bluuebunny/crossref_metadata_2025_split huggingface dataset:
Features of the renal parathyroid hormone-parathyroid hormone-related protein receptor derived from structural studies of receptor fragments
Authors: Karpf David B. , Bambino Thomas , Alford Gay , Nissenson Robert A. 
Published: February 2010

Abstract
Our earlier results indicated that the binding moiety of the renal PTH receptor is an 85 kD protein that is susceptible to proteolytic cleavage to a 70 kD form that supports high-affinity binding and Gs coupling, and to a 50–55 kD form that contains the ligand binding domain but does not couple to Gs. In the present study we used [125I]hPTHrP-(1–34)amide and a chemical cross-linking technique to discern the structural features of the intact 85 kD PTH/PTHrP receptor that are retained in the proteolyzed forms to “structurally map” the receptor. The results of lectin chromatography and endoglycosidase treatment show that the paritally proteolyzed receptor forms retain the complex, N-linked glycans present on the intact receptor. This conclusion is further supported by the finding that wheat germ agglutinin was equally effective at competitively inhibiting specific [125I]hPTHrP-(1–34)A binding to the 70 kD form and the intact 85 kD receptor. Specific binding of [125I]hPTHrP-(1–34)A to the intact 85 kD receptor or to the 70 kD form was completely abolished by treatment with disulfide reducing agents, and both partially proteolyzed receptor forms (70- and 50 kD) were shown to retain the small (≤ 14 kD) labeled fragment that is released from the intact receptor by disulfide reduction. Lectin chromatography and endoglycosidase treatment revealed that the ≤ 14 kD receptor component is not glycoslyated. The ≤ 14 kD fragment does not contain a transmembrane spanning region, as its release from the membrane can be affected without detergent solubilization. Identical partial proteolytic maps of the receptor were obtained whether the receptor was covalently labeled with [125I]hPTHrP-(1–34)amide or [125I]bPTH-(1–34). These results suggest a model of the renal PTH/PTHrP receptor binding moiety as a single-chain protein in which the sites of glycosylation, ligand binding, and the functionally critical disulfide bonds are in extracellular domains near one end of the protein and the sites of proteolysis reside near the other end of the protein. These studies also provide further confirmation that PTH and PTHrP bind to a structurally indistinguishable renal receptor and validate the use of PTHrP as a ligand for studies designed to characterize and purify the PTH receptor.
Role of prostaglandins in interleukin-1-induced bone resorption in mice in vitro
Authors: Akatsu Takuhiko , Takahashi Naoyuki , Udagawa Nobuyuki , Imamura Kazunobu , Yamaguchi Akira , Sato Kanji , Nagata Naokazu , Dr. Suda Tatsuo 
Published: February 2010

Abstract
The mechanism of bone resorption induced by interleukin 1 (IL-1) was examined in mice using three different in vitro assay systems: a fetal long bone organ culture system, a bone marrow culture system, and a co-culture system of primary osteoblastic cell populations and spleen cells. In the organ culture system, recombinant human IL-1α (rhIL-1α) increased both bone resorption and osteoclast number. Both were partially suppressed in the presence of indomethacin. In the marrow culture, both rhIL-1α and rhIL-1β stimulated osteoclastlike cell formation, which was completely inhibited by adding indomethacin concurrently. Furthermore, there was a good correlation between the number of osteoclastlike cells formed and the amount of prostaglandin E2 (PGE2) released into the culture media. This indicates that PGE2 is involved in the mechanism of IL-1-mediated osteoclastlike cell formation. In the coculture of primary osteoblastic cell populations and spleen cells, rhIL-1 again stimulated osteoclastlike cell formation, which was inhibited by adding indomethacin. In the cocultures in which direct interaction between osteoblastic cells and spleen cells was inhibited, PGE2 synthesis was similarly increased but no osteoclastlike cells were formed. These results indicate that IL-1 induces osteoclast formation by a mechanism involving PG (most likely PGE2). Furthermore, direct interaction between osteoclast progenitors and osteoblastic cells is required in the osteoclast recruitment induced by IL-1.
Longitudinal precision of dual-energy X-ray absorptiometry in a multicenter study
Authors: Orwoll Eric S. , Oviatt Shelia K. ,   The Nafarelin/Bone Study
Published: February 2010

