bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term explant culture of rabbit flexor tendon: Effects of recombinant human insulin‐like growth factor‐I and serum on matrix metabolism
Authors: Abrahamsson Sven‐Olof , Lundborg Göran , Lohmander L. Stefan 
Published: February 2005

AbstractThe effects of human recombinant insulin‐like growth factor‐I (rhIGF‐I, 50 ng/ml) on matrix metabolism in the deep flexor tendon from the tendon sheath region of the rabbit were studied in explants cultured for 3 weeks. Tendon segments cultured in medium supplemented with fetal calf serum (FCS) exhibited proliferation of the superficial cell layers. Synthesis of proteoglycan and non‐collagen protein (NCP) increased threefold during the first week and remained elevated during the next 2 weeks of culture in medium supplemented with rhIGF‐I or FCS, but not in medium without supplements (bovine serum albumin, BSA). The estimated halflife (t1/2) for elimination of newly labeled proteoglycans from the tendon explants ranged from 5.1 to 8.5 days and from 4.9 to 6.8 days for NCP in supplemented medium. Presence of rhIGF‐I or FCS did not affect degradation of matrix as compared with BSA. The total hexosamine content per tendon segment was stable during the culture period, but the non‐collagen protein content decreased by 25%. Collagen synthesis decreased to 10% of the initial level after 3 weeks in supplemented medium, but to 3% in unsupplemented medium. There was no measurable turnover of collagen in explants cultured in either medium, and the collagen content remained unchanged. Our results suggest that rhIGF‐I, as well as FCS, stimulates matrix synthesis but does not influence matrix turnover in rabbit flexor tendon explants in long‐term culture as compared with medium without supplements. We conclude that rhIGF‐I may be used as a defined growthpromoting factor in serum‐free media and may be of importance in tendon healing.
Early hemodynamic response to tibial osteotomy in rabbits: Influence of indomethacin and prostaglandin E2
Authors: Keller Johnny , Hansen Ebbe Stender , He Shu‐Zheng , Kjærsgaard‐Andersen Per , Bünger Cody 
Published: February 2005

AbstractThe hemodynamic role of prostaglandins in the inflammatory phase of bone healing was studied on day 4 after creation of a nailed midtibial osteotomy in 40 rabbits, divided into groups of 10, treated with either indomethacin (oral dosage 10 mg/kg), subcutaneous (s.c.) prostaglandin E2 (PGE2) (dosage 1 mg/kg), or PGE2 infusion into the abdominal aorta (rate 20 ng/kg/min) for a 20‐min period immediately before the animals were killed. The last group served as controls. Regional blood flow was measured by means of radioactive microspheres, and plasma volume was assessed by distribution of circulating [125I]fibrinogen. Neither indomethacin nor s.c. PGE2 treatment had any hemodynamic effects in the osteotomy area. PGE2 infusion caused increased blood flow in bone, bone marrow, and muscle of the lower limbs except in the osteotomy area. Thus, the influence of prostaglandins and indomethacin on bone healing of a rabbit midtibial osteotomy does not appear to be a direct vascular effect in the early healing phase.
Viscoelastic shear properties of the equine medial meniscus
Authors: Anderson D. Ron , Woo Savio L‐Y. , Kwan Michael K. , Gershuni David H. 
Published: February 2005

AbstractRecent studies have shown that the meniscus is highly anisotropic in tension and that its compressive creep behavior can be modeled using biphasic theory. In this study, an alternative approach is used, where viscoelastic shear properties of the meniscal fibrocartilage are measured to determine the anisotropy and inhomogeneity of this tissue with respect to specimen location and fiber orientation, Medial menisci were obtained from eight skeletally‐mature horses. Nine test specimens were taken from the circumferential midsubstance of each meniscus, at three circumferential and three axial positions. The magnitude of the complex shear modulus and the phase angle were determined for each specimen from 100–800 Hz, in 100 Hz increments. Data were gathered shearing and perpendicular to the circumferentiallyoriented fibers. The magnitude of the shear modulus and the phase angle were both found to be frequency dependent, anisotropic, and inhomogeneous. The magnitude of the shear modulus increased with frequency, and was greatest in specimens from the posterior superior region, shearing parallel to the fibers. The phase angle decreased slightly with frequency and was lowest in specimens from the midsubstance of the anterior region, shearing perpendicular to the fibers. Our data demonstrated that collagen fibers substantially stiffen the meniscus in the direction of its fibers and that the solid matrix of the meniscus, like articular cartilage, behaves largely as an elastic material.
Effects of Alar ligament transection on upper cervical spine rotation
Authors: Panjabi Manohar , Dvorak Jiri , Crisco Joseph John , Oda Takenori , Wang Ping , Grob Dieter 
Published: February 2005

