bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for P2-purinoceptors on human osteoblast-like cells
Authors: Schöfl Christof , Cuthbertson K.S. Roy , Walsh Cathy A. , Mayne Caroline , Cobbold Peter , von Zur Mühlen Alexander , Hesch Rolf-Dieter , Dr. Gallagher James A. 
Published: February 2010

Abstract
ATP released from damaged cells or by controlled secretion could be an important factor in the formation or remodeling of bone. In a variety of other tissues ATP has been shown to control cellular processes by acting on P2-purinoceptors and activating the calcium signaling pathway. Here we demonstrate for the first time that extracellular ATP increases the intracellular free calcium [Ca2+]i concentration in normal human osteoblasts and in SaOS-2 cells, a human osteosarcoma-derived cell line, but not in ROS 17/2.8 cells. The ATP-induced increase in [Ca2+]i was dose dependent, and the concentrations of ATP required were similar to those reported to regulate cellular functions in other cell types. Although ATP is metabolized rapidly by bone cells, the effects on [Ca2+]i appeared to be mediated directly by ATP rather than one of its metabolites. Adenosine 3-thiotriphosphate, a nonhydrolyzable analog of ATP, induced similar changes in [Ca2+]i. This indicates that P2-purinoceptors are present on osteoblast-like cells and that extracellular ATP from various sources might be an important factor in the regulation of osteoblast functions.
Renal na+-phosphate cotransport in X-linked hyp mice responds appropriately to NA+ gradient, membrane potential, and pH
Authors: Harvey Nathalie , Tenenhouse Harriet S. 
Published: February 2010

Abstract
To investigate the mechanism for the 50% decrease in Vmax of the high-affinity phosphate transport system in the renal brush-border membrane of X-linked Hyp mice, we compared the effects of external Na+ concentration, membrane potential, pH, phosphonoformic acid (PFA), and arsenate on Na+-Pi cotransport in brush-border membrane vesicles prepared from normal mice and Hyp littermates. The affinity of the Na+-Pi cotransport system for Na+ (apparent Km = 60 ± 7 and 64 ± 2 mM for normal and Hyp mice, respectively) and the Na+-Pi stoichiometry estimated from Hill plots (2.5 ± 0.2 and 2.9 ± 0.6 for normal and Hyp mice, respectively) were similar in brush-border membranes of both strains. Inside-negative membrane potential, generated by anions of different permeabilities, stimulated Na+-Pi cotransport and inside-positive membrane potential generated by valinomycin, and a K+ gradient (outside &gt; inside) inhibited Na+-Pi cotransport to the same extent in brush-border membranes derived from normal mice and Hyp littermates. The pH dependence of Na+-Pi cotransport was similar in brush-border membrane vesicles of normal and Hyp mice. The ratio of Na+-Pi cotransport measured at pH 7.5 relative to that at pH 6.5 was 2.9 ± 0.6 in normal mice and 2.9 ± 0.7 in Hyp mice. PFA was a competitive inhibitor of Na+-Pi cotransport in brush-border membranes of both normal and Hyp mice. However, the apparent Ki for PFA was significantly lower in Hyp mice (0.31 ± 0.01 and 0.19 ± 0.02 mM in normal and Hyp mice, respectively, P &lt; 0.05). In contrast, a similar Ki for arsenate inhibition was observed in brush-border membranes of normal and Hyp mice. These results demonstrate that the decrease in Vmax of the high-affinity Na+-Pi cotransport system in renal brush-border membranes of X-linked Hyp mice cannot be attributed to an impaired response of the transporter to the Na+ gradient driving force, membrane potential, or external pH.
Longitudinal effect of tiludronate on bone mineral density, resonant frequency, and strength in monkeys
Authors: Geusens P. , Nijs J. , van der Perre G. , van Audekercke R. , Lowet G. , Goovaerts S. , Barbier A. , Lacheretz F. , Remandet B. , Jiang Y. , Dequeker J. 
Published: February 2010