Abstract
Reproducibility is a key issue in both clinical and research applications of bone mineral density (BMD) measurements. To examine the longitudinal precision of dual-energy x-ray absorptiometry (DEXA) for the measurement of mineral density in vivo and in vitro, the performance of a group of instruments in the course of a multicenter longitudinal clinical trial was monitored. Measures were performed on eight identical machines (Hologic QDR1000) and analyzed using the same automated software program. Short-term precision was good in vitro, [anthropomorphic spine phantoms; mean intrasite coefficient of variation (CV) 0.42 ± 0.1% (SD)] and in vivo (lumbar spine; CV 1.1 ± 0.5%). Intersite measures of a single spine phantom (specified mineral content −57.8 g) revealed a range of 57.3–58.4 g (CV 0.7%). In two subjects intersite CV in vivo were 3.7 and 2.1% (spine) and 1.8 and 3.2% (femoral neck). At five sites frequent phantom measures were performed over a 1 year period (mean number of measures 196) and revealed a mean all-point CV of 0.43% (range 0.35–0.53%). Longitudinal precision in vivo was somewhat less (mean CV of spinal measures 1.1%, femoral neck 1.2%, trochanter 1.3%, and Ward's area 2.4%). At one additional site large variations in phantom measures heralded repeated mechanical failures that eventually required machine replacement. In summary, DEXA demonstrates good in vitro and in vivo longitudinal precision, providing the basis for expanded clinical and research usefulness. Nevertheless, stringent quality assurance measures are required to detect and respond to system malfunctions.
Normocalcemia without hyperparathyroidism in vitamin D-deficient rats
Authors: Kollenkirchen Uwe , Fox John , Walters Marian R. 
Published: February 2010

Abstract
Despite numerous attempts, no reliable dietary regimen exists to achieve vitamin D deficiency (-D) in rats without attendant changes in plasma parathyroid hormone (PTH), Ca, or phosphate. This represents an important obstacle to proper investigations of the physiologic role(s) of vitamin D metabolites in the function of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] target tissues. This paper describes the successful development of such a diet, which uses a combination of high Ca content, properly controlled Ca/P ratio, and lactose. Normal weanling rats were fed diets containing A, 0.8% Ca, 0.5% P, +D3, or -D diets containing B, 0.8% Ca and 0.5% P; C, 2.0% Ca and 1.25% P; or D, 2.0% Ca, 1.25% P, and 20% lactose. After 6 diet weeks group D rats remained normocalcemic and normophosphatemic, but diet groups B and C became hypocalcemic (6.9 ± 0.8 and 7.2 ± 0.4 mg/dl, respectively). Thus high dietary Ca and P was incapable of maintaining normal plasma Ca levels in the absence of dietary lactose. The normocalcemia in group D was not maintained by elevated PTH secretion because N-terminal PTH levels were also normal (14 ± 3 versus 20 ± 5 pg/ml). In contrast, PTH levels were markedly elevated in hypocalcemic groups B and C (47 ± 7 and 48 ± 10 pg/ml, respectively). Plasma 25-OHD3 and 1,25-(OH)2D3 levels were reduced to &lt; 120 and &lt; 12 pg/ml, respectively, in all -D groups. Thus the high-Ca diet and the use of normal weanlings did not impede the development of vitamin D deficiency. This rat model of normocalcemic vitamin D deficiency will greatly facilitate elucidation of the physiologic role(s) of vitamin D metabolites in the normal functioning of 1,25-(OH)2D3 targets.
Androgen treatment prevents loss of cancellous bone in the orchidectomized rat
Authors: Wakley Glenn K. , Schutte Harold D. , Hannon Kathleen S. , Turner Russell T. 
Published: February 2010

Abstract
This report describes histomorphometric evidence for an important role of androgens in maintaining cancellous bone balance at a remodeling site in vivo. Rats were orchiectomized (ORX) at 7 weeks of age and received either androgens or vehicle 1 week later (testosterone, 1-dehydrotestosterone, or 5-dihydrotestosterone) by subcutaneous pellet, producing controlled release of the drug for 3 weeks. Intact male rats and untreated ORX animals served as controls. After 4 weeks untreated ORX resulted in undetectable serum testosterone levels and marked atrophy of seminal vesicles compared with intact controls. Histomorphometry revealed severe cancellous osteopenia in the secondary spongiosa of the proximal tibial metaphysis. The length of bone surface lined by apparently “active” osteoblasts and number of osteoclasts per length of cancellous bone surface were increased following ORX. Testosterone treatment at 5 mg (per 21 days) produced subphysiologic serum testosterone levels. In contrast, 10 and 25 mg pellets resulted in serum testosterone levels comparable to those in intact rats. Testosterone treatment of ORX rats prevented the bone effects of ORX, and the degree of protection was dose dependent. 1-Dehydro- and 5-dihydrotestosterones displayed a bone-protective effect similar to that of testosterone. The results demonstrate that gonadal insufficiency results in a cancellous osteopenia that is preventable by testosterone treatment. Further, because a similar protective action was achieved using the nonaromatizable androgen 5-dihydrotestosterone, the results suggest that this bone-sparing effect is mediated by androgen rather than by metabolism of the androgen to an estrogen.
Smoking and bone loss among postmenopausal women
Authors: Krall Elizabeth A. , Dawson-Hughes Bess 
Published: February 2010

