bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of short‐term hypomagnesemia on the chemical and mechanical properties of rat bone
Authors: Boskey Adele L. , Rimnac Clare M. , Bansal Manjula , Federman Micheline , Lian Jane , Boyan Barbara D. 
Published: February 2005

AbstractMagnesium is known to have an essential role in determining the properties of bone, but the way in which Mg exerts its actions remains unclear. Although long‐term Mg deficiency is known to produce osteopenia, the effects of short‐term Mg deficiency have not been established. To test the hypothesis that Mg deficiency results in an altered pattern of initial mineralization and concomitant altered bone properties, the radiographic, histologic, chemical, and mechanical properties of the bones of rats given a Mg‐deficient diet were compared to those of rats pair‐fed the same diet supplemented with Mg. Short‐term Mg‐deficiency in the diet of growing rats produced a significant decrease in both the trabecular bone volume and the mineral content of the newly formed metaphysis, a significant increase in the Ca:P ratio, and a slight, but significant increase in hydroxyapatite crystallite size and/or perfection in the metaphysis. Comparable, but not significant, trends were found in the diaphyses. Metaphyseal bone osteocalcin levels were reduced in the Mg‐deficient rats and lipid was more easily extracted from their bones. No detectable alterations in radiographic microstructure were noted. Mechanically, a significant decrease in the maximum three‐point bend strength of the femurs of Mg‐deficient rats was observed. These data support the hypothesis that short‐term Mg deficiency affects the pattern of bone mineral formation.
Partial pressures of oxygen and carbon dioxide in bone and their correlation with bone‐blood flow: Effect of decreased arterial supply and venous congestion on intraosseous oxygen and carbon dioxide in an animal model
Authors: Kiær Thomas , Dahl Benny , Lausten Gunnar 
Published: February 2005

AbstractPathological changes in bone have been related to a preceding impediment of the arterial or venous bone circulation and hypoxia. In this study, we analyzed the feasibility of mass spectrometry in measuring intraosseous oxygen and carbon dioxide. The partial pressures were also measured in intraosseous blood samples, and blood flow in bone was measured with the radioactive microspheres technique. The average partial pressure of oxygen in the lateral femoral condyle was 34 ± 1.6 mm Hg when measured in intraosseous blood samples and 36.3 ± 2.3 mm Hg when measured with the on‐line mass spectrometer, with significant correlation between the methods. The absolute value of the partial pressure of carbon dioxide measured in situ with mass spectrometry was correlated with the value in the withdrawn blood. There was no significant difference in partial pressures of oxygen and carbon dioxide between the two sides or between repetitive measurements. Arterial occlusion resulted in severe hypoxia, whereas more moderate changes followed venous occlusion.
Failure of perfusion with oxygenated Krebs‐Ringer solution to preserve the eccrine function of the vascular endothelium in bone
Authors: Moran Christopher G. , Wood Michael B. 
Published: February 2005

AbstractAn ex vivo canine tibia preparation was perfused at a constant rate with aerated (95% O2‐5% CO2) Krebs‐Ringer solution for 24 h. Bolus injections of norepinephrine (0.125‐0.5 μg) were given and then acetylcholine (5 × 10−5 M) was used to stimulate endothelial production of smooth muscle relaxing factors. Following 1 h of perfusion the addition of acetylcholine resulted in significant attenuation of the response to norepinephrine (p < 0.001). After 4 h perfusion acetylcholine did not attenuate the norepinephrine response, but addition of I‐arginine (the precursor of endothelial‐derived relaxing factor) resulted in significant attenuation in the presence of acetylcholine (p < 0.005). At 6, 12, and 24 h the acetylcholine did not attenuate the norepinephrine response. It is concluded that normothermic, continuous perfusion with oxygenated Krebs‐Ringer solution results in normal endothelial eccrine activity up to 1 h. Following this period there is substrate depletion but endothelial eccrine function can be demonstrated for up to 4 h. At 6 h this function cannot be demonstrated, suggesting degradation of the functional integrity of the endothelium.
Rigid immobilization alters matrix organization in the injured rat medial collateral ligament
Authors: Padgett Larry R. , Dahners Laurence E. 
Published: February 2005

