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Biomedical subjects

F Vargas

Publications and source records attributed to F Vargas.

At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

Acidifying enemas (lactitol and lactose) vs. nonacidifying enemas (tap water) to treat acute portal-systemic encephalopathy: a double-blind, randomized clinical trial.

A double-blind, controlled trial to study the efficacy of acidifying enemas of lactitol, a new galactoside-sorbitol disaccharide, and lactose vs. nonacidifying tap-water enemas was performed in 45 episodes of acute portal-systemic encephalopathy. At the time of randomization, all patients had encephalopathy of at least Grade 2+ severity, delay in the performance of number connection tests and hyperammonemia. A sequential analysis was performed which revealed after the inclusion of the first 20 patients, a significant failure of the nonacidifying enemas as compared to the lactitol enemas (p less than 0.004). The tap-water enema group was, therefore, suspended but the rest of the study continued after rerandomization for lactose and lactitol groups. A favorable response to treatment was obtained in 19 (86%) of the patients receiving lactitol enemas and in 14 (78%) of those receiving lactose enemas. A similar significant improvement in portal-systemic encephalopathy parameters and index was observed after both treatments. Both types of acidifying enemas induced a significant pH decrease in stool (p less than 0.05). These data suggest that acidifying agents like lactose and lactitol are effective and superior to tap-water enemas for the treatment of acute nitrogenous portal-systemic encephalopathy.

Ammonia↗
PubMedDate not supplied

Clinical healing of antimony-resistant cutaneous or mucocutaneous leishmaniasis following the combined administration of interferon-gamma and pentavalent antimonial compounds.

In an open trial, longer courses of pentavalent antimonials (Sbv) at sub-optimal doses (10 mg/kg body weight), in association with recombinant human interferon-gamma (IFN-gamma) (100 micrograms/m2 of body surface area) were administered, by daily intramuscular injections, to 13 patients with diagnoses of cutaneous or mucocutaneous leishmaniasis unresponsive to Sbv. Four patients presented with large skin ulcers, and 9 had mucosal involvement as the main manifestation, the latter affecting the nose (3 cases), nose and septum (2 cases), nose and oral cavity (1 case), and nose, pharynx and larynx (3 cases). Except for one case with severe involvement of the upper respiratory tract, the lesions were fully resolved by the end of therapy (mean duration 40 +/- 12 [SD] d, range 30-60 d) in the 11 patients who completed therapy. The main side effects were headache and fever (7 cases), together with leucopenia and eosinophilia (4 cases). It is concluded that combined administration of low doses of Sbv plus IFN-gamma may provide a novel therapeutic approach for the treatment of antimony-resistant cutaneous or mucocutaneous leishmaniasis. The possible mechanisms by which IFN-gamma contributes to resolution of the disease are discussed.

Adolescent↗
PubMedDate not supplied

Natural ecotopes of Triatoma infestans dark morph and other sylvatic triatomines in the Bolivian Chaco.

A survey of natural ecotopes of Triatoma infestans dark morph and other triatomine sylvatic species was performed in an uninhabited area of the Bolivian Chaco. Among the 321 triatomines collected by light trapping, only 4 T. infestans dark morph specimens were identified. Predominant flying species were T. guasayana and T. sordida group 2 (51.7% and 37.1% of capture, respectively). The same species prevailed in terrestrial and epiphytic bromeliads where scarce T. infestans dark morph nymphal instars were also detected. In parrot nests T. delpontei prevailed broadly over other species (90.2% of the capture) and only 4 T. infestans dark morph adults were collected. In contrast, T. infestans dark morph was the predominant species captured in hollow trees (46.0% of the total collected). The abundance of immature forms (88.2% of the collection) shows that hollow trees constitute a favourable ecotope for this species. Of the 421 trees investigated, 33.7% were positive for triatomines. T. infestans dark morph, found inside 15.0% of them, also had higher apparent density than other species (average number of T. infestans in positive trees, 2.0 +/- 1.6 vs 1.3 +/- 0.6 for other species). Light trapping seems to be an efficient method to sample the T. sordida-T. guasayana complex in that it shows a similar distribution to that observed in natural ecotopes; however, this method is ineffective for the assessment of the local abundance of T. infestans dark morph.

