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Biomedical subjects

J A Amaral

Publications and source records attributed to J A Amaral.

11 recordsLinked to original sources
PubMed2006

Systemic antibody response to diarrheagenic Escherichia coli and LPS O111, O157 and O55 in healthy Brazilian adults.

Enterohaemorrhagic Escherichia coli (EHEC) can cause a variety of human illnesses ranging from uncomplicated diarrhoea to haemorrhagic colitis and haemolytic uremic syndrome. The serotype O157:H7 has been associated with numerous outbreaks worldwide, but in Brazil the infection is rare. Brazilian adults present antibodies reactive with the principal virulence factors of enteropathogenic E. coli (EPEC) that have many genetic and antigenic similarities with EHEC. Lipopolysaccharides (LPS) are components of outer membranes and important virulence factors of Gram-negative bacteria. LPS O111 is present in EPEC and EHEC strains. LPS O157 is found only in EHEC strains, but it has some structural similarities with LPS O55 present in EPEC strains. This study investigates the levels of IgG and IgM seric antibodies reactive with EHEC O157:H7, EHEC O111:H-, EPEC O111:H- and the levels of anti-LPS O111, LPS O157 and LPS O55 antibodies in healthy adults living in São Paulo, Brazil. The antibody levels were determined by an enzyme-linked immunosorbent assay for 100 individual serum samples, and the presence of anti-bacterial and anti-LPS seric antibodies was confirmed. Positive correlations were found among the three kinds of antibodies. The concentrations of IgM anti-LPS were significantly higher than those of IgG, and surprisingly, the concentrations of anti-LPS O157 were high in view of the infrequent isolation of O157 bacteria in Brazil. Our results suggest that there is a cross-reacting immunity to EHEC in the Brazilian population, which may be a result of the immunity to EPEC antigens. Alternatively, Brazilians may be exposed to EHEC more frequently than has previously been thought.

Adult↗
PubMed2004

Treatment emergent affective switch: a controlled study.

OBJECTIVE: To study the clinical features of treatment emergent affective switch (TEAS) in comparison with spontaneous mania. METHODS: Twelve patients with TEAS within a 12-week period (average) of starting standard antidepressant medication were compared with 12 patients with spontaneous mania. RESULTS: Patients with TEAS were older, had longer duration of illness, more previous episodes, higher prevalence of subclinical hypothyroidism, and reported more previous episodes of mania associated with antidepressant use. TEAS was less severe, with a lower incidence of psychotic symptoms, lower Young Mania Rating Scale index score and rarely required hospitalization. The interval from intervention to response and remission was similar in both groups. CONCLUSION: TEAS was less severe, but had similar duration when compared with spontaneous mania. These results cannot directly answer the question of whether there is a causal relationship between antidepressant use and TEAS. While it is also possible that patients with longer duration of illness and higher cycle frequencies are more likely to experience episodes, it is difficult to attribute lesser severity of TEAS episodes to these clinical factors. Our observations are consistent with the suggestion that patients with longer duration of illness and previous history of TEAS may be at a greater risk of switching to mania during the use of antidepressants.

Adolescent↗
PubMed2002

Anti-enteropathogenic Escherichia coli immunoglobulin Y isolated from eggs laid by immunised Leghorn chickens.

IgY, the egg yolk immunoglobulin, equivalent to the IgG from mammals, has been used in veterinary practice for passive immunisation against bacterial or viral infectious diseases. Enteropathogenic Escherichia coli (EPEC) is the main etiological agent of infantile diarrhoea in Brazil and other developing countries. Our aims were to isolate immunoglobulin IgY from egg yolk laid by EPEC -immunised Leghorn chickens and to study its reactivity to the antigens from this pathogen, including some virulence factors. Leghorn chickens were immunised with a bacterial suspension intramuscularly (three hens) or intravenously (three hens) or with PBS (two hens). Eggs were collected over a period of 17 weeks. IgY isolation procedures were carried out by salt precipitation (ammonium sulphate, in solid form) followed by centrifugations and dialysis. Final preparations were submitted to sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS - PAGE), enzyme-linked immunosorbent assay (ELISA) and immunoblotting. All immunised animals developed good levels of antibodies reactive to whole bacteria or lipopolysaccharide (LPS), in contrast to the control ones. Immunoblottings allowed the recognition of several antigenic fractions of bacterial antigens, some of which had a molecular weight compatible with bacterial virulence factors, confirming the efficacy of the immunisation and the adequacy of the method.

