bluuebunny/crossref_metadata_2025_split huggingface dataset:
Urinary hydroxypyridinium crosslinks of collagen in population-based screening for overt vertebral osteoporosis: Results of a pilot study
Authors: Seibel M.J. , Woitge H. , Scheidt-Nave C. , Leidig-Bruckner G. , Duncan A. , Nicol P. , Ziegler R. , Robins S.P. 
Published: February 2010

Abstract
The urinary pyridinium crosslinks pyridinoline (PYD) and deoxypyridinoline (DPD) have been shown to provide valid indices of bone resorption. At present, both crosslink components are determined by reversed-phase HPLC, a time-consuming method precluding the use of these markers for routine purposes. Therefore, efforts have been made to develop simple immunoassays for the rapid measurement of urinary crosslinks, and their application to large-scale osteoporosis screening has been proposed. To evaluate the applicability and diagnostic validity of pyridinium crosslink measurements for screening purposes, urinary concentrations of total and free PYD and DPD were determined by HPLC and immunoassay technique (ELISA) in a sample of 269 individuals (male to female ratio = 130:139; age 50-81 years) recruited at random within a population survey of vertebral osteoporosis. On a molar basis, ELISA measures of crosslink-related epitopes were highly correlated with both total and free PYD and DPD as determined by HPLC (r &gt; 0.82, p &lt; 0.001). Age-specific means for creatinine-corrected total and free pyridinium crosslinks were significantly higher in females than in males (p &lt; 0.001). In both sexes, neither age nor anthropometric variables (weight, height, and body mass index) showed a linear effect on the urinary crosslink/creatinine ratio. On average, 50% of the total amount of urinary crosslinks were present in free form. For both PYD and DPD, this proportion was significantly higher in women than in men (p &lt; 0.05), but no change was observed with age or anthropometric measures. The excretion of pyridinium crosslinks was higher in osteoporotic (n = 18) than in nonosteoporotic individuals (n = 208) from the same population. However, this difference was statistically significant (p &lt; 0.05) only for total PYD, total DPD, and free DPD as determined by HPLC, whereas no significant difference was seen with the ELISA. However, ROC analysis showed none of the crosslink measurements to provide sufficient diagnostic validity for screening purposes with regard to vertebral osteoporosis. Our results demonstrate that (1) the immunoassay technique provides measurements of pyridinium crosslinks that are highly correlated with HPLC findings; (2) beyond age 50, urinary concentrations of total and free pyridinium crosslinks are not linearly influenced by age or anthropometric factors but change with sex independently of osteoporotic status; and (3) although pyridinium crosslink excretion provides a valid and clinically useful measure of bone resorption, a single determination lacks the sensitivity necessary to screen successfully for vertebral osteoporotic fractures.
Improved method for analysis of whole bone torsion tests
Authors: Levenston Marc E. , Beaupré Gary S. , van der Meulen Marjolein C. H. 
Published: February 2010

Abstract
Structural tests, such as whole bone torsion tests, have become widely accepted methods for assessing average bone material properties. To simplify interpretation of these tests, the nonuniform bone geometry is often analyzed as a tube with a constant cross section (prismatic) and the areal properties of the smallest bone section. This approach may not adequately represent the true torsional behavior of the cross section and does not account for any lengthwise variations in bone geometry. The errors introduced by these approximations are particularly significant when comparing bones of different sizes and geometries. In this paper, we examine the effects of approximating the cross-sectional torsional behavior and of neglecting lengthwise variations in bone geometry. We then present a simple, standardized procedure utilizing a FORTRAN computer program for accurate determination of material properties. We examine first simple idealized bone geometries and then a complex three-dimensional model of the femur from a 26-day-old male Sprague-Dawley rat. For these models, the conventional methods for interpreting torsion tests introduce errors of up to 42% in the shear modulus and up to 48% in the maximum shear stress; a straightforward extension of these methods reduces the errors to within 3%.
Regulation of protein kinase C by transforming growth factor β1 in rat costochondral chondrocyte cultures
Authors: Sylvia V.L. , Mackey S. , Schwartz Z. , Schuman L. , Gomez R. , Boyan B.D. 
Published: February 2010

