bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exoestrogens: Mechanisms of action and strategies for identification and assessment
Authors: Gillesby Bradley E , Zacharewski Timothy R. 
Published: March 2010

Abstract
Public attention has recently been focused on the increased incidence of hormone-dependent cancers. However, less than one half of these increases can be attributed to improved detection methods and/or recently identified genetic factors. Consequently, it has been suggested that certain exogenous compounds are able to modulate the endocrine system by augmenting the sex steroid burden. This hypothesis is supported by a number of studies demonstrating physiologic and morphologic changes in wildlife exposed to high concentrations of environmental contaminants that are capable of eliciting responses typically induced by sex steroids. Due to associated steroidlike activities, these chemicals have been termed endocrine disrupters. The most well-characterized endocrine disrupters are exoestrogens, whose effects are similar to those produced by endogenous estrogens such as 17β-estradiol, although they are structurally unrelated. This broad structural diversity suggests that exoestrogens may elicit effects through a number of divergent pathways including direct binding and activation of the estrogen receptor (ER); binding to other nuclear receptors, which then interact with an estrogen responsive element; and through other receptor and/or signal transduction pathways. One such pathway involves the aryl hydrocarbon receptor (AhR), which binds a number of environmental contaminants such as polychlorinated biphenyls, dioxins, and furans. Several mechanisms have been elucidated that partially explain the AhR-mediated antiestrogenic activities of dioxins and related compounds. These include increased estrogen metabolism, down-regulation of estrogen receptor protein levels and binding activity, and decreased ER-mediated gene expression. A number of assays, both in vitro and in vivo, have been developed to identify and assess the endocrine disrupting potential of a compound. However, due to the broad structural diversity and number of potential mechanisms of action, a battery of complementary in vitro and in vivo assays is required to comprehensively assess the endocrine disrupting capability of exoestrogens.
Fish reproduction: An ecologically relevant indicator of endocrine disruption
Authors: Arcand-Hoy Lisa D , Benson William H 
Published: March 2010

Abstract
Endocrine-disrupting compounds have the potential to alter hormone pathways that regulate reproductive processes. With the exception of endocrine effects leading to reproductive impairment and population declines in a few wildlife species (e.g., Great Lake [USA] bald eagles, Lake Apopka [Florida, USA] American alligators), the ecological implications of exposure to endocrine disrupting compounds has not been adequately investigated. For example, male fish exposed to estrogenic compounds show induced production of vitellogenin, an egg yolk precursor, but the biological significance of elevated vitellogenin levels is speculative. The development of techniques to predict and more accurately assess the ecological relevance of exposure to endocrine-disrupting compounds is needed. In this review, we focus on fish reproduction as an ecologically relevant indicator of endocrine disruption, specifically estrogenic activity. The following will provide a brief review of gonochoristic reproductive and endocrine physiology, as well as outline some of the commonly used techniques to screen for estrogenic activity in fish. Last, a proposed model reproductive assay using Japanese medaka (Oryzias latipes) is presented.
A critical evaluation of safety (uncertainty) factors for ecological risk assessment
Authors: Chapman Peter M , Fairbrother Anne , Brown Derek 
Published: March 2010

Abstract
Evaluation of environmental risks posed by potentially hazardous substances requires achieving a balance between over- and underprotection, i.e., between societal benefits posed by the use of particular substances and their potential risks. Uncertainty (e.g., only laboratory data may be available, field or epidemiological data may be limited and less than clear-cut, etc.) will always exist and is often conservatively dealt with by the use of so-called “safety” or “uncertainty” factors, some of which remain relatively little changed since their origin in 1945. Extrapolations involving safety factors for both aquatic and terrestrialenvironments include inter- and intraspecies, acute-to-chronic, lowest- to no-observed-effect concentration (NOEC), and laboratory-to-field extrapolation (e.g., extrapolation of laboratory results to the field). To be realistic, such extrapolations need to have a clear relationship with the field effect of concern and to be based on good science. The end result is, in any case, simply an estimate of a field NOEC, not an actual NOEC. Science-based versus policy-driven safety factors, including their uses and limitations, are critically examined in the context of national and international legislation on risk assessment. Key recommendations include providing safety factors as a potential threshold effects range instead of a discrete number and using experimental results rather than defaulting to safety factors to compensate for lack of information. This latter recommendation has the additional value of rendering safety factors predictive rather than simply protective. We also consider the so-called “Precautionary Principle”, which originated in 1980 and effectively addresses risk by proposing that the safety factor should be infinitely large.
The value of mechanistic studies in laboratory animals for the prediction of reproductive effects in wildlife: Endocrine effects on mammalian sexual differentiation
Authors: Gray L Earl , Ostby Joseph , Wolf Cynthia , Lambright Christy , Kelce William 
Published: March 2010

