bluuebunny/crossref_metadata_2025_split huggingface dataset:
Restoring and maintaining bone in osteopenic female rat skeleton: I. Changes in bone mass and structure
Authors: Tang Li Ya , Jee Webster S.S. , Ke Hua Zhu , Kimmel Donald B. 
Published: February 2010

AbstractThis experiment contains the crucial data for the lose, restore, and maintain (LRM) concept, a practical approach for reversing existing osteoporosis. The LRM concept uses anabolic agents to restore bone mass and architecture (+ phase) and then switches to an agent with the established ability to maintain bone mass, to keep the new bone (± phase). The purpose of this study was to learn whether switching to an agent known chiefly for its ability to maintain existing bone mass preserves new bone induced by PGE2 in osteopenic, estrogen-depleted rats. The current study had three phases, the bone loss (-), restore (+), and maintain (±) phases. We ovariectomized (OX) or sham ovariectomized (sham-OX) 5.5-month-old female rats (- phase). The OX rats were treated 5 months postovariectomy with 1–6 mg PGE2 per kg/day for 75 days to restore lost cancellous bone mass (+ phase), and then PGE2 treatment was stopped and treatment began with 1 or 5 μg/kg of risedronate, a bisphosphonate, twice a week for 60 days (± phase). During the loss (-) phase, the cancellous bone volume of the proximal tibial metaphysis in the OX rat fell to 19% of initial and 30% of age-matched control levels. During the restore (+) phase, the cancellous bone volume in OX rats doubled. When PGE2 treatment was stopped, however, and no special maintenance efforts were made during the maintain (±) phase, the PGE2-induced cancellous bone disappeared. In contrast, the PGE2-induced cancellous bone persisted when the PGE2 treatment was followed by either a 1 or 5 μg treatment of risedronate per kg given twice a week for 60 days during the maintain (±) phase. The tibial shaft demonstrated very little cortical bone loss during the loss (-) phase in OX rats. The tibial shaft cortical bone fell some 8%. During the restore (+) phase, new cortical bone in OX rats increased by 22%. When PGE2 treatment was stopped and nothing was given during the maintain (±) phase, however, all but the PGE2-induced subperiosteal bone disappeared. In contrast, when PGE2 treatment was stopped and 1 μg risedronate per kg twice a week for 60 days was administered during the maintenance (±) phase, the PGE2-induced subperiosteal bone and some of the subendocortical bone and marrow trabeculae persisted. When 5 μg risedronate per kg was given twice a week, all the PGE2-induced bone persisted. The study shows that most of the new cancellous and cortical bone induced by PGE2 can be maintained for at least 60 days after discontinuing PGE2 by administering enough of the resorption inhibitor, risedronate. The lower dose of risedronate was not adequate to save most of the PGE2-induced endocortical bone.
Demonstration of sodium/calcium exchange in rodent osteoblasts
Authors: Krieger Nancy S. 
Published: February 2010

AbstractBased on the inhibition of stimulated Ca release from cultured bone by several different agents that alter Na transport, we proposed that hormonally stimulated bone resorption requires Na/Ca exchange. Calcemic hormones appear to interact primarily directly with the osteoblast, which then mediates the activation of osteoclast activity. In organ culture it is not possible to determine whether Na/Ca exchange is involved in this initiating step in the osteoblast or directly in osteoclast-mediated Ca release, and there have been no prior direct measurements of Na/Ca exchange in bone or bone cells. The purpose of this study was to demonstrate the presence of Na/Ca exchange transport in the osteoblast. Thus, we characterized Na-dependent Ca transport in osteoblast-like rat osteosarcoma cells (UMR-106) and primary bone cells isolated from neonatal mouse calvaria. Cells were loaded with the Ca-sensitive dye fura-2 in the presence of physiologic NaCl and the absence of Ca with or without 0.3 mM ouabain. Changes in free cytosolic Ca after the extracellular addition of 1.5 mM Ca were measured spectrofluorimetrically. An outward Na gradient was generated by decreasing extracellular Na while maintaining isotonicity. UMR-106 cells that were Na loaded by ouabain inhibition of Na,K-ATPase activity exhibited 30% greater Ca uptake than control cells. Similar results were obtained with primary bone cells. This uptake required extracellular Ca, was not inhibited by 200 μM verapamil, and was reversible upon reversal of the Na gradient. These data demonstrate the presence of a Na/Ca exchange transport system in osteoblasts.
Release of oxygen radicals by articular chondrocytes: A study of luminol-dependent chemiluminescence and hydrogen peroxide secretion
Authors: Rathakrishnan Chamu , Tiku Katherine , Raghavan Anuradha , Tiku Moti L. 
Published: February 2010

