bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extracellular Calcium Is a Potent Inducer of Cyclo-oxygenase-2 in Murine Osteoblasts Through an ERK Signaling Pathway
Authors: Choudhary Shilpa , Wadhwa Sunil , Raisz Lawrence G , Alander Cynthia , Pilbeam Carol C 
Published: April 2006

Abstract
[Ca2+]e may be important in bone turnover. We found [Ca2+]e induces COX-2 transcription and PGE2 production in primary calvarial osteoblasts through an ERK signaling pathway. Inhibition of PGE2 production inhibited the [Ca2+]e stimulation of osteoblastic differentiation but not the increase in cell number. Hence, some effects of [Ca2+]e on bone may be mediated by COX-2.
Introduction: Local changes in extracellular calcium ([Ca2+]e) may play an important role in bone turnover. We examined the possibility that prostaglandins produced by cyclo-oxygenase-2 (COX-2) could mediate some of the effects of [Ca2+]e on osteoblasts.
Methods: We examined the [Ca2+]e induction of COX-2 expression and prostaglandin E2 (PGE2) production in primary osteoblasts (POBs) obtained by sequential enzymatic digestion of mouse calvariae. We measured mRNA and protein levels by Northern and Western analyses and PGE2 production in culture medium by radioimmunoassay (RIA). COX-2 promoter activity was measured as luciferase activity in calvarial osteoblasts derived from mice transgenic for 371 bp of the COX-2 promoter fused to a luciferase reporter gene.
Results and Conclusions: COX-2 mRNA and protein expression were induced by 3–40 mM of [Ca2+]e. [Ca2+]e (5 mM) induced COX-2 mRNA within 30 minutes; levels peaked at 6–9 h and remained elevated at 24 h. Cumulative medium PGE2 was increased at 3 h, with levels rising to 30 nM at 24 h. PGE2 production in POBs from mice with only COX-1 gene expression was 1/40th of that in POBs from mice with both COX-1 and COX-2 gene expression. [Ca2+]e increased alkaline phosphatase activity and osteocalcin mRNA, and this increase was blocked by inhibiting PGE2 production. [Ca2+]e stimulation of COX-2 promoter activity correlated with the induction of COX-2 mRNA expression. [Ca2+]e induced rapid and transient phosphorylation of extracellular signal-regulated kinase (ERK) in POBs, which peaked at 5–10 minutes. Inhibition of ERK phosphorylation with the specific inhibitors, PD-98059 and U-0126, decreased the [Ca2+]e induction of both COX-2 mRNA and luciferase activity by 70–80 %. Although less effective than [Ca2+]e, strontium [Sr2+]e also induced COX-2 mRNA and promoter activity in POBs through an ERK signaling pathway. We conclude that [Ca2+]e is a potent transcriptional inducer of COX-2 expression and PGE2 production in osteoblasts through an ERK signaling pathway.
Does the Combination of Two BMD Measurements Improve Fracture Discrimination?
Authors: Blake Glen M , Patel Rajesh , Knapp Karen M , Fogelman Ignac 
Published: April 2006

