Biomedical subjects

James M Williams

Publications and source records attributed to James M Williams.

17 recordsLinked to original sources

PubMed2007

Spinal arachnoid calcifications.

Arachnoid calcifications have been imaged on axial-CT and MRI. These often clinically asymptomatic deposits have been attributed to trauma, myelography (particularly with the use of oil-based contrast), subarachnoid hemorrhage, and spinal anesthesia. This report describes calcified arachnoid plaques in an 86-year-old male cadaver located in the dorsal thoracic level. A laminectomy from C4 to the lumbo-sacral junction was performed and the dura mater was transected and pinned aside. Three plaques between T2-T3, 3 at T7, 2 at T9 were noted. Plaques were 1.0 mm in thickness and ranged from 0.5 cm to 1.0 cm in diameter. The spinal cord or nerve roots were not displaced. The plaques stained positively with Von Kossa and Alizarin Red S staining, confirming that the deposits included calcium phosphate and calcium. Arachnoid calcifications are an incidental finding in cadavers and typically do not compress the spinal cord or nerve roots. However such plaques may be precursors to spinal arachnoid ossificans, a more serious condition that may cause spinal cord or nerve root compression.

Aged, 80 and over↗

PubMed2006

Biocompatibility of a polymer patch for rotator cuff repair.

Both mechanical and biological factors influence the high re-tear rate after rotator cuff repair. Mechanical factors have largely been addressed by the introduction of better implants and modification of suture configuration, but further improvements are needed to address the often poor tissue quality of the degenerated rotator cuff tendons. Current biological solutions provide only short-term reinforcement and have been associated with pseudo-infectious reactions. This pre-clinical animal study investigates the biological response to a novel polycarbonate polyurethane patch used for tissue augmentation in a rat rotator cuff repair model. Bilateral defects were created in the supraspinatus tendons of 12 Sprague Dawley rats. One side was repaired with a patch as a tissue augmentation device. The contralateral side acted as internal control without patch augmentation. After 6 weeks the tissues were harvested and underwent histologic and histomorphometric analyses. Histological evaluation demonstrated no inflammatory reaction; histomorphometry revealed tissue ingrowth of 79.9%. In conclusion, the polycarbonate polyurethane patch for tissue extension or augmentation in rotator cuff repair has demonstrated no inflammatory response and excellent tissue integration in a rat rotator cuff repair model.

Animals↗

PubMed2006

Chronic hypoxic decreases in soluble guanylate cyclase protein and enzyme activity are age dependent in fetal and adult ovine carotid arteries.

The present study tests the hypothesis that chronic hypoxia enhances reactivity to nitric oxide (NO) through age-dependent increases in soluble guanylate cyclase (sGC) and protein kinase G (PKG) activity. In term fetal and adult ovine carotids, chronic hypoxia had no significant effect on mRNA levels for the beta1-subunit of sGC, but depressed sGC abundance by 16% in fetal and 50% in adult arteries, through possible depression of rates of mRNA translation (15% in fetal and 50% in adult) and/or increased protein turnover. Chronic hypoxia also depressed the catalytic activity of sGC, but only in fetal arteries (63%). Total sGC activity was reduced by chronic hypoxia in both fetal (69%) and adult (37%) carotid homogenates, but this effect was not observed in intact arteries when sGC activity was measured by timed accumulation of cGMP. In intact arteries treated with 300 microM 3-isobutyl-1-methylxanthine (IBMX), chronic hypoxia dramatically enhanced sGC activity in fetal (186%) but not adult (89%) arteries. This latter observation suggests that homogenization either removed an sGC activator, released an sGC inhibitor, or altered the phosphorylation state of the enzyme, resulting in reduced activity. In the absence of IBMX, chronic hypoxia had no significant effect on rates of cGMP accumulation. Chronic hypoxia also depressed the ability of the cGMP analog, 8-(p-chlorophenylthio)-cGMP, to promote vasorelaxation in both fetal (8%) and adult (12%) arteries. Together, these results emphasize the fact that intact and homogenized artery studies of sGC activity do not always yield equivalent results. The results further suggest that enhancement of reactivity to NO by chronic hypoxia must occur upstream of PKG and can only be possible if changes in cGMP occurred in functional compartments that afforded either temporal or chemical protection to the actions of phosphodiesterase. The range and age dependence of hypoxic effects observed also suggest that some responses to hypoxia must be compensatory and homeostatic, with reactivity to NO as the primary regulated variable.

