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Biomedical subjects

H A Rangel

Publications and source records attributed to H A Rangel.

18 recordsLinked to original sources
PubMed1999

Lymphoid organ alterations enhanced by sub-lethal doses of coronaviruses in experimentally induced Trypanosoma cruzi infection in mice.

The effect of sub-lethal doses of coronaviruses on the course of disease in CBA mice experimentally infected with a mildly pathogenic strain of Trypanosoma cruzi was investigated. Mice were inoculated with either T. cruzi, 0.1 median lethal dose (LD50) of coronavirus (mouse hepatitis virus [MHV-3] or virus X), or both pathogens. Levels of parasitemia, mortality, and the extent of pathologic alterations in lymphoid organs were determined. Mice inoculated with T. cruzi had mild alterations in their lymphoid organs and survived infection. In contrast, mice inoculated with both pathogens died, and had significantly higher levels of parasitemia and profound alterations in lymphoid organs. These results indicate that the pathologic profile of T. cruzi infection can be profoundly altered by subclinical infection with coronaviruses.

Animals↗
PubMed1998

Immunodepression induced by Trypanosoma cruzi and mouse hepatitis virus type 3 is associated with thymus apoptosis.

Trypanosoma cruzi-infected mice show disturbance in the peripheral immune system such as polyclonal lymphocyte activation, autoantibody production, and immunosuppression of T lymphocytes. Previous observations in our laboratory showed that some stocks of T. cruzi can be contaminated with mouse hepatitis virus type 3 (MHV-3). Literature has shown that MHV-3 infection induces immunologic disorders characterized by thymic involution with marked cell depletion. However, the effects of interactions between MHV-3 and the parasite on the immune system are not well understood. In the present study specific-pathogen-free CBA mice were inoculated with MHV-3, alone or associated with different stocks of T. cruzi. Concurrent murine virus infection resulted in increased pathogenicity of T. cruzi infection shown by profound thymic atrophy; loss of cortical thymocytes; depletion of Thy1.2+, CD4+, and CD8+ cells; enhancement of in situ labeling of nuclear DNA fragmentation; and eventually, death of the animals. Such lines of evidence show that the mechanism underlying this thymic atrophy is associated with apoptosis. These results also suggest that MHV-3 can account for the increased immunosuppression observed during experimental infection with the parasite.

Animals↗
PubMed1992

Anti-Trypanosoma-cruzi-proteinase antibodies and immunoprotection in experimental Chagas' disease.

To verify whether anti-Trypanosoma-cruzi-proteinase antibodies are able to play a role in the development of Chagas' disease, CBA/J and C57BL/6 mice were immunized with purified proteinase fractions: antibody production was studied and passive immunization experiments were carried out. No significant differences were observed in the titre, isotype composition and specificity of the antibodies produced by the mouse strains. Immune sera produced in one strain was able to protect mice of both strains, provided that the challenge did not exceed the number of parasites corresponding to 30-fold the LD50. The data presented suggest that anti-proteinase antibodies may play a role in immunoprotection.

Animals↗
PubMed1991

Trypanosoma cruzi: early resistance induced by culture-derived trypomastigotes.

Previous observations in this laboratory showed that injection of culture-derived trypomastigotes (CT), in CBA/J mice, induced an early increased resistance that was detected 24-72 hr after antigen injection and permitted mice to survive a challenge of 10(5) blood trypomastigotes (BT) corresponding to 2000 LD50%. Present experiments were conducted to determine the optimal conditions for inducing this early resistance and to investigate the early morphological changes which occurred in blood and lymphoid organs of mice infected with either BT or CT. Among nine antigens tested, only living CT showed a protective effect permitting most of mice to survive 30 days after BT challenge, while control mice injected with PBS or other antigens died at 10 +/- 1 days. A dose-response relationship was seen when different doses of CT were tested, higher doses of CT inducing higher survival and lower parasitemia. Injection of CT by either an im or ip route induced similar degrees of resistance but significantly different results were obtained when mice were challenged by using ip or im routes. Higher parasitemia and lower survival were always obtained when animals were challenged by the ip route. Within 72 hr, mice injected with BT presented a lymphopenia which reached a maximum at 48 hr, a depletion of thymic cortical zone, and splenomegaly with hyperplasia of the white pulp and congestion of the red pulp. No gross alterations were observed in animals infected with CT. Overall data suggest that the early resistance is a specifically induced phenomenon and that BT and CT induce different early reactions in the CBA/J lymphoid organs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Immunological comparison of hemorrhagic principles present in venoms of the Crotalinae and Viperinae subfamilies.

