摘要:

AbstractTo study the association between smoking habits and the incidence of hip fracture, adjusted for leanness and physical inactivity, a cohort study with 3 years follow‐up was conducted. Subjects were 34,856 adults aged 50 years or older who attended a health screening in Nord‐Trøndelag County in Norway in 1984–1986 (91% of eligible subjects in 1986,n= 38,356). Of these, 421 suffered a hip fracture during the years 1986–1989. Using Cox regression models, the relative risk (with 95% confidence interval) of suffering a hip fracture for female smokers versus nonsmokers was 1.5 (1.0–2.4). These results refer to females when the female body mass index (BMI) was set at 25 kg/m2in the female model (the mean BMI for the smoking female population in this study). Among thinner females, however, smoking had a much stronger effect. For instance, if the female BMI was set at 20 kg/m2, the relative risk was 3.0 (1.8–5.0). The relative risk of hip fracture for male smokers versus nonsmokers was 1.8 (1.2–2.9) irrespective of BMI. Smoking is associated with incidence of hip fracture in both sexes and also after adjusting for body mass index and physical inactivity (the effect of physical inactivity was adjusted for self‐reported ill health because ill health was included in the model). For lean females, the association with current smoking was large, as large as if they added 10 ye

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091102

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 investigated the determinants of bone formation at individual remodeling sites (BMUs) in cancellous bone from 8 osteologically normal, sex hormone‐replete women with endometriosis. All were tetracycline double‐ labeled (2, 12, 2, and 4 day regime) before iliac bone biopsy. At each BMU the mineral apposition rate (MAR) was determined conventionally from the distance between label midpoints (MAR 1) and also from the distance between the mineralization front and the trailing edge of the second label (MAR 2). MAR 1 and 2 were compared with within‐BMU measurements of osteoid width (O.Wi) and the activities of osteoblastic alkaline phosphatase (AP) and succinic dehydrogenase (SDH, an enzyme in the Krebs cycle), both quantitated by microdensitometry. A total of 143 BMUs were evaluated, of which 88 were satisfactory for all measurements and 132 were satisfactory for all but SDH. There was a weak correlation (r= 0.34) between MAR 1 and 2 at individual sites, with a mean difference of 0.49 μm/day (mean MAR 0.82 μm/day). The mean MAR of individual subjects tended to be either increasing or decreasing (F= 16.1,p<0.01). In linear regressions, MAR 2 was statistically dependent on O.Wi, AP, and SDH (73% of the variance accounted for). In contrast, MAR 1 was weakly correlated with O.Wi and only 30% of its variance was accounted for by AP, SDH, and O.Wi. The variance in the MAR 2 data was inversely increased (p<0.01) compared with MAR 1 as the number of days of bone formation represented. The data are best explained by large within‐BMU variations in MAR over periods of up to a few days and longer term trends affecting all BMUs. Correlations between fluctuation in MAR and osteoblastic AP and SDH activity suggest that bone formation depends partly on AP activity and osteoblast energy balance. Random obliquity of sectioning has considerable theoretical effects on some correlations (e.g., between O.Wi and MAR), but further investigation emphasized the likely biologic importance of the correlations involving enzyme a

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091103

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:

AbstractMonoclonal antibodies (MAb) may provide valuable tools for studying osteoblast differentiation. We therefore raised a panel of MAb reactive with cells of this phenotype using 1,25(OH)2D3‐treated human trabecular osteoblast‐like cells (HOBS) as the immunogen. Immunohistochemical studies on various tissues, including undecalcified cryostat sections of fetal and adult human bone, identified 11 bone cell‐reactive MAb. Of these, 2 demonstrated particularly selective reactivities against osteocytes (OB/M) and osteoblasts (OB/L). These reactivities were also seen in developing bone from rat, rabbit, and marmoset. OB/L and OB/M demonstrated limited reactivity against a small number of human tissues from the extensive panel of substrates tested. Both MAb exhibited reactivity against discrete populations of cells in the large and small intestine. In addition, OB/L reacted with cells in the basal epidermis of skin and OB/M with cells in blood vessel walls. Both antibodies demonstrated reactivity against a variety of cultured osteoblast‐like cell lines and other cultured cell types. These MAb may therefore provide a valuable means of studying osteoblast o

