bluuebunny/crossref_metadata_2025_split huggingface dataset:
Osteocalcin secretion by the human osteosarcoma cell line MG-63
Authors: Lajeunesse Daniel , Frondoza Carmelita , Schoffield Brian , Sacktor Bertram 
Published: February 2010

Abstract
The human osteosarcoma cell line MG-63 has been used to study the production of the bone-specific protein, osteocalcin. In the absence of any stimuli, MG-63 cells secreted very low levels of osteocalcin. The secretion of osteocalcin started after a lag time of 10-12 h upon 1,25-(OH)2D3 treatment. Osteocalcin secretion was measured at doses as low as 0.03 nM (fourfold increase, p &lt; 0.05), and this activity increased further with higher doses of 1,25-(OH)2D3 to reach a plateau at 50 nM. The secretion increased transiently from very low levels in sparse cell cultures to peak values in subconfluent cultures (+ 40%), two- to threefold above values obtained for confluent cells. Values for confluent cells average 55.9 + 2.0 ng/ml protein per 48 h. A similar behavior is observed for 1,25-(OH)2D3 receptor concentration under similar experimental conditions. Bmax increased transiently from sparse to subconfluent cell cultures (40 -60% confluent) and reached values 50% lower in confluent cells. However, the receptor affinity was not affected by cell density. MG-63 cells also possessed an alkaline phosphatase isoenzyme of the bone-liver-kidney type that was stimulated by 1,25-(OH)2D3 treatment (two- to threefold) and inhibited by parathyroid hormone (40 nM, -25%, p &lt; 0.025). PTH and PGE2 increased cAMP production in a dose-dependent manner, but the cells were irresponsive to salmon calcitonin. Basal and PTH-responsive cyclic AMP production were also modulated by cell density. Dexamethasone pretreatment (100 nM, 48 h) stimulated the PTH-dependent cAMP production but failed to influence the response to PGE2. Vitamin D3-induced osteocalcin secretion was inhibited by 40 nM PTH (-20%, p &lt; 0.01) and 5 nM PGE2 (-36%, p &lt; 0.005), a situation that could be related to the ability of these hormones to stimulate cAMP in these cells. These results show that the MG-63 cell line is a good human osteoblastlike cell model in which bone-specific protein synthesis (osteocalcin and alkaline phosphatase) is modulated in response to 1,25-(OH)2D3 and PTH.
Sequential histomorphometric changes in cancellous bone from ovariohysterectomized dogs
Authors: Boyce R.W. , Franks A.F. , Jankowsky M.L. , Orcutt C.M. , Piacquadio A.M. , White J.M. , Bevan J.A. 
Published: February 2010

AbstractTo evaluate potential pharmacologic agents for the prevention or treatment of the bone loss associated with ovarian insufficiency, a predictable animal model is needed. To assess the potential utility of the ovariohysterectomized dog as a model of this condition, we characterized the sequential histomorphometric changes in canine cancellous bone in response to the loss of ovarian function. A group of 25 adult beagle dogs were ovariohysterectomized and terminated at 1, 3, 6, and 10 months following surgery. Iliac biopsies were performed following double-fluorochrome labeling at the time of surgery and at termination. Static and dynamic histomorphometry was performed on undecalcified sections. By 3 months postovariohysterectomy, there was activation of cancellous bone remodeling as indicated by significant increases in mineralizing surface and bone formation rate. Increases in osteoid surface, mineralizing surface, and bone formation rate were also apparent at 1 month postovariohysterectomy, and although not statistically significant, these trends suggest the skeletal response to acute loss of ovarian function was rapid. This increase in bone remodeling was transient. By 6 months, mineralizing surface and bone formation rate were depressed below presurgical levels. In addition to a reduction in bone formation, a reduction in osteoblast function characterized by reduced labeling of osteoid and a disproportionate increase in eroded surface also occurred. By 10 months postovariohysterectomy, cancellous bone remodeling was not significantly different from presurgical levels. At no time was a significant reduction in bone volume detected. These data suggest that the changes in cancellous bone remodeling in the ovariohysterectomized dog are a series of transient phenomena. The duration and/or magnitude of these changes do not appear to be sufficient to effect a sizable or significant reduction in bone volume. The brief nature of the transients in bone remodeling and the lack of a sizable bone loss in the ovariohysterectomized dog limit the utility of this model for the routine assessment of agents for either the prevention or treatment of bone disease associated with ovarian insufficiency.
Stimulation of collagenase production by rat osteosarcoma cells can occur in a subpopulation of cells
Authors: Strege David W. , Kahn Arnold J. , Jeffrey John J. , Dr. Partridge Nicola C. 
Published: February 2010

