bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bone mass measurements in the distal forearm using dual-energy X-ray absorptiometry and γ-ray computed tomography: A longitudinal, in vivo comparative study
Authors: Dr. Overton Thomas R. , Wheeler Garry D. 
Published: February 2010

Abstract
Indices of bone mass were measured in 23 volunteers weekly over 14–16 weeks using dual-energy x-ray absorptiometry (DEXA) and special-purpose computed tomography (γ-CT). In vitro, the precision for both systems was excellent (coefficient of variation &lt; 0.5%). Over 4 months, the precision in vivo (average CV for all subjects) for DEXA measures (BMD, g/cm2, and BMC, g/cm) varied between 0.6 and 1.1%; with γ-CT it varied from 1.1% for TBD (g/cm3) to 2.2% for CBD (g/cm3). Correlation between the indices of bone mass measured using DEXA and γ-CT at the ultradistal site was moderate, but these indices were not correlated at the distal third site. When BMD and BMC were derived from the CT index IBD, however, the correlation between these γ-CT indices and the corresponding DEXA indices was high for both ultradistal and proximal radial sites.
Isolation and purification of osteocytes
Authors: van der Plas A. , Nijweide P.J. 
Published: February 2010

Abstract
An isolation method for osteocytes is described. After removal of the periostea, bone cells were isolated from calvariae of 18-day-old chicken embryos by alternating treatments with collagenase and EDTA. Osteocytes were purified from the heterogeneous bone cell population with the help of the osteocyte-specific MAb OB 7.3 bound to protein G-conjugated magnetic beads. The purity of the osteocyte population ultimately obtained was more than 95%. Osteocytes were found to adhere rapidly to glass or plastic substrates. They showed numerous processes of various types. These processes could branch and make contact with those of other osteocytes. After 1–2 days of culture, the isolated osteocytes formed a network of apparently interconnected cell processes very similar to the osteocyte network in bone.
Identification of a functional mononuclear precursor of the osteoclast in chicken medullary bone marrow cultures
Authors: Prallet Bernard , Male Philippe , Neff Lynn , Baron Roland 
Published: February 2010

Abstract
Mononuclear cells were isolated from the peritrabecular bone marrow from the medullary bone of laying hens maintained on a calcium-deficient diet for 1 week. These cells were cultured for up to 7 days on devitalized bovine bone slices after removing the nonadherent fraction. The mononuclear precursors of the osteoclast that are present in such cultures adhere to bone matrix. These cells are TRAP+, express the vitronectin receptor at high levels, and also express high levels of sodium pumps and of carbonic anhydrase, enzymes that are characteristically enriched in the mature osteoclast. Finally, the most mature mononuclear precursors were found to be capable of resorbing the extracellular bone matrix before forming multinucleated osteoclasts.
Contrasting effects of parathyroid hormone and insulin-like growth factor I in an aged ovariectomized rat model of postmenopausal osteoporosis
Authors: Ibbotson Kenneth J. , Orcutt Christopher M. , D'Souza Sharyn M. , Paddock Carol L. , Arthur Jay A. , Jankowsky Maryann L. , Boyce Rogely W. 
Published: February 2010

Abstract
Agents that exert anabolic effects on bone have generally been tested in young or estrogen-replete animals. It is unclear whether these agents exert similar effects in older ovariectomized (Ovx) animals. In this single study we examined the effects of intermittent (daily) human PTH-(1–34) and continuous infusion of human recombinant IGF-I alone and in combination on bone resorption and formation over a 14 day period in an aged Ovx rat model of postmenopausal osteoporosis (2-year-old rats, Ovx at 1 year). Compared to Ovx controls, PTH treatment increased bone mineral content (BMC) and bone volume and stimulated bone formation but had no effect on bone resorption. In contrast, IGF-I treatment reduced BMC and stimulated resorptive activity as assessed by increases in marrow volume, cortical porosity, osteoclast-positive eroded surfaces, and urinary hydroxyproline excretion. IGF-I had no effect on bone formation, but when combined with PTH, IGF-I blunted the response to PTH on the periosteal and endocortical surfaces. In summary, PTH stimulated bone formation in a manner similar to that observed in younger animals and IGF-I stimulated bone resorption rather than formation and blunted the bone-forming response to PTH. The effects of IGF-I in older Ovx rats may differ from those observed in younger estrogen-replete animals.
Dietary restriction of calcium, phosphorus, and vitamin D elicits differential regulation of the mrnas for avian intestinal calbindin-D28K and the 1,25-dihydroxyvitamin D3 receptor
Authors: Meyer Julia , Fullmer Curtis S. , Wasserman Robert H. , Komm Barry S. , Haussler Mark R. 
Published: February 2010

