bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin-6 messenger RNA expression and interleukin-6 protein secretion in cells isolated from normal human bone: Regulation by interleukin-1
Authors: Linkhart Thomas A. , Linkhart Susan G. , MacCharles Daniel C. , Long Dana L. , Strong Donna D.
Published: February 2010

Recent evidence suggests that cytokines, in addition to regulating hematopoiesis and immune functions, may be important paracrine regulators of bone turnover. Interleukin-1 (IL-1) and IL-6 are cytokines that are produced by and affect both hematopoietic and nonhematopoietic cell types. IL-1 stimulates bone resorption and inhibits osteoblast proliferation and collagen production. Previous reports that IL-6 was secreted in murine osteoblast and bone organ cultures in response to IL-1 and PTH suggested that IL-6 has paracrine effects on bone resorption or formation. To determine whether IL-6 has a paracrine function in human bone, IL-6 expression in cells isolated from normal human bone was investigated. IL-6 mRNA levels in untreated cultures were low and variable, and IL-6 secretion was undetectable. PTH had no effect on IL-6 mRNA levels or IL-6 secretion. IL-1β increased IL-6 mRNA levels, maximally 40-fold at 12 h. IL-1β increased IL-6 secretion to 0.13 nM, more than 80-fold that of untreated controls at 12 h. IL-1β also increased IL-1β mRNA levels, maximally 9-fold at 12 h, but did not increase cellular levels or secretion of IL-1β protein. Recombinant human IL-6 at 0.5–5 nM stimulated resorption in neonatal mouse calvarial organ cultures but had no effect on human bone-derived cell DNA synthesis or type I procollagen mRNA levels. The results suggest that IL-6 production by human osteoblasts may function to enhance osteolytic activity of IL-1 but does not affect proliferative and matrix biosynthetic aspects of bone formation that were tested. Because osteoblasts and bone marrow cells are in close proximity, IL-6 produced by osteoblasts may also function to amplify IL-1 stimulation of immune responses and hematopoiesis in bone marrow.
Effects of a combined estrogen-gestagen regimen on serum levels of the carboxy-terminal propeptide of human type I procollagen in osteoporosis
Authors: Hasling Claus , Eriksen Erik F. , Melkko Jukka , Risteli Leila , Charles Peder , Mosekilde Leif , Risteli Juha
Published: February 2010

Estrogen stimulates osteoblastic collagen production in vitro, but whether the same stimulation takes place in vivo is still unknown. To test the stimulatory effects of a combined estrogen-gestagen regimen in vivo we monitored serum levels of the carboxy-terminal propeptide of human type I procollagen (S-PICP) in a group of 12 osteoporotic women over a 150 week treatment period. Spinal bone mineral content (BMC) increased to a maximum of 5% over pretreatment values around week 90. Serum alkaline phosphatase (S-AP) and serum bone gla protein (S-BGP) both fell from initial values of 220 U/liter and 39 ng/ml, respectively, to 146 U/liter (p < 0.01) and 27.2 ng/ml (NS) around week 60 and remained reduced over the remaining treatment period. S-PICP also fell from 117 to 68 μg/liter at week 60 and 70 μg/ml at week 150 (P < 0.01). This is equal to a reduction to 32 ± 10% pretreatment levels. The reduction in S-PICP was not significantly different from that of the other two markers of bone formation (S-AP and S-BGP). Thus, provided the metabolic clearance of PICP remains unaltered after hormone replacement therapy, no major stimulation of osteoblastic collagen type I synthesis was demonstrable during estrogen-gestagen treatment in this population of osteoporotic women. The changes in bone markers seen in this study are therefore consistent with an estrogen-mediated reduction in the frequency of remodeling activation. Because of the reduction in bone turnover and methodologic limitations of bone marker assays, however, smaller increases in the amount of bone formed per activation could remain undetectable.
Effects of acid and basic fibroblast growth factor and heparin on resorption of cultured fetal rat long bones
Authors: Simmons Hollis A. , Raisz Lawrence G.
Published: February 2010

We tested acid and basic fibroblast growth factor (aFGF and bFGF), members of the heparin binding FGF family, for their ability to stimulate bone resorption as measured by the release of previously incorporated 45Ca from cultured fetal rat long bones in the presence and absence of heparin. Purified low-molecular-weight heparin (LMW heparin) at 5–125 μg/ml had no direct stimulatory effect. There was little effect from aFGF (10−11-10−8 M) alone, but increased resorption was observed in the presence of LMW heparin. With bFGF, increased bone resorption was observed at 10−9 M but not at 10−8 M. The stimulatory effects of aFGF and bFGF in the presence of LMW heparin were not blocked by the addition of indomethacin (10−6 M), which blocks prostaglandin production, or hydroxyurea (10−3 M), which blocks DNA synthesis. However, pretreatment with aphidicolin (3 × 10−5 M), a potent inhibitor of DNA synthesis, blocked the effect of acid FGF and diminished the effect of bFGF. These results indicate that both aFGF and bFGF can stimulate bone resorption by a prostaglandin-independent mechanism, particularly in the presence of heparin. The activation of FGF-mediated bone resorption by heparin could play a role in producing the osteoporosis that has been described with heparin therapy and mastocytosis.
Actions of calcipotriol (MC 903), a novel vitamin D3 analog, on human bone-derived cells: Comparison with 1,25-dihydroxyvitamin D3
Authors: Evans Dean B. , Thavarajah Mannicam , Binderup Lise , Kanis John A.
Published: February 2010

