Showing papers by "University of São Paulo published in 1991"

5-HT and mechanisms of defence.

Abstract: are concerned with adaptive responses to aversive events. Aversive stimuli can be defined as stimuli which motivate avoidance behaviour. This definition encompasses negative incentives and reinforcers and much of what passes under vaguer terms such as ’punishers’ and ’stresses’. Aversive stimuli can be considered in three groups and we suggest they bring different anatomical structures and 5-HT systems into play. Dysfunction in these central mechanisms of aversion results in different groups of psychological symptoms. The three forms of aversion are summarized below and they form the basis of this article.

Value Segmentation: A Model for the Measurement of Values and Value Systems

Abstract: This article develops a model for the measurement of human values that, rather than obtain aggregate measurements, identifies distinct value systems within a pop­ulation and classifies individuals according to them. These value systems are inferred from the stated priority rankings, obtained from each individual via the Rokeach value survey.

Restaging of colorectal cancer based on the identification of lymph node micrometastases through immunoperoxidase staining of cea and cytokeratins

Abstract: The present study was performed to identify tumor cells in lymph nodes from colorectal adenocarcinomas considered free of disease by the classic hematoxylin-eosin stain, based on the detection of the carcinoembryonic antigen (CEA) and cytokeratins in neoplastic epithelial cells. For this purpose, 603 lymph nodes from 46 lesions were stained by the peroxidase-antiperoxidase technique. Tumor cells were detected in 22 nodes from 12 patients, mainly in the subcapsular sinuses, permitting a restaging of these patients into two groups: those now considered to have metastatic disease and those free of metastases. However, the 5-year follow-up showed no statistical differences in survival between the two groups.

First-principles statistical mechanics of structural stability of intermetallic compounds.

Abstract: While as elemental solids, Al, Ni, Cu, Rh, Pd, Pt, and Au crystallize in the face-centered-cubic (fcc) structure, at low temperatures, their 50%-50% compounds exhibit a range of structural symmetries: CuAu has the fcc-based L1o structure, CuPt has the rhombohedral L1& structure, and CuPd and A1Ni have the body-centered-cubic B2 structure, while CuRh does not exist (it phase separates into Cu and Rh). Phenomenological approaches attempt to rationalize this type of structural selectivity in terms of classical constructs such as atomic sizes, electronegativities, and electron/atom ratios. More recently, attempts have been made at explaining this type of selectivity in terms of the (quantum-mechanical) electronic structure, e.g. , by contrasting the self-consistently calculated total electron+ion energy of various ordered structures. Such calculations, however, normally select but a small, O(10) subset of "intuitive structures" out of the 2 possible configurations of two types of atoms on a fixed lattice with X sites, searching for the lowest energy. We use instead first-principles calculations of the total energies of O(10) structures to define a multispin Ising Hamiltonian, whose ground-state structures can be systematically searched by using methods of lattice theories. Extending our previous work on semiconductor alloys [S.-H. Wei, L. G. Ferreira, and A. Zunger, Phys. Rev. B 41, 8240 (1990)], this is illustrated here for the intermetallic compounds A1Ni, CuRh, CuPd, CuPt, and CuAu, for which the correct ground states are identified out of -65000 configurations, through the combined use of the densityfunctional formalism (to extract Ising-type interaction energies) with a simple configurational-search strategy (to find ground states). This establishes a direct and systematic link between the electronic structure and phase stability.

Effects of acute nitric oxide inhibition on rat glomerular microcirculation.

Abstract: Endothelium-derived relaxing factor (EDRF), recently identified as nitric oxide (NO), has been shown to be released by glomerular endothelial cells and might influence the glomerular microcirculation. To examine this hypothesis, we studied in rats the renal effect of acute administration of NG-monomethyl-L-arginine (L-NMMA), a specific inhibitor of NO synthesis. Adult male Munich-Wistar rats were studied before and after intravenous administration of either pure saline or a bolus injection of L-NMMA (20 mg) followed by a continuous infusion of the inhibitor (0.4 mg/min). Although saline alone had no effect on systemic or glomerular hemodynamics, L-NMMA promoted marked systemic hypertension, glomerular arteriolar vasoconstriction, and glomerular hypoperfusion. Since efferent resistance was disproportionately increased, glomerular hydraulic pressure was also markedly elevated. The glomerular ultrafiltration coefficient (Kf) fell to 42% of control. Single-nephron glomerular filtration rate was unaffected. Striking polyuria was also observed. These findings suggest that EDRF exerts a basal relaxing effect on the glomerular microcirculation.

