bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression and Regulation of Na-Dependent Pi Transport in Matrix Vesicles Produced by Osteoblast-like Cells
Authors: Montessuit C. , Bonjour J.P. , Caverzasio J. 
Published: February 2010

Abstract
Extracellular matrix vesicles (MV) are the loci of initial mineralization in several calcifying tissues. We recently reported that MV isolated from chicken epiphyseal cartilage are equipped with a Na-dependent Pi transport (NaPiT) system. The activity of the NaPiT system appeared to be crucial for the development of MV-mediated calcification. In the present study we investigated the expression of NaPiT activity in MV produced by the osteoblast-like cells MC3T3-E1. The relationship between changes in NaPiT activity in the intact cells and in the released MV was also examined. NaPiT activity in MV harvested from cultured MC3T3-E1 cells was transiently expressed. It was markedly increased between Days 8 and 10 (5- to 6-fold), and then gradually decreased. NaPiT activity was enriched in MV as compared with the parent osteoblast-like cells, while the Na-dependent transport system for alanine (NaAIaT) was not. When NaPiT activity was enhanced in osteoblast-like cells by fetal calf serum (FCS) or Pi depletion, Pi transport stimulation was observed in the derived MV as well. Alkaline phosphatase (AP) was differentially expressed and regulated in MV from MC3T3-E1 cell cultures, as compared with NaPiT. In contrast to the transient expression of NaPiT, AP activity in MV increased continuously with time in culture. It was stimulated by FCS treatment of the parent cells, but decreased in MV obtained from Pi-depleted cultures. These results suggest that the presence in osteogenic cells of selective regulatory mechanisms for the insertion and enrichment of Pi transport activity in released MV. This process is probably of biological significance for the regulation of the cascade of events that leads to the mineralization of the bone matrix.
Effects of endothelin-1 on Ca2+ signaling and secretion in parathyroid cells
Authors: Fujii Yoshio , Tomić Melanija , Stojilković Stanko S. , Iida Toshihiko , Brandi Maria Luisa , Ogino Yoshio , Dr. Sakaguchi Kazushige 
Published: February 2010

Abstract
It has been previously reported that parathyroid cells express endothelin (ET) receptors and secrete ET-1 in an extracellular Ca2+ concentration ([Ca2+]e)-dependent manner. Here, we examined the effects of ET-1 on intracellular signaling and parathyroid hormone (PTH) secretion in dispersed bovine parathyroid (bPT) cells, which comprise several cell types including epithelial and endothelial cells, in two cell lines, the rat parathyroid epithelial (PT-r) and the bovine parathyroid endothelial (BPE-1) cells. An RNA-polymerase chain reaction analysis revealed that both ETA and ETB receptors are expressed in bovine parathyroid tissue and BPE-1 cells, and only the ETA receptor is expressed in PT-r cells. PT-r cells also expressed an inositol 1,4,5-trisphosphate (Ins[1,4,5]P3) receptor, and ionomycin induced an increase in the intracellular Ca2+ concentrations ([Ca2+]i) in a Ca2+-deficient medium, indicating the presence of an operative intracellular Ca2+ pool in these cells. In cells bathed in 1 mM [Ca2+]e, ET-1 induced a rapid and transient increase in the Ins(1,4,5)P3 production, which was associated with a similar profile of increase in [Ca2+]i and with a peak response of about 800 nM. No changes in the profile of [Ca2+]i responses were observed in ET-1–stimulated cells in the presence of Ca2+ channel blockers, or in Ca2+-deficient medium, indicating that Ca2+ mobilization was not associated with Ca2+ entry. Furthermore, a sustained stimulation with ET-1 induced a decrease in [Ca2+]i below the prestimulatory level in a large population of cells, and the percentage of the cell population that shows the sustained decrease of [Ca2+]i increased in higher ET-1 concentrations. [Ca2+]i in PT-r cells was also controlled by a [Ca2+]e-dependent mechanism that changed [Ca2+]i from 28 to 506 nM in a 0.1–3 mM concentration range with an EC50 of 1.2 mM, which is comparable to that reported for bPT cells. In the same range of [Ca2+]e, PTH secretion from bPT cells was inhibited with an IC50 of 1 mM, and ET-1 increased PTH release in a dose-dependent manner but without affecting the IC50 for the [Ca2+]e-dependent inhibition. Thus, the parathyroid epithelial cells appear to respond to ET-1 in a unique way, and the ET autocrine system can be regarded as a possible mechanism to modulate the sensitivity of [Ca2+]e-dependent PTH release.
Surface-associated proteins from Staphylococcus aureus demonstrate potent bone resorbing activity
Authors: Dr. Nair Sean , Song Yu , Meghji Sajeda , Reddi Kris , Harris Malcolm , Ross Alistair , Poole Stephen , Wilson Michael , Henderson Brian 
Published: February 2010

