bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative Trait Loci Affecting Peak Bone Mineral Density in Mice
Authors: Klein Robert F. , Mitchell Steve R. , Phillips Tamara J. , Belknap John K. , Orwoll Eric S. 
Published: April 2006

Abstract
Peak bone mass is a major determinant of risk of osteoporotic fracture. Family and twin studies have found a strong genetic component to the determination of bone mineral density (BMD). However, BMD is a complex trait whose expression is confounded by environmental influences and polygenic inheritance. The number, locations, and effects of the individual genes contributing to natural variation in this trait are all unknown. Experimental animal models provide a means to circumvent complicating environmental factors, and the development of dense genetic maps based on molecular markers now provides opportunities to resolve quantitative genetic variation into individual regions of the genome influencing a given trait (quantitative trait loci, QTL). To begin to identify the heritable determinants of BMD, we have examined genetically distinct laboratory mouse strains raised under strict environmental control. Mouse whole-body bone mineral content by dual-energy X-ray absorptiometry (DXA) correlated strongly with skeletal calcium content by ashing, and peak whole-body BMD by DXA in female mice occurred at ∼80–90 days of age. We therefore determined mean body weight and peak whole body BMD values in 12-week-old female mice from a panel of 24 recombinant inbred (RI) BXD strains, derived from a cross between C57BL/6 and DBA/2 progenitors. The distribution of body weight and BMD values among the strains clearly indicated the presence of strong genetic influences on both of these traits, with an estimated narrow sense heritability of 60% and 35%, respectively. The patterns of differences in body weight and peak whole body BMD in the BXD strains were then integrated with a large database of genetic markers previously defined in the RI BXD strains to generate chromosome map sites for QTL. After correction for redundancy among the significant correlations, QTL analysis of the BXD RI strain series provisionally identified 10 chromosomal sites linked to peak bone mass development in the female. Several of the identified sites map near genes encoding hormones, structural proteins, and cell surface receptors that are intricately involved in skeletal homeostasis. Four QTL for body weight were also identified. One of these loci was also strongly linked to inherited variation in BMD. This finding suggests that body weight and peak BMD may be influenced by linked genes or perhaps by common genes with pleiotropic effects. Our phenotyping in the RI BXD strains has allowed us to map a number of specific genetic loci strongly related to the acquisition of peak BMD. Confirmation of these findings will likely result in the understanding of which genes control skeletal health.
Molecular Mechanism of Action of Fluoride on Bone Cells
Authors: Lau K.-H. William , Baylink David J. 
Published: April 2006

Abstract
Fluoride is an effective anabolic agent to increase spinal bone density by increasing bone formation, and at therapeutically relevant (i.e., micromolar) concentrations, it stimulates bone cell proliferation and activities in vitro and in vivo. However, the fluoride therapy of osteoporosis has been controversial, in large part because of a lack of consistent antifracture efficacy. However, information regarding the molecular mechanism of action of fluoride may improve its optimum and correct usage and may disclose potential targets for the development of new second generation drugs that might have a better efficacy and safety profile. Accordingly, this review will address the molecular mechanisms of the osteogenic action of fluoride. In this regard, we and other workers have proposed two competing models, both of which involve the mitogen activated protein kinase (MAPK) mitogenic signal transduction pathway. Our model involves a fluoride inhibition of a unique fluoride-sensitive phosphotyrosine phosphatase (PTP) in osteoblasts, which results in a sustained increase in the tyrosine phosphorylation level of the key signaling proteins of the MAPK mitogenic transduction pathway, leading to the potentiation of the bone cell proliferation initiated by growth factors. The competing model proposes that fluoride acts in coordination with aluminum to form fluoroaluminate, which activates a pertussis toxin-sensitive Gi/o protein on bone cell membrane, leading to an activation of cellular protein tyrosine kinases (PTKs), which in turn leads to increases in the tyrosine phosphorylation of signaling proteins of the MAPK mitogenic signal transduction pathway, ultimately leading to a stimulation of cell proliferation. A benefit of our model, but not the other model, is that it accounts for all the unique properties of the osteogenic action of fluoride. These include the low effective fluoride dose, the skeletal tissue specificity, the requirement of PTK-activating growth factors, the sensitivity to changes in medium phosphate concentration, the preference for undifferentiated osteoblasts, and the involvement of the MAPK. Unlike fluoride, the mitogenic action of fluoroaluminate is not specific for skeletal cells. Moreover, the mitogenic action of fluoroaluminate shows several important, different characteristics than that of fluoride. Thus, it is likely that our model of a fluoride-sensitive PTP represents the actual molecular mechanism of the osteogenic action of fluoride.
Conditionally Immortalized Murine Osteoblasts Lacking the Type 1 PTH/PTHrP Receptor
Authors: Divieti P. , Lanske B. , Kronenberg H. M. , Bringhurst F. R. 
Published: April 2006

