bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bone formation by marrow osteogenic cells (MBA-15) is not accompanied by osteoclastogenesis and generation of hematopoietic supportive microenvironment
Authors: DR. Benayahu D. , Gurevitch O. , Zipori D. , Wientroub S. 
Published: February 2010

Abstract
This study was aimed at elucidating the relationship between osteogenic activity of marrow stromal cells and their ability to support hematopoiesis followed by the bone-remodeling process. We used the MBA-15 cell line, which expresses osteoblastic phenotype in vitro and forms bone in diffusion chamber. We have compared bone formation and hematopoietic responses elicited in vivo by these cells with the implantation of freshly isolated bone marrow cells (BMC) or demineralized tooth matrix (DTM). Both MBA-15 cells and BMC, implanted under the kidney capsule, yielded intramembraneous bone, but DTM, implanted subcutaneously, elicited endochondral bone. MBA-15 formed primary bone, mimicking only the initial sequential stages of the ossification process. Neither histologic signs of bone resorption and remodeling nor tartrate-resistant acid phosphatase (TRAP)-positive cells and marrow formation were observed. Bone formation was monitored biochemically. Functions for hematopoietic stem and committed cell content were measured by GM-CFU and BFU-E assays that confirmed the morphologic observations. In both BMC and DTM implantation, bone formation was followed by hematopoietic activity, osteoclastogenesis, and remodeling. We conclude that MBA-15 osteoprogenitor cells, despite their extensive bone formation ability, are unable to form a microenvironment supportive for hematopoiesis and osteoclastogenesis or to initiate bone remodeling.
Expression of monocyte chemoattractant protein 1 in human osteoblastic cells stimulated by proinflammatory mediators
Authors: Zhu Jian-Fu , Valente Anthony J. , Lorenzo Joseph A. , Carnes David , Dr. Graves Dana T. 
Published: February 2010

Abstract
Monocyte chemoattractant protein 1 (MCP-1) is a member of the chemokine superfamily of genes that induces chemotaxis of monocytes in inflammatory processes. The effects of interleukin-1β (IL-1β), tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), transforming growth factor β (TGF-β), platelet-derived growth factor (PDGF-BB), parathyroid hormone (PTH), and 1,25(OH)2D3 on MCP-1 expression in human osteoblastic cells were compared. Inflammatory or proinflammatory cytokines stimulated the production of MCP-1 in normal human osteoblastic cells as determined by RIA. The osteotrophic mediators PTH and 1,25(OH)2D3 and PDGF-BB had no effect on MCP-1 expression. In further studies, the steady-state mRNA and MCP-1 protein levels in two human osteoblastic cell lines, MG-63 and SaOS-2, were examined. MCP-1 expression at both the protein and mRNA levels was greatly increased by IL-1β and TNF-α. At the mRNA level, IL-1β and TNF-α strongly induced MCP-1 expression; TGF-β and IL-6 induced MCP-1 but to a lesser extent. No significant changes in MCP-1 mRNA or MCP-1 protein secretion were observed when cells were treated with PDGF-BB, PTH, and 1,25(OH)2D3. When tested on preosteoclasts, MCP-1 was shown to have no effect on the formation of multinucleated, tartrate-resistant acid phosphatase (TRAP)-positive osteoclastic cells.
Upregulation of c-Fos protooncogene expression in pagetic osteoclasts
Authors: Hoyland Judith , Sharpe Paul T. 
Published: February 2010

Abstract
Using in situ hybridization we show that expression of the c-fos oncogene, a gene normally associated with osteosarcomas, is greatly elevated in osteoclasts of patients with Paget's disease. Immunohistochemical staining with c-fos antibodies also shows increased protein in pagetic osteoclasts. In light of transgenic mouse experiments showing a key role for c-fos in bone resorption, we propose that elevated c-fos gene expression in pagetic osteoclasts is an important component in producing the pagetic phenotype. Levels of c-fos gene and protein expression in pagetic osteoblasts are lower than those detected in osteoclasts but still higher than in nonpagetic osteoblasts. This may provide an explanation for the increased incidence of osteosarcomas in patients with Paget's disease because overexpression of c-fos in osteoblasts of transgenic mice induces osteosarcoma formation.
Bound phosphoproteins enhance mineralization of alkaline phosphatase-collagen complexes in vivo
Authors: DR. van den Bos Theo , Beertsen Wouter 
Published: February 2010