Abstract
The effect of Tiludronate on bone was studied in 72 growing monkeys (Papio papio), 36 males and 36 females, aged 4–7 years. They were randomly allocated into four groups (18 animals per group, 9 males and 9 females): group I, controls; group II, 10 mg/kg/day; group III, 20 mg/kg/day; and group IV, 40 mg/kg/day of Tiludronate. A total of 12 animals (6 males and 6 females) in each group were sacrificed at the end of treatment (1 year) and 6 animals (3 males and 3 females) per group 1 year later. Bone mineral density (BMD) was measured by dual-photon absorptiometry. Biomechanical properties were evaluated by an impact torsion test and by resonant frequency analysis. Bone mineral measurements indicated that at the end of 1 year of treatment BMD was significantly higher, especially at the distal epiphysis of the radius, than in controls. No significant differences between groups were found in BMD 1 year after stopping treatment. Biomechanical analyses indicated that torsional stiffness increased after treatment. No differences between groups were found 1 year after stopping treatment. Results of resonant frequencies indicated an increased calculated transversal stiffness after treatment and 1 year later and an increased buckling strength 1 year after stopping treatment. In conclusion, the results on the effect of Tiludronate in growing monkeys indicate a profound effect of this drug on bone density and biomechanical properties. The biomechanical results indicate that this drug is safe, with conservation of bone strength despite a change in intrinsic mechanical properties of the bone.
Endurance Training Associated with Slightly Lowered Serum Estradiol Levels Decreases Mineral Density of Canine Skeleton
Authors: Puustjärvi K. , Karjalainen P. , Nieminen J. , Arokoski J. , Parviainen M. , Helminen H.J. , Soimakallio S. 
Published: February 2010

Abstract
The effects of long-term running exercise were studied in 20 beagle dogs. A total of 10 dogs ran from the age of 15 weeks to the age of 70 weeks in a progressive program for up to 40 km/day. A total of 10 sister dogs spent the study period in individual cages. When the dogs were 70 weeks old, bone mineral density of the vertebrae, hip, and radius was analyzed by dual-energy x-ray absorptiometry (DEXA; Lunar) and the vertebrae were also assessed by quantitative computed tomography (QCT; Siemens DR 1). Mineral density was lower in the running dogs than in the controls. The difference was greatest in the spine in the QCT analysis. Blood chemistry analyses revealed that the metabolism of the bone was significantly accelerated. The estradiol levels showed the trend to be reduced in the running group. The beneficial effect of exercise on mineral density has been shown in many earlier studies. However, in this study we demonstrate the possibility of adverse effects of long-term exercise on bone tissue. The change was associated with a decrease of serum estradiol level.
Radial bone mineral density in pre- and perimenopausal women: A prospective study of rates and risk factors for loss
Authors: Sowers Maryfran R. , Clark M. Kathleen , Hollis Bruce , Wallace Robert B. , Jannausch Mary 
Published: February 2010

Abstract
Radial bone mineral density (BMD) of 217 white women aged 22–54 years from a single rural community was evaluated in 1984 using single-photon absorptiometry. BMD was measured at a site one-third the distance from the wrist to the elbow, a site that represents predominantly cortical bone tissue. Most of these women (181; 83%) were reexamined 5 years later. The overall average 5 year radial BMD loss was -5.6%. The average rate of loss was -4.5% for women retaining positive estrogen status at follow-up (n = 108) and -7.4% for women who were in negative estrogen status at follow-up (n = 73). Baseline radial BMD measures were highly predictive of the follow-up BMD values (r = 0.80). Women with positive estrogen status and greater baseline BMD also had less BMD change. Greater baseline BMD did not predict the amount of change in women with negative estrogen status. The bone turnover markers osteocalcin and bone-specific alkaline phosphatase were significantly associated with BMD change in women with negative, but not positive estrogen status. There was no conclusive evidence of a “peak age” in the baseline and follow-up BMD measures. Based on rates of BMD change, “peak” bone mineral content appears to occur before age 25 years. Factors significantly associated with lower levels of BMD were menopause without estrogen replacement, nulliparity, smoking, and age at first pregnancy. Factors associated with more bone loss were menopause without estrogen replacement, smoking, shorter duration of oral contraceptive use, and older age. Quetelet index, muscle area, number of lost pregnancies, ever breast-feeding, or calcium intake were not associated with BMD level or its 5 year rate of loss. Physical activity and alcohol intake were not associated with BMD level or change after data were adjusted for age or estrogen status.
Activation and inhibition of protein kinase c in cultured bovine parathyroid cells: Effect on the release of c-terminal fragments of parathyroid hormone
Authors: Watson Patricia H. (Wood) , Mortimer Shane T. , Tanguay Karen E. , Hanley David A. 
Published: February 2010