The actions of a novel vitamin D3 analog calcipotriol (MC 903), on human bone-derived cells were compared to those of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Both calcipotriol and 1,25-(OH)2D3 inhibited the proliferation of human osteoblast-like cells in a dose-dependent manner (10−10-10−6 M), an effect observed at different cell densities. Lower concentrations of either agent exerted no marked effect on the growth of the cells compared to untreated cultures. Calcipotriol and 1,25-(OH)2D3 were equipotent in stimulating the activity of alkaline phosphatase and the synthesis of osteocalcin in human osteoblast-like cells. The stimulation of alkaline phosphatase activity and osteocalcin synthesis by both compounds was evident by 24 h and was increased progressively up to 96 h in a dose-dependent manner over the concentration range of 10−10-10−6 M. The increment in both proteins was dependent on cell density and was attenuated at higher cell densities. In contrast to these actions, neither calcipotriol nor 1,25-(OH)2D3 (10−14-10−6 M) affected the synthesis of prostaglandin E2. These studies indicate that calcipotriol and 1,25-(OH)2D3 exhibit a similar spectrum of activity on human osteoblast-like cells in vitro.
Relation of fractional 47Ca retention to season and rates of bone loss in healthy postmenopausal women
Authors: Krall Elizabeth A. , Dawson-Hughes Bess
Published: February 2010

Fractional Whole-Body Retention Of 47Ca (retention fraction) in 58 healthy postmenopausal women participating in a calcium supplementation trial was examined for seasonal variation and for relationships to rates of bone loss and plasma vitamin D levels. Retention fraction was measured after 18 months in the trial. Bone mineral densities of the radius, femoral neck, and lumbar spine were measured at baseline, 12 months, and 24 months in the trial, and plasma 1,25-dihydroxyvitamin D [1,25-(OH)2D] and 25-hydroxyvitamin D (25-OHD) at 12, 18, and 24 months. The adjusted retention (retention fraction adjusted for total calcium intake, smoking status, and log years since menopause) was significantly higher in women evaluated in the months of August through October (mean ± SD, 19.8 ± 4.1%, n = 13) than in March through May (mean ± SD, 17.0 ± 4.7%, n = 18, p = 0.05). Plasma 25-OHD was associated with retention fraction only in women with low calcium intakes (partial r = 0.69 controlling for total calcium intake and log body mass index, n = 14, p = 0.01). Plasma 1,25-(OH)2D was not related to retention fraction. Adjusted retention, independent of total calcium intake, log years since menopause, smoking status, and season, explained 8% of the variability in the annual change in radius density (partial r = 0.29, p < 0.05). No significant associations were seen at the spine and femur. These results indicate there is seasonal variation in calcium retention, that calcium retention is positively correlated with plasma 25-OHD levels in women with low calcium intakes, and that an increased level of retained calcium is associated with a lower rate of bone loss from the radius.
Journal of Bone and Mineral Research
Authors: Dr. Melton L. Joseph
Published: February 2010

The impact of primary hyperparathyroidism (HPT) on the population has not been well documented, and even less information is available for asymptomatic HPT. Only 57 deaths were attributed to the condition in the United States in 1986, for a reported HPT death rate of 0.24 per million per year. Many more patients were affected, however, and the incidence of hospitalization for HPT was 6.6 per 100,000 in 1986, counting all listed diagnoses, and 2.9 per 100,000 counting only first-listed diagnoses. Surgery was performed on approximately 10,000 hospitalized patients in the United States in 1986, for a parathyroidectomy rate of about 4.2 per 100,000 per year. When nonhospitalized cases are included, the rates are even higher. The estimated annual incidence of HPT was 42.1 per 100,000 in Rochester, Minnesota in 1974–1976; the prevalence of HPT was 4.3 per 1000 in a population survey in Sweden. By any of these measures, HPT is more common in women than men and increases with aging in both sexes. The potential cost of HPT could be as high as $420 million/year in the United States, but no formal estimates have been made. Disability related to HPT or its treatment has not been quantified; randomized clinical trials to determine the utility of parathyroidectomy have not been performed; and no assessment of cost benefit or cost effectiveness of any therapeutic modality has been carried out. Until patient management and cost issues are resolved, it is premature to consider an aggressive program to screen the general population for HPT.
Journal of Bone and Mineral Research
Authors: Heath Hunter
Published: February 2010

Over the last 25 years, the perceived clinical spectrum of primary hyperparathyroidism (HPT) has changed dramatically from a disorder characterized by severe bone and renal disease to one typically manifested by few or mild symptoms and little evidence of organ damage. Reasons for this change in spectrum include changing demographics (primary HPT is primarily a disease of the middle-aged and elderly), diffusion of medical knowledge leading to a higher index of suspicion, and improved clinical laboratory technology (especially inexpensive and accurate determination of serum calcium and parathyroid hormone). In the first 343 cases of primary HPT seen at the Massachusetts General Hospital, 57% had renal stones, 23% had hyper-parathyroid bone disease, and < 1% had no symptoms. By contrast, studies dating from the availability of automated serum calcium measurement found renal stones and hyperparathyroid bone disease in < 5% of cases, and about half of cases had few or no symptoms. Most patients with primary HPT today have mild, nonspecific symptoms, such as weakness, fatigue, and mental depression, and such signs as arterial hypertension and osteopenia, and detection of their hypercalcemia is generally serendipitous. The mildness and slow progression seen in many cases of primary HPT has resulted in much controversy about appropriate management.
Journal of Bone and Mineral Research
Authors: Professor Ljunghall Sverker , Jakobsson Sören , Joborn Charlotte , Palmér Mats , Rastad Jonas , Åkerström Göran
Published: February 2010