AbstractFresh human cadaveric specimens of occiput (C0) to C3 were subjected to axial torque. The resulting physiological motions were studied in an unconstrained three‐dimensional manner. Effects of sequential transections of the left and right alar ligaments on the relative motions of C0–C1 and C1–C2 were studied. After transection of the left alar ligament, ranges of motion—due to 1.5 Nm torque—increased at both the C0–C1 and C1–C2 joints. Increases were small, on average 1.9° to each side and at each level. Increases due to subsequent cutting of the right alar ligament were, on average, only 0.5° and statistically not significant. In general, neutral zones showed greater increases, e.g., 3.9° to each side at the C1–C2 joint. Comparing right and left axial rotations, after transection of the left alar ligament, showed greater percentage increases for the right, as compared to the left, axial rotation, at both C0–C1 and C1–C2 joints. Functional loss of the alar ligaments indicates a potential for rotatory instability, which, however, must be determined in conjunction with other clinical findings, such as neurological dysfunction, pain, and deformity.
Mechanical characteristics of the stem‐cement interface
Authors: Mann Kenneth A. , Bartel Donald L. , Wright Timothy M. , Ingraffea Anthony R. 
Published: February 2005

AbstractThe mechanical characteristics of the interface between a metallic stem and the surrounding poly(methyl methacrylate) bone cement were determined from experimental tests and finite element analyses. Push‐through‐stem tests of straight and tapered titanium alloy stems, surrounded by cement columns, were performed and the resulting load‐displacement behavior and strain distribution on the surface of the cement column were measured for loading, unloading, and reloading. Test geometries were modelled using nonlinear, axisymmetric, finite element analyses, which incorporated Coulomb friction elements at the titanium alloy‐cement interface. Initial residual stresses, due to curing of the cement column, were modeled by thermal contraction of the cement. Good agreement was obtained between load‐displacement curves and surface strains predicted from the nonlinear analysis and those obtained from experiments, when a coefficient of friction of 0.3 was assumed for the stem‐cement interface. These results show that, in the absence of chemical adhesion, the load‐displacement behavior of a stem‐cement composite can be described completely in terms of the friction at the interface and the residual stresses normal to the interface.
Vascularization and endochondral bone development: Changes in plasminogen activator activity
Authors: DeSimone D. P. , Reddi A. H. 
Published: February 2005

AbstractChanges in plasminogen activator activity were studied during the sequential developmental stages of matrix‐induced cartilage, bone, and bone marrow development. The morphological transitions were correlated with biochemical parameters. Morphologic evidence of vascularization of calcified hypertrophic cartilage was accompanied by a concomitant rise in plasminogen activator activity. Thereafter, a steady decline during mineralization and deposition of new bone was observed. Maximal plasminogen activator activity occurs at approximately the same time as peak activity of alkaline and acid phosphatase. These results imply a role for plasminogen activator during angiogenesis, vascular invasion, and attendant bone differentiation.
Osteoporosis after spinal cord injury
Authors: Garland Douglas E. , Stewart Charles A. , Adkins Rodney H. , Hu Serena S. , Rosen Charles , Liotta Ferdinand J. , Weinstein David A. 
Published: February 2005

