Eleanor Johnson Tobie

CO2 fixation studies with the culture form of Trypanosoma cruzi

Abstract 1. 1. Succinate production of the culture form of Trypanosoma cruzi is completely dependent on CO2 under anaerobic conditions; under aerobic conditions CO2 greatly enhances succinate production. 2. 2. Anaerobically, variously labeled species of glucose-C14 are metabolized in a way consistent with the Embden-Meyerhof glycolytic scheme followed by CO2 fixation on pyruvate, resulting in the formation of succinic acid. 3. 3. Aerobically, succinate is formed by two pathways. First, experiments with variously labeled species of glucose-C14 indicate that a large part of the glucose is metabolized according to the Embden-Meyerhof scheme followed by the tricarboxylic acid cycle. Second, succinate is also formed by CO2 fixation. 4. 4. Succinate formed either by tricarboxylic acid cycle reactions or by CO2 fixation is partly excreted into the medium. Part of the succinate formed, as well as the precursor dicarboxylic acids of the second pathway mentioned above, appear to be further metabolized by the tricarboxylic acid cycle, since malonate increases the yield of succinate while causing no significant change in CO2 production. It is therefore considered that the intermediates of both pathways are mixed in the cell.

The sterols of Trypanosoma cruzi and Crithidia fasciculata

Abstract 1. 1. Six sterols have been detected in Trypanosoma cruzi cultured on serum-free medium. Four of these are ergosterol, 22,23-dihydroergosterol, 7-dehydroporiferasterol and 7-dehydroclionasterol (or their C24 isomers from which they cannot be distinguished with the small quantities available). The remaining two sterols may be 24-methylene-7-dehydrocholesterol and 24-ethylidene-7-dehydrocholesterol but this has not been proven. 2. 2. In addition to these six sterols, cholesterol is also a major component of T. cruzi cultured in the presence of serum. 3. 3. Ergosterol (or its C24 isomer) was the only sterol detected in Crithidia fasciculata cultured in serum-free medium. When grown in the presence of serum the cells also contained cholesterol and 22,23-dihydroergosterol (or its C24 isomer).

Chemical composition of the culture form of Trypanosoma cruzi.

Abstract 1. 1. The culture form of T. cruzi contains considerably more lipids than carbohydrates. 2. 2. No glucose polysaccharide was found. A galactose-containing polysaccaride was observed but it could not be separated from nucleic acid derivatives. 3. 3. The nature of the nucleic acid derivatives indicated that T. cruzi contains both deoxyribonucleic acid and ribonucleic acid, the latter representing in part at least the volutin granules. 4. 4. A large part of the unsaponifiable fraction consists of cholesterol. The presence of a small amount of a 5,7-diene was indicated by ultraviolet spectroscopy.

Observations on the development of Trypanosoma rangeli in the hemocoel of Rhodnius prolixus.

Abstract The development of Trypanosoma rangeli in the hemocoel of Rhodnius prolixus was studied with the idea of elucidating the function of the forms found there. When flagellates from cultures of T. rangeli that have decreased in virulence are introduced into the hemocoel of R. prolixus the salivary glands are not invaded regularly or, if invaded, the infection does not persist. However, the parasite lives and multiplies in the hemocoel. Crithidial forms enter the plasmotocytes where they roll up and divide. This hemocyte becomes greatly enlarged due to the dividing leishmania forms within its cytoplasm. Eventually the cell ruptures releasing numerous crithidias, some of which transform into trypanosomes as evidenced by the presence of metacyclic as well as long forms. These observations also help explain the pathogenic action of T. rangeli to its invertebrate host.

Experimental transmission and biological comparison of strains of Trypanosoma rangeli

Abstract The infectivity of strains of Trypanosoma rangeli is compared under experimental conditions. The various strains react differently in the white rat, a vertebrate host, as well as in Rhodnius prolixus, an invertebrate host. The survival of T. rangeli in the bloodstream of the rat and infections in the intestine, hemolymph, and salivary glands of R. prolixus are discussed. Evidence suggests that R. prolixus may not be the natural invertebrate host for all strains of T. rangeli or that trypanosomes designated as T. rangeli actually represent more than one species. Passage through the insect host enhanced the ability of one strain to invade the salivary glands following inoculation into the hemocoele. Maintenance of the strain was thus possible by cyclical transmission.

The cultivation and metabolism of trypanosomes in the presence of trehalose with observations on trehalase in blood serum

1. n1. Trypanosoma cruzi cultivated in the liquid phase of diphasic blood agar medium (medium I) or in the same medium prepared with blood inactivated at 56 ° for 30 min seemed unable to utilize trehalose per se, but the hydrolysis of this disaccharide was due to a trehalase present in these media. When this enzyme was denatured by autoclaving the base, it was apparent that trehalose was a non-utilisable substrate. n n2. n2. Neither T. gambiense grown in the overlay from diphasic blood agar medium containing inactivated blood (medium II) or from the same medium but with the base subjected to autoclaving (medium III) nor T. rhodesiense grown in medium III could utilize trehalose. The infectivity of these culture organisms was not restored even after prolonged exposure to trehalose. n n3. n3. The endogenous respiration of T. cruzi cultivated in the less favorable autoclaved medium was 7-fold less than that of these organisms cultivated in medium I, whereas glucose stimulated the respiration relatively more. Trehalose had no effect on the endogenous respiration in either case. n n4. n4. Rabbit blood serum was found to be the source of trehalase in the medium. This enzyme displayed considerable specificity towards trehalose. It was also found in human, dog, and cat blood.

Further studies on arsenic resistance in Trypanosoma gambiense

Abstract 1. (1) Repeated exposures to sodium arsenite in vitro of a normal strain of Trypanosoma gambiense and one highly resistant to reduced tryparsamide failed to induce resistance to this compound. 2. (2) A normal strain of T. gambiense remained infective after exposures to somewhat higher concentrations of sodium arsenite than a tryparsamide-resistant strain, although the respiration of the latter was slightly more resistant to sodium arsenite than that of the former. 3. (3) The exposures to sodium arsenite had no influence on the response of the respiration of the trypanosomes to reduced tryparsamide, sodium arsenite, or compound NF 114. 4. (4) The resistance to reduced tryparsamide had measurably decreased during 21 months when the strain had no contact with the drug. 5. (5) The slight resistance to sodium arsenite induced previously by exposure to tryparsamide as measured by the oxygen consumption or the similarly induced hypersensitivity to the nitrofurane derivative NF 114 appear to be stable characters.