bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transfer of carbon and a polychlorinated biphenyl through the pelagic microbial food web in a coastal ecosystem
Authors: Wallberg Petra , Andersson Agneta 
Published: March 2010

Abstract
In order to estimate fluxes of carbon within the microbial community, seawater was collected in a coastal area off Zanzibar Island, Tanzania, during a rainy season (November 1994) and a dry season (September 1996). Diel experiments were conducted in a 24-L polycarbonate bottle and samples were retrieved every third hour over a period of 30 to 33 h. Abundance and production rates of bacteria, nanoflagellates, and microplankton were determined. To determine possible connections between the fluxes of carbon and the fate of 2,2′,4,4′,5,5′-hexachlorobiphenyl International Union of Pure and Applied Chemistry (IUPAC) no. 153, a time-course experiment was conducted after the diel experiment. The initial PCB partitioning was similar in the two experiments, but the subsequent distribution among the organism groups was different. In the rainy season experiment, the PCB concentration in the largest size fraction was almost three times higher than during the dry season experiment. This was in line with results from the diel experiments where the carbon flux through the microbial food web was approximately three times higher during the rainy season than during the dry season experiment. These results suggest that the transfer rate of 2,2′,4,4′,5,5′-hexachlorobiphenyl through the microbial food web is coupled to the carbon flux.
Mutual in vivo interactions between benzo[a]pyrene and tributyltin in brook trout (Salvelinus fontinalis)
Authors: Padrós Jaime , Pelletier Émilien , Reader Stéphanie , Denizeau Francine 
Published: March 2010

AbstractTributyltin (TBT), an organometal used as an antifouling biocide, has been reported to inhibit cytochrome P450 (P450) 1A isozyme. Benzo[a]pyrene (BaP), a widespread carcinogenic polycyclic aromatic hydrocarbon, is both metabolized and bioac-tivated to carcinogenic BaP diol-epoxide (BPDE) metabolites primarily by hepatic P450 1A. Hence, TBT may inhibit the metabolism and bioactivation of BaP This study was therefore designed to examine the potential in vivo interactions between BaP and TBT in a model fish. Male brook trout (Salvelinus fontinalis) were given a single intraperitoneal injection of either BaP (10 mg/kg), TBT (10 mg/kg), or both in combination. After 48 h, blood, bile, and liver samples were collected and analyzed for a suite of biomarkers associated with P450 activity, BaP metabolism and bioactivation, and TBT metabolism. The results showed that TBT significantly (p &lt; 0.05; two-way analysis of variance) inhibited (a) the induction of hepatic P450 1A-mediated ethoxyresorufin O-deethylase (EROD) and P450-mediated 3-cyano-7-ethoxycoumarin-O-deethylase (CN-ECOD) activities by BaP, (b) the formation of biliary BaP metabolites, and (c) the formation of (+)-anti-BPDE-plasma albumin adducts as measured by high-performance liquid chromatography/fluorescence. Notably, TBT alone did not inhibit EROD activity but induced CN-ECOD activity (p &lt; 0.05). Gas chromatography/mass spectrometry analysis indicated that the combined BaP + TBT dose resulted in higher levels of dibutyltin metabolites in the bile (p &lt; 0.05). The present study supports the hypothesis that a single, high dose of TBT can antagonize the metabolism and bioactivation of BaP at least by inhibiting the induction of P4501A. On the other hand, BaP unexpectedly potentiated the metabolism of TBT, suggesting that hepatic isoforms other than P4501A may be responsible for TBT metabolism. Finally, this study supports the utility of a biomarker approach to screen potential xenobiotic interactions in aquatic organisms and to obtain mechanistic insights.
Methodology for the evaluation of cumulative episodic exposure to chemical stressors in aquatic risk assessment
Authors: Morton Michael G , Dickson Kenneth L , Waller William T , Acevedo Miguel F , Mayer Foster L , Ablan Magdiel 
Published: March 2010

