Showing papers by "Federal University of Rio de Janeiro published in 1988"

Visuotopic organization and extent of V3 and V4 of the macaque

Abstract: The representation of the visual field in areas V3 and V4 of the macaque was mapped with multiunit electrodes. Twelve Macaca fascicularis were studied in repeated recording sessions while immobilized and anesthetized. V3 is a narrow strip (4-5 mm wide) of myeloarchitectonically distinct cortex located immediately anterior to V2. It contains a systematic representation of the central 35-40 degrees of the contralateral visual field; the representation of the upper quadrant is located ventrally in the hemisphere and that of the lower quadrant, dorsally. There is a small gap between the dorsal (V3d) and ventral (V3v) portions of V3. The representation of the horizontal meridian is adjacent to that in V2 and forms the posterior border of both V3d and V3v. Most or all of the anterior border of V3d consists of the representation of the lower vertical meridian. The entire anterior border of V3v consists of the representation of the upper vertical meridian. V4 is a strip of myeloarchitectonically distinct cortex 5-8 mm wide, immediately anterior to V3. It contains a coarse, but systematic, representation of approximately the central 35-40 degrees of the contralateral visual field. The representation of the upper visual field is located ventrally in the hemisphere. Most of the representation of the lower visual field is located dorsally. The posterior border of V4 corresponds to the representation of the vertical meridian, and the representation of the horizontal meridian is located at or near its anterior border. In both V3 and V4, the representation of the central visual field is magnified relative to that of the periphery. In both areas, the size of receptive fields increases with increasing eccentricity; however, at a given eccentricity, the receptive fields of V4 are larger than those of V3.

Topographical organization of cortical afferents to extrastriate visual area PO in the macaque: a dual tracer study.

Abstract: We have examined the origin and topography of cortical projections to area PO, an extrastriate visual area located in the parieto-occipital sulcus of the macaque. Distinguishable retrograde fluorescent tracers were injected into area PO at separate retinotopic loci identified by single-neuron recording. The results indicate that area PO receives retinotopically organized inputs from visual areas V1, V2, V3, V4, and MT. In each of these areas the projection to PO arises from the representation of the periphery of the visual field. This finding is consistent with neurophysiological data indicating that the representation of the periphery is emphasized in PO. Additional projections arise from area MST, the frontal eye fields, and several divisions of parietal cortex, including four zones within the intraparietal sulcus and a region on the medial dorsal surface of the hemisphere (MDP). On the basis of the laminar distribution of labeled cells we conclude that area PO receives an ascending input from V1, V2, and V3 and receives descending or lateral inputs from all other areas. Thus, area PO is at approximately the same level in the hierarchy of visual areas as areas V4 and MT. Area PO is connected both directly and indirectly, via MT and MST, to parietal cortex. Within parietal cortex, area PO is linked to particular regions of the intraparietal sulcus including VIP and LIP and two newly recognized zones termed here MIP and PIP. The wealth of connections with parietal cortex suggests that area PO provides a relatively direct route over which information concerning the visual field periphery can be transmitted from striate and prestriate cortex to parietal cortex. In contrast, area PO has few links with areas projecting to inferior temporal cortex. The pattern of connections revealed in this study is consistent with the view that area PO is primarily involved in visuospatial functioning.

Mercury inputs into the Amazon Region, Brazil

Abstract: Mercury inputs into the Brazilian Amazon ecosystem due to goldmining activities are quantified based on data from various Brazilian Mineral and Environmental Agencies as well as field works. Total losses of Hg were estimated to be 1.32 kg Hg/kg Au from which 45% are released into rivers and 55% into the atmosphere. Total Hg input to the Amazon may contribute with up to 6% of the global anthropogenic Hg emissions to the atmosphere and the releases into the rivers are at the same order of magnitude as the inputs into the North Sea.

Tranylcypromine in social phobia.