Abstract
We examined the effect of smoking on bone mineral density (BMD), rates of bone loss, and fractional whole-body retention of 47Ca in healthy postmenopausal women enrolled in a 2-year calcium supplementation trial. Bone density was measured by single- and dual-photon absorptiometry.
BMD of the radius at the study baseline was inversely related to pack-years of exposure when controlled for body mass index and years since menopause (partial r = -0.18, p = 0.05, n = 125). The adjusted mean (±SD) annualized rate of bone change from the radius was greater among smokers than nonsmokers (-0.914 ± 2.624%/year, n = 34, versus 0.004 ± 2.568%/year, n = 278, respectively; p = 0.05). Similar trends were observed at the femoral neck, os calcis, and spine. Rates were adjusted for caffeine intake, alcohol use, supplement type, and, at the spine only, menopausal status. At entry into the trial higher serum levels of alkaline phosphatase and lower levels of total and ionized calcium were found in smokers compared to nonsmokers. These differences did not persist with supplementation. In 44 women studied fractional 47Ca retention was lower in the 8 smokers than the 36 nonsmokers (16.6 versus 19.1%, respectively; p = 0.03).
These results demonstrate an increased rate of bone loss at the radius after menopause and suggest that smoking is associated with decreased calcium absorption.
The giant cells recruited by subcutaneous implants of mineralized bone particles and slices in rabbits are not osteoclasts
Authors: Dr. Marks Sandy C. , Chambers Timothy J. 
Published: February 2010

Abstract
We have compared structural and functional characteristics of native osteoclasts and the multinucleated giant cells (MNGC) recruited by subcutaneous implants of mineralized bone particles and slices in normal rabbits. Weekly evaluation of the implants for 5 weeks showed distinct differences between MNGC and osteoclasts in the host with respect to morphology and the ability to stain for tartrate-resistant acid phosphatase and acid ATPase. An osteoclast-specific monoclonal antibody bound strongly to osteoclasts but not MNGC. Ground bone slices similarly implanted were surrounded by MNGC but did not show resorption pits by scanning electron microscopy. These data show that the MNGC recruited to subcutaneous implants of mineralized bone particles and slices lack the enzymatic, cell surface, and functional features of osteoclasts.
Familial aggregation of paget's disease of bone
Authors: Siris Ethel S. , Ottman Ruth , Flaster Edith , Kelsey Jennifer L. 
Published: February 2010

AbstractThis epidemiologic study of Paget's disease of bone used data from 788 cases and 387 spouse controls to investigate the following: (1) the extent to which this disorder aggregates in families; (2) the cumulative incidence of the disease in first-degree relatives of patients throughout life; and (3) the influence of age at diagnosis (&lt;55 versus 55+ years) and presence of bone deformity in the case on risk of Paget's disease in relatives.A positive family history in parents or siblings was reported by 12.3% of cases and 2.1% of controls. The rate of Paget's disease was approximately seven times as high in relatives of cases as in relatives of controls, and this increased rate did not differ according to gender of case or control or gender of relatives. Cumulative incidence of Paget's disease to age 90 was much higher in relatives of cases (8.9 + 1.0% SEM) than in relatives of controls (1.8 + 0.9% SEM). Among relatives of cases, cumulative risk was highest when the case had both early age at diagnosis and bone deformity (20.7 + 3.6% SEM) compared with risk when the case had early age at diagnosis but not bone deformity (10.8 + 3.2% SEM), bone deformity but not early age at diagnosis (5.8 + 1.3% SEM), or neither bone deformity nor early age at diagnosis (3.6 + 0.8% SEM). Risk in siblings of cases was higher when a parent was affected (22.1 + 8.0% SEM) than when both parents were unaffected (6.7 + 1.1% SEM).These findings suggest that first-degree relatives of patients with Paget's disease have increased risk of developing the disorder, especially if the affected relatives have early age at diagnosis or deforming bone disease.
Estrogen binding and estrogenic responses in normal human osteoblast-like cells
Authors: Benz David J. , Dr. Haussler Mark R. , Komm Barry S. 
Published: February 2010