Animals↗
PubMed2001

Lipid and acute-phase protein alterations in HIV-1 infected patients in the early stages of infection: correlation with CD4+ lymphocytes.

Lipid and acute-phase protein alterations have been described in various infection diseases, and they have been recorded during the early stages of HIV infection. Lipid and acute-phase protein profiles also have been correlated with cellular immunological abnormalities. To document these correlations during HIV infection, we studied 75 HIV-infected patients and 26 HIV-negative controls. Patients were classified according to the criteria proposed by the Walter Reed Army Institute: as WR-1 (CD4 lymphocytes, 1154 +/- 268/mm3), WR-2 (CD4, 793 +/- 348/mm3) and WR3/4 (CD4, 287+/-75 mm3). Triglycerides, total cholesterol and HDL-cholesterol concentrations were measured by enzymatic methods. Immunoglobulins (IgA and IgG) and acute-phase proteins (haptoglobin, alpha1-acid glycoprotein, C-reactive protein and transferrin) were determined by immunonephelometry. Haptoglobin levels were significantly increased in HIV-positive patients and correlated with the progression of HIV-infection (control<WR1<WR2<WR3/4). WR-2 and WR-3/4 patients had lower total cholesterol, HDL-cholesterol, and albumin concentrations, however, alpha1-acid glycoprotein and IgA levels were higher, when compared to HIV-negative controls. Elevated triglyceride levels (1.51+/-0.75 mmol/L) were found only in WR3/4 patients, when compared to the control individuals (1.05+/-0.04 mmol/L). No differences were found in transferrin and C-reactive protein concentrations among the studied groups. CD4+ lymphocyte counts were inversely correlated with triglycerides, IgA, alpha1-acid glycoprotein and haptoglobin, and they were positively correlated with albumin, total cholesterol and HDL-cholesterol. Multiple linear regression analysis showed that increased haptoglobin and IgA levels were the best predictive variables of a decreasing CD4+ lymphocyte count. In conclusion, our data showed that: 1) a decrease in total cholesterol, HDL-cholesterol and albumin levels occurred earlier than hypertriglyceridemia in the course of HIV infection; 2) increased levels of haptoglobin occurred earlier than that of alpha1-acid glycoprotein and IgA; 3) haptoglobin and IgA were the best predictive variables of a decreasing CD4+ lymphocyte count. Decreases in HDL-cholesterol and albumin levels with increases in haptoglobin, alpha1-acid glycoprotein, IgA, and triglycerides levels are indications of disease progression in HIV-infected patients.

Acute-Phase Proteins↗
PubMed1998

Effect of selected monoterpenes on methane oxidation, denitrification, and aerobic metabolism by bacteria in pure culture.