Abstract
We previously established that normal articular chondrocytes, like macrophages, express class II major histocompatibility antigens, present antigen, and induce mixed and autologous lymphocyte stimulation. In a recent study using the trapped indicator 2′,7′-dichlorofluorescein diacetate, we were able to measure levels of intracellular hydrogen peroxide within normal articular chondrocytes (J Immunol 245:690–696, 1990). In the present study, we utilized the technique of chemiluminescence and the biochemical method of quantitating hydrogen peroxide release to measure the production of reactive oxygen intermediates by articular chondrocytes. Chondrocytes, in suspension or adherent to coverslips, showed luminol-dependent chemiluminescence that was dependent on the number and viability of cells. There was a dose-dependent increase in chemiluminescence in response to soluble stimuli, such as phorbol myristate acetate (PMA), concanavalin A (ConA), and f-Met-Leu-Phe (FMLP). Azide inhibited chemiluminescence, suggesting that the light emission in chondrocytes is myeloperoxidase dependent. The antioxidant, catalase, inhibited chemiluminescence but superoxide dismutase had no effect, suggesting that luminol-dependent chemiluminescence in chondrocytes mostly measured hydrogen peroxide. Chemiluminescence was also observed in fragments of live cartilage tissue, indicating that chondrocytes that are cartilage matrix bound can generate the respiratory burst response. Using the scopoletin oxidation assay, we confirmed the release of increasing amounts of hydrogen peroxide by chondrocytes exposed to interleukin-1, rabbit interferon, and tumor necrosis factor α. Tumor necrosis factor α had both priming and enhancing effects on reactive oxygen intermediate production by chondrocytes. Reactive oxygen intermediates have been shown to play a significant role in matrix degradation. We suggest that reactive oxygen intermediates produced by chondrocytes play an important role in the degradation of matrix in arthritis.
Zeolite a increases proliferation, differentiation, and transforming growth factor β production in normal adult human osteoblast-like cells in vitro
Authors: Keeting Philip E. , Oursler Merry Jo , Wiegand Karl E. , Bonde Susan K. , Spelsberg Thomas C. , Riggs B. Lawrence 
Published: February 2010

Abstract
Silicon in trace amounts enhances bone formation, and the silicon-containing compound zeolite A (ZA) increases eggshell thickness in hens. In the studies reported here, treatment of nearly homogeneous strains of normal human osteoblast-like cells for 48 h with ZA at 0.1–100 μg/ml induced a dose-dependent increase (r = 0.35, P &lt; 0.001) in DNA synthesis (n = 31) to 162 ± 16% (mean ± SEM) of control and in the proportion of cells in mitosis (n = 4) from 9.1 ± 1.8 to 27.0 ± 4.5% (r = 0.69, P &lt; 0.005). ZA treatment also increased alkaline phosphatase activity (P &lt; 0.05) and osteocalcin release (P &lt; 0.05) but did not significantly affect collagen production per individual cell. The mitogenic action of ZA was dependent on cell seeding density over the range of 1250–40,000 cells per cm2, which is consistent with induction of an autocrine factors). TGF-β is a potent mitogen for osteoblasts. ZA treatment increased the steady-state mRNA levels of transforming growth factor β1 (TGF-β1) and induced the release of the latent form of TGF-β protein into the conditioned medium within 6 h. We conclude that ZA induces the proliferation and differentiation of cells of the osteoblast lineage.
Preparation and characterization of a mouse osteoclast-like multinucleated cell population
Authors: Akatsu Takuhiko , Tamura Tatsuya , Takahashi Naoyuki , Udagawa Nobuyuki , Tanaka Sakae , Sasaki Takahisa , Yamaguchi Akira , Nagata Naokazu , Dr. Suda Tatsuo 
Published: February 2010

