Host parasite relationships in Trypanosoma (duttonella) vivax with special reference to the influence of antigenic variation

A mouse model system was used to study various aspects of host and parasite relationships in Trypanosoma vivax infections. These included the phenomenon of antigenic variation, the variable parasite antigens responsible for this phenomenon, parasite-host adaption, host immune responses and the role of genes in the major histocompatibility complex in the control of infection. While the mouse model system has allowed investigation of these aspects of host parasite relationships, it is clear that the system is much more limited than those generally used in T. brucei spp and T. congolense infections. This is indicated by the discovery that not all VATs of T. vivax were equally infective for mice, though in some cases infectivity could be improved by bovine serum supplementation and/or immunosuppression of the mouse host. In the case of rats, infection was even restricted to a smaller number of the VATs studied. It was, however, possible to biochemically characterize the variable surface antigen carried by T. vivax and show its similarity to those carried by T. brucei and T. congolense. The H-2 complex was found not to influence acquired resistance of inbred strains. Cyclic transmissions of T. vivax infections to goats combined with chemotherapy were carried out in an attempt to induce protection to subsequent infection as has been shown in T. brucei and T. congolense infections. Such protection could, however, not be obtained, The failure of the metacyclic VATs to induce immunity, was perhaps due to rapid decrease in antibody titres to bloodstream VATs found after treatment and prior to rechallenge. The usefulness of the mouse model system in elucidating the mechanisms responsible for the non-H-2 linked differences in susceptibility to T. vivax infections should be further explored and its relevance to mechanisms of trypanotolerance in domestic ruminants defined.     

Molecular aspects of the potato — Phytophthora infestans interaction

The fungal pathogenPhytophthora infestans is the causal organism of late blight, one of the most devastating diseases of potato. In the past, various aspects of the potato-P. infestans interaction have been studied extensively. In this paper we briefly review the current knowledge of the molecular events associated with the interaction and in addition we discuss a new approach for analyzing the molecular basis of pathogenicity ofP. infestans.     

The subacute and subchronic toxicity of chlorophacinone in Japanese quail (Coturnix c. japonica)

Accordingly to the subacute toxicity of chlorphacinone to Japanese quail (LC 50: 60 mg/kg feed), the uptake of Delicia-chlorphacinone-baits for several days can be lethal to birds as a matter of principle. A subchronic study resulted in a "no-observed-effect-level" of 1 mg chlorphacinon/kg feed. Reproduction is not affected until dose levels which resulted in lethality or are accompanied by physiological changes (coagulability of blood, microcytic anaemia). Increased sensibility of descendants to chlorphacinone cannot be derived from the findings.     

Reproductive performance of nili-ravi buffaloes after a single injection of GnRH earlypost partum

Summary Sixty dairy buffaloes (second to fourth lactation) from a large buffalo farm were used to compare the effects of single intramuscular injections of 100 µg gondadotrophin releasing hormone (GnRH), 250 µg GnRH or saline given on day 14post partum. The buffaloes had calved at the end of the breeding season (December). Milk samples for progesterone determination were taken at the time of injection and then three times a week either until first insemination or until around day 90post partum. GnRH given at 14 dayspost partum resulted in quicker completion of uterine involution, earlier resumption of ovarian activity, shorter intervals between calving and conception and a better first service conception rate in non-suckled dairy buffaloes. Differences between the results obtained by a GnRH dose level of 100 µg and 250 µg were non-significant. In the post-treatment period cases of prolonged luteal activity were common in all groups of buffaloes. Therefore the sequential administration of GnRH and prostaglandin is suggested for the management of post-partum reproductive activity in problem herds.

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Desempeno Reproductivo De Bufalos Nili-Ravi Despues De Una Sola Inyeccion De GnRH Temprano Despues Del Post-Parto

Resumen Sesenta búfalos lecheros (segunda a cuarta lactancia) pertenecientes a un hato grande fueron utilizados para comparar los efectos de inyecciones intramusculares de 100 µg de GnRH, 250 µg y de solución salina, aplicadas 14 días después del parto. Los búfalos habian parido al final de la estación de pariciones (diciembre). Se tomaron muestras de leche para medir progesterona, en el momento de la inyección y después tres veces por semana hasta la primera inseminación, o hasta cerca de los 90 días post-parto. La GnRH administrada 14 días post-parto, dio como resultado una rápida involución uterina, más rápido retorno a la actividad ovárica, más cortos intervalos entre partos y concepción, y un mejor índice servicio-concepción en búfalos lecheros que no estaban amamantando. Los resultados de dosis de 100 µg y 250 µg no fueron significativos. En el período post-tratamiento, los casos de actividad luteal prolongada fueron comunes en todos los grupos de búfalos. Se sugiere entonces, la administración secuencial de GnRH y prostaglandina, parar el manejo de la actividad reproductiva post-parto en hatos problema.

