bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of 1,25-dihydroxyvitamin D3 on bone resorption and natural immunity in osteopetrotic (ia) rats
Authors: Dr. Schneider Gary B. , Relfson Melanie , Langman Craig B. 
Published: February 2010

Abstract
Osteopetrois is an inherited bone disease characterized by an excessive accumulation of bone throughout the skeleton. The disease in the ia (incisors absent) rat is the result of reduced bone resorption caused by defective, although numerous osteoclasts. In addition to the bone defects, ia rats have suppressed natural immunity, even though these animals have excessive numbers of natural killer (NK) cells. The osteopetrotic condition also appears to have an associated abnormality in vitamin D metabolism. Because 1,25-dihydroxyvitamin D3[1,25-(OH)2D3] stimulates bone resorption and has a role in the immunoregulation of NK cells, mutant and normal rats were infused with 1,25-(OH)2D3 for 14 days in an attempt to correct the defects in this mutant. Serum levels of osteocalcin, 25-OHD3, and 1,25-(OH)2D3, as well as NK function and parameters of bone resorption, were evaluated after the infusion period. Serum levels of osteocalcin and 1,25-(OH)2D3 were elevated in both ia and normal rats treated with 1,25-(OH)2D3. Serum 25-OHD3 levels were significantly reduced in the treated animals. The elevated percentage of NK cells normally found in ia rats was reduced to normal in the treated mutants, and NK cell function was elevated to normal levels of lytic activity. The percentage of NK cells and NK function remained unchanged in the treated normal rats. The bone marrow cavity size was significantly increased in the 1,25-(OH)2D3-treated mutants, as was the percentage of osteoclasts exhibiting normal morphology. Radiographically, the mutant bones were less dense. No net change in the bone resorption was noted in the treated normal rats. 1,25-(OH)2D3 appears to correct both the bone resorption and natural immune defects in the ia osteopetrotic mutant.
Lack of involution of hyperplastic parathyroid glands in dogs: Adaptation via a decrease in the calcium stimulation set point and a change in secretion profile
Authors: Cloutier M. , Brossard J.H. , Gascon-Barré M. , D'Amour Pierre 
Published: February 2010

