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Effective Concentration (effective + concentration)
Selected AbstractsToxicity and disruption of midgut physiology in larvae of the European corn borer, Ostrinia nubilalis, by anion transporter blockersARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009Dhana Raj Boina Abstract In this study, four blockers of anion transporters (ATs) belonging to four different classes of organic acids, including DIDS (4, 4'-diisothiocyanatostilbene-2, 2'- disulfonic acid; a stilbene disulfonic acid), NPPB [(5-nitro-2-(3-phenylpropylamino) benzoic acid; an anthranilic acid)], 9-AC (anthracene-9-carboxylic acid; an aromatic carboxylic acid), and IAA-94 (indanyloxy acetic acid; an indanyloxy alkanoic acid), were tested for their toxicity against the European corn borer (ECB), Ostrinia nubilalis. All the AT blockers inhibited the growth of larvae, increased the developmental time, and decreased survival compared to controls, when second-instar ECB larvae were fed for seven days on treated diet. In general, DIDS and NPPB were the most active compounds, with the rank order of activity being DIDS>NPPB>IAA-94>9-AC. All the AT blockers decreased the midgut alkalinity in fifth-instar larvae when fed for 3,h on treated diet. Effective concentrations required for 50% decrease in midgut alkalinity (EC50) ranged between 29.1 and 41.2,ppm and the rank order of activity was NPPB>DIDS>IAA-94>9-AC. Similarly, all the tested AT blockers inhibited 36Cl, uptake from the midgut lumen in fifth-instar larvae when fed for 3,h on treated diet. Concentrations required for 50% inhibition of 36Cl, uptake (IC50) ranged between 7.4 and 11.0,ppm and the rank order of activity was DIDS>NPPB>9-AC >IAA-94. Modest to highly strong positive correlations observed among growth, midgut alkalinity, and midgut Cl, ion transport in AT blocker,fed larvae suggested that these effects are causally related to each other. Finally, AT blockers have the potential to become good candidates for development of insecticides with a unique mode of action. © 2009 Wiley Periodicals, Inc. [source] Approach to procedures in neonatesDERMATOLOGIC THERAPY, Issue 2 2005Valerie B. Lyon ABSTRACT:, Physical constraints and metabolic differences in neonates require that special attention is given to performing procedures in this patient group. Neonates have a thinner dermis and a greater surface-to-weight ratio, allowing for easier invasion through the skin barrier. The enzymes for metabolism of agents and defense against organisms inside the body are not fully developed in infants. Very premature neonates also have less circulating albumin, making the effective concentration of circulating agent even greater. The infant is prone to unanticipated movement during procedures, such as rolling on the procedure table. The neonatal period is the most common time period for malformations to become manifest on the skin, and invasion of some of these lesions can produce morbidity. These and other factors affect the choice of the type of procedure used, the timing for intervention, and the approach to intervention in this age group. This article reviews the important considerations for approaching procedures and offers suggestions for safe and effective methods of reliably producing the intended outcome. [source] Three structurally homologous isothiocyanates exert "Janus" characteristics in human HepG2 cellsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 3 2009Evelyn Lamy Abstract In this study, we used the single cell gel electrophoresis (SCGE) assay and the micronucleus (MN) test to investigate the DNA damaging effects and the antigenotoxic potencies of three structurally related ITCs in human HepG2 cells. The results show that all three ITCs possess the characteristic of a "Janus" compound, i.e., they exert both significant genotoxicity and antigenotoxicity, depending on the concentrations used in the test systems applied. Regression line analysis of the results derived by SCGE analysis showed genotoxic potency of the ITCs in the following order: 3-methylthiopropyl ITC (MTPITC) > 4-methylthiobutyl ITC (MTBITC) > 5-methylthiopentyl ITC (MTPeITC); however, this order in genotoxic potency was not confirmed by MN analysis. Additionally, the MN test showed significant mutagenicity of the test substances at higher concentrations when compared with the SCGE assay. Twenty-four hour-treatment of the cells with the ITCs, followed by a 1-hr recovery period, showed significant DNA repair in the SCGE assay at a concentration ,10 ,M MTPITC, ,3 ,M MTBITC, and ,0.1 ,M MTPeITC, respectively. In antigenotoxicity studies, the most effective concentration of MTPITC and MTPeITC toward B(a)P-induced DNA damage was 0.1 ,M in both test systems. MTBITC suppressed MN formation in B(a)P-treated cells to the background level at a concentration of 1 ,M. The ambivalent character of the ITCs under studymust be further clarified, especially in the possiblecontext of high dose therapeutic applications. Environ. Mol. Mutagen. 2009. © 2009 Wiley-Liss, Inc. [source] Effects of 4-nonylphenol on the endocrine system of the shore crab, Carcinus maenasENVIRONMENTAL TOXICOLOGY, Issue 3 2008Christina M. Lye Abstract There is a considerable body of evidence to suggest that many anthropogenic chemicals, most notably xeno-estrogens, are able to disrupt the endocrine system of vertebrates. There have been few comparable studies on the effects of exposure to these chemicals that may serve as biomarkers of endocrine disruption in aquatic invertebrate species. In addition, the evidence available is complex, conflicting, and far from conclusive. The present study aimed to investigate the impact of the xeno-estrogen 4-nonylphenol (4-NP, nominal concentrations 10,100 ,g L,1) on the regulation and functioning of the endocrine system of the shore crab Carcinus maenas. It also set out to establish whether 4-NP are causing the effects (i.e., changes of exoskeletons including secondary sexual characteristics, pheromonally mediated behavior and ecdysone levels, and the presence of vt in the male hepatopancreas) found recently in wild shore crabs (Lye et al.,2005). The study utilizes morphological (e.g., gonadosomatic and hepatosomatic indices) and hormonal (ecdysteroid moulting hormone levels and the induction of female specific proteins, vitellins) biomarkers using radioimmunoassay and an indirect enzyme linked immunosorbent assay applied to the soluble protein fraction of adult male hepatopancreatic homogenates. Exposure of C. maenas to an effective concentration as low as 1.5 ,g L,1 4-NP resulted in a reduced testis weight, increased liver weight, and altered levels of ecdysone equivalents compared to controls. Induction of vitellin-like proteins was absent in all samples tested. The ecological implications and the possible mechanisms for the action of 4-NP on the response of the shore crab to xeno-estrogen exposure are discussed. