bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of deflazacort on aspects of bone formation in cultures of intact calvariae and osteoblast-enriched cells
Authors: Dr. Canalis Ernesto , Avioli Louis 
Published: February 2010

Abstract
Deflazacort, a synthetic glucocorticoid reported to have bone-sparing properties in vivo, and Cortisol were compared for their effects on bone formation in vitro. Deflazacort and Cortisol were studied for their effects on DNA and collagen synthesis in cultures of intact fetal rat calvariae and of osteoblast-enriched (Ob) cells from 21- to 22-day-old fetal rat parietal bone. Both steroids were also examined for their effects on skeletal insulin-like growth factor (IGF) I production, which is decreased by Cortisol and appears relevant to its mode of action. After 24 h of culture, deflazacort and Cortisol had limited effects on the parameters studied, although Cortisol at 100 nM decreased [3H]proline incorporation into collagen in intact calvariae. In contrast, after 72 h deflazacort and Cortisol at 1–100 nM inhibited the incorporation of [3H]thymidine into DNA and at 100 nM decreased the incorporation of [3H]proline into collagen and noncollagen protein in intact calvariae. Deflazacort and Cortisol at 10–1000 nM decreased calvarial collagen degradation to a similar extent. Both steroids had a similar activity, and at 100 nM for 72 h they decreased IGF-I production by calvariae; however, Cortisol at 10 nM was somewhat more effective than deflazacort in decreasing IGF-I levels. Deflazacort and Cortisol had analogous effects in Ob cell cultures. After 24 h of treatment, deflazacort at 100–1000 nM and Cortisol at 10–1000 nM decreased the labeling of DNA, and both steroids at 100–1000 nM caused a similar decrease in [3H]proline incorporation into collagen in Ob cells. In addition, deflazacort and Cortisol at 100 nM decreased IGF-I levels by about 60% in Ob cell cultures. In conclusion, deflazacort and Cortisol have similar inhibitory actions on bone DNA and collagen synthesis, collagen degradation, and IGF-I concentrations in vitro.
Expression of helix-loop-helix regulatory genes during differentiation of mouse osteoblastic cells
Authors: Murray Samuel S. , Glackin Carlotta A. , Winters Katherine A. , Gazit Dan , Kahn Arnold J. , Murray Elsa J. 
Published: February 2010

Abstract
Although much is known about the hormonal regulation of osteoblastic cell differentiation, much less is known about the nuclear regulatory molecules that affect this process. We analyzed the expression of several regulatory molecules of the helix-loop-helix (H-L-H) group in primary mouse calvarial cells and in MC3T3-E1 mouse osteoblastic cells in situations representing different degrees of cellular differentiation. H-L-H class regulators are known to participate directly in directing cell fate and differentiation decisions in other mesodermal lineages. Two of the molecules that we studied, Id and E12, have well-established roles in this process. The other, mTwi, the murine homolog of the Drosophila twist gene, is a newly cloned mammalian H-L-H gene. Levels of E12 RNA remained unchanged during differentiation. On the other hand, in both primary osteoblastic cells and MC3T3-E1 cells, the abundance of Id and mTwi declined with cell maturation; mTwi less dramatically than Id. That Id expression is causally related to differentiation is suggested by the finding that MC3T3-E1 cells transfected with an Id-expression plasmid fail to undergo differentiation. We conclude that helix-loop-helix regulatory genes are expressed in mouse osteoblastic cells, where they are likely to participate in differentiation. The E12 gene product is likely to function as a positive modulating factor. In contrast, Id inhibits differentiation, probably by sequestering other H-L-H gene regulators, including E12, in inactive complexes. The precise role of mTwi is more speculative at this time, but the observed pattern of expression is consistent with a role in early and midmesodermal specification that is terminated as cells differentiate.
Lateral spine densitometry is a more sensitive indicator of glucocorticoid-induced bone loss
Authors: Dr. Reid Ian R. , Evans Margaret C. , Stapleton Joanne 
Published: February 2010

