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Biomedical subjects

A Osuna

Publications and source records attributed to A Osuna.

At least 91 records · Page 5Linked to original sources
PubMed1992

Superoxide dismutase from Trichuris ovis--inhibition by benzimidazoles and pyrimidine derivatives.

Three superoxide dismutase isoenzymes of different cellular location were detected in an homogenate of Trichuris ovis. Each of these molecular forms was purified by differential centrifugation and precipitation with ammonium sulphate, followed by chromatography on DEAE-cellulose and Sephadex G-75 columns. The activity levels of the two molecular forms detected in the mitochondrial (one cyanide sensitive Cu-Zn-SOD and the other cyanide insensitive Mn-SOD) were higher than that of the superoxide dismutase detected in the cytoplasmic fraction (cyanide sensitive Cu-Zn-SOD). All molecular forms present evident differences to the SODs contained in the host liver. Molecular mass and some of the physical and chemical properties of the enzyme was determined for all three molecular forms. An inhibitory effect on the SOD of the parasite an the host was detected with a series of compounds, some of which markedly inhibited parasite enzyme but not host enzyme.

Animals↗
PubMed1992

[The unique image of Luis Razetti].

The author highlights the role played by Luis Razetti (1864-1932) in the "Renaissance of the Venezuelan Medicine", because of his condition of qualified professional and significant personality, defining him as "excellent scientific". Finally he presented him as a historical case to confront the dilemma specialized investigator - socially significant scientific and he concludes that his contributions to the formation of a scientific attitude is highly important.

History, 19th Century↗
PubMed1991

Phloretin and citrate promote the differentiation rate from epimastigote to metacyclic forms of Trypanosoma cruzi.

We have investigated the effects of the metabolic inhibitors, phloretin, 2-deoxy-D-glucose, maleate and trans-aconitate, as well as two intermediates of the tricarboxylic-acid cycle, acetate and citrate, on the growth and metacyclogenesis of Trypanosoma cruzi. 0.1 mM phloretin increased the percentage of metacyclic forms about 2.7-fold without affecting growth rate, whereas the other inhibitors had no apparent effect on either growth or differentiation rates. The addition of 5 mM citrate stimulated differentiation by about 2.6-fold. When either 10 mM citrate or 10 mM acetate were added, on the other hand, both the growth and differentiation rates were severely inhibited.

Acetates↗
PubMed1991

[Gabriel Trompiz and the institutionalization of science in Venezuela].

A testimonial to Dr. Trompiz, owing to the first lustrum of his death (August 23th, 1895). He was born in Falcon State (1907), graduated as medical doctor at UCV (1932) and postgraduated in Germany and Spain. Several analyses are made in order to consider D'Trompiz' position on the poor situation of science in Venezuela: 1) The historical comparison of science between Europe and Latin America; 2) The work presented by Garcia Gallo in the UNESCO Conference (Chile, 1965); 3) The H. Jaguaribe's work in CORDIPLAN (1974); 4) The Santis' evaluation on scientific investigation in our country.

History, 20th Century↗
PubMed1991

The immunohomeostatic role of hydatid cyst toxins (Echinococcus granulosus).

It is obvious that during the evolution of a host-parasite relationship, in which one animal is needing the other, while the latter is trying to expel or destroy the former, both partners tend to reach an equilibrium. In many cases they are still far off, but in hydatidosis (Echinococcus granulosus) it would appear that a lot has been achieved. As the near equilibrium is mainly related to the state of the immunological relationship, it is in fact a case of immunohomeostasis. The immunological reactions of the host involve both humoral and cellular phenomena. The nature of the humoral response varies greatly according to host species, parasite strain and several factors of the infection and analysis procedures. The cell-mediated defense mechanism involves various types of cells, but activated macrophages appear to be most important. With regards to the modes of immunoevasion, attention is paid to the barrier role of the laminated layer, the inactivation of complement and the interference with the activities of host immune cells. The role of toxic substances released by protoscoleces and cysts is especially emphasized. The toxins appear extremely vulnerable to host macrophages and play a very important role in the establishment of a hydatid cyst. However, they have only a local influence and do not jeopardize the development of concomitant immunity. Observations in experimental secondary echinococcosis led to the conclusion that the establishment of a hydatid cyst depends on the speed of the parasite's toxic effect versus the host immunological reaction. Survival of the parasite is based on the continued balancing effects of both.