Antibodies were raised against hemorrhagic factors HF1, HF2 and HF3 isolated from the venom of Bothrops jararaca and NHFa,b from the venom of Bothrops neuwiedi. Crude venoms of different species of snakes were assayed with the rabbit antisera specific for the hemorrhagic factors. Results of immunodiffusion, neutralization of hemorrhagic activity and micro-complement fixation indicated that there is an immunological relationship between the venom hemorrhagic components of the Bothrops species and those of other species of the Crotalinae subfamily. The factors of Bothrops species seem to be structurally similar. The hemorrhagic proteins from the venoms of Lachesis, North American Crotalus, Asian Trimeresurus and Agkistrodon species show some resemblance to the Bothrops factors. The venom hemorrhagic principles from snakes of the Viperinae subfamily (Bitis and Vipera species) might have few epitopes similar to those of Bothrops species as the only relation shown was the partial neutralization by the immune sera.

Animals↗
PubMed1983

Trypanosoma cruzi: surface antigenic determinants.

A fraction (FAd) capable of inhibiting specific agglutination reactions of anti-epimastigote sera (anti-LE) was obtained by extracting the sediment of lyophilized epimastigote lysates (LE) with 0.05 M phosphate buffered saline, at 37 degrees C for 1 h. These conditions favored the action of parasite proteinase whose presence was detected by tandem-crossed immunoelectrophoresis experiments. As expected from the proteinase properties, the addition of 2-mercaptoethanol or sodium iodoacetate to the extracting solution resulted, respectively, in either increased or decreased amounts of protein in the resulting FAd. FAd components could be precipitated by the addition of Concanavalin A, methylated albumins or 0.1 N HCl. This fraction presented a single component when subjected to electrophoresis in 1% agarose gel with an electrophoretic mobility 1.2 times higher than that of human albumin. FAd component(s) were unable to penetrate 15% polycrylamide gel matrix unless 1% SDS was used. Under this condition four glycopeptide components, with Rm of 0.5, 0.55, 0.6 and 0.86, were detected. The antigenic determinants present in FAd resisted heating at 100 degrees C for 30 min and the prolonged action of pronase. However, these determinants were completely destroyed by the action of 25 mM sodium periodate, thus suggesting polysaccharide characteristics. Immunization of rabbits with FAd induced the production of antibodies that were unable to precipitate with either FAd or with parasite proteinase. These antibodies exhibited positive agglutination reactions with epimastigote forms and positive immunofluorescence and immunoperoxidase reactions with trypomastigote and amastigote forms of the different strains tested. FAd was able to inhibit these reactions as well as those obtained with anti-LE and anti-FA immune sera, whereas purified proteinase was unable to inhibit any of these reactions.

Animals↗
PubMed1981

Detection of a proteinase common to epimastigote, trypomastigote and amastigote of different strains of Trypanosoma cruzi.

Trypanosoma cruzi epimastigote lysates presented proteolytic activity both at pH 7.0 (Km = 2.5 mg casein/ml, Km = 12.2 mg hemoglobin/ml) and at pH 3.0 (Km = 2.5 mg hemoglobin/ml). A proteinase was isolated from these lysates by using three different steps: 1) Precipitation at -20 degrees C, pH 4.5, with 80% acetone; 2) Sephadex G200 chromatography and 3)Affinity chromatography on columns of Sepharose 4B coupled to p-aminophenylmercuri-acetate. The isolated proteinase, which is probably an SH-dependent enzyme, was able to hydrolyze hemoglobin at pH 3.0 and both casein and hemoglobin at pH 7., but was unable to hydrolyze the esterase synthetic substrate tested. A single enzyme of molecular weight 60,000 could be detected in purified preparations when analysed by disc gel electrophoresis, crossed immunoelectrophoresis, SDS-polyacrylamide gel electrophoresis and Sephadex chromatography. Antibodies induced by the purified proteinase, shown to be specific for proteinase molecules by line immunoelectrophoresis experiments, reacted with epimastigota of the Y strain and with trypomastigota and amastigota of five different strains tested. Electron microscopy observations of peroxidase labeled preparations indicated that the proteinase could be found at the surface of different forms of the parasite.

Animals↗
PubMed1980

Surface antigenic determinant of epimastigote forms common to trypomastigote and amastigote forms of different strains of Trypanosoma cruzi.