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Performances De Reproduction Du Buffle Nili-Ravi Apres Une Injection Unique PrecocePost Partum De Gonadotrophine (GnRH)

Résumé Soixante bufflesses laitières (de la seconde à la quatrième lactation), appartenant à une grande ferme d'élevage de buffles, ont été utilisées pour comparer les effets d'une injection unique intramusculaire de 100 µg de gonadotrophine, ou de 250 µg du même produit ou d'une solution de sérum physiologique. Les bufflesses avaient mis bas à la fin de la saison de reproduction soit en décembre. Des prélèvements de lait ont été effectués pour déterminer le taux de progestérone au moment de l'injection d'une part, puis trois fois par semaine d'autre part jusqu'à la première insémination ou aux alentours d'une période de 90 jours après le part. La gonadotrophine, libérée sous forme d'hormone (GnRH), injectée 14 jours après la mise bas a eu pour effet un retour complet plus rapide de l'involution utérine et des intervalles plus courts entre la mise bas et la conception ainsi qu'un meilleur taux de conception à la première monte chez les femelles laitières non allaitantes. Les différences entre les résultats obtenus par une dose de 100/µg ou de 250/µg de gonadotrophine (GnRH) n'étaient pas significatives. Pendant la période post-thérapeutique, des cas d'activité lutéale prolongée ont été courants dans tous les groupes de bufflesses. En conséquence, l'administration séquentielle de GnRH et de prostaglandine est conseillée pour contrôler l'activité post-partum de reproduction dans les troupeaux qui présentent des problèmes de cet ordre.

     

The effect of Prussian blue and sodium-ethylenediaminetetraacetic acid on the faecal and urinary elimination of thallium by the dog.

After oral administration of sublethal doses of thallium (lower than 10 mg/kg) to dogs, 75.5 +/- 3.9 per cent of the dose was eliminated from the body--47 per cent faecal and 28 per cent urinary. Cumulative excretion reached 50 and 70 per cent after 10 and 25 days respectively, and was almost complete after 75 days. This was slightly lower at higher doses. The total body-burden of thallium, calculated from the cumulative excretion, decreased exponentially for at least the first 40 days with a half-time (T 1/2) of 6.5 days. Oral doses of Prussian blue after 10 days resulted in an acceleration of the thallium elimination from the body (T 1/2 2.5 days), an increase of the faecal (49 per cent) and a decrease of the urinary excretion (18 per cent). Nevertheless, the cumulative faecal and urinary thallium excretion was not influenced. Minor transitory influences of Prussian blue on the faecal thallium excretion could be observed up to day 26. After 40 days, Prussian blue could no longer influence the faecal thallium excretion. At no time did sodium-ethylenediaminetetraacetic (Na2EDTA) acid significantly change faecal or urinary thallium excretion.     

Inhibition of chitin synthesis by two 1-(2,6-disubstituted benzoyl)-3-phenylurea insecticides. II

The knowledge of the biochemical mode of action of 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea (diflubenzuron) is presented, explaining the insecticidal effect. Like its structural analog, 1-(2,6-dichlorobenzyl)-3-(3,4-dichlorophenyl)urea (Du 19111), it inhibits chitin synthesis in the cuticle of larvae. Virtually complete inhibition was demonstrable 15 min after the application of diflubenzuron. Neither diflubenzuron nor Du 19111 has any effect upon chitinase activity either in vivo or in vitro. The insecticidal effect upon the cuticle, therefore, must be explained as an inhibition of chitin synthesis and not as an activation of chitin degradation. In contrast to the action of Du 19111, no accumulation of N-acetylglucosamine occurs upon treatment of larvae with diflubenzuron. Similarities and differences in the mode of action of both compounds are discussed, together with other effects reported in the literature.     

Excessive oral administration of iron to sheep. 1. Digestibility of rations, results of fattening and carcass yields]

4 digestibility trials (4 male sheep per group) and 2 growth trials were carried out with 24 (V 1) and 32 (V 2) fattening lambs to investigate the effect of abundant oral Fe doses on the digestibility of crude nutrients in a ration of barley + dried green feed and on the results of fattening and carcass yields. Fe supplementation (less than 1400 mg per sheep/day) did not significantly change the digestibility coefficients of crude nutrients. Increasing Fe levels in the concentrates decreased the rates of liveweight increase and food consumption in both growth trials. Well-established statistical evidence was provided for the decline in absolute carcass yields resulting from the lower weight of the lambs at the end of the fattening period after Fe supplementation.     

Testing of the protective effect of cell-free lyophilized vaccine against Marek's disease in field trials]

The protective effect of a lyophilized vaccine against Marek's disease ("Keramvac"--Pfizer), prepared from a cell-free turkey's herpesvirus (strain FC 126), was compared in field trials with losses in the group of non-vaccinated chickens. Under the indicated conditions, the vaccine had only a 50.86% effectiveness. The possible causes of the reduced vaccination effect are discussed with regard to the pathomorphological and virological findings suggesting, among others, an increased incidence of the symptoms of the classical form of Marek's disease in the population investigated.     

Effect of diet composition and slaughter weight on animal performance, carcass and meat quality, and fatty acid composition in veal calves

The effect of true milk use in the diet of Spanish Brown Swiss male calves on animal performance, carcass and meat quality, and fatty acids composition was studied. In experiment 1, the effect of milk intake [ad libitum continuous (ADLIB) feed vs. restricted 0.7 during 75 days followed by ad libitum feed (RESTR)] and slaughter endpoint (225 kg vs. 5 month) were studied. In experiment 2, ad libitum concentrate feeding [grain-fed (GF)] was compared with milk supplementation until slaughter [milk-fed (MF)] in calves slaughtered at 345 kg. As regards to milk intake, carcass weight and degree of fatness were higher in the ADLIB group (P<0.05). The RESTR group revealed a higher percentage of saturated fatty acids (P<0.05). In experiment 2, the MF group exhibited a higher fat percentage (P<0.05), lower press and cooking losses (P<0.05), and higher scores for tenderness and juiciness (P<0.05) than the GF group. The percentage of saturated fatty acids was higher in the MF group (P<0.05). The results suggest that true milk use in veal production could be an advantageous alternative in terms on production costs, animal performance, and carcass and meat quality.