1-Methyl-3-isobutylxanthine↗

PubMed2006

Chronic hypoxia modulates endothelium-dependent vasorelaxation through multiple independent mechanisms in ovine cranial arteries.

Acclimatization to chronic hypoxia involves numerous compensatory changes in many tissues, including blood vessels. The present data demonstrate that in addition to well-documented changes in contractility, chronic hypoxia also produces important changes in the mechanisms mediating endothelium-dependent vasodilatation. At the level of the endothelium, hypoxia attenuates endothelial release of NO and this appears to be mediated through reductions in eNOS specific activity; chronic hypoxia has little effect on eNOS abundance. In contrast, chronic hypoxia depresses the abundance of sGC, which functions as the downstream vascular receptor for NO released from the endothelium. The decreased abundance of sGC produced by chronic hypoxia occurs without changes in sGC specific activity and results in decreased rates of NO-induced cGMP synthesis. Nonetheless, the vasodilator efficacy of NO is enhanced in hypoxic arteries, which suggests that mechanisms downstream from sGC are upregulated by hypoxia. Consistent with this view, chronic hypoxia significantly depresses PDE activity, which serves to prolong cGMP half-life and enhance its vasodilator effects. It remains possible that chronic hypoxia may also enhance PKG activity and/or the abundance of its substrates; this possibility remains a promising topic for future investigation. Overall, it is important to recognize that the mechanisms of adaptation to chronic hypoxia identified in the present study may be somewhat unique to adult carotid arteries. Adaptive responses to chronic hypoxia can vary considerably between small and large arteries, and also between immature and adult arteries . Still, the present data clearly demonstrate that both the endothelium and vascular smooth muscle of major arteries are profoundly influenced by chronic hypoxia, and thereby participate fully in whole-body adaptation to reduced oxygen availability.

Animals↗

PubMed2006

Chondrolysis after continuous intra-articular bupivacaine infusion: an experimental model investigating chondrotoxicity in the rabbit shoulder.

PURPOSE: Postoperative pain pumps are increasingly used to deliver a continuous infusion of local anesthetic into the surgical wound or the joint. Recently, there have been concerns that the use of such devices may be associated with chondrotoxicity and even cases of chondrolysis in the shoulder. An experimental model is presented that investigates potential chondrotoxic effects of a continuous intra-articular infusion of bupivacaine in the rabbit shoulder. METHODS: We divided 30 rabbits into 3 groups that received continuous infusions of either saline solution, bupivacaine, or bupivacaine with epinephrine into the glenohumeral joint over a period of 48 hours. Animals were killed after 1 week, and osteochondral and synovial samples from the glenohumeral joint underwent analyses with confocal microscopy for live/dead cell assay, metabolic sulfate uptake assessment, and conventional histologic analysis. RESULTS: Infusion of bupivacaine with epinephrine and without epinephrine decreased sulfate uptake by 56% (P = .009) and 50% (P = .02), respectively, when compared with saline solution; cell viability decreased by 20% (P = .08) and 32% (P = .02), respectively. Histologic analysis yielded significantly worse scores for bupivacaine infusion with epinephrine (P = .004) and without epinephrine (P = .02). The results for bupivacaine with or without epinephrine were not significantly different. CONCLUSIONS: Continuous intra-articular infusion of bupivacaine with and without epinephrine led to significant histopathologic and metabolic changes in articular cartilage. CLINICAL RELEVANCE: Bupivacaine showed profound chondrotoxic effects in an experimental model that closely followed the current clinical application of postoperative pain pumps. The results caution against the use of such devices in applications for smaller joints with minimal clearance or dilution as a result of hematoma, where continuous exposure of cartilage to bupivacaine is expected.

