bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Phosphate on Parathyroid Hormone Secretion In Vivo
Authors: Estepa Jose C. , Aguilera-Tejero Escolastico , Lopez Ignacio , Almaden Yolanda , Rodriguez Mariano , Felsenfeld Arnold J. 
Published: April 2006

Abstract
Alterations in phosphate homeostasis play an important role in the development of secondary hyperparathyroidism in renal failure. Until recently, it was accepted that phosphate retention only increased parathyroid hormone (PTH) secretion through indirect mechanisms affecting calcium regulation and calcitriol synthesis. However, recent in vitro studies have suggested that phosphate may directly affect PTH secretion. Our goal was to determine whether in vivo an intravenous phosphate infusion stimulated PTH secretion in the absence of changes in serum calcium. Three different doses of phosphate were infused intravenously during 120 minutes to increase the serum phosphate concentration in dogs. Sulfate was also infused intravenously as a separate experimental control. A simultaneous calcium clamp was performed to maintain a normal ionized calcium concentration throughout all studies. At the lowest dose of infused phosphate (1.2 mmol/kg), serum phosphate values increased to ∼3 mM, but PTH values did not increase. At higher doses of infused phosphate (1.6 mmol/kg and 2.4 mmol/kg), the increase in serum phosphate to values of ∼4 mM and 5 mM, respectively, was associated with increases in PTH, even though the ionized calcium concentration did not change. Increases in PTH were not observed until 30–60 minutes into the study. These increases were not sustained, since by 120 minutes PTH values were not different from baseline or controls despite the maintenance of marked hyperphosphatemia. During the sulfate infusion, serum sulfate values increased by ∼3-fold, but no change in PTH values were observed. In conclusion, an acute elevation in serum phosphate stimulated PTH secretion in the intact animal, but the magnitude of hyperphosphatemia exceeded the physiologic range. Future studies are needed to determine whether PTH stimulation is more sensitive to phosphate loading in states of chronic phosphate retention. Moreover, the mechanisms responsible for the delay in PTH stimulation and the failure to sustain the increased PTH secretion need further evaluation.
Depolarization of Osteoclast Plasma Membrane Potential by 17β-Estradiol
Authors: Brubaker Kristen D. , Gay Carol V. 
Published: April 2006

Abstract
The effect of estrogen on plasma membrane potential of isolated avian osteoclasts was examined through the use of a fluorescent potential-sensitive dye, bis-(1,3-dibutylbarbiturate) trimethine oxonol, also known as bis-oxonol. A decrease in potential was observed within seconds of addition of 17β-estradiol. Ouabain, a specific Na+K+-ATPase inhibitor, and BaCl2, an inhibitor of the inwardly rectifying K+ channel, blocked the estrogen response. Verapamil and lanthanum chloride (LaCl3), inhibitors of inward Ca2+ channels, and 4′4-diisothiocyanatostilbene-2′2-disulfonic acid (DIDS), an inhibitor of Cl− channels, did not affect the depolarization. Herbimycin A, a tyrosine kinase inhibitor, also had no effect on the decreased membrane potential. These data provide evidence which suggests that estrogen regulates osteoclasts through ion channel activities. The change in K+ channel activity was observed within seconds of addition of 17β-estradiol, indicating an action at the level of the plasma membrane.
Stromelysin (MMP-3) Synthesis Is Up-Regulated in Estrogen-Deficient Mouse Osteoblasts In Vivo and In Vitro
Authors: Breckon Jeremy J. W. , Papaioannou Stelios , Kon Luke W. M. , Tumber Anthony , Hembry Rosalind M. , Murphy Gillian , Reynolds John J. , Meikle Murray C. 
Published: April 2006

