bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of compressive loading and unloading on the synthesis of total protein, proteoglycan, and fibronectin by canine cartilage explants
Authors: Burton‐Wurster Nancy , Vernier‐Singer Margaret , Farquhar Tony , Lust George 
Published: February 2005

AbstractFull‐thickness canine articular cartilage explants were subjected to compressive loads equivalent to a uniaxial stress of 0.025–1.2 MPa. A single cycle (18 h) of unconfined compression resulted in inhibition of total protein, proteoglycan, and fibronectin synthesis. The inhibition of fibronectin synthesis followed that of total protein synthesis. The magnitude of inhibition increased nonlinearly with increasing load levels. The signal that depressed synthesis remained effective for several hours after removal of load, but by 24 h proteoglycan synthesis had partially recovered and fibronectin and protein synthesis had fully recovered and sometimes exceeded the rate of synthesis in free‐swelling controls. Forty‐eight hours after five cycles of intermittent unconfined compression with similar loads, proteoglycan content and synthesis did not differ in loaded disks and in disks that were never loaded in vitro. Interestingly, the percentage of water in disks that had never been loaded in vitro increased significantly after 10 days in culture, relative to the percentage of water in free‐swelling disks on the day of harvest. Intermittent compressive loading in the range of 0.5–1.2 MPa partially prevented this increase. Our results confirmed the previously reported inhibition of biosynthesis with static loading but also suggested that exposure to intermittent compressive loading may help to maintain the normal ratio of dry to wet weight in the explant.
Preservation of bone graft vascularity with the University of Wisconsin cold storage solution
Authors: Moran Christopher G. , Adams Mary L. , Wood Michael B. 
Published: February 2005

AbstractThe preservation of the microcirculation of bone has been evaluated with use of an in vitro canine tibia perfusion model. The production of relaxing factors by the osseous vascular endothelium was used as a metabolic marker for viability. This endothelial eccrine function was preserved for 5 days (120 h) by cold storage without continuous perfusion after a washout with the University of Wisconsin (UW) solution. This synthetic perfusate was superior to Krebs Ringer solution (p < 0.05), but storage without perfusion failed to prevent a significant rise in vascular resistance. Two techniques were effective for the preservation of bone vascularity for 24 h: washout with UW solution followed by nonperfusion cold (4°C) storage, and vascular washout with mannitol solution followed by continuous hypothermic (5°C) microperfusion (0.03 ml/min) with UW solution. The most consistent, and lowest, vascular resistance was produced by the microperfusion technique. However, UW solution does not consistently prevent an increase in vascular resistance with hypothermic ischemia. This technique may prove useful for the preservation of vascularized bone grafts, but it needs to be evaluated in a transplantation model.
Localized hyperthermic treatment of experimental bone tumors with ferromagnetic ceramics
Authors: Ikenaga Minoru , Ohura Kouichiro , Yamamuro Takao , Kotoura Yoshihiko , Oka Masanori , Kokubo Tadashi 
Published: February 2005

AbstractLocalized hyperthermic treatment was carried out with use of a metastatic bone tumor model in rabbits. The experimental bone tumor was created by transplantation of pieces of tumor line VX2 into the medullary canal of rabbit tibiae. Two weeks after the transplantation, a ferromagnetic ceramic pin was inserted in the medullary canal. Then, hyperthermia (HT) of the tumor was accomplished with use of an alternating magnetic field for 50 min. All the rabbits were killed 5 weeks after tumor transplantation, and the therapeutic effect was evaluated histologically and roentgenographically. Almost all the tumor cells within the bone marrow were killed by the procedure. The area of the tumor necrosis in the HT group was significnatly larger than in the control group. The pathological fracture rate and displacement rate were reduced significantly by this treatment (38.5 and 0%) compared with the controls (92.3 and 92.3%). Therefore, HT with the use of ferromagnetic ceramics was effective for local control of malignant bone tumors and seems to be a promising new method of treatment.
Low intensity ultrasound treatment increases strength in a rat femoral fracture model
Authors: Wang Shyu‐Jye , Lewallen David G. , Bolander Mark E. , Chao Edmund Y. S. , Ilstrup Duane M. , Greenleaf James F. 
Published: February 2005

