bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of vitamin D metabolites on collagen production and cell proliferation of growth zone and resting zone cartilage cells in vitro
Authors: Schwartz Z. , Schlader D. L. , Ramirez V. , Kennedy M. B. , Dr. Boyan B. D. 
Published: February 2010

Abstract
Previous studies have suggested that vitamin D metabolites directly influence the differentiation and maturation of chondrocytes in calcifying cartilage. Recently, this laboratory has shown that the response of chondrocyte plasma membrane and matrix vesicle enzymes to 1,25-(OH)2D3 and 24,25-(OH)2D3 is both cell and membrane specific. The current study demonstrates that cell replication and matrix protein synthesis are also modulated by vitamin D. Confluent, third-passage growth zone (GC) and resting zone (RC) costochondral chondrocytes were incubated in medium containing 10−13-10−7 M 1,25-(OH)2D3 or 10−12-10−6 M 24,25-(OH)2D3. The amount of collagenase-digestible protein (CDP) secreted into the media was inversely proportional to the concentration of fetal bovine serum (FBS). At 10% FBS, greater than 80% of the CDP was incorporated into the matrix. 1,25-(OH)2D3 stimulated CDP and percentage collagen synthesis by GC cells but had no effect on the synthesis of noncollagenous protein (NCP). 1,25-(OH)2D3 inhibited CDP and percentage collagen synthesis by RC cells but did not alter NCP synthesis. [3H]thymidine incorporation was inhibited in both cell types, whether confluent or subconfluent cultures were examined. At 10−6 and 10−7 M 24,25-(OH)2D3, there was a significant decrease in CDP production and percentage collagen synthesis by RC cells but no effect on NCP. However, at 10−9 and 10−10 M hormone there was an increase in NCP production but no effect on CDP, resulting in a decrease in percentage collagen synthesis. CDP and NCP production were unaffected by 24,25-(OH)2D3 in GC cells. High concentrations of hormone inhibited [3H]thymidine incorporation in both cell types. 24,25-(OH)2D3 also stimulated [3H]uridine incorporation at 10−8 and 10−9 M in RC cells. These data support the hypothesis that vitamin D metabolites influence the development and maturation of calcifying cartilage and that the response of cells to hormone is dependent on their state of differentiation.
Effect of arachidonic acid metabolites on bone resorption by isolated rat osteoclasts
Authors: Fuller Karen , Chambers Timothy J. 
Published: February 2010

Abstract
Arachidonic acid metabolites (eicosanoids) have major effects on bone but their role is unclear. Many are known to stimulate bone resorption in organ culture, but paradoxically, previous work has suggested that at least some of them act as direct inhibitors of osteoclastic function. In an attempt to clarify the role of eicosanoids in bone physiology, we have defined the duration of action and relative potencies of prostaglandin (PG) E1and E2 and have extended the range of eicosanoids tested on isolated osteoclasts. We have found that PGE1 and PGE2 inhibited bone resorption by isolated osteoclasts for at least 6 h. Inhibition was followed by recovery to control, not supranormal levels. Bone resorption was inhibited in the range 10−5-10−9 M for PGE1 and PGE2, and the rank order as resorption inhibitors was PGE1 &gt; 6-keto PGE1 &gt; PGE2 &gt; PGA2 &gt; PGB2. None of the products of lipoxygenase metabolism showed a significant direct effect. The effects of PGE1 and PGE2 were not antagonistic. Prostaglandin production does not seem to be implicated as a second messenger for the action of calcitonin. Although inhibition of osteoclasts by PGs was less prolonged than that observed in the presence of calcitonin, the sensitivity of osteoclasts to inhibition by PGs, and the duration of the effect without subsequent direct stimulation, suggests that inhibition of osteoclastic resorption is a major physiological role of PG production in bone.
Stimulation of experimental endochondral ossification by low-energy pulsing electromagnetic fields
Authors: Aaron Roy K. , Ciombor Deborah McK. , Jolly Grant 
Published: February 2010

Abstract
Pulsed electromagnetic fields (PEMFs) of certain configuration have been shown to be effective clinically in promoting the healing of fracture nonunions and are believed to enhance calcification of extracellular matrix. In vitro studies have suggested that PEMFs may also have the effect of modifying the extracellular matrix by promoting the synthesis of matrix molecules. This study examines the effect of one PEMF upon the extracellular matrix and calcification of endochondral ossification in vivo. The synthesis of cartilage molecules is enhanced by PEMF, and subsequent endochondral calcification is stimulated. Histomorphometric studies indicate that the maturation of bone trabeculae is also promoted by PEMF stimulation. These results indicate that a specific PEMF can change the composition of cartilage extracellular matrix in vivo and raises the possibility that the effects on other processes of endochondral ossification (e.g., fracture healing and growth plates) may occur through a similar mechanism.
Serum albumin and its acid hydrolysis peptides dominate preparations of mineral-bound enamel proteins
Authors: Dr. Limeback Hardy , Sakarya Harry , Chu Willa , Mackinnon Mary 
Published: February 2010