Abstract
Osteoblasts synthesize and mineralize bone matrix and are principal target cells for parathyroid hormone (PTH). The type 1 PTH/PTH-related protein (PTHrP) receptor (PTH1R), cloned from rat osteoblastic cells, activates multiple intracellular signaling mechanisms. The specific roles of these PTH1R signals, or of responses to other types of PTH receptors that may be expressed, in regulating osteoblast function are incompletely understood. Use of established mammalian osteoblastic cell lines has led to much understanding of PTH action in bone, although such cells are of neoplastic origin or have other characteristics that compromise their validity as models of normal osteoblasts. To examine the role of the PTH1R in osteoblast biology, we have isolated a series of clonal murine calvarial osteoblastic cell lines that are only conditionally immortalized, via expression of a transgene encoding the tsA58 temperature-sensitive SV40 large T antigen, and that lack both functional alleles of the PTH1R gene. When cultured under nontransforming conditions, these cells stopped proliferating, expressed a series of characteristic osteoblastic genes (including the nonfunctional remnant of the PTH1R gene), and, after 3–4 weeks, produced mineralized bone nodules in a manner that was regulated by 1,25-dihydroxyvitamin D3 but not by PTH(1–84). Cyclic AMP measurements revealed no evidence of expression of alternate species of Gs-linked PTH receptors. Stable transfection with PTH1R cDNA reconstituted both PTH binding and adenylyl cyclase activation, increased basal osteocalcin expression, and supported PTH stimulation of c-Fos expression and matrix mineralization. These conditionally transformed, PTH1R(−/−) clonal osteoblastic cell lines should prove useful for studies of the regulation of osteoblast differentiation and function by both endogenous nonclassical species of PTH (or PTHrP) receptors and mutant signal-selective PTH1Rs.
Linkage of a QTL Contributing to Normal Variation in Bone Mineral Density to Chromosome 11q12–13
Authors: Koller D. L. , Rodriguez L. A. , Christian J. C. , Slemenda C. W. , Econs M. J. , Hui S. L. , Morin P. , Conneally P. M. , Joslyn G. , Curran M. E. , Peacock M. , Johnston C. C. , Dr. Foroud T. 
Published: April 2006

Abstract
Osteoporosis is a leading public health problem that is responsible for substantial morbidity and mortality. A major determinant of the risk for osteoporosis in later life is bone mineral density (BMD) attained during early adulthood. BMD is a complex trait that presumably is influenced by multiple genes. Recent linkage of three Mendelian BMD-related phenotypes, autosomal dominant high bone mass, autosomal recessive osteoporosis-pseudoglioma, and autosomal recessive osteopetrosis to chromosome 11q12–13 led us to evaluate this region to determine if the underlying gene(s) could also contribute to variation in BMD in the normal population. We performed a linkage study in a sample of 835 premenopausal Caucasian and African–American sisters to identify genes underlying BMD variation. A maximum multipoint LOD score of 3.50 with femoral neck BMD was obtained near the marker D11S987, in the same chromosomal region as the three Mendelian traits mentioned above. Our results suggest that the gene(s) underlying these Mendelian phenotypes also play a role in determining peak BMD in the normal population and are the first using linkage methods to establish a chromosomal location for a gene important in determining peak BMD. These findings support the hypothesis that a gene responsible for one or more of the rare Mendelian BMD traits linked to chromosome 11q12–13 has an important role in osteoporosis in the general population.
Effect on the Femur of a New Hip Fracture Preventive System Using Dropped-Weight Impact Testing
Authors: Okuizumi Hiroyasu , Harada Atsushi , Iwata Hisashi , Konishi Nobuo 
Published: April 2006