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Chronic copper toxicity in the estuarine copepod Acartia tonsa at different salinitiesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2010Mariana M. Lauer Abstract Chronic Cu toxicity was evaluated in the euryhaline copepod Acartia tonsa. Male and female copepods were exposed (6 d) separately to different combinations of Cu concentration and water salinity (5, 15, and 30 ppt) using different routes of exposure (waterborne, waterborne plus dietborne, and dietborne). After exposure, groups of one male and three female copepods were allowed to reproduce for 24,h. In control copepods, egg production augmented with increasing water salinity. However, egg hatching rate did not change. Copper exposure reduced egg production and hatching rate in all water salinities tested, but the reproductive response was dependent on the route of Cu exposure. Median effective concentration (EC50) values for egg production after waterborne exposure were 9.9, 36.8, and 48.8,µg/L dissolved Cu at water salinities of 5, 15, and 30 ppt, respectively. For waterborne plus dietborne exposure, they were significantly higher (40.1, 63.7, and 109.9,µg /L, respectively). After dietborne exposure, approximately 40% decrease in egg production was observed, independently of Cu concentration and water salinity tested. At water salinities of 5 and 30 ppt, egg hatching rate reduced after waterborne exposure, together or not with the dietborne exposure. At water salinity of 15 ppt, Cu toxicity was only observed after dietborne exposure. Data indicate that egg production is a more reliable reproductive endpoint to measure chronic Cu toxicity in copepods than egg hatching rate in a wide range of water salinities. They also suggest that both water salinity and route of Cu exposure should be taken into account in the development of a chronic biotic ligand model version for estuarine and marine environments. Environ. Toxicol. Chem. 2010;29:2297,2303. © 2010 SETAC [source] Early signs of lethal effects in Daphnia magna (Branchiopoda, Cladocera) exposed to the insecticide cypermethrin and the fungicide azoxystrobinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2010Ursula Friberg-Jensen Abstract This study presents the effects of sublethal concentrations of pesticides cypermethrin and azoxystrobin on the activity of several physiological parameters of egg-carrying Daphnia magna studied using a video-image technique. Single tethered daphnids were continuously recorded for 24,h of pesticide exposure, and the activity of the heart, the filtering limbs, the mandibles, and the focal spine were subsequently analyzed. Acute toxicity tests based on the criteria of immobilization were performed on egg-carrying D. magna, and sublethal concentrations of 0.1, 1.0, and 10,µg/L cypermethrin and 0.5, 1.0, and 2.0,mg/L azoxystrobin were established. At a concentration as low as 0.1,µg/L cypermethrin, the 5% effective concentration after 24,h of exposure (EC5,24h), the activity of the focal spine increased and the filtering limb activity decreased. The activity of the mandibles was reduced by exposure to 1.0 (EC18,24,h) and 10,µg/L (EC41,24,h) cypermethrin, whereas heart activity increased at a concentration of 10,µg/L (EC41,24,h). With regard to azoxystrobin, the activity of all response parameters except the focal spine decreased by exposure to 0.5,mg/L (EC4,24h) azoxystrobin. The focal spine was not affected by azoxystrobin. The results show that physiological mechanisms important for ingestion of food in D. magna may be impaired by low concentrations of commonly used pesticides. Environ. Toxicol. Chem. 2010;29:2371,2378. © 2010 SETAC [source] Dual enantioselective effect of the insecticide bifenthrin on locomotor behavior and development in embryonic,larval zebrafishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2010Meiqing Jin Abstract Bifenthrin (BF) is a synthetic pyrethroid that targets the nervous system of insects and may have adverse effects on the behavior and development of nontarget organisms. However, no reports have been issued on the effects of different enantiomers on locomotor behavior for synthetic pyrethroids (SPs) in zebrafish, and whether locomotor activity is associated with the developmental toxicities remains unclear. In this study, enantioselectivity of BF (1S and 1R) on the acute locomotor activity and developmental toxicities of embryonic,larval zebrafish were first evaluated. The results indicated that 1R -BF was more toxic, causing morphological impairments, with a 96-h median effective concentration (EC50) of 226,µg/L for pericardial edema and 145,µg/L for curved body axis. Administration of 20,µg/L of one enantiomer of BF had differential effects on the locomotor activity of zebrafish larvae at 4 d postfertilization (dpf) under alternating light and dark conditions. Larvae treated with 1R -BF were not sensitive to the alteration of light to dark, and the locomotor activities were reduced to a level similar to that observed in light, which otherwise increased rapidly and markedly. However, 1S -BF did not alter the general pattern of zebrafish response to the light or dark compared with the control. The results demonstrated that the differential effects on development might have contributed to the enantioselectivity in the locomotor activity. The consistency of enantioselectivity with insecticidal activity may also indicate a common mode of action. Furthermore, 1R -BF accelerated the spontaneous movement and hatching process, whereas 1S -BF seemed to be inhibitory. The results suggest the need to link behavioral changes to developmental toxicities in order to achieve more comprehensive health risk assessments of chiral pesticides. Environ. Toxicol. Chem. 2010;29:1561,1567. © 2010 SETAC [source] Effects of 17 ,-estradiol exposure on Xenopus laevis gonadal histopathologyENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2010Jeffrey C. Wolf Abstract The natural estrogen 17 ,-estradiol (E2) is a potential environmental