Abstract
Sex steroids are important regulators of bone cell function and osteoblast-derived matrix metalloproteinases (MMPs) are key mediators of bone resorption during the initial stage of osteoid removal prior to osteoclast attachment. To investigate the mechanism of bone loss following estrogen deficiency, we examined the effects of estrogen on osteoblast synthesis of MMPs and tissue inhibitor of metalloproteinases (TIMPs). Immunolocalization in mouse bone samples ex vivo and primary mouse osteoblast (MOB) cultures was used to document the synthesis of mouse interstitial collagenase (MMP-13), stromelysin-1 (MMP-3), gelatinase-A (MMP-2), and gelatinase-B (MMP-9). Endosteal bone lining cells from distal femoral head and lumbar vertebral body showed an increase in the pattern of synthesis of stromelysin-1 following ovariectomy, compared with sham-operated controls; the synthesis of other MMPs was unaffected. The expression of all classes of MMPs and TIMP-1 and TIMP-2 by MOB in culture was demonstrated by reverse transcriptase-polymerase chain reaction. Following the withdrawal of 17β-estradiol, MOB cultures showed a significant increase in the number of cells synthesizing stromelysin-1; this effect was enhanced by stimulation with either interleukin-1 or interleukin-6. Northern blot analysis showed only a slight increase in stromelysin-1 mRNA message following the withdrawal of 17β-estradiol. Our data show an unexpected up-regulation of stromelysin-1 synthesis by osteoblasts both in vivo and in vitro following estrogen withdrawal. Although this effect was not reflected in a significant change in stromelysin-1 mRNA expression in vitro, there is evidence to suggest a role for this enzyme in the early stages of bone loss during the pathogenesis of osteoporosis.
Skeletal Dysplasia and Defective Chondrocyte Differentiation by Targeted Overexpression of Fibroblast Growth Factor 9 in Transgenic Mice
Authors: Garofalo Silvio , Kliger-Spatz Michal , Cooke Jeremy L. , Wolstin Orit , Lunstrum Gregory P. , Moshkovitz Sharon M. , Horton William A. , Yayon Avner 
Published: April 2006

Abstract
Mutations in fibroblast growth factor receptor 3 (FGFR3) cause several human chondrodysplasias, including achondroplasia, the most common form of dwarfism in humans. From in vitro studies, the skeletal defects observed in these disorders have been attributed to constitutive activation of FGFR3. Here we show that FGF9 and FGFR3, a high-affinity receptor for this ligand, have similar developmental expression patterns, particularly in areas of active chondrogenesis. Targeted overexpression of FGF9 to cartilage of transgenic mice disturbs postnatal skeletal development and linear bone growth. The growth plate of these mice exhibits reduced proliferation and terminal differentiation of chondrocytes similar to that observed in the human disorders. The observations provide evidence that targeted, in vivo activation of endogenous FGFR3 inhibits bone growth and demonstrate that signals derived from FGF9–FGFR3 interactions can physiologically block endochondral ossification to produce a phenotype characteristic of the achondroplasia group of human chondrodysplasias.
Deep Zone Articular Chondrocytes In Vitro Express Genes That Show Specific Changes with Mineralization
Authors: Sun Yongliang , Kandel Rita 
Published: April 2006

Abstract
We have developed a method to form reconstituted mineralized articular cartilagenous tissue in vitro from isolated deep zone chondrocytes. The aim of this study was to characterize further these cultures prior to and during mineralization. Histologic examination of the cells up to 8 days in culture showed that the chondrocytes had formed cartilagenous tissue. Similar to the in vivo cartilage, the chondrocytes expressed aggrecan, types II, I, and X collagens, osteopontin, and alkaline phosphatase (ALP). No osteocalcin mRNA expression was detected in either the in vivo cartilage or in vitro–generated tissue. Addition of β-glycerophosphate (β-GP) to the medium on day 5 induced mineralization and changes in gene expression. Expression of type X collagen, type II collagen, aggrecan core protein, and ALP were inhibited significantly between 2 h and 24 h after the addition of β-GP. At 72 h, expression of these genes were still significantly depressed. These changes correlated with a decrease in collagen and proteoglycan synthesis, and ALP activity. Osteopontin expression increased within 8 h but returned to constitutive levels by 72 h. No change in type I collagen expression was detected. The changes in gene expression were not due to a direct effect of β-GP itself, because similar gene changes occurred in the presence of phosphoethanolamine, another agent which induces mineralization. No changes in gene expression were seen in nonmineralizing cultures. In summary, articular chondrocytes grown on filter culture show expression of similar genes to the chondrocytes in the deep zone of articular cartilage and that changes in expression of specific genes were observed during tissue mineralization, suggesting that it is a suitable model to use to study the mechanism(s) regulating the localized mineralization of articular cartilage.
Isoforms of Bone Alkaline Phosphatase: Characterization and Origin in Human Trabecular and Cortical Bone
Authors: Magnusson Per , Larsson Lasse , Magnusson Martin , Davie Michael W. J. , Sharp Christopher A. 
Published: April 2006

