摘要:

AbstractThe rate of bone change among postmenopausal women may vary depending upon the initial bone mass. Examining this possibility is difficult, however, because of a negative statistical bias that occurs when change is regressed against the initial value of the same variable. In this article, four statistical methods were applied to measure the association between bone mass and the rate of bone change. The study population was Japanese‐American women, who were monitored for approximately 5 years. Bone changes were determined for the calcaneus and the distal and proximal radius. The results were consistent across the bone sites but differed between statistical methods. Three of the four methods indicated that the women with the greater bone mass had the greater loss rates. The fourth method did not support this association. Possible reasons for the discordant results are discussed. Using the “best” estimate of the relationship, a gradual convergence of bone mass was projected over time toward the population mean. The convergence occurred because women with higher bone mass had a somewhat faster loss rate than women with lower bone mass. Overall, however, the variation in bone mass between individuals was large compared to the rate of conver

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070702

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis study of the in vitro synthesis and mineralization of bovine bone demonstrates that sheets of mineralized matrix can be produced consistently within 18–24 days of cell isolation. Mineralization surpasses that achieved by other systems with other species: The deposition of mineral extends beyond nodules to form branching trabeculae and then solid wafers of bone. Comparison of the fetal age of the bone source, enzyme digestion methods, seeding density, culture surface, nutritive media, and concentration of fetal calf serum and other additives, including insulin and ascorbic acid, has yielded a set of optimal culture conditions. In the presence of ascorbic acid and β‐glycerol phosphate, insulin has a dose‐dependent effect on the morphology of the mineralized bone matrix produced. Quantitative analysis shows that in these cultures calcium accumulates most rapidly between days 6 and 10 after the introduction of mineralization medium but that mineral accretion continues throughout 14–16 days of culture. Alkaline phosphatase levels rise up to 200‐fold, concomitant with a rapid increase in the number of cells per culture during the early mineralization phases; both fall as mineralization proceeds. This system has been used to study the induction of mRNA of type I collagen, alkaline phosphatase, and several noncollagenous bone proteins during the course of mineralization. Because of the degree of mineralization achieved with this system, it has many potential ap

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070703

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn the accompanying study, we report an in vitro culture system from bovine bone cells that can be applied to investigate bone cell growth and differentiation. In this system, bovine bone cells placed in mineralization medium formed multilayers (days 2–3), began deposition of mineral (days 5–6), and eventually acquired a mineralized matrix sheet (days 14–20) through the stages of mineralizing nodules and trabecular‐like structure. In the current study we used this system to investigate the relative expression of bone matrix genes that may play an important role in bone development and metabolism. α1(I)‐collagen, alkaline phosphatase, osteonectin, biglycan (PgI), decorin (PgII), osteopontin, and bone sialoprotein mRNA gene expression were measured on days 0, 2, 6, 10, and 20 (date when the cells were placed in mineralization medium as day 0). Total RNA was purified and analyzed by northern blot using radiolabeled cDNA encoding these genes. To comprehend the relationship between gene expression and mineralization, total calcium content in the cultures was also measured. During the culture period we observed several very different gene expression profiles. The expression of both α1(I)‐collagen and biglycan increased 3‐ to 4‐fold by day 6 and then returned to basal levels by day 20. The osteonectin gene was highly expressed throughout the culture, with no significant increase in induction found during any time of culture. A significant induction of alkaline phosphatase (13.8‐fold) gene expression was observed by day 6. Osteopontin showed a similar profile to that of alkaline phosphatase but had a much greater level of relative expression (26‐fold) compared to day 0. Interestingly, downregulation during mineral accumulation seemed a common occurrence among many of the genes measured. In contrast, the bone sialoprotein gene showed a significant and distinct expression pattern, increasing rapidly after the onset of mineralization on day 6 and ultimately reaching 140‐fold that of day 0. Decorin (Pg II) showed an increasing pattern, with the final relative level of induction 5‐fold on day 20. These data suggest that the development of the mature osteoblastic phenotype, complete with the ability to produce a thick mineralized matrix, requires the differential regulation of a series of genes and their gene product

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070704

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

年代:1992

数据来源: WILEY

摘要:

AbstractBone mineral density (BMD) in the contralateral proximal femur in 100 female elderly patients with hip fracture and the 35 controls without hip fracture were investigated using dual‐photon absorptiometry. The hip fracture patients were divided into intracapsular fracture (n= 53) and extracapsular fracture (n= 47) groups, and these two groups were further divided into five subgroups according to fracture site: intracapsular fracture type 1 (transcervical fracture,n= 29) and type 2 (subcapital fracture,n= 24); extracapsular fracture type 1 (intertrochanteric line fracture,n= 13), type 2 (pertrochanteric fracture,n= 28), and type 3 (combined type of pertrochanteric and subtrochanteric fracture,n= 6). The intracapsular fracture group showed BMD values similar to those of controls; the extracapsular fracture group showed significantly lower BMD values than controls. When these two were subclassified into five subgroups, different results were seen in terms of BMD value in the proximal femur and fracture types; intracapsular fracture type 1 showed BMD values equivalent to those of controls; on the other hand, type 2 showed significantly lower BMD value than controls, and the BMD distribution in the proximal femur among the extracapsular fracture subgroups 1–3 differed, although all of them showed significantly lower BMD values than controls. The degree of trauma causing the fractures was also assessed according to available anamnestic data, but no significant difference was found in trauma tendency between the intra‐ and the extracapsular fracture group or among the subgroups in each group. Based on these results, it is suggested that BMD distribution in the proximal femur is involved in determining hip fracture type in the el

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070705

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

年代:1992

数据来源: WILEY

摘要:

AbstractA substantial body of cross‐sectional data and a smaller number of intervention trials generally justify optimism that regular physical activity benefits the skeleton. We conducted an 8 month controlled exercise trial in a group of healthy college women (mean age = 19.9 years) who were randomly assigned to a control group or to progressive training in jogging or weight lifting. We measured the following variables: bone mineral density (BMD) of the spine (L2–4) and right proximal femur using dual‐energy x‐ray absorptiometry, dynamic muscle strength using the 1‐RM method, and endurance performance using the 1.5 mile walk/run field test. A total of 31 women completed the 8 month study. For women completing the study, compliance, defined as the percentage of workout sessions attended, was 97% for the runners (range 90–1009/0) and 92% (range 88–100%) for the weight trainers. Body weight increased by approximately 2 kg in all groups (p<0.05). Weight training was associated with significant increases (p<0.01) in muscle strength in all muscle groups. Improvement ranged from 10% for the deep back to 54% for the leg. No significant changes in strength scores were observed in the control or running groups. Aerobic performance improved only in the running group (16%,p<0.01). Lumbar BMD increased (p<0.05) in both runners (1.3 ± 1.6%) and weight trainers (1.2 ± 1.8%). These results did not differ from each other but were both significantly greater than results in control subjects, in whom bone mineral did not change. No measure of bone mineral at the proximal femur changed significantly in any group. These results demonstrate that 8 months of supervised progressive training in either running or resistance exercise modestly increases lumbar spine mineral

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070706

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of heparin on osteoclastic bone resorption was studied in vitro using the disaggregated osteoclast resorption assay. Bone resorption was assessed by counting the resorption lacunae on bone slices by light microscopy. Low concentrations of heparin (5 μg/ml) increased bone resorption by isolated chick and rat osteoclasts. Among other glycosaminoglycans tested at 5 μg/ml, only dextran sulfate showed a small but significant stimulation of resorption. Chondroitin sulfates A, B, and C were without effect at 25 and 100 μg/ml, whereas resorption was increased by 100 μg/ml of heparan sulfate. With chick osteoclasts, which could be maintained in serum‐free conditions, a stimulatory effect of heparin was found both in the presence of 5% fetal calf serum and in serum‐free media containing insulin, transferrin, and selenium. The magnitude of the heparin‐induced increase in resorption was similar in the presence or absence of serum. The stimulation of resorption was associated with an increase in the number of osteoclasts on bone slices. Pretreatment of the bone slices with heparin also enhanced resorption. In time course experiments, 5 μg/ml of heparin caused a doubling of chick osteoclast activity index (number of resorption pits per number of osteoclasts) at 12 and 24 h. In 24 h cultures, treatment with 10 μg/ml of the arginine‐rich basic protein, protamine, 1 μg/ml of the immunosuppressant, cyclosporine A, or 5 μg/ml of the cysteine‐proteinase inhibitor, leupeptin, negated the heparin effect on bone resorption. Leupeptin also inhibited basal resorption. We conclude that heparin causes an increase in bone resorption in vitro both by increasing the number of differentiated osteoclasts and by enhancing the activity of indiv