Analgesia, Patient-Controlled↗

PubMed2006

Micro-computed tomography evaluation of the glenoid fossa and mandibular condyle bone after bilateral vertical ramus mandibular distraction in a canine model.

The aim of this study was to quantify bone microarchitecture within the glenoid fossa and mandibular condyle following mandibular distraction osteogenesis. Eight 6- to 9-month-old male beagle dogs underwent bilateral vertical mandibular distraction with semiburied distractors (12 days of distraction at 1 mm per day). One unoperated animal served as control. After distraction the animals were divided into two groups (N = 4) and killed after 1 or 2 months of consolidation. Three-dimensional trabecular architecture was analyzed by micro-computed tomography (microCT). At both sites the overall trends were similar. In the glenoid fossa, there was decreased bone volume, trabecular number, and connectivity density and increased trabecular separation at 1 month and decreased trabecular thickness and increased structure model index compared with the control (P < 0.05). In the mandibular condyle, there was decreased bone volume, trabecular number, and connectivity density at both 1 and 2 months, with decreased trabecular thickness and increased structure model index at 2 months only compared with the control (P < 0.05). The bone became less dense and more rodlike. These bone changes are similar to those seen by the effects of aging or impaired normal function. Thus, in the short term, changes occur in the bone microstructure of the glenoid fossa and mandibular condyle after vertical mandibular ramus distraction in the canine model.

Animals↗

PubMed2006

Micro-computed tomography evaluation of the glenoid fossa and mandibular condyle bone after bilateral vertical ramus mandibular distraction in a canine model.

The aim of this study was to quantify bone microarchitecture within the glenoid fossa and mandibular condyle following mandibular distraction osteogenesis. Eight 6- to 9-month-old male beagle dogs underwent bilateral vertical mandibular distraction with semiburied distractors (12 days of distraction at 1 mm per day). One unoperated animal served as control. After distraction the animals were divided into two groups (N = 4) and killed after 1 or 2 months of consolidation. Three-dimensional trabecular architecture was analyzed by micro-computed tomography (muCT). At both sites the overall trends were similar. In the glenoid fossa, there was decreased bone volume, trabecular number, and connectivity density and increased trabecular separation at 1 month and decreased trabecular thickness and increased structure model index compared with the control (P < 0.05). In the mandibular condyle, there was decreased bone volume, trabecular number, and connectivity density at both 1 and 2 months, with decreased trabecular thickness and increased structure model index at 2 months only compared with the control (P < 0.05). The bone became less dense and more rodlike. These bone changes are similar to those seen by the effects of aging or impaired normal function. Thus, in the short term, changes occur in the bone microstructure of the glenoid fossa and mandibular condyle after vertical mandibular ramus distraction in the canine model.

Animals↗

PubMed2005

Age-dependent modulation of endothelium-dependent vasodilatation by chronic hypoxia in ovine cranial arteries.

