bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell cycle analysis of proliferative zone chondrocytes in growth plates elongating at different rates
Authors: Wilsman Norman J. , Farnum Cornelia E. , Green Eric M. , Lieferman Ellen M. , Clayton Murray K. 
Published: February 2005

AbstractRegulation of postnatal growth of long bones occurs in multiple levels of chondrocytic activity, including stem cell proliferation, proliferative zone cycling, and regulation of changes in chondrocytic shape during hypertrophy. The differentiation sequence of chondrocytes is the same in all growth plates, but rates of elongation at a single point in time and over a period of time differ widely among individual growth plates, which suggests that the rates of sequential gene activation and suppression in this phenotypic pattern can vary. The purpose of this study was to investigate, directly and in vivo, parameters of the cell cycle of proliferative chondrocytes in growth plates growing at widely different rates at a single point in time in order to analyze the relationship between cell cycle time, including the duration of each phase of the cell cycle (G1, S, G2, and M), and the rate of growth. The experimental design used repeated pulse labeling with bromodeoxyuridine and was analyzed using a regression model of time of pulse label with increasing labeling index. Total cell cycle time was calculated as the inverse of the slope of the relationship of the labeling index and the time between labels. The y intercept was the calculated labeling index at time zero. Multiple comparison contrasts were used to test for individual differences among four growth plates with growth rates ranging from approximately 50 to 400 μm per 24 hours from 28‐day‐old rats. The estimate of total cell cycle time for the proximal tibial growth plate was 30.9 hours. Cell cycle times for the other three growth plates were 34.0, 48.7, and 76.3 hours for the distal radius, distal tibia and proximal radius, respectively. Although the times for the proximal tibia and distal radius did not differ significantly, all other times were significantly different (p < 0.05) Almost all differences in total cell cycle time were attributable to significant differences in the length of the G1 phase. The S phase was estimated at 3.4–6.1 hours; the G2 phase, at 3.0 hours; and the M phase, at 0.5‐0.6 hours. The current study suggests that regulation through cell cycle parameters, specifically in the G1 phase, may be involved in overall regulation of differential postnatal long bone growth. It has previously been established that increase and shape change of cellular volume during hypertrophy may be regulated at the level of individual growth plates and that both are significant in understanding differential growth of long bone at this level. By demonstrating that chondrocytes in the proliferating zone have different cell cycle times that are regulated primarily through differences in the duration of G1, this study suggests that, in addition to systemic controls of chondrocyte proliferation, local controls may modulate rates of proliferation of individual growth plates and thus may be another locally mediated regulator of differential growth.
Acceleration of experimental endochondral ossification by biophysical stimulation of the progenitor cell pool
Authors: Aaron Roy K. , Mc Ciombor Deborah K. 
Published: February 2005

AbstractEndochondral ossification can be modulated by a number of biochemical and biophysical stimuli. This study uses the experimental model of decalcified bone matrix‐induced endochondral ossification to examine the effect of one biophysical stimulus, an electromagnetic field, on chondrogenesis, calcification, and osteogenesis. A temporal acceleration and quantitative increase in sulfate incorporation, glycosaminoglycan content, and calcification suggests that the stimulation of endochondral ossification is due to an increase in extracellular matrix synthesis. The locus of that stimulation is identified in the mesenchymal stage of endo‐chondral bone development, and stimulation at this stage is essential for accelerated bone formation. The data suggest that enhanced differentiation of mesenchymal stem cells present at this stage is most likely responsible for the increase in extracellular matrix synthesis and bone maturation.
Osteoinductive ability of confluent Saos‐2 cells correlates with enhanced expression of bone morphogenetic proteins
Authors: Raval Prafulla , Hsu Howard H. T. , Anderson H. Clarke 
Published: February 2005

