bluuebunny/crossref_metadata_2025_split huggingface dataset:
Responsiveness of clonal limb bud cell lines to bone morphogenetic protein 2 reveals a sequential relationship between cartilage and bone cell phenotypes
Authors: Rosen Vicki , Nove John , Song Jeffrey J. , Thies R. Scott , Cox Karen , Wozney John M. 
Published: February 2010

Abstract
There is growing evidence to suggest that BMPs are among the signals necessary to create the embryonic skeleton, but how these regulatory molecules enter the pathways of embryonic bone formation remains to be defined. The earliest steps of endochondral bone formation, consisting of mesenchymal condensation and chondrogenesis, have been shown to result directly from BMP-2 action. To determine whether the transition from chondrogenesis to osteogenesis occurring later in endochondral bone formation is also the result of BMP activity, we tested the effects of BMP-2 on immortalized endochondral skeletal progenitor cells derived from mouse limb bud. The cell lines established by this process were found to fall into three general categories: undifferentiated skeletal progenitor cells, which in the presence of BMP-2 first express cartilage matrix proteins and then switch to production of bone matrix proteins; prechondroblast-like cells that constitutively express a subset of markers associated with chondrogenesis and, in the presence of BMP-2, shut off synthesis of these molecules and are induced to produce bone matrix molecules; and osteoblast-like cells that are not significantly affected by BMP-2 treatment. These data suggest that BMP-2 initiates the differentiation of limb bud cells into cells of both the cartilage and bone lineages in a sequential manner, making BMP-2 a potent regulator of skeletal cell differentiation.
Parathyroidectomy does not prevent bone loss in the oophorectomized rat
Authors: Sims N.A. , Dr. Morris H.A. , Moore R.J. , Durbridge T.C. 
Published: February 2010

Abstract
The evidence for a role of parathyroid hormone in the bone loss after the menopause remains controversial. This study examines the effect of parathyroidectomy on femoral trabecular bone volume, thickness, and spacing and biochemical markers of bone turnover in the oophorectomized rat. Female Sprague-Dawley rats 3 months old were double sham operated (sham), oophorectomized (OPX), parathyroidectomized (PTX), or oophorectomized and parathyroidectomized (O/P) under halothane anesthesia. At 9 weeks postoperation, femoral trabecular bone volume (BV/TV) was lower in OPX and O/P rats compared with sham or PTX animals (BV/TV, %, mean + SEM): sham 25.9 + 0.5, OPX 15.1 + 0.9, PTX 24.1 + 0.9, O/P 17.3 + 0.5; p &lt; 0.001). Urinary hydroxyproline excretion, serum osteocalcin, and alkaline phosphatase activity were higher in OPX and O/P rats compared with control animals at 3 weeks postoperation (OHPE μM GF, mean + SEM: sham 1.37 + 0.16, OPX 2.16 + 0.26, PTX 0.95 + 0.21, O/P 1.92 + 0.22, p &lt; 0.005; osteocalcin, μg/liter, sham 31.8 + 1.8, OPX 33.7 + 2.7, PTX 24.5 + 2.1, O/P 34.3 + 2.1, p &lt; 0.025; alkaline phosphatase, U/liter, sham 90 + 3, OPX 125 + 9, PTX 87 + 9, O/P 116 + 11, p &lt; 0.005). These data indicate postoophorectomy bone loss is not prevented by parathyroidectomy.
Structural requirements for bisphosphonate actions in vitro
Authors: van Beek Ermond , Hoekstra Monique , van De Ruit Marjan , Löwik Clemens , Papapoulos Socrates 
Published: February 2010

Abstract
We investigated the structural requirements for the binding of bisphosphonates to bone mineral and the relation between their affinity for bone and their effects on bone resorption in vitro. For this we used fetal mouse long bones in culture and bisphosphonates with variable R1 and R2 structures. In addition, we studied the effect of structural differences in the incorporation of calcium into bone. We found that bisphosphonates containing a hydroxyl group in the R1 position have the highest affinity for bone mineral. This was related to their capacity to inhibit the incorporation of calcium into long bones but not to their antiresorptive potency. The latter was primarily determined by R2. Furthermore, the effect of bisphosphonates on calcification, but not on resorption of bone explants, was mainly determined by the mode of addition. The continuous presence of bisphosphonate during culture inhibited calcification even at very low concentrations, but short incubation of the bones with relatively high concentrations had no effect. This is probably a result of differences in the availability of the compound to the process of calcification. Because, in vivo, the more potent bisphosphonates inhibit resorption without adversely affecting mineralization of the skeleton and they disappear rapidly from the circulation after administration, we suggest that cultures of bone explants incubated with bisphosphonates for short times rather than cultures in which the drugs are continuously present provide more accurate information about the in vivo effect of these compounds on both resorption and calcification.
Cholera toxin-stimulated bone resorption in cultured mouse calvarial bones not inhibited by calcitonin: A possible interaction at the stimulatory g protein
Authors: Dr. Ransjö Maria , Lerner Ulf H. , Ljunggren Östen 
Published: February 2010

