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  • 1
    Electronic Resource
    Electronic Resource
    Adhesion, growth, and matrix production by osteoblasts on collagen substrata (1992)
    Springer
    Calcified tissue international 51 (1992), S. 202-212 
    Details
    ISSN: 1432-0827
    Keywords: Osteoblasts ; Collagen type I ; “On gel” cultures ; Collagen sponges ; Osteocalcin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A number of studies have demonstrated the pivotal role of collagen molecules in modulating cell growth and differentiation. In order to analyze the direct effects of collagen type I on the osteoblastic phenotype, we have devised an in vitro culture system for studying the interactions between bovine collagen type I and Saos-2 cells, a human osteoblastic cell line. Saos-2 cells were cultured both on top of collagen-coated culture dishes as well as inside a three-dimensional collagen network. Plating on dishes treated with collagen induced maximal adhesion of Saos-2 cells after 24-hour incubation. Cells cultured on collagen gel matrix expressed about 2.5-fold more alkaline phosphatase when compared with untreated plastic dishes. On collagen-coated dishes the responsiveness of Saos-2 cells to parathyroid hormone was decreased, whereas no modifications were observed in the effect of vasoactive intestinal peptide on these cells. Using a microfluorimetric measurement of DNA, an increase of proliferation was observed in Saos-2 cells cultured on collagen gel Saos-2 cells were also able to colonize collagen sponges and in this three-dimensional network they were able to synthesize osteocalcin, as assessed both by immunocytochemistry and radioimmunoassay. In this study we have demonstrated that bovine collagen type I exhibits favorable effects on attachment and functional and growth activities of a human osteoblastic cell line, encouraging its use as a bone graft material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334548
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  • 2
    Electronic Resource
    Electronic Resource
    Interactions between ipriflavone and the estrogen receptor (1995)
    Springer
    Calcified tissue international 56 (1995), S. 160-165 
    Details
    ISSN: 1432-0827
    Keywords: Ipriflavone ; Estrogen receptor ; Osteoclasts ; Bone resorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Estrogen replacement therapy is effective in the prevention of postmenopausal osteoporosis, and a direct action of 17-β-estradiol (17βE2) on osteoblastic and osteoclastic cells has been demonstrated. The inhibition of bone resorption by ipriflavone (IP), an isoflavone derivative devoid of estrogenic properties but active in potentiating the effects of estroge on bone tissue, has been shown in in vitro and in vivo studies and confirmed by clinical data. To investigate the molecular mechanisms that underlie IP effect, we studied the possible interactions of IP and its four main in vivo metabolites (I, II, III, and V) with the estrogen receptor (ER) in the human preosteoclastic cell line FLG 29.1, whose growth and function are modulated by the compound. In parallel experiments, the human breast cancer cell line MCF7 was also analyzed. IP binding sites were demonstrated in the nuclear fraction of FLG 29.1 cells. 17βE2 and other steroid compounds failed to displace IP binding to intact FLG 29.1 cells. Similarly, IP and metabolites I, III, and V were not able to displace 17βE2 binding to intact MCF7 cells, whereas metabolite II showed an IC50 of 61 nM. 17βE2 binding to FLG 29.1 cells was increased after preincubation with metabolites I, III, and V. IP and its metabolites did not induce FR-dependent gene expression in FLG 29.1 and MCF7 cells transfected with a reporter gene and an estrogen response element (ERE). These results suggest that IP effects on osteoclast precursors are not mediated by a direct interaction with the ER, even if a crosstalk between the mechanisms of action of IP and 17βE2 cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296349
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  • 3
    Electronic Resource
    Electronic Resource
    Natural and Synthetic Isoflavones in the Prevention and Treatment of Chronic Diseases (1997)
    Springer
