bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell signaling and estrogens in female rat osteoblasts: A possible involvement of unconventional nonnuclear receptors
Authors: Dr. Lieberherr Michèle , Grosse Brigitte , Kachkache Moustapha , Balsan Sonia 
Published: February 2010

AbstractEstrogen deficiency is associated with bone loss, and estrogen replacement is an effective treatment of this osteoporotic process. This study examines the early (5–120 s) effects of 17β-estradiol on the intracellular calcium and phospholipid metabolism in confluent female rat osteoblasts. The cytosolic free Ca2+ concentration ([Ca2+]i) was determined using fura-2/AM as Ca2+ probe. Cells were labeled with myo-[2-3H]inositol or [14C]arachidonic acid for inositol or lipid determination. Inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG) production were determined by either mass measurement or anion-exchange chromatography or by thin-layer chromatography, respectively. 17β-Estradiol (1 pM to 1 nM) increased [Ca2+]i in a biphasic manner within 10 s via Ca2+ influx from the extracellular milieu, as shown by the effects of the calcium chelator EGTA and the Ca2+ channel blockers nifedipine and verapamil, and via Ca2+ mobilization from the endoplasmic reticulum (ER), as shown by the effects of thapsigargin. 17β-Estradiol (1 pM to 1 nM) induced a biphasic and concomitant increase in IP3 and DAG formation. Estradiol immobilized on bovine serum albumin (BSA) [E-(O-carboxymethyl)oxime BSA] and its derivative (O-carboxymethyl)oxime rapidly increased ([Ca2+]i, IP3, and DAG and were full agonists, although they were less potent than the free estradiol. They had the same action time course and acted via Ca2+ influx and Ca2+ mobilization from ER. Tamoxifen, a potent inhibitor of genomic steroid responses, did not block the rapid increase in Ca2+, IP3, and DAG induced by estradiol. Finally, inhibitor of phospholipase C (neomycin) and pertussis toxin abolished the effects of 17β-estradiol on IP3 and DAG formation. These results suggest that female rat osteoblasts bear non-genomic unconventional cell surface receptors for estradiol, belonging to the class of the membrane receptors coupled to a phospholipase C via a pertussis toxin-sensitive G protein.
Human 25-hydroxyvitamin D 24-hydroxylase cytochrome P450 subunit maps to a different chromosomal location than that of pseudovitamin D-deficient rickets
Authors: Labuda Malgorzata , Lemieux Nicole , Tihy Fréderique , Prinster Chiara , Dr. Glorieux Francis H. 
Published: February 2010

Abstract
We have cloned part of the human 25-OHD 24-hydroxylase cytochrome P450 (P450cc24) cDNA. The characterized sequence consists of 776 bp of the coding and 720 bp of the 3′-untranslated region interrupted by an intron. In the coding region we found 79.8% similarity in DNA and 87.5% in deduced amino acid sequences between human and rat, with no similarity in the 3-untranslated region. By Southern blot hybridization of DNA from human-hamster somatic cell hybrids and by in situ immunofluorescence hybridization, we mapped P450cc24 to human chromosome 20q13.1. This location of P450cc24 is different from that of pseudovitamin D-deficient rickets (PDDR), previously assigned to chromosome 12q14 by linkage analysis, thus excluding it as a target of the PDDR mutation. Since it is likely that PDDR is caused by a mutation in the 25-OHD 1α-hydroxylase P450 subunit (P450cc1α) our results do not support the hypothesis that the two cytochromes are encoded by a single gene.
Relationship between quadriceps strength and bone mineral density of the proximal tibia and distal forearm in women
Authors: Dr. Madsen Ole Rintek , Schaadt Ole , Bliddal Henning , Egsmose Charlotte , Sylvest Jesper 
Published: February 2010