Abstract
We investigated the regulation of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]-induced calbindin-D28k (CaBP) and of the vitamin D receptor (VDR) by evaluating CaBP protein, CaBP mRNA, and VDR mRNA under conditions of altered intake of vitamin D, calcium, or phosphorus. Chickens were maintained for 10 days on one of four diets: vitamin D-deficient, normal (1.0% Ca and 1.1% P), low calcium (0.1% Ca and 1.2% P), and low phosphorus (1.1% Ca and 0.3% P). CaBP was undetectable in D-deficient duodena and was elevated above normal values by low-calcium (3.1-fold) and low-phosphorus (2.3-fold) intake. Contradictory to published data, we observed a correlation between CaBP protein and mRNA levels in that the CaBP mRNA was absent in D-deficient intestine and augmented threefold and twofold in low-calcium and low-phosphate duodena, respectively. In contrast, VDR mRNA concentrations were identical in vitamin D-deficient and normal duodena, implying that intestinal VDR is not dependent upon 1,25-(OH)2D3 for basal expression. Chickens fed a low-phosphorus diet displayed a twofold increase in VDR mRNA, but those fed a low-calcium diet exhibited a dramatic decrease in VDR mRNA. These data show that CaBP mRNA and protein levels are modulated in a tightly coupled fashion, and they are consistent with previous conclusions that augmented circulating 1,25-(OH)2D3 stimulates CaBP expression when dietary calcium or phosphorus is limiting. However, a more complex regulation of VDR expression occurs in that low-phosphorus restriction enhances VDR mRNA levels, possibly via increased circulating 1,25-(OH)2D3. Conversely, reduced dietary calcium diminishes VDR mRNA despite increased circulating 1,25-(OH)2D3, indicating that another factor, such as parathyroid hormone, is a predominant downregulator of VDR.
Developmental regulation of creatine kinase activity in cells of the epiphyseal growth cartilage
Authors: Dr. Shapiro Irving M. , Debolt Kristine , Funanage Vicky L. , Smith Susan M. , Tuan Rocky S. 
Published: February 2010

Abstract
During the process of endochondral bone formation, the maturing chondrocyte exhibits profound changes in energy metabolism. To explore the mechanism of energy conservation in cartilage we examined the expression of creatine kinase, an enzyme that catalyzes the formation of ATP in tissues under oxygen stress. Measurement of creatine kinase activity and cytochemical assessment of enzyme distribution clearly showed that the level of enzyme activity was related to chondrocyte maturation. Thus, as the cells hypertrophied, there was a progressive increase in creatine kinase activity. Similarly, an elevation in creatine kinase activity was noted in chondrocyte cultures as the cells assumed an hypertrophic state. When cartilage calcification was disturbed by rickets, there was a decrease in enzyme activity in the hypertrophic region. Studies were performed to examine the creatine kinase isozyme profile of cells of the epiphysis. In resting and proliferating cartilage, the isoform was MM. In hypertrophic cartilage, the predominant isoforms were MB and BB. In terms of the creatine phosphate content, the highest values were seen in the proliferative region; lower amounts were present in hypertrophic and resting cartilage; and no creatine phosphate was detected in calcified cartilage. These data suggest that turnover of creatine phosphate is greatest in the mineralized region of the epiphysis. The results of these investigations point to creatine kinase as being under developmental control. The activity of the enzyme in cartilage cells should serve as a marker of developmental events associated with chondrocyte proliferation, hypertrophy, and mineralization.
Identification of proteins secreted by human osteoblastic cells in culture
Authors: Johansen Julia S. , Williamson Matthew K. , Rice Jeffrey S. , Price Paul A. 
Published: February 2010

