bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence that human bone cells in culture secrete insulin-like growth factor (IGF)-II and IGF binding protein-3 but not acid-labile subunit both under basal and regulated conditions
Authors: Kanzaki Susumu , Baxter Robert C. , Knutsen Raymond , Baylink David J. , Mohan Subburaman 
Published: February 2010

Abstract
Insulin-like growth factors (IGFs) are found in human circulation predominantly as part of a growth hormone (GH)–dependent complex of 125–150 kD, which is composed of three subunits: IGF-I or IGF-II, an acid stable IGF binding protein (IGFBP)-3, and an acid labile subunit (ALS). Although recent studies demonstrate that a number of cell types in culture secrete IGFs and IGFBP-3, very little is known with regard to the origin of circulating ALS. To test the hypothesis that human bone cells (HBCs), which produce abundant amounts of IGF-II and IGFBP-3, also produce ALS, we measured the IGF-I, IGF-II, IGFBP-3, and ALS levels using specific radioimmunoassays (RIAs) in the conditioned medium (CM) of untransformed normal HBCs and SaOS-2 osteosarcoma cells treated with various effectors (IGF-II, osteogenic protein-1 [OP-1, bone morphogenetic protein-7] and human GH) for 48 h. No detectable levels (&lt;3 ng/ml) of ALS were found in the CM of various HBC types under basal conditions. In contrast, CM collected from liver explants in culture contained significant amount of ALS prepared and assayed under identical conditions. The IGF-I level was also undetectable in the CM of various HBC types. In the IGF-II (3, 30 ng/ml)-treated HBC CM, the IGFBP-3 level was increased in a dose-dependent manner but neither IGF-I nor ALS could be detected. In the SaOS-2 cell culture, OP-1 (1, 100 ng/ml) increased both IGF-II and IGFBP-3 secretion but neither ALS nor IGF-I secretion. Treatment of HBCs with GH (1, 10, 100 ng/ml) had no significant effect on the secretion of either IGF-I, IGF-II, IGFBP-3, or ALS. The level of IGF-II in the CM of various HBC types correlated positively with that of IGFBP-3 (r = 0.84). From these results, we conclude that the production of ALS and IGFBP-3 are not concomitantly regulated by the same effectors in HBCs. The finding of this study together with the previous findings that GH regulates ALS secretion in liver cells suggest that the primary functions of IGFs produced in the bone and liver may be different (i.e., local versus endocrine effects).
A study of the relationship between mineral content and mechanical properties of turkey gastrocnemius tendon
Authors: Dr. Landis William J. , Librizzi Joseph J. , Dunn Michael G. , Silver Frederick H. 
Published: February 2010

Abstract
The vertebrate skeletal system undergoes adaptation in response to external forces, but the relation between the skeletal changes and such forces is not understood. In this context, the variation in the amount and location of calcification has been compared with changes in mechanical properties of the normally mineralizing turkey gastrocnemius tendon using ash weight measurements, X-ray radiography, and mechanical testing. Radiographic evidence from 12- to 17-week-old birds showed calcification in only portions of gastrocnemius tendons proximal to the tarsometatarsal joint. Mechanical testing of these dissected proximal regions demonstrated an increased ultimate stress and modulus and a decreased maximum strain that appeared to parallel calcification. Further, stress–strain curves of portions of uncalcified turkey gastrocnemius tendon were shaped similar to those of other typical unmineralized tendon curves while highly calcified tendons yielded curves resembling those of bone. The proximal portions of the gastrocnemius where mineralization begins were observed to have a decreased tendon cross-sectional area compared with distal portions which do not mineralize. Based on the resultant measures of mineral content and location and mechanical properties, it is hypothesized that increased calcification is a result of increased stresses at certain locations of the tendon, perhaps the consequence of the natural forces exerted by the large leg muscles of the bird into which the gastrocnemius inserts. More specifically, tendon calcification may be the result of stress-induced exposure of charged sites on the surfaces of collagen molecules, fibrils, or fibers so that deposition of mineral and subsequent mechanical reinforcement occur in the tissue. The concept of stress-induced calcification of avian tendon is found to be consistent with other examples of biological mineralization and supports the view that vertebrate calcification is an adaptive process mediated in part by the accommodation of natural or applied forces.
Impact of soft tissue on in vivo accuracy of bone mineral measurements in the spine, hip, and forearm: A human cadaver study
Authors: Dr. Svendsen Ole L. , Hassager Christian , Skødt Vera , Christiansen Claus 
Published: February 2010

