bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purified staphylococcal culture medium stimulates neutral metalloprotease secretion from human articular cartilage
Authors: Williams Riley J. , Smith R. Lane , Schurman David J. 
Published: February 2005

AbstractHuman articular cartilage released significantly increased levels of metal‐dependent enzymes capable of degrading collagen, casein, and gelatin at a neutral pH following exposure to a sterile, purified fraction of Staphylococcus aureus culture medium. Neutral metalloprotease activity was determined by radiolabeled substrate assays and substrate gel analysis. The enzymes were activated with 4‐aminophenylmercuric acetate and were inhibited by 1, 10‐phenanthroline and ethylenediamine tetraacetic acid. Protein immunoblots demonstrated that type I collagenase and stromelysin (matrix metalloproteinase III) secretion was increased following staphylococcal medium challenge. The profile of enzymatic activity induced by staphylococcal medium was directly comparable to that observed with interleukin‐1, which was used as a positive control. The staphylococcal medium had no inherent proteolytic activity. Increased production of the neutral metalloproteases collagenase and stromelysin may significantly contribute to the extensive cartilage destruction noted in staphylococcal septic arthritis.
Effect of Staphylococcus epidermidis on adherence of Pseudomonas aeruginosa and Proteus mirabilis to polymethyl methacrylate (PMMA) and gentamicin‐containing PMMA
Authors: Chang Chung Che , Merritt Katharine 
Published: February 2005

AbstractThe goals of this study were to determine (1) effect of Staphylococcus epidermidis adherence and biofilm production on adherence of the opportunistic pathogens Proteus mirabilis and Pseudomonas aeruginosa to polymethyl methacrylate (PMMA); (2) if the biofilm killed by autoclaving altered adherence of other organisms; (3) if adherence of S. epidermidis to gentamicin‐containing PMMA altered adherence of the opportunistic pathogens P. mirabilis and P. aeruginosa to gentamicin‐containing PMMA. Results show that biofilms formed by S. epidermidis, whether alive or dead, significantly increased adherence of Pseudomonas. Adherence of Proteus was significantly increased on dead biofilms and increased, but not significantly (p = < 0.1), on live ones. Greatest adherence seen in the study was to autoclaved biofilms. Significant adherence of Proteus and Pseudomonas was found on gentamicin‐containing PMMA specimens, which were preincubated with S. epidermidis for formation of the biofilm. These results indicate that a biofilm is formed on PMMA‐gentamicin specimens and this may impair the ability of gentamicin to kill other organisms.
Ischemic necrosis of cartilage in spontaneous and experimental lesions of osteochondrosis
Authors: Carlson C. S. , Meuten D. J. , Richardson D. C. 
Published: February 2005

AbstractThis study was designed to examine the association of spontaneous lesions of osteochondrosis with vascular supply to epiphyseal cartilage, and to determine whether similar lesions could be experimentally reproduced by selective interruption of cartilage canal blood supply. The vascular supply to the articular–epiphyseal cartilage complex of the distal end of the femur was studied in 27 microfil‐ or barium‐injected and cleared specimens and 24 serially sectioned microangiographic specimens from 27 clinically normal female swine (3.6 to 71.0 kg). Blood vessels supplying the articular‐epiphyseal cartilage complex were consistently restricted to the epiphyseal region and the number of vessels decreased as the pigs increased in weight (p < 0.001). Spontaneous lesions of osteochondrosis (i.e., cartilage necrosis) were initially seen in the first areas of epiphyseal cartilage to become avascular and were associated with necrotic blood vessels. The number and size of foci of necrotic cartilage increased as the pigs increased in weight (p < 0.001). Blood supply to epiphyseal cartilage from cartilage canal vessels was surgically interrupted in a highly vascular area of the medial femoral condyle in eight additional 23‐kg female swine. This procedure resulted in necrosis of blood vessels within cartilage canals followed by necrosis of surrounding cartilage, lesions that appeared to be identical to early spontaneous lesions of osteochondrosis. These results suggest that the viability of epiphyseal cartilage in the articularepiphyseal cartilage complex is highly dependent on an adequate blood supply from cartilage canal vessels, and strongly implicates a defect in blood supply in the pathogenesis of osteochondrosis.
Effect of extracellular fatty acids on lipid metabolism in cultured rabbit articular chondrocytes
Authors: Nagao Masato , Ishii Seiichi , Murata Yoshihisa , Akino Toyoaki 
Published: February 2005

