摘要:

AbstractA new immunoassay using an ELISA approach for measuring urinary excretion of cross‐linked N‐telopeptides of type 1 collagen was evaluated as a specific measure of bone resorption. The assay was applied to 65 early postmenopausal women who participated in a placebo‐controlled trial of the aminobisphosphonate, alendronate sodium. Eight blood and urine samples were collected over a 9 month interval. Baseline cross‐linked peptide excretion varied from 26 to 216 pmol BCE (bone collagen equivalents)/μmol Cr. Within‐subject variability (CV) for cross‐linked peptide excretion was 20.2% over the 9 months in placebo‐treated subjects, substantially less than that observed for other biochemical markers of bone resorption: 45, 53, and 63% for fasting urinary calcium and hydroxyproline and 24 h urinary lysylpyridinoline (HPLC assay), respectively. Baseline cross‐linked peptide excretion correlated significantly (p<0.001) with baseline total urine lysylpyridinoline and serum osteocalcin, but not with the other biochemical markers. Initial peptide excretion also correlated inversely with lumbar spine bone mineral density at entry (r= −0.26,p<0.05). Treatment for 6 weeks with alendronate produced a dose‐dependent suppression of cross‐linked peptide excretion (0 ± 8, 29 ± 6, 56 ± 5, and 64 ± 3% for 0, 5, 20, and 40 mg, respectively,p<0.01 versus placebo for treatment effect), with a return toward pretreatment values during follow‐up. Measurement of the urinary cross‐linked N‐telopeptides of type I collagen by this new ELISA approach appears promising as a simple and reliable method to assess overall bone resorption. It may prove especially useful in monitoring the treatment of osteoporotic women with antiresorptive therapy. Its utility in identifying those women in the high resorption range at menopause who may be at greater risk for osteoporosis should al

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090202

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

年代:1994

数据来源: WILEY

摘要:

AbstractBasic fibroblast growth factor (bFGF) has been detected in bone cells and stimulates osteoblast proliferation; however, its role in the regulation of bone metabolism remains speculative. We demonstrated that the human osteocalcin promoter is activated by bFGF when transfected into rat osteoblastic (ROS 17/2.8) cells. This effect is concentration dependent, with a twofold induction at 10 ng/ml detected after 20 h. The bFGF response is independent of both the 1,25‐dihydroxyvitamin D3[1,25‐(OH)2D3] and retinoic acid activation of the osteocalcin promoter. To identify the promoter sequences through which bFGF exerts its effect, we tested a series of promoter deletion constructs for their response to bFGF. Deletion of the upstream region between −673 and −588 bp results in a significant loss of induction. Gel‐shift analysis demonstrates that proteins present in ROS 17/2.8 nuclear extracts bind specifically to these sequences. This region alone was unable to confer the bFGF response on a minimal osteocalcin or an heterologous promoter. However, sequences between −678 and −476 bp, which also includes the vitamin D response element (VDRE), were able to confer bFGF inducibility on both a minimal osteocalcin and a heterologous promoter. These data suggest that induction of the human osteocalcin promoter by bFGF requires the interaction of more than one seq

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090203

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of long‐term tamoxifen therapy on bone remodeling were studied in 41 women with breast cancer, 22 treated with tamoxifen for a minimum of 15 months (mean 33) and 19 untreated. Transiliac crest bone biopsies were obtained and a comprehensive histomorphometric analysis performed using a semiautomatic image analysis system. There were no statistically significant differences between the two groups in bone area, osteoid perimeter and area, or osteoid width. Mineral appositional rate, adjusted appositional rate, and mineralization lag time were also similar in the two groups; however, tissue‐based bone formation rate was significantly lower in the tamoxifen‐treated women (p= 0.05) and the remodeling period significantly longer (p<0.05). Mean and maximum resorption cavity depth and cavity area were significantly reduced in the tamoxifen‐treated patients compared to the untreated patients (p<0.01,p<0.01, andp<0.03, respectively). Calculated and directly measured indices of cancellous bone structure were similar in the two groups, although the data indicated a trend toward greater connectedness in the tamoxifen‐treated group. These data indicate that tamoxifen does not exert an antiestrogenic effect on bone remodeling in the human and are consistent with a weak estrogen

