bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phorbol esters modulate the high Ca2+-stimulated accumulation of inositol phosphates in bovine parathyroid cells
Authors: Dr. Kifor Olga , Congo Dale , Brown Edward M. 
Published: February 2010

Abstract
We examined the effects of TPA on the high Ca2+-stimulated accumulation of inositol phosphates in bovine parathyoid cells to determine whether protein kinase C modulates phosphoinositide turnover in a fashion similar to that observed in other cell types stimulated by more classic Ca2+ mobilizing hormones. Following exposure of parathyroid cells to TPA (10−6 M) for 10 or 30 minutes, there was a time- and dose-dependent inhibition of the accumulation of inositol monophosphate (IP), inositol bisphosphate (IP2), and inositol trisphosphate (IP3) stimulated by 3 mM Ca2+. Half the maximal observed inhibition took place at 1–10 nM TPA, with 50–60% inhibition of high Ca2+-stimulated accumulation of inositol phosphates at 10−6 M TPA. The active phorbol ester, 4β-phorbol didecanoate, produced similar effects; the inactive derivative, 4α-phorbol didecanoate, was without effect. When parathyroid cells were exposed to TPA (10−6 M) for varying times and were then incubated with high (3 mM) Ca2+, inhibition of inositol phosphate accumulation was observed with 10 or 30 minutes preincubation. In contrast, preincubation of cells with TPA for 3 or 18 h markedly enhanced the high (3 mM) Ca2+-induced increase in inositol phosphates. In cells preincubated with TPA for 18 h, binding sites for [3H]phorbol dibutyrate and total protein kinase C (PKC) activity were reduced by greater than 95% and by 71%, respectively, consistent with downregulation of the enzyme. These results suggest that the high extracellular Ca2+-stimulated increase in accumulation of inositol phosphates in parathyroid cells, which has been postulated to result from a receptorlike process, can be modulated by agonists of protein kinase C in a fashion similar to that observed with more classic Ca2+ mobilizing hormones. Activators of kinase C initially inhibit the generation of inositol phosphates, presumably as a result of reduced turnover of phosphoinositides, but subsequently enhance inositol phosphate accumulation, probably because of down-regulation of protein kinase C.
Bone-resorbing activity and prostaglandin E produced by human periodontal ligament cells in vitro
Authors: Saito Shigeru , Dr. Rosol Thomas J. , Saito Mayumi , Ngan Peter W. , Shanfeld Joseph , Davidovitch Zeev 
Published: February 2010

Abstract
Human periodontal ligament (PDL) cells were derived from healthy premolars extracted for orthodontic treatment and were utilized for in vitro experiments in passages 4–6. Human PDL cells were seeded in tissue culture tubes and incubated with interleukin-1α (Il-1α), IL-1β, tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), indomethacin, parathyroid hormone (PTH), or their combinations, for 1 h. The medium was then replaced with serum-free BGJb medium and incubated for 24 h without further additions. Prostaglandin E (PGE) concentrations in the conditioned media (CM) were measured by radioimmunoassay, and bone-resorbing activity was measured using 45Ca-labeled neonatal mouse calvariae. The results of this study indicated that (1) unstimulated cultured PDL cells produced PGE, and PDL CM stimulated bone resorption; (2) cytokine-treated (IL-1α, IL-1β, and TNF-α) PDL cells had increased production of PGE and bone-resorbing activity compared to unstimulated PDL cells; (3) indomethacin completely inhibited PGE production from unstimulated PDL cells but only partially inhibited bone-resorbing activity, indicating that PDL cells produced nonprostaglandin bone-resorbing factor(s); (4) IFN-γ did not change PGE or bone-resorbing activity production by cytokine-stimulated PDL cells; and (5) PTH treatment of PDL cells in addition to cytokines (IL-1α, IL-1β, and TNF-α) had additive effects on the production of bone-resorbing activity and synergistic effects on PGE production compared to cytokine treatment alone.
Bisphosphonates in vitro specifically inhibit, among the hematopoietic series, the development of the mouse mononuclear phagocyte lineage
Authors: Dr. Cecchini Marco G. , Fleisch Herbert 
Published: February 2010

