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S Oliveira

Publications and source records attributed to S Oliveira.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of the Desulfovibrio gigas transcriptional unit containing rubredoxin (rd) and rubredoxin-oxygen oxidoreductase (roo) genes and upstream ORFs.

Rubredoxin-oxygen oxidoreductase, an 86-kDa homodimeric flavoprotein, is the final component of a soluble electron transfer chain that couples NADH oxidation with oxygen reduction to water from the sulfate-reducing bacterium Desulfovibrio gigas. A 4.2-kb fragment of D. gigas chromosomal DNA containing the roo gene and the rubredoxin gene was sequenced. Additional open reading frames designated as ORF-1, ORF-2, and ORF-3 were also identified in this DNA fragment. ORF-1 encodes a protein exhibiting homology to several proteins of the short-chain dehydrogenase/reductase family of enzymes. The N-terminal coenzyme-binding pattern and the active-site pattern characteristic of short chain dehydrogenase/reductase proteins are conserved in ORF-1 product. ORF-2 does not show any significant homology with any known protein, whereas ORF-3 encodes a protein having significant homologies with the branched-chain amino acid transporter AzlC protein family. Northern blot hybridization analysis with rd and roo-specific probes identified a common 1.5-kb transcript, indicating that these two genes are cotranscribed. The transcription start site was identified by primer extension analysis to be a guanidine 87 bp upstream the ATG start codon of rubredoxin. The transcript size indicates that the rd-roo mRNA terminates downstream the roo-coding unit. Putative -10 and -35 regulator regions of a sigma(70)-type promoter, having similarity with E. coli sigma(70) promoter elements, are found upstream the transcription start site. Rubredoxin-oxygen oxidoreductase and rubredoxin genes are shown to be constitutively and abundantly expressed. Using the data available from different prokaryotic genomes, the rubredoxin genomic organization and the first tentative to understand the phylogenetic relationships among the flavoprotein family are reported in this study.

Amino Acid Sequence↗
PubMed2001

Impact of a toxic and a non-toxic strain of Microcystis aeruginosa on the crayfish Procambarus clarkii.

The occurrence of cyanobacteria in many water bodies where crayfish such as Procambarus clarkii are abundant leads to the possibility of toxin accumulation and food chain transfer. This paper describes the accumulation and depuration of microcystins from a microcystin and a non-microcystin producing strain of Microcystis aeruginosa, on the survivorship, growth and nutritional status of P. clarkii. Crayfish larvae were resistant to cyanobacteria and their toxins, surviving cyanobacteria densities during acute exposures. Juvenile crayfish tolerated toxic cyanobacteria better than non-toxic ones. This effect was also observed when analysing nutritional status of crayfish fed toxic and non-toxic cyanobacteria with the former having better lipid and protein contents than those fed non-toxic Microcystis. P. clarkii accumulated up to 2.9 microg MCYST/dry crayfish weight and the depuration pattern was similar to that observed for mussels by other authors. Due to the fact that the major part of the toxin is accumulated in the intestine and in the hepatopancreas, there is no significant risk in terms of human health if these parts are removed prior to crayfish consumption. Nevertheless, their use in dairy food and the possible transference of toxins along food chains should not be disregarded.

Animals↗
PubMed2001

Rhizobia of chickpea from southern Portugal: symbiotic efficiency and genetic diversity.

AIMS: In order to evaluate differences between chickpea rhizobial populations from three geographical areas in southern Portugal (Beja, Elvas and Evora), isolates from the three regions were obtained and analysed. METHODS AND RESULTS: The genetic characterization of the isolates was done by plasmid profiles and restriction analysis of the nifH gene. Symbiotic efficiency of the isolates was also determined. Relationships between geographical origin, symbiotic efficiency and molecular characteristics were established. Beja soil revealed a larger rhizobia population as well as the presence of some of the isolates with higher symbiotic efficiency values. Isolates with a single plasmid showed a significantly higher symbiotic efficiency. CONCLUSION: Genetic and phenotypic differences were detected between the natural rhizobial populations from the three locations. SIGNIFICANCE AND IMPACT OF THE STUDY: The different yield potential with cultivars of chickpea usually obtained in the three regions of southern Portugal could be due to their different natural rhizobial populations.

Genetic Variation↗
PubMed2001

Outer membrane proteins and DNA profiles in strains of Haemophilus parasuis recovered from systemic and respiratory sites.

