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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 9 (1972), S. 140-151 
    ISSN: 1432-0827
    Keywords: Cartilage ; Epiphysis ; Cell ; Differentiation ; Endoplasmic reticulum ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une étude ultrastructurale de chondrocytes hypertrophiques est rendue possible par suite d'une meilleure méthode de fixation. Contrairement à l'opinion qui veut que les cellules hypertrophiques meurent, nos résultats suggèrent nettement une activité cellulaire allant du début de la croissance de la cellule au stade où la lacune s'ouvre. La séquence des altérations cellulaires est décrite, en allant de l'augmentation de l'ergastoplasme à la présence de ribosomes libres et de granules denses aux électrons dans les mitochondries. Les diverses fonctions possibles de la cellule sont décrites. Il est possible que les chondrocytes hypertrophiques se transforment en cellules osseuses.
    Abstract: Zusammenfassung Eine verbesserte Fixationsmethode ermöglichte die Untersuchung der Feinstruktur des hypertrophischen Chondrocyten. Im Gegensatz zur allgemeinen Annahme, daß die hypertrophischen Zellen absterben, weisen unsere Resultate deutlich darauf hin, daß die Zellaktivität vom Moment der Zellvergrößerung bis zum Stadium, in welchem die Lacunen aufbrechen, vorhanden ist. Der Ablauf der Veränderungen innerhalb der Zelle wurde beschrieben, wobei die hervorstechendsten Charakteristika die Zunahme des endoplasmatischen Reticulums, das Auftreten von vielen freien Ribosomen und das Vorkommen von elektronenmikroskopisch dichten Granula in den Mitochondrien waren. Die möglichen Funktionen der Zelle wurde besprochen. Es ist äußerst interessant, daß dadurch die Hypothese, wonach die hypertrophischen Chondrocyten schließlich zu Knochenzellen werden, unterstützt wird.
    Notes: Abstract A study of the ultrastructure of the hypertrophic chondrocyte has been made possible by an improved method of fixation. In contrast to the general belief that the hypertrophic cells die, our results strongly suggest cell activity from the beginning of enlargement of the cell up to the stage where the lacuna breaks open. The sequence of alterations within the cell have been described, with the increase of endoplasmic reticulum contents, the appearance of many free ribosomes and the occurrence of electron-dense granules in the mitochondria as the most prominent characteristics. The possible functions of the cell have been discussed. Most interesting is the support for the hypothesis that hypertrophic chondrocytes may ultimately become bone cells.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 34 (1982), S. 488-494 
    ISSN: 1432-0827
    Keywords: Bone resorption ; Macrophages ; Epithelioid cells ; Giant cells ; Subplasmalemmal linear densities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Implantation of mineral-containing bone fragments into calvarial defects in rats initiates a rapid and reproducible resorption of the bone matrix. After 7 days, a dense tissue develops with mononucleated as well as multinucleated cells surrounding and between the bone fragments. Electron microscopy revealed that these cells belong to the mononuclear phagocytic system; they were identified as macrophages, epithelioid cells, foreign body giant cells, and Langerhans cells. In addition to the common ultrastructural characteristics, these cells had electron-dense, focal specializations along their cell membrane with a coating on the exterior, corresponding to subplasmalemmal linear densities. Small, unidentified cells with electron-dense ground cytoplasm were often seen in close proximity to more differentiated cells. No halisteresis had occurred on the surfaces of the bone fragments. Indentations resembling Howship's lacunae were frequent; these contained mononucleated as well as multinucleated cells. Some surfaces were frayed and collagen fibers were exposed, but the cells apposed to these surfaces did not have ruffled borders as are seen in osteoclasts. Some bone fragments were broken up and cell processes had penetrated deep into the cracks, separating pieces of matrix. Small matrix particles were phagocytosed by macrophages, but not by epithelioid cells or giant cells. It appears that enzymes capable of degrading bone matrix components were secreted by the more differentiated cells of the mononuclear phagocytic system. They eroded the bone surface in a way reminiscent of osteoclastic bone resorption. They also entered the canaliculi to act from within the bone fragment, a process possible only in dead bone. We suggest a possible relationship of these cells with osteoclasts.
    Type of Medium: Electronic Resource
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