Animals↗
PubMed1990

Differential energetic metabolism during Trypanosoma cruzi differentiation. II. Hexokinase, phosphofructokinase and pyruvate kinase.

The activities of hexokinase (ATP:hexose-6-phosphate transferase, E.C. 2.7.1.1), phosphofructokinase (ATP:fructose-6-phosphate 1-phosphotransferase, E.C.2.7.1.11) and pyruvate kinase (ATP:pyruvate transferase, E.C. 2.7.1.40), and their kinetic behaviour in two morphological forms of Trypanosoma cruzi (epimastigotes and metacyclic trypomastigotes) have been studied. The kinetic responses of the three enzymes to their respective substrates were normalized to hyperbolic forms on a velocity versus substrate concentration plots. Hexokinase and phosphofructokinase showed a higher activity in epimastigotes than in metacyclics, whereas pyruvate kinase had similar activity in both forms of the parasite. The specific activity of hexokinase from epimastigotes was 102.00 mUnits/mg of protein and the apparent Km value for glucose was 35.4 microM. Metacyclic forms showed a specific activity of 55.25 mUnits/mg and a Km value of 46.3 microM. The kinetic parameters (specific activity and Km for fructose 6-phosphate) of phosphofructokinase for epimastigotes were 42.60 mUnits/mg and 0.31 mM and for metacyclics 13.97 mUnits/mg and 0.16 mM, respectively. On the contrary, pyruvate kinase in both forms of T. cruzi did not show significant differences in its kinetic parameters. The specific activity in epimastigotes was 37.00 mUnits/mg and the Km for phosphoenolpyruvate was 0.47 mM, whereas in metacyclics these values were 42.94 mUnits/mg and 0.46 mM, respectively. The results presented in this work, clearly demonstrate a quantitative change in the glycolytic pathway of both culture forms of T. cruzi.

Animals↗
PubMed1990

Trypanosoma cruzi: calcium ion movement during internalization in host HeLa cells.

The role of cytosolic Ca2+ and cytoplasmic calcium movement during the parasitization of HeLa cells by T. cruzi were studied. The level of calcium in parasitized cells increased compared to the control cells. Our experiments demonstrate that this cytosolic calcium originates from the release of the intracellular calcium deposits, especially from the mitochondria of the host cell. The parasitization rates decreased after the cells were treated with drugs to increase the cytosolic Ca2+ levels to inhibit the host-cell calmodulin.

Animals↗
PubMed1990

Influence of electrolytes and non-electrolytes on growth and differentiation of Trypanosoma cruzi.

The influence of electrolytes and non-electrolytes, especially NaCl and sorbitol, on the metacyclogenesis and growth of Trypanosoma cruzi has been studied. The addition of 50 or 100 mEq/l NaCl to the culture media significantly increased the development of metacyclic forms. Other electrolytes and non-electrolytes had no effect on epimastigote-metacyclic differentiation. The growth rate was never modified to any extent. The influence of sodium concentration, osmotic pressure, among other factors, are discussed. Electrophoresis showed proteins bands which could be related either to the adaptation of T. cruzi to the new culture media or to the initiation of differentiation processes.

Animals↗
PubMed1990

Self-reports in chronic schizophrenic patients with primary negative symptoms: preliminary results.

The Frankfurt well-being scale (FBS), an instrument for evaluating the global inner state in schizophrenic patients, was used in a pilot study with 26 chronic schizophrenic inpatients simultaneously with the Munich version of the Andreasen scale (SANS). 11 of 26 patients were able to complete the FBS questions. These patients had weaker negative symptomatology (SANS total score) and the difference was highly significant (p less than 0.01) for the score "alogia". The major goal of the investigation was to contribute to the identification of those subgroups of schizophrenic patients who are not capable of filling in a self-report questionnaire. The results suggest that self-reports of actual mood in chronic schizophrenic patients are possible only in a subgroup of patients with no more than moderate primary negative symptoms, particularly those with a low alogia score. Further efforts to evaluate the subjective well-being of chronic patients differing in severity of negative symptoms complexes, could improve methods for evaluating the effect of psychotropic drugs.

Chronic Disease↗
PubMed1989

In vitro action of platinum (II) and platinum (IV) complexes on Trypanosoma cruzi and Leishmania donovani.