Abstract
Osteoporosis is a common complication of glucocorticoid therapy. Bone density measurement is now commonly used in assessing which steroid-treated patients require specific interventions to reduce fracture risk. The recently developed techniques for the measurement of bone mineral density (BMD) of the vertebral body alone, by dual-energy x-ray absorptiometry (DXA) in the lateral projection, may be particularly useful in this context since steroid-induced bone loss is most marked in trabecular-rich regions like the vertebral body. This possibility has been assessed in the present study by the measurement of BMD in the lateral and anterioposterior (AP) projections in 28 women receiving chronic glucocorticoid treatment. The two BMD measurements were significantly related (r = 0.62, p &lt; 0.001). When expressed in relation to age-appropriate normal values, lateral BMDs were lower than AP BMDs both in percentage terms (70.8 ± 4.4 versus 90.3 ± 2.6%, p &lt; 0.001) and in terms of Z scores (-1.42 ± 0.22 versus −0.91 ± 0.24, p = 0.027). AP BMD Z scores classified 12 patients as osteopenic, whereas a further 7 were so categorized by lateral BMD Z score. It is concluded that lateral DXA scanning is a more sensitive indicator of glucocorticoid-induced osteopenia than conventional BMD measurement in the AP projection.
Protein kinase C modulates parathyroid hormone- but not prostaglandin E2-mediated stimulation of cyclic AMP production via the inhibitory guanine nucleotide binding protein in UMR-106 osteosarcoma cells
Authors: Koch Helena M. , Muir Helen , Gelderblom Dalene , Hough Stephen 
Published: February 2010

Abstract
In UMR-106 osteosarcoma cells we found that PTH activated both the cAMP/protein kinase A and the Ca2+-dependent phosphoinositide/protein kinase C (PKC) pathways, but prostaglandin E2 (PGE2) activated only the cAMP pathway. Activation of PKC by the phorbol ester PMA had no effect on cAMP production but enhanced PTH-stimulated cAMP production by 50% or more; the effect on PGE2-induced cAMP was negligible. Inhibition of the α-subunit of the inhibitory guanine nucleotide binding protein (Gi) by pertussis toxin pretreatment also enhanced PTH-mediated cAMP production but had no effect on PGE2-induced cAMP production. These results suggest that although PTH-mediated adenylate cyclase activity is regulated via both the stimulatory (Gs) and inhibitory (Gi) guanine nucleotide binding proteins, only Gs regulates PGE2-mediated adenylate cyclase activity in UMR-106 cells. Costimulation with pertussis toxin and PMA did not increase PTH-stimulated cAMP production above that obtained with PMA alone. This implies a similar target of action for pertussis toxin and PMA, that is, the α-subunit of Gi. The α-subunit of Gi was found to be a substrate for in vitro PKC phosphorylation of membrane fractions from UMR-106 cells, seen as a ±40 kD band on SDS-PAGE. Stimulation of in situ 32P-labeled cells with either PMA or PTH also enhanced incorporation of 32P into the 40 kD band. Using the peptide antisera AS/7 and EC/2, we showed that pertussis toxin-labeled subunits of both Gi1α/Gi2α and Gi3α could be immunoprecipitated, respectively, but immuinoprecipitation of membrane proteins after in situ phosphorylation and stimulation with PMA precipitated only Gi2α. We therefore conclude that modulation of adenylate cyclase activity by phorbol esters in UMR-106 osteosarcoma cells can be ascribed, at least in part, to PKC-mediated phosphorylation of the α-subunit of the Gi2 component of the adenylate cyclase regulatory complex.
Reduced vertebral bone density in hypercalciuric nephrolithiasis
Authors: Pietschmann Flavia , Breslau Neil A. , Pak Charles Y.C. 
Published: February 2010

Abstract
Dual-energy x-ray absorptiometry and single-photon absorptiometry were used to determine bone density at the lumbar spine and radial shaft in 62 patients with absorptive hypercalciuria, 27 patients with fasting hypercalciuria, and 31 nonhypercalciuric stone formers. Lumbar bone density was significantly lower in patients with absorptive (-10%) as well as in those with fasting hypercalciuria (-12%), with 74 and 92% of patients displaying values below the normal mean, whereas only 48% of the nonhypercalciuric stone formers had bone density values below the normal mean. In contrast, radial bone density was similar in all three groups of renal stone formers investigated. The comparison of urinary chemistry in patients with absorptive hypercalciuria and low normal bone density compared to those with high normal bone density showed a significantly increased 24 h urinary calcium excretion on random diet and a trend toward a higher 24 h urinary uric acid excretion and a higher body mass index in patients with low normal bone density. Moreover, among the patients with absorptive hypercalciuria we found a statistically significant correlation between the spinal bone density and the 24 h sodium and sulfate excretion and the urinary pH. These results gave evidence for an additional role of environmental factors (sodium and animal proteins) in the pathogenesis of bone loss in absorptive hypercalciuria. In conclusion, our data suggest an osteopenia of trabecular-rich bone tissues in patients with fasting and absorptive hypercalciurias.
Measurement of serum osteocalcin with a human-specific two-site immunoradiometric assay
Authors: Garnero Patrick , Grimaux Marc , Demiaux Brigitte , Preaudat Corinne , Seguin Patrick , Dr. Delmas Pierre D. 
Published: February 2010

