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  • 1995-1999
  • 1990-1994  (5)
  • 1975-1979
  • 1994  (5)
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  • 1995-1999
  • 1990-1994  (5)
  • 1975-1979
Year
  • 1
    Electronic Resource
    Electronic Resource
    Endogenous hormone levels during direct somatic embryogenesis in Medicago falcata (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Endogenous indole-3-acetic acid, abscisic acid and cytokinins (zeatin, zeatin riboside, N-isopentenyladenine and N-isopentenyladenosine) were evaluated in initial explants (leaves) of in vitro propagated plants of alfalfa (Medicago falcata L.) lines varying in embryogenic capacity and during the somatic embryogenesis process. Fast embryo-genic induction was correlated with high IAA and low ABA levels in the initial explants. No significant differences were observed in the cytokinin contents. Our results suggest that a certain hormone balance is necessary to allow the expression of the embryogenic potential. The consistent stages of the direct somatic embryogenesis are also characterized by changes in hormonal levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb06658.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Modeling the 3-D RNA distribution in the Balbiani Ring granule (1994)
    Springer
    Chromosoma 103 (1994), S. 302-310 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Mature Balbiani Ring (BR) granules in situ were stained with the nucleic acid specific stain, osmium ammine-B, recorded by electron spectroscopic imaging and reconstructed by electron microscope tomography to examine the three-dimensional (3-D) distribution of BR heterogeneous nuclear RNA (hnRNA). The BR2 granules contain ca. 37 kb of mRNA. Reconstructed BR granules were selected to emphasize one of the prevalent conformations seen in the sectioned salivary glands, the en face or “pin-wheel” conformation. A variety of image processing and volume-rendering operations were applied to the set of reconstructed BR granules. Some of the conclusions of this study are the following: (1) RNA distribution is not uniform throughout the granule; (2) RNA is condensed into about ten particles per granule, which all appear to possess approximately the same RNA stain density; (3) heterogeneity exists in the positions and sizes of particles within the various BR granules. These data argue for the folding of a beaded ribbon, consisting of connected particulate condensations of BR mRNA, possessing considerable 3-D flexibility, even in the packaged state. A comparison of this beaded-ribbon model and a prior folded hnRNP fiber model is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417877
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Modeling the 3-D RNA distribution in the Balbiani Ring granule (1994)
    Springer
    Chromosoma 103 (1994), S. 302-310 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mature Balbiani Ring (BR) granules in situ were stained with the nucleic acid specific stain, osmium ammine-B, recorded by electron spectroscopic imaging and reconstructed by electron microscope tomography to examine the three-dimensional (3-D) distribution of BR heterogeneous nuclear RNA (hnRNA). The BR2 granules contain ca. 37 kb of mRNA. Reconstructed BR granules were selected to emphasize one of the prevalent conformations seen in the sectioned salivary glands, the en face or “pin-wheel” conformation. A variety of image processing and volume-rendering operations were applied to the set of reconstructed BR granules. Some of the conclusions of this study are the following: (1) RNA distribution is not uniform throughout the granule; (2) RNA is condensed into about ten particles per granule, which all appear to possess approximately the same RNA stain density; (3) heterogeneity exists in the positions and sizes of particles within the various BR granules. These data argue for the folding of a beaded ribbon, consisting of connected particulate condensations of BR mRNA, possessing considerable 3-D flexibility, even in the packaged state. A comparison of this beadedribbon model and a prior folded hnRNP fiber model is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417877
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Cometary-like bodies in the protoplanetary disk aroundβ pictoris (1994)
    Springer
    Astrophysics and space science 212 (1994), S. 147-157 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Repeated spectroscopic observations ofβ Pictoris have been performed since 1985 and revealed the presence, in many metallic lines likeCa II, Mg II, Fe II, ..., of strong sporadic circumstellar absorption, redshifted by tens to hundreds of km s−1 with respect to the star, and highly time-variable (time-scales of days or hours). We have tentatively interpreted these variable events as the spectral signature of infalling cometary-like bodies, when evaporating in the vicinity of the star. This scenario has been furthermore theoretically studied, and we showed that it could indeed explain correctly the observations with their peculiar characteristics, like (1) the behavior difference between visible and UV lines, (2) the unusual line ratios, (3) the surprising presence of Al III absorption lines. Constraints deduced from both observational data and theoretical study allowed us to suggest that a planet within the disk could be responsible, by perturbations, of this high rate infall of small bodies towards the star (〉 100 per year).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00984518
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Inner part observation of theβ pictoris disk (1994)
    Springer
    Astrophysics and space science 212 (1994), S. 173-180 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The inner regions of the circumstellar disk aroundβ Pictoris might be dust-free due to a possible planet which may have cleared up dust particles. We present a new observational technique based on the use of an anti-blooming CCD in order to directly image this zone. The structure of the disk is revealed down to 2 arcsec from the star (30 AU). We show that theβ Pic disk brightness is neutral inV, R, andI C , but drops down when going inward inB, possibly related to a change in the dust composition. Also, a slight disk asymmetry is present but inverted from the outer to the inner zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00984521
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    Paper (German National Licenses)
    Fulltext
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