bluuebunny/crossref_metadata_2025 huggingface dataset:
The collagens and glycosaminoglycans of the extracellular matrices secreted by bone marrow stromal cells cultured in vivo in diffusion chambers
Authors: Ashhurst Doreen E. , Ashton Brian A. , Owen Maureen E.
Published: February 2005

When rabbit bone marrow cells are cultured in a diffusion chamber implanted into the peritoneal cavity of an athymic mouse, the stromal cells proliferate, differentiate, and produce tissues that have the morphological features of loose fibrous tissue, woven or chondroid bone, and cartilage. The collagens synthesized during the development of the tissues from 7 to 28 days after implantation were identified using specific antibodies to rabbit types I, II, III, and V and rat type IX collagens, while the glycosaminoglycans were characterized histochemically using the dye, Alcian blue. Fibrous tissue forms in the first week and it contains types I, III, and V collagens and hyaluronan. Bone and cartilage develop within the fibrous tissue from about 12 days onwards. The bone matrix contains types I and V collagens, and chondroitin and keratan sulphates. The cartilaginous matrix contains types II and IX collagens, and chondroitin and keratan sulphates. Small amounts of type III collagen are found in the bone, and types I, III, and V collagens in the cartilage. These are thought to be the remnants of the fibrous matrix and decrease as the matrices mature. It is concluded that the tissue in diffusion chambers, formed by a small number of early precursor cells present in the soft tissues of the endosteum and marrow of young rabbits, contains extracellular matrix macromolecules similar to those found in bone and cartilage.
The influence of flexibility on the economy of walking and jogging
Authors: Gleim Gilbert W. , Stachenfeld Nina S. , Nicholas James A.
Published: February 2005

The relationship of 11 measures of trunk and lower limb flexibility to the economy of treadmill walking and jogging as measured by steady‐state oxygen consumption (VO2) was studied. Subjects (38 women, 62 men, aged 20–;62 years) were tested at six speeds between 53.6 and 187.7 m/min. By combining scores from all flexibility tests, and beginning at speeds of 107.3 m/min, the “tightest” third used significantly less O2/m/kg (9%, p < 0.05) than the “loosest” third, with “normals” in between. Two tests, trunk rotation and lower limb turnout, gave the best separation for walking/jogging economy, with the “tightest” third differing significantly from the “loosest” (8–12%) at all speeds tested (ANOVA with Scheffe). We conclude that nonpathological musculoskeletal tightness was associated with a decreased steady‐state VO2 for treadmill walking and jogging.
Torsional strength reduction due to cortical defects in bone
Authors: Edgerton Bradley C. , An Kai‐Nan , Morrey Bernard F.
Published: February 2005

This study correlated torsional strength reduction with circular defect size in cortical bone, to define the “stress riser” and “open‐section” effect of the defects. The experimental model was developed and verified. Circular defects from 10 to 60% of bone diameter were then created in paired sheep femora and the bones loaded to failure. Contrary to theory, this experimental study suggests that small defects (10%) of bone diameter cause no significant torsional strength reduction. A 20% defect caused a 34% decrease in strength, representing the “stress riser” dimension. Defects between 20 and 60% of bone diameter decreased strength linearly as a function of defect size, and thus no discrete “open section” dimension was identified. For circular defects we were unable to demonstrate a discrete “open section” effect at which dramatic strength reduction is observed. These data may prove to be helpful when planning surgery that involves placing defects in bone such as for infection, biopsy, and prosthesis removal. The accepted guideline to avoid defects of greater than 50% of the bone diameter may be too great. Our data reveal this 62% reduction in torque strength and 88% energy to failure exist with a 50% circular defect.
Dose‐dependent variations in blood flow evaluation of canine nerve, nerve graft, tendon, and ligament tissue by the radiolabeled‐microsphere technique
Authors: Riggi Kayvon , Wood Michael B. , Ilstrup Duane M.
Published: February 2005

