摘要:

AbstractThe comparison of patient data among different dual x‐ray absorptiometry (DXA) scanners is complicated because no universally accepted cross‐calibration procedure or standard currently exists. This study was performed under the auspices of the International DXA Standardization Committee to establish appropriate cross‐calibration parameters. Posteroanterior (PA) lumbar spine measurements of 100 women, ages 20–80 years (mean 52.6 + 16, range of BMD = 0.4–1.6 g/cm2) were obtained on a Norland XR26 Mark II, a Lunar DPX‐L, and a Hologic QDR 2000 densitometer using standard procedures (pencil beam mode for all three scanners). Area, BMC, and BMD results from the different scanners were compared for all patients. In addition, the European spine phantom (ESP) and the European spine phantom prototype (ESP prototype), as well as standard phantoms from all three manufacturers, were evaluated on the three systems. To achieve universal scanner calibration, we used the intercept and slope of the patient's correlations and the value of the middle vertebra of the ESP as a reference point in a series of standardization formulas, and we have expressed the results as sBMD (mg/cm2). The correlations of the patients' spinal BMD values were excellent for each of the three scanner pairs. The average absolute difference in patient spinal BMD values (L2–4) between Hologic and Norland was 0.012 g/cm2(1.3%); it was 0.113 g/cm2(11.7%) between Hologic and Lunar and 0.118 g/cm2(12.2%) between Norland and Lunar. The phantoms' regression lines approximated those of the patient regression lines, and the phantoms with only one measurement point were very close to the patients' regression lines. After applying the standardization formulas, the average absolute differences for the 100 patients were 28 mg/cm2(2.7%) for Hologic/Norland, 23 mg/cm2(2.2%) for Hologic/Lunar, and 29 mg/cm2(2.8%) for Norland/Lunar. Average BMD results for the patients before correction were 0.972 g/cm2for Hologic, 1.100 g/cm2for Lunar, and 0.969 g/cm2for Norland. After correction, sBMD results for patients were 1045 mg/cm2for Hologic, 1047 mg/cm2for Lunar, and 1043 mg/cm2for Norland. The standardization approach as performed in our study provided compatibility of DXA results obtained on diffe

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091002

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 computer simulation of the bone‐remodeling transient is described, in which the focus is explicitly on changes in clinically measurable bone mass (or density). Based upon quantitative remodeling data accumulated by histomorphometry and calcium tracer kinetics, the simulation shows that much of the apparent gain in bone produced by several agents currently employed to treat osteoporosis can be explained as a remodeling transient rather than as a fundamental alteration of remodeling balance. Even gains as large as 30% or more can be produced by nothing more than the remodeling transient under certain plausible combinations of basal remodeling rate, remodeling period, and degree of bone loss. The simulation further highlights the importance, in evaluating bone‐active agents, of separating the response across the first remodeling period from bone changes that may ensue thereaf

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091003

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:

AbstractTo assess bone mineral density (BMD) in idiopathic calcium nephrolithiasis, dual‐energy x‐ray absorptiometry was performed at lumbar spine, upper femur (femoral neck, Ward's triangle, and total area), distal tibial diaphysis, and distal tibial epiphysis in 110 male idiopathic calcium stone formers (ICSF); 49 with and 61 without hypercalciuria on free‐choice diet). Results were compared with those obtained in 234 healthy male controls, using (1) noncorrected BMD, (2) BMD corrected for age, height, and BMI, and (3) a skeletal score based on a tercile distribution of BMD values at following four sites: lumbar spine, Ward's triangle, tibial diaphysis, and tibial epiphysis. After correction, BMD—and therefore also skeletal score—tended to be lower in the stone formers than in controls at five of the six measurement sites, that is, lumbar spine, upper femur, Ward's triangle, tibial diaphysis, and tibial epiphysis, limit of significance being reached for the last two sites without difference between hypercalciuric (HCSF) and normocalciuric stone formers (NCSF). Estimated current daily calcium intake was significantly lower in patients (616 + 499 mg/24 h, mean + SEM) than in controls (773 + 532,p= 0.02). Of 17 patients who in the past had received a low‐calcium diet for at least 1 year, 10 had a low skeletal score (4‐6) whereas only 1 had a high score (10‐12;p= 0.037). Of the 12 stone formers in the study with skeletal score 4 (i.e., the lowest), 8 had experienced in the past one or more fractures of any kind versus only 19 of the remaining 77 patients with skeletal score 5‐12 (p= 0.01). Significant correlations were found between corrected BMD at various sites and 24 h sulfate, uric acid and sodium excretion, and urinary pH, as well as serum uric acid concentration. BMD at tibial diaphysis was negatively correlated with pyridinoline/ creatinine concentration ratio in 24 h urine samples, and skeletal score was negatively correlated with fasting hydroxyprolinuria. In summary, there is a slight decrease in skeletal mineral content in idiopathic calcium stone formers at the tibial site that appears to be related at least in part to dietary habits (low‐calcium diet and animal protein and sodium intake) experience

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091004

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:

AbstractWe examined the in vivo effects of recombinant murine IL‐4 (rmIL‐4) on spontaneous and stimulated mouse osteoclast formation. EC‐GI cells, which produce PThrP and IL‐1α, were explanted in nude mice. These EC‐GI cell‐bearing nude mice developed hypercalcemia (4.90 + 0.68 mM), and the calcium levels were decreased to near normal (3.48 + 0.73 mM,p<0.05) at day 3 by continuous infusion of rmIL‐4 at a dose of 7 μg/day. When infused with 0.6 nmol/day of PTHrP(1‐34) in ICR mice, rmIL‐4 at a dose of 1 or 5 μg/day for 3 days caused a marked inhibitory effect on hypercalcemia induced by PTHrP(1‐34) (3.73 + 0.56‐2.54 + 0.14 mM,p<0.01). However, rmIL‐4 alone did not change the serum calcium in mice. Histomorphometric analysis revealed that rmIL‐4 inhibits both spontaneous and PTHrP(1‐34)‐stimulated osteoclast formation in mice, with a decrease in osteoclastic surface and in the number of osteoclasts per mm bone surface, respectively. We conclude that IL‐4 inhibits spontaneous and stimulated bone resorption resulting from inhibition of osteoclast formation and modulates the development of h

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091005

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:

AbstractSodium fluoride treatment of osteoporosis is known to stimulate bone formation and to increase bone mass, but recent clinical trials failed to prove its antifracture effectiveness. The formation of bone with abnormal structure and, therefore, increased fragility is discussed as a possible explanation. Until now, however, exact information on the mineral structure of osteoporotic bone after fluoride treatment has been lacking. Bone biopsies were taken from three patients with postmenopausal osteoporosis before and after fluoride treatment (60 mg NaF/day for 1‐2 years), from one patient with iatrogenic fluorosis, as well as from three normal controls. The mineral in these samples was investigated by a combination of backscattered electron imaging and small‐angle x‐ray scattering. Depending on the total dose of fluoride, an increasing amount of new bone is laid down on the surface of preexisting trabeculae. Its mineral structure is identical to that of heavy fluorosis and is characterized by the presence of additional large crystals, presumably located outside the collagen fibrils. These large crystals, which are not present in the controls or in osteoporotic bone before fluoride treatment, contribute to increase the mineral density without significantly improving the biomechanical properties of the bone. The possible success of fluoride treatment depends not only on the amount of newly formed bone but also on the rate of bone turnover. Indeed, as soon as significant amounts of fluoride are present, bone turnover leads to the replacement of old (normal) bone by new (pathologically mineralized) bone. In particular, in the case of high turnover rates we expect fluoride therapy even to lead to a deterioration in the overall mechanical stability of the ske