Abstract
This study analyzes the parathyroid function in four dogs before and after 2 years of a low-calcium, high-sodium, vitamin D-deficient diet and the involution of the same function following (1) correction of dietary calcium deficiency and administration of IV 1,25-(OH)2D (0.25 μg twice per day) during 1 month, (2) after an additional month of normal dog chow supplemented with oral vitamin D (25 μg per day), and, finally, (3) after 5 and 17 months of a diet with normal levels of calcium and vitamin D. The parathyroid function was evaluated through IV infusion of CaCl2 and Na2 EDTA with measurement of intact (I) and carboxyl-terminal (C) immunoreactive parathyroid hormone (iPTH). The C-iPTH/I-iPTH ratio was calculated to assess the modulation of molecular forms of iPTH induced by the various treatments. The 2 years of calcium and vitamin D deprivation lowered ionized calcium (1.23 ± 0.04, p &lt; 0.05) and 25-OHD (4.02 ± 2.06 nM, p &lt; 0.005) and tended to decrease 1,25-(OH)2D (80.8 ± 8.6 pM); it increased basal I- and C-iPTH levels approximately eightfold (I-iPTH, 40.2 ± 20.7, p &lt; 0.05; C-iPTH, 185.4 ± 94.9, p &lt; 0.05) and stimulated I-iPTH (60.2 ± 23.0 pM, p &lt; 0.05) and C-iPTH (239.6 ± 80.7 pM, p &lt; 0.05) fivefold. A greater rise in nonsuppressible I-iPTH levels than in C-iPTH levels led to a decreased C-iPTH/I-iPTH ratio in hypercalcemia (12.5 ± 2.8 versus 27.8 ± 6.05 pM, p &lt; 0.005). Dietary deprivation also decreased the I-iPTH calcium stimulation set point (1.25 ± 0.05 pM, p &lt; 0.05). Treatment with dietary calcium and IV 1,25-(OH)2D normalized ionized calcium (1.34 ± 0.02 mM) and basal I-iPTH level (6.09 ± 5.48 pM) more than basal C-iPTH (69.8 ± 48.8 pM), causing the C-iPTH/I-iPTH ratio to increase from 4.80 ± 0.81 to 14.8 ± 6.1 (p &lt; 0.05). Stimulated I-iPTH decreased (46.1 ± 15.3 pM, p &lt; 0.05), but stimulated C-iPTH secretion did not change (282.4 ± 90.9 pM). A greater fall in the nonsuppressible I-iPTH level as opposed to C-iPTH level led the C-iPTH/I-iPTH ratio to increase back to a normal value (23.8 ± 1.40). The I-iPTH calcium stimulation set point remained low at 1.28 mM. Further consecutive treatment modalities over 18 months did not cause additional significant change in basal, stimulated, or nonsuppressible C-iPTH levels, but the same I-iPTH levels tended to decrease further. This explained why all three C-iPTH/I-iPTH ratios tended either to increase (basal) or to increase significantly (stimulated and nonsuppressible, p &lt; 0.05). The I-iPTH calcium stimulation set point again remained low. This study reveals that animals with hyperplastic parathyroid glands can control their I-iPTH level by maintaining a lower set point of I-iPTH stimulation by calcium and by changing their secretion profile with respect to carboxyl-terminal fragments of the PTH molecule.
Bone mineral density measured by dual-energy X-ray absorptiometry and novel markers of bone formation and resorption in patients on antiepileptic drugs
Authors: Dr. Välimäki Matti J. , Tiihonen Mikko , Laitinen Kalevi , Tähtelä Riitta , Kärkkäinen Merja , Lamberg-Allardt Christel , Mäkelä Pekka , Tunninen Riitta 
Published: February 2010

Abstract
In patients on antiepileptic drugs, bone loss has been mainly demonstrated at radial sites using old technology and has been ascribed to drug-induced vitamin D deficiency rather than to any direct effects of the treatment on bone cells. We examined 38 epileptic patients (24 women and 14 men) aged 20–49 years who were using either carbamazepine or phenytoin or both. Bone mineral density (BMD) at the lumbar spine and three femoral sites was measured by dual-energy x-ray absorptiometry (DXA) and serum and urine markers of bone and mineral metabolism were determined. The latter included the C-terminal extension peptide of type I procollagen (PICP), a putative serum marker of bone formation, and the cross-linked carboxyl-terminal telopeptide of human type I collagen (ICTP), a novel serum marker of bone matrix degradation. In female patients on phenytoin, weight- and height-adjusted BMD was reduced at the femoral neck and the Ward's triangle (p &lt; 0.05) but was at the control level in the other patient groups at all four measurement sites. Compared with controls, the serum concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were reduced by 26% (p &lt; 0.01) and by 27% (p &lt; 0.001) in female patients. These changes were independent of the therapy used. They were not present in male patients. For both genders the serum levels of vitamin D binding protein were normal. Both female and male patients had hypocalcemia, but women only showed hypocalciuria. The serum intact parathyroid hormone was 42% higher (p &lt; 0.01) in women and 26% (p = 0.07) in men. The serum markers of bone formation, bone alkaline phosphatase, osteocalcin, and PICP, were higher for both sexes, the percentage elevations being more striking in men (104%, p &lt; 0.001; 66%, p &lt; 0.001; and 63%; p &lt; 0.001, respectively) than in women (33%, p &lt; 0.01; 13%, p = NS; and 27%, p &lt; 0.05, respectively). Serum ICTP was 46% higher (p &lt; 0.001) in women and 22% (p &lt; 0.05) in men. We conclude that in patients on antiepileptic drugs, bone turnover is accelerated independently of the presence of hypovitaminosis D. Such biochemical alterations do not necessarily lead to reduced bone mass, however.
Lithium inhibits calcitriol-stimulated formation of multinucleated cells in human long-term marrow cultures
Authors: Pepersack Thierry , Corazza Francis , Demulder Anne , Guns Martine , Fondu Pierre , Bergmann Pierre 
Published: February 2010