Abstract
Recent studies have indicated that neutral collagenase can be produced in bones of rats. In addition, it has been demonstrated by in vitro studies that the enzyme is likely secreted by osteoblasts. Cells of the osteoblastic tumor cell line UMR-106 can be stimulated to produce not only collagenase, but also collagenase inhibitor and plasminogen activator. However, it is conceivable that not all osteoblasts produce all of these proteins. In this study, in which UMR cells were maximally stimulated with PTH, only a subpopulation of cells was observed to produce enhanced levels of collagenase but all cells had the ability to synthesize plasminogen activator.
Cells of the rat osteosarcoma line UMR-106-01 were stained for the presence of collagenase and tissue plasminogen activator using an immunohistochemical procedure. In many cases, the cells were exposed to monensin for the final 3 h of incubation as well as to the inducing agent PTH. Monensin prevented export of the enzymes, enabling them to be visualized within their cell of origin. Maximal stimulation of collagenase was demonstrated to occur 8 h after exposure to 10−8-10−7 M PTH. Under these conditions, 14-17% of the cells appeared to synthesize elevated amounts of collagenase (as determined by intense staining). Without PTH stimulation, there was a low level of collagenase in all cells, but &lt; 1% of the cells stained heavily for the enzyme. In contrast, strong staining for plasminogen activator was observed in all cells with or without PTH treatment. This suggests that the regulation of collagenase production in osteoblasts occurs at the level of the individual cell such that there appear to be subpopulations of cells that respond differently to PTH stimulation.
Human parathyroid hormone-(1-34) prevents bone loss and augments bone formation in sexually mature ovariectomized rats
Authors: Dr. Liu Chung-Ching , Kalu Dike N. 
Published: February 2010

Abstract
A group of 3-month-old Sprague-Dawley rats were sham operated or ovariectomized and given daily injections of human PTH-(1-34) (8 or 16 μg per 100 g body weight) for 5 weeks. At the termination of the study histomorphometric techniques were used to examine changes in cortical and cancellous bone in the diaphysis and proximal metaphysis of the tibia. Ovariectomy resulted in a 50% decrease in cancellous bone that was accompanied by a 41 and 120% increase in osteoclasts and osteoblasts, respectively. In contrast, in the ovariectomized animals treated with PTH, the metaphyseal cancellous bone increased by over 300% to a level in excess of that present in the sham-operated control animals. The increase in cancellous bone induced by PTH was associated with an over 70% increase in osteoblasts and tetracycline-labeled area and an unexpected decrease in trabecular osteoclasts. In the tibial diaphysis PTH also decreased endosteal osteoclasts and at the same time increased osteoblast size and number as well as endosteal and periosteal bone formation; ovariectomy increased only periosteal bone formation. Our findings demonstrate that intermittent administration of PTH prevents ovariectomy-induced bone loss and augments cancellous and cortical bone formation in sexually mature ovariectomized rats. Although the basis of the bone anabolic action of PTH remains elusive, our data indicate that it may involve the uncoupling of bone formation and resorption such that the latter is inhibited as bone formation is enhanced. Our findings are also compatible with the view that intermittent administration of PTH increases bone mass, in part by stimulating the proliferation and differentiation of osteoblast progenitors while inhibiting osteoclast proliferation.
Human PTH-(3–34) inhibited the effects of human parathyroid hormone-related protein on phosphate uptake in a cultured renal cell line (OK cells)
Authors: Dr. Nakai Masamichi , Fukase Masaaki , Yamaguchi Toru , Tsukamoto Tatsuo , Fujii Nobutaka , Fujita Takuo 
Published: February 2010

