bluuebunny/crossref_metadata_2025 huggingface dataset:
Signal pathways and ligament cell adhesiveness
Authors: Sung K‐L. Paul , Whittemore Darren E. , Yang Li , Amiel David , Akeson Wayne H.
Published: February 2005

The influence of signal pathways involved in the adhesion of fibroblasts from the anterior cruciate and medial collateral ligaments to fibronectin was investigated. Specific emphasis was paid to the cyclic adenosine monophosphate and Ca2+/phospholipid pathways to determine the signaling mediated by integrin receptors during cell binding and spreading on a fibronectin‐coated glass surface and to compare the roles of these two pathways in integrin‐mediated adhesion in fibroblasts from the two ligaments. Individual cell adhesion strengths were determined using a micropipette‐micromanipulation system after the cells were treated with signal pathway inhibiting agents. Adhesion in fibroblasts from the medial collateral ligament was significantly reduced by inhibiting agents for Gi protein, protein kinase A, protein kinase C, protein kinase G, phospholipase C, and calmodulin, which suggests a crucial role for cyclic adenosine monophosphate and Ca2+/phospholipid signaling in integrin‐mediated adhesion of these fibroblasts. Adhesion in fibroblasts from the anterior cruciate ligament, however, was reduced only by a protein kinase C inhibiting agent and was increased by inhibiting agents for protein kinase A, protein kinase G, and calmodulin, which suggests only a partial role of Ca2+/phospholipid signaling in integrin‐mediated adhesion of these fibroblasts. On the basis of additional parallel studies on the role of intracellular calcium in integrin‐mediated adhesion, medial collateral ligament and anterior cruciate ligament fibroblast adhesion was calcium dependent throughout the 60 minute time course of adhesion experiments. Fibroblasts from the medial collateral ligament demonstrated a 2.2‐fold increase in cytosolic free calcium upon binding to fibronectin, whereas fibroblasts from the anterior cruciate ligament demonstrated no significant increase in calcium. Overall, the study of the intrinsic differences between anterior cruciate ligament and medial collateral ligament fibroblasts in their signal pathways upon binding to fibronectin may reveal information important for further explaining the lack of functional healing response in the anterior cruciate ligament after injury.
Exponential model for the tensile true stress‐strain behavior of as‐irradiated and oxidatively degraded ultra high molecular weight polyethylene
Authors: Kurtz S. M. , Rimnac C. M. , Santner T. J. , Bartel D. L.
Published: February 2005

Following sterilization by gamma radiation, ultra high molecular weight polyethylene components for total joint replacement undergo oxidative degradation upon exposure to air and the in vivo environment. Oxidative degradation is accompanied by an increase in density. The primary objective of this study was to develop a mathematical model to predict the monotonic tensile mechanical behavior of these sterilized components as a function of changes in density arising from oxidative degradation. Tensile specimens of ultra high molecular weight polyethylene were sterilized with gamma radiation and then oxidatively degraded in an air furnace. The average density of each specimen was measured using a density gradient column. Differential scanning calorimetry and Fourier transform infrared spectroscopy were conducted on selected specimens to characterize the physical and chemical changes due to accelerated aging as opposed to ambient shelf aging. Mechanical testing was conducted in monotonic uniaxial tension. An exponential model was fitted to the true stress‐strain data (up to a true strain of 0.12). The observed fitted stress had a correlation coefficient of 0.996. The model permits a quantitative prediction of the association between the true stress‐strain curve and density for the ultra high molecular weight polyethylene components. The proposed exponential model effectively describes changes in the large‐strain monotonic tensile behavior of as‐irradiated and oxidatively degraded ultra high molecular weight polyethylene components.
Altered load history affects periprosthetic bone loss following cementless total hip arthroplasty
Authors: Bryan J. M. , Sumner D. R. , Hurwitz D. E. , Tompkins G. S. , Andriacchi T. P. , Galante J. O.
Published: February 2005

Dual energy x‐ray absorptiometry was used to measure periprosthetic, distal femoral, and proximal tibial bone mass in the affected and contralateral limbs of eight patients 10 years after unilateral total hip arthroplasty with a cementless, porous‐coated titanium alloy femoral stem. Gait analyses to assess the presence of asymmetries in loading of the lower extremities were also performed 10 years postoperatively. The patients had excellent clinical results and no other significant lower extremity pathology. On the basis of comparison of the affected and unaffected proximal femora, bone loss adjacent to the proximal medial aspect of the femoral stem was determined to be 34% (p < 0.001). However, the patients also had 16% less bone in the ipsilateral proximal tibia (p = 0.003) and 15% less bone in the ipsilateral femur 3 cm distal to the prosthesis (p = 0.007) compared with the contralateral limb. When normalized to the asymmetry in tibial bone mineral content, the estimated proximal medial periprosthetic bone loss was still statistically significant, but the magnitude was reduced from 34 to 17% (p = 0.009). The gait analyses indicated that several measures that influence the loads at the hip and knee joints were reduced in the involved limb compared with the contralateral limb. Furthermore, the bilateral difference in the vertical component of the external force acting on the proximal tibia was correlated with the bilateral difference in tibial bone mineral content (r = 0.80, p = 0.02). These data suggest that two mechanical factors, the local stress‐shielding effect of the prosthesis and the global effect of decreased loading of the limb, can both make significant contributions to periprosthetic bone loss. It is apparent that the magnitude of the periprosthetic bone loss related to stress‐shielding has been overestimated by as much as 50% in retrospective studies.
In vitro measurement of strain in the bone cement surrounding the femoral component of total hip replacements during simulated gait and stair‐climbing
Authors: O'Connor Daniel O. , Burke Dennis W. , Jasty Murali , Sedlacek Ronald C. , Harris William H.
Published: February 2005