AbstractThe response of the parathyroid gland to low Ca2+ may be mediated in part by protein kinase C (PKC). We assessed the effect of two PKC activators, SC-9 and SC-10, and one PKC inhibitor, H-7, on Ca2+-regulated PTH release and degradation in primary cultures of bovine parathyroid cells. Both SC-9 and SC-10 stimulated PTH release, compared to high Ca2+ alone, in parathyroid cells incubated in high Ca2+, with maximal PTH release of at least twofold occurring at a concentration of either activator of 10 nM (p &lt; 0.05). We have previously shown that another PKC activator, PMA, not only enhances PTH release in the presence of high Ca2+ but suppresses low Ca2+-stimulated PTH secretion. In the present study, neither SC-9 nor SC-10 caused a comparable suppression of PTH release at low Ca2+. However, the PKC inhibitor, H-7 (1 μM), blocked low Ca2+-stimulated (compared to the low Ca2+ control) PTH secretion by approximately 50% (p &lt; 0.01) and did not affect high Ca2+ suppression of PTH secretion. H-7 (1 μM) was able to oppose the stimulation of PTH release by the PKC activators SC-9, SC-10, and PMA at high Ca2+ and negated the PTH release-inhibiting effect of PMA at low Ca2+. Culture medium from these experiments was subjected to reversed-phase HPLC and the eluted fractions analyzed by RIA for the presence of intact and C-terminal fragments of PTH. The release of C-terminal fragments of PTH, when expressed as a percentage of total (fragment plus intact) PTH released, was greatest at high Ca2+ (∼80%) and considerably less at low Ca2+ (∼57%). Although the relative proportion of intact PTH released was increased when SC-9 and SC-10 stimulated PTH secretion at high Ca2+, analysis of variance suggests that the level of extracellular Ca2+ was the major determinant of PTH degradation to C-terminal fragments. At low Ca2+, H-7 blocked the previously reported ability of PMA to suppress PTH secretion but did not block the ability of PMA to enhance PTH degradation. These results indicate that (1) PKC activation is an important component of low Ca2+-stimulated PTH release, (2) the Ca2+ effect on PTH degradation may not be entirely mediated by PKC, and (3) the PMA effect on PTH degradation is not mediated through PKC.
Expression of human transforming growth factor α by chinese hamster ovarian tumors in nude mice causes hypercalcemia and increased osteoclastic bone resorption
Authors: Yates A.J. , Boyce B.F. , Favarato G. , Aufdemorte T.B. , Marcelli C. , Kester M.B. , Walker R. , Langton B.C. , Bonewald L.F. , Mundy G.R. 
Published: February 2010

Abstract
Transforming growth factor α (TGF-α) is a polypeptide regulator of cell growth produced by many malignant tumors. It stimulates osteoclastic resorption in bone organ culture and osteoclast-like cell formation in marrow culture. To determine whether tumor production of TGF-α can cause hypercalcemia in vivo, we used Chinese hamster ovarian (CHO) cells transfected with the human TGF-α gene (TCHO), which stably express and secrete TGF-α. We used nontransfected CHO cells as controls (CCHO). TCHO and CCHO were inoculated intramuscularly into one hindlimb of nude mice and grew as local solid tumors. After 4 weeks of TCHO tumor growth, plasma ionized calcium (Ca2+) increased to reach 1.48 ± 0.03 mM (mean ± SEM), whereas mice bearing similarly sized CCHO tumors and non-tumor-bearing mice (NTB) remained normocalcemic (normal range for Ca2+, 1.15–1.30 mM). Plasma TGF-α was undetectable by an ELIFA assay in all NTB mice, was markedly increased in all TCHO mice (5.75 ± 0.78 ng/ml), and was slightly increased in CCHO mice (0.50 ± 0.22 ng/ml). Quantitative bone histomorphometry showed a prominent increase in osteoclastic bone resorption in TCHO mice. These data suggest that TGF-α is a mediator of hypercalcemia and increased osteoclastic bone resorption in tumors that produce it in sufficient quantity.
Parathyroid hormone-related protein stimulates prostaglandin E2 release from human osteoblast-like cells: Modulating effect of peptide length
Authors: Mitnick Maryann , Isales Carlos , Paliwal Indu , Insogna Karl 
Published: February 2010