Abstract
Bisphosphonates (BP) are powerful inhibitors of bone resorption. We have previously shown that 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP), 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (AHPrBP), and dichloromethylenebisphosphonate (Cl2MBP) inhibit the proliferation of macrophages in vitro at concentrations that do not affect the viability of nonproliferating cells. In this study we further investigated whether the antiproliferative effect of these three BP is, among the hematopoietic series, preferential to the mononuclear phagocyte lineage. BP were unable to inhibit more than 30–40% of the [3H]thymidine (3H-TdR) incorporation into bone marrow cells stimulated to proliferate by multilineage colony-stimulating activity containing conditioned medium (multi-CSA). From the analysis of the colonies induced in semisolid medium by multi-CSA and recombinant murine granulocyte-macrophage colony stimulating factor (rmGM-CSF), a dose-dependent disappearance specific to the macrophage-containing colonies emerged. In contrast, the number and composition of colonies other than macrophage and, in particular, the granulocyte colonies were not affected by these compounds, even at high concentrations (100 μM) previously also shown to be toxic for nonproliferating macrophages. Since the macrophages, differently from polymorphonuclear phagocytes, are known to be highly pinocytotic, it is possible that by this means they selectively concentrate BP intracellularly, leading to toxic concentrations. We postulate tht BP may also act in vivo in addition to their effect on osteoclast activity, by a similar mechanism on osteoclast precursors and on bone resident macrophages, a source of cytokines stimulating bone resorption and leading to impaired osteoclast recruitment and activity. Furthermore, their specific effect on the mononuclear phagocyte lineage may also be relevant in other pathologic situations in which these cells are involved.
Effect of naproxen on cancellous bone in ovariectomized rats
Authors: Dr. Lane Nancy , Coble Toni , Kimmel Donald B. 
Published: February 2010

AbstractNonsteroidal anti-inflammatory drugs (NSAIDs) affect bone metabolism in vitro and in vivo. They delay but do not alter the outcome of healing processes in bone. In some bone loss models, they block bone resorption and slow the rate of loss. We studied the effect of naproxen, a potent NSAID, on cancellous bone of the proximal tibial metaphysis of 6-month-old adult female ovariectomized rats.Animals were ovariectomized, divided into groups, and fed standard diets differing only in naproxen content for 42 days. The rats of the groups ate 2.0, 5.5, 12.7, and 32 mg naproxen per kg body weight per day, respectively. Serum levels of naproxen were determined. Bone volume, mineralizing surface, osteoblast activity, osteoclast surface, and bone resorption rate were determined by bone histomorphometric techniques.The rats' dose-related serum naproxen levels ranged from 4 to 28 μg/ml. Naproxen inhibited up to 70% of the bone loss occurring after ovariectomy at a serum level of 4 μg/ml. We deduced that naproxen blocked bone resorption in ovariectomized rats by slowing osteoclast activity at all doses. In contrast, naproxen slowed bone formation only at serum levels &gt; 20 μg/ml in ovariectomized rats. These findings may have clinical relevance in helping to prevent postmenopausal bone loss in women.
Treatment of humoral hypercalcemia of malignancy in rats with inhibitors of carbonic anhydrase
Authors: Brown Gregory M. , Morris Carol A. , Mitnick Mary Ann , Insogna Karl L. 
Published: February 2010