A fraction (FA) has been isolated from the sediment obtained from Trypanosoma cruzi of epimastigote lysates centrifuged at 1500 x g, for 30 min. This fraction, obtained by extracting sediments, for 10 min, with ice-cold 0.1 N NaOH, exhibited a single component, a glycoprotein, when analysed by electrophoresis in 1% agarose gel and presented a single faint precipitation line in immunoelectrophoresis experiments. FA components were unable to penetrate polyacrylamide gel matrix, even when 1% SDS 4% polyacrylamide gels were used, unless previously hydrolyzed by parasite proteinase. Under this condition FA preparations presented at least four glycoproteins components as detected by electrophoresis in 1% SDS 15% polyacrylamide gels. FA obtained from Y strain was able to inhibit agglutination reactions between anti-epimastigote sera and epimastigote of either Y or Nic strains. Anti-FA antibodies, elicited in 4 out of 12 rabbits inoculated with this fraction, gave positive immunofluorescence and immunoperoxidase reactions with blood trypomastigota and tissue amastigota, obtained from mice infected with any of 6 different strains of T. cruzi. These reactions which were inhibited by FA preparations were completely abolished if antisera were absorbed with living epimastigota of Y or Nic strains.

Agglutination Tests↗
PubMed1980

A fraction (FAd) from Trypanosoma cruzi epimastigotes depresses the immune response in mice.

The primary immune response to SRBC in BALB/c mice was depressed when they were injected with a fraction (FAd) obtained from Trypanosoma cruzi epimastigotes grown in LIT medium. Plaque-forming cell (PFC) number was 50% less than controls when FAd was injected i.v. 15 min before antigen in doses ranging from 70 microgram up to 400 microgram of protein. Similar depression was observed when 100 microgram FAd was injected up to 6 h before antigen. There was no shift in the peak response to SRBC, neither was depression detected, when a total of 100 microgram FAd protein was given in 20 microgram amounts twice a day before immunization. Mice injected with FAd fraction only showed no increase in background PFC. Both secondary IgM and secondary IgG PFC were depressed when FAd was given before the boosting injection. However, only IgG PFC were depressed when FAd was injected before the priming dose. The delayed-type hypersensitivity reaction to DNFB was depressed when animals were injected either during the 3 days after sensitization or with a single dose of 100 microgram of protein of FAd on day of challenge. Bone marrow colony-forming units in spleens of mice injected with FAd were depressed and nodules in the treated animals were smaller than in controls. We conclude that FAd affects humoral and cell-mediated immune responses by interfering with cell division at some stage of the cell cycle.

Animals↗
PubMed1978

Swiss and inbred mice in the infant mouse test for the assay of Escherichia coli thermostable enterotoxin.

Swiss and inbred mice (C3H, ASn, B10A, and C57) were used to assay different thermostable enterotoxins prepared from Escherichia coli strains 3 (human), E57 (swine), B41 (cattle), and S13 (sheep). All strains of mice detected enterotoxins, but some reacted better to a given thermostable enterotoxin preparation than other inbred strains. Since the results obtained with Swiss mice were more consistent than with inbred mice, the former are apparently more suitable in the infant mouse test.

Analysis of Variance↗
PubMedDate not supplied

Isolation and characterization of partially purified leptospiral antigens.

The methanol extract of Leptospira interrogans serovar canicola was purified by precipitation with acetone or acetone and chloroform. The antigenicity of the antigen was not altered by heating or treatment with pepsin and pronase. However the antigenicity was lost when the antigen was treated with periodic acid. Chemical analysis revealed the presence of 40% carbohydrate (22% methylpentose, 28% hexoses), 4% protein, 20% lipid and 2.7% phosphate. The complement fixation test with sera from patients with leptospirosis agreed with the microscopic agglutination reaction.

Agglutination Tests↗
PubMedDate not supplied

The use of 4,4'-biphenylbisdiazonium fluoroborate as a coupling agent for passive haemolysis tests.

The possibility of use a stable diazonium compound, to replace bisdiazotized benzidin (BDB) for conjugating antigens to red blood cells was investigated. Five different batches of 4,4'-biphenylbisdiazonium fluoroborate (BDF) were prepared and tested in conjugation experiments. The sensitivity to specific lysis of red cells coated with different antigens (EG cells) was assayed by both direct and indirect passive haemolysis tests. Optimal conditions for the preparation of EG cells with different protein antigens were established. With the exception of the concentration of the bifunctional reagent, these conditions were similar to those previously reported for BDB. The antibody content of different anti-protein sera could be determined, with a 10 % error, by using EG cells prepared under optimal conditions in indirect passive haemolysis tests. The amount of antibody detected by this method varied from 7 to 12 ng N Ab/ml, depending upon the nature of the antigen fixed to red cell. The content of BSA in dilute solutions could be estimated by the specific inhibition of the indirect passive haemolysis tests. Testing different samples of BDF maintained at different conditions showed that the compound could be kept at room temperature, during the least four years, without appreciable loss of the conjugating properties, provided it was kept in the dry state and in the dark.

Animals↗