The strains in the cement mantle surrounding the cemented femoral component of a total hip replacement were measured in vitro, using strain gauges embedded within the cement mantle adjacent to the femoral component in femurs from cadavers under physiologic loads simulating both single‐limb stance and stair‐climbing. Cement strains in the most proximal portion of the cement mantle were measured with and without full contact of the collar of the femoral stem on the cortex of the medial portion of the femoral neck during both loading conditions. To our knowledge, these are the first studies to contrast by direct measurement the strain profile in the cement mantle of a cemented femoral component under simulated stair‐climbing with that occurring under simulated single‐limb stance. They extend the findings from finite element analyses and from clinical specimens retrieved at autopsy in identifying those regions of the cement mantle most likely to fail. At two specific foci, the magnitude of the strain in the cement mantle approaches values that could lead to early fatigue failure of the cement. The two regions in which the strains were highest (greater than 1,000 microstrain) were the most proximal portions of the cement mantle and near the tip of the femoral component. Although these two regions are recognized areas of high strain and also common sites of cement debonding and cement mantle failure, the strain‐gauge studies showed that the magnitude of cement strains in the proximal portion of the cement mantle were highest during stair‐climbing; in contrast, high strains at the tip region occurred in both gait and stair‐climbing. Contact between the collar and the medial portion of the femoral neck reduced the strain in the proximal portion of the cement mantle not only in single‐limb stance but in stair‐climbing as well. The level of strain recorded in these studies for a simulated person weighing 115 pounds (52 kg) could lead to cement fracture during extended in vivo service life of a cemented femoral component, from either single‐limb stance or stair‐climbing. This risk would be increased if a void or defect existed in the cement mantle at these sites. Moreover, the increase in strain in the cement mantle was linear with increases in body weight between 100 and 200 pounds (45 and 91 kg) of spinal load, indicating that strains in a heavy patient could readily exceed the fatigue limit of the cement, particularly if a stress riser such as a pore in the cement or a sharp corner of the prosthesis were present. These data reemphasize the need to continue efforts to develop methods to strengthen bone cement and to reduce those factors that increase the strain in the cement mantle of cemented femoral components of total hip arthroplasty, particularly proximally and near the tip.
Endothelin‐a receptors mediate vascular smooth‐muscle response to moderate acidosis in the canine tibial nutrient artery
Authors: Coessens Bruno C. , Miller Virginia M. , Wood Michael B.
Published: February 2005

Perfusate pH may influence the tone of vascular smooth muscle by affecting the release of endothelium‐derived vasoactive factors or by directly modulating function of the smooth muscle. This study was designed to investigate the role of endothelium‐derived factors on acidosis‐induced responses of isolated canine tibial nutrient artery suspended in an organ chamber for the measurement of isometric contractile force. To investigate the specific role of the endothelium in half the rings, the endothelium was removed mechanically. Concentration‐response curves to KCl were obtained in the absence or presence of inhibition of two important endothelium‐derived relaxing factors, nitric oxide and prostacyclin, and an inhibitor of receptors for the endothelium‐derived contracting factor, endothelin‐1. Acidification of the perfusate from pH 7.45 to 7.0 significantly attenuated the contractions to KCl in arterial rings with endothelium (the mean of the effective concentration causing 50% of the maximal response for KCl at pH 7.45 and 7.0 was 12.31 ± 0.40 nM and 14.60 ± 0.55 nM, respectively). This difference was abolished by mechanical removal of the endothelium. In rings with endothelium, inhibition of nitric oxide or prostacyclin did not abolish the attenuation of KCl‐induced contractions occurring with acidosis (the mean of the effective concentration causing 50% of the maximal response for KCl at pH 7.45 and 7.0 was 11.18 ± 0.60 nM and 13.60 ± 0.60 nM, respectively). Inhibition of endothelin‐A receptors did not alter contractions to KCl at pH 7.45. However, the acidosisinduced attenuation of contractions with KCl was abolished by the endothelin‐A‐receptor antagonist BQ‐123 (the mean of the effective concentration causing 50% of the maximal response at pH 7.45 and 7.0 was 13.8 ± 1.34 nM and 13.2 ± 1.34 nM, respectively). These results suggest that acidosis‐induced relaxation of canine tibial nutrient artery is endothelium dependent and that activation of endothelin‐A receptors during acidosis is coupled to a release of an endothelium‐derived relaxing factor.
Long‐term study of the biochemistry and biomechanics of anterior cruciate ligament‐patellar tendon autografts in goats
Authors: Ng Gabriel Y. F. , Oakes Barry W. , Deacon Owen W. , McLean Iain D. , Eyre David R.
Published: February 2005