Abstract
Parathyroid hormone-related protein (PTHrP) is a potent bone-resorbing protein that frequently mediates the humoral hypercalcemia of malignancy syndrome. Since prostaglandins may mediate the bone-resorptive action of certain hormones, we examined the effect of PTHrP on prostaglandin E2 (PGE2) secretion by human osteoblast-like cells. There was low-level basal secretion of PGE2 by Saos-2 cells (8.1 + 0.6 pg/ml). Using four different preparations of PTHrP, it was observed that with increasing peptide length, from 36 to 141 amino acids, a significant increase in efficacy for PGE2 release was seen in these cells. All forms of PTHrP were agonists for PGE2 release, with effects seen at concentrations as low as 10−12 M in 48 h conditioned media. The amino terminus of the molecule appeared critical for this effect since the truncated derivative PTHrP-(7–34) did not induce significant PGE2 secretion. However, the influence of peptide length could not be explained by differential activation of adenylate cyclase since [Tyr26]PTHrP-(1–36)amide was equipotent to the longest peptide preparation, PTHrP-(1–141), in stimulating cyclic AMP accumulation in the Saos-2 cells. In contrast, PTHrP-(1–141) was significantly more effective than [Tyr35]PTHrP-(1–36)-amide in inducing a rise in cytosolic calcium. Further, this effect was noted at concentrations lower than those that caused significant cyclic AMP accumulation in the Saos-2 cells. PTHrP-(1–141) induced the release of PGE2 from primary human bone cell cultures to levels entirely comparable to those seen in the Saos-2 cells. PTHrP-(1–141) also induced PGE2 release by cultured fetal rat long bones at 72 h. We conclude that the carboxy-terminal region of PTHrP has important effects on cellular signal transduction pathways and on the release of a potent bone-active cytokine, PGE2.
Qualitative defects in natural killer cell function in ia osteopetrotic rats
Authors: Schneider Gary B. , Relfson Melanie , Ellis Thomas M. 
Published: February 2010

Abstract
Recent studies have provided evidence that cells of the immune system and their associated cytokines function in the regulation of bone turnover. The incisors absent (ia) osteopetrotic rat represents a model in which a defect in the immune system and bone resorption can be studied. Osteopetrosis in the ia rat is characterized by a generalized excess accumulation of bone as a result of reduced bone resorption by defective osteoclasts that lack a ruffled border and the ability to exocytose their osteolytic enzymes. Previous attempts to identify associated defects in the ia immune system have proven unsuccessful; ia rats demonstrate normal delayed hypersensitivity, mitogenic activity, and macrophage function. Inasmuch as the skeletal manifestations of the ia mutation may be the result of a defect in exocytosis, related defects may be evident in immune cells utilizing exocytosis of granules or enzymes for their cytolytic function. Natural killer (NK) cells function by such a mechanism. Therefore, these studies were undertaken to evaluate the natural immune system in ia rats. NK activity assessed by 51Cr release assays was significantly reduced in ia animals compared to normal littermates. Mononuclear cells isolated from the peripheral blood of ia rats revealed a significantly greater percentage of large granular lymphocytes than normal littermates. Comparison of NK cell phenotypes using two phenotypic parameters for NK cells (OX8+, OX 19− cells and 3.2.3+ cells) revealed that the mononuclear isolates of spleen and peripheral blood of mutant animals had significantly greater percentages of OX8+, OX 19− and 3.2.3+ cells than normal controls. Levels of BLT esterase (BLTE), a serine protease associated with the cytolytic mechanism of NK cells, were found to be greater in unsorted ia mononuclear cells than in normal cells but were equivalent in normal and mutant 3.2.3+ cells isolated by fluorescence-activated cell sorting. BLTE activity was enhanced but equal in normal and mutant 3.2.3+ cells stimulated with IL-2. The 3.2.3+ NK isolates demonstrated equal lytic activity in ia and normals, but when normal or mutant 3.2.3− cells (non-NK cells) were added to the 3.2.3+ia cells the lytic activity was significantly reduced. 3.2.3− cells had no effect on the activity of 3.2.3+ normal cells. The results indicate that 3.2.3+ mutant NK cells have normal lytic activity and BLTE activity and can respond to IL-2. The NK cells in the mutant are suppressed by a non-NK mononuclear cell, resulting in the lytic defect. A known suppressor of NK cells, prostaglandin, does not appear to be responsible for the NK defect in this mutant, because indomethacin, an inhibitor of prostaglandin synthesis, did not correct the defect.
Developmental expression of bone sialoprotein mRNA in rat mineralized connective tissues
Authors: Chen Jinkun , Shapiro Howard S. , Sodek Jaro 
Published: February 2010