Abstract
We examined the effect of calcitonin in cultured mouse calvarial bones after prestimulation with different activators of adenylyl cyclase. Calcitonin (100 ng/ml), added after 48 h of culture, inhibited bone resorption (assessed as release of 45Ca from prelabeled bones cultured for 96-144 h) stimulated with parathyroid hormone (PTH, 10 nM; 0-144 h) or the adenylyl cyclase stimulator forskolin (2 μM; 0-144 h). However, no effect of calcitonin was demonstrated when bone resorption was prestimulated with the adenylyl cyclase stimulator cholera toxin, at and above 1 ng/ml, at any time point studied. In contrast, two other types of inhibitors of bone resorption in vitro, the carbonic anhydrase inhibitor acetazolamide (10 μM) and the aminobisphosphonate AHPrBP (10 μM), significantly inhibited cholera toxin-stimulated bone resorption. No cyclic AMP response to calcitonin was seen after preculture for 48 h with cholera toxin (0.1-100 ng/ml), although bones precultured in basic medium, in the absence or presence of forskolin, were still able to respond to calcitonin with elevation of cyclic AMP. Binding studies with [125I]calcitonin demonstrated that the preculture with cholera toxin did not affect the binding of calcitonin to the receptor. In summary, our data show that cholera toxin pretreatment makes calvarial bones insensitive to calcitonin-induced inhibition of bone resorption as a result of an interaction with cholera toxin at the level of calcitonin receptor-linked signal transduction. We suggest that the interaction, distal to the calcitonin receptor, is caused by the irreversible activation of G s produced by cholera toxin. The study suggests that a functional G s coupled to adenylyl cyclase is required for transduction of the inhibitory action of calcitonin on bone resorption.
Femoral bone loss progresses with age: A longitudinal study in women over age 65
Authors: Greenspan Susan L. , Maitland Lauri A. , Myers Elizabeth R. , Krasnow Meryl B. , Kido Tamiko H. 
Published: February 2010

Abstract
Although previous longitudinal studies suggest bone loss ceases at the spine and radius in women over age 65, few data are available to determine whether femoral bone loss continues in this age group. Because a low femoral bone mass is associated with an increased risk of hip fracture and current therapies for fracture prevention focus on halting bone loss, it is imperative to determine whether femoral bone loss occurs in those who sustain 90% of hip fractures: women over age 65. To determine the annual rate of femoral bone loss, the association of bone loss and age, and the relationship between femoral and spinal bone loss in this age group, we prospectively followed femoral and spinal bone mineral density (BMD) in 85 healthy, community-dwelling, ambulatory women over age 65 (mean 77 years, range 66-93 years). Measurements of femoral and spinal BMD were assessed twice over 1 year using dual-energy x-ray absorptiometry. Cross-sectional analysis of site-specific baseline BMD suggested a significant bone loss in the femoral neck (-0.76% per year, p &lt; 0.01), total hip (-0.70% per year, p &lt; 0.01), trochanter (-0.71% per year, p &lt; 0.05), intertrochanter (-0.88% per year, p &lt; 0.01), and Ward's triangle (-0.86% per year, p &lt; 0.01) but no significant change at the spine. Longitudinal analysis (mean + SD) revealed a similar loss of bone at the total hip (-0.95 + 2.88% per year, p &lt; 0.01), trochanter (-0.74 + 3.62% per year, p &lt; 0.01), and intertrochanter (-1.14 + 3.54% per year, p &lt; 0.01), with a significant gain in lumbar BMD (0.94 + 3.34% per year, p &lt; 0.05). The annual percentage change in BMD at the total hip was negatively correlated with age (p &lt; 0.05). These data demonstrate that femoral bone loss is present in women over age 65 and that measurements of spinal BMD may be a misleading reflection of femoral skeletal integrity in this age group. Furthermore, these data provide the scientific rationale to develop and implement femoral bone loss prevention strategies in this important target group.
Bone-forming ability of 24r,25-dihydroxyvitamin d3 in the hypophosphatemic mouse
Authors: Yamate Tomoo , Tanaka Hiroyuki , Nagai Yumiko , Yamato Hideyuki , Taniguchi Nobuyuki , Nakamura Toshitaka , Seino Yoshiki 
Published: February 2010