AbstractThe effects of mobilization on matrix reorganization and density after ligament injury were studied in rat medial collateral ligaments using scanning electron microscopy (SEM). Both medial collateral ligaments of 14 Sprague‐Dawley rats were sharply incised transversely at their midpoint. A 1.14‐mm threaded Kirschner wire was driven through the tibia and into the femur of the right leg (through the knee) to immobilize that knee at 90° of flexion. Four additional rats were used as controls. The right medial collateral ligament of the control rats was exposed in the same manner as the experimental rats and the wound closed without damaging the ligament. Rats were sacrificed on the 7th and 14th days postinjury and the ligaments evaluated by SEM. The electron micrographs from this study demonstrated that early on, the tissue at the injury site is disorganized on a gross scale with large bundles of poorly organized matrix. Large “defects” were present between bundles in the substance of the ligament and appeared as holes in the ligament around the injury site. As healing progressed, the matrix in the mobilized specimens appeared to bridge the injury site more rapidly and completely with fewer “defects” and thus higher density than the immobilized specimens.
Blood flow changes in the tibia during external loading
Authors: McDonald F. , Ford T. R. Pitt 
Published: February 2005

AbstractThe influence of external load on the blood flow of the rabbit tibia was assessed by laser Doppler flowmetry (LDF). Blood flow readings were obtained from three adolescent and three adult female New Zealand White rabbits whose tibiae previously had been pinned with modified orthopaedic pins. Readings were obtained from the exposed mid‐shaft of the tibia of each hind leg before, during, and after loading. The loading was either static or sinusoidal intermittent. The LDF resulted in a reading from the tibia which was consistent with the recordings of blood flow; the traces were similar to the pulsatile nature of pulse pressure recordings. After loading of the tibia, in both the adolescent and adult rabbits the effects were an increase in blood flow, as measured with LDF, on the tensile aspect, and a decrease in flow on the compressive side. These changes were statistically significant (p < 0.01) as measured by a Student t test. This change in flow reached a plateau with change in strain. Furthermore, the changes in flow produced by loading continued as long as the load was applied. A response similar to reactive hyperaemia occurred on the compressive aspect of the tibia; there was an increase of blood flow above the resting level after removal of the static load. The effect of a sinusoidal intermittent load was less than that of a static load, and the differences in flow between tensile and compressive aspects was not significant. The changes induced offer further insight into factors controlling bone remodelling.
A quantitative study of the routes of blood flow to the tibial diaphysis after an osteotomy
Authors: Triffitt Paul D. , Cieslak Catharine A. , Gregg Paul J. 
Published: February 2005

AbstractTechniques of tissue exclusion have been used previously in qualitative investigations of the vascularity of long bones, after experimental fracture; we quantified their effects on bone blood flow in rabbits. Thirty‐six adult rabbits were divided into three groups in which flow was measured, with the microsphere technique, 1 and 2 weeks after osteotomy. In Group 1, osteotomy of the tibial shaft only was done; in Group 2, osteotomy was done with exclusion of the periosteum and muscle by a silicone rubber sheath; and in Group 3, osteotomy was done with exclusion of the marrow by reaming and insertion of an intramedullary nail. All involved limbs were immobilized in a cast. In Group 1, cortical flow increased but marrow flow did not change, which suggests that the changes in cortical flow were mediated by a supply paralleling that of the marrow. In Group 2, the changes in cortical flow were abolished, which implies that this parallel supply is from the periosteum and extraosseous tissues. In Group 3, cortical flow was not significantly reduced, which demonstrates reeruitment of this periosteal and extraosseous supply. These results lend support to the hypothesis that the blood supply to the healing diaphysis is principally from the periosteum and extraosseous tissues during the early peak period of blood flow.
The mechanical properties of skeletally mature rabbit anterior cruciate ligament and patellar tendon over a range of strain rates
Authors: Danto Michael I. , Woo Savio L‐Y. 
Published: February 2005

