bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of glucocorticoid administration on intestinal, renal, and cerebellar calbindin-D28K in chicks
Authors: Dr. Tohmon Miyo , Fukase Masaaki , Kishihara Michizo , Kadowaki Seizo , Fujita Takuo 
Published: February 2010

Abstract
A radioimmunoassay for chick intestinal calcium-binding protein (calbindin-D28K, CaBP-28K) has been developed in our laboratory with a detection limit of 0.3 ng/ml. The values for CaBP-28K in vitamin D-deficient (-D) chicks ranged from a high value for the cerebellum (21,400 ± 580 ng/mg protein) to a scarcely detectable level in the liver (19.6 ± 2.2 ng/mg protein). After administration of vitamin D (vitamin D3 500 IU p.o. for 7 days) (+ D), the levels of CaBP-28K increased in the duodenum (52,300 ± 5,100 ng/mg protein), ileum (45,200 ± 740 ng/mg protein), cerebellum (22,000 ± 470 ng/mg protein), colon (15,200 ± 330 ng/mg protein), and kidney (13,460 ± 540 ng/mg protein). However, the increment in the level of CaBP-28K in each tissue after vitamin D administration was different; levels of CaBP-28K in the duodenum, ileum, and colon increased dramatically more than 200 times after vitamin D administration, whereas that in the kidney showed only a 2.5-fold increase and was unaltered in the cerebellum. On the other hand, glucocorticoid administration (dexamethasone, 1 mg/kg BW i.m. for 2 days) markedly inhibited the vitamin D-stimulated (vitamin D3 500 IU p.o. for 3 days) levels of CaBP-28K in the duodenum (from 23,373 ± 3,117 to 8,261 ± 968 ng/mg protein, p &lt; 0.001), ileum (from 6,443 ± 1,342 to 3,712 ± 691 ng/mg protein, p &lt; 0.01), and colon (from 4,335 ± 174 to 2,316 ± 590 ng/mg protein, p &lt; 0.01. whereas glucocorticoid further increased the vitamin D-stimulated level of CaBP-28K in the kidney (from 3,922 ± 776 to 5,593 ± 450 ng/mg protein, p &lt; 0.01). The level of CaBP-28K in the cerebellum was unaffected either in the presence or absence of vitamin D or glucocorticoid. Although the precise action of glucocorticoid on CaBP-28K is still unclear, these results indicate that glucocorticoid is inhibitory in the intestine and colon, but is augmentative in the kidney, promoting an increase in the vitamin D-stimulated CaBP-28K production. However, glucocorticoid did not affect the level of CaBP-28K in the cerebellum, irrespective of the presence or absence of vitamin D, suggesting a vitamin D- and glucocorticoid-independent control mechanism for CaBP-28K production in the cerebellum. As a final observation, bidirectional regulatory mechanisms of the vitamin D-dependent CaBP-28K may exist in chicks, one stimulatory, the other inhibitory.
Adhesion patterns and cytoskeleton of rabbit osteoclasts on bone slices and glass
Authors: Dr. Turksen Kursad , Kanehisa Junya , Opas Michal , Heersche Johan N.M. , Aubin Jane E. 
Published: February 2010

Abstract
The ability of osteoclasts (OC) to migrate and resorb bone is thought to be dependent on cytoskeletal function and adhesion. Therefore, we investigated the cytoskeleton and the adhesion patterns of rabbit OC on glass and on devitalized bone slices, using specific antibodies to cytoskeletal elements and fluorescence and interference reflection microscopy. Microtubules (MT) were similar in OC on both substrata, and appeared in a pattern typical of that described for many cells. Multiple centriolar complexes were observed in most OC, either as one large aggregate in the center of the cell or dispersed singly or in small aggregates close to individual nuclei. Staining of microfilaments (MF) was similar on both substrata and appeared primarily as an F-actin network. MF distribution was different in OC associated with resorption lacunae with intense staining over those regions. In the OC on glass, high F-actin staining was detectable at the periphery in dots and rosette-like structures, which also stained for vinculin. The adhesion patterns indicated that OC on glass do not make large focal contacts, but appear to make a few tiny focal contacts that are not associated with the rosette-like structures. Most of the undersurface of the OC appeared either to be involved in close contacts or to be separated by distances of &gt;100 nm from the substratum. These studies indicate that the MF distribution and the adhesion patterns of rabbit OC are typical of motile cells, that the distribution of the cytoskeleton of rabbit OC on glass and on bone slices is similar, and that MF may be involved in the morphological changes associated with resorption.
The influence of Vitamin D metabolites on the calcification of cartilage matrix and the C-propeptide of type II collagen (Chondrocalcin)
Authors: Hinek Aleksander , Dr. Poole A. Robin 
Published: February 2010

