bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscoelastic properties of proteoglycan solutions with varying proportions present as aggregates
Authors: Hardingham T. E. , Muir H. , Kwan M. K. , Lai W. M. , Mow V. C. 
Published: February 2005

AbstractMonomer and aggregated proteoglycans were prepared from piglaryngeal cartilage. Vascoelastic flow properties, comprising linear complex dynamic shear modulus, nonlinear steady‐state shear‐rate dependent viscosity, and primary normal stress difference, were measured in proteoglycan solutions containing varying proportions of aggregate (0–80%) and at different concentrations (10–50 mg/ml). Results were analyzed using the simple Oldroyd four‐parameter nonlinear rate‐type rheological equation. All solution properties were strongly dependent on proteoglycan concentration and on the proportion of aggregates present. Aggregation was found to have a great effect on the zero shear‐rate viscosity at 50 mg/ml, which increased fivefold from 0–100% aggregate. The results showed that network formation in proteoglycan solutions increased with concentration from 10–50 mg/ml and also increased with aggregation. All proteoglycan solutions showed shear thinning, which was most marked with aggregated proteoglycan at high concentration (50 mg/ml), where the viscosity decreased tenfold from the zero shear‐rate limit to the infinite shear‐rate limit. The intermolecular interactions in the network were therefore increasingly disrupted by increasing shear rate, but repeated measurements showed that these were reversible changes and that testing did not induce disaggregation or degradation of proteoglycan. These rheological properties show that aggregation is likely to immobilize proteoglycan at high concentration within cartilage and to contribute to the material properties of the porous solid matrix of articular cartilage that are important for its load‐bearing function.
Cytosolic calcium concentration in bovine growth plate chondrocytes
Authors: Star Andrew M. , Iannotti Joseph P. , Brighton Carl T. , Armstrong Peter F. 
Published: February 2005

AbstractThe cytosolic free calcium ion concentration for mammalian cell systems is believed to be maintained within a narrow range compatible with cellular homeostasis. Growth plate chondrocytes have been shown to accumulate large quantities of calcium within their mitochondria, but the cytosolic free calcium concentration has not been determined. This study measures the cytosolic free ionic calcium concentration in growth plate chondrocytes using two variations of the Quin II fluorescence technique. The results indicate that in isolated growth plate chondrocytes, the cytosolic free ionic calcium concentration is similar to other nonmineralizing mammalian cell types (106–137 nM).
Experimental study on the repair of full thickness articular cartilage defects: Effects of varying periods of continuous passive motion, cage activity, and immobilization
Authors: Shimizu Tomio , Videman Tapio , Shimazaki Kazuhisa , Mooney Vert 
Published: February 2005

AbstractIn order to clarify the dose/response characteristics of continuous passive motion (CPM), the repair response of full thickness articular cartilage defects was studied in a rabbit model. The following combinations of CPM and immobilization, 16 h/day; (3) CPM, 2 h/day and Imm 22 h/day; (4) Imm 24 h/day; and (5) normal cage activity. These regimens were used only in the initial week and then all rabbits were permitted to move freely in their cages, except for a sixth Imm‐CPM group that was kept immobilized in the initial week and then CPM 24 h/day for another week. The CPM 24 h/day and the CPM 8 h/day groups (groups 1 and 4, respectively) showed better repair than the other groups, i.e., better surface congruity, larger positive Safranin‐O staining area, and greater number of chondrocytes in the repair tissue. The CPM 2 h/day group (group 3), however, showed only slightly better repair than the Imm group (group 4). The CPM following immobilization was not effective to overcome the harmful effect of immobilization. We conclude that in the present model, CPM for 8 or 24 h/day is effective for adequate cartilage repair even with some component of immobilization. Its application should be at least 8 h/day. On the contrary, if CPM is delayed for a week following immobilization, the effect of CPM on cartilage will be reduced.
Osteoregulatory nature of mechanical stimuli: Function as a determinant for adaptive remodeling in bone
Authors: Rubin Clinton T. , Lanyon Lance E. 
Published: February 2005

