Growth of Chlamydia in pig lung alveolar macrophages; Preparation of macrophages and demonstration of growth

The harvesting, storing and utilisation in tissue culture of lung alveolar macrophages from 2–3 weeks old piglets were investigated. An average yield of 4×10⁸ cells was obtained, which in culture usually remained healthy for at least 8 days. In liquid nitrogen at –173°C about 50% of the cells were still viable after 3 months. Pig cells sustained the growth of ovineChlamydia psittaci and a rising titre was demonstrated over 4 passages.     

Atypical myoglobinuria: an acute myopathy in grazing horses

Four out of 12 horses grazing a field in Berkshire, England, suffered a prostrating illness and died within 12 to 72 h. Serum biochemical abnormalities, including markedly elevated muscle enzymes, were demonstrated and at post mortem widespread myodegeneration was found in both skeletal muscle and myocardium. Urine analysis revealed myoglobinuria, and renal changes were seen histologically. Although similar pathologically, the clinical syndrome and circumstances of the outbreak were not typical of equine exertional rhabdomyolysis (EER). The outbreak bore a striking resemblance to other reported sporadic outbreaks of an atypical myoglobinuria occurring in grazing horses. A number of potential aetiological and contributory factors (including herbicide toxicity) were considered, but the aetiology remains unresolved.     

Interaction between coccidia and Nematodirus battus in lambs on pasture

Five thousand oocysts of each of two species of coccidia, Eimeria crandallis and E ovinoidalis or 30,000 infective larvae of Nematodirus battus, given as single infections to three- to five-week-old lambs, caused only transient diarrhoea and had no effect on growth. Lambs infected first with coccidia and two weeks later with N battus suffered severe diarrhoea, weight loss and some deaths. Simultaneous administration of the coccidia and the nematodes increased the clinical severity of the syndrome and increased the numbers of nematode eggs produced.     

FACTORS PREDISPOSING TO PARTURIENT PARESIS

SUMMARY: In a study of 64 dairy herds in south-western Victoria it was found that pasture and animal management practices were associated with the incidence of parturient paresis. The incidence was higher when pastures were treated with higher rates of superphosphate and potash and when longer pasture was available to cows during the preparturient period. When pasture available was in limited supply, the incidence was inversely related to the amount of hay fed to cows. The incidence was also influenced by age, breed and body condition of cows.     

Effects of Pasteurella haemolytica culture supernate on bovine tracheal smooth muscle.

Pasteurella haemolytica leukotoxin is a ruminant specific leukotoxin that has been implicated in the pathogenesis of shipping fever in cattle. The present study was undertaken to determine the effect of this toxin on bovine airway smooth muscle. In vitro, the addition of culture supernate containing leukotoxin to bovine tracheal smooth muscle resulted in contraction of 55% of the muscle strips tested. Maximum responses were reached rapidly during cumulative additions of this material. In 95% of the muscle strips that responded, maximum responses were obtained after the addition of one or two cumulative doses. Repeated additions of culture supernate resulted in decreased responsiveness. Since responsiveness to other agonists was not affected, these results suggest the development of a condition similar to tachyphylaxis. The contractions were inhibited by antihistamines. Diphenhydramine, at a concentration of 10(-6) M (dose-ratio 7), and mepyramine, at a concentration of 2 x 10(-7) M (dose-ratio 56), blocked the contractions by 84% and 100% respectively. In addition, the contractions were blocked by the muscarinic antagonist atropine, but this inhibition was much weaker (46%) and was present at high concentrations only. Inhibition of the contractions by H1 receptor antagonists suggests that the contractions are mediated via H1 receptors. Since the dose-response relationship is not typical of a drug-receptor interaction, it appears unlikely that the leukotoxin is a direct agonist of H1 receptors. It is proposed that an indirect mechanism of action involving the release of histamine by tissue mast cells is responsible for the leukotoxin-induced contractions.     

The Effects of Cesarean Section Anesthesia on Heat Loss and Heat Production in the Newborn Rabbit

The newborn of some smaller animals rely upon heat produced by nonshivering thermogenesis in the brown fat to prevent a fall in body temperature after birth. Because of their pharmacological properties, some drugs may affect nonshivering thermogenesis. Therefore, in this study, the ability of newborn rabbits delivered under Innovar-Vet, ketamine hydrochloride, methoxyflurane and epidural anesthesia to maintain the rectal, subcutaneous interscapular and lumbar temperature was investigated at an ambient temperature of 35°C or 22°C and the results compared with control newborns delivered without anesthesia. When the newborns were exposed to 35°C, the anesthetics studied had no effect on the ability of the newborn to maintain the rectal temperature and the subcutaneous temperature over the interscapular fat pad was similar to the lumbar subcutaneous temperature thereby indicating that nonshivering thermogenesis was not activated. However, at an ambient temperature of 22°C Innovar-Vet or methoxyflurane reduced the temperature difference between interscapular and lumbar temperatures to 1.6°C compared to 2.5°C in controls and the difference between core temperature and ambient temperature to 3.5°C greater compared to 7.5°C in controls. Ketamine hydrochloride or lidocaine hydrochloride plus meperidine has less effect because these compounds lack adrenergic blocking properties. These data suggest that newborns delivered under anesthetics or tranquillizers that have adrenergic blocking properties require a warm (35°C) environment to prevent a fall in core temperature.     

The effects of high intensity exercise on the plasma concentration of lactate, potassium and other electrolytes

To study the effect of short term high intensity exercise on plasma lactate, potassium, sodium and chloride concentrations, five Thoroughbred horses were galloped on a treadmill at a 5 degree incline. Following a standardised warm-up period, they were galloped at 8, 10, or 12 metres/sec for 2 mins. One horse also galloped at 14 metres/sec for 1.5 mins. Sequential arterial and/or venous blood samples were collected during exercise and recovery. At 12 metres/sec, the effect of different recovery modes, ie, standing, walking or trotting, on the electrolytes was also examined. There was a progressive rise in plasma potassium concentration during galloping, with peak values occurring at the end of the exercise bout. In some cases, values above 10 mmol/litre were recorded at the highest workloads. Plasma lactate concentrations peaked during early recovery, with values up to 32 mmol/litre. A high correlation existed between peak potassium and lactate concentrations (venous r = 0.923, and arterial r = 0.989). Following exercise there was a rapid return to baseline plasma potassium concentrations, but by 12 mins recovery there was still an elevated lactate concentration, the extent depending on the intensity of the exercise bout and the recovery mode. There was a small rise in plasma sodium but no significant change in plasma chloride concentrations during exercise. However, when adjusted for the decrease in plasma volume, as determined from total plasma protein concentration, there was a decrease in circulating amounts of both electrolytes.