In 1969, a health survey was offered to all inhabitants of a town district in Sweden. A clinical examination was carried out, and among other variables, a measurement was made of serum calcium. The same procedure was repeated in 1971. From these two investigations a cohort of 176 individuals (1.1%) with sustained hypercalcemia was identified who could be followed during the subsequent 15 years. Comparisons were made with an age- and sex-matched control group from the same health survey. Survival was significantly lower in the hypercalcemic cohort than in the control group. This reduction was related to the degree of hypercalcemia and apparently mainly due to diseases of the circulatory organs. There was no marked deterioration of renal function, and although there was in some patients a moderate progression of the hypercalcemia, none developed a hypercalcemic crisis during 15 years of follow-up. In consecutively referred patients with primary hyperparathyroidism, psychiatric disturbances of mainly a depressive character were found upon detailed analysis within a majority of the patients, and parathyroid surgery resulted in a clear improvement in mental health.
Effects of Gallium on Bone in the Rat
Authors: Wakley Glenn K. , Garand Joseph , Brown Daniel , Szukalski Bernard W. , Bell Norman H. , Turner Russell T.
Published: February 2010

Gallium nitrate lowers the serum calcium in patients with hypercalcemia caused by malignancy and is available for clinical use. The mechanism for the hypocalcemic action is unknown, however. The present studies were undertaken to determine the effects of gallium on bone metabolism. Normal male rats were implanted subcutaneously with mineralized allogeneic bone matrix. Histomorphometry of the implants and of tibiae was determined after three doses of tetracycline administered at intervals of 1 week. Gallium as nitrate was administered daily by intraperitoneal injection at doses of 0.9, 1.8, and 3.6 mg elemental gallium per kg body weight for 21 days in one study and at 3.5 mg/kg for 33 days in a second study. All the gallium-treated rats gained weight. Rats given gallium at doses of 3.5 mg/kg or more grew at a lower rate than untreated controls (-7 and -10% at doses of 3.5 and 3.6 mg/kg, respectively; p < 0.05). At a dose of 0.9 mg/kg, gallium did not inhibit bone resorption or lower serum calcium but inhibited bone formation by 32% and bone apposition by 36% at the endosteal surface of the tibia. At a dose of 1.8 mg/kg, gallium produced modest hypocalcemia, prevented a rise in circulating 1,25-dihydroxyvitamin D [1,25-(OH)2D], inhibited bone resorption in implants, and inhibited bone formation by 19% and bone apposition by 18%. At a dose of 3.5 mg/kg, gallium lowered the serum calcium and serum 1,25-(OH)2D, inhibited growth, and accentuated the antiresorptive and antiformative effects seen at the two lower doses. The results indicate that gallium inhibits bone resorption, produces hypocalcemia, alters vitamin D metabolism, and inhibits bone formation at doses below those that inhibit bone resorption. The mechanism for hypocalcemia may be by direct action on bone and could involve an indirect effect on calcium metabolism mediated by changes in the metabolism of vitamin D.
Platelets contribute to circulating levels of bone sialoprotein in human
Authors: Chenu C. , Delmas P.D.
Published: February 2010

Bone sialoprotein (BSP) is a major bone-related protein. Although a few other tissues contain trace amounts of BSP message, bone cells and bone matrix are the major sources of BSP, suggesting that this protein could be a potential marker of bone metabolism. Purified bovine BSP showed a 70% homology of its first 13 amino acid N-terminal sequence with human BSP and was used to raise antibodies in rabbit and to develop a specific radioimmunoassay (RIA). Using this RIA, we have shown that BSP is present in serum with values in the range of 10–30 ngEq/ml in the serum of normal adults. Values obtained in plasma prepared without platelet activation are about one-half of those in matched sera, suggesting that BSP present in serum is in part derived from platelets during the activation process. Using Western blot and RIA techniques, we confirmed that platelets contain immunoreactive BSP and that the protein is released after thrombin stimulation of these cells. In addition to BSP, platelets contain a 45 kD immunoreactive material that has not been precisely identified. Available evidence indicates that this material is not osteonectin or osteopontin and that it may be a BSP-like protein rather than a degradation product of BSP. Platelets from a patient having a gray platelet syndrome, characterized by a deficiency in platelet α-granules and in the α-granule secretory proteins, did not show any deficiency of BSP, suggesting that immunoreactive BSP present in platelets is not endogenously synthesized by megakaryocytes but rather originates from plasma by endocytosis.
Composite index of skeletal mass: Principal components analysis of regional bone mineral densities
Authors: Feingold Marcia , Nelson Dorothy A. , Parfitt A. Michael
Published: February 2010

Principal components analysis is a statistical method that is used to reduce and explore data to facilitate further analyses. This method was applied to bone mineral densities measured at seven sites in 109 black and 44 white women, ages 22–80, at an internal medicine clinic in urban Detroit. We excluded subjects with a history of diseases or drugs known to affect bone metabolism. Principal components analysis was used to summarize the interrelationship of the densities and yielded two major results. First, the seven site measurements were reduced to a single, composite index (PC1) of skeletal mass that accounted for 73% of the variation in density among subjects. PC1 had roughly equal weights among the sites. A second combination of the seven sites indicated that the contrast between axial and appendicular regional densities accounted for another 10% of the variation among subjects. In investigating the relationship of density to age, body mass index, and ethnic group, we found that the principal components composite index had a stronger correlation with age (r = -0.58) and with body mass index (r = 0.34) than almost all of the regional densities. Black-white differences were larger for the composite index than for any single site density. A multiple regression of the composite index on ethnicity, body mass index, and age yielded a larger R2 (0.46) than any of the individual site densities. The second principal component, although of theoretical interest, showed a minimal ability to discriminate among subjects using the three independent variables of this study.
Weight-training effects on bone mineral density in early postmenopausal women
Authors: Pruitt Leslie A. , Jackson Rebecca D. , Bartels Robert L. , Lehnhard Holly J.
Published: February 2010