Abstract
We developed a sensitive and specific two-site radioimmunoassay (IRMA) for human osteocalcin using human osteocalcin as a standard and two monoclonal antibodies raised against human osteocalcin purified from human cortical bone, a solid-phase anti-25–37 region and a tracer anti-5–13 sequence of the molecule. A wide range of osteocalcin levels (up to 300 ng/ml) can be measured with a sensitivity of 0.4 ng/ml. The intra- and interassay coefficients of variation are less than 4 and 6%, respectively. The recovery of human osteocalcin from serum samples ranges from 96 to 103%. IRMA was linear for serial sample dilutions in a wide range of serum osteocalcin levels, even in patients with chronic renal failure on hemodialysis. Depletion of serum in intact osteocalcin demonstrated that IRMA detects, in addition to the intact peptide, a large N-terminal midregion fragment that represents about 50% of total osteocalcin levels in normals and patients with Paget's disease and up to 75% in patients with chronic renal failure. This large fragment, previously unrecognized because it cannot be distinguished from intact osteocalcin with gel filtration chromatography, is not generated in vitro by incubation of the serum up to 26 h. We measured osteocalcin in the serum of 309 healthy adults (180 men and 129 women, age range 20–95 years), 36 patients with Paget's disease, 12 patients with primary hyperparathyroidism, 70 patients with chronic renal failure on hemodialysis, and 10 patients on corticosteroid therapy, simultaneously with human IRMA and with a conventional radioimmunoassay (RIA) based on bovine reagents. A tight correlation (r = 0.889) was observed between the two assays in the normal population, but the values obtained with IRMA were about threefold higher (mean 23.3 ± 10.5 versus 7.5 ± 3.4 ng/ml) than those obtained with RIA. Reported as Z scores, that is, number of standard deviations from the predicted normal mean adjusted for sex and age, these two assays (IRMA and RIA) gave concordant results in patients with Paget's disease (4.05 ± 6.21 versus 2.41 ± 2.53), primary hyperparathyroidism (4.14 ± 7.17 versus 2.13 ± 2.28), chronic renal failure (25.32 ± 24.49 versus 6.93 ± 5.48), and glucocorticoid treatment (-1.48 ± 0.78 versus −1.11 ± 0.57). However, IRMA was more discriminant from controls for all these metabolic bone diseases because the absolute values of mean Z scores with IRMA were significantly higher than those obtained with the RIA (p &lt; 0.05–0.0001). We conclude that this new human-specific IRMA of osteocalcin may be more sensitive than bovine RIA for the clinical investigation of metabolic bone diseases.
Osteoporosis in anorexia nervosa: The influence of peak bone density, bone loss, oral contraceptive use, and exercise
Authors: Seeman Ego , Szmukler George I. , Formica Carmelo , Tsalamandris Con , Mestrovic Robert 
Published: February 2010