AbstractCombining information from different types of BMD measurement should improve the evaluation of patients' risk of fracture. This study used a bivariate gaussian model to examine the effect of combining two different BMD measurements. The results show that, in practice, there is little benefit unless the measurements are completely unrelated.Introduction: Intuitively, the combination of information from two or more different types of bone densitometry investigation should improve our ability to identify patients at high risk of fracture. However, the best way to combine measurements and the resulting gain in fracture discrimination are not known.Materials and Methods: In this study, we used a bivariate gaussian model to investigate the effect of combining two different types of bone densitometry measurements. The measurements had individual relative risk values RR1 and RR2 and a correlation coefficient r between their Z-scores. Different approaches to the combination of the two measurements were compared by calculating the area under the curve (AUC) for the receiver operating characteristic (ROC) curve, which was obtained by plotting the percentage of fracture patients against the percentage of the whole population with a Z-score below some chosen threshold. ROC curves were calculated for three cases: (1) one type of measurement only; (2) two different types of measurements combined using their mean Z-score weighted according to the theoretical optimum weighting factors predicted by the bivariate gaussian model; and (3) two different types of measurements combined using the conventional World Health Organization (WHO) approach, where one or other measurement is below a set threshold. The theoretical model was tested using measurements of speed of sound (SOS) in the radius, phalanx, and metatarsal in patients with vertebral and Colles' fractures.Results: Results were calculated for RR values of 1.5, 2.0, and 2.5 and r = 0, 0.5, and 0.7. Although a significant improvement in fracture discrimination was obtained when r = 0 and RR1 = RR2, the improvements obtained when r ≥ 0.5 or RR1 ≠ RR2 were relatively modest. Slightly better fracture discrimination was obtained using the weighted mean Z-score approach compared with the WHO approach, although the differences were small. The results of the in vivo study in Colles' and vertebral fracture patients showed close agreement with the predictions of the bivariate gaussian model.Conclusion: In practice, from a theoretical point of view, there is unlikely to be any benefit from combining information from different types of bone densitometry measurements unless they are completely unrelated.
Variation in the TNF Gene Promoter and Risk of Osteolysis After Total Hip Arthroplasty
Authors: Wilkinson J Mark , Wilson A Gerard , Stockley Ian , Scott Ian R , Macdonald David A , Hamer Andrew J , Duff Gordon W , Eastell Richard 
Published: April 2006

Abstract
Genetic factors may influence implant failure caused by osteolysis after THA. In an association study of 481 subjects after THA, we found that carriage of the TNF-238A allele was associated with an increased incidence of osteolysis versus noncarriage (odds ratio, 1.7) and was independent of other risk factors. Genetic and environmental factors influence implant survival after THA.
Introduction: Tumor necrosis factor (TNF) is thought to play a role in osteolysis, the major cause of implant failure after total hip arthroplasty (THA). Natural sequence variations at −238 and −308 in the TNF gene promoter are associated with differences in susceptibility to several TNF-mediated diseases. We tested whether these polymorphisms are associated with osteolysis after THA.
Materials and Methods: A total of 481 whites (214 with failed versus 267 with intact implants) were recruited 11.7 ± 4 years after cemented THA. Genomic DNA was extracted from peripheral blood and genotyped for the −238 and −308 polymorphisms using the Taqman 5′ nuclease method. Healthy controls (n = 500) from the background population were also genotyped to establish the local prevalence of these alleles.
Results: The carriage of −238A was 8.8% in the background population and 10.9% in the THA controls (p &gt; 0.05). Carriage of −238A in the osteolysis group was 17.3% (odds ratio, 1.7; 95% CI, 1.0–2.9). Carriage was highest (20.5%) in patients with more widespread osteolysis (OR, 2.1; 1.2–3.8). The association of −238A with osteolysis was independent of other risk factors for osteolysis (logistic regression analysis: OR, 1.8; 1.0–3.2). Carriage of −308A was not associated with osteolysis.
Conclusion: Genetic, as well as environmental factors, influence implant failure after THA. Whether the TNF-238 polymorphism causes a biological change that predisposes to loosening or is in linkage disequilibrium with such a locus is not yet known.
The Renal Clearance of Free and Peptide-Bound Deoxypyridinoline: Response to Pamidronate Treatment of Paget's Disease
Authors: Naylor KE , Jackson B , Eastell R 
Published: April 2006

Abstract
Bisphosphonate treatment of Paget's disease results in a large decrease in urinary peptide-bound pyridinolines but a smaller decrease in urinary free pyridinolines. This discrepancy could be explained by changes in renal handling of pyridinoline forms. We studied eight patients with Paget's disease treated with pamidronate. We collected blood and urine at baseline and at 3 and 14 days after treatment. We measured free and total deoxypyridinoline (DPD) in serum (S) and urine (U) by high-performance liquid chromatography (HPLC). The ratio of free to total DPD at baseline was (mean ± SE) 13 ± 1% in serum and 37 ± 3% in urine; at 3 days, this had increased to 25 ± 3% in serum and 62 ± 7% in urine. Peptide-bound (pb) DPD decreased significantly 3 days after treatment: UpbDPD -63 ± 11%, p &lt; 0.001; SpbDPD -51 ± 8%, p &lt; 0.01. Free DPD decreased in the urine after 14 days: UfDPD −48 ± 5%, p &lt; 0.01; there was no significant change in SfDPD. The fractional excretion of pbDPD relative to creatinine was less than one at all time-points; however, the fractional excretion of fDPD was significantly greater than one throughout the study. As a consequence, the proportion of free DPD in the urine increased as bone turnover decreased. This resulted in a smaller decrease in urine free compared with peptide-bound DPD in response to bisphosphonate therapy. Thus, the conversion of peptide-bound to free DPD in the kidney may become more efficient as bone turnover decreases as a consequence of pamidronate treatment.
Aging Does Not Lessen the Effectiveness of TGFβ2-Enhanced Bone Regeneration
Authors: Sumner DR , Turner TM , Cohen M , Losavio P , Urban RM , Nichols EH , McPHERSON JM 
Published: April 2006

