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  • 1
    ISSN: 1432-0878
    Keywords: Scale formation ; Mineralization ; Epidermis ; Cichlasoma octofasciatum, (Teleostei) ; Hemichromis bimaculatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The region between the epidermis and the surface of the overlapping part of scales has been studied in two cichlid teleosts using transmission electron microscopy. In a few specimens only, numerous mineralized spherules (∼1 μm in diameter) are observed in the loose dermis and at the scale surface, and form a large part of the superficial outer limiting layer of the scale. In the loose dermis (stratum laxum) and close to the scale surface spherules are either free or included in dermal cells. When free, they are dispersed in the extracellular matrix of the dermis, among the fibrils of anchoring bundles, and fused with the scale surface. When included in cell vacuoles, they lie close to the lamina densa and to the scale surface. Steps in the formation of the mineralized spherules are only seen in the lamina densa of the basement membrane. The spherules contain needle-like mineral crystals radially orientated and an organic matrix of stippled material and dense granules, some of which form concentric lines around the centre of the spherules. The results suggest that mineralized spherules form in the lamina densa and pass through the dermis to the scale surface in which they are incorporated.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 260 (1990), S. 85-94 
    ISSN: 1432-0878
    Keywords: Osteoclasts ; Bone resorption ; Salmo fario, Myleus rhomboidalis, Eigenmannia virescens, Astatotilapia elegans, Astatotilapia burtoni, Hemichromis bimaculatus (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This paper reports the common occurrence of osteoclasts during normal and experimental bone resorption in a number of teleost fishes. Light-microscopical observations on osteoclasts are presented in resorption areas on perichondral bone (mandibula and pharyngeal jaws of cichlids and vertebrae of gymnotids), on dermal bone (mandibula of salmonids and characoids and frontal bone of cichlids), on chondroid bone (pharyngeal jaws of cichlids), and on elasmoid body scales (eichlids and gymnotids). Osteoclasts acting along the bone surface usually lie in a Howship's lacuna whereas others are wrapped around bone extremities. Electronmicroscopical observations reveal that teleost osteoclasts show features similar to those of higher vertebrate osteoclasts, c.g., the presence of a ruffled border and the occurrence of numerous vacuoles, lysosomes and mitochondria. The multinucleated aspect that characterizes osteoclasts in other vertebrate groups is not a distinct feature of teleost osteoclasts since some are possibly mononucleated. Teleost osteoclasts are also able to resorb uncalcified tissues adjoining bone resorption areas, either as a primary process directed toward the tissue (basal plate of elasmoid scale) or as a secondary phenomenon (cartilage).
    Type of Medium: Electronic Resource
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