Publications by authors named "John F Tarlton"

25 Publications

  • Page 1 of 1

Rearing experience with ramps improves specific learning and behaviour and welfare on a commercial laying farm.

Sci Rep 2021 Apr 23;11(1):8860. Epub 2021 Apr 23.

Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, Hertfordshire, UK.

To access resources in commercial laying houses hens must move between levels with agility to avoid injury. This study considered whether providing ramps during rear improved the ability of birds to transition between levels. Twelve commercial flocks (2000 birds/flock) on a multi-age site were examined between 1 and 40 weeks of age. All birds had access to elevated perching structures from 4 days of age. Six treatment flocks were also provided with ramps during rear to facilitate access to these structures. Flocks were visited three times during rear and three times at lay to record transitioning behaviour and use of the elevated structures, together with scores for keel bone and feather damage. Ramp reared flocks used the elevated structures to a greater extent at rear (P = 0.001) and at lay, when all flocks had ramps, showed less hesitancy [i.e. pacing (P = 0.002), crouching (P = 0.001) and wing-flapping (P = 0.001)] in accessing levels. Mean levels of keel bone damage were reduced in ramp reared flocks (52%) compared with control flocks (64.8%) at 40 weeks of age (P = 0.028). The early life experience of the ramp reared flocks enabled specific learning that translated and persisted in later life and resulted in overall welfare benefits.
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http://dx.doi.org/10.1038/s41598-021-88347-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8065128PMC
April 2021

Stiffness-matched biomaterial implants for cell delivery: clinical, intraoperative ultrasound elastography provides a 'target' stiffness for hydrogel synthesis in spinal cord injury.

J Tissue Eng 2020 Jan-Dec;11:2041731420934806. Epub 2020 Jul 2.

The Royal Veterinary College, University of London, Hatfield, UK.

Safe hydrogel delivery requires stiffness-matching with host tissues to avoid iatrogenic damage and reduce inflammatory reactions. Hydrogel-encapsulated cell delivery is a promising combinatorial approach to spinal cord injury therapy, but a lack of clinical spinal cord injury stiffness measurements is a barrier to their use in clinics. We demonstrate that ultrasound elastography - a non-invasive, clinically established tool - can be used to measure spinal cord stiffness intraoperatively in canines with spontaneous spinal cord injury. In line with recent experimental reports, our data show that injured spinal cord has lower stiffness than uninjured cord. We show that the stiffness of hydrogels encapsulating a clinically relevant transplant population (olfactory ensheathing cells) can also be measured by ultrasound elastography, enabling synthesis of hydrogels with comparable stiffness to canine spinal cord injury. We therefore demonstrate proof-of-principle of a novel approach to stiffness-matching hydrogel-olfactory ensheathing cell implants to 'real-life' spinal cord injury values; an approach applicable to multiple biomaterial implants for regenerative therapies.
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http://dx.doi.org/10.1177/2041731420934806DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7336822PMC
July 2020

Behavioural and physiological responses of laying hens to automated monitoring equipment.

Appl Anim Behav Sci 2018 Feb;199:17-23

School of Veterinary Sciences, University of Bristol, Langford house, Langford, BS40 5DU, United Kingdom.

Automated monitoring of behaviour can offer a wealth of information in circumstances where observing behaviour is difficult or time consuming. However, this often requires attaching monitoring devices to the animal which can alter behaviour, potentially invalidating any data collected. Birds often show increased preening and energy expenditure when wearing devices and, especially in laying hens, there is a risk that individuals wearing devices will attract aggression from conspecifics. We studied the behavioural and physiological response of 20 laying hens to backpacks containing monitoring devices fastened with elastic loops around the wing base. We hypothesised that backpacks would lead to a stress-induced decrease in peripheral temperature, increased preening, more aggression from conspecifics, and reduced bodyweights. This was evaluated by thermography of the eye and comb (when isolated after fitting backpacks), direct observations of behaviour (when isolated, when placed back into the group, and on later days), and weighing (before and after each 7-day experimental period). Each hen wore a backpack during one of the two experimental periods only and was used as her own control. Contrary to our hypothesis, eye temperature was higher when hens wore a backpack (No backpack: 30.2 °C (IQR: 29.0-30.6) vs. Backpack: 30.9 °C (IQR: 30.0-32.0), P < 0.001). Eye temperature of hens wearing a backpack was strongly correlated to the time spent preening (r = 0.8, P < 0.001), suggesting that the higher temperatures may have been due to preening itself, or to a low head position or decreased heat dissipation when preening under the wings. Aggressive behaviour was very rare and no effect of the backpacks was found. In line with our hypothesis, backpacks increased preening on the day of fitting, both when isolated (No backpack: 0% (IQR: 0-1) vs. Backpack: 22% (IQR: 1-43), P < 0.01) and when back in the group (No backpack: 0% (IQR: 0-27) vs. Backpack: 43% (IQR: 5-77), P < 0.001). However, no effect on preening was observed 2-7 days afterwards. Other behavioural changes suggested that on the day of fitting hens prioritized attempts to (re)move the backpack and were less attentive to their surroundings. However, only equipment pecking (i.e., pecking the backpack or leg rings) was still affected 2-7 days after fitting (No backpack: 0 pecks/hen/minute (IQR: 0-0), vs. Backpack: 0 (IQR: 0-0.07), P < 0.05). We found no effect of our backpacks on bodyweight. In conclusion, our backpacks seem suitable to attach monitoring equipment to hens with only a very minor effect on their behaviour after a short acclimation period (≤2 days).
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http://dx.doi.org/10.1016/j.applanim.2017.10.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805850PMC
February 2018

Biomechanical comparison of canine fascia lata and thoracolumbar fascia: an in vitro evaluation of replacement tissues for body wall reconstruction.

