bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical characterization of an electrogenic vacuolar proton pump in purified chicken osteoclast plasma membrane vesicles
Authors: Bekker Petrus J. , Dr. Gay Carol V. 
Published: February 2010

Abstract
A well-characterized chicken osteoclast plasma membrane vesicle preparation manifested Mg2+-dependent ATP hydrolyzing activity of 0.213 μmol inorganic phosphate released per mg protein per minute (n = 7). The Mg2+ dependence showed a high-affinity component with a Kmg of 1.293 μM and Vmax of 0.063 μmol Pi per mg protein per minute, and a low-affinity component with a KMg of 297.6 μM and a Vmax of 0.232 μmol Pi per mg protein per minute. The Mg2+-ATPase activity was inhibited by N, N1-dicyclohexylcarbodiimide (DCCD, 0.2 mM, 50.7%), N-ethylmaleimide (0.5 mM, 34.6%), nolinium bromide (1 mM, 29.9%), 4,4′-di-isothiocyano-2,2′-stilbene sulfonic acid (DIDS, 1 mM, 45.1%), and p-chloromercuribenzoic acid (PCMB, 0.1 mM, 33.8%). Sodium orthovanadate (Na3VO4) at 1 μM had no effect but caused 29.5% inhibition at 1 mM. Na+ could substitute for K+ without loss of activity, NO3 caused 19.5% inhibition when substituted for CI−, and acetate replacement of CI− resulted in 36.4% stimulation of Mg2+-ATPase. ATP, GTP, ITP, CTP, and ADP were all hydrolyzed effectively.
DCCD (0.2 mM), NEM (0.5 mM), nolinium bromide (1 mM), and DIDS (50 μM) almost completely abolished proton transport as measured spectrofluorometrically by acridine orange quenching. Na3VO4 (1 mM) had no effect, and duramycin (80 μg/ml) inhibited transport 52.7%. K+ replacement of Na+ caused a 79.2% increase in initial proton transport rate. NO3- and acetate substitution of CI− resulted in a 46.1 and 55.7% decrease in transport, respectively. ATP supports transport far more effectively than the other nucleotides tested. ADP was ineffective. Experiments using the potassium ionophore, valinomycin, indicated that the proton pump functions electrogenically, with CI− most likely cotransported by an anion transporter. The proton pump also seems to have at least one anion-sensitive site, elucidated by experiments in the presence of NO3- and CI−.
Muscle strength as a predictor of bone mineral density in young women
Authors: Snow-Harter Christine , Bouxsein Mary , Lewis Barbara , Charette Susan , Weinstein Pamela , Marcus Robert 
Published: February 2010

Abstract
It is widely accepted that physical activity is beneficial to bone. However, the specific relationships of muscle strength to bone mineral density (BMD) are poorly understood. We examined strength and BMD in 59 women aged 18-31 years who ranged in exercise patterns from sedentary to active. Mineral density of the right proximal femur (hip) and spine (L2-4) was evaluated by dual-energy x-ray absorptiometry. BMD at the midradius was measured by single-photon absorptiometry. Dynamic strength (one repetition maximum) was measured for the following muscle groups: back, elbow flexors (biceps), leg extensors (quadriceps), and the hip flexors, extensors, adductors, and abductors. Isometric grip strength was assessed by dynamometry.
Mineral density at the hip correlated independently with muscle strength and body weight, but not with age. Specifically, femoral neck BMD was significantly correlated with back strength and weight, whereas trochanter and overall hip mineral density were significantly related to biceps, back, and hip adductor strength. Hip mineral density was not related to strength of the quadriceps group or to that of the hip flexors, extensors, or abductors. In addition, muscle strength was an independent predictor of lumbar spine and midradius mineral density. In stepwise multiple regression analysis, biceps strength proved the most robust predictor of hip BMD and grip strength best predicted bone density at the lumbar spine and radius.
We conclude that muscle strength is an independent predictor of bone mineral density, accounting for 15-20% of the total variance in bone density of young women. In addition, it appears that muscle groups with attachments that are distant from the spine and hip may exert an important influence on bone mineral density at these sites.
Aluminum-induced neo-osteogenesis: A generalized process affecting trabecular networking in the axial skeleton
Authors: Quarles L. Darryl , Murphy Gayle , Vogler James B. , Drezner Marc K. 
Published: February 2010

