The Ultrastructure of Leishmania donovani

Abstract

Electron micrographs of ultra-thin sections of the intra- and extracellular forms of Leishmania donovani reveal the same basic structures. The intracellular form has a nucleus bounded by a double membrane and a homogeneous karyosome within its granular nucleo-plasm. The cytoplasm is limited by a double cell membrane composed of a smooth outer layer and a ridged inner layer. In the cytoplasm are fine granules, vacuoles, osmophilic droplets and a reduced flagellum with a basal granule at its proximal end. The flagellum consists of a fibrillar axoneme surrounded by a coiled protoplasmic sheath. The extracellular form has a single cell membrane and a single nuclear membrane. The flagellum extends beyond the cell membrane as a free flagellum. The basal granule shows internal banding, the significance of which is obscure. Osmophilic droplets were not observed in the extracellular form.