Vet Surg 2015 Jan 28;44(1):126-34. Epub 2014 Jul 28.

Department of Clinical Veterinary Science, University of Bristol, Bristol, United Kingdom.

Objectives: To compare the suitability of thoracolumbar fascia (TLF) and fascia lata (FL) for body wall defect repair in dogs, by examining their biomechanical properties and useable surface area.

Study Design: Experimental.

Animals: Dogs (n = 8).

Methods: Fresh TLF and FL grafts were obtained, surface area was calculated before testing to failure in 2 different modes: tensile testing and resistance to suture pullout, in 2 perpendicular orientations.

Results: Useable TLF surface area was significantly greater than for FL. Maximum load, energy to break, and elastic modulus of FL was significantly greater than that of TLF in tensile testing, but no apparent difference in the ultimate stress or strain was identified. There was no overall difference in suture pullout load between TLF and FL. During tensile testing, tissue orientation had a significant influence on ultimate load, stress, and elastic modulus for both tissue types, with strain and energy to break only having significant effects for TLF and FL, respectively.

Conclusions: The greater tensile strength and stiffness of FL compared to TLF was not reflected in its material properties, implying any difference was a consequence of greater thickness. Suture pullout was not significantly different between the 2 tissues, perhaps limiting the clinical significance of the tissue mechanics. Tissues were anisotropic with respect to mechanical properties, thus orientation may be an important factor.
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http://dx.doi.org/10.1111/j.1532-950X.2014.12247.xDOI Listing
January 2015

Subchondral bone plate thickening precedes chondrocyte apoptosis and cartilage degradation in spontaneous animal models of osteoarthritis.

Biomed Res Int 2014 18;2014:606870. Epub 2014 Jun 18.

School of Clinical Sciences, University of Bristol, Musculoskeletal Research Unit, Avon Orthopaedic Centre, Southmead Hospital, Bristol BS10 5NB, UK.

Osteoarthritis (OA) is the most common joint disorder characterised by bone remodelling and cartilage degradation and associated with chondrocyte apoptosis. These processes were investigated at 10, 16, 24, and 30 weeks in Dunkin Hartley (DH) and Bristol Strain 2 (BS2) guinea pigs that develop OA spontaneously. Both strains had a more pronounced chondrocyte apoptosis, cartilage degradation, and subchondral bone changes in the medial than the lateral side of the tibia, and between strains, the changes were always greater and faster in DH than BS2. In the medial side, a significant increase of chondrocyte apoptosis and cartilage degradation was observed in DH between 24 and 30 weeks of age preceded by a progressive thickening and stiffening of subchondral bone plate (Sbp). The Sbp thickness consistently increased over the 30-week study period but the bone mineral density (BMD) of the Sbp gradually decreased after 16 weeks. The absence of these changes in the medial side of BS2 may indicate that the Sbp of DH was undergoing remodelling. Chondrocyte apoptosis was largely confined to the deep zone of articular cartilage and correlated with thickness of the subchondral bone plate suggesting that cartilage degradation and chondrocyte apoptosis may be a consequence of continuous bone remodelling during the development of OA in these animal models of OA.
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http://dx.doi.org/10.1155/2014/606870DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4086372PMC
March 2015

Increased chondrocyte apoptosis is associated with progression of osteoarthritis in spontaneous Guinea pig models of the disease.

Int J Mol Sci 2013 Aug 29;14(9):17729-43. Epub 2013 Aug 29.

Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK.

Osteoarthritis (OA) is the most common joint disease characterised by degradation of articular cartilage and bone remodelling. For almost a decade chondrocyte apoptosis has been investigated as a possible mechanism of cartilage damage in OA, but its precise role in initiation and/or progression of OA remains to the determined. The aim of this study is to determine the role of chondrocyte apoptosis in spontaneous animal models of OA. Right tibias from six male Dunkin Hartley (DH) and Bristol Strain 2 (BS2) guinea pigs were collected at 10, 16, 24 and 30 weeks of age. Fresh-frozen sections of tibial epiphysis were microscopically scored for OA, and immunostained with caspase-3 and TUNEL for apoptotic chondrocytes. The DH strain had more pronounced cartilage damage than BS2, especially at 30 weeks. At this time point, the apoptotic chondrocytes were largely confined to the deep zone of articular cartilage (AC) with a greater percentage in the medial side of DH than BS2 (DH: 5.7%, 95% CI: 4.2-7.2), BS2: 4.8%, 95% CI: 3.8-5.8), p > 0.05). DH had a significant progression of chondrocyte death between 24 to 30 weeks during which time significant changes were observed in AC fibrillation, proteoglycan depletion and overall microscopic OA score. A strong correlation (p ≤ 0.01) was found between chondrocyte apoptosis and AC fibrillation (r = 0.3), cellularity (r = 0.4) and overall microscopic OA scores (r = 0.4). Overall, the rate of progression in OA and apoptosis over the study period was greater in the DH (versus BS2) and the medial AC (versus lateral). Chondrocyte apoptosis was higher at the later stage of OA development when the cartilage matrix was hypocellular and highly fibrillated, suggesting that chondrocyte apoptosis is a late event in OA.
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http://dx.doi.org/10.3390/ijms140917729DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3794750PMC
August 2013

Development of an ex vivo protocol to model bone fracture in laying hens resulting from collisions.