Selected monoterpenes inhibited methane oxidation by methanotrophs (Methylosinus trichosporium OB3b, Methylobacter luteus), denitrification by environmental isolates, and aerobic metabolism by several heterotrophic pure cultures. Inhibition occurred to various extents and was transient. Complete inhibition of methane oxidation by Methylosinus trichosporium OB3b with 1.1 mM (-)-alpha-pinene lasted for more than 2 days with a culture of optical density of 0.05 before activity resumed. Inhibition was greater under conditions under which particulate methane monooxygenase was expressed. No apparent consumption or conversion of monoterpenes by methanotrophs was detected by gas chromatography, and the reason that transient inhibition occurs is not clear. Aerobic metabolism by several heterotrophs was much less sensitive than methanotrophy was; Escherichia coli (optical density, 0.01), for example, was not affected by up to 7.3 mM (-)-alpha-pinene. The degree of inhibition was monoterpene and species dependent. Denitrification by isolates from a polluted sediment was not inhibited by 3.7 mM (-)-alpha-pinene, gamma-terpinene, or beta-myrcene, whereas 50 to 100% inhibition was observed for isolates from a temperate swamp soil. The inhibitory effect of monoterpenes on methane oxidation was greatest with unsaturated, cyclic hydrocarbon forms [e.g., (-)-alpha-pinene, (S)-(-)-limonene, (R)-(+)-limonene, and gamma-terpinene]. Lower levels of inhibition occurred with oxide and alcohol derivatives [(R)-(+)-limonene oxide, alpha-pinene oxide, linalool, alpha-terpineol] and a noncyclic hydrocarbon (beta-myrcene). Isomers of pinene inhibited activity to different extents. Given their natural sources, monoterpenes may be significant factors affecting bacterial activities in nature.

Aerobiosis↗
PubMed1994

Ca2+ binding to occluded sites in the CrATP-ATPase complex of sarcoplasmic reticulum: evidence for two independent high-affinity sites.

Occluded Ca2+ sites in the CrATP-ATPase complex are studied by first forming the complex in the presence of EGTA so that the sites can be occluded while vacant. 45Ca2+ binding to the occluded sites is then studied under equilibrium conditions. Binding curves are produced for two independent Ca2+ sites with Kd(1) = 0.2 microM and Kd(2) = 1.6 microM. When both sites are saturated, only the Ca2+ bound to the lower affinity site can exchange with free Ca2+. On addition of EGTA (15 vs 0.5 mM Ca2+) all bound Ca2+ dissociates, the net dissociation rate of one-half of the Ca2+ being approximately 10-fold greater than that of the other one-half (at 37 degrees C). When Ca2+ is bound only to the higher affinity site, this Ca2+ will exchange slowly if the concentration of free Ca2+ is below the saturation level of the lower affinity site. An ionophore dependency of the rates of binding and dissociation indicates that the access to the sites is through the interior of the vesicle. Solubilization in C12E9 releases the Ca2+ in the higher affinity site. Our observations are consistent with a model of the ATPase where the lower affinity of two transport sites is associated with the interior position (closest to the lumen) in a transmembrane channel. It is further evident that when in the occluded state, the higher affinity site is available without Ca2+ first being bound to the lower affinity site, eliminating cooperativity from the binding mechanism. In turn, this implies a connection between the integrity of the high-affinity binding site and the linking of sections of the catalytic site by CrATP.

Adenosine Triphosphate↗
PubMed1994

Methane metabolism in a temperate swamp.

Comparisons between in situ CH(4) concentration and potential factors controlling its net production were made in a temperate swamp. Seasonal measurements of water table level and depth profiles of pH, dissolved CH(4), CO(2), O(2), SO(4), NO(3), formate, acetate, propionate, and butyrate were made at two adjacent sites 1.5 to 2 m apart. Dissolved CH(4) was inversely correlated to O(2) and, in general, to NO(3) and SO(4), potential inhibitors of methanogenesis. At low water table levels (August 1992), maximal CH(4) (2 to 4 muM) occurred below 30 cm, whereas at high water table levels (October 1992) or under flooded conditions (May 1993), CH(4) maxima (4 to 55 muM) occurred in the top 10 to 20 cm. Higher CH(4) concentrations were likely supported by inputs of fresh organic matter from decaying leaf litter, as suggested by high acetate and propionate concentrations (25 to 100 muM) in one of the sites in fall and spring. Measurements of potential CH(4) production (and consumption) showed that the highest rates generally occurred in the top 10 cm of soil. Soil slurry incubations confirmed the importance of organic matter to CH(4) production but also showed that competition for substrates by nonmethanogenic microorganisms could greatly attenuate its effect.

Journal Article↗