AbstractBilateral closed femoral shaft fractures were made in 22 male Long‐Evans rats. In 16 animals, ultrasound was applied to one limb for 15 minutes daily 10 times within the first 14 postoperative days. The treated limbs received a 200 μsec burst of 1.5 or 0.5 MHz sine waves repeated at 1.0 KHz at a spatial average and temporal average intensity of 30 mW/cm2. The contralateral limb of each animal served as a nontreated control. Six remaining animals with fractures and six additional animals without fractures received sham ultrasound treatment to control for the effects of anesthesia and handling. Fracture repair was evaluated on postoperative day 21 by radiography, mechanical testing in torsion, and histology. Five of 16 ultrasound‐treated fractures showed obliteration of the fracture gap on radiographs, whereas none of the 28 controls did. The average maximum torque of fractures treated with either signal was 22% greater than that of the contralateral controls (p < 0.05). The stiffness of treated fractures was greater than that of control fractures, but the difference was significant only in animals treated with the 1.5 MHz signal (p < 0.02). Sham treatment did not affect repair in the control group. These results indicate that low‐intensity pulsed ultrasound at either 0.5 or 1.5 MHz can accelerate fracture repair at 21 days in this highly controlled model.
Decreased microvascular perfusion in the rabbit ear after six hours of ischemia
Authors: Pollock F. Edward , Smith Thomas L. , Andrew Koman L. , Holden Martha B. , Smith Beth P. 
Published: February 2005

AbstractThe cellular injury produced by reperfusion of ischemic tissue with oxygen‐rich blood has been studied in numerous tissues but has not been investigated extensively in thermoregulatory tissue. This study was designed (a) to compare 4 and 6 hours of ischemia to document the evidence of impaired capillary perfusion after resumption of blood flow (reperfusion injury) in a thermoregulatory end organ (the rabbit ear), and (b) to examine, with use of vital capillaroscopy (VC) and laser Doppler flowmetry (LDF), the altered microvascular blood flow in the rabbit ear after ischemia and reperfusion. One ear from each of five rabbits underwent warm ischemia for 4 hours. VC showed no deficits of capillary perfusion in these ears after reperfusion; LDF measurements in both ears also demonstrated no significant difference between control and reperfusion blood flow. One ear from each of eight additional rabbits underwent 6 hours of warm ischemia. LDF values were significantly reduced in the ischemic ear after reperfusion as compared with baseline measurements for that ear and as compared with the control ear. VC showed arrested perfusion and static plasma gaps within three to five capillaries per high‐power field (an area of 300 × 500 μm) in the ischemic ear and good perfusion of all vessels in the contralateral control ear. This evidence of reperfusion injury in a thermoregulatory end organ may help to explain the poor functional result that often occurs after replantation of an amputated digit.
Collagens in the injured porcine intervertebral disc
Authors: Kääpä E. , Holm S. , Han X. , Takala T. , Kovanen V. , Vanharanta H. 
Published: February 2005

AbstractSpinal pain often is thought to be due to degeneration and mechanical failure of the intervertebral disc. Since the mechanical strength of the tissue depends on collagen fibers, the present study was designed to investigate the reactions in collagen metabolism after an experimentally induced disc injury. Five domestic pigs underwent an incision in the anterior part of the annulus fibrosus of disc L4‐L5 through a retroperitoneal approach. The animals were killed 3 months postoperatively, and the injured discs and intact discs (controls) from different animals were removed for chemical analysis. Slices were cut from seven different parts across the disc. The concentration of total collagen (hydroxyproline [Hyp]), the activities of the two key enzymes in collagen biosynthesis (prolyl 4‐hydroxylase [PH] and galactosylhydroxylysyl glucosyltransferase [GGT]), and the concentration of mature collagen crosslinks (hydroxypyridinium [HP]) were determined. In all experimental discs, the morphology had changed considerably: the nucleus pulposus was small, fibrous, and yellowish. The annular lamellar structure was partially destroyed and had been replaced by granulation tissue in the region of the injury. Large osteophytes had formed at the ventral edges of the vertebral bodies. In the nucleus pulposus, the Hyp concentration and the activities of PH and GGT were significantly increased, whereas the water content had decreased. The concentration of HP crosslinks was decreased in the anterior annulus fibrosus.
Mechanical evaluation of a canine intervertebral disc spacer: In situ and In vivo studies
Authors: Vuono‐Hawkins M. , Zimmerman M. C. , Lee C. K. , Carter F. M. , Parsons J. R. , Langrana N. A. 
Published: February 2005