Abstract
Phosphoproteins (PP) covalently bound to a collagenous matrix have been reported to promote its mineralization in vitro. It was the aim of the present study to determine whether PP also enhance the mineralization of collagen in vivo. To this end, collagen slices were prepared from demineralized bovine cortical bone. Following immobilization of rat dentin phosphoprotein (PP) to the slices, bovine intestinal alkaline phosphatase (ALP) was bound according to the SATA-MHS coupling method. Controls were without enzyme. The slices were implanted into skin pockets prepared over the skull of female Wistar rats (6–10 weeks old). After 3–31 days the implants were removed and analyzed for calcium and phosphate content. It was shown that slices of PP-treated bone collagen mineralized more rapidly and to a greater extent than bone collagen slices without PP. Controls remained free of mineral. It is concluded that mineralization of collagenous matrices, induced by alkaline phosphatase, is enhanced by bound phosphoproteins following implantation in subcutaneous connective tissue.
Evaluation of urinary pyridinium crosslink excretion as a marker of bone resorption in the rat
Authors: Egger Chantal D. , Mühlbauer Roman C. , Felix Rolf , Delmas Pierre D. , Marks Sandy C. , Fleisch Herbert 
Published: February 2010

Abstract
The aim of this study was to evaluate the value of the urinary excretion of the pyridinium crosslinks, pyridinoline (Pyr) and deoxypyridinoline (D-Pyr), as markers of bone resorption in the rat. The excretion of the crosslinks was compared with that of urinary [3H]tetracycline ([3H]TC) excretion from chronically [3H]TC-prelabeled animals, a technique established to monitor bone resorption in the rat. Bone resorption was modulated by Ca restriction, infusion of PTH, thyroparathyroidectomy, and administration of different bisphosphonates. Furthermore, the urinary crosslinks were assessed in three different osteopetrotic mutations in the rat. We found a delayed response of Pyr and D-Pyr excretion to acute changes in bone resorption compared with [3H]TC excretion. This delay was 1 day after Ca restriction and longer after other treatments, such as PTH administration or bisphosphonate treatment, with which it was more than 3 weeks. In contrast, chronic states with stimulation or inhibition of bone resorption showed similar changes in excretion of the urinary crosslinks and [3H]TC, except after PTH administration. The excretion of the crosslinks was greatly reduced in osteopetrotic rats (op/op, tl/tl, and ia/ia) and increased to normal levels in tl/tl rats after stimulation of bone resorption by M-CSF administration. These results suggest that, in rats, urinary excretion of the pyridinium crosslinks reflects bone resorption in chronic but not always in acute conditions. The cause of this discrepancy is still unclear.
Retinoic acid induces a shift in the energetic state of hypertrophic chondrocytes
Authors: Dr. Shapiro Irving M. , Debolt Kristine , Hatori Masashi , Iwamoto Masahiro , Pacifici Maurizio 
Published: February 2010

Abstract
In the epiphyseal growth plate, chondrocyte maturation is accompanied by dramatic alterations in energy metabolism. To explore the relationship between these two events, we used retinoic acid (RA) to promote chondrocyte maturation in culture. The specific question that was addressed was, does RA treatment of cultured chondrocytes in vitro induce a change in energy status similar to that seen in hypertrophic chondrocytes in vivo. Maturing chondrocytes isolated from the cephalic region of day 18 chick embryo sterna were allowed to grow for 7–14 days in monolayer until confluent and then treated with 10–300 nM RA. Immature chondrocytes from the caudal region of sternum were grown in parallel and served as control cells for the study. We found that in maturing cephalic cell cultures, RA had a rapid and profound effect on oxidative metabolism. The retinoid caused a reduction in the energy charge ratio (ECR) and the ATP/ADP ratio and a sharp decrease in cell ATP levels. Maximum inhibition was observed when the RA concentration was 10–35 nM. Compared with the adenine nucleotides, creatine phosphate levels were decreased to a lesser extent by RA, although there was substantial inhibition of creatine kinase activity. We expected to find a compensatory elevation in glycolytic activities; however, the lactate levels in the medium of the treated cells indicated that anaerobic glycolysis was depressed. In contrast to the cephalic chondrocytes, when caudal cell cultures were treated with RA, lactate formation was stimulated and there were minimal effects on oxidative metabolism. To determine the mechanism of inhibition of glycolysis, we measured the activity of pyruvate kinase in RA-treated cephalic cells. We found that the activity of this key glycolytic enzyme was profoundly and rapidly inhibited by the retinoid. The unique energy state of the RA-treated chondrocytes was termed the minimal energy state. This condition may be expected to influence activities associated with plasma membrane ion pumps and gene transcription. Both these factors would promote chondrocyte hypertrophy and lead to terminal differentiation.
Overexpression of estrogen receptor in HTB 96 human osteosarcoma cells results in estrogen-induced growth inhibition and receptor cross talk
Authors: Dr. Watts C. K. W. , King R.J.B. 
Published: February 2010

