Trypanosoma cruzi and Trypanosoma rangeli: Glutamate dehydrogenases and proteolytic activities

• 1.1. Trypanosoma (Herpetosoma) rangeli contains proteolytic activity with azocasein, casein and BAPA as substrates, and aminopeptidase activity with Arg-BNA as substrate. The respective pH optima were 5.5, 7.0, 8.5 and 7.0.
• 2.2. The effect of the protease inhibitors PMSF, TLCK and trasylol was studied. 0.5 mM TLCK caused considerable inhibition of all these activities, whereas 1 mM PMSF was much less effective. Trasylol (0.14 mg/ml) inhibited the activities with azocasein and Arg-BNA as substrates.
• 3.3. Trypanosoma (Schizotrypanum) cruzi contains very similar proteolytic activities, with some slight differences in pH optima and in response to inhibitors. Thus Trasylol was not effective on any activity, and the activity on Arg-BNA was little sensitive to TLCK.
• 4.4. The levels of these enzymes, and also of the NAD- and NADP-linked glutamate dehydrogenases, were studied in six stocks of T. (Sch.) cruzi and three stocks of T. (H.) rangeli. There was no significant difference in the NAD-gluDH, nor in the proteolytic activity with BAPA. On the other hand, the other enzymes tested presented differences which ranged from about 3-fold for the aminopeptidase to nearly 100-fold for the NADP-gluDH. The electrophoretic behaviour of the latter was identical in all the stocks of both species, thus showing that the difference was only quantitative.
• 5.5. The three stocks of T. (H.) rangeli were more similar to some T. (Sch.) cruzi stocks (Tul 2) than the latter were to each other, thus emphasizing at a biochemical level the similarities between these two species.

     

Antigenic significance of a Trypanosoma rangeli sialidase

The Trypanosoma rangeli-secreted sialidase was purified by bovine submaxillary gland mucin-sepharose affinity chromatography. In immunoblotting analysis, antibodies raised against this molecule recognized polypeptides of 73 kDa in T. rangeli medium supernatant (TrSialr) and of 70 kDa in the cell lysates of T. rangeli (TrSials) and T. cruzi (TcSialL) epimastigotes. TrSialr, TrSials, and TcSialL were subjected to proteolytic cleavage with papain; the resultant peptide pattern displayed differences in the immunoblotting profiles. TrSials was purified by immunoprecipitation, and this protein band was recognized by sera from T. cruzi-infected chronic mice and Chagas' disease patients. In contrast, TrSialr was not recognized by these sera. The antibodies from the infected mice also recognized a band of 70 kDa present in the medium. These preliminary observations imply that the released and somatic sialidases are partially different molecules, with probably different biological roles. The related proteins recognized in T. rangeli and T. cruzi epimastigotes share many antigenic characteristics but have some structural differences, probably related to their function in the parasitic cell. On the basis of the strong antigenicity of TrSials, this molecule is proposed as the antigen for the detection of antibodies arising during T. cruzi infection.     

The taxonomic position of Chaetopeltis

The flagella-like but immobile pseudocilia of the green alga Chaetopeltis are described. Examination of the pseudocilia reveals a similarity to those previously described for other members of the Tetrasporales. The taxonomic position of Chaetopeltis, in relation to other members of the Tetrasporales, is shown to be in the family Chaetopeltidaceae.     

Action of Trypanosoma rangeli in infections with virulent Trypanosoma cruzi populations

In experimental murine infections with Trypanosoma rangeli it has been observed development immune response to Trypanosoma cruzi. The aim of the present work was to analyze the result of antigenic stimuli and the protective effect with T. rangeli in T. cruzi infections. Mice groups immunized with metacyclic trypomastigotes of T. rangeli (Choach -2V strain), derived from haemolymph and salivary gland and reinfected with T. cruzi virulent populations (Tulahuen strain, SA strain and Dm28c clone) from infected in vitro cells, showed decrease severity of disease outcomes, low parasitemia levels and 100% survival of all mice immunized, in comparison with groups infected only with T. cruzi populations, which demonstrated tissue affection, high parasitemia levels and the death of all animals. The above mentioned data contribute to understand the biological behaviour of T. cruzi and T. rangeli and their interaction with vertebrate host.     

Trypanosoma saimirii Rodhain, a junior synonym of Trypanosoma rangeli Tejera

In the present study, we used sodium dodecyl sulfate-polyacrylamide gel electrophoresis to compare polypeptides of trypanosomes isolated by hemoculture of squirrel monkeys displaying Trypanosoma saimirii blood trypomastigotes, with other trypanosomes that infect primates to evaluate the validity of T. saimirii. The polypeptide profiles of trypanosomes isolated directly from squirrel monkeys or after their passage in mice were identical to those of 3 standard strains of T. rangeli, but they were distinct from those of T. cruzi, T. conorhini, and T. minasense. These results strengthen previous morphological and biological findings by Rodhain on trypanosomes of the squirrel monkey and lead to the conclusion that T. saimirii is indeed a junior synonym of T. rangeli.     

