bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time‐varying magnetic fields: Effects of orientation on chondrocyte proliferation
Authors: Elliott J. P. , Smith R. L. , Block C. A. 
Published: February 2005

AbstractThe purpose of this study was to determine the effect of orientation of pulsed electromagnetic fields (PEMFs) on cellular proliferation and extracellular matrix synthesis. Bovine articular chondrocytes were cultured in PEMFs (repetitive pulse at 72 Hz) generated using Helmholtz coils oriented either parallel (horizontal) or perpendicular (vertical) to the plane of cell adhesion. Dissipation of signal energy in the form of heat increased the temperature of the PEMF coils by 2°C and the tissue culture medium by 1°C. Therefore, control coils, which emitted no PEMFs, were heated to the temperature of PEMF coils by circulating water. Chondrocytes were cultured in 16‐mm‐well culture plates, and the data for individual wells were pooled as triplicates. Although not observed by microscopic examination of individual wells, positionally dependent electric field effects may be minimized by this approach. PEMFs generated by coils oriented vertically significantly decreased chondrocyte proliferation. The effect was dependent on the concentration of serum in the culture media. At 3% serum concentration, the total cell number attained after 10 days of culture was reduced by 50% in stimulated cultures when compared with controls. At 5% serum concentration, there was no effect. PEMFs applied by coils oriented horizontally did not alter proliferation of articular chondrocytes. PEMFs had no effect on synthesis of extracellular matrix by chondrocytes plated at high density, irrespective of orientation.
Limb lengthening by low rate epiphyseal distraction. An experimental study in the caprine tibia
Authors: Fjeld Terje O. , Steen Harald 
Published: February 2005

AbstractLow‐rate epiphyseal distraction of the left proximal tibia using a modified bilateral Hoffmann external fixation device, was accomplished in 14 goats (age 6–7 months). Daily distraction at a rate of 0.5 mm was continued for 5.5 weeks. Epiphysiolysis occurred after 5–9 days. After distraction had been discontinued, the external device was left in situ for fixation for 4 weeks. The animals in group 1 (n = 5), group 2 (n = 3), and group 3 (n = 5) were killed at 4, 16, and 32 weeks, respectively, from the end of the distraction period. The proximal growth plate of the elongated tibia appeared radiolucent at the conclusion of the study but was less distinct and reduced in height as compared with the control leg. The gained length at the end of the distraction period was on the average 2.2 cm (11.9%). This gain in length was reduced with further growth. In group 3, the final gain in length was reduced to half. A reduced cortical thickness of the bone within the area subjected to distractional force was observed. This finding is attributable to stress protection. An interesting observation comparing control and operated tibia was an increase of the cross‐sectional diameter of the elongated bone. Both tibiae of all animals were tested mechanically. The torsional strength of the elongated tibiae as compared with controls was on the average 29% in group 1, 79% in group 2, and 95% in group 3. We conclude that leg lengthening by low‐rate epiphyseal distraction in the proximal tibia is a justifiable alternative to other lengthening procedures in individuals approaching adolescence. In juveniles, lengthening by epiphyseal distraction may result in reduction in the longitudinal growth.
Keratan sulfate is a component of proteoglycans in the compressed region of adult bovine flexor tendon
Authors: Vogel Kathryn G. , Thonar Eugene J‐M. A. 
Published: February 2005

AbstractA monoclonal antibody (ET‐4‐A‐4) was used to identify keratan sulfate (KS) as a constituent of bovine flexor tendon. KS was present in at least 500‐fold higher amounts in the fibrocartilaginous region of the tendon that is subjected to compressive forces in vivo (mean = 0.03% of tissue dry weight) than in the more proximal regions subjected only to tensional forces. The KS was associated with proteoglycans of three size categories that could be separated by Sepharose CL‐4B chromatography. The largest proteoglycan (Vo) contained ∼4% KS and was predominant in the surface region of the tendon subjected directly to compressive forces. A population of somewhat smaller molecules (Kav ≅0.3) contained ≤20% KS and proportionately less chondroitin sulfate (CS) or dermatan sulfate (DS). The KS chains of this population were not digested by keratanase. This population was dominant in tissue from the middle layer of the fibrocartilaginous region. A third population of small KS proteoglycans or fragments (Kav ≅ 0.6) comprised 40% of the KS found in the deepest layer of the compressed tendon region. This smaller component was independent of the small DS proteoglycans.
Evaluation of fluorescein diacetate for flow cytometric determination of cell viability in orthopaedic research
Authors: Bell R. S. , Bourret L. A. , Bell D. F. , Gebhardt M. C. , Rosenberg A. , Berrey H. B. , Treadwell B. V. , Tomford W. W. , Mankin H. J. 
Published: February 2005