AbstractThe effect of strain rate on the mechanical properties of the rabbit anterior cruciate ligament (ACL) and patellar tendon (PT) was evaluated. The medial portion of the ACL was loaded to tensile failure at rates of 0.003, 0.3, and 113 mm/s, and the middle third of the PT was loaded at rates of 0.008, 0.8, and 113 mm/s. The load was recorded with a high‐speed measurement plotting system, and each test was videotaped for strain analysis. The nonlinear portion of the stress‐strain curve was curve‐fit to an exponential function having two nonlinear constants, representing the initial modulus, and rate of change of the modulus. The modulus of the rabbit PT was found to be 89% higher than that of the ACL. The initial modulus and rate of change of the modulus also were greater for the PT than for the ACL. The modulus of the PT was shown to be more sensitive to strain rate than that of the ACL; a 94% increase was observed for the PT, and a 31% increase was observed for the ACL; a 94% increase was observed for the PT, and a 31% increase was observed for the ACL. There was no effect of strain rate on the mode of failure of either the ACL or the PT; all but three of the specimens failed at the insertion site.
Double‐level cauda equina compression: An experimental study with continuous monitoring of intraneural blood flow in the porcine cauda equina
Authors: Takahashi Keisuke , Olmarker Kjell , Holm Sten , Porter Richard W. , Rydevik Björn 
Published: February 2005

AbstractCompression of the spinal nerve roots may occur clinically at multiple levels at the same time; however, the basic pathophysiology of multilevel compression is largely unknown. In this study, the intraneural blood flow was analyzed continuously in the uncompressed segment between two compression balloons, with a pig used as an experimental model and a thermal diffusion method. At 10 mm Hg compression, there was a 64% reduction of total blood flow in the uncompressed segment compared with pre‐compression values. Total ischemia occurred at pressures 10‐20 mm Hg below the mean arterial blood pressure. After two‐level compression at 200 mm Hg for 10 min, there was a gradual recovery of the intraneural blood flow towards the baseline. Recovery was less rapid and less complete after 2 h of compression. Double‐level compression of the cauda equina can thus induce impairment of blood flow, not only at the compression sites, but also in the intermediate nerve segments located between two compression sites, even at very low pressures. These findings may have clinical importance in the understanding of the pathophysiology of multiple‐level cauda equina compression.
Torque history of electrically stimulated human quadriceps: Implications for stimulation therapy
Authors: Lieber Richard L. , Kelly M. Jeanne 
Published: February 2005

AbstractThe time course of knee extension torque was measured in human quadriceps muscles during 30 min of transcutaneous neuromuscular electrical stimulation (NMES). Ninety subjects were divided into six experimental groups (n = 15 per group), which received stimulation at one of the following frequency/duty cycle combinations: 10 Hz/50%, 30 Hz/50%, 50 Hz/50%, 10 Hz/70%, 30 Hz/70%, and 50 Hz/70%. Two‐way analysis of variance revealed that the magnitude of the relative torque decrease (the percentage of decrease in torque relative to the initial value) was significantly different between frequencies (p < 0.005) and duty cycles (p < 0.02), with no significant interaction (p > 0.6). Increasing either frequency or duty cycle caused a greater decrease in torque. In spite of this result, there was no significant difference between groups in the total activity (torque‐time integral) achieved during the 30 min treatment session. The magnitude of this activity corresponded to only about 7–14 maximum voluntary contractions. Finally, the average torque during the treatment session was significantly different among groups (p < 0.001), being greatest for the 50 Hz/50% group and least for the 10 Hz/70% group. Taken together, these data suggest that a smaller number of longer duration contractions produces the greatest muscle tension. They also suggest that the absolute torque levels achieved with NMES are relatively low compared with voluntary muscular activity.
Effects of solvent preservation with or without gamma irradiation on the material properties of canine tendon allografts
Authors: Maeda A. , Inoue M. , Shino K. , Nakata K. , Nakamura H. , Tanaka M. , Seguchi Y. , Ono K. 
Published: February 2005