This study evaluates the dose‐dependent accuracy of the radionuclide‐labeled microsphere technique for blood flow evaluation in nerve, nerve graft, tendon, and ligament. In eight dogs, blood flows were determined for nerve, nerve graft, tendon, and ligament tissue by simultaneous injection of high‐ and low‐ dose microsphere with different radiolabels. The results demonstrated no significant differences in blood flow as measured from the small number of microsphere (less than 400) and the high number (more than 400) for nerve and tendon tissue. For nerve tissue, microsphere counts of 50 to 100, 100 to 200, 200 to 300, and more than 300 produced mean percentage errors of 12.74% (n= 5, SEM = 4.52), 5.45% (n = 13, SEM = 1.12), 10.22% (n = 6, SEM = 4.37), and 17.08% (n = 12, SEM = 3.30), respectively. For tendon tissue, the same microsphere subdivisions had mean percentage errors of 7.47% (n = 4, SEM = 2.66), 3.63% (n = 6, SEM = 1.34), 15.54% (n = 4, SEM = 4.43), and 12.91% (n = 1), respectively. For ligament tissue, percentage errors were consistently higher; microsphere counts of 30 to 100, 100 to 200, and 200 to 300 produced mean errors of 20.14% (n = 4, SEM = 6.38), 18.66% (n = 4, SEM = 6.24), and 25.78% (n = 2, SEM = 1.97), respectively. Although there was no direct relationship between percentage error and number of microspheres retrieved, we suggest that microsphere counts in the range of 100 to 200 should be considered acceptable for nerve and tendon in the canine. Ligament tissue seems to be less well suited to the microsphere technique; however, further study is warranted.
Monkey bone matrix induces bone formation in the athymic rat, but not in adult monkeys
Authors: Aspenberg Per , Lohmander L. Stefan , Thorngren Karl‐Göran
Published: February 2005

Demineralized bone matrix from young and adult monkeys was implanted intramuscularly for 6 weeks in athymic rats and adult monkeys. Cartilage and bone induction was evaluated by histology and calcium content. In the athymic rat, most implants induced cartilage or bone. In the monkeys, cartilage was formed only on rare occasions and there was no sign of bone formation. We conclude that (a) adult monkey bone matrix contains bone inductive properties; (b) these properties are not sufficient to induce bone formation in adult monkey muscle sites.
A new technique for the in vitro measurement of nucleus pulposus swelling pressure
Authors: Glover M. G. , Hargens A. R. , Mahmood M. M. , Gott S. , Brown M. D. , Garfin S. R.
Published: February 2005

Swelling of the intervertebral disc nucleus pulposus may be a contributing factor in lower back pain syndromes. We have designed and tested a new osmometer for in vitro determination of nucleus pulposus swelling pressure. The functionl principle of the osmometer involves compressing a sample of nucleus pulposus with nitrogen gas until saline pressure gradients across a 0.45‐μm Millipore filter are eliminated. Swelling pressures of both pooled dog and pooled pig lumbar disc nucleus pulposus were measured on the new osmometer and were compared with swelling pressures determined using the equilibrium dialysis technique. The osmometer measured swelling pressures comparable to those obtained by the dialysis technique. This osmometer provides a rapid, direct, and accurate measurement of swelling pressure of the nucleus pulposus.
The influence of scoliosis and ageing on proteoglycan heterogeneity in the human intervertebral disc
Authors: Melrose James , Gurr Kevin R. , Cole Tak‐Chun , Darvodelsky Anne , Ghosh Peter , Taylor Thomas K. F.
Published: February 2005

Proteoglycans (PGs) purified from 19‐year‐old male (19M), 53‐year‐old female (53F), and 15–16‐year‐old adolescent idiopathic scoliotic (AIS) disc tissues were characterised by their aggregation properties with hyaluronic acid (HA), glycosaminoglycan (GAG), and amino acid composition, electrophoretic mobilities by composite agaroe polycrylamide gel electrophoresis (CAPGE), and hydrodynamic size by Sepharose CL2B gel permeation chromatography. Proteoglycan levels were similar in the AIS and 53F discs, but considerably higher levels were found in the 19M discs. Proteoglycan populations assessed by the aforementioned criteria demonstrated a similar level of heterogeneity in the AIS and 53F discs but this differed with the 19M sample. Two small Mr, low buoyant density PG species were particularly prominent in AIS and 53F discs: these were similar to two nonaggregating PG species formerly reported by di Fabio et al.; however, the corresponding PG species in 19M discs were of somewhat different composition. Collectively, these data suggest similar processing of PGs in the AIS and 53F discs. Furthermore, the pattern of normal age changes in the PGs from AIS discs appears to be disturbed, most likely arising as a consequence of the abnormal biomechanical forces intrinsic to the deformity.
The significance of skeletal magnetic resonance imaging after open bone biopsy
Authors: Schwartz Herbert S. , Shockley T. E. , Lennington W. J. , Mackey E. S.
Published: February 2005

The performance of a bone biopsy results in a dramatically altered magnetic resonance image (MRI) signal in both the biopsied segment and the surrounding bone. An experimental canine model was used to determine the cause and imaging sensitivity of this postbiopsy signal change in the adjacent intraosseous contents. Six dogs were used in the study. Half of the dogs had the cortical window left open, and the other half had a polymethylmethacrylate plug inserted. After hemostatic closure, images were obtained immediately postbiopsy and 6 weeks thereafter. MRI defect length was examined on both T1 and T2 weighted sequences at both time periods. After the final image was taken at 6 weeks, the bone was harvested and examined grossly and histologically for the purpose of making pathoradiographic correlations.