Abstract
Transforming growth factor β (TGF-β) regulates the proliferation and differentiation of chondrocytes; however, the mechanism of TGF-β signal transduction remains unclear. We examined whether the response to TGF-β is mediated by protein kinase C activity in chondrocytes at different stages of maturation. The aims were to examine the effect of recombinant human TGF-β1 (rhTGF-β1) on protein kinase C in rat costochondral chondrocyte cultures; determine the major isoform present; assess the involvement of phospholipase C or tyrosine kinases; determine whether genomic or nongenomic pathways are involved; and test whether these mechanisms differ as a function of the stage of cell maturation. Dose-dependent increases in protein kinase C activity were observed in confluent, fourth-passage cultures of rat costochondral growth zone and resting zone chondrocytes treated with rhTGF-β1. In growth zone cells, elevated activity was observed at 12 h and decreased markedly by 24 h. In resting zone cells, elevated activity was observed at 9 h, maximum stimulation occurred at 12 h, and activity returned to baseline levels after 48 h. Immunoprecipitation studies showed protein kinase C α is the major isoform present in both untreated and treated cells. Neither the phospholipase C inhibitor, U73122, nor the tyrosine kinase inhibitor, genistein, significantly reduced the protein kinase C response to rhTGF-β1. Actinomycin D and cycloheximide, inhibitors of transcription and translation, produced dose-dependent inhibition of rhTGF-β1 stimulated protein kinase C activity in both resting zone and growth zone chondrocytes. The time course of activation and insensitivity to U73122 suggest that phospholipase C-mediated events are not involved in rhTGF-β1 stimulation of protein kinase C in costochondral chondrocytes. Similarly, because genistein had no effect, tyrosine kinases are not implicated. Rather, the reduction in protein kinase C activity observed when rhTGF-β1 is administered along with actinomycin D or cycloheximide indicates that new gene expression and protein synthesis are required for the response. These results indicate that the effect of rhTGF-β1 is mediated by protein kinase C; however, it is very slow and may require new protein kinase C production, perhaps via a cytokine cascade. Moreover, the classic mechanism of activation of protein kinase C by phospholipase C was not found, suggesting a novel mechanism of activation. Finally, the effects of rhTGF-β1 on protein kinase C are dependent on the state of cell maturation with respect to onset and duration of response.
In situ hybridization to show sequential expression of osteoblast gene markers during bone formation in vivo
Authors: Zhou H. , Choong P. , McCarthy R. , Chou S.T. , Martin T.J. , DR. Ng Kong Wah 
Published: February 2010

Abstract
We investigated the sequence of expression of osteoblast gene markers during bone formation in vivo by in situ hybridization. Cylindrical lesions were induced in the femora of sheep with titanium analytic bone implants that allow removal of serial core samples to study bone formation. At 2 weeks (2W), granulation tissue made up of spindle-shaped cells had partially replaced the blood clot. Islands of osseous tissue, first noted in the periphery of the ingrowing tissue at 3W, became the predominant tissue by 6W. The surfaces of newly forming bone at 3W were apposed by cuboidal cells, which in some areas were several layers thick. By 6W, most of the cells lining bone trabeculae had assumed a flattened morphology. The temporal and spatial distribution of osteoblast gene markers was examined by in situ hybridization with nonradioactive digoxigenin probes for α1(I) procollagen, alkaline phosphatase (ALP), osteopontin (OP), and bone Gla protein (BGP). The spindle-shaped cells in the granulation tissue expressed mRNA for α1(I) procollagen, ALP, and OP but not BGP, suggesting that they may be osteoblast precursor cells. α1(I) procollagen mRNA was strongly expressed by all cells on the surface of bone, with a peak intensity at 3W and then reducing sharply by 6W. Initially, only pockets of cuboidal cells on bone surfaces expressed ALP mRNA, with a peak intensity at 5W. Similarly, only a proportion of cuboidal cells expressed OP mRNA early in bone formation, but the number of cells expressing OP mRNA increased with time. Clumps of cuboidal cells expressed BGP mRNA only when bone was present, and the degree of expression increased with the amount of bone formed. This model allows the study of temporal and spatial sequence of gene expression in cells participating in osteogenesis. The temporal sequence is similar to that shown in vitro in other models of mineralization. The geographic localization of cells expressing mRNA for α1(I) procollagen, ALP, OP, and BGP implies subspecialization of osteoblasts in bone formation.
Universal standardization for dual X-ray absorptiometry: Patient and phantom cross-calibration results
Authors: Genant Harry K. , Grampp Stephan , Glüer Claus C. , Faulkner Kenneth G. , Jergas Michael , Engelke Klaus , Hagiwara Satoshi , van Kuijk Cornelis 
Published: February 2010