contaminant commonly employed as a positive control substance in bioassays involving estrogenic effects. The aquatic anuran Xenopus laevis is a frequent subject of reproductive endocrine disruptor research; however, histopathological investigations have tended to be less than comprehensive. Consequently, a study was designed to characterize gross and microscopic changes in the gonads of X. laevis as a result of E2 exposure. Additional goals of this study, which consisted of three separate experiments, included the standardization of diagnostic terminology and criteria, the validation of statistical methodology, and the establishment of a half maximal effective concentration (EC50) for E2 as defined by an approximately 50% conversion of presumptive genotypic males to phenotypic females. In the first experiment, frogs were exposed to nominal concentrations of 0, 0.2, 1.5, or 6.0,µg/L E2. From these experimental results and those of a subsequent range finding trial, the EC50 for E2 was determined to be approximately 0.2,µg/L. This E2 concentration was utilized in the other two experiments, which were performed at different facilities to confirm the reproducibility of results. Experiments were conducted according to Good Laboratory Practice guidelines, and the histopathologic evaluations were peer reviewed by an independent pathologist. Among the three trials, the histopathological findings that were strongly associated with E2-exposure (p,<,0.001 to 0.0001) included an increase in the proportion of phenotypic females, mixed sex, dilated testis tubules, dividing gonocytes in the testis, and dilated ovarian cavities in phenotypic ovaries. A comparison of the gross and microscopic evaluations suggested that some morphologic changes in the gonads may potentially be missed if studies rely entirely on macroscopic assessment. Environ. Toxicol. Chem. 2010;29:1091,1105. © 2010 SETAC [source] The antimicrobial triclocarban stimulates embryo production in the freshwater mudsnail Potamopyrgus antipodarum,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010Ben D. Giudice Abstract Recent research has indicated that the antimicrobial chemical triclocarban (TCC) represents a new type of endocrine disruptor, amplifying the transcriptional activity of steroid hormones and their receptors while itself exhibiting little affinity for these receptors. The effects of TCC were studied in the freshwater mudsnail Potamopyrgus antipodarum. Specimens were exposed to concentrations ranging from 0.05 to 10.5 µg/L dissolved TCC and were removed and dissected, and embryos contained within the brood pouch were counted and classified as shelled or unshelled after two and four weeks of exposure. After four weeks, environmentally relevant TCC concentrations of 1.6 to 10.5 µg/L resulted in statistically significant increases in the number of unshelled embryos, whereas 0.2, 1.6, and 10.5 µg/L exposures significantly increased numbers of shelled embryos. The lowest observed effect concentration (LOEC) was 0.2 µg/L, the no observed effect concentration (NOEC) was 0.05 µg/L; the 10% effective concentration (EC10) and the median effective concentration (EC50) for unshelled effects were 0.5 µg/L and 2.5 µg/L, respectively. Given the widespread occurrence of TCC in the environment and the effects shown at environmentally relevant concentrations, these results indicate that TCC may be causing reproductive effects in the environment. Furthermore, the present study indicates that environmental risk from a new class of endocrine-disrupting chemicals (EDCs) is both qualitatively and quantitatively similar to risk from existing classes of EDCs. Environ. Toxicol. Chem. 2010;29:966,970. © 2009 SETAC [source] Arsenate toxicity for wheat and lettuce in six Chinese soils with different propertiesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2009Qing Cao Abstract To assess soil arsenic (As, in the form of arsenate) toxicity to plants, 6-d root elongation tests on wheat (Triticum aestivum L.) and lettuce (Lactuca sativa) were conducted in six Chinese soils freshly spiked with As. Plants were treated with 7 or 10 levels of As to establish concentration-effect curves. Median effective concentration and 10% effective concentration values were derived with regression analysis to measure As toxic potencies, and no-observed-effect concentration was determined by comparison with a control to elucidate thresholds of As to the two plant species. The median effective concentration values for As varied from 159 to 683 mg/kg for wheat and 59 to 426 mg/kg for lettuce, and the 10% effective concentration values varied from 79 to 270 mg/kg for wheat and 20 to 156 mg/kg for lettuce. The result suggests that lettuce is a more sensitive species for monitoring soil As contamination. With the same level of As spiked, soil toxicity for a plant showed a tendency of fluvoaquic soil toward red soil or black soil toward paddy soil. The phytotoxicity of As was negatively correlated with soil amorphous iron content extracted with ammonium oxalate. The overall results from the present work illustrate the necessity of considering soil properties in assessing soil As contamination. [source] Chronic toxicity of five structurally diverse demethylase-inhibiting fungicides to the crustacean Daphnia magna: A comparative assessmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2009Enken Hassold Abstract Demethylase inhibitors (DMIs) are broad-spectrum fungicides that are ubiquitously used in agriculture and medicine. They comprise chemically heterogeneous substances that share a common biochemical target in fungi, the inhibition of a specific step in sterol biosynthesis. Several DMIs are suspected to disrupt endocrine-mediated processes in a range of organisms and to inhibit ecdysteroid biosynthesis in arthropods. It is unclear, however, whether and, if so, to what extent different DMI fungicides have a similar mode of action in nontarget organisms, which in turn would lead to a common chronic toxicity profile. Therefore, we selected a representative of each of the major DMI classes,-the piperazine triforine, the pyrimidine fenarimol, the pyridine pyrifenox, the imidazole prochloraz, and the triazole triadimefon,-and comparatively investigated their chronic toxicity to Daphnia magna. No toxicity was detectable up to the limit of solubility of triforine (61 ,mol/L). All other DMIs reduced reproductive success by delaying molting and development and by causing severe developmental