bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interspecies comparison of renal cortical receptors for parathyroid hormone and parathyroid hormone-related protein
Authors: Orloff John J. , Goumas Douglas , Wu Terence L. , Stewart Andrew F. 
Published: February 2010

Abstract
Parathyroid hormone (PTH) and PTH-related proteins (PTHrP) interact with a common receptor in rat bone cells and in canine renal membranes with similar affinity, but PTHrP are substantially less potent than PTH in stimulating adenylate cyclase in canine renal membranes; in contrast, PTH and PTHrP are equipotent in stimulating adenylate cyclase in rat bone cells. This discrepancy has been largely viewed as reflecting differences in the relative efficiency of signal transduction for PTHrP between bone and kidney assay systems. To test the alternative (but not mutually exclusive) hypothesis that these differences could reflect interspecies differences in PTH receptors, we have characterized the bioactivity of amino-terminal PTHrP and PTH in rat and human renal cortical membranes (RCM) and compared them to results we previously reported in canine RCM.
The stability of PTH and PTHrP peptides under binding and adenylate cyclase assay conditions was greater than 80% for each species. Competitive inhibition of [125I](Tyr36)hPTHrP-(1–36)NH2 binding to rat RCM by bPTH-(1–34) and (Tyr36)hPTHrP-(1–36)NH2 yielded nearly identical binding dissociation constants (3.7 and 3.6 nM, respectively), and binding to human RCM demonstrated slightly greater potency for PTHrP (0.5 nM) than for PTH (0.9 nM). Similarly, adenylate cyclase stimulating activity was equivalent for the two peptides in rat RCM, but PTHrP was twofold more potent than PTH in human RCM. Covalent photoaffinity labeling of protease-protected rat RCM yielded an apparent 80 kD receptor protein, and crosslinking of human RCM labeled an 85 kD receptor, indistinguishable in size from the canine renal PTH receptor.
We conclude that rat, canine, and human renal cortical PTH receptors exhibit species specificity. The previously observed differences between rat bone cells and canine renal membranes in the efficiency of signal transduction by PTHrP may be explained, at least in part, by these species differences.
Effects of voluntary exercise on bone mineral content in rats
Authors: Newhall Katherine M. , Rodnick Kenneth J. , van der Meulen Marjoleine C. , Carter Dennis R. , Marcus Robert 
Published: February 2010

Abstract
We used a voluntary running model to explore the relationship between average daily running distance and bone mineral status of rats. A total of 60 male Sprague-Dawley rats were randomly assigned at 6 weeks of age to a sedentary control group (n = 22) or to a group with unlimited access to a running wheel (n = 38). The running distance of exercising rats was monitored daily, and steady-state running levels ranged from 3.2 to 18.1 km/day. At the end of the experimental period, femora and tibiae were dissected and bone mineral content (BMC, g/cm) and bone mineral density (BMD, g/cm2) were measured by single-photon absorptiometry. Cross-sectional morphometry was examined by taking a transverse section of the femoral middiaphysis. Hindlimb percentage fat was significantly higher in controls than in runners (20.0 ± 1.2 versus 11.1 ± 0.6, p &lt; 0.001), and soleus mass was greater in runners than in controls (371 ± 8.1 versus 320 ± 0.8 mg, p &lt; 0.001). Femoral and tibial lengths, weights, and volumes were significantly higher in runners than in controls (p &lt; 0.005). BMC and BMD were higher in runners than in controls at all sites apart from the distal femur. Cross-sectional areas at the femoral midshaft were greater in running rats than in sedentary controls (6.26 ± 0.1 versus 5.45 ± 0.3 mm2, p &lt; 0.02), as was the polar moment of inertia (15.6 ± 0.6 versus 12.7 ± 0.2 mm4, p &lt; 0.05). No positive correlation was found between distance run and BMC, BMD, cross-sectional area, or polar moment of inertia. Conversely, there was a highly significant positive correlation between body weight and most bone measurements and a negative correlation between distance run and body weight and femoral and tibial wet weight and volume. Partial correlations correcting for differences in body weight suggested that exercise level was not an independent predictor of BMC. In summary, voluntary running activity markedly increased femoral and tibial BMC in young male rats compared to weight-matched sedentary controls. However, within the exercising group substantially higher running distances produced no further increase in BMC.
Lack of a direct effect of estrogen on proliferation and differentiation of normal human osteoblast-like cells
Authors: Keeting Philip E. , Scott Robert E. , Colvard Douglas S. , Han In K. , Spelsberg Thomas C. , Riggs B. Lawrence 
Published: February 2010