Polyserositis caused by Haemophilus parasuis is an important disease that affects mostly weaned pigs. Recent studies have shown that virulence can differ among strains recovered from distinct body sites and also that it may be related to the presence of certain outer membrane proteins (OMPs). The objective of this study was to compare the OMP and DNA profiles of H. parasuis strains isolated from systemic and respiratory sites from diseased and healthy pigs. Strains evaluated in this study were processed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and repetitive-PCR techniques. Two experiments were conducted in order to better define the relationship among genotype, phenotype, and site of isolation. Experiment 1 included 53 H. parasuis isolates recovered from healthy and diseased pigs from unrelated herds. Experiment 2 included 31 isolates of H. parasuis obtained from diseased pigs involved in an outbreak in a large, multifarm system. Results showed that strains recovered from systemic sites had more homogeneous OMP and DNA profiles than those isolated from respiratory sites. Evaluation of isolates involved in the multifarm outbreak showed that only two H. parasuis strains were causing disease. These strains had homogeneous OMP and DNA profiles. However, it was noted that these two parameters were unrelated, since strains classified in the same genotype group expressed different OMP profiles. The homogeneity of OMP and DNA profiles of strains isolated from systemic sites strongly suggests the existence of clonal relationships between virulent strains and also suggests that expression of certain OMP profiles may be related to virulence.

Animals↗
PubMed2001

Courtship song genes and speciation in sand flies.

Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera: Psychodidae: Phlebotominae) is a vector of visceral leishmaniasis in the Americas and it might represent a complex of sibling species. Reproductive isolation between closely related species often involves differences in courtship behaviour. cacophony (cac) and period (per) are two Drosophila genes that control features of the "lovesong" males produce during courtship that has been implicated in the sexual isolation between closely related species. We are using gene fragments from L. longipalpis' homologues of these two genes to study the speciation process in this putative species complex.

Animals↗
PubMed2001

Experimental colonization of piglets and gilts with systemic strains of Haemophilus parasuis and Streptococcus suis to prevent disease.

Haemophilus parasuis and Streptococcus suis are both major causes of losses during the nursery period, especially in herds using the segregated early weaning system. In this system, only a few piglets may be colonized with the herd's prevalent systemic strain, which results in infection of naive penmates late in the nursery. In view of these factors, the objectives of this study were: (1) to evaluate the early colonization of piglets with the farm's prevalent systemic strain of H. parasuis and S. suis as an alternative method for disease prevention; and (2) to evaluate 2 different protocols for experimental colonization: direct colonization of piglets and colonization of piglets through nose-to-nose contact with inoculated sows. Haemophilus parasuis and S. suis isolates recovered from diseased nursery pigs were characterized by the rep-PCR technique and the herd's prevalent strains were used for colonization. Piglets in the experimentally colonized groups were inoculated at 5 days of age by the oral route using a spray pump. Sows were colonized at 2 weeks prior to farrowing using a similar protocol. Although both colonization protocols were successful in getting the piglets colonized, direct inoculation of 5-day-old piglets with the herd's systemic strains of H. parasuis and S. suis tended to be more effective in reducing the morbidity and the mortality than the colonization of piglets by nose-to-nose contact with inoculated sows.

Animals↗
PubMed2000

Molecular cloning of the gene encoding flavoredoxin, a flavoprotein from Desulfovibrio gigas.

Sulfate-reducing bacteria are rich in unique redox proteins and electron carriers that participate in a variety of essential pathways. Several studies have been carried out to characterize these proteins, but the structure and function of many are poorly understood. Many Desulfovibrio species can grow using hydrogen as the sole energy source, indicating that the oxidation of hydrogen with sulfite as the terminal electron acceptor is an energy-conserving mechanism. Flavoredoxin is an FMN-binding protein isolated from the sulfate-reducing bacteria Desulfovibrio gigas that participates in the reduction of bisulfite from hydrogen. Here we report the cloning and sequencing of the flavoredoxin gene. The derived amino acid sequence exhibits similarity to several flavoproteins which are members of a new family of flavin reductases suggested to bind FMN in a novel mode.

Amino Acid Sequence↗
PubMed2000

Structure of a dioxygen reduction enzyme from Desulfovibrio gigas.

Desulfovibrio gigas is a strict anaerobe that contains a well-characterized metabolic pathway that enables it to survive transient contacts with oxygen. The terminal enzyme in this pathway, rubredoxin:oxygen oxidoreductase (ROO) reduces oxygen to water in a direct and safe way. The 2.5 A resolution crystal structure of ROO shows that each monomer of this homodimeric enzyme consists of a novel combination of two domains, a flavodoxin-like domain and a Zn-beta-lactamase-like domain that contains a di-iron center for dioxygen reduction. This is the first structure of a member of a superfamily of enzymes widespread in strict and facultative anaerobes, indicating its broad physiological significance.

Amino Acid Sequence↗
PubMed2000

A DNA fragment of Desulfovibrio gigas genome containing replication origin related genes.