AbstractAccurate estimation of cellular viability is important both in research and in aspects of orthopaedic clinical practice. We have been interested in the potential for flow cytometric application of fluorescein diacetate (FDA) in evaluating chondrocyte survival following cryopreservation of osteochondral allografts as well as in the assessment of sarcoma necrosis following preoperative chemotherapy. In order to evaluate the suitability of this method for cell viability assays, this study compared FDA with more traditional methodology (trypan blue, clonigenic assay, metabolic activity analysis, measurement of DNA synthesis, and histological assessment of necrosis). Both chondrocytes and sarcoma cells were exposed to various experimental injuries prior to viability analysis. Although it is evident from these experiments that FDA accurately reflects cell survival after physical injury, it underestimates the effect of chemotherapy on cell reproductive potential in vitro. However, FDA is highly correlated with histological assessment of tumor viability after chemotherapy in vivo. It is apparent that the methodology chosen for determination of viability should be appropriate for the type of experimental injury and should analyze the cell function (i.e., metabolic activity or reproductive capacity) that is appropriate for the experimental model.
Pressure distribution in the wrist joint
Authors: Tencer A. F. , Viegas S. F. , Cantrell J. , Chang M. , Clegg P. , Hicks C. , O'Meara C. , Williamson J. B. 
Published: February 2005

AbstractWe performed a study to determine pressure distribution properties of the normal radio‐carpal joint. A system was developed for measurement of the contact pressure within the wrist joint surfaces. The transducer was based on Fuji pressure‐sensitive paper, which was inserted into the joint space through a dorsal capsular incision. The hand was then positioned using a jig that permitted free axial loading of the joint. Each of five specimens was tested in 36 positions combining flexion/extension with radio/ulnar deviation and supination/pronation. The transducers were analyzed for contact area, scapholunate contact area ratio, pressure, and centroid locations using a microcomputer‐based video‐imaging system. The scaphoid and lunate contact areas on the radius and traingular fibrocartilage were separate and distinct in all wrist positions. Together these contact areas accounted for a relatively small fraction of the total joint surface area (average contact area/total joint area = 0.206, SD = 0.0495). For an applied 103 Newton compressive load, the high pressure averaged 3.17 MPa (SD = 0.83 MPa). Overall, the scaphoid contact area was 1.47 times that of the lunate, although variations occurred with position, as in flexion, in which the scaphoid/lunate area ratio was 0.83. The highpressure centroids of both scaphoid and lunate contact areas shifted palmarly from 20° of flexion to 20° of extension and then dorsally with further extension. The scaphoid‐lunate intercentroid distance averaged 14.91 mm with a range of 10–20 mm.
Strength reduction and the effects of treatment of long bones with diaphyseal defects involving 50% of the cortex
Authors: Leggon Robert E. , Lindsey Ronald W. , Panjabi Manohar M. 
Published: February 2005