Abstract
We have reported that numerous tartrate-resistant acid phosphatase-positive osteoclast-like multinucleated cells (TRAP+ MNCs) are formed when mouse osteoblastic cells and spleen cells are cocultured in the presence of 1α25-dihydroxyvitamin D3 [1α,25-(OH)2D3] (Endocrinology 123:2600, 1988). In this study, we prepared a TRAP+ MNC population using a modified coculture system and examined its osteoclastic properties. TRAP+ MNCs were formed in cocultures of mouse osteoblastic cells and marrow cells on 10 cm collagen gelcoated dishes. The TRAP+ MNC population was prepared by treating the dishes with 0.2% bacterial collagenase followed by density gradient centrifugation. The yield of TRAP+ MNCs was 20,000–40,000 cells per dish, much higher than that of osteoclasts (OCLs) isolated from neonatal rat bones (∼ 1000 cells per head). The purity of TRAP+ MNCs was 5.6 ± 0.6% in cell number and about 30% in the number of nuclei. The recovery of TRAP+ MNCs after density gradient centrifugation was 30–40%. Acid production by MNCs was demonstrated by vital staining with acridine orange. Numerous resorption pits were formed when the MNC population was cultured for 48 h on bone slices. Autoradiography using [125I]salmon calcitonin (CT) showed abundant CT binding in most TRAP+ MNCs. Saturation analysis of [125I]salmon CT indicated a dissociation constant Kd for TRAP+ MNCs of 8.9 ± 0.7 × 1010 M and 16.5 ± 1.5 ± 106 binding sites per cell. These results were similar to the value (3.5 × 10−10 M) and the number of binding sites (3.3 × 106 per cell) in isolated rat OCLs. Displacement curves for [125I]salmon CT with unlabeled salmon and human CT were similar in MNC and OCL preparations. Salmon and human CT increased cAMP production (maximal response: salmon CT at 10−10 M, human CT at 10−8 M; ED50: salmon CT, 2.2 × 10−11 M, human CT, 1.3 × 10−9 M) in the MNC preparation. These results indicate that a large number of mouse TRAP+ MNCs possessing OCL characteristics can be easily prepared from in vitro cultures. This procedure will facilitate examination of mammalian OCL functions.
Interrelationship between parathyroid hormone and insulin: Effects on DNA synthesis in UMR-106–01 cells
Authors: Felsenfeld Arnold J. , Iida-Klein Akiko , Hahn Theodore J. 
Published: February 2010

Abstract
UMR-106–01 osteoblast-like cells respond to high concentrations of parathyroid hormone (PTH) in vitro by decreasing thymidine incorporation, a marker of DNA synthesis and cell proliferation. This response is different from in vivo conditions, such as primary and secondary hyperparathyroidism, in which high PTH levels are associated with an increased number of osteoblasts. When the response of UMR-106–01 cells to PTH is evaluated in vitro, however, these cells are exposed to only a single hormone. The present study was designed to evaluate the combined effects of two hormones, PTH and insulin, on the DNA synthesis of UMR-106–01 cells. PTH is known to decrease and insulin to increase thymidine incorporation by UMR-106–01 cells. To examine the interaction of these hormones, acute studies, defined as a 24 h exposure to hormone, and chronic studies, defined as a 7 day exposure to hormone, were performed. Both acute and chronic exposure to 10−9 M PTH decreased thymidine incorporation by UMR-106–01 cells, with suppression ranging from 27 to 81% (P &lt; 0.05). Both acute and chronic exposure to 10−8 M insulin (INS) increased thymidine incorporation by UMR-106–01 cells; this ranged from 26 to 58% (P &lt; 0.05). However, chronic exposure to 10−9 M PTH followed by an acute exposure to 10−8 M INS resulted in a 710% increase in thymidine incorporation (P &lt; 0.01). Reversing the sequence by chronically exposing UMR-106–01 cells to 10−8 M INS followed by acute exposure to 10−9 M PTH resulted in a 53% decrease in thymidine incorporation (P &lt; 0.01). When 10−9 M PTH and 10−8 M INS were administered simultaneously, the increase in thymidine incorporation produced by acute and chronic administration ranged from 35 to 56% of nontreated control values (P &lt; 0.05). In conclusion, the timing of PTH and insulin administration may produce different responses in thymidine incorporation by UMR-106–01 cells. Whether during hyperparathyroidism in vivo, pulsatile increases in insulin secretion are important for osteoblast proliferation remains to be determined.
Effects of high extracellular calcium concentrations on phosphoinositide turnover and inositol phosphate metabolism in dispersed bovine parathyroid cells
Authors: Kifor Olga , Kifor Imre , Brown Edward M. 
Published: February 2010

