bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of pertussis toxin on parathyroid hormone-stimulated cyclic AMP production in cultured kidney cells
Authors: Dr. Rizzoli R. , Bonjour J.-P. 
Published: February 2010

Abstract
The effect of pertussis toxin, which inactivates the guanine nucleotide binding regulatory proteins Gi and Go on cAMP production in response to parathyroid hormone PGE2 or forskolin, was examined in confluent opossum kidney (OK) cells. This effect was compared with that caused by dexamethasone. The response to PTH was increased in cells preincubated with either agent. The effect of pertussis toxin was selective for PTH, since cAMP production in response to neither PGE2 nor forskolin was increased. In contrast, the response to forskolin was enhanced in dexamethasone-treated cells. These results indicate that both stimulatory and inhibitory guanine nucleotides binding regulatory proteins modulate PTH-induced cAMP producion in OK cells. Moreover, pertussis toxin and dexamethasone appear to affect different levels of the PTH-receptor-adenylate cyclase complex.
Calcitonin-like effects of forskolin and choleratoxin on surface area and motility of isolated rabbit osteoclasts
Authors: Dr. Ransjö Maria , Lerner Ulf H. , Heersche Johan N. M. 
Published: February 2010

Abstract
We have previously found that the adenylate cyclase stimulators forskolin and choleratoxin increase cyclic AMP and transiently inhibit bone resorption in cultured mouse calvaria, suggesting that the compounds, directly or indirectly, may inhibit osteoclast activity. In the present study, forskolin and choleratoxin were investigated for their direct effects on surface area and motility of isolated rabbit osteoclasts, and the effects were compared to those of calcitonin (CT). Osteoclasts were cultured on coverslips for different times in the absence or presence of the compounds. The effect on osteoclast mean area was quantified on fixed and stained osteoclasts, and in addition effects were recorded with time-lapse cinemicrography. The effects of CT (100 mU/ml) on mean area and motility were seen within minutes and were maximal after 10–60 minutes. Forskolin (10–30 μmol/liter) produced a rapid (15–60 minutes) inhibition of motility and decrease in area (contraction) of osteoclasts. Choleratoxin (1 μg/ml) treatment also resulted in cell contraction and inhibition of motility; however, the response was not seen before 45–60 minutes. The difference in the kinetics of the osteoclast response between forskolin, CT, and choleratoxin is similar to differences in time course for the effect on cyclic AMP in calvarial bones, which we reported earlier. Although cells were incubated continuously with forskolin, choleratoxin, or CT, the effects were transient. Thus, after 7–8 h incubation with CT, 3–4 h treatment with forskolin, or 4–6 h with choleratoxin, the osteoclasts started to recover from contraction and immotility. The effect of forskolin and choleratoxin on the mean surface area of osteoclasts was dose dependent.
The present study shows that forskolin and choleratoxin have a direct inhibitory action on osteoclast activity and thus provide further evidence that cyclic AMP is a mediator of the action of CT on bone resorption.
Tumor necrosis factor α and interleukin-1 stimulate bone resorption in vivo as measured by urinary [3H]tetracycline excretion from prelabeled mice
Authors: König Adrian , Mühlbauer Roman C. , Fleisch Herbert 
Published: February 2010

Abstract
Tumor necrosis factor α (TNF-α) and interleukin-1 (IL-1) have been shown to stimulate bone resorption in vitro. We have now investigated whether these cytokines also cause a similar action when administered in vivo. This was made possible by the adaptation of a newly developed technique that enables the continual assessment of bone resorption in vivo in mice by measuring urinary excretion of 3H from [3H]tetracycline-prelabeled animals.
Experiments using maneuvers known to influence bone resorption, such as a change in dietary calcium or administration of parathyroid hormone or dichloromethylenebisphosphonate, indicate that the technique is reliable and sensitive in mice.
Daily intravenous administration of either recombinant human or recombinant murine TNF-α, as well as subcutaneous administration of recombinant human IL-1α, were found to stimulate bone resorption in a dose-dependent manner. The effect was maximal within 2 days. Thus, exogenous TNF-α and IL-1α can stimulate bone resorption in vivo, suggesting that these cytokines may also exert a systemic effect on bone.
A differentiation-inducing factor produced by the osteoblastic cell line MC3T3-E1 stimulates bone resorption by promoting osteoclast formation
Authors: Abe Etsuko , Ishimi Yoshiko , Takahashi Naoyuki , Akatsu Takuhiko , Ozawa Hiroyuki , Yamana Hiromi , Yoshiki Shusaku , Dr. Suda Tatsuo 
Published: February 2010

