ISSN:0884-0431    

DOI:10.1002/jbmr.5650090902

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 cross‐sectional population‐based study examined the effect of age and sex on bone mineral density (BMD) in the elderly. BMD was measured at the spine and hip using dual‐energy x‐ray absorptiometry and at midshaft and ultradistal radius using single‐photon absorptiometry in 672 men and 981 women aged 50–98 years. In both sexes, mean BMD levels decreased significantly with age at all sites except the male spine. In linear regression models, the slope of loss was significantly greater in women than in men at all sites except the ultradistal radius. The slope was steeper at most sites in women aged 50‐59 years than in older women, 60‐98 years. In both age groups, mean age‐adjusted BMD levels were lower at all sites in women who were past or never users of replacement estrogen than in women who were current estrogen users. Current estrogen users generally had lower slopes of loss with age than never or past estrogen users; however, few of these differences were statistically significant. We conclude that BMD levels decrease in old age in both sexes. Continued bone loss in old age raises the possibility that intervention to retard further loss may still be warrant

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090903

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:

AbstractEpidemiologic evidence suggests that lifestyle factors, such as exercise, calcium intake, and tobacco consumption, have effects on bone density. However, the influence of these factors in the elderly has not been well documented. To examine the effects of lifestyle factors in the elderly, we measured bone density (BMD) at the lumbar spine and proximal femur in 709 elderly men and 1080 women participating in the Dubbo Osteoporosis Epidemiology study (DOES), a community‐based, longitudinal, epidemiologic study of osteoporosis in men and women over the age of 60. BMD was significantly higher in men than in women (20% at all sites). There was an age‐related decline in BMD at the femoral neck in both sexes and at the lumbar spine in women. Between the ages of 60 and 80, the decrease in BMD at the femoral neck among women was 18.9%, which is almost twice the decrease in BMD among men (10.1%). Tobacco consumption was associated with a reduction in BMD at both sites in both sexes (5‐8%), and this effect was independent of calcium intake or body weight. Exsmokers had BMD intermediate between that of current smokers and never smokers, suggesting the influence of tobacco was partially reversible. Quadriceps strength predicted bone density at the proximal femur in elderly men but not in women. Analyzing BMD (adjusted for age and weight) in tertiles of muscle strength and calcium intake revealed an interaction between calcium intake and muscle strength on bone density; BMD at the femoral neck among those with higher quadriceps strength and calcium intake was approximately 5% higher (P<0.05) than in those with low quadriceps strength and calcium intake in both men and women. These data indicate that lifestyle factors, such as tobacco consumption, calcium intake, and physical activity, may influence bone density in the elderly. Modification of these lifestyle factors may influence osteoporotic fracture risk in elderly men and

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090904

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:

AbstractGrowth factors, such as transforming growth factor β (TGF‐β) and insulin‐like growth factors (IGF) I and II, have been shown to exert anabolic effects on bone cells in vitro. Hormones, such as PTH and probably insulin and growth hormone, were recently shown to stimulate bone formation in vivo as well. The aim of the present study was to assess by northern blots, which were quantitated by densitometry, the effects of these anabolic growth factors and hormones in two osteogenic cell populations: CRP 10/30 cells, a clonal cell population derived from primary rat calvarial cells, and IRC 10/30‐myc cells, which were established from CRP 10/30 by immortalization. Transcripts for α1(I) collagen, biglycan, osteonectin, osteopontin, and osteocalcin were detected in both cell populations, which is consistent with the phenotype expressed by mature osteoblasts. There were no difference in the basal expression of bone matrix mRNAs between the two cell populations. PTH increased α1(I) collagen mRNA levels in both osteoblastic cells but had no effect on the biglycan transcripts. Neither insulin nor growth hormone affected mRNA levels of either matrix protein after 24 h exposure. All three growth factors, TGF‐β, IGF‐I, and IGF‐II, increased α1(I) collagen transcripts in a time‐ and dose‐dependent manner in both cell populations. Biglycan mRNA levels were enhanced in both osteoblastic lines only by IGF‐I and IGF‐II, but not TGF‐β. The transcriptional effect was ascertained by nuclear run‐on assays or actinomycin inhibition. When the effects of TGF‐β, IGF‐I, and IGF‐II on the expression of α1(I) collagen and biglycan mRNAs were compared in the two cell populations, there was a similar pattern of response. The only significant difference between the immortalized cell line and the parent cell population was a stronger stimulation of α1(I) collagen mRNA by TGF‐β and a delayed increase in biglycan mRNA levels in IRC 10/30‐myc. The results show that the immortalized cell line IRC 10/30‐myc is useful to study the modulation of two osteoblastic markers, α1(I) collagen and biglycan mRNA, in response to exogenous factors. Biglycan is little modulated and only by IGFs, whereas PTH, IGF‐I and II, and TGF‐β strongly increase α1(I) collagen transcripts, con

