Veterinary Biosciences - Research Publications
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Investigating canine elbow joint stabilisation through mechanical constraints of the deep fascia and other soft tissues
The objective of this research was to investigate how the range of flexion and extension of the canine elbow joint is constrained by the mechanical connections and attachments of soft tissue structures. The skin, a section of deep fascia and several muscles from both forelimbs from six adult greyhounds and seven other breeds were sequentially transected or removed, over 13 steps. During each step, repeated measurements of elbow flexion and extension were recorded using a goniometer. Only marginally significant changes to the range of flexion occurred in any of the 13 steps or overall for the greyhounds. Clearly significant changes to extension occurred in several dissection steps. Removing the skin resulted in a significant increase in elbow extension of 1.7° ± 0.3 (P < 0.001) in the greyhounds and 1.6° ± 0.3 (P < 0.001) in the other breeds. Severing the deep fascia from the humerus and its connections across the elbow joint resulted in the largest significant change in elbow extension of 9.9° ± 0.3 (P < 0.001) in the greyhounds and 6.9° ± 0.7 (P < 0.001) in the other breeds. Transecting the biceps brachii m. close to the elbow resulted in an increase of 2.8° ± 0.3 (P < 0.001) in the greyhounds but a non-significant change in the other breeds. Transecting the extensor carpi radialis m. from its origin resulted in an increase of 5.5° ± 0.4 (P < 0.001) in the greyhounds and 3.9° ± 0.7 (P < 0.001) in the other breeds. These results suggest that the collagenous framework and attachments of the skin, deep fascia, and extensor carpi radialis m., play a significant role in the function of the canine elbow by restricting it from overextension and hence stabilising it during periods of loading, in a variety of different canine breeds, and that these structures are functionally integrated into the way the forelimb supports the bodyweight separately from any involvement of muscle tone or muscle movements. Observations on the anatomical connections of the deep fascia between the cranial distal humerus and the antebrachial fascia highlighted its probable importance in relating movements between the shoulder and the carpus.
Superoxide dismutase from Helicobacter pylori suppresses the production of pro-inflammatory cytokines during in vivo infection
BACKGROUND: Helicobacter pylori has undergone considerable adaptation to allow chronic persistence within the gastric environment. While H. pylori-associated diseases are driven by an excessive inflammation, severe gastritis is detrimental to colonization by this pathogen. Hence, H. pylori has developed strategies to minimize the severity of gastritis it triggers in its host. Superoxide dismutase (SOD) is well known for its role in protecting against oxidative attack; less recognized is its ability to inhibit immunity, shown for SOD from mammalian sources and those of some bacterial species. This study examined whether H. pylori SOD (HpSOD) has the ability to inhibit the host immune response to these bacteria. MATERIALS AND METHODS: The ability of recombinant HpSOD to modify the response to LPS was measured using mouse macrophages. A monoclonal antibody against HpSOD was generated and injected into H. pylori-infected mice. RESULTS: Addition of HpSOD to cultures of mouse macrophages significantly inhibited the pro-inflammatory cytokine response to LPS stimulation. A monoclonal antibody was generated that was specific for SOD from H. pylori. When injected into mice infected with H. pylori for 3 months, this antibody was readily detected in both sera and gastric tissues 5 days later. While treatment with anti-HpSOD had no effect on H. pylori colonization at this time point, it significantly increased the levels of a range of pro-inflammatory cytokines in the gastric tissues. This did not occur with antibodies against other antioxidant enzymes. CONCLUSIONS: SOD from H. pylori can inhibit the production of pro-inflammatory cytokine during in vivo infection.
Biomechanical testing of the calcified metacarpal articular surface and its association with subchondral bone microstructure in Thoroughbred racehorses
BACKGROUND: Palmar/plantar osteochondral disease (POD) and third metacarpal/-tarsal condylar fractures are considered fatigue injuries of subchondral bone (SCB) and calcified cartilage due to repetitive high loads in racehorses. In combination with adaptive changes in SCB in response to race training, the accumulation of SCB fatigue is likely to result in changes of joint surface mechanical properties. OBJECTIVES: To determine the spatial relationship and correlation of calcified articular surface biomechanical properties with SCB microstructure and training history in the distal palmar metacarpal condyle of Thoroughbred racehorses. STUDY DESIGN: Cross-sectional study. METHODS: Third metacarpal condyles were examined from 31 Thoroughbred horses with micro-computed tomography (microCT). Hyaline cartilage was removed and reference point indentation (RPI) mechanical testing of the calcified articular surface was performed. Training histories were obtained from trainers. The association among indentation distance increase (IDI, an inverse RPI measure of toughness), and microCT and training variables was assessed using a mixed-effects generalised linear model. RESULTS: Untrained horses had higher IDI than horses that had commenced training (P<0.001). Death as a result of musculoskeletal bone fatigue injury (P = 0.044) and presence of POD (P = 0.05) were associated with higher IDI. The microCT variables connectivity density and trabecular pattern factor were positively (P = 0.002) and negatively (P<0.001) correlated with IDI respectively. MAIN LIMITATIONS: The application of RPI to the calcified articular surface is novel and there is a potential for measurement variability with surface unevenness. CONCLUSION: Commencement of race training is associated with altered material properties of the calcified articular surface in horses. Reduced articular surface material properties can also be detected in horses that have fatigue injuries of the distal metacarpus and at other sites in the skeleton. Measures of SCB connectivity and trabecular surface shape may be more important determinants of resistance to failure of the calcified articular surface than traditional measures such as SCB volume and density.
