bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parathyroid Cells Cultured in Collagen Matrix Retain Calcium Responsiveness: Importance of Three-Dimensional Tissue Architecture
Authors: Ritter Cynthia S , Slatopolsky Eduardo , Santoro Samuel , Brown Alex J 
Published: April 2006

Abstract
Primary cultures of bovine parathyroid cells rapidly lose calcium responsiveness. Here, we show that bovine parathyroid cells grown in collagen coalesce into an organoid (“pseudogland”) with stable calcium responsiveness. These findings also illustrate the importance of 3-D cellular architecture in parathyroid gland function.
Introduction: The ability of extracellular calcium to suppress parathyroid hormone (PTH) secretion is quickly lost in primary monolayer cultures of bovine parathyroid cells. This has been attributed to a decrease in the expression of the cell surface calcium-sensing receptor (CaR), but other factors, including normal cell-to-cell interaction, may be critical. Here we describe a novel system for culturing bovine parathyroid cells that promotes re-formation of a three-dimensional (3-D) cellular architecture and re-establishment of calcium responsiveness.
Materials and Methods: Dispersed bovine parathyroid cells were cultured as monolayers or were mixed with type I collagen and placed in culture plates. CaR mRNA and the calcium regulation of PTH secretion were measured over a period of several weeks in parathyroid cells cultured both in collagen matrix and as monolayers. Calcium regulation of PTH mRNA was also investigated.
Results and Conclusions: Within 1–2 weeks in collagen culture, parathyroid cells coalesced into a small mass approximately 1–2 mm in size (referred to as a pseudogland). Suppression of PTH secretion by high calcium was blunted at 1 day in collagen, but returned within 1 week, and was retained through 3 weeks; the calcium set point (1.05 ± 0.04 mM) was similar to that reported for freshly dispersed cells. PTH mRNA was also suppressed by increasing extracellular calcium. CaR mRNA expression was decreased at 1 day in collagen and increased with time in culture, although never reaching the level found in dispersed cells. In bovine parathyroid cells cultured as monolayers, however, suppression of PTH by calcium was observed only at day 1 in culture. CaR mRNA content fell by 70% at day 1 but remained stable thereafter. Thus, a total loss of calcium responsiveness in monolayers was observed despite significant residual expression of CaR, suggesting that loss of the calcium response cannot be attributed solely to decreased CaR. In summary, the pseudogland model illustrates the importance of the 3-D cellular architecture in parathyroid gland function and provides a useful model in which to investigate calcium-mediated control of parathyroid gland functions, especially those requiring extended treatment.
A Unique Insertion/Substitution in Helix H1 of the Vitamin D Receptor Ligand Binding Domain in a Patient With Hereditary 1,25-Dihydroxyvitamin D-Resistant Rickets
Authors: Malloy Peter J , Xu Rong , Cattani Andreina , Reyes M Loreto , Feldman David 
Published: April 2006

