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  • 1
    Electronic Resource
    Electronic Resource
    Impact near the hip dominates fracture risk in elderly nursing home residents who fall (1993)
    Springer
    Calcified tissue international 52 (1993), S. 192-198 
    Details
    ISSN: 1432-0827
    Keywords: Hip fracture ; Falls ; Osteoporosis ; Biomechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Hip fractures among the elderly are a significant and rapidly growing public health problem. The prevailing view is that most hip fractures are the consequence of age-related bone loss or osteoporosis. However, because over 90% of hip fractures are the result of falls, we have undertaken a falls surveillance study to determine if factors related to the mechanics of falling are associated with increased risk of hip fracture. Case subjects with hip fracture and control subjects without hip fracture were sampled from falls recorded at the Hebrew Rehabilitation Center for Aged, a chronic care facility. Fall information was obtained by interview of the subject and witnesses if the fall was witnessed. Data were analyzed by multiple logistic regression. Increased risk of hip fracture from a fall was associated with impacting on the hip or side of the leg and potential energy associated with the fall. Quetelet, or body mass index, was inversely related to fracture risk. The adjusted odds ratio of hip fracture for a fall involving impact on the hip region was 21.7 (95% confidence interval, 8.2–58). The potential energy associated with these falls was an order of magnitude greater than the average energy required to fracture elderly, cadaveric, proximal femurs in earlier in vitro experiments. We conclude, therefore, that a fall from standing height should no longer be considered minimal trauma but rather trauma of sufficient magnitude to pose a high risk of hip fracture if impact occurs on the hip and if energy-absorbing processes are inadequate. These new findings suggest that fall mechanics play an important role in the etiology of hip fracture among the elderly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298717
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  • 2
    Electronic Resource
    Electronic Resource
    Permafrost aggradation and peat accumulation since 1200 years B.P. in peat plateaus at Tuchitua, Yukon Territory (Canada) (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 3-17 
    Details
    ISSN: 1573-0417
    Keywords: peat types ; peat depositional rates ; permafrost development ; peat plateaus ; climatic change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Floating and grounded peat plateaus were studied in fens in the Yukon Territory (Canada). The peat deposit may be over 4 m thick and consists of a lower bed of aquatic peat overlain by humic fen peat, mesic fen peat and woody peat. Permafrost in the grounded peat plateaus is older than the 1200 year old White River Ash, whereas permafrost in the floating peat plateau is younger. Peat accumulation rates since 1200 years B.P. were greater in the fens (85–100 cm) than on the surface of the peat plateaus (25–55 cm). Where the peat plateau is free-floating, it will persist until the climate changes, causing the icy core to thaw. Where the peat plateau is frozen to the mineral substrate, it slowly drowns since the fen peat accumulates faster than the woody peat. This drowning results in degradation of the landform independently of the climate. Only degradation of floating peat plateaus can be used to identify climatic changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00677986
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  • 3
    Electronic Resource
    Electronic Resource
    Eigentheory of the inhomogeneous Fokker-Planck equation (1977)
    Springer
    Journal of statistical physics 17 (1977), S. 377-381 
    Details
    ISSN: 1572-9613
    Keywords: Fokker-Planck equation ; eigentheory ; Brownian motion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ambiguities that occur in the existing eigentheory of the inhomogeneous Fokker-Planck equation are resolved. The eigenfunction expansion is shown to be identical to the known exact solution, generalizing an earlier result for the space-homogeneous case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01014405
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  • 4
    Electronic Resource
    Electronic Resource
    Hall coefficient in solution for a simple dynamical model (1970)
    Springer
    Journal of statistical physics 2 (1970), S. 379-385 
    Details
    ISSN: 1572-9613