Abstract
Although osteoblasts contain estrogen receptors, it is unclear whether estrogen has direct effects on osteoblast proliferation and differentiation. We evaluated the effects of 17β-estradiol treatment (1 pM to 10 nM) on the proliferation and differentiation of cultured normal adult human cells that expressed many of the phenotypic characteristics and hormonal sensitivities of mature osteoblasts (hOB cells). Treatment of hOB cells with estradiol for as long as 144 h did not affect the rate of DNA synthesis and had minimal, if any, effects on differentiated function. Whereas alkaline phosphatase activity was increased by nearly twofold (P &lt; 0.01) when the hOB cells were treated with 1 nM 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], treatment with estradiol had no effect when given alone and did not affect the cells' response to 1,25-(OH)2D3. Similarly, the release of bone gla protein (BGP, osteocalcin) was induced by treatment with 1,25-(OH)2D3 (P &lt; 0.05), but estradiol treatment did not affect this response. Cellular levels of mRNA for alkaline phosphatase and BGP were not altered by estradiol treatment. We conclude that estradiol treatment does not have major effects on the growth or differentiation of cultured hOB cells. These results are consistent with previous observations in vivo that indicate estrogen acts principally to decrease bone resorption, not to modulate its formation.
Immunoaffinity purification of parathyroid hormone-related protein from bovine milk and human keratinocyte-conditioned medium
Authors: Stewart Andrew F. , Wu Terrence L. , Insogna Karl L. , Milstone Leonard M. , Burtis William J. 
Published: February 2010

Abstract
Parathyroid hormone-related proteins (PRHrP) are a novel family of proteins that appear to be responsible for humoral hypercalcemia of malignancy. Although PTHrP derived from human tumors have been purified and their N-terminal amino acid sequence determined, and although the structure of the PTHrP gene and its alternatively spliced mRNA transcripts have been defined, the secretory and circulating form(s) of the protein are unknown. Purification of PTHrP in the past has been difficult, requiring multiple chromatographic steps and months or years to complete.
To define naturally occurring PTHrP species we have developed a rapid and efficient immunoaffinity purification method. Bovine milk (250 ml) and human keratinocyte-conditioned medium (3000 ml) were affinity purified using a 300 μl affinity-purified polyclonal anti-PTHrP-(1–36) antibody column and a single RP-HPLC step. Purification required only 7–10 days and yielded a 3–4% recovery. Quantities of PTHrP sufficient for silver-stained SDS-PAGE, Western analysis, and N-terminal amino acid sequence were obtained.
In contrast to conventional purification schemes, affinity purification of PTHrP is rapid and efficient and can be applied to biologic samples that contain PTHrP in low abundance. These methods can be applied to the purification and characterization of the as yet undefined secretory and circulating forms of PTHrP.
Effect of chronic carbonic anhydrase inhibitor therapy on bone mineral density in white women
Authors: Dr. Pierce William M. , Nardin George F. , Fuqua Margaret F. , Sabah-Maren Emily , Stern Steven H. 
Published: February 2010

Abstract
A limited, dual-photon absorptiometry, single-center study of bone mineral density (BMD) was conducted on white female glaucoma subjects who were chronic users of the carbonic anhydrase (CA) inhibitors acetazolamide (Az) or methazolamide (Mz). In postmenopausal subjects long-term (&gt;4 years) CA inhibitor use was associated with a bone-sparing effect as judged by spinal BMD in comparison to controls matched for age, sex, weight, and ethnic group or in comparison to a national normative data base. Short-term (0-2 years) postmenopausal CA inhibitor users and premenopausal subjects using CA inhibitors showed no sparing of spinal BMD. Femoral neck BMD was not affected by CA inhibitor therapy in any of the groups. This study supports a proposed role for carbonic anhydrase in human bone resorption and suggests a possible future utility for carbonic anhydrase inhibitors in prophylaxis or management of primary involutional osteoporosis. Future studies are necessary to verify and expand these findings, assess the effects of CA inhibitors on bone mechanical competence, and further develop CA inhibitors with some specificity for bone.
Isolation of avian osteoclasts: Improved techniques to preferentially purify viable cells
Authors: Oursler Merry Jo , Collin-Osdoby Patricia , Anderson Fred , Li Ling , Webber David , Dr. Osdoby Philip 
Published: February 2010