Although abundant evidence indicates that chronic hypoxia can induce pulmonary vascular remodeling, very little is known of the effects of chronic hypoxia on cerebrovascular structure and function, particularly in the fetus. Thus the present study explored the hypothesis that chronic hypoxemia also influences the size and shape of cerebrovascular smooth muscle and endothelial cells, with parallel changes in the reactivity of these cells to endothelium-dependent vasodilator stimuli. To test this hypothesis, measurements of endothelial and vascular smooth muscle cell size and density were made in silver-stained common carotid and middle cerebral arteries from term fetal and nonpregnant adult sheep maintained at an altitude of 3,820 m for 110 days. Chronic hypoxia induced an age-dependent remodeling that led to smooth muscle cells that were larger in fetal arteries but smaller in adult arteries. Chronic hypoxia also increased endothelial cell density in fetal arteries but reduced it in adult arteries. These combined effects resulted in an increased (adult carotid), decreased (adult middle cerebral), or unchanged (fetal arteries) per cell serosal volume of distribution for endothelial factors. Despite this heterogeneity, the magnitude of endothelium-dependent vasodilatation to A23187, measured in vitro, was largely preserved, although sensitivity to this relaxant was uniformly depressed. N(G)-nitro-L-arginine methyl ester, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, and endothelium denudation each independently blocked A23187-induced vasodilation without unmasking any residual vasoconstrictor effect. Indomethacin did not significantly attenuate A23187-induced relaxation except in the hypoxic adult middle cerebral, where a small contribution of prostanoids was evident. Vascular sensitivity to exogenous nitric oxide (NO) was uniformly increased by chronic hypoxia. From these results, we conclude that chronic hypoxia reduced endothelial NO release while also upregulating some component of the NO-cGMP-PKG vasodilator pathway. These offsetting effects appear to preserve endothelium-dependent vasodilation after adaptation to chronic hypoxia.

Aging↗

PubMed2005

Reliability of diffraction enhanced imaging for assessment of cartilage lesions, ex vivo.

OBJECTIVE: The assessment of articular cartilage integrity is of value for the detection of early degenerative joint disease in both the clinical and the research settings. It was the purpose of this study to determine the accuracy and reliability of identifying articular cartilage defects through Diffraction Enhanced Imaging (DEI), a high contrast radiographic imaging technique. DEI provides two new sources of image contrast to radiography: refraction and scatter rejection, besides the absorption of conventional radiography. DESIGN: Cadaveric tali were DEI imaged in the anterior-posterior position at the National Synchrotron Light Source. Two independent observers provided gross score evaluations (on a five point scale) of the trochlear surfaces. The DEI image of each trochlear surface was then graded (on a five point scale) by two additional independent observers who were blinded with regard to the gross evaluation of the articular surfaces. Inter-observer agreement for DEI grades was assessed with the weighted kappa statistic. Correlation of diffraction enhanced image score to the gross score was assessed with Spearman correlation coefficient. RESULTS: The defects of articular cartilage of talar trochleae could be visualized through DEI. The Spearman correlation of gross grades with DEI grades on the 165 talar regions for observers 1 and 2 were 0.91 and 0.91, respectively. The overall weighted kappa value for inter-observer agreement was 0.93, thus considered high agreement. CONCLUSIONS: DEI is accurate and reliable for detection of articular cartilage defects ex vivo. Even early stages of degeneration of cartilage can be visualized with this high contrast technique. Future studies will focus on the application of DEI to the identification of such lesions in vivo.

Aged↗

PubMed2005

Prolonged-fresh preservation of intact whole canine femoral condyles for the potential use as osteochondral allografts.

Defects in articular cartilage are often repaired with fresh osteochondral grafts. While fresh allografts provide viable chondrocytes, logistic limitations require surgical implantation within seven days of graft harvest. Here, we provide information on cold preservation of whole intact osteochondral materials that retains cartilage cell viability and function, and histologic and biochemical integrity for 28 days. Canine femoral condyles were obtained and stored at 4 degrees C for 14, 21 or 28 days. At the end of the storage period, cartilage was assessed for cell viability, 35S uptake, proteoglycan content and histologic parameters. The most noticeable histologic change was reduced Safranin-O near the cartilage surface with 14 days of cold preservation, but had recovered with 21 and 28 days. Cartilage thicknesses did not vary significantly. Cell viability was >95% at 14 days, 75-98% at 21 days and reduced to 65-90% at 28 days. Cell function measures showed that the level of 35SO4 incorporation was suppressed in samples stored at 4 degrees C. However, no significant differences were seen among groups at 14, 21 or 28 days of cold preservation. This data has implications for tissue banking protocols for osteochondral allograft material obtained for transplantation suggesting that cold preserved allograft material be implanted within 28 days.

