Showing papers by "Federal University of Rio de Janeiro published in 1994"

The use of allozyme electrophoresis in invertebrate systematics

Abstract: The role of enzyme electrophoresis is discussed as it applies to taxonomy and systematics. particularly of invertebrates. Details are given of methods for distinguishing and identifying cryptic or sibling species and the different approaches to sympatric and allopatric populations are reviewed. The calculation and uses of genetic distance measures are outlined. as are the empirical relationship of such measures to different levels of taxonomic separation. Defficulties. drawbacks and limitations of the technique are explained together with the advantages. Evidence for molecular clocks is outlined briefly and their role in systematic studies is discussed, as are methods of analysing genetic divergence data for systematic purposes. References to studies covering a wide range of invertebrate taxa are tabulated.

Use of molecular probes and PCR for detection and typing of Leishmania - a mini-review

Abstract: The use of molecular tools to detect and type Leishmania species in humans, reservoirs or sandflies has been pursued using different approaches. The polymerase chain reaction provided sensitivity to case this task, since the use of hybridization procedures alone employing specifics probes is hampered due to the low detection limit. In this report, we describe the different molecular targets used in our laboratory, aiming at the detection and specific typing of these protozoa. Different kits based on hybridization assays and PCR amplification using kinetoplast and nuclear targets are described and the results obtained from their use are reported.

An efficient controller for an adjustable speed induction motor drive

Abstract: The induction motor (IM) is a high-efficiency machine when working close to its rated operating point. However, at torques and/or speeds far from the rated values the efficiency is greatly reduced. In this work a new approach is proposed that minimizes the total copper and iron losses in a variable speed and/or torque IM drive, while keeping a good dynamic response. This method is based on a simple IM model that includes iron losses. The model, which only requires the knowledge of conventional IM parameters, is referred to a field-oriented frame. Using this model, the IM losses are quantified and an algorithm, based on a field-oriented scheme, is deduced. Simulation and experimental results are presented to validate the proposed method. >

Analysis and design of I/O based variable structure adaptive control

Abstract: This paper presents an overview of a technique for the design of variable structure model reference adaptive control (VS-MRAC) systems, using only input-output data. The main ideas underlying the design and the analysis, as well as the main properties of the controller, are described having as point of departure a well known parameter adaptive MRAC scheme. Then, asymptotic properties of the VS-MRAC system are established taking into account the effect of the averaging filters necessary to implement some equivalent control signals. In particular, global exponential stability of the associated error system with respect to a small residual set is demonstrated. The effect of linear zones in the relay functions is assessed showing that they can alleviate the chattering phenomena. This is related with the fact that the VS-MRAC has a high-gain stability property. A procedure for noise sensitivity reduction is also proposed. Simulations illustrate the very satisfactory performance of the VS-MRAC in adverse operating conditions. >

Cellular mechanism of the conduction abnormalities induced by serum from anti-Ro/SSA-positive patients in rabbit hearts.

Abstract: In this study, IgG fractions from sera of SLE patients with anti-Ro/SSA or anti-Ro/SSA and anti-La/SSB activity were tested in Langendorff preparations of adult rabbit hearts, aiming to reproduce the cardiac manifestations observed in neonatal lupus in an experimental model. The hearts were perfused with normal Tyrode's solution for 30 min, followed by perfusion with Tyrode's containing 0.3 mg/ml of anti-Ro/SSA- (or anti-Ro/La-) positive IgG (nine sera), anti-ribonucleoprotein (RNP)-positive IgG (five sera), or IgG fractions from normal donors (five sera). In one third of the experiments done with anti-Ro/La-positive IgG, heart block was observed. With the remaining fractions, a decrease in heart rate of 17.1% was observed, but normal sinus rhythm was maintained. The IgG fractions with anti-RNP activity (five experiments) and from normal sera (six experiments) reduced heart rates by 12.9 and 3.3%, respectively, but heart block was not observed. To further characterize the cellular mechanisms involved in the conduction disturbances observed in the whole rabbit hearts, we conducted experiments with ventricular myocytes isolated from young rabbit hearts, studied by whole cell patch-clamp technique. In these experiments, the slow inward currents were analyzed during the superfusion of the cell with normal Tyrode's solution and 5 min after superfusion with Tyrode's solution containing 0.3 mg/ml of anti-Ro/SSA- (or anti-Ro/La-) positive IgG (five sera), anti-RNP-positive IgG (three sera), or IgG from normal donors (four sera). Resting and action potential amplitudes were not affected by any of the sera used. The anti-Ro/SSA IgG fraction induced a mean reduction in the peak slow inward current of 31.6%. IgG fractions with anti-RNP activity reduced slow inward current by 4.4%, whereas IgG fractions from normal donors increased this current by 3.3%. IgG-free fractions from sera of patients with anti-Ro/SSA activity did not alter the peak slow inward current. These results show, for the first time, that the presence of anti-Ro/SSA or anti-Ro/SSA and anti-La/SSB antibody activity in IgG fractions from lupus patients' sera can induce cardiac conduction disorders similar to those observed in neonatal lupus.

