minnesota, Lamberton, MN 56152
| | - Ian V MacRae
- Department of Entomology, Northwest Research and Outreach Center, University of Minnesota, 2900 University Avenue, Crookston, MN 56716
| | - Erin W Hodgson
- Department of Entomology, Iowa State University, Ames, IA 50011
| | - Robert L Koch
- Department of Entomology, University of Minnesota, St. Paul, MN 55108
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14
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Lotufo GR, Farrar JD, Biedenbach JM, Laird JG, Krasnec MO, Lay C, Morris JM, Gielazyn ML. Effects of sediment amended with Deepwater Horizon incident slick oil on the infaunal amphipod Leptocheirus plumulosus. MARINE POLLUTION BULLETIN 2016; 109:253-258. [PMID: 27267114 DOI: 10.1016/j.marpolbul.2016.05.073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 05/04/2016] [Accepted: 05/28/2016] [Indexed: 06/06/2023]
Abstract
Crude oil released from the Deepwater Horizon disaster into the Gulf of Mexico posed potential impacts to infaunal invertebrates inhabiting near shore habitats. The effects of sediment-associated weathered slick oil on the amphipod Leptocheirus plumulosus was assessed using 28-d exposures to total PAH sediment concentrations ranging from 0.3 to 24mg/kg (sum of 50 PAHs or tPAH50). Survival and growth rate were significantly decreased in the 2.6, 11.4 and 24.2mg/kg treatments, but only growth in 5.5mg/kg. Offspring production was dramatically decreased but was variable and significantly different only for 24.2mg/kg. The concentrations associated with 20% decreases relative to reference were 1.05 (95% CI=0-2.89) mg/kg tPAH50 for growth rate and 0.632 (95% CI=0.11-2.15) mg/kg tPAH50 for offspring production. The concentrations of PAHs affecting amphipods are within the range of concentrations measured in marsh areas reportedly impacted by DWH oil after its release.
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Affiliation(s)
- Guilherme R Lotufo
- U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA.
| | - J Daniel Farrar
- U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA
| | - James M Biedenbach
- U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA
| | - Jennifer G Laird
- U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, USA
| | | | | | | | - Michel L Gielazyn
- National Oceanic and Atmospheric Administration, Assessment & Restoration Division, St. Petersburg, FL 33701, USA
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15
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Responsiveness of electrical nociceptive detection thresholds to capsaicin (8 %)-induced changes in nociceptive processing. Exp Brain Res 2016; 234:2505-14. [PMID: 27142052 PMCID: PMC4978767 DOI: 10.1007/s00221-016-4655-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 04/15/2016] [Indexed: 12/25/2022]
Abstract
Pain disorders can be initiated and maintained by malfunctioning of one or several mechanisms underlying the nociceptive function. Psychophysical procedures allow the estimation of nociceptive detection thresholds using intra-epidermal electrical stimuli. By varying the temporal properties of electrical stimuli, various contributions of nociceptive processes to stimulus processing can be observed. To observe the responsiveness of nociceptive thresholds to changes in nociceptive function, a model of capsaicin-induced nerve defunctionalization was used. Its effect on nociceptive detections thresholds was investigated over a period of 84 days. A cutaneous capsaicin (8 %) patch was applied for 60 min to the upper leg of eight healthy human participants. Single- and double-pulse electrical stimuli were presented in a pseudo-random order using an intra-epidermal electrode. Stimuli and corresponding responses were recorded on both treated and untreated skin areas prior to capsaicin application and on days 2, 7, 28, and 84. Increases in electrical detection thresholds at the capsaicin area were observed on days 2 and 7 for single-pulse stimuli. Detection thresholds corresponding to double-pulse stimuli were increased on days 7 and 28, suggesting a delayed and longer lasting effect on double-pulse stimuli. In the present study, it was demonstrated that the responsiveness of detection thresholds to capsaicin application depends on the temporal properties of electrical stimuli. The observation of capsaicin-induced changes by estimation of detection thresholds revealed different time patterns of contributions of peripheral and central mechanisms to stimulus processing.
