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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of 2-hydroxybenzoate (2-OHB, salicylate) on the mineralization rate of [14C]naphthalene, the population density of naphthalene-degrading bacteria, and the concentration of genes encoding for naphthalene dioxygenase in a soil bacterial community was investigated. Six different concentrations of 2-OHB (10, 20, 50, 100, 150 and 200 μg g−1 soil) were tested in 100-g portions of soil. The addition of 10, 20 or 50 μg 2-OHB g−1 soil produced a general increase in total soil bacterial population density, whereas the addition of 100 μg or 200 μg 2-OHB g−1 soil specifically increased the proportion of naphthalene degraders relative to the total population. The addition of 50 μg 2-OHB g−1 soil produced a fourfold increase (the maximum observed) in the rate of naphthalene mineralization relative to the rate in unamended soil. The concentration of 2-OHB (≤ 100 μg/g) added to soil correlated with the population density of naphthalene degraders (r=0.961). Addition of up to 200 μg 2-OHB g−1 correlated with the abundance of DNA sequences homologous to known naphthalene dioxygenase genes (nahAB) (r=0.958). However, mineralization of [14C]naphthalene was stimulated significantly only by the addition of 50 μg 2-OHB g−1 soil. Results of the mineralization experiments were supported by the detection of nahAB mRNA extracted directly from soil. The specificity of the effect of 2-OHB on naphthalene biodegradation was confirmed in a control experiment using equivalent concentrations of 4-OHB which repressed naphthalene mineralization by about 50%. Addition of ammonium nitrate to the soil also increased the rate of naphthalene mineralization. Ammonium nitrate added together with 2-OHB reduced the mineralization enhancement effect of either compound alone. The study confirmed that specific induction of biodegradative genes can enhance chemical pollutant removal in situ.
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to study phenotypic and genotypic alterations in response to selected conditions of stress, Pseudomonas aeruginosa PU21, harboring the multi-resistance plasmid, Rip64 (142.5 kb), was adapted by serial subcultivation on selective agar plates, amended with either Hg2+, carbenicillin, or gentamicin. Concentrations of the selective agents, to which P. aeruginosa PU21 Rip64 carried plasmid-encoded resistance genes, were close to or slightly above the respective minimal inhibitory concentration. Three different substrains were obtained: R64-M was adapted to Hg2+, R64-C to carbenicillin, and R64-G to gentamicin. All three substrains showed elevated levels of Hg2+ and carbenicillin resistance. Resistance to other antibiotics was either increased, decreased or unaffected. Increased Hg2+ resistance in all adapted substrains was accompanied by higher activity and less stringent induction of mercury reductase, as determined by Hg-volatilization assays with resting cells. No plasmid alterations compared to the non-adapted strain were detected in R64-C, but in R64-M and R64-G plasmid sizes increased by approx. 23 kb, as detected by pulsed field gel electrophoresis and the occurrence of additional DNA fragments after digestions with several restriction endonucleases. The plasmid localized gene rearrangements were accompanied by additional DNA fragments hybridizing with a merA gene probe.
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  • 3
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to study phenotypic and genotypic alterations in response to selected conditions of stress, Pseudomonas aeruginosa PU21, harboring the multi-resistance plasmid, Rip64 (142.5 kb), was adapted by serial subcultivation on selective agar plates, amended with either Hg2+, carbenicillin, or gentamicin. Concentrations of the selective agents, to which P. aeruginosa PU21 Rip64 carried plasmid-encoded resistance genes, were close to or slightly above the respective minimal inhibitory concentration. Three different substrains were obtained: R64-M was adapted to Hg2+, R64-C to carbenicillin, and R64-G to geneamicin. All three substrains showed elevated levels of Hg2+ and carbenicillin resistance. Resistance to other antibiotics was either increased, decreased or unaffected. Increased Hg2+ resistance in all adapted substrains was accompanied by higher activity and less stringent induction of mercury reductase, as determined by Hg-volatilization assays with resting cells. No plasmid alterations compared to the non-adapted strain were detected in R64-C, but in R64-M and R64-G plasmid sizes increased by approx. 23 kb, as detected by pulsed field gel electrophoresis and the occurrence of additional DNA fragments after digestions with several restriction endonucleases. The plasmid localized gene rearrangements were accompanied by additional DNA fragments hybridizing with a merA gene probe.
