Biomedical subjects

C B Mello

Publications and source records attributed to C B Mello.

7 recordsLinked to original sources

PubMed1999

Studies on a haemolymph lectin isolated from Rhodnius prolixus and its interaction with Trypanosoma rangeli.

We demonstrated that in Rhodnius prolixus haemocyte monolayers, both Trypanosoma cruzi and Trypanosoma rangeli are capable of inducing haemocyte/parasite clump formation. We also purified, by one-step affinity chromatography, a haemolymph galactoside-binding lectin from R. prolixus which we believe could play an important role in the development of T. rangeli in the haemocoel of the insect vector. This lectin markedly enhanced the activation of clump formation by T. rangeli in R. prolixus haemocyte monolayers, with an increase in clump size and haemocyte aggregation. The haemolymph lectin also significantly affected the motilitity and survival of T. rangeli culture short forms, but not the long forms, when they were incubated in vitro. This molecule is also one of the few described in insects with agglutination activity independent of calcium ions. The partial N-terminal amino acid sequence of this lectin demonstrated similarity to a bacterial xylulose kinase and in preliminary experiments the purified haemolymph lectin phosphorylated a tyrosine kinase substrate in a dose-dependent manner. The possible role of this haemolymph lectin in the life cycle of T. rangeli is discussed.

Amino Acid Sequence↗

PubMed1999

Influence of brain and azadirachtin on Trypanosoma cruzi development in the vector, Rhodnius prolixus.

Studies on the effects of decapitation, head transplantation, azadirachtin, and ecdysone therapy on the ultrastructural organization of the midgut of Rhodnius prolixus, a vector of the protozoan Trypanosoma cruzi, show a distinct effect on the organization of the epithelial cells. When insects are decapitated or treated with azadirachtin, the ultrastructural organiza tion of these compartments changed significantly and drastically blocked the development of T. cruzi infection. In converse experiments, head transplantation or oral therapy with ecdysone significantly re versed the T. cruzi infectivity and reestablished the organization of the stomach and intestine in decapitated or azadirachtin-treated insects. These results indicat that a brain factor, possibly the prothoracicotropic hormone which stimulates ecdysteroid production on the prothoracic glands, may act directly or indirectly on both the midgut cell organiza tion and the intestinal microenvironment, interfering in the trypanosome survival and infection of the vector R. prolixus.

Animals↗

PubMed1996

Differential in vitro and in vivo behavior of three strains of Trypanosoma cruzi in the gut and hemolymph of Rhodnius prolixus.

A comparison was made of the agglutination and lysis of three strains of Trypanosoma cruzi in gut extracts and hemolymph of Rhodnius prolixus and the results obtained were correlated with the success or failure of the parasite strain to infect the digestive tube or to survive in the hemocel after inoculation. Both T. cruzi strains Dm28c and Cl urine 35 days after feeding with parasites. Concomitantly, both of these strains were agglutinated but not lysed by the crop extracts. In contrast, T. cruzi Y strain parasites rapidly disappeared from the gut and showed no agglutination, but some lysis, in the crop extract. Following inoculation into the hemocel, only the Cl strain survived at high levels and was also the only strain agglutinated significantly in the hemolymph. Both Dm28c and Y strains rapidly disappeared from the hemocel with the former parasite being removed more slowly than the latter, probably due to clearance by the cellular defenses. The rapid clearance of the Y strain was correlated with the presence of a high titer lysin in the hemolymph. Subsequent experiments using FITC-labeled lectins and FACS to probe the carbohydrates on the parasite surfaces showed significant differences between the three strains. Thus, only Dm28c was stained strongly by Arachis hypogea (PNA) lectin, indicating the presence of galactose/N-acetylgalactosamine residues, and Dm28c and Y strains by Phytolacca lectin for N-acetyl glucosamine moieties. Finally, the fact that, in contrast to Dm28c and Y, the Cl strain strongly interacted with Triticum vulgaris (WGA) but not with Phytolacca lectin may be due to the presence of N-acetyl neuraminic acid residues on these organisms. These surface carbohydrate differences may be correlated both to the behavior and agglutination variations between the three strains recorded in this work.

