Biomedical subjects

A Alcina

Publications and source records attributed to A Alcina.

26 records · Page 2Linked to original sources

PubMed1988

The detection of a spectrin-like protein in Trypanosoma cruzi with a polyclonal antibody.

A rabbit serum raised against sheep erythrocyte spectrin stained mainly the flagella of epimastigote forms of the parasitic protozoan Trypanosoma cruzi. In Western blots of T. cruzi proteins solubilized with Nonidet P-40 it recognized mainly a polypeptide doublet with an apparent molecular weight of about 240 kDa, while a pre-immune rabbit serum and a tubulin monoclonal antibody did not. The results are consistent with the idea that a spectrin-like protein may be involved in cytoskeleton-membrane interactions in flagella of T. cruzi.

Animals↗

PubMed1988

Effect of heterocyclic analogues of triphenylmethane dyes against Trypanosoma cruzi.

Several heterocyclic analogues of triphenylmethane dyes have been synthesized. Their in vitro activity has been evaluated using the epimastigote forms of Trypanosoma cruzi as an assay system. The malachite green and gentian violet dyes previously reported as trypanocidal agents were also tested for comparison. Among the compounds tested, the 2-benzothienyl-bis-(4,4'-dimethylaminophenyl) derivative proved to be the most interesting, because of its high selectivity in killing parasites. The ID50, defined as the concentration which produced 50% reduction in (3H) thymidine incorporation in DNA after 18 hours or in viable parasites after five days of incubation with the above compounds, was 0.2 ng ml-1 and less than 1 ng ml-1, respectively. The relative toxicity, measured by its effect on cultured human HeLa cells, was over 10,000-fold higher. By contrast, gentian violet only showed a ten-fold higher inhibitory effect for T. cruzi. The other derivatives synthesized were active in various degrees. According to these results, a structure-activity relationship for these compounds is proposed.

Animals↗

PubMed1988

Activity of P536, a UDP-glucose analog, against Trypanosoma cruzi.

P536, a UDP-glucose analog which was previously described as an antiviral agent (M. J. Camaraza, P. Fernández Resa, M. T. García López, F. G. de las Heras, P. P. Mendez-Castrillón, B. Alarcón, and L. Carrasco, J. Med. Chem. 28:40-46, 1985), has a potent and selective activity against the intracellular and extracellular stages of Trypanosoma cruzi in vitro. It had a 50% inhibitory concentration of less than 5 micrograms/ml for T. cruzi extracellular cultured forms (epimastigote) and of 25 micrograms/ml for T. cruzi intracellular forms (amastigote) growing inside J774G8 macrophagelike cells. In contrast, the 50% inhibitory concentration was 100 micrograms/ml or greater for cultured mammalian cells and 180 micrograms/ml for the proliferation of mouse spleen lymphocytes. Furthermore, the addition of P536 (50 micrograms/ml) to T. cruzi-infected J774G8 cells cured the infected macrophages, making them able to grow and function normally. Studies on the mechanism of action of this drug indicated that it inhibited incorporation of [35S]methionine, [3H]thymidine, [3H]mannose, [14C]-N-acetylglucosamine, and [3H]uridine into macromolecules by T. cruzi epimastigotes, the last being the most sensitive.

Animals↗

PubMed1987

A colorimetric assay based on cell viability for the indirect detection of intracellular replication and killing of Trypanosoma cruzi.

We have developed an 'in vitro' colorimetric assay for the detection of replication and/or destruction of the intracellular amastigote form of Trypanosoma cruzi. The assay can be applied to other intracellular parasites having lytic effects on the infected cells. The assay is based on the relationship between the content of the lysosomal enzyme hexosaminidase and the number of viable cells. The level of this enzyme can be detected by a simple and sensitive procedure in microtiter wells using a p-nitrophenol derivative as enzyme substrate and scanning the absorbance at 405 nm. Macrophages or other suitable host cells which support T. cruzi intracellular replication have detectable levels of this enzyme whereas the protozoan parasites do not. The assay exhibited a good inverse correlation between the number of amastigotes released and the amount of enzyme in the infected cultures. Furthermore, the method was used for the detection of macrophage-activating factors and gave results similar to those obtained by microscopical examination of the cells. The advantages of the procedure are objectivity, sensitivity and simplicity.

Animals↗

PubMed1987

Stimulation of the trypanocidal and endoribonuclease activities by the interferon induced (2'-5') oligoadenylates.