abnormalities among offspring. Prochloraz was most toxic (median effective concentration [EC50] for fecundity reduction, 0.76 ,mol/L), followed by fenarimol (EC50, 1.14 ,mol/L), pyrifenox (EC50, 3.15 ,mol/L), and triadimefon (EC50, 5.13 ,mol/L). Mean effect concentrations for fecundity reduction were related to lipophilicity and followed baseline toxicity. However, triadimefon and fenarimol (but none of the other tested DMIs) caused severe eye malformations among exposed offspring. Affected neonates did survive, but a reduced ecological fitness can be assumed. Offspring exposed to fenarimol in mater matured earlier. The investigated different life-history parameters were affected in a substance-specific manner. These qualitatively different toxicity profiles suggest additional, substance-specific mechanisms of action in D. magna that probably are related to an antiecdysteroid action. [source] Single- and two-species tests to study effects of the anthelmintics ivermectin and morantel and the coccidiostatic monensin on soil invertebratesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009John Jensen Abstract Soil invertebrates in arable land are potentially exposed to veterinary medicines excreted by husbandry. The toxicity of three widely used pharmaceuticals was therefore investigated with the use of common soil invertebrates exposed in the laboratory in single- or two-species test system. The anthelmintic morantel did not cause significant mortality to either Folsomia fimetaria or Enchytraeus crypticus even at the highest tested concentration of 900 mg kg,1 dry soil. The coccidiostatic monensin affected the reproduction of F. fimetaria and E. crypticus with soil concentrations estimated to cause a 10% effect at values of approximately 109 and 71.8 mg kg,1 dry soil, respectively, but caused no mortality to adult. The anthelmintic ivermectin did not affect the survival of adult Hypoaspis aculeifer. Reproduction of H. aculeifer declined approximately 45% in response to ivermectin exposure of 5 mg kg,1 dry soil. Ivermectin was highly toxic to F. fimetaria and affected the survival of adults with soil concentrations estimated to cause a 50% mortality at values of 5.3 mg kg,1 dry soil in the single-species test system and 0.14 mg kg,1 dry soil in the two-species test system. Reproduction of F. fimetaria was reduced by ivermectin with 10% effective concentration at 0.19 mg kg,1 dry soil in the single-species test system and 0.02 mg kg,1 dry soil in two-species test system. It was shown that species interactions may influence the response of test organisms to toxic substances. The data from this study and previously published data showed that, whereas ivermectin is likely to pose a risk to soil-dwelling invertebrates, adverse effects of morantel and monensin are unlikely to occur as a result of residue excretion from treated farm animals. [source] Response of the freshwater alga Chlorella vulgaris to trichloroisocyanuric acid and ciprofloxacin,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2008Xiangping Nie Abstract The effects of trichloroisocyanuric acid (TCCA) and ciprofloxacin (CPFX) on the freshwater alga Chlorella vulgaris were assessed by toxicity bioassays and by the values of biomarkers in phase I and phase II. The biomarkers included growth rate, concentration of chlorophyll a, activities of 7-ethoxyresorufin- O -dealkylases (EROD), glutathione S -transferase (GST), catalase (CAT), and total glutathione (GSH). Ciprofloxacin was a weaker growth inhibitor than TCCA but, at a concentration of greater than 12.5 mg/L, decreased the growth of C. vulgaris. Concentration of chlorophyll a showed a similar trend. The 96-h median effective concentration (EC50; i.e., 50% reduction in growth relative to the control) of CPFX was 20.6 mg/L. Trichloroisocyanuric acid was a strong growth inhibitor and, at concentrations of greater than 0.80 mg/L, caused 100% inhibition on 24-h exposure. The 96-h EC50 of TCCA was 0.313 mg/L. Ciprofloxacin and TCCA affected the phase I and phase II enzyme activities differently. On exposure to CPFX, both EROD and GSH decreased at low CPFX concentrations (<5.0 mg/L) and increased at high CPFX concentrations (>12.5 mg/L), and CAT and GST exhibited induction at low concentrations and inhibition at high concentrations. In TCCA exposure, GST activity was significantly stimulated, and GSH concentration was increased. Catalase activity increased only at TCCA concentrations of greater than 0.12 mg/L, and no change in EROD activity was observed. [source] Weathering and aging of 2,4,6-trinitrotoluene in soil increases toxicity to potworm Enchytraeus crypticusENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2005Roman G. Kuperman Abstract Energetic materials are employed in a wide range of commercial and military activities and often are released into the environment. Scientifically based ecological soil-screening levels (Eco-SSLs) are needed to identify contaminant explosive levels in soil that present an acceptable ecological risk. Insufficient information for 2,4,6-trinitrotoluene (TNT) to generate Eco-SSLs for soil invertebrates necessitated toxicity testing. We adapted the standardized Enchytraeid Reproduction Test and selected Enchytraeus crypticus for these studies. Tests were conducted in Sassafras sandy loam soil, which supports relatively high bioavailability of TNT. Weathering and aging procedures for TNT amended to test soil were incorporated into the study design to produce toxicity data that better reflect the soil exposure conditions in the field compared with toxicity in freshly amended soils. This included exposing hydrated TNT-amended soils in open glass containers in the greenhouse to alternating wetting and drying cycles. Definitive tests showed that toxicity for E. crypticus adult survival and juvenile production was increased significantly in weathered and aged soil treatments compared with toxicity in freshly amended soil based on 95% confidence intervals. The median effect concentration and 20% effective concentration for reproduction were 98 and 77 mg/kg, respectively, for TNT freshly amended into soil and 48 and 37 mg/kg, respectively, for weathered and aged TNT soil treatments. These findings of increased toxicity to E. crypticus in weathered and aged TNT soil treatments compared with exposures in freshly amended soils show that future investigations should include a weathering and aging component to generate toxicity data that provide more complete