On a class of globally stable neural circuits

Abstract: The authors show that diagonal stability of the interconnection matrix leads to a simple proof of the existence, uniqueness, and global asymptotic stability of the equilibrium of a Hopfield-Tank neural circuit, without making some common restrictive assumptions used in earlier results. It is also shown that the same condition guarantees structural stability, which ensures the desirable property of persistence of global asymptotic stability under general C/sup 1/ perturbations. >

Glycosaminoglycan fractions from human arteries presenting diverse susceptibilities to atherosclerosis have different binding affinities to plasma LDL.

Abstract: The topographic distribution of atherosclerotic lesions is influenced by biochemical factors intrinsic to the arterial wall. In the present work we have investigated whether the composition/chemical structure of glycosaminoglycans constitutes one of these factors. Normal human arteries were obtained at necropsy, and in order of decreasing susceptibility to atherosclerosis, consisted of the abdominal and thoracic aortas and the iliac and pulmonary arteries. The results showed similar concentrations of total glycosaminoglycan and collagen. Of the glycosaminoglycans known to interact with low-density lipoprotein (LDL), dermatan sulfate was present in all arteries in comparable concentrations, but the aortas had a 30% higher content of chondroitin 4/6-sulfate, which in turn was slightly enriched in 6-sulfated disaccharide units. LDL-affinity chromatography with dermatan sulfate+chondroitin 4/6-sulfate fractions demonstrated that increasing affinity to LDL matched an increasing susceptibility to atherosclerosis. Analysis of glycosaminoglycans in the eluates indicated a positive correlation between affinity to LDL and increasing molecular weight and the existence of a fraction of glycosaminoglycans of high affinity to LDL in the aortas only. These results suggest that arterial glycosaminoglycans participate in the multifactorial mechanisms that modulate the differential localization of atherosclerotic lesions.

O-glycosidically linked N-acetylglucosamine-bound oligosaccharides from glycoproteins of Trypanosoma cruzi

Abstract: In this report we describe studies on the structures of the O-linked carbohydrate units in cell-surface glycoproteins of epimastigote forms of the G-strain of Trypanosoma cruzi. Mild alkaline reductive degradation of the 38/43 kDa glycoproteins resulted in beta-elimination of glycosylated threonine and/or serine residues, and the liberation of N-acetylglucosaminitol, galactobiosyl-, galactotriosyl-, galactotetraosyl- and galactopentaosyl-N-acetylglucosaminitol. The structures of these oligosaccharide alditols were established by n.m.r. spectroscopy and methylation analysis as: Galf beta 1-4(Galp beta 1-6)GlcNAc-ol; Galp beta 1-3Galp beta 1-6(Galf beta 1-4)GlcNAc-ol; [(Galp beta 1-3)(Galp beta 1-2)Galp beta 1-6](Galf beta 1-4)GlcNAc-ol; [(Galp beta 1-3)(Galp beta 1-2)Galp beta 1-6](Galp beta 1-2Galf beta 1-4)GlcNAc-ol.

Global analysis of antibody repertoires. 1. An immunoblot method for the quantitative screening of a large number of reactivities.

