Paul C. Mills

Effects of exercise intensity and environmental stress on indices of oxidative stress and iron homeostasis during exercise in the horse.

The effects of prolonged variable-intensity and short-term high-intensity exercise on indices of oxidative stress and iron homeostasis were compared in six fit horses under cool [20°C, 40% relative humidity (RH)] or hot/humid (30°C, 80% RH) environmental conditions. The exercise protocols were designed to simulate equine competition, including racing (intense exercise) or the speed and endurance phase of a 3-day event (prolonged exercise). Increased plasma concentrations of lipid hydroperoxides and haemolysate concentrations of oxidised glutathione (GSSG) were measured within 30 min of the completion of exercise, indicating production of reactive oxygen species (ROS) and lipid membrane peroxidation. The horses were unable to complete the prolonged exercise protocol at high temperature and humidity. This coincided with higher maximal values of lipid hydroperoxides [138.2 (17.7) μM and GSSG [110.6 (18.2) μM], compared to high-intensity [105.2 (14.9) μM and 63.6 (8.6) μM, respectively] or prolonged [100.7 (18.7) μM and 86.2 (9.1) μM, respectively] exercise performed under cooler environmental conditions. Significant correlations were found between the duration of the final stage of exercise during hot/humid environmental conditions and increased levels of lipid hydroperoxides (r = 0.85), GSSG (r = 0.94), xanthine (r = 0.92) and uric acid (r = 0.96). Excerise also decreased the iron (Fe)-binding antioxidant activity of the plasma and increased the total plasma Fe levels, although this was only significant for prolonged exercise in ambient conditions. There was no detectable free Fe in the plasma at any stage of exercise. Other changes in biochemical parameters had returned to pre-exercise levels within 24 h after exercise. The results show that exercise can induce changes in biochemical parameters that are indicative of oxidative stress in the fit horse and that this was, exacerbated during exercise at high temperature and humidity.

Blastocystis subtypes in symptomatic and asymptomatic family members and pets and response to therapy

Blastocystis is a common, enteric parasite. The pathogenicity of the organism is uncertain, but subtypes (ST) 1 and 3 have been reported more likely to cause irritable bowel‐like symptoms.

Effect of allopurinol on the formation of reactive oxygen species during intense exercise in the horse

Allopurinol was administered to six horses in a cross-over study to determine the relative contribution of xanthine oxidase (XO) activity to the formation of reactive oxygen species (ROS) in the horse during intense exercise. Exercise increased the mean (SEM) plasma lipid hydroperioxide concentration to a maximum of 492.7 (33.4) microM within one minute of exercise completion and maximum levels of both oxidised glutathione (GSSG) in haemolysates of red blood cells and the glutathione redox ratio (GRR) occurred 20 minutes after exercise (87.2 [12.2] microM and 8.9 [0.9] per cent, respectively). Allopurinol significantly reduced lipid hydroperoxides, GSSG and the GRR at the corresponding maximal times after exercise measured during control exercise (217.5 [32.1] microM. 63.8 [8.6] microM and 6.8 [0.7] per cent, respectively). Significantly higher levels of hypoxanthine and xanthine were measured after exercise in the plasma of horses that received allopurinol than in control horses, although uric acid levels remained constant. In control horses, plasma uric acid concentrations increased after exercise to a maximum 20 minutes after exercise of 28.1 (2.6) microM, significantly higher than in horses given allopurinol (9.6 [1.3] microM). The results show that the inhibition of XO by allopurinol leads to a decrease in the formation of ROS during exercise, and thus a reduction in oxidative stress.

Nitric oxide and exercise in the horse.

