ISSN:0736-0266    

DOI:10.1002/jor.1100140102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe cellular and biochemical mechanisms that direct destruction of bone at the site of tumor osteolysis are unknown. In order to understand this process better, a murine model designed for the study of tumor osteolysis was developed and the influence of osteolytic and nonosteolytic tumors on bone was investigated. Tumors developed following femoral intramedullary injection of sarcoma (2472) and melanoma (G3.26) cell lines: however, only tumors from the 2472 cell line caused osteolysis. It was determined that 2472 tumor‐induced osteolysis commenced 6 days after the femora had been inoculated with 2472 cells. There were more osteoclasts per millimeter of bone surface in 2472 tumor‐bearing limbs (16.7 ± 5.0) than in sham‐injected limbs (3.8 ± 0.9) (p<0.015). In addition, an increase in the osteoclast size (area) was detected in 2472 tumor‐bearing limbs: 412 ± 65 μm2compared with 187 ± 17 μm2(p<0.01).In vitrobone resorption experiments indicated that 2472 tumor cells had a limited ability to destroy bone in comparison with macrophages and osteoclasts. Taken in total, these findings define a model that is useful for the study of tumor osteolysis, and the data from analyses of the model demonstrate that the cellular mechanisms responsible for 2472 tumor‐induced osteolysis include both an increase in the number of osteoclasts and activation of mat

ISSN:0736-0266    

DOI:10.1002/jor.1100140103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractWith use of a solenoid to generate uniform time‐varying electric fields, the effect of extremely low frequency electric fields on osteoclast‐like cell formation stimulated by 1,25(OH)2D3was studied in primary murine marrow culture. Recruitment of osteoclast‐like cells was assessed by counting multinuclear, tartrateresistant acid phosphatase positive cells on day 8 of culture. A solenoid was used to impose uniform time‐varying electric fields on cells: sham exposures were performed with an identical solenoid with a null net electric field. During the experiments, both solenoids heated interiorly to approximately 1.5°C above ambient incubator temperature. As a result of the heating, cultures in the sham solenoid formed more osteoclast‐like cells than those on the incubator shelf (132 ± 12%). For this reason, cells exposed to the sham solenoid were used for comparison with cultures exposed to the active coil. Marrow cells were plated at 1.4 × 106/cm2in square chamber dishes and exposed to 60 Hz electric fields at 9.6 μV/cm from days 1 to 8. Field exposure inhibited osteoclast‐like cell recruitment by 17 ± 3% as compared with sham exposure (p<0.0001). Several variables, including initial cell plating density, addition of prostaglandin E2to enhance osteoclast‐like cell recruitment, and field parameters, were also assessed. In this secondary series, extremely low frequency fields inhibited osteoclast‐like cell formation by 24 ± 4% (p<0.0001), with their inhibitory effect consistent throughout all variations in protocol. These experiments demonstrate that extremely low intensity, low frequency sinusoidal electric fields suppress the formation of osteoclast‐like cells in marrow culture. Thein vitroresults supportin vivofindings that demonstrate that electric fields inhibit the onset of osteopenia and the progression of osteonecrosis: this suggests that extremely low frequency fields may inhibit osteoc

ISSN:0736-0266    

DOI:10.1002/jor.1100140104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe adaptive bone remodeling in the proximal tibia following medial meniscectomy was measured quantitatively by dual photon absorptiometry. Thirty‐three patients who had undergone a meniscectomy (randomized to either total [n = 19] or partial [n = 14]meniscectomy) performed by open joint surgery approximately 12 years earlier were included in the study. Bone mineral density was measured in the previously injured legs and in the healthy contralateral legs in areas located medially and laterally in the cortical bone of the subchondral plates and below in the trabecular bone of the medial and lateral tibial condyles. The distribution of bone mineral within the proximal tibia showed a characteristic and significant pattern. In the trabecular bone of the healthy contralateral knees, bone mineral density was 15% higher in the medial tibial condyles compared with the values laterally: a total or partial meniscectomy increased this difference to 25%. With regard to the cortical bone of the subchondral plates, the bone mineral density in the healthy knees was 24.8–29.4% higher medially than laterally, whereas after total and partial meniscectomy the differences were, respectively, 37.7 and 41.4%. No significant differences in the distribution of bone mineral density, at either cortical or trabecular measuring sites, were found between totally and partially meniscectomized kn