Abstract: This paper describes a procedure for analysing multiple antibody reactivities that explores a commercially available immunoblot system, and is based on a double staining of nitrocellulose membranes, revealing both antibody reactivities and the migration position of the blotted proteins in the membrane. Quantification of both stainings by densitometry allowed the accurate superposition of the immunoreactivity and total protein profiles of each lane. Moreover, the protein stainings of the different lanes could be adjusted with a simple-scale transformation algorithm, correcting for possible distortions during electrophoretic migration, and allowing for the precise comparison of the immunoreactivity profiles in different lanes. The procedure is discriminatory enough to identify unique reactivity patterns in random pools of 10(4) activated B cells, and to define strain-specific natural antibody repertoires. The utility of this immunoblot method as an assay for simultaneously scoring multiple reactivities to hundreds of antigens in complex mixtures of antibodies, and thus defining antibody repertoires in a global manner, is discussed.

First report of microcystins from a Brazilian isolate of the cyanobacteriumMicrocystis aeruginosa

Abstract: This is the first report on microcystins, cyclic heptapeptide hepatotoxins, from Brazilian water supplies. A colony isolate (NPJB-1) of the colonial cyanobacteriumMicrocystis aeruginosa from Lagoa das Garcas, Sao Paulo, was cultured under non-axenic conditions. Exponential phase cells were harvested, concentrated and lyophilized for mouse bioassays and toxin extraction. The LD100 of lyophilized cell suspensions was approximately 31 mg kg−1 (dry cell weight/animal weight). Isolation, purification and characterization of the toxins were carried out by reversed phase HPLC, HPLC amino acid analysis and fast atom bombardment mass spectrometry. Strain NPJB-1 produces two different hepatotoxic heptapeptide microcystins. The main one was microcystin-LR, the most commonly reported microcystin from cyanobacteria. The other was microcystin-LF, the phenylalanine variant of microcystin-LR. This is the first published report for microcystin-LF.

Coinfection With Human T-Cell Lymphotropic Virus Type I and HIV in Brazil: Impact on Markers of HIV Disease Progression

Abstract: Objectives. —To study the effect of human T-cell lymphtropic virus type I (HTLV-I) on markers of human immunodeficiency virus (HIV) disease progression. Design. —A retrospective, nested case-control study. Setting. —A university hospital outpatient HIV clinic in Rio de Janeiro, Brazil. Participants. —Human immunodeficiency virus—seropositive adults participating in a prospective HIV cohort study. Main Outcome Measures. —The HIV clinical stage, CD4 + lymphocyte counts, and other laboratory parameters in 27 individuals infected with HIV and HTLV-I (coinfection) and 99 age-matched, HIV-seropositive, HTLV-seronegative controls (single infection). Results. —Variables independently associated with coinfection included higher CD4 + lymphocyte count (odds ratio [OR], 2.3; 95% confidence limits [CL], 1.3,4.1), higher CD4 + percentage (OR, 2.0; 95% CL, 1.3, 3.2), β 2 -microglobulin level of 254 nmol/L or more (OR, 6.8; 95% CL, 1.3, 35.4), World Health Organization stages 3 and 4 (OR, 4.4; 95% CL, 1.1,18.0), and reporting a parenteral risk factor (OR, 7.4; 95% CL, 1.4, 38.9). When stratified by p24 antigenemia, coinfection was associated with an estimated 82% higher CD4 + lymphocyte count ( P Conclusion. —Coinfection was associated with higher CD4 + lymphocyte counts, more advanced clinical disease, and higher β 2 -microglobulin levels than HIV infection alone. The higher mean CD4 + lymphocyte count does not appear to offer immunologic benefit. Caution should be exercised when using CD4 + lymphocytes as a surrogate marker in studies of HIV infection in populations where HTLV-I is prevalent. Further studies are needed to address whether current CD4 + lymphocyte values for the initiation of antiretroviral therapy and chemoprophylaxis against opportunistic infections in HIV infection are appropriate in coinfection. ( JAMA . 1994;271:353-357)

Pharmacological Screening of Plants Recommended by Folk Medicine as Snake Venom Antidotes; IV. Protection against Jararaca Venom by Isolated Constituents1.

Abstract: Fifteen compounds, isolated from plants reputed as snake venom antidotes, belonging to different classes of natural products, were shown to protect mice to a significant degree against the lethal action of the venom of Bothrops jararaca snakes. Administration was by the oral route, one hour prior to envenomation. The substances are nitrogen-free, low-molecular-weight compounds for which some kind of biodynamic activity has previously been reported. The fact that they are mostly trivial, naturally-occurring compounds should explain why plants used as snake-bite antidotes are so widely distributed over the plant kingdom.