AbstractCurrently, three criteria are accepted as indications for prophylactic internal fixation of metastatic disease in long bone, including lesions (a) destroying 50% or more of the cortex; (b) 2.5 cm or greater in diameter; or (c) with pain unrelieved by radiation therapy. Using an oblong defect configuration in which one half of the cross‐sectional area was destroyed, canine femora were torsion‐tested at high speed to determine (a) the actual strength reduction incurred by a lesion destroying 50% of the cortical circumference, and (b) the effects and benefits of internal fixation using polymethylmethacrylate and/or a six‐hole compression plate on such a defect. The femurs with a 50% circumferential cortical defect demonstrated only 12.7 ± 3.8% of intact strength. Defects treated with a combination of plating (all screws bicortical) and polymethylmethacrylate (torque to failure 4.39 ± 0.90 times greater than the defect alone or TE/TD = 4.39 ± 0.90) were statistically stronger than defects treated with polymethylmethacrylate alone (TE/TD = 2.48 ± 0.66; p < 0.025) or by plating alone (TE/TD = 2.61 ± 0.91; p < 0.025), but torque‐to‐failure was only increased to approximately 56% of an intact bone. Plated intact bones (TE/TD = 5.33 ± 0.41) were significantly weaker than intact bones (TE/TD = 8.50 ± 2.52; p < 0.001). Our results substantiate the need for using polymethylmethacrylate and internal fixation in combination when prophylactically fixing pathologic lesions of this proportion.
Juxtaarticular bone loss in experimental inflammatory arthritis
Authors: Bogoch Earl , Gschwend Norbert , Bogoch Barbara , Rahn Berton , Perren Stephan 
Published: February 2005

AbstractThe osteopenia associated with experimental inflammatory arthritis was studied by a histomorphometric method that exphasized net changes in bone composition. Juxtaarticular trabecular bone volume and turnover were studied in the carrageenan injection model of inflammatory arthritis of the mature rabbit knee. Trabecular bone volume was studied by histomorphometry of the femoral condyles and confirmed by photodensitometry on standard macroradiographs. Osteogenesis was studied by imaging of calcein fluorochrome‐labeled newly formed bone in undecalcified histological sections. A significant net loss of cancellous bone (∼20%) occurred over 49 days in both the medial and the lateral femoral condyle in the arthritis group compared with normal controls. Total osteogenesis was increased fourfold and it was calculated that an even greater increase in total bone resorption was responsible for the negative bone balance. There is evidence that the periarticular bone loss of human rheumatoid arthritis is also associated with increased bone turnover. Quantitative studies of the kinetics of bone remodeling in inflammatory arthritis will provide the basis for therapeutic attempts to prevent or reverse arthritis‐induced bone loss. Fracture risk in inflammatory arthritis may be increased not only by osteopenia, but additionally by the presence of a large proportion of newly formed (and presumably less mineralized) bone.
Metabolic and biochemical abnormalities of articular cartilage induced by implantation of a sterile sheet of polyethylene in the rabbit patellofemoral joint
Authors: Front Philippe , Garcia Fernando , Guillermet Veronique , Darmon Nicole , Garcia Gladys , Mitrovic Dragoslav R. 
Published: February 2005

AbstractA polyethylene sheet was implanted in the patellofemoral joint of the right knee of the rabbit and the biochemical and metabolic changes in the articular cartilage from femoral trochleas (in contact with the implant) and femoral condyles (free of direct contact) were compared with those in their sham‐operated counterparts 7, 15, and 30 days after joint implantation. The results showed that there was an increase in the water content; the extraction yields of uronic acid‐, 35SO4−, and [3H]glycine‐containing compounds; and the incorporation of [3H]thymidine, [3H]glycine, and 35SO4. Concomitantly, the contents of uronic acid‐, hexosamine‐, neutral sugars‐, and hydroxyproline‐containing substances decreased in the femoral trochlear cartilage and, to a musch lesser extent, in the femoral condylar cartilage from implanted joints. The increased capacity of viable chondrocytes to incorporate metabolic radiolabeled precursors into newly synthesized macromolecules may represent a reparative cell response to the tissue injury induced by the implant. This is therefore a useful model for studying the response of chondrocytes to mechanical injury and tissue tolerance to intraarticularly implanted prosthetic materials.
Venous drainage of the femur permits passage of 100‐μm particles
Authors: Janssen Herbert F. , Robertson William W. , Berlin Sueleal 
Published: February 2005