We tested the hypothesis that weight training would be an effective modality in maintaining or increasing bone mineral density (BMD) at the lumbar spine, femoral neck, and bone mineral content (BMC) at the distal wrist in early postmenopausal women. A total of 17 women completed a 9 month weight-training program, and 9 women served as a control group. Resistance training occurred three times per week using exercises designed to increase muscular strength. Mean change in lumbar BMD in the weight-trained group (1.6 ± 1.2%, mean ± SEM) was significantly different from the change in the control group (-3.6 ± 1.5%, p < 0.01) over the 9 month period. No significant weight-training effect was detected at the femoral neck or distal wrist site. We conclude that weight training may be a useful exercise modality for maintaining lumbar BMD in early postmenopausal women.
Incidence of clinically diagnosed vertebral fractures: A population-based study in rochester, minnesota, 1985-1989
Authors: Cooper Cyrus , Atkinson Elizabeth J. , MichaelO'Fallon W. , Dr. Melton Joseph L.
Published: February 2010

Vertebral fractures are the classic hallmark of osteoporosis, yet little is known of their epidemiology. The incidence of clinically diagnosed vertebral fractures was therefore directly assessed in the predominantly white (European descent) population of Rochester, Minnesota. Altogether, 341 Rochester residents were radiologically diagnosed for the first time with one or more vertebral fractures in the 5 year study period, 1985–1989. The overall age- and sex-adjusted incidence rate was 117 per 100,000 person-years (95% CI, 105 to 130). The age-adjusted rate in women (145 per 100,000 person-years) was almost twice that in men (73 per 100,000 person-years). Of all fractures, 47 (14%) followed severe trauma, 282 (83%) followed moderate or no trauma, and 12 (3%) were pathologic. Incidence rates for fractures following moderate trauma were higher in women than in men and rose steeply with age in both genders. In contrast, fractures following severe trauma were more frequent in men, and their incidence increased less with age. These Rochester rates are greater than those previously reported from studies in Britain and Sweden but lower than the incidence rates extrapolated from a prevalence study in this population.
Perspectives: The role of changes in mechanical usage set points in the pathogenesis of osteoporosis
Authors: Frost Harold M.
Published: February 2010

Mechanical usage (MU) effects on modeling drifts and BMU-based remodeling affect bone mass in defined ways. Decreased MU stops additions of bone by modeling and increases removal of bone next to marrow by remodeling. The latter effect thins cortices and reduces trabecular number, thickness, and connectivity. Return to normal MU makes remodeling begin conserving existing bone and leaves modeling still off. Hypervigorous MU can make modeling increase bone mass during growth and makes remodeling keep conserving it in children and adults. These effects can be said to begin when typical bone strains rise through two threshold ranges, one for remodeling and a higher one for modeling. Raising the thresholds while normal MU continues should give bone a spurious disuse message, whereupon disuse effects would begin. The bone anatomic and tissue dynamic patterns in acute and chronic disuse resemble those seen in developing and acquired postmenopausal osteoporosis and in other forms of osteoporosis, too. If some hormones, drugs, and other agents increase those thresholds, this could explain such similarities.
The effect of ethnic group on appendicular bone mass in children
Authors: Patel Deepak N. , Pettifor John M. , Becker Pieter J. , Grieve Cathryn , Leschner Klaus
Published: February 2010

The prevalence of senile and postmenopausal osteoporotic fractures is considerably higher in white than black women. Although the reasons for the genetic difference have not been elucidated, it has been suggested that ethnic differences in peak bone mass may be partially responsible. The present study examined appendicular bone mass (single-photon absorptiometry, SPA) in black and white children between the ages of 6 and 20 years. The sample was stratified for ethnic group, age, and sex. The effect of weight, height, puberty, and skinfold thickness on bone mass was also assessed. The bone width (BW) and bone mineral content (BMC) of males were significantly higher than those of females (p < 0.0001). There were no statistically significant differences in bone mineral content normalized for bone width (BMC/BW) between the sexes (p = 0.1743 for whites and p = 0.5456 for blacks). The bone mass parameters of black girls were generally lower than those of white girls. After adjusting for height, BMC and BMC/BW of black girls tended to be greater than those of white girls (unadjusted p = 0.0258 for BMC and p = 0.0340 for BMC/BW). White boys tended to have greater bone mass parameters than black boys. After adjusting for height the trends disappeared. Thus, unlike the studies of bone mass in adults from the United States, we were unable to show that age-matched black children have higher bone mass than whites. After adjusting for height, however, the bone mass of black children (especially black girls) was marginally, but not significantly, greater than that of white girls.
Human cystatin C, a cysteine proteinase inhibitor, inhibits bone resorption in vitro stimulated by parathyroid hormone and parathyroid hormone-related peptide of malignancy
Authors: Dr. Lerner Ulf H. , Grubb Anders
Published: February 2010