Abstract
Staphylococcus aureus infections are associated with rapid bone destruction in conditions such as osteomyelitis, bacterial arthritis, and infected orthopedic implant failure. How this bacterium induces bone destruction has not been defined. In studies of the role of oral Gram-negative bacteria in periodontal pathology, we have established that cell surface-associated proteins (SAPs) are potent stimulators of bone resorption. The surface-associated components from S. aureus have now been isolated and demonstrated to be extremely potent stimulators of bone resorption in the murine calvarial bone resorption assay. Bone resorption appears to be due to proteins, is not the result of contamination with lipoteichoic acid or muramvl dipeptide, and is potently inhibited by indomethacin and can be completely blocked by high concentrations of interleukin-1 receptor antagonist or TN3–19.12, a neutralizing monoclonal antibody to murine TNF. The SAP fraction can stimulate fibroblasts or monocytes to release osteolytic cytokines, but only at high concentrations. Fractionation of the SAPs by high performance liquid chromatography demonstrated that a number of fractions were osteolytically active. The most active contained a heterodimeric protein of molecular weight 32–36 kD. The presence of this osteolytically active surface-associated fraction may account for the bone resorption associated with local infection with S. aureus.
Rapamycin: A bone sparing immunosuppressant?
Authors: Romero David F. , Buchinsky Farrel J. , Rucinski Boguslaw , Cvetkovic Mirjana , Bryer Haldon P. , Liang Xiao G. , Ma Yanfei F. , Jee Webster S. S. , Dr. Epstein Solomon 
Published: February 2010

Abstract
Immunosuppressant therapy is associated with osteoporosis both clinically, post-transplantation, and experimentally. In rats, cyclosporin A (CsA) and FK506 induce a state of high turnover rapid bone loss. After 14 days of administration in immunosuppressive doses, the more recently discovered immunosuppressant, rapamycin, resulted in no change of cancellous bone volume. A longer study over 28 days has now been carried out; contrasting the new drug with CsA and FK506. Sixty, 10-week-old Sprague–Dawley rats were randomly divided into five groups of 12 rats each. The first group served as an aging control. The remaining four groups received, by daily gavage, a combined vehicle placebo, CsA 15 mg/kg, FK506 5 mg/kg, and rapamycin 2.5 mg/kg, respectively. CsA- and FK506-treated rats, but not those treated with rapamycin, demonstrated high turnover osteoporosis with raised serum 1,25(OH)2D (p &lt; 0.05) and elevated serum osteocalcin (p &lt; 0.05). The trabecular bone area was decreased by 66% (p &lt; 0.01) in the CsA group and 56% (p &lt; 0.05) in the FK506-treated group compared with the control animals. The CsA- and the rapamycin-treated groups failed to gain weight and developed severe hyperglycemia (&gt;20 mmol/l, p &lt; 0.001) by day 14 but which largely resolved by day 28. Unlike the groups treated with CsA and FK506, rapamycin-treated rats had no loss of trabecular bone volume but there was increased modeling and remodeling and a decreased longitudinal growth rate. Rapamycin may thus confer a distinct advantage over the established immunosuppressants in not reducing bone volume in the short term. However, the increased remodeling may pose a problem with long-term use, and the decrease in longitudinal bone growth would make the drug unsuitable for growing individuals.
Normal human osteoblast-like cells consistently express genes for insulin-like growth factors I and II but transformed human osteoblast cell lines do not
Authors: Okazaki Ryo , Conover Cheryl A. , Harris Steven A. , Spelsberg Thomas C. , Riggs Lawrence B. 
Published: February 2010