AbstractDual‐photon absorptiometry characterized bone loss in males aged <40 years after complete traumatic paraplegic and quadriplegic spinal cord injury. Total bone mass of various regions and bone mineral density (BMD) of the knee were measured in 55 subjects. Three different populations were partitioned into four groups: 10 controls (healthy, age matched); 25 acutely injured (114 days after injury), with 12 reexamined 16 months after injury; and 20 chronic (>5 years after injury). Significant differences (p < 0.0001) in bone mass mineral between groups at the arms, pelvis, legs, distal femur, and proximal tibia were found, with no differences for the head or trunk. Post hoc analyses indicated no differences between the acutely injured at 16 months and the chronically injured. Paraplegic and quadriplegic subjects were significantly different only at the arms and trunk, but were highly similar at the pelvis and below. In the acutely injured, a slight but statistically insignificant rebound was noted above the pelvis. Regression techniques demonstrated early, rapid, linear (p < 0.0001) decline of bone below the pelvis. Bone mineral loss occurs throughout the entire skeleton, except the skull. Most bone loss occurs rapidly and below the pelvis. Homeostasis is reached by 16 months at two thirds of original bone mass, near fracture threshold.
The inositol phosphate pathway as a mediator in the proliferative response of rat calvarial bone cells to cyclical biaxial mechanical strain
Authors: Brighton Carl T. , Sennett Brian J. , Farmer James C. , Iannotti Joseph P. , Hansen Carl A. , Williams John L. , Williamson John 
Published: February 2005

AbstractIsolated newborn rat calvarial bone cells grown in monolayer on polyurethane membranes in specially constructed culture chambers and subjected to a cyclical biaxial mechanical strain of 0.17% at a frequency of 1 Hz for 30 min demonstrated a 16% increase in DNA synthesis during the subsequent 24 h. The metabolites of the inositol phosphate pathway, shown to be an important second messenger in many cell types, were shown to be elevated using high‐performance liquid chromatography to separate and quantitate the various inositol polyphosphates. Inositol 1,4,5‐trisphosphate, inositol 1,4‐bisphosphate, and inositol 1,3,4,5‐tetrakisphosphate reached peak accumulations after 20 s of mechanical strain. Inositol 1,3,4‐trisphosphate reached a peak accumulation after 2 min, and inositol 1,2,3,4,5,6 phosphate reached a peak accumulation after 60 min of mechanical strain. Neomycin, an inhibitor of phospholipase C, a membrane‐bound enzyme that hydrolyzes phosphatidyl inositol 4,5‐bisphosphate to start the inositol phosphate cascade, completely inhibited accumulation of the above inositol phosphates during mechanical straining of the bone cells. Neomycin also completely abolished the increase in DNA synthesis that was seen after a mechanical strain of 0.17%. It is concluded from this study that the inositol phosphate pathway is activated by mechanical strain in bone cells and that this pathway is an important and primary mediator in the transduction of mechanical strain into cellular proliferation in these cells.
Dynamic response of the occipito–atlanto–axial (C0‐C1‐C2) complex in right axial rotation
Authors: Chang Han , Gilbertson Lars G. , Goel Vijay K. , Winterbottom John M. , Clark Charles R. , Patwardhan A. 
Published: February 2005

AbstractThe torque‐angular deformation in right axial rotation until failure of the ligamentous occipito‐atlanto‐axial complex subjected to variable loading rate (dynamic) axial torque was characterized using a biaxial MTS system. A special fixture and gear box that permitted right axial rotation of the specimen until failure without imposing any additional constraints were used to obtain the data. The specimens were divided into three groups and tested until failure at three different dynamic loading rates: 50, 100, and 400°/s. A previous study by the authors provided data for quasi‐static (4°/s) loading conditions. The torque versus rotation curves can be divided into two straight regions and two transition zones. The plots clearly indicated that at loading rates higher than 4°/s, the specimens became stiffer in the region of steadily increasing resistance prior to failure. The increase in stiffness was maximum at 100°/s. The stiffness decreased somewhat at 400°/s in comparison with 100°/s, but this decrease was not significant. The resulting torque‐right axial rotation curves were also exmined to estimate the magnitude of maximum resistance (torque) and the corresponding angular rotation value. The average maximum resistance torque increased from 13.6 Nm at 4°/s to 27.8 Nm at 100°/s. The corresponding right angular rotation data (65–78°), however, did not show any significant variation with loading rate. Posttest dissection of the specimens indicated that the type of injury observed was related to the rate of axial loading imposed on a specimen during testing. In the previous study, fracture of the dens (due to avulsion of the alar ligament) was observed in half of the specimens tested at the 4°/s loading rate. Furthermore, the alar ligament did not exhibit midsubstance rupture in any of the specimens in these quasi‐static tests. In the dynamic tests (50, 100, and 400°/s rates of loading) of the current study, partial or complete midsubstance rupture of the alar ligament was observed, and “dens fracture” did not occur in any of the specimens. The results revealed that at the higher rates of loading, (a) the specimens became stiffer and the torque required to produce “failure” in right axial rotation increased significantly; (b) the corresponding right angular rotations did not significantly change; and (c) the incidence of the alar ligament midsubstance rupture increased and that of “dens fracture” decreased.
Contact characteristics of the subtalar joint: Load distribution between the anterior and posterior facets
Authors: Wagner Ulrich A. , Sangeorzan Bruce J. , Harrington Richard M. , Tencer Allan F. 
Published: February 2005

