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  • Electronic Resource  (2)
  • Pigment migration  (1)
  • Ultrastructure  (1)
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  • Electronic Resource  (2)
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  • 1
    ISSN: 1432-0878
    Keywords: Melanophores ; Pigment migration ; Xenopus laevis ; Cell culture ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Tail-fin melanophores of tadpoles of Xenopus laevis (Daudin) in primary culture were examined scanning electron microscopically in the aggregated and in the dispersed state. After isolation, the melanophores are spherical, but within 24 h they develop thin filopodia for attachment to the substratum. Subsequently, cylinder-like as well as flat sheet-like processes are formed, which adhere to the substratum with terminal pseudopodia and filopodia. The processes of adjacent melanophores contact each other, thus forming an interconnecting network between the melanophores. In the aggregated state the central part of the melanophore is spherical and voluminous. Both the central part and the processes bear microvilli. In melanophores with dispersed melanosomes the central part is much flatter; the distal parts have a thickness that equals a monolayer of melanosomes. The surface of the cell bears only scarce microvilli. These features indicate that melanophores do not have a fixed shape and that pigment migration is accompanied by reciprocal volume transformation between the cell body and its processes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Melanophores ; Periodic albinism ; Ultrastructure ; Physiology ; Xenopus laevis, tadpoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pigment of tail-fin melanophores in periodic albino Xenopus laevis tadpoles is dispersed in response to darkness and to α-MSH in a manner similar to wild-type melanophores. However, periodic albino tadpoles lack the response to different background conditions and the melatonin-induced aggregation in darkness. The tyrosinase activity in cells of the latter type tadpoles is weak compared to the wild-type cells. Ultrastructural examination of melanophores from periodic albino mutants and cells from wild-type tadpoles shows similar organelles at corresponding sites. A morphological difference can be observed in the fine structure of the melanosomes, which in albinos resembles an earlier stage of development. It is postulated that periodic albino Xenopus laevis possess the cellular mechanism to disperse pigment in the melanophores, but that under physiological conditions the release of α-MSH appears to be absent or scarce.
    Type of Medium: Electronic Resource
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