Abstract
Estrogenic effects on the proliferation and differentiated cellular functions of bone cells have been described in vivo and in vitro. In particular, stimulatory effects on the growth rate of osteoblasts have been observed, although these are generally small. In an attempt to produce a more sensitive model for the study of estrogen action in bone, HTB 96 human osteoblast-like osteosarcoma cells, which lack endogenous estrogen receptor (ER), were stably transfected with an expression vector coding for the human ER gene. Several HTB 96 sublines expressing ER protein, detected by ligand binding and immunoassay, were isolated. The ability of 17β-estradiol (E2) to induce chloramphenicol acetyltransferase (CAT) activity from a cotransfected reporter vector containing the CAT gene linked to the Xenopus vitellogenin A2 gene estrogen response element demonstrated that the expressed ER was functional. ER continued to be expressed over a 30 week culture period. E2 but not other steroids significantly reduced growth rates and produced an altered morphology in HTB 96 sublines expressing higher levels of ER. The antiestrogen 4-hydroxytamoxifen partially reversed the E2 effect on growth rate. Transient transfection of cells expressing ER with a vector containing the CAT gene linked to the mouse mammary tumor virus long terminal repeat sequence, which contains response elements for the glucocorticoid receptor but not the ER, showed that E2 was able to inhibit CAT induction by dexamethasone. This result suggests that in ER-transfected HTB 9 cells the effects of E2 may result not from direct activation of endogenous genes but instead by transcriptional interference. Thus the mechanisms responsible for the effects of over-expression of ER in ER-negative HTB 96 osteoblast-like bone cells in vitro may differ from those that mediate the effects of estrogens on bone observed in vivo.
Modulation of ecto-nucleoside triphosphate pyrophosphatase activity of human osteoblast-like bone cells by 1α,25-dihydroxyvitamin D3, 24R, 25-dihydroxyvitamin D3, parathyroid hormone, and dexamethasone
Authors: Oyajobi Babatunde O. , Russell R. Graham G. , Caswell Alison M. 
Published: February 2010

Abstract
Extracellular inorganic pyrophosphate (PPi) is involved in the regulation of mineralization, and there is evidence that the cell surface enzyme, NTP pyrophosphatase, is a major source of this metabolite in bone. Osteotrophic agents that influence bone turnover may exert their effects, in part, by modulating the activity of ecto-NTP pyrophosphatase in bone cells. We investigated the effect of 1,25(OH)2D3,24,25(OH)2D3, dexamethasone, and parathyroid hormone (PTH) on the activity of this enzyme in cultured human trabecular bone-derived osteoblast-like cells. 1,25(OH)2D3 at 10−11-10−9 M induced a dose- and time-dependent increase in activity (at 96 h; maximum 10−9 M, p &gt; 0.001), whereas higher concentrations (10−8 and 10−7 M) had no effect. In contrast, 24,25(OH)2D3 was effective only at 10−8 and 10−6 M (at 96 h; p &gt; 0.01). Dexamethasone (10−9-10−7 M) caused a dose-dependent decrease in ecto-NTP pyrophosphatase activity (10−7 M, p &gt; 0.001); concentrations higher than 10−7 M did not evoke greater inhibition. This effect became apparent by 48 h and was significantly enhanced after 72 h. The response to dexamethasone was attenuated by cycloheximide, indicating a requirement for de novo protein synthesis. Interestingly, the stimulatory effect of 10−9 M 1,25(OH)2D3 on ecto-NTP pyrophosphatase activity was significantly enhanced in the presence of dexamethasone (10−9-10−7 M). Human PTH(1-34) and bovine PTH(1-34) in the range 10−10-10−7 M had no effect on enzyme activity over a 72 h period. The effects of vitamin D3 on the expression of bone ecto-NTP pyrophosphatase may be tissue or cell type specific because the ecto-NTP pyrophosphatase activity of subject-matched skin-derived fibroblasts showed no sensitivity to 1,25(OH)2D3. These data suggest a possible role for both vitamin D3 metabolites and glucocorticoids in the regulation of the mineralization process in vivo via modulation of PPi production.
Immunohistochemical localization of heparan sulfate proteoglycan in rat tibiae
Authors: Nakamura Hiroaki , Ozawa Hidehiro 
Published: February 2010