Abstract
Insulin-like growth factors I (IGF-I) and II (IGF-II) are anabolic for osteoblastic cells. Although expression of IGF-I and IGF-II mRNA has been demonstrated in rodent osteoblastic cells, little is known about IGF gene expression in human osteoblastic cell models. In this study we characterized IGF-I and -II mRNA expression in (1) normal human osteoblast-like (hOB) cells, (2) a simian virus 40 immortalized hOB (HOBIT) cell line, and (3) human osteosarcoma cell lines SaOS-2, TE-85, MG-63, and U-2. Since cross-hybridization of IGF cDNA probes with ribosomal RNA obscures detection of some of the multiple IGF transcripts in human cells, we replaced Northern analysis with the more specific ribonuclease protection assay (RPA). We also used the reverse transcriptase-polymerase chain reaction (RT-PCR) to assess whether mRNAs were present at trace levels. IGF-I mRNA expression was consistently observed in normal hOB cells only and by both RT-PCR and RPA. Among IGF-I transcript variants, Ea IGF-I mRNA was more abundant than the Eb mRNA in normal hOB cells. Trace levels of IGF-I mRNA were variably detected in SaOS-2 and U-2 osteosarcoma cells when RT-PCR was performed, but we found no IGF-I mRNA in HOBIT, TE-85, or MG-63 cells. IGF-II mRNA was expressed in normal hOB, HOBIT, TE-85, and U-2 cells as assessed by either method. Trace levels of IGF-II mRNA were observed only in one of three SaOS-2 cell preparations and only by RT-PCR. IGF-II mRNA was absent in MG-63 cells. Thus, our data indicate that (1) normal hOB cells express both IGF-I and IGF-II mRNA and (2) transformation of human osteoblastic cells may alter IGF gene expression. These results provide a basis for selecting appropriate cell models for the study of IGFs in human bone.
IGF-II receptor number is increased in TE-85 osteosarcoma cells by combined magnetic fields
Authors: Fitzsimmons Robert J. , Ryaby James T. , Magee Frank P. , Baylink David J. 
Published: February 2010

Abstract
Human osteosarcoma–derived osteoblast-like cells, TE-85, were used to assess the effect of a low frequency alternating magnetic field in combination with a controlled static magnetic field (combined magnetic fields, CMF) on insulin-like growth factor receptor regulation. In our culture system, application of a 15.3 Hz CMF induces a calculated maximum electrical potential in the culture media of 10−5 V/m. Initial characterization of TE-85 cells demonstrated that (a) TE-85 cells contain both type I insulin-like growth factor (IGF-I) and IGF-II receptors and (b) dose dependence for IGF-stimulated cell proliferation were comparable to the affinities of the IGFs binding to membrane binding sites (i.e., receptors had dissociation constants in the low nanomolar concentration range). The studies with CMF exposure revealed that CMF treatment for 30 minutes increased the number of IGF-II receptors in a frequency-dependent manner without affecting the number of IGF-I receptors. The CMF-dependent increase in IGF-II receptor number was associated with a significant increase in the IGF-II dissociation constant. These results indicate that membrane receptor levels can be altered by short-term exposure to low-energy, low-frequency electromagnetic fields and suggest a potential biochemical mechanism for electromagnetic effects on bone formation and remodeling.
Differences in calcium absorption and kinetics between black and white girls aged 5–16 years
Authors: Abrams Steven A. , O'Brien Kimberly O. , Liang Lily K. , Stuff Janice E. 
Published: February 2010

Abstract
To assess racial differences in calcium (Ca) metabolism, we measured Ca absorption and kinetics in 89 girls (38 black and 51 white) aged 4.9–16.7 years using a dual-tracer stable isotope technique. We found significantly greater rates of fractional (0.44 ± 0.13 vs. 0.25 ± 0.08, p &lt; 0.0001) and total calcium absorption (406 ± 142 vs. 234 ± 82 mg/day, p &lt; 0.0003) in black than in white postmenarcheal girls. Fractional absorption of Ca was also greater in black than in white premenarcheal girls (039 ± 0.14 vs. 0.30 ± 0.10, p = 0.01). Fractional absorption of Ca was more closely correlated to Ca intake in white (r = –0.42, p = 0.002) than in black girls (r = –0.25, p = 0.14). Urinary Ca excretion was significantly lower in pre- but not postmenarcheal black girls than in white girls. Calcium kinetic values associated with bone calcium deposition were greater in black girls, indicating a greater rate of bone Ca deposition in both pre- and postmenarcheal black girls. These results suggest that the greater bone mass accumulated during childhood and adolescence in black than in white females is due, in part, to greater rates of Ca absorption in black girls.
Effects of the bisphosphonate YM175 on bone mineral density, strength, structure, and turnover in ovariectomized beagles on concomitant dietary calcium restriction
Authors: Motoie Hiroyuki , Dr. Nakamura Toshitaka , O'Uchi Naoto , Nishikawa Haruko , Kanoh Hiroyuki , Abe Tetsushi , Kawashima Hiroyuki 
Published: February 2010