Abstract
Serum albumin is a major noncollagenous protein component of bone, dentine, and, according to our results, enamel. Preparations of mineral-bound proteins from porcine developing enamel contain a single 67 kD protein at neutral pH or three proteins (67, 63, and 53 kD) at low pH that were assumed to be enamelins, a minor class of enamel proteins.(15) A more complete analysis of these proteins in this study showed that they were derived from porcine serum albumin (PSA). This was demonstrated by amino acid analysis, by N-terminal sequence analysis, by immunoblot studies using an anti-PSA antibody, and by SDS-PAGE analysis of the acid hydrolysis, cyanogen bromide, and tryptic peptides. Examination of enamel at different developmental stages showed that PSA deposited in enamel from the enamel organ and from the dentine during development, not during the dissection process. These results indicate that true enamelins must represent a very small fraction of the total mineral-bound protein matrix in porcine developing teeth, and this has important implications on the role of mineral-bound proteins during mineralization of enamel.
Analysis of parathyroid hormone in bovine parathyroid cysts
Authors: Ayer Linda M. , Szarka Roderick J. , Mortimer Shane T. , Alexander Fred J. , Martin Justin M. E. , Andersen Melvin A. , Dr. Hanley David A. 
Published: February 2010

Abstract
Parathyroid cysts were found in 2–5% of beef steers and heifers while collecting parathyroids at a local abattoir. The cyst fluid contained parathyroid hormone (PTH), averaging 15 ng/ml of fluid. Reversed-phase high-performance liquid chromatographic (HPLC) analysis of the fluid using an acetonitrile-trifluoroacetic acid solvent system, followed by carboxyl-terminal specific PTH radioimmunoassay of the eluant fractions, revealed two major peaks of PTH immunoreactivity. The first eluted at approximately 25% acetonitrile, a position similar to the commercially available human carboxyl terminal fragment of PTH-(39–84). The second peak, at approximately 37% acetonitrile, corresponded to the elution position for bovine PTH-(1–84). The cyst fluid was tested for enzyme activity by incubation of 125I-labeled bovine PTH with cyst fluid for 30 minutes at 37°C, which resulted in no fragmentation of the labeled peptide. Immunohistochemistry of the cells lining the parathyroid cyst indicated that they contained PTH.
Effects of altered calcium intake on diurnal and calcium-stimulated plasma calcitonin in normal women
Authors: Tiegs Robert D. , Heath Hunter 
Published: February 2010

Abstract
We sought to determine if any protective effect of dietary calcium (Ca) or Ca supplements on bone could be at least partially mediated by increased calcitonin (CT) secretion. First we studied 10 healthy premenopausal women (median age, 35.5 years) who were randomized to high or low dietary Ca intake (1752 versus 391 mg elemental Ca per day) for 2 weeks and then crossed over. At the end of each dietary period, blood was drawn on 1 day at 0800, 1200, 1700, and 2000 h to assess diurnal variation of plasma CT levels. CT secretory reserve was assessed on the next day by Ca infusion (2 mg Ca per kg body weight over 5 minutes). Next, we studied 10 healthy premenopausal women who took a low-Ca diet (∼ 400 mg Ca per day) for a 2 week control period. The women were then randomized to high- or low-Ca intake [400 mg dietary Ca ± 1500 mg Ca per day (as supplemental CaCO3)] and then crossed over. At the end of each study period, the diurnal variation in CT was tested on day 1; the CT secretory reserve was assessed on day 3 by an oral Ca load (500 mg as CaCO3)] and on day 5 by Ca infusion. Plasma immunoreactive CT was measured in whole plasma (iCT) and after silica extraction (exCT), predominantly monomeric CT. Neither increased dietary Ca nor Ca supplements affected the diurnal levels of iCT or exCT or augmented plasma CT responses to an oral Ca load. Furthermore, there was no change in secretory reserve for iCT or exCT after Ca infusion. We conclude that short-term Ca administration, in the form of dietary Ca or Ca salts, at the extremes of normal dietary intake and in doses normally used to treat osteoporosis, respectively, does not affect CT secretion in healthy premenopausal women. It seems unlikely that any potential beneficial effects of ingested Ca on the skeleton in women are mediated by CT.
Parathyroid hormone-related protein relaxes rat gastric smooth muscle and shows cross-desensitization with parathyroid hormone
Authors: Mok Lester L. S. , Ajiwe Eberechukwu , Martin T. John , Thompson James C. , Cooper Cary W. 
Published: February 2010