Abstract
We previously showed that high extracellular calcium (Ca2+) concentrations raise the levels of inositol phosphates in bovine parathyroid cells, presumably via the G protein-coupled, “receptor-like” mechanism through which Ca2+ is thought to regulate these cells. To date, however, there are limited data showing Ca2+-evoked hydrolysis of phosphoinositides with attendant increases in the levels of the biologically active 1,4,5 isomer of inositol trisphosphate (IP3) that would be predicted to arise from such a receptor-mediated process. In the present studies we used HPLC and TLC, respectively, to quantify the high Ca2+-induced changes in various inositol phosphates, including the isomers of IP3, and phosphoinositides in bovine parathyroid cells prelabeled with [3H]inositol. In the absence of lithium, high Ca2+ dose dependently elevated the levels of inositol-1,4,5-trisphosphate [I(1,4,5)P3], with a maximal, 4- to 5-fold increase within 5 s; the levels of inositol 1,3,4-trisphosphate [I(1,3,4)P3] first rose significantly at 5–10 s and remained 5- to 10-fold elevated for at least 30 minutes. These changes were accompanied by reciprocal 29–36% decreases in PIP2 (within 5–10 s, the earliest time points examined), PIP (within 60 s), and PI (within 60 s). These results document that, as in other cells responding to more classic “Ca2+-mobilizing” hormones, the high Ca2+-evoked increases in inositol phosphates in bovine parathyroid cells arise from the hydrolysis of phosphoinositides, leading to the rapid accumulation of the active isomer of IP3. The latter presumably underlies the concomitant spike in the cytosolic calcium concentration (Cai) in parathyroid cells.
In vivo assessment of forearm bone mass and ulnar bending stiffness in healthy men
Authors: Myburgh Kathryn H. , Zhou Lin-Juin , Steele Charles R. , Arnaud Sara , Marcus Robert 
Published: February 2010

Abstract
The cross-sectional bending stiffness EI of the ulna was measured in vivo by mechanical resistance tissue analysis (MRTA) in 90 men aged 19–89 years. MRTA measures the impedance response of low-frequency vibrations to determine EI, which is a reflection of elastic modulus E and moment of inertia I for the whole ulna. EI was compared to conventional estimates of bone mineral content (BMC), bone width (BW), and BMC/BW, which were all measured by single-photon absorptiometry. Results obtained from the nondominant ulna indicate that BW increases (r = 0.27, p = 0.01) and ulnar BMC/BW decreases (r = −0.31, p ≤ 0.005) with age. Neither BMC nor EI declined with age. The single best predictor of EI was BW (r2 = 0.47, p = 0.0001), and further small but significant contributions were made by BMC (r2 = 0.53, p = 0.0001) and grip strength (r2 = 0.55, p = 0.0001). These results suggest that the resistance of older men to forearm fracture is related to age-associated changes in the moment of inertia achieved by redistributing bone mineral farther from the bending axis. We conclude that the in vivo assessment of bone geometry offers important insights to the comprehensive evaluation of bone strength.
Adhesion molecules in skeletogenesis: I. transient expression of neural cell adhesion molecules (NCAM) in osteoblasts during endochondral and intramembranous ossification
Authors: Lee Yun-Shain , Chuong Cheng-Ming 
Published: February 2010

Abstract
We report that neural cell adhesion molecules (NCAM) are expressed transiently in developing chicken osteoblasts during osteogenesis using immunostaining on cryostat sections. NCAM is strongly expressed in most osteoblasts along bone trabeculae that coincide with the presence of collagen I and alkaline phosphatase activity. In endochondral ossification, NCAM is highly expressed in osteogenic buds as seen in the epiphysis and diaphysis of tibia and vertebrae. In intramembranous ossification, NCAM is seen in osteogenic condensation of calvaria and in the periosteum of tibial diaphysis. The expression is transient because NCAM is not expressed in mesenchymal cells before osteogenic condensation and NCAM expression is lost in osteocytes in later stages. The staining pattern suggests that NCAM is present on the cell membrane of osteoblasts. Using a specific monoclonal antibody, the osteoblast NCAM is shown to contain polysialic acid, which is enriched in embryonic brain. Northern blot analysis using chicken brain NCAM cDNA as probes showed two major sizes of mRNA at 6.4 and 4.2 kb in calvarial mRNA as opposed to bands at 7.2, 6.4, and 4.2 kb in the brain. An immunoblot showed major proteins at Mr 165 and 110 kd, unlike brain NCAM, which are 180, 140, and 120 kD. That NCAM is involved in bone morphogenesis is consistent with the general hypothesis that NCAM plays pivotal roles in mesenchymal condensation, as shown in the formation of muscle, kidney, skin, and cartilage. The results establish NCAM as a cell surface molecule expressed transiently during osteoblast lineage. The implication that NCAM may mediate osteoblast interaction and regulate skeletal morphogenesis is discussed.
Absence of calbindin-D28 expression in nonclassical 1,25-dihydroxyvitamin D targets: Analysis by polymerase chain reaction
Authors: Dr. Walters Marian R. , Hunziker Willi 
Published: February 2010

