Degeneration Phenomena of Trypanosoma gambiense

Abstract

After treatment with arsenophenylglycin the number of trypanosomes in an infected animal immediately begins to decrease, and the parasites disappear from the peripheral circulation 6—7 hours after the time of injection, the short stumpy forms being the last to degenerate. One of the first changes noticed in the trypanosomes after treatment is the rounding up of their posterior extremities caused by the retraction of the protoplasm behind the kineto-nucleus. Meanwhile the tropho-nucleus becomes filled with granules of volutinose, which are extruded into the cytoplasm and pass along the axial filament towards the anterior extremity of the body. In dividing forms the granules form two longitudinal rows, being distributed along the two axial filaments. Finally, the granules lose their regular arrangement and become scattered throughout the cytoplasm, being more abundant, however, at the anterior end. The kineto-vacuole, when present, enlarges considerably and may become filled with chromatic substance derived from the kineto-nucleus. The axial filament begins to degenerate soon after treatment, often breaking up into a row of granules. Occasionally, however, chromatic substance from the kineto-nucleus passes along the axial filament, and it then appears as a thick black band extending along the middle of the cell eventually to the anterior extremity. Subsequently it breaks up into granules which dissolve in the cytoplasm of the cell. Chromatic bodies are given off from the kineto-nucleus both before and after treatment and do not seem to be a characteristic feature of degeneration. Sometimes the tropho-nucleus completely disappears before the cytoplasm breaks up into fragments, but at other times it preserves its form long after all other parts of the trypanosome, with the exception of the flagellum, have disappeared. These free nuclei resemble the “latent bodies” described by Salvin-Moore and Breinl, but as they, along with the fragments of cytoplasm, granules etc., are ingested by the leucocytes, it seems possible that they are merely one of the results of degeneration and not part of the life-cycle of this parasite. These investigations have been carried on partly with the aid of a grant from the Tropical Diseases Research Fund (Colonial Office).