AbstractRabbit articular chondrocytes were cultured for 8 h in the presence of various concentrations (5–500 μM) of [14C] oleic, [14C] linoleic, and [3H] arachidonic acids. The radioactive unsaturated fatty acids were incorporated into triacylglycerol (TG) and phosphatidylcholine (PC) in a concentration‐dependent manner; more fatty acids were incorporated into TG than into PC, at higher concentrations of extracellular fatty acids. Among these fatty acids, arachidonic acid was incorporated into TG much more than into PC, in spite of a very low concentration of arachidonic acid in TG. After transfer of the labeled cells to maintenance medium, the radioactivity in TG declined rapidly and [3H] arachidonic acid radioactivity in PC increased continuously during the chase time periods. Palmitoyl‐unsaturated species were mainly formed in PC when cultured at a concentration of 5 μM of each fatty acid. However, when cultured at 500 μM, unsaturated‐unsaturated species, specific for each unsaturated fatty acid were actively formed. These findings indicate that (1) fatty acid composition of TG and PC in articular chondrocytes is influenced by the degree of fatty acid supply, (2) formation and turnover of TG plays a role in fatty acid metabolism of cells, and (3) fatty acid pairing in PC is modulated by extracellular fatty acid concentrations.
Fatigue rates of vastus medialis oblique and vastus lateralis during static and dynamic knee extension
Authors: Grabiner M. D. , Koh T. J. , Miller G. F. 
Published: February 2005

AbstractFatigue rates of the vastus medialis oblique and vastus lateralis muscles were compared from static and dynamic exercise. Based upon clinical observations, it was expected that the vastus medialis oblique would demonstrate greater fatigability than the vastus lateralis. However, based upon physiological and morphological considerations, it was expected that the vastus lateralis would exhibit greater fatigability than the vastus medialis oblique. In the static exercise condition, nine subjects—having no history of knee problems—maintained an isometric knee extension torque at 30 and 60% of their maximum value until exhaustion, during which time electromyography (EMG) data were collected every 10 s. The knee angle was 20° flexion. In the dynamic exercise condition, a different group of seven subjects performed exercise sets consisting of eight cycles of concentric‐eccentric knee extension, with a resistance equal to 40% of the maximum isometric value. The range of motion was restricted to the terminal 30° of knee extension. Each set of eight repetitions was followed by a 1 s 50% maximum isometric knee extension, during which time EMG data were collected. The raw EMG data were numerically processed to extract the median frequency of the power density spectrum, which has been shown to reflect the metabolic processes associated with fatigue. Linear regression generated a slope coefficient representing the rate of change of the median frequency, with respect to contraction duration for each subject, muscle, and condition. Analyses of variance, with repeated measures from both exercise conditions suggest that “short‐arc” quadriceps exercise did not selectively fatigue either the vastus medialis oblique or vastus lateralis, thereby supporting neither clinical nor physiological expected outcomes. Therefore, the clinical contention that short‐arc quadriceps exercises selectively strengthen the vastus medialis oblique is questioned.
Relationship between lower limb dynamics and knee joint pain
Authors: Radin Eric L. , Yang King H. , Riegger Cheryl , Kish Vince L. , O'Connor John J. 
Published: February 2005