Abstract
CaBP-D28 mRNA expression in rat heart, testis, and lung was assessed by polymerase chain reaction (PCR). The animal model used was the hyperinduced vitamin D-treated rat (100 ng 1,25-dihydroxyvitamin D subcutaneously, daily for 7 days). For the PCR studies, two pairs of 20 mer oligonucleotide primers (designated 1–4 according to their position on the coding strand, but with primers 3 and 4 in reverse orientation) derived from the rat CaBP-D28 cDNA sequence were tested in various combinations. Optimal conditions were established using a 1:100 dilution of cDNA from normal rat kidney. Bands of the predicted sizes of 869 (1, 3), 994 (1, 4), 725 (2, 3), and 850 (2, 4) nucleotide base pairs resulted, but with varying intensities: 2,4 ∼ 1,3 &gt; 1,4 &gt; 2,3. Repeat PCR (recycling after 1:100 dilution and readdition of reagents and primers with at least one different primer) provided strong additional amplification, particularly with the 1,4/2,4 combination. Under these conditions, mixing experiments showed that CaBP-D28 transcripts were detectable at 10−7-to 10−9-fold lower levels of expression than in D+ kidney. When RNA was isolated and cDNA generated from test tissues from 4 individual vitamin D-stimulated (D+) and vitamin D-deficient (D∼) rats, repeat PCR (1,4/2,4 primer combination) provided no evidence of significant CaBP-D28 mRNA expression in the nonclassic target tissues, in contrast to strong bands in both the D− kidney (undiluted) and D+ kidney (1:100 dilution) preparations. Thus, these data demonstrate that if CaBP-D28 mRNA is expressed in rat heart, testis, or lung, it is present at levels at least 107- to 109-fold lower than in kidneys of D+ rats.
Journal of Bone and Mineral Research
Authors: Burger Elisabeth H. , Klein-Nulend Jenneke , Veldhuijzen J. Paul 
Published: February 2010

Abstract
The use of hydrostatic pressure to apply mechanical stress to bone organ cultures is reviewed. Ossifying long bones and calvarial rudiments are sensitive to this type of stress. Intermittent hydrostatic compression of near physiologic magnitude (ICF) has anabolic effects on mineral metabolism in such rudiments, and continuous hydrostatic stress of high magnitude (CCP) has catabolic effects. The effects of ICF may be ascribed to shear stress generated at tissue interphases of different chemical and mechanical properties. Local factors, such as prostaglandins and growth factors, seem to be involved in the tissue response to mechanical stress.
Journal of Bone and Mineral Research
Authors: Oettmeier Ralf , Arokoski Jari , Roth Andreas J. , Helminen Heikki J. , Tammi Markky , Abendroth Klaus 
Published: February 2010

Abstract
All tissues of the joint are affected in some way in osteoarthritis because the joint is an interactively functioning unit. Our goal was to investigate the combined responses of articular cartilage and subchondral bone to altered loading conditions to improve our understanding of the physiology of these two components and, ultimately, the pathophysiology of osteoarthritis. A group of 20 female beagle dogs were divided pairwise into runners (n = 10) and controls (n = 10). The running training on a treadmill started at the age of 15 weeks, and during the following 40 weeks the running distance was gradually increased to 40 km/day with a 15° uphill inclination. With this daily running distance the beagles ran another 15 weeks. The samples for histology were taken from 11 different locations of the knee joint. Subchondral bone and articular cartilage histomorphometry was carried out in three different regions of the specimens (central, middle, and peripheral regions) using an image-analyzing system and an eyepiece graticule. In all regions of the articular cartilage, both the uncalcified and calcified cartilage showed slightly increased thickness in the runner dogs. The change was more evident in the peripheral and the central areas. The thickness of the subchondral bone plate tended to be higher in runners, too. Bone histomorphometric parameters showed significant signs of increased remodeling. The most notable change was the enlargement of the bone formation surface. The most intense remodeling was usually observed either centrally or peripherally in the articular surface. The strongest increase in trabecular bone volume and thickness of the cartilage was recorded in the femoropatellar area. These topographically confined and separate responses of the articular cartilage and subchondral bone to long-distance running are presumably adaptive processes that provide better congruence and biomechanical stability to the articulating bone ends. Under pathologic conditions these processes may initiate the subchondral etiopathogenesis of osteoarthritis by impairing the shock-absorbing capacity of the joint.