Abstract
We have reported that the differentiation-inducing factor (DIF) is present in conditioned medium of mouse osteoblast-like cell (MC3T3-E1) cultures (Ref. 12). In the present study, the DIF from conditioned medium of MC3T3-E1 cells was partially purified and its biologic activity was examined. The DIF was purified by monitoring the induction of phagocytic activity of mouse myeloblastic leukemia cells (M1). The DIF induced differentiation of not only M1 cells but also mouse myelomonocytic cells (WEHI-3). Furthermore, the DIF increased the in vitro bone-resorbing activity and the osteoclast number in mouse calvaria. The increases were inhibited by the addition of either salmon calcitonin or indomethacin. When mouse bone marrow cells were cultured with the DIF for 8 days, formation of osteoclast-like multinucleated cells was stimulated dose dependently. The DIF from MC3T3-E1 cells appeared to be different from interleukin-1 (IL-1), tumor necrosis factor (TNF), and transforming growth factor β (TGF-β). These results suggest that the DIF partially purified from osteoblast-like cell cultures stimulates osteoclastic bone resorption by promoting differentiation and fusion of osteoclast progenitors to form multinucleated osteoclasts.
The direct examination of three-dimensional bone architecture in vitro by computed tomography
Authors: Feldkamp Lee A. , Goldstein Steven A. , Parfitt Michael A. , Jesion Gerald , Kleerekoper Michael 
Published: February 2010

Abstract
We describe a new method for the direct examination of three-dimensional bone structure in vitro based on high-resolution computed tomography (CT). Unlike clinical CT, a three-dimensional reconstruction array is created directly, rather than a series of two-dimensional slices. All structural indices commonly determined from two-dimensional histologic sections can be obtained nondestructively from a large number of slices in each of three orthogonal directions. This permits a comprehensive description of structural variation within a specimen and greatly facilitates the study of structural anisotropy. A measure of three-dimensional connectivity (Euler number/tissue volume) has been determined for the first time in human cancellous bone and shown to correlate with several two-dimensional histomorphometric indices. The method has the potential for overcoming many of the limitations of current approaches to the study of bone architecture at the microscopic level.
Prostaglandins promote osteoclastlike cell formation by a mechanism involving cyclic adenosine 3′,5′-monophosphate in mouse bone marrow cell cultures
Authors: Akatsu Takuhiko , Takahashi Naoyuki , Debari Kazuhiro , Morita Ikuo , Murota Seiitsu , Nagata Naokazu , Takatani Osamu , Suda Tatsuo 
Published: February 2010

Abstract
We have developed a mouse bone marrow culture system in which multinucleated osteoclast (OC)-like cells are formed within 8 days.(10) Using this culture system, we examined the effect of prostaglandins (PGs), potent bone-resorbing agents, on OC-like cell formation. Four PGs (PGE1 and PGE2 at 10−8-10−5 M, 6-keto-PGF1α at 10−5 M, and PGF2α at 10−6-10−5 M) significantly stimulated the formation of OC-like cells. The potency of the PGs in inducing OC-like cell formation was the highest in PGE1 and PGE2, followed by PGF2α and 6-keto-PGF1α in that order, and the order was highly correlated with the order of the potency in increasing the production of cyclic adenosine 3′,5′-monophosphate (cAMP) in bone marrow cells. Addition of dibutyryl-cAMP also induced OC-like cell formation. Moreover, isobutylmethylxanthine (IBMX), a potent inhibitor of phosphodiesterase, potentiated the OC-like cell formation induced by PGE2, whereas salmon calcitonin greatly inhibited it. Calcitonin induced cAMP production in cultures treated with PGE2, but not in cultures with vehicle. When bone marrow mononuclear cells were cultured on dentine slices in the presence of PGE2, multinucleated OC-like cells were similarly formed and they resorbed calcified dentine, resulting in so-called Howship's lacunae. These results suggest that PGs stimulate resorption of calcified tissues by promoting osteoclast formation. The activity of PGs in inducing OC-like cell formation is considered mediated mainly by a mechanism involving cAMP.
Effects of transforming growth factors β1 and β2 on a mouse clonal, osteoblastlike cell line MC3T3-E1
Authors: Dr. Ibbotson Kenneth J. , Orcutt Christopher M. , Anglin Ann-Marie , D'Souza Sharyn M. 
Published: February 2010

