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Biomedical subjects

R Docampo

Publications and source records attributed to R Docampo.

At least 145 records · Page 8Linked to original sources
PubMed1978

In vitro and in vivo evaluation of the toxicity of 1,4-naphthoquinone and 1,2-naphthoquinone derivatives against Trypanosoma cruzi.

The toxic effect of lapachol, beta-lapachone and several 1,2-naphthoquinone derivatives on the growth, viability and infectivity of Trypanosoma cruzi were compared. beta-lapachone was the most active compound in vitro. No inhibition was observed in suspensions which contained inactivated foetal calf serum or rabbit haemoglobin solution. The infectivity of trypomastigotes in mice was not affected when cells were previously incubated with beta-lapachone or one of several other naphthoquinone derivatives in vitro in the presence of blood. It is suggested that beta-lapachone and the other compounds can be inactivated either by reduction in the presence of oxyhaemoglobin or by interaction with serum proteins. A beta-lapachone derivative, allyl-beta-lapachone, was not inactivated in the presence of blood and remained effective in suppressing trypomastigote infectivity.

Animals↗
PubMed1978

Generation of free radicals from phenazine methosulfate in Trypanosoma cruzi epimastigotes.

A significant growth inhibition of Trypanosoma cruzi epimastigotes by phenazine methosulfate (PMS) was observed in Warren's medium. This toxic activity could be related to the following parameters: a) formation of phenazinium free radical, b) generation of superoxide anion in intact cells incubated with PMS, and c) PMS also increased significantly the rate of O2- generation in epimastigotes mitochondrial and microsomal fractions using NADH as electron donor.

Electron Spin Resonance Spectroscopy↗
PubMed1976

Localization of peroxidase activity in Trypanosoma cruzi microbodies.

Electron microscopic observation of Trypanosoma cruzi epimastigotes reveals the presence of microbody-like structures (microperoxisomes) in which 3,3'-diaminobenzidine (DAB) is peroxidized to electron-opaque material. The role of peroxidase in DAB peroxidation is supported by the enzyme demonstration in disrupted epimastigotes and the microbody-containing cell fractions.

Animals↗
PubMedDate not supplied

Free radical metabolites in the mode of action of chemotherapeutic agents and phagocytic cells on Trypanosoma cruzi.

There are a number of biologic oxidations in Trypanosoma cruzi that generate O2- and/or H2O2. In addition, intracellular reduction followed by autoxidation yielding O2- and H2O2 has been suggested as the mode of action of several trypanocidal agents active both in vitro (e.g., naphthoquinones) and in vivo (nifurtimox) and as the basis of nifurtimox toxicity in mammals. Moreover, oxygen-reduction products have been implicated in the mechanism of killing of T. cruzi by phagocytic cells; this suggests an important role for this mechanism in host resistance and/or pathogenesis of Chagas' disease. T. cruzi possesses superoxide dismutases but lacks catalase and is partially deficient in peroxidases. This deficiency has been correlated with its sensitivity to both intracellular generators of oxygen-reduction intermediates and cell-derived oxygen metabolites. In addition, free radical intermediates apparently not related to oxygen-reduction products have also been found in the metabolic pathways of other trypanocidal drugs (benznidazole and crystal violet) used clinically in the treatment or prevention of Chagas' disease.

Free Radicals↗
PubMedDate not supplied

Chemotherapy for Chagas' disease: a perspective of current therapy and considerations for future research.

Our current knowledge of the biology of Trypanosoma cruzi and its relation to the development of chemotherapy for Chagas' disease are reviewed. This includes recent developments in the understanding of kinetoplast DNA and glycosomes; the action of oxygen radicals; intermediary metabolism of purines, pyrimidines, and folic acid; and the formation of microtubules. At this time, these organelles and metabolic pathways appear to be the most promising for potential exploitation for chemotherapeutic purposes. Compounds of current experimental interest also are discussed. These are agents that have shown promise in the laboratory and for which data exist regarding probable mechanisms of action. The activities of these agents correlated, in so far as is possible, with those structures or metabolic pathways in the trypanonsome that are affected by their actions. The compounds are of two general groups: nitro compounds and purine analogues.

Animals↗
PubMedDate not supplied

Disruption of Ca2+ homeostasis in Trypanosoma cruzi by crystal violet.

We have demonstrated previously that crystal violet induces a rapid, dose-related collapse of the inner mitochondrial membrane potential of Trypanosoma cruzi epimastigotes. In this work, we show that crystal violet-induced dissipation of the membrane potential was accompanied by an efflux of Ca2+ from the mitochondria. In addition, crystal violet inhibited the ATP-dependent, oligomycin-, and antimycin A-insensitive Ca2+ uptake by digitonin-permeabilized epimastigotes. Crystal violet also induced Ca2+ release from the mitochondria and endoplasmic reticulum of digitonin-permeabilized trypomastigotes. Furthermore, crystal violet inhibited Ca2+ uptake and the (Ca(2+)-Mg2+)-ATPase of a highly enriched plasma membrane fraction of epimastigotes, thus indicating an inhibition of other calcium transport mechanisms of the cells. Disruption of Ca2+ homeostasis by crystal violet may be a key process leading to trypanosome cell injury by this drug.