    Calcified tissue international 61 (1997), S. S005 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Isoflavones — Phytoestrogens — Chronic diseases.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The evidence that natural isoflavones protect against several chronic diseases is both observational and experimental. In humans, epidemiologic findings clearly show a higher incidence of some common types of cancer (i.e., breast, prostate, and colon) and of coronary heart diseases in Western populations exposed to limited amounts of soybean isoflavones (i.e., genistein, daidzein) in the diet. Further evidence for cancer and cardiac protection and antiatherogenic effects resulting from soybean isoflavones administration has been noted in various experimental animal models. Isoflavones may also prevent postmenopausal bone loss and osteoporosis. In fact, genistein has been reported to be as active as estrogens in maintaining bone mass in ovariectomized rats. Moreover, the synthetic isoflavone derivative ipriflavone is able to reduce bone loss in various types of animal models of experimental osteoporosis providing a rationale on its use in the prevention and treatment of postmenopausal and senile osteoporosis in humans. The mechanism through which isoflavones may exert the above-mentioned effects seems to depend, at least in part, on their mixed estrogen agonist-antagonist properties. An alternative hypothetical mechanism could derive from other biochemical actions of isoflavones such as inhibition of enzymatic activity, in particular protein kinases, or activation of an ``orphan'' receptor distinct from the estrogen type I receptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900376
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  • 4
    Electronic Resource
    Electronic Resource
    Bone endothelial cells as estrogen targets (1993)
    Springer
    Calcified tissue international 53 (1993), S. 312-317 
    Details
    ISSN: 1432-0827
    Keywords: Bone endothelium ; Estrogen receptors ; Parathyroid hormone response ; Angiogenesis ; Bone remodeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In the present study, we investigated the effects of estrogens on bone endothelial cell metabolism and the presence of estrogen binding sites in the same cells. For these studies, we have used a continuous cell line of clonal bovine bone endothelial cells for evidence of a direct response to estrogensin vitro. Receptor analysis to intact viable cells was steroid specific and saturable, with an apparent dissociation constant of 17.2 nM and a Bmax of 3.2 × 104 sites/cell. Northern blot analysis revealed a 6.5-kilobase mRNA that hybridized with a cDNA to human estrogen receptor. The 6.5-kilobase size is in close agreement with the reported size of the human estrogen receptor mRNA.In vitro estrogen responses of bone endothelial cells included a stimulation of cell proliferation as well as an inhibition of parathyroid hormone responsiveness. These findings clearly demonstrate the presence of functional estrogen receptors in bone endothelial cellsin vitro, suggesting a role of estrogens in bone angiogenesis and in the entire process of bone remodeling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01351835
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  • 5
    Electronic Resource
    Electronic Resource
    P-glycoprotein is expressed in parathyroid epithelium and is regulated by calcium (1995)
    Springer
    Calcified tissue international 56 (1995), S. 170-174 
    Details
    ISSN: 1432-0827
    Keywords: Multidrug resistance ; P-glycoprotein ; Parathyroid ; Calcium regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract P-glycoprotein (Pgp), the multidrug resistance (mdr) gene product, has been described in normal tissues with diverse physiologic functions. A broad role as a transporter protein for toxins, hormones, and physiologic metabolites has been provisionally deduced, based on structural analysis and immunoanatomic localization. Recently, significant levels of Pgp have been demonstrated in endocrine and hormonally responsive tissues and tumors. We examined calcium-regulated, clonal parathyroid epithelial (PT-r) and endothelial cells (BPE-1) and frozen parathyroid tissue from normal human parathyroid, parathyroid hyperplasia, parathyroid adenoma, and parathyroid carcinoma for expression of the multidrug resistance gene (Mdr1) and Pgp utilizing Northern and Western analysis and immunohistochemistry. We also investigated the effect of extracellular calcium (eCa) on Pgp expression in PT-r cells at the molecular/cellular level. Immunohistochemistry, utilizing three murine monoclonal antibodies (MAbs)—C494, JSB-1, and C219—which recognize spatially distinct cytoplasmic epitopes of Pgp, revealed strong immunoreactivity in PT-r cells, normal parathyroid, and parathyroid hyperplasia, and weak immunostaining in parathyroid adenomas. BPE-1 cells, endothelial cells, and parathyroid carcinoma were negative. PT-r cells showed a single 130 kDa band (120 KDa after glycosidase treatment) on Western blot and a 4.6 kb transcript on Northern analysis, consistent with Pgp. Western and Northern blot analysis of PTr cells cultured in different eCa concentrations showed that eCa up-regulated Pgp expression. Northern analysis of doxorubicin-resistant human breast carcinoma cells (Adr1) (MCF-7) exhibited constitutive expression of Pgp mRNA without modifications, with increasing eCa concentrations. We conclude that N-glycosylated Pgp is expressed in parathyroid epithelial cells and that calcium responsiveness of Pgp expression appears cell specific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296351
