bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enantiospecific toxicity of the β-blocker propranolol to Daphnia magna and Pimephales promelas
Authors: Stanley Jacob K. , Ramirez Alejandro J. , Mottaleb Mohammad , Chambliss C. Kevin , Brooks Bryan W 
Published: July 2006

Abstract
Propranolol is a widely prescribed, nonselective β-adrenergic receptor–blocking agent. Propranolol has been detected in municipal effluents from the ng/L to the low-μg/L range. Like many therapeutics and other aquatic contaminants, propranolol is distributed as a racemic mixture ((R,S)-propranolol hydrochloride). Although the (S)-enantiomer is the most active form in mammals (up to 100-fold difference), no information is available regarding the enantiospecific toxicity of propranolol to aquatic organisms. Acute and chronic studies were conducted with Daphnia magna and Pimephales promelas to determine enantiospecific toxicity of propranolol to a model aquatic invertebrate and vertebrate, respectively. Also, enantiospecific effects of propranolol on D. magna heart rate were examined. Propranolol treatment levels were verified using high-performance liquid chromatography/mass spectrometry. Acute (48-h) responses of both organisms were similar for all enantiomer treatments. Chronic P. promelas responses to propranolol enantiomers followed the hypothesized relationship of (S)-propranolol being more toxic than (R)-propranolol, but chronic D. magna responses did not. This is potentially the result of a lack of β-type receptors in cladocerans. No enantiospecific effects on daphnid heart rate were observed in acute exposures. Interestingly, some propranolol enantiomer treatments produced significant increases in reproduction before causing reproduction to decrease at higher treatment levels. To our knowledge, this research represents the first study of enantiospecific toxicity of chiral pharmaceutical pollutants.
Cumulative impacts assessment along a large river, using brown bullhead catfish (Ameiurus nebulosus) populations
Authors: West David W. , Ling Nicholas , Hicks Brendan J. , Tremblay Louis A. , Kim Nick D. , van den Heuvel Michael R. 
Published: July 2006

Abstract
The effects of point-source and diffuse discharges on resident populations of brown bullhead catfish (Ameiurus nebulosus (LeSueur, 1819)) in the Waikato River (New Zealand) were assessed at sites both upstream and downstream of point-source discharges. At each site, the population parameters, relative abundance, age structure, and individual indices, such as condition factor, organ (gonad, liver, and spleen) to somatic weight ratios, and number and size of follicles per female, were assessed. Physiological (blood), biochemical (hepatic ethoxyresorufin-O-deethylase [EROD] and plasma steroids), and other indicators (bile chemistry and liver metals) of exposure or response also were measured. No impacts on brown bullhead health were obvious at individual geothermal, municipal sewage, or thermal discharge sites or cumulatively along the river. Brown bullhead from the bleached kraft mill effluent site showed elevated levels of EROD, decreased numbers of red blood cells, increased numbers of white blood cells, and depressed levels of sex steroids. However, growth rates, condition factor, age structure, and gonadosomatic index suggest that discharges with significant heat or nutrients benefit catfish despite physiological impairment at one site. Consideration of brown bullhead population-level responses to discharges in a monitoring framework revealed three different population-level response patterns resulting from the point-source discharges.
Relative toxicological importance of aqueous and dietary metal exposure to a freshwater crustacean: Implications for risk assessment
Authors: Wilding Joanna , Maltby Lorraine 
Published: July 2006

AbstractAbstract—Aquatic organisms can take up toxicants from water (aqueous exposure) and from food (dietary exposure), yet current environmental regulations often fail to consider the toxic effects of dietary exposure. Such unrealistic exposure scenarios may lead to ineffective water-quality standards or discharge consents that fail to provide adequate protection of the receiving water. Both dietary and aqueous exposure routes contributed to the bioaccumulation of zinc by Gammarus pulex, and both influenced the lethal and sublethal effects of zinc exposure. However, little concordance was found between body burden and magnitude of effect on feeding rate, and the duration of the postexposure response differed between exposure routes. Feeding inhibition, resulting from water-only or simultaneous aqueous and dietary exposure, persisted after the contaminant was removed, but feeding inhibition resulting from dietary exposure alone did not. These results imply that whereas aqueous exposure resulted in either irreversible or slowly reversible physiological damage, feeding inhibition in response to dietary zinc exposure involved an avoidance response. Water-only exposure studies underestimated the effects of simultaneous exposure to contaminated food and contaminated water. Therefore, regarding compounds for which dietary exposure is important, regulatory toxicity tests should either incorporate dietary exposure routes or be subjected to an additional uncertainty factor.
Toxicity of silver in water and sediment to the freshwater amphipodHyalella azteca
Authors: Call Daniel J. , Polkinghorne Christine N. , Markee Thomas P. , Brooke Larry T. , Geiger Dianne L. , Gorsuch Joseph W. , Robillard Kenneth A. 
Published: July 2006