AbstractThe enzyme carbonic anhydrase has been suggested as a critical participant in osteoclast-mediated bone resorption. In humoral hypercalcemia of malignancy (HHM) intense osteoclastic bone resoprtion is principally responsible for the observed hypercalcemia. We therefore undertook to examine the effect of the carbonic anhydrase inhibitor acetazolamide on the hypercalcemia induced by the H500 Leydig cell tumor in Fisher rats, a well-described model of HHM. Acetazolamide treatment for 10 h at 10 mg/h resulted in a significant fall in serum calcium in the five drug-treated animals (14.2 ± 0.9 to 11.5 ± 0.1 mg/dl, p &lt; 0.05). Conversely, the six animals infused with vehicle alone showed a significant rise in serum calcium (12.5 ± 0.5 to 13.8 ± 0.1 mg/dl, p &lt; 0.05). At the end of the infusion, the acetazolamide-treated animals had a significantly lower mean serum calcium than those receiving vehicle alone (11.5 ± 0.1 versus 13.8 ± 0.1, p &lt; 0.05). There was no significant change in serum phosphorus, urine calcium, urine phosphorus, or nephrogenous cyclic AMP excretion between the two groups. Acetazaolamide and HTS 5-(3-hydroxybenzoyl)-2-thiophenesulfonamide, another carbonic anhydrase inhibitor, both significantly inhibited in vitro bone resorption induced by 5 × 10−9 M 36Tyr(1–36)-PTHrP-amide (PTHrP, parathyroid hormone-related protein). Acetazolamide also inhibited the resorption induced by 10−8 M (1–141)-PTHrP and 2.5 × 10−9 M (1–74)-PTHrP. We conclude that acetazolamide is effective in lowering the serum calcium in animals with humoral hypercalcemia of malignancy. The data are consistent with the hypothesis that the mechanism of action for this effect is direct inhibition of osteoclast-mediated bone resorption.
Structural determinants of the capacity of heparin to inhibit collagen synthesis in 21-day fetal rat calvariae
Authors: Hurley Marja M. , Kream Barbara E. , Raisz Lawrence G. 
Published: February 2010

Abstract
Earlier work from our laboratory demonstrated that heparin inhibits type I collagen and DNA synthesis in fetal rat calvariae in vitro. In this paper we have analyzed the structural features of heparin that determine its inhibitory effect on collagen synthesis. These experiments were performed using unmodified heparins and low-molecular-weight heparins from different manufacturers, nonheparin glycosaminoglycans, desulfated heparins, anticoagulant and nonanticoagulant heparin, and chemically defined heparin oligosaccharides. Low-molecular-weight heparin (Mr 3700–5100) inhibited collagen synthesis, but oligosaccharides (disaccharides to decasaccharide, Mr 665–3000) did not. The glycosaminoglycans chondroitin sulfate B, heparan sulfate, and hyaluronic acid did not alter collagen synthesis but dextran sulfate was as inhibitory as unmodified heparin. Nonanticoagulant as well as anticoagulant low-molecular-weight heparin fractions inhibited collagen synthesis. Modification of heparin by total desulfation, O-desulfation, or N-desulfation and re-N-acetylation resulted in the loss of inhibitory property, suggesting that the degree of sulfation contributed to heparin's inhibitory effect. Low-molecular-weight heparins from different manufacturers were just as inhibitory as native heparin on collagen synthesis. We therefore conclude that low-molecular-weight heparin compounds offer no protection against heparin-induced osteoporosis. Our findings also suggest that the size and sulfation of a heparin-derived oligosaccharide contribute to its ability to inhibit collagen synthesis in bone.
Regulation of alkaline phosphatase by 1,25-dihydroxyvitamin D3 and ascorbic acid in bone-derived cells
Authors: Franceschi Renny T. , Young Jock 
Published: February 2010