Abstract
We observed that lithium (3 mM) blocked the 1,25-dihydroxyvitamin D [1,25-(OH)2D3]-stimulated bone resorption in fetal rat long bones in culture. Because this inhibitory effect was not seen when bone resorption was stimulated by parathyroid hormone or interleukin-1, we reasoned that Li specifically inhibited events involved in the 1,25-(OH)D3-stimulated bone resorption. The increased bone resorption induced by vitamin D in culture is associated with differentiation and/or fusion of osteoclast progenitors. In the present work, we studied the effect of Li on the basal and 1,25-(OH)2D3-stimulated generation of multinucleated osteoclast-like cells (MNC) and MNC containing tartrate-resistant acid phosphatase (TRAP+) in long-term human bone marrow cultures. Total MNC and TRAP+ cells were counted after 3 weeks of culture. In the absence of both lithium and 1,25-(OH)2D3, total MNC and TRAP+ cell numbers were 146 ± 22 and 110 ± 18 per well, respectively (mean ± SEM); in the presence of Li, corresponding figures were 79 ± 17 and 59 ± 14. When the generation of MNC and TRAP+ cells was stimulated with 1,25-(OH)2D3, (10−8 M), total MNC and TRAP+ cells were 521 ± 66 and 473 ± 63, respectively, in the absence of Li and 251 ± 44 and 155 ± 27 in the presence of Li (p &lt; 0.05). The inhibitory effect of Li was dose dependent and was not observed when the cultures were exposed to parathyroid hormone instead of 1,25-(OH)2D3. When Li was added to the cells the first week of culture only, we observed the full inhibitory effect; conversely, if Li was added for the last week of culture only, no inhibitory effect was seen. These data show that Li interferes with the recruitment of osteoclast-like cells from their precursors, probably at an early stage of differentiation.
Transient and localized expression of bone morphogenetic protein 4 messenger RNA during fracture healing
Authors: Nakase Takanobu , Nomura Shintaro , Yoshikawa Hideki , Hashimoto Jun , Hirota Seiichi , Kitamura Yukihiko , Oikawa Shinzo , Ono Keiro , Takaoka Kunio 
Published: February 2010

Abstract
Temporal and spatial distribution of a gene encoding murine bone morphogenetic protein 4 (mBMP-4) during fracture repair were investigated in mice by RT-PCR and in situ hybridization. For in situ hybridization, fractured ribs and surrounding tissues were decalcified and hybridized with a mBMP-4-specific complementary RNA probe labeled with digoxigenin-11 UTP. mBMP-4 messenger RNA (mRNA) was not detected in ribs without fracture, whereas it was detected only in the early phase of fracture from 12 to 72 h after the onset of fracture before new cartilage or bone formation. The mBMP-4 mRNAs were present in cells distributed in three distinct regions, namely, the proliferating periosteum, the medullary cavity, and the muscles near the fracture site. These BMP-4-positive cells did not express bone gla protein mRNA, which is a marker of the mature osteogenic cell. RT-PCR also showed a transient increase in the level of BMP-4 mRNA in the early phase of fracture repair. The findings provide us with some new information. (1) The BMP-4 gene is produced by less differentiated osteoprogenitor cells, not by differentiated osteoblasts. (2) The BMP-4 gene is enhanced by the impact of fracture and localized in callus-forming tissue before callus formation. Together with the activities of BMP-4, as was previously described, our results suggest that newly produced BMP-4 gene product is one of the local contributing factors in callus formation in the early phase of fracture healing.
Effects of gallium nitrate in nude mice bearing a canine adenocarcinoma (CAC-8) model of humoral hypercalcemia of malignancy
Authors: Merryman Joyce I. , Capen Charles C. , Dr. Rosol Thomas J. 
Published: February 2010