AbstractWildlife populations from contaminated ecosystems display a variety of reproductive alterations, including cryptorchidism in the Florida panther, small baculum in young male otters, small penises in alligators, sex reversal in fish, and altered social behavior in birds. The formation of biologically plausible hypotheses regarding disruption of reproduction in wildlife can be facilitated by mechanistic studies on laboratory animals. To this end, we are investigating the in vivo and in vitro effects of endocrine-disrupting toxicants in rodents. In vitro studies have used receptor binding and transfected cell assays to confirm the suspected mechanism of action, whereas in vivo rodent studies examine altered sexual differentiation. Antiandrogenic pesticides compete with the natural ligands for both rat and human androgen receptors, block androgen-induced gene expression in vitro and in vivo, delay puberty, reduce sex accessory gland size, and alter male rat sex differentiation. In contrast, xenoestrogens affect female central nervous system sex differentiation and fecundity without producing malformations or infertility in male offspring. Prenatal administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or the TCDD-like polychlorinated biphenyls produce yet another profile of effects in the offspring, reducing numbers of ejaculated sperm in male progeny and inducing urogenital malformations in females. Although phthalates are reported to be estrogenic in vitro, in vivo exposure causes developmental alterations that more closely resemble antiandrogenic activity. The mammalian data indicate that exposure to endocrine-disrupting chemicals produces effects that are pathognomonic for mechanisms by which they act. Mechanistic information derived from mammalian studies can enhance our ability to predict toxicant effects on reproduction in fish and wildlife.
Effects of mercury on wildlife: A comprehensive review
Authors: Wolfe Marti F , Schwarzbach Steven , Sulaiman Rini A 
Published: March 2010

Abstract
Wildlife may be exposed to mercury (Hg) and methylmercury (MeHg) from a variety of environmental sources, including mine tailings, industrial effluent, agricultural drainwater, impoundments, and atmospheric deposition from electric power generation. Terrestrial and aquatic wildlife may be at risk from exposure to waterborne Hg and MeHg. The transformation of inorganic Hg by anaerobic sediment microorganisms in the water column produces MeHg, which bioaccumulates at successive trophic levels in the food chain. If high trophic level feeders, such as piscivorous birds and mammals, ingest sufficient MeHg in prey and drinking water, Hg toxicoses, including damage to nervous, excretory and reproductive systems, result. Currently accepted no observed adverse effect levels (NOAELs) for waterborne Hg in wildlife have been developed from the piscivorous model in which most dietary Hg is in the methyl form. Such model are not applicable to omnivores, insectivores, and other potentially affected groups, and have not incorpotated data from other important matrices, such as eggs and muscle. The purpose of this paper is to present a comprehensive review of the Hg literature as it relates to effects on wildlife, including previously understudied groups. We present a critique of the current state of knowledge about effects of Hg on wildlife as an aid to identifying missing information and to planning research needed for conducting a complete assessment of Hg risks to wildlife. This review summarizes the toxicity of Hg to birds and mammals, the mechanisms of Hg toxicity, the measurement of Hg in biota, and interpretation of residue data.
Patterns of common loon (Gavia immer) mercury exposure, reproduction, and survival in wisconsin, USA
Authors: Meyer Michael W , Evers David C , Hartigan Jerry J , Rasmussen Paul S 
Published: March 2010

