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David R. Brown - One of the best experts on this subject based on the ideXlab platform.

  • Prion protein reduces both oxidative and non-oxidative Copper Toxicity.
    Journal of neurochemistry, 2006
    Co-Authors: Cathryn L. Haigh, David R. Brown
    Abstract:

    The prion protein is a membrane tethered glycoprotein that binds Copper. Conversion to an abnormal isoform is associated with neurodegenerative diseases known as prion diseases. Expression of the prion protein has been suggested to prevent cell death caused by oxidative stress. Using cell based models we investigated the potential of the prion protein to protect against Copper Toxicity. Although prion protein expression effectively protected neurones from Copper Toxicity, this protection was not necessarily associated with reduction in oxidative damage. We also showed that glycine and the prion protein could both protect neuronal cells from oxidative stress. Only the prion protein could protect these cells from the Toxicity of Copper. In contrast glycine increased Copper Toxicity without any apparent oxidative stress or lipid peroxidation. Mutational analysis showed that protection by the prion protein was dependent upon the Copper binding octameric repeat region. Our findings demonstrate that Copper Toxicity can be independent of measured oxidative stress and that prion protein expression primarily protects against Copper Toxicity independently of the mechanism of cell death.

Colin R. Janssen - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Varying Physicochemistry of European Surface Waters on the Copper Toxicity to the Green Alga Pseudokirchneriella subcapitata
    Ecotoxicology (London England), 2005
    Co-Authors: Dagobert G. Heijerick, Karel De Schamphelaere, Bart T.a. Bossuyt, M.b.m. Indeherberg, M. Mingazzini, Colin R. Janssen
    Abstract:

    Most standard Toxicity test results, used in present environmental risk assessment and water quality criteria (WQC) setting procedures are obtained with standard test media that are not representative for natural surface waters when metal Toxicity modifying factors like pH, water hardness and dissolved organic carbon (DOC) are considered. The aim of this study was, using the green alga Pseudokirchneriella subcapitata, (1) to investigate the individual effects of Ca, Mg (the hardness cations) and pH on the Toxicity of Copper in reconstituted artificial test waters and (2) to study the Copper Toxicity in 13 spiked surface waters originating from different European eco-regions. Surface waters were selected such that a broad range of DOC (1.55–20.4 mg/l), pH (5.52–8.30) and water hardness (7–238 mg CaCO3/l) was covered. Tests in reconstituted artificial waters demonstrated that the 72 h-EbC50 (expressed as dissolved Cu) increased by about a factor of 3 when the Ca and Mg concentrations increased from 0.25 to 2.5 mM. When pH was increased from 5.8 to 8.0, dissolved 72 h-EbC50 decreased by a factor of 3. It is suggested that competition between Cu2+, Ca2+, Mg2+ and H+ ions at the cell surface are the most likely explanation for these observations. Dissolved 72 h-EbC50s in the natural surface waters varied between 32.0 and 245 μg Cu/l and were up to a factor 15 higher than the 72 h-EbC50 in standard artificial medium (16.5±4.8 μg Cu/l). Consequently, Water Effect Ratio’s (WER, the ratio between the EC50 in natural water to the EC50 in standard test water) ranged from 1.9 to 14.8. Linear regression analysis revealed that higher EbC50 were significantly related to higher DOC-concentration of the natural waters (R 2 = 0.69), but that water hardness and pH did not show a significant relation with Copper Toxicity in these surface waters. In European surface waters, a positive correlation is observed between water hardness and pH. As a result, hardness and pH effects on Copper Toxicity are counteractive in European surface waters, resulting in the highly significant relation between the 72 h-EbC50 and DOC-concentration. Normalisation of the obtained effect concentrations using a Biotic Ligand based predictive Cu-Toxicity model revealed that variation in DOC and pH are mainly responsible for the observed differences of Cu-Toxicity in natural waters.