AbstractHypercalcemic nude mice bearing a canine adenocarcinoma (CAC-8) model of humoral hypercalcemia of malignancy (HHM) were treated daily with gallium nitrate (60 mg/kg of elemental gallium subcutaneously (SC) on day 0, followed by 20 mg/kg/day) for 5 days. Gallium nitrate significantly decreased (p &lt; 0.01) serum calcium in tumor-bearing animals on days 2 and 5 of treatment (mean 13.7 ± 0.7 mg/dl on day 0 versus 11.6 ± 0.3 on day 2 and 12.4 ± 0.5 on day 5). Urinary calcium excretion was decreased (p &lt; 0.05) in the gallium-treated, tumor-bearing animals (0.11 ± 0.01 mg calcium/mg creatinine) compared with hypercalcemic tumor-bearing mice (0.30 ± 0.06). Both nontumor control and tumor-bearing mice treated with gallium nitrate lost body weight during the treatment period (p &lt; 0.01). Gallium nitrate had no effect on tumor growth. Histomorphometric evaluation of lumbar vertebrae stained for tartrate-resistant acid phosphatase revealed a significant decrease (p &lt; 0.05) in the number of osteoclasts/mm trabecular bone and perimeter of trabecular bone lined by active osteoblasts (p &lt; 0.01) in the gallium-treated tumor-bearing mice compared with tumor-bearing controls. Osteoclast length (mm) was significantly increased in both the nontumor and tumor-bearing gallium-treated animals (p &lt; 0.05) compared with nontumor and tumor-bearing control mice. Serum tumor necrosis factor α (TNF-α) levels were increased in tumor-bearing animals, but gallium nitrate had no effect on circulating levels (not detectable in nontumor control mice versus 82 ± 21 pg/ml in tumor-bearing mice and 107 ± 12 pg/ml in gallium-treated tumor-bearing mice). Concentrations of gallium in bone were undetectable in untreated control mice (&lt;0.00005 μg/g bone), but markedly elevated concentrations were present in gallium-treated mice (235 ± 6 μg/g bone in nontumor-bearing and 155 ± 18 in tumor-bearing). These results indicate that gallium nitrate decreased osteoclastic bone resorption and serum calcium levels in a nude mouse model of HHM.
Studies on the mechanism of desensitization of the parathyroid hormone-stimulated calcium signal in UMR-106 cells: Reversal of desensitization by alkaline phosphatase but not by protein kinase C downregulation
Authors: Lee Suk Kyeong , Dr. Stern Paula H. 
Published: February 2010

Abstract
The involvement of protein kinase C (PKC), cAMP-dependent protein kinase (PKA), and other phosphorylation mechanisms in the rapid desensitization of the [Ca2+]i response to parathyroid hormone (PTH) stimulation was investigated in osteoblast-like UMR-106 cells. A 5 minute preincubation of the cell suspension with phorbol 12,13-dibutyrate (PDB) decreased the response to PTH in a concentration-dependent manner. 1-Oleoyl-2-acetyl-r-glycerol (OAG) pretreatment likewise decreased the PTH response. Staurosporine, a potent protein kinase inhibitor, completely prevented the desensitization caused by PDB. These PDB and staurosporine effects were also observed in 3 mM EGTA-containing medium ([Ca2+]free &lt; 10−8 M). A 5 minute pretreatment of cells with 1 μM forskolin had no effect on the calcium response to PTH. Homologous and PDB-induced desensitizations differed in several respects. Staurosporine pretreatment resulted in only a slight restoration of the PTH response under conditions of homologous desensitization. Chronic treatment with phorbol ester prevented the desensitization of the PTH response by acute phorbol treatment but not the homologous desensitization. Both homologous and PDB-induced desensitization were relieved by alkaline phosphatase treatment, consistent with the involvement of phosphorylation in the desensitization. This alkaline phosphatase effect on desensitization was inhibited by L-phenylalanine. These results suggest that PTH receptor homologous desensitization involves phosphorylation process(es) other than or in addition to those of PKC.
Estrogen enhances the stimulation of bone collagen synthesis by loading and exogenous prostacyclin, but not prostaglandin E2, in organ cultures of rat ulnae
Authors: DR. Cheng Ming Zhao , Zaman Gul , Lanyon Lance E. 
Published: February 2010