Abstract
A long-term study was initiated in 1992 to investigate whether elevated Hg exposure measured in Wisconsin common loons was associated with reduced reproductive performance or survival. Adults loons (n = 99) and chicks (n = 56) were captured on 45 lakes during 1992 and 1993, each was individually color-marked with plastic leg bands, and blood and feathers were collected for Hg analysis. Adult return rates and reproductive outcome were then recorded for the 45 lakes from 1993 to 1996. A significant linear relationship was observed between lake pH and log-transformed adult blood Hg (r2 = 0.22, p &lt; 0.01) and chick blood Hg (r2 = 0.56, p &lt; 0.001) concentrations. Egg Hg concentrations (mean = 0.9 ± 0.3 μg Hg/g fresh weight) were within the range associated with reduced hatching success or reduced survival of embryos or hatchlings in other sensitive avian species. Chick production was lower at lakes where chick blood Hg concentrations were elevated. However, no relationship was observed between levels of adult Hg exposure and reproductive performance or annual adult return rates (an index of survival). Establishing a cause-and-effect relationship between Hg exposure and loon fitness is complicated by the negative correlation between lake pH and Hg exposure and potential confounding with other influences on productivity that may also be related to lake pH.
Mercury exposure in breeding common loons (Gavia immer) in central Ontario, Canada
Authors: Scheuhammer Anton M , Atchison Carolyn M , Wong Allan H K , Evers David C 
Published: March 2010

Abstract
Total Hg concentrations were determined in blood and feather samples of breeding common loons (Gavia immer) and their chicks from 24 lakes in Ontario with a range of water chemistry and fish Hg concentrations. In paired comparisons, males had significantly higher blood (p &lt; 0.005) and feather (p &lt; 0.05) Hg concentrations than their female mates. Sex differences in Hg concentrations were attributable to size differences between the two sexes and to the possible transfer of Hg to eggs by females during egg-laying. Significantly higher blood (p &lt; 0.001) and feather (p &lt; 0.01) Hg concentrations were found in adult loons compared to their chicks. Adult blood Hg concentrations were significantly correlated with those of their chicks (r = 0.62, p &lt; 0.05). Adult blood concentrations averaged about 13 times those of corresponding chicks. Both adult and chick blood Hg concentrations were positively correlated with fish Hg concentrations (r = 0.71 and 0.51, respectively), indicating that adult loons in central Ontario, like their chicks, probably feed mainly on their breeding lakes and reflect the fish Hg concentrations of those lakes. Three of 24 lakes had 20- to 50-g fish (mainly perch and sunfish) with Hg concentrations at or exceeding the critical concentration (0.3–0.4 μg/g wet weight or ∼1–2 μg/g dry weight) reported to cause reproductive impairment in loons. Monitoring Hg in blood (adult and chick) and feathers (chicks only) is useful for assessing the local bioavailability of methylmercury and the degree of current dietary Hg exposure in loons and other piscivorous birds.
Mercury levels, reproduction, and hematology in western grebes from three California Lakes, USA
Authors: Elbert Ruth Anne , Anderson Daniel W 
Published: March 2010

Abstract
Twenty-three healthy adult western and Clark's grebes (Aechmophorus occidentalis and Aechmophorus clarkii) were collected at three study sites in California, USA, in 1992: Clear Lake, Lake County; Eagle Lake, Lassen County; and Tule Lake, Siskiyou County. Liver, kidney, breast muscle, and brain were analyzed for total mercury (Hg) concentration (ppm wet weight), and blood was analyzed for various blood parameters. Clear Lake birds (n = 13) had greater Hg concentrations in kidney, breast muscle, and brain than birds from the other two lakes (p &lt; 0.05), whereas liver concentrations were not statistically different (p &gt; 0.05). Average concentrations for Clear Lake birds were 2.74 ppm for liver, 2.06 ppm for kidney, 1.06 ppm for breast muscle, and 0.28 ppm for brain. The tissue levels of kidney, breast muscle, and brain at the other two study sites were one half the levels found at Clear Lake. These mean tissue levels were near, but below, those known to cause adverse effects. When data from all sites were merged, kidney, breast muscle, and brain concentrations are positively correlated to each other (p &lt; 0.05). Liver concentrations were not correlated to any other value. Brain Hg concentrations were also negatively correlated to blood potassium and blood phosphorus levels (n = 11, p &lt; 0.05). Kidney Hg levels were positively correlated to percent blood heterophils and negatively correlated to percent eosinophils (n = 13, p &lt; 0.05), suggesting that mercury levels might be affecting immune function. These biomarkers could not be related to any obvious ecological effects.
Investigation of the photochemistry of urea herbicides (chlorotoluron and isoproturon) and quantum yields using polychromatic irradiation
Authors: Millet Maurice , Palm Wolf-Ulrich , Zetzsch Cornelius 
Published: March 2010

