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The LOCHNESS (large opening closing high speed net and environmental sampling system) for quantitative sampling of micronekton is described. It consists of five nets, each 14 m long by 2.3 m square mouth opened, contained within a steel framework. The sampler is towed at a speed of 1.5-2.5 ms−1 and the nets are opened sequentially by remote control using a through-water acoustic command and telemetry system. Mounted on the sampler are sensors to indicate depth, water flow, battery voltage, and net status. This information is transmitted to the surface via the acoustic link and displayed in real-time on a visual display unit. The sampler also carries a separate, independent system to log depth, conductivity, temperature, and other parameters as required, which can be down-loaded to a computer on recovery. The sampler can thus collect biological samples and environmental data simultaneously. The engineering design, construction, and early trials are described and some initial results are presented showing both its mechanical and catching performance. [ABSTRACT FROM PUBLISHER]

Using trypanosomes labelled with [75Se]-methionine a series of experiments was conducted to investigate antibody production in mice with acute fulminating T. brucei infections. As measured by the hepatic uptake of radiolabelled parasites, we were unable to demonstrate any evidence of antibody-mediated uptake by the liver in such mice. It was concluded that this was not due to impaired macrophage function but was caused by the inability of antibody production to cope with the massive parasitaemias produced by rapidly-replicating infections so that effective opsonization of the parasites did not occur. In contrast, a strain of trypanosome which causes a more chronic infection, although initially having a similar replication rate, subsequently switched to a slower one and thereby allowed antibody to reach levels which permitted effective opsonization. There was no evidence that the parasite caused any significant suppression of antibody responses in these acute infections since inoculation with trypanosomes of one stock at the same time as vaccination with irradiated organisms of a second stock did not prevent the development of antibody to the latter, as measured by the hepatic uptake of radiolabelled parasites. [ABSTRACT FROM AUTHOR]

Using trypanosomes labelled with [75Se]- methionine a series of experiments was conducted to investigate the respective roles of antibody, macro- phage activation and complement in the removal of trypanosomes from the circulation of immune mice. It was found that clearance in such animals is largely accomplished by antibody-mediated hepatic phagocytosis, which, at least in passively immunized animals, is dependent on opsonization involving C3. No evidence was found to suggest that intravascular lysis or activated macroph ages are involved in immune clearance. [ABSTRACT FROM AUTHOR]

The production of ovalbumin-induced anaphylaxis in rats passively immunized with antiserum to Nippostrongylus brasiliensis produced a significant reduction in their transplanted populations of adult worms compared to: (a) rats which were passively immunized alone, and (b) rats subjected to ovalbumin anaphylaxis alone. This result suggests that the physical changes associated with anaphylaxis facilitated the passage of antibody into the sub-epithelial spaces and intestinal lumen where its effect was specifically directed against the worms. Since in naturally infected rats an intestinal lesion is present, which grossly and microscopically resembles that induced by ovalbumin anaphylaxis, it was concluded that this lesion plays a similar role in the self-cure reaction. [ABSTRACT FROM AUTHOR]

Experiments are described on the immunity to Dictyocaulus viviparus infection produced by the administration of 3rd stage D. viviparus larvae partially inactivated by X-irradiation. A high degree of immunity was obtained by this method. [ABSTRACT FROM AUTHOR]

It has been shown experimentally that infection of calves with D. viviparus confers a high degree of resistance to a subsequent reinfection. This acquired immunity can result from a single infection with a sub-lethal dose of larvae or from a series of repeated doses of small numbers of larvae. Animals immunized by a previous infection exhibit on challenge a rapid antibody response and a striking reduction (in some cases to zero) in the numbers of worms reaching the lungs, and in the numbers of larvae appearing in the faeces. [ABSTRACT FROM AUTHOR]