bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bone resorption and response to calcium-regulating hormones in the absence of tissue or urokinase plasminogen activator or of their type 1 inhibitor
Authors: Leloup Gaetane , Lemoine Pascale , Carmeliet Peter , Dr. Gilbert Vaes  
Published: February 2010

Abstract
Plasminogen activators (PA) are implicated in cell migration and tissue remodeling, two componets of the bone resorption processes. Uning mice with inactivated tissue PA (tPA), urokinase PA (uPA), or type 1 PA inhibitor (PAI-1) genes, we evaluated whether these processes, or their stimulation by parathyroid hormone (PTH) or 1,25-dihydroxyvitamin (1,25{oH}2D3) are dependent on these genes. Two culture models were used, one involving 19-day fetal calvariae, to evaluate the direct resorptive activity of osteoclasts, and the other involving 45Ca-labeled 17-day fetal metatarsals, in which this activity depends on preliminary (pre)osteoclast migration. PTH similarly increased (about 10-fold) PA activity in calvariae from wild-type tPA+/+ and uPA+/+ or deficient uPA−/− and PAI−/− mice; it affected only tPA, not uPA. In tPA−/− bones, the low PA levels, due to uPA, were not influenced by PTH. Calcitonin did not affect PA responses to PTH. No differences were observed between tPA+/+, tPA−/−, uPA+/+, and uPA−/− calvariae for any parameter related to bone resorption (development of lacunae, release of calcium and lysosomal enzymes, accumulation of collagenase, loss of hydroxyproline), indicating similar responses to PTH or calcitonin. The progressive 45Ca release was largely similar in cultures of tPA+/+, tPA−/−, uPA+/+ uPA−/−, PAI+/+, or PAI−/− metatarsals and it was similarly enhanced by PTH or 1,25(OH)2D3. However, uPA−/− metatarsals released 45Ca at a slower rate at the beginning of the cultures, suggesting an impaired recruitment of the (pre)osteoclasts, which migrate at that time from the periosteum into the calcified cartilage. Thus, it appears that the direct resorptive activity of the osteoclasts does not necessitate the presence of either tPA or uPA, but uPA is likely to facilitate the migration of the (pre)osteoclasts toward the mineralized surfaces. Although considerably enhanced by PTH, tPA does not mediate the actions of PTH (nor of 1,25{OH}2D3) evaluated in these models.
Epitope mapping of nine monoclonal antibodies against osteocalcin: Combinations into two-site assays affect both assay specificity and sample stability
Authors: Hellman Jukka , Käkönen Sanna-Maria , Matikainen Marja-Terttu , Karp Matti , Lövgren Timo , Väänänen H. Kalervo , Pettersson Kim 
Published: February 2010

Abstract
Nine monoclonal antibodies (Mabs) were raised against human recombinant osteocalcin fusion protein (rGST-hOC) or bovine osteocalcin (bOC) and selected to develop two-site immunoassays for human osteocalcin (hOC). The detection system was based on the time-resolved measurement of the fluorescence of europium chelates conjugated to the tracer Mabs. Based on the ability of the Mabs to recognize different forms of hOC (carboxypeptidase Y-digested, alkylated hOC, thermally decarboxylated hOC, recombinant forms of hOC, and tryptic peptides derived from hOC) and the information obtained from combinations of the Mabs in two-site assays, an epitope map was created. The epitope map was useful in understanding the behavior of the two-site combinations of the Mabs with serum samples. The two-site combinations could be divided into subgroups detecting either full-length hOC or full length + large NH2-terminal fragment as simulated by the carboxypeptidase Y-digested form of hOC (it lacks four COOH-terminal residues), which with intact specific assays showed cross-reactivities ranging from 7 to 14% when compared with full-length hOC. In addition, differences were observed in the ability of the combinations to detect thermally decarboxylated hOC (lacks γ-carboxylation at residues 17, 21, and 24) with cross-reactivities ranging from 8 to 85% when compared to γ-carboxylated hOC. The analysis of human serum samples showed considerable differences in the concentration and stability of serum OC. This was attributed as the varying ability of the Mabs to detect different proteolytic fragments derived from hOC and/or differences in the degree of γ-carboxylation of hOC. The in vitro generation of the large NH2-terminal fragment during incubation of the serum samples at room temperature (RT) and during prolonged storage at −20°C in an undercooled state was detectable as loss of immunoreactivity (ranging from −42 ± 17 to −50 ± 15% in 16 h at RT, n = 3) with Mab combinations detecting only full-length hOC. Two-site combinations detecting full-length + large NH2-terminal fragment showed no loss of immunoreactivity after incubation of the serum samples at RT for 16 h. With all assays, an increase of serum OC ranging from 16 to 38% was found in postmenopausal samples (n = 24) when compared with premenopausal samples (n = 17), but the degree of statistical significance varied from not significant to p &lt; 0.01.
Factors associated with bone mineral density in middle-aged men
Authors: Bendavid Eli J. , Shan Jun , Barrett-Connor Elizabeth 
Published: February 2010