    Keywords: Ion, solvent fluid ; applied electrical and magnetic fields ; transport coefficients ; non-Brownian effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A model Liouville equation is proposed for a system composed of an ion moving in a solvent fluid. Using this model, explicit results are obtained for the Ohmic conductivityL and the Hall conductivityh. These results are then used to calculate the Hall coefficientR = ehL−2, which is a measure of the effect of non-Brownian motion, for several charge carriers of interest. Our results are in agreement with earlier findings based on a stochastic model which predictR 〉 1 for H+(aq). Our results also indicate thatR ≈ 1 for charge carriers such as Na+, Cl−, and K+ which have a mass greater than that of a solvent molecule (here taken as 18 amu).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01020444
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  • 5
    Electronic Resource
    Electronic Resource
    Bone Morphogenetic Protein 2 (BMP-2) Enhances BMP-3, BMP-4, and Bone Cell Differentiation Marker Gene Expression During the Induction of Mineralized Bone Matrix Formation in Culturesof Fetal Rat Calvarial Osteoblasts (1997)
    Springer
    Calcified tissue international 60 (1997), S. 283 -290 
    Details
    ISSN: 1432-0827
    Keywords: Key words: BMP-2 — BMP-3 — BMP-4 — mRNA expression — Paracrine — Bone cell differentiation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Normal bone formation is a prolonged process that is carefully regulated and involves sequential expression of growth regulatory factors by osteoblasts as they proliferate and ultimately differentiate. Since this orderly sequence of gene expression by osteoblasts suggests a cascade effect, and BMP-2 is capable of initiating and maintaining this effect, we examined the effects of BMP-2 on expression of other BMPs and compared these effects with the expression pattern of bone cell differentiation marker genes in primary cultures of fetal rat calvarial (FRC) osteoblasts. To examine the gene expression profile during bone cell differentiation and bone formation, we also examined the effects of rBMP-2 on bone formation in vivo and in vitro. rBMP-2 stimulated bone formation on the periosteal surface of mice when 500 ng/day rBMP-2 was injected subcutaneously. When rBMP-2 was added to primary cultures of FRC osteoblasts, it accelerated mineralized nodule formation in a time and concentration-dependent manner (10–40 ng/ml). rBMP-2 (40 ng/ml) enhanced BMP-3 and -4 mRNA expression during the mineralization phase of primary cultures of FRC osteoblasts. Enhancement of BMP-3 and -4 mRNA expression by rBMP-2 was associated with increased expression of bone cell differentiation marker genes, alkaline phosphatase (ALP), type I collagen, osteocalcin (OC), osteopontin (OP), and bone sialoprotein (BSP). These results suggest that BMP-2 enhances expression of other BMP genes during bone cell differentiation. BMP-2 may act in a paracrine fashion in concert with other BMPs it induces to stimulate bone cell differentiation and bone formation during remodeling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900230
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of broadband ultrasound attenuation to single X-ray absorptiometry measurements at the calcaneus in postmenopausal women (1994)
    Springer
    Calcified tissue international 54 (1994), S. 87-90 
    Details
    ISSN: 1432-0827
    Keywords: Calcaneus ; Ultrasound ; Bone mineral density ; Precision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Broadband ultrasound attenuation (BUA), a radiation-free and portable technology, may be useful in assessing bone density and fracture risk. In this study, we compared cross-sectional BUA measurements to the more established single energy X-ray absorptiometry measurements of bone mineral density (BMD) at the calcaneus in 259 healthy postmenopausal women, aged 45–76 years. Paired measurements with repositioning of the subject's dominant heel were made consecutively by each method. A coefficient of variation (CV) for each method was calculated for each individual from the paired scans. BUA and BMD of the heel were also compared with BMD of the lumbar spine and femoral neck, as measured by dual energy X-ray absorptiometry. BUA was significantly correlated with BMD at the calcaneus (r=0.66, P〈0.01). Heel BUA was also correlated with lumbar spine BMD (r=0.43, P〈0.01) and femoral neck BMD (r=0.43, P〈0.01) but the correlations were lower than those between heel BMD and spine (r=0.63, P〈0.01) or femoral neck BMD (r=0.62, P〈0.01). The mean CV for heel BUA (3.60±3.50%) was significantly greater than that for heel BMD (1.06±0.99%, P〈0.01). The moderate correlation of calcaneal BUA and BMD, the lower correlations of BUA than heel BMD with both spine and hip BMD, and lower precision of BUA indicate BUA does not predict bone density as effectively as absorptiometry, the current standard methodology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296056