Abstract: Thirty-two patients meeting DSM-III criteria for social phobia entered a 1-year drug treatment with tranylcypromine in dosages between 40 and 60 mg/day. After exclusion of the early dropouts, improvement was rated as marked and moderate in 62% and 17% of the sample (N = 29), respectively. Alcohol abuse was associated with a poor outcome. Side effects were frequent and in some cases delayed the attainment of efficacious dosages until the third month of treatment. No serious adverse reactions occurred. The findings, relative to efficacy, are in accordance with a previous trial with phenelzine but need confirmation in double blind controlled studies.

Representation of the visual field in the second visual area in the Cebus monkey.

Abstract: The representation of the visual field in the second visual area (V2) was reconstructed from multiunit visual responses and anatomical tracers. Receptive field plotting was performed during multiple recording sessions in seven Cebus apella monkeys under N2O/O2 and immobilized with pancuronium bromide. V2 forms a continuous belt of variable width around striate cortex (V1) except at the most anterior portion of the calcarine sulcus. In each hemisphere V2 contains a visuotopic representation of the contralateral visual hemifield. The representation of the vertical meridian is adjacent to that of V1 and forms the posterior border of V2. The representation of the fovea of V2 is adjacent to that of V1. The representation of the horizontal meridian (HM) is continuous with that of V1; then it splits to form the anterior border of V2, both dorsally and ventrally. The lower quadrant of the visual field is represented dorsally and the upper quadrant ventrally. The visual topography of V2 is coarser than that of V1. In V2, receptive fields corresponding to recording sites separated by a cortical distance of up to 4 mm may represent the same portion of the visual field. In three additional animals, combined injections of fluorescent tracers along the HM representation in V1 yielded two projection sites at the anterior border of V2. The split of the HM representation is estimated to occur at an eccentricity below 1 degree. Quantitative analysis showed that in V2 the representation of the central visual field is magnified relative to that of the periphery. The cortical magnification factor is greater along the isopolar dimension than along the isoeccentric one. Receptive field size in V2 increases with increasing eccentricity. In sections stained for myelin by the Heidenhein-Woelcke method V2 can be distinguished from the surrounding cortex for most of its extent.

Presence of laminin-binding proteins in trichomonads and their role in adhesion.

Abstract: Adhesion is regarded as an important feature in the pathogenesis of various microorganisms. Ability to recognize extracellular matrix proteins, such as laminin or fibronectin, has been correlated with invasiveness. We report that laminin enhances the adhesion of the parasitic protozoa Trichomonas vaginalis and Tritrichomonas foetus to a polystyrene substrate and to the surface of epithelial cells (Madin-Darby canine kidney cell line) in vitro. The enhancement was higher for T. vaginalis than for T. foetus. Addition of anti-laminin antibodies to medium significantly inhibited the adhesion of parasites to polystyrene substrate. Indirect immunofluorescence and transmission electron microscopy of replicas of the parasite's surface labeled with antibody-gold complexes showed laminin-binding sites distributed over the parasite surface. Iodinated P1 fragment of laminin, which retains the laminin-binding site, binds saturably to the parasite surface with a Kd of 19.5 nM, for about 3 X 10(5) binding sites per cell. Immunoblotting analysis of whole parasite extracts showed that a protein of 118 kDa is responsible for laminin binding.

Cytoplasmic organelles of trypanosomatids: a cytochemical and stereological study.

Abstract: The cytoplasmic organelles of different protozoa of the family Trypanosomatidae were characterized by ultrastructural cytochemistry and stereology. Data were obtained for mitochondria, lipid inclusions, glycosomes (peroxisome-like organelle), empty membrane-bounded vacuoles, reservosomes of Trypanosoma spp., multivesicular body of Crithidia fasciculata and dense granules of Crithidia oncopelti. The stereological analysis (D = mean diameter, Vv = volume density and Nv = numerical density) was performed in glutaraldehyde-formaldehyde and osmium tetroxide-potassium ferricyanide fixed parasites, which showed an excellent preservation of the membranes and cytoplasmic organelles. Lipid inclusions, not limited by a unit membrane, appeared electron-dense after post-fixation in an osmium-imidazole buffered solution. Catalase, a peroxisomal enzyme, was detected only in the glycosomes of the lower trypanosomatids. Empty membrane-bounded vacuoles showed positive reaction when the cells were incubated in a medium specific for the detection of the lysosomal enzyme acid phosphatase. The reservosomes of Trypanosoma spp., sub-genus Schizotrypanum, could be differentiated from the multivesicular bodies of other trypanosomatids, since they lack true vesicles. They contain lipid inclusions dispersed in an electron-dense matrix which stained positively when the cells were incubated in ethanolic phosphotungstic acid to detect basic proteins.