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090204

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

年代:1994

数据来源: WILEY

摘要:

AbstractA monoclonal anti‐chondroitin sulfate antibody (CS‐56) that recognizes native chondroitin sulfate glycosaminoglycans (CSGAG) was used to quantify changes in CSGAG labeling levels in mineralizing human fetal osteoblast‐like cell multilayers up to 40 days postconfluence. In control cultures, mean labeling of CSGAG increased in nonmineralized areas from around eight gold probes per μm2(gpm) at 20 days to 26 gpm at 40 days. Labeling was markedly increased in the mineralized tissue, to 560 gpm at 30 days and 580 gpm at 40 days. In β‐glycerophosphate‐treated cultures, the mineralized areas were increased and appeared earlier (20 days) than in the control cultures. In these cultures, mean CSGASG labeling increased in nonmineralized areas from around 5 gpm at 20 days to 26 gpm at 30 days and was further increased in mineralized areas to 270 gpm at 20 days and 298 gpm at 30 days. Mineralization was not noted in cultures treated with 10−8M 1,25‐dihydroxyvitamin D, and CSGAG labeling remained low (<5 gpm) during the study period. These results indicate that an increase in immunoreactive CSGAG is associated with mineralization in this culture system. One possible interpretation of these findings is that proteoglycan molecules or at least their CSGAG side chains may be involved in the mineral

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090205

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn experiment was designed to test part of the hypothesis that physiologic amounts of dietary boron enhance utilization of or, alternatively, compensate for, inadequate concentrations of active vitamin D metabolites to normalize energy substrate utilization and mineral metabolism. Day‐old cockerel chicks were fed a ground corn, high‐protein casein, corn oil‐based diet (<0.18 mg B/kg) supplemented with physiologic amounts of boron (as orthoboric acid) at 0 (non‐PSB) or 1.4 (PSB) mg/kg and vitamin D3(as vitamin D3powder in corn endosperm carrier) at 3.13 (inadequate, IVD) or 15.6 (adequate, AVD) μg/kg. After 26 days, IVD decreased food consumption and plasma calcium concentrations and increased plasma concentrations of glucose, β‐hydroxybutyrate, triglycerides, triiodothyronine, cholesterol, and alkaline phosphatase activity. In the IVD chicks, PSB returned plasma glucose and triglycerides to concentrations exhibited by the AVD chicks and increased food consumption in both IVD and AVD chicks. Histologic findings suggested that PSB enhanced maturation of the growth plate. A ninefold increase in dietary boron yielded only a twofold increase in plasma boron concentration and no increase in femur boron concentration, which suggests that boron is under homeostatic control. The findings suggest that boron acts on at least three separate metabolic sites because it compensates for perturbations in energy substrate utilization induced by vitamin D3deficiency, enhances major mineral content in bone, and, independently of vitamin D3, enhances some indices of growth cartilage

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090206

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe steady‐state mRNA levels of different osteogenic markers and their modulation by 17β‐estradiol in the murine osteogenic cell line MN7 during proliferation and differentiation in vitro were examined. mRNA of collagen type I, osteopontin, bone morphogenetic protein 2, plasminogen activator inhibitor 1, alkaline phosphatase, and osteocalcin were isolated from MN7 cultures grown for 7, 11, 14, and 17 days. Northern blot analysis revealed steady‐state transcript levels depending on MN7 cell density. The order of appearance of Col I, OP, ALP, and OC resembled the pattern of gene expression observed during osteoblast maturation in vitro. Furthermore, PAI‐1 steady‐state transcript levels peaked during subconfluence (day 11) but BMP‐2 RNA levels reached their maximum after the culture had become confluent. 17β‐Estradiol showed a dose‐dependent stimulation of the different osteoblast‐related transcripts present in a subconfluent MN7 culture at the time of analysis. Furthermore, the effects of 17β‐estradiol (17βE2) at different time points of MN7 growth varied according to cell density. 17βE2added to subconfluent MN7 cultures modulated the transcript level in a negative way, but RNA levels of the investigated osteogenic markers in confluent cultures were stimulated with 100 nM 17β‐estradiol. No effect of 17β‐estradiol on proliferation was detected. The present studies have revealed differential osteoblast gene expression related to MN7 cell proliferation and differentiation in vitro and emphasize the importance of 17βE2in the regulation of growth of this pre