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091104

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:

AbstractAlthough the osteocyte is the most abundant among the highly differentiated cells of mature bone (osteocytes, lining cells, osteoblasts, and osteoclasts), its properties and functions are the least known and understood. Here we isolated osteocytes from mixed populations of bone cells liberated from fetal chick calvariae by alternate treatments with collagenase and EDTA. The osteocytes were removed from the bone cell populations by binding them via an osteocyte‐specific antibody (MAb OB 7.3) to magnetic beads and removing the beads together with the coupled osteocytes from the population using a magnet. Isolated osteocytes were found to be highly differentiated, postmitotic cells that required their typical stellate morphology in culture. Osteocyte populations had alkaline phosphatase (ALP) activity somewhat lower than that of the osteoblast‐like cell populations from which they were separated by the immunodissection procedure. On the single‐cell level, the ALP activity was highly variable. Parathyroid hormone (PTH) receptors were found to be present on osteocytes as well as on osteoblast‐like cells, but not on fibroblast‐like cells of the outer periosteum. In response to PTH, osteocytes increased their intracellular levels of cAMP, as did the osteoblast‐like cells. Osteocytes appeared to be somewhat more sensitive to PTH than osteoblasts. When seeded onto dentin slices, osteocytes did not corrode the dentin surface to any appraisable degree. We therefore found no evidence to support the notion that osteocytes play a role in the calcium homeostasis through osteocytic osteolysis. Whether osteocytes play an important role in perceiving and transducing hormonal and/or mechanical stimuli remains open for futu

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091105

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:

AbstractAbundant multinucleated cells (MNCs) are formed in cocultures of mouse osteoblastic cells and marrow cells in the presence of 1α, 25‐dihydroxyvitamin D3[1α, 25(OH)2D3], and these cells have the properties of osteoclasts (OCs). In this study using the mammalian OCs, we tried to clarify the role of glucocorticoids (GCs) in calcitonin receptors (CTR) and CT‐responsive cAMP production in OCs. Dexamethasone (DEX) dose and time dependently enhanced the specific binding of [125I]salmon calcitonin (sCT). When the MNCs were preincubated with DEX for 24 h, the effect was evident at 10−9M and the maximum effect was obtained at 10−7M. The effect developed over 12–48 h at doses of 10−9and 10−6M DEX. The numbers of CTR‐positive mononuclear cells and MNCs were not altered by the DEX treatment. Prednisolone and triamcinolone reproduced the DEX effect, but 17 β‐estradiol, progesterone, testosterone, aldosterone, and 1α, 25(OH)2D3did not. RU486, a GC receptor antagonist, attenuated the effect of DEX to enhance the specific binding of [125I]sCT. From a Scatchard plot analysis, DEX enhanced CTR number (212 ± 64%) with a minimal change in the affinity to sCT. Autoradiographic studies using [125I]sCT showed that DEX enhanced the density of the grains on the tartrate‐resistant acid phosphatase (TRAP)‐positive MNCs and mononuclear cells, but not on other types of cells. DEX preincubation also enhanced sCT‐stimulated but not prostaglandin E2‐ or forskolin‐stimulated cAMP production. Inhibition of enhancement was possible with cycloheximide, indicating this effect was mediated through de novo protein synthesis. The present study showed that GCs play an important role in the regulation of CT effect through the upregulation of CTR on OCs, and this effect would explain, at least partly, a potentiation by GCs of hypocalcemic action

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091106

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:

AbstractType X collagen is produced by hypertrophic chondrocytes and serves as a highly specific marker for chondrocyte maturation. This study was designed to compare the expression of type II and type X collagen in growth plate sections and in distinct populations of chondrocytes in culture by in situ hybridization. Growth plate sections were treated with type II and type X collagen cDNA probes. Type II collagen mRNA was present throughout the growth plate but greatest in the lower proliferating and upper hypertrophic regions. In contrast, type X collagen was expressed only in the hypertrophic region. Northern analysis confirmed the specificity of the probe for type X collagen mRNA. Chick growth plate chondrocytes were separated by countercurrent centrifugal elutriation into five distinct populations and plated in serum‐containing medium. These cultures were examined at varying times after plating for the expression of type II and type X collagen mRNA. At 3 h, type II collagen was present in the majority of the cells in all fractions, and approximately 15–20% of the cells expressed type X collagen mRNA. The cells expressing type X were from the hypertrophic region. At 24 h, however, nearly all cells in culture expressed type X mRNA, and there was a decrease in expression of type II collagen mRNA. Similar results were obtained in cultures in the absence of serum, and SDS‐PAGE analysis of collagen synthesis confirmed the expression of type X collagen in all populations of fractionated cells at 24 h at the protein level. Type X collagen is an important marker through which cellular matruation can be evaluated in culture. The rapid induction of type X collagen in culture and its evaluation through in situ hybridization permit the investigation of factors that enhance or delay the development of cell hypertrophy and maturation. This may have important implications for the understanding and study of endochondral ossification and fracture r

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091107

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 mechanisms underlying the effects of recombinant human growth hormone (rhGH) on vitamin D, mineral, and bone metabolism are not known. We examined whether these effects are mediated by parathyroid hormone (PTH) by measuring renal phosphorus (P) and calcium (Ca) handling, serum calcitriol, and markers of bone turnover for 24 h before and 72 h after an infusion of hPTH(1–34) in eight healthy postmenopausal women at baseline and following short‐term (1 week) and sustained (5 weeks) rhGH treatment. On short‐term rhGH, serum phosphorus and basal TmP/GFR were unaffected, but the fall in TmP/GFR after hPTH infusion was exaggerated (integrated response: −99.2 ± 22.3 versus −144.1 ± 15.0 minute‐mg/dl,P= 0.0021). Basal calcitriol levels rose from 115 ± 17 to 163 ± 16 pM (P= 0.0002), but the increase in calcitriol following hPTH infusion was unaffected by short‐term rhGH. The basal Ca excretion index (CEI) rose from 0.054 ± 0.005 to 0.073 ± 0.007 mM (P= 0.0095), but markers of bone turnover were unaffected. With sustained rhGH treatment, serum P (1.47 ± 0.05 mM), basal TmP/GFR (4.29 ± 0.24 mg/dl), and basal CEI (0.067 ± 0.005 mM) were elevated compared with control values, and the PTH‐induced lowering of TmP/GFR was again enhanced (‐ 158.7 ± 22.8 minute‐mg/dl,P= 0.0021). Basal calcitriol concentrations returned to control levels (108 ± 10 pM), but the calcitriol response to hPTH remained unchanged. Markers of bone remodeling were elevated with sustained rhGH treatment. Neither short‐term nor sustained rhGH affected plasma ionized Ca, serum PTH levels, or the magnitude of the acute hydroxyproline, calcitriol, or cAMP responses to hPTH. We conclude that GH has PTH‐independent effects on renal phosphate handling and 1α‐hydroxylase activity, exerting its effects at a postreceptor ste

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091108

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:

AbstractThis study determined the areal bone mineral density (BMD) from the lumbar spine (L2–4), right distal radius and ulna, and the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia, and calcaneus of both extremities in 29 men who had a femur shaft fracture 10 years earlier. For evaluation of the patients' BMDs in the spine and distal forearm, 29 age‐, weight‐, and height‐matched normal men were also measured. Compared with normal men (mean ± SD = 1.123 ± 0.153), the spinal BMDs of the patients were significantly (p= 0.0054) lower (1.018 ± 0.119, −9.3%). Distal radius and distal ulna showed no significant group differences. In patients, the mean BMD of the injured extremity (compared with the uninjured side) was significantly lower in the distal femur (‐6.8%;p= 0.0000), patella (‐5.4%;p= 0.0000), proximal tibia (‐4.7%;p= 0.0000), and calcaneus (‐2.2%;p= 0.0259). In the proximal femur, this value was at the same level (femoral neck 1.3%, NS) or higher (trochanter area 6.3%,p= 0.0002) than that in the uninjured extremity. The relative BMDs of the injured extremity did not associate with the fracture type, fracture location, age, muscle strength, follow‐up time, or non‐weight‐bearing time but showed significant (r= 0.33–0.64) positive correlation with low pain assessment and high functional scores of the injured extremity. The relative BMDs were especially strongly associated with the four‐step functional classification of the International Knee Documentation Committee: the higher the functional class of the injured extremity, the less bone loss caused by the injury (p= 0.0001–0.0328). In conclusion, the femur shaft fracture results in permanently reduced bone density in the lumbar spine and lower parts of the injured extremity. The proximal femur is not affected. The observed decrease (9% in spine and 5–7% in the knee region of the injured limb) is clinically important with respect to age‐related bone loss of 1% per year after the age of peak bone mass. Additional follow‐up is needed to determine any increased risk of osteoporotic fractures in spine and injured extremity. Recovery of normal limb function seem

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091109

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:

AbstractPrevious research in our laboratory has shown basic fibroblast growth factor (bFGF) to be a permissive mitogen for isolated avian growth plate chondrocytes. The present study was conducted to determine whether bFGF is present in avian growth plate and, if present, to determine its localization within the tissue. Immunohistochemical studies revealed that bFGF is present in the resting proliferative and hypertrophic calcifying zones of the growth plate but is absent from the prehypertrophic zone. Basic FGF appears to be associated with the extracellular matrix of the proliferative zone, but it is predominantly intracellular in the hypertrophic and mineralizing zone chondrocytes. Partial purification of cartilage‐derived bFGF was performed on crude extracts of cartilage using heparin‐Sepharose affinity chromatography. The presence of bFGF in the heparin‐Sepharose column fractions was confirmed by immunoblotting and radioimmunoassay. Furthermore, western blot analysis of the extracts showed multiple protein bands having bFGF immunoreactivity, in the molecular weight range 14.4–18 kD. The data support the hypothesis that bFGF has a dual role in the growth plate. In the proliferative zone it acts as a chondrocyte mitogen, whereas when released from terminal hypertrophic chondrocytes, bFGF may serve as a chemotactic signal for metaphyseal blood vessel prolif

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091110

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:

AbstractBone mineral density (BMD) of the phalanges of the hand was measured by the technique of radiographic absorptiometry (RA) in 199 older postmenopausal women previously determined to have normal BMD by dual‐energy x‐ray absorptiometry (DXA) and quantitative computed tomography (QCT). The average age of the women was 66.8 ± 4.9 years, and they were 19.9 ± 6.7 years postmenopause. In the 54 black women, phalangeal BMD was 11.7% greater than in the 145 white women, a difference comparable to that found using DXA at the radial midshaft, the lumbar spine, and femoral neck. A correlation matrix comparing BMD measured by RA to BMD measured by DXA and QCT indicates that, in general, RA was related to the various DXA and QCT measurement sites as well as these sites were related to each other. When results for RA, DXA, and QCT obtained in our cohort of older women were compared to available reference data for peak adult bone mass, the average difference (SD units) from peak value was greatest for RA (‐1.77 radius, −1.24 spine, −2.13 femoral neck, −2.34 QCT spine, and −2.71 phalanges). We conclude that RA is an acceptable measure of phalangeal BMD and that the data in our cohort can serve as reference data for older white and black women aged 55–75 years. Once the ability of RA to predict future fracture occurrence has been demonstrated, it could be rapidly deployed as a low‐cost, widely available bone mass me

ISSN:0884-0431    

DOI:10.1002/jbmr.5650091111

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