AbstractHyalella azteca was exposed to Ag as AgNO3 over a 10-d period in water and two lake sediments that were selected on the basis of their differences in metal-binding properties. The median lethal concentrations (LC50s) for waterborne exposures were 5.4 and 4.9 μg/L for total and dissolved Ag, respectively. In the sediment containing a lesser quantity of total Ag-binding ligands (i.e., Bond Lake, Douglas County, WI, USA, sediment), an Ag-amended sediment toxicity test resulted in a 10-d LC50 of 0.084 g (i.e., 84,000 μg) Ag/kg dry sediment or 8.6 μg Ag/L of pore water (PW). The no-observed-effect concentration (NOEC) to lowest-observed-effect concentration (LOEC) range was 0.012 to 0.031 g Ag/kg dry sediment, or less than 5.0 to 6.0 μg Ag/L of PW. In the sediment with a greater quantity of total Ag-binding ligands (i.e., West Bearskin Lake, Cook County, MN, USA, sediment), the 10-d LC50 was 2.98 g Ag/kg dry sediment, and the NOEC to LOEC range was 2.15 to 4.31 g Ag/kg dry sediment. Because “dissolved” concentrations of Ag in PW were less than 5.0 μg/L at the critical exposures in the latter test, the bioavailable and toxic form of Ag may have been a weakly associated coprecipitate or colloidal complex with hydrous iron oxides that competitively partitioned to the surface of the gills.
Predicting effects on aquatic organisms from fluctuating or pulsed exposure to pesticides
Authors: Ashauer Roman , Boxall Alistair , Brown Colin 
Published: July 2006

Abstract
Exposure of aquatic nontarget organisms to pesticides almost always occurs as pulses or fluctuating concentrations. Extrapolation from laboratory to field thus depends on an understanding and ability to simulate effects resulting from these types of exposure. This paper reviews models that may be used to predict effects on aquatic organisms resulting from time-varying exposure to pesticides. We evaluate and compare the theoretical basis of these models and their applicability to the simulation of effects from fluctuating exposures. The many different models rest on only a few basic concepts with differing degrees of mechanistic character. Building on this critical review, we select the most appropriate models and propose modifications. Two process-based models, the threshold hazard model and the modified damage assessment model, represent the optimum descriptions that are available at present. They could facilitate a better understanding of the ecotoxicity of different compound and species combinations and even mixtures of noninteracting compounds. The possibility to model lethal and sublethal effects allows applications in risk assessment, standard setting, and ecological modeling.
Influence of salinity and organic carbon on the chronic toxicity of silver to mysids (Americamysis bahia) and silversides (Menidia beryllina)
Authors: Ward Timothy J. , Boeri Robert L. , Hogstrand Christer , Kramer James R. , Lussier Suzanne M. , Stubblefield William A. , Wyskiel Derek C. , Gorsuch Joseph W. 
Published: July 2006

AbstractTests were conducted with mysids (Americamysis bahia) and silversides (Menidia beryllina) to evaluate the influence of salinity and organic carbon on the chronic toxicity of silver. During 7- and 28-d tests conducted at 10, 20, and 30‰ salinity, higher concentrations of dissolved silver generally were required to cause a chronic effect as the salinity of the seawater was increased. The 28-d mysid and silverside 20%-effective concentration values (expressed as dissolved silver) ranged from 3.9 to 60 and from 38 to 170 μg/L, respectively, over the salinity range. This pattern was not observed when the same test results were evaluated against the concentrations of free ionic silver (measured directly during toxicity tests), as predicted by the free-ion activity model. Increasing the concentration of dissolved organic carbon from 1 mg/L to the apparent maximum achievable concentration of 6 mg/L in seawater caused a slight decrease in chronic toxicity to silversides but had no effect on the chronic toxicity to mysids. The possible additive toxicity of silver in both food and water also was investigated. Even at the maximum achievable foodborne concentration, the chronic toxicity of silver added to the water was not affected when silver was also added to the food, based on the most sensitive endpoint (growth). However, although fecundity was unaffected at all five tested concentrations during the test with silver in water only, it was significantly reduced at the two highest waterborne silver concentrations (12 and 24 μg/L) during the test with silver dosed into food and water.
Use of paired fathead minnow (Pimephales promelas) reproductive test. Part 1: Assessing biological effects of final bleached kraft pulp mill effluent using a mobile bioassay trailer system
Authors: Rickwood Carrie J. , Dubé Monique G. , Hewitt L. Mark , Kovacs Tibor G. , Parrott Joanne L. , MacLatchy Deborah L. 
Published: July 2006