This study examined the change in type‐III collagen concentration and hydroxypyridinium crosslink density of anterior cruciate ligament‐patellar tendon autografts and their correlations with Young's modulus of the anterior cruciate autografts and anterior cruciate controls for as long as 3 years after surgery. Fifteen adult female goats (two control and 13 experimental) were tested. Each experimental animal received an anterior cruciate ligament‐patellar tendon autograft to the right knee. These animals were tested at 0 (n = 2), 6 (n = 2), 12 (n = 2), and 24 (n = 1) weeks and 1 (n = 3) and 3 (n = 3) years after surgery. After mechanical testing, the anterior cruciate autograft and control tissues were analysed for type‐III collagen concentration and hydroxypyridinium crosslink density. The results of sodium dodecyl sulfate gel electrophoresis showed a trend of initial increase in the percentage of type‐III collagen in the anterior cruciate ligament autografts and a subsequent decrease after 24 weeks following surgery. There was a nonsignificant (p > 0.05) negative correlation between type‐III collagen concentration and Young's modulus. The hydroxypyridinium crosslink density was highest at 1 year after surgery. There was a significant (p < 0.05) positive correlation between hydroxypyridinium crosslink density and Young's modulus in the anterior cruciate autografts and controls. This suggests that hydroxypyridinium crosslink density has a good linear relationship with the material strength of the anterior cruciate ligament autograft and hence could be used as an objective guide for rehabilitation with anterior cruciate autografts.
Migration of press‐fit cups fixed with poly‐L‐lactic acid or titanium screws: A randomized study using radiostereometry
Authors: Thanner J. , Kärrholm J. , Malchau H. , Herberts P. , Wallinder L.
Published: February 2005

The early migration of porous acetabular cups was studied in 43 patients with osteoarthrosis. The patients were randomly allocated to additional fixation of the cup with either biodegradable poly‐L‐lactic acid screws or titanium screws. Radiostereometric evaluation was done during the first 2 years after the procedure in 43 hips (23 with poly‐L‐lactic acid screws and 20 with titanium screws). At the 2‐year follow‐up, cups fixed with poly‐L‐lactic acid screws had migrated significantly more in the proximal‐distal (p < 0.05) and medial‐lateral (p < 0.05) directions. Cups with titanium screws displayed more pronounced rotations around the longitudinal axis (p < 0.05). Postoperatively, on the lateral view, there was an increased occurrence of radio‐lucencies at the dome of the cups fixed with poly‐L‐lactic acid screws (p < 0.05). The clinical result did not differ between the two groups. Inferior implant‐bone contact in the poly‐L‐lactic acid group, local changes of the bone quality, and diminishing support of the poly‐L‐lactic acid screws caused by their degradation with time could be reasons for the different pattern of migration observed.
Osteogenic potential of allogeneic rat marrow cells in porous hydroxyapatite ceramics: A histological study
Authors: Sempuku Takeo , Ohgushia Hajime , Okumur Motoaki , Tamai Susumu
Published: February 2005

Hydroxyapatite ceramics facilitate osteogenesis but cannot induce bone formation by themselves. We studied the feasibility of bone formation supported by allogeneic bone marrow cells in porous hydroxyapatite ceramics. Coralline hydroxyapatite discs were soaked in a marrow cell suspension harvested from either ACI (RT1a), Lewis (RT11), or Fischer 344 (RT11v) male rats, and these discs were implanted subcutaneously into 56 male Fischer 344 rats. FK‐506 (tacrolimus hydrate), an immunosuppressant, or saline was injected intramuscularly into the recipients every day for 2 weeks after surgery, and additional injections were given to 19 of the rats every 2 days for 2 more weeks. Neither of the mismatched major (ACI rat) or minor (Lewis rat) marrow cell transplants showed any bone formation without administration of FK‐506. However, in rats treated with FK‐506, bone formed in the pores of all the three types of ceramics implanted, which each contained the marrow cells from one of the three kinds of rats used. There were no differences among the three groups of donors with regard to the bone formation ratio. We previously reported that subcutaneous implantation of porous hydroxyapatite combined with isogeneic marrow cells resulted in consistent bone formation, even at ectopic sites. Since it would be difficult to harvest a large number of autologous marrow cells in clinical cases, we attempted to use allogeneic marrow cells and have shown the allogeneic murine marrow cells to have osteogenic potential.
Effect of human adrenomedullin on a canine tibial perfusion model in the absence of vascular endothelium
Authors: Kato Teiji , Bishop Allen T. , Wood Michael B.
Published: February 2005