AbstractThe capacity for functional adaptation within the skeleton was studied using the functionally isolated turkey ulna preparation. The results of this study would suggest that adaptive bone remodeling is extremely sensitive to alterations in both the magnitude and distribution of the strain generated within the bone tissue. At present, it appears that a loading regime can only influence bone remodeling when it is dynamic in nature. The full osteogenic potential of its influence is then achieved after only an extremely short exposure to this stimulus. The potency of the stimulus appears to be proportional to the magnitude of the strain engendered. As strain levels that are acceptable in one location induce adaptive remodeling in others, it would appear that each region of each bone is “genetically programmed” to accept a particular amount and pattern of intermittent strain as “normal.” Deviation from this “optimal strain enviroment” will stimulate changes in the bone's remodeling balance, resulting in adaptive increases or decreases in its mass.
Experimental vascularized bone grafts: Histopathologic correlations with postoperative bone scan: The risk of false‐positive results
Authors: Shaffer J. W. , Field G. A. , Wilber R. G. , Goldberg V. M. 
Published: February 2005

AbstractA positive bone scan in an experimental model of bilateral ulna diaphyseal bone grafts demonstrated early bone repair in both vascularized and nonvascularized orthotopic ulna autografts. A positive bone scan did not correlate with the perfusion of the vascularized and nonvascularized grafts as measured by microangiograms done 1 week postoperatively. In this model, if the bone scan is intended to monitor the circulatory status and viability of the bone graft, it must be done earlier than 1 week postoperative prior to the onset of creeping repair in both vascularized and nonvascular ulna autografts.
Valgus stability of the elbow
Authors: Hotchkiss Robert N. , Weiland Andrew J. 
Published: February 2005

AbstractThe valgus stabilizers of the elbow have been identified anatomically, but their relative importance has not been quantified. The purpose of this study was to analyze the acute changes of the torque‐displacement curve to valgus stress following (a) section of the posterior portion of the medial collateral ligament; (b) excision of the radial head; (c) prosthetic replacement of the radial head; and (d) excision of the anterior portion of the medical collateral ligament. Thirty cadaver specimens underwent load‐displacement testing in three positions: 0°, 45°, and 90° of flexion. The anterior portion of the medial collateral ligament was the primary stabilizer of the elbow to valgus stress. The relative contribution of the posterior ligament was minimal. After excision of the radial head alone, the slope of the load‐displacement curve decreased an average of 30%. Silicone rubber radial head replacement did not significantly improve the stability to valgus stress after radial head excision.
Site‐related variations in glycosaminoglycan content and swelling properties of bovine flexor tendon
Authors: Koob Thomas J. , Vogel Kathryn G. 
Published: February 2005

AbstractThe presence of morphologically distinct tissues within the adult bovine deep flexor tendon presented a model which we examined for correlations between proteoglycan content and tissue swelling properties. The proximal portion which experiences only tensile forces contained low levels of glycosaminoglycan (0.2% glycosaminoglycan hexosamine as percentage of dry weight) that were evenly distributed throughout its length and thickness. Collagen accounted for 80% of tissue mass, and collagen fibers formed parallel arrays running longitudinal to the direction of tensile force. In equilibrium bulk swelling tests, the properties of proximal tissue were uniform throughout the tissue and typical of collagenous tissues in which the response to equilibration in low ionic strength buffers or acid pH is dominated by the collagen network. The anterior aspect of the distal deep flexor tendon articulates with the stiff paratendinous sheath and sesamoid bones and is subjected to compressive and frictional forces in addition to longitudinal tensile forces. Along this anterior surface and extending partially into the tendon is tissue that resembles fibrocartilage with collagen fibers organized as a random network. Greatest glycosaminoglycan hexosamine contents (2–3% of dry weight) were found in the distal surface layer, and large proteoglycans were concentrated at the site receiving direct compressive and frictional loads. Equilibrium bulk swelling tests on distal tissue showed that the articulating surface layer possessed unique material properties. Distal surface layers swelled when counter ions were washed from the tissue, whereas lowered pH had little effect on distal tissue volume. Swelling properties of distal tissue correlated directly with proteoglycan content and were similar to swelling properties of articular cartilage. These results suggest that the articulating layer of distal flexor tendon is adapted for a unique set of mechanical requirements and that an elevated proteoglycan content at the site of compressive and frictional forces contributes to meeting these functional needs.
Mechanical behavior of the human lumbar spine. II. Fatigue strength during dynamic compressive loading
Authors: Hansson T. H. , Keller T. S. , Spengler D. M. 
Published: February 2005

