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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 12 (1973), S. 125-136 
    ISSN: 1432-0827
    Keywords: Mineralization ; Molt ; Isopod ; Chemistry ; Light microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Au cours de la phase inhabituelle de mue d'un isopode d'eau courante,Lirceuts brachyrus, la moitié postérieure de l'exosquelette est éliminée 24 heures avant la moitié antérieure. A ce stade, une reminéralisation se développe dans la partie postérieure alors que la partie antérieure est dans un stade de pré-mue. Le pourcentage de différence en calcium dans les deux moitiés à mi-mue et mue complète est respectivement de 22% (p〈0.01) et 33% (p〈0.01), indiquant une complexation du calcium pendant la mue. La rapidité de la reminéralisation est illustrée par le fait que le contenu minéral total double dans la partie postérieure entre la mi-mue et la mue totale et dans la partie antérieure entre la fin de la mue et un jour après. Le carbonate de calcium, sous forme de calcite, a pu être identifié par diffraction électronique de coupes fines des téguments.
    Abstract: Zusammenfassung Während der ungewöhnlichen Häutungssequenz des Frischwasser-IsopodenLirceus brachyurus (Harger) wird die hintere Hälfte des äußeren Skeletts 24 Std vor der vorderen Hälfte abgestoßen. In der halbgehäuteten Phase erfolgt Remineralisation im hinteren Teil, während der vordere Teil in einem Vorhäutungszustand ist. Der prozentuale Unterschied des Calciums in den zwei Hälften bei Halb- und Vollhäutungszustand ist 22% (p〈0,01) bzw. 33% (p〈0,01), was andeutet, daß Calcium während der Häutung abgesondert wird. Die Geschwindigkeit der Remineralisation erhellt aus der Tatsache, daß sich der Gesamtmineralgehalt im hinteren Teil zwischen Halt- und Vollhäutung, in der vorderen Hälfte jedoch zwischen Endhäutung und einem Tag nach der Häutung verdoppelt. Calciumcarbonat in kristalliner Calcitform wurde mittels Elektronendiffraktion von dünnen Hautschnitten nachgewiesen.
    Notes: Abstract During the unusual molt sequence of the fresh-water isopod,Lirceus brachyrus (Harger), the posterior half of the exoskeleton is shed 24 hours before the anterior half. At the half-molt stage, occurs in the posterior part while the anterior portion is in a pre-molt condition. The percentage difference in calcium in the two halves at half-molt and full-molt is22 (p〈0.01) and33 (p〈0.01) respectively, an indication that calcium is sequestered during The rapidity of remineralization is illustrated by the fact that the total mineral content doubles in the posterior part between half and full molt and in the anterior half between the end of molt and one day after ecdysis. Calcium carbonate in the calcite cystalline form was demonstrated by electron diffraction of thin sections of the integument.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 149 (1974), S. 147-158 
    ISSN: 1432-0878
    Keywords: Skin ; Fish ; Salmon ; Microridges ; Fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Both the epidermis and dermis of the anadromous coho salmon, Oncorhynchus kisutch, have a full complement of the protective structures found in fish. The living epidermal surface is protected by mucous secretions which are prevented from ablation by the intricately patterned microridges of the surface keratinocytes, as seen by scanning electron microscopy. Bundles of filaments are dispersed throughout the keratinocytes but not to the extent that ribosomes, endoplasmic reticulum, and Golgi apparatus are excluded. In the yearling salmon, the straight basal lamina of the embryo has changed to a convoluted border invaded by dermal reticular fibers. The complex dermis has an upper region of loosely organized collagen fibers, which is interspersed with fibroblasts and pigment cells, and a deeper, highly ordered zone of orthogonally arranged collagen. Coho salmon also have overlapping calcified scales that extend at an angle from the upper dermis to the epidermis and push an enclosing sheath of epidermal tissue with them to the skin's surface. The other major component of fish skin, the chromatophores, are discussed in an adjacent paper.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 149 (1974), S. 159-172 
    ISSN: 1432-0878