AbstractAn ecological risk assessment method was developed to evaluate the magnitude, duration, and episodic nature of chemical stressors on aquatic communities. The percent of an ecosystem's species at risk from a designated chemical exposure scenario is generated. In effects assessment, probabilistic extrapolation methods are used to generate estimated safe concentrations (ESCs) for an ecosystem using laboratory toxicity test results. Fate and transport modeling is employed to generate temporal stressor concentration profiles. In risk characterization, area under the curve integration is performed on predicted exposure concentration profiles to calculate a cumulative exposure concentration (CEC) for the exposure event. A correction is made to account for the allowable exposure duration to the stressor ESC. Finally, the CEC is applied to the extrapolation model (curve) of the stressor to predict percent species at risk to the episodic exposure. The method may be used for either prospective or retrospective risk assessments. The results of a retrospective risk assessment performed on the Leadenwah Creek, South Carolina, USA, estuarine community are presented as a case study. The creek experienced periodic episodes of pesticide-contaminated agricultural runoff from 1986 through 1989. Although limited biological data were available for method validation, the risk estimates compared well with the Leadenwah Creek in situ bioassay results.
Offspring fitness inDaphnia: Is theDaphniareproduction test appropriate for extrapolating effects on the population level?
Authors: Hammers-Wirtz Monika , Ratte Hans Toni 
Published: March 2010

AbstractIn the Daphnia reproduction test, the number of living offspring per living parent, mortality, and, occasionally, growth and time to first brood are used as endpoints for the determination of no-observed-effect concentration (NOEC)/lowest-observed-effect concentration (LOEC), or 50% effective concentration (EC50). It is known that chemicals can influence not only the number of neonates but also the offspring size (and, thus, possibly the neonate fitness) in daphnids. Changes in neonate size and fitness have not been routinely recorded in Daphnia reproduction tests, although they are an important factor in population growth. Some of our previous research with some dispersants showed clear effects on offspring quality (smaller neonates with enhanced mortality). We tested one of these dispersants in two different test designs: the reproduction test and a population growth experiment. The results from these two experimental designs differed completely: in the reproduction test, the living offspring number was increased (by up to 10.2 mg/L of the dispersant Dispersogen A) in comparison with the control, whereas in the population growth experiment, the population size was already reduced at concentrations of 1.64 mg/L. A F1-reproduction test, conducted in control medium with neonates born in the reproduction test, showed that neonate fitness was significantly reduced at concentrations of 1.64 mg/L and higher. Therefore, it appears absolutely necessary to take neonate fitness into account if we intend to assess population-level effects. This is easily considered in a population growth experiment but not in the Daphnia reproduction test. To evaluate the fitness of the neonates, an additional test with neonates (F1 test) or another test design (population growth experiment) is necessary.
Fate of 2,4,6-trinitrotoluene in axenic sand culture systems containing smooth bromegrass
Authors: Sun Wen-Hao , Horst Garald L , Drijber Rhae A , Elthon Thomas E 
Published: March 2010

Abstract
Plants have the potential to metabolize the munition 2,4,6-trinitrotoluene (TNT) in contaminated soils, sediments, and natural waters. However, microbial interference must be eliminated to demonstrate an intrinsic capacity for the metabolism of TNT by plants. An axenic sand culture system for smooth bromegrass (Bromus inermis Leyss) was established to investigate the influence of TNT on smooth bromegrass growth and metabolism. Shoot length growth was inhibited by 40% after 14 d of exposure to TNT at 36 mg/L in the sand solution, whereas photosynthetic and respiration rates were similar to controls. Addition of [14C]-labeled TNT to the system resulted in the roots containing 21.3% and the shoots containing 3.8% of the radioactivity. The [14C]TNT in media that contained plants was reduced about 50% compared to media without plants. Trace amounts (0.03%) of the initial [14C]TNT was converted to 14CO2 during a 5-d incubation period. The TNT and its metabolites were observed in root and shoot extracts by radiochromatographic analysis. The major TNT metabolites identified were 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene. Previous exposure of the plants to TNT did not increase TNT metabolism or prevent reduction of shoot length growth. From these results we concluded that smooth bromegrass is capable of taking up and metabolizing TNT.
Prominent chlorobornane residues in estuarine sediments contaminated with toxaphene
Authors: Maruya Keith A , Wakeham Stuart G , Vetter Walter , Francendese Leo 
Published: March 2010