Abstract
The impact of soft tissue in vivo on accuracy of bone mineral density (BMD) measurements of the spine and hip by dual energy X-ray absorptiometry and of the forearm by single photon absorptiometry was assessed by use of 14 human cadavers. The in vivo accuracy errors (SEE%) were: forearm 3–5%, anteroposterior spine 5.3%, lateral spine 10–12%, and femoral greater trochanter, neck, total, intertrochanteric, and Ward's triangle 3%, 6.5%, 6.7%, 8%, and 11–13%, respectively. Except from the lateral spine and the greater trochanter, the slopes of the linear regressions of in vivo BMD against in vitro BMD were not significantly different from 1 (p &gt; 0.05). The calculated random accuracy error of BMD measurements due to fat inhomogeneity was estimated to 3–4% for the anteroposterior spine and 9–14% for the lateral spine (from abdominal computed tomography in 26 healthy women). In conclusion, acceptable accuracy errors below 6–7% (of soft tissue in vivo) of BMD measurements were obtained in the anteroposterior spine, the forearm, and the neck, greater trochanter, and total proximal femur.
Cell-to-cell communication in osteoblastic networks: Cell line–dependent hormonal regulation of gap junction function
Authors: Dr. Donahue Henry J. , Mcleod K.J. , Rubin C.T. , Andersen J. , Grine E.A. , Hertzberg E.L. , Brink P.R. 
Published: February 2010

Abstract
We have characterized the distribution, expression, and hormonal regulation of gap junctions in primary cultures of rat osteoblast-like cells (ROBs), and three osteosarcoma cell lines, ROS 17/2.8, UMR-106, and SAOS-2, and a continuous osteoblastic cell line, MC3T3-E1. All cell lines we examined were functionally coupled. ROS 17/2.8 were the more strongly coupled, while ROB and MC3T3-E1 were moderately coupled and UMR-106 and SAOS-2 were weakly coupled. Exposure to parathyroid hormone (PTH) for 1 h increased functional coupling in ROB cells in a concentration-dependent manner. Furthermore, PTH (3–34), an analog of PTH with binds to the PTH receptor and thus attenuates PTH-stimulated cAMP accumulation, also attenuated PTH-stimulated functional coupling in ROB. This suggests that PTH increases functional coupling partly through a cAMP-dependent mechanism. A 1 h exposure to PTH did not affect coupling in ROS 17/2.8, UMR-106, MC3T3-E1, or SAOS-2. To examine whether connexin43 (Cx43), a specific gap junction protein, is present in functionally coupled osteoblastic cells, we characterized Cx43 distribution and expression. Indirect immunofluorescence with antibodies to Cx43 revealed that ROS 17/2.8, ROB, and to a lesser extent MC3T3-E1 and UMR-106, expressed Cx43 immunoreactivity. SAOS-2 showed little if any Cx43 immunoreactivity. Cx43 mRNA and Cx43 protein were detected by Northern blot analysis and immunoblot analysis, respectively, in all cell lines examined, including SAOS-2. Our findings suggest that acute exposure to PTH regulates gap junction coupling, in a cell-line dependent manner, in osteoblastic cells. Furthermore, Cx43 is expressed in osteoblastic cells regardless of the degree to which the cells are functionally coupled or the degree to which coupling is regulated by PTH.
The BsmI vitamin D receptor restriction fragment length polymorphism (BB) predicts low bone density in premenopausal black and white women
Authors: Dr. Fleet James C. , Harris Susan S. , Wood Richard J. , Dawson-Hughes Bess 
Published: February 2010