PLoS One 2013 13;8(6):e66215. Epub 2013 Jun 13.

School of Veterinary Sciences, University of Bristol, Lower Langford, North Somerset, England.

Fractures of the keel bone, a bone extending ventrally from the sternum, are a serious health and welfare problem in free range laying hens. Recent findings suggest that a major cause of keel damage within extensive systems is collisions with internal housing structures, though investigative efforts have been hindered by difficulties in examining mechanisms and likely influencing factors at the moment of fracture. The objectives of this study were to develop an ex vivo impact protocol to model bone fracture in hens caused by collision, to assess impact and bird-related factors influencing fracture occurrence and severity, and to identify correlations of mechanical and structural properties between different skeletal sites. We induced keel bone fractures in euthanized hens using a drop-weight impact tester able to generate a range of impact energies, producing fractures that replicate those commonly found in commercial settings. The results demonstrated that impact energies of a similar order to those expected in normal housing were able to produce fractures, and that greater collision energies resulted in an increased likelihood of fractures and of greater severity. Relationships were also seen with keel's lateral surface bone mineral density, and the peak reactive force (strength) at the base of the manubrial spine. Correlations were also identified between the keel and long bones with respect to both strength and bone mineral density. This is the first study able to relate impact and bone characteristics with keel bone fracture at the moment of collision. Greater understanding of these relationships will provide means to reduce levels of breakage and severity in commercial systems.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0066215PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3681979PMC
January 2014

Use of modified superabsorbent polymer dressings for protease modulation in improved chronic wound care.

Wounds 2013 Feb;25(2):51-7

First Water Ltd, Ramsbury, Marlborough, Wiltshire, UK.

Unlabelled:  With more than 6 million patients affected with them in the United States, chronic ulcers represent one of the greatest problems in wound care. High levels of corrosive proteases, particularly matrix metalloproteinases (MMPs), within the wound environment are thoughtto contribute to the persistence of these wounds through denaturation of connective tissue proteins crucial to healing progression. Therefore, there is considerable interest in protease modulation using wound dressings to promote healing in chronic wounds. Such modulation could be achieved by direct absorption of proteases, by depleting co- factors within the wound, or by release of protease inhibitors.

Method: The aim of this study is to examine protease modulation of a range of dressings with different chemistries, particularly those having demonstrated efficacy in chronic wound healing.

Results: XTRASORB® HCS (dressing A) and XTRASORB® Foam (dressing B) were able to modulate proteases by both direct absorption of MMPs and depleting metal ion co-factors, and resulted in complete elimination of protease activity in the assay used. Duoderm® (dressing C) was able to modulate proteases by direct absorption only, and not by co-factor depletion. Promogran® (dressing D) was able to reduce MMP activity, but this was shown to be pH dependant, with any protease modulation being lost at neutral pH. Neither Allevyn® (dressing E) nor Vigilon® (dressing F) were able to modulate proteases by any mechanism. None of the protease modulating dressings acted through the release of protease inhibitors.

Conclusion: Of the dressings studied, dressing A and dressing B were the most effective protease modulators due to their acting through 2 separate mechanisms. .
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February 2013

IL-13 promotes collagen accumulation in Crohn's disease fibrosis by down-regulation of fibroblast MMP synthesis: a role for innate lymphoid cells?

PLoS One 2012 31;7(12):e52332. Epub 2012 Dec 31.

School of Veterinary Science, University of Bristol, Bristol, United Kingdom.

Background: Fibrosis is a serious consequence of Crohn's disease (CD), often necessitating surgical resection. We examined the hypothesis that IL-13 may promote collagen accumulation within the CD muscle microenvironment.

Methods: Factors potentially modulating collagen deposition were examined in intestinal tissue samples from fibrotic (f) CD and compared with cancer control (C), ulcerative colitis (UC) and uninvolved (u) CD. Mechanisms attributable to IL-13 were analysed using cell lines derived from uninvolved muscle tissue and tissue explants.

Results: In fCD muscle extracts, collagen synthesis was significantly increased compared to other groups, but MMP-2 was not co-ordinately increased. IL-13 transcripts were highest in fCD muscle compared to muscle from other groups. IL-13 receptor (R) α1 was expressed by intestinal muscle smooth muscle, nerve and KIR(+) cells. Fibroblasts from intestinal muscle expressed Rα1, phosphorylated STAT6 in response to IL-13, and subsequently down-regulated MMP-2 and TNF-α-induced MMP-1 and MMP-9 synthesis. Cells with the phenotype KIR(+)CD45(+)CD56(+/-)CD3(-) were significantly increased in fCD muscle compared to all other groups, expressed Rα1 and membrane IL-13, and transcribed high levels of IL-13. In explanted CD muscle, these cells did not phosphorylate STAT6 in response to exogenous IL-13.