Animals↗
PubMedDate not supplied

Low probability of transmission of Trypanosoma cruzi to humans by domiciliary Triatoma sordida in Bolivia.

The role of Triatoma sordida in the domestic transmission of Trypanosoma cruzi was assessed in 7 rural localities in Velasco Province, Department of Santa Cruz, Bolivia. Tri. sordida, the only triatomine species identified in these localities, was found inside 58.0% of houses but not in large numbers (3.1 bugs per infested house on average). A total of 220 faecal samples from domiciliary bugs was examined microscopically and by the polymerase chain reaction for the presence of trypanosomes: 21.4% were infected. Analysis of blood meals of domiciliary Tri. sordida showed that humans were the commonest host (70.4%), followed by chickens and dogs. Four of 418 persons tested were seropositive for Tryp. cruzi. Only 2 of a second group of 62 persons living in dwellings infested by Tri. sordida were seropositive. Tryp. cruzi infection was demonstrated in dogs and domestic rats. Three other species of small mammals were found to be infected with trypanosomes. In our study area, domestic Tri. sordida are mainly incriminated in the transmission of Tryp. cruzi to synanthropic animals, whereas transmission to humans is very rare. The presence in houses of small populations of Tri. sordida infected with Tryp. cruzi is therefore currently insufficient for this insect to constitute a major epidemiological risk factor.

Animals↗
PubMedDate not supplied

In vitro antioxidant and photo-oxidant properties of dipyridamole.

The in vitro antioxidant and photo-oxidant activity of dipyridamole was studied by its effect on superoxide- and singlet oxygen-mediated photohemolysis and viability of neutrophils. Dipyridamole was found to be phototoxic when examined by the photohemolysis on human erythrocytes and on linoleic acid as lipid peroxidation model at concentrations above 3.0 x 10(-5) M. On the contrary, when lower concentrations (1.0 x 10(-5) to 1.0 x 10(-6) M) were used, dipyridamole showed a protector action against singlet oxygen-mediated photohemolysis by other phototoxic compounds like triamterene. This antioxidant property is proposed to result from quenching of triamterene mediated by fluorescence energy transfer. Auto-oxidation and fluorescence-energy transfer is clearly an important mechanism for protection for this drug.

Antioxidants↗
PubMedDate not supplied

In vivo and in vitro effects of phenytoin (PHT) on ATPases and [14C]-PHT binding in synaptosomes and mitochondria from rat cerebral cortex.

The effect of phenytoin (PHT) on Na(+)-K(+)-ATPase and Mg(2+)-ATPase activities and on [14C]-PHT binding in vitro to synaptosomal and mitochondrial subcellular fractions from rat cerebral cortex was studied after chronic PHT treatment. Synaptosomal and mitochondrial fractions were characterized with plasma membrane and mitochondrial enzymatic markers. Synaptosomal Na(+)-K(+)-ATPase was not affected in vitro by PHT 1-200 microM or by chronic treatment with 2-50 mg/kg/day of the unlabeled drug for 8 days. Mitochondrial Mg(2+)-ATPase was significantly stimulated by PHT after chronic treatment with 5 mg/kg/day for 8 days; reaching maximal effect (76%), at 10-25 mg/kg. PHT had no effect on mitochondrial Mg(2+)-ATPase when added in vitro. [14C]-PHT binding in vitro to the subcellular fractions was determined by dialysis to assess in vivo binding of the unlabeled PHT during chronic treatment. Indeed, [14C]-PHT bound to synaptosomes was significantly reduced by chronic PHT treatment from 218 +/- 10 to 119 +/- 11 pmol/mg protein after 1 week of treatment; a similar effect was obtained after 2-3 weeks with 10 mg/kg/day. Mitochondrial fraction bound 117 +/- 10 pmol/mg protein labeled PHT. Chronic treatment with unlabeled PHT also reduced the amount of [14C]-PHT bound to 19.9 +/- 2.2 pmol/mg protein. These results show slow reversible PHT in vivo binding to synaptosomes and mitochondrias from rat cerebral cortex, supporting the idea that the modulatory action of PHT on Na+ and Ca2+ permeabilities are mediated through these slow reversible binding proteins. The data also suggest a possible role of intrasynaptosomal mitochondria in [Ca2+]i buffering.