Abstract
Transforming growth factors (TGF-β1 and TGF-β2) are polypeptide growth factors with a wide range of effects on the growth and differentiated function of a variety of cell types. Transforming growth factors of the β class (TGF-β) are found in large quantities in bone matrix and are synthesized by osteoblasts. For these reasons, it has been suggested that TGF-β may play a major role in the regulation of bone cell metabolism. We have studied the effects of porcine TGF-β1 and the recently described porcine TGF-β2 in a mouse clonal, osteoblastlike cell line MC3T3-EI that has previously been shown to have many characteristics of osteoblasts.
In serum-containing medium, TGF-β1 inhibited alkaline phosphatase activity. The inhibition of alkaline phosphatase activity persisted for at least 72 h following a brief (24 h) exposure to TGF-β1, TGF-β1 also caused a marked change in cell morphology. High doses inhibited collagen synthesis; lower concentrations caused a small increase. Under serum-free conditions, TGF-β1 had biphasic effects on alkaline phosphatase activity inhibiting at high but stimulating at low concentrations and had only a slight stimulatory effect on collagen synthesis. Under the experimental conditions used, the effects of TGF-β1 on alkaline phosphatase activity and collagen synthesis were independent of effects on cell proliferation. In serum-containing medium, TGF-β2 inhibited alkaline phosphatase activity, an effect that was independent of changes in cell proliferation and caused shape changes in an identical fashion to that observed with TGF-β1.
Treatment of congenital osteopetrosis in the rabbit with high-dose 1,25-dihydroxyvitamin D
Authors: Popoff Steven N. , McGuire James L. , Zerwekh Joseph E. , Dr. Marks Sandy C. 
Published: February 2010

Abstract
Osteopetrosis is a congenital metabolic bone disease characterized by skeletal sclerosis resulting from defective osteoclast-mediated bone resorption. Osteopetrosis has been decribed in several animal species (mouse, rat, and rabbit) and in children. Bone marrow transplantation, originally shown to reverse the skeletal sclerosis in some animal mutations, has been effective in curing osteopetrosis in some children. Unfortunately, not all children with osteopetrosis are candidates for or respond to bone marrow transplantation. Recent studies have shown that several animal mutations and some children inheriting osteopetrosis have significantly elevated serum levels of 1,25-(OH)2D. Based on the possibility that there may be a resistance to 1,25-(OH)2D, high-dose calcitriol therapy has been used to treat some children and stimulated some parameters of resorption. In this study, we have examined the effects of high-dose calcitriol therapy on various serum and skeletal parameters in the osteopetrotic rabbit. Mutant rabbits and normal littermates were given continuous infusions of calcitriol via subcutaneously implanted osmotic minipumps for 2 weeks at a dose of 0.5, 2.5, or 25 μg/kg/per day. Untreated mutant rabbits are hypocalcemic and hypophosphatemic in the presence of elevated serum 1,25-(OH)2 levels in comparison with their normal littermates. Calcitriol infusions resulted in dose-dependent increases in circulating 1,25-(OH)2D levels in both normal and mutant rabbits. However, evaluation of other serum parameters and the skeletal response demonstrated significant differences between osteopetrotic and normal rabbits. At the highest dose, normal animals rapidly became hypercalcemic and osteoporotic, accompanied by weight loss and a failure to thrive; mutants remained hypocalcemic and osteopetrotic but did not exhibit the deleterious physical effects seen in treated normal littermates. Although the number of osteoclasts increased in both mutants and normals, osteoclast phenotype in the former remained abnormal. These data indicate that although very high levels of circulating 1,25-(OH)2D were achieved in osteopetrotic mutants, activation of osteoclast-mediated bone resorption with subsequent improvement of skeletal sclerosis was not observed.
Histomorphometric effects of calcium or calcium plus 25-hydroxyvitamin D3 therapy in senile osteoporosis
Authors: Orwoll Eric S. , McClung Michael R. , Oviatt Shelia K. , Recker Robert R. , Weigel Ronald M. 
Published: February 2010