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16
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Vignier J, Donaghy L, Soudant P, Chu FLE, Morris JM, Carney MW, Lay C, Krasnec M, Robert R, Volety AK. Impacts of Deepwater Horizon oil and associated dispersant on early development of the Eastern oyster Crassostrea virginica. MARINE POLLUTION BULLETIN 2015; 100:426-437. [PMID: 26320981 DOI: 10.1016/j.marpolbul.2015.08.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 07/27/2015] [Accepted: 08/02/2015] [Indexed: 06/04/2023]
Abstract
The explosion of the Deepwater Horizon (DWH) oil platform resulted in large amounts of crude oil and dispersant Corexit 9500A® released into the Gulf of Mexico and coincided with the spawning season of the oyster, Crassostrea virginica. The effects of exposing gametes and embryos of C. virginica to dispersant alone (Corexit), mechanically (HEWAF) and chemically dispersed (CEWAF) DWH oil were evaluated. Fertilization success and the morphological development, growth, and survival of larvae were assessed. Gamete exposure reduced fertilization (HEWAF: EC201h=1650μg tPAH50L(-1); CEWAF: EC201h=19.4μg tPAH50L(-1); Corexit: EC201h=6.9mgL(-1)). CEWAF and Corexit showed a similar toxicity on early life stages at equivalent nominal concentrations. Oysters exposed from gametes to CEWAF and Corexit experienced more deleterious effects than oysters exposed from embryos. Results suggest the presence of oil and dispersant during oyster spawning season may interfere with larval development and subsequent recruitment.
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Affiliation(s)
- J Vignier
- Department of Marine and Ecological Sciences, College of Arts and Sciences, Florida Gulf Coast University, Fort Myers, FL 33965, USA; Laboratoire des Sciences de l'Environnement Marin (UMR 6539-LEMAR), IUEM-UBO, Technopole Brest Iroise, 29280 Plouzané, France
| | - L Donaghy
- Department of Marine and Ecological Sciences, College of Arts and Sciences, Florida Gulf Coast University, Fort Myers, FL 33965, USA
| | - P Soudant
- Laboratoire des Sciences de l'Environnement Marin (UMR 6539-LEMAR), IUEM-UBO, Technopole Brest Iroise, 29280 Plouzané, France
| | - F L E Chu
- Virginia Institute of Marine Science (VIMS), College of William and Mary, Department of Aquatic Health Sciences, Gloucester Point, VA 23062, USA
| | | | | | - C Lay
- Abt Associates, Boulder, CO 80302, USA
| | - M Krasnec
- Abt Associates, Boulder, CO 80302, USA
| | - R Robert
- Ifremer, Unité Littoral, Centre Bretagne - ZI de la Pointe du Diable - CS, 10070-29280 Plouzané, France
| | - A K Volety
- Department of Marine and Ecological Sciences, College of Arts and Sciences, Florida Gulf Coast University, Fort Myers, FL 33965, USA.
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17
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Doll RJ, Maten ACA, Spaan SPG, Veltink PH, Buitenweg JR. Effect of temporal stimulus properties on the nociceptive detection probability using intra-epidermal electrical stimulation. Exp Brain Res 2015; 234:219-27. [PMID: 26438507 PMCID: PMC4713721 DOI: 10.1007/s00221-015-4451-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 09/18/2015] [Indexed: 12/19/2022]
Abstract
Chronic pain disorders can be initiated and maintained by malfunctioning of one or several mechanisms underlying the nociceptive function. Although several quantitative sensory testing methods exist to characterize the nociceptive function, it remains difficult to distinguish the contributions of individual mechanisms. Intra-epidermal electrical stimulation of nociceptive fibers allows defining stimuli with temporal properties within the timescale of these mechanisms. Here, we studied the effect of stimulus properties on the psychophysical detection probability. A psychophysical detection experiment was conducted including 30 healthy human participants. Participants were presented with electrical stimuli having various temporal properties. The pulse-width was varied for single pulse stimuli (either 420 or 840 μs), and the inter-pulse interval for double pulse stimuli (10, 50, or 100 ms). Generalized linear mixed models were used to obtain estimates of thresholds and slopes of the psychophysical function. The 840-μs single pulse resulted in a lower threshold and steeper slope of the psychophysical function than the 420-μs single pulse. Moreover, a double-pulse stimulus resulted in a lower threshold and steeper slope than single pulse stimuli. The slopes were similar between the double pulse stimuli, but thresholds slightly increased with increasing inter-pulse intervals. In the present study, it was demonstrated that varying the temporal properties of intra-epidermal electrical stimuli results in variations in nociceptive processing. The estimated thresholds and slopes corresponding to the selection of temporal properties suggest that contributions of peripheral and central nociceptive mechanisms can be reflected in psychophysical functions.
