[New aspects of the biology of Entamoeba histolytica]

To determine the mechanism of mitosis in E. histolytica, a study was carried out with axenic cultures of trophozoites in Coplin jars with glass slides to stain them in situ with Giemsa and fluorescent antibodies for actin. Tobuline and myosin. Sedimented amoeba of cultures were used also for ultrastructural studies after glutaraldehyde fixation, and inclusion in spon-araldite. Giemsa stained trophozoites showed duplication by budding or fission with production of polykaryons, mononuclei, micronuclei and apparent polyploidy and DNA reduction. Tubuline was present in nuclei and cytoplasm, actin and myosin had a peripheral distribution with low contents of the latter in large amoeba, resulting in polynucleated cells. The findings are suggestive of endomeiosis with chromosomal recombination which would render virulent and non virulent strains producing either invasive or asymptomatic amoebiasis.