AbstractReproductive effects have been recorded in wild fish in waters receiving pulp mill effluent (PME) since the mid to late 1980s. Laboratory assays with fathead minnow (FHM; Pimephales promelas) have been developed to better understand fish responses to PME. However, observations from laboratory studies have been variable, making it difficult to establish cause/effect relationships. A lack of environmental relevance in these laboratory studies may have contributed to the variability observed. The objectives of the present study were, first, to determine the effects of bleached kraft PME (BKME) on FHM under environmentally realistic conditions (i.e., ambient water and effluent quality) and, second, to determine the suitability of pair-breeding FHM to better link BKME-induced changes in indicators at the biochemical, individual, and population levels. A mobile bioassay trailer was situated on-site at a bleached kraft mill for 60 d, allowing supply of both ambient water (Lake Superior, Canada) and final BKME. The reproductive output of FHM was initially assessed for 21 d to obtain baseline data pre-exposure. At the end of the pre-exposure period, selected breeding pairs were exposed to final BKME (100% v/v and 1% v/v) for 21 d. Results demonstrated a stimulatory response pattern at 1% BKME (e.g., increased egg production) compared to control. In the 100% treatment, spawning events were reduced and fewer eggs were produced during the first two weeks of exposure. Exposure to 100% (v/v) BKME also resulted in ovipositor development in males and development of male secondary sex characteristics in females. Obtaining pre-exposure data and use of pair-breeding FHM in this assay gave a sensitive indication of effluent effects and allowed accurate comparisons of endpoints to be made.
Use of paired fathead minnow (Pimephales promelas) reproductive test. Part 2: Source identification of biological effects at a bleached kraft pulp mill
Authors: Rickwood Carrie J. , Dubé Monique G. , Hewitt L. Mark , Kovacs Tibor G. , MacLatchy Deborah L. 
Published: July 2006

AbstractReproductive effects of pulp mill effluents on fish continue to be reported in Canadian waters. Spawning delays, reduced gonad size, and altered levels of sex steroid hormones have been found in both sexes of various fish species exposed to effluents. We initiated a project to identify the source/cause of such effects. In part 1 of this two-part series, we exposed mature adult fathead minnow (FHM; Pimephales promelas) for 21 d to final treated effluent (1% and 100% v/v) from a bleached kraft pulp mill in Terrace Bay (ON, Canada). Results suggested pulp mill effluent from this mill affected reproductive indicators in FHM and effects were dependent on effluent concentration, duration of exposure, and method of data analysis. The main objective of this paper was to use the FHM assay to identify waste stream sources within the mill that affect reproductive indicators. Various process streams were selected, characterized with respect to effluent chemistry and acute toxicity, and a subset was tested on-site with the 21-d FHM bioassay. Results showed that both the combined mill effluent (before secondary treatment) and the combined alkaline stream (CALK) caused both decreased spawning events (∼55% for both streams) and decreased egg production (28 and 74%, respectively), and the CALK stream resulted in significant male ovipositor development. By comparing response patterns we were able to identify the CALK stream as a source of compounds at this mill affecting reproductive indicators in FHM and highlight this stream for further toxicity identification evaluation.
Effect of piperonyl butoxide on permethrin toxicity in the amphipodHyalella azteca
Authors: Amweg Erin L. , Weston Donald P. , Johnson Cathy S. , You Jing , Lydy Michael J. 
Published: July 2006

