Tegumental alterations in adult Schistosoma mansoni treated with imidazolidine derivatives

Ultrastructural observations were made on the tegument of Schistosoma mansoni after 24 h in vitro incubation with three imidazolidine derivatives at a concentration of 120 mu g/ml. Treatment with (Z)-3-(4-chloro-benzyl)-5-(4-fluoro-benzylidene)-1-methyl-2-thioxo-imidazoUdin-4-one caused slight damage to the tegument. Male worms exhibited shortening of the ridges in close proximity to the tubercules and numerous tiny protuberances emerging from the tegument; female worms exhibited peeling and focal erosion of the surface. After treatment with (Z)-3-(4-chloro-benzyl)-5-(4-nitro-benzylidene)-imidazolidine2,4-dione, the body of male worms appeared wrinkled, there was damage to the oral sucker, a reduction in size and disorganization of the tubercules, whereas in females the most prominent alteration was severe tegurnental erosion with peeling or rupture of the surface. Treatment with (Z)-5-(4-fluoro-benzylidene)-1methyl-3-(4-phenyl-benzyl)-2-thioxo-imidazo-lidin-4-one, resulted in severe tegumental damage in male worms, including erosion with exposure of internal structures. In female worms there were numerous protuberances and deep grooves all over the tegument. The range of ultrastructural abnormalities in the S. mansoni tegument caused by imidazolidine derivatives possibly indicates that these are new antischistosomal compounds.