Change of liver metabolism of 1,2-dibromoethane during simultaneous treatment with carbon tetrachloride

The combination of carbon tetrachloride (CCl₄) and 1,2-dibromoethane (DBE) in isolated rat hepatocytes led to a significant potentiation of both lipid peroxidation and of plasma membrane damage observed after a single treatment with CCl₄. Such a synergistic effect appeared to be related to the CCl₄-induced shift of DBE metabolism from the cytosolic conjugation with glutathione towards the microsomal transformation into toxic intermediates. In fact, CCl₄ significantly inactivated hepatocyte total GSH-transferase, i.e. the DBE detoxification pathway. Furthermore, while the microsomal metabolism of CCl₄ was not affected by the simultaneous presence of DBE, the amount of DBE reactive metabolities covalently bound to hepatocyte protein was significantly enhanced in the presence of CCl₄.     

Aphid Herbivory Drives Asymmetry in Carbon for Nutrient Exchange between Plants and an Arbuscular Mycorrhizal Fungus

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Bioaccumulation of heavy elements by Armadillidium vulgare (Crustacea,Isopoda) exposed to fallout of a municipal solid waste landfill

This paper reports the response of isopods exposed to fallout of a municipal solid waste landfill located in central Italy. Soil samples and specimens of Armadillidium vulgare were collected at different distances from the landfill and analyzed to determine the concentrations of heavy elements such as As, Cd, Co, Cr, Cu, Ni, Pb, Sb, V and Zn. The isopod analysis was performed on unpurged and purged specimens. Analytical data indicate that the soil contents of heavy elements were quite uniform and within the respective local geochemical background. Slight enrichments of Cu and Pb were found in some soils collected within the solid waste. Purged isopods showed an accumulation of As, Co, Cr, Ni, Sb and V whose body levels decreased as the distance from the landfill increased. Cd, Cu, Pb and Zn concentrations in purged specimens were rather uniform and no significant variation trend occurred. This result probably was due to the fact that the isopods are provided with physiological mechanisms of regulation for these heavy elements. Analytical data also indicate the ability of A. vulgare to adsorb differently the heavy elements according to the following order: As > Co > Ni > Pb > V. The contents of heavy elements in unpurged specimens were higher than in purged ones. This finding suggested that the defecation has marked effects on the tissue levels of heavy elements in isopods. This study indicates that the isopods provide useful information about environmental quality in areas characterized by low and discontinuous emission of heavy elements and their low accumulation in soil.     

Effect of Different Carbon and Nitrogen Sources on Clostridium argentinense Toxigenicity in Coculture withPseudomonas mendocina

The effect of different carbon and nitrogen sources on the production of toxin by Clostridium argentinense was examined. The toxin production by C. argentinense in coculture with Pseudomonas mendocina increased in all the cases in relation to that produced by monocultures independent of the nature of the source. Using dextrin as carbon source C. argentinense produced the highest levels of toxin both in monocultures (300 LD₅₀/mL) and in cocultures with P. mendocina (5000 LD₅₀/mL). Experiments run in a microfermenter showed that the slow growth of cocultures associated with the assimilation of dextrin and the pH and Eh profiles favoured the production of toxin. Of the nitrogen sources assayed, corn steep liquor sustained the highest levels of toxin in both monocultures and cocultures with 3 and 2.8 fold increases with respect to that obtained using proteose peptone. The toxin production by C. argentinense cultures and C. argentinense–P. mendocina cocultures was highly dependent on the nature of the carbon and nitrogen sources used in the culture media. Growth of C. argentinense on substrates slowly assimilated stimulated the production of toxin.     

X-ray absorption spectroscopy of selenium-containing amino acids

Received: 2 April 1999 / Accepted: 17 September 1999     

Decreased hydraulic conductance in plants at elevated carbon dioxide

Previous work indicated that long-term exposure to elevated carbon dioxide levels can reduce hydraulic conductance in some species, but the basis of the response was not determined. In this study, hydraulic conductance was measured at concentrations of both 350 and 700 cm³ m^–3 carbon dioxide for plants grown at both concentrations, to determine the reversibility of the response. In Zea mays and Amaranthus hypochondriacus , exposure to the higher carbon dioxide concentration for several hours reduced whole-plant transpiration rate by 22–40%, without any consistent change in leaf water potential, indicating reversible reductions in hydraulic conductance at elevated carbon dioxide levels. Hydraulic conductance in these species grown at both carbon dioxide concentrations responded similarly to measurement concentration of carbon dioxide, indicating that the response was reversible. In Glycine max , which in earlier work had shown a long-term decrease in hydraulic conductance at elevated carbon dioxide levels, and in Abutilon theophrasti , no short-term changes in hydraulic conductance with measurement concentration of carbon dioxide were found, despite lower transpiration rates at elevated carbon dioxide. In G. max and Medicago sativa , growth at high dew-point temperature reduced transpiration rate and decreased hydraulic conductance. The results indicate that both reversible and irreversible decreases in hydraulic conductance can occur at elevated carbon dioxide concentrations, and that both could be responses to reduced transpiration rate, rather than to carbon dioxide concentration itself.