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Affiliation(s)
- Robert J Doll
- Biomedical Signals and Systems, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Zuidhorst, ZH-222, Drienerlolaan 5, PO BOX 217, Enschede, The Netherlands.
| | - Annefloor C A Maten
- Biomedical Signals and Systems, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Zuidhorst, ZH-222, Drienerlolaan 5, PO BOX 217, Enschede, The Netherlands
| | - Sjoerd P G Spaan
- Biomedical Signals and Systems, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Zuidhorst, ZH-222, Drienerlolaan 5, PO BOX 217, Enschede, The Netherlands
| | - Peter H Veltink
- Biomedical Signals and Systems, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Zuidhorst, ZH-222, Drienerlolaan 5, PO BOX 217, Enschede, The Netherlands
| | - Jan R Buitenweg
- Biomedical Signals and Systems, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Zuidhorst, ZH-222, Drienerlolaan 5, PO BOX 217, Enschede, The Netherlands
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18
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Abstract
Abstract
Background:
Neosaxitoxin (NeoSTX) is a site-1 sodium channel blocker undergoing clinical trials as a prolonged-duration local anesthetic. Rat sciatic block and intravenous infusion models were used to assess efficacy and local and systemic toxicities for NeoSTX in saline (NeoSTX-Saline), bupivacaine (Bup), and their combination (NeoSTX-Bup). Exploratory studies evaluated the effects of addition of epinephrine to NeoSTX-Bup (NeoSTX-Bup-Epi).
Methods:
Rats received percutaneous sciatic blocks with escalating doses of NeoSTX-Saline or NeoSTX-Bup. Sensory-nocifensive block was assessed using modified hotplate and Von Frey filaments. Motor-proprioceptive function was assessed by extensor postural thrust. Nerves were examined histologically after 7 days and scored on the Estebe–Myers scale. Median lethal dose was estimated for NeoSTX-Saline and in combinations. Accidental intravenous overdose was simulated in isoflurane-anesthetized, spontaneously breathing rats receiving NeoSTX-Saline (n = 6), Bup (n = 7), or NeoSTX-Bup (n = 13), with respiratory, hemodynamic, and electrocardiographic endpoints. Additional groups received blocks with NeoSTX-Bup-Epi (n = 80). Investigators were blinded for behavioral and histologic studies.
Results:
NeoSTX-Bup produced more prolonged sensory and motor block compared with NeoSTX-Saline or Bup. NeoSTX-Bup-Epi further prolonged median time to near-complete recovery for 3 μg/kg NeoSTX-Bup (hotplate: 48 vs. 6 h, P < 0.001). With sciatic injections, addition of Bup did not worsen the systemic toxicity (median lethal dose) compared with NeoSTX-Saline. Intravenous NeoSTX-Saline infusion had significantly longer times to apnea, first arrhythmia, and asystole compared with Bup (P < 0.001 for each). Histologic injury scores overall were low for all groups, with median scores of 0 (interquartile range, 0 to 0) on a 5-point scale.
Conclusion:
NeoSTX-Bup and NeoSTX-Bup-Epi hold promise for prolonged-duration local anesthesia.