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of Quantitative Calcaneal Ultrasound and Dual Energy X-ray Absorptiometry in the Evaluation of Osteoporotic Risk in Children with Chronic Rheumatic Diseases (2000)
    Springer
    Calcified tissue international 67 (2000), S. 19-23 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Broadband ultrasound attenuation — Contact ultrasound bone analyzer — Bone mineral density — Dual energy X-ray absorptiometry — Chronic rheumatic diseases.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Osteoporosis is a common complication in children with chronic rheumatic diseases (CRD). Although dual energy X-ray absorptiometry (DXA) is increasingly being used to determine bone mineral density (BMD) in children, it exposes the subject to ionizing radiation and does not provide a measure of true bone density; in fact, in growing bones the increase in BMD is mainly caused by the increase in bone size. In recent years, quantitative ultrasound techniques (QUS) have been used in radiation-free assessment of bone density and ``bone quality'' by measurement of the ultrasound waves attenuation by bone (BUA). In the present study we made a direct comparison of BUA in the calcaneum, determined by the pediatric contact ultrasound bone analyzer (CUBA) with lumbar BMD measured by DXA, in a group of 6–18-year-old patients with CRD. The study group consisted of 53 patients affected with juvenile rheumatoid arthritis (n = 29), systemic lupus erythematosus (n = 13), and juvenile dermatomyositis (n = 11). Mean age was 13.02 ± 2.69 years. In 22 patients (19 girls, 3 boys) both DXA and CUBA were repeated after 1 year in order to assess the mean percentage rate of BMD and BUA change over this time. Both lumbar spine BMD and calcaneal BUA measurements were lower in the CRD patients compared with a control group (P 〈 0.001). Calcaneal BUA was significantly correlated (r = 0.83, P 〈 0.001) with lumbar spine BMD. Age and sex correction (Z-score) did not change the relationship between BUA and BMD (r = 0.80, P 〈 0.001). A significant correlation between the mean percentage of variation (Δ%) of BMD and BUA (r = 0.76, P 〈 0.001) was also demonstrated in the 22 patients who were evaluated prospectively. Portability, ease of use, lower cost, and absence of radiation make CUBA a promising means of evaluating BMD in children.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00223001090
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of Ipriflavone on Perialveolar Bone Formation (1998)
    Springer
    Calcified tissue international 63 (1998), S. 312-319 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Ipriflavone—Bone formation—Rat perialveolar bone—Periodontal ligament—Osteoblasts.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The effect of ipriflavone (IP), a synthetic isoflavonoid derivative, on in vivo bone formation was studied in rat perialveolar bone by surgically producing a hole in the mandibular bone. The holes were filled either with powdered IP or with compounds containing no osteoinductive properties such as biostite and Htr (hard tissue replacement). In control animals, the holes were left to heal spontaneously. The animals were killed 3, 28, and 40 days after surgery and a detailed morphological and morphometric study was performed on the perialveolar bone surrounding the wounds. Three days after surgery (inflammatory phase) the bone wounds were occupied by hemorragic and inflammatory cells in both the untreated and IP-treated bone defects. Twenty-eight days after surgery, bone formation was evident with new bone spiculae particularly concentrated in the area of the bone lesion closest to the adjacent periodontal ligament. Morphometric measurements of the areas occupied by new bone showed that the synthesis of perialveolar bone was significantly stimulated by IP. The repair of the bone defects by new bone formation progressed by day 40, but only in the presence of IP were the original holes almost completely repaired. Conversely, biostite and Htr did not influence promotion of new bone formation. In conclusion, the results of the present study are consistent with a role of IP in stimulating osteogenesis and suggest that this compound could represent a potential therapeutic tool to promote repair of injured perialveolar bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900533
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  • 8
    Electronic Resource
    Electronic Resource
    Sequence of different types of nonlinear current oscillation in n-GaAs (1989)
    Springer
    Applied physics 48 (1989), S. 143-147 
    Details
    ISSN: 1432-0630
    Keywords: 05.40 ; 72.70 ; 72.20J