The effect of human recombinant cystatin C, a cysteine proteinase inhibitor, on bone resorption in vitro was evaluated. Bone resorption was assessed by analyzing the release of 45Ca and 3H from mouse calvarial bones prelabeled in vivo by injections with 45Ca or [3H]proline, respectively. In 24 h cultures, cystatin C (50 μg/ml) significantly inhibited the release of 45Ca and 3H stimulated by parathyroid hormone (PTH, 15 nmol/liter) or parathyroid hormone-related peptide of malignancy (PTHrP, 15 nmol/liter). The degree of inhibition caused by cystatin C in these 24 h cultures was similar to that caused by calcitonin (30 ng/ml). The inhibitory effect of cystatin C on 45Ca release induced by PTH was sustained in 96 h cultures, whereas the initial inhibition caused by calcitonin was transient. Cystatin C, 10–100 μg/ml, caused a dose-dependent inhibition of PTH (15 nmol/liter), and PTHrP (15 nmol/liter) stimulated 45Ca release. Addition of 50 μg/ml of cystatin C to mouse bone cultures inhibited the release of 45Ca induced by PTH and PTHrP at a wide range of submaximal and maximal concentrations of hormones (0.01–10 nmol/liter). No effect of cystatin C on 45Ca release in dead bones could be observed, nor did the inhibitor decrease the release of calcium in control bones. The inhibition by cystatin C on PTH-induced mineral mobilization was reversible. Cystatin C (1–100 μg/ml) did not affect protein synthesis or mitotic activities in mouse calvarial bones as assessed by the incorporation of I'HIproline and [3H]thymidine, respectively. These data show that cystatin C is a potent inhibitor of mineral mobilization and matrix degradation in cultured bones stimulated to resorb by PTH and PTHrP and that this effect is not due to general cytotoxicity.
1,25-Dihydroxyvitamin D3 analog structure-function assessment of the rapid stimulation of intestinal calcium absorption (transcaltachia)
Authors: Zhou Li-Xin , Nemere Ilka , Professor Norman Anthony W.
Published: February 2010

The possibility is now emerging that 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] can mediate biologic responses via both genomic and nongenomic pathways. To understand the molecular basis of the nongenomic response of transcaltachia, defined as the 1,25-(OH)2D3-mediated rapid (2–10 minutes) stimulation of calcium transport from the brush border to the basal lateral membrane of the epithelial cell in vitamin D-replete chick intestine, and to address the issue of whether the same receptor for the secosteroid serves as the signal transducer for both genomic and nongenomic pathways, we carried out structure-function studies using seven analogs of 1,25-(OH)2D3 with different affinities for the classic nuclear 1,25-(OH)2D3 receptor as measured by determination in a steroid competition assay of the relative competitive index (RCI). The RCI of 1,25-(OH)2D3 is by definition 100. 1,25-(OH)2D3 initiates transcaltachia within 2–10 minutes of vascular perfusion and yields a biphase response curve. Dose-dependent stimulations of Ca2+ transport by the seven analogs indicates that different structural features are essential for initiating the transcaltachic response as contrasted with binding to the classic nuclear receptor. Vascular perfusion with analogs AT (25-OH-16-ene-23-yne-D3) and Y (25-OH-23-yne-D3), which are known to activate Ca2+ channels but bind very poorly to the classic receptor (RCI < 0.5), are efficient in stimulating Ca2+ transport. By comparison, compounds BT [1α,24S-(OH)2-22-en-26,27-dehydrovitamin D3] and V (1,25-(OH)2-16-ene-23-yne-D3], which bind very well to the classic nuclear receptor (RCI 75–111) but do not activate Ca2+ channels, are inefficient in stimulating Ca2+ transport. These results indicate that the membrane components that respond to the analogs of 1,25-(OH)2D, with activation of Ca2+ channels have a different ligand specificity than the classic nuclear receptor.
Is caffeine consumption a risk factor for osteoporosis?
Authors: Cooper Cyrus , Atkinson Elizabeth J. , Wahner Heinz W. , O'Fallon W. Michael , Riggs B. Lawrence , Judd Howard L. , Dr. Melton L. Joseph
Published: February 2010

High caffeine consumption has been proposed as a risk factor for osteoporotic fracture, but the evidence associating high caffeine intake with low bone density is inconsistent. We therefore examined the influence of caffeine consumption on bone mineral at six skeletal sites in an age-stratified random sample of white women residing in Rochester, Minnesota. After age adjustment, there was no association between overall caffeine consumption and bone mineral at five of the six sites. In the femoral shaft, however, there was a statistically significant interaction between age and caffeine consumption so that high caffeine intake was associated with slight reductions in bone mineral among elderly subjects but with modestly increased bone mineral at younger ages. When caffeine intake was categorized by source, no consistent influence of coffee, tea, or other caffeinated beverage consumption could be detected on bone mineral. Caffeine intake was, however, positively associated with cigarette smoking and alcohol consumption. After adjusting for age, caffeine consumption was not correlated with biochemical indices of bone turnover, circulating concentrations of estradiol and estrone, or other dietary and musculoskeletal variables. These data suggest that caffeine intake in the range consumed by a representative sample of white women is not an important risk factor for osteoporosis. Among elderly women, however, in whom calcium balance performance is impaired, high caffeine intake may predispose to cortical bone loss from the proximal femur.
Evidence for P2-purinoceptors on human osteoblast-like cells
Authors: Schöfl Christof , Cuthbertson K.S. Roy , Walsh Cathy A. , Mayne Caroline , Cobbold Peter , von Zur Mühlen Alexander , Hesch Rolf-Dieter , Dr. Gallagher James A.
Published: February 2010