AbstractImplants of defatted, freeze‐dried Saos‐2 human osteosarcoma cells grown to confluency induce de novo bone formation in athymic mice. These cells are also richly endowed with bone morphogenetic proteins and express mRNA for bone morphogenetic proteins 1, 2, 3, 4, and 6, as well as for transforming growth factor‐β1. Our aim was to study whether the ability to induce bone formation is related to the level of expression of bone morphogenetic protein. We studied the osteoinductive abilities and levels of expression of bone morphogenetic protein of Saos‐2 cells both during the growth phase and after confluency was reached. Subconfluent cells were at least 70% less effective in their osteoinductive ability than confluent cells. Comparison of bone morphogenetic protein mRNA expression in confluent and subconfluent cells revealed that the latter had lower expression of all the mRNAs studied. The expression of bone morphogenetic protein‐1, bone morphogenetic protein‐2, and bone morphogenetic protein‐6 mRNAs was 2, 3, and 6 to 10‐fold lower, respectively, in subconfluent cells. These results suggest that the ability of Saos‐2 cells to induce de novo bone formation may be correlated with the relative expression of these proteins; the expression of bone morpho‐genetic proteins in Saos‐2 cells also may be dependent on the cell cycle.
Adaptiive finite element modeling of long‐term polyethylene wear in total hip arthroplasty
Authors: Maxian Tina A. , Brown Thomas D. , Pedersen Douglas R. , Callaghan John J. 
Published: February 2005

AbstractAdaptive remeshing capability was addded to an existing sliding‐distance‐coupled finite element model of polyethylene wear in total hip arthroplasty. This augmentation allowed earlier postoperative wear simulation to be extended to the clinically more significant long‐term regimen (as long as 20 years). Loads and femoral head excursions were taken from a physically validated gait analysis model of a patient with an instrumented total hip replacement. For otherwise identical 22, 28, and 32 mm components, the least volumetric wear but the most linear wear occurred for the 22 mm head. When the polyethylene thickness in a 22 mm component was reduced to the same as that in a 32 mm component, the volumetric wear rate for the 22 mm component was still much less than that for the larger component, indicating that sliding distance (head size). rather than polyethylene liner thickness, was primarily responsible for the difference in rates, A “28 mm” series, for which head sizes were varied across the range of currently accepted industrial tolerances, showed that although initial wear rates were greatest for the least congruent articulations, the long‐term volumetric wear was nearly the same, regardless of initial clearance.
Contents and distributions of the proteoglycans decorin and biglycan in normal and osteoarthritic human articular cartilage
Authors: Poole A. Robin , Rosenberg Lawrence C. , Reiner Agnes , Ionescu Mirela , Bogoch Earl , Roughley Peter J. 
Published: February 2005

AbstractThe study was designed to determine the contents and distributions of the proteoglycans decorin and biglycan in adult human femoral condylar cartilage and whether these may change in osteoarthritis. New radioimmunoassays were established using peptides representing the amino‐terminal 21 amino acid sequence of each proteoglycan (to which a tyrosine was added for radioiodination) and antibodies in a rabbit antiserum raised to both these molecules. Cartilage was extracted with 4 M guanidine HCl to determine total content, and extracts were analyzed by chromatography to determine molecular sizes. Frozen sections were cut parallel to the articular surface and were extracted to determine distribution within the tissue. Gel chromatography on Sepharose CL‐2B under dissociative conditions revealed molecules with a partition coefficient of 0.7–0.75 in both normal and osteoarthritic cartilage. In normal adult cartilage, the mean contents of the core proteins of biglycan and decorin were calculated to be approximately 0.34 and 0.48 mg per gram wet weight, respectively. These represented molar contents similar to that of aggrecan. In osteoarthritic cartilage, there were no overall significant changes in the content and distribution of these molecules. There was, however, considerable individual variation in both distribution and content. Analyses indicated that there was a trend in osteoarthritic cartilage toward a loss of biglycan and decorin from the more superficial layers of intact cartilage, where both these molecules are normally more concentrated. This was accompanied by maintenance of proteoglycan content deeper in the cartilage, regardless of the degree of degeneration.
Autocrine/paracrine mechanism of insulin‐like growth factor‐1 secretion, and the effect of insulin‐like growth factor‐1 on proteoglycan synthesis in bovine intervertebral discs
Authors: Osada Ryusuke , Ohshima Hiroshi , Ishihara Hirokazu , Yudoh Kazuo , Sakai Kiyoshi , Matsui Hisao , Tsuji Haruo 
Published: February 2005