Exposure and sensitization to dust mite allergens among asthmatic children in São Paulo, Brazil.

Abstract: Summary A group of 20 mite allergic asthmatic children aged 6-12 years old. living in Sao Paulo, Brazil, was studied regarding their degree of sensitization to house dust mites and exposure to mite allergens in their homes. In 18 out of 20 houses at least one dust sample was obtained which contained > 10 μg Der p I/g of dust. The highest levels of Dermatophagoides pteronyssinm allergens, Der p I and Group II, were measured in bedding samples (geometric mean 38.4 and 36.6 μg/g, respectively), followed by bedroom floor, TV room and kitchen. Mite allergen levels in Brazilian houses were as high as those reported to be associated with sensitization and acute attacks of asthma in other parts of the world. In keeping with previous reports that D. farinae is rarely found in Brazil, Der fl was undetectable or found in very low levels ( 8 μg/g of dust were obtained only in 2 houses only. Cockroach allergen Bia g I was detected in five out of 20 houses. Levels of IgE antibodies to D. pteronyssinus were > 200 RAST U/ml in 19 out of 20 children (geometric mean 1588 RAST U/ml). IgE antibodies to cat, cockroach, A. fumigatus, ragweed and rye grass pollens were undetectable or 200 RAST U/ml were observed in 13 out of 20 sera. Immunoabsorption studies demonstrated that the bulk of the IgE- antibody to B. tropicafis (64%) was to species-specific allergens and that 36% were cross-reactive with D. pteronyssinus. The implication of our results is that management of children with asthma in Sao Paulo should include skin testing for allergy to both Dermatophagoides and B. tropicalis as well as recommendations about environmental control of house dust mite exposure.

Critical droplets and metastability for a Glauber dynamics at very low temperatures

Abstract: We consider the metastable behavior in the so-called pathwise approach of a ferromagnetic spin system with a Glauber dynamics in a finite two dimensional torus under a positive magnetic field in the limit as the temperature goes to zero. First we consider the evolution starting from a single rectangular droplet of spins +1 in a sea of spins −1. We show that small droplets are likely to disappear while large droplets are likely to grow; the threshold between the two cases being sharply defined and depending only on the external field. This result is used to prove that starting from the configuration with all spins down (−1) the pattern of evolution leading to the more stable configuration with all spins up (+1) approaches, as the temperature vanishes, a metastable behavior: the system stays close to −1 for an unpredictable time until a critical square droplet of a precise size is eventually formed and nucleates the decay to +1 in a relatively short time. The asymptotic magnitude of the total decay time is shown to be related to the height of an energy barrier, as expected from heuristic and mean field studies of metastability.

Possible oral transmission of acute Chagas' disease in Brazil

Abstract: In October, 1986, 7 to 22 days after a meeting at a farm in Paraiba state, 26 individuals presented with a febrile illness associated with bilateral eyelid and lower limb edema, mild hepatosplenomegaly, lymphadenopathy and, occasionally a skin rash. A 11-year-old boy exhibited atrial premature complexes and a 74-year-old patient developed acute heart failure. In two patients hospitalized in Sao Paulo city, acute Chagas' disease was diagnosed by the demonstration of circulating Trypanosoma cruzi. At autopsy in a fatal case, acute Chagas' cardiomyopathy was demonstrated. Xenodiagnosis were positive in 9 out of 14 tested patients. A specific IgG immune response was found in all patients and specific IgM antibodies were identified in 20 out of 22 tested patients. A epidemiological survey showed the existence of Triatoma brasiliensis in the outbuildings of this farm, but none in the house where most of the guests stayed. A high rate of infection with Trypanosoma cruzi was found in opossums. These observations together with those related to the food consumed by the patients, lead the authors to suggest that the human infections resulted from oral contamination probably originating from naturally infected marsupials in the area or crushed infected bugs.

Anxiolytic effect in the elevated plus-maze of the NMDA receptor antagonist AP7 microinjected into the dorsal periaqueductal grey

Abstract: In order to localise the often reported anxiolytic action of N-methyl-D-aspartate (NMDA) receptor antagonists, 2-amino-7-phosphonoheptanoic acid (AP7) was injected into the dorsal periaqueductal grey (DPAG) of rats exposed to the elevated plus-maze model of anxiety. Doses of 0.2, 2 and 20 nmol AP7 caused a dose-dependent increase in the percentage of open arm entries, the effect of the last two doses being significantly different from control. A non-significant tendency to increase the percentage of time spent on the open arms of the maze was also noticed. In contrast, the total number of entries into either the open or enclosed arms was not affected. Injections of AP7 localized outside the DPAG were ineffective. Therefore, microinjection of AP7 into the DPAG caused a selective anxiolytic effect in the elevated plusmaze. It may be suggested that the DPAG is a site of the anxiolytic action of NMDA antagonists reported following systemic administration.