Animals↗

PubMed2005

Effect of hip hemiarthroplasty on articular cartilage and bone in a canine model.

The purpose of this study was to determine if acetabular articular cartilage damage occurs in the presence or absence of changes in subchondral plate thickness or porosity and trabecular bone architecture after hip hemiarthroplasty. Eight canines were sacrificed 6 months after receiving unilateral hemiarthroplasties in which a cobalt chrome alloy femoral head was used. The acetabular cartilage, subchondral plate, and trabecular bone were quantitatively evaluated. Although the articular cartilage in the treated hip showed gross and histologic degenerative changes, there were no differences in the treated and contralateral hips in any of the trabecular bone parameters or subchondral plate thickness. However, the subchondral plate porosity was increased 2.6-fold in the treated hip. Therefore, degradation of cartilage can occur in the absence of thickening of the subchondral plate or alterations in the supporting trabecular bone architecture. These observations provide a better understanding of the role that periarticular bone has in the degenerative process after hemiarthoplasty.

Acetabulum↗

PubMed2005

Chronic hypoxia modulates relations among calcium, myosin light chain phosphorylation, and force differently in fetal and adult ovine basilar arteries.

The present study tests the hypothesis that age-related differences in contractility of cerebral arteries from hypoxic animals involve changes in myofilament Ca2+ sensitivity. Basilar arteries from term fetal and nonpregnant adult sheep maintained 110 days at 3,820 m were used in measurements of cytosolic calcium concentration ([Ca2+]i), myosin light chain phosphorylation, and contractile tensions induced by graded concentrations of K+ or serotonin (5-HT). Slopes relating [Ca2+]i to tension were similar in fetal (0.83 +/- 0.07) and adult (1.02 +/- 0.08) arteries for K+ contractions but were significantly greater for fetal (3.77 +/- 0.64) than adult (2.00 +/- 0.13) arteries for 5-HT contractions. For both K+ and 5-HT contractions, these relations were left shifted in fetal compared with adult arteries, indicating greater Ca2+ sensitivity in fetal arteries. In contrast, slopes relating [Ca2+]i and %myosin phosphorylation for K+ contractions were less in fetal (0.37 +/- 0.08) than adult (0.81 +/- 0.07) arteries, and the fetal curves were right shifted. For 5-HT contractions, the slope of the Ca2+-phosphorylation relation was similar in fetal (0.33 +/- 0.09) and adult (0.33 +/- 0.23) arteries, indicating that 5-HT depressed Ca2+-induced myosin phosphorylation in adult arteries. For slopes relating %myosin phosphorylation and tension, fetal values (K+: 1.52 +/- 0.22, 5-HT: 7.66 +/- 1.70) were less than adult values (K+: 2.13 +/- 0.30, 5-HT: 8.29 +/- 2.40) for both K+- and 5-HT-induced contractions, although again fetal curves were left shifted relative to the adult. Thus, in hypoxia-acclimatized basilar arteries, a downregulated ability of Ca2+ to promote myosin phosphorylation is offset by an upregulated ability of phosphorylated myosin to produce force yielding an increased fetal myofilament Ca2+ sensitivity. Postnatal maturation reprioritizes the mechanisms regulating hypoxic contractility through changes in the source of activator Ca2+, the pathways governing myosin light chain phosphorylation, and its interaction with actin.

Adaptation, Physiological↗

PubMed2004

Maturational modulation of endothelium-dependent vasodilatation in ovine cerebral arteries.