Abstract
To evaluate the effects of calcium and 25-OHD in the therapy of senile osteoporosis, we studied a group of 39 women aged 69 + 7 (standard deviation, SD) years with severe osteoporosis. The group was characterized histomorphometrically by depressed bone remodeling rates without hyperosteoidosis. No subject had risk factors for osteopenia other than their age and postmenopausal status, and no subject was receiving therapy for bone disease at the onset of the study. Subjects were followed for 2 years after randomization to receive either 1200 mg/day of calcium (as calcium carbonate) and 40 μg/day of 25-OHD (calcium-25-OHD group), or 1200 mg/day of calcium plus placebo (calcium-placebo group). Calcium-25-OHD resulted in a clear increase in 25-OHD levels (p &lt; 0.001) and an increase in calcium absorption as indicated by urinary calcium excretion. Nevertheless, there was no significant change in fasting serum calcium, phosphorus, alkaline phosphatase, PTH, or 1,25-(OH)2D in either group. Radial and phalangeal bone mineral content and trabecular bone volume in the biopsied patients remained stable in both groups over the 2 year period. Unexpectedly, repeat bone biopsies revealed a clear improvement in the rate of mineralization in both groups, presumably as a result of the calcium supplementation alone. In summary, calcium-placebo and calcium-25-OHD treatment were both associated with stable appendicular bone mineral content in women with senile osteopenia. The finding of an effect of calcium supplementation on the rate of mineralization indicates that relative calcium deficiency may impair the mineralization phase of remodeling. Calcium therapy may thus provide some benefit in the therapy of osteoporosis characterized by prolonged remodeling rates.
Cosecretion of calcitonin and calcitonin gene-related peptide from cultured rat medullary thyroid C cells
Authors: Seitz Patricia K. , Cooper Cary W. 
Published: February 2010

AbstractWhether C cells cosecrete calcitonin (CT) and CGRP was examined by exposing cultured rat medullary thyroid carcinoma 6–23 cells for 2 h to high medium Ca and to agents with a potential for affecting Ca-dependent secretion. In every experiment exposure of cells to high medium Ca (2.0–2.5 mM) provoked an increased release of both peptides that was highly correlated (r = 0.73). With other test substances, also, changes in both hormones occurred in parallel. The Ca-channel activator, BAY-K-8644 (10 μM) increased secretion, and this was inhibited by the Ca channel blocker, nitrendipine (10 μM). The Ca2+ ionophore, ionomycin (5 μM), increased release, and the calmodulin-Ca channel inhibitor, phenytoin (100 μM), inhibited Ca-induced release. The active 4β isomer of phorbol-12,13-didecanoate (0.1 μM), but not the inactive 4α isomer, increased secretion. The findings suggest that pathways mediating C cell secretion include plasma membrane Ca channels, intracellular [Ca2+], calmodulin, and protein kinase C. The results show that the secretory process in rat C cells involves the release of CGRP as well as CT.
Ultradistal and cortical forearm bone density in the assessment of postmenopausal bone loss and nonaxial fracture risk
Authors: Dr. Price Roger I. , Barnes Marion P. , Gutteridge Donald H. , Baron-Hay Margaret , Prince Richard L. , Retallack Robert W. , Hickling Caroline 
Published: February 2010

Abstract
Forearm bone mineral density (BMD) was measured by single-energy photon absorptiometry in 360 healthy females without known axial fractures, 202 of whom were postmenopausal. The three sites addressed included an ultradistal (U) region containing approximately 60% trabecular bone. The other sites, distal (D) and shaft (S), were progressively more cortical. Reproducibility was 1.7–1.9% CV. The earliest evidence of a significant correlation between BMD and years since menopause was seen in trabecular bone in subjects aged 45–55 years. Fractional decrease in BMD, relative to the premenopausal value, was significantly larger at U than at S for the decades 55–65 years and above. Fractional rates of bone loss at all sites were a maximum in the first postmenopausal decade, the rate at U being 0.035, approximately 1.5 times that at D or S. A total of 33 subjects reported 54 previous minimally traumatic nonaxial (MTNA) fractures. When BMD measurements of the entire study were divided into quintiles, the prevalence of MTNA fracture cases in the lowest quintile was eight times that of each of the upper three quintiles. Prevalence of fracture cases ranked by quintiles of BMD were not different for the three scan sites. Therefore, ultradistal measurements confer no advantages over distal or shaft BMD for discriminating past MTNA fracture cases but do show larger fractional rates of loss during the first postmenopausal decade. When early postmenopausal women (with years since menopause ≤ 10) having BMD at U below the 15th age-corrected percentile, and their high BMD peers above the 75th percentile, were studied prospectively over 9–24 months there were no differences in their mean fractional rates of bone loss. These rates confirmed cross-sectional measurements based on years since menopause ≤ 10 but without selection for BMD.
Thyroid hormone 5′-deiodinase activity, nuclear binding, and effects on mitogenesis in umr-106 osteoblastic osteosarcoma cells
Authors: Lebron Barbara A. , Pekary A. Eugene , Mirell Carol , Hahn Theodore J. , Hershman Jerome M. 
Published: February 2010