The results suggest that magnatic resonance imaging is a sensitive method that accurately reflects the defect caused by bone biopsy and the surrounding hemorrhage. The defect length increased in size over time. The image was slightly smaller than the corresponding histologic response. Insertion of a cortical plug had no predictable effect on defect length, which depended upon the amount of pressurization used during insertion. We conclude that MRI may be useful in the staging of intraosseous primary neoplasms of bone after bone biopsy, especially in the detection of an iatrogenically induced tumor/hemorrhage margin. This may be critical when planning an intraosseous surgical resection in which short, wide margins are anticipated.
The effect of acute denervation on the microcirculation of skeletal muscle: Rat cremaster model
Authors: Chen Long‐En , Seaber Anthony V. , Bossen Edward , Urbaniak James R.
Published: February 2005

Although tissue is denervated during replantation of a severed part, tissue transfer, or muscle transplantation, there are few studies concerning the effects of acute denervation on muscle microcirculation. We have described a surgical procedure that totally denervates the rat cremaster muscle. Histological examination of the denervated tissue has given convincing evidence of nerve degeneration and skeletal muscle atrophy, accompanied by electrophysiological evidence of total denervation. The diameters of each component of the microcirculation were measured before and after denervation. Arterioles and arteries ranging in size from 10 to 70 μm in diameter were found to increase significantly in size immediately after acute denervation. Larger arteries and veins did not undergo significant diametrical increases. These findings suggest that total acute denervation significantly increases the diameter of small arteries and arterioles, thereby decreasing the resistance in the arterial bed and increasing blood flow. Since this phenomenon is of limited duration (20 min), it would appear to be ineffective in enhancing reperfusion and oxygenation at the time of reattachment of amputated parts or during vascularized tissue transfers, until methods of prolonging it for several hours or more are found.
Cell association of fretting corrosion products generated in a cell culture
Authors: Merritt Katharine , Wenz Lisa , Brown Stanley A.
Published: February 2005

The nature and distribution of corrosion products released into the body from orthopaedic implants remains an important issue. Various approaches to study this problem have been taken, such as the injection of metal salts, the injection of corrosion products, analysis of retrieved implants and adjacent tissue, and stimulated corrosion in vivo, with collection of body fluids and tissues for analysis. Tissue culture techniques have also been used to study the cellular response to metal salts or to corrosion or wear products that were generated in a separate environment. In this study, fretting corrosion of stainless steel plates and screws and of cobalt‐chromium alloy plates with stainless steel screws was undertaken within a cell culture. The results showed that the cell cultures remained viable despite considerable metal ion release. Nickel was released in all cultures with fretting corrosion and was found minly in the tissue culture medium (supernatant of the harvested cultures). Cobalt was detected only in those cultures with fretting corrosion of the cobalt‐chromium alloy and it was present mainly in the tissue culture medium. Chromium was released in all cultures with fretting corrosion, and it was found to be associated mainly with the cells with little in the culture medium. This compartmentalization of cell‐associated chromium and fluid‐associated cobalt and nickel supports in vivo studies showing chromium accumulation in red blood cells or tissue sites and comparatively low levels of nickel and cobalt.
Interspecies comparisons of in situ intrinsic mechanical properties of distal femoral cartilage
Authors: Athanasiou K. A. , Rosenwasser M. P. , Buckwalter J. A. , Malinin T. I. , Mow V. C.
Published: February 2005

