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  • 1
    Electronic Resource
    Electronic Resource
    Marrow stromal cell commitment to mineralization under the effect of a prolyl hydroxylase inhibitor (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 54 (1994), S. 354-364 
    Details
    ISSN: 0730-2312
    Keywords: cis-hydroxyproline ; rhodamine 123 ; mitochondria ; rat bone marrow ; dexamethasone ; osteoprogenitor cells ; differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mitochondrial response to the effect of a hydroxylase (PH) inhibitor was tested in marrow stromal cells during stimulation of osteoprogenitor cell (OPC) differentiation. The rationale for this was to explore pathways of regulatory interactions between procollagen synthesis and mitochondrial respiration that could be linked to the commitment of OPCs to mineralization. Stimulated OPCs exposed to the PH inhibitor cis-hydroxyproline (cis-HP), compared to the noninhibiting isomer trans-HP, for 11 days showed a dose-dependent decrease in cell proliferation, the surviving cells showed increased alkaline phosphatase activity. Trans-HP did not influence the cis-HP effect on ALP and on proliferation arrest. Short time exposures, 2-3 days, to cis-HP at different periods suggested that Days 0-3 and 3-5 were critical for the commitment to Day 21 mineralization of OPCs. On Days 0-3 cells were most sensitive to cis-HP, since on Day 11, 8 days after removal of cis-HP, they were too scarce to be counted by the staining method. However, the presence of 5.0 mM cis-HP in the cultures during Days 3-5 has induced on Day 21 close to 24-fold more mineralization/cell than controls, compared to the trans-HP effect, which was only close to 3-fold. The presence of cis-HP in the cultures on Days 0-3 has augmented the mitochondrial Day 3 retention of rhodamine 123 (Rho) in the stromal cells, relative to controls, compared to the presence of trans-HP. However, the presence of cis-HP during Days 3-5 or 3-6 resulted in lower Day 5 Rho retention, relative to controls, which was not significantly different from the retention that resulted from trans-HP. Since Rho retention is related to the final result of aerobic respiration level, these results are interpreted as a cis-HP inhibitory effect on procollagen peptidyl-proline hydroxylation, which may in turn release oxygen surpluses, to be available for mitochondrial consumption. The fall in Rho retention responses to cis-HP between Days 0-3 and 3-5 is suggesting either abrupt decrease in proline hydroxylation or poor mitochondrial sensitivity to oxygen in Day 3-5 cultures.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240540311
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  • 2
    Electronic Resource
    Electronic Resource
    Cell-mediated mineralization in culture at low temperature associated with subtle thermogenic response (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 63 (1996), S. 229-238 
    Details
    ISSN: 0730-2312
    Keywords: thermogenesis ; osteoprogenitor cells ; valinomycin ; mitochondria ; inner membrane ; rhodamine 123 ; uncoupling ; oxidative phosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In both the growth plate and in marrow stromal cell cultures cell-mediated mineralization is preceded by characteristics of anaerobic and low efficiency energy metabolism. Reagents that increase mineralization like malonate and dexamethasone (DEX) also increase the mitochondrial membrane potential (MtMP) especially 1 week after DEX stimulation. Contrarily, levamisole, which decreases mineralization, also decreases MtMP. Modulation of MtMP and energy metabolism could be linked to regulation of mineralization by the uncoupling of oxidative phosphorylation. This uncoupling should be associated with thermogenesis in cells that induce mineralization. We examined whether cold temperature affects mineralization, and whether cellular thermogenesis takes place at cold temperature in parallel to changes in MtMP. Osteoprogenitor cells (OPC) induced, in DEX stimulated rat marrow stroma, higher mineralization at 33°C than at 37°C. Increased mineralization by cold temperature required long incubation since incubation in the cold during short intervals, 3-4 days, did not increase mineralization relative to (37°C) controls. Marrow stromal cells in the presence of valinomycin responded to incubation at 33°C by retaining all the vital dye after 4 h, unlike the cells at 37°C; however, after 24 h the level of dye retention at 33°C was the same as at 37°C. The delayed response of the temperature-dependent (〉 37°C) K+ ionophor to incubation in the cold indicated that certain cells may respond to low temperature by local intracellular heating, and by heat conduction to the plasma membrane. DEX-stimulated stromal cells, unlike unstimulated cells, showed increased mitochondrial rhodamine 123 retention in the presence of valinomycin after 24 h in the cold, which corresponds to day 4 of OPC induction. This is consistent with the concept that valinomycin-induced cell damage is mediated by (cold-induced) local heating. The mechanism of this cell damage should selectively prefer non-thermogenic (rhodamine retaining) over thermogenic (rhodamine leaking) cells such as OPC. At cold temperature DEX-stimulated stromal cells showed the best anti-OPC selection under exposure to valinomycine between days 3-7, concurrent with the period of rhodamine leakage from the mitochondria. These results indicate that thermogenesis is enhanced during the period of low MtMP in mineralizing cells, and prolonged exposure to cold increases mineralization also due to induction of subtle thermogenesis. © 1996 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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