The Experts below are selected from a list of 441258 Experts worldwide ranked by ideXlab platform

Alice Hontela - One of the best experts on this subject based on the ideXlab platform.

  • cytotoxic and endocrine disrupting potential of atrazine diazinon endosulfan and mancozeb in adrenocortical steroidogenic cells of rainbow trout exposed in vitro
    Toxicology and Applied Pharmacology, 2002
    Co-Authors: Marjolaine Bisson, Alice Hontela
    Abstract:

    An in vitro bioassay for detection and quantitative assessment of chemicals with the capacity to disrupt adrenal steroidogenesis has been developed and used to compare the cytotoxic and endocrine-disrupting potential of four pesticides. Enzymatically dispersed adrenocortical cells of rainbow trout (Oncorhynchus mykiss) were exposed in vitro to atrazine, diazinon, endosulfan, and mancozeb, and cortisol secretion in response to ACTH or dibutyryl-cAMP (dbcAMP) and cell viability were determined. The effective concentration, EC50 (concentration that inhibits cortisol secretion by 50%), the median lethal concentration, LC50 (concentration that kills 50% of the cells), and the LC50/EC50 ratio were established for the test pesticides. The pesticides were ranked as follows: EC50, endosulfan < diazinon < mancozeb < atrazine; LC50, diazinon < endosulfan < mancozeb < atrazine, with diazinon as the most cytotoxic. Endosulfan and mancozeb disrupted sites downstream of the cAMP-generating step of the cortisol synthetic pathway while atrazine seemed to act upstream from the cAMP step. The in vitro adrenal bioassay can be used for screening of adrenotoxicants and for mechanistic studies of adrenotoxicity.

  • Effects ofin VitroExposures to Cadmium, Mercury, Zinc, and 1-(2-Chlorophenyl)-1-(4-chlorophenyl)-2,2-dichloroethane on Steroidogenesis by Dispersed Interrenal Cells of Rainbow Trout (Oncorhynchus mykiss)
    Toxicology and Applied Pharmacology, 1999
    Co-Authors: Vincent S Leblond, Alice Hontela
    Abstract:

    Abstract Numerous environmental xenobiotics can act as endocrine disrupters in wildlife species. Fish chronically exposed to pollutants exhibit a deficiency in the synthesis of cortisol, a glucocorticosteroid hormone secreted by interrenal steroidogenic cells in response to ACTH by a mechanism mediated by cAMP. The capacity of a series of heavy metals (CdCl 2 , ZnCl 2 , HgCl 2 , and CH 3 HgCl) and 1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2-dichloroethane (o,p′-DDD) to disrupt cortisol secretion was determined in dispersed interrenal cells of rainbow trout ( Oncorhynchus mykiss ) exposed in vitro to the toxicant, by measuring cortisol secretion stimulated with ACTH or dibutiryl-cAMP (dbcAMP) and by assessing cell viability. The effect of cadmium in presence of zinc on the interrenal cells was also determined. The median lethal concentration (LC50, dose that kills 50% of the cells), median effective concentration (EC50, dose that inhibits cortisol secretion by 50%), and LC50/EC50 ratio were determined for each chemical to compare its endocrine toxicity and to test the specificity of the toxicants to act as endocrine disrupters. HgCl 2 had the lowest EC50 and LC50; it was the most toxic of the chemicals tested. The LC50/EC50 ratio was the highest for ZnCl 2 and CdCl 2 , indicating that these toxicants had the most specific endocrine toxicity. The mechanism of toxicity of heavy metals on cortisol-secreting cells involves a site situated downstream from the step generating cAMP, while o,p′-DDD seemed to impair a step located between adenyl cyclase activation and the ACTH binding. No evidence for a protector effect of zinc against cadmium toxicity was found.

William A Stubblefield - One of the best experts on this subject based on the ideXlab platform.