AbstractSoils and sediments contaminated with residues of technical toxaphene may require remedial action to reduce human health and ecological risks. Sediments were collected from a coastal wetland impacted by discharge from a former toxaphene production facility and analyzed by gas chromatography–electron capture detection and conventional and enantioselective gas chromatography-mass spectrometry in the electron capture negative ion mode. The prominent chlorobornanes (CHBs) in all samples were 2-exo,3-endo,6-exo,8,9,10-hexachlorobornane (B6-923 or Hx-Sed) and 2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane (B7-1001 or Hp-Sed), metabolites of higher chlorinated components of technical toxaphene (CTTs). Pentachlorobornanes, toxaphene homologs not previously reported in environmental samples, and likely precursor CTTs were also detected. Several CHB congeners were enantioresolved, the majority of which exhibited racemic composition. These results indicate that the profile of CHBs persisting in estuarine sediment is highly modified relative to the technical mixture, and also provides strong evidence of in situ reductive dechlorination, a process that if enhanced could act to reduce bioaccumulation and toxicity of sediment-bound CTTs at toxaphene-contaminated sites.
Tissue disposition of benzo[A]pyrene in blue mussel (Mytilus edulis) and effect of algal concentration on metabolism and depuration
Authors: Magnusson Kerstin , Ekelund Rolf , Ingebrigtsen Kristian , Granmo Åke , Brandt Ingvar 
Published: March 2010

AbstractIn vivo metabolism and depuration of benzo [a]pyrene (BaP) was studied in the blue mussel Mytilus edulis. In one experiment, the animals were injected with 3H-BaP and thereafter exposed to either a high (H) or a low (L) concentration of the alga Isochrysis galbana. Mussels were sampled after 2, 4, 8, 16, and 32 d and temporal changes in the metabolite profiles were analyzed using nonpolar and polar solvents. The metabolic fate and the depuration rate of BaP from the two feeding groups were compared. In a second experiment, mussels were exposed to [3H]-BaP or [14C]-BaP either injected or via the surrounding water, and the tissue distribution of radiolabeled compound was studied. The half-life of BaP was 15–17 days and unaffected by the food concentration. The metabolic profile differed slightly between the two treatments. Animals in the L group had a significant peak in the quantity of macromolecular adducts eight days after the injection, whereas the H group had a fairly stable amount of adducts throughout the experimental period. The tissue distribution study revealed that the radiolabeled compound was mainly present in the epithelial cells of the hepatopancreas and the ciliated epithelial cells of the gills. A fraction of the radioactivity was firmly bound.
Interaction of pyrethroids with ion transport pathways present in frog skin
Authors: Cassano Giuseppe , Bellantuono Vito , Quaranta Angelo , Ippolito Cosima , Ardizzone Concetta , Lippe Claudio 
Published: March 2010

Abstract
We measured the ability of deltamethrin and permethrin to stimulate the ion transport operated by the frog skin. Ion transport was monitored by measuring the short-circuit current. Deltamethrin and permethrin, added to the fluid bathing the internal surface of the isolated frog skin, showed a seasonal feature and were more effective in increasing short-circuit current in the period between June and October. Transepithelial influxes and outfluxes of 22Na+ and 36C1− across symmetrical parts of the short-circuited skin were then measured. Deltamethrin was found to increase net Na+ absorption and, to a lesser extent, Cl1 secretion. The presence of a Cl− secretory mechanism is supported by two observations, those being that the short-circuit current value, recorded when deltamethrin and amiloride (inhibitor of Na+ channels) were simultaneously present, was higher than that obtained in the presence of amiloride alone and that bumetanide, a classic inhibitor of Cl− secretion, completely inhibited the component of the Cl− outflux that was induced by the deltamethrin stimulation. The stimulations of short-circuit current respectively caused by deltamethrin (type II pyrethroid) and permethrin (type I) were comparable and similarly affected by indomethacin (an inhibitor of cyclooxygenase) and W7 (an inhibitor of the Ca2+/calmodulin system). These findings suggest that, in frog skin, the cellular mechanism of action of type I and type II pyrethroids is similar.
Organochlorine and trace element contamination in wintering and migrating diving ducks in the southern great lakes, USA, since the zebra mussel invasion
Authors: Custer Christine M , Custer Thomas W 
Published: March 2010