Elapid snake envenomation in horses: 52 cases (2006-2016)
BACKGROUND: Snake envenomation is a cause of morbidity and mortality in domestic animals worldwide. The clinical features of crotalid snake (pit viper) envenomation are widely reported and well described in horses but elapid snake envenomation is poorly characterised. OBJECTIVES: To describe the presentation, clinical and laboratory findings, treatment and outcome of horses with a diagnosis of elapid snake envenomation in Australia. STUDY DESIGN: Retrospective case series. METHODS: Medical records of horses with a diagnosis of elapid snake envenomation (2006-2016) at several university and private veterinary practices were reviewed. Inclusion criteria comprised one or more of the following: 1) observed snakebite, 2) positive snake venom detection kit (SVDK) result, 3) appropriate clinical response to treatment with antivenom or 4) supportive post-mortem findings. RESULTS: Fifty-two cases met the inclusion criteria. Most cases (94%) demonstrated clinical signs of neurotoxicity, characterised by generalised neuromuscular weakness. Associated neurologic signs included staggering gait, muscle fasciculations, recumbency, mydriasis, ptosis and tongue paresis. Concurrent clinically important conditions included rhabdomyolysis (50%) and haemolysis (19%). Of 18 urine samples evaluated with a SVDK, only three (17%) were positive. Overall survival was favourable (86%) among 49 horses who received antivenom. Eighteen surviving horses (43%) required more than one vial of antivenom. MAIN LIMITATIONS: Possible cases within the searchable database were not included if horses died acutely or responded to symptomatic treatment without receiving antivenom. CONCLUSIONS: Elapid snake envenomation is primarily a syndrome of neuromuscular weakness. Supportive anamnesis or an obvious bite site is rarely encountered. In endemic areas, this diagnosis should be considered for horses with generalised neuromuscular weakness, altered mentation, rhabdomyolysis and/or haemolysis; especially during spring and summer months. Diagnostic suspicion is best confirmed by response to treatment with antivenom.
Diagnostic accuracy of pre-treatment biopsy for grading cutaneous mast cell tumours in dogs
Mast cell tumours (MCTs) are common tumours of the canine skin, and are estimated to represent up to 20% of all skin tumours in dogs. Tumour grade has a major impact on the incidence of local recurrence and metastatic potential. In addition to helping the clinician with surgical planning, knowledge of the tumour grade also assists in proper prognostication and client education. For pre-treatment biopsies to be useful, there must exist a high level of correlation between the histopathological grade obtained from the pre-treatment biopsy and the actual histopathological grade from the excisional biopsy. The aim of this study was to determine concordance of tumour grade between various biopsy techniques (wedge, punch, needle core) and the "gold standard" excisional biopsy method. We found an overall concordance rate of 96% based on the Patnaik grading system, and an overall concordance rate of 92% based on the Kiupel grading system. The accuracy of the various biopsy techniques (wedge, punch and needle core) when compared with excisional biopsy was 92%, 100% and 100%, respectively, based on the Patnaik grading system, and 90%, 95% and 100%, respectively, based on the Kiupel grading system. Of the cases with discordant results, the pre-treatment biopsies tended to underestimate the grade of the tumour. Based on these results, we conclude that pre-treatment biopsies are sufficiently accurate for differentiating low-grade from high-grade MCTs, regardless of biopsy technique or tumour location.
Polypoid cystitis as a cause of haematuria in a pony mare
A 15‐year‐old pony mare was presented for investigation of haematuria of 2 weeks' duration. On cystoscopy, multiple small pedunculated soft tissue structures were observed on the bladder mucosa. Histopathological analysis of the masses was consistent with chronic polypoid cystitis. The polypoid lesions and associated haematuria resolved following prolonged antibiotic treatment. Polypoid cystitis has not previously been described in horses. This condition should be considered a differential for haematuria, requiring cystoscopy and biopsy to confirm a diagnosis.