Abstract
To reduce hip fractures during falls, we devised a new hip fracture preventive system to attenuate impact on the greater trochanteric region and studied the effects of the system on the femur. Twelve coupled, embalmed, cadaveric femora were used. Right femora were fractured without protection as a control and compared with left femora covered by the protection system, which consisted of a silicone gel pad or the silicone gel pad combined with a resin cover. The impact of a fall was simulated by mounting a femur in the horizontal plane and dropping an 8.4 kg mass on its greater trochanteric region. The impact load and time were measured using a load cell within the mass. The maximum strain during impact at the inferior side of the femoral neck was determined from an attached strain gauge. Trochanteric fractures were produced in 18 of the 24 femora (75%). The mean impact load for a drop height of 25 cm was reduced from 3117 N to 2176 N by silicone gel (p &lt; 0.01) and to 1681 N by the addition of the resin cover (p &lt; 0.01). The mean maximum strain was similarly reduced from 2276 με to 1872 με (p = 0.15) and to a mean 1559 με (p &lt; 0.05). The mean impact time was prolonged from 13 ms to 20 ms (p &lt; 0.01) and 22 ms (p &lt; 0.01), respectively. The effect of the cover became more conspicuous as height increased. We concluded that the silicone gel pad provided effective impact attenuation, and the addition of the rigid cover was even more effective for impact reduction. This system was thought to be clinically useful in preventing hip fractures.
The Mouse Mammary Tumor Cell Line, MMT060562, Produces Prostaglandin E2 and Leukemia Inhibitory Factor and Supports Osteoclast Formation In Vitro Via a Stromal Cell–Dependent Pathway
Authors: Akatsu Takuhiko , Ono Katsuhiro , Katayama Yasuyuki , Tamura Tatsuya , Nishikawa Miyuki , Kugai Nobuo , Yamamoto Michiko , Nagata Naokazu 
Published: April 2006

Abstract
Osteoclastic bone resorption increases at the site of bone metastasis, but little is known about how tumor cells induce osteoclast (OC) recruitment in the bone marrow microenvironment. To clarify this point, we examined the effects of various mouse tumor cells on OC recruitment using cocultures of tumor cells and mouse marrow cells. The mouse mammary tumor cell lines, MMT060562 (MMT), BALB/c-MC, Jyg-MC(A), or other nonmammary tumor cell lines, LLC and B16, were cocultured with mouse marrow cells, and OC recruitment from marrow cells was determined by counting the number of tartrate-resistant acid phosphatase–positive multinucleated cells (TRAP(+) MNCs) formed. Of the tumor cells examined, MMT and BALB/c-MC stimulated OC formation, but other tumor cells did not. OC formation with MMT was dependent on the number of MMTs inoculated, and only ten cells per well were sufficient to induce OC development. OCs appeared on day 4, and the number reached a maximum on days 5–8 and decreased thereafter. TRAP(+) MNCs induced by MMT satisfied the major criteria of OCs, such as the presence of calcitonin receptors and the ability to resorb calcified tissues. The majority of OCs were formed adjacent to the stromal cells, which were positive for alkaline phosphatase. When spleen cells were cocultured with MMT, no OCs were formed. In contrast, when osteoblastic cells were added to cocultures of spleen cells and MMT, many OCs were formed. The cultured media (CM) of MMT induced OC formation in mouse marrow cultures. Neither parathyroid hormone–like nor interleukin 1-like activity was present in the CM. MMT constitutively produced prostaglandin E2 (PGE2) and OC formation in cocultures was completely inhibited by indomethacin. Fractionation of the CM of MMT by ultrafiltration indicated that the OC-inducing activities were present not only in the fraction with molecular weight below 3 kDa but also in the fraction with molecular weight above 3 kDa. OC-inducing activity with high molecular weight was eluted around 50 kDa by Bio-Gel P-60 column chromatography. The active fractions also possessed leukemia inhibitory factor (LIF) activity, and OC-inducing activity of the peak fraction was inhibited in the presence of anti-LIF neutralizing antibody. The results of this study indicated that MMTs release PGE2 and LIF, which in turn stimulate OC formation via a stromal cell–dependent pathway. These culture systems will help to clarify the mechanisms by which tumor cells induce OC formation in a bone marrow microenvironment.
The Preventive and Interventional Effects of Raloxifene Analog (LY117018 HCL) on Osteopenia in Ovariectomized Rats
Authors: Li Xiaodong , Takahashi Masaaki , Kushida Kazuhiro , Inoue Tetsuo 
Published: April 2006