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19
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Brown-Peterson NJ, Krasnec M, Takeshita R, Ryan CN, Griffitt KJ, Lay C, Mayer GD, Bayha KM, Hawkins WE, Lipton I, Morris J, Griffitt RJ. A multiple endpoint analysis of the effects of chronic exposure to sediment contaminated with Deepwater Horizon oil on juvenile Southern flounder and their associated microbiomes. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2015; 165:197-209. [PMID: 26092636 DOI: 10.1016/j.aquatox.2015.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 06/01/2015] [Accepted: 06/02/2015] [Indexed: 06/04/2023]
Abstract
Exposure to oiled sediments can negatively impact the health of fish species. Here, we examine the effects of chronic exposure of juvenile southern flounder, Paralichthys lethostigma, to a sediment-oil mixture. Oil:sediment mixtures are persistent over time and can become bioavailable following sediment perturbation or resuspension. Juvenile flounder were exposed for 32 days under controlled laboratory conditions to five concentrations of naturally weathered Macondo MC252 oil mixed into uncontaminated, field-collected sediments. The percent composition of individual polycyclic aromatic hydrocarbons (PAHs) of the weathered oil did not change after mixing with the sediment. Spiked exposure sediments contained 0.04-395mg/kg tPAH50 (sum of 50 individual PAH concentration measurements). Mortality increased with both exposure duration and concentration of sediment-associated PAHs, and flounder exposed to concentrations above 8mg/kg tPAH50 showed significantly reduced growth over the course of the experiment. Evident histopathologic changes were observed in liver and gill tissues of fish exposed to more than 8mg/kg tPAH50. All fish at these concentrations showed hepatic intravascular congestion, macrovesicular hepatic vacoulation, telangiectasia of secondary lamellae, and lamellar epithelial proliferation in gill tissues. Dose-dependent upregulation of Cyp1a expression in liver tissues was observed. Taxonomic analysis of gill and intestinal commensal bacterial assemblages showed that exposure to oiled sediments led to distinct shifts in commensal bacterial population structures. These data show that chronic exposure to environmentally-relevant concentrations of oiled sediments produces adverse effects in flounder at multiple biological levels.
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Affiliation(s)
- Nancy J Brown-Peterson
- Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, United States.
| | - Michelle Krasnec
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, Colorado 80302, United States.
| | - Ryan Takeshita
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, Colorado 80302, United States.
| | - Caitlin N Ryan
- The Institute of Environmental and Human Health, Department of Environmental Toxicology, Texas Tech University, Box 41163, Lubbock, TX 79409, United States.
| | - Kimberly J Griffitt
- Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, United States.
| | - Claire Lay
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, Colorado 80302, United States.
| | - Gregory D Mayer
- The Institute of Environmental and Human Health, Department of Environmental Toxicology, Texas Tech University, Box 41163, Lubbock, TX 79409, United States.
| | - Keith M Bayha
- Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, United States.
| | - William E Hawkins
- Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, United States.
| | - Ian Lipton
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, Colorado 80302, United States.
| | - Jeffrey Morris
- Abt Associates, 1881 Ninth Street, Suite 201, Boulder, Colorado 80302, United States.
| | - Robert J Griffitt
- Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, United States.
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20
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Chandrasekhar R, Shi Y, Hutson AD, Wilding GE. A Novel Approach to Testing for Average Bioequivalence Based on Modeling the Within-Period Dependence Structure. J Biopharm Stat 2015; 25:1320-38. [PMID: 25671781 DOI: 10.1080/10543406.2014.1000677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Bioequivalence trials are commonly conducted to assess therapeutic equivalence between a generic and an innovator brand formulations. In such trials, drug concentrations are obtained repeatedly over time and are summarized using a metric such as the area under the concentration vs. time curve (AUC) for each subject. The usual practice is to then conduct two one-sided tests using these areas to evaluate for average bioequivalence. A major disadvantage of this approach is the loss of information encountered when ignoring the correlation structure between repeated measurements in the computation of areas. In this article, we propose a general linear model approach that incorporates the within-subject covariance structure for making inferences on mean areas. The model-based method can be seen to arise naturally from the reparameterization of the AUC as a linear combination of outcome means. We investigate and compare the inferential properties of our proposed method with the traditional two one-sided tests approach using Monte Carlo simulation studies. We also examine the properties of the method in the event of missing data. Simulations show that the proposed approach is a cost-effective, viable alternative to the traditional method with superior inferential properties. Inferential advantages are particularly apparent in the presence of missing data. To illustrate our approach, a real working example from an asthma study is utilized.
