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The effects of various treatments on the surfaces of the cercariae and schistosomula of Schistosoma mansoni

Published online by Cambridge University Press:  06 April 2009

J. R. Kusel
J. R. Kusel
Affiliation:
Biochemistry Department, Faculty of Medicine, Khartoum, Sudan
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Extract

In order to learn more about the nature of the chemical bonds stabilizing the surface membranes of the cercariae and schistosomula of Schistosoma mansoni, these organisms were treated with a variety of reagents. The cercarial surface was dissolved by 8 M urea alone (pH 9·0) but was protected from such dissolution if a certain critical concentration of cation or anion was included in the 8 M urea solution. Divalent cations were more effective than monovalent cations in this protective effect. The 8 M urea was also unable to dissolve the cercarial surface at any pH below 5·8. The cercarial surface was very rapidly dissolved by sodium hydroxide solutions at pH 11·4 and above. The divalent cation calcium, if included in the sodium hydroxide solution, slowed down the rate of surface solution by sodium hydroxide. The schistosomular surface was stable to 8 M urea at pH 9·0 but was readily dissolved in 8 M urea at pH 10·7 and 11·7. The schistosomular surface was stable in aqueous sodium hydroxide solutions at pH 12·0. Anionic detergents were very effective in dissolving the cercarial surface at concentrations above 0·001%. Cationic and non-ionic detergents were ineffective at 0·01% or below. A saturated solution of digitonin if diluted 1:100 caused destruction of the cercarial surface. At higher concentrations it caused expansion and stabilization of this surface.

It is suggested that in both the cercarial and the schistosomular surface, bonds between carboxyl (—COO′) and amino (—NH3+) groups are very important in maintaining structure. The origin of the —NH3+ group is possibly from —NH2 lysyl group in cercariae, and a guanido group in schistosomula. The suggestion that cations are incorporated into the cercarial surface and stabilize it during and after penetration has been tested by treating schistosomula with EDTA. The EDTA had no visible effect on the surface, nor did it labilize the surface to other reagents.

I should like to thank very warmly Dr S. A. Ibrahim, in whose Department this work was carried out. My grateful thanks are given to the Medical Research Council (U.K.) for a grant. I should also like to thank Mr J. R. Lauder, Mr Ahmed Gandour and Mr Saleh for their help during the work. I am very grateful to Dr J. A. Clegg and Dr S. R. Smithers for helpful discussions.

Type
Research Article
Information
Parasitology , Volume 62 , Issue 2 , April 1971 , pp. 199 - 207
Copyright
Copyright © Cambridge University Press 1971

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References

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