Abstract
Bone sialoprotein (BSP) is a phosphorylated and sulfated glycoprotein that is a major noncollagenous protein of bone and other mineralizing connective tissues. BSP is characterized by the presence of several polyglutamic acid segments and an RGD motif that mediates cell attachment through a vitronectin-like receptor. Although the precise function of BSP is unknown, the expression of BSP in conjunction with bone formation in vitro indicates a role for this protein in the biomineralization of connective tissues. In this study we used Northern hybridization and in situ hybridization to determine the tissue-specific and developmental expression of BSP during embryogenesis and growth of rat tissues. Analysis of tissues obtained from 13, 17, and 21 day fetuses, and from 4-, 14-, and 100-day-old animals indicates that BSP mRNA expression is restricted to cells actively forming the mineralizing tissues of bone, dentin and cementum. BSP mRNA transcripts were first evident in fully differentiated osteoblasts of 17 day fetal tissues at sites of de novo intramembranous and endochondral bone formation, with maximal expression observed at 21 days of gestation. Thereafter, BSP mRNA levels decreased markedly, and in adult bone hybridization was detected only in the primary spongiosa of long bones. In comparison, mRNAs for osteopontin (OPN), alkaline phosphatase (ALP), and osteocalcin (OC) peaked at 4–14 days postpartum before declining. In the tibiae, Northern hybridization revealed a second peak of mRNA for BSP, ALP, and OPN at 14 days, reflecting an increased osteogenic activity due to the formation of the secondary centers of ossification in the epiphyseal cartilage. In situ hybridization also revealed BSP mRNA in hypertrophic chondrocytes at sites of bone formation, in odontoblasts of the incisor during dentinogenesis, and in cementoblasts during cementogenesis. In view of the restricted distribution and temporal changes in the expression of BSP mRNA that we observed together with the chemical properties of BSP, we believe that this protein has a specific role in mediating the initial stages of connective tissue mineralization.
Perspective how many women have osteoporosis?
Authors: Dr. Melton L. Joseph , Chrischilles Elizabeth A. , Cooper Cyrus , Lane Ann W. , Riggs B. Lawrence 
Published: February 2010

Abstract
Osteoporosis is widely viewed as a major public health concern, but the exact magnitude of the problem is uncertain and likely to depend on how the condition is defined. Noninvasive bone mineral measurements can be used to define a state of heightened fracture risk (osteopenia), or the ultimate clinical manifestation of fracture can be assessed (established osteoporosis). If bone mineral measurements more than 2 standard deviations below the mean of young normal women represent osteopenia, then 45% of white women aged 50 years and over have the condition at one or more sites in the hip, spine, or forearm on the basis of population-based data from Rochester, Minnesota. A smaller proportion is affected at each specific skeletal site: 32% have bone mineral values this low in the lumbar spine, 29% in either of two regions in the proximal femur, and 26% in the midradius. Although this overall estimate is substantial, some other serious chronic diseases are almost as common. More importantly, low bone mass is associated with adverse health outcomes, especially fractures. The lifetime risk of any fracture of the hip, spine, or distal forearm is almost 40% in white women and 13% in white men from age 50 years onward. If the enormous costs associated with these fractures are to be reduced, increased attention must be given to the design and implementation of control programs directed at this major health problem.
Is heritability a risk factor for postmenopausal osteoporosis?
Authors: Hansen Marc Allan , Hassager Christian , Jensen Signe Birk , Christiansen Claus 
Published: February 2010

Abstract
We investigated heritability as a risk factor for the development of osteoporosis in two randomly selected populations of postmenopausal women and their premenopausal daughters. We determined the familial resemblance in bone mass at three sites; the distal forearm, lumbar spine, and proximal femur, premenopausally and with increasing maternal postmenopausal age. We also examined the bone mass of daughters in relation to mothers with and without osteoporotic fractures. Peak bone mass among premenopausal siblings was significantly correlated at all sites (r = 0.30–0.42, p &lt; 0.001). The same levels of resemblance were found between early postmenopausal mothers and premenopausal daughters. There was no significant difference in bone mass at any skeletal site between daughters of women with either peripheral or spinal fractures and daughters of women without fractures. We also examined familial resemblance with four biochemical markers of bone turnover (fasting urinary calcium and hydroxyproline, both corrected for creatinine, serum alkaline phosphatase, and plasma bone Gla protein). A generally significant resemblance were seen in premenopausal siblings (r = 0.25–0.39, hydroxyproline NS), but not between premenopausal daughters and postmenopausal mothers. We conclude that peak bone mass is hereditary in the distal forearm, lumbar spine, and proximal femur, but the mother-daughter resemblance explains only about 16% of the variability in daughters' bone mass. Furthermore, daughters of women with a moderate state of osteoporotic fractures are not substantially at an increased risk of having a low peak bone mass compared to the daughters of women without fractures.