Abstract
The hyperthyroid state in vivo is associated with an increase in osteoblast number and activity, suggesting that thyroid hormone may stimulate osteoblast replication and function. We therefore examined the effects of T3 (16–1170 pM) on replication rate as assessed by cell counts in UMR-106 osteoblastic osteosarcoma cells cultured for 5–10 days in medium supplemented with 10% hormone-stripped fetal calf serum (FCS). Despite the virtual absence of thyroid hormone in the control medium (total T3 concentration, 0.02 ng/ml), the addition of T3 in concentrations to 1000 pM did not increase the cell replication rate. At higher T3 concentrations, a slight decrease in growth rate was observed. No significant 5′-monodeiodinase activity was detected in UMR-106 cell homogenates. However, nuclear binding of T3 was demonstrated in intact cells. A high-affinity nuclear binding component was identified with a Ka of 2.6 × 1010 M−1 and a maximum binding capacity of 7.7 pg T3 per mg DNA, equivalent to 51 binding sites per cell nucleus. A lower affinity nuclear T3 binding component with a Ka of 1.8 × 109 M−1 was also identified. Thus, despite the presence of nuclear T3 receptors, UMR-106 cells do not exhibit a mitogenic response to T3.
Bone demineralization, biochemical indices of bone remodeling, and estrogen replacement therapy in adults with turner's syndrome
Authors: Dr. Štěpán Jan J. , Musilová Jana , Pacovský Vladimír 
Published: February 2010

Abstract
The study centered on a controversy about whether long-term estrogen replacement therapy may ameliorate the osteoporosis seen in patients with Turner's syndrome. This study comprised 26 adult patients with Turner's syndrome (9 treated and 17 untreated or insufficiently treated) and 12 adult women with pure gonadal dysgenesis (8 untreated and 4 treated). A low bone density below -2 standard deviations from the age- and sex-matched predicted normal mean was documented by dual-photon absorptiometry of the lumbar spine in all the untreated and insufficiently treated patients, but only in 6 treated patients. The biochemical indices of bone resorption (urinary hydroxyproline excretion and plasma tartrate-resistant acid phosphatase activity), as well as osteoblastic function (serum osteocalcin and bone alkaline phosphatase isoenzyme), were significantly increased in untreated and insufficiently treated patients compared with treated patients. A significant negative correlation was found between biochemically documented osteoresorption and spinal bone mineral density corrected for age of the patients. Significant positive correlations were found between serum osteocalcin and bone alkaline phosphatase isoenzyme and between biochemical indices of bone resorption and formation. Although in the patients there was an evidence of a high bone remodeling rate, the rate of bone mass loss seemed to be low, comparable with that seen in oophorectomized women who had already passed their accelerated phase of bone loss. The results indicate that long-term hormonal replacement therapy is justified in gonadal dysgenesis, regardless of the karyotype of the patient, to prevent further bone mass loss.
Increased incidence of hip fracture in osteoporotic women treated with sodium fluoride
Authors: Hedlund L. Rune , Gallagher J. C. 
Published: February 2010

Abstract
There has been controversy as to whether fluoride therapy increases the risk of fracture in the appendicular skeleton. In the present study we compared the incidence of hip fracture in four groups of osteoporotic women: 22 treated with placebo, 17 with fluoride and calcium, 18 treated with fluoride and calcitriol, and 21 with calcitriol alone. Four hip fractures occurred in 3 patients on fluoride and calcitriol, and two hip fractures occurred in 2 patients on fluoride and calcium. No hip fractures occurred in patients receiving either calcitriol alone or placebo. The difference in fracture rates for fluoride versus nonfluoride treatment is significant (p = 0.006). Moreover, the six hip fractures occurring in patients receiving fluoride during 72.3 patient years of treatment is 10 times higher than would be expected in normal women of the same age. The probability of observing six fractures in 2 years is extremely small (0.0003). In four of the hip fracture cases, the history suggested a spontaneous fracture. These findings suggest that fluoride treatment can increase the risk of hip fracture in osteoporotic women.