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  • 11
    Electronic Resource
    Electronic Resource
    Biochemical characterization of 1,25(OH)2D3 receptors in chick embryonal duodenal cytosol (1982)
    Springer
    Calcified tissue international 34 (1982), S. 265-269 
    Details
    ISSN: 1432-0827
    Keywords: 1,25(OH)2D3 Receptor ; Chicken Duodenal Cytosol ; Chicken Embryo ; Affinity ; 1,25(OH)2D3 Concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary This study presents measurements of serum vitamin D metabolites, calcium and phosphorus as well as measurements of the equilibrium dissociation constant for duodenal 1,25(OH)2D3 receptor in 15-, 18-, 19-, and 20-day chick embryos in comparison to that in 1- and 118-day-old chicks and to vitamin D-deficient chicks. The present results showed that: (a) serum 1,25(OH)2D and 24,25(OH)2D levels rise from 15 and 18 to days 19 and 20 of embryonic development while serum phosphate levels are stable; (b) serum calcium levels rise at hatching to adult levels; (c) the duodenal 1,25(OH)2D3 receptor is detectable in 15-day-old embryo and has a Kd similar to that of 118-day-old vitamin D-replete chicks; and (d) the activity of 1,25(OH)2D3 receptor in chick duodenal cytosol is maximal at hatching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411248
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  • 12
    Electronic Resource
    Electronic Resource
    Phosphate transport in osteoblasts from normal and X-linked hypophosphatemic mice (1994)
    Springer
    Calcified tissue international 54 (1994), S. 505-510 
    Details
    ISSN: 1432-0827
    Keywords: Cultured cells ; Vitamin D-resistant rickets ; Mouse ; cAMP ; Alkaline phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Human hypophosphatemic vitamin D-resistant rickets (X-linked hypophosphatemia-XLH) is characterized by hypophosphatemia, a decreased tubular reabsorption of phosphate (Pi) and defective skeleton mineralization. Utilizing a mouse model (Hyp) of XLH, which demonstrates biological abnormalities and skeletal defects of XLH, we analyzed sodium-dependent phosphate transport in isolated osteoblasts derived from the calvaria of normophosphatemic and hypophosphatemic mice. Initial rates of phosphate uptake by normal and Hyp osteoblasts showed similar slopes. Osteoblasts from both normal and Hyp mice exhibited saturable, sodium-dependent phosphate transport with apparent Vmax and Km values not significantly different (normal mice, Vmax=24.30±3.45 nmol/mg prot. 10 min, Km=349.49±95.20 μmol/liter; Hyp mice, Vmax=23.03±3.41 nmol/mg prot. 10 min, Km=453.64±106.93 μmol/liter, n=24). No differences were found in the ability of normal and Hyp osteoblasts to respond to Pi transport after 5 hours of Pi deprivation. Both cell types exhibited a similar increase in cAMP in response to PTH. The accumulated results demonstrate that Pi uptake and transport in normal and Hyp mouse osteoblasts is a sodium-dependent saturable process. As osteoblast Pi uptake and transport is apparently normal in the Hyp mouse model of XLH, the “osteoblastic failure” described for the Hyp mouse should be attributed to other mechanism(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334333
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  • 13
    Electronic Resource
    Electronic Resource
    Skeletal Casein Kinase Activity Defect in the HYP Mouse (1997)
    Springer
    Calcified tissue international 61 (1997), S. 256 -259 
    Details
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract: The Hyp mouse, a model for human X-linked hypophosphatemia (XLH), is characterized by phosphate wasting and defective mineralization. Since osteopontin (OPN) is considered pivotal for biological mineralization, we examined the biosynthesis of OPN in osteoblasts of +/Y and Hyp/Y mice. Immunoprecipitation analyses using a specific antibody to OPN revealed that Hyp/Y and +/Y osteoblasts secrete similar levels of OPN as determined by [35S]-methionine biosynthetic labeling, but a reduced phosphorylation was noted after 32P-PO4 biosynthetic labeling. Northern blot hybridization analysis of +/Y and Hyp/Y mice osteoblast mRNAs, using a cDNA probe for mouse OPN, revealed no difference in the steady state levels of osteopontin mRNA. Analysis of casein kinase II activity in +/Y and Hyp/Y mice osteoblast, kidney, heart and liver membrane fractions revealed that casein kinase II activity in the Hyp/Y mice osteoblasts and kidney is only 35%-50%, respectively, of that of the +/Y mice tissues. The accumulated data are consistent with a post-translation defect in the Hyp/Y mouse osteoblast which results in the under-phosphorylation of osteopontin and subsequent under-mineralization of bone matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900331
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  • 14
    Electronic Resource
    Electronic Resource
    Corticosteroids and bone (1984)
    Springer
    Calcified tissue international 36 (1984), S. 4-7 
    Details
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405286
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  • 15
    Electronic Resource
    Electronic Resource
    Characterization of osteoblast-like cells from normal adult rat femoral trabecular bone (1992)
    Springer
    Calcified tissue international 50 (1992), S. 93-95 
    Details
    ISSN: 1432-0827