AbstractTo determine if aluminum-induced neo-osteogenesis occurs in the axial skeleton, we compared spinal bone density and vertebral histology of beagles treated with aluminum for 8 and 16 weeks to that of untreated normals. Administration of aluminum (1.25 mg/kg) did not alter serum calcium, phosphorus, or creatinine but did result in a significant elevation of vertebral bone density, measured by quantitative computed tomography, after both 8 (286.7 ± 12.4 mg/ml) and 16 (361.7 ± 46.5 mg/ml) weeks of treatment compared with controls (212.2 ± 4.5 mg/ml). In accord with the increased bone density, biopsies from the spine displayed evidence of neo-osteogenesis, including the presence of woven bone, both mineralized and unmineralized, within the marrow space. The genesis of such woven bone units resulted after 16 weeks in a significant increase in trabecular bone volume, woven and lamellar (51.2 ± 4.4 versus 32.4 ± 1.2%; p &lt; 0.05), woven bone volume (9.1 ± 3.6 versus 0 ± 0%; p &lt; 0.05), and trabecular number (4.5 ± 0.3 versus 3.5 ± 0.2 per mm; p &lt; 0.05). In addition, scanning electron microscopic evaluation of the bone biopsies confirmed the existence of new trabecular plates that provided interconnections between existent units.These observations illustrate that aluminum-induced neo-osteogenesis positively influences trabecular networking in the axial skeleton. Such enhancement of bone histogenesis contrasts with the effects of other pharmacologic agents that solely alter the thickness of existing trabecular plates or rods within the vertebral spongiosa.
Influence of age and body weight on spine and femur bone mineral density in U.S. white men
Authors: Mazess Richard B. , Barden Howard S. , Drinka Paul J. , Bauwens Steven F. , Orwoll Eric S. , Bell Norman H. 
Published: February 2010

Abstract
Bone mineral density (BMD) was measured in normal white males using 153 Gd dual-photon absorptiometry. Measurements were made on the lumbar spine (n = 315) and on the proximal femur (n = 282) utilizing three regions of interest. There was a small but significant age-related decrease in spinal BMD (r = -0.11; -0.001 g/cm2 per year) and trochanteric BMD (r = 0.27; -0.002 g/cm2 per year). The BMD of the other femoral sites decreased more rapidly; the femoral neck (r = -0.58; -0.005 g/cm2 per year) and Ward's triangle (r = -0.69; -0.007 g/cm2 per year) declined by about 21 and 34%, respectively, from age 20 to age 70. These femoral BMD decreases were three to four times greater than those usually seen in the peripheral skeleton in males but less than the decreases of 25-30 and 40% in the femoral neck and Ward's triangle of white females. This pattern of aging bone loss may partially explain the paucity of spine fractures and the lower incidence of hip fractures in males versus females.
Quantitative evaluation of anticalciuretic effects of synthetic parathyroid hormonelike peptides
Authors: Scheinman Steven J. , Mitnick Maryann E. , Stewart Andrew F. 
Published: February 2010

Abstract
The PTH-like peptide (PTHLP) responsible for hypercalcemia in many patients with humoral hypercalcemia of malignancy (HHM) acts on PTH receptors in bone and kidney, and large doses of PTHLPs have been shown to reduce urinary calcium excretion. However, PTHLPs have not been assessed quantitatively for effects on renal calcium excretion at concentrations (5-100 pM) now known to be found in the serum of patients with HHM. We perfused isolated rat kidneys with synthetic [tyr-36] PTHLP-(1-36)amide [PTHLP-(1-36)], PTHLP-(1-74), and synthetic bovine PTH-(1-34). The ratio of calcium to sodium clearances (Cc2/CN2), a measure of distal tubular calcium transport, was reduced to the same extent by PTH, PTHLP-(1-36), and PTHLP-(1-74) (54.3 ± 3.9, 52.9 ± 3.9, and 52.7 ± 1.3% reductions from control), respectively at maximal doses (35-50 pM and higher), with half-maximal effects at 10, 18, and 32 pM, respectively. PTH, PTHLP-(1-36), and PTHLP-(1-74) all increased fractional phosphate excretion over control (p &lt; 0.05 each). All three peptides were natriuretic, at least doubling fractional Na excretion (p &lt; 0.05 or less). Urinary cAMP excretion was increased by all three. None had any effect on GFR or renal vascular resistance.
These results indicate that clinically relevant concentrations of PTHLPs are anticalciuretic and natriuretic, with maximal effects similar to those of PTH. Differences in anticalciuretic potencies are small but may explain differences among patients, depending on the size(s) and concentrations of the native circulating form(s) of the peptide.
Ascertainment of risk factors for osteoporosis: Comparison of interview data with medical record review
Authors: Beard C. Mary , Dr. Melton L. Joseph , Cedel Sandra L. , Richelson L.S. , Riggs B. Lawrence 
Published: February 2010