information on ecotoxicological effects of energetic contaminants in soil. [source] Evaluation of the ishikawa cell line bioassay for the detection of estrogenic substances from sediment extractsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005Shinya Hashimoto Abstract This study examines the application of Ishikawa human endometrial adenocarcinoma cells to measure the estrogenic activity of fractionated extracts of sediments from Tokyo Bay, Japan. Estrogen stimulates alkaline phosphatase activity in this cell line. The results of these assays were compared with those of a yeast estrogen screen (YES) assay. The Ishikawa cell line bioassay showed higher sensitivity to 17,-estradiol (median effective concentration [EC50], 10.7 pM) than did the YES assay (EC50, 480 pM). Fractionation of sediment extracts (all samples collected from 5 sites) showed that the nonpolar fraction was poisonous to yeast cells; the estrogenic activity of this fraction, therefore, could not be measured by YES. However, the nonpolar fraction did not kill the Ishikawa cells. The 17,-estradiol-equivalent values of 15 extracts (3 fractions from each of 5 sediment samples) ranged from 5.7 to 697 pg/g dry weight according to the Ishikawa cell line bioassay. Chemical analysis using gas chromatography-mass spectrometry revealed that the highest concentrations of endocrine-disrupting chemicals were observed at the sampling station near the sewage treatment plant. The results support that the Ishikawa cell line bioassay is suitable for measuring the estrogenic activity of sediment samples. [source] Copper toxicity in relation to surface water-dissolved organic matter: Biological effects to Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2004Kees J.M. Kramer Abstract Water quality standards for copper are usually stated in total element concentrations. It is known, however, that a major part of the copper can be bound in complexes that are biologically not available. Natural organic matter, such as humic and fulvic acids, are strong complexing agents that may affect the bioavailable copper (Cu2+) concentration. The aim of this study was to quantify the relation between the concentration of dissolved natural organic matter and free Cu2+ in surface waters, and the biological effect, as measured in a standardized ecotoxicological test (48 h-median effective concentration [EC50] Daphnia magna, mobility). Six typical Dutch surface waters and an artificial water, ranging from 0.1 to 22 mg/L dissolved organic carbon (DOC), were collected and analyzed quarterly. Chemical speciation modeling was used as supporting evidence to assess bioavailability. The results show clear evidence of a linear relation between the concentration of dissolved organic carbon (in milligrams DOC/L) and the ecotoxicological effect (as effect concentration, EC50, expressed as micrograms Cu/L): 48-h EC50 (Daphnia, mobility) = 17.2 × DOC + 30.2 (r2 = 0.80, n = 22). Except for a brook with atypical water quality characteristics, no differences were observed among water type or season. When ultraviolet (UV)-absorption (380 nm) was used to characterize the dissolved organic carbon, a linear correlation was found as well. The importance of the free copper concentration was demonstrated by speciation calculations: In humic-rich waters the free Cu2+ concentration was estimated at ,10,11 M, whereas in medium to low dissolved organic carbon waters the [Cu2+] was ,10,10 M. Speciation calculations performed for copper concentrations at the effective concentration level (where the biological effect is considered the same) resulted in very similar free copper concentrations (,10,8 M Cu) in these surface waters with different characteristics. These observations consistently show that the presence of organic matter decreases the bioavailability, uptake, and ecotoxicity of copper in the aquatic environment. It demonstrates that the DOC content must be included in site-specific environmental risk assessment for trace metals (at least for copper). It is the quantification of the effects described that allows policy makers to review the criteria for copper in surface waters. [source] Wastewater treatment polymers identified as the toxic component of a diamond mine effluentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2004Simone J. C. de Rosemond Abstract The EkatiÔ Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (,0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE. [source] Effect of culture water hardness on the sensitivity of Ceriodaphnia dubia to copper toxicityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2003Rami B. Naddy Abstract We examined whether the sensitivity of Ceriodaphnia dubia to copper toxicity was influenced by the hardness of the water in which they were reared or in which they were exposed. Organisms cultured in very hard water were 1.5-fold less sensitive to copper than those in moderately hard water. However, the hardness of the exposure water had a greater (2.5-fold) effect on copper median effective concentration (EC50s). [source] Copper toxicity thresholds for important restoration grass species of the western United States,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2002Mark W. Abstract Copper toxicity thresholds for plant species that are used in restoration activities in western North America have not been established. As a result, ecological risk assessments must rely on toxicity thresholds established for agronomic species, which usually differ from those of species used in restoration. Thus, risk assessors have the potential for classifying sites as phytotoxic to perennial, nonagronomic species and calling for intensive remediation activities that may not be necessary. The objective of this study was to provide a better estimate of Cu toxicity thresholds for five grass species that are commonly used in restoration efforts in the western United States. We used a greenhouse screening study where seedlings of introduced redtop (Agrostis gigantea Roth.), the native species slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners var. Pryor), tufted hairgrass (Deschampsia caespitosa [L.] Beauvois), big bluegrass (Poa secunda J. Presl var. Sherman), and basin wildrye (Leymus cinereus [Scribner&Merrill] A. Löve var. Magnar) and the agricultural species common wheat (Triticum aestivum L.) were grown in sand culture and exposed to supplemental concentrations of soluble Cu of 0 (control), 50, 100, 150, 200, 250, and 300 