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091006

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 expression of the mRNAs for osteonectin (ON), osteopontin (OPN), osteocalcin (OC), and matrix Gla protein (MGP) was studied by in situ hybridization during the healing process of an experimental fracture in adult rat femora. At day 1 postoperatively, ON mRNA was detected in the proliferating periosteum. At day 3, ON, OPN, and OC mRNAs were detected in woven bone. From day 5, MGP and ON mRNAs were detected in the immature chondrocytes. From day 7, ON, OPN, and OC mRNAs were detected in the osteoblastic cells in newly formed endosteal trabecular bone. OPN mRNA was also detected in some of the osteocytes in trabecular bone. From day 14, OPN and MGP mRNAs were detected in newly formed periosteal hypertrophic chondrocytes, and the ON, OPN, and OC mRNAs were detected in osteoblastic cells in newly formed periosteal trabecular bone. Although the cell types that expressed each mRNA in fractured bones were similar to those in embryonic bones, the time course of these mRNA expression in fractured bones was different from that in embryonic bones. We considered that this system is useful to investigate the phenotypic change in osteogenic and chondrogenic lineage cells that appears during fracture healing at the molecular level.

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091007

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 effect of treadmill exercise on bone loss in ovariectomized (OVX) rats was studied in two different sets of experiments. In the first experiment rats were either ovariectomized (n= 38) or sham operated (n= 18) at the age of 12 weeks. Half the OVX rats were trained twice a day for 30 minutes by running at 10 m/minute for 7 or 17 weeks. In the second experiment 40 female rats, aged 12 weeks, were divided into five groups (n= 8). One group of rats was sacrificed on day 0 for the baseline data. Other rats were sham operated or ovariectomized for 9 weeks. Half of both groups were trained using the same training program as in the first experiment. OVX reduced trabecular bone volume (TBV) in the distal femur to 42.7 and 48.3% in 8 and 18 weeks, respectively. Exercise opposed this effect significantly but could not prevent it totally. Exercise did not have any significant effect on sham‐operated animals. OVX induced a 17.7 and 30.7% decrease in maximal failure load of femoral neck in 8 and 18 weeks, respectively. A corresponding decrease was also observed in the torque capacity of tibia. Exercise was able to prevent almost totally the decrease in bone strength of femoral neck, tibia, and humerus. In conclusion, our results suggest that the measurement of bone strength in aging female rat femoral neck can be used as a useful indicator of the deleterious effect of OVX in bone. These results further indicate that exercise can overcome a significant part of the decrease in trabecular bone volume and maintain the mechanical strength of femoral neck and tibial shaft in the OVX rat

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091008

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:

AbstractDiseased or necrotic tissue can become calcified in a way that resembles bone. We examined soft tissues for the presence and regulation of the mRNA for the bone‐associated protein, osteocalcin (OC). RNA was isolated from liver, kidney, lung, brain, muscle, and bone of young (2 months) male SD rats and analyzed for β‐actin, IGF‐I, metallothionein IIa, α1collagen, calbindin‐D9k(CaBP), and OC mRNA by reverse transcription‐polymerase chain reaction (RT‐PCR). All PCR products but CaBP were found in bone; CaBP was present only in duodenum, kidney, and lung. OC product was detected in all tissues; the identity of the PCR product was confirmed by sequencing. Bone OC mRNA levels were calculated to be 1000‐fold higher than duodenal levels. Rats fed a 0.8% strontium diet for 7 days to drive down serum 1,25‐dihydroxyvitamin D3levels [1,25(OH)2D3] and then injected with 300 ng 1,25(OH)2D3/100 body weight had increased duodenal CaBP (2.5‐fold) and femur OC mRNA (2.2‐fold) 24 h after treatment. Duodenal OC mRNA was unchanged. OC mRNA was found in nondiseased human aortae, and the amount of message was elevated in calcified aorta and calcified aortic plaques. These results demonstrate that (1) tissues other than bone have low basal expression of OC mRNA, (2) OC mRNA is not regulated by vitamin D in nonosteoid tissue, and (3) expression of OC mRNA in atherosclerotic aorta reflects a role for bone‐forming cells in ectopic bone formation observed in cer

