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  • 1
    Electronic Resource
    Electronic Resource
    Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture (1992)
    Springer
    Archives of toxicology 66 (1992), S. 471-477 
    Details
    ISSN: 1432-0738
    Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin ; 1,2,3,7,8-Pentachlorodibenzo-p-dioxin ; 1,2,3,4,7,8-hex achlorodibenzo-p-dioxin ; 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin ; Acute toxicity ; Mixture ; Structure-activity relationship ; Toxic equivalency factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There is presently no scientifically proven method to assess the toxicity of environmental samples containing complex mixtures of chlorinated dibenzo-p-dioxins (CDDs) of known composition. Their risk assessment is currently based on the interim concept of toxicity equivalency factors (TEFs), with the unproven assumption that all interactions of CDDs are additive. To address this problem we conducted acute toxicity studies with four different CDDs, viz 2,3,7,8-tetrachlorodibenzo-p-dioxin (tetra-CDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (penta-CDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (hexa-CDD) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (hepta-CDD), all containing chlorine substituents in the crucial 2,3,7,8-positions. The homologues, dissolved in corn oil/acetone, were administered to groups of five male Sprague Dawley rats at several doses (at least three) by gastric intubation. The obtained mortality data were employed to calculate the LD20,50 and80 for each homologue. These data were subsequently used to prepare equipotent doses (expected mortality of 20, 50 and 80%) of a mixture containing all four homologues, each of them contributing one fourth of the toxicity, under the assumption of additive toxicity. The obtained LD50 value and (TEF) was for tetra-CDD 43 μg/kg (1), penta-CDD 206 μg/kg (0.2) hexa-CDD 887 μg/kg (0.05) and hepta-CDD 6325 μg/kg (0.007), respectively. The dose-response to the mixture confirmed the hypothesis of strict additivity in the acute toxicity of the four CDD homologues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970671
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture (1992)
    Springer
    Archives of toxicology 66 (1992), S. 478-483 
    Details
    ISSN: 1432-0738
    Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin ; 1,2,3,7,8-Pentachlorodibenzo-p-dioxin ; 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin ; 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin ; Mixture ; Structure-activity relationship ; Acute toxicity ; Phosphoenolpyruvate carboxykinase ; Pyruvate carboxylase ; γ-Glutamyl transpeptidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Male Sprague-Dawley rats were treated with an LD20, LD50 and LD80 respectively, of tetra-, penta-, hexa-,hepta-CDD and a mixture of the four CDDs, all carrying chlorine substituents in the biologically crucial 2, 3, 7, and 8 positions. Specific activities of two key enzymes of gluconeogenesis, viz, phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC), as well as the activity of the preneoplastic marker enzyme γ-glutamyl transpeptidase (γ-GT), were determined in livers of CDD-treated and ad libitum-fed control animals. PEPCK activity showed evidence for dose-related inhibition on the second day after dosing; PC activity was slightly reduced, whereas γ-GT activity was dose-dependently inhibited. By 8 days after dosing PEPCK activities were dose-dependently decreased after administration of all four CDDs and their mixture. PC activities were significantly reduced, but no dose-response was evident. The activity of γ-GT was dosedependently inhibited, but only to a value of 25% below control activities. It is concluded that CDDs share a common mechanism of acute toxicity, viz, inhibition of glucocorticoid-dependent enzymes which results in a derailment of intermediary metabolism not compatible with survival of the animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970672
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture (1992)
    Springer
    Archives of toxicology 66 (1992), S. 484-488 
    Details
    ISSN: 1432-0738
    Keywords: 2,3,7,8-Tetrachlorodibenzo-p-dioxin ; 1,2,3,7,8-Pentachlorodibenzo-p-dioxin ; 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin ; 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin ; Mixture ; Structure-activity relationship ; Acute toxicity ; Plasma tryptophan ; Ethoxyresorufin O-deethylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Male Sprague-Dawley rats were treated with an LD20, an LD50, and an LD80 of 2,3,7,8-tetrachlorodibenzop-dioxin (tetra-CDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (penta-CDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (hexa-CDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (hepta-CDD), respectively, and a mixture of the four homologues where each CDD was represented at one-fourth its previously established LD20, LD50, and LD80, respectively. Plasma tryptophan levels, liver ethoxyresorufin O-deethylase (EROD) activities, and liver weights were determined at 2 and 8 days after treatment. Plasma tryptophan levels were dose-dependently elevated, particularly at 8 days after treatment, by as much as 75% over control levels. EROD activity in CDD-treated animals was induced 27- to 28-fold, as compared with vehicle-treated controls, but did not show any dose-response. Liver weights were also significantly increased by the CDD treatments, but the increase was not dose related. There was no correlation between plasma tryptophan levels, a biomarker of acute toxicity of CDDs, and EROD activity, a biomarker of arylhydrocarbon (Ah) receptor-mediated enzyme induction. It is concluded that the acute toxicity of CDDs, which correlates and shows perfect structure-activity relationship with reduced activities of key enzymes of intermediary metabolism, and the induction of enzymes by much lower doses of CDDs in the liver, have different mechanisms of action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970673
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    Paper (German National Licenses)
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