Abstract
Among the many different methods that have been used to obtain and study isolated osteoclasts from a variety of species, the egg-laying hen maintained on a low-calcium diet has proven to be one of the richest sources of relatively large numbers of osteoclasts. However, recent reports and our own observations indicate that only a very small proportion of the osteoclasts harvested by such methods are viable.(1) The difficulty in obtaining large numbers of viable osteoclasts has restricted studies of osteoclast function and regulation, and so new isolation methods were sought. This report describes an osteoclast isolation procedure designed to substantially enrich for large numbers of viable authentic osteoclasts. Size and cell density differences between osteoclasts and contaminating mononuclear cells have been exploited in developing the methods for osteoclast enrichment. Sequential nonenzymatic and enzymatic procedures, followed by cell density separations, have yielded three populations of osteoclasts derived from chick hatchlings maintained on a low-calcium diet. A corresponding decrease in bone-associated osteoclasts during the sequential isolation scheme has been monitored using an osteoclast-directed monoclonal antibody, 121F. The first two populations contain 40% osteoclasts, which are predominantly (&gt;99%) nonviable, but the third population contains 8-fold more viable osteoclasts, effectively increasing the proportion of viable osteoclasts more than 25-fold in comparison with the first two populations. The osteoclast-like nature of the isolated viable population 3 cells was established by demonstrating ruffled border formation, possession of the 121F monoclonal antibody-reactive osteoclast antigen, bone particle resorption activity, and resorption pit formation on cortical bone slices revealed by transmission and scanning electron microscopy.
Estrogen and diphosphonate treatment provide long-term protection against osteopenia in ovariectomized rats
Authors: Dr. Wronski T.J. , Yen C.-F. , Scott K.S. 
Published: February 2010

Abstract
The goal of this study is to determine whether the previously observed, short-term protective effect of estrogen and diphosphonate compounds against osteopenia in ovariectomized (OVX) rats can be maintained for an entire year. Sham-operated control and OVX rats were treated intermittently with vehicle alone, estrogen, or the diphosphonate compounds etidronate disodium (EHDP) and risedronate (NE-58095) for 360 days after surgery. Their proximal tibiae and first lumbar vertebrae were processed undecalcified for quantitative bone histomorphometry. Both skeletal sites in vehicle-treated OVX rats were characterized by decreased cancellous bone volume and increases in most cellular and fluorochrome-based indices of bone formation and resorption. Treatment of OVX rats with estrogen or diphosphonate compounds depressed bone turnover and provided nearly complete protection against cancellous bone loss. Long-term EHDP treatment induced a moderate mineralization defect, as indicated by increased absolute osteoid volume and a high proportion of osteoid surfaces devoid of adjacent osteoblasts. In contrast, NE-58095 had minimal effects on bone mineralization. These findings indicate that diphosphonate compounds and estrogen provide long-term protection against tibial and vertebral osteopenia in OVX rats. They further indicate that diphosphonate compounds merit consideration as an alternative to estrogen for the prevention of postmenopausal bone loss.
Inhibition of bone resorption by inorganic phosphate is mediated by both reduced osteoclast formation and decreased activity of mature osteoclasts
Authors: Yates A. John , Oreffo Richard O.C. , Mayor Kevin , Mundy Gregory R. 
Published: February 2010

Abstract
High concentrations of inorganic phosphate (Pi) are known to inhibit bone resorption, although the mechanism(s) underlying this effect is unclear. To investigate whether Pi can inhibit the formation of osteoclasts we studied the effects of changes in Pi concentration between 1 and 4 mM on osteoclast-like cell formation in 1 week cultures of mouse bone marrow. Osteoclast-like cells were identified by multinuclearity, positive staining for tartrate-resistant acid phosphatase (TRAP), and contraction in response to calcitonin. Increasing concentrations of Pi inhibited formation of these cells in a dose-dependent manner. To study effects of Pi on the bone-resorbing activity of mature osteoclasts we isolated osteoclasts from calcium-deficient egg-laying hens or rat pups and incubated them on sperm whale dentine slices. High Pi concentrations markedly reduced both the number of resorption pits formed per dentine slice and the mean area of each pit in both avian and mammalian systems. These data indicate that high concentrations of Pi act on bone directly, both to inhibit generation of new osteoclasts from their precursor cells and to inhibit bone resorption by mature osteoclasts. These effects of extracellular Pi concentration may play an important modulatory role on bone turnover in vivo and have potential importance in several disease states in which Pi metabolism is perturbed.
Inhibiting and stimulating effects of TGF-β1 on osteoclastic bone resorption in fetal mouse bone organ cultures
Authors: Dieudonné S.C. , Foo P. , Van Zoelen E.J.J. , Burger E.H. 
Published: February 2010