AbstractSeventeen cadaveric human lumbar motion segments from eight spines were cyclically loaded in vitro under axial compression. Loading frequency and magnitude were chosen to simulate rigorous activity within an in vivo physiological level. The load magnitude was determined as a percentage of the ultimate compressive load, the latter estimated from the bone mineral content (BMC) of lumbar vertebrae determined by dual‐photon absorptiometry. Following testing, the degree of macroscopic disc degeneration was assessed and the type of fracture in each specimen was determined from serial sagittal sections. Fractures were found in all but one specimen. Three types of fractures were formed: the node of Schmorl and Junghanns (type I), central endplate fracture (type II), and a crush or burst fracture (type III). The results suggested that type I fractures were predominantly associated with segments with normal disce, type II fractures were found primarily in segments with moderately degenerated discs, and type III fractures were associated with segments that failed on the first cycle. Segment stiffness and fatigue strength (cycles to failure) were correlated with disc degeneration, age, and segment BMC, the latter an in vivo measure of bone density. Fatigue strength also decreased in proportion to a power coefficient with increasing relative stress (cyclic stress range/ultimate stress).
Load displacement behavior of the human Lumbo‐sacral joint
Authors: McGlashen K. M. , Miller J. A. A. , Schultz A. B. , Andersson G. B. J. 
Published: February 2005

AbstractThe three‐dimensional load displacement behavior of nine fresh adult L5‐S1 spine motion segments was studied. Static test forces up to 160 N in anterior, posterior, and lateral shear, test forces up to 320 N in compression, and test moments up to 15.7 Nm in flexion, extension, lateral bending, and torsion were used. The six displacements of the center of the inferior L5 endplate were measured 15 and 60 s after the load was applied. Specimens were then retested after posterior element excision. The results show that at the maximum test force, intact specimen mean (sd) displacements ranged from 1.65 mm (0.63 mm) in lateral shear to 2.21 mm (0.87 mm) in posterior shear. Posterior element excision resulted in an average 1.66‐fold increase in shear translations. At the maximum moment, rotations ranged from 3.38° (1.03°) in torsion to 7.19° (1.77°) in flexion. Posterior element excision resulted in an average 2.09‐fold increase in bending rotations and a 2.74‐fold increase in the average torsional rotation. In general, these L5‐S1 joints were stiffer than more cranial lumbar segments in flexion, extension, and lateral bending and were less stiff in torsion tests.
Chondrons in cartilage: Ultrastructural analysis of the pericellular microenvironment in adult human articular cartilages
Authors: Poole C. Anthony , Flint Michael H. , Beaumont Brent W. 
Published: February 2005

AbstractA combination of scanning and transmission electron microscopy was used to investigate the morphology and ultrastructure of normal human articular cartilage sampled from adult amputation specimens. This study confirms our previous observations on canine articular cartilage, which showed middle and deep layer chondrocytes surrounded by a pericellular matrix and enclosed within a pericellular capsule composed of filamentous and fine fibrillar materials. Pores in the “felt‐like” organization of the capsular weave progressively decreased in size from the inner to the outer border of the capsule. Matrix vesicles were found embedded within the capsular weave and distributed throughout the territorial matrix. It is suggested that the chondrocyte, its pericellular matrix, and capsule together constitute the “chondron,” a primary functional and metabolic unit of cartilage that acts hydrodynamically to protect the integrity of the chondrocyte and its pericellular microenvironment during compressive loading.
Protease inhibitors decrease rabbit cartilage degradation after meniscectomy
Authors: Caputo Claudia B. , Sygowski Linda A. , Patton Steven P. , Wolanin Donald J. , Shaw Andrew , Roberts Richard A. , Dipasquale Gene 
Published: February 2005