Abstract
The action mechanism of hPTH and hPTHrP-(1–34) on phosphate uptake in opossum kidney (OK) cells was studied using [Nle8,18Tyr34]hPTH-(3–34)-NH2, a potent competitive inhibitor of adenylate cyclase-coupled PTH receptor. We examined the effects of hPTH-(1–34), hPTHrP-(1–34), and hPTH-(3–34) separately or in combination on the change in renal cyclic AMP production and phosphate uptake in OK cells. Both hPTH-(1–34) and hPTHrP-(1–34) stimulated intracellular cyclic AMP production to the same degree at concentrations between 10−10 and 10−7 M and inhibited phosphate uptake equipotently on a molar basis (27.5 ± 2.0 and 33.2 ± 1.2% inhibition at 10−7 M, respectively). Both exogenous addition of (Bu)2cAMP and endogenous stimulation of cAMP by forskolin inhibited phosphate uptake in a dose-dependent manner. Cyclic AMP production induced by either hPTH-(1–34) or hPTHrP-(1–34) was inhibited by both [Nle8,18Tyr34]-hPTH-(3–34)-NH2 and [Tyr34]-hPTH-(7–34)-NH2. However, [Nle8,18Tyr34]hPTH-(3–34)-NH2 and [Tyr34]-hPTH-(7–34)-NH2 inhibited hPTH-induced cAMP production more strongly. The inhibitory action of phosphate uptake by hPTH-(1–34) and hPTHrP-(1–34) was prevented in the presence of a 100-fold greater concentration of [Nle8,18Tyr34]hPTH-(3–34)-NH2. The antagonistic action of [Nle8,18Tyr34]hPTH-(3–34)-NH2 on the inhibition of phosphate uptake induced by hPTH-(1–34) and hPTHrP-(1–34) became weaker with time (0–120 minutes), and [Nle8,18Tyr34]hPTH-(3–34)-NH2 did not antagonize the inhibition of phosphate uptake induced by hPTHrP-(1–34) at 120 minutes of incubation. Our results indicated that PTHrP inhibits renal phosphate transport, at least in part through an adenylate cyclase-cAMP-coupled PTH receptor, but the response to the competitive inhibition of this peptide-induced cAMP production and inhibition of phosphate uptake with PTH receptor antagonists was different. PTH receptor heterogeneity in OK cells may exist and contribute to this phenomenon.
Characterization of the major parathyroid hormone target cell in the endosteal metaphysis of rat long bones
Authors: Rouleau Marie F. , Mitchell Jane , Dr. Goltzman David 
Published: February 2010

Abstract
The majority of in vivo competitive binding of parathyroid hormone (PTH) in the endosteal metaphysis of rat long bones was recently shown to be localized in the intertrabecular tissue to a cell that is distinct from a differentiated osteoblast. In the present report we have further characterized this cell, termed a parathyroid hormone target (PT) cell, by light and electron microscopy using radioautography and histochemical techniques. These studies demonstrate that the PT cell is a mononuclear cell with a large cell body located at times between clusters of differentiated osteoblasts, as well as in other regions of the intertrabecular tissue. Its long cytoplasmic processes extend from the bone matrix through the intertrabecular region toward vascular structures, interdigitating with various cells of the endosteum. A distinctive tubular structure originating in the Golgi system and often associated with long mitochondria and glycogen particles extends throughout the cytoplasmic processes of the PT cell. Based on its capacity to incorporate [3H]thymidine, the PT cell appears to divide rather slowly. The identification of occasional hybrid cells with ultrastructural features of both the PT cell and the differentiated osteoblast and the presence of histochemical evidence for alkaline phosphatase activity suggest that the PT cell is of the osteoblast lineage. These studies therefore morphologically define a major osseous target cell for PTH that, although of the osteoblast lineage, is not a differentiated osteoblast and provide in vivo evidence that characteristics of the “osteoblast phenotype” are not restricted to a sole osseous cell type.
Ultrastructural localization of a tartrate-resistant acid ATPase in bone
Authors: Dr. Reinholt Finn P. , Widholm Silwa Mengarelli , Ek-Rylander Barbro , Andersson Göran 
Published: February 2010

Abstract
Osteoclasts are effector cells in bone breakdown, and the active bone resorption is confined to the ruffled border zone of these cells. An acid milieu is maintained in this zone which is probably a prerequisite for bone resorption. Tartrate-resistant acid phosphatase (TRAP) activity has been recognized as a characteristic property of osteoclasts and in several studies proposed as a cytochemical marker of osteoclasts. We have previously isolated and characterized a tartrate-resistant and iron-activated acid ATPase (TrATPase) from rat bone, the enzyme being a member of the TRAP family. In the present study the ultrastructural localization of this enzyme was delineated by employing immunogold technique on low temperature-embedded maxillar rat bone. Intensive immunolabeling was seen on the bone surfaces facing the ruffled border zone while lower amounts of marker were seen in adjacent bone areas, that is, on the bone surfaces facing the clear zone and deeper into the bone. Within the osteoclasts gold markers were observed mainly in vesicular structures interpreted as lysosomes. Immunolabeling was also observed in the recently described endocytic cells located near osteoblasts and osteoclasts. Also in these cells, the marker was confined to lysosomelike structures. The amount of label in bone facing osteoblasts was low, as was the amount within osteoblasts. Our observation of extracellular localization, in particular accumulation of TrATPase in bone matrix facing the ruffled border area of the osteoclasts, favors the view that the enzyme is exported to areas of active bone resorption, thereby indicating a potential role for the enzyme in this process.
In vivo effects of human recombinant transforming growth factor β on bone turnover in normal mice
Authors: Marcelli Christian , Yates A. John , Dr. Mundy Gregory R. 
Published: February 2010