Abstract
To determine whether 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] exerts unique biologic effects on bone, we examined the effects of the vitamin D metabolites, 24R,25(OH)2D3 and 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3], on the hypophosphatemic (Hyp) mouse, a model for X-linked hypophosphatemic rickets in humans. The Hyp mice were administered 1-10,000 μg/kg/day of 24R,25(OH)2D3, 0.01-10 (μg/kg/day of 1α,25(OH)2D3, or vehicle alone, given daily for 28 days by intraperitoneal injection. 24R,25(OH)2D3 at doses of 1-1000 μg/kg/day had dose-dependent effects in increasing bone size, dry bone weight, and bone mineral content without causing hypercalcemia. 1α,25(OH)2D3 at doses of 1 or 10 μg/kg/day, which we considered to have activity similar to that of 1000 μg/kg/day of 24R,25(OH)2D3 with respect to cell differentiation activity, caused severe bone resorption and hypercalcemia. At 0.1 μg/kg/day, 1α,25(OH)2D3 increased bone size, similarly to a dose of 1000 μg/kg/day of 24R,25(OH)2D3, without significantly affecting dry bone weight or bone mineral content, as did 1000 μg/kg/day of 24R,25(OH)2D3. These findings suggest that 24R,25(OH)2D3 exerts unique activity in the Hyp mouse rather than merely mimicking the activity of 1α,25(OH)2D3.
Premenopausal and postmenopausal changes in bone mineral density of the proximal femur measured by dual-energy x-ray absorptiometry
Authors: Ravn Pernille , Hetland Merete Lund , Overgaard Kirsten , Christiansen Claus 
Published: February 2010

Abstract
Total and regional bone mineral density (BMD) of the proximal femur was measured by DXA in 1238 healthy white women. In the 389 premenopausal women, aged 21-54 years, no bone loss was observed before the menopause, except in the femoral neck and Ward's triangle, in which BMD decreased by 0.3%/year (SEE 0.2-0.9%/year, p &lt; 0.001) and 0.6%/year (SEE 0.4-0.8%/year, p &lt; 0.001), respectively. In the postmenopausal women aged 48-75 years, there was a highly significant exponential decay in BMD with age and years since menopause (YSM) in all regions (-0.58 &lt; r &lt; -0.48, p &lt; 0.001). However, YSM was a better predictor of BMD than age. The decrease in BMD in the First 5 years postmenopause reached values of 9-13%. The estimated bone loss after 20 years was 17-30%, greatest in Ward's triangle and smallest in the intertrochanteric region. BMD correlated highly significantly with BMI (0.26 &lt; r &lt; 0.48, p &lt; 0.001). In conclusion, the present study indicates a stable premenopausal bone mass of the proximal femur and a postmenopausal bone loss, which is influenced mainly by YSM within the first 10-15 years after menopause. BMD correlated with body mass index (BMI) in the postmenopausal years, confirming that low BMI constitutes a potential risk factor for osteoporosis.
Direct demonstration that the vitamin k-dependent bone gla protein is incompletely γ-carboxylated in humans
Authors: Cairns James R. , Dr. Price Paul A. 
Published: February 2010

