HISTOCHEMICAL STUDIES ON THE BLOOD AND CULTURE FORMS OF TRYPANOSOMA RHODESIENSE

Abstract

This chapter discusses the histochemical studies on the blood and culture forms of Trypanosoma rhodesiense. Trypanosomes of the brucei subgroup during the course of their life cycle in the mammalian host and tsetse fly vector undergo a considerable amount of morphological and physiological variation. Preliminary experiments carried out with blood forms of Trypanosoma rhodesiense obtained from rats and with forms obtained in diphasic blood culture have led to two microscopical tests with a physiological basis. Culture forms, which have an operative tricarboxylic acid cycle, are able to use a number of organic acids as alternatives to glucose to support respiration and motility. Trypanosomes washed free from extracellular substrate are incubated with α-oxoglutarate in phosphate buffer at pH 6.0, control samples being incubated without substrate or with glucose. When motility has died out in substrate-free controls, but is still normal in the presence of glucose, microscopical examination shows culture forms to be active, while blood forms are immotile; motility studies of this type should indicate at which point in the life cycle the tricarboxylic acid cycle becomes effective and when it becomes redundant.