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Self-generated chaotic current fluctuations in the post-breakdown regime of a n-GaAs layer at 4.2 K have been analyzed in detail. Without an external magnetic field only regular oscillations were observed. Increasing the magnetic field strength up to 100 mT generates a sequence of quasiperiodic and frequency-locking current oscillations and finally a Ruelle-Takens-Newhouse scenario with chaos. This may be understood by assuming two coupled oscillatory processes caused by dielectric relaxation and energy relaxation in the distribution of free carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01141276
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  • 9
    Electronic Resource
    Electronic Resource
    Salmon calcitonin and cGMP production by human kidney: Studies in vivo and in vitro (1983)
    Springer
    Calcified tissue international 35 (1983), S. 273-278 
    Details
    ISSN: 1432-0827
    Keywords: Calcitonin ; Cyclic GMP ; Kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary In order to evaluate whether or not the action of salmon calcitonin (sCT) at the kidney level could be mediated through specific receptors for the hormone, we have studied the effects of sCT infusions on urinary excretion of cyclic nucleotides in humans. Parallel in vitro studies have been conducted by evaluating the effects of sCT on cyclic nucleotide levels in primary cultures of cortical and medullary human kidney cells. In vivo experiments showed that sCT induced an increase in cGMP in human urine, which was rapid and short-lasting, being superimposable on the increase of urinary excretion of calcium and magnesium. The increase of inorganic phosphate urinary excretion was delayed and appeared to parallel that of urinary cAMP. On the other hand, our in vitro experiments showed that sCT stimulated the guanylate cyclase—cGMP system of human kidney cortical cells at nanomolar concentrations, while higher concentrations of the hormone were required to activate the adenylate cyclase—cAMP system. In addition, sCT was not able to significantly modify the cellular levels of either nucleotide in human kidney medullary cells. Present data demonstrated a direct effect of sCT on human kidney cortical cGMP production, while the efficacy of sCT on the kidney cortex adenylate cyclase—cAMP system appears to be delayed and/or reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405045
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  • 10
    Electronic Resource
    Electronic Resource
    Glucocorticoid-induced osteoporosis in the lumbar spine, forearm, and mandible of nephrotic patients: A double-blind study on the high-dose, long-term effects of prednisone versus deflazacort (1992)
    Springer
    Calcified tissue international 50 (1992), S. 490-497 
    Details
    ISSN: 1432-0827
    Keywords: Deflazacort-Forearm ; lumbar ; mandibular BMC-Nephrotic syndrome-Prednisone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The long-term effects of high dose steroid treatment with either prednisone (PDN) or deflazacort (DFZ) were examined on various parts of the skeleton in 29 patients with nephrotic syndrome. All had normal skeleton at the start of the steroid treatment. At the beginning, PDN was given as 80 mg/day and tapered down to 20 mg/day for 1 year and DFZ was given in an equipotent dosage. Twenty-three patients completed 6 months of treatment, and 18 patients completed 12 months of treatment. Beside laboratory parameters to ensure the effect of treatment on the nephrotic syndrome, all had measurements of the bone mineral content (BMC) at 0, 6, and 12 months of treatment. BMC was measured by single photon absorptiometry of both forearms and by dual photon absorptiometry of the mandible, forearms, and lumbar spine. The effect of DFZ was compared to that of PDN due to a potential “calcium sparing” effect of DFZ. The therapeutical effects on the nephrotic syndrome were not different between the two drugs. Urinary 24-hour protein decreased from 9.9 to 1.1 g in the DFZ-treated patients and from 8.0 to 1.4 g in the PDN-treated patients. Plasma albumin concentration normalized in both groups. Both groups of steroid-treated patients had a significant reduction of the BMC levels in all parts of the skeleton. However, the bone decay rates per month were significantly different between different bone regions and between different drug regimes. In the forearm, the bone decay rate was 5.3%/year in the PDN group and 2.0%/year in the DFZ group (P〈0.001). In the mandible, decay rate was 7.0%/year in both groups, and in the lumbar spine it was 12.5%/year in the PDN group and 6.8%/year in the DFZ group (P〈0.01). Thus, the bone loss in the PDN-treated group was significantly higher than that of the DFZ-treated patients, despite a similar therapeutical effect on the nephrotic syndrome. Therefore, the detrimental effect of long-term steroid treatment on the skeleton may not be abolished, but can be reduced significantly by using deflazacort instead of prednisone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582160
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