AbstractIn vitro proteoglycan (PG) synthesis and release were measured on cartilage removed from rabbit knees within 1 week of meniscectomy. Three days following partial lateral meniscectomy, 72% of the femurs and 82% of the tibias had visible ulcers. Cartilage from the weight‐bearing areas incorporated 2.0–2.9 times more 35S‐sulfate in vitro than cartilage from the opposite, unoperated knees. 3H‐thymidine incorporation was 2.5–3.4 times higher for surgical than control groups. 35S‐sulfate incorporation by the surgical group was inhibited by 22% in the presence of 10−4 M U24522, an inhibitor of rabbit chondrocyte metalloprotease (CMP). 3H‐thymidine incorporation by the surgical group was inhibited by 28% by 10−4 M U24522. In vitro PG release from cartilage removed 2 days after surgery was 1.6–3.7 times higher for the surgical than the control group. PG release by the surgical group after 22 h of incubation was reduced to the control level by three CMP inhibitors, U24278, U24279, and U24522. PG release by cartilage from the nonsurgical group was also reduced by these compounds at 22 h. These results suggest that both the anabolic and catabolic processes that are stimulated by surgery can be isolated in vitro and that CMP may be involved in the catabolic process.
Biochemistry of fusion mass consolidation in the sheep spine
Authors: Slater Robert , Nagel Donald , Smith R. Lane 
Published: February 2005

AbstractWe report here the biochemistry of fusion mass consolidation in sheep spines during a 1‐year period following autogenous cortical‐cancellous bone grafting and stabilization with Harrington distraction rods. Biochemical analysis of vertebral fusion mass included determination of wet weight and dry weight and quantification of glycosaminoglycan, collagen, calcium, and phosphate following extraction with neutral EDTA and proteolytic hydrolysis with papain. Our results showed that at 1 week after surgery, the fusion mass consisted of original cortical and cancellous bone graft material. The cortical bone graft was partially resistant to EDTA‐papain treatment, resulting in a residue containing hydroxyproline and mineral. At 12 weeks after surgery, the fusion mass had become a homogeneous material, which, like cancellous bone graft, was completely susceptible to treatment by EDTA‐papain. Collagen content of consolidating fusion mass was highest at 16 weeks after surgery when normalized to dry weight; glycosaminoglycan content was highest within 6 weeks after surgery. Mineral content was lowest at the 6‐week stage but by 12 weeks after surgery, it was comparable with original bone grafting material. At 24 and 52 weeks after surgery, fusion mass consolidation was characterized by an increase in the proportion of organic and mineral components resistant to EDTA‐papain. The appearance of the EDTA‐papain‐resistant material in the fusion mass coincided with formation of lamellar bone and successful consolidation.
Response of immature chicken meniscus to strenuous exercise: Biochemical studies of proteoglycan and collagen
Authors: Pedrini‐Mille Angiola , Pedrini Vittorio A. , Maynard Jerry A. , Vailas Arthur C. 
Published: February 2005

AbstractMale white Leghorn chickens were exercised on a treadmill at 70–80% of their maximal oxygen consumption starting at 4 weeks and continuing up to 20 weeks of age. The effect of the strenuous exercise regime on the extracellular matrix of menisci was followed through studies of proteoglycans and collagen. Avian menisci contain type I collagen, chondroitin sulfate proteoglycans, which increase with age in amount and degree of aggregation, and dermatan sulfate proteoglycans, which decrease with age. Five weeks of exercise cause a premature decrease of dermatan sulfate proteoglycans, while the chondroitin sulfate–containing molecules become significantly more aggregrated than those of the tissue of age‐matched controls. Strenuous exercise also causes a significant decrease in the number of pyridinoline crosslinks per mole of collagen in the menisci of young runners. The exercise‐induced changes of proteoglycan and collagen occur only during the period of active growth, and all parameters return to normal when the animals reach skeletal maturity. The early proteoglycan aggregation and dermatan sulfate decrease induced by exercise are probably an adaption to the increased loading. Although the mechanism by which strenuous exercise reduces or delays the formation of collagen pyridinoline crosslinks in menisci of skeletally immature animals is unknown, their decrease could negatively affect the mechanical properties of the tissue during the period of active growth.
Intramuscular pressure in the supraspinatus muscle
Authors: Järvholm Ulf , Palmerud Gunnar , Styf Jorma , Herberts Peter , Kadefors Roland 
Published: February 2005