Abstract
Controversy exists over the potency of bone healing in the aged skeleton, and there is concern that enhancement of bone regeneration after use of bone-stimulating growth factors may not be effective in the aged. In this study, 30 skeletally mature beagles (1–2 or 10–12 years old) had titanium implants placed bilaterally in the proximal humerus for a period of 4 weeks in a model of intramembranous bone regeneration. A bony defect made at the time of surgery created a 3-mm gap between the implant surface and the host bone. Some of the implants were treated with recombinant human TGFβ2 (rhTGFβ2) at various does (0.32–35 μg per implant), and some served as paired controls. The dose response was similar in young and old animals. The most effective dose, 35 μg, led to a 3-fold increase in the volume fraction of new bone within the gap in both the young (p = 0.001) and old (p = 0.002) animals. At this dose, there was a 5-fold increase in osteoblast surface. While age did not significantly affect the quantity of new bone formed as assessed by backscatter scanning electron microscopy, the older animals had thinner regenerated trabeculae that tended to be spaced more closely than the younger animals. Coupled with the finding that the increase in osteoid was greater in the old animals compared with the young animals, these qualitative differences suggest that there may have been a slight delay in the rate or a defect of mineralization in the old animals.
Functional Type I PTH/PTHrP Receptor in Freshly Isolated Newborn Rat Keratinocytes: Identification by RT-PCR and Immunohistochemistry
Authors: Errazahi Amina , Bouizar Zhor , Lieberherr Michele , Souil Evelyne , Rizk-Rabin Marthe 
Published: April 2006

Abstract
The presence of identical or distinct type I parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptors in keratinocytes is still a matter of debate. We studied the expression and functionality of PTHrP receptors in freshly isolated keratinocytes from newborn rat skin. Four overlapping primers, amplifying different regions in the rat PTH receptor, were used for reverse transcriptase-polymerase chain reaction (RT-PCR). The first region corresponded to the N-terminal extracellular region and the first transmembrane domain (S/M1), the second region amplified the connecting intracellular and extracellular loops transmembrane domain (E2/M5), the third spanned the range from the transmembrane to the intracellular domain (M4/T), and the fourth region amplified the C-terminal tail (M6/7/T). The PCR products from the keratinocyte RNA were identical to those from kidney RNA of the same rats. The cloned four transcripts showed 100% of homologies with the cDNA sequence from bone ROS cells. Keratinocytes, freshly isolated or present in situ in the epidermis, recognized an anti-PTH receptor antibody (PTH-II) directed against the receptor extracellular domain. Western blotting showed the same protein patterns in keratinocytes, kidney, and ROS cell extracts. Low doses of PTHrP(1–34) (10−12–10−9 M) increased the cell number studied by [3H]thymidine incorporation and DNA content. Treatment with the PTH/PTHrP receptor antagonist [Asn10, Leu11, D Trp12] PTHrP(7–34) or two different PTH receptor antibodies inhibited the increase in cell proliferation induced by PTHrP(1–34). All these findings indicate that newborn rat epidermis and keratinocytes express functional PTHrP receptors, which are identical to type I PTH/PTHrP receptor and are recognized by PTHrP(1–34).
Microarchitectural and Physical Changes During Fetal Growth in Human Vertebral Bone
Authors: Nuzzo S , Meneghini C , Braillon P , Bouvier R , Mobilio S , Peyrin F 
Published: April 2006

