Schistosoma mansoni: in vitrotransformation of cercariae into schistosomula

Abstract

The transformation of cercariae ofSchistosoma mansoniinto schistosomula has previously been achieved by passage through membranes of biological origin. This transformation has now been effected in the absence of a membrane. Chemical stimulus for transformation results from contact with human or rat skin lipid and fractionation of the latter led to localization of the active component in a fraction containing phospholipids. The series of processes involved in transformation was subsequently found to be set in motion by the action of egg lecithin-water mixtures on an aqueous suspension of cercariae and yields of 90% of live schistosomula may be obtained reproducibly with crude egg lecithin-water in the ratio 1:50. The juvenile worms were found, by accepted criteria, to be identical to those produced by the normal penetration procedure. Purified lecithin does not produce the same stimulus and the effect of the physical state and of possible impurities present in crude egg lecithin is discussed.This work was supported by the Conselho Nacional de Pesquisas (Brazil), the Banco Nacional de Desenvolvimento Econâmico FUNTEC contracts nos. 99 and 110 (Brazil), U.S. Army Grants nos. DAHC-19-70-G-0017 (to B.G.) and DAHC-19-70-G-0070 (to J.P.) and by the FORGE Foundation. Contribution no. 18 from the Schistosomiasis Research Unit, Institute of Biological Sciences, Federal University of Minas Gerais, Brazil.