AbstractWe studied the effects of solvent preservation with and without gamma irradiation on the material properties and morphology of canine tendons. Twenty‐four paired tendons were harvested from both hind limbs of eight dogs. The tendons from the right legs were divided into three treatment groups of eight tendons each. In the first group, the tendons were subjected to solvent preservation for sterilization and drying (solvent group). In the second group, the tendons were treated in the same manner and then were sterlized by gamma irradiation (solvent/gamma group). The same treatments were applied to the tendons in the third group but in reverse order (gamma/solvent group). Tendons from the contralateral left legs were frozen immediately for use as controls for each corresponding treatment group. Histologically, the tendons treated with solvent, with or without gamma irradiation, had a more prominent wavy pattern in the collagen fibers than the control tendons. Mechanically, the tangent moduli for the solvent, solvent/gamma, and gamma/solvent groups were 58.53, and 99%, respectively, of each contralateral control. The respective tensile strengths were 85, 39, and 86% of that of the contralateral control. The tendons in the solvent/gamma group underwent the most severe changes in material properties: the tendons in the gamma/solvent group changed the least. This suggests that gamma irradiation followed by solvent drying is the procedure of choice for the preservation of tendon allografts.
Immunolocalization of selected cytokines and proteases in canine articular cartilage after transarticular loading
Authors: Pickvance E. A. , Oegema Theodore R. , Thompson Roby C. 
Published: February 2005

AbstractCytokines and proteases are thought to play a role in the destruction of cartilage and the development of osteoarthritis. The purpose of this study was to document chronological involvement of interleukin‐1 beta (IL‐1β), tumor necrosis factor‐alpha (TNF‐α), stromelysin (MMP‐3), fibronectin, and alteration in the chondroitin sulphate sulfation pattern. Canine patellae underwent a closed‐joint impact to induce the development of osteoarthritis. The animals were killed at 2, 12, 24, and 52 weeks. The patellar damage included cracks in the superficial zone of cartilage and the zone of the calcified cartilage‐bone interface, vertical step‐off fractures in the zone of calcified cartilage, and loss of proteoglycan around the cracks in the deep and superficial zones of cartilage. With avidin‐biotin immunohistochemistry, these specimens were stained with antibodies to IL‐1β, TNF‐α, MMP‐3, fibronectin, and altered proteoglycan sulfate with the monoclonal antibody 3‐B‐3. Three of the four specimens obtained at 2 weeks demonstrated a strong cellular and weak matrix staining‐pattern for IL‐1β, TNF‐α, MMP‐3, and fibronectin around the cracks in the superficial and transitional zones of cartilage. No consistent staining pattern was noted in the cracks in the deep zone. None of the specimens obtained at 12, 24, or 52 weeks stained for these antibodies. No staining for the abnormal sulfation with the 3‐B‐3 antibody was evident in any specimen. The specimens obtained at 52 weeks showed healing of the step‐off fractures and a filling‐in of the proteoglycan loss. This model probably reflects the short‐term cartilaginous changes in the patella after trauma; thus, only transient elevations in the cytokines and proteases were evident.
The use of coccygeal discs to study intervertebral disc metabolism
Authors: Oshima H. , Ishihara H. , Urban J. P. G. , Tsuji H. 
Published: February 2005

AbstractThere have been very few studies on the metabolism of the intervertebral disc. One possible reason is that lumbar discs suitable for in vitro synthesis studies are difficult to obtain. We have examined some properties of coccygeal discs to see if those discs are a suitable alternative. The properties measured appear similar to those of lumbar discs, with collagen content lowest in the nucleus and highest in the outer annulus, while hydration and glycosaminoglycan content were highest in the nucleus and of a similar level to those of canine lumbar discs (approximately 83% water). The discs were under mechanical load in vivo, resulting in an equilibrium swelling pressure of 0.25–0.3 MPa. The 35S‐sulphate incorporation rate was 2–5 × 10−5 mmol/g dry weight per hour in the inner annulus and nucleus, in comparison with 2–3 × 10−5 mmol/g dry weight per hour in rabbit and canine lumbar discs. Coccygeal discs are a readily obtainable and cheap source of disc material, and they are easy to dissect out. Since the general properties of these discs are similar to those of lumbar discs, we suggest that they are a suitable model for the study of the metabolic and other properties of lumbar discs.
Effect of fetal thyroid hormone (RT3) on sarcoma cells in culture
Authors: Dutkowsky Joseph P. , Smith Richard A. , Calandruccio Rocco A. , Carnesale Peter G. 
Published: February 2005