Abstract
Alkaline phosphatase (ALP) is a glycoprotein and functions as an ectoenzyme attached to the cell membrane by a hydrophobic glycosyl-phosphatidylinositol (GPI) anchor. Three bone ALP (BALP) isoforms in human serum were separated and quantitated by high-performance liquid chromatography. B/I, a minor fraction, is composed on average of bone (70%) and intestinal (30%) ALP, and two major isoforms, B1 and B2. Treatment with GPI-specific phospholipase C (GPI-PLC) did not influence the activities or retention times for B1 and B2, indicating that the biochemical differences between B1 and B2 are likely to be due to different glycosylation patterns. The B/I fraction in serum, on average 4% of total ALP, was found to be composed of B1 and B2 isoforms, each with an intact hydrophobic GPI cell membrane anchor. We investigated the origin of these three BALP isoforms and osteocalcin in human femora from five healthy individuals (four males), mean age 51 years, obtained from a tissue bank. Bone was sampled from three sites: cortical bone, trabecular bone from the diaphysis, and trabecular bone from the greater trochanter. Trabecular bone, from both sites, had higher BALP activities compared with cortical bone. Conversely, the osteocalcin content of cortical bone was more than 3-fold greater than that of trabecular bone. Cortical bone had approximately 2-fold higher activity of B1 compared with B2, whereas trabecular bone had ∼2-fold higher activity of B2 compared with B1. We observed a previously undescribed BALP isoform (B1x) in all bone samples. B1x was also observed in sera from some patients (60%) with severe renal insufficiency and on chronic dialysis therapy (n = 20). The isoforms of BALP may provide information relating to bone metabolism within specific bone compartments.
Tibolone, a Steroid with a Tissue-Specific Hormonal Profile, Completely Prevents Ovariectomy-Induced Bone Loss in Sexually Mature Rats
Authors: Ederveen A. G. H. , Kloosterboer H. J. 
Published: April 2006

Abstract
Tibolone (Org OD 14) is a synthetic steroid with combined estrogenic, progestagenic, and androgenic properties and behaves as a tissue-specific steroid. In the current study, we determined the effects of a 4-week treatment with different doses of tibolone on estrogen deficiency–induced bone loss in mature 3-month-old rats. As a reference, 17α-ethinyl estradiol (EE2) was used. The frequency of administration, once or twice a day, was also studied. Bone parameters were determined in sham operated controls, ovariectomized (OVX) controls and OVX-treated rats. Bone loss was assessed by peripheral quantitative computed tomography directly and by quantitative Roentgen densitometry after defatting to exclude influence of fat changes. Femoral bone geometric parameters, plasma osteocalcin level, and urinary deoxypyridinoline/creatinine ratio were also determined. Ovariectomy caused a significant decrease in trabecular bone mineral density in the distal metaphyseal part of the femur using both methods, whereas no change in cortical bone density was found. Trabecular bone loss was prevented in a dose-dependent manner by tibolone (250, 1000, and 4000 μg/rat/day) when given once or twice daily. EE2 also prevented trabecular bone loss but its efficacy was dependent upon the frequency of dosing. Both tibolone and EE2 induced a significant reduction in the urinary deoxypyridinoline/creatinine ratio and plasma osteocalcin level. Tibolone and EE2 had no effect on other femoral bone parameters except a reduction in femoral length. In conclusion, treatment with tibolone for 4 weeks prevented OVX-induced bone loss by suppressing both bone resorption and bone turnover in a similar way as EE2. However, the frequency of dosing is more important for EE2 than for tibolone. Tibolone acts in this animal model for postmenopausal bone loss as an estrogen agonist on bone.
Impaired Development of Bone Mineral Density During Chemotherapy: A Prospective Analysis of 46 Children Newly Diagnosed with Cancer
Authors: Arikoski Pekka , Komulainen Jorma , Riikonen Pekka , Parviainen Markku , Jurvelin Jukka S. , Voutilainen Raimo , Kröger Heikki 
Published: April 2006

