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  • 1975-1979  (2)
Materialart
Erscheinungszeitraum
Jahr
  • 1
    ISSN: 1432-0827
    Schlagwort(e): Parathyroid hormone ; Osteoclasts ; Electron microscopy ; Morphometry ; Metaphysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The effects of parathyroid hormone (PTH) on the size of the osteoclasts, nuclei, ruffled borders, and clear zones in long bones of thyroparathyroidectomized (TPTX) rats were quantitated as a function of time. These data were compared with the number of osteoclasts in the bone and with plasma calcium levels. A significant increase in the average size of the ruffled borders was demonstrated 30 min after injection of 50 U of purified bovine PTH, and of the clear zones 30–90 min after PTH. This was followed at 90 min by an increase in the average size of the cells. The sizes of ruffled borders and clear zones dropped sharply to control levels after 6 h, whereas the size of the cells remained elevated up to 12 h and returned to control values at 24 h. Plasma calcium levels were increased, but not significantly, between 30 min and 6 h. An increase in the number of osteoclasts was significant after 12 h. Removal of the parathyroid glands did not diminish the normal activity of osteoclasts. In animals with intact glands injection of 50 U of PTH did not cause a significant change in cell size or resorbing apparatus. It is concluded that PTH acts to rapidly stimulate the bone resorptive activity of osteoclasts and to cause a delayed increase in their number.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-0827
    Schlagwort(e): 1,25(OH)2D3 ; PGE2 ; OAF ; PTH ; Osteoclasts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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