Abstract
The effects of LY117018 HCL (LY) treatment on bone metabolism, spine bone mineral density (BMD), bone mineral content (BMC), and serum cholesterol were studied in ovariectomized (OVX) rats. Experiment 1 was designed to observe the preventive effects of LY on bone loss due to ovariectomy (OVX; prevention study). The rats were divided into three groups: sham group, OVX + vehicle, and OVX + LY. LY was administrated at the same time of OVX. Experiment 2 was designed to investigate the interventional effects of LY on OVX rats with osteopenia (intervention study). The rats were divided into the sham and OVX groups, first. The OVX rats were allowed to lose bone for 6 weeks. At 6 weeks post-OVX, the OVX rats were divided into two groups: OVX + vehicle and OVX + LY. The longitudinal effects of LY on bone were studied by dual-energy X-ray absorptiometry and biochemical markers including urinary pyridinoline (Pyr), deoxypyridinoline (Dpyr), and serum osteocalcin. Urinary Pyr and Dpyr increased maximally at 6 weeks post-OVX, decreased at 12 and 18 weeks post-OVX, although the OVX rats had significantly higher levels of Pyr and Dpyr than the sham group during the experiment. LY was a very potent inhibitor of Pyr and Dpyr excretion while at the same time only partially reducing the bone loss in the high turnover phase at 6 weeks postovariectomy. However, at the later time points at 12 and 18 weeks, no further bone loss occurred in rats treated with LY, while the vehicle-treated group lost another 10% in spine BMD and BMC. LY also completely blocked further bone loss when used in an intervention protocol. LY significantly reduced serum cholesterol levels in OVX rats. The results suggest that LY is not fully protective during the early rapid bone loss phase, but the compound is fully protective during the later slow phase of bone loss in both the protocols.
The Chemokine Interleukin-8 Regulates Parathyroid Secretion
Authors: Angeletti Ruth Hogue , D'Amico Thomas , Ashok Sheela , Russell John 
Published: April 2006

Abstract
Interleukin-8 (IL-8) is a chemokine important in inflammatory processes. Homology cloning experiments performed using bovine parathyroid cDNA and degenerate primers encoding transmembrane regions III and VI of peptide and protein hormone G-protein coupled receptors identified a set of known receptors not previously identified in the parathyroid. Among these was the IL-8 type B receptor. Incubation of freshly isolated bovine parathyroid cells with recombinant IL-8 for 6–48 h produced an increase in the levels of mRNA for parathyroid hormone (PTH). The levels of PTH secreted in response to nanomolar amounts of IL-8 were also elevated in cells incubated for 1 h with IL-8. Differential display analysis of mRNA from parathyroid cells, incubated in the presence and absence of IL-8, permitted the identification of cDNA clones for RNA species whose expression was either elevated or suppressed. These experiments suggest that IL-8 and inflammatory events play a role in bone homeostasis through actions on the parathyroid gland.
Chinese Hamster Ovary Cells Expressing α4β1 Integrin Stimulate Osteoclast Formation In Vitro
Authors: Akatsu Takuhiko , Ono Katsuhiro , Murakami Takehiko , Katayama Yasuyuki , Nishikawa Miyuki , Wada Seiki , Yamamoto Michiko , Kugai Nobuo , Matsuura Nariaki , Takada Yoshikazu , Nagata Naokazu 
Published: April 2006

Abstract
It is reported that Chinese hamster ovary cells transfected with human α4 cDNA (α4CHOs) and expressing functional α4β1 integrin developed bone metasasis in nude mice. To clarify the role of α4β1 integrin in bone metastasis, in terms of tumor-mediated bone destruction, we examined whether α4CHOs stimulate osteoclast formation in cocultures with mouse bone marrow cells. The number of osteoclast-like cells identified as tartrate-resistant acid phosphatase positive multinucleated cells (TRAP(+) MNCs) formed from bone marrow cells increased with the increasing number of α4CHOs cocultured. The effects of 1,25-dihydroxyvitamin D3(1,25(OH)2D3) and prostaglandin E2 (PGE2) on TRAP(+) MNC formation were enhanced in cocultures with α4CHOs. TRAP(+) MNCs induced by α4CHOs possessed calcitonin receptors and resorbed calcified tissues. In cocultures, α4CHOs and bone marrow stromal cells were in contact with each other and bone marrow stromal cells expressed vascular cell adhesion molecule-1 (VCAM-1), which is one of the ligands for α4β1 integrin. TRAP(+) MNC formation was not stimulated in cocultures where direct contact between α4CHOs and bone marrow cells was inhibited by membrane filters. α4CHOs do not support TRAP(+) MNC formation in cocultures with spleen cells but do support TRAP(+) mononuclear cell and MNC formation from spleen cells in the presence of osteoblastic cells. Cultured media from α4CHOs, bone marrow cells, and cocultures of α4CHOs and bone marrow cells did not stimulate TRAP(+) MNC formation or enhance the effects of 1,25(OH)2D3 and PGE2 in bone marrow cultures. The concentrations of PGE2 and interleukin-6 (IL-6) in cultured media were not different between the cultures of bone marrow cells and the cocultures of bone marrow cells and α4CHOs. Anti-human α4 and anti-mouse VCAM-1 antibodies inhibited TRAP(+) MNC formation induced by α4CHOs. These results indicate that α4CHOs stimulated TRAP(+) MNC formation through direct cell-to-cell interaction between α4β1 and VCAM-1. It is suggested that in addition to various soluble factors regulating osteoclast formation, cell-to-cell interaction between tumor cells and bone marrow cells is important for inducing osteoclasts at the site of bone metastasis and leading to bone destruction.
The Escherichia coli Chaperonin 60 (groEL) Is a Potent Stimulator of Osteoclast Formation
Authors: Reddi Krisanavane , Meghji Sajeda , Nair Sean P. , Arnett Timothy R. , Miller Andrew D. , Preuss Monika , Wilson Michael , Henderson Brian , Hill Peter 
Published: April 2006

