bluuebunny/crossref_metadata_2025_split huggingface dataset:
Derivation of osteoclasts from hematopoietic colony-forming cells in culture
Authors: Kerby J. A. , Hattersley G. , Collins D. A. , Chambers T. J. 
Published: February 2010

Abstract
The osteoclast is known to be derived from the hematopoietic stem cell, but its lineage remains controversial. There is evidence that osteoclastic differentiation is induced through a contact-dependent interaction between bone marrow stromal cells and hematopoietic precursors. To analyze osteoclastic lineage, colonies were generated in semisolid medium from mouse spleen cells in the presence of Wehi-conditioned medium, interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), or macrophage colony-stimulating factor (M-CSF) with or without erythropoietin (epo). After 5–8 days colonies were picked and phenotyped and incubated with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] on bone slices or coverslips with bone marrow-derived cell lines (ts8 or ST2) that induce osteoclastic differentiation. Cells of osteoclastic phenotype [as judged by calcitonin receptor (CTR) expression or bone resorption] were observed only in multilineage colonies. The ability of cells that generate macrophage colonies (CFU-M) to generate osteoclasts was tested by incubating alveolar or peritoneal macrophages on ts8 or ST2 cells. Despite colony formation, no osteoclastic differentiation was detectable. Last, individual cells from blast cell colonies were incubated (1 cell per culture well) on ts8 or ST2 cells in the presence of 1,25-(OH)2D3 and epo (to expose the lineage potential of the plated cell). We found CTR-positive (CTRP) cells in 6 of 66 macrophage colonies, 7 of 12 granulocyte-macrophage (GM) colonies, and 49 of 50 colonies containing multiple lineages other than GM colonies. No single-lineage CTRP colonies were observed. Although most macrophage colonies did not contain CTRP, no CTRP were observed in colonies from which macrophages were absent. These results suggest that osteoclasts are derived from a multilineage precursor rather than from CFU-M.
Longitudinal study of bone metabolism after ethanol withdrawal in alcoholic patients
Authors: Pepersack Thierry , Dr. Fuss Michel , Otero Julio , Bergmann Pierre , Valsamis JosÉ , Corvilain Jacques 
Published: February 2010

Abstract
The pathogenesis of osteopenia in chronic alcoholism remains unclear, and many ethanol-related abnormalities have been advocated to explain bone loss. A direct inhibitory effect of ethanol on osteoblast function was suggested by in vivo and in vitro studies. We measured biochemical markers of bone turnover in 12 alcoholic men before and during a 2 week period of alcohol withdrawal, and we compared the results with those obtained in 15 nonalcoholic men. Our alcoholic patients presented with (1) decreased serum concentrations of bone gla protein (BGP), suggesting decreased bone formation; (2) increased urinary excretion of hydroxy-proline, suggesting increased bone resorption; (3) increased renal threshold of phosphate excretion without modification of serum PTH concentration, suggesting a direct effect of ethanol on the renal handling of phosphate. The rapid increase in serum BGP concentrations following ethanol withdrawal suggests that low serum BGP concentrations in alcoholics may result from a direct toxic effect of ethanol on osteoblast function and/or numbers.
Effects of phorbol myristate acetate on rat and chick osteoclasts
Authors: Murrills Richard J. , Stein Linda S. , Horbert Wendy R. , Dr. Dempster David W. 
Published: February 2010

Abstract
The role of protein kinase C in the regulation of osteoclast function is not known. We therefore compared the effect of phorbol myristate acetate (PMA), which activates protein kinase C, on the resorptive function, motility, and morphology of osteoclasts from rat and chick. PMA caused a significant reduction in resorption pit number in both species; rat osteoclasts were more sensitive, being significantly inhibited at doses of 10−9-10−6 M compared with 10−7-10−6 M for chick osteoclasts. The inactive analog PMA-α was without significant effect, and inhibition was not blocked by 10−6 M indomethacin. In time course experiments, inhibition at 24 h was similar to or greater than inhibition at 6 h, indicating a persistent or progressive effect on bone resorption. Removal of PMA after 6 h prompted partial recovery of bone-resorptive ability in chick osteoclasts but not rat, at least over a 48 h incubation. In time-lapse video studies of rat osteoclasts, 10−6 M PMA produced an immediate but transient cessation of motility and retraction of the cell margin into prominent filopodia. Motility resumed within 2.5 h after addition, but the osteoclasts remained partially contracted. Chick osteoclasts behaved similarly but showed no formation of filopodia at the cell periphery and a more rapid recovery of motility than rat osteoclasts; chick osteoclasts also underwent a transient vacuolation following PMA exposure, whereas rat osteoclasts did not. Despite differences in the sensitivity of rat and chick osteoclasts to PMA, these results suggest a fundamental role for protein kinase C in the inhibition of osteoclasts from both species.
Retention of etidronate in human, dog, and rat
Authors: Kasting Gerald B. , Francis Marion D. 
Published: February 2010

