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  • 1
    Electronic Resource
    Electronic Resource
    Selective stimulation of net calcium efflux from chick embryo tibiae by parathyroid hormone in vitro (1978)
    Springer
    Calcified tissue international 25 (1978), S. 227-232 
    Details
    ISSN: 1432-0827
    Keywords: Parathyroid hormone ; Bone ; Calcium ; Chick embryo ; Organ culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The purpose of this study was to measure in an in vitro system the movement of Ca and phosphate (Pi) out of bone when treated with parathyroid hormone (PTH). Tibiae from 13-day chick embryos were incubated for up to 8 h in a defined medium containing 1.8 mM Ca. Medium samples were collected every 2 h and were analyzed for Ca, Pi and lactate. Net effluxes from the bones were calculated. When bones were incubated with PTH in the medium (1 U/ml), net Ca efflux was increased 44, 60 and 100% at 4, 6 and 8 h, respectively. At no time was net Pi efflux affected by the hormone. The well known PTH-stimulated lactate production was not seen until 8 h. Lower doses of PTH (0.1 and 0.3 U/ml) were also effective. Comparing PTH (1 U/ml) responsiveness at higher (2.2 mM) and lower (0.9 mM) medium Ca concentrations, showed that with 2.2 mM Ca no increased Ca efflux was seen, while with 0.9 mM Ca significant elevation in medium Ca occurred 2 h sooner than in the experiments using 1.8 mM Ca. In another experiment, varying the medium Pi level from 1 to 2 mM had no effect on the Ca response to PTH. In neither experiment was Pi release affected by PTH. The results of this study have led to the following conclusions: (1) PTH acts on bone to cause an early dose related increase in net Ca efflux; (2) the effect is specific for Ca, since it is not accompanied by an increased Pi efflux, and may be saturated by raising the medium Ca level; and (3) PTH-stimulated Ca efflux in this system is not correlated with, and is probably not a result of increased lactate production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010774
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of ascorbic acid on the glycolytic and respiratory metabolism of embryonic chick tibias (1968)
    Springer
    Calcified tissue international 2 (1968), S. 77-82 
    Details
    ISSN: 1432-0827
    Keywords: Bone ; Metabolism ; Ascorbic Acid ; Tissue Culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Du tissu osseux, cultivé pendant 5 jours dans un milieu chimiquement défini, présente une augmentation de la consommation en O2 et une diminution de la production d'acide lactique lorsqué de l'acide lactique (50 μg/mI) est présent dans le milieu de culture. Ces paramètres ont été mesurés pendant des incubations de courte durée, en cultures de tissus. En n'ajoutant de l'acide lactique qu'au dernier jour de culture ou pendant les 4 premiers jours, et non le dernier jour, les valeurs en O2 et en acide lactique sont identiques à celles observées lorsque la vitamine est présente pendant 5 jours. Des produits similaires à l'acide ascorbique (50 μg/ml), administrés pendant 5 jours donnent des résultats identiques à ceux de la vitamine C. Une expérience préliminaire pour évaleur la vitesse d'oxydation de l'acide ascorbique dans le milieu de culture a permis de montrer que la vitamine doit être remplacée quotidiennement lorsque les cultures sont traitées avec 20% d'O2 et plus fréquemment avec des concentrations d'O2 plus élevées. Les changements dans le métabolisme énergétique, liés à l'acide ascorbique et observés dans cette étude, indiquent que la vitamine pourraît être un facteur important de stimulation du métabolisme squelettique aérobique.