Abstract
Osteopenia and osteoporosis are becoming increasingly recognized in children with cancer, though reasons for these changes are poorly understood. The purpose of the present study was to evaluate longitudinal changes in bone mineral density (BMD) and bone turnover in newly diagnosed children with a malignancy. Lumbar spine (L2–L4) and femoral neck bone mineral density (BMDareal, g/cm2) was measured by dual-energy X-ray absorptiometry in 46 children (age 2.9–16.0, median 8.0 years; 15 leukemias, 12 lymphomas, 19 solid tumors) at diagnosis, and after 6 months from the baseline. The apparent volumetric bone mineral density (BMDvol) was calculated to minimize the effect of bone size on BMD. Serum levels of osteocalcin (OC), type I collagen carboxy-terminal propeptide (PICP), and type I collagen carboxy-terminal telopeptide (ICTP) were analyzed at diagnosis, and during a 6-month follow-up. A significant decrease in lumbar BMDvol (–2.1%, p &lt; 0.05), and in femoral BMDareal (–9.9%, p = 0.0001) and BMDvol (–8.5%, p = 0.0001) was observed after 6 months when compared with baseline measurements. The markers of bone formation (PICP, OC) were significantly decreased, and the marker of bone resorption (ICTP) was significantly increased at diagnosis as compared with normal values. By the end the follow-up, the levels of PICP and OC were normalized, whereas the level of ICTP continued to increase indicating that there was a negative balance in bone turnover. A deficient accumulation of bone mass might predispose children with a malignancy to impaired development of peak bone mass. A controlled study determining the benefits of an early intervention on bone turnover should be considered in these patients.
Severe Osteoporosis in Familial Hajdu–Cheney Syndrome: Progression of Acro-Osteolysis and Osteoporosis During Long-Term Follow-up
Authors: Leidig-Bruckner G. , Pfeilschifter J. , Penning N. , Limberg B. , Priemel M. , Delling G. , Ziegler R. 
Published: April 2006

Abstract
Hajdu–Cheney syndrome is an autosomal dominant inherited osteodysplastic bone disease with the hallmarks of acro-osteolysis, skull deformations, and generalized osteoporosis. Very few patients have been followed long-term with respect to the prognosis of acro-osteolysis and osteoporosis. Here we describe a 39-year-old woman and her 19-year-old daughter who are both affected with the Hajdu–Cheney syndrome. Skeletal lesions were followed in the mother between the ages of 22 and 39 years. The acro-osteolytic lesions progressed markedly and caused shortening of several fingers; some end phalanges had completely disappeared. Severe spinal osteoporosis with serial vertebral fractures was found at the age of 22 years. New vertebral fractures developed until the age of 33 years, but did not progress afterward. High turnover osteoporosis was found in the bone histology of iliac crest biopsies performed at the ages of 22 and 34 years. Bone mineral content (BMC) was strikingly decreased at the age of 34 years (T score –5.1 SD) and did not significantly change during further follow-up. In the daughter, BMC failed to increase between the ages of 12 and 19 years and was also markedly decreased (T score –4.4 SD). This suggests that osteoporosis in Hajdu–Cheney syndrome is related to a low peak bone mass and a high bone turnover, leading to insufficient bone formation compared with the increased bone resorption.
Short-Term Therapy with Oral Olpadronate in Active Paget's Disease of Bone
Authors: González Diana C. , Mautalen Carlos A. 
Published: April 2006

Abstract
One of the aims of the treatment of Paget's disease with bisphosphonates should be the normalization of the activity of the disease with the shortest possible exposure to the drug. Olpadronate (OPD) is a new bisphosphonate characterized by the dimethylation of the amino group, its potency is near to alendronate, and more soluble in the digestive media than other aminobisphosphonates. We treated 46 patients (28 men and 18 women, mean age 70 years) with active Paget's disease with oral OPD, 200 mg/day for 12 ± 2 days, except 2 patients who received 400 mg/day. Eight patients had never been treated before, and 38 had previously received antiosteolytic drugs. The period without treatment prior to OPD was (X ± 1 SD) 14 ± 12 months. Baseline bone alkaline phosphatase (BALP) (levels fell from (X ± 1 SD) 54.0 ± 62.7 IU/ml (range 22–396) to a lowest mean value of 16.2 ± 6.4 IU/ml (range 8–45) (normal range 5–21 IU/ml). Forty patients normalized BALP values, in most of the cases within the first 3 months after OPD treatment. Two patients showed partial response (&gt; 50% decrease from baseline), three patients presented poor response (&lt; 50% decrease from baseline), and one patient did not respond at all. Two patients complained of gastric discomfort, and one patient had diarrhea, which disappeared after discontinuation of the drug. Follow-up was carried out on 36 patients; 22 patients are still in remission, with an average length of 9.0 ± 2.6 months. Fourteen patients experienced relapse after 9 ± 2 months remission. In conclusion, a 12-day treatment with 200 mg/day of OPD proved to be a very effective and well tolerated therapy of Paget's disease and induced biochemical remissions in the vast majority of patients, even in those with very active disease.
Zoledronate Is a Potent Inhibitor of Myeloma Cell Growth and Secretion of IL-6 and MMP-1 by the Tumoral Environment
Authors: Derenne Sophie , Amiot Martine , Barillé Sophie , Collette Madeleine , Robillard Nelly , Berthaud Patrice , Harousseau Jean-LUC , Bataille Régis 
Published: April 2006