Abstract
The comparison of patient data among different dual x-ray absorptiometry (DXA) scanners is complicated because no universally accepted cross-calibration procedure or standard currently exists. This study was performed under the auspices of the International DXA Standardization Committee to establish appropriate cross-calibration parameters. Posteroanterior (PA) lumbar spine measurements of 100 women, ages 20–80 years (mean 52.6 + 16, range of BMD = 0.4–1.6 g/cm2) were obtained on a Norland XR26 Mark II, a Lunar DPX-L, and a Hologic QDR 2000 densitometer using standard procedures (pencil beam mode for all three scanners). Area, BMC, and BMD results from the different scanners were compared for all patients. In addition, the European spine phantom (ESP) and the European spine phantom prototype (ESP prototype), as well as standard phantoms from all three manufacturers, were evaluated on the three systems. To achieve universal scanner calibration, we used the intercept and slope of the patient's correlations and the value of the middle vertebra of the ESP as a reference point in a series of standardization formulas, and we have expressed the results as sBMD (mg/cm2). The correlations of the patients' spinal BMD values were excellent for each of the three scanner pairs. The average absolute difference in patient spinal BMD values (L2–4) between Hologic and Norland was 0.012 g/cm2 (1.3%); it was 0.113 g/cm2 (11.7%) between Hologic and Lunar and 0.118 g/cm2 (12.2%) between Norland and Lunar. The phantoms' regression lines approximated those of the patient regression lines, and the phantoms with only one measurement point were very close to the patients' regression lines. After applying the standardization formulas, the average absolute differences for the 100 patients were 28 mg/cm2 (2.7%) for Hologic/Norland, 23 mg/cm2 (2.2%) for Hologic/Lunar, and 29 mg/cm2 (2.8%) for Norland/Lunar. Average BMD results for the patients before correction were 0.972 g/cm2 for Hologic, 1.100 g/cm2 for Lunar, and 0.969 g/cm2 for Norland. After correction, sBMD results for patients were 1045 mg/cm2 for Hologic, 1047 mg/cm2 for Lunar, and 1043 mg/cm2 for Norland. The standardization approach as performed in our study provided compatibility of DXA results obtained on different scanners.
Localization of the mRNA for bone matrix proteins during fracture healing as determined by in situ hybridization
Authors: Hirakawa Kimiaki , Hirota Sehchi , Ikeda Tohru , Yamaguchi Akira , Takemura Teiji , Nagoshi Junsuke , Yoshiki Shusaku , Suda Tatsuo , Kitamura Yukihiko , Nomura Shintaro 
Published: February 2010

Abstract
The expression of the mRNAs for osteonectin (ON), osteopontin (OPN), osteocalcin (OC), and matrix Gla protein (MGP) was studied by in situ hybridization during the healing process of an experimental fracture in adult rat femora. At day 1 postoperatively, ON mRNA was detected in the proliferating periosteum. At day 3, ON, OPN, and OC mRNAs were detected in woven bone. From day 5, MGP and ON mRNAs were detected in the immature chondrocytes. From day 7, ON, OPN, and OC mRNAs were detected in the osteoblastic cells in newly formed endosteal trabecular bone. OPN mRNA was also detected in some of the osteocytes in trabecular bone. From day 14, OPN and MGP mRNAs were detected in newly formed periosteal hypertrophic chondrocytes, and the ON, OPN, and OC mRNAs were detected in osteoblastic cells in newly formed periosteal trabecular bone. Although the cell types that expressed each mRNA in fractured bones were similar to those in embryonic bones, the time course of these mRNA expression in fractured bones was different from that in embryonic bones. We considered that this system is useful to investigate the phenotypic change in osteogenic and chondrogenic lineage cells that appears during fracture healing at the molecular level.
Effects of free mobilization and low- to high-intensity treadmill running on the immobilization-induced bone loss in rats
Authors: Kannus Pekka , Sievänen Harri , Järvinen Teppo L.N. , Järvinen Markku , Kvist Martti , Oja Pekka , Vuori Ilkka , Jozsa Laszlo 
Published: February 2010