  • the interactive toxicity of cadmium copper and zinc to ceriodaphnia dubia and rainbow trout oncorhynchus mykiss
    Environmental Toxicology and Chemistry, 2015
    Co-Authors: Rami B Naddy, Adam S Cohen, William A Stubblefield
    Abstract:

    Traditionally, aquatic toxicity studies examine the toxicity of a single chemical to an organism. Organisms in nature, however, may be exposed to multiple toxicants. Given this is a more realistic exposure scenario in situ, the authors sought to understand the interactive toxicity of multiple metals to aquatic organisms. The authors performed a series of studies using equitoxic mixtures of cadmium, copper, and zinc to 2 aquatic organisms, rainbow trout (Oncorhynchus mykiss) and the waterflea, Ceriodaphnia dubia. Single metal toxicity tests were conducted to determine the acute median lethal concentration (LC50) values for O. mykiss and short-term, chronic median effective concentration (EC50) values for C. dubia. All 3 metals were then combined in equitoxic concentrations for subsequent mixture studies using a toxic unit (TU) approach (i.e., 1 TU = EC50 or LC50). For C. dubia, the mixture study showed greater-than-additive effects in hard water (TU-based EC50 = 0.74 TU), but less-than-additive effects in soft water (TU-based EC50 = 1.93 TU). The mixture effects for O. mykiss showed less-than-additive effects in both hard and soft waters, with TU-based LC50 values of 2.33 total TU and 2.22 total TU, respectively. These data are useful in helping understand metal mixture toxicity in aquatic systems and indicate that although in most situations the assumption of additivity of metal mixture toxicity is valid, under certain conditions it may not be sufficiently protective. Environ Toxicol Chem 2015;34:809–815. © 2014 SETAC

Yan Li - One of the best experts on this subject based on the ideXlab platform.

  • comparison of r metalaxyl and rac metalaxyl in acute chronic and sublethal effect on aquatic organisms daphnia magna scenedesmus quadricanda and danio rerio
    Environmental Toxicology, 2009
    Co-Authors: Zhenghua Duan, Zhongzhi Chen, Yan Li
    Abstract:

    Chiral pesticides are used widely in the world, and at present, older racemic products are being replaced by enantiopure products because of accelerated development of asymmetry synthesis techniques. Pesticides as xenobiotic released into environment impose a great stress on nontarget organisms. Although it is a necessary procedure for pesticides to have a registration based on toxicological data from nontarget organism, until now ecological risk assessment about metalaxyl only depend on racemic products. Hence, we investigated the acute, chronic, and sublethal toxicity of R-metalaxy and rac-metalaxyl on aquatic organisms such as D. magna (Daphnia magna), algae (Scenedesmus quadricanda), and adult zebrafish (Danio rerio). The results showed a significant difference in toxicity between R-metalaxyl and rac-metalaxyl. R-Metalaxy was about 20-fold more toxic to algae than rac-metalaxyl with IC50 of 222.89 ± 1.18 mg/L and 19.95 ± 1.12 mg/L, respectively. Similarly, R-metalaxyl was about fourfold toxic to D. magna than rac-metalaxyl according to the individual 24-h-LC50 values, and sixfold toxic than rac-metalaxyl based on 24-h-EC50 values. In the light of 48-h-LC50 and EC50, this difference in toxicity was more significant. As for adult zebrafish, there was no pronounced difference in acute toxicity, in addition, at sublethal level a different pattern in inducing Na+,K+-ATPase activity between them was found. In general, R-metalaxyl seemed more toxic to aquatic organisms than rac-metalaxyl. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.

  • Comparison of R‐metalaxyl and rac‐metalaxyl in acute, chronic, and sublethal effect on aquatic organisms: Daphnia magna, Scenedesmus quadricanda, and Danio rerio
    Environmental Toxicology, 2009
    Co-Authors: Zhenghua Duan, Zhongzhi Chen, Yan Li
    Abstract:

    Chiral pesticides are used widely in the world, and at present, older racemic products are being replaced by enantiopure products because of accelerated development of asymmetry synthesis techniques. Pesticides as xenobiotic released into environment impose a great stress on nontarget organisms. Although it is a necessary procedure for pesticides to have a registration based on toxicological data from nontarget organism, until now ecological risk assessment about metalaxyl only depend on racemic products. Hence, we investigated the acute, chronic, and sublethal toxicity of R-metalaxy and rac-metalaxyl on aquatic organisms such as D. magna (Daphnia magna), algae (Scenedesmus quadricanda), and adult zebrafish (Danio rerio). The results showed a significant difference in toxicity between R-metalaxyl and rac-metalaxyl. R-Metalaxy was about 20-fold more toxic to algae than rac-metalaxyl with IC50 of 222.89 ± 1.18 mg/L and 19.95 ± 1.12 mg/L, respectively. Similarly, R-metalaxyl was about fourfold toxic to D. magna than rac-metalaxyl according to the individual 24-h-LC50 values, and sixfold toxic than rac-metalaxyl based on 24-h-EC50 values. In the light of 48-h-LC50 and EC50, this difference in toxicity was more significant. As for adult zebrafish, there was no pronounced difference in acute toxicity, in addition, at sublethal level a different pattern in inducing Na+,K+-ATPase activity between them was found. In general, R-metalaxyl seemed more toxic to aquatic organisms than rac-metalaxyl. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.

Niloufar Sangak Sani Bozhgani - One of the best experts on this subject based on the ideXlab platform.

  • sublethal effects of atropa belladonna herbal extract on biological performance of the two spotted spider mite tetranychus urticae koch acari tetranychidae
    The Journal of Agricultural Science, 2018
    Co-Authors: Ayad Alsendi, Mohammadreza Havasi, Niloufar Sangak Sani Bozhgani
    Abstract:

    The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most important pests of agricultural products. Using chemical pesticides is one of the main methods for its management. Due to undesirable effects of synthetic pesticides, this research was conducted to achieve alternative safe compounds. In this study sublethal effect of Atropa belladonna herbal extract including LC10, LC20, LC30 and distilled water were evaluated on biological parameters (such as r, λ, GRR, R0 and T) of T. urticae. The experiments were done under laboratory condition at 25±2 °C, 60±5% RH, and a photoperiod of 16:8 (L: D) hours. The crude data were analyzed based on age-stage, two-sex life table analysis. The results indicated significant reduction in female’s duration of maturation, oviposition period and total fecundity by increasing examined dose. The highest and lowest values of the net reproductive rate (R0) were obtained 38.41 and 18.08 offspring/individual in control and LC30, respectively. The maximum values of intrinsic rate of increase (r) was 0.2201 day-1that occurred on control treatment while the minimum values was obtained 0.1937 day-1 in LC30 concentration. Finite rate of increase (λ) had significantly descended with concentration enhancing from LC20 to LC30, compared with the control. The results demonstrated that Atropa belladonna herbal extract could be incorporated in integrated pest management (IPM) programs of T. urticae.

Rami B Naddy - One of the best experts on this subject based on the ideXlab platform.

  • the interactive toxicity of cadmium copper and zinc to ceriodaphnia dubia and rainbow trout oncorhynchus mykiss
    Environmental Toxicology and Chemistry, 2015
    Co-Authors: Rami B Naddy, Adam S Cohen, William A Stubblefield
    Abstract:

    Traditionally, aquatic toxicity studies examine the toxicity of a single chemical to an organism. Organisms in nature, however, may be exposed to multiple toxicants. Given this is a more realistic exposure scenario in situ, the authors sought to understand the interactive toxicity of multiple metals to aquatic organisms. The authors performed a series of studies using equitoxic mixtures of cadmium, copper, and zinc to 2 aquatic organisms, rainbow trout (Oncorhynchus mykiss) and the waterflea, Ceriodaphnia dubia. Single metal toxicity tests were conducted to determine the acute median lethal concentration (LC50) values for O. mykiss and short-term, chronic median effective concentration (EC50) values for C. dubia. All 3 metals were then combined in equitoxic concentrations for subsequent mixture studies using a toxic unit (TU) approach (i.e., 1 TU = EC50 or LC50). For C. dubia, the mixture study showed greater-than-additive effects in hard water (TU-based EC50 = 0.74 TU), but less-than-additive effects in soft water (TU-based EC50 = 1.93 TU). The mixture effects for O. mykiss showed less-than-additive effects in both hard and soft waters, with TU-based LC50 values of 2.33 total TU and 2.22 total TU, respectively. These data are useful in helping understand metal mixture toxicity in aquatic systems and indicate that although in most situations the assumption of additivity of metal mixture toxicity is valid, under certain conditions it may not be sufficiently protective. Environ Toxicol Chem 2015;34:809–815. © 2014 SETAC