AbstractThe present study was undertaken to investigate the effect of insulin‐like growth factor‐1 on proteoglycan synthesis and the autocrine/paracrine mechanisms involving insulin‐like growth factor‐1 in the bovine coccygeal intervertebral disc. Insulin‐like growth factor‐1 stimulated proteoglycan synthesis in cultured cells of the nucleus pulposus of bovine intervertebral discs in a dose‐dependent manner, and the effect was inhibited by an anti‐insulin‐like growth factor‐1 monoclonal antibody. In situ hybridization histochemistry revealed the expression of insulin‐like growth factor‐1 mRNA in the cultured cells, and its production in these cells was demonstrated by radioimmunoassay. Insulin‐like growth factor‐1 receptor in the cultured cells was also demonstrated immunohistochemically. Scatchard analysis using an [125I]insulin‐like growth factor‐1 binding assay showed that the cells cultured in monolayer had a single type of insulin‐like growth factor‐1 receptor, whose affinity and number were estimated to be 7.38 × 108/M and 9.27 × 104/cell, respectively. These results suggest that insulin‐like growth factor‐1 stimulates proteoglycan synthesis in cells of the nucleus pulposus and that these cells in culture have an insulin‐like growth factor‐1 autocrine/paracrine mechanism. The expressions of insulin‐like growth factor‐1 mRNA and insulin‐like growth factor‐1 receptor in disc tissue were greater in cells of the nucleus pulposus of fetal bovine intervertebral discs than in those of the adult discs. These findings suggest that the action of autocrine/paracrine insulin‐like growth factor‐1 is more active in cells of the young nucleus pulposus than in cells of mature subjects.
Interaction of tobramycin and pH in cultured chick tibiae
Authors: Murakami Takanori , Murakami Hiroko , Ramp Warren K. , Hanley Edward N. 
Published: February 2005

AbstractThe toxicity of tobramycin at concentrations released from antibiotic‐impregnated polymethylmeth‐acrylate beads was determined using cultured embryonic chick tibiae. Because previous results from this laboratory have shown that osteoblast metabolism is inhibited at low pH and because of the potential for a low local pH in infected bone, the antibiotic was tested in medium with pH values from 6.8 to 7.4. Bone metabolism was evaluated by measuring the rates of glycolysis (lactate production), protein synthesis ([3H]proline uptake), and collagen synthesis ([3H]proline hydroxylation). Tobramycin at the concentrations released from the beads (1.0–1.5 mg/ml) contributed to lowering the pH of the medium. At pH 7.4, the antibiotic produced as much as a 30, 39, and 48% decrease in glycolysis, protein synthesis, and collagen synthesis, respectively. Tibiae exposed to tobramycin for 3 days, followed by 2 days without the antibiotic, showed only a partial recovery from its toxic effects. Although tobramycin was relatively less toxic in an acidic environment, the overall metabolic activity of the bones was poorest when the tobramycin concentration was high (2.0 mg/ml) and pH was low (6.8). The results of this study support the following conclusions: (a) tobramycin at high concentrations is toxic to bone, (b) a combination of high tobramycin concentration and low pH in the bone microenvironment may greatly inhibit bone metabolism, and (c) treatment and prevention of osteomyelitis by means of tobramycin‐impregnated beads may be augmented by preventing the pH from decreasing in traumatized areas.
In vitro fatigue behavior of the equine third metacarpus: Remodeling and microcrack damage analysis
Authors: Martin R. B. , Gibson V. A. , Stover S. M. , Gibeling J. C. , Griffin L. V. 
Published: February 2005