AbstractAnorexia nervosa occurs early in life and predisposes to osteoporosis. Exercise may be protective. We asked: (1) Does failure to attain peak bone density contribute to the deficit in bone density? (2) Does oral contraceptive use protect against osteoporosis? (3) Is any protective effect of exercise confined to weight‐bearing sites? Areal bone density (g/cm2) and body composition were measured by dual x‐ray absorptiometry in 65 patients with anorexia nervosa and 52 controls. Comparing the 12 patients with primary amenorrhea and the 37 patients with secondary amenorrhea, bone density (mean ± SEM) at the lumbar spine was 0.88 ± 0.04 versus 1.06 ± 0.03 (P = 0.001), respectively. Bone density at the femoral neck was 0.80 ± 0.04 versus 0.92 ± 0.03 (P < 0.05), respectively. These values differed before, but not after, adjusting for the respective duration of illness (73.0 ± 10.3 versus 34.1 ± 4.8 months, P < 0.001) and fat‐free mass (31.6 ± 1.3 versus 35.4 ± 0.5 kg, P < 0.01). Bone density at the lumbar spine in the 16 patients with 31.8 ± 8.3 months of contraceptive exposure was higher than in the 49 patients with no contraceptive exposure (1.14 ± 0.05 versus 1.02 ± 0.02 P < 0.02) but was lower than in controls (1.14 ± 0.05 versus 1.27 ± 1.02, P < 0.01). No protective effect of contraceptive exposure was detectable at the femoral neck. Nevertheless, bone density at both sites correlated positively with the duration of contraceptive exposure (lumbar spine, R 0.63, P < 0.02; femoral neck, R = 0.66 P < 0.01) and negatively with duration of amenorrhea (lumbar spine, R = −0.53, P < 0.01; femoral neck, R = −0.49, P < 0.01, respectively). In the 19 patients who exercised vigorously, bone density was higher than in the 30 sedentary patients at the femoral neck (0.97 ± 0.04 versus 0.85 ± 0.03, P < 0.05), but not at the lumbar spine. Anorexia nervosa of earlier onset is likely to impose a greater fracture risk because of larger deficits in bone density. The deficits are more likely to be due to bone loss than low peak bone density, although a contribution to the deficit by low peak bone density cannot be excluded. Bone density of the lumbar spine may be more sensitive to estrogens than bone density of the proximal femur, and the proximal femur may be more sensitive to weight‐bearing exercise. Because partial protection against osteoporosis may be obtained at the spine using oral contraceptives and at the proximal femur by weight bearing, these modalities may warrant consideration as part of the treatment of this illness.
Journal of Bone and Mineral Research
Authors: Lanyon Lance E. 
Published: February 2010

Abstract
The continuing ability of the skeleton to withstand functional loads without damage requires that bone mass and architecture are adjusted according to the loads experienced. Load bearing is the only functional influence that requires a particular bone architecture, and functionally engendered strains within the bone tissue provide the only feedback containing the necessary information on the relationship between current architecture and prevailing load history. The specific strain-related objectives of the adaptive modeling and remodeling response to load bearing have not been adequately defined. They appear to be different for cortical and cancellous bone and vary according to cortical location. Experiments suggest that adaptive modeling and remodeling is sensitive to dynamic but not static strain change and that the osteogenic response to a period of dynamic strain is quickly saturated but is higher when the rate of change in strain is high and the distribution of strain unusual. Presumably it is the cumulative effect of this osteogenic response to load bearing that normally maintains bone mass above that seen in disuse situations. Through their independent effects on bone cell behavior, nutritional and hormonal factors can enable, enhance, limit, or frustrate full expression of the osteogenic response to strain change. However, such systemic factors do not appear to be able to engender or successfully imitate the sustained cumulative local response to load bearing that normally maintains functionally appropriate bone mass and architecture. Experiments in vivo and in vitro suggest that in osteocytes and surface osteoblasts the almost immediate response to strain change is increased production of prostacyclin. Surface osteoblasts also produce prostaglandin E. Only 5 minutes after loading, glucoses-phosphate dehydrogenase activity in osteocytes is increased in a local strain magnitude-related manner, and 24 h later there is an increase in osteocyte RNA. Exogenous PGE2 and PGI2 imitate the G6PD response in both osteocytes and osteoblasts, but only PGI2 imitates the loading-related increase in RNA in these two cell types. Indomethacin reduces the osteogenic response to loading in vivo and both the G6PD and RNA responses to loading in vitro. We hypothesize that the strain-related increase in PGE influences the synthetic activity of surface bone cells directly, whereas the strain-related increase in PGI2 additionally influences modeling and remodeling through the production of a cytokine or growth factor for which the loading-related RNA is coded. It may be at the stage of cytokine interaction that the potentially competing or complementary effects on modeling and remodeling of the loading and hormonal environments is resolved.
Journal of Bone and Mineral Research
Authors: Müller-Gerbl Magdalena , Putz Reinhard , Kenn Rolf 
Published: February 2010

Abstract
Since the work of Pauwels and his successors, it has been possible to use the distribution of subchondral bone density within a joint surface as a metric parameter that can reflect the principal long-term stress acting upon a joint. However, the x-ray densitometry method he employed cannot be applied to living people. A procedure was therefore developed whereby CT osteoabsorptiometry (CT OAM), based on the use of computed tomography, allows the distribution pattern of the density to be demonstrated in living subjects. This method has now been further developed, so that the form of the individual joint surfaces can be included by means of a three-dimensional reconstruction program. This method is presented here. In addition, selected representative examples of various joints from normal people, athletes, and patients are used to demonstrate the use of CT OAM. In these examples from living subjects, regularly occurring, reproducible distribution patterns of subchondral bone density can be recorded, reflecting changes in mechanical stresses on a joint (increased stress, reduced stress, and disorders of joint mechanics). CT osteoabsorptiometry is demonstrated as a suitable noninvasive technique for investigating the individual long-term stresses (loading history) acting on a living joint.
Physicochemical effects of acidosis on bone calcium flux and surface ion composition
Authors: Bushinsky David A. , Wolbach Wendy , Sessler Nelson E. , Mogilevsky Radion , Levi-Setti Riccardo 
Published: February 2010

