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Biomedical subjects

A M Soares

Publications and source records attributed to A M Soares.

At least 55 records · Page 3Linked to original sources
PubMed2000

Experimental paracoccidioidomycosis of the Syrian hamster: fungicidal activity and production of inflammatory cytokines by macrophages.

Phagocytic cells play an important role in nonspecific resistance to fungal infection by mediating an inflammatory response and by a direct fungicidal action. In this study, the functional activity of peritoneal macrophages obtained from hamsters experimentally infected with strain Pb18 of Paracoccidioides brasiliensis was evaluated during 16 weeks of infection. The results showed that macrophages had a higher spreading ability associated with increased production of tumor necrosis factor alpha (TNF-alpha) and enhanced fungicidal activity during the early periods of infection. TNF-alpha levels remained elevated during all periods studied, while low levels of interleukin-1 beta (IL-1 beta) were produced during the infection. A necrotic area with dead fungi was observed at the inoculation site and the infection disseminated only to liver and lymph nodes in a few animals. These results suggest that during the early stages of infection with P. brasiliensis, macrophage activation by the high levels of TNF-alpha limited fungal dissemination. In contrast, in the later stages of infection, high levels of TNF-alpha were observed while the fungicidal activity of macrophages was lower and the animals presented loss of vitality resulting in their death. These observations suggest a complex role of TNF-alpha in experimental paracoccidioidomycosis of Syrian hamsters, involving not only resistance but also pathogenesis.

Animals↗
PubMed2000

Experimental paracoccidioidomycosis in high and low antibody responder mice of Selection IV-A.

High (H) and low (L) responder mice were selected for their ability to produce antibodies against sheep and human erythrocytes (Selection IV-A). In this selection, the difference in antibody responsiveness between H and L lines (HIV-A and LIV-A mice, respectively) was shown to depend mainly on macrophage function. The more rapid catabolism of antigens by macrophages in L mice has been suggested as the main cause of the low antibody production. Due to this high macrophage activity, L animals have been described as more resistant than H animals to intracellular pathogens. These animals were utilized as an experimental model of paracoccidioidomycosis. HIV-A and LIV-A mice were infected with Paracoccidioides brasiliensis by the intravenous route. As expected, H mice were more susceptible to P. brasiliensis with a shorter survival time and higher levels of specific antibodies when compared to L mice. Contrasting with the survival time, the lungs, spleen and liver from H mice showed typical nodular granulomas containing epithelioid and giant cells and few fungi. On the other hand, in LIV-A mice, the lesions of these organs were characterized by looser granulomas with irregular borders and the presence of a large number of fungi. However, the adrenal gland showed different lesion patterns. In H mice these lesions were extensive and characterized by loose granulomas with numerous fungi, while in LIV-A mice the lesions were small and limited to the cortex. Moreover the HIV-A mice presented higher levels of serum corticosterone when compared to LIV-A ones. The higher susceptibility of H mice could be attributed to the extensive lesions of the adrenal glands. These results suggest the use of the H line from the IV-A Selection as an experimental model for further studies of adrenal involvement in paracoccidioidomycosis.

Adrenal Glands↗
PubMed2000

Correlation among immune response, morphogenesis of the granulomatous reaction and spleen lymphoid structure in murine experimental paracoccidioidomycosis.

We studied the correlation among cellular immune response, the pattern of lung granulomatous lesions and alterations in spleen lymphoid structure in Swiss mice inoculated intravenously with Paracoccidioides brasiliensis strain 18. The animals were evaluated at 24, 48 and 96 h after infection and further studied weekly for 18 weeks by: (i) the macrophage migration inhibition test with phytohemagglutinin (PHA) and P. brasiliensis antigen (PbAg); and (ii) histopathology of the lung and spleen lesions. One group of animals was gamma-irradiated (8 Gy), infected under the same conditions and evaluated for the pattern of lung granulomatous lesions and spleen lymphoid structure at 24, 48 and 96 h after infection. During the first week of infection, the non-irradiated animals presented a positive response to PHA and PbAg, compact granulomas in the lungs and a typical hyperplasia of the spleen white pulp. However, from weeks 2 to 5, a depression of the cell-mediated immunity (CMI) response to PHA and PbAg was observed in association with granulomas presenting only large mononuclear cells and lacking both giant cells and a peripheral halo of small mononuclear cells. This pattern of granuloma formation was similar to that seen in gamma-irradiated animals, whose cells involved in CMI were absent. After week 7, the non-irradiated animals showed granulomas characterized by the presence of giant cells and a peripheral halo of small mononuclear cells. This type of granuloma was formed concomitantly with recovery of the CMI and of the lymphoid structure of the spleen. The results showed a correlation among granulomas composed of large mononuclear cells, hypoplasia of the splenic tissue and impaired CMI. This correlation indicated that although granuloma morphogenesis per se does not depend on the activation of CMI, this response is important at later stages during modulation of the cellular composition of the granulomas.