Abstract
Incomplete vitamin K-dependent γ-carboxylation has been found in bone Gla protein (BGP) isolated from each of 20 different human bone samples. Using N-terminal protein sequencing of the methyl-esterified protein (Anal Biochem 1991;199:93-97), a method that directly measures the percentage of γ-carboxylation at each target glutamate residue, the extent of incomplete BGP γ-carboxylation was found to depend strongly on sequence position, with (x̄ + SD) 67 + 14% γ-carboxylation at residue 17, 88 + 9% γ-carboxylation at residue 21, and 93 + 4% γ-carboxylation at residue 24. There is a strong correlation between the incomplete γ-carboxylation at glutamate residues 17 and 21 for BGP purified from the 20 bone samples (p &lt; 0.001), which suggests that individual differences in the efficiency of BGP γ-carboxylation during synthesis probably cause the observed differences in percentage BGP γ-carboxylation between bone samples. These results have been interpreted using a kinetic treatment of γ-carboxylation. This treatment predicts the existence of differences in the extent of γ-carboxylation between glutamate residues in BGP, as well as the correlation between percentage carboxylation at Glu17 and Glu21. Although the molecular basis of incomplete BGP γ-carboxylation is at present unknown, if incomplete BGP γ-carboxylation were caused only by differences in the availability of vitamin K in bone cells, this kinetic treatment predicts that the range in BGP γ-carboxylation observed in the 20 human bone samples studied here could be explained by a relatively modest fivefold range in the vitamin K levels of these individuals.
Effects of passive immunization against parathyroid hormone-related protein: PTHrP is the responsible factor in mediating hypercalcemia in the walker carcinosarcoma 256 rat model
Authors: Schilling Tobias , Blind Eberhard , Baier Reinhard , Sinn Hans-Peter , Moallem Eli , Silver Justin , Ziegler Reinhard , Raue Friedhelm 
Published: February 2010

Abstract
The Walker carcinosarcoma (WCS) 256 is a well-characterized rat model of humoral hypercalcemia of malignancy (HHM). We addressed the question of whether parathyroid hormone-related protein (PTHrP) is the factor responsible for mediating HHM in this model. WCS 256 cells were subcutaneously implanted in female rats. We examined the plasma at days 0,2,4,6, and 8. The midregional PTHrP measured by radioimmunoassay (RIA) and the plasma calcium increased significantly. Measuring PTHrP by a two-site immunoradiometric assay (IRMA) showed comparable results. There was a strong positive correlation between plasma calcium and midregional PTHrP (r = 0.85, p &lt; 0.0001). A strong positive correlation between tumor weight and both midregional PTHrP (r = 0.83, p &lt; 0.0001) and plasma calcium (r = 0.87, p &lt; 0.0001) was also found. After surgical removal of the tumor at day 5, both plasma calcium and plasma PTHrP levels fell to within the normal range. Ip administration of native polyclonal antiserum against PTHrP(53–84) led to a significant decrease of plasma calcium. Extracted WCS 256 tumor showed 5-fold increased levels of midregional PTHrP compared with liver. Immunohistochemistry and Western blot were positive for PTHrP. RNA from the WCS 256 tumor was positive for PTHrP whereas liver tissue RNA was negative. WCS 256 cells grown in vitro also secreted PTHrP into the medium. We conclude that PTHrP is synthesized and secreted by WCS 256 and that PTHrP is the factor responsible for mediating hypercalcemia in the WCS 256 rat model.
Prostaglandin E2 administration prevents bone loss induced by orchidectomy in rats
Authors: Li M. , Jee Webster S. S. , Ke H.Z. , Tang L.Y. , Ma Y.F. , Liang X.G. , Setterberg R.B. 
Published: February 2010

Abstract
The objects of this study were to investigate whether prostaglandin E2 (PGE2) can prevent orchidectomy (ORX)-induced cancellous bone loss in growing male rats, and to determine the differential effects of PGE2 on sham-operated (sham) and ORX male rats. Fourteen-week-old Sprague-Dawley male rats were divided into groups of basal, vehicle-treated sham, PGE2-treated sham, vehicle-treated ORX, and PGE2-treated ORX rats for either 3 or 9 weeks. PGE2 was given at 6 mg/kg body weight daily by subcutaneous injection. Static and dynamic cancellous bone histomorphometry were performed on double-fluorescent labeled undecalcified proximal tibial metaphyseal sections. No effect was observed by ORX on body weight or longitudinal bone growth rate when compared with sham-operated controls. However, androgen deficiency caused significant increases in percent eroded perimeter, mineral apposition rate, and bone turnover (bone-volume-referent-bone formation rate), which resulted in a significant decrease in trabecular bone number, increase in trabecular separation, and a nonsignificant decrease in trabecular bone area by 3 weeks of ORX. After 9 weeks of ORX, trabecular bone area and number were significantly decreased, and trabecular separation, percent eroded perimeter, and the index of bone turnover (bone-volume-referent-bone formation rate) remained significantly increased while the index of bone formation (tissue-volume-referent-bone formation rate) was nonsignificantly decreased when compared with sham controls. When 6 mg PGE2kg/day was given for 3 and 9 weeks, similar anabolic effects were observed in sham and ORX rats. PGE2 caused significant decreases in body weight and longitudinal bone growth rate and significant increases in trabecular bone area, thickness, labeling perimeter, mineral apposition rate, and tissue-volume-referent-bone formation rate in both sham and ORX rats when compared with their respective controls. In sham-operated rats, PGE2 had no effect on percent eroded perimeter after 3 weeks of treatment, whereas after 9 weeks PGE2 caused a significant increase in this index. PGE2 partially inhibited the increase in percent eroded perimeter induced by ORX at week 3, but had no effect on this parameter at week 9 as compared with ORX controls. In summary, the new findings from current study indicated that PGE2 can prevent bone loss induced by ORX and the anabolic skeletal effect of PGE2 independent of the presence of androgen and longitudinal growth and occurs mainly on the pre-existing bone surface.
Interleukin-1 modulates phosphorylation of proteins in human osteoblastic cells
Authors: Kang Yung-Ming , Yeh Yu-Ling , Dr. Graves Dana T. 
Published: February 2010

