schistosoma mansoni: a comparative study on two cercarial transformation methods

ABSTRACT

An agar gelatin plate method, incorporating varying concentrations of linoleate was devised to measure cercarial penetration and transformation in vitro. Schistosoma mansoni cercaria were stimulated over a wide range of linoleate concentrations, while the transformation process occurred over a narrow range. Penetration rates rose gradually until at linoleate concentrations of 0.3 mM and greater, where penetration approached 100%, while transformation just started to occur. The latter then reached maximum [90%] at 3 mM. This optimal concentration of linoleate leading to maximal transformation was then compared with a mechanical transformation method in relation to proteolytic activity and nuclear content. It was found that, proteolytic activity was higher by the chemical than by the mechanical transformation method. The nuclear content decreased by both techniques. This decrease was greater when the mechanical transformation method was applied