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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 23 (1977), S. 185-188 
    ISSN: 1432-0827
    Keywords: Matrix vesicles ; Bone ; Ultracrytomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Matrix vesicles were observed in femurs of 8-day-old chick embryos prepared by ultracryotomy. Some of the sections were subjected to ultramicroincineration. The unfixed tissues never came into contact with solutions, and thereby artifacts due to dissolution, redistribution, or rearrangement of the mineral constituents were avoided. In the osteoid, electron dense objects with the size and appearance of matrix vesicles were seen, although limiting membranes were not visible. After ultramicroincineration the vesicles were observed to contain small crystals and a less dense amorphous mineral material which may be the precursor of bone mineral. In addition, a ring of ash enclosed the crystalline and amorphous mineral and appeared to occupy the position of the vesicle membrane as seen in conventionally prepared material.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 7 (1971), S. 201-211 
    ISSN: 1432-0827
    Keywords: Autoradiography ; Calcium ; Oviduct ; Shell-gland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La localisation cellulaire du calcium de la muqueuse de l'oviducte d'oiseaux a été étudiée par autoradiographie au45Ca, à partir de tissus préparés soit par incubation dans le45Ca, soit par injection intraveneuse du45Ca. La congélation — substitution est utilisée pour retenir le calcium aisément diffusible dans le tissu. L'épithelium cylindrique de la glande de la coquille s'enrichit significativement plus en45Cain vitro, en fonction de l'augmentation du temps d'incubation, de une à dix minutes et/ou en élevant la température de 0° à 42°. Ces effets sont diminués par l'adjonction de dinitrophenol au milieu d'incubation. Les glandes tubulaires de ce tissu réagissent à peine. Généralement, après injection intravenieuse de45Ca, la glande de la coquille retient plus de radionuclide que les autres régions de l'oviducte. Lorsqu'une coquille d'œuf est en voie de calcification, l'épithelium cylindrique de cette glande contient plus de grains que les glandes tubulaires, mais, en cas d'absence de formation d'œuf, le nombre de grains est identique dans les 2 types cellulaires. Il semble que l'épithélium cylindrique de la glande de la coquille a une affinité plus grande et plus variable pour le45Ca que la glande de la coquille les glandes tutulaires ou les cellules muqueuses d'autres régions de l'oviducte. Ces résultats indiquent sans le prouver, que l'épithélium cylindrique est plus actif dans le transfert du calcium des vaisseaux sanguins vers la lumière de la glande de la coquille.
    Abstract: Zusammenfassung Die celluläre Verteilung von Calcium in der Eileitermucosa von Hühnern wurde anhand von45Ca-Autoradiographien in Gewebe studiert, welches entweder durch Inkubation mit45Ca oder durch intravenöse Injektion von45Ca präpariert wurde. Gefriersubstitution wurde verwendet, um leicht diffundierbares Calcium im Gewebe zurückzuhalten.In vitro nahm das Cylinderepithel der Schalendrüse auffallend mehr45Ca auf, wenn die Inkubationszeit von einer auf zehn Minuten verlängert wurde und/oder wenn die Temperatur von 0° auf 42° erhöht wurde. Diese Wirkungen wurden durch die Zugabe von Dinitrophenol zum Inkubations-medium vermindert. Die Tubulärdrüsen dieses Gewebes reagierten kaum. Im allgemeinen schlossen die Schalendrüsen nach intravenöser Injektion von45Ca mehr Radionuklid ein als andere Teile des Eileiters. Wenn eine Eierschale calcifizierte, zeigte das Cylinderepithel der Schalendrüse bei der Autoradiographie eine höhere Anzahl von Silberkörnern als die Tubulärdrüsen, aber wenn keine Schale gebildet wurde, war sie bei beiden Zelltypen ähnlich. Die Resultate zeigen, daß das Cylinderepithel der Schalendrüse, eine größere und unterschiedlichere Affinität für45Ca hat als Schalendrüse Tubulärdrüsen oder Schleimhautzellen aus anderen Gebieten des Eileiters. Die Befunde deuten darauf hin, aber beweisen es nicht, daß das Cylinderepithel beim Transport von Calcium aus den Blutgefäßen in die Schalendrüse das aktivste ist.
    Notes: Abstract The cellular location of calcium in the mucosa of the avian oviduct has been studied by45Ca autoradiography in tissue prepared either by incubation with45Ca or by intravenous injection of45Ca. Freeze-substitution was used to retain easily diffusible calcium in the tissue.In vitro, columnar epithelium of the shell gland acquired significantly more45Ca as the length of incubation time was increased from one to ten minutes and/or when the temperature was raised from 0° to 42°. These effects were diminished by the addition of dinitrophenol to the incubation medium. The tubular glands of this tissue responded minimally. Genrally, after intravenous injection of45Ca, the shell gland sequestered, more radionuclide than the other regions of the oviduct. When an egg shell was being calcified, the columnar epithelium of the shell gland revealed a higher grain count than the tubular glands, but when a shell was not forming, grain counts were similar over the two types of cells. The results show that the columnar epithelium of the shell gland has a greater and more variable affinity for45Ca than have the shell gland tubular glands or mucosal cells from other regions of the oviduct. The data suggest, but do not prove, that the columnar epithelium is the most active in translocation of calcium from the blood vessels to the lumen of the shell gland.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 23 (1977), S. 215-223 
    ISSN: 1432-0827
    Keywords: Amorphous mineral ; Bone ; Electron microscopy ; Ultracryotomy ; Ultramicro-incineration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The fine structure of the extracellular phase of avian medullary bone and embryonic chick femur was examined in thin sections prepared by ultracryotomy and ultramicroincineration. Since contact with solutions was completely avoided, little or no loss or dislocation of mineral constituents could occur. Amorphous bone mineral (ABM) was present in two forms: as 15–30 nm spheres and as a structure-free haze. Removal of all organic material by low temperature ashing left the ABM intact. Crystals were usually associated with the ABM. In newly ossifying regions clusters or nodules of randomly oriented crystals and ABM appeared to coalesce when they reached approximately 1 μm in diameter. In highly calcified regions crystals appeared to be oriented along collagen fibers. ABM did not appear to be associated with collagen. Unmineralized collagen was visible in osteoid after staining with dry OsO4 vapor and it appeared to be diverted around nodules. Structures which resembled matrix vesicles were present. Selected area electron diffraction patterns indicated the presence of hydroxyapatite.
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