Conclusions: The data indicate that in fibrotic intestinal muscle of Crohn's patients, the IL-13 pathway is stimulated, involving a novel population of infiltrating IL-13Rα1(+), KIR(+) innate lymphoid cells, producing IL-13 which inhibits fibroblast MMP synthesis. Consequently, matrix degradation is down-regulated and this leads to excessive collagen deposition.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0052332PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3534115PMC
July 2013

Reduced bone breakage and increased bone strength in free range laying hens fed omega-3 polyunsaturated fatty acid supplemented diets.

Bone 2013 Feb 9;52(2):578-86. Epub 2012 Nov 9.

Matrix Biology Research Group, University of Bristol, Langford, Bristol BS40 5DU, UK.

Introduction: The omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) are the immediate precursors to a number of important mediators of immunity, inflammation and bone function, with products of omega-6 generally thought to promote inflammation and favour bone resorption. Western diets generally provide a 10 to 20-fold deficit in omega-3 PUFAs compared with omega-6, and this is thought to have contributed to the marked rise in incidence of disorders of modern human societies, such as heart disease, colitis and perhaps osteoporosis. Many of our food production animals, fed on grains rich in omega-6, are also exposed to a dietary deficit in omega-3, with perhaps similar health consequences. Bone fragility due to osteoporotic changes in laying hens is a major economic and welfare problem, with our recent estimates of breakage rates indicating up to 95% of free range hens suffer breaks during lay.

Methods: Free range hens housed in full scale commercial systems were provided diets supplemented with omega-3 alpha linolenic acid, and the skeletal benefits were investigated by comparison to standard diets rich in omega-6.

Results: There was a significant 40-60% reduction in keel bone breakage rate, and a corresponding reduction in breakage severity in the omega-3 supplemented hens. There was significantly greater bone density and bone mineral content, alongside increases in total bone and trabecular volumes. The mechanical properties of the omega-3 supplemented hens were improved, with strength, energy to break and stiffness demonstrating significant increases. Alkaline phosphatase (an osteoblast marker) and tartrate-resistant acid phosphatase (an osteoclast marker) both showed significant increases with the omega-3 diets, indicating enhanced bone turnover. This was corroborated by the significantly lower levels of the mature collagen crosslinks, hydroxylysyl pyridinoline, lysyl pyridinoline and histidinohydroxy-lysinonorleucine, with a corresponding significant shift in the mature:immature crosslink ratio.

Conclusions: The improved skeletal health in laying hens corresponds to as many as 68million fewer hens suffering keel fractures in the EU each year. The biomechanical and biochemical evidence suggests that increased bone turnover has enhanced the bone mechanical properties, and that this may suggest potential benefits for human osteoporosis.
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http://dx.doi.org/10.1016/j.bone.2012.11.003DOI Listing
February 2013

Repair of meniscal cartilage white zone tears using a stem cell/collagen-scaffold implant.

Biomaterials 2010 Mar 6;31(9):2583-91. Epub 2010 Jan 6.

Department of Clinical Science at North Bristol, University of Bristol, UK.

Injuries to the avascular region of knee meniscal cartilage do not heal spontaneously. To address this problem we have developed a new stem cell/collagen-scaffold implant system in which human adult bone marrow mesenchymal stem cells are seeded onto a biodegradable scaffold that allows controlled delivery of actively dividing cells to the meniscus surface. Sandwich constructs of two white zone ovine meniscus discs with stem cell/collagen-scaffold implant in between were cultured in vitro for 40 days. Histomorphometric analysis revealed superior integration in the stem cell/collagen-scaffold groups compared to the cell-free collagen membrane or untreated controls. The addition of TGF-beta1 to differentiate stem cells to chondrocytes inhibited integration. Biomechanical testing demonstrated a significant 2-fold increase in tensile strength in all constructs using the stem cell/collagen-scaffold compared to control groups after 40 days in culture. Integration was significantly higher when collagen membranes were used that had a more open/spongy structure adjacent to both meniscal cartilage surfaces, whereas a collagen scaffold designed for osteoinduction failed to induce any integration of meniscus. In conclusion, the stem cell/collagen-scaffold implant is a potential therapeutic treatment for the repair of white zone meniscal cartilage tears.
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http://dx.doi.org/10.1016/j.biomaterials.2009.12.023DOI Listing
March 2010

Induction of cartilage integration by a chondrocyte/collagen-scaffold implant.

Biomaterials 2009 Sep 17;30(26):4277-86. Epub 2009 Jun 17.

Stem Cell Biology, Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom.