Abstract
This cross-sectional population-based study examined the association of anthropometric and lifestyle risk factors with bone mineral density (BMD) in 218 white ambulatory men aged 50–64 from the Rancho Bernardo, California cohort. BMD was measured at the lumbar spine and hip using dual-energy X-ray absorptiometry and at the ultradistal wrist and midshaft radius of the forearm using single-photon absorptiometry. Body mass index (BMI) was significantly correlated with BMD at all four skeletal sites. Overall, 17.0% of men aged 55–64 were osteopenic (BMD ≥ 2 SD below the distribution for ages 50–54) at one skeletal site, 16.5% were osteopenic at two sites, and 13.6% were osteopenic at three or more sites. Men who reported regular exercise had significantly higher BMD levels at the spine and hip. Men meeting the recommended daily allowance (RDA) for calcium intake (≥800 g/day) had significantly higher BMD levels at the spine and wrist. Alcohol intake and smoking were associated with differences of borderline significance in BMD at the spine. In analyses adjusted for BMI, weight change, exercise, smoking, drinking, and calcium intake, there was a significant independent age-related decline in BMD at the hip (0.008 g/cm2/year; p = 0.001), at the wrist (0.004 g/cm2; p &lt; 0.01), at the forearm (0.006 g/cm2; p &lt; 0.01), but not at the spine (0.005 g/cm2). These data, although cross-sectional, strongly suggest that age-related bone loss occurs in middle-aged men and that both physical activity and an adequate calcium intake are associated with better bone density.
Abnormal modulation of serum osteocalcin by dietary phosphate and 1,25-dihydroxyvitamin D3 in the hypophosphatemic mouse
Authors: Tsuji H. , Cawthorn C. , Ecarot B. 
Published: February 2010

Abstract
We evaluated in normal and hypophosphatemic (Hyp) mice whether changes in serum levels of osteocalcin in response to dietary phosphate supplementation, parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) administration were related to perturbations in calcium phosphate homeostasis. In normal mice, serum osteocalcin levels were not altered by phosphate supplementation. In contrast, phosphate supplementation in Hyp mice led to a 2-fold decrease in serum osteocalcin to normal levels after 3 days and to an increase in osteocalcin levels after 14 days. The decrease in osteocalcin was associated with normophosphatemia, severe hypocalcemia, and marked increases in circulating 1,25(OH)2D3 levels, whereas the increase in osteocalcin levels was associated with normophosphatemia and no change in serum calcium and 1,25(OH)2D3. Administration of PTH decreased serum osteocalcin in both genotypes. Infusion of 1,25(OH)2D3 for 3 days elicited increases in serum osteocalcin and calcium levels in normal mice, whereas in Hyp mice it produced significant decreases in osteocalcin levels and no change in serum calcium. However, with a more prolonged infusion of 1,25(OH)2D3, hypercalcemia and increases in serum osteocalcin were induced in mutant mice. Our results suggest that the abnormal osteocalcin response of Hyp mice is not directly attributable to an osteoblast dysfunction but is secondary, at least in part, to perturbations in factors that modulate the osteoblast activity, especially serum calcium and/or PTH.
Anabolic effects of prostaglandins in cultured fetal rat calvariae: Structure-activity relations and signal transduction pathway
Authors: Woodiel Florence N. , Fall Pamela M. , Raisz Lawrence G. 
Published: February 2010