Serine hydroxymethyltransferase activity in Trypanosoma cruzi, Trypanosoma rangeli and American Leishmania spp

Serine hydroxymethyltransferase (SHMT) was studied in several American trypanosomatids, Trypanosoma cruzi epimastigotes displaying, in contrast with T. rangeli, high enzymatic activity. Several Leishmania spp. members, including L. braziliensis, L. mexicana and L. garnhami promastigotes, under identical assay conditions, showed low enzymatic activity. The T. cruzi and leishmanial enzymes presented several different kinetic properties, and thus apparent Km for THF was 0.30 mM for the trypanosomal SHMT vs 0.60 mM for the leishmanial enzyme, while the apparent Km for serine was 0.40 mM for trypanosomal SHMT vs 0.15 mM for leishmanial enzyme. There were significant variations in the specific activity of SHMT between the several different trypanosomatids strains studied, but the meaning of these results is not clear because they showed no correlation either with taxonomy or infectivity.     

Revisiting Trypanosoma rangeli Transmission Involving Susceptible and Non-Susceptible Hosts

Trypanosoma rangeli infects several triatomine and mammal species in South America. Its transmission is known to occur when a healthy insect feeds on an infected mammal or when an infected insect bites a healthy mammal. In the present study we evaluated the classic way of T. rangeli transmission started by the bite of a single infected triatomine, as well as alternative ways of circulation of this parasite among invertebrate hosts. The number of metacyclic trypomastigotes eliminated from salivary glands during a blood meal was quantified for unfed and recently fed nymphs. The quantification showed that ~50,000 parasites can be liberated during a single blood meal. The transmission of T. rangeli from mice to R. prolixus was evaluated using infections started through the bite of a single infected nymph. The mice that served as the blood source for single infected nymphs showed a high percentage of infection and efficiently transmitted the infection to new insects. Parasites were recovered by xenodiagnosis in insects fed on mice with infections that lasted approximately four months. Hemolymphagy and co-feeding were tested to evaluate insect-insect T. rangeli transmission. T. rangeli was not transmitted during hemolymphagy. However, insects that had co-fed on mice with infected conspecifics exhibited infection rates of approximately 80%. Surprisingly, 16% of the recipient nymphs became infected when pigeons were used as hosts. Our results show that T. rangeli is efficiently transmitted between the evaluated hosts. Not only are the insect-mouse-insect transmission rates high, but parasites can also be transmitted between insects while co-feeding on a living host. We show for the first time that birds can be part of the T. rangeli transmission cycle as we proved that insect-insect transmission is feasible during a co-feeding on these hosts.     

Action of pyrazolopyrimidine derivatives on Trypanosoma rangeli culture forms

The capacity of 54 different pyrazolo(3,4-d)- or pyrazolo(4,3-d)pyrimidine derivatives to inhibit the multiplication of Trypanosoma rangeli culture forms was evaluated. Among pyrazolo(3,4-d)pyrimidines, 14 derivatives showed trypanostatic activity, 4-aminopyrazolo-(3,4-d)pyrimidine (APP) being the most active, with 4-hydroxypyrazolo(3,4-d)pyrimidine (HPP) lacking trypanostatic activity. 7-Hydroxy-3-beta-D-ribofuranosylpyrazolo(4,3-d)pyrimidine (FoB) was as active as 7-amino-3-beta-D-ribofuranosylpyrazolo(4,3-d)pyrimidine (FoA), both compounds being five-fold less inhibitory than APP. It can be concluded that, regarding T. rangeli, the chemical analogy to hypoxanthine or inosine of pyrazolo(3,4-d)- and pyrazolo(4,3-d)pyrimidine, respectively, is not absolutely critical, as different modifications on the heterocyclic ring did not abolish the inhibitory activity of these compounds.     

The evolutionary position of nematodes

Background  

The complete genomes of three animals have been sequenced by global research efforts: a nematode worm (Caenorhabditis elegans), an insect (Drosophila melanogaster), and a vertebrate (Homo sapiens). Remarkably, their relationships have yet to be clarified. The confusion concerns the enigmatic position of nematodes. Traditionally, nematodes have occupied a basal position, in part because they lack a true body cavity. However, the leading hypothesis now joins nematodes with arthropods in a molting clade, Ecdysozoa, based on data from several genes.     