AbstractPiperonyl butoxide (PBO) is a synergist of pyrethroid pesticides found in many products for structural pest control, mosquito control, and home and garden uses. Because both PBO and pyrethroid residues potentially co-occur in urban creeks, this study determined if environmental levels of PBO were capable of synergizing pyrethroids in the environment. Three types of toxicity tests were conducted with the amphipod Hyalella azteca to determine the minimum PBO concentration required to increase toxicity of the pyrethroid permethrin: Sediment was spiked with permethrin only; permethrin and overlying water spiked with PBO; and permethrin, PBO, and overlying water spiked with PBO. In tests with PBO added to both water and sediment, PBO concentrations of 2.3 μg/L in water and 12.5 μg/kg in sediment reduced the permethrin median lethal concentration (LC50) nearly 50% to 7.3 mg/kg organic carbon (OC). Higher concentrations of PBO increased permethrin toxicity up to sevenfold. In exposures with PBO in water alone, 11.3 μg/L was required to increase permethrin toxicity. Urban creek sediments from California and Tennessee, USA, had PBO concentrations in the low μg/kg range; only one water sample was above the detection limit of 0.05 μg/L. Wetlands in northern California also were sampled after application of pyrethrins and PBO for mosquito abatement. Sediment and water PBO concentrations within 12 h of abatement spraying peaked at 3.27 μg/kg and 0.08 μg/L, respectively. These results suggest that environmental PBO concentrations rarely, if ever, reach concentrations needed to increase pyrethroid toxicity to sensitive organisms, though available data on environmental levels are very limited, and additional data are needed to assess definitively the risk.
Bioavailability of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to the prairie vole (Microtus ochrogaster)
Authors: Fellows Robert J. , Driver Crystal R. , Cataldo Dominic A. , Harvey Scott D. 
Published: July 2006

Abstract
Concerns have been raised over potential bioavailability and biotransfer of energetic materials such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The present study assessed plant-incorporated [14C]RDX and plant-derived [14C]RDX-metabolite ingestion by the prairie vole (Microtus ochrogaster). The animals were fed labeled chow (maximum, ≤ 10 g/d) for 5 or 7 d, followed by a 6- or 4-d chase period. More than 95% of all label presented was recovered in the summed excreta, with 74% of this in the fecal nonabsorbed bulk. Greater than 20% of the presented [14C]RDX and plant-derived [14C]RDX metabolites were absorbed by the animals' digestive tracts. These materials were either metabolized to 14CO2 (8–10% of the total label) or removed as nitrogenous waste through the kidneys (10–14%). Both 14C-urine and 14CO2 excretion continued after the feces cleared, indicating ongoing metabolism of the labeled material. Approximately 4% was retained within the tissues at death, with the highest total activity in the liver and the highest specific activity in the testes. Other labeled tissues included the lung, heart, brain, spleen, skeletal muscle, bone, and pancreas. All these tissues containing [14C]RDX-derived materials are available to subsequent predators, indicating a potential for transfer to a higher trophic level.
Chronic sublethal sediment toxicity testing using the estuarine amphipod,Melita plumulosa(Zeidler): Evaluation using metal-spiked and field-contaminated sediments
Authors: Gale Sharyn A. , King Catherine K. , Hyne Ross V. 
Published: July 2006

AbstractThe present study describes the development of a 42-d chronic sublethal sediment toxicity test using the estuarine amphipod Melita plumulosa (Zeilder). This test was shown to predict the toxicity of metal-contaminated sediments previously found to adversely affect benthic community structure. Metals initially were tested individually by spiking reference sediment under conditions that ensured low metal concentrations in pore waters. Fertility was the most sensitive sublethal endpoint for copper- and zinc-spiked sediments, whereas cadmium-spiked sediments were not toxic to M. plumulosa, despite their high bioaccumulation of cadmium. The 42-d chronic sediment test was reproducible; however, variation between reference sediments collected from the same field location over time or from different locations did affect the reproduction of M. plumulosa. Sensitivity of M. plumulosa to metal-spiked sediments suggested that the interim sediment-quality guidelines (ISQGs) were too conservative. However, toxicity testing of sediments collected from field sites known to affect community assemblages significantly (p &lt; 0.001) reduced the fertility of M. plumulosa, reflecting benthic community survey results and supporting the ISQGs. Bioaccumulation of cadmium and copper by M. plumulosa was elevated following chronic exposure to both laboratory and field-contaminated sediments; however, zinc bioaccumulation could be measured only in M. plumulosa exposed to field-contaminated sediments.
Linking feeding activity and maturation of Daphnia magna following short-term exposure to fenvalerate
Authors: Reynaldi Sebastián , Duquesne Sabine , Jung Klaus , Liess Matthias 
Published: July 2006