Abstract
Previously, we reported that parathyroid hormone (PTH) is a potent and effective relaxant of rat gastrointestinal smooth muscle. Since the recently discovered PTH-related protein (PTHrP) has amino-terminal homology with PTH and acts like PTH on bone and kidney, we decided to study the effects of synthetic PTHrP analogs on the isometric tension of rat fundic strips. Rat (r) PTH-(1–34), human (h) PTHrP-(1–34), and [Tyr0]hPTHrP-(1–34) relaxed acetylcholine-stimulated fundic strips in a dose-dependent manner, with an IC50 of 6, 10, and 31 nM, respectively. However, maximal doses of [Tyr0]hPTHrP-(1–34) were considerably less effective than the other two peptides. Addition of rPTH-(1–34) or hPTHrP-(1–34) to a maximally effective dose of [Tyr0]hPTHrP-(1–34) produced no further relaxation, indicating that [Tyr0]hPTHrP-(1–34) also has antagonistic properties. Bovine PTH-(3–34), an established in vitro antagonist of PTH, partially inhibited the relaxant effect of PTHrP. Fundic strips that had been desensitized by preincubation for 30–45 minutes with either rPTH-(1–34) or hPTHrP-(1–34) (330–500 nM) were also insensitive to the relaxant action of either peptide, but in the same preparations, the relaxation produced by vasoactive intestinal peptide was unaffected. These studies indicate that PTHrP and PTH can interact with the same receptor. Whether PTHrP influences gastrointestinal motility in normal or tumor-bearing persons remains to be investigated.
Muscle strength, physical fitness, and weight but not age predict femoral neck bone mass
Authors: Pocock Nicholas , Dr. Eisman John , Gwinn Tom , Sambrook Philip , Kelly Paul , Freund Judith , Yeates Michael 
Published: February 2010

Abstract
Hip fractures are the most serious complication of osteoporosis. Although low proximal femoral bone mineral density (BMD) does not cause hip fractures directly, it is clearly a prerequisite for the increased risk associated with aging. To investigate the mechanism of the age-related decline in proximal femoral bone mineral density, we have examined the relative importance of muscle strength, physical fitness, and body mass index (BMI) in addition to age in the determination of proximal femoral BMD in 73 healthy female volunteers age 20–75 years.
Muscle strength was an independent predictor of BMD at all three sites in the proximal femur as well as in the lumbar spine and forearm; proximal femur BMD was also predicted by physical fitness. BMI was a positive predictor of bone mass at all sites. In the proximal femur, age was not an independent predictor of BMD at any site.
In postmenopausal women muscle strength was a significant predictor of bone mass in the femur and forearm, but not in the spine. However, BMI remained predictive of bone mineral at all sites.
Muscle strength, physical fitness, and weight appear to exert independent effects upon bone mass. Age effects may be mediated indirectly through associated changes in these factors. The integrated physical load on the skeleton may be a final common pathway.
Resorption is not essential for the stimulation of bone growth by hPTH-(1-34) in rats in vivo
Authors: Dr. Hock J. M. , Hummert J. R. , Boyce R. , Fonseca J. , Raisz L. G. 
Published: February 2010

Abstract
Chronic low doses of hPTH-(1–34) stimulate bone growth in rats in vivo. The objective of these studies was to determine if the anabolic effect of hPTH-(1–34) on rat bone in vivo is dependent on an initial stimulation of resorption by blocking resorption with either salmon calcitonin (CT) or dichloromethylene diphosphonate (Cl2MDP).
Male Sprague-Dawley rats, 70–100 g, were treated with daily subcutaneous (SC) injections of vehicle (V) or hPTH-(1–34), 8 μg per 100 g (PTH), for 12 days. In experiment 1, rats were given CT for 3 (CT3) or 12 (CT12) days, either alone or in combination with hPTH-(1–34) (CT3-PTH and CT12-PTH) or vehicle for 12 days. In experiment 2, rats were pretreated for 4 days with Cl2MDP or its vehicle before starting the daily PTH or vehicle injections. Rats were then killed. Sera, femora, tibiae, and kidneys were removed for chemical and histomorphometric analyses.
PTH, PTH-CT3, and PTH-CT12 rats showed significant increases in total bone calcium (18–23%), dry weight (DW, 13–25%), and bone-forming surfaces compared with their respective controls. Eroded (resorption) surfaces were comparable between the groups. Although weight gain and serum calcium were normal in rats treated for 3 days with CT, rats treated for 12 days with CT gained 14% less weight than controls and were hypophosphatemic, with reduced serum calcium and urea nitrogen. Total bone mass increased both in Cl2MDP rats (Ca 21%, DW 2%), where resorption was presumably blocked, and in PTH rats (Ca 31%, DW 19%). The increase in bone mass was greater in PTH-Cl2MDP rats (Ca 48%, DW 29%) than in rats treated with Cl2MDP alone, suggesting that although Cl2MDP blocked resorption, the anabolic response to PTH was not altered. As neither short-term treatment with CT nor Cl2MDP blocked the anabolic response of bone to hPTH-(1–34), this response does not appear to depend on the early stimulation of resorption.
Evaluation of the osteoclastic population in iliac crest biopsies from 36 normal subjects: A histoenzymologic and histomorphometric study
Authors: Dr. Palle S. , Chappard D. , Vico L. , Riffat G. , Alexandre C. 
Published: February 2010