Abstract
Reports of the effects of TGF-β on bone cells are conflicting and controversial. Different cell culture and organ culture models for both osteoblasts and osteoclasts have given different responses. In some the effects are dependent on prostaglandin synthesis, and in others they are prostaglandin independent. To determine the effects of TGF-β on osteoblasts and osteoclasts in vivo and the role of prostaglandins in mediating these effects, we injected 2.5–5 μg TGF-β into the subcutaneous tissue overlying the calvariae of normal mice for 2–5 days and compared the morphologic responses in underlying calvarial bone with those in mice injected with vehicle alone. TGF-β treatment had no effect on plasma calcium concentration. However, TGF-β caused a marked increase in periosteal thickness (fivefold) and cellularity, morphologic changes in osteoblasts, and new mineralized bone formation. These effects were localized to the site of injection and were partially inhibited by concomitant indomethacin treatment. There was a parallel increase in osteoclast numbers in adjacent marrow spaces, and the osteoclasts formed were unusually large. In contrast, no increase in the numbers of osteoclasts was seen in indomethacin-treated animals. These data show that TGF-β has powerful effects on local bone cell function in vivo and that these effects may be mediated, in part, by prostaglandin generation.
Synergistic effect of transforming growth factor β and fibroblast growth factor on DNA synthesis in chick growth plate chondrocytes
Authors: Crabb Ian D. , O'Keefe Regis J. , Puzas J. Edward , Rosier Randy N. 
Published: February 2010

Abstract
Transforming growth factor β and fibroblast growth factor are mitogens for chick growth plate chondrocytes. TGF-β stimulated a 3.5-fold increase, and FGF a 13.5-fold increase in the rate of thymidine incorporation after a 24 h exposure. TGF-β and FGF were synergistic in chondrocytes, causing a 73-fold stimulation in thymidine incorporation compared with control. This synergistic response was not dependent upon the simultaneous presence of both mitogens. Sequential exposure of chondrocytes to TGF-β and FGF in either order reproduced in large part the synergistic interaction observed when both growth factors were present simultaneously. The time required for induction of the subsequent synergistic response was brief and, in the case of TGF-β, corresponded to the time required for [125I]TGF-β receptor binding. EGF and PDGF were not mitogenic for chondrocytes, and neither of these factors enhanced the response of the cells to either TGF-β or FGF. Finally, TGF-β and FGF did not, either alone or in combination, elevate intracellular cAMP levels. These results emphasize the importance of examining growth factor effects in the context of other growth regulators. Furthermore, this specific and dramatic synergistic stimulation of thymidine incorporation may provide a useful tool in elucidating the mitogenic mechanism of the individual growth factors.
Inhibition of mediator release in systemic mastocytosis is associated with reversal of bone changes
Authors: Graves Leland , Stechschulte Daniel J. , Morris David C. , Lukert Barbara P. 
Published: February 2010

Abstract
A 59-year-old male presented with systemic mastocytosis with extensive skeletal involvement resulting in vertebral compression fractures and bone pain. Histomorphometric analysis of bone revealed increased mast cells, elevated static parameters of bone resorption, and low bone formation. Serum calcium, phosphorus, and alkaline phosphatase were normal; however, serum 1,25-dihydroxyvitamin D3 and osteocalcin levels were low. Histamine levels in plasma and urine were elevated. Following therapy with ketotifen, the patient had resolution of bone pain along with decreased flushing and pruritus. Elevated plasma and urine histamine levels normalized, as did 1,25-dihydroxy vitamin D3 and osteocalcin levels. Indices of low bone formation improved on therapy. Eroded surfaces improved but remained elevated. This case is the first demonstration that bone symptoms and histomorphometric change in systemic mastocytosis are reversed with inhibition of mast cell degranulation. The role of mast cells and their products in bone metabolism is poorly understood, but the therapy of bone disease in systemic mastocytosis should include inhibition of the release of mast cell products along with the use of histamine antagonist.
Corticosteroid effects on proximal femur bone loss
Authors: Dr. Sambrook Philip , Birmingham Joan , Kempler Susan , Kelly Paul , Eberl Stefan , Pocock Nicholas , Yeates Michael , Eisman John 
Published: February 2010