Abstract
The ossification process in human vertebra during the early stage of its formation was studied by X-ray diffraction (XRD) and X-ray microtomography (μCT) at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. Twenty-two samples taken from vertebral ossification centers of human fetal bone (gestational age ranging between 16 and 26 weeks) were investigated. The analysis of three-dimensional images at high spatial resolution (∼10 and ∼2 μm) allows a detailed quantitative description of bone microarchitecture. A denser trabecular network was found in fetal bone compared with that of adult bone. The images evidenced a global isotropic structure clearly composed of two regions: a central region (trabecular bone) and a peripheral region (immature bone). XRD experiments evidenced hydroxyapatite-like crystalline structure in the mineral phase at any fetal age after 16 weeks. Interestingly, the analysis of XRD patterns highlighted the evolution of crystalline structure of mineralized bone as a function of age involving the growth of the hydroxyapatite crystallites.
p21WAF1/CIP1 Acts as a Brake in Osteoblast Differentiation
Authors: Bellosta Paola , Masramon Laia , Mansukhani Alka , Basilico Claudio 
Published: April 2006

Abstract
Continuous fibroblast growth factor signaling inhibits the differentiation of primary osteoblasts and osteoblastic cell lines. We studied the expression of several cell cycle regulatory molecules in response to fibroblast growth factor, and found that fibroblast growth factor strongly upregulates the expression of p21WAF1/CIP1, a CDK inhibitor that has also been implicated in the regulation of apoptosis and cell differentiation. To test the hypothesis that p21 mediated the fibroblast growth factor effects on osteoblasts, we studied the differentiation of primary osteoblasts and osteoblastic cell lines derived from p21 null mice in the presence or absence of fibroblast growth factor. While the results obtained indicate that p21 is not the major mediator of the inhibition of osteoblast differentiation by fibroblast growth factor, we found that p21 per se acts as a brake on osteoblast proliferation and differentiation. p21 is strongly downregulated during differentiation and is highly expressed in osteoblastic cell lines expressing activated FGFR2, which do not differentiate. p21 null osteoblasts differentiate faster than wild-type cells, are more susceptible to the differentiation-promoting action of BMP-2, and undergo increased differentiation-related apoptosis. Furthermore, transient overexpression of p21 from an adenovirus vector delayed the onset of differentiation both in wild-type and in p21 null osteoblasts. These results highlight a new function for p21 in osteoblast differentiation.
Distinct Phases of Coordinated Early and Late Gene Expression in Growth Plate Chondrocytes in Relationship to Cell Proliferation, Matrix Assembly, Remodeling, and Cell Differentiation
Authors: Tchetina E , Mwale F , Poole Ar 
Published: April 2006

Abstract
Although much has been learned about growth plate development and chondrocyte gene expression during cellular maturation and matrix remodeling in the mouse, there has been a limited study of the interrelationships of gene expression between proteinases, growth factors, and other regulatory molecules in the mouse and in other species. Here we use RT-PCR of sequential transverse sections to examine the expression profiles of genes involved in chondrocyte growth, differentiation, matrix assembly, remodeling, and mineralization in the bovine proximal tibial growth plate. Specifically, we studied the expression of genes encoding COL2A1 and COL10A1, the latter a marker of cellular hypertrophy, the matrix metalloproteinases (MMP), MMP-13 and MMP-9, as well as the transcriptional factors, Sox9 and Cbfa1, the growth factors basic fibroblast growth factor (bFGF), parathyroid hormone-related peptide (PTHrP), transforming growth factor (TGF)β1, and β2, Indian hedgehog (Ihh), and the matrix protein osteocalcin. These were analyzed in relationship to cell division defined by cyclin B2 expression. Two peaks of gene expression activity were/observed. One was transient, limited, and located immediately before and at the onset of cyclin B2 expression in the early proliferative zone. The other was generally much more pronounced and was located in the early hypertrophic zone. The upregulation of expression of COL2A1, its transcriptional activator Sox9, osteocalcin, MMP-13, and TGFβ2 was observed immediately before and at the onset of cyclin B2 expression and also in the hypertrophic zones. The upregulation of COL10A1, Cbfa1, MMP-9, TGFβ-1, and Ihh gene expression was associated exclusively with the terminal differentiation of chondrocytes at the time of mineral formation in the extracellular matrix. In contrast, bFGF and PTHrP expression was observed in association with the onset of cyclin B2 expression and hypertrophy. This initial cluster of gene expression associated predominantly with matrix assembly and onset of cell proliferation is therefore characterized by expression of regulatory molecules distinct from those involved at hypertrophy. Together these results identify separate phases of coordinated gene expression associated with the development of the physis in endochondral bone formation.
Relationships Between Pharmacokinetics and Rate of Bone Turnover After Intravenous Bisphosphonate (Olpadronate) in Patients With Paget's Disease of Bone
Authors: Cremers Serge CLM , Eekhoff Marelise EMW , Den Hartigh Jan , Hamdy Neveen AT , Vermeij Pieter , Papapoulos Socrates E 
Published: April 2006