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  • 7
    Electronic Resource
    Electronic Resource
    Weight, Body Composition, and Bone Density in Postmenopausal Women (1996)
    Springer
    Calcified tissue international 59 (1996), S. 428-432 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Body composition — Body weight — Bone density — Postmenopausal women — DXA.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Associations of body weight and body composition with bone mineral density (BMD) were examined in 261 postmenopausal women. BMD, body fat, and body nonfat soft tissue (NFST) were measured by dual-energy X-ray absorptiometry (DXA). A height-independent BMD variable (HIBMD) was calculated to correct for differences among individuals in bone thickness, a dimension that is ignored by DXA scanners. HIBMD was calculated as BMD divided by height at the spine and femoral neck, and BMD divided by the square root of height at the total body. Weight, fat, and nonfat soft tissue were all positively correlated with both BMD and HIBMD, but the magnitudes of regression and correlation coefficients were lower when HIBMD was the dependent variable. The weight-independent associations of body composition with HIBMD were examined by including weight and % NFST together in linear models. In these analyses, weight was positively associated with HIBMD at all three skeletal sites (r = 0.22–0.26, P 〈 0.05), % NFST was not associated with HIBMD at the spine or femoral neck (r = 0.01–0.02), and there was only a weak inverse correlation of % NFST with total body BMD (r =−0.12, P 〈 0.05). These findings are consistent with those of previous studies demonstrating positive associations between body weight and BMD. In addition, they demonstrate that once bone thickness and body weight are taken into account, body composition appears to have little if any independent effect on bone density at the skeletal sites measured. This finding is consistent with the hypothesis that the protective effect of body weight is brought about predominantly through its mechanical force on the skeleton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369205
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  • 8
    Electronic Resource
    Electronic Resource
    Weight, body composition, and bone density in postmenopausal women (1996)
    Springer
    Calcified tissue international 59 (1996), S. 428-432 
    Details
    ISSN: 1432-0827
    Keywords: Body composition ; Body weight ; Bone density ; Posimenopausal women ; DXA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Associations of body weight and body composition with bone mineral density (BMD) were examined in 261 postmenopausal women. BMD, body fat, and body nonfat soft tissue (NFST) were measured by dual-energy X-ray absorptiometry (DXA). A height-independent BMD variable (HIBMD) was calculated to correct for differences among individuals in bone thickness, a dimension that is ignored by DXA scanners. HIBMD was calculated as BMD divided by height at the spine and femoral neck, and BMD divided by the square root of height at the total body. Weight, fat, and nonfat soft tissue were all positively correlated with both BMD and HIBMD, but the magnitudes of regression and correlation coefficients were lower when HIBMD was the dependent variable. The weight-independent associations of body composition with HIBMD were examined by including weight and % NFST together in linear models. In these analyses, weight was positively associated with HIBMD at all three skeletal sites (r=0.22–0.26, P〈0.05), % NFST was not associated with HIBMD at the spine or femoral neck (r=0.01–0.02), and there was only a weak inverse correlation of % NFST with total body BMD (r=-0.12, P〈0.05). These findings are consistent with those of previous studies demonstrating positive associations between body weight and BMD. In addition, they demonstrate that once bone thickness and body weight are taken into account, body composition appears to have little if any independent effect on bone density at the skeletal sites measured. This finding is consistent with the hypothesis that the protective effect of body weight is brought about predominantly through its mechanical force on the skeleton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369205
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of Human Tumor Cell Lines on Local New Bone Formation In Vivo (1997)