We measured the in situ biomechanical properties of knee joint cartilage from five species (bovine, canine, human, monkey, and rabbit) to examine the biomechanical relevance of animal models of human knee joint injuries and osteoarthritis. In situ biphasic creep indentation experiments were performed to simultaneously determine all three intrinsic material coefficients (aggregate modulus, Poisson's ratio, and permeability) of the cartilage as represented by the linear KLM biphasic model. In addition, we also assessed the effects of load bearing on these intrinsic properties at “high” and “low” weight‐bearing regions on the distal femur. Our results indicate that significant differences exist in some of these material properties among species and sites. The aggregate modulus of the anterior patellar groove within each species is the lowest among all sites tested, and the permeability of the patellar groove cartilage is the highest and does not vary among species. Similarly, the Poisson's ratio in the patellar groove is the lowest in all species, except in the rabbit. These results lead to the conclusion that patellar groove cartilage can undergo greater and faster compression. Thus, under high compressive loads, the cartilage of the patellar groove surface can more rapidly compress to create a congruent patellofemoral joint articulation. For any given location, no differences were found in the aggregate modulus among all the species, and no correlation was found between aggregate modulus and thickness at the test site. Thus, in the process of selecting a suitable experimental animal model of human articular cartilage, it is essential to consider the significant interspecies differences of the mechanical properties.
Linear relationship between the volume of hypertrophic chondrocytes and the rate of longitudinal bone growth in growth plates
Authors: Breur G. J. , Vanenkevort B. A. , Farnum C. E. , Wilsman N. J.
Published: February 2005

In this study, we tested the hypothesis that hypertrophic cell volume varies directly with the rate of longitudinal bone growth. The volume of hypertrophic chondrocytes (using stereological techniques) and longitudinal bone growth per 24 h (using oxytetracycline labeling techniques) were measured in the proximal and distal radial growth plates and the proximal and distal tibial growth plates of 21‐ and 35‐day‐old hooded rats and 21‐ and 35‐day‐old Yucatan pigs. We demonstrated a high coefficient of correlation (rats 0.98, pigs 0.83) between the final volume of hypertrophic chondrocytes and the rate of longitudinal bone growth over a wide range of growth rates and volumes of hypertrophic chondrocytes. In addition, we demonstrated a positive linear relationship between the rate of longitudinal bone growth and the final volume of hypertrophic chondrocytes. The slope of the regression line was different for rats than for pigs. The relationship was independent of the location of the growth plate in the animal and the age of the animal. The data suggest that mechanisms regulating volume changes in hypertrophic chondrocytes may exist and that chondrocytic volume increase is a major determinant of the rate of longitudinal bone growth. However, the relative contribution of cellular hypertrophy to longitudinal bone growth may be different in rats than in pigs.
Type I procollagen gene expression in normal and early healing of the medial collateral and anterior cruciate ligaments in rabbits: An in situ hybridization study
Authors: Wiig M. E. , Amiel D. , Ivarsson M. , Nagineni C. N. , Wallace C. D. , Arfors K‐E.
Published: February 2005

The purpose of this study was to compare the levels of procollagen type I messenger RNA (mRNA) in normal and healing medial collateral ligament (MCL) and anterior cruciate ligament (ACL) in a rabbit model. Our method of injury involved a surgical model with identical partial lacerations in the midsubstance of the MCL and ACL. Paraffin sections of normal ligaments, and ligaments 3, 7, 14, and 28 days postlaceration were studied by in situ hybridization to compare and follow the level of type I procollagen mRNA in the two ligaments. A complementary DNA (cDNA) probe corresponding to α1(I) procollagen mRNA was labeled with [32P]d‐CTP. After hybridization, autoradiography, and staining of the sections, the level of procollagen mRNA was assessed by microscopic examination. A higher level of procollagen mRNA was consistently detected in normal MCL than in normal ACL, suggesting higher collagen synthetic activity in the MCL. At the injury sites of the MCL and ACL, the levels of type I procollagen mRNA increased at all postlaceration periods, reaching its highest level at 14 days postsurgery. The MCL healing site had a considerably higher level of procollagen mRNA than the ACL healing site (i.e., injury site) at all postoperative intervals. The results demonstrate that procollagen mRNA levels in MCL tissue are higher than those in ACL tissue under normal conditions, as well as in response to injury. The differences in the procollagen mRNA levels of MCL and ACL may reflect the synthesis of collagen in these tissues, and may contribute to the differences in their healing capacities.
Bypassing femoral cortical defects with cemented intramedullary stems
Authors: Larson J. E. , Chao E. Y. S. , Fitzgerald R. H.
Published: February 2005