The effect of human adrenomedullin was investigated using an ex vivo perfused canine tibial model in the absence of vascular endothelium. Adrenomedullin is a novel peptide with known vasodilator properties. In this model. a 0.1 ml bolus injection of 10−5 M of either acetylcholine or adrenomedullin decreased vascular resistance in tibial preparations precontracted with prostaglandin F2α by 88.3 ± 3.0% and 92.8 ± 2.8%, respectively, in the presence of vascular endothelium. Conversely, a 0.1 ml bolus injection of 10−5 M acetylcholine produced a constrictor response after removal of vascular endothelium. A 0.1 ml bolus injection of 10−5 M adrenomedullin decreased the baseline perfusion pressure in a dose‐dependent manner for a duration of 20 minutes and also attenuated the pressor response to exogenous norepinephrine injection for at least 10 minutes compared with the control study (p < 0.05) in the absence of vascular endothelium. These data suggest that human adrenomedullin relaxes blood vessels in bone by a direct action on vascular smooth‐muscle cells. In addition, the attenuation effect of human adrenomedullin on pressor responses to exogenous norepinephrine injection is independent of vascular endothelium.
Technique for generating submicrometer ultra high molecular weight polyethylene particles
Authors: Shanbhag Arun S. , Hasselman Carl T. , Rubash Harry E.
Published: February 2005

Ultra high molecular weight polyethylene wear debris is believed to have a major role in aseptic loosening of prosthetic joints. In order to study the cellular and host response to this and other such particulate debris, a source of fine ultra high molecular weight polyethylene debris is needed. We have described a technique to fracture the GUR 4150 primary ultra high molecular weight polyethylene grain, which reproducibly generated particles less than 1 μm in size. Furthermore, the particle morphology was similar to that of ultra high molecular weight polyethylene particles generated in vivo and retrieved from interfacial tissues. The fabricatd polyethylene particls ranged from 0.1 to 33 μm in diameter, with a mean of 2.3 ± 0.2 μm. Sixty percent of the particles were smaller than 1 μm and 90% were smaller than 7 μm. Using filtration and sedimentation, it is possible to acquire finer particle fractions. These particles are currently being used for biological response studies.
Human monocyte/macrophage response to cobalt‐chromium corrosion products and titanium particles in patients with total joint replacements
Authors: Lee S‐H. , Brennan F. R. , Jacobs J. J. , Urban R. M. , Ragasa D. R. , Glant T. T.
Published: February 2005

The responses of human peripheral blood monocytes of 10 normal volounteers and 14 patients with total hip replacements to particles of commercially pure titanium and chromium orthphosphate (a corrosion product from cobalt‐chromium alloy implants) were studied. In addition, these phagocytosable particles were added to cultured mononuclear cells isolated from the interfacial membrane of 14 patients with failed implants. Peripheral blood monocytes from patients who had had a total hip replacement produced significantly higher levels of interleukin‐1 (both interleukin‐1α and interleukin‐1β) and prostaglandin E2 follwing particulate stimulation than those from normal volunteers. Supernatants from both titanium and chromium orthophosphate‐stimulated peripheral blood monocytes from the volunteers and patients with total hip replacement induced bone resorption (assayed in organ cultures of newborn mouse calvariae)and the proliferation of human fibroblasts. The levels of bone resorption were significantly higher (p < 0.05) in patients with implants that in normal volunteers. There were no significant differences in the responses of cells between patients with focal osteolysis and those without osteolysis. Interfacial membrane mononuclear cells also produced high levels of interleukin‐1α, interleukin‐1β, and prostaglandin E2 and expressed bone resorptive activities following stimulation with either titanium or chromium orthophosphate. More importantly, interfacial membrane mononuclear cells “spontaneously” produced high levels of prostaglandin E2 that were comparable with the response of peripheral blood monocytes stimulated with particulate wear debris. The clinical relevance of this study is 2‐fold. First, mononuclear cells from patients with total hip replacement were some‐how “sensitized” to metal particles in comparison with mononuclear cells from individuals without an implant. Second, the chromium orthophosphate corrosion product was a potent macrophage/monocyte activator and may contribute to macrophage‐mediated osteolysis and aseptic loosening.
Effects of ionizing radiation on the mechanical properties of human bone
Authors: Currey John D. , Foreman James , Laketić Ira , Mitchell Julie , Pegg David E. , Reilly Gwendolen C.
Published: February 2005

Allogeneic bone grafts are frequently sterilized by means of ionizing radiation. We investigated the effects of ionizing radiation on both quasistatic and impact mechanical properties of human bone. Specimens from four paired femora of four donors received doses of 29.5 kGy (“Standard” frequently used by tissue bandks), 94.7 kGy (“high”) or 17 kGy (“low”) of ionizing radiation. Young's modulus was unchanged by any level of radiation. Radiation significantly reduced bending strength, work to fracture, and impact energy absorption; in each case, the severity of the effect increased from low to standard to high doses of radiation. Work to fracture was particularly severely degraded; specimens irradiated with the high dose absorbed only 5% of the energy of the controls. Radiation. even at relatively low doses, makes the bone more brittle and thereby reduces its energy‐absorbing capacity. We suggest that because the level of radiation required to produce an acceptable level of viral inactivation (90 kGy) produces an unacceptable reduction in the mechanical integrity of the bone. low levels of radiation, sufficient to produce bacterial safety, should be used in conjunction with biological tests to ensure viral safety.
Comparison of the fixation of subcapital femoral neck osteotomies with absorbable self‐reinfoced poly‐L‐lactide lag‐screws or metallic screws in sheep
Authors: Jukkala‐Partio Kirsi , Laitinen Outi , Partio Esa K. , Vasenius Jarkko , Vainionpää Seppo , Pohjonen Timo , Törmälä Pertti , Rokkanen Pentti
Published: February 2005

Seven subcapital femoral osteotomies of adult sheep were each fixed with two absorbable selfreinforced poly‐L‐lactide lag‐screws, and seven other osteotomies were each fixed with two metallic cancellous bone screws. At 3 and 12 weeks, radiographs were taken and callus formation, displacement, and union were evaluated. At 12 weeks, the animals were killed and strength measurements were carried out. According to the radiographs, union was achieved in six of seven osteotomies in both groups, while after 3 weeks one fixation in both the group treated with absorbable screws and the group treated with metallic screws had failed. There were no statistical differences between the groups with respect to callus formation or displacement. Regarding the strength of the ostecotomized bones, at 12 weeks there were no statistically significant differences in the load‐carrying capacity between the bones fixed with self‐reinforecd poly‐L‐lactide screws and those fixed with metallic screws. These results showed that self‐reinforced poly‐L‐lactide screws, which have been used successfully in fractures and osteotomies in cancellous bone, are strong enough to support this more demanding fixation of weight‐bearing bones.
Calcitonin gene‐related peptide, substance P, and tyrosine hydroxylase‐immunoreactive innervation of rat bone marrows: An immunohistochemical and ultrastructural investigation on possible efferent and afferent mechanisms
Authors: Imai Shinji , Tokunaga Yoshimitsu , Maeda Toshihiro , Kikkawa Masanori , Hukuda Sinsuke
Published: February 2005

The presence of nerve fibers in bone marrow has been noted by various investigators, and recent developments in immunohistochemistry have enabled differential localization of the intramedullary nerve fibers. Much interest has been devoted to the efferent activities of the afferent fibers, which probably act on the target tissues by secreting a variety of neurotransmitters. The present study aimed to further characterize intramedullary substance P, calcitonin gene‐related peptide, and tyrosine hydroxylase‐immunoreactive nerve fibers of the rat lower limb by comparing those of the knee, ankle, and tarsal joints. The ultrastructural details of intramedullary calcitonin gene‐related peptide‐immunoreactive axons were also investigated to provide a morphological basis for their possible efferent actions. Intramedullary calcitonin gene‐related peptide and substance P‐immunoreactive fibers in the proximal tibia and the knee joint were found to be as reported earlier, but the marrow of the distal metaphysis was also noted to be richly innervated, and the tarsal joints displayed dense innervation at the subchondral regions that underlie the joint cartilage. The articular and intramedullary innervations that function for joint protection might participate in characteristic clinical features of joint damage secondary to the neuropathies. Ultrastructurally, the intramedullary calcitonin gene‐related peptide‐immunoreactive axons were minimally engulfed by the Schwann cell, and naked intramedullary calcitonic gene‐related peptide‐immunoreactive axons were noted along an extraordinarily long extension, suggesting much efferent activity.
Compressive strains at physiological frequencies influence the metabolism of chondrocytes seeded in agarose
Authors: Lee David A. , Bader Dan L.
Published: February 2005

Articular cartilage is subjected to dynamic compressive loading that is known to influence chondrocyte metabolism. While the exact signalling mechanisms are unclear, it has been proposed that cell deformation plays a role and may stimulate a metabolic response through distinctive pathways. In this study, a well characterized model system in which chondrocytes are embedded in agarose was used to study the effect of dynamic cellular strain on three key metabolic processes, namely the synthesis of glycosaminoglycan, of DNA, and of total protein. Using a specially designed apparatus, 15% compressive strain amplitude was applied to agarose‐chondrocyte cylinders statically or dynamically over a range of frequencies (0.3‐3 Hz). Static and low‐frequency strain (0.3 Hz) inhibited the synthesis of glycosaminoglycan, while a frequency of 1 Hz stimulated synthesis. Static strain reduced the level of thymidine uptake, whereas dynamic strain at all frequencies induced an increase in chondrocyte proliferation. Incorporation of tritiated proline was suppressed by all strain regimens tested. The three parameters investigated were each influenced by the dynamic strain regimens in a distinct manner, implying that the signalling mechanisms involved are uncoupled.
Calcitonin gene‐related peptide and reperfusion injury
Authors: Allen Diane M. , Chen Long‐En , Seaber Anthony V. , Urbaniak James R.
Published: February 2005

Calcitonin gene‐related peptide is a potent intrinsic vasodilator, can induce prostacyclin release, and may inhibit membrane lipid peroxidation. This study examines the effect of calcitonin gene‐related peptide on vessel diameters, capillary perfusion and contractile function of skeletal muscle after 4 or 5 hours of ischemia and during immediate reperfusion using the rat cremaster muscle model. Forty‐two male rats were used; half of these received 0.2 ml of 10−7 M calcitonin gene‐related peptide after 0, 15, and 30 minutes of reperfusion, while the other half received normal saline as a control. By means of intravital videomicroscopy, the diameters of 10 vessels per muscle were measured prior to ischemia and during reperfusion. The fluorescein filling area was determined at 15, 30, and 60 minutes of reperfusion. After 1 hour of reperfusion, muscle function was examined in vitro by quantifying the contractile response to electric field stimulation of the muscles in an organ bath system. There was a significant increase in the diameter of the arterioles, but not the small arteries, at every time point from 10 to 60 minutes of reperfusion. The fluorescein filling area was increased in treated muscles at every time point. Contractile function was not significantly preserved. In light of the ability of calcitonin gene‐related peptide to relieve vasospasm and improve capillary perfusion, it may be useful in reducing reperfusion injury in the future.
Biochemical and density assessment of the new bone in late remodeling after callus distraction
Authors: Lammens Johan , Aerssens Jeroen , Nijs Jos , Mokassa Luc , Dequeker Jan , Bouillon Roger , Fabry Guy
Published: February 2005