Abstract
After histochemical staining of tartrate-resistant acid phosphatase (TRAP) activity, the total and active trabecular resorption surfaces and the number of osteoclasts were determined by histomorphometry on iliac crest biopsies from 36 healthy volunteers. The subjects were separated into three groups according to age and sex. Total trabecular resorption surface showed no significant variation in any group, but the fraction of active resorption surface was significantly higher in the older population. The number of TRAP cells per mm2 of section area, related to trabecular bone volume or surface, showed a significant increase in elderly subjects. The mean osteoclast interface was similar in all the groups. We found a significant decrease in resorption depth between young and old populations. These results are consistent with a reduced activity of bone-resorbing cells in advancing age. These normal values, established after histochemical identification of osteoclasts, may be applied for evaluating abnormal bone-resorbing cell activity in metabolic bone diseases.
Effect of long-distance running on bone mass in women
Authors: Kirk Shelley , Sharp Charles F. , Elbaum Nancy , Endres D.B. , Mohler John G. , Rude Robert K. , Simons Steven M. 
Published: February 2010

Abstract
The effect of long-distance running on bone mass was assessed in 10 premenopausal and 9 estrogen-deprived postmenopausal women and compared to that in closely matched sedentary control women. Vertebral trabecular bone density (VBD) was determined by computed tomography and radial cortical bone density (CBD) by single-photon absorptiometry. Physical fitness was assessed by determining maximal oxygen consumption (VO2max) on a treadmill run to exhaustion. VBD was 183 + 7 mg/cm3 and VO2max was 48 + 1 ml/kg per minute in young women runners and 163 + 8 mg/cm3 and 32 + 2 ml/kg per minute in sedentary young women. A positive correlation was noted between VBD and VO2max in these groups (r = 0.509, p &lt; 0.03). Despite a significantly higher VO2max in postmenopausal women runners compared with sedentary controls (37 + 2 versus 24 + 2 ml/kg per minute), VBD was identical (112 + 5 versus 111 + 5 mg/cm3) and no correlation was seen between VBD and VO2max (r = 0.187, p = 0.457). Radial cortical bone density was not different between the runners or sedentary groups in young women (0.738 + 0.01 versus 0.732 + 0.1 g/cm2) or postmenopausal women (0.617 + 0.3 versus 0.665 + 0.4 g/cm2). These results suggest that although physical fitness enhances vertebral bone density in premenopausal women, it does not appear to prevent age-and/or sex steroid deficiency-induced bone loss in postmenopausal women.
Articular chondrocytes lose their proliferative activity with aging yet can be restimulated by PTH-(1–84), PGE1, and Dexamethasone
Authors: Livne Erella , Weiss Anna , Dr. Silbermann Michael 
Published: February 2010

Abstract
Mouse mandibular condyles develop spontaneous degenerative changes by 6 months of age, hence providing a good in vivo model for studies related to processes associated with the onset and progression of age-related osteoarthritis. Further, this joint provides an appropriate system to investigate the potential of articular cartilage to respond to hormones and local growth factors in old age. The present study examined (1) the age-related changes in [3H]thymidine incorporation by articular chondrocytes in the mouse mandibular condyle, and (2) the effect of systemic and local factors upon the tissue's ability to resume DNA synthesis. Condyles of female CW-1 mice ranging from 3 to 18 months of age were cultured in the presence of PTH-(1–84) (2 μ/g/ml), PGE1 (20 μ/ml), dexamethasone (10−7 M), and MSA (5 μg/ml) and were concomitantly labeled with [3H]thymidine. Autoradiographs were analyzed quantitatively and revealed (1) a significant (p &lt; 0.01) age-related decrease (–80%) in the labeling index of the articular cartilage, and (2) the ability of old tissues to resume DNA synthesis following in vitro treatment with PTH-(1–84), PGE1, and dexamethasone. Concomitant quantitative incorporation studies further substantiated the autoradiographic findings. Hence, these factors possess a direct stimulatory effect upon senescent chondrocytes involved in an advanced stage of spontaneous osteoarthritis.
Interferon γ and calcitonin induce differential changes in cellular kinetics and morphology of osteoclasts in cultured neonatal mouse calvaria
Authors: Klaushofer Klaus , Hoffmann Oskar , Czerwenka Erwin , Koller Kristian , Hörandner Helmut , König Uwe , Peterlik Meinrad 
Published: February 2010