Abstract
A finite human cell line was established from trabecular bone explants obtained from a 48-year-old woman. These cells, designated BG688, were characterized as osteoblast-like in phenotype using the following independent criteria: (1) the presence of histochemically detectable alkaline phosphatase (AP) activity; (2) response to the calciotropic hormone 1,25-(OH)2D3 as assessed by increased AP activity; (3) synthesis and secretion of the osteoblast-specific marker bone gla protein; and (4) expression of α1(I)-procollagen and α1(III)-procollagen mRNAs in a pattern similar to that of other osteoblast-like cell lines. In addition to these classic osteoblast markers, BG688 cells also possess approximately 2400 high-affinity (Kd = 0.45 nM) 17β-estradiol (E2) binding sites per cell. The binding of E2 to these sites is specific, and of the steroid hormone agonists tested, E2 and diethylstilbestrol elicited the greatest amount of competition with radiolabeled E2. BG688 cells were also shown to respond to a physiologic concentration (10 nM) of E2. In vitro translation products of poly(A)+ RNA obtained from control and hormone-treated cells revealed a pleiotropic influence of E2 on the relative abundance of several mRNAs as assessed by two-dimensional gel electrophoretic analysis of their corresponding peptides. E2 also elicits a twofold increase in the steady-state concentration of α1(I)-procollagen mRNA as demonstrated by northern blot hybridization. Thus, we here extend our previous data obtained in osteoblast-like osteosarcoma cells to indicate that a normal osteoblastic cell line is a target for the action of estrogen. The E2 responsiveness of these cells, coupled with their osteoblast-like phenotype, renders BG688 cells an attractive system in which to investigate the role of estrogens in the regulation of osteoblast function.
Genetic determinants of bone mass in adult women: A reevaluation of the twin model and the potential importance of gene interaction on heritability estimates
Authors: Dr. Slemenda Charles W. , Christian Joe C. , Williams Christopher J. , Norton James A. , Johnston C. Conrad 
Published: February 2010

Abstract
We estimated genetic effects on bone density in pre- and postmenopausal twins and critically considered the assumptions of the twin model. Bone mass in the radius, lumbar spine, and hip, anthropometric measurements, usual calcium and caffeine intake, tobacco and alcohol use, number of pregnancies and live births, menstrual history, usual physical activity, and medical history were measured in a volunteer sample of 171 twin pairs [124 monozygotic (MZ) and 47 dizygotic (DZ)], aged 25–80, free of diseases known to affect bone mass or mineral metabolism. At all skeletal sites, MZ intraclass correlations exceeded DZ correlations for both pre- and postmenopausal women, yielding highly significant estimates of heritability for bone mass. Adjustments for height, age, and environmental characteristics did not reduce the heritability estimates. However, many of these estimates were unrealistically high, suggesting some violation(s) of the assumptions of the twin model. Thus, the familial resemblance in bone mass is due primarily to genetic effects at all skeletal sites and at all ages, although the importance of genetic effects is diminished with aging, as evidenced by increasing within-MZ pair variability in older women. Because of failures in the assumptions of the twin model, however, particularly the greater MZ environmental similarity and the probability of gene interaction, heritability estimates are probably too high and require cautious interpretation.
Estrogen therapy and variable-resistance weight training increase bone mineral in surgically menopausal women
Authors: Notelovitz Morris , Martin Daniel , Tesar Rogene , Khan Farouk Y. , Probart Claudia , Fields Carol , McKenzie Lynda 
Published: February 2010

Abstract
This study was undertaken to examine the effect of estrogen replacement therapy alone and estrogen replacement therapy plus variable-resistance weight training on the bone mineral content of surgically menopausal women. A total of 20 surgically menopausal women were randomized and treated with either 0.625 mg conjugated estrogen daily or the same dose of estrogen plus a closely monitored exercise program involving the use of Nautilus muscle strengthening/endurance equipment. After 1 year's observation, the bone mineral density (BMD) of the spine determined by dual-photon absorptiometry increased in the exercising subjects by 8.3 ± 5.3% (p = 0.004), 95% confidence limits (CL) 3.9–12.8%; the group with estrogen replacement therapy alone maintained their BMD: 1.5 ± 12.4% (p = 0.36; 95% CL = −6.9–9.8%). The total body BMD of the exercising group increased by 2.1 ± 1.5% (p = 0.003; 95% CL = 0.8–3.3%); the nonexercising women had a nonsignificant 0.6 ± 2.9% change (p = 0.30; 95% CL = −1.4–2.5%). A significant increase of 4.1 ± 4.3% (p = 0.01; 95% CL = 0.8–7.4%) in the radial midshaft BMD of the exercising group was found; the estrogen alone group recorded a nonsignificant change of −0.3 ± 3.1% (p = 0.33; 95% CL = −1.7–2.4%). The results of this study suggest that variable-resistance training in estrogen-replete women adds bone to both the axial and appendicular skeleton.
Biphasic effect of calcitonin on tartrate-resistant acid phosphatase activity in isolated rat osteoclasts
Authors: Yumita S. , Professor Nicholson G.C. , Rowe D.J. , Kent G.N. , Martin T.J. 
Published: February 2010