Abstract
The shafts of ulnae from 110 g male rats were cultured, and after a period of 5 h preincubation one of each pair of bones was either loaded cyclically (500 g, 1 Hz, 8 minutes) to produce physiologic strains (-1300 με) or treated with exogenous prostacyclin (PGI2) or prostaglandin E2 (10−6 M, 8 minutes) in the presence or absence of 17β-estradiol (10−8 M). PGI2, PGE2, and loading stimulated almost immediate increases in glucose 6-phosphate dehydrogenase (G6PD) activity in osteocytes and osteoblasts. This increase was uniform throughout the section with exogenous PGs in the medium but was related to local strain magnitude in loading. Elevated G6PD levels in response to loading and PGI2 persisted for 18 h, by which time, ALP activity in surface osteoblasts was elevated and [H]proline incorporation into collagen increased. PGE2 produced similar immediate and sustained increases in G6PD activity and [H]proline incorporation after 18 h but no change in ALP activity. Bones cultured for 18 h with 17β-estradiol increased their [H]proline incorporation, as did those loaded, and treated with PGI2 and PGE2. Loading and PGI2 but not PGE2 produced similar proportional increases in [H]proline incorporation above the increased baseline of estradiol alone. These results suggest that estrogen and loading together produce a greater osteogenic response than either separately. If so, estrogen withdrawal would result in a rapid fall in bone mass to establish a new equilibrium appropriate to the reduced effectiveness of the loading-related stimulus. Such a fall in bone mass is a characteristic feature of estrogen withdrawal at the menopause.
Effects of ascorbic acid on collagen matrix formation and osteoblast differentiation in murine MC3T3-E1 cells
Authors: Franceschi Renny T. , Iyer Bhanumathi S. , Cui Yingqi 
Published: February 2010

Abstract
Treatment of mouse MC3T3-E1 cells with ascorbic acid initiates the formation of a collagenous extracellular matrix and synthesis of several osteoblast-related proteins. We recently showed that ascorbic acid dramatically increases alkaline phosphatase and osteocalcin mRNAs and that this induction is blocked by inhibitors of collagen triple-helix formation (Franceschi and Iyer, J Bone Miner Res 7:235). In the present study, the relationship between collagen matrix formation and osteoblast-specific gene expression is explored in greater detail. Kinetic studies revealed that ascorbic acid increased proline hydroxylation in the intracellular procollagen pool within I h and stimulated the cleavage of type 1 collagen propeptides beginning at 2.5 h. Mature α1(I) and α2(I) collagen components were first detected at 10 h and continued to increase in both cell layer and culture medium for up to 72 h. Ascorbic acid also increased the rate of procollagen secretion from cell layers to culture medium. The secretion of another matrix protein, fibronectin, was only slightly affected. Alkaline phosphatase or its mRNA was first detected 2–3 days after ascorbic acid addition, but osteocalcin mRNA was not seen until day 6. Two inhibitors of collagen triple-helix formation, ethyl-3,4-dihydroxybenzoate and 3,4-dehydroproline, inhibited procollagen hydroxylation and alkaline phosphatase induction. 3,4-Dehydroproline also inhibited the induction of alkaline phosphatase and osteocalcin mRNAs. Surprisingly, induction was not blocked if cells were exposed to ascorbic acid before inhibitor addition. Alkaline phosphatase was also partially inhibited if cells were grown in the presence of purified bacterial collagenase. These results indicate that the induction of osteoblast markers by ascorbic acid does not require the continuous hydroxylation and processing of procollagens and suggest that a stable, possibly matrix-associated signal is generated at early times after ascorbic acid addition that allows subsequent induction of osteoblast-related genes.
Expression of Mac-2 antigen in the preosteoclast and osteoclast identified in the op/op mouse injected with macrophage colony-stimulating factor
Authors: Niida Shumpei , Amizuka Norio , Hara Fumiko , Ozawa Hidehiro , Kodama Hiroaki 
Published: February 2010