AbstractThe structure-activity relations and signal transduction pathways for the anabolic effects of prostaglandins were examined in cultured fetal rat calvariae. In the presence of cortisol prostaglandins of the E and F series (10−9 to 10−5 M) produced a dose-related increase in [3H]thymidine incorporation up to 4-fold at 24 h. Prostaglandin E2 (PGE2) was also effective in the absence of cortisol. Butaprost (10−6 M), a selective EP-2 receptor agonist, produced partial stimulation. Prostaglandin D2, prostacyclin, sulprostone, an EP-1 and EP-3 receptor agonist, and fluprostenol, an FP receptor agonist, were ineffective. Forskolin (10−4 M) increased [3H] thymidine incorporation 3-fold, while phorbol myristate acetate (PMA) (10−6 M) produced a 1.8-fold increase. Isobutylmethylxanthine (IBMX) increased [3H] thymidine incorporation in control cultures, in the absence of cortisol, and increased the response to PGE2 in control and cortisol-treated cultures. [3H] proline incorporation into collagen and noncollagen protein was measured in the continuous presence of prostaglandins and cortisol for 72–96 h (continuous model) or when prostaglandins and cortisol were applied for 24 h, followed by culture for 48 h in control medium (on/off model). The effects on collagen were greater than on noncollagen proteins, so that the percent of collagen synthesis increased. The effects of prostaglandins and forskolin paralleled their mitogenic effects. PMA increased only noncollagen protein. Indomethacin did not diminish the anabolic response, while aphidicolin produced only partial inhibition. We conclude that the anabolic effects of prostaglandins on replication and differentiation of osteoblasts are likely to be mediated by an EP-2 receptor that stimulates adenylate cyclase.
Osteochondrogenic potential of marrow mesenchymal progenitor cells exposed to TGF-β1 or PDGF-BB as assayed in vivo and in vitro
Authors: Cassiede Pierre , Dennis James E. , Ma Felix , Caplan Arnold I. 
Published: February 2010

Abstract
Mesenchymal progenitors cells can be isolated from rat bone marrow and mitotically expanded in vitro. When these cells, which we operationally call mesenchymal stem cells (MSCs), are placed in an appropriate environment, they have the capacity to differentiate into bone and/or cartilage. This capacity is called osteochondrogenic potential. In this study, preconfluent MSCs were exposed in vitro to 5 ng/ml transforming growth factor-β1 (TGF-β1) or platelet-derived growth factor, isoform BB (PDGF-BB) for a pulse of 48 h and assayed for cell proliferation, alkaline phosphatase activity, and osteochondrogenic potential; untreated MSC's served as controls. In these cell culture conditions, TGF-β1 or PDGF-BB had similar effects on proliferation and alkaline phosphatase activity. Both growth factors increased cell proliferation and decreased alkaline phosphatase activity of MSCs. Sister cultures of TGF-β1- or PDGF-BB-treated MSCs and untreated MSCs were trypsinized. For each type of culture, the trypsinised MSCs were split in two parts: one part was replated in an osteogenic medium to assess its in vitro osteogenic potential, whereas the other part was seeded into porous calcium phosphate ceramics and implanted subcutaneously in syngeneic rats to assess its in vivo osteochondrogenic potential. PDGF-pretreated MSCs showed no difference in in vivo and in vitro osteochondrogenesis from that of control MSCs, while TGF-β1 pretreatment blocked the osteochondrogenic potential of MSCs when assayed in vitro for bone nodule formation. However, when tested in vivo, TGF-β1-pretreated MSCs were able to form bone and cartilage. These data show that measurements of proliferation and alkaline phosphatase activity of preconfluent MSCs immediately after exposure to growth factor were not predictive of their subsequent osteochondrogenic potential. Moreover, the variation of the osteochondrogenic potential of MSCs after exposure to growth factor was further modulated by the environment in which the MSCs were assayed.
Mineral anisotropy in mineralized tissues is similar among species and mineral growth occurs independently of collagen orientation in rats: Results from acoustic velocity measurements
Authors: Takano Yuichi , Turner Charles H. , Burr David B. 
Published: February 2010