Biochemical changes in a canine bone‐lengthening model were characterized 5 months after surgery. The mineral content and the total amount of EDTA‐extractable noncollagenous proteins, insulin‐like growth factor‐I, and osteocalcin were determined for the lengthened callus, and a gradient density fractionation analysis of bone powder particles was performed. The results were compared with two other areas of the lengthened tibia and one region of the contralateral tibia. The mineral and osteocalcin contents showed significant decreases, whereas the hydroxyproline concentration was significantly increased. Neither the insulinlike growth factor‐I content nor the concentration of EDTA‐extractable proteins was significantly different in any of the examined regions.
Small‐angle HeNe laser light scatter and the compressive modulus of articular cartilage
Authors: Kovach Ian S. , Athanasiou Kyriacos A.
Published: February 2005

Light scattering is a widely used technique for probing the microarchitecture and interactions of biological materials and solutions. In this paper, we describe the use of this method in the study of articular cartilage. The experiments presented utilize small‐angle static scattering of HeNe laser light (632.8 nm) from 40 μm thick samples of cartilage taken from the superficial zone of baboon femoral condyle. The specimens were taken from a total of 26 sites in eight animals of various ages. In addition to measuring the dependence of the intensity of scattered light on scatter angle, we performed mechanical testing at the test sites using creep‐indentation techniques. The results from the optical and mechanical experiments were compared, and a significant correlation was noted between the average scatter angle and the compressive aggregate modulus. In addition, it was noted that the cartilage of skelelally immature animals had a smaller aggregate modulus and scattered to a higher average angle than the cartilage of skeletally mature animals. A quantitative theory was developed to explain the relation between mechanical and optical properties in terms of the degree of order in the spatial arrangement of the collagen fibers in cartilage.
Treatment with recombinant human macrophage colony‐stimulating factor resorbs blood clot and restores osteoclastogenesis in heterotopic bone induced by partially purified native bone morphogenetic protein in osteopetrotic (op/op) mice
Authors: Miyazawa Ken , Urist Marshall R.
Published: February 2005

Native bone morphogenetic protein and associated noncollagenous proteins induced the formation of heterotopic bone in the hindquarter muscles of osteopetrotic (op/op) mice and those of their phenotypically normal littermates (+/?). In op/op mice, the heterotopic bone consisted of a disorganized, densely packed mixture of irregular calcified cartilage, osleoid, Chondro‐osteoid, and fibrous tissue. Injections of recombinant human macrophage colony‐stimulating factor initiated bone resorption that began in the peripheral vascularized regions of the metaphyses and continued in central areas of uncalficified avascular chondro‐osteoid. On vascularized surfaces, osteoclasts were stained with tartrate‐resistant acid phosphatase. In op/op mice treated with macrophage colony‐stimulating factor, the osteoclasts were small, with only two or three nuclei and they did not exhibit tartrate‐resistant acid phosphatase staining. In untreated op/op mice, surgical blood clots persisted in the heterotopic sites as late as 3 weeks after the operation, whereas in treated op/op mice, the blood clots were absorbed almost as rapidly as in normal mice. Histologically, recombinant human macrophage colony‐stimulating factor restored normal macrophage functions: absorption and organization of blood clot, osteoclastogenesis. synthesis of tartrate‐resistant acid phosphatase, bone remodeling, islands of myelopoiesis, and construction of an ossicle complete with a cortex and a medulla filled with functioning hematopoietic bone marrow.
Studies of ischemia‐reperfusion injury in skeletal muscle: Efficacy of 21‐aminosteroids on microcirculation and muscle contraction after an extended period of warm ischemia
Authors: Korompilias Anastasios V. , Chen Long‐En , Seaber Anthony V. , Urbaniak James R.
Published: February 2005

