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  • 1
    ISSN: 1432-041X
    Keywords: Forg skin ; Organ culture ; Keratinization ; Transepithelial ionic gradient ; Ionic active transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Isolated frog skins were maintained, in organ culture in a modified Ussing chamber for up to 9 days with or without transepithelial NaCl gradient and aldosterone. Without gradient, (86 mM NaCl Ringer in the mucosal compartment and Wolf and Quimby amphibian medium culture in the serosal compartment), the structural organization of the epithelium, moulting cycle, keratinization and active sodium transport were similar to those observed before culture. In the absence of gradient, aldosterone slightly intensified keratinization and was necessary to maintain a high rate of active sodium transport. In the presence of a transepithelial ionic gradient (5 mM NaCl Ringer in the mucosal compartment and Wolf and Quimby amphibian medium culture in the serosal compartment), skins evolved towards the ultimate stage of the moulting cycle and the rate and the degree of keratinization were strongly enhanced. Aldosterone obviously promoted overlapping of the last two phases of the cycle and further intensified keratinization. It also strikingly raised active sodium transport. The epithelia of trypsinized skins, stripped of their stratum corneum and stratum granulosum were able to restructure themselves in culture. In this newly formed epithelium, the former regular structural organization was not preserved and the moulting cycle was no longer distinguishable. Moreover, when there was no transepithelial gradient, the keratinization process slowed down considerably. The presence of a gradient (28 mM NaCl Ringer in the mucosal compartment and Wolf and Quimby culture medium in the serosal compartment) promoted keratinization and led to the formation of cornified layers, which were sometimes detached from the underlying epithelial layers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 252 (1988), S. 157-163 
    ISSN: 1432-0878
    Keywords: Frog skin culture ; Desmogenesis ; Interdigitations ; Lamellipodia ; Ultrastructure ; Rana esculenta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Small trypsinized explants from ventral skin of frogs (Rana esculenta) were maintained in culture for 4 days during which a newly formed epithelium differentiated along the cut edges of the dermis. During the first 6 h adjacent cells produced numerous interdigitating lamellipodia. After 2 days, epithelial polarity was restored by the formation of zonulae occludentes and the epithelial cells were joined by a few small newly formed desmosomes and by numerous interdigitations. Bipartite junctional complexes consisting of a zonula occludens, followed by a series of typical desmosomes, and characteristic of adult frog epidermis were formed only after 4 days. When cultured in the presence of an inhibitor of protein synthesis (cycloheximide) the trypsinized epidermis no longer formed desmosomes. Therefore pools of one or more crucial desmosomal proteins must be very low or non-existent. However, cycloheximide did not prevent the formation of cell contact specializations, consisting of a highly developed system of complex lamellar interdigitations, between adjacent cells.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 188 (1990), S. 212-220 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The pigmentation pattern of ventral skin of the frog Rana esculenta consists mainly of melanophores and iridophores, rather than the three pigment cells (xanthophores, iridophores, and melanophores) which form typical dermal chromatophore units in dorsal skin. The present study deals with the precise localization and identification of the types of pigment cells in relation to their position in the dermal tracts of uncultured or cultured frog skins. Iridophores were observed by dark-field microscopy; both melanophores and iridophores were observed by transmission electron microscopy.In uncultured skins, three levels were distinguished in the dermal tracts connecting the subcutaneous tissue to the upper dermis. Melanophores and iridophores were localized in the upper openings of the tracts directed towards the superficial dermis (level 1). The tracts themselves formed level 2 and contained melanophores and a few iridophores. The inner openings of the tracts made up level 3 in which mainly iridophores were present. These latter openings faced the subcutaneous tissue.In cultured skins, such pigment-cell distribution remained unchanged, except at level 2 of the tracts, where pigment cells were statistically more numerous; among these, mosaic pigment cells were sometimes observed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 192 (1991), S. 89-95 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In anuran amphibians, the specific color pattern of the skin is expressed after metamorphosis, and its formation involves pigment cell migrations. Pigment cells are differently distributed in the tadpole, larval, and froglet skin. To learn more about their fate during metamorphic climax and in the young froglet, we focused our attention on the different localizations of larval melanophores and iridophores in the ventral skin of Rana esculenta before and during skin homing. Localizations of melanophores and iridophores can be elucidated at the developmental stages suggested by Taylor and Kollros (TK stages).At TK stage II (during early premetamorphosis), large melanophores beneath the larval skin are detected. At TK stage X, dispersed melanophores lie under bundles of muscular striated fibrils near the larval skin; they are also observed at the vascular level. At TK stage XVII (prometamorphosis), melanophores are extended on the inner side of the basement lamellar collagen. At the end of prometamorphosis, iridophores are located with melanophores in the separating space between attached basement collagen and derived basement collagen. At TK stage XX (earlier climax), melanophores and iridophores are detected inside the upper extremities of fractures opened in the derived basement collagen. At TK stage XXIV (later climax), both types of larval pigment cells are observed in the inner extremities of breaks derived from the fractures. During climax, these pigment cells occupy the well-formed breaks. At TK stage XXV in young froglet, the pigment cells remain alone in the breaks formed in the derived basement collagen.Briefly, breaks in the basement lamellar collagen are opened by invading cell processes of mesenchymal cells. The cells move through the fractures toward the epidermis, followed in later stages by melanophores and iridophores.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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