AbstractBecause of the potential for increased trophic transfer of contaminants by zebra mussels (Dreissena sp.) to higher trophic levels, we collected four species of waterfowl (n = 65 ducks) from four locations in Lake Erie, Lake St. Clair, and Lake Michigan, USA, between 1991 and 1993 for organochlorine contaminant and trace element analyses. Geometric mean concentrations of total polychlorinated biphenyls (PCBs) and p, p′-dichlorodiphenyldichloroethylene (DDE) were 1.35 and 0.15 μg/g wet weight in lesser scaup (Aythya affinis) carcasses and were below known effect levels. Total PCBs in 80% of carcasses, however, were above the U.S. Food and Drug Administration's threshold of 3.0 μg/g lipid weight for consumption of poultry. With the exception of selenium, trace elements were also at background or no-effect levels. Selenium concentrations in livers of 95% of lesser scaup, 90% of bufflehead (Bucephala albeola), and 72% of common goldeneye (Bucephala clangula) were in the elevated (&gt;10 μg/g dry wt) or potentially harmful range (&gt;33 μg/g dry wt). The effects of these high selenium concentrations are unknown but should be investigated further based on reproductive effects observed in field and laboratory studies of dabbling ducks and because lesser scaup populations are declining. Concentrations of total PCBs in dreissenid mussels in western Lake Erie were 10 times higher than in the upper Mississippi River but were similar to concentrations in other industrialized rivers in Europe and the United States. Metal concentrations were similar to other industrialized sites where zebra mussels have been sampled.
Mean extinction time of populations under toxicant stress and ecological risk assessment
Authors: Tanaka Yoshinari , Nakanishi Junko 
Published: March 2010

AbstractPopulation-level effects of chemical pollutants are evaluated in terms of decrements of mean extinction time of populations. Analytical solutions of the mean extinction time based on the diffusion approximation were applied to published chronic ecotoxicological data provided from life table experiments or population growth experiments. Assuming a fairly large population (a million) with environmental fluctuation of an observed magnitude, chemical exposure with a concentration of 10% of LC50 is expected to cause, on average, an extinction risk of 16% reduction in the mean extinction time, which is equivalent to that induced by a 1.2% reduction of the population size (or habitat area). Although the ecological risk assessment based on mean extinction time has many limitations, it may present a possibility for interpreting the ecological risk of chemical pollutants in the context of population vulnerability.
Effects of short-term oxygen depletion on fish
Authors: Seager John , Milne Ian , Mallett Mike , Sims Ian 
Published: March 2010

AbstractLaboratory experiments were undertaken to investigate the influences of exposure duration and frequency on the toxicity of short-term pulses of low dissolved oxygen (DO) to fish. For the investigation of exposure duration, rainbow trout (Oncorhynchus mykiss [Walbaum]) and roach (Rutilus rutilus L.) were exposed to a range of DO concentrations in single pulses of 1, 6, or 24 h. For the investigation of exposure frequency, brown trout (Salmo trutta L.) were exposed to 24-h pulses of DO concentrations of 4.0 and 5.5 mg/L at frequencies of once or twice weekly over a period of 75 d. The results suggest that, for a given duration, there is a narrow threshold concentration range above which mortality does not occur and below which mortality rapidly becomes high. This threshold concentration range increases as exposure duration increases. Roach were able to survive lower DO concentrations than trout. Observations on experimental animals following exposure indicated no significant postexposure effects, even at very low DO levels. For the exposure frequencies used here, DO concentration rather than frequency of exposure was the important factor in terms of effect on fish. No significant effects on growth rate were observed but there were significant differences in hemoglobin levels, hematocrit, and organ weights. These results have important implications for the derivation of environmental quality standards aimed at the control of episodic pollution in rivers.
Cytochrome P450 induction by nitrated polycyclic aromatic hydrocarbons, azaarenes, and binary mixtures in fish hepatoma cell line PLHC-1
Authors: Jung Detlev K J , Klaus Thomas , Fent Karl 
Published: March 2010