Abstract
It is well known that there is a relationship between muscle strength and bone density, but it is uncertain whether this relationship is site specific. The aim of this study was to assess the relationship of quadriceps strength to site-specific bone mineral density (BMD) of the tibia and to BMD of the forearm. In 66 healthy women, aged 21–78 years, BMD was measured in the proximal tibia and the distal forearm by dual-photon absorptiometry. Isometric and isokinetic strength of the quadriceps was measured using an isokinetic dynamometer (Cybex II). Highly significant correlations between BMD of the proximal tibia and quadriceps strength were found (RS ranging from 0.79 to 0.84, p &lt; 0.0001). Also, BMD of the distal forearm was correlated with quadriceps strength (RS ranging from 0.59 to 0.62, p &lt; 0.0001). In a stepwise multiple regression analysis, quadriceps strength was a better predictor of tibial BMD than age, body height, or weight. However, age, height, and weight were more predictive of forearm BMD than quadriceps strength. When studying the pre- and postmenopausal women separately, quadriceps strength was correlated with BMD of the proximal tibia but not to forearm BMD. In conclusion, the study provides support for a site-specific relationship between muscle and bone.
Effect of 1,25,28-trihydroxyvitamin D2 and 1,24,25-trihydroxyvitamin D3 on intestinal calbindin-D9K mRNA and protein: Is there a correlation with intestinal calcium transport?
Authors: Wang Y.-Z. , Li H. , Bruns M.E. , Uskokovic M. , Truitt G.A. , Horst R. , Reinhardt T. , Dr. Christakos Sylvia 
Published: February 2010

Abstract
Although analogs and metabolites of vitamin D have been tested for their calciotropic activity, very little information has been available concerning the effects of these compounds on gene expression. In this study one analog of vitamin D, 1,25,28-trihydroxyvitamin D2 [1,25,28-(OH)3D2], and one metabolite, 1,24,25-trihydroxyvitamin D3 [1,24,25-(OH)3D3], were tested for their effect on intestinal calbindin-D9K mRNA and protein as well as for their effect on intestinal calcium absorption and bone calcium mobilization. These compounds were also evaluated for their ability to compete for rat intestinal 1,25-(OH)2D3 receptor sites and to induce differentiation of human leukemia (HL-60) cells as indicated by reduction of nitro blue tetrazolium. In vivo studies involved intrajugular injection of 12.5 ng 1,25-(OH)2D3 or test compound to vitamin D-deficient rats and sacrifice after 18 h. 1,25,28-Trihydroxyvitamin D2 had no effect on intestinal calcium absorption, bone calcium mobilization, or intestinal calbindin-D9K protein and mRNA. Competitive binding to 1,25-(OH)2D3 receptors was 0.8% of that observed using 1,25-(OH)2D3. However, 20- and 40-fold higher doses of 1,25,28-(OH)3D2 (250 and 500 ng) resulted in significant inductions in calbindin-D9K protein and mRNA (3.5 to 7.4-fold), although doses as high as 800 ng were found to have no effect on intestinal calcium absorption or bone calcium mobilization. 1,25,28-Trihydroxyvitamin D2, although lacking in calciotropic activity, was found to induce differentiation of HL-60 cells at high concentrations [ED50 = 15 × 10−8 M compared to ED50 = 2.5 × 10−8 M for 1,25-(OH)2D3]. 1,24,25-Trihydroxyvitamin D3 was 93% as active as 1,25-(OH)2D3 in stimulating intestinal calcium transport but was relatively inactive in stimulating bone calcium mobilization. Competitive binding to the 1,25-(OH)2D3 receptor was 8% of that observed using 1,25-(OH)2D3. Although 1,24,25-(OH)3D3 was 93% as active as 1,25-(OH)2D3 in stimulating intestinal calcium absorption, this compound was found to be 50% as active as 1,25-(OH)2D3 in stimulating calbindin-D9K protein and mRNA. The lack of a direct correlation between calbindin protein and mRNA and intestinal calcium transport after 1,24,25-(OH)3D3 administration or after administration of high doses of 1,25,28-(OH)3D2 suggests that factors in addition to calbindin are involved, at least in part, in vitamin D-regulated intestinal calcium transport.
Parathyroid hormone-related peptide may increase mammary blood flow
Authors: Davicco Marie-Jeanne , Rouffet Josette , Durand Denis , Lefaivre Jacques , Barlet Jean-Pierre 
Published: February 2010

Abstract
Amino-terminal fragments of PTHrP were previously shown to increase regional blood flow in laboratory animals. Since PTHrP is produced in the lactating mammary gland and associated nutrient vessels, we examined the effects of peptide fragments of PTHrP on the hemodynamics of the mammary gland of dried sheep. The left arterial mammary blood flow measured using ultrasonic flow probes in four dried Lacaune ewes was 233 ± 11 ml/minute. It was significantly increased when synthetic human PTHrP-(1–34) or (1–86) fragments were injected into the mammary artery. The effect was dose dependent for PTHrP-(1–34), varying between 0.0075 and 0.3 nmol/kg body weight. PTHrP-(140–173) fragment lacked any vasorelaxant activity. Synthetic human endothelin (ET1) decreased arterial blood flow in a dose-dependent manner. This decrease was inhibited by PTHrP-(1–34), and this inhibition was PTHrP dose related. When ET1 (10 pmol/kg body weight) was injected together with PTHrP-(1–86) (100 pmol/kg body weight), only a significant increase in mammary blood flow was observed. Thus, PTHrP produced by the lactating mammary gland may be involved in the regulation of mammary blood flow.
Journal of Bone and Mineral Research
Authors: Raisz Lawrence G. 
Published: February 2010