AbstractTo test the hypothesis that appropriate and timely neuromuscular control of limb motions plays an important role in the preservation of joint health, we kinematically and kinetically examined the behavior of the legs of young adult subjects at heel strike during natural walking. We compared a group of 18 volunteers, who, we presumed, were preosteoarthrotic because of mild, intermittent, activity‐related knee joint pain, with 14 age‐matched asymptomatic normal subjects. The two groups of subjects exhibited similar gait patterns with equivalent cadences, walking speeds, terminal stance phase knee flexion, maximum (peak) swing angular velocity, and overall shape of the vertical ground reaction. However, our instrumentation detected statistically significant differences between the two groups within a few milliseconds of heel strike. In the knee pain group, the heel hit the floor with a stronger impact in this brief interval. Just before heel strike, there was a faster downward velocity of the ankle with a larger angular velocity of the shank. The follow‐through of the leg immediately after heel strike was more violent with larger peak axial and angular accelerations of the leg echoed by a more rapid rise of the ground reaction force. This sequence of events represents repetitive impulsive loading, which consistently provoked osteoarthrosis in animal experiments. We refer to this micro‐incoordination of neuromuscular control not visible to the naked eye as “microklutziness.”
Macrophage exposure to polymethyl methacrylate leads to mediator release and injury
Authors: Horowitz Stephen M. , Gautsch Thomas L. , Frondoza Carmelita G. , Riley Lee 
Published: February 2005

AbstractTo understand further the role of macrophages in the loosening of cemented arthroplasty, several in vitro effects of polymethyl methacrylate (PMMA) particle exposure in these cells were studied. The kinetics of arachidonic acid and derived inflammatory mediator release was characterized following macrophage exposure to either PMMA or control polystyrene particles. Temporal release of radiolabeled products by [14C]arachidonate–labeled cells was determined by sequential scintillation counting. Significant dosedependent release of arachidonic acid mediators by macrophages was observed within half an hour of exposure to either PMMA or styrene particles. Unexposed control cells incubated in media alone did not release detectable amounts of radiolabeled products. The leakage of intracellular lactate dehydrogenase (LDH), a marker of cell injury, was detected spectrophotometrically 4 h following exposure to PMMA but not styrene. PMMA‐induced LDH release was dose depedent. In contrast, polystyrene exposure failed to increase LDH release above unexposed control cells. These in vitro studies reveal that macrophages rapidly released arachidonic acid and derived inflammatory mediators in response to both PMMA and styrene particles. However, cells exposed to PMMA are lethally damaged, as reflected by the subsequent leakage of their intracellular LDH. We propose that a similar sequence of events may occur when macrophages encounter PMMA particles at the bone‐cement interface. This is characteristic of a foreign body granulomatous response.
Estimation of mechanical properties of cortical bone by computed tomography
Authors: Snyder Susan M. , Schneider Erich 
Published: February 2005

AbstractIt is difficult to assess from conventional x‐rays the amount of loading that a bone can tolerate. The question therefore was asked whether the mechanical properties of cortical bone could be estimated by using a computed tomography (CT) system typically employed in the clinical setting. In vitro cross sectional diaphyseal scans of adult human tibiae were made using a GE 9800 scanner and linear attenuation coefficients determined in several regions of the central cross sections. Samples from the mid‐diaphyses of these tibiae were harvested, tested in three‐point bending to failure, and mechanical properties as well as density and ash fraction determined. The respective relationships between CT measurements, mechanical properties and physical properties were calculated using regression analysis. In addition a solid calibration phantom (tricalciumphosphate) was scanned to evaluate the variability of CT measurements. The physical parameters measured in this study were found to be comparable with data from other authors but correlations coefficients with CT data: r = 0.55 (Young's modulus), r = 0.50 (strength), r = 0.65 (apparent density) and r = 0.46 (ash fraction). The correlation coefficients of these regressions for both linear and power fits were not significantly different. A high linear correlation (r = 0.99) was found between the chamber densities and the measured attenuation coefficients, but accuracy varied between 2 and 6%. The small range of specimen mechanical properties as well as the limitations inherent with the methods employed may explain these results. We conclude that clinical equipment as used in this study is not sufficient to accurately estimate the mechanical properties of cortical bone.
Experimental transplantation of the swarm rat chondrosarcoma into bone: Radiological and pathological studies
Authors: Kenan Samuel , Steiner German C. 
Published: February 2005