Abstract
We conducted a study to determine whether a recently described restriction fragment length polymorphism in the vitamin D receptor gene (VDR-RFLP) predicts bone mineral density (BMD) in unrelated, premenopausal women as well as to determine the racial contribution to any genotypic influences on BMD. White (n = 83) and black (n = 72) women between 20 and 40 years of age were genotyped based on the presence (b) or absence (B) of a Bsm1 restriction enzyme site in the VDR gene, and BMD in the lumbar spine and femur neck was determined for each subject. There were 16 BB, 73 Bb, and 66 bb women. No significant difference was observed in genotypic distribution between the racial groups. The interaction of race by genotype on age- and body mass index (BMI)-adjusted BMD was not significant at either site. Age- and BMI-adjusted BMD was higher in black women at the spine (by 7.2%, p = 0.046) and femur neck (7.3% higher, p = 0.004). In the group as a whole, mean BMD in the femur neck was lower in the BB women than the bb (by 8.1%, p = 0.034) or Bb women (by 9.3%, p = 0.015) after controlling for age, BMI, race, and the race by genotype interaction. Adjusted lumbar spine BMD was lower in the BB women than the Bb women (6.4% lower, p = 0.036) in the group as a whole. No differences were detected between Bb and bb women at either site. A similar pattern of low BMD at the femur neck and the lumbar spine was seen in BB women of both races. These data provide support for an association between low bone density and the BB genotype in a racially mixed, premenopausal population and suggests that this genotype may limit peak bone mass. Furthermore, racial differences in BMD appear to be independent from the VDR genotype.
Characterization of MCSF-induced proliferation and subsequent osteoclast formation in murine marrow culture
Authors: Biskobing Diane M. , Fan Xian , Rubin Janet 
Published: February 2010

Abstract
To clarify events involved in 1,25(OH)2D3-stimulated osteoclast-like cell (OCLC) formation in primary murine marrow culture, we have characterized kinetics of precursor proliferation and fusion and their dependence on macrophage colony-stimulating factor (MCSF). 3H-thymidine nuclear incorporation in tartrate-resistant acid phosphatase positive multinucleated cells (TRAP+ MNCs) was assessed: 3H-thymidine incorporation was greatest when tracer was added during day 4 or 5, with labeled nuclei in 81% (day 4) and 90% (day 5) of the TRAP+ MNCs counted at the end of day 7. The percentage of total nuclei labeled was highest when 3H-thymidine was dosed on day 4 (58%), decreasing to 2% by day 7. Final TRAP+ MNC numbers were depleted by 80% when treated for 24 h with hydroxyurea on either day 3 or 4; this inhibition dropped to 57% and 12% when hydroxyurea was pulsed during days 5 or 6, respectively. The absence of 1,25(OH)2D3 during days 1–4 caused 70% attenuation of TRAP+ MNC formation; however, exposure to 3H-thymidine during day 4 in this experiment resulted in subsequent labeling of 81% of the TRAP+ MNCs formed, indicating that precursor proliferation occurred in the absence of 1,25(OH)2D3. To demonstrate that proliferation required MCSF, cultures were exposed to a monoclonal anti-MCSF antibody during days 3, 4, 5, 6, or 7. Inhibition of TRAP+ MNC formation was 85% when antibody was added during day 3. Antibody treatment after day 5 had little effect on the OCLC number. Fusion of precursors showed steady progression with OCLCs containing 4.8 ± 03 nuclei at the end of day 4, 8.3 ± 0.5 nuclei after day 5, 12.0 ± 1.3 after day 6, and 13.7 ± 1.5 at the end of day 7. This steady accretion of nuclei was unaffected by doses of MCSF antibody which blocked proliferation. In conclusion, we have shown that OCLCs arise from an MCSF-dependent expansion of the precursor pool occurring during days 3 and 4. Fusion of these precursors, which begins as proliferation diminishes, is able to progress in the presence of anti-MCSF antibody. These results should help refine the analysis of factors affecting proliferation and fusion of osteoclasts in murine marrow culture.
Influence of high glucose on 1,25-dihydroxyvitamin D3-induced effect on human osteoblast-like MG-63 cells
Authors: Inaba Masaaki , Terada Makoto , Koyama Hidenori , Yoshida Osamu , Ishimura Eiji , Kawagishi Takahiko , Okuno Yasuhisa , Nishizawa Yoshiki , Morii Hirotoshi , Otani Shuzo 
Published: February 2010

