Glycogen depletion patterns in horses competing in day 2 of a three day event

Muscle biopsy samples were collected from the left middle gluteal muscle of the horses participating in day 2 (speed and endurance test) of a three day event. Six Thoroughbred horses were biopsied the day before and within 30 minutes of completion of the speed and endurance test. Serial muscle sections were reacted histochemically for myosin adenosine triphosphatase activity after acid pre-incubation to demonstrate Type I, IIA and IIB fibers and the glycogen content in the individual fibers was assessed using the periodic acid Schiff (PAS) reaction. Total glycogen in muscle was measured fluorometrically after hydrolysis to glucose. A significant decrease (P less than 0.001) in total muscle glycogen of 306.0 +/- 34.6 mmoles glucose units/kg (dry weight) (mean +/- SE) occurred when samples collected before exercise were compared to those collected following exercise. A significant decrease (P less than 0.05) in the percentage of Type I fibers having medium PAS staining intensity occurred when pre and post-exercise samples were compared. Significant decreases (P less than 0.01 and P less than 0.001 respectively) in the percentage of Type IIA and IIB fibers classified as having high PAS staining intensity occurred when post-exercise samples were compared with those pre-exercise. There were significant increases (P less than 0.01 and P less than 0.001 respectively) in the percentage of Type IIA and IIB fibers classified as having medium PAS staining intensity when the samples collected after the exercise were compared with those before the exercise.     

High frequency jet ventilation in horses: an experimental study

High frequency jet ventilation (HFJV) is a recently developed mode of ventilation that delivers small tidal volumes at frequencies greater than 60 cycles per min via an injection catheter to the animal's airway. The construction of a high frequency jet ventilator suitable for use in adult horses is described. The effectiveness of this ventilator in maintaining normal arterial blood-gas tension was evaluated in five healthy adult horses. The horses were anaesthetised with intravenous acetylpromazine, guaifenesin, and thiamylal, positioned in lateral recumbency and baseline measurements were made during spontaneous ventilation. The horses were then paralysed with succinylcholine and ventilated for at least 20 mins with HFJV. Air was delivered from the ventilator to the animal by a polyethylene tube. The tip of this tube remained within and approximately 30 cm from the cuffed end of a standard 30 mm internal diameter large animal orotracheal tube. Frequency of flow interruption was 3 Hz with a constant source pressure of 275 kPa and an inspiratory to expiratory ratio of approximately 1:2.6. Gas delivery to the horse, as estimated with a resonator system was approximately 2 litres/breath. During HFJV, arterial carbon dioxide tension was significantly reduced and arterial oxygen tension significantly increased above measurements made when the horses were spontaneously breathing air.     

Cardiopulmonary effects of halothane anesthesia in cats

The cardiopulmonary effects of 2 planes of halothane anesthesia (halothane end-tidal concentrations of 1.78% [light anesthesia] and 2.75% [deep anesthesia]) and 2 ventilatory modes (spontaneous ventilation [SV] or mechanically controlled ventilation [CV]) were studied in 8 cats. Anesthesia was induced and maintained with halothane in O2 only, and each cat was administered each treatment according to a Latin square design. Cardiac output, arterial blood pressure, pulmonary arterial pressure, heart rate, respiratory frequency, and PaO2, PaCO2, and pH were measured during each treatment. Stroke volume, cardiac index, and total peripheral resistance were calculated. A probability value of less than 5% was accepted as significant. In the cats, cardiac output, cardiac index, and stroke volume were reduced by deep anesthesia and CV, although only the reduction attributable to CV was significant. Systemic arterial pressure was significantly reduced by use of deep anesthesia and CV. Respiratory frequency was significantly lower during CV than during SV. Arterial PO2 was significantly decreased at the deeper plan of anesthesia, compared with the lighter plane. At the deeper plane of anesthesia, arterial PCO2 and pulmonary arterial pressure were significantly lower during CV than during SV. The deeper plane of halothane anesthesia depressed cardiopulmonary function in these cats, resulting in hypotension and considerable hypercapnia. Compared with SV, CV significantly reduced circulatory variables and should be used with care in cats. Arterial blood pressure was judged to be more useful for assessing anesthetic depth than was heart rate or respiratory frequency.     

Acute nephropathy in young lambs

Acute renal failure was diagnosed by clinical, necropsy and histological criteria in 39 flocks (20 low ground, 13 hill and six marginal upland) in areas served by six veterinary investigation centres. Forty-eight lambs of 12 different breeds or crosses were investigated. The mean age of affected lambs was 38 days (range seven to 84 days); 21 lambs (44 per cent) were aged seven to 28 days, while only eight (17 per cent) were older than two months. Mortality in clinically affected lambs was almost 100 per cent, with no response to various treatments. Histological examination showed that 40 lambs (83 per cent) had nephrosis, while the rest had toxic tubular necrosis, interstitial nephritis or tubular damage associated with oxalate crystal deposits. Only about half of the lambs had any evidence of enteric infections or enteropathy. Acutely ill lambs had azotaemia, haemoconcentration and proteinuria; some lambs had glycosuria or haematuria. Samples of plasma from 22 lambs with nephrosis were compared with similar samples from 82 incontact but asymptomatic lambs. The clinically affected group had significantly elevated plasma urea, creatinine, total protein, globulin, phosphorus and chloride concentrations and significantly reduced plasma calcium concentrations compared with healthy lambs. Affected lambs had a significant reduction also in the calcium:phosphorus ratio. No significant differences between groups was found in plasma concentrations of albumin, glucose, lactate, glycerol, creatine kinase, alkaline phosphatase, sodium, potassium or magnesium.     