AbstractThe Swarm rat chondrosarcoma has been the subject of extensive biochemical studies. However, to our knowledge, there are no previous reports in the literature on transplantation of this tumor into bone. This article describes the natural history of the tumor when implanted into the bone of the rat, and correlates its histological growth pattern with its radiological appearance. Our results showed that the tumor grows slowly in the bone. The rate of intramedullary growth, however, was variable and was not the same in all the animals. Its growth pattern resembles human chondrosarcoma, with extensive invasion of the marrow and cortex. In the first few weeks after implantation, the only radiological changes noted were mild medullary radiopacities. At a later stage, 12–14 weeks postimplantation, as the tumor infiltrated the bone, significant radiological abnormalities were observed in the medullary cavity and cortex. Periosteal reaction was seen after the tumor invaded the cortex with the production of a soft‐tissue mass. Distant dissemination was rare; only 1 of 24 rats developed pulmonary metastases. The Swarm rat chondrosarcoma is a well‐differentiated malignant tumor that histologically resembles welldifferentiated human chondrosarcoma. Transplanted into bone, it may be useful as an experimental model for comparative studies with human chondrosarcoma.
An anatomic basis for spinal instability: A porcine trauma model
Authors: Oxland T. R. , Panjabi M. M. , Southern E. P. , Duranceau J. S. 
Published: February 2005

AbstractTo determine the anatomic basis for spinal instabilities, 16 porcine cervical spine specimens were subjected to a well‐defined sagittal plane trauma. The multidirectional instability of each specimen was measured before and after trauma. Detailed anatomic dissections were performed on each traumatized specimen to quantitate the extent of injury to several distinct anatomic structures and columns. Multiple regression models were constructed to determine which anatomic structures and columns correlated best with each multidirectional instability. Flexion instability correlated best with injury to the interspinous/supraspinous ligaments and the ligamentum flavum. Extension instability correlated best with anterior longitudinal ligament and pedicle injury. Axial rotation instability correlated best with anterior disc–end‐plate and capsular ligament injuries, while lateral bending instability correlated best with posterior disc–end‐plate injuries. Anterior column injuries correlated best with extension, axial rotation, and lateral bending instabilities, while posterior column injuries correlated best with flexion instability. Finally, individual anatomic structural injuries had higher correlations with multidirectional instabilities than did the injuries defined by the anatomic columns.
The effect of oxygen tension on proteoglycan synthesis and aggregation in mammalian growth plate chondrocytes
Authors: Clark Charles C. , Tolin Brad S. , Brighton Carl T. 
Published: February 2005

AbstractGrowth plate chondrocytes isolated from the proliferative and hypertrophic zones of bovine costochondral junctions were grown in vitro in the presence of various oxygen tensions ranging from 3 to 60%. Using [35S] sulfate as an index of glycosaminoglycan synthesis, incorporation was found to be maximal at 21% O2. In contrast, proteoglycan aggregation under the same conditions was found to be maximal at 3% O2. There were no consistent differences in response between cells from the different morphologic zones even though they are exposed to different oxygen tension in situ. These results show that proteoglycan synthesis and aggregation in growth plate chondrocytes in vitro are differentially affected by the ambient oxygen environment.
Evaluation of a new injury model to study medial collateral ligament healing: Primary repair versus nonoperative treatment
Authors: Weiss Jeffrey A. , Woo Savio L‐Y. , Ohland Karen J. , Horibe Shuji , Newton Peter O. 
Published: February 2005