AbstractIatrogenic metastasis of bone tumor is reportedly increased if aggregates of tumor cells enter the circulation. The current study used a previously developed animal model to explore the movement of 25‐, 50‐, and 100‐μ‐diameter particles from an experimental femur biopsy site into the circulation. The results indicate that cell aggregate‐sized particles can enter the circulation from the femur at a rate similar to that of the 15‐μm particles used in previous studies. Arterial blood samples collected during and after the injection of particles contained no 50‐ or 100‐μm particles, suggesting that the lung is an effective filter for these larger particles.
Pulsed electromagnetic fields alter phenotypic expression in chondroblasts in tissue culture
Authors: Norton Louis A. , Witt Davis W. , Rovetti Leslie A. 
Published: February 2005

AbstractWe hypothesize that pulsed electromagnetic fields (PEMF) alter phenotypic expression of chondroblasts by promoting the production of alkaline phosphatase (AP) and altering the structure of proteoglycans. Chondroblasts from the hypertrophic zone of tibial epiphyses (HC), sternum (SC), and skin fibroblasts (F) were cultured from 16 day chick embryos. Cultures were randomly designated control (C) or experimental (E). E received PEMF for 24 h in a 6 h on. 6 h rest sequence. The controls were in the same incubator shielded by Mu metal. Assays for AP activity were performed and normalized to protein content. Proteoglycan synthesis assay involved labeling with 35S fractionating in a 5% to 20% surcrose gradient determining total protein and chondroitin sulfate content. PEMF showed no change of AP activity on F. A high AP basal activity was found in HC, but was not increased above the control. PEMF increased AP in the SC samples (E/C ratio). The sucrose gradient data showed a shift in peaks for SC only altering the ratio of carbohydrate to protein for the SC. Analysis of carbohydrate and protein indicated that the effect was decreased synthesis or degradation of protein. We conclude that PEMF alters the phenotypic expression of sternal chondroblasts in our in vitro system.
Inhibition of epiphyseal cartilage collagenase by tetracyclines in low phosphate rickets in rats
Authors: Greenwald Robert A. , Simonson Barry G. , Moak Susan A. , Rush Scott W. , Ramamurthy N. S. , Laskin Richard S. , Golub Lorne M. 
Published: February 2005

AbstractDrugs in the tetracycline family can inhibit mammalian tissue collagenase both in vitro and in vivo by a mechanism that is independent of antibiotic action. The epiphyseal cartilages of rachitic rats contain extremely high levels of collagenase (CGase), and we have used this model to study further the phenomenon of tetracycline inhibition of tissue CGase. Rickets was induced in rats by phosphate/vitamin D deficiency and parameters of gross bone morphology, bone chemistry, and serum chemistry were evaluated in both rachitic and nonrachitic animals with and without treatment with oral tetracyclines (TETs). Minocycline (or doxycycline) partially suppressed the appearance of many of the expected changes in the rachitic animals, including gross bone hardness, growth plate widening, long bone length, suppression of weight gain, and decreased bone ash content. The effects were dose dependent and were associated with marked suppression of the enhanced CGase activity. Examination of collagen breakdown products by SDS‐PAGE documented that the rachitic enzyme behaved like other mammalian collagenases including in vitro inhibition with minocycline 10–20 μg/ml and with a nonantibiotic tetracycline. No evidence of TET osseous toxicity was noted, and, in fact, administration of TET to nonrachitic animals had a mildly favorable effect on growth and development. TET suppression of CGase can be demonstrated in a well defined model system and this form of pharmacologic enzyme inhibition can be a useful probe for delineating the role of the enzyme in connective tissue pathology.
Limb lengthening by diaphyseal corticotomy, callus distraction, and dynamic axial fixation. An experimental study in the ovine femur
Authors: Steen Harald , Fjeld Terje O. , Bjerkreim Ingjald , Tevik Asbjørn , Aldegheri Roberto , Trivella Giampaolo 
Published: February 2005

