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Further studies of Schistosoma mansoni cercarial stimulation by crude egg lecithin and other lipids*

Published online by Cambridge University Press:  06 April 2009

Extract

The stimulus provided to cercariae by the skin fat of their definitive hosts is not the same for Schistosoma mansoni and Austrobilharzia terrigalensis. Cercariae of the former parasite are stimulated by unsaturated fatty acids, those of the latter by cholesterol.

A reinvestigation of the penetration stimulant factors present in crude egg lecithin, which contains both cholesterol and free fatty acids as impurities, has shown that the latter are responsible for the stimulus in S. mansoni. The phospholipid fraction is inactive as is pure cholesterol. A little excitation of cercariae is produced by the monoglyceride fraction. These results fully confirm earlier findings.

Of surface active agents other than lecithin, stimulatory activity was found only in one product which possessed carboxyl groups. Of the C18 acids examined, stearic (18:0) is inactive, oleic (18:1) slightly active, linoleic (18:2) and linolenic (18:3) acids highly active. Oleic acid was shown by GC-mass spectrometry to be the most abundant acid in crude egg lecithin and is probably the main penetration stimulus present.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1974

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Footnotes

*

The opinions and assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Navy Department or the Naval service at large.

References

REFERENCES

Austin, F. G., Stirewalt, M. A. & Danziger, R. (1972). Schistosoma mansoni: stimula tory effect of rat skin lipid fractions on cercarial penetration behaviour. Experimental Parasitology 31, 217–24.CrossRefGoogle Scholar
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Bolwig, N. (1955). An experimental study of behavior and host recognition in schistosome cercariae. South African Journal of Science 51, 338–44.Google Scholar
Clegg, J. A. (1969). Skin penetration by cercariae of the bird schistosome Austrobilharzia terrigalensis: the stimulatory effect of cholesterol. Parasitology 59, 973–89.Google ScholarPubMed
Gilbert, B., da Rosa, M. N., Borojevic, R. & Pellegrino, J. (1972). Schistosoma mansoni in vitro transformation of cercariae into schistosomula. Parasitology 64, 333–9.CrossRefGoogle ScholarPubMed
MacInnis, A. J. (1969). Identification of chemicals triggering cercarial penetration responses of Schistosoma mansoni. Nature, London 224, 1221–2.CrossRefGoogle ScholarPubMed
Shiff, C. J., Cmelik, S. H. W., Ley, H. E. & Kriel, R. L. (1972). The influence of human skin lipids on cercarial penetration responses of Schistosoma haematobium and Schistosoma mansoni. Journal of Parasitology 58, 476–80.CrossRefGoogle ScholarPubMed
Stirewalt, M. A. (1963). Cercaria vs Schistosomule (Schistosoma mansoni): absence of the pericarial envelope in vivo and the early physiological and histological metamorphosis of the parasite. Experimental Parasitology 13, 395406.CrossRefGoogle Scholar
Stirewalt, M. A. (1971). Penetration stimuli for schistosome cercariae. In Aspects of the Biology of Symbiosis (ed. Cheng, T. C.), pp. 123. University Park Press: Baltimore, Md.Google Scholar
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