Animals↗
PubMed2000

Supernatants from macrophages stimulated with microcystin-LR induce electrogenic intestinal response in rabbit ileum.

Microcystin-LR is a cyclic heptapeptide hepatotoxin produced by the cyanobacterium Microcystis aeruginosa. This microorganism often forms toxic blooms in freshwater lakes and reservoirs for drinking water supply, producing serious disorders in humans and animals. Some have suggested that certain biological activities of microcystin may depend upon the stimulation of immune cells. Therefore, the aims of this research were to examine electrogenic intestinal secretion, in vitro, caused by the supernatants from macrophages stimulated with microcystin-LR, as well as to investigate the presence of interleukin-1beta and tumour necrosis factor-alpha in these supernatants. We found that the supernatants of macrophages stimulated with microcystin-LR (0.1, 0.3 and 1.0 microg/ml) caused electrogenic intestinal effects (change in short circuit currents (delta SCC)=57.6, 50.8 and 73.3, respectively, versus control=19.6 microA.cm(-2)) in a time-dependent way (microcystin-LR (1.0 microg/ml)=63.2, 108.8, 120.4 and 132.3 microA.cm(-2) at time 0, 40, 50 and 60 min., respectively). In addition, the intestinal secretory activity present in these supernatants was blocked (57%) by the prior treatment of macrophages with dexamethasone. We also demonstrated that microcystin-LR (0.1, 0.3 and 1.0 ,microg/ml) is capable of stimulating the synthesis of tumour necrosis factor-alpha (375.4, 369.0 and 610.8 pg/ml, respectively, versus control=165.0 pg/ml) and interleukin-1beta (198.9, 189.3 and 522.1 pg/ml, respectively, versus control=39.7 pg/ml). These findings demonstrate that microcystin-LR induces the release of interleukin-1beta and tumour necrosis factor-alpha by peritoneal macrophages in vitro, and that the supernatants from these macrophages induce electrogenic secretion in rabbit ileal mucosa.

Animals↗
PubMed1999

A Daphnia magna first-brood chronic test: An alternative to the conventional 21-Day chronic bioassay?

In this study a comparison was made of the results obtained in Daphnia magna chronic bioassays after first-brood release and after 21 days of exposure, using inhibition of normal reproduction and growth as effect criteria and EC10, EC20, EC50, no-observed-effect concentration (NOEC), and lowest-observed-effect concentration (LOEC) as statistical parameters. Test substances were sodium bromide (NaBr), 3,4-dichloroaniline (DCA), cadmium, and parathion. For NaBr, DCA, and cadmium, toxicity evaluated after the first-brood release was similar to toxicity evaluated after 21 days, using reproduction as end point. Parathion did not affect either reproduction or growth. Thus, LC50, NOEC, and LOEC were calculated using mortality as the endpoint for parathion. Results indicate that the period until release of the first brood is sufficient to predict the toxicity of some chemicals to D. magna. Values estimated on the basis of a logistic model (EC10, EC20, and EC50) were more appropriate than NOECs and LOECs for evaluating toxicity of the test substances. Furthermore, classic endpoints used for the evaluation of chronic toxicity (inhibition of normal reproduction and growth) may not be adequate to evaluate the sublethal toxicity of compounds that induce cumulative effects leading to mortality within the test period and causing no observable effects on the reproduction and growth of the species. Endpoints indicative of biochemical stress or effects on specific targets of the test compound may be useful in sublethal toxicity evaluation.

Aniline Compounds↗
PubMed1999

Discriminating the ecotoxicity due to metals and to low pH in acid mine drainage.