Abstract
A young Chilean boy with severe rickets was found to have hereditary vitamin D-resistant rickets without alopecia. He had a unique insertion/substitution mutation in the ligand-binding domain of the vitamin D receptor. The in-frame mutation disrupted ligand binding and co-activator binding and resulted in 1,25(OH)2D3 resistance.
Introduction: Hereditary vitamin D-resistant rickets (HVDRR) is a genetic disorder caused by mutations in the vitamin D receptor (VDR). In this study, we examined the VDR in a young boy who exhibited the typical clinical features of HVDRR but without alopecia.
Materials and Methods: The patient's VDR was studied using cultured dermal fibroblasts, and the recreated mutant VDR was analyzed in transfected cells.
Results: The patient's fibroblasts were resistant to 1,25-dihydroxyvitamin D [1,25(OH)2D3], exhibiting only a slight induction of 24-hydroxylase gene expression when treated with 1 μM 1,25(OH)2D3. [3H]1,25(OH)2D3 binding was absent in cell extracts from the patient's fibroblasts. Sequence analysis of the VDR gene uncovered a unique 5-bp deletion/8-bp insertion in exon 4. The mutation in helix H1 of the ligand-binding domain deletes two amino acids (H141 and T142) and inserts three amino acids (L141, W142, and A143). In transactivation assays, the recreated mutant VDR was 1000-fold less active than the wildtype (WT) VDR. In glutathione S-transferase (GST) pull-down assays, the mutant VDR bound GST-retinoid X receptor (RXR) weakly in the absence of 1,25(OH)2D3; however, the binding did not increase with increasing concentrations of ligand. The mutant VDR did not bind to GST-vitamin D receptor interacting protein (DRIP) 205 at concentrations up to 1 μM 1,25(OH)2D3. We also examined effects of the three individual mutations on VDR transactivation. Only the insertion of A143 into the WT VDR disrupted VDR transactivation to the same extent observed with the natural mutation.
Conclusion: We describe a novel insertion/substitution mutation in helix H1 of the VDR ligand-binding domain (LBD) that abolishes ligand binding and result in the syndrome of HVDRR. This is the first time an insertion/substitution has been found as the defect-causing HVDRR.
Osteoblast-Like Cells From Estrogen Receptor α Knockout Mice Have Deficient Responses to Mechanical Strain
Authors: Jessop Helen L , Suswillo Rosemary FL , Rawlinson Simon CF , Zaman Gul , Lee Karla , Das-Gupta Vicky , Pitsillides Andrew A , Lanyon Lance E 
Published: April 2006

Abstract
Osteoblast-like cells in primary cultures derived from ERα−/− mice do not proliferate in response to mechanical strain, unlike those from their ERα+/+ littermates. ERα−/− cells also lack strain-related NO production and responsiveness to IGFs. Proliferative responsiveness to strain is rescued by transfection with functional ERα. ERα number or function in bone cells may limit bones' adaptability to mechanical loading.
Introduction: In vivo, bones' osteogenic response to mechanical loading involves proliferation of surface osteoblasts. This response is replicated in vitro and involves ERK-mediated activation of the estrogen receptor (ER) α and upregulation of estrogen response element activity. This proliferative response can be blocked by selective estrogen receptor modulators and increased by transfection of additional ERα.
Materials and Methods: We have now investigated the mechanisms of ER involvement in osteoblast-like cells' early responses to strain by comparing the responses of primary cultures of these cells derived from homozygous ERα knockout (ERKO) mice (ERα−/−) with those from their wildtype (ERα+/+) and heterozygous (ERα+/−) littermates and from ERβ knockout (BERKO) mice (ERβ+/+, ERβ+/−, and ERβ−/−).
Results: Whereas ERα+/+, ERα+/−, ERβ+/+, and ERβ−/− cells proliferate in response to a single 10-minute period of cyclic strain, ERα−/− cells do not. Transfection of fully functional, but not mutant, ERα rescues the proliferative response to strain in these cells. The strain-related response of ERα−/− cells is also deficient in that they show no increased activity of an AP-1 driven reporter vector and no strain-related increases in NO production. Their strain-related increase in prostacyclin production is retained. They proliferate in response to fibroblast growth factor-2 but not insulin-like growth factor (IGF)-I or IGF-II, showing the importance of ERα in the IGF axis and the ability of ERα−/− cells to proliferate normally in response to a mitogenic stimulus that does not require functional ERα.
Conclusions: These data indicate ERα's obligatory involvement in a number of early responses to mechanical strain in osteoblast-like cells, including those that result in proliferation. They support the hypothesis that reduction in ERα expression or activity after estrogen withdrawal results in a less osteogenic response to loading. This could be important in the etiology of postmenopausal osteoporosis.
Bone Morphogenetic Protein 2 Induces Cyclo-oxygenase 2 in Osteoblasts via a Cbfa1 Binding Site: Role in Effects of Bone Morphogenetic Protein 2 In Vitro and In Vivo
Authors: Chikazu Daichi , Li Xiaodong , Kawaguchi Hiroshi , Sakuma Yoko , Voznesensky Olga S. , Adams Douglas J. , Xu Manshan , Hoshi Kazuto , Katavic Vedran , Herschman Harvey R. , Raisz Lawrence G. , Pilbeam Carol C. 
Published: April 2006