Abstract
The present study compares the effects of calcitonin (CT) and interferon γ (IFN-γ) on the size, distribution, and ultrastructure of osteoclasts in cultured neonatal mouse calvaria. The number and cross-sectional area of osteoclasts in cultured bones was increased by the addition of parathyroid hormone (PTH) to the culture medium for 24–48 h. Prolonged treatment (up to 72 h) with PTH led to extensive rarefication and formation of holes in the mineralized matrix. PTH-activated osteoclasts exhibited an elaborate ruffled border and showed a typical zonal arrangement of intracellular organelles with the outer cytoplasmic region containing numerous membrane-bound vesicles. CT (20 mU/ml) within 90 minutes caused a complete loss of the ruffled border in PTH-activated osteoclasts. The typical zonal architecture disappeared with intracellular vesicles spread through the entire cytoplasm. Prolongation of CT treatment to 24–48 h led to the appearance of vesicles with dark granular content in inactivated osteoclasts. This morphologically distinct vesicle population allowed us to identify the latter cells as “postosteoclasts” and thereby to distinguish them from osteoclasts precursors. Small active osteoclasts that had originated very likely from these precursors appeared in calvarial bones coincidentally with escape from CT inhibition of bone resorption and resulted in increased total number of osteoclasts. In contrast, IFN-γ (500 U/ml) acting as a proliferation inhibitor, reduced the total number of osteoclasts. In the presence of PTH it caused no immediate (90 minutes) change in the ultrastructure of PTH-induced osteoclasts apart from an increase in the number of autophagic vacuoles. After prolonged exposure (24–48 h) in the presence of PTH, osteoclasts with low resorbing activity exhibited intermediate borders at their contact zone with the mineralized matrix. In the absence of PTH, the short-term effect of the immune interferon on osteoclast morphology was almost comparable to that of CT. After prolonged treatment in the absence of PTH, postosteoclasts comparable in vesicle population and size to those after CT treatment were found.
Identification and characterization of parathyroid hormone receptors in rat renal cortical plasma membranes using radioligand binding
Authors: Nickols G. Allen , Metz-Nickols Maureen A. , Roberts M. Scot , Cooper Cary W. , Pang Peter K.T. 
Published: February 2010

Abstract
Parathyroid hormone (PTH) receptors have been described in renal tissue from several species, but not in the rat. In this study, radioligand binding techniques were used to identify and characterize PTH receptors in rat kidney cortical membranes. The sulfur-free PTH analog [Nle8,18Tyr34]bovine PTH-(1–34)amide was iodinated using the iodogen method. This ligand was suitable for use in identifying PTH receptors in canine renal membranes, but not rat renal membranes. Synthetic, unsubstituted rat PTH-(1–34) was iodinated using the milder, lactoperoxidase technique and was purified by HPLC on a C8 column. [125I]rat PTH-(1–34) bound rapidly to both rat and dog renal membranes. At 22°C the reaction reached steady state within 20 minutes, and this level was maintained for at least 3 h. Specific binding was routinely &gt;90% for rat kidney and &gt;95% for dog kidney. Similar results were obtained at 4°C with a longer time required to attain steady state (approximately 45 minutes). Binding was reversible as demonstrated by dissociation of bound ligand after either infinite dilution or displacement with excess nonradioactive PTH. Binding was saturable and of high affinity (rat kidney: Bmax = 2.3 pmol/mg protein, Kd = 3.1 nM, dog kidney: Bmax = 2.1 pmol/mg protein, Kd = 3.7 nM). Rat renal cortical adenylate cyclase activity was stimulated by rat PTH in a dose-dependent manner with an EC50 of 4 nM, a value in good agreement with the binding data. This study demonstrates the feasibility of identifying and characterizing parathyroid hormone receptors in rat renal cortical plasma membranes using radioligand binding techniques.