The objective of this investigation was to examine the effect of cemented intramedullary stem bypass on bone torsional property in the presence of femoral cortical defect. We intended to test two hypotheses; first, intramedullary fixation without bypass will accentuate the stress concentration effect and second, there will be an optimal length of stem bypass beyond the defect. Cemented intramedullary stems were used to bypass 50% diaphyseal diameter unicortical defects in paired, fresh‐frozen canine femora. One member of each pair served as an unaltered control and all specimens were tested to failure in torsion. Both single‐tailed paired t‐test and analysis of variance were used for data analysis. Bones subjected to the cortical defect and no bypass were substantially weakened, exhibiting only 44 ± 8% of control side maximum torque (p < 0.001). Positioning of the intramedullary stem with its tip at the center of the defect provided a small degree of strength improvement, achieving 60 ± 7% of control side maximum torque. One and two diaphyseal diameter bypass, however, significantly (p < 0.01) improved bone torsional strength, resulting in 80 ± 6% and 84 ± 13% of control side maximum torque, respectively. Three diameter bypass achieved only 68 ± 8% of control side maximum torque. This significant (p < 0.05) decline in strength when compared to two diameter bypass appears to indicate that the length of stem bypass beyond the cortical defect does have an optimum, probably due to the geometric characteristics of the canine femora.
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

The 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

The 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

Recent 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

Fresh 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

The 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

Changes 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

Dual‐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

Isolated 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

The 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

The 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

Systemic 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

The 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

Streaming 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

Twenty‐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.
Histological and biochemical analysis of the fibrous tissue induced by implantation of synthetic ligament (Dacron): An experimental study in a rat model
Authors: Irie Kazunori , Kurosawa Hisashi , Oda Hiromi
Published: February 2005

We conducted a comparative study to evaluate the quality and true nature of the fibrous tissue formed around synthetic grafts when used in ligament replacement. In one group of Lewis rats, a patellar ligament was replaced with a Dacron prosthesis; the comparison group received a tail tendon isograft. Two‐, 4‐, 8‐, 12‐, and 24‐week comparisons showed histological and biochemical changes in the Dacron group alone that were consistent with foreign‐body reaction. Specifically, the Dacron group showed infiltration by large numbers of macrophages and foreign‐body, multinucleated giant cells. In addition, the capsule of fibrous tissue that developed around the Dacron ligaments was characterized by lower collagen solubility, a higher content of noncollagenous protein, and a higher proportion of type III collagen than that comprising the isografted tendons. The results of this study call into question the suitability of synthetics for ligament replacement.
Ultrastructural changes of articular cartilage chondrocytes associated with freeze‐thawing
Authors: Tavakol K. , Miller R. G. , Bazett‐Jones D. P. , Hwang W. S. , McGann L. E. , Schachar N. S.
Published: February 2005

In an attempt to justify the use of cryopreserved versus fresh articular cartilage (AC) allografts, we used transmission electron microscopy (TEM) to study the ultrastructure of fresh versus frozen‐thawed AC with or without a dimethyl sulfoxide (DMSO) treatment. AC explants were cut aseptically from the femoral condyles of healthy, mature rabbits when they were killed. Half of all explants were incubated in Ham's F‐12 medium, supplemented with antibiotics and with or without 7.5% DMSO, frozen to −80°C, stored for 24 h, and thawed rapidly. These, and the control explants, were fixed with glutaraldehyde, paraformaldehyde, and acrolein in cacodylate buffer. Sections were stained for acid phosphatase (APase), postfixed with osmium, embedded, and examined under TEM. The typical organization of the matrix and the cells was noted in control sections. The chondrocytes contained intact nuclei, organelles, and discrete plasma membrane. Although some endoplasmic reticula and nuclear membrane appeared intact, distinct ultrastructural changes were observed in frozen‐thawed samples treated with DMSO. These changes included condensation of chromatin, large lipid droplets, partly disrupted plasma membrane, and pericellular precipitation of APase‐positive crystalites. In sections not treated with DMSO, the cytoplasm was extensively vacuolated and no distinct organelies could be detected in the chondrocytes. Little difference was noted between the matrix organization of fresh or frozen‐thawed samples. Our results suggest that distinct ultrastructural changes occur in the chondrocytes following freeze‐thawing of intact AC and that DMSO pretreatment may contribute to improvement in the cryopreservation of AC.
Physeal replacement with cultured chondrocytes of varying developmental time: Failure to reconstruct a functional or structural physis
Authors: Barr Stephen J. , Zaleske David J. , Mankin Henry J.
Published: February 2005

Reconstruction of physeal regions excised from the distal femoral chondroepiphysis was attempted in a murine model. Cultured chondrocytes of varying developmental time from the same inbred strain of mice were used for replacement. Vascularity, matrix formation, and cell division, as well as growth, were assessed. The cultured chondrocytes did not produce growth. Consistent with this, cell division, as assessed with incorporation of tritiated thymidine, was not normal. However, the cultured chondrocytes did receive a nutritional supply from the host and did continue matrix formation after transplantation.