Iron is the intracellular metal involved in the production of DNA damage by oxygen radicals

Abstract: The metal chelators 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline (neocuproine) showed distinct abilities to prevent hydroxyl radical formation from hydrogen peroxide and Cu+ or F2(2+) (Fenton reaction) as determined by electron spin resonance. o-Phenanthroline prevented both Fe- and Cu-mediated Fenton reactions whereas neocuproine only prevented the Cu-mediated Fenton reaction. Because only 1,10-phenanthroline but not neocuproine prevented DNA strand-break formation in hydrogen peroxide-treated mammalian fibroblasts it appears that the Fe-mediated, as compared to the Cu-mediated, intranuclear Fenton reaction is responsible for DNA damage.

Are free radicals involved in lead poisoning

Abstract: 1. The enolamine form of 5-aminolaevulinic acid (ALA), a haem precursor that accumulates in lead poisoning and in acute intermittent porphyria (AIP), undergoes fast autoxidation at slightly alkaline pH with concomitant generation of reactive oxygen species.2. The transmembrane potential, Ca2+ ion fluxes and state-4 respiratory rate, of isolated rat liver mitochondria are severely affected by mM addition of ALA; the toxic role of ALA-produced oxygen radicals was demonstrated by use of appropriate scavengers.3. Induction of superoxide dismutase biosynthesis in lead-exposed workers, in AIP carriers and in ALA-treated rats, is viewed as a protective response against oxygen radical toxicity.4. 5-Aminolaevulinic acid-generated oxygen radicals, together with Pb-stimulated Fe-dependent lipid peroxidation, might be involved in the aetiology of the neuropsychiatric manifestations of both plumbism and acute intermittent porphyria.

Possible Climatic Impacts of Tropical Deforestation

Abstract: Large-scale conversion of tropical forests into pastures or annual crops will likely lead to changes in the local microclimate of those regions. Larger diurnal fluctuations of surface temperature and humidity deficit, increased surface runoff during rainy periods and decreased runoff during the dry season, and decreased soil moistrue are to be expected.

The effects of climate and bee race on Varroa jacobsoni Oud infestations in Brazil

Abstract: mdash; Varroa jacobsoni infestation rates on adult Africanized and Italian/Africanized hybrid honey bees were measured in 3 different climatic regions of Brazil : Ribeir ão Preto, Rio do Sul and São Joaquim (mean temperatures 21, 18 and 13 °C, respectively), over a 2-yr period. The mean infestation rates were 3.5, 5.11 and 11.37 mites per 100 bees in the 3 regions respectively, demonstrating that climate type has a strong influence and that infestation rates are higher in the cooler regions. The type of bee also had an important effect, as the Italian hybrids were significantly more infested than the Africanized bees (7.53 and 5.78 mites per 100 bees, respectively).

Evidence for superoxide radical-dependent coronary vasospasm after angioplasty in intact dogs.

Abstract: BACKGROUND Active oxygen species can influence vascular tone and platelet activation through a variety of mechanisms. This study assessed the role of the superoxide anion, the hydroxyl radical, and hydrogen peroxide in vasoconstriction and mural thrombosis after coronary artery angioplasty in intact dogs. METHODS AND RESULTS Injury was induced by inflation of a balloon catheter 50 +/- 6% above baseline arterial diameter; dogs were followed for 2 hours before death. Epicardial coronary diameters at arteriography and extent of thrombus deposition at serial histological sections were analyzed in controls (n = 20) and in dogs pretreated with superoxide dismutase (SOD, a superoxide radical scavenger, n = 10); other dogs were pretreated with the hydrogen peroxide scavenger catalase (n = 8), the iron chelator deferoxamine (n = 6), or the hydroxyl radical scavenger 1,3-dimethyl-2-thiourea (n = 9). Angioplasty-induced injury was similar among groups. After angioplasty, control dogs exhibited localized and persistent vessel constriction, which was maximal at the initial 5 minutes (28.9 +/- 6.3% diameter decrease versus baseline). Corresponding arterial diameters of SOD-treated dogs were 24-69% larger (95% confidence interval, p less than 0.001) than controls at 5 minutes and, on average, 32% larger than controls thereafter (p less than 0.01). Vasoconstriction was not prevented by the other treatments. The SOD dose used accounted for inhibition of zymosan-stimulated blood cytochrome c reduction versus baseline (7 +/- 3 versus 30 +/- 6 nmol/min/10(6) cells, respectively, p = 0.003); such inhibition occurred in no other group. Prevalence of mural thrombosis was similar among all groups, but large thrombi (greater than 15% of lumen area) were absent in SOD-treated dogs, contrary to control group (p = 0.028); other groups were similar to control. In the absence of injury, SOD alone induced no change in coronary diameter, coronary blood flow, or platelet aggregation. CONCLUSIONS These data provide evidence implicating the superoxide radical in the genesis of vasoconstriction after coronary angioplasty in vivo. Such effects seem to be independent of its conversion to hydroxyl radicals and availability of hydrogen peroxide or catalytic iron complexes.