Trypanosoma rangeli (Tejera, 1920): observations upon pleomorphism.

Meta-trypomastigotes of Trypanosoma rangeli Tejera, 1920, harvested from LIT medium, were inoculated i.p. or s.c. into 6, 16, and 26 g NMRI mice, these representing increasing degrees of immunological maturity. In all cases, similar pleomorphic patterns were observed. Four morphobiometrically differentiable types of trypanosome were encountered in an overlapping temporal sequence. These observations, taken in comparison with those on pleomorphism in this and other species of Trypanosoma by other workers, are consistent with the hypothesis that the pleomorphic types represent the natural development of the parasite, rather than the result of the immune response of the mammal host. Small, slender trypanosomes prevalent at the onset of the parasitemia either reinvade the tissue cells for relatively limited subsequent generations of tissue reproduction, or else differentiate toward the forms that are only capable of colonizing the insect vector.     

Purification and partial characterization of a cysteine proteinase from Trypanosoma rangeli

Abstract Epimastigotes of the American Trypanosome Trypanosoma rangeli contain a very low cysteine proteinase (CP) activity. The enzyme was purified to homogeneity by affinity chromatography on ConA-Sepharose and Cystatin-Sepharose. This CP had a similar apparent molecular mass and an identical N-terminal sequence (15 amino acids) as compared with cruzipain from Trypanosoma cruzi ; cross-reacted immunologically with the latter enzyme, it was inhibited by E-64 and TLCK, but not by PMSF, o-phenanthroline or Pepstatin, and was able to use the same substrates, although with different order of effectiveness and optimum pH.     

Trypanosoma rangeli sialidase: cloning, expression and similarity to T.cruzi trans-sialidase

Sialidases are hydrolytic enzymes present from virus to highereukaryotes, catalyzing the removal of sialic acid from glycoconjugates.Some protozoa Trypanosomatidae secrete high levels of sialidaseinto the medium. We have now purified the secreted sialidasefrom Trypanosoma rangeli Its N-terminal sequence reveals 100%identity with the corresponding region of the trans-sialidasefrom T.cruzi Trans-sialidase, although homologous to viral andbacterial sialidases, displays a novel sialyltransferase activityand is involved in host cell invasion. Several homologous trans-sialidase-likegenes were cloned from genomic DNA of T.rangeli, and groupedin three subfamilies. Active siali-dase-encoding genes werefound in one of them. The re-combinant sialidase shows similarproperties to those of the native enzyme, including undetectabletrans-sialidase activity. Nevertheless, it has an overall identityof 68.9% with the catalytic domain of T.cruzi trans-sialidase,increasing to 86.7% admitting conservative substitutions. Onlythree other eukaryotic sialidases have been previously cloned,none of them showing significant homology to trans-sialidase.The isolation of a highly similar sialidase is relevant to furtheridentify the molecular determinants allowing trans-sialidaseactivity. As a first approach, chimeric constructs between sialidaseand trans-sialidase were generated, one of them rendering asialidase with three times lower K_m than the natural enzyme. eukaryotic sialidase gene family glycosidase parasite sialic acid     

Trypanosoma rangeli Tejera, 1920. VIII. Response to reinfections in 2 mammals

Under experimental conditions, the course of the infection and the response to the reinfection by Trypanosoma rangeli in mice and Didelphis marsupialis, are studied. During the initial infection the mice show a relatively low parasitaemia and a short patent period. A scanty parasitaemia level of four days length, was observed following the first reinfection, being the mice resistant to new reinfections by T. rangeli. In opossums a lower parasitaemia and a longer patent period than that detected in mice, were observed during the initial infection. The response to reinfections in this mammal, was similar to that observed in mice. After reinfection with T. rangeli, haemagglutinant antibodies in immune-sera of both mice and opossums, were detected. The possible immune-response at the site of deposition against the metacyclic-forms of T. rangeli, and the action of circulating antibodies against the blood forms of the parasite, are speculated to explain the resistance of mice and opossums to the reinfection by T. rangeli.     

Reconciling evolutionary theory and taxonomic practice

The notion of evolution is a notion of change; yet, biologists customarily define each species as if it were a static class. One approach to this supposed disconnect between evolutionary theories and taxonomic practices would be to change those practices. Instead, the author claims this alleged disparity is a misreading. For the most part, it disappears under a proposed modified essentialist species concept involving unique species‐specific developmental suites. Each suite specific to a natural species is envisioned as a number of dispositional alternatives expressed distributively among the organisms in that species. There is support for this species concept in recent work in comparative genomics and developmental genetics. The concept is compatible with intraspecific variation and gradual evolution, and unifies practice and theory. It leads to an extended model of speciation and to an observational protocol for testing the concept and model.