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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 173 (2000), S. 1-9 
    ISSN: 1432-072X
    Keywords: Key words Metal ion transport ; ABC transporter ; Permease family ; Metalloregulatory protein ; Nickel-containing enzymes ; Metal resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transition metal Ni is an essential cofactor for a number of enzymatic reactions in both prokaryotes and eukaryotes. Molecular analyses have revealed the existence of two major types of high-affinity Ni2+ transporters in bacteria. The Nik system of Escherichia coli is a member of the ABC transporter family and provides Ni2+ ion for the anaerobic biosynthesis of hydrogenases. The periplasmic binding protein of the transporter, NikA, is likely to play a dual role. It acts as the primary binder in the uptake process and is also involved in negative chemotaxis to escape Ni overload. Expression of the nik operon is controlled by the Ni-responsive repressor NikR, which shows functional similarity to the ferric ion uptake regulator Fur. The second type of Ni2+ transporter is represented by HoxN of Ralstonia eutropha, the prototype of a novel family of transition metal permeases. Members of this family have been identified in gram-negative and gram-positive bacteria and recently also in a fission yeast. They transport Ni2+ with very high affinity, but differ with regard to specificity. Site-directed mutagenesis experiments have identified residues that are essential for transport. Besides these uptake systems, different types of metal export systems, which prevent microorganisms from the toxic effects of Ni2+ at elevated intracellular concentrations, have also been described.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4919
    Keywords: clofibric acid ; diethylmaleate ; DOCA-salt induced hypertension in Sprague-Dawley rats ; hepatic antioxidant status ; hepatic nitric oxide synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of 8-week diethylmaleate (DEM) and clofibric acid (CFA) supplemented diet on blood pressure, body and liver weights, liver antioxidant status and nitric oxide synthase (NOS) activity were investigated in 8-week DOCA-salt treated and untreated Sprague-Dawley male rats. It appeared that DEM and particularly CFA treatments were associated with a significant decrease in blood pressure in DOCA-salt treated rats, and an accentuation of the decreases in body weights in both diet supplemented groups. This was not associated with increases in NO production in the liver. In contrast, hepatic lipid peroxidation was significantly decreased in both DOCA-salt treated and untreated groups on DEM and particularly on CFA supplemented diet. The protective effects of CFA and DEM against hepatic cellular damage could be involved in the decreases in blood pressure in DOCA-salt treated rats, where CFA was more efficient than DEM. In CFA supplemented groups, there was a strong increase in hepatic superoxide dismutase (SOD), glutathione-peroxidase (GSH-Px), and catalase (CAT) activities and in DEM supplemented groups, increases in SOD and CAT activities and in GSH levels were observed. Our data suggest that normalization of blood pressure in DOCA-salt treated rats by CFA was due to an enhancement of the half-life of NO while DEM increased its availability.
    Type of Medium: Electronic Resource
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