Abstract
Interleukin-1 (IL-1) is a potent bone resorbing cytokine with diverse biological effects. We previously reported that IL-1 inhibits PDGF-AA-induced biological activities including PDGF-AA-induced tyrosyl phosphorylation. In the present studies, we first investigated and compared the tyrosyl phosphorylation pattern induced by EGF, IGF-1, PDGF-AA, and bFGF in human osteoblastic cells. We then examined the effect of IL-1 on the tyrosyl phosphoproteins induced by each ligand. Immunoblot analyses show that EGF, IGF-1, and PDGF-AA each elicit a different pattern of tyrosyl phosphorylated proteins in normal human osteoblastic cells. IL-1β inhibits PDGF-AA induced autophosphorylation by down-regulation of the PDGF-α receptor, as demonstrated by immunoprecipitation experiments. For other ligand-induced tyrosyl phosphoproteins, IL-1β reduced the intensity of EGF-induced pp55,000, and IGF-1 induced pp185,000 and pp 175,000. These experiments indicate that IL-1 inhibits phosphorylation of specific proteins induced by growth factors. By using inhibitors of secondary message pathways, we determined that the inhibitory effect of IL-1β on PDGF-AA receptor binding and receptor tyrosyl autophosphorylation was not dependent on protein kinase A, protein kinase C, or the formation of prostaglandins. These data suggest the existence of an alternative pathway that may participate in IL-1β signaling.
Cyclical treatment of osteopenic ovariectomized adult rats with PTH(1–34) and pamidronate
Authors: Cheng P.-T. , Chan C. , Müller K. 
Published: February 2010

Abstract
Administration of PTH(1–34) at low intermittent doses stimulates bone formation in vivo. However, the new bone is quickly resorbed after drug withdrawal.(24) Following the concept of lose, restore, and maintain,(27) we studied the possibility of maintaining the PTH(1–34)-mediated new bone by APD post-treatment and the effect of a second PTH(1–34)-APD cycle in osteopenic ovariectomized (OVX) adult rats. Eighty OVX rats (6-months-old, 3 months after OVX) and 10 sham-operated rats were divided into nine groups. One OVX group was killed as baseline (BL). Five OVX groups were injected with PTH(1–34) (20 μg/kg/day, subcutaneously) for 3 weeks (5 days/week). The remaining two OVX groups and the sham group (S) were injected with saline as controls. One PTH(1–34) group (A) and one control group (B) were then killed. Three PTH(1–34) groups were post-treated with APD injections (250 μg/kg/day, subcutaneously) for 5 days; the remaining PTH(1–34) group, the other control group, and group S were injected with saline; and all these groups were left untreated for 3 weeks. At the end, one PTH-APD group (C), the PTH-saline group (D), and the saline-saline group (E) were killed. Another PTH-APD cycle was applied to the remaining two PTH-APD groups, with group F killed after the second PTH treatment and group G killed after two complete cycles. We found a 90% increase in cancellous bone volume (Cn.BV/TV) and a 28% increase in trabecular thickness (Tr.Th) in group A over group B. Group C had a 78% increase in Cn.BV/TV and a 64% increase in Tr.Th over group E, but groups D and E were not different. Group G had another 15% increase in Cn.BV/TV over group C, but groups F and C were not significantly different. The results showed that APD post-treatment did maintain the PTH(1–34)-mediated new bone and that the effect of a second PTH(1–34)-APD cycle was minor, probably due to the prolonged inhibitory effect of APD on bone formation.