1. The effects of exercise on the production rate of nitric oxide (NO) in exhaled air (VNO) and the effects of inhaled NO (80 p.p.m.) on cardiovascular and respiratory parameters were investigated in five Throughbred horses. 2. The concentration of NO ([NO]) in exhaled air collected from within the nasal opening was lower when collected at a high flow rate of 80 l min‐1 than at a low flow rate of 20 l min‐1: when trotting at 3.7 m s‐1 the values were 0.78 +/‐ 0.15 and 1.23 +/‐ 9.14 p.p.b., respectively, and when cantering at 9 m s‐1 the values were 1.69 +/‐ 0.31 and 2.25 +/‐ 0.32 p.p.b., respectively. 3. Nebulized methoxamine (40 mg ml‐1 for 60 s), an alpha 1‐adrenergic agonist, further reduced [NO] during the 9 m s‐1 canter to 1.05 +/‐ 0.14 and 1.99 +/‐ 0.41 p.p.b. when collected at 80 and 20 l min‐1, respectively, and induced cyclical changes in the breathing pattern. 4. Exercise induced a linear increase in VNO with work intensity to a maximum (428.1 +/‐ 31.6 pmol min‐1 kg‐1) which coincided with the maximal oxygen uptake for the horses (138.3 +/‐ 11.7 ml min‐1 kg‐1), although a further increase in VNO (779.3 +/‐ 38.4 pmol min‐1 kg‐1) occurred immediately after exercise. The changes in VNO correlated well with the tidal volume (r = 0.968; P < 0.01) and the haematocrit (r = 0.855; P < 0.01). 5. In the first 2 min of high intensity exercise, inhaled NO (80 p.p.m.) significantly (P < 0.05) reduced the pulmonary artery pressure: during the first minute, pulmonary artery pressure was 83.1 +/‐ 7.6 mmHg compared with a control value of 94.4 +/‐ 6.3 mmHg, and during the second minute, 84.2 +/‐ 7.1 mmHg compared with a control value of 98.4 +/‐ 4.7 mmHg. There were no other significant changes in cardiovascular or respiratory indices, including cardiac output, measured during exercise between control and inhaled NO tests. 6. The results show that exhaled NO is released from the airways of the horse and may contribute to the regulation of pulmonary vascular tone during exercise.

Pharmacokinetics of the novel atypical opioid tapentadol following oral and intravenous administration in dogs

Tapentadol (TAP) is a novel opioid pain reliever drug with a dual mechanism of action (mu opioid receptor agonist and noradrenaline reuptake inhibitor). It is used as an analgesic in humans, but could be of interest for veterinary species if it has a suitable pharmacokinetic profile. Six dogs were randomly assigned to two treatment groups, using an open, single-dose, two-treatment, two-period, and randomised cross-over design. Each subject received TAP at 50 and 200mg by intravenous (IV) and oral route, respectively, with a 1-week wash-out period between administrations. Blood was collected at regular intervals and the plasma concentration of TAP in each sample was measured using a validated HPLC-FL method. After IV administration, concentrations of TAP were detectable in plasma for up to 6h with a half-life in the range 38-68 min. After oral administration, drug absorption was rapid (T(max), time required to reach the maximum concentration of 47.5 min), but its bioavailability was low (4.4%). Some dose-related adverse effects, including salivation and sedation, were observed, particularly following IV administration. In summary, this study showed that TAP may be useful as an analgesic in the dog, but further studies, including in dogs requiring analgesia, are required to confirm efficacy.

Distances travelled by feral horses in 'outback' Australia.

REASONS FOR PERFORMING STUDY The distance travelled by Australian feral horses in an unrestricted environment has not previously been determined. It is important to investigate horse movement in wilderness environments to establish baseline data against which the movement of domestically managed horses and wild equids can be compared. OBJECTIVES To determine the travel dynamics of 2 groups of feral horses in unrestricted but different wilderness environments. METHODS Twelve feral horses living in 2 wilderness environments (2000 vs. 20,000 km(2)) in outback Australia were tracked for 6.5 consecutive days using custom designed, collar mounted global positioning systems (GPS). Collars were attached after darting and immobilising the horses. The collars were recovered after a minimum of 6.5 days by re-darting the horses. Average daily distance travelled was calculated. Range use and watering patterns of horses were analysed by viewing GPS tracks overlaid on satellite photographs of the study area. RESULTS Average distance travelled was 15.9 ± 1.9 km/day (range 8.1-28.3 km/day). Horses were recorded up to 55 km from their watering points and some horses walked for 12 h to water from feeding grounds. Mean watering frequency was 2.67 days (range 1-4 days). Central Australian horses watered less frequently and showed a different range use compared to horses from central Queensland. Central Australian horses walked for long distances in direct lines to patchy food sources whereas central Queensland horses were able to graze close to water sources and moved in a more or less circular pattern around the central water source. CONCLUSIONS The distances travelled by feral horses were far greater than those previously observed for managed domestic horses and other species of equid. Feral horses are able to travel long distances and withstand long periods without water, allowing them to survive in semi-arid conditions.