AbstractLimb lengthening of the left femur was performed in 12 sheep, 7–8 months of age. After weakening of the cortex by drill holes, a controlled fracture was created in the diaphysis. The bone segments were fixed in reduced position using a unilateral external fixation device. The fixator was left in neutral position for 10 days postoperatively when lengthening started. By means of daily distraction at a rate of 1.0 mm once a day for 3 weeks, an average lengthening of 1.9 cm (11.9%) was obtained. Two weeks after distraction had been discontinued, distinct callus bridging of the lengthening zone was confirmed radiographically in all animals. At this time the rigid state of fixation was converted to a system allowing axial compression by loading in half the animals. The other half of the animals served as controls with the fixator remaining unchanged. The external device was left on until 5 weeks after the end of distraction. At this time the animals were killed. Both femora of all animals were tested mechanically in torsion. The average ultimate torsional strength of the elongated femur compared with control was 71% in the group with dynamic axial fixation and 65% in the control group. No significant difference in relative strength of the tested bones in the two groups was found. We conclude that intermittent axial compression by loading during consolidation had no significant effect on the bone‐healing process evaluated by radiography and mechanical testing.
Correlations between mechanical stress history and tissue differentiation in initial fracture healing
Authors: Carter D. R. , Blenman P. R. , Beaupré G. S. 
Published: February 2005

AbstractA general theory for the role of intermittently imposed stresses in the differentiation of mesenchymal tissue is presented and then applied to the process of fracture healing. Two‐dimensional finite element models of a healing osteotomy in a long bone were generated and the stress distributions were calculated throughout the early callus tissue under various loading conditions. These calculations were used in formulating theoretical predictions of tissue differentiation that were consistent with the biochemical and morphological observations of previous investigators. The results suggest that intermittent hydrosatic (dilatational) stresses may play an important role in influencing revascularization and tissue differentiation and determining the morphological patterns of initial fracture healing.
Mechanical and physicochemical determinants of the chondrocyte biosynthetic response
Authors: Gray Martha L. , Pizzanelli Angelina M. , Grodzinsky Alan J. , Lee Raphael C. 
Published: February 2005

AbstractThe relation between mechanical loading of cartilage and chondrocyte activity in vivo may be mediated by several physical transduction mechanisms including: cell deformation, hydrostatic pressure gradients, fluid flow, streaming currents, and physicochemical changes. We have developed an organ culture system designed to study chondrocyte biosynthetic response to such physical stimuli. This study focuses on the effects of static compression and physicochemical changes. Cartilage disks harvested from the reserve zone of the epiphyseal plate of 1–2‐week‐old calves were subjected to static compressive stresses of 0–3 MPa in unconfined compression and the incorporation of [35S]sulfate and [3H]proline was measured during the 12‐h loading period. Incorporation of both proline and sulfate decreased monotonically with increasing stress. Compressive loading also produces physicochemical changes including a decreased water content and increased matrix fixed‐charge density, with a concomitant increase in interstitial counterion concentrations (e.g., K+, H+) and decreased coion concentrations (e.g., SO42−). We therefore examined the possibility that specific changes in interstitial mobile ion concentrations may be linked to chondrocyte response to static compression by measuring biosynthesis in the absence of mechanical compression while independently altering the SO42−, K+, and H+ composition of the bathing medium. We found that proline and sulfate incorporation were strongly dependent on pH, but independent of [SO42−]and [K+] in the range studied. These results suggest that compression‐induced changes in local, interstitial pH may account for the observed biosynthetic response to static compression.
The role of mechanical loading histories in the development of diarthrodial joints
Authors: Carter Dennis R. , Wong Marcy 
Published: February 2005

AbstractThe possible role of mechanical loading history in chondroosseous development at the ends of long bones is explored using two‐dimensional finite element models of chondroepiphyses. Loading histories are characterized in terms of discrete loading cases defined by joint contact pressure distributions and an associated number of loading cycles. An osteogenic stimulus throughout the chondroepiphyses is calculated following the theory that cyclic octahedral shear stresses promote endochondral ossification and cyclic compressive dilatational stresses inhibit ossification. The resulting distributions for the osteogenic stimulus predict the appearance of the secondary ossific nucleus and the shape of the developing bony epiphysis. The zone of Ranvier and the formation of articular cartilage and the growth plate are also predicted by the models. These findings are consistent with the hypothesis that tissue stress histories constitute an important influence during skeletal morphogenesis. Further study and testing of the concepts introduced in this study are appropriate.