Interferon or 2'-5' oligoadenylates (2'-5' An) activated the microbicidal activity of primary cultures of rat glia cells and of the mouse macrophage transformed cell line J774 against infection by Trypanosoma cruzi. Pretreatment with gamma-interferon (gamma-IFN) or 2'-5' A3 of rat glia cells or direct addition of these compounds during the incubation with the parasite enhanced the uptake of metacyclic trypanosomes by the cells. Furthermore, glia cells treated with gamma-IFN or 2'-5' A3 were able to restrict the growth and to eventually destroy intracellular amastigotes. Bacterial lipopolysaccharide (LPS) synergized with gamma-IFN as well as with 2'-5' A3 and 2'-5' A4, but not with dephosphorylated 'core' molecules or ATP, to induce a partial trypanocidal activity in J774 cells. In addition, those treatments with gamma-IFN or 2'-5' A3 activated to a similar extent an endoribonuclease, which degraded ribosomal RNA, in rat glia cells, suggesting a role of this enzyme in the mechanism of the trypanocidal activity of gamma-IFN.

Adenine Nucleotides↗

PubMed1987

Activation by synergism between endotoxin and lymphokines of the mouse macrophage cell line J774 against infection by Trypanosoma cruzi.

The mouse macrophage cell line J774 was easily infected by T. cruzi epimastigotes which were transformed to amastigotes that multiplied inside the cells. Spleen-T-cells from T. cruzi immune mice stimulated with Concanavalin A or T. cruzi, but not with unrelated antigens, released lymphokines into the supernatants that when added to J774 cells were unable to induce complete trypanocidal activity, although they were able to delay the rate of infection by protecting the cells from being infected. Addition of bacterial lipopolysaccharide (LPS), although inactive by itself, acted synergistically with the supernatants in inducing complete trypanocidal activity without affecting the susceptibility of J774 cells to infection. Gamma-interferon (gamma-IFN) activity was detected in the supernatants, however, but was not solely responsible for the trypanocidal inducing activities, since: there was no correlation between the levels of gamma-IFN and macrophage activation; gamma-IFN alone was less effective than the supernatants alone; and two active fractions of 100,000-150,000 mol. wt and 30,000 mol. wt were separated by gel filtration chromatography of the lymphokine preparations. The latter, which showed the characteristics of gamma-IFN with respect to size, pH 2 sensitivity and antiviral activity, had some trypanocidal activity alone. However, the 100,000-150,000 mol. wt fraction was active only in the presence of LPS. Finally, this trypanocidal inducing activity of the supernatants was not due to the induction of synthesis of gamma-IFN by the J774 cells.

Animals↗

PubMed1986

A Trypanosoma cruzi monoclonal antibody that recognizes a superficial tubulin-like antigen.

A monoclonal antibody (MAB 10), obtained from mice infected with Trypanosoma cruzi, was found to recognize a superficial antigen in living or fixed parasites. It reacted more strongly with T. cruzi than with related parasites such as T. brucei and Leishmania. In immunoblots it recognized a single trypanosoma polypeptide and also brain tubulin, both of which had the same electrophoretic mobility. Further analysis suggested that the alpha-tubulin subunit contained the epitope recognized by MAB 10. These results suggest that a surface tubulin-like protein is present is T. cruzi.

Animals↗

PubMed1985

Suppressor factor of T-cell activation and decreased interleukin 2 activity in experimental African trypanosomiasis.

Spleen cells from Trypanosoma brucei-infected BALB/c mice were unable to respond to a T-cell mitogen, concanavalin A. Moreover, they were unable to produce detectable amounts of the growth factor required for T cell proliferation, interleukin 2. In addition, supernatants from 24-h in vitro cultures of these cells produced a slight but detectable suppressive activity of the interleukin 2-dependent proliferation of a T-cell line. Infected spleen cells also suppressed the response of T. brucei-immunized spleen cells as well as normal spleen cells to concanavalin A. However, a major difference was shown in the mechanism of the suppression in both systems. Suppression of normal spleen cells required cell-to-cell contact. In contrast, suppression of 30-day T. brucei-immune cells could be mediated by a soluble suppressor factor released by in vitro culture of infected spleen cells. This molecule had an apparent molecular weight of 18,000. Finally, similar suppression could be generated in 30-day T. brucei-immune spleen cells but not in normal cells, with living cells but not with extracts of T. brucei.

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