ISSN:0736-0266    

DOI:10.1002/jor.1100140105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractOur goal was to understand developmental determinants of femoral structure during growth and sexual maturation by relating femoral measurements to gender and developmental factors (age, pubertal stage, height, and body mass). The bone mineral content of the femur was measured by dual energy x‐ray absorptiometry in 101 healthy Caucasian adolescents and young adults, 9–26 years of age. After some simplifying assumptions had been made, cross‐sectional geometric properties of the femoral midshaft were estimated. Two geometry‐based structural indicators, the section modulus and whole bone strength index, were calculated to assess the structural characteristics of the femur. Femoral strength, as described by these structural indicators, increased dramatically from childhood through young adulthood. Regressions were performed between these femoral measurements and the developmental factors. Our data show that of age, pubertal stage, body mass, and height, body mass is the strongest predictor of femoral cross‐sectional properties, and the correlation of body mass with femoral cross‐sectional structure is independent of gender. A model including all four developmental factors and gender did not substantially increase the accuracy of predictions compared with the model with body mass alone. In light of previous research, we hypothesize that body mass is an indicator ofin vivoloading and that thisin vivoloading influences the cross‐sectional growth of t

ISSN:0736-0266    

DOI:10.1002/jor.1100140106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the role of tumor necrosis factor alpha in bone resorption secondary to mediator release from macrophages exposed to cement particles. The J774 mouse macrophage cell line was exposed to polymethylmethacrylate particles for 24 hours and the resulting conditioned medium was analyzed for prostaglandin E2, tumor necrosis factor alpha, interleukin‐1 alpha and beta, and the ability to stimulate release of prostaglandin E2and45Ca from radiolabeled mouse calvaria. Macrophage exposure to polymethylmethacrylate particles led to a 9‐fold increase in release of tumor necrosis factor alpha (p<0.01), but did not lead to a significant increase in release of prostaglandin E2, interleukin‐1 alpha, or interleukin‐1 beta when compared to unexposed cells. Exposure of the macrophages to polymethylmethacrylate particles over a time course from 30 minutes to 96 hours led to an increase in the release of tumor necrosis factor alpha that was initially detected at 30 minutes and was maximum at 48 hours. Incubation of the macrophage‐polymethylmethacrylate conditioned medium with rat calvaria significantly increased the release of45Ca and prostaglandin E2from the bone. To study the role of release of tumor necrosis factor alpha in bone resorption, the macrophage‐polymethylmethacrylate conditioned medium was then preincubated with anti‐tumor necrosis factor alpha antibody prior to exposure of the conditioned medium to the calvaria. This preincubation was successful in significantly inhibiting45Ca release by calvaria (p<0.01) to levels that were not significantly different from the levels of release by unexposed calvaria. Tumor necrosis factor alpha appears to play a critical role in initiating particulate‐induced bone resorption. Exposure of macrophages to polymethylmethacrylate particles leads to a significant release of tumor necrosis factor alpha in a time‐dependent fashion. This macrophage‐polymethylmethacrylate conditioned medium stimulated release of prostaglandin E2and bone resorption in bone organ culture. The addition of anti‐tumor necrosis factor alpha antibody to thisin vitrosystem inhibited the bone resorption stimulated by the macrophage‐polymethylmethacrylate conditioned medium and partially suppressed the production of prostaglandin E2. The sequence of events in this model for particulate‐induced bone resorption appears to be initiated by the production of tumor necrosis factor alpha by the macrophage, followed by production of prostaglandin E2by cells in bone, an

ISSN:0736-0266    

DOI:10.1002/jor.1100140107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractLarge cyclic movements between the femoral stem and bone during the first weeks after total hip arthroplasty may hamper bone ingrowth and adversely affect the eventual success of the arthroplasty. Little is known, however, about the magnitude of the motions and its relationship to design and surgical factors. A two‐dimensional finite element model of a cementless prosthesis inserted into the proximal femur was constructed to study the effects of two mechanical variables—the stiffness of the implant and the coefficient of friction between bone and implant—on the magnitude of the motions. We investigated the influences of these variables on the subsidence of the prosthesis, the magnitudes of the cyclic motions, and the level of the interface stresses. The presence of friction reduced cyclic motions by about 85% compared with a frictionless interface. Once friction was assumed, varying the coefficient of friction had little effect. The effect of friction on the interface stress state and gross subsidence of the prosthesis was not as great as on cyclic motion. Implant stiffness also affected the magnitudes and distributions of the cyclic motions along the interface. A flexible stem generated motions about three to four times larger proximally than those of a stiff stem, which generated larger motions distally. The influence of stem stiffness on interface stresses and prosthetic subsidence was less than on cyclic motion. The location of the peak shear stresses at the interface around a bonded prosthesis corresponded to the location where cyclic interface motion was maximal for an unbonded prosthesis. However, no direct relationship was found between the magnitudes of peak stresses and the amplitudes of cyclic mo