Abstract
Chaperonins (cpns) are intracellular oligomeric protein complexes that fold and refold proteins in a catalytic manner and aid in the transmembrane transport of cellular proteins. We reported previously that the lipopolysaccharide-free recombinant cpn60 of Escherichia coli (groEL) is able to stimulate the breakdown of murine calvarial bone in culture and showed that such resorption is potently inhibited by an inhibitor of the enzyme cyclo-oxygenase and to a lesser extent by inhibitors of 5-lipoxygenase. In this study, we have investigated the effects of groEL on the resorptive activity and formation of osteoclasts in culture. In low density, osteoclast-containing cultures from neonatal rats incubated for 24 or 96 h on dentine discs, groEL (1–1000 ng/ml) stimulated resorption pit formation up to 4-fold, but this effect was essentially dependent on cell number. Using 12-day cultures of mouse bone marrow to assess osteoclast recruitment, groEL (1–1000 ng/ml) caused a dramatic dose-dependent stimulation of the formation of tartrate-resistant acid phosphatase-positive multinucleated cells and the resorption of the dentine on which bone marrow cells were cultured. Osteoclast formation elicited by groEL was almost completely abolished by indomethacin, an inhibitor of cyclo-oxygenase, but was unaffected by inhibitors of 5-lipoxygenase, suggesting that prostaglandins but not leukotrienes may mediate the action of groEL on osteoclastogenesis. It is possible that bacterial cpn60s such as groEL may play a role in the osteolysis associated with bone infections. Whether endogenous (“self”) chaperonins have a role in other bone loss disorders, such as osteoporosis, is an intriguing possibility.
Bone Mineral Density and Bone Turnover in Asthmatics Treated with Long-Term Inhaled or Oral Glucocorticoids
Authors: Ebeling Peter R. , Erbas Bircan , Hopper John L. , Wark John D. , Rubinfeld A. Roman 
Published: April 2006

Abstract
Inhaled glucocorticoids are pivotal in maintenance therapy of chronic bronchial asthma; however, conflict exists over their effects on bone and mineral metabolism. We measured bone mineral density (BMD), bone turnover markers, and adrenal steroid hormones in 53 patients (34 female, 19 male) with chronic bronchial asthma who had taken either inhaled beclomethasone or budesonide in doses of ≥ 1500 μg/day for at least 12 months to determine pathogenetic mechanisms of bone loss. To account for the effect of prior oral glucocorticoid exposure we divided patients into two groups: one with (OG) and the other without (IG) a past history of maintenance (&gt; 1 month) oral glucocorticoid therapy. Lumbar spine (LS) and proximal femur BMDs were ∼1 SD lower in men and women taking OG or high-dose IG for chronic bronchial asthma, potentially equivalent to a doubling of the risk of fracture at these sites. Prior exposure to OG in women was also associated with lower LS and proximal femur BMDs, while men were more sensitive to the adverse effects of IG on LS and Ward's triangle BMDs. Bone formation markers were decreased; however, bone resorption marker concentrations were normal. All patients had evidence of suppression of both endogenous glucocorticoid and adrenal androgen production. Both total duration of OG and biochemical bone turnover marker concentrations were negatively related to proximal femur and rib BMDs and total body bone mineral content, but not to LS BMD. These were stronger for bone resorption markers. Uncoupling of ongoing normal bone resorption from suppressed bone formation may therefore contribute to glucocorticoid-associated bone loss in asthma. Adrenal androgen suppression may also increase the susceptibility of postmenopausal women in particular to bone loss with OG. Although the effects of high-dose IG on BMD are associated with lower LS BMD in men, this observation should now be investigated further in prospective studies.