AbstractThe pressure distribution properties of the normal talocalcaneal joint were studied in 13 fresh cadaver specimens using pressure‐sensitive film. The film was inserted into the joint through a posterior approach for the posterior facet and an anteromedial approach for the anterior/middle facet. Specimens, comprising the distal half of the tibia and fibula and the intact ankle and foot, were positioned in neutral in the sagittal plane. In the coronal plane, specimens were positioned in neutral, inversion, or eversion, and the contact characteristics were determined in varying positions, with and without loading the fibula, under axial loads of 350 N, 700 N, 1,050 N, and 1,400 N. The transducers were video imaged for quantitative analysis of area and pressure. The contact/joint area ratio increased significantly with applied load in the posterior facet [e.g., in eversion from 0.336 (SD = 0.195) at 350 N to 0.631 (SD = 0.225) at 700 N], as did the proportion of the contact area >6 MPa, indicating an increase in contact pressure. The contact/joint area ratio was significantly lower in inversion than in any other position of the foot; however, high‐pressure zones were similar, indicating that higher pressures occur in inversion. In the anterior/middle facets both contact/joint area ratio and high pressure/contact area ratios increased significantly to 700 N, but not with further load increase. At 350 N the anterior/middle facet contact area was 31% that of the posterior facet, yet it carried 63.3% of the load of the posterior facet, so its mean contact pressure was 1.44 MPa compared with 0.93 MPa for the posterior facet. Increasing the percentage of the total load carried by the fibula from 0 to 10% increased the posterior facet contact/joint area ratio from 0.595 (SD = 0.152) to 0.774 (SD = 0.117).
Effect of controlled local release of sodium fluoride on trabecular bone
Authors: Guise J. M. , McCormack A. , Anderson P. A. , Tencer A. F. 
Published: February 2005

AbstractSystemic sodium fluoride has been used in the treatment of osteoporosis. Recent studies have shown that it has a positive risk/benefit ratio for use in increasing spinal trabecular bone density. However, thinning of the cortices of the long bones with a resulting increase in fracture incidence has been observed. This study was designed to determine the response of bone to sodium fluride released from a biodegradable polymer matrix, a technique which could potentially deliver it locally to a site of need in the skeleton which has a positive response to fluoride. In one group of mature New Zealand white rabbits, cylindrical poly(D, L‐lactic acid) (PLA) implants, with or without impregnated sodium fluoride, were implanted into the contralateral femoral trochanters and tibial metaphyses. In a second group, similar implants were placed in adjacent vertebrae. Four weeks postimplantation, the femora, tibiae, and vertebrae were removed, sectioned, cleaned of all but mineralized tissue, and the surfaces of the sections stained. The stained surfaces were imaged and analyzed for morphometric properties of the trabeculae. Comparing contralateral vertebrae, those exposed to sodium fluoride had significantly thickened trabeculae, with decreased spacing between them and a greater bone fraction. A similar increase in trabecular width was found in the subchondral bone of the proximal tibiae exposed to local release fluoride. Femoral sections showed no difference, possibly due to the lack of extensive trabecular bone in the region chosen for study.
Interaction of basic fibroblast growth factor with bovine growth plate chondrocytes
Authors: Trippel S. B. , Whelan M. C. , Klagsbrun M. , Doctrow S. R. 
Published: February 2005

