Sialoglycolipids in Trypanosoma cruzi

Mild oxidation of epimastigote forms of T.cruzi followed by sodium borotritide reduction incorporates radioactivity into glycolipid fractions. Column chromatography on silica gel of the chloroform:methanol (2:1) extract separated two main peaks of radioactivity. Treatment with neuraminidase released 30% and 18% of the radioactivity, respectively. Paper chromatography showed peaks of radioactivity with relative migration to NANA7 of 1.33 in fraction A and 1.33 and 1.51 in fraction B. When unlabeled cells were submitted to a Folch extraction, thin layer chromatography of the upper phase showed at least two components detected with the resorcinol-copper reagent. Enzymatic and mild acid hydrolysis released a sialic acid with a migration relative to NANA of 1.22. These results suggest that a substituted sialic acid is present in glycolipids of the epimastigote form of T.cruzi.     

Intermediary metabolism of Trypanosoma cruzi

In this article, Julio Urbino discusses the characteristics o f the intermediary metabolism of Trypanosoma cruzi (the causative agent of Chagas disease), which are responsible for the unusual capacity of this parasite to use carbohydrates or amino acids as carbon and energy sources without drastic changes in its catabolic enzyme levels(1-3). Many, but not all, o f the metabolic capabilities of this organism are shared with Leishmania and the procyclic form o f the African trypanosomes, and the reviewer presents a metabolic model which is also consistent with the information available on these other parasites(2,4).     

The gamma-glutamyltranspeptidase of Trypanosoma cruzi

Trypanosoma cruzi epimastigotes show gamma-glutamyltranspeptidase activity which has characteristics significantly different than the mammalian enzyme. The protozoan enzyme is localized in the cytosolic fraction, it has a Km of 1.6 mM and a Vmax of 17.4 nmol/min/mg protein with L-gamma-glutamyl-p-nitroanilide as gamma-glutamyl donor, and an optimun pH range from 7.5 to 8.0. The best amino acid acceptors were L-histidine, L-asparagine, L-aspartate, L-glutamate and L-proline, but L-glutamine was a very poor acceptor. The enzyme was very sensitive to inhibition by 6-diazo-5-oxo-L-norleucine (k2 = 4.0 X 10(5)/M per min) and O-diazo-acetyl-L-serine (k2 = 1.1 X 10(4)/M per min). Phenobarbital (k2 = 8.38/M per min) and L-serine borate (Ki = 34 mM) were poor inhibitors. The activity of the enzyme was not correlated with the logarithmic phase of growth of the parasites and steadily decreases with the age of the cultures.     

A New Aspect of Trypanosoma cruzi Life-Cycle in the Invertebrate Host

SYNOPSIS. Trypanosoma cruzi blood trypomastigotes transform, in the stomach of the invertebrate host, into round or pear-shaped forms. A certain number form attached pairs or large masses of aggregated amastigotes. Cytoplasmic bridges and membrane leaks may be observed between apposed parasites. There are fusion of the organisms, an apparent disorganization of the DNA-containing organelles and thickening of the borders of the parasite aggregates. From those borders single or small clumps of flagellates begin to detach and liberate. The meaning of this heretofore overlooked sequence of events as well as the possibility of genetic exchange among the parasites in the early stages of development are discussed.     

Plasminogen interaction with Trypanosoma cruzi

The ability of Trypanosoma cruzi to interact with plasminogen, the zimogenic form of the blood serin protease plasmin, was examined. Immunohistochemistry studies revealed that both forms, epimastigotes and metacyclic trypomastigotes, were able to fix plasminogen in a lysine dependant manner. This interaction was corroborated by plasminogen activation studies. Both forms of the parasite enhanced the plasminogen activation by tissue-type plasminogen activator.The maximal enhancements obtained were 15-fold and 3.4-fold with epimastigotes and metacyclic trypomastigotes, respectively, as compared to plasminogen activation in absence of cells. Ligand-blotting analysis of proteins extracted with Triton X-114 from a microsomal fraction of epimastigotes revealed at least five soluble proteins and one hydrophobic protein able to bind plasminogen.     

Karyotype variability in Trypanosoma cruzi

Like many other protozoam parasites, Trypanosoma cruzi (the causative agent of Chagas disease) has a plastic genome. Chromosome size polymorphisms occur in different strains of T. cruzi as well as among clones originating from the same strain, Despite this polymorphism, major interchromosomal rearrangements appear to be rare since several linkage groups of chromosomal markers are well conserved among different T. cruzi strains. In addition, some correlation has been found between karyotype variability and classification by multilocus enzyme electrophoresis. In this review, Jan Henriksson, Lena Aslund and Ulf Petterson discuss the genomic variability and suggest that amplication of repetitive sequences or members of gene families make a major contribution to the chromosomal size variation