Abstract
In an effort to define the major unanswered questions in bone cell biology and suggest new approaches to answering these questions, I have outlined the bone remodeling cycle and briefly described the major local and systemic factors that regulate bone cell function. These factors include calcium-regulating and systemic hormones as well as locally produced prostaglandins, cytokines, and growth factors. To understand the individual roles of this large number of regulators, it will be necessary to develop new approaches to measure their production and activity in bone under physiologic and pathologic conditions. Quantitative methods in molecular and cellular biology have been developed that should make this identification possible.
Journal of Bone and Mineral Research
Authors: Christiansen Claus 
Published: February 2010

Abstract
Osteoporosis is characterized by decreased bone mass and increased susceptibility to fractures. The clinical consequences of osteoporosis are fracture, most commonly seen at the wrist, the spine, and the hip. The prevalence of osteoporotic fracture is extremely high with 30%–40% of 70-year-old women having had at least one osteoporotic fracture. The prevalence in men is lower but may constitute a larger problem than expected. Osteoporotic fracture is, therefore, a significant cause of morbidity and mortality and represents a major problem of health care. Bone is the site of substantial metabolic exchanges, with bone resorption and formation continuing throughout life. The turnover processes are carried out by osteoclasts and osteoblasts in specialized cellular units. After cessation of growth, the skeleton probably consolidates to reach the peak bone mass at the age of 35–40 years. The relatively slow subsequent age-related bone loss occurs in both men and women, but women are additionally exposed to accelerated bone losses after the menopause. Estrogen deficiency is the dominating pathogenetic factor for osteoporosis in women. The role of disturbances in the calcium-regulating hormones and vitamin D deficiency is less sure. The pathophysiologic mechanisms of osteoporosis in men are not well investigated. Those who are endowed with a low peak bone mass and/or are exposed to a large bone loss are at particular risk of developing symptomatic osteoporosis. Several risk factors have been recognized but are insufficiently sensitive and specific to predict an individual's overall risk of developing osteoporosis.
Journal of Bone and Mineral Research
Authors: Prockop Darwin J. , Colige Alain , Helminen Heikki , Khillan J.S. , Pereira Ruth , Vandenberg Philipp 
Published: February 2010

Abstract
Work by a large number of investigators over the last decade has established that over 90% of patients with osteogenesis imperfecta have mutations in one of the two genes for type I procollagen, that most unrelated probands have different mutations in the genes, and that the mutations found in most of the serious variants of the disease cause synthesis of abnormal proα chains of the protein. The results have demonstrated that synthesis of structurally abnormal but partially functional proα chains can interfere with folding of the central region of the protein into a triple-helical conformation, prevent processing of the N-terminal propeptides of procollagen, or produce subtle alterations in conformation that interfere with the self-assembly of the protein into collagen fibrils. One of the unsolved mysteries about the disease is why some mutations produce severe phenotypes, whereas very similar mutations produce mild phenotypes. Recent studies in transgenic mice suggest that nongenetic factors, such as stochastic events during development, may determine the severity of the disease phenotype produced by a specific mutation. Also, recent results raised the possibility that strategies of antisense gene therapy may be effective in treating the disease some time in the future. Specific inhibition of expression of a mutated collagen gene has been obtained with antisense oligonucleotides in cell culture experiments. However, there is no means of selective delivery of antisense oligonucleotides to the appropriate tissues.
Journal of Bone and Mineral Research
Authors: Delmas Pierre D. 
Published: February 2010