Abstract
Impaired bone formation due to defective osteoblast function, as reflected in a decreased serum osteocalcin (OC) concentration in the patients with diabetes, has been implicated in the development of diabetic osteopenia. The role of hyperglycemia in this decrease in serum OC concentration was investigated. 1,25-dihydroxyvitamin D3 (1,25[OH]2D3), an active form of vitamin D3, stimulated OC secretion from the human osteosarcoma cell line MG-63 in a dose-dependent manner. Exposure of the cells to high concentrations of glucose for 7 days significantly impaired 1,25(OH)2D3-induced OC secretion as compared with that observed with cells maintained under normal glucose (5.5 mM) or high mannitol conditions. The inhibitory effect of glucose was in a dose-dependent manner up to 55 mM. High glucose (55 mM) also attenuated the 1,25(OH)2D3-induced increase in OC mRNA abundance in MG-63 cells, suggesting that the inhibition of the 1,25(OH)2D3-induced increase in OC secretion by exposure to a high concentration of glucose was, at least in part, mediated at the transcriptional level. High glucose significantly decreased the number of 1,25(OH)2D3 receptors in MG-63 cells, without any change in the dissociation constant for 1,25(OH)2D3; this effect was not mimicked by high mannitol, indicating specificity for glucose. These observations suggest that a high glucose concentration significantly impairs the ability of osteoblastic cells to synthesize OC in response to 1,25(OH)2D3 by reducing 1,25(OH)2D3 receptor number, and that impaired cell function caused by sustained exposure to high glucose contributes to the defect in bone formation observed in the patients with diabetic osteopenia. (
The effects of calcium supplementation (milk powder or tablets) and exercise on bone density in postmenopausal women
Authors: Prince Richard , Devine Amanda , Dick Ian , Criddle Arthur , Kerr Deborah , Kent Neil , Randell Andrew , Price Roger 
Published: February 2010

Abstract
The etiology of age-related bone loss is unclear but both lack of exercise and dietary calcium deficiency have been implicated in its causation. This 2-year randomized placebo-controlled study was designed to examine the effects of increased dietary calcium and exercise in 168 women who were more than 10 years postmenopausal. The subjects were randomized into one of 4 groups: placebo, milk powder containing 1 g of calcium, calcium tablets 1 g/night, and calcium tablets 1 g/night and an exercise regimen. The exercise group aimed to undertake 4 h of extra weight-bearing exercise per week and were undertaking 10% more activity than other groups at 2 years. Bone mineral density at the lumbar spine, three hip sites, and two sites of the tibia close to the ankle joint were measured at 6 month intervals. Dietary intake was evaluated by a weighed food record, exercise was evaluated by an exercise diary, and blood and urine samples were obtained to examine effects on calcium homeostasis. Individual data points were compared using repeated measures ANOVA and least squares regression. Calcium supplementation by either the calcium tablets or the milk powder resulted in cessation of bone loss at the intertrochanteric hip site (placebo, calcium tablets, calcium and exercise, milk powder −0.81, +0.17, +0.23, and +0.07% per year, respectively; p &lt; 0.05 for all supplementation groups compared with placebo) with similar results at the trochanteric hip site. The calcium and exercise group had less bone loss at the femoral neck site when compared with calcium supplementation alone (placebo, calcium tablets, calcium and exercise, milk powder −0.67, −0.18, +0.28, and −0.18% per year, respectively; p &lt; 0.05 for calcium and exercise compared with calcium alone). There was a significant reduction in the rate of bone loss at the ultradistal site of the tibia (placebo, calcium tablets, calcium and exercise, milk powder −2.5, −1.6, −1.0, and −1.5% per year, respectively; p &lt; 0.05 for all supplementation groups compared with placebo). There was no significant bone loss at the spine site in any group. These data support the implementation of a simple public health regimen to prevent age-related bone loss with calcium supplementation either by calcium tablet or by milk powder. The extra effect of exercise plus calcium at the femoral neck site suggests a site-specific effect of physical activity on bone density in addition to its possible effect to prevent fracture by maintenance of muscle strength and coordination. (
Maxillary molar extraction causes increased bone loss in the mandible of ovariectomized rats
Authors: Elovic Rebecca P. , Hipp John A. , Hayes Wilson C. 
Published: February 2010

