Intracelluar structures in Strigomonas oncopelti: I. Cytoplasmic structures containing ribonucleoprotein

Abstract

Basophilic, rod-like particles have been observed in the cytoplasm of the trypanosomid flagellate Strigomonas oncopelti. These structures have been observed in unfixed preparations by phase contrast microscopy; organisms contain either one or two of these structures which are always located at the posterior end of the cell. They are present in organisms harvested at all stages of growth, and starvation does not result in a loss of these structures. The results of cytochemical tests suggest that ribonucleic acid is associated with the particles; there is no evidence for the presence of polysaccharide or metaphosphate. Particles have been liberated from cells and separated from other cell components. Analysis of isolated particles shows that they are composed largely of ribonucleoprotein and contain ca. 10–15 per cent of the total ribonucleic acid of whole organisms. Electron microscope studies of isolated particles and of ultra-thin sections of whole organisms show that these rod-like structures are bounded by a thin membrane and that they probably divide by transverse fission.