摘要:

AbstractTwo intermolecular cross‐linking amino acids, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), are promising markers in urine of collagen resorption because their levels in urine should reflect only collagen resorption and, unlike hydroxyproline, should not be influenced by degradation of either newly synthesized collagen molecules or noncollagenous proteins. Changes with age in the urinary excretion of HP and LP were studied in 24 h collections of urine from a group of 22 male and 27 female healthy subjects aged from 2 to 70 years. The pyridinolines were quantitated, utilizing their natural fluorescence, after resolution by reversed‐phase HPLC. Levels of both pyridinolines were higher in children than in adults, but in adults no evidence of age or sex variations were observed except in the 20–30 year age group. Mean values of HP/Cr and LP/Cr in 37 adults (21–70 years) were 27.2 ± 1.9 and 8.8 ± 0.8 μol/mol, respectively; in the 12 children (2–15 years) the mean values were 14.4 and 12.4 times higher than the respective adult values. Making certain assumptions, the mean amount of bone resorbed in normal adults was tentatively estimated at 1.9 g per 24 h. The finding that differences between children and adults in these relatively specific markers were greater than with hydroxyproline suggests that hydroxyproline values may considerably underestimate the actual amount of bone turnover occurring in growing children or overestimate the adult t

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050702

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractProstaglandins are important local regulators of bone cell function and have been shown to have multiple effects on osteoclasts. Using a human bone marrow culture system in which multinucleated cells with osteoclast characteristics form, we have recently shown that TGF‐β is a potent inhibitor of osteoclastlike cell formation and appears to act at several stages of their development. Because it has been suggested that the effects of TGF‐β are mediated via a prostaglandin‐dependent mechanism, we determined the effects of prostaglandin E2(PGE2) on total and osteoclastlike cell formation (detected by reactivity with the 23c6 monoclonal antibody, which identifies osteoclasts) in human marrow cultures and tested whether prostaglandin synthesis was responsible for the inhibitory effects of TGF‐β on multinucleated cell formation. These studies show that PGE2is a potent inhibitor of both 23c6‐positive and negative multinucleated cell formation in human marrow cultures and that the effects of TGF‐β on multinucleated cell formation are not m

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050703

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractWe examined changes in cAMP and inositol phosphate metabolism to assess the contribution of the guanine nucleotide regulatory (G) protein(s) regulating adenylate cyclase and phospholipase C in mediating the stimulatory effects of GppNHp on PTH release from permeabilized bovine parathyroid cells. To examine the role ofGs, the G protein stimulating adenylate cyclase, and cAMP on PTH release, permeabilized cells were incubated with either GppNHp or isoproterenol, and the effects of these agents on PTH release and cellular cAMP content were determined by RIA. To study the effects of GppNHp on inositol phosphate accumulation, permeabilized cells prelabeled with [3H]inositol were exposed to GppNHp, and inositol phosphates were measured using ion‐exchange chromatography. These studies revealed that isoproterenol produced a dose‐dependent increment in cAMP content in permeabilized cells with no significant effect on PTH release. Conversely, GppNHp rapidly and markedly elevated PTH release with a smaller and delayed rise in cAMP content. GppNHp‐ also promoted a dose‐dependent increase in inositol monophosphate (IP), inositol bisphosphate (IP2), and inositol trisphosphate (IP3) accumulation, suggesting activation of phosphoinositide hydrolysis. Addition of dioctanoylglycerol, however, a synthetic diacylglycerol (DG) that activates protein kinase C, produced a much smaller increment in PTH release than GppNHp. Moreover, reducing the free calcium concentration to<10−9M by adding 10 mM EGTA to the permeabilization medium dissociated the effects of GppNHp and DG on secretion, increasing GppNHp‐stimulated PTH release while reducing PTH secretion evoked by DG. In summary, (1) changes in cAMP content cannot account for the effects of GppNHp on PTH release; and (2) GppNHp increases the hydrolysis of phosphoinositides, but the addition of exogenous diacylglycerol does not mimic quantitatively the effects of GppNHp on hormone release. Thus, a G protein may be involved in the control of PTH release in permeabilized cells, perhaps by directly stimulating secretion at a locus distal to the regulation of cAMP or phosphoinositide