ISSN:0736-0266    

DOI:10.1002/jor.1100140108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe effects of fetal bovine serum, insulin‐like growth factor‐I, and fibnoblast growth factor‐2 on the regulation of the functional physical properties of adult bovine cartilage explants during an incubation period of 18–20 days was determined, and the relationship between the measured functional properties of the cartilage and the tissue composition was assessed. Cartilage disks were tested in the uniaxial radially confined configuration by the application of low amplitude oscillatory displacement and measurement of the resultant load and streaming potential. For the control cartilage terminated just after explant, the modulus was 0.39 ± 0.28 MPa, the open circuit hydraulic permeability was 2.0 ± 1.0 × 10−15m2/(Pa•c), and the electrokinetic (streaming potential) coefficient was −2.3 ± 0.6 mV/MPa. Incubation of cartilage in medium supplemented with serum or insulin‐like growth factor‐I resulted in maintenance of the modulus and electrokinetic coefficient, whereas incubation in basal medium or medium supplemented with fibroblast growth factor‐2 led to a marked decrease from control values in the modulus and the amplitude of the electrokinetic coefficient. All of the culture conditions examined resulted in an increase in permeability that was not statistically significant. The variation in the electromechanical properties of all the cartilage samples tested was related to the density of tissue proteoglycan and collagen (hydroxyproline). The modulus was correlated with both the density of tissue proteoglycan (+0.014 MPa/[mg/ml]) and the density of tissue hydroxyproline (+0.008 MPa/[mg/ml]). The electrokinetic coefficient was also correlated with the density of proteoglycan (−0.080 [mV/MPa]/[mg/ml]) and the density of hydroxyproline (+0.064 [mV/MPa]/[mg/ml]). These data indicate that the regulation of chondrocyte matrix metabolism by growth factors can significantly affect the physical properties

ISSN:0736-0266    

DOI:10.1002/jor.1100140109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThis study tested the effects of hydrostatic pressure (10 MPa) on adult articular chondrocyte mRNA and extracellular matrix synthesisin vitro. High density primary cultures of bovine chondrocytes were exposed to hydrostatic pressure applied intermittently at 1 Hz or constantly for 4 hours in serum‐free medium or in medium containing 1% fetal bovine serum, mRNAs for aggrecan, types I and II collagen, and β‐actin were analyzed by Northern blots and quantified by slot blots. Proteoglycan synthesis was quantified by35SO4uptake into cetylpyridinium chloride‐precipitable glycosaminoglycans, and cell‐associated aggrecan and type‐II collagen were detected by immunohistochemical techniques. In serum‐free medium, intermittent pressure increased aggrecan mRNA signal by 14% and constant pressure decreased type‐II collagen mRNA signal by 16% (p<0.05). In the presence of 1% fetal bovine serum, intermittent pressure increased aggrecan and type‐II collagen mRNA signals by 31% (p<0.01) and 36% (p<0.001), respectively, whereas constant pressure had no effect on either mRNA. Intermittent and constant pressure stimulated glycosaminoglycan synthesis 65% (p<0.001) and 32% (p<0.05), respectively. Immunohistochemical detection of cell‐associated aggrecan and type‐II collagen was increased in response to both intermittent and constant pressure. These data support the hypothesis that physiologic hydrostatic pressure directly influences the extracellular matrix metabolism of ar

ISSN:0736-0266    

DOI:10.1002/jor.1100140110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe mechanical strength of connective tissues is dependent on the integrity of their fibrillar collagen frameworks. The objective of the present study was to assess type‐II collagen damage (denaturation) in the adult human intervertebral disc compared with articular cartilage, in order to determine whether damage to this molecule may vary in different anatomical sites in the same person. A new immunochemical assay was used to measure the amounts of denatured and total type‐II collagen in the annulus fibrosus and nucleus pulposus of the L5‐S1 disc and in cartilage from the femoral condyles of the same individuals (n = 7). Denaturation of type‐II collagen was significantly higher in both the annulus fibrosus and the nucleus pulposus than in articular cartilage. Such increased damage to type‐II collagen in the adult disc may have relevance to the more pronounced degenerative changes observed in this tissue compared with articular

ISSN:0736-0266    

DOI:10.1002/jor.1100140111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY