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  • Alkaline phosphatase  (1)
  • Femur  (1)
  • 1
    ISSN: 1432-0827
    Keywords: Cortisol ; Cortical bone ; Bone biomechanics ; Rat ; Femur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Doses of 8, 16 (low), 32, 48, 64 (medium), and 150 (high) mg/kg/day of cortisol were administered to groups of 8 growing rats each during 16 days, and their femurs were then submitted to 3-point bending tests at low strain rate. Low doses had no effect. Medium doses, previously shown to improve calcium (Ca) balance and weight gain in the species, augmented diaphyseal elastic and ultimate strength, stiffness, and plastic-to-elastic deformation ratio with respect to untreated controls. This effect was achieved either by enhancing bone mass (volume, sectional moment of inertia, wall/lumen ratio) without changes in material quality parameters (32 mg/kg/day) or, conversely, by increasing bone tissue mechanical properties (stress, modulus of elasticity) not affecting bone geometry (48 and 64 mg/kg/day). The highest dose, known to depress Ca balance and weight gain, impaired diaphyseal mechanical performance in controls by substantially reducing bone mass without major variation in bone material properties, that is, developing a true osteopenic state in mechanical terms. The energy elastically absorbed per unit volume (proportional to the risk of comminute fractures) was greater with the highest dose because of enhanced deformability and diminished bone mass. The biphasic dose-response curves obtained, grossly parallel to those previously demonstrated for metabolic actions of cortisol in the same species, showed that biomechanical repercussion of this treatment on bone depends on different, dose-dependent effects which vary independently in temporal course, intensity, and sign.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 14 (1974), S. 169-175 
    ISSN: 1432-0827
    Keywords: Galactose ; Glucose-6-phosphate ; Resorption ; Pyrophosphate ; Hydroxyproline ; Alkaline phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'effet du galactose sur le métabolisme osseux est étudié en soumettant de jeunes rats à un régime semi-synthétique contenant 35% de ce monosaccharide. Les animaux témoins reçoivent le même régime sans galactose, avec du glucose. L'effet d'une consommation de Ca−P, normal et faible, est étudié chez les témoins et les groupes soumis au galactose. La glucose-6-phosphate deshydrogénase osseuse est inhibée lorsque le galactose s'accumule dans les tissues. L'excrétion urinaire de calcium, pyrophosphate, aminopolysaccharides, hydroxyproline en phosphatase alcaline plasmatique (isoenzyme osseuse) est augmentée de façon significative par rapport aux témoins. Les animaux, recevant du galactose avec un régime faible en Ca et P, présentent une balance négative en Ca, due surtout à un excretion fécale plus élevée que les apports. Un rapport inverse est observé entre la balance calcique et l'ingestion alimentaire. L'effet nocif du galactose sur le métabolisme du calcium pourrait agir par l'intermédiaire d'une action sur les cellules osseuses et les fonctions rénales et intestinales, en rapport, peut-être, avec un trouble inconnu du métabolisme hydro-carboné.
    Abstract: Zusammenfassung Die Wirkung von Galaktose auf den Knochenstoffwechsel junger Ratten wurde untersucht, indem diese eine semisynthetische Nahrung erhielten, welche 35% dieses Monosaccharids enthielt. Kontrolltiere erhielten dieselbe Nahrung ohne Galaktose, aber mit Glukose. Die Kontrollgruppe und die Gruppe mit Galaktosenahrung erhielten eine niedrige und eine normal Ca−P-Einnahme. Die Glukose-6-Phosphat-Dehydrogenase des Knochens wurde gehemmt, wenn Galaktose im Gewebe zunahm. Die Urinausscheidung von Calcium, Pyrophosphat, Aminopolysacchariden, Hydroxyprolin und alkalischer Phosphatase des Plasmas (Knochen-Isoenzym) war signifikant höher als bei den Kontrollen. Die Tiere mit Galaktosezusatz und niedriger Ca−P-Aufnahme zeigten eine negative Calciumbilanz, die hauptsächlich durch eine fäkale Ausscheidung bedingt war, welche höher war als die Einnahme. Es wurde eine umgekehrt proportionale Beziehung zwischen Calciumbilanz und Nahrungseinnahme beobachtet. Die nachteilige Wirkung von Galaktose auf den Calciumstoffwechsel mag von einer Wirkung auf die Knochenzellen und auf die Nieren- und Darmfunktion herrühren, vielleicht im Zusammenhang mit einer noch unbestimmten Störung des Kohlenhydratstoffwechsels.
    Notes: Abstract The effect of galactose on bone metabolism was studied by feeding young rats a semisynthetic diet containing 35% of this monosaccharide. Control animals received the same diet without galactose but with glucose. Both a low, and a normal, Ca−P intake were studied in the control and galactose fed groups. Bone glucose-6-phosphate dehydrogenase was inhibited as galactose accumulated in the tissue. Urinary excretion of calcium, pyrophosphate, aminopolysaccharides, hydroxyproline and plasma alkaline phosphatase (bone isoenzyme) were significantly increased above control levels. Galactose fed animals on a low Ca and P diet showed a negative Ca balance, primarily due to a fecal excretion which was greater than intake. An inverse relationship between calcium balance and food intake was observed. The adverse effect of galactose on calcium metabolism may be mediated by an effect on bone cells and on renal and intestinal function, related perhaps to an as yet non-defined disturbance of carbohydrate metabolism.
    Type of Medium: Electronic Resource
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