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050704

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractTo determine the accuracy of self‐reported risk factors for osteoporosis, an age‐stratified random sample of Rochester, MN, women was studied. Results from a structured face‐to‐face interview were compared with information documented in contemporary inpatient and outpatient health care records in the community. Using the × statistic to evaluate concordance of these two data sources, we found substantial agreement for a history of proximal femoral and distal forearm fractures, peptic ulcer disease, estrogen replacement therapy and oral contraceptive use, and cigarette and alcohol exposure. Moderate agreement was seen for histories of other age‐related fractures, hysterectomy or oophorectomy, thyroidectomy, and use of thyroid supplements. Poor agreement was found for prior thyroid disease, gastrectomy, and corticosteroid or anticonvulsant use. This study demonstrates a need for greater attention to the quality of self‐reported risk factor data in studies of bone loss a

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050705

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractSlices of osteoclast‐enriched endosteal surfaces of 3 week chick tibia were cultured for 1‐3 days. Osteoclasts on the bone surface were made visible by acridine orange fluorescence. Osteoclast area was measured by image analysis. Parathyroid hormone (PTH) caused osteoclasts to increase in area about 40%, and calcitonin (CT) caused a decrease in area also of about 40%. Subsequent addition of dibutyryl cyclic AMP to PTH‐ or to CT‐treated cells resulted in a further change of 40 and 30%, respectively. Application of the cyclic AMP analog alone had no effect. All responses were rapid, occurring in 2‐

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050706

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractMuch of the clinical research in osteoporosis is directed toward documenting a reduction in vertebral fracture rate, but there is considerable disagreement about defining and quantifying vertebral fractures. We have evaluated the technique of digitizing landmarks identified on lateral radiographs of thoracic and lumbar vertebrae and computing vertebral body area. Reduction in area indicates that fractures occurred. Radiographs from 10 patients with osteoporosis and vertebral fractures were obtained from each of two centers, Henry Ford Hospital (HFH) and Mayo Clinic (MC), and vertebral area for each individual in the complete set of 20 radiographs was calculated at each center.Measurements at the two centers differed by a multiplicative constant related to the method of recording landmarks on the radiographs that was estimated using 300 x‐rays from HFH. After adjusting the MC areas for this multiplicative relationship, the average ratio of the HFH areas to the transformed MC areas of individual vertebrae (T4‐L5) ranged from 0.98 to 1.06. The correlation between HFH and transformed MC areas for individual vertebrae averaged 0.85, with slopes between 0.87 and 1.00, intercept average ‐0.57. Within‐patient rank correlation averaged 0.97. We conclude that radiographic digitization is a reliable and reproducible method of determining vertebral body dimensions that is suitable for evaluating radiographs obtained at different clinical sites and for comparison with normal data. This technique should prove useful for documenting the presence of a vertebral fracture that may not be readily apparent on visual inspection of radiographs and for monitoring serial changes in vertebral body dimensions in long‐term epidemiologic and therapeuti

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050707

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractHuman bone matrix is known to contain a battery of polypeptide growth factors. Since dentin is a mineralized tissue similar to bone in composition and perhaps in formation, human dentin was assayed for the presence of similar growth factors.Root dentin proteins were extracted by demineralization in 4 M guanidine hydrochloride (Gu) and 30 mM Tris (pH 7.4) containing 20% EDTA and proteinase inhibitors. Gu‐EDTA extracts were desalted and used for the following assays: (1) bone cell proliferation in chick calvarial cell mitogenic assay using the incorporation of [3H]thymidine into TCA‐insoluble material; (2) osteocalcin by radioimmunoassay (RIA); (3) insulinlike growth factor I (IGF‐I) by RIA; (4) skeletal growth factor/insulinlike growth factor II (SGF/IGF‐II) by radioreceptor assay; and (5) transforming growth factor beta (TGF‐β) by bioassay.Gu‐EDTA extracts stimulated bone cell proliferation. At 10 μg/ml, dentin proteins increased the incorporation of [3H]thymidine by calvarial cells to 320% of that by BSA‐treated control cells. Consistent with the presence of mitogenic activity, growth factors were found in dentin in the following concentrations (ng/μg Gu‐EDTA protein): (1) IGF‐I, 0.06; (2) SGF/IGF‐II, 0.52; and (3) TGF‐β, 0.017. All three growth factors were present in concentrations lower than that found in human bone. Osteocalcin was detected at a concentration of 3.0 mg/g Gu‐EDTA protein, also m

