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  • 1
    Digitale Medien
    Digitale Medien
    Unsaturated fatty acid requirement inEscherichia coli: Mechanism of palmitate-induced inhibition of growth of strain WN1 (1982)
    Springer
    The journal of membrane biology 65 (1982), S. 31-40 
    Details
    ISSN: 1432-1424
    Schlagwort(e): lipids ; membranes ; Escherichia coli ; temperature adaptation ; fatty acids ; phase separations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The minimum requirement for unsaturated fatty acids was investigated inE. coli using a mutant impaired in the synthesis of vaccenic acid. Exogenously supplied palmitic acid was incorporated by this mutant which led to a reduction in the proportion of cellular unsaturated fatty acids. Growth was impaired as the level of saturated fatty acids approached 76% at 37°C and 60% at 30°C. The basis of this growth inhibition was investigated. Most transport systems and enzymes examined remained active in palmitate-grown cells although the specific activities of glutamate uptake and succinic dehydrogenase were depressed 50%. Fluorescent probes of membrane organization indicated that fluidity decreased with palmitate incorportation. Temperature scans with parinaric acid indicated that rigid lipid domains exist in palmitategrown cells at their respective growth temperature. Freeze-fracture electron microscopy confirmed the presence of phase separations (particle-free areas) in palmitate-grown cells held at their growth temperature prior to quenching. The extent of this separation into particle-free and particle-enriched domains was equivalent to that induced by a shift to 0°C in control cells. The incorporation of palmitate increased nucleotide leakage over threefold. The cytoplasmic enzyme β-galactosidase was released into the surrounding medium as the concentration of unsaturated fatty acid approached the minimum for a particular growth temperature. Lysis was observed as a decrease in turbidity when cells which had been grown with palmitate were shifted to a lower growth temperature. From these results we propose that leakage and partial lysis are the major factors contributing to the apparent decrease in growth rate caused by the excessive incorporation of palmitate. Further, we propose that membrane integrity may determine the minimum requirement for unsaturated fatty acids inE. coli rather than a specific effect on membrane transport and/or membrane-bound enzymes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01870466
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  • 2
    Digitale Medien
    Digitale Medien
    The rescue of Wahlenbergia larrainii in robinson crusoe island, Chile
    Amsterdam : Elsevier
    Biological Conservation 68 (1994), S. 89-93 
    Details
    ISSN: 0006-3207
    Schlagwort(e): Juan Fernandez Archipelago ; Wahlenbergia larrainii ; conservation measures ; electrophoresis ; propagation
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1016/0006-3207(94)90338-7
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  • 3
    Digitale Medien
    Digitale Medien
    Coherent operation of injection-locked monolithic surface-emitting diode laser arrays (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2634-2636 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A row of six surface-emitting GaAlAs laser diode arrays was locked in a coupled resonator configuration by means of interconnecting waveguides. An external master oscillator was injected into the first array in order to achieve single longitudinal mode operation and wavelength tunability. Spectral data show all six devices were locked in a single longitudinal mode, with tunable operation of over 60 A(ring). Far-field fringe visibilities greater than 60% were achieved at 100 mW output powers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101042
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  • 4
    Digitale Medien
    Digitale Medien
    Influence of acetaldehyde, dietary protein, carbon tetrachloride and butylatedhydroxytoluene on the toxicity of methylmercury in rats (1978)
    Springer
    Bulletin of environmental contamination and toxicology 20 (1978), S. 102-110 
    Details
    ISSN: 1432-0800
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Medizin
    Notizen: Abstract The influence of environmental or dietary factors on the toxicity of methylmercury (MeHg) was investigated due to possibilities that humans exposed to methylmercury may have been sensitized. Groups of 8 rats were exposed to 0, 20 or 40 ppm MeHg in a semisynthetic diet and fed 0.5% BHT, 5% protein (instead of 15%), or injected with 250 mg/kg CCl4, or acetaldehyde. In control rats neurotoxicity occurred at 4 weeks and 9 weeks with 40 and 20 ppm MeHg, respectively. Mortality was observed at 6 weeks with 40 ppm and 1 rat died in week 9 with 20 ppm MeHg. Acetaldehyde injected rats died at week 4 and 6 when fed 40 or 20 ppm MeHg. Neurotoxicity was observed in week 3 and 5 in these groups, respectively. Treating rats with the low protein or BHT accelerated neurotoxicity and mortality by 1 week with 40 ppm MeHg. These agents had killed all test animals within 7 weeks at 20 ppm MeHg. Neither acetaldehyde nor BHT influenced 0 ppm MeHg controls while 5% protein induced precipitous weight loss. In the case of CCl4, the rats lived longer in combination experiments than one would have expected from the individual treatments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01683493
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  • 5
    Digitale Medien
    Digitale Medien
    Potentiation of methylmercury toxicity by piperonyl butoxide (1978)
    Springer
    Bulletin of environmental contamination and toxicology 20 (1978), S. 9-16 
    Details
    ISSN: 1432-0800
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik , Medizin
    Notizen: Summary Methylmercury (MeHg) is an extremely potent neurotoxin about 25% of which is degradedin vivo to inorganic mercury. Piperonyl butoxide (PB) is a widely used pesticidal synergist which inhibits many mammalian detoxification reactions. In a preliminary experiment with the high doses of PB and MeHg, PB induced a 12% decrease in mean survival time and a 20% decrease in mean latency time to neurotoxicity. The weight loss in PB-MeHg group was far greater than the control MeHg group. In a dose response experiment, mean survival times in rats fed 40 ppm MeHg-Cl were5.75, 5.3, and 5.0 weeks at 0,0.5, and 1% PB, respectively. By the ninth week 25% of rats fed 20 ppm MeHg-Cl showed neurotoxicity and 63% of the 0.5% PB fed showed neurotoxicity with some mortality. In experiments at 20 ppm MeHg-Cl both PB fed groups weighed considerably less than corresponding controls.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01683477
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