Abstract
The influence of vitamin D metabolites (at 1 × 10−10M) on the calcification of cartilage matrix (measured by 45Ca2+ uptake) and the C-propeptide of type II collagen (measured by radioimmunoassay) has been studied using organ cultures and chondrocytes isolated from growth plates of vitamin D-deficient and -sufficient 11-day-old rats. Vitamin D-deficient rats had reduced amounts of C-propeptide in their serum and freshly isolated growth plate chondrocytes. In all chondrocytes cultured from vitamin D-deficient animals, the C-propeptide content was maximal at 24 hr whereas calcification continued to increase for up to 72 hr. In organ and chondrocyte cultures of tissue from vitamin D-sufficient rats, both 1,25-dihydroxycholecalciferol (1,25(OH)2D3) and 24,25-dihydroxycholecalciferol (24,25(OH)2D3) were required for maximal stimulation of calcification and maximal increases in C-propeptide content. In these D-replete tissues, 24,25-(OH)2D3 had a less stimulatory effect on both calcification (organ and cell cultures) and C-propeptide (organ cultures only), while 1,25(OH)2D3 alone had no effect in cell cultures but an inhibitory effect in organ cultures.
In all of these studies, maximal stimulation by vitamin D metabolites of 45Ca2+ incorporation was always accompanied by a maximal net increase in CPII content. Since increases were often quantitatively and temporally different, if would appear that the C-propeptide does not simply accumulate by a process of passive binding to mineral but that its increased concentration is the result of an active process that may be causally related to calcification.
These observations clearly demonstrate that 24,25(OH)2D3 is alone required for maximal calcification of cartilage matrix in growth plate cartilages of vitamin D-deficient rats and that this metabolite also produces maximal increases in the synthesis of the C-propeptide. Moreover, 1,25(OH)2D3 is required with 24,25(OH)2D3 for the maximal calcification and maximal increases in the amount of C-propeptide which are observed in vitamin D-sufficient animals.
Characterization of specific thyroid hormone receptors in bone
Authors: Dr. Krieger Nancy S. , Stappenbeck Thad S. , Stern Paula H. 
Published: February 2010

Abstract
Thyroid hormones stimulate bone turnover in vivo and increase Ca release from bone in vitro. To investigate further the effects of thyroid hormones in bone, we have characterized specific nuclear receptors for [125]triiodothyronine (T3) in neonatal mouse calvaria. Maximal specific binding of [125I]T3 to isolated nuclei occurred within 60 min at 22°C. [125I]T3 binding was completely and rapidly displaced by the addition of 10−6M unlabeled T3; the dissociation appears to be first order with t1/2 = 36 min. The IC50 for competition by unlabeled T3 was approximately 10−8M. The relative affinity of thyroxine (T4) for the receptor was ˜10 × lower than T3, consistent with its lower biological potency in most target tissues for thyroid hormones. Only weak competition was observed with diiodotyrosine at concentrations up to 10−4M. We have previously shown that the cardiotonic agent milrinone stimulates bone resorption in vitro with characteristics similar to those of T4. Structural homology between milrinone and T4 was recently reported. Milrinone, like diiodotyrosine, was only a weak competitor for binding at concentrations up to 10−4M. Milrinone inhibited collagen synthesis in the calvaria. The results suggest that the effects of milrinone on bone turnover in calvaria in vitro are probably not mediated through a thyroid hormone receptor.
Fluoride content in human iliac bone: Results in controls, patients with fluorosis, and osteoporotic patients treated with fluoride
Authors: Boivin Georges , Chapuy Marie-Claire , Baud Charles A. , Meunier Pierre J. 
Published: February 2010