Abstract
The noninvasive assessment of bone turnover has received increasing attention over the past few years because of the need for sensitive markers in the clinical investigation of osteoporosis. Markers of bone formation include the serum measurement of total and bone-specific alkaline phosphatase, osteocalcin, and type I collagen extension peptides. Assessment of bone resorption can be achieved with measurement of fasting urinary calcium and hydroxyproline, urinary hydroxylysine glycosides, urinary excretion of the pyridinium cross-links (pyridinoline and deoxypyridinoline), and plasma tartrate-resistant acid phosphatase activity. Several studies performed in a variety of metabolic bone diseases have shown these markers to be of unequal sensitivity and specificity. In addition, some of them are not fully characterized. For assessment of the level of bone turnover in women with vertebral osteoporosis, serum osteocalcin and urinary pyridinoline appear to be the most sensitive markers so far. Programs combining bone mass measurement and assessment of bone turnover by several markers in women at the time of menopause are being developed in an attempt to improve the assessment of the risk for osteoporosis. Efforts are being made to develop more convenient assays and to identify other markers of bone turnover. A battery of various specific markers is likely to improve the assessment of the complex and subtle anormalities of bone metabolism that characterize metabolic bone diseases, especially the various aspects of osteoporosis.
Journal of Bone and Mineral Research
Authors: Boyan Barbara D. , Schwartz Zvi 
Published: February 2010

AbstractStudy of oral tissues to understand the mechanisms of osteoporosis and oral bone loss includes histologic, biochemical, and molecular assessments of the tissue itself, as well as in vivo analysis of the biology of resident cells. Tissue sampling is limited by the nature of the defect and the use of appropriate controls (contralateral site vs same site, different subjects vs repeated measures of the same sites). Experimental parameters may include histomorphometrics, histochemistry, immunohistochemistry, and in situ hybridization. Molecular and biochemical technology also can be used to study the tissue in vivo. The presence of mineral is a confounding variable. To understand the underlying mechanisms of oral bone loss, cell culture is a powerful tool. The location in the oral cavity, the type of tissue (periosteum/cortical bone/trabecular bone), and the presence of pathology (periodontal disease) affect the biology of the cultured cells. Enzymatic release of cells from their extracellular matrix yields heterogeneous cell populations. Migratory cells from explant cultures are more homogeneous but less differentiated. Fibroblastic and bacterial contamination may be problems. Although cell culture data must be considered in the context of the intact tissue, the potential exists for developing bone cell function tests with diagnostic use in the treatment of bone disease.
Journal of Bone and Mineral Research
Authors: Rubin Clinton T. , Donahue Henry J. , Rubin Janet E. , McLeod Kenneth J. 
Published: February 2010

Abstract
The discovery of piezoelectric potentials in loaded bone was instrumental in developing a plausible mechanism by which functional activity could intrinsically influence the tissue's cellular environment and thus affect skeletal mass and morphology. Using an in vivo model of osteopenia, we have demonstrated that the bone resorption that normally parallels disuse can be prevented or even reversed by the exogenous induction of electric fields. Importantly, the manner of the response (i.e., formation, turnover, resorption) is exceedingly sensitive to subtle changes in electric field parameters. Fields below 10 μV/em, when induced at frequencies between 50 and 150 Hz for 1 h/day, were sufficient to maintain bone mass even in the absence of function. Reducing the frequency to 15 Hz made the field extremely osteogenic. Indeed, this frequency-specific sinusoidal field initiated more new bone formation than a more complex pulsed electromagnetic field (PEMF), though inducing only 0.1% of the electrical energy of the PEMF. The frequencies and field intensities most effective in the exogenous stimulation of bone formation are similar to those produced by normal functional activity. This lends strong support to the hypothesis that endogenous electric fields serve as a critical regulatory factor in both bone modeling and remodeling processes. Delineation of the field parameters most effective in retaining or promoting bone mass will accelerate the development of electricity as a unique and site-specific prophylaxis for osteopenia. Because fields of these frequencies and intensities are indigenous to bone tissue, it further suggests that such exogenous treament can promote bone quantity and quality with minimal risk or consequence.
Journal of Bone and Mineral Research
Authors: Legeros Racquel Z. , Craig Ronald G. 
Published: February 2010