Abstract
To determine the accuracy of self-reported risk factors for osteoporosis, an age-stratified random sample of Rochester, MN, women was studied. Results from a structured face-to-face interview were compared with information documented in contemporary inpatient and outpatient health care records in the community. Using the × statistic to evaluate concordance of these two data sources, we found substantial agreement for a history of proximal femoral and distal forearm fractures, peptic ulcer disease, estrogen replacement therapy and oral contraceptive use, and cigarette and alcohol exposure. Moderate agreement was seen for histories of other age-related fractures, hysterectomy or oophorectomy, thyroidectomy, and use of thyroid supplements. Poor agreement was found for prior thyroid disease, gastrectomy, and corticosteroid or anticonvulsant use. This study demonstrates a need for greater attention to the quality of self-reported risk factor data in studies of bone loss and fractures.
Measurement of vertebral area on spine X-rays in osteoporosis: Reliability of digitizing techniques
Authors: Nelson Dorothy , Peterson E. , Tilley B. , Otallon W.M. , Chao E. , Riggs B.L. , Kleerekoper M. 
Published: February 2010

Abstract
Much of the clinical research in osteoporosis is directed toward documenting a reduction in vertebral fracture rate, but there is considerable disagreement about defining and quantifying vertebral fractures. We have evaluated the technique of digitizing landmarks identified on lateral radiographs of thoracic and lumbar vertebrae and computing vertebral body area. Reduction in area indicates that fractures occurred. Radiographs from 10 patients with osteoporosis and vertebral fractures were obtained from each of two centers, Henry Ford Hospital (HFH) and Mayo Clinic (MC), and vertebral area for each individual in the complete set of 20 radiographs was calculated at each center.
Measurements at the two centers differed by a multiplicative constant related to the method of recording landmarks on the radiographs that was estimated using 300 x-rays from HFH. After adjusting the MC areas for this multiplicative relationship, the average ratio of the HFH areas to the transformed MC areas of individual vertebrae (T4-L5) ranged from 0.98 to 1.06. The correlation between HFH and transformed MC areas for individual vertebrae averaged 0.85, with slopes between 0.87 and 1.00, intercept average -0.57. Within-patient rank correlation averaged 0.97. We conclude that radiographic digitization is a reliable and reproducible method of determining vertebral body dimensions that is suitable for evaluating radiographs obtained at different clinical sites and for comparison with normal data. This technique should prove useful for documenting the presence of a vertebral fracture that may not be readily apparent on visual inspection of radiographs and for monitoring serial changes in vertebral body dimensions in long-term epidemiologic and therapeutic studies.
Promotion of calvarial cell osteogenesis by endothelial cells
Authors: Villanueva Jorge E. , Nimni Marcel E. 
Published: February 2010

Abstract
Bone development and remodeling are associated with changes in the pattern of vascularization. Here we show that endothelial cells isolated from rat liver or bovine aorta can greatly enhance bone formation when implanted in diffusion chambers with rat fetal calvarial cells. The latter cells are unable to form bone when implanted alone at low initial cell density. The amount of mineralization measured by calcium deposition was 70 times higher in chambers containing calvarial cells mixed with endothelial cells from isologous liver or bovine aorta than in chambers containing endothelial or calvarial cells alone. Alkaline phosphatase activity was increased 20-fold. Calvarial cells in the presence of demineralized bone matrix powder did not form bone when implanted under similar conditions. Endothelial cells implanted alone seemed to enhance neovascularization around the Millipore diffusion chambers.
Release of parathyroid hormonelike peptides by fetal rat long bones in culture
Authors: Bergmann P. , Wolf N. Nijs-De , Pepersack T. , Corvilain J. 
Published: February 2010

Abstract
We observed that culture medium conditioned with fetal rat long bones stimulated cyclic AMP production by canine renal cortical membranes. This cyclase-stimulating activity (CSA) was retained by an ultrafiltration membrane with a molecular weight cutoff of 5000; three biologically active peaks with an approximate molecular weight of 18,000-25,000, 9000-12,000, and 4000-6000 were separated by high-performance liquid chromatography. The biologic activity was destroyed by trypsin digestion. The stimulation of adenylate cyclase by the medium and by the three peaks was inhibited by [N-leu8.18, Tyr34]parathyroid hormone-(3-34)-amide and by [Tyr34]parathyroid hormone-(7-34)amide. Preincubation of the bone culture medium and of the three peaks with an antibody raised against human parathyroid hormone-(l-34) did not decrease the biologic activity more than incubation with nonimmune serum. However, the biologic activity of the three active peaks was significantly suppressed after preincubation with an antiserum directed against the N-terminal region of the parathyroid hormone-related peptide of malignancy. The release of CSA into the bone culture medium was enhanced by parathyroid hormone induction and by 1,25-dihydroxycholecalciferol. It was decreased by calcitonin. We conclude that fetal murine bones in culture release peptides that stimulate the adenylate cyclase of renal cortical membranes. These peptides are antigenically similar to the parathyroid hormone-related peptide of malignancy. Their release from bones is modulated by hormones that control bone resorption.
Bilirubin as an inhibitor of cartilage metabolism: Effect on avian chondrocyte proliferation in cell culture
Authors: Vassilopoulou-Sellin Rena , Rey-Bear Norse , Oyedeji Caroline O. 
Published: February 2010