Abstract
We tested the hypothesis that induction of cyclo-oxygenase (COX) 2 mediates some effects of bone morphogenetic protein (BMP) 2 on bone. BMP-2 induced COX-2 mRNA and prostaglandin (PG) production in cultured osteoblasts. BMP-2 increased luciferase activity in calvarial osteoblasts from mice transgenic for a COX-2 promoter-luciferase reporter construct (Pluc) and in MC3T3-E1 cells transfected with Pluc. Deletion analysis identified the -300/-213-bp region of the COX-2 promoter as necessary for BMP-2 stimulation of luciferase activity. Mutation of core-binding factor activity 1 (muCbfa1) consensus sequence (5′-AACCACA-3′) at -267/-261 bp decreased BMP-2 stimulation of luciferase activity by 82%. Binding of nuclear proteins to an oligonucleotide spanning the Cbfa1 site was inhibited or supershifted by specific antibodies to Cbfa1. In cultured osteoblasts from calvariae of COX-2 knockout (-/-) and wild-type (+/+) mice, the absence of COX-2 expression reduced the BMP-2 stimulation of both ALP activity and osteocalcin mRNA expression. In cultured marrow cells flushed from long bones, BMP-2 induced osteoclast formation in cells from COX-2+/+ mice but not in cells from COX-2−/− mice. In vivo, BMP-2 (10 μg/pellet) induced mineralization in pellets of lyophilized collagen implanted in the flanks of mice. Mineralization of pellets, measured by microcomputed tomography (μCT), was decreased by 78% in COX-2−/− mice compared with COX-2+/+ mice. We conclude that BMP-2 transcriptionally induces COX-2 in osteoblasts via a Cbfa1 binding site and that the BMP-2 induction of COX-2 can contribute to effects of BMP-2 on osteoblastic differentiation and osteoclast formation in vitro and to the BMP-2 stimulation of ectopic bone formation in vivo.
Suppressed Bone Turnover by Long-Term Bisphosphonate Treatment Accumulates Microdamage but Maintains Intrinsic Material Properties in Cortical Bone of Dog Rib
Authors: Komatsubara Satoshi , Mori Satoshi , Mashiba Tasuku , Li Jilliang , Nonaka Kiichi , Kaji Yoshio , Akiyama Tomoyuki , Miyamoto Kensaku , Cao Yongping , Kawanishi Jun , Norimatsu Hiromichi 
Published: April 2006

Abstract
Effects of long-term suppression of bone remodeling by bisphosphonate were investigated in cortical bone of dog rib. Although microdamage was accumulated, BMD was increased without increasing cortical bone area. Consequently, the intrinsic material properties were not reduced.
Introduction: Recently, we have reported that long-term suppression of bone remodeling increases microdamage accumulation but is not necessarily associated with vertebral fragility because of compensated increase of bone mass and improved microarchitecture. This study aimed to investigate the effect of long-term suppression of bone remodeling by bisphosphonate on the degree of mineralization, accumulation of microdamage, and mechanical properties of cortical bone in the same dogs.
Materials and Methods: Twenty-nine 1-year-old beagles (15 males, 14 females) were divided into three groups and treated daily with vehicle (CNT) or with incadronate at a dose of 0.3 (LOW) or 0.6 mg/kg/day (HIGH) orally for 3 years. After death, pQCT, histomorphometry, microdamage measurements, and three-point bending mechanical test were performed using the ninth rib.
Results: Cortical BMD was increased in the incadronate-treated groups. Cortical activation frequency was suppressed by 82% and 70% in HIGH and LOW, respectively, compared with CNT, without impairment of mineralization. Microdamage accumulation was increased in both incadronate-treated groups. Although there were no significant differences in total and cortical area among the three groups, structural mechanical properties were significantly increased after incadronate treatment while intrinsic material properties were not changed in the incadronate-treated groups.
Conclusion: This study suggests that long-term suppression of bone remodeling by bisphosphonate increases microdamage accumulation. However, this was not necessarily associated with a reduction of intrinsic material properties probably because of an increased degree of mineralization.
A Single-Dose Placebo-Controlled Study of AMG 162, a Fully Human Monoclonal Antibody to RANKL, in Postmenopausal Women
Authors: Bekker Pirow J , Holloway Donna L , Rasmussen Amy S , Murphy Robyn , Martin Steven W , Leese Philip T , Holmes Gregory B , Dunstan Colin R , DePaoli Alex M 
Published: April 2006