Association of human leukocyte class II antigens with rheumatic fever or rheumatic heart disease in a Brazilian population.

Abstract: BACKGROUND The incidence of rheumatic heart disease is great in Brazil. We analyzed the distribution of human leukocyte (HLA) antigens in a Brazilian population sample with rheumatic fever or rheumatic heart disease, with the aim of better understanding the mechanisms involved. METHODS AND RESULTS HLA class I (A, B, and C) and class II (DR and DQ) antigen distribution was studied in 40 patients with diagnosis of rheumatic fever or rheumatic heart disease and compared with a control group of 617 healthy individuals for class I typing, from which 118 were drawn for class II typing. A strong correlation between rheumatic fever and rheumatic heart disease and HLA-DRw53 (72.9% in the disease group versus 39% in the control group: p = 0.00061, relative risk, 4.2; etiologic fraction, 0.43) was found. We also found an increase in the frequency of HLA-DR7 (57.5% in the disease group versus 26.3% in control group: p = 0.00715; relative risk, 3.8; etiologic fraction, 0.56). HLA class I and HLA-DQ typing did not point to any association with these diseases. CONCLUSIONS HLA-DR7 and HLA-DRw53 are markers for susceptibility to rheumatic fever and rheumatic heart disease in Brazil. These results could be explained by genetic differences resulting from racial or geographical diversity.

Undecidability and incompleteness in classical mechanics

Abstract: We describe Richardson's functor from the Diophantine equations and Diophantine problems into elementary real-valued functions and problems. We then derive a general undecidability and incompleteness result for elementary functions within ZFC set theory, and apply it to some problems in Hamiltonian mechanics and dynamical systems theory. Our examples deal with the algorithmic impossibility of deciding whether a given Hamiltonian can be integrated by quadratures and related questions; they lead to a version of Godel's incompleteness theorem within Hamiltonian mechanics. A similar application to the unsolvability of the decision problem for chaotic dynamical systems is also obtained.

Direct Vital Microscopic Study of Defective Leukocyte-Endothelial Interaction in Diabetes Mellitus

Abstract: The number of leukocytes rolling along the venular endothelium of the vascular network of the internal spermatic fascia was determined in nondiabetic control rats and diabetic rats with television microscopy. A marked decrease in the number of rolling cells was observed in animals rendered diabetic by the injection of alloxan 10, 30, or 180 days before relative to matching controls. Blood leukocyte counts, however, were equivalent in both control and diabetic rats. Under the influence of a local inflammatory stimulus, cells emerged into the perivascular tissue in control animals, and this was accompanied by a reduction in the number of rolling leukocytes. In diabetic rats, the number of rolling leukocytes remained unaltered, and only a few cells accumulated in the connective tissue adjacent to the vessel. Reversal of the defective leukocyte-endothelial interaction was attained by treatment of diabetic animals with insulin. Inhibitors of arachidonic acid metabolism were ineffective to improve leukocyte-endothelial interactions in diabetic animals. Control rats injected intravenously with lyophilized plasma constituents, obtained after dialysis of diabetic rat plasma with 12,000-Mr retention dialysis tubing, behaved as diabetic animals in that they exhibited a reduced number of leukocytes rolling along the venular endothelium. In contrast, material obtained from control rat plasma produced no effect. Heating of active samples for 1 h at 56 degrees C resulted in the complete loss of the inhibitory effect. We conclude that a substance or substances present in diabetic plasma induce a defective leukocyte-endothelial interaction that further impairs resistance to infection.