Biochemical and haematological evidence of endotoxic shock in gnotobiotic lambs with watery mouth disease

Eight gnotobiotic lambs deprived of colostrum were infected by mouth when two hours old with nonenterotoxigenic strains of Escherichia coli. All developed clinical signs of watery mouth disease and seven died within 24 hours. The mean concentrations of several blood constituents were determined in samples taken at intervals until 24 hours after infection in infected lambs and in four control lambs. The biochemical and haematological changes observed in the lambs developing watery mouth disease were those characteristic of endotoxic shock.     

Disentangling the identities and distribution patterns of the introduced beachfleas Orchestia gammarellus and Platorchestia platensis (Crustacea: Amphipoda: Talitridae) in South Africa

Two introduced beachfleas, Orchestia gammarellus and Platorchestia platensis, have been recorded from South Africa, but have been misidentified by some earlier researchers and, prior to this study, each was also known from just a few, scattered observations, such that their true distributions remained obscure. We illustrate both species to clarify the features that identify and distinguish them and determine their true distributions by re-examining historical samples and by collecting new material from estuaries and lagoons along the west and south coasts of South Africa. Adult males of O. gammarellus have slender antennae and characteristic expanded, flattened, oar-like distal segments on pereopod 7. Adult males of P. platensis have the peduncle of antenna 2 strongly swollen and have bulbous, but not flattened, distal segments on pereopod 7. Both species occur under wrack and other debris along the banks of estuaries and sheltered lagoons. Orchestia gammarellus is found only along the south-west coast, in the Berg River Estuary, Langebaan Lagoon and the Diep River Estuary. Previous records from Knysna were misidentifications of P. platensis. Platorchestia platensis is found at one west coast site, Langebaan Lagoon, but is widely distributed from Cape Point eastwards to at least Algoa Bay. Both species share the same habitats as several other native beachfleas and competitive interactions between native and introduced species merit investigation.     

Evidence of Australian bat lyssavirus infection in diverse Australian bat taxa

Historically, Australia was considered free of rabies and rabieslike viruses. Thus, the identification of Australian bat lyssavirus (ABLV) in 1996 in a debilitated bat found by a member of the public precipitated both public health consternation and a revision of lyssavirus taxonomy. Subsequent observational studies sought to elaborate the occurrence and frequency of ABLV infection in Australian bats. This paper describes the taxonomic diversity of bat species showing evidence of ABLV infection to better inform public health considerations. Blood and/or brain samples were collected from two cohorts of bats (wild‐caught and diagnostic submissions) from four Australian states or territories between April 1996 and October 2002. Fresh brain impression smears were tested for ABLV antigen using fluorescein‐labelled anti‐rabies monoclonal globulin (CENTOCOR) in a direct fluorescent antibody test; sera were tested for the presence of neutralising antibodies using a rapid fluorescent focus inhibition test. A total of 3,217 samples from 2,633 bats were collected and screened: brain samples from 1,461 wild‐caught bats and 1,086 submitted bats from at least 16 genera and seven families, and blood samples from 656 wild‐caught bats and 14 submitted bats from 14 genera and seven families. Evidence of ABLV infection was found in five of the six families of bats occurring in Australia, and in three of the four Australian states/territories surveyed, supporting the historic presence of the virus in Australia. While the infection prevalence in the wild‐caught cohort is evidently low, the significantly higher infection prevalence in rescued bats in urban settings represents a clear and present public health significance because of the higher risk of human exposure.     

Comparative spermatology of two morphologically similar species of Solen (Mollusca: Bivalvia)

The fine structure of the spermatozoa and spermatogenesis in Solen cylindraceus and S. capensis were studied by electron microscopy. The morphology of the sperm of both species is similar. Both are of the primitive type with a head about 1,5 μm long), mid-piece of five mitochondria, and tail. The head comprises a barrel-shaped electron-opaque nucleus (about 1,1 μm × 1,2 μm) which is capped by a small conical acrosome. The morphology of the acrosome of Solen is typical of heterodont bivalves, however, each species has an acrosome of differing dimensions which can thus be used to separate these two closely related bivalves. During spermatogenesis the pattern of nuclear chromatin condensation is granular. The acrosome is formed by a single Golgi body, and the five large mitochondria of the mid-piece are probably formed by fusion of several small mitochondria.