Workshop on irradiated larval vaccines

The development of anthelmintic resistance in gastrointestinal parasites of sheep and goats has meant that there is an urgent need for non-chemical control of these parasites. In order to investigate a potential alternative method of control, a workshop on irradiated larval vaccines (ILV) was held in conjunction with the Second International Conference on Novel Approaches to the Control of Helminth Parasites of Livestock. The objectives of the workshop were to: (1) Review knowledge of irradiated helminth vaccines through the presentation of invited and contributed papers. (2) Identify opportunities for an ILV and in which host/parasite/production systems. (3) Determine what are the gaps in knowledge required to produce and apply an ILV. The workshop concluded that ILVs could be useful as research tools in the further definition of immune responses to parasites and in stimulating the immune response in young sheep and goats to facilitate the estimating of heritability of faecal egg counts. Although the workshop identified some problems associated with a live attenuated vaccine, an ILV could be a useful control measure in the production systems identified by the workshop. Before an ILV could be used on farms, additional research is required into the period of protection afforded by an ILV especially under field conditions. The efficacy of an ILV could be improved by interaction between host genotype and nutritional status and is deserving of further investigation.     

Effects of UV-B irradiated algae on zooplankton grazing

We tested the effects of UV-B stressed algae on grazing rates of zooplankton. Four algal species (Chlamydomonas reinhardtii, Cryptomonas sp., Scenedesmus obliquus and Microcystis aeruginosa) were used as food and fed to three zooplankton species (Daphnia galeata, Bosmina longirostris and Brachionus calyciflorus), representing different taxonomic groups. The phytoplankton species were cultured under PAR conditions, and under PAR supplemented with UV-B radiation at two intensities (0.3 W m^–2 and 0.7 W m^–2, 6 hours per day). Ingestion and incorporation experiments were performed at two food levels (0.1 and 1.0 mg C l^–1) using radiotracer techniques. The effect of food concentration on ingestion and incorporation rate was significant for all three zooplankton species, but the effect of UV-B radiation was more complex. The reactions of the zooplankton species to UV-B stressed algae were different. UV-B stressed algae did not affect Daphnia grazing rates. For Bosmina the rates increased when feeding on UV-B stressed Microcystis and decreased when feeding on UV-B stressed Chlamydomonas, compared with non-stressed algae. Brachionus grazing rates were increased when feeding on UV-B stressed Cryptomonas and UV-B stressed Scenedesmus, and decreased when feeding on UV-B stressed Microcystis, compared with non-stressed algae. These results suggest that on a short time scale UV-B radiation may result in increased grazing rates of zooplankton, but also in decreased grazing rates. Long term effects of UV-B radiation on phytoplankton and zooplankton communities are therefore difficult to predict.     

Radiobiology of irradiated leukocytes

Summary The paper continues a series of the author's investigations regarding the determination of certain biochemical and biophysical parameters of the leukocytes taken from animals internally irradiated with³²P. The parameters determined here are the respiratory capacity of PMN leukocytes from Wistar rats submitted to 1 and 2 Ci/g³²P internal irradiations, the proteolytic power and the level of the microelements Zn, Cu and Mn in the same cells and under identical irradiation conditions.The results show a diminished consumption of oxygen only during phagocytosis, a maximum diminution of the proteolytic activity of leukocytes at the 12th day of internal irradiation and a decreasing tendency of Zn, Cu and Mn amounts in leukocytes of irradiated animals, most prominently appearing in the case of Mn.Dedicated to Prof. Dr. Dr. h. c. B. Rajewsky on the occasion of his 80th birthday.