AbstractThe basic fibroblast growth factor (bFGF) family of peptides influences a wide range of cellular actions. To better understand the possible role of bFGF in the growth plate, we have characterized the interaction of this growth factor with isolated bovine growth plate chondrocytes. Basic FGF interacts with two classes of binding sites on these cells. One is consistent with high‐affinity bFGF receptors and the other with low‐affinity heparin‐like binding sites on the chondrocyte surface. Radiolabeled bFGF binding studies revealed approximately 4 × 106 binding sites per cell, with a Kd of approximately 42 nM. Graded concentrations of heparin or NaCl competed with [125I]‐labeled bFGF in a dose‐dependent fashion, reducing [125I]‐labeled bFGF binding by 75 and 97%, respectively. The data suggest the presence of a high‐capacity, low‐affinity class of binding sites with the properties of a heparin‐like moiety. Affinity cross‐linking of [125I]‐labeled bFGF to chondrocytes labeled two principal species with apparent molecular masses of 135 and 160 kDa. Labeled bFGF was specifically displaced from both species by subnanomolar concentrations of unlabeled bFGF. These high‐affinity, low‐capacity binding sites are characteristic of classical bFGF receptors. Binding of [125I]‐labeled bFGF to these sites was also influenced by heparin, consistent with coregulation of binding to the two classes of binding sites. The data suggest that bFGF participates in the regulation of skeletal growth at the growth plate and that this regulation may involve bFGF interaction with at least two distinct classes of binding sites.
A comparative analysis of streaming potentials in vivo and in vitro
Authors: Otter Mark W. , Palmieri Vincent R. , Wu Dadong D. , Seiz Kristin G. , MacGinitie Laura A. , Cochran George Van B. 
Published: February 2005

AbstractStreaming potentials (SPs) measured in vivo at a specific site on intact cortical bone (canine tibia) have been compared with measurements from the same site in vitro, tested as an excised bone strip soaked in Hank's balanced salt solution. The amplitude of SPs per periosteal strain in vitro was larger in 13 tibias than in vivo (by an average X6.5 at 1 Hz), but values per transcortical strain difference were similar. In vitro, SP magnitudes rose more sharply to an asymptotic value as a function of bending frequency than did in vivo signals, possibly because of a difference in the internal state of canaliculi and/or Haversian systems. Similarly, SP response to step‐loading decreased to zero more slowly with time in vitro than in vivo. Difficulties encountered in preliminary measurements due to electrical shunting through electrolyte and soft tissues suggest the need for caution in using both in vivo and in vitro SP measurements to extrapolate to electric field strengths on the cellular level.
Ligament tension pattern in the flexed knee in combined passive anterior translation and axial rotation
Authors: Ahmed A. M. , Burke D. L. , Duncan N. A. , Chan K. H. 
Published: February 2005

AbstractTwenty‐two fresh‐frozen specimens were used to measure tensions generated in selected bands of the major ligaments of the flexed knee (40–90°) when an axially prerotated tibia is subjected to passive anterior shear and when an anteriorly pretranslated tibia is subjected to passive axial torque. The tensions were measured using the buckle transducer attached to the anteromedial band of the anterior cruciate ligament [ACL (am)], the posterior fibers of the posterior cruciate ligament [PCL (pf)], the long fibers of the medial collateral ligament [MCL (lf)], and in the total lateral collateral ligament [LCL]. The knee specimens were subjected to the combined motions in a 6‐df passive loading apparatus. The results indicated that the joint resistance to anterior translation increased markedly with internal prerotation and only marginally with external prerotation. This increase in joint resistance, however, was associated with a decrease in ACL function. It has been inferred that the posterior structures, capsular and meniscal, contribute significantly to joint resistance when the tibia is prerotated in either sense. For internal prerotation, the interference between the medial femoral condyle and the central tibial eminence was found to be an additional mechanism of resistance to anterior translation. Also, it has been found that although the ACL (am) tension increased with internal rotation in the normal case, it decreased with internal rotation in the presence of an anterior pretranslation. It is concluded that ACL response to combined joint motion cannot be ascertained by a simple summation of its responses to individual motions.