AbstractWe studied remodeling and microcrack damage in specimens of Thoroughbred racehorse third metacarpal bone that had been subjected to monotonic or fatigue failure. We asked three questions. What effects does mechanical loading have on histologically observable microcrack damage? Are there regional variations in remodeling of the equine cannon bone, and do these variations correlate with mechanical properties? To what extent are remodeling and microcrack damage age‐dependent? Machined beams from the medial, lateral, and dorsal cortices were loaded to fracture in four‐point bending monotonically, or cyclically at a load initially producing 10,000 microstrain. Specimens were then bulk‐stained in basic fuchsin, and cross sections were prepared from loaded and load‐free regions of each beam. Current and past remodeling, porosity, and microcrack density and length were determined histomorphometrically. Stained and unstained microcracks were observed. Unstained cracks were associated with regions of woven bone and appeared to be damaged Sharpey's fibers. Their density (approximately 30/mm2) did not increase after failure, but their length (approximately 25 μm) did, especially near the surfaces of the beam. Stained cracks were wider and longer than unstained cracks and were located primarily near the fracture surface and on the compressed side of the beam. Stained cracks after failure were more numerous in those beams having a higher elastic modulus, a shorter fatigue life, or greater deformation at failure. The extent of past remodeling increased with age, especially in the medial region; the rate of current remodeling generally declined with age, but not in the dorsal region, which has the best fatigue resistance. In summary, while remodeling varied with age and region, its effects on bone structure did not appear to influence microdamage. Basic fuchsin staining of damage in fractured equine bone was independent of age and region and confined to near the fracture surfaces. Distributed microdamage consisted only of what appeared to be subtle disruptions of Sharpey's fibers.
Exposure to low‐intensity ultrasound increases aggrecan gene expression in a rat femur fracture model
Authors: Yang Kyu‐Hyun , Parvizi Javad , Wang Shyu‐Jye , Lewallen David G. , Kinnick Randall R. , Greenleaf James F. , Bolander Mark E. 
Published: February 2005

AbstractThe effects of ultrasound stimulation on various parameters of bone repair after diaphyseal injury were assessed in a standard rat femur fracture model. Bilateral closed femoral fractures were made in 79 skeletally mature male Long‐Evans rats. An ultrasound signal consisting of a 200 microsecond burst sine wave of 0.5 MHz repeating at 1 kHz, with an intensity of 50 or 100 mW/cm2 spatial and temporal average, was applied to one fracture in each animal. The contralateral fracture was not exposed to ultrasound and served as a control. Mechanical testing of the healing fracture was performed 3 weeks after injury. In fractures treated with a 50 mW/cm2 ultrasound signal, the average maximum torque (223.5 ± 50.5 Nmm compared with 172.6 ± 54.9 Nmm, p = 0.022, paired t test) and average torsional stiffness (13.0 ± 3.4 Nmm/° compared with 9.5 ± 2.9 Nmm/°, p = 0.017) were significantly greater in treated than in control fractures. In animals treated with a 100 mW/cm2 ultrasound signal, the average maximum torque and torsional stiffness were greater in treated than in control fractures, but this trend did not reach statistical significance. Biochemical analysis of callus in ultrasound‐treated and control fractures failed to demonstrate significant differences in cell number, collagen content, or calcium content. Evaluation of gene expression in fractures treated with 50 mW/cm2 ultrasound demonstrated a shift in the expression of genes associated with cartilage formation; aggrecan gene expression was significantly higher on day 7 after fracture and significantly lower on day 21 (p = 0.033 and 0.035, respectively). αl (11) procollagen gene expression was similarly modified, but this trend did not reach statistical significance. Expression of genes coding for bone‐related proteins, including α1(I) procollagen, bone γ‐carboxyglutamic acid protein, alkaline phosphatase, and transforming growth factor‐β1, did not differ between ultrasound‐treated and control fractures. These data suggest that ultrasound stimulation increased the mechanical properties of the healing fracture callus by stimulating earlier synthesis of extracellular matrix proteins in cartilage, possibly altering chondrocyte maturation and endochondral bone formation.
Correlation of bony ingrowth to the distribution of stress and strain parameters surrounding a porous‐coated implant
Authors: Qin Yi‐Xian , McLeod Kenneth J. , Guilak Farshid , Rubin Clinton T. , Chiang Fu‐Pen 
Published: February 2005