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091009

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:

AbstractIt has been shown that a specific inhibitor of vacuolar H+‐ATPases, bafilomycin A1, inhibits bone resorption by isolated chicken osteoclasts by blocking the proton pump in the ruffled border membrane. We report here the effects of bafilomycin A1on bone resorption in vivo. Using a cannulated osmotic minipump delivery system, we infused bafilomycin locally to the eruption pathway of permanent premolars of beagle dogs. We used pit formation by osteoclasts in vitro to estimate the concentrations and heat stability of bafilomycin to be used in vivo. In this model, osteoclasts were cultured on thin bone slices, in which they form pits indicative of resorption. After 2 weeks preincubation at 37°C, bafilomycin concentrations of 10−6and 10−7M but not 10−8M completely inhibited the resorptive activity of cultured osteoclasts, and the two larger doses were chosen for use in vivo. Local delivery of 10−6M bafilomycin to the eruption pathway of the fourth permanent mandibular premolar during mideruption inhibited tooth eruption by blocking bone resorption as assayed by radiography, light microscopy, and scanning electron microscopy. Bafilomycin at 10−7M had similar but less intensive effects. Moreover, osteoclasts in the alveolar bone of crypts treated with 10−7M bafilomycin A1stained very weakly for tartrate‐resistant acid phosphatase. The effect of bafilomycin on bone resorption was shown to be very local, and no side effects of treatment with bafilomycin were observed in adjacent teeth or the behavior of dogs. We report here, for the first time, inhibition of tooth eruption caused by inhibited bone resorption using bafil

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091010

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:

AbstractEffects of calcitonin peptides, including human calcitonin (hCT), salmon calcitonin (sCT), and calcitonin gene‐related peptide (CGRP), on the secretion of testosterone and luteinizing hormone (LH) in male rats were studied. Male rats were injected intravenously with human chorionic gonadotropin (hCG), calcitonin peptides, or hCG plus calcitonin peptides. Blood samples were collected at several intervals following hormone challenge. In an in vitro experiment, testis blocks were incubated with hCG (0, 0.05, 0.5, or 5 IU/ml) or hCG (0.5 IU/ml) plus calcitonin peptides (0–10−9or 10−6M) at 34°C for 30 minutes. Both medium and plasma samples were extracted by ether and analyzed for testosterone by radioimmunoassay (RIA). The concentration of calcium in each plasma sample was measured by an automatic calcium analyzer. The anterior pituitary gland (AP) was incubated with or without calcitonin peptides (0–10 nM) at 37°C for 30 minutes. They were then incubated with gonadotropin releasing hormone (GnRH, 10 nM) for a further 30 minutes. The concentration of LH in AP medium was measured by RIA. The accumulation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in both testicular tissues and APs were measured by RIA. A single intravenous injection of calcitonin peptides decreased the basal and hCG‐stimulated levels of plasma testosterone gradually from 60 to 180 or 360 minutes after challenge. The plasma calcium was not altered by the injection of calcitonin peptides and/or hCG. Administration of calcitonin peptides in vitro resulted in a dose‐dependent inhibition of both basal and hCG‐stimulated release of testosterone. Meanwhile, calcitonin peptides caused a dose‐dependent inhibition of the basal release of LH in vitro from rat APs. The content of cAMP in both testes and APs was increased by all calcitonin peptides. Neither hCT nor sCT altered the content of cGMP in testes and APs. These results suggest that calcitonin peptides, including hCT, sCT, and CGRP, inhibit the spontaneous and gonadotropin‐stimulated secretion of testosterone by acting directly at testes and reducing the release of pituitary LH through a mechanism involving an increa

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091011

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