Abstract
Elevated levels of bilirubin and other tetrapyrroles are common to a number of chronic hematologic and liver diseases that can result in growth failure. This report establishes a cellular model system for the study of these endogenous growth inhibitors. Primary chondrocyte cultures were prepared from embryonic chick cartilage; cells were incubated (0.3 ± 105 cells per plate) in tissue culture medium containing 10% fetal bovine serum (FBS) with or without added bilirubin, 0.01-0.10 mM. Bilirubin caused profound, dose-dependent inhibition of chondrocyte proliferation: after 7 days, control incubations contained 11.45 ± 2.0 ± 105 cells per plate versus 4.92 ± 0.55 ± 105 cells per plate for wells with added 0.01 mM bilirubin and 1.76 ± 0.30 ± 105 for cultures with added 0.05 mM bilirubin. In chondrocytes cultured for 3 days, the addition of 0.05 mM bilirubin was associated with inhibition of [3H]thymidine incorporation into DNA (47 ± 5% of control), [3H]uridine incorporation into RNA (11 ± 0.05% of control), and [14C]leucine incorporation into proteins (16 ± 1% of control). The inhibition of chondrocyte proliferation induced by a range of bilirubin concentrations (0.01-0.10 mM) was in no way attenuated by the addition of physiologic concentrations of albumin (4 g/dl). After 3 days in media containing bilirubin or heme (at equimolar concentrations), chondrocytes were subsequently incubated in FBS alone for an additional 3 days; only partial reversal of the bilirubin (or heme)-induced inhibition was then observed. Our data show that bilirubin (and heme) produces profound, dose-dependent, partially reversible inhibition of chondrocyte proliferation in culture without affecting cell viability, supporting the concept that these endogenous tetrapyrroles are potent growth inhibitors. We also conclude that chick chondrocytes in cell culture are a suitable model for delineating the mechanisms of tetrapyrrole tissue action.
Long-term effects of physiologic concentrations of dexamethasone on human bone-derived cells
Authors: Wong Min-Min , Rao Leticia G. , Ly Hao , Hamilton Lynn , Tong Jeffrey , Sturtridge William , Mcbroom Robert , Aubin Jane E. , Dr. Murray Timothy M. 
Published: February 2010

Abstract
Bone cells derived from human trabecular explants display osteoblastic features. We examined the modulation of alkaline phosphatase activity and cAMP production as the result of exposing trabecular explants to physiologic concentrations of dexamethasone for 4 weeks during cellular outgrowth and subculture. Cells treated with dexamethasone were observed to grow generally more slowly than control cells. Cells appeared larger and more polygonal, and staining for alkaline phosphatase was more intense in the dexamethasone-exposed cultures. There was a progressive increase in cellular PTH responsiveness with increasing duration of exposure of cells to dexamethasone. Cells grown for 6 weeks in 3 x 10−8 M dexamethasone had a 10-fold increase in PTH-stimulated cyclic AMP accumulation. Dexamethasone-treated cells also had a significantly increased alkaline phosphatase activity. 1,25-(OH)2D3-stimulated alkaline phosphatase activity was increased approximately 20-fold. cAMP responses were significantly increased to PTH (21.7-fold), PGE, (2.67-fold), and forskolin (4.81-fold), but not to cholera toxin. Dexamethasone-treated cells also had a mean decrease in 1,25-(OH)2D3-stimulated osteocalcin production to 26.2% of control values (p &lt; 0.001). Hydrocortisone treatment gave rise to similar effects but of smaller magnitude than those of dexamethasone. Testosterone did not have a significant effect on alkaline phosphatase activity or cAMP production. Skin fibroblasts showed a significant enhancement of alkaline phosphatase activity in response to dexamethasone, but of a much smaller magnitude than in bone cells. The phenotypic changes induced by long-term culture in dexamethasone are consistent with the promotion of a more differentiated osteoblastic phenotype.
Different pattern of alkaline phosphatase, osteopontin, and osteocalcin expression in developing rat bone visualized by in situ hybridization
Authors: Weinreb Miron , Shinar Doron , Rodan Gideon A. 
Published: February 2010