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Affiliation(s)
- Rameela Chandrasekhar
- a Department of Biostatistics , Vanderbilt University School of Medicine , Nashville , Tennessee , USA
| | - Yi Shi
- b Department of Biostatistics , University at Buffalo , Buffalo , New York , USA
| | - Alan D Hutson
- b Department of Biostatistics , University at Buffalo , Buffalo , New York , USA
| | - Gregory E Wilding
- b Department of Biostatistics , University at Buffalo , Buffalo , New York , USA
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21
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Goolsby EW, Mason CM, Wojcik JT, Jordan AM, Black MC. Acute and chronic effects of diphenhydramine and sertraline mixtures in Ceriodaphnia dubia. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2013; 32:2866-2869. [PMID: 23996615 DOI: 10.1002/etc.2378] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 04/21/2013] [Accepted: 08/25/2013] [Indexed: 06/02/2023]
Abstract
Ceriodaphnia dubia were tested to evaluate the acute and chronic interactive effects of diphenhydramine and sertraline. Observed effects were compared with 2 reference toxicity models, the concentration addition model and the independent action model. Results indicate that the 2 drugs exhibit additive toxicity in C. dubia. In some cases, individually sublethal concentrations of the chemicals resulted in 100% mortality when combined, demonstrating the potentially severe impact of trace environmental contaminants.
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Affiliation(s)
- Eric W Goolsby
- Department of Environmental Health Science, University of Georgia, Athens, Georgia, USA
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22
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Ritz C, Gerhard D, Hothorn LA. A Unified Framework for Benchmark Dose Estimation Applied to Mixed Models and Model Averaging. Stat Biopharm Res 2013. [DOI: 10.1080/19466315.2012.757559] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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23
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Paige RL, Chapman PL, Butler RW. Small Sample LD50 Confidence Intervals Using Saddlepoint Approximations. J Am Stat Assoc 2011. [DOI: 10.1198/jasa.2011.tm09784] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Carrozzo M, Moscatelli A, Lacquaniti F. Tempo rubato : animacy speeds up time in the brain. PLoS One 2010; 5:e15638. [PMID: 21206749 PMCID: PMC3012081 DOI: 10.1371/journal.pone.0015638] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 11/18/2010] [Indexed: 11/25/2022] Open
Abstract
Background How do we estimate time when watching an action? The idea that events are timed by a centralized clock has recently been called into question in favour of distributed, specialized mechanisms. Here we provide evidence for a critical specialization: animate and inanimate events are separately timed by humans. Methodology/Principal Findings In different experiments, observers were asked to intercept a moving target or to discriminate the duration of a stationary flash while viewing different scenes. Time estimates were systematically shorter in the sessions involving human characters moving in the scene than in those involving inanimate moving characters. Remarkably, the animate/inanimate context also affected randomly intermingled trials which always depicted the same still character. Conclusions/Significance The existence of distinct time bases for animate and inanimate events might be related to the partial segregation of the neural networks processing these two categories of objects, and could enhance our ability to predict critically timed actions.
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Affiliation(s)
- Mauro Carrozzo
- Institute of Neuroscience, National Research Council, Rome, Italy
- Laboratory of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy
| | | | - Francesco Lacquaniti
- Laboratory of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy
- Centre of Space BioMedicine, University of Rome Tor Vergata, Rome, Italy
- Department of Neuroscience, University of Rome Tor Vergata, Rome, Italy
- * E-mail:
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25
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26
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Affiliation(s)
- Gary L Grunkemeier
- Providence Health System Cardiovascular Study Group, Providence Health & Services, Portland, Oregon, USA
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