Abstract
The bone, liver, and kidney isozyme of alkaline phosphatase (ALP) has been measured in MG-63 human osteosarcoma cells after treatment with ascorbic acid (AA) and/or 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Both compounds were required to achieve maximum ALP activity. When grown in the absence of 1,25-(OH)2D3 cells had low basal ALP activity regardless of whether media contained AA. In AA-free medium, 1,25-(OH)2D3 (10 nM) increased ALP activity fourfold. Addition of AA further increased levels of ALP activity induced by 1,25-(OH)2D3 to 10–15 times those found in -AA controls. The earliest effects of 1,25-(OH)2D3 were seen after 24–48 h, and ALP activity continued to increase for 6–8 days. AA and 1,25-(OH)2D3 had similar effects on ALP activity in ROS 17/2.8 rat osteosarcoma cells. In MG-63 cells the effects of AA and 1,25-(OH)2D3 could not be simply explained by the ability of these compounds to inhibit cell growth because another mitotic inhibitor, hydroxyurea, had a minimal effect on ALP activity. 1,25-(OH)2D3-specific induction of ALP ± AA was totally blocked by inhibitors of protein and RNA synthesis. Maximal ALP induction was obtained when cells were plated at low density. Consistent with our previous report (Franceschi et al. 1988 J Biol Chem 263:18938–18945), 1,25-(OH)2D3 rapidly stimulated type 1 collagen synthesis and acid-precipitable hydroxyproline production in MG-63 cells and this stimulation was further increased by AA. These results suggest that induction of the osteoblast marker, ALP, is directly or indirectly coupled to collagen matrix synthesis and/or accumulation.
Sex differences in peak adult bone mineral density
Authors: Kelly Paul J. , Twomey Lance , Sambrook Philip N. , Dr. Eisman John A. 
Published: February 2010

Abstract
Osteoporotic fractures are more common in women than men. Although accelerated bone loss following the menopause is recognized as of major importance, it is generally considered that a lower peak adult bone mass in females also contributes to their increased risk of osteoporosis in later life. To examine potential sex differences in peak adult bone mass we studied 29 pairs of dizygotic twins of differing within-pair sex in whom the female twin was premenopausal (mean age 37 years, range 21–55). Bone mineral density (BMD, g/cm2) was measured at the lumbar spine and femoral neck by dual-photon absorptiometry; 22 pairs also had BMD measured in the distal and 21 pairs in the ultradistal radius by single-photon absorptiometry. There was no significant difference in usual dietary calcium intake or tobacco consumption between the twin pairs. Consistent with accepted dogma, BMD at both radial sites were higher (+27%) in the males than their female cotwins. In contrast, there was no sex difference (male versus female) in BMD (mean ± SEM) in the femoral neck (0.96 ± 0.02 versus 0.97 ± 0.03), and surprisingly, the females had a greater lumbar spine BMD than their male cotwins (1.19 ± 0.03 versus 1.26 ± 0.03, p &lt; 0.05). This difference was observed despite the fact that the males were taller (p = 0.033). If the femoral neck BMD values in the females were corrected for this difference in BMI, their values (0.99 ± 0.03 g/cm2) were significantly higher than those in their male cotwin (p &lt; 0.05). Alternatively if the lumbar spine BMD in the female twins was corrected for the sex difference in anterior-posterior vertebral dimension (measured in cadaveric vertebrae) the female values were then 15% greater than those of their male cotwin. Therefore, a sex difference in peak adult bone density at the lumbar spine or femoral neck does not contribute to the higher incidence of osteoporotic fracture at these sites in aging women. Rather, the data suggest that before the menopause the female sex is associated with a bone density greater than expected on the basis of muscle strength or body size or weight.
Glucocorticoids stimulate resorption in fetal rat parietal bones in vitro
Authors: Dr. Gronowicz Gloria , McCarthy Mary Beth , Raisz Lawrence G. 
Published: February 2010

