Benign cranial mediastinal lesions in three cats

Cranial mediastinal lesions were detected in three cats, associated with respiratory impairment (case one), spontaneous pneumothorax (case two) and myasthenia gravis (case three), respectively. On gross and histological examination, the first case was considered either a lymphangioma or a branchial cystic mass of the thymic region of the mediastinum; a cystic lesion was suggested by sonographic detection of multiple anechoic cavitations within a circumscribed mass, while fine needle aspiration cytology excluded lymphosarcoma. The second case was diagnosed histologically as a cystic thymoma, but the third case was not examined microscopically. The masses were amenable to surgical excision in the first two cats, while this proved unnecessary in the third case because of resolution following treatment with dexamethasone. Corticosteroid responsiveness was unhelpful in distinguishing between these benign lesions and lymphosarcoma, as in two cases there was a partial or complete response to dosing with prednisolone or dexamethasone. These cases are presented to emphasise that conditions other than lymphosarcoma can produce cranial mediastinal lesions in cats, and that the prognosis for surgical treatment of lymphangiomas, multilocular thymic cysts and cystic thymomas can be excellent.     

Myotonia associated with hyper-adrenocorticism in two dogs

Two dogs developed a disabling gait abnormality characterised by stiffness. The abnormality was consistent with a diagnosis of myotonia secondary to hyper-adrenocorticism. The first dog had iatrogenic hyperadrenocorticism, and its signs improved substantially after corticosteroid administration was gradually withdrawn. The second had pituitary-dependent hyperadrenocorticism, but myotonic signs progressed despite effective mitotane therapy. Procainamide administration reduced the myotonic stiffness in the second case.     

Congenital biliary atresia and jaundice in lambs and calves

An outbreak of congenital biliary atresia and jaundice is described, in which approximately 300 crossbred lambs and 9 crossbred calves died. The affected animals failed to thrive, developed jaundice and white scours and died within 4 weeks of birth. A common feature of this outbreak and a similar occurrence 24 years previously was the grazing of plants growing on the exposed silt foreshores of Burrinjuck Dam by ewes and cows in the early stages of pregnancy. Epidemiological and pathological findings suggested that a toxic insult to the foetus in early gestation caused choledysgenesis and biliary atresia, leading to diffuse, subacute to chronic cholangiohepatopathy and cirrhosis.     

Relationships between elm spanworm, Ennomos subsignaria, juvenile density and defoliation on mature sycamore maple in an urban environment

Using field surveys, we established sampling procedures for estimating defoliation resulting from elm spanworm, Ennomos subsignaria (Hübner) (Lepidoptera: Geometridae), feeding on mature sycamore maple, Acer pseudoplatanus L. (Aceraceae), in St. John's, Newfoundland and Labrador. We also determined whether densities of E. subsignaria eggs, egg masses, early- or late-instar larvae could predict the amount of defoliation at the end of the larval feeding period. Defoliation estimates acquired by sampling branches from only the lower, mid or upper crown explained ≥80% of the variation in tree-level defoliation, suggesting that density–defoliation relationships established using defoliation data from any crown level would also be useful for predicting tree-level defoliation. In linear regressions, egg and egg mass densities explained ≤20% of variation in defoliation and thus only provide a crude relative estimate of the amount of defoliation that will occur. Early- and late-instar larval density in the lower crown explained 53 and 29%, respectively, of the variation in defoliation in the lower crown, where defoliation levels were highest. Thus monitoring early-instar density in the lower crown should provide pest managers with reliable information for decisions regarding whether to apply suppression tactics while allowing enough time to implement these tactics, if necessary.     

Evidence for extreme climatic warmth from late cretaceous arctic vertebrates

A Late Cretaceous (92 to 86 million years ago) vertebrate assemblage from the high Canadian Arctic (Axel Heiberg Island) implies that polar climates were warm (mean annual temperature exceeding 14 degreesC) rather than near freezing. The assemblage includes large (2.4 meters long) champsosaurs, which are extinct crocodilelike reptiles. Magmatism at six large igneous provinces at this time suggests that volcanic carbon dioxide emissions helped cause the global warmth.     

Primary hypoparathyroidism in two horses

Two Thoroughbred horses were presented with various clinical signs which included sweating, agitation, muscle twitching and synchronous diaphragmatic flutter. These signs were associated with profound hypocalcaemia. A diagnosis of primary hypoparathyroidism was made on the basis of low serum ionised calcium concentration, hyperphosphataemia and markedly reduced serum immunoreactive parathyroid hormone concentrations in the presence of normal renal function. Treatment with a combination of intravenous calcium and subsequently oral calcium, magnesium and a vitamin D analogue (dihydrotachysterol) for up to 65 days resulted in complete remission of clinical signs. Horse 1 was euthanased 12 months after the initial recognition of signs. Results of necropsy were unremarkable apart from an absence of detectable parathyroid tissue. Horse 2 returned to athletic activities while receiving only maintenance doses of oral calcium carbonate.     

Effect of acute haemorrhage on QRS amplitude of the lead II canine electrocardiogram

OBJECTIVE: To examine the effect of acute haemorrhage on the QRS amplitude of the canine lead II surface electrocardiograph (ECG). DESIGN: Ten adult racing Greyhounds were tranquilised, anaesthetised, positioned in right lateral recumbency and connected to recording electrodes of an ECG unit. Baseline six-lead ECG traces were recorded, and further traces were obtained after one unit (460 mL) of blood, and then a second unit, were collected from the femoral artery. RESULTS: There was a consistent and progressive reduction in amplitude of the QRS complex in all leads during acute haemorrhage. QRS amplitude in lead II after removal of two units of blood averaged 74% of the baseline voltage, with individual values of 61 to 91% (P < 0.0001). There were even greater reductions in QRS amplitudes in lead aVL during haemorrhage. In three additional dogs, reductions in QRS voltages were shown to be accompanied by reductions in end-diastolic left ventricular internal dimensions measured echocardiographically. Furthermore, the effects of haemorrhage on the QRS amplitude and echocardiographic measurements were reversed when circulating blood volume was restored by re-infusion of blood removed previously. CONCLUSION: Acute haemorrhage corresponding to an approximately one-third reduction in blood volume caused a substantial reduction in QRS voltage of the surface ECG. It is postulated that this resulted from diminished ventricular distension as a consequence of reduced venous return. A similar mechanism may account for the small-amplitude ECG complexes associated with pericardial effusion, severe dehydration and hypovolaemia.     

Silicon oxynitride stability

Silicon oxynitride occurs as a mineral (sinoite) in meteorites. Equilibrium measurements are reported which provide information on the approximate ratios of pressures of oxygen to nitrogen required for existence of this phase under equilibrium conditions at elevated temperatures. This ratio is approximately 10-(15) at 1400 degrees to 1500 degrees C.