Abstract
The retention of radioactivity in human, rat, and dog following a single injected dose of radiolabeled etidronate disodium (EHDP) is shown to follow power-law decay curves with similar slopes for times up to 4, 60, and 80 days, respectively. During this period retention declines with time according to a weak inverse power of the time since dosing, with an exponent ranging from −0.05 (dog) to −0.09 (human and rat). Direct analyses of dog bones either 90 days after a single dose or 365 days after cessation of chronic dosing indicate a more rapid bone clearance of EHDP than predicted by the initial power law. Direct skeletal analysis also shows a more rapid loss of radioactivity in the rat between 60 and 365 days, indicative of either a second power law or a terminal exponential phase in the retention function occurring after 60 days. These data are used to estimate the minimum and maximum amounts of drug that would remain in the body following long-term treatment in humans. For the intermittent cyclic EHDP treatment (ICT) regimen for osteoporosis (repeated cycles of 14 daily doses of 400 mg orally followed by 76 days drug free), the projected retention of EHDP after 3 years of treatment is 25–50 times the daily absorbed dose. Thus, for a 60 kg woman with a daily absorbed dose of 12 mg, the retained mass of EHDP would be about 300–600 mg. The surface area available for diphosphonate adsorption combined with measured bone-remodeling rates in ICT-treated subjects dictates that this mass would be distributed into a sufficiently large volume of mineral such that the fractional occupancy of active bone surfaces is only a few percent. The predicted retained mass of diphosphonate is well below that known to inhibit mineralization. This analysis is consistent with the clinical histopathology of bone from ICT-treated subjects, which has indicated that no mineralization defect ensues from this treatment regimen with EHDP.
Specific binding of parathyroid hormone to living osteoclasts
Authors: Agarwala Neena , Gay Carol V. 
Published: February 2010

Abstract
We show that osteoclasts bind parathyroid hormone (PTH) in a manner that displays the properties of receptor-dependent hormone binding, that is, saturability, time dependence, temperature dependence, and hormone specificity. Osteoclasts were isolated from the endosteum of 2 to 3 week chick tibiae and maintained in culture for 4–6 days. Bovine PTH-(1–84) was biotinylated with N-hydroxysuccinimidobiotin. Biotinyl-PTH (btPTH, 10−5-10−11 M) was added to the cultured osteoclasts for 2–20 minutes. After rinsing away unbound btPTH, fluorescein isothiocyanate-labeled avidin (FITC-avidin) at a concentration of 66 μg/ml was applied. Receptor binding characteristics were assessed: (1) saturation occurred at around 10−6 M btPTH; (2) competition of excess unlabeled PTH was found, namely, a 10-fold excess abolished fluorescence; (3) specificity was shown by adding other polypeptide hormones (insulin, glucagon, and calcitonin) in 10- to 100-fold excess—no effect on PTH binding was observed; and (4) affinity of btPTH for its binding site was indicated by half-maximal binding ≅10−7 M for both osteoclasts and osteoblasts. Biotin (10−5 M) or FITC-avidin (66 μg/ml) alone did not cause fluorescence. The time course of btPTH on the cell exterior was short: at 2 and 5 minutes dots of fluorescence were randomly dispersed over the cell surface, by 10 minutes most of the fluorescence was clustered in one region of the membrane, and by 20 minutes most of the hormone was no longer present on the surface of the cells. This sequence of events and the finding that maintaining the cells at 4°C blocked the clustering process indicates that occupied receptors were rapidly internalized by endocytosis. Fibroblasts and osteoblasts were more intensely stained by btPTH-FITC-avidin than osteoclasts, and no internalization of label was observed over the time period studied. This study shows direct, short-term binding of PTH to osteoclasts through specific receptors. The binding of PTH to both osteoclasts and osteoblasts suggests dual control of bone resorption.
Prostaglandin e2 promotes osteoclast formation in murine hematopoietic cultures through an action on hematopoietic cells
Authors: Collins D.A. , Chambers T.J. 
Published: February 2010