Abstract
The effects of TGF-β1 on osteoclastic resorption of fetal mouse calvaria and long bones at various stages of development was studied in organ culture. In resorbing calvariae and long bones with an established marrow cavity TGF-β1 (4–10 ng/ml) had a stimulating effect on 45Ca release that was partially inhibited by indomethacin. In primitive long bones, however, which were explanted before osteoclast invasion and excavation of a marrow cavity had started, TGF-β1 (1–4 ng/ml) inhibited 45Ca release by an indomethacin-insensitive mechanism.
Histomorphometry of long bones after staining for tartrate-resistant acid phosphatase (TRAP) revealed that TGF-β1 treatment inhibited the migration of TRAP-positive cells from periosteum to developing marrow cavity and inhibited cell fusion. However, the formation of (mononuclear) TRAP-positive cells in the periosteum-perichondrium was strongly enhanced.
These data suggest that TGF-β1 modulates various steps in the cascade of osteoclast development, recruitment, and activation in different ways, involving both prostaglandin-mediated and prostaglandin-independent pathways. Therefore the net effect of exogenous TGF-β1 on osteoclastic resorption in bone organ cultures depends on the relative prevalence of osteoclast progenitors, precursors, and mature osteoclasts in the tissue under study.
Spinal bone mineral density in 335 normal and obese children and adolescents: Evidence for ethnic and sex differences
Authors: Mccormick David P. , Ponder Stephen W. , Fawcett H. Daniel , Palmer Judy L. 
Published: February 2010

Abstract
Spinal bone mineral density (BMD) and anthropometric measures were studied in 312 nonobese and 23 obese black, white, and Hispanic children and adolescents age 5.00–18.99 years. In adolescents BMD correlated with age, weight, height, fat-free density, body mass index, and midarm circumference.
Utilizing the entire group of 312 nonobese subjects, mean Z scores were calculated for comparison versus reference subgroups for bone mineral density index (BMDI, BMD/weight). BMDI was greater for black than for white and Hispanic children and adolescents across all ages studied. Female adolescents accumulated spinal mineral more rapidly than male adolescents. Black males had greater mineral than white and Hispanic males. Differences in BMDI between subgroups could not be explained by differences in body weight or spinal vertebral size. BMDI proved a more sensitive measure for comparing subgroups than did BMD.
The study provides normative data and a quantitative methodology for analyzing differences in spinal mineral between groups of children and adolescents.
Structural studies of the mineral phase of calcifying cartilage
Authors: Rey C. , Beshah K. , Griffin R. , Glimcher M.J. 
Published: February 2010

Abstract
The calcified cartilage of the epiphyseal growth plate of young calves has been studied by x-ray diffraction, Fourier transform infrared spectroscopy, magic angle 31P nuclear magnetic resonance spectroscopy, and chemical composition. The powdered tissue was separated by density centrifugation as a function of mineral content and thus qualitatively of the age of the calcium-phosphorus mineral phase. The individual density centrifugation fractions were examined separately. X-ray diffraction of the samples, especially of the lowest density fractions, revealed very poorly crystalline apatite. Fourier transform infrared spectroscopy and 31P nuclear magnetic resonance spectroscopy revealed the presence of significant amounts of nonapatitic phosphate ions. The concentration of such nonapatitic phosphates increases during the early stages of mineralization but then decreases as the mineral content steadily rises until full mineralization is achieved.
The total concentration of carbonate ions was found to be much lower in calcified cartilage than in bone from the same organ (scapula). The carbonate ions are located in both A sites (OH−) and B sites (PO43-), with a distribution similar to that found in bone mineral. However, discrepancies between infrared resolution factors of phosphate and carbonate bands are consistent with a heterogeneous distribution of carbonate ions in poorly organized domains of the solid phase of calcium phosphate. These initial studies permit one to characterize the calcium phosphate mineral phase as a very poorly crystalline, immature calcium phosphate apatite, rich in labile nonapatitic phosphate ions, with a low concentration of carbonate ions compared with bone mineral of the same animal, indeed from the bone of the same organ (scapula).
In vitro studies on bone resorption in neonatal mouse calvariae using a modified dissection technique giving four samples of bone from each calvaria
Authors: Ljunggren Östen , Ransjö Maria , Lerner Ulf H. 
Published: February 2010