Postmortem Diagnostic Investigation of Disease in Free-Ranging Marine Turtle Populations: A Review of Common Pathologic Findings and Protocols

Over the past few decades, there have been increasing numbers of reports of diseases in marine turtles. Furthermore, in recent years, there have been documented instances of apparently new diseases emerging in these species of which the etiology and/or pathogenesis remain unknown. These instances i) raise concern for the survival of marine turtles, and ii) question the health and stability of the benthic marine environments in which turtles live. Knowledge of common disease processes and pathologic changes in lesions, along with a standardized approach to postmortem and sample collection are required to document and understand the host-agent-environment interactions in marine turtle health. This review combines, for the first time, a standardized approach to the postmortem of marine turtles for veterinary clinicians, with a concurrent descriptive review of the gross and microscopic pathologic changes in lesions commonly seen.

Monitoring distances travelled by horses using GPS tracking collars

OBJECTIVE The aims of this work were to (1) develop a low-cost equine movement tracking collar based on readily available components, (2) conduct preliminary studies assessing the effects of both paddock size and internal fence design on the movements of domestic horses, with and without foals at foot, and (3) describe distances moved by mares and their foals. Additional monitoring of free-ranging feral horses was conducted to allow preliminary comparisons with the movement of confined domestic horses. PROCEDURES A lightweight global positioning system (GPS) data logger modified from a personal/vehicle tracker and mounted on a collar was used to monitor the movement of domestic horses in a range of paddock sizes and internal fence designs for 6.5-day periods. RESULTS In the paddocks used (0.8-16 ha), groups of domestic horses exhibited a logarithmic response in mean daily distance travelled as a function of increasing paddock size, tending asymptotically towards approximately 7.5 km/day. The distance moved by newborn foals was similar to their dams, with total distance travelled also dependent on paddock size. Without altering available paddock area, paddock design, with the exception of a spiral design, did not significantly affect mean daily distance travelled. Feral horses (17.9 km/day) travelled substantially greater mean daily distances than domestic horses (7.2 km/day in 16-ha paddock), even when allowing for larger paddock size. CONCLUSIONS Horses kept in stables or small yards and paddocks are quite sedentary in comparison with their feral relatives. For a given paddock area, most designs did not significantly affect mean daily distance travelled.

Oxidant injury, nitric oxide and pulmonary vascularfunction: Implications for the exercising horse

The athletic ability of the horse is facilitated by vital physiological adaptations to high-intensity exercise, including a thin (but strong) pulmonary blood-gas barrier, a large pulmonary functional reserve capacity and a consequent maximum oxygen uptake (VO2max) far higher than in other species. A high pulmonary artery pressure also serves to enhance pulmonary function, although stress failure of lung capillaries at high pulmonary transmural pressures, and the contribution of other factors which act in the exercising horse to increase pulmonary vascular tone, may lead to pathological or pathophysiological sequelae, such as exercise-induced pulmonary haemorrhage (EIPH). Reactive oxygen species (ROS) are an important component of the mammalian inflammatory response. They are released during tissue injury and form a necessary component of cellular defences against pathogens and disease processes. The effects of ROS are normally limited or neutralized by a multifactorial system of antioxidant defences, although excessive production and/or deficient antioxidant defences may expose healthy tissue to oxidant damage. In the lung, ROS can damage pulmonary structures both directly and by initiating the release of other inflammatory mediators, including proteases and eicosanoids. Vascular endothelial cells are particularly susceptible to ROS-induced oxidant injury in the lung, and both the destruction of the pulmonary blood-gas barrier and the action of vasoactive substances will increase pulmonary vascular resistance. Moreover, ROS can degrade endothelium-derived nitric oxide (NO), a major pulmonary vasodilator, thereby, with exercise, synergistically increasing the likelihood of stress failure of pulmonary capillaries, a contributing factor to EIPH. This review considers the implications for the exercising horse of oxidant injury, pulmonary vascular function and NO and the contribution of these factors to the pathogenesis of equine respiratory diseases.

Virtual Microscopy with Extended Depth of Field

In this paper, we describe a virtual microscope system, based on JPEG 2000, which utilizes extended depth of field (EDF) imaging. Through a series of observer trials we show that EDF imaging improves both the local image quality of individual fields of view (FOV) and the accuracy with which the FOVs can be mosaiced (stitched) together. In addition, we estimate the required bit rate to adequately render a set of histology and cytology specimens at a quality suitable for on-line learning and collaboration. We show that, using JPEG 2000, we can efficiently represent high-quality, high-resolution colour images of microscopic specimens with less than 1 bit per pixel.