Abstract
Osteoclast deficiency in op/op mice is cured by a single injection of 5 μg recombinant human macrophage colony-stimulating factor (rhM-CSF). In this study, we found that mouse osteoclasts are positive for Mac-2 antigen, but not for F4/80, MOMA-2, Mac-1, or BM8 antigen. By using F4/80 and MOMA-2 monoclonal antibodies, we confirmed the absence of mature macrophages in the femora of op/op mice and found that multiple injections of rhM-CSF are required for the recruitment of macrophages in the bones. After a single rhM-CSF injection, we found Mac-2 positive mononuclear cells in the femora of op/op mice. The time course of the appearance of Mac-2-positive cells was very similar to that of tartrate-resistant acid phosphatase (TRAP)-positive cells. In bone sections prepared from the mutant mice that received rhM-CSF 3 days earlier, 91% of the TRAP-positive mononuclear cells were also positive for Mac-2 antigen. These results demonstrate the expression of Mac-2 antigen in preosteoclasts. The antigen was detected on the plasma membrane of preosteoclasts, as well as in their cytoplasm and nucleus, and in the extracellular matrix in the space between the cells and bone. Since Mac-2 is a galactose-specific lectin, a potential role of the lectin in cell-cell and cell-matrix adhesion during osteoclast differentiation is suggested.
Relationship of the plasminogen activator/plasmin cascade to osteoclast invasion and mineral resorption in explanted fetal metatarsal bones
Authors: Leloup Gaetane , Delaisse Jean-Marie , DR. Vaes Gilbert 
Published: February 2010

Abstract
An attempt was made to establish whether the activation of plasminogen into plasmin is necessary either for the preparatory phases to bone resorption, involving the recruitment of osteoclast precursors, their migration toward mineralized surfaces, and their final differentiation, or for the subsequent osteoclastic resorption phase. 45Ca-labeled fetal (17 day) mouse metatarsals were cultured under conditions in which they pursue their modeling for a few days. In this model, the resorption phase, monitored by the release of 45Ca into the medium, is entirely dependent on the preparatory phases affecting osteoclast precursors. It was, as expected, stimulated by parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D3 and inhibited by calcitonin. PTH also enhanced the activity of tissue-type plasminogen activator (PA) in extracts of metatarsals but not that of urokinase (which is, however, the main PA present in the mouse fetal metatarsal culture model). The resorption processes were not dependent on the presence of plasminogen in the media, even when the rudiments were precultured with tranexamic acid to remove their endogenous plasminogen. Moreover, they were not influenced by inhibitors of plasmin, either the plasma inhibitors α2-antiplasmin, α2-macroglobulin, and α1-antitrypsin, or aprotinin, which was tested under a variety of conditions. Aprotinin also did not influence the resorption (loss of calcium and hydroxyproline) of 19 day fetal mouse calvariae cultured with PTH in a medium devoid of plasminogen. It is concluded that the various steps implicated in the bone resorption processes that occur in the metatarsals and in the calvariae culture models are not dependent on the activity of plasmin. The function of PAs in bone, however, could be exerted through direct proteolysis of extracellular proteins other than plasminogen or be mediated by a molecular structural domain distinct from their catalytic domain.