Distribution of chondroitin 4-sulfate and chondroitin 6-sulfate in human articular and growth cartilage.

Abstract: The relative concentrations of chondroitin 4- and chondroitin 6-sulfate in different normal human cartilages are reported. Articular cartilages contained higher concentrations of chondroitin 6-sulfate, whereas growth cartilages contained nearly equal amounts of chondroitin 4- and chondroitin 6-sulfate. Adult cartilages, in which the calcification process is already complete, contained only chondroitin 6-sulfate. The results suggest that chondroitin 6-sulfate is related to the integrity of the articular surfaces, whereas chondroitin 4-sulfate seems to be an important factor in the calcification process. The pathogenesis of the bone and cartilage alterations that occur in patients affected by heritable disorders of the sulfation of chondroitin sulfate are discussed in view of these findings.

Metabolism and mode of action of gentian violet

Abstract: Gentian violet has been used in medicine for almost 100 years: as an antiseptic for external use, as an antihelminthic agent by oral administration, and more recently, as a blood additive to prevent transmission of Chagas' disease. To date, no serious side effects have been reported when used externally. However, oral administration can cause gastrointestinal irritation, and intravenous injection can cause depression in the white blood cell count. Surprisingly, no acute toxic side effects were reported after administration of large amounts of gentian violet-treated blood. No studies have been done on long-term effects (chronic toxicity, carcinogenicity) of gentian violet-treated blood either in humans or in laboratory animals. Gentian violet is a mutagen, a mitotic poison, and a clastogen. The carcinogenic effects of gentian violet in rodents have been reported recently. In addition, a number of triphenylmethane-classed dyes, of which gentian violet is a member, have been recognized as animal and human carcinogens. A photodynamic action of gentian violet, apparently mediated by a free-radical mechanism, has been described in bacteria and in T. cruzi. However, the main target of gentian violet toxicity in the dark is the mitochondrion. Gentian violet is actively demethylated by liver microsomes from different animals and is reduced to leucogentian violet by intestinal microflora. Although the first process may represent a detoxication reaction, the second pathway may have toxicological significance because the completely demethylated derivative leucopararosaniline has been demonstrated to be carcinogenic in rats. A free-radical derivative of gentian violet is also formed by the action of rat liver microsomes, but whether this radical is involved in the cytotoxic effects of gentian violet in mammalian cells remains to be elucidated. Other pathways of gentian violet metabolism have recently been investigated that involve its oxidative N-demethylation by peroxidases. The N-demethylation of gentian violet by prostaglandin synthetase deserves further study. In this regard, the PGS system is being studied as an alternative activating pathway in xenobiotic metabolism because some carcinogenic intermediates can be formed during this cooxidation reaction.

Non‐linear heat conduction in composite bodies: A boundary element formulation

Abstract: The present paper discusses the numerical solution of steady-state non-linear heat conduction problems in composite bodies by using the boundary element method. Two kinds of non-linearities are considered: the temperature dependence of the thermal conductivity and boundary conditions of the radiative type. By introducing the integral of conductivity as a new variable the governing equation of the problem becomes linear in the transform space. Transformed boundary conditions of the Dirichlet and Neumann types are also linear but convective boundary conditions become non-linear. Also, discontinuities arise in the value of the integral of conductivity across the interface between materials with different properties since continuity of temperature is imposed. The problem is numerically solved by discretizing the external and interface boundaries of the region under consideration with constant boundary elements and applying an iterative scheme of the Newton–Raphson type.