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070707

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

年代:1992

数据来源: WILEY

摘要:

AbstractPursuing the hypothesis that quantitation of skeletal alkaline phosphatase (ALP) activity in canine serum would provide an index of the rate of bone formation, we compared three methods for isoenzyme‐specific identification of skeletal ALP activity in canine serum: heat inactivation, wheat germ agglutinin (WGA) precipitation, and concanavalin A (ConA) precipitation. ALP isoenzyme activities were extracted from canine bone, intestine, and liver, diluted into heat‐inactivated canine serum (i.e., serum without ALP activity), and used as calibrators of ALP isoenzyme activities. Differential sensitivity to inhibition by 10 mM L‐homoarginine was used to distinguish intestinal ALP activity from hepatic and skeletal ALP activities (i.e., 9, 80, and 72% inhibition, respectively). To allow resolution of skeletal ALP activity from hepatic ALP activity, we tested two established methods (heat inactivation and WGA precipitation) and a novel method, ConA precipitation. The organ‐derived skeletal and hepatic ALP isoenzyme activities were used to compare these three methods with respect to linearity, isoenzyme separation, and precision. All three methods were linear, but the WGA and ConA methods afforded greater isoenzyme separation and precision. The relative extent of isoenzyme separation (i.e., the difference in percentage remaining skeletal and hepatic ALP isoenzyme activities) averaged 23, 40, and 47% remaining ALP activity for the heat, WGA, and ConA methods, respectively. However, when these methods were applied to the quantitation of skeletal ALP activity in sera from 10 young and 10 adult beagles, the WGA method was found to be unacceptable because most of the results fell outside the range of the WGA assay calibrators (i.e.,>100% skeletal ALP activity). The heat and ConA methods showed that the amount of skeletal ALP activity in the beagle sera decreased with age, both as ALP activity per liter and as percentage of total serum ALP activity (p<0.001 for each). Skeletal ALP activity levels determined by ConA were correlated with values determined by heat inactivation (r= 0.87,p<0.001) but not with WGA‐determined levels (r = 0.26). Intestinal ALP activity was detected in only 1 of these 20 sera. We conclude that ConA precipitation can be used for quantitation of skeletal ALP activity in bea

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070708

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis study compares the synthesis of mutant type I collagen in cultured dermal fibroblasts and trabecular osteoblasts that were isolated from a patient with moderately severe osteogenesis imperfecta (type IV). Previous study of this patient's dermal fibroblasts revealed a 2000 dalton deletion located in cyanogen bromide peptide 4 of α2(D‐collagen. The phenotype of the bone cell cultures was defined by a 3–4 day logarithmic phase doubling time, predominantly type I collagen production over type III and alkaline phosphatase activity 13.5 times dermal fibroblast levels. The current study revealed that both fibroblasts and osteoblasts synthesized a normal and a shortened α2(I) chain, each as the product of separate alleles. Following pepsin treatment of the procollagens, a shortened α1(I) chain was also seen in both cell types. Cyanogen bromide peptide mapping of osteoblast α‐chains demonstrated the same deletions in the cyanogen bromide peptide 4 as observed in the fibroblast cyanogen bromide maps. PAGE analysis of oligonucleotide‐specific cDNA that was reverse transcribed from RNA isolated from fibroblasts and osteoblasts also demonstrated the presence of two bands, one the normal size of α2(I) cDNA and a second species that was smaller by 54 base pairs. Sequencing of polymerase chain reaction‐amplified cDNA fragments revealed an in‐frame deletion of exon 12. This finding was confirmed by the RNase protection method. Genomic DNA sequencing detected a T→G point mutation in the second position of the 5′ splice donor site of intron 12. Therefore, in this patient with osteogenesis imperfecta there was no qualitative alteration in the osteoblast‐specific expression of this mutant α2(I)‐collagen allele compa