The nucleotide sequence of a 10,772 base pair (bp) region from Desulfovibrio gigas genome was determined. This sequence, which is adjacent to the region containing the coding units for the metalloproteins rubredoxin-oxygen oxidoreductase (ROO) and rubredoxin, includes the flavodoxin gene. Additionally, it also contains four open reading frames (ORFs) related to genes frequently found in replication origin regions of prokaryotes. These hypothetical encoded polypeptides are: the response regulator proteins (PhoP and PhoR) from the phosphate regulon, a DNA partitioning protein and an asparagine synthetase.

Amino Acid Sequence↗
PubMed1999

Desulfovibrio gigas neelaredoxin. A novel superoxide dismutase integrated in a putative oxygen sensory operon of an anaerobe.

Neelaredoxin, a small non-heme blue iron protein from the sulfate-reducing bacterium Desulfovibrio gigas [Chen, L., Sharma, P., LeGall, J., Mariano, A.M., Teixeira M. and Xavier, A.V. (1994) Eur. J. Biochem. 226, 613-618] is shown to be encoded by a polycistronic unit which contains two additional open reading frames (ORF-1 and ORF-2) coding for chemotaxis-like proteins. ORF-1 has domains highly homologous with those structurally and functionally important in methyl-accepting chemotaxis proteins, including two putative transmembrane helices, potential methylation sites and the interaction domain with CheW proteins. Interestingly, ORF-2 encodes a protein having homologies with CheW proteins. Neelaredoxin is also shown to have significant superoxide dismutase activity (1200 U. mg-1), making it a novel type of iron superoxide dismutase. Analysis of genomic data shows that neelaredoxin-like putative polypeptides are present in strict anaerobic archaea, suggesting that this is a primordial superoxide dismutase. The three proteins encoded in this operon may be involved in the oxygen-sensing mechanisms of this anaerobic bacterium, indicating a possible transcriptional mechanism to sense and respond to potential stress agents.

Amino Acid Sequence↗
PubMed1997

Studies on the redox centers of the terminal oxidase from Desulfovibrio gigas and evidence for its interaction with rubredoxin.

Rubredoxin-oxygen oxidoreductase (ROO) is the final component of a soluble electron transfer chain that couples NADH oxidation to oxygen consumption in the anaerobic sulfate reducer Desulfovibrio gigas. It is an 86-kDa homodimeric flavohemeprotein containing two FAD molecules, one mesoheme IX, and one Fe-uroporphyrin I per monomer, capable of fully reducing oxygen to water. EPR studies on the native enzyme reveal two components with g values at approximately 2.46, 2.29, and 1.89, which are assigned to low spin hemes and are similar to the EPR features of P-450 hemes, suggesting that ROO hemes have a cysteinyl axial ligation. At pH 7.6, the flavin redox transitions occur at 0 +/- 15 mV for the quinone/semiquinone couple and at -130 +/- 15 mV for the semiquinone/hydroquinone couple; the hemes reduction potential is -350 +/- 15 mV. Spectroscopic studies provided unequivocal evidence that the flavins are the electron acceptor centers from rubredoxin, and that their reduction proceed through an anionic semiquinone radical. The reaction with oxygen occurs in the flavin moiety. These data are strongly corroborated by the finding that rubredoxin and ROO are located in the same polycistronic unit of D. gigas genome. For the first time, a clear role for a rubredoxin in a sulfate-reducing bacterium is presented.

Amino Acid Sequence↗
PubMed1997

[Quality of quality: a workers' health perspective]

In Brazil, new forms of labor organization based on the so-called Japanese management model are characterized by the implementation of Total Quality Programs, heavily altering relations in the labor force. Pressures brought to bear by modernity, such as demand for quality, affect workers and result in physical and mental disturbances. A case study focusing on a textile industry in Nova Friburgo, Rio de Janeiro State, aimed at elucidating how such programs are formulated in such a way as to increase product quality without changing quality of life for workers. We detected precarious work conditions alongside sophisticated requirements, including abstraction, internalized control, dissemination of the supplier/client concept, etc., running up against a labor force with limited schooling, thus creating a tense atmosphere with a steady speed-up in the work pace, albeit with no real gains for workers.

Journal Article↗
PubMed1996

T lymphocyte mediated protection against facultative intracellular bacteria.

Acquired immunity against intracellular bacteria is T cell dependent. T cells play a major role in protection against intracellular bacteria, but bacterial antigens recognized by T cells have been studied less extensively than bacterial antigens recognized by B cells. Using T lymphocytes from animals immunized against Brucella abortus, we have screened a bacterial genomic library for genes encoding antigens recognized by T cells. Lymphocytes that proliferated to B. abortus proteins were characterized for phenotype and cytokine activity. Bovine and murine lymphocytes recognized common bacterial antigens and possessed similar cytokine profiles, suggesting an analogous immune response in these two animal species. In vivo protection afforded by a particular cell type is dependent on the bacterial antigens presented and mechanisms of antigen presentation. MHC class I and class II gene knockout animals infected with B. abortus have demonstrated that protection to B. abortus is especially dependent on CD8+ T cells. Knowing the cells required for protection, vaccines can be designed to elicit the protective subset of lymphocytes. Currently, we are testing several recombinant B. abortus proteins using different immunization strategies. Finally, bacterial genes activated following intracellular phagocytosis are being examined using a novel, reporter system adapted to B. abortus.