AbstractAn elastomeric intervertebral disc spacer with hydroxyapatite ingrowth surfaces was implanted in a canine model. We studied (a) the mechanical behavior of motion segments at time 0 and at 3, 6, and 12 months and (b) the effect of the interface between the spacer and vertebral bone on implant stability and bone ingrowth. A polymeric spacer was designed with compressive and torsional properties similar to those of the isolated canine lumbar disc. Implantation of the spacer in canine cadaver motion segments permitted in situ biomechanical evaluation at time 0. An in vivo study permitted continuous neurological monitoring of animals, with evaluation of mechanical behavior, stability, and ingrowth at 3, 6, and 12 months. Mechanical testing of cadaver motion segments with the spacer in situ resulted in decreased compressive and torsional stiffnesses, averaging 25 and 42%, respectively. This decrease was due to a combination of the surgical insult to the annulus and decortication of adjacent vertebral endplates. In the in vivo study, all 12 animals tolerated the surgery well and none had permanent neurological impairment. The measured parameters indicated that behavior of the spacer‐motion segment composite appeared to return to normal within 3‐6 months. However, despite use of a porous hydroxyapatite on the implant surface, there was no significant bone ingrowth. Instead, a layer of dense fibrous connective tissue was formed at the spacer‐vertebral bone interface. Early migration of five of the 12 spacers resulted in eccentric loading patterns with consistent reactive osteophyte formation.
Intraosseous incorporation of composite collagen prostheses designed for ligament reconstruction
Authors: Dunn Michael G. , Maxian Suzanne H. , Zawadsky Joseph P. 
Published: February 2005

AbstractComposite collagen prostheses are potentially useful for reconstruction of the anterior cruciate ligament (ACL). We evaluated the intraosseous response to composite collagen prostheses to determine if “biological fixation” could be used to secure the prostheses within surgical bone tunnels. The rate of degradation of the prosthesis and the response of the tissue were evaluated, as a function of collagen crosslinking agent and time, in nonloaded bone tunnels in rabbits. Prostheses were fabricated by the alignment of 200 reconstituted type‐I collagen fibers (60 μm in diameter) and the embedding of the fibers within a collagen matrix. The prostheses degraded rapidly within the bone tunnels in comparison with soft‐tissue implantation sites. Dehydrothermal‐cyanamide crosslinked collagen fibers were completely degraded by 8 weeks. Only 10% of glutaraldehyde crosslinked collagen fibers remained intact at 12 weeks. Fibrous tissue and inflammatory cells rapidly infiltrated the prostheses, and new bone surrounded the circumference of the prostheses, advancing toward the center at longer times. At the lateral cortex, where fibrous tissue emerged, the bone/soft‐tissue interface was delineated by a tidemark, similar to that observed in a normal ligament insertion site. Preliminary pull‐out testing of the soft tissue; this suggests rapid incorporation of the prostheses within the bone tunnels. Composite collagen prostheses designed for ACL reconstruction degrade rapidly in bone and induce rapid ingrowth of fibrous tissue and bone. These results suggest that tissue ingrowth in the bone tunnels might provide biological fixation for collagen prostheses used for ACL reconstruction.
Structural differences between two populations of articular cartilage proteoglycan aggregates
Authors: Buckwalter Joseph A. , Pita Julio C. , Muller Francisco J. , Nessler Julie 
Published: February 2005

