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  • 1990-1994  (3)
  • 35.20.Jv  (1)
  • Aegilops tauschii (syn. Ae. squarrosa)  (1)
  • Aflatoxin B1  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Genetic analysis of aflatoxin B1 activation in rat hepatoma cells (1990)
    Springer
    Molecular genetics and genomics 222 (1990), S. 291-296 
    Details
    ISSN: 1617-4623
    Keywords: Aflatoxin B1 ; Cytochrome P450 ; Rat hepatoma cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We present a strategy to elucidate the rate-limiting steps in activation of carcinogenic compounds by cytochromes P450. The principle was to select Reuber rat hepatoma cells for resistance to a procarcinogen. The hypothesis was that resistant cells should be systematically deficient in the P450 enzyme(s) involved in the activation process. Here we present an example of the use of this approach using aflatoxin B1 (AFB1), a potent hepatocarcinogen, as the selective agent. Parental cells as well as individual and pooled colonies selected for AFB1 resistance from three independent rat hepatoma lines were characterized for their content of 1) mRNA hybridizing to cDNA and/or oligonucleotide probes for cytochromes P450IIB1, P450IIB2 and albumin; and 2) aldrin epoxidase activity. Parental aflatoxin B1-sensitive cells were shown to express P450IIB1 but not P450IIB2. The majority of the aflatoxin B1-resistant clones failed to accumulate cytochrome P450IIB1 mRNA and expressed no or only very low aldrin epoxidase activity. Albumin mRNA levels remained unchanged, demonstrating that loss of expression of cytochrome P450IIB1 was not a consequence of a general dedifferentiation event. A revertant population showing restoration of both cytochrome P450IIB1 mRNA accumulation and aldrin epoxidase activity was fully sensitive to aflatoxin B1. The correlation between expression of cytochrome P450IIB1 and sensitivity to aflatoxin B1 in both parental cells and revertants strongly suggests that cytochrome P450IIB1 is a major contributor to the activation of aflatoxin B1 in rat hepatoma cells. The kind of strategy described here could be applied to other compounds that become cytotoxic for hepatoma cells following activation by cytochromes P450.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00633831
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Rotational tunneling dynamics of methyl groups inn-alkane host lattices: An optical investigation of the internal and external isotope effect (1994)
    Springer
    The European physical journal 95 (1994), S. 493-501 
    Details
    ISSN: 1434-6036
    Keywords: 61.50.−f ; 35.20.Jv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We exploited the slow relaxation of methyl group rotational tunneling states to perform optical hole burning inn-alkane crystals. The dye probe used was dimethyl-s-tetrazine and its perdeuterated derivative. We investigatedn-octane, perdeuteratedn-octane andn-hexane as host crystals. By comparing the experimentally observed hole-antihole splitting of the protonated and perdeuterated dye probe, all parameters, i.e. the tunneling splitting in the ground-and in the electronically excited state as well as the respective heights of the potential can be determined, assuming a threefold rotational symmetry axis. We found that matrix deuteration has a severe influence on the potential heights, which increase by a factor of two. With these parameters determined, many features of the complex relaxation behavior of the tunneling states can be qualitatively understood: We found Raman-type conversion processes inn-octane-h 18, Orbach-type processes inn-octane-d 18 and inn-hexane we found, in addition, a relaxation regime governed by a Direct process. The experimental activation energies as well as the cross-over temperatures are in satisfying agreement with current theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313358
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Powdery mildew resistance in Aegilops tauschii coss. and synthetic hexaploid wheats (1994)
    Springer
    Genetic resources and crop evolution 41 (1994), S. 151-158 
    Details
    ISSN: 1573-5109
    Keywords: Triticum aestivum ; Aegilops tauschii (syn. Ae. squarrosa) ; Erysiphe graminis f. sp. tritici resistance genes ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A collection of 400 Ae. tauschii (syn. Ae. squarrosa) Coss. accessions were screened for powdery mildew resistance based on the response patterns of 13 wheat cultivars/lines possessing major resistance genes to nine differential mildew isolates. 106 accessions showed complete resistance to all isolates, and 174 accessions revealed isolate-specific resistance, among which were 40 accessions exhibiting an identical response pattern as wheat cultivar ‘Ulka/*8Cc’ which is known to possess resistance gene Pm2. Expression of both complete and isolate-specific resistance from Ae. tauschii was observed in some synthetic hexaploid wheats derived from four mildew susceptible T. durum Desf. parents, each crossed with five to 38 resistant diploid Ae. tauschii accessions. Synthetic amphiploids involving different combinations of T. durum and Ae. tauschii generally showed a decrease in resistance compared with that expressed by the Ae. tauschii parental lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00051631
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    Paper (German National Licenses)
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