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090207

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe role of integrins, cell surface receptors involved in cell adhesion to the matrix, was studied in a mineralizing organ culture system. Integrin‐mediated cell attachment to matrix proteins has been shown to depend partially on the amino acid sequence Arg‐Gly‐Asp (RGD), present in the extracellular matrix proteins. Therefore, the effect of RGD peptides on bone formation and resorption was studied in the mineralizing organ culture system derived from 18 day fetal rat parietal bones. Addition of 0.1–50 μM GRGDSPK to bones cultured for 4 days inhibited mineralization in a dose‐dependent manner as determined by measuring calcium content and % bone/unit area of tissue. A maximal decrease in calcium content and % bone/unit area of 32.5 and 42.9%, respectively, was found with 50 μM GRGDSPK. With 10 and 50 μM GRGDSPK, bone morphology was dramatically altered, with a disruption of osteoblast and mineralized matrix organization. To assess the effect of the peptides on bone resorption, fetal bones were prelabeled in vivo with45Ca and resorption was stimulated in vitro with parathyroid hormone in the presence or absence of the peptide. A significant decrease in45Ca release was found with 10 and 50 μM GRGDSPK. Osteoclast number was also significantly decreased on the bone surface. The peptide was not cytotoxic, since no effect on DNA content, dry weight, or collagen synthesis was found. GRADSP, a control peptide, had no significant effect on mineralization, resorption, or other parameters of bone growth. Visualization of β1and α2integrin in GRGDSPK‐treated bones by indirect immunofluorescence demonstrated a decreased in integrin staining, particularly in the osteoblast layer, compared to control bones and bones treated with GRADSP. The inhibition of bone formation and resorption by an RGD‐containing peptide in a mineralizing organ culture system suggests that integrins have an important role in osteoblast and osteoclast‐med

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090208

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

年代:1994

数据来源: WILEY

摘要:

AbstractMechanical loading of the living skeleton influences bone formation, mass, and strength. The primary purpose of the present study was to examine the influence of different loading schedules (days/week) on the bone response to external loading using an in vivo rat tibia four‐point bending model. Three studies were conducted to (1) characterize the loaded region, (2) examine the variation of the response within the loaded region, and (3) test the response to different loading schedules. In all studies adult female retired breeder Sprague‐Dawley rats were used (6 months, 285 g). First, the location of the loaded region during four‐point bending was determined by radiogrammetry of 7 rats. Second, 5 rats were externally loaded for 8 of 10 days at 31 N, 36 cycles, and 2 Hz (1349 ± 244 μϵ). The extent of labeled (forming) periosteal and endocortical surface in the loaded region was compared both among four serial sections from the same tibia and between the loaded and the contralateral tibiae. Finally, 50 rats were randomized into five groups: two nonloaded, control and sham, and three loaded, alternate day, Monday, Wednesday, and Friday, and daily. The rats were externally loaded for 3 weeks at 35 N, 36 cycles, and 2 Hz (1533 ± 308 μϵ). The tibia and fibula were studied for labeled surfaces and mineral apposition rate. For adult female rats with tibial length 39 mm, the loaded region was located 3.5–14 (±0.7) mm proximal to the tibia‐fibula junction (TFJ). With multiple repositionings in the same rat, the location of the distal inner pad varied from 3.2 to 3.8 mm proximal to the TFJ (95% confidence interval). The response to loading was consistent within the loaded region and reliably sampled by two cross sections from the loaded region. The bone response under the loading pads was not different from that at other points within the loaded region. There were no differences in the response to external mechanical loading among the three loading schedules (daily, alternate day, and Monday‐Wednesday‐Friday). Loading created greater formation surface on the medial periosteum of the tibia (70%) and on the fibula (92%) of externally loaded legs than in nonloaded legs. Loading had no effect on the lateral periosteal formation surface or on the endocortical surface of the tibia. Loading created greater mineral apposition rate in loaded than nonloaded tibia (28–72% greater) at all periosteal surfaces. The pattern of response to loading was the same in both studies 2 and 3. In an adult rat, this model produces a predictable bone response to external mechanical loading in a defined region of the tibial diaphysis. External loading 3 or 4 days/week is as effective as daily loading for increasing periosteal bone formation surface and m