mg/L. We determined six measures of toxicity: the 60-d mean lethal concentration (LC50), 60-d mean effective concentration (EC50)-plant, 60-d EC50-shoot, 60-d EC50-root, phytotoxicity threshold (PT50)-shoot, and the PT50-root. Results suggest that these restoration grass species generally have higher Cu tolerance than agronomic species reported in the past. Of the species tested, redtop appeared to be especially tolerant of high levels of substrate and tissue Cu. Values of EC50-plant for restoration grasses were between 283 and 710 mg Cu/L compared to 120 mg Cu/L for common wheat. Measured PT50-shoot values were between 737 and 10,792 mg Cu/ L. These reported thresholds should be more useful for risk assessors than those currently used, which are based largely on agronomic crops. [source] Aquatic toxicity of triclosanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2002David R. Orvos Abstract The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated-sludge microorganisms, algae, invertebrates, and fish. Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility. The 48-h Daphnia magna median effective concentration (EC50) was 390 ,g/L and the 96-h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 ,g/L, respectively. A no-observed-effect concentration (NOEC) and lowest-observed-effect concentration of 34.1 ,g/L and 71.3 ,g/L, respectively, were determined with an early life-stage toxicity test with Onco-rhynchus mykiss. During a 96-h Scenedesmus study, the 96-h biomass EC50 was 1.4 ,g/L and the 96-h NOEC was 0.69 ,g/L. Other algae and Lemna also were investigated. Bioconcentration was assessed with Danio rerio. The average TCS accumulation factor over the five-week test period was 4,157 at 3 ,g/L and 2,532 at 30 ,g/L. Algae were determined to be the most susceptible organisms. Toxicity of a TCS-containing wastewater secondary effluent to P. promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS-treated laboratory units were detected. The neutral form of TCS was determined to be associated with toxic effects. Ionization and sorption will mitigate those effects in the aquatic compartment. [source] Toxicity of tributyltin and triphenyltin to early life-stages of Paracentrotus lividus (Echinodermata: Echinoidea)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2002Alessandra Arizzi Novelli Abstract Sperm cell and embryo toxicity tests using the Mediterranean sea urchin Paracentrotus lividus were performed to assess the toxicity of tributyltin chloride, bis(tributyltin)oxide, triphenyltin acetate, and triphenyltin hydroxide. Toxicity values (mean effective concentration [EC50]) ranged from 2.97 to 18.5 ,g/L for sperm cells and from 1.11 to 2.62 ,g/L for embryos. For sperm cells, the toxicity of the two tributyl compounds was significantly greater than that of two triphenyl compounds; for embryos, the triphenyl compounds appeared to be more toxic. Study of embryotoxic effects highlighted closely concentration-dependent damages, the most sensitive stages corresponding to the crucial phases of differentiation (gastrula and prisma). Both EC50 and no-observed-effect concentration values for the four organotin compounds are similar to those reported in the literature for early life stages of other marine organisms. [source] Acute toxicity of heavy metals to acetate-utilizing mixed cultures of sulfate-reducing bacteria: EC100 and EC50ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2001Vivek P. Utgikar Abstract Acid mine drainage from abandoned mines and acid mine pit lakes is an important environmental concern and usually contains appreciable concentrations of heavy metals. Because sulfate-reducing bacteria (SRB) are involved in the treatment of acid mine drainage, knowledge of acute metal toxicity levels for SRB is essential for the proper functioning of the treatment system for acid mine drainage. Quantification of heavy metal toxicity to mixed cultures of SRB is complicated by the confounding effects of metal hydroxide and sulfide precipitation, biosorption, and complexation with the constituents of the reaction matrix. The objective of this paper was to demonstrate that measurements of dissolved metal concentrations could be used to determine the toxicity parameters for mixed cultures of sulfate-reducing bacteria. The effective concentration, 100% (EC100), the lowest initial dissolved metal concentrations at which no sulfate reduction is observed, and the effective concentration, 50% (EC50), the initial dissolved metal concentrations resulting in a 50% decrease in sulfate reduction, for copper and zinc were determined in the present study by means of nondestructive, rapid physical and chemical analytical techniques. The reaction medium used in the experiments was designed specifically (in terms of pH and chemical composition) to provide the nutrients necessary for the sulfidogenic activity of the SRB and to preclude chemical precipitation of the metals under investigation. The toxicity-mitigating effects of biosorption of dissolved metals were also quantified. Anaerobic Hungate tubes were set up (at least in triplicate) and monitored for sulfate-reduction activity. The onset of SRB activity was detected by the blackening of the reaction mixture because of formation of insoluble ferrous sulfide. The EC100 values were found to be 12 mg/L for copper and 20 mg/L for zinc. The dissolved metal concentration measurements were effective as the indicators of the effect of the heavy metals at concentrations below EC100. The 7-d EC50 values obtained from the difference between the dissolved metal concentrations for the control tubes (tubes not containing copper or zinc) and tubes containing metals were found to be 10.5 mg/L for copper and 16.5 mg/L for zinc. Measurements of the turbidity and pH, bacterial population estimations by means of a most-probable number technique, and metal recovery in the sulfide precipitate were found to have only a limited applicability in these determinations. [source] Polycyclic aromatic hydrocarbons as inducers of cytochrome P4501A enzyme activity in the rainbow trout liver cell line, RTL-W1, and in primary cultures of rainbow trout hepatocytesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001Anja Behrens Abstract In order to investigate cell-specific differences in the response of in vitro models to environmental toxicants, we compared the capacity of nine polycyclic aromatic hydrocarbons (PAHs) to induce cytochrome P4501A (CYP1A) in primary rainbow trout (Oncorhynchus mykiss) hepatocytes and a rainbow trout liver cell line, RTL-W1. Induction of CYP1A was estimated from the catalytic activity of 7-ethoxyresorufin- O -deethylase (EROD) and compared by median effective concentration (EC50) values, induction spans, and benzo[a]pyrene induction equivalency factors for inducing PAHs. The influence of culture conditions was investigated with respect to the presence or absence of serum and varying exposure times. Both in vitro systems lead to an identical classification of the PAHs in noninducing (anthracene, fluoranthene, phenanthrene, and pyrene) and inducing compounds with a similar ranking of inducing PAHs. Mean EC50 values in RTL-W1 cells were, respectively, 343 and 266 nM for benzo[a]anthracene, 57 and 92 nM for BaP, 134 and 283 nM for benzo[b]fluoranthene, 455 and 270 nM for chrysene, and 98 and 116 nM for 3-methylcholanthrene. Compared to primary hepatocytes, the RTL-W1 cell line was more sensitive in its EROD response to the presence or absence of serum and to the increase in exposure time, which led to higher EC50 values. [source] Cytotoxicity of settling particulate matter and sediments of the Neckar River (Germany) during a winter floodENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2000Henner Hollert Abstract To investigate the cytotoxic and genotoxic potentials of settling particulate matter (SPM) carried by the Neckar River, a well-studied model for a lock-regulated river in central Europe, during a flood, acute cytotoxicity was investigated using the fibroblast-like fish cell line RTG-2 with the neutral red retention, the succinic acid dehydrogenase (MTT), and the lactatedehydro-genase (LDH) release assays as well as microscopic inspection as endpoints. Genotoxicity of water, pore water, sediments, and SPM were assessed using the Ames test. Different extraction methods (Soxhlet extraction with solvents of variable polarity as well as a fluid/fluid extraction according to pH) in addition to a supplementation of biotests with S9 fractions from the liver of ,-naphthoflavone/phenobarbital-induced rats allowed a further characterization of the biological damage. Both sediments and SPM extracts caused cytotoxic effects in RTG-2 cells. Cytotoxicity was found to increase significantly with polarity of extracting solvents (NR50 = effective concentration for 50% cell death in the neutral red test: 80 [65], 100 [70], 180 [220], and 225 [270] mg/ml for ethanol, acetone, dichloromethane, and n -hexane extracts, respectively, if measured with [without] S9 supplementation). Following extraction according to pH, cytotoxicity could be attributed mainly to neutral substances (NR50: 80 and 218 mg dry SPM/ml test medium for the neutral and the acid fractions, respectively), whereas the slightly acid and basic fractions already showed little or no cytotoxicity. Samples taken during the period of flood rise showed the highest cytotoxic activities. Cytotoxicity was significantly enhanced by the addition of S9 preparations. In contrast, no genotoxic activity was found in native surface waters, pore waters, and SPM. [source] Acute toxicity of para -nonylphenol to saltwater animals,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2000Suzanne M. Lussier Abstract para -Nonylphenol (PNP), a mixture of alkylphenols used in producing nonionic surfactants, is distributed widely in surface waters and aquatic sediments, where it can affect saltwater species. This article describes a database for acute toxicity of PNP derived for calculating a national saltwater quality criterion. Using a flow-through exposure system with measured concentrations, we tested early life stages of four species of saltwater invertebrates and two species of fish. Static 96-h tests were also conducted on zoeal Homarus americanus, embryo-larval Mulinia lateralis, and larval Pleuronectes americanus. The number of organisms surviving the flow-through test was measured at 2, 4, 8, and 12 h and daily through day 7. Mortality for most species plateaued by 96 h. The ranked sensitivities (96-h 50% lethal concentrations, measured in micrograms per liter) for the species tested were 17 for Pleuronectes americanus, 37.9 (48-h 50% effective concentration) for Mulinia lateralis, 59.4 for Paleomonetes vulgaris, 60.6 for Americamysis bahia (formerly Mysidopsis bahia), 61.6 for Leptocheirus plumulosos, 70 for Menidia beryllina, 71 for Homarus americanus, 142 for Cyprinodon variegatus, and > 195 for Dyspanopius sayii. Values for the seven most sensitive of these species ranged over a factor of only 4.2. The narrow range of responses for PNP implies that exceeding a threshold concentration would endanger a large proportion of the aquatic community. [source] HCV796: A selective nonstructural protein 5B polymerase inhibitor with potent anti-hepatitis C virus activity In Vitro, in mice with chimeric human livers, and in humans infected with hepatitis C virus,HEPATOLOGY, Issue 3 2009Norman M. Kneteman Anti-hepatitis C virus (HCV) drug development has been challenged by a lack of experience with inhibitors inclusive of in vitro, animal model, and clinical study. This manuscript outlines activity and correlation across such a spectrum of models and into clinical trials with a novel selective nonstructural protein 5B (NS5B) polymerase inhibitor, HCV796. Enzyme assays yielded median inhibitory concentration (IC50) values of 0.01 to 0.14 ,M for genotype 1, with half maximal effective concentration (EC50s) of 5 nM and 9 nM against genotype 1a and 1b replicons. In the chimeric mouse model, a 2.02 ± 0.55 log reduction in HCV titer was seen with monotherapy, whereas a suboptimal dose of 30 mg/kg three times per day in combination with interferon demonstrated a 2.44 log reduction (P = 0.001 versus interferon alone) Clinical outcomes in combination with pegylated interferon and ribavirin have revealed additive efficacy in treatment naïve patients. Abnormal liver function test results were observed in 8% of HCV-796 patients treated for over 8 weeks, resulting in suspension of further trial activity. Conclusion: The RNA-dependent RNA polymerase inhibitor HCV796 demonstrated potent anti-HCV activity consistently through enzyme inhibition assays, subgenomic replicon, and chimeric mouse studies. Strong correlations of outcomes in the mouse model were seen with subsequent clinical trials, including a plateau in dose-related antiviral activity and additive impact from combination therapy with interferon. These outcomes demonstrate the