Abstract
It has been reported that the mineral crystals in long bones have their c-axis aligned with the bone axis, presumably because collagen fibrils in bone also align with the bone axis. However, the predominant collagen orientation in bone often does not appear to be aligned with the mineral crystals, especially in rat primary bone. We hypothesized that mineral orientation in bone is not necessarily related to collagen orientation. An acoustic microscope was used to measure elastic constants of mineralized tissues from rat, cow, monkey, and human bone, and mineralized turkey leg tendon (MTLT). Measurements were made before and after demineralization with 10% ethylenediaminetetraacetic acid (EDTA) or decollagenization with 7% sodium hypochlorite. The elastic anisotropy ratio (AR) was defined as the ratio of the elastic coefficient in the longitudinal direction to the elastic coefficient in the transverse direction. Anisotropy ratios of mineralized tissues were not affected by formalin fixation or plastic embedding. An evaluation of tissues from the different species showed that the AR after decollagenization was not significantly different (p &gt; 0.4, analysis of variance) among the groups, while AR after demineralization varied from 1.04 (rat bone) to 1.51 (MTLT). There was no correlation between AR after demineralization and AR after decollagenization (r = 0.13, p = 0.5). This showed that the elastic anisotropy of collagen is more variable than mineral anisotropy in bone and MTLT. Another experiment showed that mineralization of turkey leg tendon changes the elasticity of the collagen matrix, making it less anisotropic. A final, prospective experiment was performed in which tibiae of rats were subjected to mechanical loading for 16 weeks. After 12 days, new periosteal woven bone was observed on the tibiae and, after 16 weeks, this new bone was consolidated and mineralized. Mineral in the newly formed woven bone was virtually isotropic (AR = 1.07) after 12 days of loading, then became more anisotropic (AR = 1.52) after 16 weeks of mechanical loading, as the mineral density of the new bone increased. This increase in anisotropy of bone mineral occurred even though the collagen matrix was woven and had no measureable fibril orientation. We conclude that (1) collagen anisotropy and mineral anisotropy are not necessarily correlated in mineralized tissues, (2) mineralization can affect the collagen matrix elasticity of mineralized tissues, and (3) an organized mineral structure can form in the absence of an organized collagen matrix.
Strontium distribution and interactions with bone mineral in monkey iliac bone after strontium salt (S 12911) administration
Authors: Boivin Georges , Deloffre Pascale , Perrat Brigitte , Panczer Gérard , Boudeulle Micheline , Mauras Yves , Allain Pierre , Tsouderos Yannis , Meunier Pierre J. 
Published: February 2010

Abstract
The analysis of the interaction of strontium (Sr) with bone mineral is of interest because a new agent containing Sr (S 12911) has shown positive effects on bone mass in various animal models of osteoporosis and is currently being developed for preventive and curative treatment of postmenopausal osteoporosis. Iliac bone samples were obtained from 20 male monkeys: 4 untreated control animals, 12 animals sacrificed at the end of a 13-week treatment with high dose levels of S 12911 (750, 275, or 100 mg/kg/day orally), and 4 animals sacrificed 6 weeks after the end of a 13-week treatment with S 12911 (750 or 100 mg/kg/day orally). The distribution of Sr was determined and quantified by X-ray microanalysis. Changes at the crystal level were evaluated by X-ray diffraction and Raman microspectrometry. In the control animals, traces of Sr were found to be homogeneously distributed throughout the bone tissue. In the treated monkeys, Sr could only be detected in calcified matrix. In monkeys sacrificed at the end of the treatment, Sr was found to be dose-dependently incorporated into the mineral substance of the compact and cancellous bone. Sr was heterogeneously distributed with three to four times more Sr in new than in old compact bone, and approximately two and a half times more Sr in new than in old cancellous bone. The bone Sr content dramatically decreased in the animals sacrificed 6 weeks after the end of the treatment. Diffraction showed no significant changes in the characteristics of the crystal lattice. Sr appeared to be easily exchangeable from bone mineral and was slightly linked to mature crystals through ionic substitutions. Even at the highest dose level tested, less than 1 calcium ion out of 10 was substituted by 1 Sr ion in each crystal. In conclusion, taken up by bone, Sr was heterogeneously distributed with a higher concentration in new than in old bone but induced no major modifications of the bone mineral (crystallinity, crystal structure) at the crystal level. As a result, a treatment with S 12911 Sr salt should not induce any alteration of bone mineral.
The effect of weight-bearing exercise on bone mineral density: A study of female ex-elite athletes and the general population
Authors: Etherington J. , Harris P. A. , Nandra D. , Hart D. J. , Wolman R. L. , Doyle D. V. , Dr. Spector T. D. 
Published: February 2010

Abstract
The aim of this retrospective cohort study was to estimate the changes in bone mineral density (BMD) as a consequence of exercise in female ex-athletes and age-matched controls. Eighty-three ex-elite female athletes (67 middle and long distance runners, 16 tennis players, currently aged 40–65) were recruited from the original records of their sporting associations. Controls were 585 age-matched females. The main outcome measures were BMD of lumbar spine (LS), femoral neck (FN), and forearm, estimated by dual-energy X-ray absorptiometry (DXA) scan. Levels of physical activity were assessed using a modified Allied Dunbar Fitness Survey scale and classified as (a) ex-athletes, (b) active controls (≥1 h of vigorous physical activity currently and in the past), (c) low activity controls with inconsistent or intermediate levels of activity, and (d) inactive controls (&lt; 15 minutes of exercise per week). After adjustment for differences in age, weight, height, and smoking, athletes had greater BMDs than controls: 8.7% at the LS (95% confidence interval [CI] 5.4-12.0; p &lt; 0.001) and 12.1% at FN (CI 9.0-15.3; p &lt; 0.001). The benefits of exercise appeared to persist after cessation of sporting activity. Active controls (n = 22) had greater BMDs than the inactive group (n = 347): 7.9% LS (CI 2.0-13.8; p = 0.009) and 8.3% FN (CI 2.7-13.8; p = 0.004). The low activity controls (n = 216) had an intermediate BMD. Tennis players had greater BMDs compared with runners: 12.0% LS (CI 5.7-18.2; p = 0.0004) and 6.5% FN (CI −0.2-13.2; p = 0.066). The BMD of tennis players' dominant forearms were greater than their nondominant forearms. In conclusion, regular vigorous weight-bearing exercise of 1 h or more per week is associated with an increase in BMD within a normal population. This study confirms long-term weight-bearing exercise as an important factor in the regulation of bone mass and fracture prevention.
Predictors of ankle and foot fractures in older women
Authors: Seeley Dana G. , Kelsey Jennifer , Jergas Michael , Nevitt Michael C. 
Published: February 2010