    Keywords: Rat osteoblast ; Trabecular bone ; Cell culture ; PTH ; Alkaline phosphatase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Osteoblast-like cell cultures have been established from the trabecular surfaces of normal adult rat femoral trabecular bone. The cultured cells responded to stimulation by parathyroid hormone (rPTH), with a rise in intracellular cAMP in excess of 25-fold while failing to respond to incubation with sCT. Furthermore, the osteoblast-like cells exhibited a high level of alkaline phosphatase expression, both histochemically and biochemically. Incubations with 1,25(OH)2 vitamin D3 increased the alkaline phosphatase activity by 50% and stimulated bone Gla-protein (BGP) synthesis. When the cell layers were supplemented with both 50 μg/ml ascorbic acid and 10 mM β-glycerophosphate and allowed to grow past confluency for 3 weeks, they formed calcified ridges and multilayered nodules. Confirmation of the mineralization of an extracellular matrix was made by von Kossa staining. This simple isolation technique now facilitates the availability of normal adult rat osteoblastic cells for investigation of bone and mineral metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297304
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  • 16
    Electronic Resource
    Electronic Resource
    Induction of Bone Formation Using a Recombinant Adenoviral Vector Carrying the Human BMP-2 Gene in a Rabbit Spinal Fusion Model (1998)
    Springer
    Calcified tissue international 63 (1998), S. 357-360 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Spinal fusion — Stem cells — Bone morphogenetic protein — Bone induction — Gene therapy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Bone marrow-derived mesenchymal stem cells are pluripotential cells that have the capacity to differentiate into an osteoprogenitor line. It has been demonstrated that BMP-2 can enhance this differentiation process. In an attempt to prolong the transforming effect of BMP-2, we used an adenoviral vector carrying the human BMP-2 gene to transduce marrow-derived mesenchymal stem cells of New Zealand white rabbits. Assays on tissue culture demonstrated that these cells indeed produced the BMP-2 protein. These transduced stem cells were then autologously reimplanted into the donor rabbits. The cells were placed in the intertransverse process area of five rabbits. In one out of the five rabbits, this resulted in the production of new bone which was demonstrable on both radiographic and histologic examination. We conclude that it is possible to successfully transduce mesenchymal stem cells with the gene for BMP-2 such that these cells will produce the BMP-2 protein in vitro. Further, the transduction results in transformation of these cells into an osteoprogenitor line capable of producing bone in vivo. These data suggest the feasibility of employing gene therapy using recombinant adenoviral vectors as a tool for enhancing spine fusion. Further work to improve the fidelity and longevity of the gene transfer is warranted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900540
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  • 17
    Electronic Resource
    Electronic Resource
    Plasma membrane phospholipid content in non-insulin-dependent streptozotocin-diabetic rats — effect of insulin (1988)
    Springer
    Diabetologia 31 (1988), S. 315-321 
    Details
    ISSN: 1432-0428
    Keywords: Phospholipids ; membrane ; diabetes ; insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of (Ca2+ + Mg2+)-ATPase is impaired in kidney basolateral membranes from non-insulin-dependent streptozotocin-diabetic rats. To study the possible role of changes in membrane phospholipid content in the malfunction of this enzyme in kidney membranes of the diabetic animals, phospholipid (phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin) content was measured in kidney and liver membranes obtained from non-insulin-dependent diabetic rats. Total phospholipid content was similar in liver and kidney membranes of diabetic and control rats (595±47 versus 624±29 in liver and 469±22 versus 458±17 nmol Pi/mg protein in kidney respectively). Phosphatidylethanolamine content in kidney and liver membranes of diabetic rats was lower than in control rats (87.7±1.8 versus 96.4±2.2 nmol Pi/mg protein, p〈0.01 and 87.1±3.7 versus 101.8±3.5, p〈0.02 respectively). Phosphatidylinositol content was higher in kidney (28.0±0.6 versus 23.9±2.1, p〈0.02) but not liver membranes from diabetic rats. The in vitro direct effect of insulin on the phospholipid content in kidney membranes was also measured. Physiologic concentrations of insulin (718 pmol/l for 30 min) increased the phosphatidic acid content in membranes from control but not from diabetic rats by 34.2% (p〈0.02). This rise was readily measurable after 3 min of exposure to insulin. Insulin did not induce a significant change in the content of any other phospholipid in membranes from control or diabetic rats. These differences in phospholipid content demonstrated in isolated membranes obtained from non-insulin-dependent diabetic and control rats, before and after exposure to insulin, may explain, in part, the impaired function of the (Ca2++Mg2+)-ATPase observed previously in kidney membranes of the diabetic rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00277414
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