The integration of implanted cartilage is a major challenge for the success of tissue engineering protocols. We hypothesize that in order for effective cartilage integration to take place, matrix-free chondrocytes must be induced to migrate between the two tissue surfaces. A chondrocyte/collagen-scaffold implant system was developed as a method of delivering dividing cells at the interface between two cartilage surfaces. Chondrocytes were isolated from bovine nasal septum and seeded onto both surfaces of a collagen membrane to create the chondrocyte/collagen-scaffold implant. A model of two cartilage discs and the chondrocyte/collagen-scaffold sandwiched in between was used to effect integration in vitro. The resulting tissue was analysed histologically and biomechanically. The cartilage-implant-cartilage sandwich appeared macroscopically as one continuous piece of tissue at the end of 40 day cultures. Histological analysis showed tissue continuum across the cartilage-scaffold interface. The integration was dependent on both cells and scaffold. Fluorescent labeling of implanted chondrocytes demonstrated that these cells invade the surrounding mature tissue and drive a remodelling of the extracellular matrix. Using cell-free scaffolds we also demonstrated that some chondrocytes migrated from the natural cartilage into the collagen scaffold. Quantification of integration levels using a histomorphometric repair index showed that the chondrocyte/collagen-scaffold implant achieved the highest repair index compared to controls, reflected functionally through increased tensile strength. In conclusion, cartilage integration can be achieved using a chondrocyte/collagen-scaffold implant that permits controlled delivery of chondrocytes to both host and graft mature cartilage tissues. This approach has the potential to be used therapeutically for implantation of engineered tissue.
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http://dx.doi.org/10.1016/j.biomaterials.2009.02.052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2723758PMC
September 2009

The relationship between cytokine concentrations and wound healing in chronic venous ulceration.

J Vasc Surg 2008 Nov 4;48(5):1272-7. Epub 2008 Sep 4.

Department of Vascular Surgery, Cheltenham General Hospital, Gloucestershire, United Kingdom.

Objective: The importance of wound cytokine function in chronic venous leg ulcers remains poorly understood. This study evaluated the relationship between local and systemic concentrations of wound cytokines and wound healing in patients with chronic venous ulceration.

Methods: This prospective observational study was set in a community- and hospital-based leg ulcer clinic. Consecutive patients with chronic leg ulceration and ankle-brachial pressure index >0.85 were prospectively investigated. All patients were treated with multilayer compression bandaging. Wound fluid and venous blood samples were collected at recruitment and 5 weeks later. In the wound fluid and venous blood, cytokines and factors reflecting the processes of inflammation (interleukin 1beta, tumor necrosis factor-alpha), proteolysis (matrix metalloproteinases-2 and -9), angiogenesis (basic fibroblast growth factor [bFGF], vascular endothelial growth factor), and fibrosis (transforming growth factor-beta(1) [TGFbeta(1)]) were measured. Ulcer healing was assessed using digital planimetry at both assessments.

Results: The study comprised 80 patients (43 men, 37 women). Median (range) ulcer size reduced from 4.4 (0.1-142.4) cm(2) to 2.2 (0-135.5) cm(2) after 5 weeks (P < .001; Wilcoxon signed rank), although 17 of 80 ulcers increased in size. The volume of wound fluid collected strongly correlated with ulcer size (Spearman rank = 0.801, P < .01). Initial wound fluid concentrations of bFGF correlated with ulcer size (Pearson coefficient = 0.641, P < .01), and changes in wound fluid TGFbeta(1) concentrations inversely correlated with changes in ulcer size (Spearman rank = -0.645, P = .032). There were no significant correlations between changes in other factors and ulcer healing. Wound fluid and serum cytokine concentrations correlated poorly.

Conclusion: Wound fluid collection volume correlates with ulcer size. Ulcer healing correlated with increased concentrations of TGFbeta(1), possibly reflecting increased fibrogenesis in the proliferating wound. Aside from this, there was a large variation in wound and serum cytokine levels that largely limits their usefulness as markers of healing.
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http://dx.doi.org/10.1016/j.jvs.2008.06.042DOI Listing
November 2008

Memory versus naive T-cell migration.

Immunol Cell Biol 2008 Mar-Apr;86(3):226-31. Epub 2007 Nov 13.

School of Clinical Veterinary Science, University of Bristol, Langford, Bristol, UK.

Our established understanding of lymphocyte migration suggests that naive and memory T cells travel throughout the body via divergent pathways; naive T cells circulate between blood and lymph whereas memory T cells additionally migrate through non-lymphoid organs. Evidence is now gradually emerging which suggests such disparate pathways between naive and memory T cells may not strictly be true, and that naive T cells gain access to the non-lymphoid environment in numbers approaching that of memory T cells. We discuss here the evidence for naive T-cell traffic into the non-lymphoid environment, compare and contrast this movement with what is known of memory T cells, and finally discuss the functional importance of why naive T cells might access the parenchymal tissues.
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http://dx.doi.org/10.1038/sj.icb.7100132DOI Listing
July 2008

Cruciate ligament laxity and femoral intercondylar notch narrowing in early-stage knee osteoarthritis.

Arthritis Rheum 2005 Oct;52(10):3100-9

Bristol Heart Institute, University of Bristol, Bristol, UK.

Objective: The influence of the cruciate ligaments in spontaneous osteoarthritis (OA) is not understood, although ligament rupture is known to cause secondary OA. Additionally, femoral notch narrowing at the anterior cruciate ligament (ACL) insertion site is associated with disease severity, but it is unknown whether ligament deterioration precedes or follows osteophyte formation. We examined cruciate ligament mechanics and metabolism and the intercondylar notch width in OA-prone Dunkin-Hartley (DH) guinea pigs at ages up to and including the age at OA onset (24 weeks), and compared the data with those in age-matched controls (Bristol strain 2 [BS2] guinea pigs).