Abstract
This paper presents the investigation of the photochemical reaction of chlorotoluron (3-(3-chloro-4-methyl-phenyl)-1,1-dimethylurea) in CH3CN, hexane, and aqueous and buffered solutions (pH = 4, 7, and 9) and of isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) in aqueous and buffered solutions using a polychromatic light source at a temperature of 22°C. For chlorotoluron, isosbestic points were found (with the exception of hexane as solvent) and ultraviolet spectroscopy was used to obtain kinetic data. The main photoproduct for the photolysis of chlorotoluron in aqueous solutions was identified as 3-(3-hydroxy-4-methyl-phenyl)-1,1 dimethylurea. Quantum yields found in aqueous and buffered solutions were comparable (about 0.07) and 2 times lower and 10 times higher in CH3CN and hexane, respectively. No isosbestic points were found for isoproturon, and quantum yields of about 0.004 were calculated in all solutions. Chlorotoluron and isoproturon present very low molar extinction coefficients above 290 nm, and they can be assumed to be photostable with respect to direct irradiation by sunlight.
Effects of benzidine and benzidine analogues on growth of bacteria including Azotobacter vinelandii
Authors: Chung King-Thom , Chen Ssu-Ching , Wong Tit Yee , Wei Chen-I 
Published: March 2010

Abstract
Benzidine and benzidinea aloguesare mutagenic and carcinogenic metabolites ofazodyes that are widely found in the environment. The toxicities of benzidine and nine of its analogues against 18 bacterial strains including nitrogen-fixing Azotobacter vinelandii were tested using the well diffusion assay technique. 2-Aminobiphenyl and 3-aminobiphenyl were the most inhibitory to all bacterial species tested except A. vinelandii. 4-Aminobiphenyl was inhibitory to the growth of A. vinelandii using a plate count assay, although it failed to show an inhibitory effect in the well diffusion assay. 3,3′-4,4′-Tetraaminobiphenyl was inhibitory to both A. vinelandii and Aeromonas hydrophila, whereas benzidine, 3,3′-dimethoxybenzidine, 4,4′-dinitro-2-biphenylamine, 3,3′-5,5′-tetramethylbenzidine, N,N-N′,N′-tetramethylbenzidine, and o-tolidine were not inhibitory to any of the bacterial species tested. Of all these compounds tested, only 3,3′-4,4′-tetraaminobiphenyl and 4-aminobiphenyl inhibited the nitrogenase activity of A. vinelandii.
Reduction of 2,4,6-trinitrotoluene by Clostridium acetobutylicum through hydroxylamino-nitrotoluene intermediates
Authors: Hughes Joseph B , Wang Chuan Yue , Bhadra Rajiv , Richardson Adam , Bennett George N , Rudolph Fred B 
Published: March 2010

Abstract
Studies were conducted to isolate and identify intermediates of 2,4,6-trinitrotoluene (TNT) transformation by Clostridium acetobutylicum and to quantify their concentrations in active whole cell cultures. Only two intermediates of TNT reduction were detected in cell cultures and were identified as 4-hydroxylamino-2,6-dinitrotoluene and 2,4-dihydroxylamino-6-nitrotoluene. Structures were confirmed with 1H-NMR, 13C-NMR, and desorption chemical ionization mass spectroscopy. When cells were suspended in a non-growth saline medium, both hydroxylamine forms accumulated. In media capable of supporting cell growth, the 2,4-dihydroxylamino-6-nitrotoluene accumulated with concentrations of 4-hydroxylamino-2,6-dinitrotoluene remaining near detection limits. Studies using purified 2,4-dihydroxylamino-6-nitrotoluene confirmed that its biotransformation rate in active cultures greatly exceeded abiotic decomposition in aqueous medium.
Identification of fluoroquinolone antibiotics as the main source of umuC genotoxicity in native hospital wastewater
Authors: Hartmann Andreas , Alder Alfredo C , Koller Theo , Widmer Rosa M 
Published: March 2010