utility of the range of in vitro and in vivo models now available for anti-HCV drug development and support the potential utility of polymerase inhibitors in future combination therapies for HCV treatment. (HEPATOLOGY 2009.) [source] An abnormal gene expression of the ,-adrenergic system contributes to the pathogenesis of cardiomyopathy in cirrhotic rats,HEPATOLOGY, Issue 6 2008Giulio Ceolotto Decreased cardiac contractility and ,-adrenergic responsiveness have been observed in cirrhotic cardiomyopathy, but their molecular mechanisms remain unclear. To study ,-adrenergic,stimulated contractility and ,-adrenergic gene expression patterns, 20 Wistar Kyoto rats were treated with carbon tetrachloride to induce cirrhosis and 20 rats were used as controls. Left ventricular contractility was recorded in electrically driven isolated hearts perfused at constant flow with isoproterenol (10,10 to 10,6 M). A cardiac gene expression profile was obtained using a microarray for the myocyte adrenergic pathway. The cardiac contractility maximal response to isoproterenol was significantly reduced in cirrhotic rats in comparison to control rats, whereas the half-maximal effective concentration was not different. In cirrhotic rats, cardiac gene expression analysis showed a significant overexpression of G protein alpha,inhibiting subunit 2 (G,i2), cyclic nucleotide phosphodiesterase (PDE2a), regulator of G-protein signaling 2 (RGS2), and down-expression of adenylate cyclase (Adcy3). These results indicate that overexpression of G,i2, PDE2a, and RGS2 down-regulates the ,-adrenergic signaling pathway, thus contributing to the pathogenesis of cirrhotic cardiomyopathy. (HEPATOLOGY 2008;48:1913-1923.) [source] Phytotoxicity assay for seed production using Brassica rapa L.INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2010David Olszyk Abstract Although pesticide drift can affect crop yield adversely, current plant testing protocols emphasize only the potential impacts on vegetative plant growth. The present study was conducted to determine whether a plant species with a short life cycle, such as Brassica rapa L. Wisconsin Fast Plants®, can be used to indicate potential effects on seed production of herbicides applied at relatively low levels (e.g., low field application rates [FAR]). The effects of ,0.1,×,FAR of aminopyralid, cloransulam, glyphosate, primisulfuron, or sulfometuron applied 14 d after emergence (DAE), were evaluated for B. rapa grown in mineral soil in pots under greenhouse conditions. Effects were expressed as the effective concentration of the herbicide producing a 25% reduction in a response (EC25) based on nonlinear regression. Brassica rapa seed dry weight was reduced by sulfometuron at an EC25 of 0.00014,×,a field application rate (FAR) of 53,g active ingredient (a.i.) ha,1, primisulfuron at 0.008 (experiment 1) or 0.0050 (experiment 2),×,FAR of 40,g,a.i.,ha,1, cloransulam at 0.022,×,FAR of 18,g,a.i.,ha,1, glyphosate at 0.0399,×,FAR of 834,g,a.i.,ha,1, and by aminopyralid at 0.005,×,FAR of 123,g,a.i.,ha,1, but only for 1 of 2 experiments. Reduced seed production occurred at less than the FAR that reduced shoot dry weight with sulfometuron and primisulfuron, whereas neither aminopyralid, cloransulam, nor glyphosate affected shoot dry weight. A short life cycle form of B. rapa could be used to indicate reduced seed production with plants grown only 1 week longer (,35,DAE) than as the current vegetative vigor test for nontarget herbicide effects on plants. Integr Environ Assess Manag 2010;6:725,734. © 2010 SETAC [source] In vitro toxicity of several dithiocarbamates and structure,activity relationshipsJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2002N. Segovia Abstract Dithiocarbamates (DTCs) are chemicals featuring a great chelating capacity. The toxicological study of DTCs is very important in view of their relatively simple synthesis and wide array of sanitary and industrial applications. In this study, the toxicity of some of the more recently synthesized DTCs is determined using an extremely simple bioassay, described in previous studies, based on the inhibition of growth of Escherichia coli (IGEC). The lowest-observed-effect concentration (LOEC), the median effective concentration (EC50) and no-observed-effect concentration (NOEC) of the following sodium dithiocarbamates was determined: N -benzyl- N -methyldithiocarbamate·2H2O, N -benzyl- N -isopropyldithiocarbamate·3H2O, N -benzyl- N -ethyldithiocarbamate·2H2O, N -butyl- N -methyldithiocarbamate·2H2O, N,N -dibenzyldithiocarbamate·2H2O and N -benzyl-2-phenethyldithiocarbamate·4H2O. Our results showed N,N -dibenzyl-DTC to be the least toxic of the tested substances, with an EC50 value of 1269.9 µg ml,1, whereas N -butyl- N -methyl-DTC and N -benzyl- N -methyl-DTC, with respective EC50 values of 14.9 µg ml,1 and 23.5 µg ml,1, were the most toxic. Regression analysis showed, through exponential models, that the degree of toxicity of this group of substances correlated with the molecular weight of the compound, the molecular weight of the smallest chemical radical linked to the dithiocarbamate group and the number of benzene rings present in the molecule. The consideration of these models allows us to establish that in general terms the toxicity of DTCs decreases exponentially with a greater molecular weight and the number of benzene rings. Copyright © 2002 John Wiley & Sons, Ltd. [source] OPTIMIZATION OF GUAVA JUICE AND POWDER PRODUCTIONJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2001CHETAN A. CHOPDA Enzyme treatment of guava puree was optimized for yield and clarity by first determining the most effective concentration, then varying both incubation time and temperature. Application of Pectinex Ultra SP-L® was optimal using 700 ppm enzyme for 1.5 h at 50C. Clarified guava juice was clearer (89.6%) when prepared using ultrafiltration (MW cut-off 40,60 kDa) rather than plate and frame filtration (82.8%); however, the latter was higher in both soluble solids and ascorbic acid. Clarified guava juice powders were made using freeze-drying, spray drying and tunnel drying. The freeze-dried product had superior quality; however, the spray-dried product was stable and may be more economical. Sensory panelists ranked the cloudy juice prepared from aseptic guava puree highest, and there were no significant differences between the juices from pasteurized, clear nectar, freeze-dried puree powder or juice powder. [source] | |||||||||||||||||||