Abstract
The safety and bone antiresorptive effect of a single subcutaneous dose of AMG 162, a human monoclonal antibody to RANKL, was investigated in 49 postmenopausal women. AMG 162 is a potent antiresorptive agent for diseases such as osteoporosis.
Introduction: RANKL is an essential osteoclastic differentiation and activation factor.
Materials and Methods: The bone antiresorptive activity and safety of AMG 162, a fully human monoclonal antibody to RANKL, were evaluated in postmenopausal women in this randomized, double-blind, placebo-controlled, single-dose, dose escalation study. Six cohorts of eight to nine women were randomly assigned to receive a single subcutaneous injection of either AMG 162 or placebo (3:1 ratio). AMG 162 doses were 0.01, 0.03, 0.1, 0.3, 1.0, and 3.0 mg/kg. Subjects were followed up to 6 months in all cohorts and 9 months in the three highest dose cohorts. Second morning void urinary N-telopeptide/creatinine (NTX; Osteomark), serum NTX, and serum bone-specific alkaline phosphatase (BALP, Ostase) were assessed as bone turnover markers.
Results and Conclusions: Forty-nine women were enrolled. A single subcutaneous dose of AMG 162 resulted in a dose-dependent, rapid (within 12 h), profound (up to 84%), and sustained (up to 6 months) decrease in urinary NTX. At 6 months, there was a mean change from baseline of −81% in the 3.0 mg/kg AMG 162 group compared with −10% in the placebo group; serum NTX changes were −56% and 2%, respectively. BALP levels did not decrease remarkably until after 1 month, indicating that the effect of AMG 162 is primarily antiresorptive. Intact parathyroid hormone (PTH) levels increased up to ∼3-fold after 4 days in the 3.0 mg/kg dose group, but returned toward baseline with follow-up. Albumin-adjusted serum calcium did not decrease &gt;10% on average in any group, and no subject had values beiow 2 mmol/liter. AMG 162 was well tolerated. No related serious adverse events occurred. No clinically meaningful laboratory changes, other than those described above, were observed. In summary, a single subcutaneous dose of AMG 162 resulted in a dose-dependent rapid and sustained decrease from baseline in bone turnover and could be an effective and convenient treatment for osteoporosis.
Nitrogen-Containing Biphosphonates Inhibit the Mevalonate Pathway and Prevent Post-Translational Prenylation of GTP-Binding Proteins, Including Ras
Authors: Luckman Steven P. , Hughes David E. , Coxon Fraser P. , Russell R. Graham G. , Dr. Rogers Michael J. 
Published: April 2006