Abstract
Bisphosphonates are the treatment of choice of Paget's disease, but variable responses have been reported, and despite the availability of potent bisphosphonates, biochemical remission is not achieved in a substantial number of patients. This may, in part at least, be because of the influence of pharmacokinetics of bisphosphonates on their pharmacodynamics. That is the response of bone turnover to treatment. To address this issue, we examined the pharmacokinetics and pharmacodynamics of the bisphosphonate olpadronate given intravenously to 75 patients with Paget's disease, using a specific assay for olpadronate concentrations in serum and urine. The skeletal uptake of olpadronate varied greatly among patients and ranged between 10% and 90% of the administered dose. The two major determinants of skeletal uptake were renal function and prevalent rate of bone turnover. Serum and urinary data were well described by a physiology-based four-compartment pharmacokinetic model that takes into account the distribution of the bisphosphonate in the bone and its subsequent elimination. Bone turnover was suppressed to well within the normal range in virtually all patients. This, together with the absence of resolution of effect during 1 year, does not allow the construction of an adequate integrated pharmacokinetic/pharmacodynamic model. However, the pharmacokinetic model, described for the first time in Paget's disease, can accurately simulate the amount of bisphosphonate delivered to the skeleton with different dose regimens as well as the amount still present in bone after 1 year. Such approaches can lead to improved patient care and individualization of treatment of Paget's disease with bisphosphonates.
Randomized Trial of Physical Activity and Calcium Supplementation on Bone Mineral Content in 3- to 5-Year-Old Children
Authors: Specker Bonny , Binkley Teresa 
Published: April 2006

Abstract
A meta-analysis of adult exercise studies and an infant activity trial show a possible interaction between physical activity and calcium intake on bone. This randomized trial of activity and calcium supplementation was conducted in 239 children aged 3-5 years (178 completed). Children were randomized to participate in either gross motor or fine motor activities for 30 minutes/day, 5 days per week for 12 months. Within each group, children received either calcium (1000 mg/day) or placebo. Total body and regional bone mineral content by DXA and 20% distal tibia measurements by peripheral quantitative computed tomography (pQCT) were obtained at 0 and 12 months. Three-day diet records and 48-h accelerometer readings were obtained at 0, 6, and 12 months. Higher activity levels were observed in gross motor versus fine motor activity groups, and calcium intake was greater in calcium versus placebo (1354 ± 301 vs. 940 ± 258 mg/day, p &lt; 0.001). Main effects of activity and calcium group were not significant for total body bone mineral content or leg bone mineral content by DXA. However, the difference in leg bone mineral content gain between gross motor and fine motor was more pronounced in children receiving calcium versus placebo (interaction, p = 0.05). Children in the gross motor group had greater tibia periosteal and endosteal circumferences by pQCT compared with children in the fine motor group at study completion (p &lt; 0.05). There was a significant interaction (both p ≤ 0.02) between supplement and activity groups in both cortical thickness and cortical area: among children receiving placebo, thickness and area were smaller with gross motor activity compared with fine motor activity, but among children receiving calcium, thickness and area were larger with gross motor activity. These findings indicate that calcium intake modifies the bone response to activity in young children.