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Biomedical subjects

A Osuna

Publications and source records attributed to A Osuna.

At least 73 records · Page 4Linked to original sources
PubMed1996

Inhibition of superoxide dismutase from Ascaris suum by benzimidazoles and synthesized pyrimidine and glycine derivatives.

Copper-zinc superoxide dismutase was purified from Ascaris suum (Nematoda). Four benzimidazole derivatives, six recently synthesized pyrimidine derivatives and eleven recently synthesized glycine derivatives were shown to inhibit: (1) purified extracts of A. suum superoxide dismutase; (2) superoxide dismutase from host liver, and (3) purified extracts of superoxide dismutase from living A. suum incubated in the presence of these drugs. Thiabendazole compounds, with a documented effect against helminth parasites, were found to affect the superoxide dismutase. The inhibitory effects of some pyrimidine and glycine derivatives were higher than those of benzimidazoles, and the pyrimidine compounds failed to inhibit the host's enzyme. These derivatives are candidate anthelmintics, acting as inhibitors of certain metalloenzymes in parasites.

Analysis of Variance↗
PubMed1996

Effects of methimazole in the early and established phases of NG-nitro-L-arginine methyl ester hypertension.

In the present study we evaluated the effects of methimazole, an antithyroid drug, on blood pressure and other variables in the early and established phases of hypertension induced by the inhibition of nitric oxide synthesis with the oral administration of NG-nitro-L-arginine methyl ester (L-NAME), 75 mg/100 ml in the drinking water. Moreover, we also evaluated the acute pressor effect of L-NAME on systemic blood pressure in control and rats treated chronically with methimazole, administered via drinking water (30 mg/100 ml). Oral administration of methimazole maintained the blood pressure of L-NAME-treated rats at normal levels 25 days after induction of hypertension. However, after 25 days of methimazole treatment in rats made hypertensive with L-NAME (for 25 days), high blood pressure was similar in methimazole-treated and non-treated L-NAME rats, despite the fact that a hypothyroid state had been achieved in the methimazole-treated rats. Acute intravenous injection of L-NAME caused a similar increase in mean arterial pressure in control and methimazole-treated rats at the lowest dose; however, smaller pressor responses were observed with increasing doses in hypothyroid rats. These results clearly demonstrate that hypothyroidism induced by methimazole prevents, but does not reverse, L-NAME hypertension and reduces the acute pressor responsiveness to L-NAME administration.

Administration, Oral↗
PubMed1996

In vitro activity and biochemical effectiveness of new organometallic complexes of osmium(III) against Leishmania donovani and Trypanosoma cruzi.

In the present paper, the in vitro activities of 10 osmium(III) complexes with [OSIII(L)] degrees structure against promastigote forms of Leishmania donovani and epimastigote forms of Trypanosoma cruzi haven been assayed. The complexes OSIII-2,4dinitroimidazole dithiocarbamate, OSIII-4-nitroimidazole dithiocarbamate, OSIII-benznidazole dithiocarbamate and OSIII-2-amino-6-Br-benzothiazole dithiocarbamate induced high percentages of growth inhibition in the parasites. The four compounds showed moderate cell toxicity. The inhibitory effects of these complexes on macromolecule synthesis have been evaluated using [3H]-thymidine, [3H]-uridine and [3H]-leucine incorporation. These metal-drug complexes clearly inhibit the DNA, RNA and protein synthesis, as well as the enzymatic activities of succinate dehydrogenase, malate dehydrogenase and pyruvate kinase.

Animals↗
PubMed1995

Metabolic studies by 1H NMR of different forms of Trypanosoma cruzi as obtained by 'in vitro' culture.

By culturing Trypanosoma cruzi epimastigotes in modified Grace's medium with 10% foetal bovine serum, a significant quantity of metacyclic forms could be obtained. Transformation was observed after 8 days of culture, with metacyclic forms reaching 75%. Cultured Vero cells were infected with metacyclic forms and maintained until free-amastigote forms were obtained. Additionally, amastigote-like forms could be obtained by subjecting metacyclic cultures to heat shock. Parasites were grown with glucose as the major carbon source. The metabolites produced and excreted during culture were identified by difference proton nuclear magnetic resonance spectroscopy and quantified by enzymatic methods. The final products of glucose catabolism differed not only quantitatively but also qualitatively for the three major life-cycle stages of T. cruzi. The end products of metabolism produced by epimastigote forms were mainly acetate and pyruvate and, to a lesser extend, L-alanine and ethanol. Differences between epimastigotes and metacyclic forms were only quantitative. However, free amastigotes as well as amastigote-like forms, excreted acetate, glycerol, and pyruvate and to a lesser extent succinate, but no L-alanine or ethanol.

Animals↗
PubMed1995

Leishmania donovani: in vitro culture and [1H] NMR characterization of amastigote-like forms.

