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  • Visual membrane  (2)
  • Springer  (2)
  • American Society of Hematology
  • Deutsches GeoForschungsZentrum GFZ
  • Oxford University Press
  • 2005-2009
  • 2000-2004  (1)
  • 1980-1984  (1)
Collection
Publisher
  • Springer  (2)
  • American Society of Hematology
  • Deutsches GeoForschungsZentrum GFZ
  • Oxford University Press
Years
  • 2005-2009
  • 2000-2004  (1)
  • 1980-1984  (1)
Year
  • 1
    ISSN: 1615-6102
    Keywords: Electron microscopy ; Photoreceptor ; Visual membrane ; Photic radiation damage ; Retina ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Visual membranes of the crayfish eye either belong to the small, distally placed rhabdomere of retinula cell R8 or are part of the much more voluminous proximal rhabdom, made up of rhabdomeres belonging to cells R1–R7. Under various conditions of environmental stress (e.g., prolonged darkness, elevated temperature, bright light with and without a concomitant rise in temperature, flickering lights) the visual membranes of R8 prove far more resistant to structural damage than those of R1–R7. Membrane damage is known to occur when dormant lipoxygenases become activated, for example through heat. Since R8 is the only type of visual cell in the crayfish retina that does not contain grains of screening pigment, the view that screening-pigment granules could “aggravate” or even “trigger” membrane damage in times of stress is strengthened. Functionally, R8's strong resistance to physical damage when exposed to flickering lights points to a role of the distal rhabdom in the movement detection system of the crayfish eye.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Photoreceptors ; Temperature effects ; Compound eye ; Visual membrane ; Crustaceans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The amphipod, Orchomene plebs, and the isopod, Glyptonotus antarcticus, both adapted to live in seawater of a temperature of-2° to 0° C, were kept for 7h at the unphysiologically high temperature of +10° C. Temperature elevation appeared to mimic light adaptation with regard to the position of the screening pigment granules within the visual cells, but not with respect to ultrastructural changes in the microvillar array of the rhabdom, i.e. the visual membranes. Cellular metabolism, membranous fatty acid composition, and ion fluxes, all known to be readily affected by an increase in temperature, are thought to be responsible for the observed effects. Pigment granules could possibly cause an elevation of intracellular temperatures due to the fact that they are dark and dissipate absorbed energy as heat.
    Type of Medium: Electronic Resource
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