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  • 4
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Diets supplemented with 0.01 or 0.05 ppm (mg/kg) of 3,4,5,3′,4′,5′-hexachlorobiphenyl (345-HCB) were fed to mink to investigate the toxicological manifestations of this toxic polychlorinated biphenyl congener in a sensitive species. Dietary exposure of mink to 0.05 ppm 3,4,5,3′,4′,5′-hexachlorobiphenyl for 135 days resulted in 50% mortality while no deaths occurred on 0.01 ppm 345-HCB. Clinical signs of toxicity included anorexia, bloody stools, disrupted molting patterns, and thickened, elongated and deformed nails. Ascites and gastric ulcers were present in animals that died. Statistically significant increases in liver, kidney, and adrenal gland weights were found in the 345-HCB-treated mink. Decreases in total and free triiodothyronine concentrations were observed in mink fed the 345-HCB-treated diets and total thyroxine was decreased in the mink fed 0.05 ppm 345-HCB. No consistent histopathologic lesions were found in the thyroid or adrenal glands of the 345-HCB-treated mink, nor were there any statistically significant differences between the 345-HCB-treated and the control mink in serum epidermal growth factor levels, plasma 17β-estradiol and progesterone concentrations, hepatic aminopyrine N-demethylase, and benzo(α)pyrene hydroxylase activities, hypothalamic norepinephrine, dopamine, and serotonin concentrations or in the incorporation of (3H) thymidine by concanavalin-A-stimulated lymphocytes.
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  • 5
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract River sediment, sludge, and soil samples were collected and analyzed for Hg, MeHg, Cd, Cr, Cu, Ni, Pb, and Zn. Volatile solids, chloride, sulphate, and sulphide were also assessed. Heavy metal contamination was present in all the samples, particularly soil and sediment. The 'k values for Cu were less than those for Hg and lower for soil than for river sediment. Complexation may be a major factor in Hg methylation as high 'k values reflected low MeHg levels. High chloride concentration was associated with low ratios of methyl to total Hg. Using DNA probe technology, the occurrence of DNA sequences typical of transposons Tn21 and Tn501 were determined for the samples. Observable (phenotypic) Hg resistance was greatest at sites of high Hg and chloride concentrations although genetic variation was greatest in soil and sediment samples with lower Hg concentrations. Isolation of Tn501-like elements increased when Hg was added to the medium. Mercury resistance systems which are not homologous at high stringency to themer operon appear to be common in soil, activated sludge, and river sediments.
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  • 6
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In 1953 cephalosporin N was reported to be a new type of penicillin, and it was suggested that cephalosporin N and synnematin might be identical7. In the meantime, synnematin was separated into two components called synnematin A and synnematin B, the former being apparently less soluble in methanol ...
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1552-6909
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: One hundred women patients at a midwestern university health center were randomly assigned to a control or experimental group to measure statistically comfort levels of new foot supports vs. traditional metal stirrups during pelvic examinations. Written comments were also obtained. Analyses using the t test demonstrated a significant positive change in attitude in the experimental group.
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  • 9
    ISSN: 0887-6266
    Keywords: glass transition ; polymer blends ; free volume ; positron annihilation ; composition dependence of Tg ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: High-Vinyl Polybutadiene (HVBD)/cis-Polyisoprene (CPI) blends were characterized by Differential Scanning Calorimetry (DSC) and Positron Annihilation Lifetime Spectroscopy (PALS). A single DSC glass transition temperature Tg is observed, whose composition dependence strongly deviates from additivity, and shows an apparent cusp when the weight fraction of HVBD ≈ 0.75. The free-volume hole size, Vh, and the scaled fractional free volume, hps/C, = I3Vh were determined by PALS from the orthopositronium (o-Ps) intensities, I3, and lifetimes, τ3, over a temperature range encompassing Tg and the temperature at which “positronium bubble” formation occurs. In the glass, Vh and hps/C are smaller for CPI than for HVBD, but the thermal expansion coefficient for hole volume, αf, is larger in the melt for CPI than for HVBD; thus, an iso-hole volume temperature occurs in these blends at Tiso ≈ -34°C. Above and below Tiso, Vh and hps/C each show a negative departure from additivity. A quantitative interpretation of the cusp in the composition dependence of Tg can be obtained, via a modified analysis of Kovacs, using free-volume quantities from PALS, with the ratio of scaling constants CCPI/CHVBD as an adjustable parameter. At high temperatures, the positron bubble size is smaller in CPI than in HVBD. This agrees with the observation that the thermal expansivity of hole volume, and, hence the internal pressure are larger in the equilibrium melt of CPI. The effect of e+-irradiation on the o-Ps intensity was investigated. I3 decreases more rapidly in the melt as T → Tg, and then more slowly in the glass, suggesting that the effect is due to trapping of radical or ionic species which inhibit o-Ps formation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 861-871, 1998
    Additional Material: 6 Ill.
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  • 10
    ISSN: 1476-5535
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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