Abstract
Osteoclastic differentiation is induced from hematopoietic cells in the presence of 1,25-(OH)2D3 by stromal cells that are present in bone but not in hematopoietic spleen. Recent evidence suggests that prostaglandins (PGs) are essential for this process. In this communication we describe experiments in which we have examined further the role of PGE2 in osteoclast formation. We found a marked reduction in basal, 1,25-(OH)2D3, and IL-3-induced production of calcitonin receptor (CTR)-positive cells and bone resorption by cyclooxygenase inhibitors, which was restored by PGE2 addition. Although some stromal cell types (ST2 cells) that support osteoclast formation from spleen cells produced PGs in response to 1,25-(OH)2D3, others (ts8 and calvarial cells) did not, either alone or in combination with spleen cells. On the other hand, both bone marrow and spleen cells produced amounts of PGE2 in response to 1,25-(OH)2D3 that were sufficient to account for osteoclast formation. Osteoclast-inductive ts8 cells were able to support osteoclast formation from spleen cells in the presence of 1,25-(OH)2D3 or PGE2 even if devitalized. Incubation of ts8 cells in these agents before devitalization did not avoid the requirement for the presence of PGE2 or 1,25-(OH)2D3 during subsequent incubation with spleen cells. Thus, hematopoietic cells produce sufficient PGE2 for osteoclast formation, and the PGE2 thus produced acts on hematopoietic precursors, which can be induced in the presence of PGE2 to express CTR and resorb bone on contact with osteoclast-inductive stromal cells. The ability of osteoclast-inductive cells to support osteoclast formation appears not to rest on their ability to produce, induce, or respond to PGE2.
X-linked hypophosphatemic rickets: A study (with literature review) of linear growth response to calcitriol and phosphate therapy
Authors: Petersen Deborah J. , Boniface Anne M. , Schranck Francine W. , Rupich Reta C. , Whyte Michael P. 
Published: February 2010

Abstract
Not all children with X-linked hypophosphatemia (XLH) have demonstrated improved linear growth with calcitriol [1,25-(OH)2D3] and inorganic phosphate (Pi) therapy. To assess which factors are associated with a favorable growth response during this treatment, we retrospectively compared demographics and biochemical parameters of bone metabolism to the linear growth patterns of 20 children with XLH who were prepubertal and had not required osteotomy. A total of 15 patients had family histories consistent with XLH; 5 appeared to be sporadic cases. During 3 years of therapy, the growth velocities of 12 patients had been at or above the mean for age (good growers) and those of 8 patients had been below the mean (poor growers). Data from the two groups were contrasted. We found no difference between the good growers and poor growers before or after the 3 year period of therapy in mean age, dietary calcium, calcitriol dose or compliance, or Pi dose or compliance. Both groups increased their mean fasting serum Pi levels with treatment. The TmP/GFR (x + SEM) of the good growers improved with therapy (1.9 + 0.2 to 2.6 + 0.2 mg/dl, p = 0.01), and their posttreatment value was higher compared to that of the poor growers (2.6 + 0.1 versus 2.2 + 0.1 mg/dl, p = 0.02). However, their enhanced TmP/GFR was not associated with a reduction in serum iPTH levels (before, 693 + 50; after, 688 + 76 pg/ml; p = 0.9). The Z test for binomial proportions showed that the group that grew well contained a disproportionate number of girls (10 of 12, p = 0.04). Our findings suggest that calcitriol may exert a direct effect on the renal tubule to improve Pi reclamation in XLH. The observation that heterozygous girls appear to respond better than hemizygous boys to calcitriol and Pi therapy provides evidence for a gene dosage effect in the expression of this X-linked dominant disorder.
Age-related decrements in bone mineral density in women over 65
Authors: Steiger Peter , Cummings Steven R. , Black Dennis M. , Spencer Nan E. , Genant Harry K. 
Published: February 2010

