Biomedical subjects

F S Barros

Publications and source records attributed to F S Barros.

5 recordsLinked to original sources

PubMed2000

The HIV epidemic in the Amazon Basin is driven by prototypic and recombinant HIV-1 subtypes B and F.

This paper describes genetic subtypes of HIV-1 found in blood samples from 31 HIV-1-infected people who visited the Counseling and Testing AIDS Center of Instituto de Medicina Tropical in Manaus, Brazil. Manaus, the main city in Brazil's Amazon Basin, is also the closest urban connection for more than 100,000 Indians living in the rain forests of this region. Although to date there is no evidence of increased incidence of HIV-1 infection among the indigenous population, our understanding of both the prevalence and nature of the epidemic in the region as a whole is limited. From the 31 samples analyzed by C2V3 sequencing, we found almost equal proportions of HIV-1 strains belonging to subtype B (n = 16; 51.6%) and subtype F (n = 15; 48.4%), a finding that differs from results from previous studies conducted in urban areas of southeastern Brazil. We also observed the presence of the GWGR amino-acid sequence in the critical tetra-peptide crown of the env V3 loop in the HIV-1 subtype B samples analyzed. Among these samples, we also found 14 mosaic genomes (45.16%) in which different combinations of subtypes B, C, and F were identified between the p24 gag, pro, and env regions. Our data support the hypothesis that the Amazonian HIV-1 infections linked to the urban epidemic in southeastern Brazil. The genetic diversity and the prevalence of mosaic genomes among the isolates in our study confirm an integral role of recombination in the complex Brazilian epidemic.

Adult↗

PubMed2000

Ectonucleotide diphosphohydrolase activities in Entamoeba histolytica.

In this work, we describe the ability of living cells of Entamoeba histolytica to hydrolyze extracellular ATP. In these intact parasites, whose viability was determined by motility and by the eosin method, ATP hydrolysis was low in the absence of any divalent metal (78 nmol P(i)/h/10(5) cells). Interestingly, in the presence of 5 mM MgCl(2) an ecto-ATPase activity of 300 nmol P(i)/h/10(5) cells was observed. The addition of MgCl(2) to the extracellular medium increased the ecto-ATPase activity in a dose-dependent manner. At 5 mM ATP, half-maximal stimulation of ATP hydrolysis was obtained with 1.23 mM MgCl(2). Both activities were linear with cell density and with time for at least 1 h. The ecto-ATPase activity was also stimulated by MnCl(2) and CaCl(2) but not by SrCl(2), ZnCl(2), or FeCl(3). In fact, FeCl(3) inhibited both Mg(2+)-dependent and Mg(2+)-independent ecto-ATPase activities. The Mg(2+)-independent ATPase activity was unaffected by pH in the range between 6.4 and 8. 4, in which the cells were viable. However, the Mg(2+)-dependent ATPase activity was enhanced concomitantly with the increase in pH. In order to discard the possibility that the ATP hydrolysis observed was due to phosphatase or 5'-nucleotidase activities, several inhibitors for these enzymes were tested. Sodium orthovanadate, sodium fluoride, levamizole, and ammonium molybdate had no effect on the ATPase activities. In the absence of Mg(2+) (basal activity), the apparent K(m) for ATP(4-) was 0.053 +/- 0.008 mM, whereas at saturating MgCl(2) concentrations, the corresponding apparent K(m) for Mg-ATP(2-) for Mg(2+)-dependent ecto-ATPase activity (difference between total and basal ecto-ATPase activity) was 0.503 mM +/- 0.062. Both ecto-ATPase activities were highly specific for ATP and were also able to hydrolyze ADP less efficiently. To identify the observed hydrolytic activities as those of an ecto-ATPase, we used suramin, a competitive antagonist of P(2) purinoreceptors and an inhibitor of some ecto-ATPases, as well as the impermeant agent 4'-4'-diisothiocyanostylbenzene-2'-2'-disulfonic acid. These two reagents inhibited the Mg(2+)-independent and the Mg(2+)-dependent ATPase activities to different extents, and the inhibition by both agents was prevented by ATP. A comparison among the ecto-ATPase activities of three amoeba species showed that the noninvasive E. histolytica and the free-living E. moshkovskii were less efficient than the pathogenic E. histolytica in hydrolyzing ATP. As E. histolytica is known to have a galactose-specific lectin on its surface, which is related to the pathogenesis of amebiasis, galactose was tested for an effect on ecto-ATPase activities. It stimulated the Mg(2+)-dependent ecto-ATPase but not the Mg(2+)-independent ATPase activity.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

Platelet-activating factor induction of secreted phosphatase activity in Trypanosoma cruzi.