Concentration and distribution pattern of selected micronutrients in preterm and term milk from urban Brazilian mothers during early lactation.

Abstract: The purpose of this study was to assess the concentration and binding pattern of zinc iron folate and vitamin B12 in the milk of Brazilian women of low socioeconomic status giving birth at term or preterm during early lactation. Protein fat total solids and ash concentrations were also determined. Protein and zinc concentrations decreased significantly as lactation proceeded whereas milkfat and folate increased with the lactation period. Total solids ash iron and vitamin B12 remained unchanged. Zinc was present mainly in the whey fraction while less than 1/2 of the total iron was present in this fraction with no significant change due to stage of lactation. Unsaturated folate and vitamin B12 binding capacities and % of saturation of folate binding protein increased with the stage of lactation. The vitamin B12 binding protein was highly unsaturated in all samples. There was no significant difference between term and preterm samples in the parameters investigated. Correlation analysis between milk components indicated significant relationships between total solids and fat total zinc and whey zinc folate and total folate binding capacity unsaturated and total folated binding capacity and unsaturated and total B12 binding capacity. In general the nutrient concentrations found in this study are in good agreement with published data on milk composition of women from developed countries with the possible exception of folate which was lower and iron which was higher. The correlation of folate concentration with its binding protein found in this work supports the hypothesis of a regulatory role for folate levels in milk exerted by the folate binding protein in the mammary gland. (authors)

Complete pattern of ocular dominance stripes in V1 of a New World monkey, Cebus apella.

Abstract: The presence of ocular dominance (OD) stripes in layer IVc of striate cortex (V1) is characteristic of all Old World simians so far studied. In contrast, some species of New World monkeys do not have ocular dominance stripes, and in those that do, the pattern of stripes may be different from that shown in Old World monkeys. This difference has led to the suggestion that OD stripes evolved independently in both groups. We have mapped the entire system of OD stripes in the New World monkey Cebus, by means of cytochrome oxidase histochemistry after monocular enucleation. A striking similarity was found between the patterns in Cebus and Macaca, which is suggestive of common ancestry, rather than parallel evolution.

A finitely convergent “row-action” method for the convex feasibility problem

Abstract: We present a modification of the Cyclic Subgradient Projection (CSP) method by Censor and Lent, which solves the convex feasibility problem in a finite number of steps when a Slater type condition holds, while preserving its “row-action” properties. A linear rate of convergence for the CSP method is established assuming the same hypothesis.

Bulk-viscosity-driven asymmetric inflationary universe.

Abstract: A primordial net bosonic charge is introduced in the context of the bulk-viscosity-driven inflationary models. The analysis is carried through a macroscopic point of view in the framework of the casual thermodynamic theory. The conditions for having exponential and generalized inflation are obtained. A phenomenological expression for the bulk-viscosity coefficient is also derived.

Oligosaccharide contents in the seeds of cultivated lupins

Abstract: The contents of socrose and α-galactosides of the seeds of 84 cultivated lupin samples were determined by high performance liquid chromatography (PHLC) and the data were correlated both with genotype and environment.

Mononuclear cell subsets in patients with different clinical forms of paracoccidioidomycosis.

Abstract: Seventy untreated paracoccidioidomycosis patients, 15 with the acute or subacute form of the disease and 55 with the chronic form, were compared with two normal control groups of the same age range. Peripheral blood mononuclear cell subsets were defined by monoclonal antibodies directed at total T cells, helper/inducer and suppressor/cytotoxic T cell subpopulations; B cells, cortical thymocytes and monocyte/null cells. Both groups of patients showed an increased number of monocyte/null cells, a low helper/suppressor ratio and a reduced percentage of total T cells and their helper/inducer subsets. In addition patients with the acute form of the disease exhibited high levels of suppressor/cytotoxic T cells and B cells. These findings are of importance in our attempts to understand the pathogenesis of this mycosis and also to evaluate its prognosis in individual patients.

Structure-activity relationship of reversible cholinesterase inhibitors: activation, channel blockade and stereospecificity of the nicotinic acetylcholine receptor-ion channel complex.