Abstract
Alkaline phosphatase (AP), osteopontin (OP), and osteocalcin (OC) are expressed during osteoblastic differentiation. However, previous studies suggested differences in the timing and possibly the site of their expression. In this study we used in situ hybridization to follow the distribution of these osteoblastic markers during bone development.
Frozen sections of neonatal rat long bones and calvariae were hybridized with 35S-labeled RNA probes complementary to the AP, OP, and OC mRNAs. Controls included sections hybridized with the sense (mRNA) probes or pretreated with RNase.
Positive cells were identified in all areas of bone formation of the long bones and calvariae. Based on quantitative silver grain distribution and density, high levels of OP expression were present only in osteoblasts in close proximity to bone (one to two cell layers). OC expression, apparently at lower levels than OP, was also localized to osteoblasts in contact with bone. In contrast AP, which was expressed at lower levels than OP, was present in a large number of cells, including preosteoblasts that were many layers removed from the bone-forming surface.
These findings are consistent with the asynchronous expression of phenotypically related genes and suggest that AP is an earlier differentiation marker than OP and OC during the formation of endochondral and membranous bone.
Effect of sodium warfarin on vitamin K-dependent proteins and skeletal development in the rat fetus
Authors: Feteih Rabab , Tassinari Melissa S. , Lian Jane B. 
Published: February 2010

Abstract
Sodium warfarin was administered daily to Sprague-Dawley rats from gestational day 8 to day 22 to examine the effects of this compound on the developing fetal skeleton and on the vitamin K-dependent bone and cartilage proteins. At a dose of 175 μg/kg of sodium warfarin there was a 43% mortality rate among the dams. Maternal prothrombin times and serum osteocalcin levels were slightly elevated but not significantly. In the surviving litters, fetal bone osteocalcin and γ-carboxyglutamic acid were significantly reduced (50 and 57%, respectively, on gestational day 22) when compared to age- and/or weight-matched control pups. The high correlation of osteocalcin content in long bone (R = 0.64) and calvariae (R = 0.77) to fetal body weight observed in control fetuses was not seen in the warfarin-exposed pups. Examination of alizarinstained warfarin-exposed fetal skeletons for ossification centers showed no difference from controls. However, analysis of the tibial growth showed several changes compared to control that included (1) widened hypertrophic zones, (2) increased calcification of the hypertrophic zones, and (3) disorganization of the hypertrophic cells. These results suggest that the growth plate abnormalities seen with prenatal warfarin exposure relate to the inhibition of the vitamin K-dependent proteins of the skeletal system.
Vitamin D metabolism in rats with adjuvant-induced arthritis
Authors: Langman Craig B. , Ford Kathy K. , Pachman Lauren M. , Glorieux Francis 
Published: February 2010

Abstract
Adjuvant-induced arthritis in rats shares many of the features of humans with rheumatoid arthritis, including the development of osteopenia in areas distal to erosive joint disease. We established adjuvant arthritis in male and female Sherman strain rats and then studied external calcium balances and vitamin D metabolism during the period of acute active clinical, serologic, and pathologic arthritis and osteopenia and in the preclinical period. While ingesting a calcium-sufficient vitamin D-replete diet (0.6% calcium, 0.65% phosphorus, and 2.2 IU D3 per g food), female rats with arthritis demonstrated reduced calcium balance (arthritic, 36 + 8 versus control, 169 + 13 mg per 6 days, p &lt; 0.02) because of inefficient gastrointestinal absorption of calcium (arthritic 9.7% versus control 37%). This was associated with calcitriol deficiency (arthritic 52 + 7 versus control 70 + 10 pg/ml) and reduced osteocalcin levels. Male rats with arthritis demonstrated an inability to raise serum calcitriol levels to the same degree as control rats (200 + 30 versus 440 + 70, respectively) while ingesting a calcium-deficient diet (0.002% calcium, 0.34% phosphorus, and 2.2 IU D3 per g food) and also had reduced balance (59 + 7 versus 85 + 10 mg per 6 days, respectively) due in part to decreased efficiency of absorption (55 versus 67%). No abnormalities in calcium balance or in serum calcitriol levels on the sufficient diet were present in the preclinical period. Physiologic calcitriol replacement to arthritic female rats increased osteoid available for mineralization and increased mineral apposition rates. Calcitriol deficiency in adjuvant-induced arthritis is responsible, in part, for reduced calcium balance and likely contributes to the development of osteopenia during the acute stage of the systemic inflammatory disease.