Animals↗
PubMed1995

Replication of transfected plasmid DNA by cells infected with African swine fever virus.

Recombinant plasmids containing African swine fever virus (ASFV) DNA fragments covering all the virus genome were transfected into infected cells in order to detect viral origins of DNA replication. Plasmid replication was monitored by sensitivity to MboI, which cleaves only replicated, unmethylated DNA, and resistance to DpnI, which cleaves only the same methylated sequence. All the recombinants replicated to a similar extent, indicating that ASFV does not use a preferred origin for DNA replication. Circular plasmids without viral inserts were also replicated, but linearized plasmids or lambda bacteriophage DNA were not replicated. Replicated plasmid DNA began to accumulate with a time course similar to viral DNA, starting between 6 and 12 hr p.i. and increasing steadily for about 18 hr. This apparent dependence on viral functions was confirmed by the sensitivity of plasmid replication to phosphonoacetic acid and resistance to aphidicolin and by the reduction of replication in cells infected with a mutant defective in DNA replication. Replicated plasmid DNA present as unit length circles and as large dimension forms, probably head-to-tail concatemers. The results of two-dimensional electrophoresis (neutral/alkaline) favor a rolling-circle mechanism for plasmid DNA replication.

African Swine Fever Virus↗
PubMed1991

Wide distribution of the variant form of the human malaria parasite Plasmodium vivax.

We have found polymorphism in the repetitive and nonrepetitive regions of the sporozoite vaccine antigen, the circumsporozoite (CS) protein, in Plasmodium vivax malaria parasites from two geographically distant malaria endemic regions of the world. Like the recently described variant repeat sequence of P. vivax from Thailand, the CS protein repeat sequence of the variant P. vivax parasites from Papua New Guinea and Brazil is ANGA(G/D)(N/D)QPG, which differs from the previously identified CS repeat sequence, GDRA(D/A)GQPA, of P. vivax parasites from South America, Central America, and North Korea. Comparison of the P. vivax CS protein outside the repeat region revealed restricted polymorphism in regions that have exhibited T-cell immune function and sequence heterogeneity in the CS protein of Plasmodium falciparum. Our results show that P. vivax malaria parasites with the variant CS repeat sequences are widespread in nature and that the polymorphism in the CS protein of P. vivax is also present in the nonrepeat region.

Amino Acid Sequence↗
PubMed1991

Clinical experience of emergency coronary artery bypass grafting following failed percutaneous transluminal coronary angioplasty.

From July, 1981 to December, 1988, 2431 percutaneous transluminal coronary angioplasties were performed on 1901 patients at the Heart Institute of São Paulo University Medical School. Seventy-six patients (4.0 per cent) underwent emergency coronary artery bypass grafting for failed angioplasty. The incidence of failed angioplasty was significantly higher in the impending myocardial infarction group (11.5 per cent) than in the angina group (4.8 per cent) and the acute myocardial infarction group (1.3 per cent). The mean age of the seventy-six patients was 54.4 years, and 54 patients were male. The operative mortality was 15.8 per cent, being 9 males and 3 females. Patients who had had a left main trunk dissection during angioplasty and those who were hemodynamically unstable following the failed angioplasty or who had had a cardiac arrest necessitating a cardiac massage during transportation to the operating room, had a higher mortality than patients in whom the failure occurred in other sites and those who were hemodynamically stable. Perioperative myocardial infarction was documented in 50 per cent of the patients. Patients who had had a cardiac arrest during the procedure had a higher rate of perioperative myocardial infarction than those whose preoperative hemodynamic condition was stable.

Angina Pectoris↗
PubMed1990

Genetic diversity of Plasmodium falciparum shows geographical variation.

Sixty Plasmodium falciparum isolates, 20 each from Thailand, Zimbabwe, and Brazil, were characterized for 20 variant genetic markers, including the enzymes glucose phosphate isomerase, adenosine deaminase and peptidase, 11 other proteins detected by 2-dimensional electrophoresis (2D-PAGE), 2 merozoite surface antigens (MSA-1 and MSA-2), one exported antigen (Exp-1), and sensitivity to the drugs chloroquine, pyrimethamine, and mefloquine. The study examines the extent of diversity between individual isolates and the differences in the frequency of certain variants of the markers between the 3 countries. The principal conclusions to be drawn from the study are that there is extensive polymorphism in many of the genetically determined characters of this parasite, multiple infections with greater than 1 genetically distinct parasite are common, and there are geographical variations in the frequencies with which variant forms of certain markers occur.

Alleles↗