Abstract
After an immobilization period of 3 weeks, the effects of free remobilization (8 weeks) as well as low- and high-intensity treadmill running on the bone mineral content (BMC) and density (BMD) of the hindlimbs of Sprague-Dawley rats (n = 70) were studied using a dual-energy x-ray absorptiometric scanner. In the low-intensity running program, the rats were allowed to move freely in the cage for 1 week, after which they started to run on a treadmill twice a day for 7 weeks. The speed of the treadmill was 20 cm/s, with an uphill inclination of 10°. The running time was gradually increased from 20 minutes per session to 45 minutes per session. In the high-intensity group, the program was similar, with the exception that the speed of the treadmill was 30 cm/s, with an uphill inclination of 30°. Immobilization for 3 weeks produced a significant BMC and BMD loss in the immobilized left femur and tibia (mean loss 9.6%, p &lt; 0.001) but did not affect the right free limbs. Both low- and high-intensity running restored mineral content in the immobilized limb; however, an average 5% difference (p &lt; 0.05) in mineral content of the right and left limb bones persisted. In the running groups, the values for the immobilized left limbs were at the same level or exceeded (range 3.8–11.6%, p &lt; 0.05–0.01) and those of the free right limbs exclusively exceeded (range 5.3–15.9%, p &lt; 0.05–0.01) the corresponding values of the age-matched control rats. In the group with free remobilization, the BMCs and BMDs always remained below those in the controls (range –3.2 to –12.6%, p values ranging from NS to p &lt; 0.01). Thus, this study showed the need for greater than normal activity to restore the BMC and BMD from disuse to normal.
Determinants of endogenous fecal calcium in healthy women
Authors: Heaney Robert P. , Recker Robert R. 
Published: February 2010

Abstract
Endogenous fecal calcium (EFC) excretion was measured in 518 studies in 191 normal perimenopausal women, most studied two to three times over a 15 year period. EFC averaged 102 + 25 mg/day. Absorption fraction was simultaneously determined by both double-isotope and balance methods. EFC was found to vary inversely with absorption fraction, and the observed relationship was used to calculate the total amount of calcium (TIC) entering the gut from endogenous sources. TIC averaged 140 + 34 mg/day and was found to be correlated with a number of intake and body size variables. Phosphorus intake was the most strongly correlated of all the variables (r = 0.404; P &lt; 0.0001), each increment of 0.1 g phosphorus intake being associated with an increase in TIC of 6 mg. Lean body mass was the best correlated of the body size variables, with TIC rising by 1.6 mg/day for every kg lean mass. There were also small but significant correlations with protein and energy intakes, the latter suggesting that some of the variation of TIC is related to the amount of food consumed. Caffeine, previously reported as elevating TIC, did not exhibit a significant relationship in this study.
Comparison of two parathyroid hormone assays for the rat: The new immunoradiometric and the older competitive binding assay
Authors: Jara Aquiles , Bover Jordi , Lavigne Jeffrey , Felsenfeld Arnold 
Published: February 2010

AbstractA competitive binding assay for parathyroid hormone (PTH INS) has been used since 1986 to measure PTH in rats. During the past year an immunoradiometric assay for the measurement of PTH (PTH IRMA) in the rat was developed. The purpose of the present study was to compare results obtained with the PTH INS and IRMA and to provide a framework for comparison for investigators who have used the PTH INS in previous studies. A total of 99 rats were studied; 27 rats had normal renal function, and 72 rats had surgically induced renal failure. In the azotemic rats, the magnitude of hyperparathyroidism was varied by changing the calcium and phosphorus composition of the diet. The correlation between the two PTH assays in the 99 rats was r = 0.98, p &lt; 0.001. For the 27 rats with normal renal function, the correlation even within the narrow range of normal PTH values was significant, r = 0.71, p &lt; 0.001. In the 72 azotemic rats, in which the highest INS PTH value was approximately 17 times normal, the correlation between the two PTH assays was r = 0.98, p &lt; 0.001. The PTH IRMA provides distinct advantages, such as extended standard range, shortened incubation time, increased sensitivity, and technical simplicity, but our results indicate that the PTH INS provided an accurate measurement of PTH. Furthermore, our results should provide investigators who have used the PTH INS in previous studies with a framework for comparison with studies in which the PTH IRMA was used.
Effects of transforming growth factor β2 on the regulation of osteocalcin synthesis in human mg-63 osteosarcoma cells
Authors: Pirskanen Asta , Jääskeläinen Tuna , Mäenpää Pekka H. 
Published: February 2010