  • development and field validation of a biotic ligand model predicting chronic Copper Toxicity to daphnia magna
    Environmental Toxicology and Chemistry, 2004
    Co-Authors: Karel De Schamphelaere, Colin R. Janssen
    Abstract:

    In this study, we developed a Toxicity model predicting the long-term effects of Copper on the reproduction of the cladoceran Daphnia magna that is based on previously reported Toxicity tests in 35 exposure media with different water chemistries. First, it was demonstrated that the acute Copper biotic ligand model (BLM) for D. magna could not serve as a reliable basis for predicting chronic Copper Toxicity. Consequently, BLM constants for chronic exposures were derived by multiple regression analysis of 21-d median effective concentrations (EC50s; expressed as Cu2+ activity) versus physicochemistry from a large Toxicity dataset and the results of an additional experiment in which the individual effect of sodium on Copper Toxicity was investigated. The effect of sodium on chronic Toxicity (log KNaBL = 2.91) seemed to be similar to its effect on acute Toxicity (log KNaBL = 3.19). However, in contrast to the acute BLM, no significant calcium, magnesium, or combined competition effect was observed, and an increase in proton competition and bioavailability of CuOH+ and CuCO3 complexes was noted. Some indirect evidence was also found for some limited Toxicity of complexes of Copper with two of three tested types of dissolved organic matter. Because the latter was only a minor effect, this factor was not included in the chronic Cu BLM. The newly developed model performed well in predicting 21-d EC50s and no-observed-effect concentrations in natural water samples: 79% of the Toxicity threshold values were predicted within a factor of two of the observed values. It is clear, however, that more research is needed to provide information on the exact mechanisms that have resulted in different BLM constants for chronic exposures (as opposed to acute exposures). It is suggested that the developed model can contribute to the improvement of risk assessment procedures of Copper by incorporating bioavailability of Copper in these regulatory exercises.

  • Development and field validation of a predictive Copper Toxicity model for the green alga Pseudokirchneriella subcapitata.
    Environmental toxicology and chemistry, 2003
    Co-Authors: Karel De Schamphelaere, Flavio M. Vasconcelos, Dagobert G. Heijerick, Filip Tack, Katrien Delbeke, Herbert E. Allen, Colin R. Janssen
    Abstract:

    In this study, the combined effects of pH, water hardness, and dissolved organic carbon (DOC) concentration and type on the chronic (72-h) effect of Copper on growth inhibition of the green alga Pseudokirchneriella subcapitata were investigated. Natural dissolved organic matter (DOM) was collected at three sites in Belgium and The Netherlands using reverse osmosis. A full central composite test design was used for one DOM and a subset of the full design for the two other DOMs. For a total number of 35 Toxicity tests performed, 72-h effect concentration resulting in 10% growth inhibition (EbC10s) ranged from 14.2 to 175.9 micrograms Cu/L (factor 12) and 72-h EbC50s from 26.9 to 506.8 micrograms Cu/L (factor 20). Statistical analysis demonstrated that DOC concentration, DOM type, and pH had a significant effect on Copper Toxicity; hardness did not affect Toxicity at the levels tested. In general, an increase in pH resulted in increased Toxicity, whereas an increase of the DOC concentration resulted in decreased Copper Toxicity. When expressed as dissolved Copper, significant differences of Toxicity reduction capacity were noted across the three DOM types tested (up to factor 2.5). When expressed as Cu2+ activity, effect levels were only significantly affected by pH; linear relationships were observed between pH and the logarithm of the effect concentrations expressed as free Copper ion activity, that is, log(EbC50Cu2+) and log(EbC10Cu2+): (1) log(EbC50Cu2+)= - 1.431 pH + 2.050 (r2 = 0.95), and (2) log(EbC10cu2+) = -1.140 pH -0.812 (r2 = 0.91). A Copper Toxicity model was developed by linking these equations to the WHAM V geochemical speciation model. This model predicted 97% of the EbC50dissolved and EbC10dissolved values within a factor of two of the observed values. Further validation using Toxicity test results that were obtained previously with Copper-spiked European surface waters demonstrated that for 81% of tested waters, effect concentrations were predicted within a factor of two of the observed. The developed model is considered to be an important step forward in accounting for Copper bioavailability in natural systems.

Stephen J. Klaine - One of the best experts on this subject based on the ideXlab platform.