Abstract
The major part of fluoride ingested is fixed on calcified tissues, mainly in bone tissue, and then is progressively but slowly recycled during bone remodeling. Thus, the measurement of bone fluoride content allows the determination of the extent of bone fluoride retention, and this parameter constitutes a useful complement to bone histology for the diagnosis of skeletal fluorosis and could also be used for the management of fluoride treatment of osteoporosis. A simple method is described to measure the fluoride content in calcined human iliac bone samples. Bone ashes were diluted in perchloric acid, and the measurement of the bone fluoride content was performed using a specific ion electrode combined with a reference electrode. Reference values are given for bone tissue from 76 control subjects (0.08 ± 0.05% of bone ash), from two groups of 117 and 102 untreated osteoporotic patients (0.05 ± 0.03% and 0.08 ± 0.05%, respectively), from 166 sodium fluoride-treated osteoporotic patients (mean bone fluoride content varying from 0.24 to 0.67%, depending on the duration of therapy), and from 96 patients showing typical skeletal fluorosis (mean bone fluoride content varying from 0.56 to 1.33%, depending on the etiology of fluorosis and the relationship with the amount of fluoride ingested as well as with the duration of fluoride exposure). During a prolonged exposure of adult bone tissue to fluoride, the early bone fluoride uptake is variable and depends on the remodeling activity; then it increases rapidly before becoming more or less stable at a maximum level.
Early effects of parathyroid hormone on membrane potential of rat osteoblasts in culture: Role of cAMP and Ca2+
Authors: Fritsch Jeanine , Edelman Aleksander , Balsan Sonia 
Published: February 2010

Abstract
Microelectrodes were used to investigate the possible involvement of cAMP and Ca2+ ions in the parathyroid hormone's, bPTH(1–34), effect on the membrane potential of rat osteoblasts in primary culture. Parathyroid hormone (10−7 M) depolarized cell membrane by 25.0 ± 6.1 mV (mean ± standard deviation, SD; n = 17). Blocking Ca2+ influx with the Ca channel blocker cobalt revealed two phases in the hormone effect: a rapid and slight membrane hyperpolarization followed by sustained depolarization. In addition, cobalt significantly (p &lt; 0.01) decreased the magnitude of the PTH depolarizing action. The addition of dibutyryl-cAMP (10−3 M) to the perfusion solution also resulted in a biphasic effect. At a lower concentration (10−4 M), dibutyryl-cAMP produced only membrane hyperpolarization, suggesting a cAMP dose dependence of the opposite membrane potential changes. Forskolin (10−5 M) and the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) (10−4 M) mimicked the depolarizing effect of PTH. IBMX at a low concentration (5 × 10−6 M) potentiated the depolarizing effect of PTH. Increases in [Ca2+]i using Ca2+ ionophore A23187 and intracellular injection of CaCl2 or inositol trisphosphate decreased the PTH depolarizing action, whereas intracellular injection of EGTA enhanced this effect. These results indicate that PTH evokes a biphasic change in rat osteoblast membrane potential that seems to be mediated by an increase in cAMP and modulated by intracellular calcium.
Cellular basis of inflammation-induced osteopenia in growing rats
Authors: Krempien B. , Vukičević S. , Vogel M. , Stavljenić A. , Böchele R. 
Published: February 2010

Abstract
Local nonosseous inflammation provoked by four subcutaneous talc powder injections induced a marked trabecular bone loss in rats within 7 days. The disturbance included suppression of bone elongation, inefficiency and decreased number of trabecular osteoblasts, decreased osteoprogenitor cell number in tibial metaphyses, and bone marrow expansion.
Neither the appearance and function of osteoblasts in the vicinity of the cortical bone nor the number of osteoclasts in the metaphysis were found to be altered. The loss of trabecular bone in granulomatosis was based on a suppression of bone elongation and a failure of osteoblasts to form normal secondary spongiosa.
Nucleotide sequence of cloned cDNAs encoding chicken preproparathyroid hormone
Authors: Khosla Sundeep , Demay Marie , Pines Mark , Hurwitz Shmuel , Potts John T. , Kronenberg Henry M. 
Published: February 2010

Abstract
In order to characterize an avian parathyroid hormone gene, a λgt10 cDNA library constructed from chicken parathyroid gland mRNA was screened with a human preproparathyroid hormone (preproPTH) cDNA probe. Nucleotide sequence analysis of three independent clones confirmed that they encoded chicken preproPTH. This analysis, complemented by primer extension and Northern blot analysis of mRNA, demonstrated a 5′-untranslated region for chicken preproPTH of 127 nucleotides, a coding region of 357 nucleotides, and a 3′-untranslated region of approximately 2500 nucleotides. The coding sequence predicts a mature chicken PTH of 88 amino acids in contrast to the 84 amino acids of the mammalian hormones. Comparison of the avian and the mammalian hormones shows striking homology in the region of amino acids 1–32. The middle and carboxyl-terminal portions of chicken PTH, however, differ considerably from the mammalian hormones and include deletions of sequences conserved in mammalian PTH and insertions of novel peptide sequences. Comparison of the avian and mammalian structures suggests potential alterations of the mammalian sequences that may lead to altered bioactivity and/or hormone metabolism.
Effects of infusion of human parathyroid hormone-related protein-(1–40) in nude mice: Histomorphometric and biochemical investigations
Authors: Rosol Thomas J. , Capen Charles C. , Horst Ronald L. 
Published: February 2010