AbstractThe effect of glucocorticoids on bone resorption was examined in a serum-free mineralizing organ culture system derived from 20 day fetal rat parietal bones. Bone resorption was assessed by prelabeling the fetal rats in utero with 45Ca and determining the daily release of 45Ca into the medium of cultured bones. During the first 24 h of treatment a transient stimulation of bone resorption was found; 4.5 ± 0.3% of the total 45Ca was released into the medium with 1 nM corticosterone and 4.1 ± 0.2% with 10 nM corticosterone compared to 2.9 ± 0.2% in control bones. Treatment with 1 and 10 nM dexamethasone for 24 h also showed an increase in 45Ca release compared to control bones. During the same time period 45Ca release was 6.9 ± 1.4% with 10 nM parathyroid hormone. At later time points 100 and 1000 nM corticosterone inhibited 45Ca release, but 1 and 10 nM corticosterone values were similar to controls. At 24 h the number of osteoclasts per mm2 tissue in bone lacunae was significantly elevated with 1–100 nM corticosterone and 10 nM parathyroid hormone compared to control bones. In control bones 0.10 ± 0.05 osteoclasts per mm2 of tissue were found, but 0.59 ± 0.21 osteoclasts per mm2 were seen with 10 nM corticosterone and 1.50 ± 0.34 with 10 nM parathyroid hormone. An additional assay of bone resorption, the release of lysosomal β-glucuronidase into the medium was also elevated in glucocorticoid and parathyroid hormone-treated cultures. During 0–24 h, the medium from 10 nM parathyroid hormone-treated bones contained elevated levels of β-glucuronidase activity, 7.5 ± 0.7 versus 6.0 ± 0.4 μg/ml in the control bones and, during 24–48 h, 10.5 ± 0.8 versus 7.7 ± 0.6 μg/ml of phenolphthalein in the controls. With 10 nM corticosterone there was a significant increase of 10.0 ± 0.5 μg/ml released at 24–48 h, but high concentrations of glucocorticoids decreased β-glucuronidase release. We conclude that corticosterone can cause a transient increase in bone resorption by increasing osteoclast number and activity in bone.
Intraperitoneal free fatty acids induce severe hypocalcemia in rats: A model for the hypocalcemia of pancreatitis
Authors: Dettelbach Mark A. , Deftos Leonard J. , Stewart Andrew F. 
Published: February 2010

Abstract
Indirect evidence suggests a causative role for intraperitoneal free fatty acids (FFA) in hypocalcemia associated with pancreatitis. We examined the effects of intraperitoneal injection of four naturally occurring FFAs on serum calcium in rats. Two saturated FFAs, stearate and palmitate, induced little or no hypocalcemia. Two unsaturated FFAs, oleate and linoleate, caused dramatic hypocalcemia in treated versus control rats (6.3 ± 1.4 and 5.3 ± 0.7 mg/dI, respectively, versus 10.1 ± 0.6). Dose-response studies demonstrated that minute quantities of oleate (100 μl per 250 g rat) caused marked hypocalcemia (7.2 ± 0.3 mg/dI). Treated versus control rats also revealed a decrease in ionized calcium (3.15 ± 0.2 versus 5.6 ± 0.05 mg/dI) and magnesium (1.4 ± 0.15 versus 2.0 ± 0.10), an appropriate increase in PTH levels (1670 ± 451 versus 396 ± 235 pg/ml), and a fall in calcitonin levels (70.4 ± 21.3 versus 47.5 ± 16.4 pg/ml) but no change in albumin or phosphate levels. In vitro, the Ksp of calcium dioleate was shown to be 5.3 × 10-−8 m3/liter3; thus under physiologic conditions 100 μl oleate binds 7.2 mg calcium, or approximately twice the total ECF ionized calcium in the rat.
The amounts of intraperitoneal FFA that can easily be achieved in pancreatitis complex pathophysiologically significant amounts of calcium and may lead to severe hypocalcemia.
Case report: Idiopathic acquired diffuse osteosclerosis in a young woman
Authors: Beyer H. Stephen , Parfitt A. Michael , Shih Mei Shu , Anderson Quentin , Heath Hunter 
Published: February 2010