Methods: Guinea pigs were assessed at 3, 6, 9, 12, 16, 20, 24, and 36 weeks of age. ACLs were mechanically tested, and the intercondylar notch width index (NWI) was determined. Cruciate ligament metabolism was determined by measuring the following markers of collagen turnover: matrix metalloproteinase 2 (MMP-2), tissue inhibitor of metalloproteinases 2, C-terminal type I procollagen propeptide (PICP), and the immature collagen-derived crosslink dihydroxylysinonorleucine (DHLNL).

Results: DH guinea pigs had significantly laxer ACLs than did BS2 guinea pigs, at 12, 16, and 24 weeks. We observed elevated levels of pro and active MMP-2, PICP, and DHLNL in the cruciate ligaments of DH animals at most ages, compared with BS2 guinea pigs. The NWI in DH animals was significantly lower than that in BS2 guinea pigs at 24 and 36 weeks.

Conclusion: In DH guinea pigs, laxer ACLs, which are associated with increased collagen turnover, may cause joint instability and predispose these animals to the early onset of OA. Decreased intercondylar notch width in the DH animals indicates that bone remodeling at the ACL insertion site is a response to elevated ACL laxity.
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http://dx.doi.org/10.1002/art.21340DOI Listing
October 2005

Abnormal extracellular matrix metabolism in chronically ischemic skin: a mechanism for dermal failure in leg ulcers.

J Invest Dermatol 2005 Aug;125(2):373-9

Department of Vascular Surgery, Southmead Hospital, Bristol, UK.

Extracellular matrix (ECM) metabolism and homeostasis is sensitive to changes in oxygen tension manifest in ischemia. We hypothesize that in chronically ischemic limbs, abnormalities in uninjured skin, secondary to hypoxia, predispose to dermal breakdown. Paired biopsies of uninjured distal ischemic and proximal non-ischemic skin were harvested at below knee amputation from 14 patients with peripheral vascular disease following quantification of ischemia. Age- and site-matched controls were taken at total knee replacement (TKR) and varicose vein (VV) operations. Matrix metalloproteinase (MMP)-2 and -9 expression was determined using gelatin zymography, MMP-1 by western blotting and ELISA and tissue inhibitor of MMP (TIMP) by reverse zymography. Collagen content was measured by determining hydroxyproline levels, and collagen type I synthesis by ELISA. Collagen type I synthesis was upregulated in ischemic tissue compared with non-ischemic matched pairs (p<0.001) and both TKR and VV controls, however, there was no increase in collagen deposition. Levels of MMP-2 (p<0.0005) and TIMP-2 (p<0.01), were elevated in ischemic samples. MMP-9 was unaltered, signifying no inflammatory changes. Tissue ischemia was linked to elevated ECM turnover, associated with matrix failure when compounded with problems of matrix stabilization, likely in ischemia. This represents a potential mechanism for ulcer formation.
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http://dx.doi.org/10.1111/j.0022-202X.2005.23789.xDOI Listing
August 2005

Dietary n-3 polyunsaturated fatty acids reduce disease and colonic proinflammatory cytokines in a mouse model of colitis.

Inflamm Bowel Dis 2005 Apr;11(4):340-9

Veterinary Pathology Infection and Immunity, School Clinical Veterinary Sciences, University of Bristol, Bristol, United Kingdom.

Background: n-3 polyunsaturated fatty acids (PUFAs) reduce the severity of chronic inflammatory bowel disease, probably by means of reduction of immune cell activation or enhancement of the epithelial barrier. Using the severe combined immunodeficient (SCID) mouse model of colitis, this study examined the effect of dietary n-3 PUFAs on development of colitis and on immunologic, epithelial, and matrix parameters in the intestines of control and colitic animals.

Methods: SCID mice were fed n-3-enriched or control diet for 3 weeks before colitis induction by transplantation of CD45RB T cells and maintained on the same diet for 4 to 8 weeks. Phenotype of infiltrating cells, epithelial ZO-1 protein, and mucosal type I collagen were assessed by immunohistology and tissue cytokines by ELISA.

Results: Transplanted n-3-fed animals had significantly reduced pathology scores, colonic tumor necrosis factor-alpha, interleukin-12, and interleukin-1beta compared with animals fed standard diet. Proinflammatory cytokines were reduced despite a similar level of immune cell infiltration by T cells, CD11c cells, and CD11b cells. Neutrophil infiltration was significantly reduced in n-3-fed control and colitic mice, and other myeloid populations were reduced in mice on the n-3 diet. Epithelial ZO-1 expression was increased, and myofibroblast activation significantly decreased in transplanted n-3-fed animals compared with standard diet mice. Submucosal collagen synthesis was enhanced in n-3-fed mice.

Conclusions: Dietary n-3 PUFAs reduced clinical colitis and colonic immunopathology in this model of colonic inflammation by decreasing proinflammatory cytokine synthesis, reducing myeloid cell recruitment and activation, and enhancing epithelial barrier function and mucosal wound healing mechanisms.
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http://dx.doi.org/10.1097/01.mib.0000164016.98913.7cDOI Listing
April 2005

Development of an assay for the quantification of type I collagen synthesis in the guinea pig.