Abstract
Feeding activity and maturation were investigated in Daphnia magna exposed to fenvalerate for 24 h. The feeding activity was monitored by measuring filtration rates and 15N-traced food assimilation. Exposure resulted in individuals with reduced feeding activity and smaller body size at concentrations of 0.3 μg/L or greater as well as delayed maturation at concentrations of 0.6 μg/L or greater. Filtration rates recovered within 2 d of the exposure, but long-term effects of reduced feeding activity, such as growth retardation, occurred. Because D. magna needs to reach a minimum size to mature, growth retardation may explain the observed delay in maturity. The proposed causal relationships suggest that exposure to fenvalerate reduces feeding activity, resulting in growth retardation, which leads to delayed maturity. In cases of exposure to such toxicants, the monitoring of feeding activity may predict long-term effects on population parameters.
Comparing cytotoxicity and genotoxicity in HaCaT cells caused by 6-aminochrysene and 5,6-chrysenequinone under ultraviolet A irradiation
Authors: Zhang Yi , Hwang Huey-Min , Ekunwe Stephen 
Published: July 2006

Abstract
Chrysene is one of the basic polycyclic aromatic hydrocarbons that are toxic environmental pollutants. The photoproducts of 6-aminochrysene (6AC) include 5,6-chrysenequinone (5,6-CQ) along with some minor products. In this study, cytotoxicity and genotoxicity of 6AC and 5,6-CQ to a human skin cell line, HaCaT, were measured with the fluorescein diacetate uptake (FDA) test and comet assay, respectively, in the presence or absence of ultraviolet A (UVA) irradiation. The FDA test result showed that HaCaT cell viability decreased dose dependently after exposure to UVA irradiation in both 6AC (0, 0.1, 0.5, 1, 5, 10, 50 μM) and 5,6-CQ (0, 0.05, 0.25, 0.5, 2.5, 5, 25 μM) groups, with the 6AC group having lower cell viability at the same substrate concentrations; therefore, 6AC was more cytotoxic. Results of the comet assay showed that the extent of DNA damage was also dose dependent after the combined UVA and 6AC treatment (0, 0.05, 0.1, 0.5, 1 μM), although no DNA damage was detectable in the 6AC group without UVA irradiation. In addition, no DNA damage was found in the 5,6-CQ group with or without UVA irradiation. Our study indicated that 5,6-CQ, the major photoproduct of 6AC, was less photocytotoxic than the parent compound and was not photogenotoxic to HaCaT cells under the experimental conditions.
Multisubstrate biodegradation kinetics for binary and complex mixtures of polycyclic aromatic hydrocarbons
Authors: Knightes Christopher D. , Peters Catherine A. 
Published: July 2006

Abstract
Biodegradation kinetics were studied for binary and complex mixtures of nine polycyclic aromatic hydrocarbons (PAHs): Naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 2-ethylnaphthalene, phenanthrene, anthracene, pyrene, fluorene, and fluoranthene. Discrepancies between the observed biodegradation rates and those predicted by a sole-substrate model indicate that significant substrate interactions occurred in both the binary and complex-mixture experiments. For all compounds except naphthalene, biodegradation was enhanced. The observations were compared to predictions from two multisubstrate biodegradation kinetic models: One that accounts for competitive inhibition, and one that does not. Both models are fully predictive in that parameters had been determined from an independent set of sole-substrate experiments. In the binary experiments, the major multisubstrate effect was biomass enhancement as a result of growth on naphthalene. Substrate interactions were orders of magnitude larger for most compounds in the complex mixtures, but significant competitive inhibition effects counteracted some of the biomass enhancement effect. The present study has demonstrated that the sole-substrate model is inadequate to describe multisubstrate biodegradation kinetics for a broad range of PAH mixtures. Whereas the multisubstrate model without inhibition did an adequate job of predicting the observed effects in some cases, we advocate the use of the multisubstrate model with inhibition for similar modeling efforts in light of the evidence that the model was correct more often than not. Theory supports its use because of the common enzyme pathways for biodegradation of PAHs.