Abstract
Ultrastructural and immunohistochemical studies were performed to clarify the localization of heparan sulfate proteoglycans (HSPG) and their role in cell-cell and/or cell-matrix interaction of bone cells. Ultrastructural observations using the freeze-substitution method revealed electron-dense undercoat structures on the cytoplasmic side of plasma membranes and extracellular matrices in the intercellular spaces where stromal cells came in contact with hematopoietic cells and/or osteoclasts. Immunohistochemical localization of HSPG in rat tibiae was examined using monoclonal antibody directed to glycosaminoglycan of HSPG by confocal laser scanning microscopy and transmission electron microscopy. Intense immunoreactivity was detected on the basement membranes of blood vessels, as well as the plasma membranes of fibroblast-like cells surrounding them. Immunoreactivity was also seen on extracellular matrices between fibroblast-like cells and osteoclast lineage cells. In addition, osteoblasts showed moderate immunoreactivity on those plasma membranes attached to bone matrix. A postembedding method revealed gold particles in Golgi vacuoles of osteoblasts, indicating the localization of HSPG. In osteoclasts, HSPG was localized in Golgi apparatus and lysosomal structures. These findings suggest that (1) osteoblasts and osteoclast lineage cells synthesize HSPG; (2) both membrane and matrix HSPG are localized in bone tissue; and (3) HSPG may play an important role in cell-cell interaction between fibroblast-like cells and osteoclast lineage cells by reserving heparin binding growth factors and/or heparin binding adhesion molecules, such as fibronectin.
Circulating levels of cytokines that modulate bone resorption: Effects of age and menopause in women
Authors: Mckane W. Roland , Khosla Sundeep , Peterson James M. , Egan Kathleen , Riggs B. Lawrence 
Published: February 2010

Abstract
Interleukin 1αa (IL-1α), interleukin 1β (IL-1β), and interleukin 6 (IL-6) are cytokines with potent bone-resorbing effects; some of these biologic effects are opposed by interleukin-1 receptor antagonist (IL-1ra). In vitro and animal model studies suggest that these cytokines are paracrine mediators of the increased bone resorption associated with estrogen deficiency, and increases in their production also could contribute to age-related bone loss. Therefore, we measured serum concentrations of these cytokines in 80 normal women who were 24-87 years old. IL-6 concentration correlated highly with age (p &gt; 0.001) and increased three-fold during life. However, multiple-regression analysis showed no significant correlation between serum IL-6 levels and menopausal status, serum estradiol concentration, or markers for bone turnover (serum bone alkaline phosphatase, osteocalcin, carboxyl-terminal telopeptide of type I collagen, or 24 h urinary free pyridinoline excretion). Serum IL-1α, IL-1β, or IL-1ra level did not change with age and, by multiple-regression analysis, did not correlate with markers of bone turnover, except IL-1ra weakly with ICTP. We found no relationship between bone-resorbing cytokines and ovarian function. Although the large age-related increase in serum IL-6 concentration could contribute to age-related bone loss, the lack of correlation with markers for bone turnover argues against this. However, based on the strong evidence in experimental animals that these cytokines are involved in estrogen action on bone, further studies in humans are warranted.
Sex differences in bone mineral density in 1653 men and women in the sixth through tenth decades of life: The rancho bernardo study
Authors: Blunt Barbara A. , Klauber Melville R. , Barrett-Connor Elizabeth L. , Edelstein Sharon L. 
Published: February 2010