When Leishmania donovani promastigote forms, were cultured in TC-199 medium at 28 degrees C and subsequently incubated at 38 degrees C, they turned into aflagellate (amastigote-like) forms. A return of the incubation-culture temperature to 28 degrees C these amastigote-like forms to revert to promastigotes. The amastigotes obtained by heat-shock, were viable and retained antigenic capacity being recognized by the sera of naturally infected patients. These forms, remained also capable of multiplying inside the J-774A.1 macrophages. When the amastigote-like forms are kept in culture at 38 degrees C retained their rounded appearance and their biological characteristics for more than 3 months subculturing every 6 days. These amastigote-like forms, when used for subcultures at 28 degrees C, transformed into promastigotes capable of multiplying as flagellate forms. The amastigote-like forms obtained in vitro can be used in biochemical studies related to chemotherapy and immunology studies, as part of an effort to combat this parasite. The end-products of of glycolysis were studied in both the amastigote-like and promastigote forms of L. donovani, by proton magnetic resonance analysis of the culture media. Alanine, succinate, and acetate, were predominant, and to a lesser extent pyruvate, glycine and D-lactate. Our results suggest that both forms of Leishmania use different biochemical strategies to obtain their energy.

Animals↗
PubMed1995

Isolation, in vitro culture, ultrastructure study, and characterization by lectin-agglutination tests of Phytomonas isolated from tomatoes (Lycopersicon esculentum) and cherimoyas (Anona cherimolia) in southeastern Spain.

Plants of Lycopersicon esculentum (grown in greenhouses) and Anona cherimolia cultivated in southeastern Spain were examined for the presence of trypanosomatid flagellates. Kinetoplastid protozoa were found in the fruits but not in the phloem or other plant tissues. Parasites were detected from the onset of fruiting. Isolates were detected from the onset of fruiting. Isolates were adapted to in vitro culturing in monophase media. The form and the structural organization was studied by scanning and transmission electron microscopy. The parasites showed an ultrastructural pattern similar to that of other species of the genus Phytomonas. In tomatoes experimentally inoculated with flagellates cultivated in vitro, we observed that the parasites did not lose their infectious capacity. Three strains of trypanosomatids of the genus Phytomonas, isolated from different species of Euphorbia (E. characias and E. hyssopifolia) and from Cocos nucifera, were compared with our isolates by lectin-agglutination tests. Our isolates were different from the two strains isolated from Euphorbia, but with this technique we could not differentiate our isolates from those of the coconut, nor could we differentiate between the isolates, their ultrastructural similarity together with their similar behavior in the lectin-agglutination test suggesting that these isolates have a common origin.

Agglutination Tests↗
PubMed1995

Changes in T-cell subpopulations in mice during prolonged experimental secondary infection with Echinococcus granulosus.

Balb/c mice were infected intraperitoneally with protoscoleces of Echinococcus granulosus. After 15 months of infection, and by means of flow cytometry, the expression of T-cell markers CD3, CD4, and CD8 on T cells from peripheral blood, spleen, and thymus was analyzed and compared with that of age-matched controls. Infected mice had higher percentages of CD3+, and CD4+ cells in peripheral blood, and higher percentages of CD8+ cells in the spleen, when compared with control mice. CD4+ and CD8+ cells in peripheral blood and CD8+ cells in thymus also showed higher percentages of expression of interleukin-2 receptor. The results infer a role for interleukin-2 in experimental secondary echinococcosis.

Animals↗
PubMed1995

A protein secreted by Trypanosoma cruzi capable of inducing the entry of inert particles into HeLa cells.

Trypanosoma cruzi requires an intracellular environment to multiply within its mammalian host. We describe the purification and some properties of a protein secreted exclusively by the metacyclic (infective) forms of the parasite. This permeabilizing protein (relative molecular mass 64,000) was secreted under our experimental conditions only when the parasites interacted with HeLa cells, HeLa membranes, or wheat-germ lectin. The protein is thermostable, and its biological activity is inhibited by formaldehyde but not by ethanol or acetone. At low concentrations and over short treatment times, this protein acts as a permeabilizer and induces endocytosis. No significant protease or neuraminidase activity was found. When adsorbed onto bentonite particles and incubated in the presence of non-phagocytic cells the protein facilitated the penetration of the particles into the cells. Immune serum directed against the protein neutralized its cytotoxic action and reduced the rate of penetration of metacyclic forms into both macrophages and non-phagocytic cells. Our results suggest that the protein secreted by the parasite plays a key role in the penetration of its infective form into the host cell.

Animals↗
PubMed1994

Copper-zinc superoxide dismutase from Ascaris suum (Nematoda): purification and characterization.

Copper-zinc superoxide dismutase from Ascaris suum (Nematoda) was purified in a new, more efficient, and faster manner. The process included differential centrifugation, fractionation with ammonium sulfate, and sodium dodecyl sulfate-polyacrylamide electrophoresis, yielding a 340-fold purification (specific activity of 47 units/mg). Optimal storage conditions, optimal pH range, thermostability, molecular weight and ultraviolet-visible absorption spectrum of the enzyme are described, and a new enzymatic model for pharmacological screening is suggested.

Ammonium Sulfate↗
PubMed1993

Ultrastructural study of Cryptosporidium development in Madin-Darby canine kidney cells.