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090905

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 evaluate the effects of tiludronate on the mass, structure, and turnover of cancellous bone regions in immobilized rat tibiae, we performed a 4 week dosing experiment. The right hindlimbs of 84 Sprague‐Dawley rats (5 weeks old) were neurectomized or sham operated. Animals were assigned to seven groups (n= 12 each); group 1 was sham operated, and groups 2‐7 were neurectomized. Groups 1 and 2 were given vehicle only (distilled water), and groups 3, 4, and 5 were given tiludronate orally at doses of 25, 50, and 100 mg/kg body weight (BW)/day, respectively, throughout the experimental period. Group 6 was given 100 mg/kg BW/day of the agent for the first 2 weeks only, and group 7 received vehicle only for the first 2 weeks and then 100 mg/kg BW/day of the agent for the last 2 weeks. After tetracycline labeling was performed, the right tibiae were removed from the animals and processed to yield undecalcified sections. Histomorphometry was performed in the epiphyseal, primary, and secondary spongiosa of the proximal tibia. In group 2, trabecular bone volume (BV/TV) and trabecular number (Tb.N) were significantly decreased in the primary and secondary spongiosae, but this did not occur in the epiphyseal spongiosa. Osteoid surface (OS/BS) was decreased and osteoclast surface (Oc.S/BS) was increased in the secondary spongiosa. Tiludronate increased BV/TV and Tb.N in the primary spongiosa by reducing the values for the parameters of osteoclast surface (Oc.S/BS) and osteoclast number (Oc.N/BS). Osteoid surface in this region was not decreased by the agent. In groups 4 and 5, tiludronate prevented bone loss in the secondary spongiosa by reducing both OS/BS and Oc.S/BS. In group 6, BV/TV in the primary spongiosa was maintained at the level of group 1, but Oc.S/BS and Oc.N/BS were elevated. In the secondary spongiosa, bone mass was preserved and the reduction in these parameters was maintained. In group 7, however, BV/TV was increased in the primary spongiosa as a result of a reduction in osteoclastic resorption; in the secondary spongiosa, however, BV/TV was decreased and trabecular turnover was not reduced at the end of the experiment in these growing animals. Mineral apposition rates were not reduced by tiludronate. This study clearly demonstrated that this agent prevented immobilization bone loss by inhibiting resorption. The histomorphometric data suggest that (1) tiludronate begins to act early after administration in the primary spongiosa and rather late in the secondary spongiosa, and (2) the bone matrix is involved in the antiresorbing action of this bisphosphon