To address the hypothesis that maturation enhances endothelial vasodilator function in cerebral arteries, relaxant responses to ADP and A-23187 were determined in ovine carotid and cerebral arteries harvested from 25 newborn lambs (3-7 days) and 23 adult sheep. Maturation significantly increased pD(2) values for A-23187 (newborn range: 4.9 +/- 0.3 to 5.4 +/- 0.3; adult range: 6.0 +/- 0.2 to 7.1 +/- 0.2) and the maximal vasodilator response to A-23187 by 10-18%. In contrast, maturation decreased maximum responses to ADP by 5-25% with no change in pD(2). The magnitudes of endothelium-dependent relaxation were not affected by 10 microM indomethacin but were virtually abolished by 100 microM N(G)-nitro-L-arginine methyl ester/L-nitro arginine, indicating that nitric oxide (NO) is the primary endothelium-dependent vasodilator in these arteries. Maturation also modestly decreased endothelial NO synthase (eNOS) abundance in both carotid (32%) and cerebral (26%) arteries. Together, these findings reinforce the view that receptor coupling to endothelial activation is tightly regulated and may offset underlying changes in maximal endothelial vasodilator capacity. This capacity, in turn, appears to increase with postnatal age despite major growth and expansion of endothelial cell size and vascular wall volume. In ovine cerebral arteries, endothelial vasodilator capacity appears completely dependent on eNOS activity but not on cyclooxygenase activity. In turn, eNOS activity appears to be postnatally regulated by mechanisms independent of changes in eNOS abundance alone.

Adenosine Diphosphate↗

PubMed2004

Effects of calcitonin on subchondral trabecular bone changes and on osteoarthritic cartilage lesions after acute anterior cruciate ligament deficiency.

UNLABELLED: Because SBM may contribute to cartilage breakdown in OA, experimental OA was induced in dogs by transecting the anterior cruciate ligament of the knee and treating with either CT or a placebo. CT significantly reduced both SBM and cartilage lesions. This study supports the use of CT in the treatment of canine experimental OA. INTRODUCTION: Because subchondral bone remodeling (SBM) may contribute to cartilage breakdown in osteoarthritis (OA), we evaluated to what extend calcitonin (CT) might affect cartilage and bone changes in the early stages of canine experimental OA. MATERIALS AND METHODS: Twelve dogs underwent transection of the anterior cruciate ligament (ACLT) of the right knee. After ACLT, each animal received a daily nasal spray delivering either 400 U of CT (CT-treated group; n = 6) or a placebo (PL-treated group; n = 6). At day 84 after surgery, animals were killed, and cartilage changes were graded. BMD and volume fraction (BVF) were assessed by pQCT in different regions of interest (ROIs) of the subchondral cancellous bone of tibial plateaus (TPs). Statistics included a 2 x 2 factorial analysis with +/-CT as one factor and +/-ACLT as the other. RESULTS AND CONCLUSIONS: Nonoperated (N-OP) knees were normal in both groups. In the PL-treated group, ACLT knees all exhibited OA changes, which predominated in the medial knee compartment. Furthermore, compared with N-OP knees, the BMD and BVF of ACLT joints were both markedly reduced in medial TP but not in lateral TP. In contrast, in the CT-treated group, cartilage OA lesions of ACLT knees were significantly reduced, and there was no difference in BMD and BFV between N-OP and ACLT knees. These findings suggest that the loss of subchondral trabeculae contributes to cartilage breakdown, possibly by enhancing cartilage deformation on joint loading. By counteracting bone loss, CT reduced cartilage OA lesions, and thus, might be useful in the treatment of OA in cruciate-deficient dogs.

Animals↗

PubMed2004

Treatment with calcitonin prevents the net loss of collagen, hyaluronan and proteoglycan aggregates from cartilage in the early stages of canine experimental osteoarthritis.