Effects of polymyxin-B on TNF-alpha production in equine whole blood stimulated with three different bacterial toxins
Polymyxin-B is used to treat equine systemic inflammation. Bacterial toxins other than lipopolysaccharide (LPS) contribute to systemic inflammation but the effects of polymyxin-B on these are poorly defined. Whole blood aliquots from six healthy horses diluted 1:1 with RPMI were incubated for 21 hr with 1 μg/ml of LPS, lipoteichoic acid (LTA) or peptidoglycan (PGN) in the presence of increasing concentrations of polymyxin-B (10-3000 μg/ml). A murine L929 fibroblast bioassay was used to measure TNF-α activity. Polymyxin-B significantly inhibited the effects of all three bacterial toxins. Analysis of variance showed the IC50 value for polymyxin-B for TNF-α inhibition caused by LTA (11.19 ± 2.89 μg/ml polymyxin-B) was significantly lower (p = .009) than the values for LPS (46.48 ± 9.93 μg/ml) and PGN (54.44 ± 8.97 μg/ml). There was no significant difference in IC50 values between LPS and PGN (p > .05). Maximum inhibition of TNF-α was 77.4%, 73.0% and 82.7% for LPS, PGN and LTA, respectively and was not significantly different between toxins. At the two highest concentrations of polymyxin-B, TNF-α began to increase. These data suggest that polymyxin-B may inhibit the effects of bacterial toxins other than LPS and might be a more potent inhibitor of LTA than LPS or PGN.
Antimicrobials used for surgical prophylaxis by equine veterinary practitioners in Australia
BACKGROUND: Antimicrobials are widely used in Australian veterinary practices, but no investigation into the classes of antimicrobials used, or the appropriateness of use in horses, has been conducted. OBJECTIVES: The aim of the study was to describe antimicrobial use for surgical prophylaxis in equine practice in Australia. STUDY DESIGN: Cross-sectional questionnaire survey. METHODS: An online questionnaire was used to document antimicrobial usage patterns. Information solicited in the questionnaire included demographic details of the respondents, the frequency with which antimicrobials were used for specific surgical conditions (including the dose, timing and duration of therapy) and practice antimicrobial use policies and sources of information about antimicrobials and their uses. RESULTS: A total of 337 members of the Australian veterinary profession completed the survey. Generally, the choice of antimicrobial was appropriate for the specified equine surgical condition, but the dose and duration of therapy varied greatly. While there was poor optimal compliance with British Equine Veterinary Association guidelines in all scenarios (range 1-15%), except removal of a nonulcerated dermal mass (42%), suboptimal compliance (compliant antimicrobial drug selection but inappropriate timing, dose or duration of therapy) was moderate for all scenarios (range 48-68%), except for an uninfected contaminated wound over the thorax, where both optimal and suboptimal compliance was very poor (1%). Veterinarians practicing at a university hospital had higher odds of compliance than general practice veterinarians (Odds ratio 3.2, 95% CI, 1.1-8.9, P = 0.03). MAIN LIMITATIONS: Many survey responses were collected at conferences which may introduce selection bias, as veterinarians attending conferences may be more likely to have been exposed to contemporary antimicrobial prescribing recommendations. CONCLUSIONS: Antimicrobial use guidelines need to be developed and promoted to improve the responsible use of antimicrobials in equine practice in Australia. An emphasis should be placed on antimicrobial therapy for wounds and appropriate dosing for procaine penicillin.
Herbicide efficacy for aquatic Alternanthera philoxeroides management in an early stage of invasion: integrating above-ground biomass, below-ground biomass and viable stem fragmentation
Alternanthera philoxeroides is a problematic invasive plant in many regions of the world that is difficult to control once naturalised. It poses a threat to agricultural productivity, biodiversity and social amenity values of aquatic environments. Significant research has been conducted internationally, regarding the efficacy of different herbicides for control of A.Â philoxeroides. However, no studies have looked at key aspects of control for effective management in an early stage of invasion of aquatic environments, hindering eradication and control programmes. This study evaluates theÂ efficacy of herbicides and surfactants on key A. philoxeroides response metrics, including control of aboveâ ground biomass, belowâ ground biomass and production of viable stem fragments. This study concluded that glyphosate (isopropylamine salt) minimises viable stem fragment production postâ herbicide application, compared with imazapyr and metsulfuron, thus reducing the potential for dispersal throughout catchments and waterways. In contrast, imazapyr and metsulfuron provided more effective control than glyphosate for A.Â philoxeroides growing on exposed embankments. We propose that an effective management strategy for early invasion of aquatic A.Â philoxeroides, using herbicides, would be to conduct initial applications of glyphosate to control overwater biomass and limit dispersal of viable stem fragments. Once infestations have been forced back to the embankment, imazapyr or metsulfuron treatments will provide longer term control.