Abstract
Prolonged high-dose corticosteroid therapy is known to result in an increased risk of osteoporotic fracture. Reductions in bone density have been demonstrated at the distal radius and lumbar spine in patients receiving corticosteroids; however there have been few studies of bone density in the hip (the most important site of osteoporotic fracture) in this context. To examine the effect of corticosteroids on the hip we measured bone mineral density (BMD) by dual-photon absorptiometry at three sites in the proximal femur as well as the lumbar spine in 32 patients aged 18–77 years who had been treated with corticosteroids (mean daily prednisone dose 12.7 mg) for up to 23 years. BMD was compared with the expected values using age regressions in normal subjects. BMD was significantly reduced in the femoral neck, Ward's triangle, and the trochanteric region (p &lt; 0.001 all sites). In the lumbar spine BMD was also significantly reduced (p &lt; 0.001). We also measured BMD serially in 29 patients receiving corticosteroids. BMD measurements were made in 12 patients who had already been treated with long-term corticosteroids at the time of first BMD measurement (chronic group) and from the commencement of corticosteroid therapy in 17 patients (acute group). The mean (± SEM) change in BMD (g/cm2 per year) in the lumbar spine and femoral neck were 0.006 ± 0.006 and –0.021 ± 0.007, respectively, for the chronic group and –0.02 ± 0.005 and –0.039 ± 0.006 for the acute group. The rate of bone loss from the lumbar spine was significantly greater in the acute than the chronic group (p &lt; 0.01), and a similar trend was seen in the femoral neck (p = 0.07). These data suggest that bone loss with corticosteroids is most rapid soon after starting treatment and occurs to a similar extent from the proximal femur to the lumbar spine. The bone loss at the femoral neck suggests an increased risk of fracture at that site, particularly in older subjects on long-term corticosteroid therapy.
Treatment of paget's disease with intermittent low-dose infusions of disodium pamidronate (APD)
Authors: Stone Michael D. , Hawthorne A. Barney , Kerr David , Webster Gillian , Hosking David J. 
Published: February 2010

Abstract
Disodium pamidronate (APD) is a potent inhibitor of bone resorption, with less risk of defective mineralization than earlier bisphosphonates. We assessed the response to six spaced low-dose intravenous infusions of APD given at intervals of approximately 6 weeks followed by weekly infusions if bone turnover remained abnormal. Three groups of 10 patients were studied, each group receiving infusions of 15, 30, or 45 mg. Hydroxyproline excretion fell by 62% and alkaline phosphatase was reduced by 72%, with no difference between the dose levels. A total of 21 patients (70%) achieved normal levels of bone turnover, indicating that low-dose infusions of APD are a safe and effective treatment for Paget's disease.
Interleukin-6 does not stimulate bone resorption in neonatal mouse calvariae
Authors: Al-Humidan Abdulkarim , Ralston Stuart H. , Hughes David E. , Chapman Karen , Aarden Lucien , Russell R. Graham G. , Dr. Gowen Maxine 
Published: February 2010

Abstract
Recombinant human interleukin-6 (IL-6) was assessed for its ability to stimulate bone resorption in prelabeled mouse calvariae in vitro. IL-6 had no effect on bone resorption at concentrations ranging from 300 to 10,000 U/ml (3–1000 pg/ml). Neither the presence of indomethacin nor prolonged incubation periods (96 h) affected this result. IL-6 did not affect resorption stimulated by human recombinant IL-1α (rIL-1α) but inhibited resorption stimulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. rIL-1α, PTH, and 1,25-(OH)2D3 induced IL-6 release by calvariae. We conclude from these studies that IL-6 does not stimulate bone resorption in neonatal mouse calvariae. However, it may act as a locally produced inhibitor and therefore a paracrine regulator of bone resorption induced by osteotropic hormones. IL-6 could also function as a long-range stimulator of systemic reactions and acute-phase responses to local inflammatory and neoplastic lesions in bone.