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050708

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractAmphotericin B is a polyene antifungal agent that binds to membrane sterols, creating aqueous pores that permit ion fluxes sufficient to cause cell lysis. It has also been shown to alter ion transport in mammalian cells, including proton secretion from renal tubular cells. The latter effect can lead to distal renal tubular acidosis in patients treated for systemic fungal infections. Based on the understanding that osteoclast‐mediated bone resorption is dependent on proton secretion, we examined the effect of amphotericin B on calcium efflux from neonatal mouse calvariae in organ culture. Amphotericin B (5 μg/ml) stimulated net calcium efflux from calvariae within 24 h to a level almost as great as that produced by a maximally effective concentration of parathyroid hormone. The stimulated calcium efflux was completely inhibited by both 10 ng/ml salmon calcitonin, a physiologic inhibitor of osteoclast activity, and 4 × 10−4M acetazolamide, a specific inhibitor of carbonic anhydrase, the enzyme necessary for substantial proton generation by osteoclasts. These results indicate a direct effect of amphotericin B on bone in vitro to stimulate osteoclast‐mediated calcium

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050709

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractBone development and remodeling are associated with changes in the pattern of vascularization. Here we show that endothelial cells isolated from rat liver or bovine aorta can greatly enhance bone formation when implanted in diffusion chambers with rat fetal calvarial cells. The latter cells are unable to form bone when implanted alone at low initial cell density. The amount of mineralization measured by calcium deposition was 70 times higher in chambers containing calvarial cells mixed with endothelial cells from isologous liver or bovine aorta than in chambers containing endothelial or calvarial cells alone. Alkaline phosphatase activity was increased 20‐fold. Calvarial cells in the presence of demineralized bone matrix powder did not form bone when implanted under similar conditions. Endothelial cells implanted alone seemed to enhance neovascularization around the Millipore diffusion chamber

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050710

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY

摘要:

AbstractWe observed that culture medium conditioned with fetal rat long bones stimulated cyclic AMP production by canine renal cortical membranes. This cyclase‐stimulating activity (CSA) was retained by an ultrafiltration membrane with a molecular weight cutoff of 5000; three biologically active peaks with an approximate molecular weight of 18,000‐25,000, 9000‐12,000, and 4000‐6000 were separated by high‐performance liquid chromatography. The biologic activity was destroyed by trypsin digestion. The stimulation of adenylate cyclase by the medium and by the three peaks was inhibited by [N‐leu8.18, Tyr34]parathyroid hormone‐(3‐34)‐amide and by [Tyr34]parathyroid hormone‐(7‐34)amide. Preincubation of the bone culture medium and of the three peaks with an antibody raised against human parathyroid hormone‐(l‐34) did not decrease the biologic activity more than incubation with nonimmune serum. However, the biologic activity of the three active peaks was significantly suppressed after preincubation with an antiserum directed against the N‐terminal region of the parathyroid hormone‐related peptide of malignancy. The release of CSA into the bone culture medium was enhanced by parathyroid hormone induction and by 1,25‐dihydroxycholecalciferol. It was decreased by calcitonin. We conclude that fetal murine bones in culture release peptides that stimulate the adenylate cyclase of renal cortical membranes. These peptides are antigenically similar to the parathyroid hormone‐related peptide of malignancy. Their release from bones is modulated by horm

ISSN:0884-0431    

DOI:10.1002/jbmr.5650050711

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1990

数据来源: WILEY