Abstract
Although osteoporosis is a major public health concern, its effect on oral bone has not been determined. More important may be the effect of estrogen depletion on the response of oral bone to dental treatments such as tooth extraction or pathologic processes such as periodontal disease. Our objective was to determine if maxillary molar extraction increases mandibular bone loss in the ovariectomized compared with a sham-operated control. Fifty-three ovariectomized and 53 sham-operated 6-month-old Sprague-Dawley rats were randomly assigned to the following groups: (1) ovariectomized, adult; (2) sham-operated, adult; (3) ovariectomized, adult, extraction; (4) sham-operated, adult, extraction; (5) ovariectomized, old; (6) sham-operated, old; (7) ovariectomized, old, extraction; and (8) sham-operated, old, extraction. Fourteen days following ovariectomy, the extraction groups had their bilateral maxillary molars extracted. The adult and old rats were sacrificed 114 and 200 days postovariectomy, respectively. The right mandible was tested to failure in three point bending. The bone mineral density (BMD) of the left mandible was measured with high resolution dual energy X-ray absorptiometry. The area fraction and area moment of inertia of mandible sections were determined using image processing software. In the ovariectomized rats, maxillary molar extraction resulted in decreases (p &lt; 0.05) in the failure load (21%), stiffness (39%), BMD (3%), and bone area fraction (8%) of the mandible. However, in the sham-operated rats, these decreases following maxillary molar extraction were less (p &lt; 0.05) than those in the ovariectomized rats and only present in the mandibles of the aged rats. Therefore, maxillary molar extraction resulted in a more rapid decrease in structural properties and BMD and a larger decrease in bone area fraction of the mandible in ovariectomized rats compared with those in sham-operated rats. These findings indicate that oral bone loss that occurs as a result of pathologic conditions or dental treatments may be accelerated in individuals who have estrogen depletion. (
Extracellular matrix stoichiometry in osteoblasts from patients with osteogenesis imperfecta
Authors: Fedarko Neal S. , Robey Pamela Gehron , Vetter Ulrich K. 
Published: February 2010

Abstract
In previous work, we compared the steady-state levels of specific matrix components in human bone cells derived from patients with osteogenesis imperfecta (OI) to those of age-matched controls. A remarkable finding was the observation that there was a reduction not only in the total levels of collagen, but also in osteonectin and three proteoglycans (a large chondroitin sulfate proteoglycan, biglycan, and decorin). This pattern was observed in patients with and without detectable collagen defects. More recent analysis of extracellular matrix composition have yielded that, compared with age-matched controls, bone cells from OI patients produced higher steady-state levels of fibronectin and thrombospondin. The percentage of these two proteins incorporated into the cell layer pool was also higher in OI than in age-matched controls. In addition, the steady-state levels of hyaluronan and a heparan sulfate proteoglycan were analyzed in both OI and age-matched controls. Although the total (medium + cell layer) steady-state levels of hyaluronan were reduced by 1/3, the percentage of the hyaluronan in the cell layer pool of patients with OI increased between 100–250% of age-matched control. Thus the matrix elaborated by human OI bone cells is not only quantitatively different but also qualitatively distinct from that of age-matched controls. Not only have specific bone cell matrix components (collagen, osteonectin, the large chondroitin sulfate proteoglycan, biglycan, and decorin) been found to be present in reduced levels in OI bone cells, but some matrix components (thrombospondin, fibronectin, and hyaluronan) have also been found to be present in elevated levels in the matrix of OI cells. These results suggest that putative mutations in type I collagen (present in OI bone cells) give rise to an altered gene expression of other matrix components.
Identification and cloning of human P2U purinoceptor present in osteoclastoma, bone, and osteoblasts
Authors: Bowler W.B. , Birch M.A. , Gallagher J.A. , Bilbe G. 
Published: February 2010

Abstract
Extracellular ATP acting through purinoceptors may be an important factor in the modulation of bone turnover. In this study we cloned and sequenced the P2U purinoceptor from osteoclastoma, confirming the recently published human sequence. Furthermore, by the reverse transcriptase-linked polymerase chain reaction (RT-PCR) and Southern blotting we demonstrated expression of P2U receptor mRNA in bone, primary cultures of human bone-derived cells, and two osteosarcoma cell lines, Saos2 and Te85. P2U receptor transcripts were identified in alkaline phosphatase-positive human bone-derived cells isolated by flow cytometry providing strong evidence for the expression of the P2U purinoceptor in mature osteoblasts. P2U receptor transcripts were also detected in a purified giant cell population isolated from osteoclastoma, indicating that this receptor is also expressed by osteoclasts. These data suggest that purinergic agonists may play a role in the regulation of bone metabolism.