The in vitro activities of 22 neutral Pt(II) complexes, 4 Pt(IV) complex salts, and one Pt(II) complex salt on epimastigote forms of Trypanosoma cruzi and promastigote forms of Leishmania donovani were studied. Only 2 out of the 18 complexes with cis-Pt(DDH)Xn structure completely inhibited the growth of the epimastigote forms of T. cruzi and the promastigote of L. donovani. Against T. cruzi the cis-Pt(L)n(Cl)2 complexes showed no activities, but the complex in which the (L) ligand was stilbamidine did show a limited activity against L. donovani. Of the Pt(IV)complex salts, [Pt X6]H2(L) were very active against the epimastigote forms of T. cruzi. However, the Pt(II) complex salt [cis-Pt Cl4]H2 (pentamidine) showed no activity. The actions of the Pt(IV) complex salts on the promastigote forms of L. donovani were different and only those salts in which the (L) ligand was pentamidine or stilbamidine induced parasite growth inhibition. The one Pt(II) salt tested showed no antiparasitic activity. At the same time, the known antiparasitic activities of the nifurtimox and pentamidine molecules were confirmed.

Animals↗
PubMed1988

Differential energetic metabolism during Trypanosoma cruzi differentiation. I. Citrate synthase, NADP-isocitrate dehydrogenase, and succinate dehydrogenase.

The activities of the mitochondrial enzymes citrate synthase (citrate oxaloacetatelyase, EC 4.1.3.7), NADP-linked isocitrate dehydrogenase (threo-Ds-isocitrate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.42), and succinate dehydrogenase (succinate: FAD oxidoreductase, EC 1.3.99.1) as well as their kinetic behavior in the two developmental forms of Trypanosoma cruzi at insect vector stage, epimastigotes and infective metacyclic trypomastigotes, were studied. The results presented in this work clearly demonstrate a higher mitochondrial metabolism in the metacyclic forms as is shown by the extraordinary enhanced activities of metacyclic citrate synthase, isocitrate dehydrogenase, and succinate dehydrogenase. In epimastigotes, the specific activities of citrate synthase at variable concentrations of oxalacetate and acetyl-CoA were 24.6 and 26.6 mU/mg of protein, respectively, and the Michaelis constants were 7.88 and 6.84 microM for both substrates. The metacyclic enzyme exhibited the following kinetic parameters: a specific activity of 228.4 mU/mg and Km of 3.18 microM for oxalacetate and 248.5 mU/mg and 2.75 microM, respectively, for acetyl-CoA. NADP-linked isocitrate dehydrogenase specific activities for epimastigotes and metacyclics were 110.2 and 210.3 mU/mg, whereas the apparent Km's were 47.9 and 12.5 microM, respectively. No activity for the NAD-dependent isozyme was found in any form of T. cruzi differentiation. The particulated succinate dehydrogenase showed specific activities of 8.2 and 39.1 mU/mg for epimastigotes and metacyclic trypomastigotes, respectively, although no significant changes in the Km (0.46 and 0.48 mM) were found. The cellular role and the molecular mechanism that probably take place during this significant shift in the mitochondrial metabolism during the T. cruzi differentiation have been discussed.

Animals↗
PubMed1988

Influence of saccharides and sodium chloride on growth and differentiation of Trypanosoma cruzi.

The influence of saccharides, especially glucose and fructose, on the metacyclogenesis and growth of Trypanosoma cruzi has been investigated. In the absence of glucose and fructose in the media, both the percentage of metacyclic forms and the growth increased significantly. Furthermore, the addition of NaCl to the medium without monosaccharides strongly increased the formation of metacyclic forms. Presence of NaCl and absence of monosaccharides showed a synergic effect on differentiation of T. cruzi.

Animals↗
PubMed1988

Human melanoma cell lines: an immunofluorescence and ultrastructural study.

Two human melanoma cell lines (OAL-1 and OAL-2) were obtained from primary tumors. Electron microscopy and indirect immunofluorescence for S-100 protein and human melanoma associated antigen p97a were used to characterize the cell lines. Ultrastructural correlation between primary tumor cells and cultured cells was investigated. The ultrastructural features of OAL-2 cells were similar to those of primary tumor cells. However, OAL-1 cells showed a fibroblast-like appearance, quite different from that of the primary tumor cells. This fibroblast-like appearance persisted after 50 subcultures of the OAL-2 cell line and suggests cellular dedifferentiation. No spontaneous redifferentiation of the cells to the original phenotype of the primary tumor cells was observed even after 50 subcultures.

Aged↗