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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of the effects of 1,25-dihydroxycholecalciferol, prostaglandin E2, and osteoclast-activating factor with parathyroid hormone on the ultrastructure of osteoclasts in cultured long bones of fetal rats (1979)
    Springer
    Calcified tissue international 29 (1979), S. 201-205 
    Details
    ISSN: 1432-0827
    Keywords: 1,25(OH)2D3 ; PGE2 ; OAF ; PTH ; Osteoclasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effects of 1,25-dihydroxy vitamin D3 [1,25(OH)2D3], prostaglandin (PGE2), and osteoclast-activating factor (OAF) on the size of osteoclasts, nuclei, ruffled borders, and clear zones in cultured long bones of fetal rats were quantitated. In addition, the number of osteoclasts in the bones was counted and the release of calcium from the bone into the culture medium was determined. These data were compared with the corresponding effects of parathyroid hormone (PTH). All agents tested increased the size of the ruffled borders significantly after 3 h, the size of the clear zones after 12 h, and the size of the cells after 12–24 h. No important differences in sizes were noticed between the agents tested or between the agents and PTH. The number of osteoclasts was increased after 24 h of treatment with PTH, but not after the other agents. Calcium release was significantly increased for all agents between 12 and 24 h. It is concluded that bone resorption by 1,25(OH)2D3, OAF, and PGE2 is mediated primarily by increased activity of existing osteoclasts similar to PTH activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02408081
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  • 2
    Electronic Resource
    Electronic Resource
    Cells of the mononuclear phagocytic system resorb implanted bone matrix: A histologic and ultrastructural study (1982)
    Springer
    Calcified tissue international 34 (1982), S. 488-494 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02411290
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    Paper (German National Licenses)
    Fulltext
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