AbstractTo determine if articular cartilage contains structurally distinct populations of proteoglycan aggregates, we extracted and purified proteoglycans from canine knee cartilage under associative conditions. Equilibrium density gradient centrifugation separated three proteoglycan populations, on the basis of differences in sedimentation velocity, into groups of 21, 106, and 270 S. Electron microscopic examination showed that the 21 S samples contained free aggrecan molecules and clusters of aggrecan molecules, with a mean of five aggrecan molecules per cluster. The 106 and 270 S samples contained proteoglycan aggregates consisting of central hyaluronan filaments with multiple attached aggrecan molecules. The two populations of aggregates did not differ in mean aggrecan length or in the spacing of aggrecan molecules along the hyaluronan filaments, but the slower sedimenting aggregates (106 S) had significantly shorter hyaluronan filaments as measured by electron microscopy (mean hyaluronan length, 400 compared with 1,162 nm) and one‐third as many aggrecan molecules per aggregate (mean number of aggrecan molecules per aggregate, 15 compared with 44). This study shows that articular cartilage contains aggrecan clusters and two structurally distinct populations of proteoglycan aggregates. The differences between the two types of aggregate, in particular the number of aggrecan molecules per aggregate, may reflect differences in their assembly, stability, or turnover and give them different mechanical and biological properties.
Serial kinematic analysis of the unstable knee after transection of the anterior cruciate ligament: Temporal and angular changes in a canine model of osteoarthritis
Authors: Vilensky Joel A. , O'Connor Brian L. , Brandt Kenneth D. , Dunn Elizabeth A. , Rogers Pamela I. , Delong Cynthia A. 
Published: February 2005

AbstractTransection of the anterior cruciate ligament in the dog leads to osteoarthritis. This study defines the kinematic changes in the unstable knee after transection of the cruciate ligament (six dogs) and after a sham operation (four dogs). In the dogs that were anterior cruciate ligament‐deficient (ACL‐D), the duration of stance 1 week postoperatively decreased 38% from the preoperative value, but only a 4% decrease was seen at 6 weeks. The duration of double hindlimb support increased from 6 to 19% of the entire cycle 1 week after surgery but returned to the baseline value by 18 weeks. As the unstable limb contacted the treadmill belt, the initial flexion (yield) and subsequent extension (propulsive) phases were not evident or were markedly attenuated in every ACL‐D dog throughout the 26‐week period of observation. The angular velocity patterns were characterized by a slight extension velocity at touchdown (compared with a zero value preoperatively) and a decrease in the peak velocities (both flexion and extension) during the remainder of the stance phase. None of these changes was observed in the animals that had a sham operation. These data indicate that, in the dog, the nervous system compensates for instability of the knee by altering angular, but not temporal, parameters. The extension velocity at touchdown and the reduction in peak flexion velocity during the yield component of the stance phase may reduce the ability of the limb to absorb impact forces and lead to the development of osteoarthritis of the knee. Alternatively, the reductions in flexion and extension of the knee during the stance phase and in the values for peak velocity presumably reflect protective muscular reflexes that may slow the rate of progression of joint breakdown.
Fibronectin in the tendon‐synovial complex: Quantitation In vivo and In vitro by elisa and relative mRNA levels by polymerase chain reaction and northern blot
Authors: Brigman Brian E. , Hu Peiqui , Yin Hongliang , Tsuzaki Mari , Thomas Lawrence W. , Banes Albert J. 
Published: February 2005

AbstractAn enzyme‐linked immunosorbent assay was used to quantitate fibronectin (Fn) levels in the outer synovia (epitenon) and internal fibrous portion (endotenon) of chicken flexor tendon and sheath. Primary cell cultures from these tissues and their secretions also were assayed for Fn levels. The polymerase chain reaction (PCR) was used to determine relative steady‐state levels of Fn mRNA in primary cultures of synovial and internal fibroblasts from chicken tendon, and Northern blot analysis was performed to verify relative levels of the Fn message. The epitenon contained 3.8‐fold more Fn than did the endotenon, and the sheath synovium contained 21‐fold more Fn than did the internal fibrous portion of sheath. Cells cultured from the epitenon produced 9.3 and 13‐fold more cell‐associated and secreted Fn, respectively, than did cultured endotenon fibroblasts. Sheath synovial cells produced 17 and 3.2‐fold more cell‐associated and secreted Fn, respectively, than did sheath internal fibroblasts. Levels of Fn mRNA, as measured by PCR and Northern blot, were 1.6 and 1.8‐fold greater, respectively, in tendon synovial cells compared with tendon internal fibroblasts. The biologic reason for increased Fn in tendon synovium is not known. We theorize that Fn may stabilize tendon synovium to shear stress and may play a role in the modulation of synovial rheology in the normal tendon. In the injured tendon, Fn may be involved in the organization of collagen deposition or may act through association with growth factors to aid healing.
Effect of capacitively coupled electric fields on an experimental model of delayed union of fracture
Authors: Rijal Kiran Prasad , Kashimoto Osamu , Sakurai Minoru 
Published: February 2005