ATP released from damaged cells or by controlled secretion could be an important factor in the formation or remodeling of bone. In a variety of other tissues ATP has been shown to control cellular processes by acting on P2-purinoceptors and activating the calcium signaling pathway. Here we demonstrate for the first time that extracellular ATP increases the intracellular free calcium [Ca2+]i concentration in normal human osteoblasts and in SaOS-2 cells, a human osteosarcoma-derived cell line, but not in ROS 17/2.8 cells. The ATP-induced increase in [Ca2+]i was dose dependent, and the concentrations of ATP required were similar to those reported to regulate cellular functions in other cell types. Although ATP is metabolized rapidly by bone cells, the effects on [Ca2+]i appeared to be mediated directly by ATP rather than one of its metabolites. Adenosine 3-thiotriphosphate, a nonhydrolyzable analog of ATP, induced similar changes in [Ca2+]i. This indicates that P2-purinoceptors are present on osteoblast-like cells and that extracellular ATP from various sources might be an important factor in the regulation of osteoblast functions.
Renal na+-phosphate cotransport in X-linked hyp mice responds appropriately to NA+ gradient, membrane potential, and pH
Authors: Harvey Nathalie , Tenenhouse Harriet S.
Published: February 2010

To investigate the mechanism for the 50% decrease in Vmax of the high-affinity phosphate transport system in the renal brush-border membrane of X-linked Hyp mice, we compared the effects of external Na+ concentration, membrane potential, pH, phosphonoformic acid (PFA), and arsenate on Na+-Pi cotransport in brush-border membrane vesicles prepared from normal mice and Hyp littermates. The affinity of the Na+-Pi cotransport system for Na+ (apparent Km = 60 ± 7 and 64 ± 2 mM for normal and Hyp mice, respectively) and the Na+-Pi stoichiometry estimated from Hill plots (2.5 ± 0.2 and 2.9 ± 0.6 for normal and Hyp mice, respectively) were similar in brush-border membranes of both strains. Inside-negative membrane potential, generated by anions of different permeabilities, stimulated Na+-Pi cotransport and inside-positive membrane potential generated by valinomycin, and a K+ gradient (outside > inside) inhibited Na+-Pi cotransport to the same extent in brush-border membranes derived from normal mice and Hyp littermates. The pH dependence of Na+-Pi cotransport was similar in brush-border membrane vesicles of normal and Hyp mice. The ratio of Na+-Pi cotransport measured at pH 7.5 relative to that at pH 6.5 was 2.9 ± 0.6 in normal mice and 2.9 ± 0.7 in Hyp mice. PFA was a competitive inhibitor of Na+-Pi cotransport in brush-border membranes of both normal and Hyp mice. However, the apparent Ki for PFA was significantly lower in Hyp mice (0.31 ± 0.01 and 0.19 ± 0.02 mM in normal and Hyp mice, respectively, P < 0.05). In contrast, a similar Ki for arsenate inhibition was observed in brush-border membranes of normal and Hyp mice. These results demonstrate that the decrease in Vmax of the high-affinity Na+-Pi cotransport system in renal brush-border membranes of X-linked Hyp mice cannot be attributed to an impaired response of the transporter to the Na+ gradient driving force, membrane potential, or external pH.
Longitudinal effect of tiludronate on bone mineral density, resonant frequency, and strength in monkeys
Authors: Geusens P. , Nijs J. , van der Perre G. , van Audekercke R. , Lowet G. , Goovaerts S. , Barbier A. , Lacheretz F. , Remandet B. , Jiang Y. , Dequeker J.
Published: February 2010

The effect of Tiludronate on bone was studied in 72 growing monkeys (Papio papio), 36 males and 36 females, aged 4–7 years. They were randomly allocated into four groups (18 animals per group, 9 males and 9 females): group I, controls; group II, 10 mg/kg/day; group III, 20 mg/kg/day; and group IV, 40 mg/kg/day of Tiludronate. A total of 12 animals (6 males and 6 females) in each group were sacrificed at the end of treatment (1 year) and 6 animals (3 males and 3 females) per group 1 year later. Bone mineral density (BMD) was measured by dual-photon absorptiometry. Biomechanical properties were evaluated by an impact torsion test and by resonant frequency analysis. Bone mineral measurements indicated that at the end of 1 year of treatment BMD was significantly higher, especially at the distal epiphysis of the radius, than in controls. No significant differences between groups were found in BMD 1 year after stopping treatment. Biomechanical analyses indicated that torsional stiffness increased after treatment. No differences between groups were found 1 year after stopping treatment. Results of resonant frequencies indicated an increased calculated transversal stiffness after treatment and 1 year later and an increased buckling strength 1 year after stopping treatment. In conclusion, the results on the effect of Tiludronate in growing monkeys indicate a profound effect of this drug on bone density and biomechanical properties. The biomechanical results indicate that this drug is safe, with conservation of bone strength despite a change in intrinsic mechanical properties of the bone.
Endurance Training Associated with Slightly Lowered Serum Estradiol Levels Decreases Mineral Density of Canine Skeleton
Authors: Puustjärvi K. , Karjalainen P. , Nieminen J. , Arokoski J. , Parviainen M. , Helminen H.J. , Soimakallio S.
Published: February 2010