Abstract
We describe a young woman who acquired a painful, diffuse osteosclerosis of the cervical, thoracic, and lumbar spine, pelvis, and long bones of the legs as an adult. Bone densitometry showed a large increase in apparent bone density. Skeletal radiographs demonstrated progressive endosteal and periosteal thickening of the cortices. A bone scan showed increased uptake of radiolabel. The serum total alkaline phosphatase and 1,25-(OH)2D3 levels were substantially elevated and the immunoreactive PTH was mildly elevated. Bone biopsy showed increased bone turnover, especially on endocortical and intracortical surfaces, but the structural indices were normal. By 4 years after presentation the bone pain had remitted and the serum alkaline phosphatase, 1,25-(OH)2D3, and PTH were normal. No cause for the occurrence of osteosclerosis in this patient could be found.
Rapid publication: Constitutive expression of a vitamin D 1-hydroxylase in a myelomonocytic cell line: A model for studying 1,25-dihydroxyvitamin D production in vitro
Authors: Dr. Adams John S. , Beeker Timothy G. , Hongo Takashi , Clemens Thomas L. 
Published: February 2010

Abstract
The capacity of the v-myc-transformed, chicken myelomonocytic cell line HD-11 to metabolize 25-hydroxyvitamin D3 (25-OHD3) was examined. HD-11 cells produced and secreted a metabolite of 25-OHD, that was bound with high affinity by receptor for 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. On normal-phase HPLC, this metabolite cochromatographed with authentic 1,25-(OH)2D3 in both hexane- and methylene chloride-based solvent systems. The 25-OHD, 1-hydroxylation reaction was substrate saturable with a Km of 73 nM 25-OHD3 and a maximal velocity of 167 fmol per 106 cells per h. This reaction was inhibited by keto-conazole, a recognized inhibitor of cytochrome P450 mixed-function oxidases including the authentic, renal 25-OHD3 1-hydroxylase. On the other hand, HD-11 cell 1,25-(OH)2D3 production was not affected by the antioxidant DPPD, a known inhibitor of free radical-generated 1,25-(OH)2D3. In addition to synthesizing 1,25-(OH)2D3, this monocyte-macrophage cell line also has the potential to be a target for the hormone; HD-11 cells express high-affinity receptor for 1,25-(OH)2D3 (Kin = 0.06 nM).
Division of Endocrinology and Metabolism, Cedars-Sinai Medical Center-UCLA School of Medicine, Los Angeles, CA 90048.
A comparison of morphometric definitions of vertebral fracture
Authors: Smith-Bindman Rebecca , Cummings Steven R. , Steiger Peter , Genant Harry K. 
Published: February 2010

Abstract
To compare the accuracy of several approaches for defining prevalent vertebral fractures from measurements of vertebral dimensions (morphometry), we measured the lateral dimensions of vertebral bodies of 115 normal premenopausal and 100 postmenopausal women. Of the postmenopausal women two observers agreed that 49 had definite vertebral fractures and 38 were definitely normal. Using these classifications as an independent reference, women were then classified as fractured or normal by several definitions based on vertebral morphometry. No morphometric definition of vertebral fracture agreed perfectly with the consensus classifications. In general, definitions that involved combinations of measurements of anterior (Ha), middle (Hm), and posterior (Hp) vertebral height classified women more accurately than did definitions based on a single measurement or ratio. The Ha/Hp ratio produced many false positives unless it was adjusted for normal variations in the shapes of different vertebral bodies. Definitions of fracture based on a &gt; 15% reduction in heights or ratios had higher sensitivity but more false positives than definitions that used a more stringent (&gt;20%) criterion. All morphometric definitions of vertebral fracture separated the postmenopausal women into two groups (fractured and normal) that had significantly (P &lt; 0.001) different mean spine bone density by quantitative computed tomography. Definitions that had the lowest rates of false positives also produced the largest differences in bone density between those defined as fractured and those defined as normal.