AbstractThe medial collateral ligament (MCL) of the rabbit left hindlimb was ruptured by a rod placed beneath it, resulting in a “mop‐end” tear of the ligament substance with simultaneous injury to the insertion sites. Using this model, we compared primary ligament repair and nonoperative treatment using biomechanical and histologic techniques at time zero, 10 days, and 6 and 12 weeks postoperatively. Biomechanical evaluation included measurement of varus‐valgus (V‐V) knee rotation, in situ load on the MCL, and tensile testing of the femur‐MCL‐tibia complex (FMTC). The V‐V rotation of all experimental knees decreased over time. At 12 weeks, V‐V rotation of experimental knees was still 1.3 times larger than that of controls. Primary repair initially decreased V‐V rotation, but at 6 and 12 weeks there was no statistical difference between operated and nonoperated knees. The in situ load on the MCL followed the same trends. There was no significant effect of MCL repair on any of the tensile properties. However, postoperative healing time significantly improved the FMTC structural properties in both experimental groups. Failure modes of the FMTCs and histologic sections of the ligament insertion sites indicated that after injury the ligament insertion to bone recovered more slowly than the ligament substance. Tensile testing of the FMTC showed that even at 12 weeks postoperatively the mechanical properties of the healed ligament material remained significantly different from those of the controls.
Tensions in the anterior and posterior cruciate ligaments of the knee during passive loading: Predicting ligament loads from in situ measurements
Authors: Vahey J. W. , Draganich L. F. 
Published: February 2005

AbstractCruciate ligament tensions were predicted for anteroposterior (AP) tibial translation at 20°, 30°, 80°, and 90° of knee flexion based on in vitro measurements from six cadaver knees. A three‐dimensional trigonometric equation was derived to calculate ligament tension as functions of AP force applied to the tibia and knee flexion angle (KFA). AP forces ≤ 150 N were applied. Ligament tension increased with applied AP force. The relationship between ligament tension and applied AP force appeared linear, but a Hotteling's T2 test failed to demonstrate a linear relationship. Tensions in the anterior cruciate ligament (ACL) attained magnitudes of ≅ 140 N. Tensions in the posterior cruciate ligament (PCL) attained magnitudes of ≅ 220 N. An analysis was performed to determine the sensitivity of ligament tension to hypothetical errors in the experimentally measured parameters used to compute ligament tension. The new method we report can be used to determine tensions in the ligaments of the knee or other joints for various loading conditions.
Identification of human intervertebral disc stromelysin and its involvement in matrix degradation
Authors: Liu J. , Roughley P. J. , Mort J. S. 
Published: February 2005

AbstractHuman intervertebral disc when maintained in organ culture released a latent casein‐degrading metalloproteinase into the medium in a manner analogous to cultures of human cartilage. This enzyme was demonstrated to be immunologically identical to prostromelysin. It was also found that the amount of procollagenase secreated by both cartilage and disc cells was considerably less than that of prostromelysin. Tissue extraction confirmed that the low level of procollagenase observed was not due to retention of the enzyme within the tissue. Human intervertebral disc link proteins were found to possess the same N‐termini as those of their counterparts in human articular articular cartilage, whee it appears that stromelysin is responsible for generating molecular heterogeneity. These results suggest that intervertebral disc cells are capable of secreting prostromelysin, which can become activated within the extracellular matrix and hence contribute to the age‐related and degenerative changes in the disc.
Modulation of bone loss during disuse by pulsed electromagnetic fields
Authors: Skerry T. M. , Pead M. J. , Lanyon L. E. 
Published: February 2005

AbstractThe effect of pulsed electromagnetic fields (PEMFs) on bone loss associated with disuse was investigated by applying 1.5 Hz repetitions of 30 ms bursts of asymmetric pulses, varying from +2.5 to −135 mV, to bones deprived of their normal functional loading. The proximal portion of one fibula in each of a group of ovariectomised adult female beagle dogs was isolated from functional loading in vivo by proximal and distal osteotomies. Comparison of these prepared bones with their intact contralateral controls after 12 weeks, showed a 23% reduction in cross‐sectional area. In similarly prepared bones exposed to PEMFs for 1 h per day, 5 days per week, this bone loss was substantially and significantly reduced to 9% (p = 0.029). There was no evidence of any new bone formation on the periosteal surface of prepared fibulae in treated or untreated situations. PEMF treatment was not associated with any significant change in number of osteons per mm2 formed within the cortex of the bones, their radial closure rate, or their degree of closure. The modulation in loss of bone area associated with exposure to PEMFs can, therefore, be inferred to be due to a reduction in resorption on the bone surface.