J Immunol Methods 2005 Feb 28;297(1-2):133-41. Epub 2005 Jan 28.

Matrix Biology Research Group, University of Bristol, Langford, Bristol BS40 7DY, UK.

There is a need for a reliable assay for the quantification of collagen type I synthesis in the guinea pig, an important model for many connective tissue diseases. Procollagen type I C-terminal propeptide (PICP) is the established marker of type I collagen synthesis but, to date, no assay has been developed to measure PICP in guinea pig tissue extracts. A monoclonal antibody, known to cross-react with intact guinea pig procollagen type I (anti-PICP), was tested for its ability to bind soluble guinea pig PICP in crude skin extracts using a biosensor. Anti-PICP was immobilised to the surface of a sensor chip and antibody-antigen binding was detected using the phenomenon of surface plasmon resonance (SPR). The binding component in the SPR-immunoassay was identified as PICP by purification and N-terminal sequencing. Guinea pig PICP was purified from skin by gel filtration, ion exchange chromatography and lectin affinity chromatography. Purified PICP was then biotinylated and used with anti-PICP to develop a competition ELISA that was able to selectively and sensitively measure PICP in extracts of guinea pig connective tissue.
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http://dx.doi.org/10.1016/j.jim.2004.12.016DOI Listing
February 2005

Metabolism and composition of the canine anterior cruciate ligament relate to differences in knee joint mechanics and predisposition to ligament rupture.

J Orthop Res 2005 Jan;23(1):61-6

Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU, UK.

Purpose: The objective of this study was to determine whether differences in the composition and metabolism of the extracellular matrix (ECM) in canine anterior cruciate ligaments (ACLs) might relate to mechanical properties of the canine knee. Variations in ACL biochemistry and knee mechanics could account for divergent predispositions to ligament rupture.

Methods: Eleven knee joints were obtained from both cadaveric Labrador Retrievers (rupture predisposed) and ex-racing Greyhounds (non-rupture predisposed). Anterioposterior laxity and tensile testing determined mechanical properties of the knee joints and ACL samples respectively. The thermal properties of the collagenous matrix were determined by differential scanning calorimetry (DSC) and the biochemical properties by measuring collagen content, collagen cross-links, glycosaminoglycan (GAG) levels, matrix metalloproteinase-2 (MMP-2), tissue inhibitors of metalloproteinase (TIMP).

Results: The anterioposterior laxity was significantly greater (p = 0.04) in the Labrador Retriever knee joints, and their ACLs tended to be weaker (p = 0.06). Greater collagen turnover was demonstrated by significantly higher (p = 0.02) concentrations of pro-MMP-2, and lower enthalpy of denaturation (p = 0.05) in Labrador Retriever ACLs.

Conclusions: The different metabolism of the collagenous matrix in the ACLs of dogs predisposed to rupture was related to greater knee joint laxity and lower ligament material properties (ultimate tensile stress). This may be suggestive of a link between ligament rupture and eventual knee osteoarthritis in both dogs and humans.
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http://dx.doi.org/10.1016/j.orthres.2004.05.016DOI Listing
January 2005

Investigation of the composition, turnover, and thermal properties of ruptured cranial cruciate ligaments of dogs.

Am J Vet Res 2004 Aug;65(8):1136-41

Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol, BS40 5DU, UK.

Objective: To assess different components of the extracellular matrix with regard to their thermal properties, composition, and turnover in ruptured cranial cruciate ligaments (CCLs) of dogs, compared with components of intact CCLs from a breed predisposed to CCL failure.

Sample Population: Ruptured CCLs obtained from 8 dogs of breeds predisposed to ruptured CCLs and intact CCLs from 12 cadaveric Labrador Retrievers.

Procedure: Ruptured and intact CCLs were analyzed for water content; collagen content and collagen cross-links were evaluated via hydroxyproline and amino-acid analyses, respectively. Glycosaminoglycan (GAG) content was analyzed via dimethylmethylene blue and uronic acid assays. Matrix metalloproteinases (MMPs)-2 and -9 and the tissue inhibitors of metalloproteinases (TIMPs)-1 and -2 were detected via gelatin SDS-PAGE zymography and reverse gelatin zymography. Thermal analysis of ligaments was performed by use of differential scanning calorimetry.

Results: Ruptured CCLs had significantly higher lamounts of immature cross-links, total and sulfated GAGs, and water content, compared with that of the intact ligaments. Compared with intact CCLs, concentration of pro-MMP-2 was significantly higher in ruptured CCLs; the maximum temperature of collagen denaturation was significantly lower in the ruptured CCLs.

Conclusions And Clinical Relevance: The extracellular matrix of ruptured CCLs had an increased matrix turnover indicated by increased collagen and GAG synthesis, compared with that of intact CCLs. Although the extracellular matrix changes may have occurred before ligament rupture, it is possible that these observed changes may be part of a reparative process after rupture.
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http://dx.doi.org/10.2460/ajvr.2004.65.1136DOI Listing
August 2004

Biomechanical and clinical evaluation of a modified 3-loop pulley suture pattern for reattachment of canine tendons to bone.