Abstract
Bisphosphonates are currently the most important class of antiresorptive drugs used for the treatment of metabolic bone diseases. Although the molecular targets of bisphosphonates have not been identified, these compounds inhibit bone resorption by mechanisms that can lead to osteoclast apoptosis. Bisphosphonates also induce apoptosis in mouse J774 macrophages in vitro, probably by the same mechanisms that lead to osteoclast apoptosis. We have found that, in J774 macrophages, nitrogen-containing bisphosphonates (such as alendronate, ibandronate, and risedronate) inhibit post-translational modification (prenylation) of proteins, including the GTP-binding protein Ras, with farnesyl or geranylgeranyl isoprenoid groups. Clodronate did not inhibit protein prenylation. Mevastatin, an inhibitor of 3-hydroxy-3-methylglutatyl (HMG)-CoA reductase and hence the bio-synthetic pathway required for the production of farnesyl pyrophosphate and geranylgeranyl pyrophosphate, also caused apoptosis in J774 macrophages and murine osteoclasts in vitro. Furthermore, alendronate-induced apoptosis, like mevastatin-induced apoptosis, could be suppressed in J774 cells by the addition of farnesyl pyrophosphate or geranylgeranyl pyrophosphate, while the effect of alendronate on osteoclast number and bone resorption in murine calvariae in vitro could be overcome by the addition of mevalonic acid. These observations suggest that nitrogen-containing bisphosphonate drugs cause apoptosis following inhibition of post-translational prenylation of proteins such as Ras. It is likely that these potent antiresorptive bisphosphonates also inhibit bone resorption by preventing protein prenylation in osteoclasts and that enzymes of the mevalonate pathway or prenyl protein transferases are the molecular targets of the nitrogen-containing bisphosphonates. Furthermore, the data support the view that clodronate acts by a different mechanism.
Use of Oral Corticosteroids and Risk of Fractures
Authors: Van Staa T. P. , Leufkens H. G. M. , Abenhaim L. , Zhang B. , Cooper C. 
Published: April 2006

Abstract
Treatment with oral corticosteroids is known to decrease bone density but there are few data on the attendant risk of fracture and on the reversibility of this risk after cessation of therapy. A retrospective cohort study was conducted in a general medical practice setting in the United Kingdom (using data from the General Practice Research Database [GPRD]). For each oral corticosteroid user aged 18 years or older, a control patient was selected randomly, who was matched by age, sex, and medical practice. The study comprised 244,235 oral corticosteroid users and 244,235 controls. The average age was 57.1 years in the oral corticosteroid cohort and 56.9 years in the control cohort. In both cohorts 58.6% were female. The most frequent indication for treatment was respiratory disease (40%). The relative rate of nonvertebral fracture during oral corticosteroid treatment was 1.33 (95% confidence interval [CI], 1.29–1.38), that of hip fracture 1.61 (1.47–1.76), that of forearm fracture 1.09 (1.01–1.17), and that of vertebral fracture 2.60 (2.31–2.92). A dose dependence of fracture risk was observed. With a standardized daily dose of less than 2.5 mg prednisolone, hip fracture risk was 0.99 (0.82–1.20) relative to control, rising to 1.77 (1.55–2.02) at daily doses of 2.5–7.5 mg, and 2.27 (1.94–2.66) at doses of 7.5 mg or greater. For vertebral fracture, the relative rates were 1.55 (1.20–2.01), 2.59 (2.16–3.10), and 5.18 (4.25–6.31), respectively. All fracture risks declined toward baseline rapidly after cessation of oral corticosteroid treatment. These results quantify the increased fracture risk during oral corticosteroid therapy, with greater effects on the hip and spine than forearm. They also suggest a rapid offset of this increased fracture risk on cessation of therapy, which has implications for the use of preventative agents against bone loss in patients at highest risk. (J Bone Miner Res 2000;15:993–1000)
Quantitative Trait Loci for Femoral and Lumbar Vertebral Bone Mineral Density in C57BL/6J and C3H/HeJ Inbred Strains of Mice
Authors: Beamer Wesley G. , Shultz Kathryn L. , Donahue Leah Rae , Churchill Gary A. , Sen Saunak , Wergedal Jon R. , Baylink David J. , Rosen Clifford J. 
Published: April 2006