Abstract
Age-related changes in bone density contribute to the risk of fractures. To describe the relationship between age and bone mass in elderly women, we studied a large cohort of women over age 65 years who were recruited from population-based lists in four cities in the United States. Bone density in g/cm2 was measured by single-photon absorptiometry (SPA) and dual x-ray absorptiometry (DXA) at the distal and proximal radius, the calcaneus, the lumbar spine, and the proximal femur. Centralized data collection was used to control data quality and consistency. We found a strong inverse relationship between bone density and age for most sites. Decrements in bone density between women aged 65–69 years and women 85 years and older exceeded 16% in all regions except the spine, where the difference between the two age groups was 6%. Ward's triangle and the calcaneus exhibited the largest decrements, with 26 and 21%, respectively. The estimates of annual changes in bone mineral density by linear regression at sites other than the spine ranged from -0.82% at the femoral neck and trochanter to -1.30% at Ward's triangle. Correlations between the different regions ranged from r = 0.51 between the proximal radius and Ward's triangle to r = 0.66 between the distal radius and calcaneus. We conclude that the inverse relationship between age and bone mass measured by absorptiometry techniques in white women continues into the ninth decade of life. The relationship is strongest for bone density of Ward's triangle and the calcaneus and weakest for the spine.
Axial and appendicular bone density predict fractures in older women
Authors: Black Dennis M. , Cummings Steven R. , Genant Harry K. , Nevitt Michael C. , Palermo Lisa , Browner Warren 
Published: February 2010

AbstractTo determine whether measurement of hip and spine bone mass by dual-energy x-ray absorptiometry (DEXA) predicts fractures in women and to compare the predictive value of DEXA with that of single-photon absorptiometry (SPA) of appendicular sites, we prospectively studied 8134 nonblack women age 65 years and older who had both DEXA and SPA measurements of bone mass. A total of 208 nonspine fractures, including 37 wrist fractures, occurred during the follow-up period, which averaged 0.7 years. The risk of fracture was inversely related to bone density at all measurement sites. After adjusting for age, the relative risks per decrease of 1 standard deviation in bone density for the occurrence of any fracture was 1.40 for measurement at the proximal femur (95% confidence interval 1.20–1.63) and 1.35 (1.15–1.58) for measurement at the spine. Results were similar for all regions of the proximal femur as well as SPA measurements at the calcaneus, distal radius, and proximal radius. None of these measurements was a significantly better predictor of fractures than the others. Furthermore, measurement of the distal radius was not a better predictor of wrist fracture (relative risk 1.64: 95% CI 1.13–2.37) than other sites, such as the lumbar spine (RR 1.56; CI 1.07–2.26), the femoral neck (RR 1.65; CI 1.12–2.41), or the calcaneus (RR 1.83; CI 1.26–2.64). We conclude that the inverse relationship between bone mass and risk of fracture in older women is similar for absorptiometric measurements made at the hip, spine, and appendicular sites.
Adaptive regulation of ascorbate transport in osteoblastic cells
Authors: Dixon S. Jeffrey , Wilson John X. 
Published: February 2010

Abstract
Osteoblasts possess a concentrative L-ascorbate (vitamin C) uptake mechanism involving a Na+-dependent ascorbate transporter located in the plasma membrane. The transporter is specific for ascorbate and stereoselective for L-ascorbate over D-isoascorbate. The present study examined the effects of ascorbate supplementation and deprivation on the activity of this transport system. L-ascorbate transport activity was determined by measuring uptake of the vitamin by ROS 17/2.8 osteosarcoma cells during 1 minute incubations with 5 μM L-[14C]ascorbate. The initial rate of L-[14C]ascorbate uptake by ROS 17/2.8 cells grown for 18 h in L-ascorbate-replete medium was 89 + 8 nmol/g protein per minute. Following removal of L-ascorbate from the growth medium, the initial rate of uptake increased within 6 h to 126 + 13 nmol/g protein per minute. Conversely, the initial rate of uptake by cells grown in ascorbate-free medium decreased following the addition of L-ascorbate, but not D-isoascorbate, to the medium. The effect of ascorbate pretreatment was specific for ascorbate transport in that preincubation of cultures with L-ascorbate did not affect uptake of 2-deoxy-D-glucose. Kinetic analysis revealed that modulation of ascorbate transport arose from changes in the apparent maximum rate of transport (Vmax) without changes in the affinity of the transport system for L-ascorbate. These experiments are the first to show that ascorbate transport by osteoblastic cells responds to vitamin C deprivation and supplementation. Adaptation of transport activity to substrate availability may play an important role in the physiological regulation of intracellular ascorbate levels.
Isolation and characterization of a cDNA for osteopontin-k: A kidney cell adhesion molecule with high homology to osteopontins
Authors: Crivello Joseph F. , Delvin E. 
Published: February 2010