Abstract
Osteointegration was defined as a “direct structural and functional connection between ordered living bone and the surface of a load-carrying implant.”(25) Although osteointegration was meant originally to describe a biologic fixation of the titanium dental implants, it is now used to describe the attachment of other materials used for dental and orthopedic applications as well. Analyses of material-bone interface showed that osteointegrated implants can have an intervening fibrous layer or direct bone apposition characterized by bone-bonding(62) depending on the composition and surface properties of the biomaterial. This article reviews biologic (host tissue properties and response), biomechanical, and biomaterial factors affecting osteointegration. Biologic factors include the quality of bone. Biomaterial factors include the effect of material composition on the bone-material interface. Suggested areas for future research include determining the correlation between oral bone status and osteoporosis, the effect of gender, age, and endocrine status (e.g., osteoporosis) on implant success or failure, the effect of calcium phosphate coating composition and crystallinity on in vivo performance of implants, the factors contributing to accelerated osteointegration, and development of osteoinductive implants.
Automated three-dimensional characterization of osteoclastic resorption lacunae by stereoscopic scanning electron microscopy
Authors: Fuller K. , Thong J.T.L. , Breton B.C. , Chambers T.J. 
Published: February 2010

Abstract
The use of stereoscopic scanning electron microscopy to analyze quantitatively the topography of excavations made by osteoclasts in slices of devitalized cortical bone was evaluated. Using this innovative technique, the need mechanically to tilt the specimen stage to gather three-dimensional information is obviated by instead tilting the electron beam both to produce real-time stereo pairs and to gather measurement data. Based on the comparison of two images of microscopic areas, cross-correlation is used to determine the image shift between the features in the stereo pair. This information is then used dynamically to correct the height of the tilt axis and lens focus in a feedback loop, generating a quantitative measurement of height difference. With this approach, relative heights of individual points, line profiles, area topography maps, and three-dimensional reconstructions of excavations were obtained rapidly and at high resolution. This approach combines the advantage in topographic data acquisition of confocal microscopy with the advantages of the increased resolution and focal depth of scanning electron microscopy (SEM). The technique should facilitate not only the topographic analysis of osteoclastic excavations in bone slices at high resolution but also the three-dimensional analysis of the structure of bone tissue.
Histochemical and autoradiographic studies on elcatonin internalization and intracellular movement in osteoclasts
Authors: Ikegame Mika , Ejiri Sadakazu , Professor Ozawa Hidehiro 
Published: February 2010

Abstract
The binding sites and chronologic localization of elcatonin (eCT) in osteoclasts were examined by autoradiography using [125I]elcatonin (125I-eCT). In addition to the structural changes induced by calcitonin (CT) reported so far, changes were also observed in the structure of Golgi apparatus. These changes continued until 48–72 h after incubation with eCT. Developed silver grains of 125I-eCT were localized into multinucleated osteoclasts and mononuclear cells that were ultrastructurally defined as “preosteoclasts.” The silver grains located on plasma membranes of those cells and were then internalized; they accumulated, especially in the Golgi apparatus, and remained for 48–72 h. A few silver grains were also detected in lysosomes and small vesicles. The decrease in the number of silver grains in the Golgi apparatus accompanied the recovery of osteoclast structures – Golgi apparatus and then ruffled borders. These findings suggest that (1) CT especially inhibits the sorting function of Golgi apparatus in osteoclasts, resulting in prolonged retention of CT in this organelle. (2) The CT in Golgi apparatus may keep its activity and cause the prolonged effect of CT on osteoclast activity.
Calcitriol corrects deficient calcitonin secretion in the vitamin D-deficient elderly
Authors: Quesada J.M. , Mateo A. , Jans I. , Rodriguez M. , Bouillon R. 
Published: February 2010

Abstract
The thyroid calcitonin-producing C cells possess vitamin D receptors and synthesize the vitamin D-dependent calbindin D28K. The present study evaluates the possible direct or indirect influence of vitamin D on calcitonin secretion in the elderly. Serum calcitonin was measured before and after a short calcium infusion (1.5 mg/kg over 10 minutes) in nine normal young adults (30 ± 4 years, mean ± SEM) and eight elderly subjects (78 ± 4 years). The test was repeated 48 h after the last of three intravenous injections of calcitriol (2 μg) given every other day. Basal serum calcium did not change, but basal calcitonin of the elderly increased from 7 ± 1 to 10 ± 1 pg/ml (p &lt; 0.06), similar to basal values in young adults (11 ± 1 pg/ml). The increase in calcitonin after calcium infusion increased from 8 ± 1 to 14 ± 1 pg/ml (p &lt; 0.001) after calcitriol treatment and approached the increase in young adults (18 ± 3 pg/ml). These data demonstrate that calcitriol can improve and nearly normalize the impaired calcitonin secretion of the mildly vitamin D-deficient elderly subjects without changes in serum calcium, whereas the inverse situation is observed for parathyroid hormone.