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090906

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 cause of bone loss in patients with osteoporosis is not known, but both increased bone resorption and decreased bone formation have been reported. Theoretically, these effects may result from either increased activity of osteoclasts or decreased activity of osteoblasts, or both. In vivo, growth hormone (GH) administration leads to activation of osteoclasts and osteoblasts as evidenced by increased biochemical markers of bone resorption and bone formation. To test for disturbances in responsiveness of bone cells to exogenous hormonal stimuli in osteoporosis, we compared 15 patients with postmenopausal osteoporosis with 15 healthy age‐matched postmenopausal women before and during a 3 day stimulation test with GH (0.2 IU/kg/day). Serum insulin‐like growth factor I increased in both groups (p<0.001). GH treatment increased biochemical markers of bone resorption (serum carboxyl‐terminal telopeptide of type I collagen [ICTP] [p<0.001] and, to a lesser extent, 24 h urinary hydroxyproline/creatinine) in the two groups. Similarly, biochemical markers for bone formation increased in both groups [osteocalcin (p<0.01) and procollagen type I C‐terminal propeptide, PICP (p<0.001)]. GH treatment reduced alkaline phosphatase (ALP,p<0.05) and its bone‐specific isoenzyme (bone ALP,p<0.01) in both groups. The maximal response, the area under the curve (AUC) of response curves for IGF‐I, bone resorption markers, and bone formation markers were not different between groups. Our data do not support the hypothesis that osteoporotic patients display major disturbances in responsiv

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090907

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:

AbstractPatterns of intact parathyroid hormone (iPTH) elimination and subsequent recovery of parathyroid function were studied in seven patients undergoing surgical removal of solitary hyperfunctioning parathyroid adenoma. Using a sensitive two‐site immunoradiometric assay, iPTH levels were measured pre, peri‐, and postoperatively. Blood samples were taken at very early and at late stages, including 3, 6, 9, and 15 minutes and 48, 72, and 96 h after adenomectomy. A biexponential formula was calculated to fit the decreasing values of iPTH in all patients. The PTH half‐life in the early phase was 1.4 + 1.1 minutes (95% confidence limits). The PTH half‐life in the second phase was 64.45 + 32.19 minutes (95% confidence limits). A third phase is represented by a slow, linear increase in plasma iPTH values as a result of the recovery of healthy suppressed parathyroid glands. The extrapolation to baseline of the later phase shows that the recovery of normal parathyroid function begins as soon as 240 minutes after adenomectomy and is independent of the decrease in PTH of adenomatous origin. All individual results were consistent with this model. Five patients had iPTH values below 5 pg/ml, one had 15 pg/ml, and the last had 27 pg/ml 5 h after parathyroid adenomectomy. The recovery of the hormonal activity of the remaining glands occurred rapidly. By the postoperative hour 24 the mean serum iPTH concentration was 12.28 + 8.07 pg/ml. The intraoperative serum iPTH concentration offers a model to assess both recovery of hormonal secretion from functionally suppressed parathyroid glands and disappearance of parathyroid

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090908

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:

AbstractBAPN, sodium fluoride, and hydrocortisone are reported to induce altered mineralization states. Three separate sets of experiments, one set for each agent, were performed using male New Zealand white rabbits. In each experiment the rabbits were segregated into groups, each fed a specified weight‐determined dose for 13 weeks and then sacrificed. Compact bone from the left femur and tibia were tested for density, composition, sonic velocity, longitudinal elastic modulus, equatorial diffraction spacing of mineralized collagen, diaphyseal cross‐sectional area, and relative load stress. β‐Aminopropionitrile (BAPN) induced monotonic degradation of all properties at all dose levels, corresponding to the decreasing density with dosage level. The elastic moduli show a decrease; the equatorial diffraction spacing of the collagen increases. The cross‐sectioned diaphysis resembled woven bone. The variability in properties increased with dosage. The total cross‐sectional area for a given weight increased, implying that the decreased elastic properties were compensated for by a larger area to support the weight. There was a slight increase in average density and other properties for fluoride‐treated rabbits, peaking at 20 mg/kg BW/day. For higher dosages the properties are degraded and the values were much lower at high fluoride dosages than for BAPN. There was no peak for the equatorial diffraction spacing, which increased with dosage. It is inferred that the fluorosed apatite is denser than normal apatitic mineral and therefore has a smaller specific volume. A greater weight fraction of fluorosed mineral has a smaller volume fraction than the equivalent normal apatitic mineral. The bone sections look more normal, except for the porosis. The total cross‐sectional area decreases when the bone density increases and then increases as the density falls, again implying that the area required to support body weight depends on the magnitude of the elastic moduli. There was a small change in some of the properties of the bones of the hydrocortisone‐treated rabbits, but the effects on others were undetectable within the uncertainty of the procedures. There was no change in the cross‐sectional area