Abstract
Screening of a bovine renal cDNA library with MAbs(1) resulted in the isolation of a 1447 bp cDNA. This cDNA (pBk2.1) was sequenced and shown to contain an open reading frame with a putative protein of 261 amino acids, with a molecular weight of 29,573 (minute leader sequence) and a hydrophobic leader sequence of 16 amino acids. pBk2.1 was shown to share a high level of nucleic acid sequence homology over portions of its sequence to human, porcine, mouse, and rat osteopontins (40–60%). The peptide (osteopontin-k) had a potential glycosylation site (Asn-X-Ser/Thr), a GRGDS receptor binding region, a high level of asparagine residues, and a high abundance of acid amino acids characteristic of osteopontin-like cell adhesion molecules. The N-terminal amino acid region of pBk2.1 (the first 82 amino acids) and 42 amino acids at the C terminus had the highest level of homology with the osteopontins at 86%. The middle portion of the peptide had greatly reduced homology, ranging from 50% (amino acids 83–174) to 12% (amino acids 175–219). There were also deletions and additions of sequence in osteopontin-k that were not found in the other osteopontins. The homologies suggest that these proteins are highly related and may be derived from a common gene by alternative splicing. A 678 bp cRNA probe constructed from pBk2.1, containing a region with low homology to the osteopontins (amino acids 183–219 with &lt;20% homology, plus amino acids 220–261 and untranslated sequence), was used in northern blots and RNAse protection assays. In a northern blot, this cRNA probe detected a 1.8–2.0 kb mRNA in bovine kidney. The greatest signal was seen in kidney, followed by liver and heart. Normal trabecular bone had a weak signal, with no signal in pancrease or skeletal muscle. For more accurate quantitation of mRNA levels, RNAse protection assays were used. These experiments demonstrated that this mRNA is expressed at highest levels in bovine kidney but at very low levels in osteosarcoma cells and at lower levels in liver, heart, and skeletal muscle. Treatment of bovine proximal tubule cells with 100 nM 1,25-(OH)2D3 resulted in a increase in osteopontin-k mRNA expression (2.7-fold). PTH had no effect on the expression of osteopontin-k mRNA. These results suggest that pBk2.1 represents a predominantly renal-specific cell adhesion molecule within the family of osteopontins that may be under hormonal regulation by the vitamin D system.
Factors influencing synthesis and mineralization of bone matrix from fetal bovine bone cells grown in vitro
Authors: Whitson S. William , Whitson Marcia A. , Bowers Daniel E. , Falk Michael C. 
Published: February 2010

Abstract
This study of the in vitro synthesis and mineralization of bovine bone demonstrates that sheets of mineralized matrix can be produced consistently within 18–24 days of cell isolation. Mineralization surpasses that achieved by other systems with other species: The deposition of mineral extends beyond nodules to form branching trabeculae and then solid wafers of bone. Comparison of the fetal age of the bone source, enzyme digestion methods, seeding density, culture surface, nutritive media, and concentration of fetal calf serum and other additives, including insulin and ascorbic acid, has yielded a set of optimal culture conditions. In the presence of ascorbic acid and β-glycerol phosphate, insulin has a dose-dependent effect on the morphology of the mineralized bone matrix produced. Quantitative analysis shows that in these cultures calcium accumulates most rapidly between days 6 and 10 after the introduction of mineralization medium but that mineral accretion continues throughout 14–16 days of culture. Alkaline phosphatase levels rise up to 200-fold, concomitant with a rapid increase in the number of cells per culture during the early mineralization phases; both fall as mineralization proceeds. This system has been used to study the induction of mRNA of type I collagen, alkaline phosphatase, and several noncollagenous bone proteins during the course of mineralization. Because of the degree of mineralization achieved with this system, it has many potential applications.