Abstract
Bisphosphonates have recently been introduced in the therapeutic armamentarium for the long-term treatment of patients with multiple myeloma (MM). These pyrophosphate analogs not only reduce the occurrence of skeletal-related events but also provide patients with a clinical benefit and improve the survival of some of them. We investigated the effects of two bisphosphonates, pamidronate and zoledronate, on both myeloma cells and bone marrow stromal cells (BMSCs). We show here that both bisphosphonates induce both myeloma cell and BMSC apoptosis. Furthermore, at lower concentrations, they induce a significant inhibition (40% and 60%, respectively) of the constitutive production of interleukin-6 (IL-6) by BMSCs. We have recently shown that BMSCs produce MMP-1, the major metalloproteinase involved in the initiation of bone resorption, production up-regulated by IL-1β. Here, we demonstrate that zoledronate significantly inhibits MMP-1 production by BMSCs stimulated with IL-1β more efficiently than pamidronate. However, zoledronate and to a lesser extent pamidronate are responsible for an up-regulation of MMP-2 secretion by BMSCs. MMP-2 is involved both in bone resorption and in the metastatic process. In conclusion, the apoptosis of myeloma cells and BMSCs and the inhibition of both IL-6 and MMP-1 production induced by bisphosphonates, mainly zoledronate, could have antitumoral effects in patients with MM. However, the up-regulation of MMP-2 secretion observed in vitro suggests a putative risk of tumor cell dissemination in vivo when using these new potent bisphosphonates. This potentially deleterious effect could be abolished by combining bisphosphonates with metalloproteinase inhibitors.
Coordinated Expression of Noggin and Bone Morphogenetic Proteins (BMPs) During Early Skeletogenesis and Induction of Noggin Expression by BMP-7
Authors: Nifuji Akira , Noda Masaki 
Published: April 2006

Abstract
Coordinated regulation of the activities of bone morphogenetic protein (BMP) and its inhibitors is essential for skeletal development since loss-of-function experiments show that both BMPs and BMP inhibitory signals, such as noggin, are required to establish proper formation of skeletal tissues. In this paper, we asked how and when noggin would be functional to interact with BMPs during skeletogenesis in mammals. For this purpose, we first analyzed the spatial and temporal patterns of noggin, BMP-2, BMP-4, and BMP-7 expression during early skeletogenesis in mouse embryos. In situ hybridization study revealed that noggin expression was detected at a low level in limb mesenchyme, whereas BMP-7 was expressed at a high level throughout limb mesenchyme 10.5 days postcoitum (dpc) in mouse embryos. One day later, noggin mRNA was expressed at a high level in the prechondrogenic condensations in appendicular and axial skeletal primordia, where sox9 transcripts were also expressed. At this stage, noggin-expressing cells were surrounded by those expressing BMP-7. The chondrogenic cell condensation continued to express noggin transcripts in 12.5 dpc and 13.5 dpc embryos, and again the noggin-expressing cells within the cartilaginous tissue were surrounded by those expressing BMP-7. We further examined interaction of noggin and BMPs by using organ cultures of 11.5 dpc mouse forelimbs and found that implantation of carriers containing BMP-7 protein into the forelimb explants induced noggin expression in the limb mesenchyme. BMP-7 also induced type II collagen and sox9 mRNAs in the same cell population, indicating that noggin induction occurred in the chondrogenic precursor cells. BMP-7 effects on noggin expression were observed in a dose-dependent manner within a dose range of 10–100 ng/μl. These results suggest that BMP-7 induced expression of noggin transcripts within skeletal cell condensation and that this noggin expression in turn could act antagonistically to attenuate BMP action in the early skeletogenesis.