The effects of platelet-activating factor (PAF) on the ecto-phosphatase activity of Trypanosoma cruzi were investigated. Living parasites hydrolyzed p-nitrophenyl phosphate (p-NPP) at a rate of 5.71 +/- 0.37 nmol P(i) mg(-1) min(-1). This ecto-phosphatase activity increased to 8.70 +/- 1.12 nmol P(i) mg(-1) min(-1) when the cells were grown in the presence of 10(-9) M PAF. This effect was probably due to stimulation of the release of the ecto-phosphatase and/or the secretion of an intracellular phosphatase to the extracellular medium, as suggested by cytochemical analysis. Modulation of the ecto-phosphatase activity was also observed when PAF was added during the time course of the reaction. WEB 2086, a competitive PAF antagonist, was able to revert PAF effects when both were used at the same concentration. When PAF was added to a membrane enriched fraction preparation of T. cruzi, no alteration on the phosphatase activity was observed. This result suggests an involvement of intracellular signaling, as PAF was only effective on intact cells. Sphingosine and phorbol-12-myristate-13-acetate (PMA) were then used to investigate a possible involvement of protein kinase C (PKC) with PAF-induced phosphatase secretion. Sphingosine by itself stimulated the secretion of a phosphatase but did not significantly interfere with PAF effects on this enzyme. On the other hand, PMA was able to abrogate PAF-induced release of this phosphatase. These data are highly suggestive of a putative involvement of signal transduction mediated by a ligand of mammalian origin (PAF), through PKC and a specific receptor located on the cell surface of the human parasite Trypanosoma cruzi.

Animals↗

PubMed1999

Diameter-reflux relationship in perforating veins of patients with varicose veins.

PURPOSE: Treatment of chronic venous valvular insufficiency requires understanding of the hemodynamics of perforating veins. To preserve normal veins or veins that can function normally once primary sources of valvular insufficiency are removed, a better understanding of the diameter-reflux relationship is desirable. We measured reflux and diameters in 500 perforating veins of patients with varicose veins (C(2)E(P)A(SP)P(R)). METHODS: Color flow duplex ultrasonography scanning was performed with the patient standing. Perforating veins were mapped medially in the thigh and medially, laterally, and posteriorly in the calf. Reflux was defined as reverse flow that lasted longer than 0.5 seconds. Diameters were measured on B-mode transverse projections at the crossing of the fascia. Competent versus incompetent vein diameters were compared by means of Student t test, one-way analysis of variance, and Bonferroni t test. RESULTS: Diameters of competent and incompetent perforators averaged 2.5 +/- 0.9 mm (n = 17) and 4.7 +/- 1.9 mm (n = 17) at the medial thigh (P <.0002), 2.2 +/- 0.8 mm (n = 179) and 3.7 +/- 1.0 mm (n = 210) at the medial calf (P <.0001), 2.2 +/- 0.6 mm (n = 13) and 3.5 +/- 0.8 mm (n = 37) at the posterior calf (P <. 0001), and 2.1 +/- 0.8 mm (n = 9) and 3.3 +/- 0.7 mm (n = 18) at the lateral calf (P <.003), respectively. Perforating vein diameters of 3.5 mm or larger in the calf and thigh were associated with reflux in more than 90% of the cases. CONCLUSION: An enlargement in the diameter of the perforating veins of 1 to 1.5 mm in the calf or 2 mm in the thigh of patients with varicose veins could be the difference between normal flow and reflux. Further studies are needed to confirm if elimination of reflux in patients with primary varicosity will transform incompetent perforators to competent ones.

Female↗

PubMedDate not supplied

Cellulose acetate as solid phase in ELISA for plague.

Antigen from Yersinia pestis was adsorbed on cellulose acetate discs (0.5 cm of diameter) which were obtained from dialysis membrane by using a paper punch. ELISA for human plague diagnosis was carried out employing this matrix and was capable to detect amount of 1.3 microg of antigen, 3,200 times diluted positive serum using human anti-IgG conjugate diluted 1:4,000. No relevant antigen lixiviation from the cellulose acetate was observed even after washing the discs 15 times. The discs were impregnated by the coloured products from the ELISA development allowing its use in dot-ELISA. Furthermore, cellulose acetate showed a better performance than the conventional PVC plates.

Antigens, Bacterial↗