Abstract
To better understand the biochemistry of matrix-forming cells, we developed a simple and reproducible procedure for the isolation and identification by N-terminal sequencing of proteins secreted by cells into culture medium and applied this procedure to the analysis of the major Coomassie blue-staining proteins under 100 kD that are secreted from three different human osteoblastic cell cultures. The major proteins secreted by normal human osteoblasts from adult trabecular bone were identified by N-terminal sequencing to be gelatinase, osteonectin, the C-terminal propeptides of the α1 and α2 chains of type I collagen, tissue inhibitor of metalloproteinase 1 (TIMP-1), and β2-microglobulin. The amounts of each of these proteins secreted into medium over a 24 h interval did not change over the 7 consecutive days of culture under serum-free conditions, which indicates that this pattern of protein secretion is not significantly affected by the serum-free conditions needed for protein identification by this method. In addition, radioimmunoassay for bone gla protein (BGP), a marker for osteoblast phenotype, revealed that BGP secretion remained high over 7 days of culture under serum-free conditions and was comparable to the rate of BGP secretion in control cultures with 10% serum. The major proteins secreted by MG-63 cells were identified by N-terminal sequencing to be gelatinase, a novel 40 kD human bone protein we termed YKL-40, TIMP-1, the recently discovered TIMP-2, and β2-microglobulin. Further studies revealed that YKL-40 is the only protein detectable by Coomassie staining of SDS gels of MG-63 media proteins that is induced by extended time at confluence or by treatment with 1,25-(OH)2D3. The apparent absence of detectable Coomassie-stained bands corresponding to the C-terminal propeptides of collagen in the medium of MG-63 cells suggests that these transformed cells may not be a good model for bone matrix formation. The major proteins secreted by normal fetal osteoblastic cells were identified by N-terminal sequencing to be osteonectin and the C-terminal propeptides of the α1 and α2 chains of type I collagen. Gelatinase and TIMP could not be detected among the conditioned medium proteins by these methods. These observations indicate that fetal osteoblasts primarily express proteins that are matrix constituents and adult human osteoblasts secrete, in addition to these, proteins that could function in matrix turnover.
Risk of fractures in patients with pernicious anemia
Authors: Goerss Jean B. , Kim Chung H. , Atkinson Elizabeth J. , Eastell Richard , O'Fallon W. Michael , Dr. Melton L. Joseph 
Published: February 2010

AbstractIn a series of postmenopausal women previously studied by our group, pernicious anemia was associated with reduced bone mineral density of the spine and with vertebral fractures. To determine whether osteoporotic fractures represent an important clinical problem for such patients, we conducted a population-based retrospective cohort study of all Rochester, Minnesota residents newly diagnosed with pernicious anemia from 1950 through 1979. These 131 individuals were followed through the inpatient and outpatient records of all medical care providers in the community for 1550 person-years. In comparison with fracture rates from the general community, patients with pernicious anemia had a 1.9-fold increase in proximal femur fractures, a 1.8-fold increase in vertebral fractures, and a 2.9-fold increase in distal forearm fractures (all p &lt; 0.05). Increases in the risk of proximal humerus and pelvis fractures were not statistically significant. Clinicians should be aware that pernicious anemia is associated with an increased risk of osteoporotic fractures, but the mechanism is unknown.
cAMP promotion of osteoclast-like cell development from mouse bone marrow cells requires a permissive action of 1,25-(OH)2D3
Authors: Rubin Janet , Titus Louisa , Nanes Mark S. 
Published: February 2010

Abstract
Recruitment of osteoclasts from monocytic precursors is modulated by local signals. We previously showed that monoblastic differentiation in U937 cells is stimulated by 1,25-(OH)2D3 and cAMP in series. We investigate here the combined effects of these agents to stimulate differentiation of osteoclast-like cells from mouse marrow. Cells from mouse marrow were harvested and cultured in α-MEM with 10% fetal bovine serum. The appearance of tartrate-resistant acid phosphatase-containing multinuclear cells was measured after 8 days in culture by cytochemical staining. Continuous exposure of cultures to 10 nM 1,25-(OH)2D3 positively stimulated development of these cells after 8 days (101 + 3 cells per well, n = 74). No osteoclast-like cells were found when 1,25-(OH)2D3 was added for the first 4 days followed by 4 days more with no treatment. PGE2 (1 μM) as a single agent added during the last 4 days of culture was not able to recruit osteoclast-like cells. However, cultures exposed to 1,25-(OH)2D3 during the first 4 days and 1 μM PGE2 during the second 4 days developed osteoclast-like cells at 8 days [66 + 8% of the formation seen with 1,25-(OH)2D3 alone, p &lt; 0.05]. Dibutyryl cAMP (1 μM to 3 mM) was also not effective used as a single agent, but was able to stimulate formation of TRAP-positive multinuclear cells when 1,25-(OH)2D3 preceded its addition to culture medium. cAMP analogs therefore mimicked the effect of 1 μM PGE2, but these experiments do not allow us to assign the PGE2 action entirely to activation of cAMP second messenger. We postulate that continuous 1,25-(OH)2D3 stimulation is alone sufficient to recruit osteoclasts from precursors but that the effect of cAMP to stimulate osteoclast formation occurs only when combined with a permissive action of 1,25-(OH)2D3.
Influence of oophorectomy on serum levels of sex steroids and bone metabolism and assessment of bone mineral density in lumbar trabecular bone by QCT-C value
Authors: Ohta Hiroaki , Makita Kazuya , Suda Yoshio , Ikeda Toshiyuki , Masuzawa Toshihide , Nozawa Shiro 
Published: February 2010

