摘要:

AbstractThe calcium‐mobilizing agents thapsigargin and 2.5‐di‐(tert‐butyl)‐1,4‐benzo‐hydroquinone were shown to markedly elevate the intracellular calcium concentration of chick embryo chondrocytes in a dose‐dependent manner. Under these conditions, the metabolism of macromolecules was variably affected. The synthesis and secretion of protein in general, and of collagen in particular, were significantly inhibited; in contrast, proteoglycan synthesis (but not glycosaminoglycan synthesis) was inhibited, whereas secretion was unaffected. Flunarizine, which prevented the thapsigargin‐induced intracellular calcium elevation, and EGTA, which caused only a transient thapsigargin‐induced intracellulr calcium elevation, did not reverse these alterations. It was concluded, therefore, that the observed effects of thapsigargin and 2,5‐di‐(tert‐butyl)‐1,4‐benzohydroquinone on chondrocyte macromolecule metabolism were not related to the ability of these drugs to increase the cytosolic free calcium concentration but may have been due to the specific depletion of the calcium sequestered in the endoplasmic reticulum. The differential effect of these drugs on protein and proteoglycan secretion suggests that the intracellular trafficking of these two classes of macromolecules ma

ISSN:0736-0266    

DOI:10.1002/jor.1100120502

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

年代:1994

数据来源: WILEY

摘要:

AbstractAging of articular cartilage results in accumulation of aggrecan fragments of various sizes that retain their ability to aggregate even though they may have relatively few glycosaminoglycan chains. Residual binding of partially degraded aggrecan may prevent binding of newly synthesized aggrecan subunits that have greater numbers of glycosaminoglycan chains. This study was undertaken to determine the effects of various relative molar ratios of intact aggrecan, link proteins, and hyaluronic acid binding region fragments on the structure of reconstituted aggregates. High molar ratios of link proteins relative to aggrecan decreased the spacing between adjacent aggrecan subunits; low molar ratios of hyaluronic acid binding region relative to aggrecan (4:1 or less) had no significant effect on spacing, and high molar ratios resulted in an increase in the spacing and a decrease in the percentage of aggrecan subunits found in aggregates. These data suggest that the density of aggrecan subunits on the aggregate is determined primarily by steric hindrance of the glycosaminoglycan chains of the aggrecan subunits and that, to a limited extent, partial degradation of aggrecan in an aggregate allows attachment of more aggrecan subunits.

ISSN:0736-0266    

DOI:10.1002/jor.1100120503

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

年代:1994

数据来源: WILEY

摘要:

AbstractAdjuvant chemotherapy is currently employed in the treatment of patients with osteosarcoma, but the drug regiments, although effective in improving disease‐free survival, are unsuccessful in 20–40% of patients and very toxic. It would be useful to know whether tumor cells are sensitive to a given drug prior to its use. To this end, we developed a method of assessing Adriamycin (doxorubicin) binding to tumor nuclei as a possible means of detecting sensitivity to the drug. Adriamycin‐sensitive murine osteosarcoma cells were used to develop the assay. Thein vitroconditions (drug concentration, duration of incubation, and temperature) were optimized with use of the murine osteosarcoma cells in culture. After the cells had been incubated with Adriamycin, cell viability was determined and Adriamycin fluorescence intensity was measured with a cytofluorometer. The optimal parameters for Adriamycin binding were found to be a 30‐minute incubation in a 10 μg/ml concentration of Adriamycin at 37°C the frequency of cells that emitted Adriamycin fluorescence from the nucleus compared with the total number of livin cells reached 100% under these conditions. In a murine leukemia cell line with known sensitivity to Adriamycin, the cells emitted red fluorescence from the nucleus and cytoplasm, whereas in a resistant line the cells emitted Adriamycin fluorescence from only the cytoplasm. We demonstrated that it is possible to differentiate nuclear from cytoplasmic concentration of Adriamycin in a tumor cell with use of a fluorescent microscope and that resistant cell lines can be distinguished from sensitive cell lines by this method. Since Adriamycin acts by intercalating to DNA, its absence in the nucleus probably indicates a resistant cell. This is a rapid technique that may allow prediction of drug sensitivity at the time of diagnosis o

ISSN:0736-0266    

DOI:10.1002/jor.1100120504

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

年代:1994

数据来源: WILEY

摘要:

