Search

1. 1. Chromatographic and chemical analyses show that up to four major sterols may be present in blood and culture forms of trypanosomes. 2. 2. Blood and culture forms of Trypanosoma lewisi and culture forms of T. rhodesiense biosynthesize C(24)-alkyl sterols de novo. In these trypanosomes, and in blood forms of T. rhodesiense, exogenous cholesterol is incorporated and esterified, but not further metabolized. 3. 3. Changes in sterol composition and metabolism occur in T. lewisi during “maturation” in vivo, and during in vitro culture. 4. 4. The role of sterol biosynthesis in cyclical mitochondrial biogenesis in trypanosomes is discussed, and also the evolutionary significance of the phytosterols identified in this study.

Mikamycin, an antibiotic which inhibits bacterial protein synthesis, strongly inhibits mitochondrial protein synthesis at concentrations of the order of 1 μg/ml or less. At concentrations of the order of 25–50 μg/ml it also inhibits mitochondrial respiration at a site which appears to be localized between cytochromes b and c 1 . A unitary concept for the two observed effects is discussed.

1. 1. Ten to twenty per cent of the dry weight of blood and culture forms of Trypanosoma rhodesiense and T. lewisi consist of lipid. 2. 2. Thin-layer and gas-liquid chromatographic analyses show that the major portion is phospholipid, together with neutral lipids and sterols. 3. 3. The lipids of the trypanosomes, compared with those of their host or culture environment, show differences, mainly quantitative, especially in fatty acid composition. 4. 4. These differences are discussed in relation to the structural and functional changes which occur during the trypanosome life cycle.

1. 1. Lipid biosynthesis, uptake and oxidation of fatty acids by blood and culture forms of Trypanosoma lewisi and T. rhodesiense were studied in vitro. 2. 2. With the exception of blood T. rhodesiene, trypanosomes incorporated radioactive glucose, glycerol and acetate into total lipids. Culture trypanosomes incorporated radioactive acetate into saturated and unsaturated long-chain fatty acids. Blood T. lewisi synthesized stearate only. 3. 3. Saturated and unsaturated C16 and C18 acids were absorbed, interconverted, and esterified by all trypanosomes. Highest activity was found in phospholipids of blood forms. Stearate uptake showed anomalies and α-linolenate uptake was particularly rapid in culture T. rhodesiense. 4. 4. Palmitate oxidation was low or insignificant in both species.

THE standard method used for separating trypanosomes from infected blood involves repeated differential centrifugation of a suspension of trypanosomes and blood elements in a phosphate-buffered saline solution containing glucose. The success of this procedure varies not only from one species to another but also with the degree of parasitaemia. Suspensions of the Liverpool strain of Trypanosoma rhodesiense may be obtained free of red blood cells and leucocytes in this way, but with T. vivax, T. congolense, T. lewisi and the ‘M’ and ‘J’ strains of T. rhodesiense other techniques have to be used for complete removal of blood cells and platelets1,2.