AbstractFetal thyroid hormone (RT3) is considered metabolically inactive and is present in high concentration in fetuses and in some patients with end‐stage malignant disease. In a virus‐induced erythroleukemia cell model, RT3 was found to stimulate the growth of the erythroleukemia cells in culture. The focus of this research was to test the effect of RT3, at several concentrations, on the growth of naturally occurring human sarcomas in cell culture. Cloned cell lines of Ewing sarcoma, rhabdomyosarcoma, and osteogenic sarcoma were grown in multiple flasks of serum‐free medium containing varying concentrations of RT3, ranging from 10−8 and 10−5 M. Cells grown in serum‐free medium containing no RT3 were used as a control. RT3 significantly increased the growth (total protein) of the rhabdomyosarcoma cell line in culture at concentrations between 10−8 and 10−6 M, with the maximum effect at 10−7 M. The growth of one cell line of Ewing sarcoma was not affected by RT3 for any of the concentrations tested. The growth of two Ewing sarcomas and one osteogenic sarcoma was significantly stimulated by RT3 but only at the highest concentration of 10−5 M. The growth of the other osteogenic sarcoma cell line was significantly increased at concentrations of 10−6 and 10−7 M. The stimulatory effect of RT3 on several sarcoma cell lines in culture suggests the presence of a specific receptor in the neoplastic cells and the possibility that RT3 may be useful as a model for new chemotherapeutic agents.
Energy cost of ambulation with different methods of foot and ankle immobilization
Authors: Fowler Patrick T. , Botte Michael J. , Mathewson James W. , Speth Steven R. , Byrne Thomas P. , Sutherland David H. 
Published: February 2005

AbstractIn order to measure the energy cost of immobilization of the foot and ankle during ambulation, 14 healthy male volunteers exercised while wearing various immobilization devices. Oxygen consumption, oxygen cost, cardiac output, minute ventilation, heart rate, stroke volume, stride length, and stride frequency were determined at a steady state of exercise as the subjects walked on a treadmill at 80 m/min (equivalent to the comfortable walking speed of approximately 3 mi/h). Each subject was tested with three different types of immobilization devices: a short leg walking cast, a prefabricated lower leg orthosis, and a rigid‐soled surgical shoe. The results were compared with those for the same men ambulating without an immobilization device. Ambulation with the short leg walking cast and the prefabricated lower leg orthosis required significantly more energy in comparison with control values (all p values ≤ 0.006) in terms of oxygen cost, cardiac index, oxygen consumption, and minute ventilation. However, when the rigid‐soled surgical shoe was worn, energy consumption as measured by all parameters was not significantly increased compared with control values. Comparison of the findings for the short leg walking cast and the prefabricated lower leg orthosis showed no significant differences in any parameter of energy consumption. Stride length, however, was significantly shorter in the short leg walking cast compared with all immobilizers tested.
Effects of prefracture irradiation on the biomechanical parameters of fracture healing
Authors: Widmann Roger F. , Pelker Richard R. , Friedlaender Gary E. , Panjabi Manohar M. , Peschel Richard E. 
Published: February 2005

AbstractThis study examined the effects on the biomechanical parameters of fracture healing of a single dose of 900 rad (the approximate single‐dose equivalent of 2,500 rad in 10 divided doses), given 1 day prior to closed fracture of the femur. The femurs were recovered at 2, 3, 4, 8, and 16 weeks after fracture and were mounted and tested to failure in torsion; the results were compared with those in nonirradiated controls from a previously published study. Prefracture irradiation delayed the progressive increase in biomechanical parameters of fracture healing. The delay was statistically significant up to 8 weeks after fracture. At 4 weeks, the normalized torque was 44% that of intact bone in the treated group compared with 75% for the control group. Sixteen weeks after fracture, the biomechanical and histological parameters of fracture healing of the irradiated femurs were no different from those of the nonirradiated controls. Within the treated group, the irradiated fractures remained significantly weaker than their contralateral intact bone at all time intervals, with a torque of only 79% that of intact bone at 16 weeks. Thus, femoral fractures in rats healed (or regained substantial strength) following palliative doses of radiation delivered 1 day prior to injury, but the repair process was delayed compared with that of nonirradiated controls.