Abstract
Bone resorption in a modified bone culture system, based on incubation of small fragments from neonatal mouse calvarial bones, has been studied. Four bone fragments were dissected out from each mouse calvaria and were thereafter cultured in CMRL 1066 medium in plastic multiwell dishes. Bone resorption was assessed by 45Ca release from prelabeled bones. The rate of bone resorption in response to parathyroid hormone (PTH) was less in the anterior part of the calvaria compared to the posterior part. After removing the anterior region, four parietal bone fragments that showed identical basal and PTH-stimulated release of 45Ca could be dissected out from each mouse. Excretion of lactate dehydrogenase and β-glucuronidase was the same in bones cultured submerged or on grids. Uptake of [3H]thymidine in bones cultured submerged was 54% of [3H]thymidine uptake in bones cultured on grids. Dose-response curves, established by using parietal bone fragments, showed that the sensitivity and the magnitude of the increase in 45Ca release seen after stimulation with PTH, prostaglandin E2, and 1α-hydroxyvitamin D3 were the same for bones cultured submerged or on grids. The 45Ca release in response to stimulation with PTH, prostaglandin E2, and 1α-OHD3 was the same in calvarial fragments cultured submerged and those previously obtained with calvarial halves cultured on grids. Thus, even though the rate of DNA synthesis was slower in bones cultured submerged, the rate and the magnitude of resorption were the same in bones cultured on grids or submerged. These data show that it is possible to perform studies on bone resorption with small fragments of neonatal mouse parietal bones.
On the role of cyclic AMP as a mediator of bone resorption: γ-Interferon completely inhibits cholera toxin- and forskolin-induced but only partially inhibits parathyroid hormone-stimulated 45Ca release from mouse calvarial bones
Authors: Dr. Lerner Ulf H. , Ransjö Maria , Ljunggren Östen , Klaushofer Klaus , Hoffmann Oskar , Peterlik Meinrad 
Published: February 2010

Abstract
The effects of γ-interferon (γ-IFN) on bone resorption and cyclic AMP formation stimulated by parathyroid hormone (PTH), forskolin, and cholera toxin have been studied in cultured neonatal mouse calvarial bones. Bone resorption was assessed by the release of 45Ca from prelabeled mouse calvarial bone fragments. Cyclic AMP formation was quantified by analyzing the amount of the nucleotide in calvarial bone tissue. γ-IFN completely blocked the 45Ca release response to forskolin and cholera toxin in 96 h cultures. In contrast, the 45Ca release response to PTH was only partially inhibited, an effect that was seen over a wide range of PTH concentrations. The inhibitory effect of γ-IFN was dose dependent, with a threshold for action at 10 U/ml. Forskolin-stimulated 45Ca release could only be inhibited when γ-IFN was added simultaneously with forskolin; γ-IFN added to bones prestimulated with forskolin had no effect. The inhibitory effect of γ-IFN on PTH-stimulated 45Ca release was seen first after a time lag of 48 h. In contrast, calcitonin caused an inhibition after only 3 h. PTH and cholera toxin stimulation of radioactive calcium release was also inhibited by γ-IFN in bones treated with indomethacin. γ-IFN inhibited forskolin-induced 45Ca release in bones treated with the mitotic inhibitor hydroxyurea. No effect of γ-IFN on cyclic AMP formation induced by PTH, cholera toxin, or forskolin could be seen. These data show that γ-IFN inhibits forskolin- and cholera toxin-induced bone resorption by a mechanism unrelated to prostaglandin production or mitotic activity. We suggest that γ-IFN causes a delayed inhibition of bone resorption in mouse calvariae by inhibiting the recruitment of new osteoclasts and thereby totally blocks forskolin- and cholera toxin-induced bone resorption. The bone-resorptive effect of PTH is only partially blocked since the initial stages in the mechanism of action of PTH involve rapid activation of existing osteoclasts, insensitive to inhibition by γ-IFN. These data lend further support to the view that PTH stimulation of bone resorption is not solely mediated by cyclic AMP.