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Morphological mutants in anopheline mosquitoes
LABORATORY MEETING
19
It is unlikely to be true of mosquitoes, and is not true of mites. The apparent enhancement is due to selection of mites by irradiation. The intensity of infection in the few that survive after irradiation is higher than in the many surviving controls, but the intensity of infection expressed as a fraction of the original mite population shows that irradiation of the mites before they acquire their infection reduces, to about half, the number of parasites surviving had the mites not been irradiated. It may be that the mites which survive are those which are better able to support development of the infection, and that those which die are less well able to support it.
Dr. I. J. Sinclair
Central Veterinary Laboratory, Weybridge A modification of the agar-gel double diffusion technique for improving the resolution of precipitin bands produced by nematode material The method demonstrated is designed to increase the sensitivity of the precipitin reaction in agar by increasing the concentration of antibody and antigen in the medium. This is done by using a thin layer of agar and a perspex template to hold thereactants. A standard thickness of agar is produced by placing the template, which has supports 0.8 mm. high, on a microscope slide and then flooding the slide with molten agar. After the agar has set, the holes in the templates are cleared of excess agar and filled with the reactants. It is also found that the thinness of the agar increases the ease and accuracy with which the test can be read.
Dr. J. H. Rose
Central Veterinary Laboratory, Weybridge The development of the parasitic stages of Ostertagia ostertagi Stained preparations of female worms, which had undergone periods of development ranging from 2 to 22 days in the abomasttm of the calf, were presented to demonstrate the development of the parasitic stages of Ostertagia ostertagi.
Miss Ellen E. E. Barth, Professor W. F. H. Jarrett and Dr. G. M. Urquhart
lVellcome Laboratories for Experimental Parasitology, University of Glasgow The induction of i m m u n o l o g i c a l unresponsiveness to Nippostrongylus brasiliensis in rats Adult rats infected subcutaneously with 500 or more N. brasiliensis larvae undergo a self-cure reaction characterized by the expulsion of the great majority of the worms from the intestine. Subsequently such rats are highly immune to reinfection. I n the course of a series of experiments with baby rats, we have found that an infection of N. brasiliensis acquired during the first 6 weeks of life is not eliminated in this characteristic fashion and persists well into adult life. I n the first experiment rats 3-6 weeks old were each infected with 500 larvae. Autopsies on days 10 and 26 showed means of 188 -4-22* and 213 ±32 worms respectively. T h e means of similarly infected adult rats were 118 q-31 and 33 4-6. I n a second experiment, groups of rats 2-3 weeks of age also infected with 500 larvae each and autopsied on days 52, 67 and 87 showed 143 ±12, 140 4-15 and 83 4-18 worms. These results cannot be attributed to immunological immaturity since a very strong immune response is normally developed within 2 weeks by rats 4-5 weeks younger than those on the last autopsy date. * All numbers prefixed by ± indicate standard error.
B
19
It is unlikely to be true of mosquitoes, and is not true of mites. The apparent enhancement is due to selection of mites by irradiation. The intensity of infection in the few that survive after irradiation is higher than in the many surviving controls, but the intensity of infection expressed as a fraction of the original mite population shows that irradiation of the mites before they acquire their infection reduces, to about half, the number of parasites surviving had the mites not been irradiated. It may be that the mites which survive are those which are better able to support development of the infection, and that those which die are less well able to support it.
Dr. I. J. Sinclair
Central Veterinary Laboratory, Weybridge A modification of the agar-gel double diffusion technique for improving the resolution of precipitin bands produced by nematode material The method demonstrated is designed to increase the sensitivity of the precipitin reaction in agar by increasing the concentration of antibody and antigen in the medium. This is done by using a thin layer of agar and a perspex template to hold thereactants. A standard thickness of agar is produced by placing the template, which has supports 0.8 mm. high, on a microscope slide and then flooding the slide with molten agar. After the agar has set, the holes in the templates are cleared of excess agar and filled with the reactants. It is also found that the thinness of the agar increases the ease and accuracy with which the test can be read.
Dr. J. H. Rose
Central Veterinary Laboratory, Weybridge The development of the parasitic stages of Ostertagia ostertagi Stained preparations of female worms, which had undergone periods of development ranging from 2 to 22 days in the abomasttm of the calf, were presented to demonstrate the development of the parasitic stages of Ostertagia ostertagi.
Miss Ellen E. E. Barth, Professor W. F. H. Jarrett and Dr. G. M. Urquhart
lVellcome Laboratories for Experimental Parasitology, University of Glasgow The induction of i m m u n o l o g i c a l unresponsiveness to Nippostrongylus brasiliensis in rats Adult rats infected subcutaneously with 500 or more N. brasiliensis larvae undergo a self-cure reaction characterized by the expulsion of the great majority of the worms from the intestine. Subsequently such rats are highly immune to reinfection. I n the course of a series of experiments with baby rats, we have found that an infection of N. brasiliensis acquired during the first 6 weeks of life is not eliminated in this characteristic fashion and persists well into adult life. I n the first experiment rats 3-6 weeks old were each infected with 500 larvae. Autopsies on days 10 and 26 showed means of 188 -4-22* and 213 ±32 worms respectively. T h e means of similarly infected adult rats were 118 q-31 and 33 4-6. I n a second experiment, groups of rats 2-3 weeks of age also infected with 500 larvae each and autopsied on days 52, 67 and 87 showed 143 ±12, 140 4-15 and 83 4-18 worms. These results cannot be attributed to immunological immaturity since a very strong immune response is normally developed within 2 weeks by rats 4-5 weeks younger than those on the last autopsy date. * All numbers prefixed by ± indicate standard error.
B