AbstractShoulder pain correlated to manual labour is an increasing problem. The etiology is multifactorial and often unclear. High local muscle load and muscle ischemia in the supraspinatus muscle is present in elevated arm positions, as shown in several electromyographic studies. The purpose of this study was to evaluate intramuscular pressure (IMP) as a way to describe local muscle load in the supraspinatus muscle. Measurements were made in 15 arm positions, and with hand loads of 0, 1, or 2 kg weight, in 12 shoulders. The IMP was recorded with microcapillary infusion technique. The method was found to be suitable in recording IMP at rest and during exercise. High intramuscular pressures, i.e., above 50 mm Hg (6.7kPa), were seen in moderate humeral abduction. The IMP increased further in abduction up to 90°, where mean IMP was 122 mm Hg (16.2 kPa). Added hand load increased intramuscular pressure in all positions except in shoulder flexion of 135°. The study thus demonstrated that intramuscular pressure offers important information about the load on the supraspinatus muscle in different positions of the arm. The results indicate that fatigue and shoulder pain related to elevated arm positions may be caused by muscle ischemia induced by the high intramuscular pressure present in these positions.
Pulsing electromagnetic field stimulation of the in vitro growth plate
Authors: Iannacone W. M. , Pienkowski D. , Pollack S. R. , Brighton C. T. 
Published: February 2005

AbstractSpecific pulsing electromagnetic fields (PEMFs) have been used to stimulate growth and repair of osteogenic tissues; however, the basis for this specificity is unknown. Previously, we determined the relevant electromagnetic field parameters of the clinically used PEMF and independently verified the beneficial effects of PEMFs on the rabbit fibula fracture healing model. The goal of the present study was to develop an in vitro model that would permit the effectiveness of various electric and magnetic field components of the PEMF to be determined.The costochondral junction (CCJ) of the 21‐day‐old rat was exposed in vitro to PEMFs with various electric and magnetic field component amplitudes. Response of this model to PEMFs was determined by nondestructive macrophotographic measurement of CCJ growth. Preliminary data indicated that temperature effects were present in this in vitro system. Subsequent experiments designed to separate the effects of temperature and PEMFs on the growth of CCJs in tissue culture were performed.Results indicate that accurate and frequent temperature measurements must be made for in vitro models being used to study effects of PEMFs. Small temperature differences induced by the coils used to produce PEMFs in the CCJ experimental system can have significant stimulatory effects, and the combined effects of temperature and PEMFs are not linearly additive in this model. Furthermore, our results suggest that thermal and PEMF stimuli could affect macrophotographically measured growth of the CCJ by separate mechanisms or could have a synergistic effect. Therefore, PEMF stimulation experiments should be performed under strictly “athermal” conditions.
Bone ingrowth into porous calcium phosphate ceramics: Influence of pulsing electromagnetic field
Authors: Shimizu Tomio , Zerwekh Joseph E. , Videman Tapio , Gill Kevin , Mooney Vert , Holmes Ralph E. , Hagler Herbert K. 
Published: February 2005

AbstractThe effect of a pulsing electromagnetic field (PEMF) on bone ingrowth into porous hydroxypatite (HA) and porous tricalcium phosphate (TCP) implanted in rabbit tibiae was studied. To quantitate the biological response, a recently developed method of surface measurement using a scanning electron microscope was used. The morphometrical findings in the HA pores demonstrated a significantly greater amount of bone and thicker bone trabeculae in the PEMF group as compared with the nonpulsed control group at 3 to 4 weeks postimplantation. No significant differences for these parameters were found in the TCP pores. Histologically, more bone and wider bone trabeculae were observed in the HA implants for the PEMF‐treated animals at the early time periods when compared with those of the control animals. Alternatively, the histological findings of the TCP implants were similar between these two groups. These histological results tended to correlate with the morphometrical data. Together, these results suggest that accelerated bone formation and bone maturation occurred in response to PEMF in the HA pores but was without effect in the TCP pores. This stimulatory effect is most significant after 3–4 weeks of PEMF stimulation.