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070709

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

年代:1992

数据来源: WILEY

摘要:

AbstractElectron microscopic studies of calcifying vertebrate tissues reveal the locus of de novo mineral formation within matrix vesicles (MV). The direct involvement of MV in the initiation of mineral formation is supported by the fact that MV isolated from avian growth plate cartilage rapidly accumulate large amounts of Ca2+and Piand induce mineral formation. Exploration of the constituents of MV has revealed two major protein components, a 33 and a 36 kD protein, the former of which binds to cartilage‐specific collagens. These annexin‐like proteins bind to acidic phospholipids in the presence of submicromolar levels of Ca2+. Antibodies raised against both the purified 33 and the 36 kD MV annexin do not cross‐react with the other, indicating that they are distinct proteins. Reported here are studies elucidating the primary structure of both MV proteins using both conventional protein and molecular biologic methods. These studies establish that the 33 kD protein is nearly identical to anchorin CII (annexin V) and that the 36 kD protein is identical to avian annexin II. Immunolocalization studies show that hypertrophic chondrocytes at the calcification front of avian growth plate contain the highest level of these annexins. Further, immunogold labeling indicates that the annexins are localized within MV isolated from the growth plate. Recent studies indicate that annexin V is a new type of ion‐selective Ca2+channel protein that possesses selective collagen binding properties. Since MV are tightly associated with the collagen‐ and proteoglycan‐rich matrix, it is tempting to speculate that this MV protein may be a component of stretch‐activated ion channels that enhance Ca2+uptake during mech

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070710

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe recently reported that estrogen exerts distinct effects on the GH/IGF‐1 axis that are dependent on the route of delivery, probably reflecting a first‐pass effect on hepatic IGF‐1 production. Oral administration reduces IGF‐1 and increases GH levels; transdermal administration elevates IGF‐1 without changing GH concentrations. Since mesenchymal tissue is a target for GH and IGF‐1 action, we studied changes in the GH/IGF‐1 axis following oral (ethinyl estradiol, 20 μg/day) versus transdermal (Estraderm 100 TTS, Ciba Geigy, 100 μg 17β‐estradiol per day) estrogen delivery and compared corresponding effects on connective and bone tissue metabolism. Mean 24 h GH levels, IGF‐1, markers of fibroblast (procollagen III) and osteoblast (procollagen I, osteocalcin) function, and indices of bone turnover (fasting urinary hydroxyproline and calcium to creatinine ratios, UOHPr/Cr and UCa/Cr) were measured before and after 2 months of either oral or transdermal therapy in two groups of postmenopausal women. Transdermal estrogen administration significantly (p<0.05) increased IGF‐1, procollagen III, procollagen I, osteocalcin, and UOHPr/Cr. In contrast, oral estrogen administration had a suppressive effect; the levels of IGF‐1 (p= 0.001), procollagen III (p= 0.018), procollagen I (p= 0.002), osteocalcin (p= 0.015), and UOHPr/Cr (p= 0.004) were significantly different from those measured during transdermal administration. Both treatments significantly reduced UCa/Cr (p<0.015). IGF‐1 changes during estrogen therapy were significantly related (p<0.05) to changes in procollagen III, procollagen I, osteocalcin, and UOHPr/Cr. Transdermally delivered estrogen stimulates IGF‐1 production, increases osteoblastic function, and stimulates bone and nonbone collagen synthesis. When delivered orally, estrogen reduces IGF‐1 and inhibits osteoblastic function; both routes suppress urinary calcium loss. Estrogen administration confers distinct route‐dependent effects on connective and bone tissue metabolism; the specific effects on fibroblast and osteoblast function suggest IGF‐1 dependency. The divergent effects on indices of bone turnover and connective tissue metabolism suggest that the route of estrogen replacement therapy may have different effects on the integrity of

ISSN:0884-0431    

DOI:10.1002/jbmr.5650070711

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

年代:1992

数据来源: WILEY