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090909

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 purpose of this study was to determine and compare the force attenuation properties of various external trochanteric padding materials under in vitro conditions simulating characteristic falling of the elderly. The selected materials had to be practically suitable for external hip padding so that the main criteria for the materials were good energy absorbing capacity, good durability, low weight, good recovery after compression, easy availability, and reasonable price. Eight materials met these requirements. The first six were flexible cross‐linked polyethylene foams with densities from 30 to 200 kg/m3. The seventh material was Plastazote polyethylene foam, and the eighth foam was made of ethylene‐vinyl acetate (EVA) copolymer. With a pendulum effective mass of 39 kg, impact velocity of 3.0 m/s, and impact force of 8.2 kN, the force attenuation provided by the 20 mm thick hip‐padding materials was quite small, ranging from 22 to 38%. With all these materials the peak femoral force remained above 5 kN, more than two times above the femoral fracture threshold (2 kN). In the second set of experiments, the impact force was gradually reduced until the tested materials lowered the impact force below the fracture threshold. With the most efficient material this critical falling velocity was found to be 1.6 m/s. To go below the fracture threshold with the realistic impact velocity of 3.0 m/s, the padding materials had to be 100‐140 mm thick. In conclusion, our test results strongly suggest that using reasonable thicknesses of the currently available hip padding materials, the impact forces clearly remain above the fracture threshold, and therefore, prevention of hip fractures by external protectors should be based on other ideas (increase in the impact surface and/or shunting of impact energy away from the greater trochanter) than hip paddin

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090910

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:

AbstractRabbit osteoclasts and rabbit osteoblast‐like stroma cells (OB cells) were plated onto plastic surfaces and the migration patterns of individual osteoclasts and osteoclast‐OB interactions were analyzed with time‐lapse recording. To induce directed migration, the cultures were exposed to an electrical field of 0.01 or 0.1 V/mm. At 0.1 V/mm, osteoclasts moved directly toward the anode in some cases, clearing OB cells from their path of migration. In other cases, osteoclasts migrated toward the anode for part of the time but then changed direction and moved toward groups of OB cells. Observations were made on osteoclasts interacting with single OB cells or small colonies and on osteoclasts interacting with OB monolayers, at both field strengths; the results were independent of field strength. There were several characteristic behaviors. With single OB cells and small OB colonies, retraction of OB cells upon contact with the osteoclast was the predominant mechanism whereby these cells begin to move out of the path of the osteoclast. A pronounced ruffling or blebbing of the OB cell membrane often followed retraction. When osteoclasts displaced OB cells that were part of a monolayer, extension of an osteoclast lamellipodium underneath the edge of the OB cell layer generally preceded partial retraction of the OB cells involved. It sometimes appeared as if the detached or partially detached OB cells were “pushed” by the osteoclast, which in some cases resulted in OB cells being moved hundreds of μm in a period of a few hours, at rates comparable to the normal speed for osteoclast migration (⋍100 μm/h), much faster than the normal speed for OB cells (⋍10 μm/h). These results imply that osteoclasts have mechanisms to move OB cells out of their path of migration. Further, when these cells were plated onto devitalized bone slices, resorbing osteoclasts apparently were able to clear a path through the OB cells. Laser scanning fluorescent measurements showed that there was no general intracellular [Ca2+] increase in OB cells following contact with osteoclasts, suggesting that an intracellular [Ca2+] signaling cascade does not play a role in the OB displacement. These data support the hypothesis that osteoclasts obtain access to the bone surface by actively displacing osteoblasts or lining cells at sites earmarke

ISSN:0884-0431    

DOI:10.1002/jbmr.5650090911

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