Animals↗
PubMedDate not supplied

Modulatory role of endothelium-derived relaxing factors on the response to vasoconstrictors and flow-pressure curve in the isolated perfused rat kidney.

The aim of this study was to compare the effects of the blockade of nitric oxide (NO) and of endothelium-derived hyperpolarizing factor (EDHF) on the response to vasoconstrictors (VC) and on the flow-pressure curve in the isolated perfused rat kidney. To this end, dose-response curves to phenylephrine and BaCl2 were studied in the renal vasculature under basal conditions and after the infusion of N(omega)-nitro-L-arginine methyl ester (L-NAME) and tetraethylammonium (TEA) in endothelium-intact and endothelium-denuded (CHAPS-treated) preparations. In another experiment, renal flow-pressure curves were obtained under basal conditions and after the infusion of L-NAME or TEA. The flow-pressure curve was obtained by increasing renal perfusion flow (RPF) from 2.5 to 15 ml/min/g kidney weight (KW) over the basal level (5 ml/min/g KW). L-NAME or TEA produced a leftward shift of the dose-response curves of both VC, and the simultaneous administration of L-NAME and TEA produced a greater shift to the left in the pressor response curves. CHAPS treatment produced a leftward shift of the dose-response curves of both VC, and the dose-response curves were not significantly modified by the infusion of L-NAME or TEA. L-NAME markedly shifted the flow-pressure curve upward, especially at higher levels of RPF. However, the administration of TEA, perfusate solution (Tyrode) or D-NAME did not significantly change the flow-pressure curve. These results suggest that NO is released in response to VC as well as to increased perfusion flow in the isolated renal vascular bed. However, EDHF release seems to be stimulated by VC but not by increased perfusion flow.

Animals↗
PubMedDate not supplied

Parasitological diagnosis of mucocutaneous leishmaniasis due to Leishmania b. braziliensis in Bolivia.

Parasitological diagnosis, using stained smears, culture and pathological examination of biopsy, was studied in 146 patients infected with mucocutaneous leishmaniasis, in Bolivia and Peru. The most efficient parasite detecting technique appeared to be the smear examination in cutaneous lesions (33% positive) and the pathology in case of mucous lesions (28% positive). In both, cutaneous and mucous lesions, the parasites were found most frequently in old lesions.

Adult↗
PubMedDate not supplied

Persistent asthma in adults: comparison of high resolution computed tomography of the lungs after one year of follow-up.

OBJECTIVE: The aims of this study were to evaluate the role of high resolution computed tomography of the thorax in detecting abnormalities in chronic asthmatic patients and to determine the behavior of these lesions after at least one year. METHOD: Fourteen persistent asthmatic patients with a mean forced expiratory volume in 1-second that was 63% of predicted and a mean forced expiratory volume in 1-second /forced vital capacity of 60% had two high resolution computed tomographies separated by an interval of at least one year. RESULTS: All 14 patients had abnormalities on both scans. The most common abnormality was bronchial wall thickening, which was present in all patients on both computed tomographies. Bronchiectasis was suggested on the first computed tomography in 5 of the 14 (36%) patients, but on follow-up, the bronchial dilatation had disappeared in 2 and diminished in a third. Only one patient had any emphysematous changes; a minimal persistent area of paraseptal emphysema was present on both scans. In 3 patients, a "mosaic" appearance was observed on the first scan, and this persisted on the follow-up computed tomography. Two patients had persistent areas of mucoid impaction. In a third patient, mucus plugging was detected only on the second computed tomography. CONCLUSIONS: We conclude that there are many abnormalities on the high resolution computed tomography of patients with persistent asthma. Changes suggestive of bronchiectasis, namely bronchial dilatation, frequently resolve spontaneously. Therefore, the diagnosis of bronchiectasis by high resolution computed tomography in asthmatic patients must be made with caution, since bronchial dilatation can be reversible or can represent false dilatation. Nonsmoking chronic asthmatic subjects in this study had no evidence of centrilobular or panacinar emphysema.

