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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 23 (1990), S. 3231-3236 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-5029
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 125 (1994), S. 107-117 
    ISSN: 1573-0832
    Keywords: Aflatoxin B1 ; Immunocytochemistry ; Regeneration ; Tissue culture ; Tobacco plantlets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of aflatoxin B1, (0.5–25 µg ml−1) on in vitro root and shoot development in young tobacco explants were investigated. Despite an initial apparent stimulatory effect on most measured parameters at 0.5 µg ml−1 AFB1, the number of leaves, root and leaf mass per plantlet were progressively inhibited with increasing AFB1 concentration. The number of explants developing roots was reduced to 34% at the highest (25 µg ml−1) AFB1 concentration, following 3 weeks exposure to the toxin. Leaf chlorophyll content at this toxin concentration was significantly lower than that measured for control plantlets. Thin layer chromatography confirmed the absorption of AFB1 by the plantlets. Using immunocytochemical techniques, AFB1 was immunolocated predominantly in the vacuoles, the nucleus and the cytoplasm (possibly intravesicularly). The results are discussed in terms of this immunolocation within the cell.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 125 (1994), S. 93-105 
    ISSN: 1573-0832
    Keywords: Aflatoxin B1 ; Callus ; Differentiation ; Electron microscopy ; Organogenesis ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Calli ofNicotiana tabacum (tobacco) were treated with two dose ranges of aflatoxin B1 (0.1–2.0 µg ml−1 - low does; 5–25 µg ml−1 aflatoxin B1). The ability of calli to recover following 3 weeks of toxin exposure was also investigated. The I50 (50% inhibition) value for fresh mass accumulation was approximately 2 µg ml−1 AFB1. Fresh mass accumulation was significantly lower than the control value from 0.5 µg ml−1 AFB1. Following 3 weeks growth without a toxin source, the growth of calli up to and including 10 µg ml−1 AFB1, was significantly greater than control calli, indicating reversibility of the toxic effects. With increasing toxin concentration, chlorophyll content of callus was inhibited from 0.5 µg ml−1. Transfer to a toxin-free medium resulted in a degree of recovery (up to 0.5 µg ml−1). In the dose range 5–25 µg ml−1, the levels of chlorophyll were drastically reduced, with no recovery following AFB1 removal. Electron microscopy revealed a disruption of chloroplast structure as an early deteriorative event in AFB1 exposure of callus cells. Protein levels were less sensitive, with inhibition manifested only in the high dose range. Shoot development occurred at all concentrations, but was significantly inhibited from 5 µg ml−1 AFB1. Recovery following toxin removal was minimal at these higher AFB1 concentrations. The number of necrotic calli increased progressively from 5 µg ml−1 as toxin levels increased.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 119 (1992), S. 181-190 
    ISSN: 1573-0832
    Keywords: aflatoxin B1 ; electron microscopy ; in vitro ; immature maize embryo ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immature maize (Zea mays L.) embryos were treated with aflatoxin B1 concentrations, ranging from 0.1 μg ml−1 to 25 μg ml−1. Below 5 μg ml−1 aflatoxin B1, root and shoot elongation was not significantly inhibited. Ultrastructurally, root tip cells showed little deterioration, except a possible diffused clearing in mitochondria and plastids. As the toxin concentration was increased above 5 μgml−1, shoot, and particularly root elongation, was progressively inhibited. Associated with this, there was an apparent decrease in the ribosome population. Furthermore, membranes, particularly the vacuolar membrane, became abnormal and vacuolar distension occurred. At 20 and 25 μg ml−1, these effects were exacerbated, and mitochondria and plastid structure was disrupted. At these concentrations, there was evidence of a disruption in lipid metabolism. The results are discussed in the context of known aflatoxin effects on cellular control mechanisms and ultrastructure in animal systems.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 1 (1990), S. 181-188 
    ISSN: 1042-7147
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Through electrical conductivity and ESR measurements of heat treated BBB-rigid-rod ladder polymers, we provide evidence for the existence of an irreversible transformation to another cross-linked ladder polymer with high intrinsic conductivity. The transformation occurs at a pyrolysis temperature, Tp ≅ 680°C. The results suggest a novel transport mechanism.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 1 (1990), S. 247-252 
    ISSN: 1042-7147
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Stable patterns with high local electrical conductivities and different local spin densities can be created in ladder type polymer films (5-20 μm thickness) by first preheating to a temperature (Tp) followed by spatically selective laser annealing. Two dimensional images of the spin distribution in such films were determined using ESR imaging. The 2-D images of 20 μm films exhibit peaks or dips in the spin density at the laser illuminated regions, which strongly depend on the preheating conditions. These phenomena are attributed to spin density gradients caused by a temperature gradient across the film upon illumination; it should be noted that the laser beam does not penetrate completely through such relatively thick films.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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