Abstract
Female nude mice were infused with 5.0, 3.0, or 1.0 μg/day of synthetic human parathyroid hormone-related protein (PTHrP) or control diluent with subcutaneous Alzet miniosmotic pumps for 7 days. Serum calcium was increased (p &lt; 0.01) on days 3 (13.9 mg/dl), 5 (13.6 mg/dl), and 7 (12.9 mg/dl) in mice infused with PTHrP at 5.0 μg/day compared with control nude mice (8.8 mg/dl). Serum calcium was significantly increased to a lesser degree in mice infused with 1.0 μg/day PTHrP (day 3) or 3.0 μg/day (days 3 and 7). Serum phosphorus was decreased (p &lt; 0.01) in all three groups of mice infused with PTHrP (4.6 mg/dl, 5.0 μg/day; 6.7 mg/dl, 3.0 μg/day; and 6.4 mg/dl, 1.0 μg/day) compared with controls (8.5 mg/dl). Serum 1,25-dihydroxycholecalciferol was increased (2.4-fold) in mice infused with PTHrP (5.0 and 3.0 μg/day). The urinary calcium-creatinine ratio (0.74 compared with 0.034 in controls) was increased (p &lt; 0.03) in mice infused with PTHrP (5.0 μg/day), but the urinary phosphorus-creatinine ratio was not different from that in controls. The urinary cAMP-creatinine ratio was increased (1.6-fold) in mice infused with PTHrP (5.0 μg/day). Static bone histomorphometry revealed increased (p &lt; 0.01) trabecular bone area, osteoblast perimeter, osteoid perimeter, osteoid width, wall width, osteoclast area, number of osteoclasts, and osteoclast perimeter in trabecular bone of lumbar vertebrae from mice infused with PTHrP. Dynamic bone histomorphometry demonstrated increased (p &lt; 0.01) double-labeled perimeter, mineralizing perimeter, and bone formation rate. The results of this study indicated that PTHrP increased serum calcium and 1,25-dihydroxy-cholecalciferol, decreased serum phosphorus, increased urinary excretion of calcium, phosphorus, and cAMP, and increased both bone resorption and formation in nude mice. PTHrP mimics the action of native PTH in vivo and is likely to be an important protein in the pathogenesis of humoral hypercalcemia of malignancy.
Parathyroid hormone regulation of proline uptake by cultured neonatal mouse osteoblastlike cells
Authors: Yee John A. , Sutton Julie K. 
Published: February 2010

Abstract
Regulation of proline uptake by the synthetic amino-terminal fragment of bovine parathyroid hormone [bPTH-(1–34)] has been studied in confluent primary cultures of osteoblastlike cells isolated from neonatal mouse calvaria. The initial velocity of proline transport was increased by 85% in cultures treated with 24 nM bPTH-(1–34) for 6 h. Cycloheximide, at a concentration that inhibited protein synthesis by 97%, did not prevent this effect. However, adding the inhibitor during the first 1–2 h of hormone treatment did significantly reduce its magnitude. Exposure of cells to the inhibitor alone caused a time-dependent decrease in the basal rate of proline uptake. In the absence of protein synthesis, the maximal velocity (Vmax) of transport was 60% greater in cultures treated with 24 nM bPTH-(1–34) than in controls. The concentration of proline at which half-maximal transport occurred (Km) was unchanged. In cultures treated with cycloheximide alone, proline transport decreased as a first-order exponential with a half-life of 250–280 min. Parathyroid hormone significantly reduced this decline, increasing the half-life of proline transport activity about fourfold. These effects were duplicated by 1 mM DBcAMP. It is concluded that bPTH-(1–34) increases proline transport in osteoblastlike cells by decreasing the degradation of amino acid transport system A proteins. The hormone may also affect the synthesis of these molecules. These effects appear to be mediated by cAMP.
Contrasting mechanisms of hypercalcemia in patients with early and advanced humoral hypercalcemia of malignancy
Authors: Dr. Ralston Stuart H. , Boyce Brendan F. , Cowan Robert A. , Gardner Mary D. , Fraser William D. , Boyle Iain T. 
Published: February 2010