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090209

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

年代:1994

数据来源: WILEY

摘要:

AbstractWhen bone is cultured in acid medium there is net calcium efflux (JCa) and proton influx (JH) relative to the mineral. The acid medium appears to induce physicochemical mineral dissolution as well as cell‐mediated bone resorption. To determine the independent effect of acid medium on physicochemical dissolution, we utilized cell‐free synthetic ceramic apatite (CAP) disks, which contain carbonate (5.5%) in an apatite structure chemically similar to mammalian bone. CAP disks were cultured in control (Ctl, pH ≅ 7.44) or acid (Met, pH ≅ 7.11) medium for 48 h and compared to similarly treated neonatal (4–6 days old) mouse calvariae. Medium was changed and analyzed at 3, 24, and 48 h. At 3, 24, and 48 h there was significantly greaterJCafrom the CAP disks and calvariae incubated in Met compared to Ctl; over the entire 48 h time period there was a greater progressive increase inJCafrom the CAP disks than the calvariae incubated in Met. There was no significantJCaat 3, 24, or 48 h from CAP disks or calvariae incubated in Ctl. At 3 h there was significantly greaterJHinto the CAP disks and calvariae incubated in Met compared to Ctl;JHwas greater into the CAP disks than the calvariae. Utilizing a synthetic model of bone mineral we demonstrated that acid medium induces physicochemical calcium efflux and proton influx relative to th

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090210

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

年代:1994

数据来源: WILEY

摘要:

AbstractRisedronate (NE‐58095) is a third‐generation bisphosphonate with very potent antiresorptive activity but few toxic effects. The purpose of this work was to evaluate the effect of risedronate treatment on bone metastases produced in a rat breast cancer model. Berlin Druckrey IV rats inoculated with ENU1564 mammary adenocarcinoma cells were treated daily with risedronate or a saline placebo. Survival times, dictated by extraskeletal metastases (lung, heart, and brain), were not affected by risedronate treatment. Risedronatetreated animals had skeletal changes associated with decreased remodeling of bones undergoing endochondral ossification, most prominently affecting the appendicular skeleton. Despite the skeletal alterations induced by the treatment, the distribution of bone metastases throughout the surveyed skeletal sites was similar for treated and untreated animals. Bone metastases were enumerated in histologic sections of distal femur, spine, and skull. Tumor size was estimated from area measurements obtained from histologic lesions in distal femoral metaphyses and vertebral bodies. A greater number of treated rats had no bone metastases in any of the examined sections (30 versus 16.1% of untreated rats). Multiple bone metastases were observed less frequently in treated rats (33.3 versus 71% of untreated rats). Treated rats had fewer observed bone metastases in each examined site than untreated rats (p≤ 0.025). Mean tumor areas in femora and vertebrae were smaller in treated rats (p≤ 0.05), due to the less frequent presence of very large lesions. In untreated animals, osteoclasts appeared to be active at the tumor/bone interface and osseous structures were often completely replaced by expanding tumors. In contrast, metastases in treated animals caused less disruption of skeletal histoarchitecture. The apparent lack of osteoclastic activity and retention of bone within lesions suggested a decreased contribution of osteoclasts to the bone resorptive process. An in vivo immunohistochemical cell proliferation assay failed to reveal differences in the percentage of dividing tumor cells in bone metastatic sites in treated versus untreated animals. The results demonstrate significant effects of risedronate treatment on the incidence and size of observed skeletal metastases in thi

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090211

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

年代:1994

数据来源: WILEY