The effects of long-term running exercise were studied in 20 beagle dogs. A total of 10 dogs ran from the age of 15 weeks to the age of 70 weeks in a progressive program for up to 40 km/day. A total of 10 sister dogs spent the study period in individual cages. When the dogs were 70 weeks old, bone mineral density of the vertebrae, hip, and radius was analyzed by dual-energy x-ray absorptiometry (DEXA; Lunar) and the vertebrae were also assessed by quantitative computed tomography (QCT; Siemens DR 1). Mineral density was lower in the running dogs than in the controls. The difference was greatest in the spine in the QCT analysis. Blood chemistry analyses revealed that the metabolism of the bone was significantly accelerated. The estradiol levels showed the trend to be reduced in the running group. The beneficial effect of exercise on mineral density has been shown in many earlier studies. However, in this study we demonstrate the possibility of adverse effects of long-term exercise on bone tissue. The change was associated with a decrease of serum estradiol level.
Radial bone mineral density in pre- and perimenopausal women: A prospective study of rates and risk factors for loss
Authors: Sowers Maryfran R. , Clark M. Kathleen , Hollis Bruce , Wallace Robert B. , Jannausch Mary
Published: February 2010

Radial bone mineral density (BMD) of 217 white women aged 22–54 years from a single rural community was evaluated in 1984 using single-photon absorptiometry. BMD was measured at a site one-third the distance from the wrist to the elbow, a site that represents predominantly cortical bone tissue. Most of these women (181; 83%) were reexamined 5 years later. The overall average 5 year radial BMD loss was -5.6%. The average rate of loss was -4.5% for women retaining positive estrogen status at follow-up (n = 108) and -7.4% for women who were in negative estrogen status at follow-up (n = 73). Baseline radial BMD measures were highly predictive of the follow-up BMD values (r = 0.80). Women with positive estrogen status and greater baseline BMD also had less BMD change. Greater baseline BMD did not predict the amount of change in women with negative estrogen status. The bone turnover markers osteocalcin and bone-specific alkaline phosphatase were significantly associated with BMD change in women with negative, but not positive estrogen status. There was no conclusive evidence of a “peak age” in the baseline and follow-up BMD measures. Based on rates of BMD change, “peak” bone mineral content appears to occur before age 25 years. Factors significantly associated with lower levels of BMD were menopause without estrogen replacement, nulliparity, smoking, and age at first pregnancy. Factors associated with more bone loss were menopause without estrogen replacement, smoking, shorter duration of oral contraceptive use, and older age. Quetelet index, muscle area, number of lost pregnancies, ever breast-feeding, or calcium intake were not associated with BMD level or its 5 year rate of loss. Physical activity and alcohol intake were not associated with BMD level or change after data were adjusted for age or estrogen status.
Activation and inhibition of protein kinase c in cultured bovine parathyroid cells: Effect on the release of c-terminal fragments of parathyroid hormone
Authors: Watson Patricia H. (Wood) , Mortimer Shane T. , Tanguay Karen E. , Hanley David A.
Published: February 2010

The response of the parathyroid gland to low Ca2+ may be mediated in part by protein kinase C (PKC). We assessed the effect of two PKC activators, SC-9 and SC-10, and one PKC inhibitor, H-7, on Ca2+-regulated PTH release and degradation in primary cultures of bovine parathyroid cells. Both SC-9 and SC-10 stimulated PTH release, compared to high Ca2+ alone, in parathyroid cells incubated in high Ca2+, with maximal PTH release of at least twofold occurring at a concentration of either activator of 10 nM (p < 0.05). We have previously shown that another PKC activator, PMA, not only enhances PTH release in the presence of high Ca2+ but suppresses low Ca2+-stimulated PTH secretion. In the present study, neither SC-9 nor SC-10 caused a comparable suppression of PTH release at low Ca2+. However, the PKC inhibitor, H-7 (1 μM), blocked low Ca2+-stimulated (compared to the low Ca2+ control) PTH secretion by approximately 50% (p < 0.01) and did not affect high Ca2+ suppression of PTH secretion. H-7 (1 μM) was able to oppose the stimulation of PTH release by the PKC activators SC-9, SC-10, and PMA at high Ca2+ and negated the PTH release-inhibiting effect of PMA at low Ca2+. Culture medium from these experiments was subjected to reversed-phase HPLC and the eluted fractions analyzed by RIA for the presence of intact and C-terminal fragments of PTH. The release of C-terminal fragments of PTH, when expressed as a percentage of total (fragment plus intact) PTH released, was greatest at high Ca2+ (∼80%) and considerably less at low Ca2+ (∼57%). Although the relative proportion of intact PTH released was increased when SC-9 and SC-10 stimulated PTH secretion at high Ca2+, analysis of variance suggests that the level of extracellular Ca2+ was the major determinant of PTH degradation to C-terminal fragments. At low Ca2+, H-7 blocked the previously reported ability of PMA to suppress PTH secretion but did not block the ability of PMA to enhance PTH degradation. These results indicate that (1) PKC activation is an important component of low Ca2+-stimulated PTH release, (2) the Ca2+ effect on PTH degradation may not be entirely mediated by PKC, and (3) the PMA effect on PTH degradation is not mediated through PKC.
Expression of human transforming growth factor α by chinese hamster ovarian tumors in nude mice causes hypercalcemia and increased osteoclastic bone resorption
Authors: Yates A.J. , Boyce B.F. , Favarato G. , Aufdemorte T.B. , Marcelli C. , Kester M.B. , Walker R. , Langton B.C. , Bonewald L.F. , Mundy G.R.
Published: February 2010

