A cytochemical ultrastructural study of the lysosomal system of different species of malaria parasites.

We have used ultrastructural techniques in different malarial species to demonstrate a lysosomal system. First, we have tried to localize acid phosphatase, a typical lysosomal label. Its activity was localized in the endoplasmic reticulum and in endocytic vesicles, and in dense-cored vesicles near the digestive vacuoles, especially in Plasmodium falciparum (FCR3 strain). Then, we have studied the different cellular compartments of the malarial parasite by the zinc iodide-osmium tetroxide technique that heavily contrasted the cellular compartments of the parasite. This experiment led to the observation of a profound rearrangement of the endoplasmic reticulum, especially in P. berghei. A very atypical but functional Golgi apparatus was demonstrated in all the growing stages of the parasite and lysosome-like vesicles were observed, showing a structure very similar to those of the coated vesicles of a true Golgi complex. The presence of these organelles are in favor of the existence of a lysosomal system and of the endogenicity of some enzymes involved hemoglobin degradation.