Abstract
Net calcium flux (JCa) from bone in vitro is pH dependent. When pH falls below 7.40, through a reduction in [HCO3−], there is both physicochemical and cell-mediated JCa. To characterize the physicochemical effect of acidosis on bone we inhibited the bone-resorbing cells (osteoclasts) with the specific inhibitor calcitonin and studied the effect of acidosis on JCa and bone ion composition using an analytic high-resolution scanning ion microprobe. Neonatal mouse calvariae were cultured for 48 h in physiologically neutral pH medium (Ntl, pH = 7.41, [HCO3−] = 25 nM) or in medium that modeled metabolic acidosis (Met, pH = 7.10, [HCO3−] = 12), each with or without calcitonin (CT, 3 × 10−9 M). There was net calcium efflux in Ntl (JCa = 631 ± 36 nmol per bone per 48 h), which increased in Met (1019 ± 53, p &lt; 0.01); CT inhibited JCa in Ntl (-54 ± 11, p &lt; 0.01 versus Ntl), which increased in Met (197 ± 15, p &lt; 0.01 versus Ntl + CT). In the presence of CT the increase in JCa in Met versus Ntl represents physicochemical bone dissolution. The Ntl bone surface (∼2 nm in depth) was rich in Na compared to Ca (Na/Ca = 11.9, counts/s of detected secondary ions), which fell in Met (Na/Ca = 6.0, p &lt; 0.05); CT caused a further reduction of Na/Ca (3.1, p &lt; 0.01 versus Ntl and versus Met), which was not altered in Met (2.6, p ≥ 0.05 versus Ntl + CT). The subsurface of the Ntl bone, eroded to a depth of = 100 nm with the microprobe, was also rich in Na/Ca (11.0), which fell in Met (4.1, p &lt; 0.05); CT caused a further fall in Na/Ca (3.8, p &lt; 0.01 versus Ntl), which again was not altered in Met (3.5, p ≥ 0.05 versus Ntl + CT). Acidosis causes a release of bone Ca and a fall in the ratio of bone Na/Ca, indicating a greater release of Na. Inhibition of osteoclastic function with calcitonin causes an influx of Ca to bone and a marked fall in bone Na/Ca, indicating little change in Na. Acidosis plus calcitonin causes Ca release with no change in Na/Ca, indicating that physicochemical bone mineral dissolution causes relatively equal Ca and Na release. Thus, the cell-mediated effect of acidosis-induced bone resorption appears responsible for the excess Na efflux.
Measurement of osteoclasts and bone resorption by automated image analysis
Authors: Dunstan Colin R. , Lauren Peter D. , Somers Nicole M. , Evans Richard A. 
Published: February 2010

Abstract
An automated image analysis method is described for measurement of osteoclasts and resorbing surface in calcified bone. Osteoclasts, osteoid, and mineralized bone were measured in a single section, reacted for acid phosphatase activity, and then stained with orange G and light green stain. Three images were acquired of each field with a monochromatic camera at illuminating wavelengths of 635, 540, and 480 nm (selected using a stage monochromator). These wavelengths were chosen according to the absorption spectra of the different image components to maximize absorption differences between osteoclasts (red), mineralized bone (blue/green), and osteoid (orange). These components were then discriminated according to operator-defined ranges of color density (mineralized bone) or color fraction (osteoid and osteoclasts). A gray level coded segmented image was produced, from which was determined the area, perimeter, and number of each component and the length of contact zones with the marrow and between these components. The method was evaluated by twice measuring 10 bone sections from patients with end-stage liver failure awaiting liver transplantation. The method was quite reproducible, with coefficients of variation varying between 4% for bone volume (% tissue volume) and 22% for osteoid surface (% bone surface). The sections were also measured using a previously established semiautomated method. Coefficients of variation between methods were higher varying between 4% for bone volume (% tissue volume) and 56% for osteoid volume (% bone volume). The automated method gave a substantial time saving compared to the semiautomated method. An interactive technique was used in adjacent sections to evaluate tetracycline labeling and osteoblast surfaces.