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  • 1
    Electronic Resource
    Electronic Resource
    Viral pathogenesis and resistance to defective interfering particles (1980)
    [s.l.] : Nature Publishing Group
    Nature 283 (1980), S. 311-313 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A recently isolated clone of the UBC strain of LCM, designated substrain T, was injected into outbred (ICR) mice less than 24 h old. This virus strain had a long history of tissue culture passage in our laboratory12. Ten months later, the blood of these mice exclusively contained two virus types ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/283311a0
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  • 2
    Electronic Resource
    Electronic Resource
    CONTACT INACTIVATION OF RNA AND DNA VIRUSES BY N-METHYL ISATIN BETA-THIOSEMICARBAZONE AND CuSO4 (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 284 (1977), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1977.tb21986.x
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  • 3
    Electronic Resource
    Electronic Resource
    Chromatophorenanordnungen in emersen Thalli vonFucus vesiculosus unter verschiedenen Lichtbedingungen (1979)
    Springer
    Helgoland marine research 32 (1979), S. 228-238 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of light and darkness on chromatophore arrangements inFucus vesiculosus thalli exposed to air with one side (half dry) or with both sides (dry) were investigated. Low-intensity arrangement, high-intensity arrangement and dark arrangement were induced in submerged thalli. Then the thalli were exposed to air while light conditions were either kept constant or were changed. Independently of the light conditions, in all thalli exposed to air the chromatophores arranged more or less in the inner area of the cells, in epidermal cells as well as in cortical cells. Thus the chromatophore arrangements observed in submerged thalli differ in some respect from those exposed to low-tide conditions. Based on these observations the physiological and ecological role of chromatophore displacements in seaweeds is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02189899
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  • 4
    Electronic Resource
    Electronic Resource
    Untersuchungen zur lichtinduzierten Chromatophorenverlagerung beiFucus vesiculosus (1978)
    Springer
    Helgoland marine research 31 (1978), S. 333-346 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-induced transmission changes, measured microphotometrically in the brown algaFucus vesiculosus, are mainly the result of chromatophore displacements. Dose-response curves, as well as observations by microscope, have shown that the typical low-intensity arrangement occurs at 1 000 lux and the complete high intensity arrangement at 20 000 lux. The arrangements of the chromatophores — as well as their shapes — in dim light, strong light and darkness have been investigated. The chromatophore arrangements are different in the epidermal, cortical and medullary cells. In dim light the chromatophores are relatively large. The chromatophores of the epidermis are placed in the plasma layer of the inner cell halves. In the cortical and medullary cells the chromatophores occupy mainly the cell walls facing the light. In strong light the chromatophores are shorter and tend to become spherical. In the epidermis facing the light they move into the basal part of the cells, in the cortical and medullary cells they move to the center of the cell surrounding the nucleus. After some days of darkness the chromatophores of the epidermal cells occupy the inner periclinal and 2/3 of the anticlinal cell walls. In the cortical and medullary cells they are evenly distributed in the cytoplasmic layer at the wall. Obviously, the transmission changes measured are mainly due to chromatophore displacements in the cortical cells. Changes in shape and size play a minor role.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02189486
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  • 5
    Electronic Resource
    Electronic Resource
    Do correlations exist between chromatophore arrangement and photosynthetic activity in seaweeds? (1981)
    Springer
    Marine biology 62 (1981), S. 111-117 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Dictyota dichotoma, as in many other plants, the chromatophores which at low intensities occupy the cell walls perpendicular to the light beam move to the side walls parallel to the light beam if exposed to high light intensities. The aim of this investigation was to find out whether or not the changes from low- to high-intensity arrangement and vice versa function as an active control mechanism to regulate photosynthetic activity in D. dichotoma under the respective light condition. Four different experimental approaches were made: (a) In white and blue light experiments the changes of the transmittance and of the rate of photosynthetic oxygen production in high- and low-intensity arrangement were compared. (b) The kinetics of the depression and recovery of the PS-rates, as well as of the transmittance changes, were determined during high- and low-intensity movement, respectively. (c) Transmittance and PS-rates of thalli under illumination with polarized and unpolarized light of the same intensity (1,000 1x) were compared. (d) PS-rates of thalli after darkening as well as after preirradiation with weak and strong red light, conditions under which the chromatophores occupy the same position in the cells, were measured. In all these experiments the photosynthetic activity was strongly influenced by pre-illumination, but was independent of the respective chromatophore arrangement. This finding was confirmed by experiments with two other algae: (1) In the brown alga Alaria esculenta which does not display light-induced chromatophore displacements and concomitant transmittance changes, pre-irradiation with high light intensities decreases the PS-rates. (2) In the green alga Ulva lactuca, which shows circadian chloroplast movements, the PS-rates depend on the pre-irradiation only, irrespective of the chloroplast position. Thus we may conclude that in these organisms the function of chromatophore displacements is not the regulation of photosynthetic activity. Other ecological functions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388172
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  • 6
    Electronic Resource
    Electronic Resource
    Circadian rhythms in the chromatophore movements of Dictyota dichotoma (1984)