Agglutination Tests↗

PubMed1996

Trypanosoma cruzi and erythrocyte agglutinins: a comparative study of occurrence and properties in the gut and hemolymph of Rhodnius prolixus.

The activity of agglutinins found in the gut tissues and hemolymph of Rhodnius prolixus was tested using rabbit erythrocytes, Trypanosoma cruzi, or Trypanosoma rangeli as test particles. In addition, investigations were made of the influence of parasitic infection and insect diet on the agglutination titers. A range of physicochemical tests and carbohydrate-binding studies were performed and inhibitors were subsequently found for both the crop agglutinin (p-nitrophenol-derived sugars) and the hemolymph agglutinin (galactose-type sugars). As a result, affinity chromatography was utilized for an attempted purification of these agglutinins, and a one-step purification protocol for the R. prolixus hemolymph agglutinin has been developed. Preliminary results of some biological and physicochemical characteristics of this pure agglutinin are described. These results represent a starting point for future studies of lectin/parasite interaction in this reduviid-trypanosome model.

Animals↗

PubMed1995

Trypanosoma cruzi and Trypanosoma rangeli: interplay with hemolymph components of Rhodnius prolixus.

Studies were carried out on the course of infection of Trypanosoma cruzi (clone Dm28c) and Trypanosoma rangeli (clone San Agustin) and their interactions with hemolymph components of Rhodnius prolixus. These parasites when inoculated into the hemocoel of adult R. prolixus (i) had different courses of infection (T. rangeli had high rates of both multiplication and infection and T. cruzi had no division and disappeared soon from the hemolymph); (ii) induced high but no differential increases in lysozyme levels; (iii) failed to induce any other antibacterial activity; (iv) showed similar patterns of hemolymph agglutination activity for erythrocytes and parasites, although there was evidence of limited, unquantifiable, agglutination of T. cruzi; (v) elicited different hemocyte responses with only the T. rangeli infection resulting in significantly increased hemocyte counts; and (vi) did not induce trypanolytic activity. These experiments, unlike previous studies, also showed (i) an interaction of these trypanosomes with the prophenoloxidase-activating system [phenoloxidase (PO) production was spontaneously activated by both parasites but the number of T. cruzi in the hemolymph was directly correlated with PO levels] and (ii) that the elimination of T. cruzi also corresponded to the formation of nodules in the hemolymph. The significance of these results is discussed in relation to the hypothesis that T. rangeli but not T. cruzi has the ability to escape from and perhaps utilize the vector immune system in order to successfully colonize the R. prolixus hemolymph.

Animals↗

PubMed1994

Rhodnius prolixus: salivary antihemostatic components decrease with Trypanosoma rangeli infection.

Feeding behavior and some antihemostatic properties of the saliva of Rhodnius prolixus infected with Trypanosoma rangeli were studied and compared with those of uninfected controls. Insects with salivary gland infection pierced host skin more often and drew less blood and at a lower rate than controls when feeding on a rabbit. None of these differences was observed when feeding was performed through a membrane feeder. Salivary gland homogenates from infected insects, at 30 days after feeding/infection, had a significantly lower amount of total protein/salivary gland pair and less anticoagulant activity than controls. Also, infected salivary glands exhibited significantly reduced apyrase activities and reactive nitrogen groups when compared to controls. It is concluded that salivary infection of T. rangeli impairs the ability of the vector to locate blood vessels by affecting salivary antihemostatic properties, thus enhancing the possibility of intradermal inoculation of parasites into the mammalian host.

Animals↗

PubMed1989

In vitro cytotoxicity of Rhodnius prolixus hemolytic factor and mellitin towards different trypanosomatids.

Trypanosoma cruzi strain Y and clone Dm28c and other trypanosomatids were exposed to two lytic agents, Rhodnius prolixus hemolytic factor (RHF) and mellitin, in vitro. In both cases, the result was a significant decrease in the number of parasites after a 30-min treatment at 37 degrees C. RHF and mellitin had distinct activities on different strains and species of trypanosomatids. These observations suggest that RHF may be an important factor in selecting resistant strains of trypanosomes for development in the vector's gut.

Animals↗