AbstractTo evaluate the effect of capacitively coupled electric fields (CCEF) on delayed union of fractures, an experimental model of delayed union was produced in the radius of rabbits, and the process of healing was investigated by radiography, bone mineral density (BMD) measured with dual energy x‐ray absorptiometry, and histological survey. It was confirmed radiographically and histologically that callus formation was enhanced in the group treated with CCEF. After stimulation, the average BMD increased more than 18% compared with the controls. Our experiment on a delayed union model suggests that CCEF is effective for the treatment of delayed union of fractures.
Bone response to hydroxyapatite‐coated and commercially pure titanium implants in the human arthritic knee
Authors: Carlsson L. , Regnér L. , Johansson C. , Gottlander M. , Herberts P. 
Published: February 2005

AbstractRough and smooth commercially pure (c.p.) titanium implants and hydroxy‐apatite‐coated (HA‐C) implants were inserted in arthritic human knees and left in situ in order to compare the response of bone to these three implants. Radiographic examination alone could not determine if bone apposition had occurred. After 3 and 6 months, histomorphometric analyses of undecalcified sections, 10 μm thick, revealed a statistical significance in the amount of bone apposition to rough‐surfaced and HA‐C implants as compared with smooth uncoated implants. Most of the rough‐surfaced c.p. titanium implants and the HA‐C implants had achieved bone apposition on the order of 50%. No statistically significant differences in apposition were seen between the rough‐surfaced and HA‐C implants. The smooth c.p. titanium implants were mostly encapsulated in fibrous tissue.
Particle‐induced synthesis of collagenase by synovial fibroblasts: An immunocytochemical study
Authors: Greis P. E. , Georgescu H. I. , Fu F. H. , Evans C. H. 
Published: February 2005

AbstractThe response of synoviocytes to wear particles has been implicated in several orthopaedic pathologies, including the synovitis associated with the failure of synthetic anterior cruciate ligament (ACL) replacements. To study the interactions of particles with synovial fibroblasts at the level of the individual cell, we employed immunocytochemistry, with use of antiserum, to lapine interstitial collagenase. Cultures of the HIG‐82 lapine synovial cell line showed only weak immunofluorescence under resting conditions. Incubation with phorbol myristate acetate or autocrine factors known as cell‐activating factors (CAFs) induced marked changes in morphology and intense immunofluorescence. This technique then was used to study the effects of standard particles of latex and of particles generated from two prosthetic ACL materials, Dacron and carbon. Internalized particles of latex, Dacron, and carbon all induced collagenase. Particles of latex that were too large for endocytosis failed to induce collagenase, whereas particles of carbon and, in particular, Dacron that remained extracellular, still provoked considerable synthesis of collagenase. Thus, both the size and the physical properties of these materials influence their ability to activate synoviocytes. Certain cells that appeared by visual inspection to contain no particles nevertheless produced collagenase when in co‐culture with cells that did contain particles. This is consistent with earlier biochemical data showing that phagocytosis, in addition to inducing collagenase, also provokes the release of CAFs, which then activate additional cells in the culture. More rarely, cells were identified which, although containing particles, did not stain positively for collagenase. Since carbon and Dacron are the major components of certain prosthetic ligament replacements, the cellular responses to their wear particles and to debris generated from other prosthetic materials merit further close attention.
Mathematical model for the mineralization of bone
Authors: Martin Bruce 
Published: February 2005

AbstractA mathematical model is presented for the transport and precipitation of mineral in refilling osteons. One goal of this model was to explain calcification “halos,” in which the bone near the haversian canal is more highly mineralized than the more peripheral lamellae, which have been mineralizing longer. It was assumed that the precipitation rate of mineral is proportional to the difference between the local concentration of calcium ions and an equilibrium concentration and that the transport of ions is by either diffusion or some other concentration gradient‐dependent process. Transport of ions was assumed to be slowed by the accumulation of mineral in the matrix along the transport path. The model also mimics bone apposition, slowing of apposition during refilling, and mineralization lag time. It was found that simple diffusion cannot account for the transport of calcium ions into mineralizing bone, because the diffusion coefficient is two orders of magnitude too low. If a more rapid concentration gradient‐driven means of transport exists, the model demonstrates that osteonal geometry and variable rate of refilling work together to produce calcification halos, as well as the primary and secondary calcification effect reported in the literature.