    Springer
    Marine biology 81 (1984), S. 217-222 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the brown alga Dictyota dichotoma Lamour the phaeoplasts move to the anticlinal walls (profile position) in strong light and to the periclinal walls (face position) in dim light. By these movements transmittance changes are caused. If the algae were grown in light:dark cycles of about natural daylengths, circadian oscillations of the amplitudes and the kinetics of these transmittance changes are initiated. The lengths of the free running periods vary between 24 and 29 h. In addition, light:dark grown thalli were transferred into continuous dim or strong light or darkness, in order to check whether or not the rhythms continued under these conditions. By taking photomicrographs of intact thalli and of isolated cortical cell layers, prepared by bisecting, it could be shown that the maxima and minima of circadian transmittance changes correspond well with the number of phaeoplasts at the periclinal cell walls. The ecological relevance of these phenomena is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393215
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  • 7
    Electronic Resource
    Electronic Resource
    Occurrence and biological role of light-induced chromatophore displacements in seaweeds (1979)
    Springer
    Marine biology 51 (1979), S. 77-82 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The occurrence of light-induced chromatophore displacements and concomitant transmittance changes in marine algae was investigated by microscope and photometrically with an automated recording microphotometer system; 16 brown, 6 green and 20 red algae were studied. In most of the brown algae, both phaeoplast displacements and transmittance changes were found. In some red algae which are frequently exposed to direct sun light during emergence at low tide, light-induced transmittance changes were measured, but they could not unequivocally be correlated with changes in the position of rhodoplasts. Among green algae, only Ulva lactuca shows chloroplast displacements which, however, follow circadian rhythms and are consequently not light-induced in the strict sense. The dose-response curves of light-induced chromatophore displacements were measured in the following Fucus and Laminaria species: F. spiralis, F. vesiculosus, F. serratus, L. digitata, L. saccharina and L. hyperborea. While in Fucus species correlations between light-induced transmittance changes and zonation of the intertidal area seem to exist, no significant differences have been found in the Laminaria species. The physiological role and ecological importance of light-induced chromatophore displacements for seaweeds living in the intertidal belt are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389033
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  • 8
    Electronic Resource
    Electronic Resource
    Action of ultraviolet-C on stilbene formation in callus ofArachis hypogaea (1983)
    Springer
    Planta 159 (1983), S. 25-29 
    Details
    ISSN: 1432-2048
    Keywords: Arachis cell cultures ; Isopentenyl resveratrol ; Stilbene formation ; Ultraviolet, stilbene induction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The action of light on the formation of stilbenes and the induction of stilbene synthase in dark-grown and light-grown callus of peanut (Arachis hypogaea) was investigated over the wavelength range from 250 to 400 nm. Ultraviolet light of 260–270 nm had a significant and selective effect on the formation of resveratrol and isopentenylresveratrol. The callus responded by the production of stilbene synthase, with maximal activity appearing 4 h after irradiation with a fluence rate of 1 W m-2 (270 nm) applied for 10 min. At lower fluence rates, maximal responses in enzyme activity were shifted to longer induction periods. The efficiency of the biosynthetic pathway, and the form and maxima of enzyme profiles depended on the duration of exposure. We failed to demonstrate any significant influence of red light at low energy irradiation (672 nm, 726 nm and 753 nm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00998810
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  • 9
    Electronic Resource
    Electronic Resource
    Der Vorderflügel großer Heuschrecken als Luftkrafterzeuger (1981)
    Springer
    Journal of comparative physiology 142 (1981), S. 135-140 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The functional mechanics of the forewingtwisting ofLocusta migratoria L. is described and demonstrated by means of plastic models. The upstroke-supination (“Z-profile”) is produced by elastic and aerodynamic forces only. A tonic muscle, the muscle of the axillary 3, acts as upstroke-pronator, flattening the Z-profile. The three direct wing depressor muscles (basalar muscles, subalar muscle) pronate the wing during the downstroke. The basalar muscles initiate the wing-turning at the begin of downstroke by clicking the Z-profile into a reverse clap profile. The muscle of the axillary 3 decreases the downstroke-pronation, acting in this phase as a supinator. This muscle is therefore able to increase the aerodynamical angle of attack in both wingstroke phases. The functional significance of the muscles for the control of flight is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00605485
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  • 10
    Electronic Resource
    Electronic Resource
    Photoenolisation. X.Parts VIII and IX, see [2 l, m].. An ab initio SCF-CI study (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 699-710 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processes involved in photoenolisations are theoretically simulated by an ab initio SCF-CI method, using cis-2-butenal as a prototype structure. The prominent role of the hydroxyl group conformation in the resulting transient (2a) is emphasized; its rotation ‘out of the reaction site’ allows the next reaction paths to proceed exothermally. The equilibration of the different types of twisted biradicals in the triplet manifold, which only involves a low energy barrier, is thus possible, populating in quite equal weights the precursors of both E- and Z-dienols. In the singlet state, the formation of the Z-isomer is expected to be kinetically dominant. An examination of the role of the substituents suggests that, in related systems, the steric crowding induces important structural relaxation of the dienol geometries.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620309
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