AbstractThe ability of shear strains to inhibit bony ingrowth was investigated by use of a transcortical porouscoated cylindrical plug implant in a functionally isolated turkey ulna model in which the mechanical loading environment could be accurately controlled and rigorously defined. The distribution of ingrowth at the bone‐implant interface was quantified following 8 weeks of in vivo loading consisting of 100 seconds per day of a 20 Hz sinusoidal stimulus sufficient to cause a local peak strain of approximately 100 microstrain in the cortex at the bone‐implant interface in four turkeys. A nonuniform but repeatable pattern of bony ingrowth, from 33 ± 6 to 72 ± 6% (mean ± SE), was observed. The mechanical environment in the vicinity of the bone‐implant interface was calculated using a three‐dimensional elastic orthotropic finite element model. The general stress‐strain state of the bone as predicted by the finite element model was validated in two additional turkeys using four three‐element rosette strain gauges, while high resolution moiré interferometry was used to determine the mechanical state of the region immediately adjacent to the implant itself. Shear strains and stresses were evaluated at the interface and correlated to the pattern of bony ingrowth circumscribing the implant interface. Linear regressions between ingrowth and both shear strain and shear stress were negative, with the values of R = −0.75 and R = −0.78 (p < 0.001), respectively, indicating significant inhibition of ingrowth where shear components were maximal. These results suggest that the minimization of shear stress and strain components is a major determinant in achieving successful ingrowth of bone into a prosthesis.
Novel animal model for studying the molecular mechanisms of bacterial adhesion to bone‐implanted metallic devices: Role of fibronectin in Staphylococcus aureus adhesion
Authors: Fischer Béat , Vaudaux Pierre , Magnin Marc , El Mestikawy Yousti , Vasey Harold , Lew Daniel P. , Proctor Richard A. 
Published: February 2005

AbstractInfection around metallic implants is a rare but severe complication of orthopaedic surgery. A novel animal model mimicking conditions of internal fixation devices was developed to evaluate the role of host proteins adsorbed on metallic devices in promoting adhesion and colonization of the material surfaces by Staphylococcus aureus. Small plates made of pure titanium were either fixed (three screws per plate) onto the iliac bones of guinea pigs or implanted into their subcutaneous space as controls. Five to 6 weeks after surgery, the plates and screws were removed from the previously killed animals, carefully rinsed in buffer, and tested in an in vitro assay of S. aureus adhesion to metallic surfaces. To evaluate the role of fibronectin in staphylococcal adhesion to explanted plates and screws, a mutant of S. aureus that is specifically defective in fibronectin adhesion due to decreased expression of the fibronectin adhesin was compared with its isogenic parental strain. A significant reduction in adhesion of the fibronectin adhesin‐defective mutant compared with the parental strain occurred on both the subcutaneously implanted and bone‐implanted metallic plates. The results of this specific biological assay suggest that fibronectin is present on bone‐implanted metallic devices and promotes attachment of S. aureus to their surfaces. This novel experimental model should help to characterize several parameters of bacterial adhesion to metallic orthopaedic devices and to develop novel anti‐adhesive strategies for preventing such infections.
Method for assessment of vascular reactivity in bone: In vitro studies on resistance arteries isolated from porcine cancellous bone
Authors: Lundgaard Annette , Aalkjær Christian , Mulvany Michael J. , Holm‐Nielsen Peter , Hansen Ebbe Stender 
Published: February 2005

AbstractKnowledge about vascular regulation in bone is central to the understanding of both normal and pathological bone physiology. This article describes a new method for direct assessment of the reactivity of bone blood vessels. Resistance arteries (diameter approximately 250 μm) were isolated from epiphyseal cancellous bone (porcine femoral condyle). Arterial segments (2 mm long) were mounted as ring preparations on a myograph, and isometric force development was measured continuously. Fifty‐nine vessels from 31 pigs were investigated. The active force development was maximal at 0.9 × L100 in nine of 12 investigated arteries (L100 corresponds to the circumference the vessel would have if relaxed and exposed to a luminal pressure of 100 mm Hg [13.3 kPa]). In all subsequent experiments, the vessels were stretched to 0.9 × L100. Noradrenaline (2 × 10−8 to 10−5 M) induced a concentration‐dependent vasoconstriction; mean maximal tension development was 3.69 N/m. This force development would enable the arteries to contract against a pressure of more than 22 kPa (165 mm Hg), indicating preserved function of the media smooth muscle. Response to acetylcholine (10−7 to 10−5 M) was observed in only two of 12 arteries. Bradykinin (10−11 to 10−6 M) induced a concentration‐dependent and reproducible relaxation in all vessels; the relaxation was endothelium‐dependent, since no effect of bradykinin was detected after mechanical removal of the endothelium, Sodium nitroprusside (10−4 M) induced a reproducible and endothelium‐independent vasorelaxation. The results demonstrate preserved function of both smooth muscle and endothelium in this preparation. The model allows pharmacological investigations of bone arteries under well defined conditions and enables studies on focal bone lesions and human bone tissue.