Pesquisa interpretativista em lingüística aplicada: a linguagem como condição e solução

Abstract: Neste artigo, discutimos a tradicao interpretativista da pesquisa em Linguistica Aplicada. Isso e feito atraves da comparacao entre os modos de pesquisa positivista e interpretativista, com base em seus principios ontologicos, epistemologicos e metodologicos. Argumenta-se que, uma vez que a linguagem condiciona a realidade social - isto e, os homens a constroem atraves do uso da linguagem - e oferece os meios para sua compreensao, a tradicao interpretativista parece ser mais adequada ao tipo de dados com o qual se confronta ao fazer pesquisas em Applied Linguistica. A tradicao interpretativista e exemplificada atraves da discussao de dois tipos de paradigmas de pesquisa: os paradigmas etnograficos e os introspectivos.

Eco-estratégia nas empreas brasileiras: realidade ou discurso?

Abstract: The environmental behavior of Brazilian companies is late in comparison with the behavior of developed countries firms.

Cold denaturation of a repressor-operator complex: the role of entropy in protein-DNA recognition.

Abstract: The mechanisms by which regulatory proteins recognize specific DNA sequences are not fully understood. Here we examine the basis for the stability of a protein-DNA complex, using hydrostatic pressure and low temperature. Pressure converts the DNA-binding Arc repressor protein from a native state to a denatured, molten-globule state. Our data show that the folding and dimerization of Arc repressor in the temperature range 0-20 degrees C are favored by a large positive entropy value, so that the reaction proceeds in spite of an unfavorable positive enthalpy. On binding operator DNA, Arc repressor becomes extremely stable against denaturation. However, the Arc repressor-operator DNA complex is cold-denatured at subzero temperatures under pressure, demonstrating that the favorable entropy increases greatly when Arc repressor binds tightly to its operator sequence but not a nonspecific sequence. We show how an increase in entropy may operate to provide the protein with a mechanism to distinguish between a specific and a nonspecific DNA sequence. It is postulated that the formation of the Arc-operator DNA complex is followed by an increase in apolar interactions and release of solvent which would explain its entropy-driven character, whereas this solvent would not be displaced in nonspecific complexes.

Distribution of serotypes and antimicrobial resistance of Streptococcus pneumoniae strains isolated in Brazil from 1988 to 1992.

Abstract: Forty-two serotypes were identified among 288 Streptococcus pneumoniae strains isolated from patients living in Brazil. Serotyping was determined by the capsular typing test (Quellung reaction). Types 14 (10.4%), 6B (9.8%), 23F (8.0%), 5 (7.3%), 19F (6.9%), 6A (6.0%), and 1 and 4 (4.6%) were the most commonly identified strains. Two hundred twenty (76.4%) of the strains were of serotypes that are included in the 23-valent pneumococcal polysaccharide vaccine. If vaccine-related serotypes are also considered, the proportions of coverage in the vaccine are 82.3% (if type 6B alone is added) and 85.7% (if all the vaccine-related types are considered to be cross-protecting). Decreased susceptibility to penicillin, which was identified by using the 1-microgram oxacillin disk method as a screening test, was detected in 70 (26.7%) strains. The MICs of nine antimicrobial agents were determined by using the procedures recommended by the National Committee for Clinical Laboratory Standards. Seventy (35.9%) of the strains were resistant to tetracycline, 57 (29.2%) were resistant to sulfamethoxazole-trimethoprim, 3 (1.5%) were resistant to rifampin, 2 (0.80%) were resistant to penicillin, and 1 (0.5%) was resistant to chloramphenicol. The two penicillin-resistant strains were also resistant to or had decreased susceptibilities to cephalosporins. Forty-seven (17.9%) of the strains were intermediately resistant to penicillin, 17 (8.7%) were intermediately resistant to tetracycline, 13 (6.7%) were intermediately resistant to chloramphenicol, 12 (6.1%) were intermediately resistant to erythromycin, and 6 (3.1%) were intermediately resistant to rifampin.