AbstractDemineralized bone matrix and bone morphogenetic protein have been used clinically to accelerate bone regeneration. However, the best method of sterilization has been the subject of controversy. Some investigators have used ethylene oxide, but others have reported that doses adequate for sterilization destroyed the osteoinductivity of demineralized bone matrix and that gamma irradiation was less harmful in this respect. We used partially purified bone morphogenetic protein and type‐I collagen to investigate the effects of sterilization by ethylene oxide and gamma irradiation on the activity of bone morphogenetic protein. Osteoinductivity was reduced considerably after sterilization by gamma irradiation at 2.5 Mrad and by ethylene oxide at 37°C for 4 hours and at 55°C for 1 hour; however, the reduction induced by ethylene oxide at 29°C for 5 hours was about half of the control values. This study showed that ethylene oxide at 29°C for 5 hours can be used clinically for sterilization of bone morphogenetic protein. We also investigated the effect of gamma irradiation on bone morphogenetic protein and the collagen carrier separately and found that collagen was far more labile than bone morphogenetic pr

ISSN:0736-0266    

DOI:10.1002/jor.1100120505

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe elastic moduli of calcified cartilage and subchondral bone tissues were measured experimentally with use of a three‐point bending test. Specimens were obtained from a bovine patella and the distal end of a bovine femur, from two different animals. Fifteen specimens were tested as “pure” subchondral bone beams, and 15 were tested as composite calcified cartilage/subchondral bone beams. A least‐squares optimization scheme was used to obtain modulus values from the composite beams. The elastic modulus for subchondral bone calculated from the “pure” subchondral bone beams was 2.3 ± 1.5 GPa (3.9 ± 1.5 GPa for specimens from the femur and 1.6 ± 0.7 GPa for specimens from the patella). The composite beam optimization resulted in a modulus for subchondral bone of 5.7 ± 1.9 GPa and a modulus for calcified cartilage of 0.32 ± 0.25 GPa. The modulus for the calcified cartilage was more than an order of magnitude lower than the modulus of the underlying subchondral bone. This supports the idea that the zone of calcified cartilage forms a transitional zone of intermediate stiffness between the articular cartilage and the

ISSN:0736-0266    

DOI:10.1002/jor.1100120506

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

年代:1994

数据来源: WILEY

摘要:

AbstractTo determine whether the strain patterns produced in the femoral cortex after uncemented femoral arthroplasty are influenced by the fit of the component and whether these patterns are different from those of cemented components, cortical surface strains of cadaveric femurs subjected to loads simulating single‐limb stance were measured before and after the insertion of uncemented, collared, straight‐stemmed femoral components. The effects of press fit, loose fit, and precise fit of the components were evaluated and were contrasted to the strain patterns occurring after insertion of cemented femoral components. Strains varied markedly, depending on the fit of the stem of the uncemented femoral component within the isthmus. Nearly normal patterns of femoral strain were produced when the femoral stem was fit precisely at the isthmus, and the proximal femoral strains were similar to those of the intact state. In contrast, press fit and loose fit at the isthmus altered the strain patterns. The proximal medial axial strains were significantly reduced with press fit, to a mean of 39% of normal (p<0.05), and increased with loose fit, to a mean of 141% of normal (p<0.05). The prostheses fixed with cement showed a mean reduction in proximal medial axial strains to 33% of normal, which was comparable with press fit uncemented components even though the collar was well seated. Thus, our findings indicated that, in the immediate postoperative period, femoral strain patterns can be influenced by the fit of an uncemented component within the isthmus and by the use of cem

ISSN:0736-0266    

DOI:10.1002/jor.1100120507

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe examined bone‐to‐implant relative displacements of acetabular prostheses acutely and after ingrowth in a canine model. Uncemented hemispherical acetabular cups with titanium mesh pads comprising approximately 26% of the surface of the cup were inserted in eight adult canine hemipelvesex vivo. The acetabular prostheses were fixed with 13 mm titanium screws. Zero, one, and two‐screw configurations were tested, with the order of testing randomly assigned. A load simulating 1,000 cycles of canine gait was applied to the acetabular component, and relative displacements were measured at three locations between imlant and bone to determine acute fixation. A repeated measures analysis of variance showed that two screws produced only 42% of the average relative displacement of one screw and 14% that of zero screws. Eight adult mixed‐breed dogs then underwent unilateral total hip arthroplasty. All acetabula were biologically fixed with two cancellous screws. The results at 4 months showed significantly less relative displacement between the implant and bone than was measured inex vivoimplantations (p = 0.014). Bone ingrowth filled 20 ± 6% (mean ± SD) of the available space. The relative displacements of these implants were small in all cases (12 ± 13 μm) and did not correlate with the amount of bone ingrowth. These data suggest that acetabular fixation with two screws can lead to bone ingrowth and reduced relative motion of the prosthesis under functio