    Keywords: Chromatophores ; Melanophore ; Xanthophore ; Iridophore ; Fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The chromatophore unit concept is applicable to the variety of chromatophore associations in the coho salmon, Oncorhynchus kisutch. Individual pigment cells of three general types—melanophores, xanthophores, and iridophores—vary structurally according to skin location, age, and physiological state. In growing fish, melanophores have a bimodal size distribution; in adults, they have a normal size distribution. Both melanophores and xanthophores are dendritic cells which respond to potassium and sodium ions by respectively aggregating and dispersing pigment granules. The third cell, the iridophore, is characterized by reflecting platelets of birefringent crystals of guanine of hypoxanthine and has at least two distinct shapes. In the upper dermis of the dark-colored skin, globular iridophores are encompassed by the dendritic arms of subjacent melanophores. In relation to this melanophoreiridopbore unit, the xanthophores appear to be randomly distributed and to afford an effective filter by virtue of their quantity and shape as well as their pigment granules. In deeper locations in the dermis, particularly below the stratum compactum in the shiny ventral skin, layers of dendritic iridophores are only partially shielded by the few melanophores and thus represent the nadir of chromatophore unit organization in the salmon.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Egg membrane ; Teleosts ; Micropyle ; Zona radiata ; Pore canals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Eggs of the starry flounder (Platichthys stellatus) and pink salmon (Oncorhynchus gorbuscha) were examined by scanning and transmission electron microscopy to determine differences in egg membrane structure with reference to contrasting ecological conditions in which the eggs normally develop. The egg membrane of the starry flounder constitutes 0.22–0.50 % of the egg's diameter. The zona radiata is composed of 6 continuous horizontal lamellae, covered by a thin triple layered border, and pierced by numerous regularly spaced pore canals. The micropyle canal measures 8 μm at the opening and tapers to 3.6 μm as it penetrates the membrane. In contrast, the thicker membrane of the pink salmon egg forms 0.80–1.0% of the egg's diameter, is composed of numerous short discontinuous lamellae which are pierced by pore canals, and is covered by a coating of irregular thickness. The 15–16 μm micropyle opening is surrounded by an area of protrusions, and the funnelshaped canal tapers to 2 μm at its terminal aperture. Contrasting environmental conditions during embryogenesis of these two species may be reflected by the thin membrane and simple lamellar structure in the pelagic egg of the starry flounder, and the thick membrane and complex lamellar structure in the demersal egg of the pink salmon.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 178 (1983), S. 267-284 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The surface of a mature, pelagic C-O sole egg is composed of polygonal chambers having four to eight sides, most of which are hexagonally shaped. This honeycomb pattern initially appears on primary oocytes as a thin layer of compact, electron-dense material. Discrete thickenings begin to develop on the envelope of perinuclear stage oocytes. The thickenings lengthen and thin to form the hexagonal walls of the envelope in oocytes undergoing yolk vesicle formation. The walls of each hexagonal chamber occur in an area corresponding to the lateral margins of the adjacent follicle cell, suggesting that the hexagonal walls are produced by the follicle cells. The hexagonal layer is nearly complete at the beginning of vitellogenesis, and as vitellogenesis continues, a striated envelope layer composed of fibrillar lamellae develops between the oocyte and the hexagonal layer. The striated layer appears to be secreted by the oocyte. After vitellogenesis is completed, oocytes are ovulated and double in size during a period of maturation. Concurrently, the striated primary envelope stretches and thins into eight to nine horizontal lamellae. On the mature egg surface, the polygonal chambers are about 24-31 μm in diameter. Within each chamber there is a subpattern of polygonal areas; each polygon is 1.5-2.0 μm in diameter, and circumscribes a pore canal opening. This exceptional envelope may furnish the egg with some degree of protection, resiliency, and buoyancy, but its specific functions are not known.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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