East coast fever: Cultivationin vitro of bovine spleen cell lines infected and transformed byTheileria parva

Summary Three spleen cell lines derived from 3 calves experimentally infected withTheileria parva have been established. After an apparent disappearance of parasitized cells from the cultures there was a resurgence of infected lymphoblasts in 5 to 6 weeks. The infected lymphoblasts can be readily subcultured without feeder layers in a medium consisting of Eagle’s Minimal Essential Medium and 20 per cent foetal calf serum. The plating of infected cells was greatly enhanced by implanting the cells on preformed monolayers. No evidence was obtained by the methods employed which might indicate the existence of an extracellular form of the parasite capable of reinfecting new cellsin vitro.

---

Sumario Se han establecido 3 lineas celulares de bazo derivadas de tres terneros experimentalmente infectados conTheileria parva. Despuéś de una aparente desaparición de las células parasitadas de los cultivos, hubo una resurgencia de linfoblastos infectados en 5–6 semanas. Los linfoblastos infectados pueden ser subcultivados facilmente sin capas alimentadoras en un medio consistente de Eagles, medio mínimo esencial enriquecido con 20 por ciento de suero bovino fetal. El plaqueo de las células infectadas fue grandemente estimulado mediante la implantación de das células en monocapas previamente formadas. Con los métodos utilizados no se obtuvo evidencia para indicar la existencia de una forma extra celular de el parásito capaz de reinfectar neuvas célulasen vitro.

---

Résumé Trois lignées de cellules de rate issues de trois veaux expérimentalement infectés parTheileria parva ont été établies. Après une apparente disparition des cellules parasitées dans les cultures, il y avait une résurgence de lymphoblastes infectés au bout de 5 à 6 semaines. Ceux-ci pouvaient être mis en subculture aisément sans couche de soutien dans un milieu constitué du M.E.M. de Eagle, enrichi par 20 p. 100 de sérum de foetus de veau. L’étalement des cellules infectées était grandement facilité par leur implantation sur des couches préformées. Par les méthodes employées, on obtient aucune preuve de l’existence d’une forme extracellulaire du parasite, capable de réinfecterin vitro des cellules neuves.

     

THE EFFECT OF ANTHELMINTIC TREATMENT OF MAIDEN EWES IN THE PERIPARTURIENT PERIOD ON PASTURE CONTAMINATION AND PRODUCTION OF PRIME LAMBS

SUMMARY A replicated experiment using first cross Border Leicester/Merino maiden ewes set stocked at the rate of 9.9 per hectare was conducted to examine the effects of treatment of the ewes in the periparturient period (PPP) and treatment of lambs at about 12 weeks of age on the production of prime lambs. All treatments given were thiabendazole. Four groups each of 100 ewes (4 replicates × 25) were treated either pre-lambing, 2 weeks before lambing commenced and again post-lambing, 8 weeks later when lambing was almost complete (DD), pre-lambing only (DO), post-lambing only (OD) or not treated during the lambing period (OO). Lambing commenced 24 July 1972 with the bulk of lambing (98%) occuring within the first 4 weeks of a 6 weeks lambing period. The effectiveness of the drenching regimes was judged by observing bodyweight gains per day during four overlapping intervals between birth and 18 weeks of age. The bodyweight gain of lambs up to 18 weeks and the number of lambs exceeding a target weight of 33 kg at 18 weeks of age were considered to be critical measurements of production efficiency. Significant bodyweight differences were observed within 30 days from birth, favouring DD and DO over OD and OO lambs (p < 0.01). These differences continued until 12 weeks of age at a reduced level of significance (p < 0.05). By 18 weeks of age the results favoured DD over DO (p <0.05) over both OD and OO lambs (p < 0.05). Further differences were created by the treatment of lambs at 12 weeks of age (p < 0.01). At no time during the entire experiment were any significant differences observed between OD and OO lambs. The periparturient rise (PPR) in faecal nematode egg output was monitored throughout the experiment. Anthelmintic treatment of the ewes in the PPP did not eliminate the PPR but did affect the onset, magnitude and duration of the PPR which was either delayed by the prelambing treatment or truncated by the post-lambing treatment; treatments both before and after lambing delayed and depressed the PPR and reduced total pasture contamination by 29%. An effect on bodyweight of ewes was also observed with ewes being treated pre-lambing (Groups DD, DO) being significantly heavier at 18 weeks post-lambing than OD and OO ewes (p < 0.05). The observed effects on lamb production have been attributed in the main to an apparent, though not specifically measured, effect on lactation in those ewes being treated pre-lambing. The effect of delayed (Groups DD, DO) and/or reduced (Group DD) pasture contamination was considered to be additive to the earlier lactation response. Treatment of lambs at 12 weeks did not obscure these responses.     

Use of pulsed-wave Doppler echocardiography to determine aortic and pulmonary velocity and flow variables in clinically normal dogs

Transcutaneous pulsed-wave Doppler echocardiography was used to obtain velocity signals from the aortic and pulmonary roots of clinically normal adult dogs tranquilized with acepromazine. Doppler-derived variables included peak ejection velocity, ejection time, and velocity-time integral. The cross-sectional areas of the left and right ventricular outflow tracts were estimated from diameters of the respective orifices measured from two-dimensional echocardiographic images. These data were used to calculate stroke volume and cardiac output for each ventricle. Linear, single variable regressions of ejection time, velocity-time integral, and peak velocity with body weight showed no significant correlations. Significant correlations existed between body weight and estimated left and right ventricular stroke volume and cardiac output. A close correspondence existed between pulmonary and aortic determinations of velocity-time integral, stroke volume, and cardiac output. These results provide an initial framework for interpretation of clinical data by veterinary cardiologists.     

Some observations on microbial populations and nitrogen in soils infested with the take-all fungus

Some possible causes of “take-all decline”, the decrease in the severity of attack by Gaeumannomyces graminis on cereals after several years' consecutive culture, are discussed. The possible relationships between the NO₃^?–N:NH₄⁺–N ratio in the rhizosphere, populations of rhizosphere bacteria and the incidence of take-all are considered.     

Pyrethrum dermatitis I. The allergenic properties of various extracts of pyrethrum flowers

Extracts of pyrethrum flowers were obtained by treatment with various aqueous and organic solvents. These were tested for immediate and delayed hypersensitivity reactions in guinea pigs previously sensitised to pyrethrum by single subcutaneous injection of the ground flowers suspended in Freund's complete adjuvant. Strong reactions were elicited by various aqueous extracts of the flowers; the allergens are of high molecular weight, being non-dialysable. A hexane extract (similar to pyrethrum oleoresin) produced a moderate reaction, but a commercially refined pyrethrum extract proved negative. An extract of the spent flowers with methylene chloride showed irritant effects in unsensitised guinea pigs.