Vet Surg 2004 Jul-Aug;33(4):391-7

Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, UK.

Objective: To describe a modified 3-loop pulley suture pattern for the reattachment of canine tendons to bone along with a biomechanical comparison with the locking-loop suture.

Study Design: In vitro biomechanical study and clinical case report.

Animals Or Sample Population: Biomechanical study: 10 paired gastrocnemius tendons and calcaneii harvested from 5 canine cadavers.

Case Report: a Doberman with avulsion of the gastrocnemius tendon of insertion.

Methods: Biomechanical study: paired tendons were reattached to the calcaneus with either a modified 3-loop pulley pattern or a locking-loop pattern. Tensile loading to failure was performed. A direct, non-contact, method of gap measurement, using digital video, was used to measure gap formation. Load required to initiate gap formation (defined as load at a 1 mm gap) and to produce a 3 mm gap was evaluated in addition to maximum load and gap at failure.

Results: Mean (+/-SEM) 1 mm gap loads were 31.0+/-4.2 and 17.2+/-2.5 N, mean 3 mm gap loads were 49.1+/-2.4 and 28.9+/-3.2 N, and mean maximum loads were 72.9+/-4.3 and 55.8+/-2.2 N for the modified 3-loop pulley suture and the locking-loop suture, respectively. These differences were statistically significant (P<.05). The gap at failure was similar for both repairs. The clinical case remained sound 7 months postoperatively.

Conclusions: A modified 3-loop pulley pattern is biomechanically superior to a locking-loop pattern for reattachment of the canine gastrocnemius tendon to bone and may be suitable for clinical use.

Clinical Relevance: Tendon repairs with a gap >3 mm are reported to be at increased risk of rupture during the first 6 weeks postoperatively. A modified 3-loop pulley pattern resists gap formation better than a locking-loop pattern.
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http://dx.doi.org/10.1111/j.1532-950X.2004.04057.xDOI Listing
September 2004

The three-loop pulley suture versus two locking-loop sutures for the repair of canine achilles tendons.

Vet Surg 2004 Mar-Apr;33(2):131-7

Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, Bristol, UK.

Objective: To compare a 3-loop pulley suture pattern with 2 locking-loop sutures for the repair of components of the canine Achilles mechanism.

Study Design: In vitro biomechanical study.

Animals: Forty-eight paired tendons collected from 9 canine cadavers.

Methods: Paired tendons were repaired with either a 3-loop pulley suture or 2 locking-loop sutures and tensile tested to failure. To ensure accurate anastomosis gap measurement a direct, non-contact, method of gap measurement, using digital video, was devised. Load initiating gap formation (defined as load at a 1 mm gap) and load producing a 3 mm gap were evaluated in addition to maximum load, gap at failure, mode of failure, and time spent placing the sutures.

Results: Maximum load values were similar for both repairs. The mean 1 mm gap loads were 44.0 and 18.4 N, and the mean 3 mm gap loads were 56.3 and 34.7 N, for the 3-loop pulley pattern and the 2 locking-loops, respectively; these differences were statistically significant. The 3-loop pulley pattern was faster to place and resulted in a smaller gap at failure. All but 2 repairs failed by suture pull out.

Conclusions: The 3-loop pulley pattern is more resistant to gap formation during tensile loading, and is quicker to place, than 2 locking-loop sutures.

Clinical Relevance: Gap formation can significantly delay tendon healing. Tendon repairs with a gap >3 mm are reported to be at increased risk of rupture during the first 6 weeks postoperatively.
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http://dx.doi.org/10.1111/j.1532-950x.2004.04020.xDOI Listing
May 2004

Abnormal mucosal extracellular matrix deposition is associated with increased TGF-beta receptor-expressing mesenchymal cells in a mouse model of colitis.

J Histochem Cytochem 2003 Sep;51(9):1177-89

Division of Veterinary Pathology, Infection and Immunity, Department of Clinical Veterinary Science, University of Bristol, Bristol, United Kingdom.

Transforming growth factor-beta (TGF-beta) depresses mucosal inflammation and upregulates extracellular matrix (ECM) deposition. We analyzed TGF-beta receptors RI and RII as well as ECM components using the CD4(+) T-cell-transplanted SCID mouse model of colitis. The principal change in colitis was an increased proportion of TGF-beta RII(+) mucosal mesenchymal cells, predominantly alpha-smooth muscle actin (SMA)(+) myofibroblasts, co-expressing vimentin and basement membrane proteins, but not type I collagen. TGF-beta RII(+) SMA(-) fibroblasts producing type I collagen were also increased, particularly in areas of infiltration and in ulcers. Type IV collagen and laminin were distributed throughout the gut lamina propria in disease but were restricted to the basement membrane in controls. In areas of severe epithelial damage, type IV collagen was lost and increased type I collagen was observed. To examine ECM production by these cells, mucosal mesenchymal cells were isolated. Cultured cells exhibited a similar phenotype and matrix profile to those of in vivo cells. The data suggested that there were at least two populations of mesenchymal cells responsible for ECM synthesis in the mucosa and that ligation of TGF-beta receptors on these cells resulted in the disordered and increased ECM production observed in colitic mucosa.
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http://dx.doi.org/10.1177/002215540305100908DOI Listing
September 2003