Abstract
This cross-sectional population-based study examined the effect of age and sex on bone mineral density (BMD) in the elderly. BMD was measured at the spine and hip using dual-energy x-ray absorptiometry and at midshaft and ultradistal radius using single-photon absorptiometry in 672 men and 981 women aged 50–98 years. In both sexes, mean BMD levels decreased significantly with age at all sites except the male spine. In linear regression models, the slope of loss was significantly greater in women than in men at all sites except the ultradistal radius. The slope was steeper at most sites in women aged 50-59 years than in older women, 60-98 years. In both age groups, mean age-adjusted BMD levels were lower at all sites in women who were past or never users of replacement estrogen than in women who were current estrogen users. Current estrogen users generally had lower slopes of loss with age than never or past estrogen users; however, few of these differences were statistically significant. We conclude that BMD levels decrease in old age in both sexes. Continued bone loss in old age raises the possibility that intervention to retard further loss may still be warranted in the elderly.
Lifestyle factors and bone density in the elderly: Implications for osteoporosis prevention
Authors: Nguyen T.V. , Kelly P.J. , Sambrook P.N. , Gilbert C. , Pocock N.A. , Eisman J.A. 
Published: February 2010

Abstract
Epidemiologic evidence suggests that lifestyle factors, such as exercise, calcium intake, and tobacco consumption, have effects on bone density. However, the influence of these factors in the elderly has not been well documented. To examine the effects of lifestyle factors in the elderly, we measured bone density (BMD) at the lumbar spine and proximal femur in 709 elderly men and 1080 women participating in the Dubbo Osteoporosis Epidemiology study (DOES), a community-based, longitudinal, epidemiologic study of osteoporosis in men and women over the age of 60. BMD was significantly higher in men than in women (20% at all sites). There was an age-related decline in BMD at the femoral neck in both sexes and at the lumbar spine in women. Between the ages of 60 and 80, the decrease in BMD at the femoral neck among women was 18.9%, which is almost twice the decrease in BMD among men (10.1%). Tobacco consumption was associated with a reduction in BMD at both sites in both sexes (5-8%), and this effect was independent of calcium intake or body weight. Exsmokers had BMD intermediate between that of current smokers and never smokers, suggesting the influence of tobacco was partially reversible. Quadriceps strength predicted bone density at the proximal femur in elderly men but not in women. Analyzing BMD (adjusted for age and weight) in tertiles of muscle strength and calcium intake revealed an interaction between calcium intake and muscle strength on bone density; BMD at the femoral neck among those with higher quadriceps strength and calcium intake was approximately 5% higher (P &lt; 0.05) than in those with low quadriceps strength and calcium intake in both men and women. These data indicate that lifestyle factors, such as tobacco consumption, calcium intake, and physical activity, may influence bone density in the elderly. Modification of these lifestyle factors may influence osteoporotic fracture risk in elderly men and women.
Serum parathormone profile during surgical treatment of hyperfunctioning parathyroid adenoma: A multicompartmental model
Authors: Duquenne Marc , Weryha Georges , Kaminsky Pierre , De Talance Nicole , Mathieu Pierre , Leclere Jacques 
Published: February 2010

Abstract
Patterns of intact parathyroid hormone (iPTH) elimination and subsequent recovery of parathyroid function were studied in seven patients undergoing surgical removal of solitary hyperfunctioning parathyroid adenoma. Using a sensitive two-site immunoradiometric assay, iPTH levels were measured pre, peri-, and postoperatively. Blood samples were taken at very early and at late stages, including 3, 6, 9, and 15 minutes and 48, 72, and 96 h after adenomectomy. A biexponential formula was calculated to fit the decreasing values of iPTH in all patients. The PTH half-life in the early phase was 1.4 + 1.1 minutes (95% confidence limits). The PTH half-life in the second phase was 64.45 + 32.19 minutes (95% confidence limits). A third phase is represented by a slow, linear increase in plasma iPTH values as a result of the recovery of healthy suppressed parathyroid glands. The extrapolation to baseline of the later phase shows that the recovery of normal parathyroid function begins as soon as 240 minutes after adenomectomy and is independent of the decrease in PTH of adenomatous origin. All individual results were consistent with this model. Five patients had iPTH values below 5 pg/ml, one had 15 pg/ml, and the last had 27 pg/ml 5 h after parathyroid adenomectomy. The recovery of the hormonal activity of the remaining glands occurred rapidly. By the postoperative hour 24 the mean serum iPTH concentration was 12.28 + 8.07 pg/ml. The intraoperative serum iPTH concentration offers a model to assess both recovery of hormonal secretion from functionally suppressed parathyroid glands and disappearance of parathyroid hormone.