Abstract
To determine risk factors for ankle and foot fractures, data collected from 9704 women 65 years of age or older from four areas of the United States were analyzed. Self-reported baseline questionnaires covered areas such as lifestyle factors (physical activity, diet, and smoking habits) and functional impairment (history of fracture, falling, and other diseases). Bone mineral density (BMD) and performance on neuromuscular tests were also measured. During 5.9 years of follow-up, 191 women fractured an ankle and 204 women fractured a foot. Proportional hazard models were used to estimate relative risks. In multivariable models, factors associated with ankle fracture included one or more falls in the year prior to baseline (relative risk [RR] 1.5; 95% confidence interval [CI] 1.1-2.1), greater vigorous physical activity (RR per 2 times/week, 1.2; CI 1.1-1.3), weight gain since age 25 (RR per 20% gain, 1.4; CI 1.2-1.5), self-reported osteoarthritis (RR 0.5; CI 0.3-0.8), a sister's history of hip fracture after age 50 (RR 1.7; CI 1.0-3.0), out of house ≥ 1 per week (RR 3.0; CI 1.4-6.6), and low distal radius BMD (RR per −0.1 g/cm2, 1.2; CI 1.0-1.4). Factors associated with foot fracture included insulin-dependent diabetes (RR 2.9; CI 1.2-7.2), use of seizure medications (RR 2.3; CI 1.0-5.7) or of benzodiazepines (RR 1.5; CI 1.1-2.2), history of hyperthyroidism (RR 0.5; CI 0.3-1.0), poor far depth perception (RR 0.7; CI 0.5-1.0), and low distal radius BMD (RR per −0.1 g/cm2, 1.3; CI 1.1-1.5). Ankle and foot fractures have different profiles of risk factors that are largely independent of low bone mass.
Parathyroid hormone regulates osteoblast differentiation positively or negatively depending on the differentiation stages
Authors: Isogai Yukihiro , Akatsu Takuhiko , Ishizuya Toshinori , Yamaguchi Akira , Hori Masayuki , Takahashi Naoyuki , Dr. Suda Tatsuo 
Published: February 2010

Abstract
The effects of parathyroid hormone (1-34) (PTH (1-34)) on osteoblast differentiation were investigated using primary osteoblast-like cells isolated from newborn mouse calvaria. The osteoblast-like cells cultured at low cell densities, in which the cells remained in a subconfluent state at the end of culture, were exposed for 7 days to PTH. This stimulated alkaline phosphatase (ALP) activity in a dose-dependent manner. In contrast, PTH dosedependently inhibited both ALP activity and osteocalcin production in cells inoculated at high cell densities, in which they had reached a confluent state before the end of culture. The changes of ALP activity by PTH were accompanied with the expression of ALP messenger RNA. PTH induced no changes of the hydroxyproline content in the cell layer when the cells were exposed to the hormone at a subconfluent state, but reduced the content at a postconfluent state. The stimulation of ALP activity by PTH at a preconfluent state was retained even after the removal of PTH from the culture media. The opposite effect of PTH, observed between the preconfluent and the postconfluent state, was reproduced by adding dibutyryl cyclic adenosine monophosphate (cAMP) or forskolin, but not by adding phorbol myristate acetate. In a colony-forming unit fibroblastic (CFU-F) assay, using bone marrow cells isolated from tibiae of 10-week-old mice, PTH induced no changes in the total number of CFU-Fs, but increased the proportion of ALP-positive colonies. These results indicate that PTH exerts opposite effects on the phenotypic expression of osteoblasts, depending on their differentiation stages of osteoblasts. PTH may preferentially stimulate osteoblast differentiation in immature osteoblasts but inhibit it in more mature cells.