Transforming growth factor α (TGF-α) is a polypeptide regulator of cell growth produced by many malignant tumors. It stimulates osteoclastic resorption in bone organ culture and osteoclast-like cell formation in marrow culture. To determine whether tumor production of TGF-α can cause hypercalcemia in vivo, we used Chinese hamster ovarian (CHO) cells transfected with the human TGF-α gene (TCHO), which stably express and secrete TGF-α. We used nontransfected CHO cells as controls (CCHO). TCHO and CCHO were inoculated intramuscularly into one hindlimb of nude mice and grew as local solid tumors. After 4 weeks of TCHO tumor growth, plasma ionized calcium (Ca2+) increased to reach 1.48 ± 0.03 mM (mean ± SEM), whereas mice bearing similarly sized CCHO tumors and non-tumor-bearing mice (NTB) remained normocalcemic (normal range for Ca2+, 1.15–1.30 mM). Plasma TGF-α was undetectable by an ELIFA assay in all NTB mice, was markedly increased in all TCHO mice (5.75 ± 0.78 ng/ml), and was slightly increased in CCHO mice (0.50 ± 0.22 ng/ml). Quantitative bone histomorphometry showed a prominent increase in osteoclastic bone resorption in TCHO mice. These data suggest that TGF-α is a mediator of hypercalcemia and increased osteoclastic bone resorption in tumors that produce it in sufficient quantity.
Parathyroid hormone-related protein stimulates prostaglandin E2 release from human osteoblast-like cells: Modulating effect of peptide length
Authors: Mitnick Maryann , Isales Carlos , Paliwal Indu , Insogna Karl
Published: February 2010

Parathyroid hormone-related protein (PTHrP) is a potent bone-resorbing protein that frequently mediates the humoral hypercalcemia of malignancy syndrome. Since prostaglandins may mediate the bone-resorptive action of certain hormones, we examined the effect of PTHrP on prostaglandin E2 (PGE2) secretion by human osteoblast-like cells. There was low-level basal secretion of PGE2 by Saos-2 cells (8.1 + 0.6 pg/ml). Using four different preparations of PTHrP, it was observed that with increasing peptide length, from 36 to 141 amino acids, a significant increase in efficacy for PGE2 release was seen in these cells. All forms of PTHrP were agonists for PGE2 release, with effects seen at concentrations as low as 10−12 M in 48 h conditioned media. The amino terminus of the molecule appeared critical for this effect since the truncated derivative PTHrP-(7–34) did not induce significant PGE2 secretion. However, the influence of peptide length could not be explained by differential activation of adenylate cyclase since [Tyr26]PTHrP-(1–36)amide was equipotent to the longest peptide preparation, PTHrP-(1–141), in stimulating cyclic AMP accumulation in the Saos-2 cells. In contrast, PTHrP-(1–141) was significantly more effective than [Tyr35]PTHrP-(1–36)-amide in inducing a rise in cytosolic calcium. Further, this effect was noted at concentrations lower than those that caused significant cyclic AMP accumulation in the Saos-2 cells. PTHrP-(1–141) induced the release of PGE2 from primary human bone cell cultures to levels entirely comparable to those seen in the Saos-2 cells. PTHrP-(1–141) also induced PGE2 release by cultured fetal rat long bones at 72 h. We conclude that the carboxy-terminal region of PTHrP has important effects on cellular signal transduction pathways and on the release of a potent bone-active cytokine, PGE2.
Qualitative defects in natural killer cell function in ia osteopetrotic rats
Authors: Schneider Gary B. , Relfson Melanie , Ellis Thomas M.
Published: February 2010

Recent studies have provided evidence that cells of the immune system and their associated cytokines function in the regulation of bone turnover. The incisors absent (ia) osteopetrotic rat represents a model in which a defect in the immune system and bone resorption can be studied. Osteopetrosis in the ia rat is characterized by a generalized excess accumulation of bone as a result of reduced bone resorption by defective osteoclasts that lack a ruffled border and the ability to exocytose their osteolytic enzymes. Previous attempts to identify associated defects in the ia immune system have proven unsuccessful; ia rats demonstrate normal delayed hypersensitivity, mitogenic activity, and macrophage function. Inasmuch as the skeletal manifestations of the ia mutation may be the result of a defect in exocytosis, related defects may be evident in immune cells utilizing exocytosis of granules or enzymes for their cytolytic function. Natural killer (NK) cells function by such a mechanism. Therefore, these studies were undertaken to evaluate the natural immune system in ia rats. NK activity assessed by 51Cr release assays was significantly reduced in ia animals compared to normal littermates. Mononuclear cells isolated from the peripheral blood of ia rats revealed a significantly greater percentage of large granular lymphocytes than normal littermates. Comparison of NK cell phenotypes using two phenotypic parameters for NK cells (OX8+, OX 19− cells and 3.2.3+ cells) revealed that the mononuclear isolates of spleen and peripheral blood of mutant animals had significantly greater percentages of OX8+, OX 19− and 3.2.3+ cells than normal controls. Levels of BLT esterase (BLTE), a serine protease associated with the cytolytic mechanism of NK cells, were found to be greater in unsorted ia mononuclear cells than in normal cells but were equivalent in normal and mutant 3.2.3+ cells isolated by fluorescence-activated cell sorting. BLTE activity was enhanced but equal in normal and mutant 3.2.3+ cells stimulated with IL-2. The 3.2.3+ NK isolates demonstrated equal lytic activity in ia and normals, but when normal or mutant 3.2.3− cells (non-NK cells) were added to the 3.2.3+ia cells the lytic activity was significantly reduced. 3.2.3− cells had no effect on the activity of 3.2.3+ normal cells. The results indicate that 3.2.3+ mutant NK cells have normal lytic activity and BLTE activity and can respond to IL-2. The NK cells in the mutant are suppressed by a non-NK mononuclear cell, resulting in the lytic defect. A known suppressor of NK cells, prostaglandin, does not appear to be responsible for the NK defect in this mutant, because indomethacin, an inhibitor of prostaglandin synthesis, did not correct the defect.