Abstract
Significant differences in vertebral (9%) and femoral (50%) adult bone mineral density (BMD) between the C57BL/6J (B6) and C3H/HeJ (C3H) inbred strains of mice have been subjected to genetic analyses for quantitative trait loci (QTL). Nine hundred eighty-six B6C3F2 females were analyzed to gain insight into the number of genes that regulate peak BMD and their locations. Femurs and lumbar vertebrae were isolated from 4-month-old B6C3F2 females at skeletal maturity and then BMD was determined by peripheral quantitative computed tomography (pQCT). Estimates of BMD heritability were 83% for femurs and 72% for vertebrae. Genomic DNA from F2 progeny was screened for 107 polymerase chain reaction (PCR)–based markers discriminating B6 and C3H alleles on all 19 autosomes. The regression analyses of markers on BMD revealed ten chromosomes (1, 2, 4, 6, 11, 12, 13, 14, 16, and 18) carrying QTLs for femurs and seven chromosomes (1, 4, 7, 9, 11, 14, and 18) carrying QTLs for vertebrae, each with log10 of the odds ratio (LOD) scores of 2.8 or better. The QTLs on chromosomes (Chrs) 2, 6, 12, 13, and 16 were unique to femurs, whereas the QTLs on Chrs 7 and 9 were unique to vertebrae. When the two bone sites had a QTL on the same chromosome, the same marker had the highest, although different, LOD score. A pairwise comparison by analysis of variance (ANOVA) did not reveal significant gene × gene interactions between QTLs for either bone site. BMD variance accounted for by individual QTLs ranged from 1% to 10%. Collectively, the BMD QTLs for femurs accounted for 35.1% and for vertebrae accounted for 23.7% of the F2 population variances in these bones. When mice were homozygous c3/c3 in the QTL region, 8 of the 10 QTLs increased, while the remaining two QTLs on Chrs 6 and 12 decreased, femoral BMD. Similarly, when mice were homozygous c3/c3 in the QTL region for the vertebrae, five of the seven QTLs increased, while two QTLs on Chrs 7 and 9 decreased, BMD. These findings show the genetic complexity of BMD with multiple genes participating in its regulation. Although 5 of the 12 QTLs are considered to be skeleton-wide loci and commonly affect both femurs and vertebrae, each of the bone sites also exhibited unique QTLs. Thus, the BMD phenotype can be partitioned into its genetic components and the effects of these loci on normal bone biology can be determined. Importantly, the BMD QTLs that we have identified are in regions of the mouse genome that have known human homology, and the QTLs will become useful experimental tools for mechanistic and therapeutic analyses of bone regulatory genes.
Usability Engineering von elektronischen Programmführern (EPGs) (Usability Engineering of Electronic Programme Guides (EPGs))
Authors: Elster Johanna , Huber Patrick 
Published: April 2006

Zusammenfassung
In diesem Beitrag werden elektronische Programmführer (EPGs) und ihre Bedeutung als Navigatoren für das interaktive Fernsehen vorgestellt. Neben einer Übersicht der verschiedenen Modelle werden der Nutzerhintergrund und daraus abgeleitete Anforderungen beschrieben. Diese stellen zusätzlich zu technischen Beschränkungen spezifische Herausforderungen an die Gestaltung von EPGs dar, die in einer Auswahl kritischer Usability-Aspekte beleuchtet werden.
aonDigital TV — iTV am Beispiel Telekom Austria (aonDigital TV — iTV at Telekom Austria)
Authors: Huemer Birgit 
Published: April 2006

Zusammenfassung
In diesem Praxisbericht wird die Entwicklung von interaktivem digitalem Fernsehen (iTV) in der Telekom Austria vorgestellt. Dabei zeigt der Bericht, wie mit zwei umfangreichen Usertests das Produkt verbessert werden konnte. Detaillierte Ergebnisse veranschaulichen, worauf die NutzerInnen in der Interaktion mit der grafischen Oberfläche und der Fernbedienung ihren Fokus legen, welche Schwierigkeiten in der Bedienung aufgetreten sind und wie in Folge das Design angepasst wurde, um eine qualitativ möglichst hohe Bedienbarkeit zu erreichen. Dieser Beitrag liefert einen Überblick über den Entwicklungsprozess und die wichtigsten Erkenntnisse aus den beiden Usability-Tests.