ISSN:0736-0266    

DOI:10.1002/jor.1100120508

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

年代:1994

数据来源: WILEY

摘要:

AbstractMalrotation of the humeral component of the capitellocondylar total elbow replacement is thought but not proved to be one of the major causes of postoperative dislocation. The purpose of this study was to quantitate the effect of malrotation of the humeral component on the kinematics and laxity of the capitellocondylar total elbow prosthesis. Eleven fresh previously frozen elbows were used. With the humeral component in optimal position, external rotation, or internal rotation, movements of the elbow with neutral, valgus, and varus loading were monitored with an electromagnetic tracking device. When the humeral component was positioned in external rotation, the ulna was more valgus and supinated than when the component was in optimal position, and when the component was in internal rotation the ulna was more valgus in extension and more supinated in flexion. Malrotation in external rotation decreased valgus‐varus laxity, and malrotation in internal rotation increased rotational laxity. Only one elbow became dislocated, despite constant severe maltracking between the components in all of the specimens. We concluded that although malrotation of the humeral component influences the laxity and causes maltracking, it is not the primary cause of postoperative dislocation. The contribution of other factors should be investigate

ISSN:0736-0266    

DOI:10.1002/jor.1100120509

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn order to determine the differences between ligaments and tendons in terms of change in biochemical composition during maturation, the biochemical characteristics of the anterior cruciate ligament and tibialis posterior tendon of swine were studied. The collagen content of the tibialis posterior tendon was found to increase rapidly with growth of the body, reaching a plateau prior to maturation. In contrast, the rate of increase in the anterior cruciate ligament was slow, indicating that maturation of this tissue is delayed. The quantity of glycosaminoglycan in both the anterior cruciate ligament and the tibialis posterior tendon decreased with growth. In mature animals, glycosaminoglycans in the anterior cruciate ligament included chondroitin sulfate, hyaluronic acid, and dermatan sulfate, but only trace amounts of chondroitin sulfate were found in the tibialis posterior tendon. Although the ratio of dermatan sulfate to hyaluronic acid generally increased with growth, this increase was more conspicuous in the tibialis posterior tendon than in the anterior cruciate ligament. The anterior cruciate ligament and tibialis posterior tendon both contained collagen of types I, III, and V. In mature swine, type III was increased in the anterior cruciate ligament but not in the tibialis posterior tendon. These findings demonstrate slower maturaiton for ligament than for tendon with regard to the changes in biochemical constituents, especially those in collagen type and glycosaminoglycan, during the growth process, and also suggest that the composition of these tissues changes in accordance with their changing functional requirements.

ISSN:0736-0266    

DOI:10.1002/jor.1100120510

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

年代:1994

数据来源: WILEY

摘要:

AbstractElectrical stimulation has been shown to enhance the repair of biological tissues such as bone and tendon. The objective of this study was to determine whether low level direct current enhances the early healing of injured medial collateral ligaments. Eighty‐seven rats were divided into three groups on the basis of the level of current delivered. All underwent transection of the medial collateral ligament bilaterally. The experimental medial collateral ligaments received current (which varied by group), while the contralateral medial collateral ligaments (the controls), with identical electrodes, received no current. After 12 days, each ligament was tested biomechanically with use of a hydraulic materials testing machine. Group 1 (8.6 ± 5.9 μA) showed statistically significant improvements in maximum rupture force, energy absorbed, stiffness, and laxity. The groups that had received lower levels of current did not show significant improvements. In this study, stimulation of 1–20 μA was the most effective level of direct current for the enhancement of early healing of the medial collateral li

ISSN:0736-0266    

DOI:10.1002/jor.1100120511

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

年代:1994

数据来源: WILEY