Abstract
We evaluated the effect of YM175 on bone in ovariectomized beagles fed a calcium-restricted diet for 18 months. Groups 1 (n = 6) and 2 (n = 6) underwent sham operation, and groups 3–6 were ovariectomized at the age of 21 months. Group 1 was fed standard dog chow (calcium: 1.4%), and groups 2–6 were given a low calcium diet (0.14%). Groups 3 (n = 7), 4 (n = 7), 5 (n = 7), and 6 (n = 7) were given YM175 orally at doses of 0, 0.01, 0.1, and 1.0 mg/kg/day, respectively. At the end of the experimental period, bone mineral density values measured in the lumbar (L2) vertebra, the femoral neck, and the midfemur, were reduced in groups 2 and 3. Bone strength, measured by compression tests on L2 body and L3 cancellous core specimens and by bending tests on the femoral neck, also decreased. YM175 treatment dose-dependently increased the values of these parameters. However, the reduction in torsional stiffness in the midfemur was not completely prevented. In the L4 body, trabecular thickness decreased in group 2 and trabecular separation increased in group 3. YM175 treatment prevented these changes, and the values in group 6 were maintained at the same levels as those in group 1. Bone formation rates were increased in groups 2 and 3. YM175 treatment decreased these indices, but the reduction was incomplete even with the highest dose (group 6). These results demonstrate that, in our model, YM175 maintained the mass, structure, and mechanical properties of cancellous bone. Increased bone turnover was not completely prevented by the doses employed, but the balance between net resorption and formation in one remodeling cycle would have been equilibrated by YM175.
Intermittent cyclical etidronate treatment maintains the mass, structure and the mechanical property of bone in ovariectomized rats
Authors: Katsumata Takashi , Dr. Nakamura Toshitaka , Ohnishi Hideo , Sakurama Teruo 
Published: February 2010

Abstract
We examined the mechanical properties of rat bones treated with etidronate intermittent cyclic treatment (etidronate-ICT). Fifty Fisher rats, 7 months of age, underwent ovariectomy (OVX; n = 40) or sham operation (n = 10). The OVX rats were assigned to 4 groups injected with etidronate at the respective dose of 0, 2, 4, or 8 mg/kg of body weight (bw) 5 days each week for 2 weeks, followed by a 10-week period of no treatment. This regimen was repeated for 48 weeks. At the end of the treatment period, the ultimate bending strength and structural stiffness of the femoral midshaft in the OVX-alone group were not reduced compared with the values of the sham group, while those in the etidronate-treated groups were significantly larger than the values of the OVX group. The compressive stiffness and strength of the vertebral bodies specimens prepared from L3 and L5 vertebrae were markedly decreased in the OVX group compared with those in the sham group, but the values in the etidronate-treated groups were maintained at the same levels as those in the sham group. Mechanical properties at the tissue level, such as elastic modulus and material strength of the femoral cortex, were increased in etidronate-treated groups compared with the OVX group. The flexural modulus was also increased. The compressive elastic modulus of vertebral body in treated groups was preserved at the same level as that in the sham group. These results clearly demonstrate that in ovariectomized rats long-term etidronate intermittent cyclic treatment preserves the mechanical properties both at the whole bone and the tissue level.
A comparison of the anabolic effects of parathyroid hormone at skeletal sites with moderate and severe osteopenia in aged ovariectomized rats
Authors: Qi H. , Li M. , Dr. Wronski T.J. 
Published: February 2010

Abstract
Previous studies have shown that parathyroid hormone (PTH) stimulates bone formation and completely restores lost cancellous bone at skeletal sites with moderate osteopenia in relatively young ovariectomized (OVX) rats. The current study was designed to determine whether PTH has similar bone anabolic effects in aged OVX rats and to compare the bone restorative response to PTH at skeletal sites with moderate and severe osteopenia. Female Sprague-Dawley rats were subjected to sham surgery or bilateral ovariectomy at 3 months of age and maintained untreated for the first year after surgery to allow for the development of moderate vertebral osteopenia and severe tibial osteopenia in OVX rats. Groups of baseline control and OVX rats were sacrificed at the end of this pretreatment period. The remaining OVX rats were then treated for 10 weeks with vehicle, antiresorptive agents alone (estrogen, the bisphosphonate risedronate, or calcitonin) or PTH alone. Other groups of OVX rats were treated concurrently with PTH and each of the antiresorptive agents. As expected, the proximal tibia of baseline OVX rats exhibited severe cancellous osteopenia, whereas the first lumbar vertebral body was moderately osteopenic. Treatment of OVX rats with antiresorptive agents alone failed to restore cancellous bone at both skeletal sites, whereas treatment with PTH alone markedly stimulated bone formation and completely restored lost cancellous bone in the lumbar vertebra. PTH also stimulated bone formation in the severely osteopenic proximal tibia of OVX rats but only marginally restored lost cancellous bone, possibly due to an inadequate number of bone spicules to serve as a foundation for new bone formation. Concurrent treatments with PTH and antiresorptive agents did not augment cancellous bone to a greater, or lesser, extent than treatment with PTH alone. The positive results from the moderately osteopenic lumbar vertebra indicate that cancellous bone of aged OVX rats retains its ability to respond anabolically to PTH. However, the negative results from the severely osteopenic proximal tibia of aged OVX rats may provide insight into the failure of the skeletons of some osteoporotic patients to respond adequately to anabolic agents such as fluoride or PTH.
Reproducibility of DXA absorptiometry: A model for bone loss estimates
Authors: Fuleihan Ghada El-Hajj , Testa Marcia A. , Angell Jennifer E. , Porrino Nancy , Leboff Meryl S. 
Published: February 2010

Abstract
The enhanced precision of dual-energy X-ray absorptiometry (DXA) allows the detection of very small changes in bone mineral density (BMD). True clinical changes in BMD in patients must be evaluated with the appropriate error of variance. We evaluated the responsiveness of our measures to true bone loss using a statistical variance components model that characterizes the variability associated with error introduced by the machine, operator, and subjects. Our techniques were applied to data from a prospective study of BMD measurements on spine phantoms and on pre- and postmenopausal women performed on the same day or up to 4 weeks apart with DXA (QDR 1000W, Hologic). Our model determined that most of the error in measurements was introduced by operators' and subjects' variability rather than machine performance. The false-positive rates for true bone change are significantly reduced when the appropriate CV% is used to estimate the significance of bone loss over time. Our study underscores the need to use the appropriate precision error to evaluate the clinical significance of changes in bone mass in individual subjects over time.
Effects of resistance training on regional and total bone mineral density in premenopausal women: A randomized prospective study
Authors: Lohman Timothy , Going Scott , Hall Matthew , Ritenbaugh Cheryl , Bare Lisa , Hill Anabel , Houtkooper Linda , Aickin Mikel , Boyden Thomas , Pamenter Richard 
Published: February 2010

Abstract
This study was designed to assess the effects of 18 months of resistance exercise on regional and total bone mineral density (BMD) and soft tissue lean mass (STL) in premenopausal women aged 28–39 randomly assigned to an exercise or control group. Twenty-two exercise and 34 control subjects completed the 18-month training study. All subjects were previously inactive and untrained women. Initial, 5-, 12- and 18-month assessments were made of total and regional BMD and total and regional STL using dual energy X-ray absorptiometry. All subjects consumed a 500 mg/day elemental calcium supplement throughout the study. Initial Ca intake without supplement averaged 1,023 mg/day in total sample. Serum levels of bone osteocalcin and dietary assessments using 12 randomly assigned days of diet records were also completed. Muscular strength was assessed from both 1 repetition maximum (RM) testing of 10 weightlifting exercises and by peak torque for hip abduction/adduction and knee extension/flexion. Training increased strength by 58.1% based on 1 RM testing and by 33.8% based on isokinetic testing at 18 months versus baseline. BMD increased significantly above baseline at the lumbar spine for the exercise group at 5 months (2.8%), 12 months (2.3%), and 18 months (1.9%) as compared with controls. Femur trochanter BMD increased significantly (p &lt; 0.05) in the exercise group at 12 months (1.8%) and 18 months (2.0%) but not at 5 months (0.7%) as compared with controls. No changes in total BMD, arm BMD, or leg BMD were found. There was a 20% increase in BGP in the exercise group as compared with controls at 5 months and this difference was maintained throughout the study. For STL, significant increases for total, arm, and leg were found at 5, 12, and 18 months for the exercise group versus control ranging from 1–6% over baseline. These results support the use of strength training for increasing STL and muscular strength with smaller but significant regional increases in BMD in the premenopausal population.