Animals↗
PubMedDate not supplied

Inhibition of protein synthesis and amino acid transport by crystal violet in Trypanosoma cruzi.

[35S]methionine incorporation into proteins of either T. cruzi epimastigotes or trypomastigotes was drastically inhibited by low concentrations of crystal violet in a dose-dependent manner. This inhibition was not due to ATP depletion since cellular ATP levels did not change significantly after incubation of epimastigotes with 50 microM crystal violet for similar periods of time, and was unaffected by changes in the extracellular free calcium concentration. Although crystal violet was able to inhibit protein synthesis in a cell-free system from T. cruzi epimastigotes, half maximal inhibition was at 1 mM, a concentration three orders of magnitude higher than those that inhibited protein synthesis in intact cells. On the other hand, crystal violet was able to inhibit total [35S]methionine uptake at similar concentrations to those that inhibited protein synthesis while addition of increasing concentrations of cold methionine to the incubation medium protected the cells against crystal violet inhibition. Crystal violet also inhibited total [3H]proline uptake thus indicating that it has a general inhibitory effect upon the transport of amino acids, and not specifically upon methionine. These results indicate that inhibition of protein synthesis by crystal violet is probably due to inhibition of amino acid uptake.

Adenosine Triphosphate↗
PubMedDate not supplied

The sterol composition of Trypanosoma cruzi changes after growth in different culture media and results in different sensitivity to digitonin-permeabilization.

Respiration, oxidative phosphorylation. and the corresponding changes in membrane potential (deltapsi) of Trypanosoma cruzi epimastigotes grown either in liver infusion-tryptose (LIT) or brain heart infusion (BHI) culture medium were assayed in situ using digitonin to render their plasma membrane permeable to succinate, ADP, safranine O, and other small molecules. When the cells were permeabilized with 64 microM digitonin, a concentration previously used with epimastigotes, the ability of the cells grown in LIT medium to sustain oxidative phosphorylation was demonstrated by the detection of an oligomycin-sensitive decrease in mitochondrial membrane potential induced by ADP. In contrast, the cells grown in BHI medium were not able to sustain a stable membrane potential and did not respond to ADP addition. Analyses of oxygen consumption by these permeabilized cells indicated that the rate of basal respiration, which was similar in both cell types, was significantly decreased by 64 microM digitonin. Addition of ADP to the permeabilized cells grown in LIT medium promoted an oligomycin-sensitive transition from resting to phosphorylating respiration in contrast to the cells grown in BHI medium, whose respiration decreased steadily and did not respond either to ADP or CCCP. Titration of the cells grown in BHI medium with different digitonin concentrations indicated that their mitochondria have higher sensitivity to digitonin than those grown in LIT medium. Analysis of the sterol composition of epimastigotes grown in the two different media showed a higher percentage of cholesterol in total and mitochondrial extracts of epimastigotes grown in BHI medium as compared to those grown in LIT medium, suggesting the involvement of this sterol in their increased sensitivity to digitonin-permeabilization.

Animals↗
PubMedDate not supplied

Synthetic trypanocides: growth-inhibiting properties of new 1,2,3,4-tetrahydrocarbazoles on Trypanosoma cruzi.

Several new 1,2,3,4-tetrahydrocarbazole, 5,6-dihydrobenzo(alpha) carbazole, 3-methylindole and substituted benzimidazolyl compounds were synthesized and assayed for their action on growth of Trypanosoma cruzi, cultured in Warren's liquid medium. 6-chloro and 6,8-dichloro-N-(1-ethyl-N-diethylamino)-1,2,3,4-tetrahydrocarbazole++ fumarate resulted the more active in inhibiting growth of the parasite. The new compounds were apparently more effective than those prepared previously by Poliakoff et al. (5).

Animals↗
PubMedDate not supplied

[Effect of beta and alpha-lapachone on the production of H202 and on the growth of Trypanosoma cruzi].

Addition of beta-lapachone to the epimastigote (culture) form of Trypanosoma cruzi, suspended in saline, buffered-isotonic medium (pH 7.2), determined the appearance of large amounts of H2O2 in the suspension medium, as measured spectrophotometrically by formation of the H2O2 horse radish peroxidase complex. Under similar conditions, alpha-lapachone did not induce H2O2 formmation. Using NADH as electron donor, beta-lapachone (not alpha-lapachone) increased significantly the rate of H2O2 generation by epimastigote homogenates and the same occurred with NADPH, although in a reduced extent. Similar results were obtained with the isolated mitochondrial and microsomal fractions although with the latter NADPH was more effective than NADH as electron donor for beta-lapachone reduction and peroxide generation. The distribution of peroxide generation in epimastigote fractions would indicate that about 92% of the beta-lapachone dependent formation of peroxide occurred in the mitochondria, and 8% in the endoplasmic reticulum. The growth of epimastigotes was inhibited 95% by 1 microgram/ml beta-lapachone, a concentration that determined maximal rate of H2O2 production. Since H2O2 and other intermediates of oxygen reduction such as O2- (superoxide anion) and OH (hydroxyl radical) are lethal to cells and tissues, it is possible that the effect of beta-lapachone on T. cruzi proliferation in vitro was mediated by H2O2 and related free radicals.

Culture Media↗