Abstract
Tartrate-resistant acid phosphatase (TRAP) has been implicated as being involved in osteoclastic bone resorption, and calcitonin (CT) is known to inhibit the resorptive process. This study investigates the kinetics of CT action on TRAP activity in isolated rat osteoclasts using both biochemical and quantitative cytochemical methods. The latter technique has been developed to detect very small changes in intracellular TRAP activity at the single-cell level. The biochemical study showed that 10−9 M salmon CT (sCT) decreased TRAP activity in medium throughout the experimental period; TRAP activity in the cells was increased during the first 2 h but subsequently declined and was decreased to a significant level at 6 h. TRAP activity in sCT-treated osteoclasts measured by the cytochemical method showed significant increases within the first hour. This response was dose dependent between 1016 and 10−11 M sCT with EC50 at 8 × 10−14 M. After 1 h, the initial increase in intracellular TRAP activity in CT-treated osteoclasts was followed by a decline to below control levels, reaching statistical significance at 9 h. Treatment with forskolin (10−5 M) showed a similar trend, suggesting that this response is mediated by cyclic AMP-regulated phosphorylation events. From these results, we conclude that CT has two actions on TRAP in isolated rat osteoclasts: the first to inhibit its release, the second to inhibit its synthesis and/or increase its degradation.
Effects of guanine nucleotides and parathyroid hormone on inositol 1,4,5-trisphosphate metabolism in canine renal cortical tubular cell membranes
Authors: Coleman Daniel T. , Morrow Bruce S. , Bilezikian John P. 
Published: February 2010

AbstractParathyroid hormone (PTH) and guanosine 5′-O-(3-thiotriphosphate) (GTP-γS) increase levels of the second messenger inositol 1,4,5-trisphosphate (IP3) and other inositol phosphates (IP) in several membrane preparations of PTH-responsive cells. We present evidence here indicating that in a membrane preparation of canine renal cortical tubular cells bPTH-(1–84), bPTH-(1–34), [N-Leu8,18Tyr34]bPTH-(3–34)NH2, and the human PTH related peptide fragment hPTHrP-(1–34)NH2 all increase levels of inositol phosphate (IP) but [Tyr34]-bPTH-(7–34)NH2 and hPTHrP-(7–34)NH2 have no significant effects on IP accumulation. Increases in IPs are generally attributed to increased formation of IPs and appear to be mediated by a G protein. However, increased levels of IPs may also result from inhibition of the phosphatases that are responsible for their metabolism. We investigated the effect of PTH and GTP-γS on the metabolism of IP3 in canine renal cortical tubular membranes. These membranes rapidly metabolize [3H]IP3 (47% at 15 s). Decreases in [3H]IP3 at all time points are accounted for quantitatively by increases in the sum of its breakdown products: [3H]IP2, [3H]IP1, and [3H]inositol. After 5 minutes of exposure to membranes, the vast majority of [3H]IP3 (84%) is converted to its terminal metabolite, [3H]inositol. GTP-γS (100 μM) inhibits the amount of [3H]IP3 metabolized in 15 s by 70% and reduces the amount of [3H]inositol ultimately formed in 5 minutes by 64%. ATP-γS, ATP, and 2,3-bisphosphoglycerate (100 μM) also inhibit [3H]IP3 hydrolysis in this preparation. The results demonstrating that nucleotides, such as GTP-γS, at concentrations used to demonstrate G protein-mediated increases in IP3 formation, can inhibit the metabolism of IP3 suggest that their effect to increase levels of IP3 may be due in part to inhibition of IP3 metabolism. In contrast, PTH-(1–34), PTH-(3–34), and hPTHrP-(1–34) (1 μM) do not reduce the amount of [3H]IP3 metabolized in 15 s, indicating that the site of action of PTH on IP3 levels is predominantly at steps before the hydrolysis of IP3.