  • Influence of multiple water‐quality characteristics on Copper Toxicity to fathead minnows (Pimephales promelas)
    Environmental toxicology and chemistry, 2004
    Co-Authors: Katherine L. Sciera, J. Jeffery Isely, Joseph R. Tomasso, Stephen J. Klaine
    Abstract:

    Water quality influences the bioavailability and Toxicity of Copper to aquatic organisms. Understanding the relationships between water-quality parameters and Copper Toxicity may facilitate the development of site-specific criteria for water quality and result in better protection of aquatic biota. Many studies have examined the influence of a single water-quality parameter on Copper Toxicity, but the interactions of several characteristics have not been well studied in low-hardness water. The goal of the present research was to examine the interactions among water-quality characteristics and their effects on Copper Toxicity to larval fathead minnows (Pimephales promelas). The effects of dissolved organic carbon (DOC) concentration, DOC source, pH, and hardness on acute Copper Toxicity were determined using a complete factorially designed experiment. Hardness, pH, DOC, and interaction of pH and DOC all significantly affected Copper Toxicity. A predictive model based on these data described 88% of the variability in Copper Toxicity. This model also explained 58% of the variability in Copper Toxicity for an independent dataset of South Carolina (USA) waters. The biotic ligand model underpredicted the acute Copper Toxicity to fathead minnows when compared with observed values.

  • Influence of natural organic matter source on Copper Toxicity to larval fathead minnows (Pimephales promelas): implications for the biotic ligand model.
    Environmental toxicology and chemistry, 2004
    Co-Authors: Adam C. Ryan, Joseph R. Tomasso, Eric J. Van Genderen, Stephen J. Klaine
    Abstract:

    The influence of dissolved natural organic matter (NOM) source on Copper Toxicity was investigated with larval fathead minnows (Pimephales promelas) in reconstituted moderately hard water. Ninety-six-hour static renewal Toxicity tests were conducted to investigate an assumption of the biotic ligand model (BLM) that NOM source does not need to be considered to adequately predict Copper Toxicity. The nine different NOM isolates used in these Toxicity tests were chemically well-characterized substances that were obtained by reverse osmosis as part of an NOM typing project based in southern Norway. Three median lethal concentration (LC50) values were estimated for Toxicity tests conducted with each NOM, at nominal dissolved organic carbon (DOC) concentrations of 2, 5, and 10 mg/L. Tests also were conducted in dilution waters in which no NOM was added. Regression analyses were conducted to compare NOM-specific (specific NOM source) LC50s versus DOC concentration relationships to each other, as well as to the overall LC50 versus DOC concentration relationship. Statistical differences were found regarding the effects of NOM source on Copper Toxicity. Similar analyses were conducted with humic acid (HA) concentrations and spectral absorbance, and differences in the effect of NOM source on Copper Toxicity were similarly concluded. These results do not support the assumption that Copper Toxicity can be adequately predicted by utilizing DOC concentration, regardless of NOM source. Evaluation of relationships between LC50 values and other NOM characteristics revealed that despite significant differences due to NOM source on Copper Toxicity, DOC and HA concentrations were the most effective parameters in explaining variability in LC50 values. When BLM-predicted LC50 values were compared to observed LC50 values, predicted values showed reasonable agreement with observed values, but some deviations occurred due to NOM source and DOC concentration.

Xiaoli Shi - One of the best experts on this subject based on the ideXlab platform.

  • Determination of short-term Copper Toxicity in a multispecies microalgal population using flow cytometry
    Ecotoxicology and environmental safety, 2005
    Co-Authors: Fanxiang Kong, Meilin Wang, Leilei Qian, Xiaoli Shi
    Abstract:

    Abstract This study was conducted to determine the role of algal–algal interactions in a multispecies microalgal population on their sensitivities to Copper based on an enzyme inhibition assay using flow cytometric measures. Autofluorescence (chlorophyll a and phycocyanin) was used to identify species and count algal signals. The effect of multispecies population on Copper Toxicity of Microcystis aeruginousa was detected (1) at the same initial cell density, (2) at the same surface area, and (3) in the presence and absence of Chlorella pyrenoidosa and Scenedesmus obliquus. As Copper concentrations increased, esterase activity of M. aeruginosa changed in a concentration-dependent manner. The 24 h EC50 value of M. aeruginosa in the multispecies population was significantly (P

Michael D. Norenberg - One of the best experts on this subject based on the ideXlab platform.