Abstract
Treatment of human MG-63 osteosarcoma cells with human recombinant transforming growth factor β1 (TGF-β1) was found to inhibit cell proliferation. In addition, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-induced osteocalcin synthesis was greatly influenced by TGF-β1. Dose- and time-dependent inhibition was seen both in medium osteocalcin and the corresponding mRNA concentrations. Furthermore, TGF-β1 decreased osteocalcin synthesis modulated negatively by dexamethasone or positively by retinoic acid. The stability of osteocalcin mRNA was not decreased by the TGF-β1 treatment, but in vitro transcription assays demonstrated diminished osteocalcin gene transcription caused by the TGF-β1 treatment. Binding of vitamin D receptor (VDR) to an oligonucleotide probe containing the osteocalcin vitamin D response element (VDRE) was not influenced by TGF-β1, however. Incubation of the cells with the serine/threonine kinase inhibitor H-7 did not block the ability of TGF-β1 to decrease osteocalcin synthesis but caused a further inhibition. Also, the 1,25(OH)2D3-induced osteocalcin synthesis was decreased by H-7 treatment, suggesting that phosphorylation as such is involved in the transcriptional activation mechanism of VDR. These results demonstrate that TGF-β1 is a strong inhibitor of the synthesis of osteocalcin, a calcium binding protein participating in bone mineralization, by counteracting the stimulatory effects of other hormones on its synthesis. We further suggest that TGF-β1 affects the synthesis of osteocalcin at the level of transcription through mechanism(s) different from the serine/threonine kinase pathway.
Platelet-activating factor induces pseudopod formation in calcitonin-treated rabbit osteoclasts
Authors: Gravel Michel R. , Zheng Zhu Gang , Sims Stephen M. , Dr. Dixon S. Jeffrey 
Published: February 2010

AbstractWe demonstrated previously that platelet-activating factor (PAF), a potent inflammatory mediator, acts on osteoclasts to elevate cytosolic [Ca2+] and stimulate resorption. However, it is not clear whether the effects of PAF on resorptive activity are direct or indirect. In the present study, we investigated the effects of PAF on osteoclast motility. Osteoclasts were isolated from the long bones of neonatal rabbits, and cell motility and morphology were monitored using time-lapse video microscopy. Calcitonin, a hormone known to induce retraction of pseudopods and inhibit resorptive activity, was used to render osteoclasts quiescent. Within 10 minutes of calcitonin treatment (100 ng/ml, final), pronounced retraction of pseudopods was observed in 68 of 112 cells tested. When PAF (200 nM, final) was added 10 minutes after calcitonin treatment, pseudopods were evident 1 h later in 15 of 37 calcitonin-responsive cells tested. In contrast, pseudopods were evident in only 4 of 31 calcitonin-responsive cells treated with control solutions (PAF-vehicle or S-PAF, the biologically inactive stereoisomer of PAF). Pseudopod formation was quantified by measuring the planar area of pseudopods with a computer-based video analysis system. When assessed 60 minutes following PAF treatment, the pseudopod area was significantly greater in PAF-treated cells than in control cells. In some calcitonin-treated osteoclasts, PAF induced pseudopod formation when applied focally using an extracellular micropipette, consistent with a direct action of PAF. We conclude that PAF directly induces pseudopod formation in calcitonin-inhibited osteoclasts, a morphologic response indicative of osteoclast activation.
Three-dimensional type I collagen gel system for the study of osteoblastic metastases produced by metastatic prostate cancer
Authors: Koutsilieris M. , Sourla A. , Pelletier G. , Doillon C.J. 
Published: February 2010

AbstractWe developed a three-dimensional type I collagen gel cell culture system that allows coculturing of human MG-63 osteoblast-like cells and various human cancer cells. Inoculation of human PC-3 metastatic prostate cancer cells into this type I collagen gel containing human MG-63 osteoblast-like cells produced an osteoblastic-like reaction that presented as an increased number of MG-63 cells and increased density of type I collagen around MG-63 cells adjacent to inoculated PC-3 cells by microscope analysis. Under identical experimental conditions, inoculation of cell-free medium, human KLE endometrial adenocarcinoma cells, and Calu-1 lung cancer cells did not produce this blastic-like reaction. In situ hybridization documented the uniform expression of insulin-like growth factor I (IGF-I) and of urokinase-type plasminogen activator (uPA) mRNA in MG-63 and PC-3 cells separately cultured in this substrata. The uniform expression of uPA was also documented by immunocytochemistry using a monoclonal and a polyclonal antihuman uPA antibody. The relative expression of uPA was higher in PC-3 cells than in MG-63, KLE, and Calu-1 cancer cells. We conclude that this novel cell culture system may become a useful model to study the pathophysiology of the osteoblastic reaction in vitro.