    Notes: Abstract Bones cultured for 5 days in a chemically defined medium showed an increased O2 consumption and decreased lactic acid production when ascorbic acid (50 μg/ml) was present in the culture medium. In this and the following experiments these parameters were measured in short-term incubations following tissue culture. Adding ascorbic acid for only the final day of culture or for the first 4 days and not the final day gave O2 and lactic acid results similar to those obtained when the vitamin was present for all 5 days. Ascorbic acid analogs (50 μg/ml) added for 5 days also exhibited results similar to those for vitamin C. A preliminary experiment to evaluate the oxidation rate of ascorbic acid in the culture medium established that the vitamin must be replenished daily when cultures are gassed with 20% O2 and more frequently with higher O2 concentrations. The ascorbic acid-dependent changes in energy metabolism seen in this study suggest that the vitamin may be an important factor in stimulating skeletal aerobic metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02279196
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Magnesium and the mineral metabolism of chick embryo tibiae in organ culture (1977)
    Springer
    Calcified tissue international 24 (1977), S. 93-98 
    Details
    ISSN: 1432-0827
    Keywords: Magnesium ; Bone ; Mineral ; Chick embryo ; Organ culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Using bone organ culture techniques, three concentrations of magnesium were evaluated for their effects on the mineral mass of embryonic chick tibiae incubated for 3 days with or without a metabolic inhibitor (1 mM iodoacetic acid) added to the media. Varying the medium Mg level from 0.3 to 3.0 mM had little effect on the net increase in mineral in live bones (without the inhibitor), but in dead tibiae (with the inhibitor) there was a marked net decrease in mineral deposition with increasing Mg concentration. Bone Mg mass varied directly with the level of Mg in the medium regardless of whether or not the tibiae were inhibited. Responsiveness to parathyroid hormone (PTH) with regard to mineral loss and increased lactate production was not affected by Mg even in tibiae incubated in Mg-free media. However, PTH-treated bones cultured in Mg-free media had a significantly elevated Mg mass, suggesting that the hormone may have a Mg-conserving effect on bone during severe Mg deficiency. The findings of this study support the hypothesis that bone cells regulate the level of Mg to which newly forming mineral is exposed and that PTH-responsiveness in embryonic chick tibiae is not dependent on the ambient Mg concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223301
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of parathyroid hormone on alkaline phosphatase activity and mineralization of cultured chick embryo tibiae (1979)
    Springer
    Calcified tissue international 27 (1979), S. 137-142 
    Details
    ISSN: 1432-0827
    Keywords: Parathyroid hormone ; Alkaline phosphatase ; Chick embryo ; Mineralization ; Bone organ culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The objectives of this study were (a) to determine if decreased bone alkaline phosphatase (AlPase) activity, resulting either from exposure to parathyroid hormone (PTH) or from direct inhibition of AlPase with levamisole, was concomitant with net changes in bone Ca and P content; and (b) to determine the duration of the effect of PTH on bone AlPase activity after the hormone was removed. Tibiae from 7-day chick embryos were incubated in chemically defined medium for 3–4 days. The Ca and P content of bones incubated for 72 h in this system increased from 2-to 9-fold. Addition of PTH (1 U/ml) to the medium resulted in a 60% decrease in bone AlPase activity, and this decrease was accompanied by a marked inhibition of Ca and P accumulation in bone. When levamisole, a specific inhibitor of AlPase activity, was added to the medium, a similar inhibition of bone mineral accumulation resulted. A 24-h incubation in medium containing PTH (1 U/ml) resulted in a 30% decrease in bone AlPase activity. Following the 24-h exposure to PTH, incubation was continued in medium containing no hormone. After 72 h in hormone-free medium, bones that had been exposed to PTH earlier contained more AlPase activity than paired control bones never exposed to PTH. The PTH-treated bones also recovered their ability to accumulate Ca and P. The results of this study show that: (a) decreased bone AlPase activity resulting from either exposure to PTH or direct inhibition by levamisole is associated with a marked decrease in mineral accumulation in bone; (b) exposure to PTH followed by removal of the hormone leads to recovery and even an increase in bone AlPase activity; and (c) following removal of PTH from the culture system, tibiae recover their ability to accumulate Ca and P. These results suggest that one of the ways PTH may alter mineral accretion is through its effects on bone AlPase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441176
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  • 5
    Electronic Resource
    Electronic Resource
    Electron microscopic localization of lactate dehydrogenase in osteoclasts of chick embryo tibia (1976)
    Springer
    Journal of molecular histology 8 (1976), S. 543-558 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Synopsis Lactate dehydrogenase (LDH) was localized in osteoclasts of fixed and unfixed 19-day chick embryo tibias using a copper ferrocyanide capture reaction and osmiophilic polymer generation. This study revealed that: (1) LDH activity in fixed, briefly rinsed osteoclasts was associated principally with limiting membranes of cytoplasmic vacuoles and vesicles and with the plasma membrane; (2) LDH activity in unfixed osteoclasts was associated only with mitochondria; and (3) some mitochondria were stained in fixed tissue given a long rinse. These results indicate that: cytoplasmic LDH diffused out of unfixed tissue; mitochondrial LDH was inactivated by formaldehyde in fixed tissue; and formaldehyde-inhibited mitochondrial LDH can be reactivated by a long rinse. Although the vesicles that stained for LDH activity were found in all parts of the cell, they were concentrated near the ruffled border, and there is evidence that they contained material from the bone surface. These results suggest that the LDH associated with cytoplasmic vesicles of the osteoclast may be important in processing of material resorbed from the bone surface and that osteoclastic mitochondria may utilize lactate from the bone fluid for energy production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01003844
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