OBJECTIVE: To evaluate the effect of calcitonin (CT) on the histology and biochemistry of articular cartilage from unstable operated and nonoperated knee in a canine model of experimental osteoarthritis (OA). METHODS: Eighteen dogs underwent anterior cruciate ligament transection (ACLT) of the right knee and were randomly distributed into three groups of six dogs each. From day-1 after surgery until sacrifice 84 days post-ACLT, each dog received a daily nasal spray that delivered the placebo, 100 units of CT or 400 units of CT. Histologic lesions were scored. Hyaluronan (HA) and antigenic keratan sulfate (AgKS) were quantified by enzyme-linked immunosorbent assays (ELISAs), whereas aggrecan molecules extracted under nondissociative conditions were characterized by velocity gradient centrifugation. RESULTS: All canine cruciate-deficient knees developed OA. At a daily dose of 400 units, CT had no effect on the size of osteophytes but significantly reduced the severity of cartilage histologic lesions in unstable knees. CT also enhanced the HA content as well as the size distribution and relative abundance of fast-sedimenting aggrecan aggregates in cartilage from both operated and nonoperated knees. On the other hand, in the CT-treated group, the cartilage content of AgKS increased in operated joints, but not in nonoperated joints. CONCLUSIONS: Because CT delivered as a nasal spray markedly reduced the severity of most OA changes, both at the histological and biochemical level, this form of therapy may have benefits for humans who have recently experienced a traumatic knee injury, and as well as for dogs who spontaneously rupture their ACL.

Aggrecans↗

PubMed2003

The use of intra-articular Na-hyaluronate as a potential chondroprotective device in experimentally induced acute articular cartilage injury and repair in rabbits.

OBJECTIVE: This study examined if viscosupplementation from intra-articular administration of a commercially available form of hyaluronan (HA) could promote the restoration of proteoglycan (PG) depletion induced by chymopapain and then if the repair could be maintained once HA treatment was discontinued. METHODS: Animals received cartilage injury with intra-articular chymopapain (2.0 mg) followed by weekly treatment with intra-articular HA. HA treated animals were compared to injured animals with no treatment, contralateral untreated joints and joints from normal controls. The effect of intra-articular HA alone on articular cartilage was also examined. RESULTS: Serum keratan sulfate levels confirmed degradation of the cartilage PGs in the chymopapain-injected knees. Intra-articular chymopapain resulted in marked loss of PGs. There were no significant differences among the control groups (untreated control, HA/800 treatment only). HA treatment did not affect the loss of PGs caused by chymopapain after 42 days. However, in animals receiving chymopapain injury followed by weekly HA treatment for 42 days and then 42 days of free cage activity without HA, cartilage PG contents were significantly increased. Intra-articular HA alone had no effect on the articular cartilage. CONCLUSION: The results in the present study suggest a potential protective effect of HA on chymopapain-induced acute articular cartilage injury in rabbits that, in time, permits damaged cartilage to resynthesize matrix PGs after the HA treatment is discontinued.

Animals↗

PubMedDate not supplied

Comparison of ultrasonic suture welding and traditional knot tying in a rabbit rotator cuff repair model.

The purpose of this study is to evaluate ultrasonic suture welding of monofilament suture in an animal model of rotator cuff repair with biomechanical and histologic analyses. We randomly assigned 46 shoulders in 23 rabbits to 1 of 3 treatment groups: sham-operated (n = 15), knotted (n = 15), and welded (n = 16). Supraspinatus defects were surgically created and acutely repaired with suture anchors loaded with either No. 2-0 Ethibond for knotted group or No. 2-0 nylon for welded shoulders. Eighteen weeks postoperatively, all animals were killed, and the shoulders underwent either biomechanical testing or histologic analysis. The maximum stress of the sham-operated group (20.6 N/mm2) was significantly greater than that of both the knotted (10.2 N/mm2) and welded (8.3 N/mm2) groups (P < .05), but no differences were observed between the knotted and welded groups. Although some histologic changes were noted, none was considered to be significant to distinguish either group.

Animals↗