Transmission electron microscope studies have been made into phases of the life cycle of a bovine isolate of Cryptosporidium cultured in vitro on Madin-Darby canine kidney cells. The cytoplasm of parasitized cells was noticeably altered, including marked vacuolization and the appearance of membrane structures close to the developing parasites. These changes suggest that the protozoan may release cytopathogenic factors.

Animals↗
PubMed1993

The invasion mechanism of the metacyclic forms of Trypanosoma cruzi in nonphagocytic host cells.

The invasion process of metacyclic forms of T. cruzi into HeLa cells was investigated with particular emphasis on the role of the cytoskeleton in both cells. The parasite attaches itself to the host-cell membrane and induces the formation of an endocytic vacuole, through which it penetrates into the cell by capping mechanism. The process appears to be reciprocal in that the host cell actively cooperates in the parasite's invasion. A statistically significant reduction in parasitization rates was observed when either the HeLa host cells or the parasite cells were pretreated with Cytochalasin B or Latrunculin B. This effect was even greater when the drugs were added directly to the assay medium. As these two compounds act directly on the actin microfilaments of the cytoskeleton of both T. cruzi and HeLa cells, it would seem that the cytoskeleton of both organisms plays an essential role in the internalization mechanism of the metacyclic forms into nonphagocytic host cells.

Animals↗
PubMed1993

In vitro action of new organometallic compounds against Trypanosomatidae protozoa.

The effects of 10 newly synthesized organometallic rhodium complexes (5 of Rh(I), 4 of Rh(III) and one of Rh(IV) complex salt) and 2 antimony (III) complexes against epimastigote forms of Trypanosoma cruzi and promastigote forms of Leishmania donovani have been studied in vitro. Of the 10 rhodium complexes tested three proved 100% efficient in inhibiting the growth of the epimastigote forms of T. cruzi while only one worked against the promastigote forms of L. donovani. The two antimony complexes inhibited the growth of L. donovani totally and were fairly successful against T. cruzi.

Animals↗
PubMed1993

Dose-dependent effects of hydatid fluid toxins from Echinococcus granulosus on mouse peritoneal macrophages.

Hydatid fluid (HF) from hydatid cysts of the cestode Echinococcus granulosus inhibited the phagocytosis of bacteria and yeast cells by host macrophages in vitro. Different assays were used to study the dose-dependent effect of partially purified HF toxins on peritoneal macrophages (PM phi) of the mouse. Trypan blue exclusion, as well as measuring the specific release of lactate dehydrogenase activity and 51Cr release of 51Cr-labelled PM phi, showed that incubation with HF toxins lead to the lysis of the target cells. By measuring the effect of the toxins on the reduction of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide by PM phi, and by experimental labelling using [3H]-uridine, a decrease in metabolic activity was seen. However, at non-lytic concentrations, the PM phi showed a peak of metabolic activity. The observations of the effects on macrophages by parasite-derived toxins may be related to a mechanism by which the parasite survives within an immunized host.

Animals↗
PubMed1992

In vitro multiplication of Cryptosporidium parvum in mouse peritoneal macrophages.

Cryptosporidium parvum of bovine origin was developed in vitro in unsensitized mouse peritoneal macrophages. Macrophages growing in RPMI medium were infected with sporozoites or with oocysts, and after staining infections were studied by light microscopy. A high parasitic index was obtained with multiple infections occurring commonly. This is a simple method for the study of Cryptosporidium biology, and for in vitro assays of pharmacological activity.

Animals↗
PubMed1992

Comparative cytotoxicity of secondary hydatid cysts, protoscoleces, and in vitro developed microcysts of Echinococcus granulosus.

Infection with the metacestode of Echinococcus granulosus is characterized by a concomitant immunity. Survival of established and developing hydatid cysts in the intermediate host implies a mechanism to modulate its immunological reactions. In order to investigate this mechanism, secondary hydatid cysts were isolated from intraperitoneally infected laboratory white mice (strain NMRI) 12 months p.i. A number of hydatid cysts were freed from the surrounding host adventitial tissue. Monolayer cultures of non-stimulated peritoneal macrophages of NMRI mice were prepared and incubated in the presence of the hydatid cysts. By means of a trypan blue exclusion test and by measuring the incorporation of tritium labelled uridine, it was found that the presence of hydatid cysts reduced the viability of the macrophages in vitro. Toxic substances are probably secreted since the medium of cultured hydatid cysts also displayed cytotoxic activity. Hydatid cysts with adventitia, as well as culture medium of those cysts, were less toxic. When toxins, partially purified from hydatid cyst fluid, were previously incubated on a collagen coated surface, a reduced level of toxicity was found, suggesting that collagen of the host adventitia may play a role in controlling the liberation of toxins by the hydatid cyst. Virtually no toxicity was exerted by protoscoleces or by the medium of cultured protoscoleces, in contrast to in vitro vesiculated protoscoleces (so called microcysts). The results reveal a novel feature of hydatid cysts that may play a role in the survival of the parasite in the immunized host.

Animals↗