Adult↗
PubMedDate not supplied

Genetic variability and microdistribution of Triatoma infestans genotypes and Trypanosoma cruzi clones in Arequipa region (Peru).

The genetic variability of Triatoma infestans and Trypanosoma cruzi populations was studied by isoenzyme analysis in two distinct areas of Arequipa province (Peru); one, Santa Rita de Siguas, being an endemic area for Chagas' disease, the second, Arequipa, recently infected. Analysis of T. infestans genetic variability indicates, (i) temporal stability of genotypes found in Santa Rita de Siguas, (ii) high genetic differences between Arequipa and Santa Rita de Siguas populations suggesting minor contact between them, (iii) multiple origin of the T. infestans population in Arequipa, and (iv) poor dispersal capacity of T. infestans: the panmictic unit could be reduce to a house. Parasite isoenzyme analysis was performed in 29 Peruvian stocks of T. cruzi, mainly isolated from bugs taken in a single locality, Santa Rita de Siguas. The results show, (i) a high genetic polymorphism, (ii) nine different multilocus genotypes were detected and clustered in two different clades, (iii) most of the parasite isolates pertained to one of the clade and were genetically similar to those analyzed 12 years before. This sample allowed the study of the mating system of T. cruzi in strict sympathic conditions and gave more strength to the hypothesis of the clonal structure of T. cruzi populations.

Animals↗
PubMedDate not supplied

Selection of Trypanosoma cruzi clonal genotypes (clonet 20 and 39) isolated from Bolivian triatomines following subculture in liquid medium.

Previous studies showed that two groups of Trypanosoma cruzi clonal genotypes named clonet 20 and clonet 39 were predominant in Triatoma infestans, the unique vector of Chagas disease in Bolivia. These groups of clones correspond to distinct genetic clusters. These clonets were detected in T. infestans and Rhodnius pictipes fecal samples before isolation and after culture by kDNA PCR (polymerase chain reaction) and hybridization of the amplified products with clonet specific kDNA probes named 20 and 39 as previously reported. Forty eight T. infestans and three R. pictipes infected insects captured at random in different Bolivian departments were proceeded. As previously reported the direct identification of the two major clonets in fecal samples allowed the detection of abundant mixed infections: 41% in the original sample, however after culture, only 6% of mixed infections were detected. Among the 21 parasite stocks isolated from digestive tracts where mixed infections were initially detected (clonet 20 + 39) clonet 20 alone was detected in 81% of them. This result clearly showed that the culture step selected clonet 20 parasites over those belonging to clonet 39. The taxonomic status of the isolated stocks was also confirmed by isoenzyme typing, and correlation was observed between clustering topology and hybridization patterns with the probes 20 and 39.

Animals↗
PubMedDate not supplied

Regulation of renal Na-K-Cl cotransporter NKCC2 by humoral natriuretic factors: relevance in hypertension.

A furosemide-sensitive Na-K-Cl cotransporter (NKCC2 isoform) accounts for almost all luminal NaCl reabsorption in the thick ascending limb of Henle's loop (TALH). The activity of this transport protein is regulated by humoral factors (CIF: cotransport inhibitory factors). One family of CIF compounds is represented by the urinary phytoestrogens equol and genistein, which inhibit cotransport fluxes at similar concentrations as furosemide. Moreover, they possess similar salidiuretic potency as furosemide in the isolated perfused rat kidney, but are less potent than furosemide in vivo. Thus, dietary phytoestrogens can be responsible, at least in part, for the low blood pressure of vegetarians. A second type of CIF is represented by a circulating and urinary factor which is evoked by salt-loading. This, which is not a "ouabain-like" factor, appears to be a new retropituitary natriuretic compound. Endogenous CIF is increased in hypertensive Dahl salt-sensitive rats, probably as a compensatory mechanism against the enhanced NaCl reabsorption in the TALH, which characterizes this model of hypertension. Finally, chronic excess of circulating CIF inhibits and induces up-regulation of erythrocyte Na-K-Cl cotransporter NKCC1.

Animals↗