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  • anthrax lethal toxin  (3)
  • Chemical Engineering  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Involvement of phospholipase A2 activation in anthrax lethal toxin-induced cytotoxicity (1999)
    Springer
    Cell biology and toxicology 15 (1999), S. 19-29 
    Details
    ISSN: 1573-6822
    Keywords: anthrax lethal toxin ; cytotoxicity ; macrophage ; phospholipase A2 ; protein kinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The molecular mechanism of cytotoxic effect exerted by the lethal toxin (LeTx) of Bacillus anthracis is not well understood. In the present study, using primary culture of mouse peritoneal macrophages, we have investigated possible cytotoxic mechanisms. LeTx was not found to induce high levels of nitric oxide (NO) production for NO-mediated toxicity. Fragmentation of DNA, a biochemical marker of apoptosis, was not observed in LeTx-treated cells. Pretreatment of cells with antioxidants such as melatonin and dehydroepiandrosterone (DHEA) did not protect the LeTx-induced cytotoxicity. However, addition of phospholipase A2 (PLA2) inhibitors (quinacrine, p-bromophenacyl bromide, manoalide, butacaine) to the culture medium resulted in the inhibition of cytotoxicity of LeTx in a dose-dependent manner. LeTx-induced cytotoxicity was also inhibited by the tyrosine-specific protein kinase inhibitor genistein, but not by the protein kinase C inhibitors staurosporine or H-7. The results of these studies indicate a role for PLA2 and protein kinase in the cytotoxic mechanism of macrophages by anthrax lethal toxin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007546505528
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  • 2
    Electronic Resource
    Electronic Resource
    Dehydroepiandrosterone and melatonin prevent Bacillus anthracis lethal toxin-induced TNF production in macrophages (2000)
    Springer
    Cell biology and toxicology 16 (2000), S. 165-174 
    Details
    ISSN: 1573-6822
    Keywords: anthrax lethal toxin ; cytokine ; dehydroepiandrosterone ; melatonin ; tumor necrosis factor α
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The lethal toxin of Bacillus anthracis, which is composed of two separate proteinaceous exotoxins, namely protective antigen and lethal factor, is central to the pathogenesis of anthrax. Low levels of this toxin are known to induce release of cytokines such as tumor necrosis factor α (TNF-α). In the present study we investigated the effect of dehydroepiandrosterone (DHEA), melatonin (MLT), or DHEA + MLT on production of lethal toxin-induced TNF-α in mouse peritoneal macrophages. We found that treatment with DHEA significantly inhibited the TNF-α production caused by anthrax lethal toxin. Exposure of MLT to anthrax lethal toxin-treated macrophages also decreased the release of TNF-α to the extracellular medium as compared to the control. However, combined use of DHEA and MLT also inhibited TNF-α release, but not more than single therapies. These results suggest that DHEA and MLT may have a therapeutic role in reducing the increased cytokine production induced by anthrax lethal toxin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007606921569
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Intracellular calcium antagonist protects cultured peritoneal macrophages against anthrax lethal toxin-induced cytotoxicity (2000)
    Springer
    Cell biology and toxicology 16 (2000), S. 137-144 
    Details
    ISSN: 1573-6822
    Keywords: anthrax lethal toxin ; cytotoxicity ; intracellular calcium antagonist ; macrophage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The lethal toxin ofBacillus anthracis is central to the pathogenesis of anthrax. Using primary cultures of mouse peritoneal macrophages, we have demonstrated that intracellular calcium release inhibitors protect against anthrax lethal toxin-induced cytotoxicity. The cytolytic effect of anthrax lethal toxin was markedly reduced by dantrolene, an inhibitor of calcium release from intracellular calcium stores. Pretreatment of macrophages with cyclosporin A, which has been shown to be a potent inhibitor of calcium release from mitochondria, also protected cells against cytotoxicity. These results indicate that calcium release from intracellular store may be an essential step for the propagation of anthrax lethal toxin-induced cell damage in macrophages. Thus our findings suggest that dantrolene, cyclosporin A, and possibly other drugs affecting intracellular calcium pools might be effectively preventing the toxicity from anthrax lethal toxin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007646227674
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  • 4
    Electronic Resource
    Electronic Resource
    Reaction mechanisms of polyacrylonitrile on thermal treatment (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1452-1457 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A high-temperature radical scavenger, 2,2-diphenyl-l-picryl hydrazyl (DPPH), has been used to study the reaction mechanisms of polyacrylonitrile (PAN) on thermal treatment. The effect of DPPH on the cyclization reaction of PAN in both air and nitrogen, investigated by differential scanning calorimetry (DSC), helped to verify the proposed reaction mechanisms, i.e., the free radical and the ionic ones. For PAN homopolymer, the peak temperature of the reaction exotherm shifted to higher temperatures and the heat of reaction was decreased with increasing DPPH concentration. For PAN copolymer with methylacrylate and itaconic acid, however, the effects of DPPH on DSC thermograms were insignificant. The effects of IPPH suggest that the reaction of the nitrile groups proceeds by free radicals for the homopolymer while by ions for the copolymer. The activation energies for the thermal reactions of PAN in both air and nitrogen were also estimated by the dynamic DSC method, and they proved to be highly dependent on reaction mechanism, environment of thermal treatment, and DPPH concentration.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760332203
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature dependence of the nucleation effect of sorbitol derivatives on polypropylene crystallization (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1445-1451 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The temperature dependence of the nucleation effect of three sorbitol derivatives on the crystallization of isotactic polypropylene (iPP) was studied by means of isothermal crystallization kinetic analysis. Isothermal crystallization thermograms obtained by differential scanning calorimetry (DSC) were analyzed based on the Avrami equation. The Avrami analysis for the nucleated iPP was carried out with DSC data collected to 35% relative crystallinity, and the rate constants were corrected assuming the heterogeneous nucleation and three dimensional growth of iPP spherulites. A semi-empirical equation for the radial growth rate of iPP spherulites was given as a function of temperature and was used to determine the number of effective nuclei at different temperatures. The number of effective nuclei in the nucleated samples was estimated to be 3 × 102 ∽ 105 times larger than that in the neat iPP. The logarithmic numbers of the effective nuclei decreased linearly with decreasing degree of supercooling in the range of crystallization temperatures tested. The temperature dependence of the effect of the nucleating agents on iPP crystallization was given quantitatively in terms of the deactivation factor defined as a fraction of the particles that are active at a particular temperature but inert at the temperature one degree higher. The nucleation activity and its temperature dependence are considered to be cooperative effects of many factors, including the dispersion and the physical or chemical nature of the agent as well as the interaction between the agent and the polymer. It is suggested that the temperature dependence of the effect of a nucleating agent should be treated as a characteristic of a given polymer/ nucleating agent mixture.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760332202
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    Paper (German National Licenses)
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