Abstract: 1. We have shown that all cholinesterase (ChE) inhibitors, in addition to their well-known anti-ChE activity, have multiple effects on the nicotinic acetylcholine receptor-ion channel (AChR) macromolecule resulting from interactions with the agonist recognition site and with sites located at the ion channel component. Activation, competitive antagonism and different types of noncompetitive blockade occurring at similar concentration ranges and contributing in different proportions result in complex and somewhat unpredictable alterations in AChR function. The question is now raised as to how each effect of these compounds contributes to their antidotal property against organophosphorus (OP) poisoning, and what set of actions makes one reversible ChE inhibitor a better antidote. Many lines of evidence support the importance of direct interactions with various sites on the AChR: 1) morphological and toxicological studies with (+) physostigmine showed that anti-ChE activity is not essential to protect animals against toxicity by irreversible ChE inhibitors; 2) (-)physostigmine is far more effective against OP poisoning; 3) open channel blockers such as mecamylamine with no significant anti-ChE activity enhance the protective action of (-)physostigmine; 4) neostigmine, pyridostigmine, (-)physostigmine and (+)physostigmine showed qualitatively and quantitatively distinct toxicity and damage to endplate morphology and function. 2. In prophylaxis and during the very early phase of OP poisoning, carbamates, especially (-)physostigmine combined with mecamylamine and atropine, could protect almost 100% of the animals exposed to multiple lethal doses of OPs. Electrophysiological data showed that (-)physostigmine, among several reversible ChE inhibitors, showed greater potency in depressing both endplate current (EPC) peak amplitude and tau EPC. Therefore, concerning neuromuscular transmission, it seems that the higher the potency of a drug in reducing endplate permeability, the better is its protection against OP toxicity. A reversible open channel blockade combined with some agonist property helps to decrease the effect of ACh at its agonist site and to reduce the ion permeability of open channels. It should be pointed out that, during the later phase of OP poisoning, AChR desensitization should be most prevalent. Thus, a drug that can remove the AChR from this rather irreversible state to a more reversible blocked state should be a better protector. Indeed, oximes such as 2-PAM and a more potent analog, HI-6, produce multiple alterations in AChR function that comprise increased channel activation and open-channel blockade.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of mitochondrial F1 ATPase and sarcoplasmic reticulum ATPase by hydrophobic molecules

Abstract: The hydrophobic nature of the active site of two energy-transducing ATPases was explored by comparing interactions between Pi and each of three hydrophobic drugs in the absence and presence of organic solvents. The drugs tested were the Fe · bathophenanthroline complex and the anticalmodulin drugs, calmidazolium and trifluoperazine. All inhibit the Pi⇆ ATP exchange reaction catalyzed by submitochondrial particles and the ATPase activity of both submitochondrial particles and soluble F1 ATPase. The inhibition by the three drugs is reversed by either raising the Pi concentration or by adding organic solvent (dimethylsulfoxide, ethyleneglycol or methanol) to the medium. The inhibition of the Pi⇆ ATP exchange by trifluoperazine becomes more pronounced when the electrochemical proton gradient formed across the membrane of the submitochondrial particles is decreased by the addition to the medium of the proton ionophore carbonylcyanide p-trifluoromethoxy-phenylhydrazone. The ATPase activity and the Ca2+ uptake by sarcoplasmic reticulum vesicles are inhibited by the Fe · bathophenanthroline complex, calmidazolium and trifluoperazine. Phosphorylation of the ATPases by Pi, synthesis of ATP from ADP and Pi and the fast efflux of Ca2+ observed during reversal of the Ca2+ pump are inhibited by the three drugs. The inhibition is reversed by raising the concentration of Pi or dimethylsulfoxide. The three drugs tested appear to compete with Pi for a common binding site on the Ca2+-ATPase. The data presented are interpreted according to the proposal that the catalytic site of an enzyme involved in energy transduction undergoes a hydrophobic–hydrophilic transition during the catalytic cycle.