AbstractNitrated polycyclic aromatic hydrocarbons (NP AH) and N-heterocyclic aromatic hydrocarbons (azaarenes) are as ubiquitous in the environment as their parent PAH compounds, although occurring at lower concentrations. The toxicological importance of NPAHs and azaarenes is based on their mutagenic and carcinogenic potential. Azaarenes possess a higher solubility and mobility in the environment than PAHs. However, very little is known about the toxicity and cytochrome P450 (CYP)1A induction potencies of NPAHs and azaarenes in fish. Here we report on the cytotoxicities and relative CYP1A induction potencies of 12 NPAHs, 12 azaarenes, and 11 PAHs, determined as neutral red uptake and ethoxyresorufin-O-deethylase (EROD) activity, respectively, in fish hepatoma PLHC-1 cells. Additionally, CYP1A enzyme protein was determined by ELISA for two NPAHs, azaarenes, PAHs, and binary mixtures. Compared with the structurally analogous PAHs, 2-nitronaphthalene, 3-nitrofluoranthene, 2-aza- and 7-azafluor-anthene, 1,6-dinitropyrene, benzo[a]acridine and benzo[h]quinoline revealed higher induction potencies, whereas the other compounds showed similar or less activity. The induction potency was highly dependent on the compounds structural properties, reflected by significant correlations between the half-maximal EROD induction (-log EC50) and the molecular descriptors lipophilicity (log Kow) and maximal molecular length (Lmax). Binary mixtures of 6-nitrochrysene + benzo[a]anthracene, 6-nitrochrysene + ben-zo[a]acridine, and benzo[a]acridine + benzo[a]anthracene showed an additive interaction. The CYP1A induction potencies of NPAHs and azaarenes, demonstrated here for the first time in fish hepatoma cells, suggest that their contribution to the overall CYP1A induction potencies in PAH-contaminated environmental samples have to be taken into account.
Pyrene and chrysene fate in surface soil and sand microcosms
Authors: Roper J Chadwick , Pfaender Frederic K 
Published: March 2010

Abstract
Polycyclic aromatic hydrocarbons (PAHs) are major components of wastes from municipal gas plants and many wood preservatives. Soil contaminated with these wastes is a potential threat to human health because of the carcinogenicity of many PAHs. This study follows the fate of two four-ring PAHs, pyrene and chrysene, in three matrices: an adapted soil (obtained from a site contaminated with PAHs for more than 75 years), an uncontaminated soil (with and without an inoculum of adapted soil), and sand mixed with an inoculum of adapted soil. Radiolabeled pyrene, chrysene, and salicylic acid (a metabolite of PAH biodegradation) were used to trace the mineralization, transformation, extractability, and formation of an unextractable residual over time. Linear approximations of the rates of these processes were made. High-performance liquid chromatography (HPLC) analysis of extracts from inoculated soil showed the transient formation of two known metabolites: 1-hydroxypyrene (from pyrene) and 1-hydroxy-2-naphthoic acid (from chrysene). The amount of extractable label diminished steadily over the course of the study in systems that were not inhibited with sodium azide, whereas the amount of extractable label remained relatively constant in inhibited systems. Correspondingly, the amount of nonextractable residual label generally increased during each incubation in uninhibited systems, whereas the amount of this residual label remained relatively constant in inhibited systems. In contrast, the rate and extent of mineralization varied widely across matrix types. This suggests that alterations of the PAH that impact extractability and residual formation are common, in contrast to mineralization, which was apparently limited to adapted communities.