Abstract
The mechanisms of hypercalcemia were assessed in 15 patients with humoral hypercalcemia of malignancy (HHM) who had tumors at various stages of progression. In patients with early tumors, bone biopsies were generally normal and the hypercalcemia was due to an elevation in renal tubular resorption of calcium. Conversely, osteoclastic resorption was markedly increased in patients with advanced tumors, particularly those in whom the biopsies were obtained postmortem. Osteoclast surface (Oc.S) correlated positively with the stage of tumor progression (r = 0.80, p &lt; 0.002), degree of immobility (r = 0.87, p &lt; 0.002), and level of urinary cyclic AMP excretion (r = 0.60, p &lt; 0.02). When compared with a group of ambulant patients with primary hyperparathyroidism (HPT), osteoblast surface (Ob.S%) in HHM was depressed (median and range): 1.2% (0–11.6%) versus 5.3% (1.1–32.0%) (p &lt; 0.001). However, a relatively low Ob.S (4%) and raised Oc.S (43.5%) were also seen in an immobilized patient with severe HPT.
These data suggest that the PTH-related peptides currently invoked in the pathogenesis of HHM may initially cause hypercalcemia by enhancing renal tubular calcium resorption. The increase in osteoclastic activity and depression of osteoblastic activity that subsequently occurs is probably due to the combined effects of immobilization and higher circulating levels of PTHrP on the skeleton. However, the release of other bone-resorbing factors by the tumor, which have a depressant effect on osteoblastic activity, remains possible.
A direct effect of 24,25-(OH)2D3 and 1,25-(OH)2D3 on the modeling of fetal mice long bones in vitro
Authors: Schwartz Z. , Soskolne W. A. , Atkin I. , Goldstein M. , Ornoy A. 
Published: February 2010

AbstractTo examine the effects of 24,25-(OH)2D3 and 1,25-(OH)2D3 on fetal long bone modeling the radii and ulnae of 16 day fetal mice were grown in vitro for 2 days. Their growth, mineralization, and resorption were assessed by measuring diaphyseal length, calcium and phosphorus content, hydroxyproline-protein ratios, and the release of incorporated 45Ca. The results showed that 24,25-(OH)2D3 at concentrations of 10−10-10−8 M stimulated the growth of the bones as indicated by their increased diaphyseal length, periosteal bone area, and hydroxyproline content. Calcium and phosphorus content was significantly increased; 45Ca release was unaltered. Bones incubated in media containing 10−6 M 24,25-(OH)2D3 responded in a similar fashion to bones incubated in media containing 10−10-10−8 M 1,25-(OH)2D3, with inhibition of bone growth as indicated by reduced diaphyseal length, periosteal bone area, hydroxyproline-protein ratios, and calcium and phosphorus content; 45Ca release was significantly increased. Neither metabolite affected total bone length. The results suggest a role for 24,25-(OH)2D3 in the growth of fetal mice bones in vitro and also confirm the findings from previous studies that 1,25-(OH)2D3 and high concentrations of 24,25-(OH)2D3 stimulate bone resorption.
Bone matrix stimulates osteoclastic differentiation in cultures of rabbit bone marrow cells
Authors: Fuller Karen , Chambers Timothy J. 
Published: February 2010

Abstract
Cells showing osteoclastic characteristics have not been identified outside bone. Because osteoclasts originate from an extraosseous source, this suggests that identifiable osteoclastic features do not develop until the precursors enter bone, where the local microenvironment may signal osteoclastic differentiation or maturation. We assessed the influence of bone matrix on osteoclastic differentiation by incubating bone marrow cells, after removal of pre-existing osteoclasts, on plastic coverslips or slices of devitalized cortical bone. We found that there was a threefold increase in the number of osteoclast-specific MAb-positive cells on the bone matrix compared with plastic coverslips. The number of MAb-positive cells correlated with the extent of excavation of the surface of the bone slices. Multinuclearity correlated with MAb-positive cell density, and for any given density the proportion of MAb-positive cells that were multinucleate was similar on plastic and bone. We conclude that, in the presence of 1,25-(OH)2 vitamin D3, bone matrix stimulates the generation of osteoclasts but has no demonstrable influence on the fusion of mononuclear osteoclastic precursors.