The present study was conducted to elucidate the effects of tirilazad mesylate (U‐74006F), a potent inhibitor of lipid peroxidation, on vessel diameter, capillary perfusion, and contractile function of rat cremaster muscle during a 90‐minute reperfusion period that followed 4 hours of warm ischemia. Two groups of 32 animals were treated with either 3 mg/kg U‐74006F or the vehicle (citrate buffer) alone 30 minutes before. ischemia, 90 minutes after ischemia, and immediately before reperfusion. With use of intravital videomicros‐copy, the internal luminal diameters of preselected vessels were measured prior to ischemia and during reperfusion The area that filled with fluorescein was determined at 15‐minute intervals for as long as 90 minutes of reperfusion, and contractile function was examined in vitro in an organ bath at that point. In the U‐74006F group, after 90 minutes of reperfusion the vessel diameters returned completely to baseline and the diameters of all three categories of vessels at every time point from 10 to 90 minutes of reperfusion had significantly more rapid recovery than the controls. Although some evidence of more rapid fluorescence was noted in the U‐74006F group, the two groups did not differ significantly at any time period of reperfusion. In response to tetanic stimulation, the muscles treated with U‐74006F had a significantly greater contractile force at all stimulation frequencies than the control musclss. Our findings indicate that pretreatment with U‐74006F can effectively decrease the rise of vascular resistance and preserve the contractile function of skeletal muscle during early reperfusion, thereby attenuating ischemia‐reperfusion injury.
Type‐II collagen gene expression is transiently upregulated in experimentally induced degeneration of rabbit intervertebral disc
Authors: Takaishi Hironari , Nemoto Osamu , Shiota Masanobu , Kikuchi Toshiyuki , Yamada Harumoto , Yamagishi Masaaki , Yabe Yutaka
Published: February 2005

To clarify phenotypic alterations of intervertebral disc cells during the repair process, we cloned partial type‐II collagen cDNA from rabbits and analyzed the level of expression of type‐II collagen mRNA in disc degeneration. An animal model was created by surgical denucleation of rabbit intervertebral discs through, an extraperitoneal approach. Eight animals each from an experimental and a control group were killed at 2, 4, 8, or 16 weeks postoperatively, and the disc samples were used for this study. Round chondrorcyte‐like cells that filled the herniated space showed intense signal of type‐II collagen mRNA and significant pericellular immunostaining of type‐II collagen but no clear staining of type‐I collagen. Northern. blot analysis revealed that the expression of type‐II collagen mRNA of the repair disc cells was transiently increased at 4 weeks postoperatively. The cells were able to change their morphology in response to mechanical stimulation by surgical denucleation and to induce a significant increase in the gene expression of type‐II collagen at an early phase of disc degeneration. The present results indicate the transient enhancement of repair activity in the degenerative process of injured fibrocartilage.
In vivo tensile behavior of a four‐bundle hamstring graft as a replacement for the anterior cruciate ligament
Authors: Wallace Michael P. , Howell Stephen M. , Hull M. L.
Published: February 2005

The purpose of this study was to measure the in vivo tensile behavior of a doublelooped semitendinosus and gracilis graft used to reconstruct a torn anterior cruciate ligament in the human knee. In 14 subjects, intraoperative tension was measured for each of the four graft bundles during passive motion from 0 to 90° of flexion. Two hypotheses were tested: (a) the peak tension carried by each of the four bundles was equal during passive motion, and (b) the mechanics of the bundles mimicked the functional bands of the wnative anterior cruciate ligament. The total tension was also calculated and used to determine strength requirements for fixation devices. The peak tensions of the four bundles during passive motion were not equal; however, enough tension was present in each bundle that load‐sharing occurred between bundles. The pattern of tension between the anterior and posterior bundles mimicked the reciprocating load‐sharing behavior of the functional bands of the native anterior cruciate ligament. Reciprocal tensile behavior was con sistently achieved with the use of a single femoral tunnel centered on the most isometric line without the need for two separate femoral sockets. The maximum total tension was 296 N; this was nearly equal to the strength of one commonly used fixation device.
Characterization of human bone marrow stromal cells with respect to osteoblastic differentiation
Authors: Majors Alana K. , Boehm Cynthia A , Nitto Hironori , Midura Ronald J. , Muschler George F.
Published: February 2005

Human bone marrow was harvested by means of iliac crest aspiration and cultured under conditions that promote an osteoblastic phenotype. Human bone marrow aspirates from 30 normal subjects, ages 8–80 years, with no systemic illness, yielded a mean of 92 ± 65 × 106 nucleated cells per 2 ml of aspirate. The prevalence of potential osteoblastic progenitors was estimated by counting the number of alkaline phosphatase‐positive colonies. This assay demonstrated a mean of 43 ± 28 alkaline phosphatase‐positive colonies per 106 nucleated cells, which was about one per 23,000 nucleated cells. The prevalence of these colonies was positively correlated with the concentration of nucleated cells in the original aspirate (p = 0.014) and was negatively correlated with donor age (p = 0.020). The population of alkaline phosphatase‐positive colonies in this model sequentially exhibited markers of the osteoblastic phenotype; essentially all colonies (more than 99%) stained positively for alkaline phosphatase on day 9. Matrix mineralization, which was associated with the synthesis of bone sialoprotein, was demonstrated on day 17 with alizarin red S staining. On day 45, cells that were stimulated with 1,25‐dihydroxyvitamin D3 synthesized and secreted osteocalcin at concentrations consistent with known osteoblastic cell lines. This model provides a useful method for the assay of progenitors of connective tissue from human subjects, examination of the effects of aging and selected disease states on this progenitor population, and investigation into the regulation of human osteoblastic differentiation.
Sustained proliferation accompanies distraction osteogenesis in the rat
Authors: Aronson J. , Shen X. C. , Gao G. G. , Miller F. , Quattlebaum T. , Skinner R. A. , Badger T. M. , Lumpkin C. K.
Published: February 2005