    Springer
    Calcified tissue international 60 (1997), S. 210 -215 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Bone formation — Tumor — Calvaria — Growth factor — Histomorphometry.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Although some tumors cause osteolytic lesions, there are some that stimulate new bone formation. This is an important phenomenon because the responsible mechanisms probably represent an aberration of normal physiological bone formation, and identifying the factors involved in the process may lead to new therapies for various bone diseases. To clarify our understanding of the potential mechanism responsible, we compared and quantitated the extent of new bone formation stimulated by human tumors (HeLa, Hep-2, AV-3, FL, WISH and KB), some of which have osteogenic activity in vivo [2]. Tumor cells were injected over the calvaria of nude mice to examine formation of new bone. The tumor cells produced three histologically distinct patterns of new bone growth: (1) WISH and KB stimulated appositional bone growth adjacent to periosteal bone surfaces; (2) HeLa and Hep2 induced new bone growth over calvarial surface even when distant from the tumor mass; (3) FL stimulated bone formation adjacent to periosteum as well as ectopic bone formation in sites distant from bone. All tumors except AV3 induced mean new bone thickness 〉100 μm, and Hep-2 cells produced bone 330 μm thick. PCR and Northern blot analysis of mRNA isolated from cultured tumor cells revealed that all cell lines expressed mRNA for TGFβ, (fibroblast growth factor) FGF-1, FGF-2, and IGF-I, and most cell lines produced mRNA for PDGF. Only FL expressed large amounts of mRNA for BMP2. In serum-free conditioned media from Hep2 and HeLa cells purified by heparin affinity chromatography, we have identified FGF-1, FGF-2, and PDGF by immunodetection with specific antibodies. Our results show that new bone growth caused by these tumors is likely due to the production of bone growth factors by the tumor cells, and that the overall effects on bone may be due to several factors working in concert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900216
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  • 10
    Electronic Resource
    Electronic Resource
    Estrogen Effects on Insulin-Like Growth Factor Gene Expression in a Human Osteoblastic Cell Line with High Levels of Estrogen Receptor (1998)
    Springer
    Calcified tissue international 62 (1998), S. 60-66 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Estradiol — Osteoblast — PCR — Bone.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Insulin-like growth factors (IGF)-I and IGF-II are produced by osteoblasts and are important paracrine/autocrine regulators of osteoblast proliferation and differentiation. Estrogen has been reported to increase gene expression of IGF-I in rodent osteoblasts. However, because species differences have been demonstrated in expression of various aspects of the IGF system in bone cells, it is not known whether this action also occurs in human osteoblasts. Thus, we assessed the effects of estrogen treatment on IGF-I and IGF-II gene expression in vitro in a recently developed human fetal osteoblast cell line that has high levels of estrogen receptors. As assessed by a quantitative reverse transcriptase-polymerase chain reaction method, treatment of hFOB/ER9 cells with 17β-estradiol (E2) increased steady state levels of IGF-I mRNA in a time- and dose- dependent fashion with a maximal increase of 319% ± 33% (P 〈 0.01) of control occurring after treatment with 10−7 M E2 for 48 hours. In contrast, E2 did not alter steady state levels of IGF-II mRNA. The pure (type 2) antiestrogens ICI 182,780 (10−7 M) and ICI 164,384 (10−6 M) blocked the E2- induced increase in IGF-I mRNA levels. Interestingly, 4-hydroxytamoxifen (10−7 M), a documented pure antiestrogen in reproductive tissues, also increased IGF-I mRNA to levels similar to those observed in E2-treated cells. Since E2 was shown to mediate its effects on some target genes through a cAMP-dependent pathway, we studied the interaction between E2 and agents that are known to increase intracellular cAMP. Forskolin (10−8 M) and dibutyryl cAMP (10−3 M) increased IGF-I mRNA levels sixfold, and cotreatment with E2 did not affect these changes, consistent with a possible mediation of the estrogen effect on IGF-I gene expression by cAMP. We conclude that in human osteoblastic cells, the IGF-I gene is a target for estrogen action, suggesting that IGF-I may mediate part of the effects of estrogen in human bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900395
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