Abstract
Previous work revealed genotoxic effects in the wastewater of a large university hospital using a bacterial short-term genotoxicity assay, based on a umuC::lacZ fusion gene (umuC assay). These studies ruled out disinfectants and detergents as main causative agents of the genotoxic effects. This paper focuses on specific hospital-related drugs as the cause. The ratio of theoretical mean wastewater concentrations (derived from consumption data) and lowest observable effect concentrations of selected pharmaceuticals were used to calculate umuC induction probabilities. The fluoroquinolone antibiotics Ciproxin® and Noroxin® showed the highest induction probabilities and exceeded all other investigated drugs by at least one order of magnitude in significance. Antineoplastic drugs, originally thought to be the main effectors, were found to be of marginal significance using the umuC assay. These findings were further supported by investigation of urine samples of hospital patients with the umuC assay. The determination of ciprofloxacin in native hospital wastewater by reversed-phase high-performance liquid chromatography and fluorescence detection revealed concentrations from 3 to 87 μg/L. umuC induction factor and ciprofloxacin concentrations in 16 hospital wastewater samples showed a log-linear correlation (r2 = 0.84, p &lt; 0.0001). These results suggest that the previously measured umuC genotoxicity in the wastewater of the hospital under investigation is caused mainly by fluoroquinolone antibiotics, especially by ciprofloxacin. On the basis of these findings, the role of the umuC assay as a screening tool for wastewater genotoxicity assessment is discussed.
Biomarker responses in cyprinids of the middle stretch of the River Po, Italy
Authors: Viganò Luigi , Arillo Attilio , Melodia Federico , Arlati Patrizia , Monti Cinzia 
Published: March 2010

Abstract
Fish belonging to three species of cyprinids, that is, barbel (Barbus plebejus), chub (Leuciscus cephalus), and Italian nase (Chondrostoma söetta), were collected from two sites of the River Po, located upstream and downstream from the confluence of one of its middle-reach polluted tributaries, the River Lambro. The two groups of individuals caught for each species were analyzed and compared for several microsomal and cytosolic biochemical markers. The enzymatic activities assayed in fish liver included ethoxyresorufin O-deethylase (EROD), aminopyrine-N-demethylase (APDM), uridine diphosphate glucuronyltransferase (UDPGT), glutathione S-transferase (GST), glutathione reductase, and glutathione peroxidase. In addition, the contents of reduced glutathione and nonprotein thiols were measured. Despite some differences among species, all microsomal activities (EROD, APDM, UDPGT) were found to be significantly induced in fish living downstream the River Lambro. With the exception of a higher GST enzyme activity of barbel from the downstream reach, no significant modification was evident in any of the tested cytosolic biomarkers. Results showed that barbel and nase better discriminated the two reaches of the River Po. In general, the alterations observed in feral fish are consistent with the results found in previous studies conducted with rainbow trout (Oncorhynchus mykiss) under both laboratory and field conditions in the same middle reach of the River Po. All of the data indicate that the downstream tract of the main river is exposed to the load of pollutants transported by the River Lambro, including known inducers such as polychlorinated biphenyls and polycyclic aromatic hydrocarbons (PAHs). The latter were analyzed in sediments sampled at the two sites of fish collection, and the downstream sediment showed the highest concentrations of PAHs, although their levels are comparable to those present in moderately polluted locations. Regardless of the site of exposure, barbel seem to be characterized by more efficient antioxidant defenses. This observation could partly explain the lower prevalence of pathological lesions and parasites observed in this cyprinid in a previous study.