Abstract
The present cross-sectional study was carried out to determine the influence of oophorectomy (OPX) on serum levels of sex steroids and bone metabolism, as well as bone mineral density (BMD), in OPX subjects in comparison with age- and body size-matched controls. Quantitative computed tomography (QCT) and dual-photon absorptiometry (DPA) demonstrated a remarkable reduction in BMD in OPX subjects. In particular, the QCT of the centrum of vertebral bone (QCT-C) in these subjects was no more than 69.33 + 3.40% (X + SEM) of the control value, and this parameter was much lower than the QCT integral (QCT-I) value of total lumbar vertebrae. This means that BMD decreases specifically in spongy portions after OPX. The serum level of estrone (E1) was significantly lower in OPX subjects than in controls. The hormonal action of E1 on target organs has been thought to be only one-third of that of estradiol (E2), but the marked reduction in serum E1 level seemed to be a significant cause of the reduction in BMD. The serum level of androstenedione (Δ4) significantly decreased in OPX subjects and appeared to affect bone metabolism negatively. Both bone formation and bone resorption were found to be stimulated following OPX, but the rate of bone resorption was found to be higher than that of bone formation: there was an imbalance between bone formation and bone resorption in OPX subjects. However, it was not possible to prove a relationship between Ca regulating hormone and this phenomenon. In conclusion, the QCT-C value reflects the changes in spongy vertebral BMD more sensitively than the QCT-I value or DPA. It is also necessary to limit the region of interest strictly to the spongy portion to grasp the changes in BMD.
Relationship between bone mass and rates of bone change at appendicular measurement sites
Authors: Davis James W. , Grove John S. , Ross Philip D. , Vogel John M. , Wasnich Richard D. 
Published: February 2010

Abstract
The rate of bone change among postmenopausal women may vary depending upon the initial bone mass. Examining this possibility is difficult, however, because of a negative statistical bias that occurs when change is regressed against the initial value of the same variable. In this article, four statistical methods were applied to measure the association between bone mass and the rate of bone change. The study population was Japanese-American women, who were monitored for approximately 5 years. Bone changes were determined for the calcaneus and the distal and proximal radius. The results were consistent across the bone sites but differed between statistical methods. Three of the four methods indicated that the women with the greater bone mass had the greater loss rates. The fourth method did not support this association. Possible reasons for the discordant results are discussed. Using the “best” estimate of the relationship, a gradual convergence of bone mass was projected over time toward the population mean. The convergence occurred because women with higher bone mass had a somewhat faster loss rate than women with lower bone mass. Overall, however, the variation in bone mass between individuals was large compared to the rate of convergence.
Effects of heparin on osteoclast activity
Authors: Chowdhury Majeedul H. , Hamada Chieko , Dempster David W. 
Published: February 2010

Abstract
The effect of heparin on osteoclastic bone resorption was studied in vitro using the disaggregated osteoclast resorption assay. Bone resorption was assessed by counting the resorption lacunae on bone slices by light microscopy. Low concentrations of heparin (5 μg/ml) increased bone resorption by isolated chick and rat osteoclasts. Among other glycosaminoglycans tested at 5 μg/ml, only dextran sulfate showed a small but significant stimulation of resorption. Chondroitin sulfates A, B, and C were without effect at 25 and 100 μg/ml, whereas resorption was increased by 100 μg/ml of heparan sulfate. With chick osteoclasts, which could be maintained in serum-free conditions, a stimulatory effect of heparin was found both in the presence of 5% fetal calf serum and in serum-free media containing insulin, transferrin, and selenium. The magnitude of the heparin-induced increase in resorption was similar in the presence or absence of serum. The stimulation of resorption was associated with an increase in the number of osteoclasts on bone slices. Pretreatment of the bone slices with heparin also enhanced resorption. In time course experiments, 5 μg/ml of heparin caused a doubling of chick osteoclast activity index (number of resorption pits per number of osteoclasts) at 12 and 24 h. In 24 h cultures, treatment with 10 μg/ml of the arginine-rich basic protein, protamine, 1 μg/ml of the immunosuppressant, cyclosporine A, or 5 μg/ml of the cysteine-proteinase inhibitor, leupeptin, negated the heparin effect on bone resorption. Leupeptin also inhibited basal resorption. We conclude that heparin causes an increase in bone resorption in vitro both by increasing the number of differentiated osteoclasts and by enhancing the activity of individual osteoclasts.
Quantitation of skeletal alkaline phosphatase isoenzyme activity in canine serum
Authors: Farley John R. , Hall Susan L. , Ritchie Candace , Herring Sandra , Orcutt Christopher , Miller Barbara E. 
Published: February 2010