These studies were conducted to compare the local cellular proliferation patterns in the rat tibia during distraction osteogenesis with those during nondistracted fracture healing. Bone specimens from distraction osteogenesis and nondistracted fracture groups were analyzed 2, 10, and 20 days after surgery. Proliferation was determined by metabolic labeling with [3H]thymidine and by immunocytochemistry with an antibody to proliferating cell nuclear antigen. Videomicroscopy was used to count the cells staining positively within specified regions. The number of cells incorporating [3H]thymidine was positively correlated (r2 = 0.78) with the number of proliferating cell nuclear antigen positive cells on alternating serial slides. At day 2, the latter cells were largely confined to the bone marrow and periosteum in both groups, and the cell numbers per mm2 were also equivalent. At days 10 and 20, the proliferating cell nuclear antigen positive cells predominated in both the proximal and distal primary matrix front zones in the distraction osteogenesis group. In contrast, the proliferating cell nuclear antigen positive cells in the nondistracted fracture group were scattered throughout the healing area. Significantly more of these cells were in the primary matrix front zones than in any location within the nondistracted fracture‐healing area. The number of these cells in the bone marrow adjacent to the surgical area declined from day 2 to day 10 in both groups. The results suggest that (a) proliferating cell nuclear antigen immunostaining is a reliable indicator of cycling cells; (b) by day 10, distraction osteogenesis is characterized by a zone‐specific pattern of proliferating cells; and (c) distraction osteogenesis prolongs the stimulation of proliferation within the gap after fracture.
Proprioception after an acute knee ligament injury: A longitudinal study on 16 consecutive patients
Authors: Fridén Thomas , Roberts David , Zätterström Rose , Lindstrand Anders , Moritz Ulrich
Published: February 2005

A defect in proprioception has been found in selected patient groups that have an anterior cruciate ligament deficient knee at different times after the original injury. The time of development and the extent of such defects were studied ongitudinally on 16 consecutive patients. During the first year after a primary knee injury, which included a complete rupture of the anterior cruciate ligament, we repeatedly performed three tests of proprioception: (a) one to determine the threshold for detecting a passive motion from starting positions of 20 and 40°, (b) an active reproduction of a passive angular change, and (c) a visual estimation of a passive angular change. The injured limb was compared with the uninjured limb and with the limbs of an age‐matched reference group of healthy subjects. The population did not have a normal distribution, and some patients had consistently extreme recordings in the threshold tests at the various times of testing. Significant differences were found between the groups at the starting position of 20°, when the injured knee was compared with the uninjured knee, after 1 month (p = 0.05), and after 2 months (p = 0.03). There was a trend toward a higher threshold for detecting a passive motion when the injured side was compared with the knees of the reference group at 1 month (p = 0.06) but not later on. A similar pattern was found for the injured knee at the starting position of 40°, but it was not significant. An impaired ability to detect a passive motion was registered for the nearly extended knee 1 and 2 months after a primary injury. In the active reproduction and visual estimation tests, no significant defects were found at any time during the first year in these consecutively studied patients.
Role of oxygen tension during cartilage formation by periosteum
Authors: O'Driscoll Shawn W. , Fitzsimmons James S. , Commisso Cinzia N.
Published: February 2005

Tissue engineering makes regeneration of cartilage possible but requires optimization of culture conditions. The effects of oxygen tension on cartilage metabolism are controversial in the literature, and we could find no information detailing the optimal oxygen concentration for growing new cartilage (neochondrogenesis). Periosteal cells and tissues can be used to grow cartilage in vivo and in vitro. In this study, using a standard periosteal organ culture model, we found that cartilage formation by periosteal explants is affected by the ambient oxygen concentrations. A total of 480 periosteal explants from 30 2‐month‐old New Zealand White rabbits were cultured in agarose suspension at different oxygen concentrations (1‐90%) for 6 weeks. Chondrogenesis, which was analyzed by histomorphometry and quantitative collagen typing, was maximal at 12–15% oxygen. There were no significant differences in chondrogenesis in the range of 12–45%. There was inhibition of cartilage and type II collagen formation at very high (90%) and very low (1–5%) oxygen concentrations. However, contrary to what some have thought, chondrogenesis is maximal under aerobic conditions. If this is true for systems other than periosteal implants, it would have important implications for growing cartilage in vitro.
Characterisation of human deltoid muscle in patients with impingement syndrome
Authors: Kronberg Margareta , Larsson Peter , Broström Lars‐Åke
Published: February 2005

Muscle biopsies from the anterior and medial parts of the deltoid of 11 male patients and six male controls were analysed with morphological and immunohistochemical methods. The distribution, area, and capillarization of the muscle fibres were determined, and the amount of connective tissue was measured with staining for type‐III collagen. Compared with the controls, the patients with impingement syndrome had more type‐I than type‐II fibres, but the areas of the different types were almost the same. There was no difference in capillarization per fibre type between patients and controls, but the patients had more connective tissue. The results indicate that patients with impingement syndrome have morphological changes in the deltoid muscle, probably due to immobilisation and pain. They support the hypothesis that the deltoid muscle, the medial part in particular, is affected in patients with impingement syndrome.