AbstractPursuing the hypothesis that quantitation of skeletal alkaline phosphatase (ALP) activity in canine serum would provide an index of the rate of bone formation, we compared three methods for isoenzyme-specific identification of skeletal ALP activity in canine serum: heat inactivation, wheat germ agglutinin (WGA) precipitation, and concanavalin A (ConA) precipitation. ALP isoenzyme activities were extracted from canine bone, intestine, and liver, diluted into heat-inactivated canine serum (i.e., serum without ALP activity), and used as calibrators of ALP isoenzyme activities. Differential sensitivity to inhibition by 10 mM L-homoarginine was used to distinguish intestinal ALP activity from hepatic and skeletal ALP activities (i.e., 9, 80, and 72% inhibition, respectively). To allow resolution of skeletal ALP activity from hepatic ALP activity, we tested two established methods (heat inactivation and WGA precipitation) and a novel method, ConA precipitation. The organ-derived skeletal and hepatic ALP isoenzyme activities were used to compare these three methods with respect to linearity, isoenzyme separation, and precision. All three methods were linear, but the WGA and ConA methods afforded greater isoenzyme separation and precision. The relative extent of isoenzyme separation (i.e., the difference in percentage remaining skeletal and hepatic ALP isoenzyme activities) averaged 23, 40, and 47% remaining ALP activity for the heat, WGA, and ConA methods, respectively. However, when these methods were applied to the quantitation of skeletal ALP activity in sera from 10 young and 10 adult beagles, the WGA method was found to be unacceptable because most of the results fell outside the range of the WGA assay calibrators (i.e., &gt;100% skeletal ALP activity). The heat and ConA methods showed that the amount of skeletal ALP activity in the beagle sera decreased with age, both as ALP activity per liter and as percentage of total serum ALP activity (p &lt; 0.001 for each). Skeletal ALP activity levels determined by ConA were correlated with values determined by heat inactivation (r = 0.87, p &lt; 0.001) but not with WGA-determined levels (r = 0.26). Intestinal ALP activity was detected in only 1 of these 20 sera. We conclude that ConA precipitation can be used for quantitation of skeletal ALP activity in beagle serum.
Dual-energy X-ray absorptiometry of the forearm: Reproducibility and correlation with single-photon absorptiometry
Authors: Leboff Meryl S. , Fuleihan Ghada El-Hajj , Angell Jennifer E. , Chung Susan , Curtis Kate 
Published: February 2010

Abstract
Although single-photon absorptiometry (SPA) has been the predominant tool used to assess bone mineral density (BMD) in the forearm, the development of dual-energy x-ray absorptiometry (DEXA) provides the benefits of greater source stability, reduced scanning time, and improved image resolution compared to SPA. In the present study we used the DEXA bone densitometer (Hologic, Inc., Waltham, MA) to (1) measure BMD in the one-third radius and ultradistal radius; (2) examine the reproducibility of these BMD measurements; and (3) compare the BMD at the one-third radius with SPA (SP2, Lunar Corp., Madison, WI). In 65 normal women (ages 22–74 years) we examined changes in the forearm DEXA BMD with age, revealing significant quadratic regression equations. The reproducibility of DEXA BMD (mean ± SEM) in 7 normal subjects aged 22–50 years is 0.85 ± 0.16% for the predominantly cortical one-third radius site and 0.97 ± 0.15% for the more trabecular ultradistal site. The regression relationship between DEXA and SPA of the one-third radius in 26 subjects (ages 22–68 years) is DEXA BMD = 0.105 + 0.826 (SPA BMD); R = 0.97, R2 = 0.94, p &lt; 0.0001. Bone densitometry of the forearm using DEXA may be performed relatively rapidly, providing reproducibility and image resolution that are generally superior to those observed with SPA.