Several techniques have been developed to assess the ecotoxicity of contaminated watercourses. Most of these techniques involve chemical alterations of water samples, by diluting it or by adding chelating agents. These changes become particularly severe when assessing the toxicity of samples with very low pH and with high quantities of contaminants. Trying to overcome this problem, a novel toxicity test, specific for acid waters, was previously developed and field validated. The toxicity of acid samples is assessed using the survival time of Ceriodaphnia dubia. During this study, the novel test was applied to a field situation, where an aquatic system is seriously impacted with acid mine drainage. Its efficiency was tested and compared with two classical toxicity tests: the Microtox and the median lethal dilution with C. dubia. The survival time test was performed without adjusting pH and after adjusting pH to a fixed value (pH 2, 3, and 4). At pH 2 and 4 no acceptable results were obtained; at pH 3 it was possible to distinguish the toxicity due to pH from the toxicity due to other toxicants. The test conducted at local pH was able to discriminate toxicity sources only for highly contaminated samples. The toxicity evaluation of acid mine drainage samples was possible neither with the median lethal dilution test nor with Microtox.

Animals↗
PubMed1999

In vitro populations of rotifer Brachionus plicatilis Müller demonstrate inhibition when fed with copper-preaccumulating microalgae.

Four marine microalgal species (Chlorella autotrophyca, Nannochloropsis gaditana, Tetraiselmis chuii, and Isochrysis aff. galbana) were exposed for 24 h to 1 mg L(-1) dissolved copper and then transferred to fresh medium. After that, a group of 10 neonate rotifers were fed with these four microalgal species. The levels of accumulated copper in cellular concentrations of the microalgae were checked, with the result of around 40% of original concentration, with the exception of I. aff. galbana (25% of original concentration). In all cases, cells with preaccumulated metal caused a delay of 1 or 2 days in populational development of rotifers (increase in "lag phase"). The microalgae that were not fed to rotifers (disposed in parallel series) did not significantly transfer metal to the medium after the first day.

Animals↗
PubMed1999

Novel bioassay based on acetylcholinesterase and lactate dehydrogenase activities to evaluate the toxicity of chemicals to soil isopods.

This study developed a bioassay with the isopod Porcellio dilatatus based on the activity of the enzymes acetylcholinesterase (AChE) and lactate dehydrogenase (LDH). The in vivo effects of the insecticides parathion-ethyl and endosulfan-sulfate on AChE and LDH activities of P. dilatatus under laboratory conditions were investigated. The route of uptake of the pesticides was through the food (alder leaves). Isopods were exposed to a wide range of concentrations of parathion or endosulfan (0.1, 1, 10, 25, 50, 100, 250, and 500 microg/g of food) for 21 days. After this period, the activity of AChE and LDH was determined. Parathion induced significant depression of both AChE and LDH activities. Animals fed with endosulfan-contaminated food exhibited lower LDH activities than control animals, while AChE activity was similar in all treatments. The results of the present investigation suggest that the isopod. P. dilatatus is a suitable species for use in toxicity tests and indicate that the enzymes AChE and LDH could be used as effect criteria both in laboratory and in field studies with this species.

Acetylcholinesterase↗
PubMed1999

Common arterial trunk associated with atrioventricular septal defect.

Described are the clinical, cross-sectional echocardiographic, electrocardiographic and angiographic findings, together with the results at autopsy, in a 5-month old infant with a common arterial trunk associated with an atrioventricular septal defect. As far as is known, this is only the 13th such case to be reported in the literature. A particularly unusual feature of this case was an intact atrial component of the atrioventricular septal defect.

Coronary Angiography↗
PubMed1999

Isolation and characterization of an arginine ester hydrolase from Bothrops jararacussu venom which induces contractions of the isolated rat uterus.

The isolation and partial characterization of a serine protease with arginine ester hydrolase activity from Bothrops jararacussu snake venom are described. The purification procedure consisted of a gel filtration of the crude venom on Sephadex G-75 followed by an ion-exchange chromatography of the active fraction on DEAE-cellulose and a rechromatography on Bio-Rex 70 resin. The esterase fraction (DI-III), M(r) = 25,000 by SDS-PAGE, showed proteolytic activity on fibrinogen and casein. After 2 hr incubation, the A alpha and B beta chains of fibrinogen were intensely hydrolysed, while the gamma chain kept apparently intact, even after 20 hr of incubation. In spite of that, DI-III did not clot fibrinogen. DI-III induced edema in the rat paw. Although unable to release bradykinin, it induced contractions of the isolated rat uterus. DI-III did not catalyse the hydrolysis of bradykinin. Its arginine ester hydrolase activity was completely inhibited by diisopropyl fluorophosphate after 1 hr incubation, but not by phenylmethylsulfonyl fluoride under the same conditions.

Animals↗
PubMed1999

Purification and partial characterization of a new proteolytic enzyme from the venom of Bothrops moojeni (CAISSACA).

A basic serine protease which is active on casein and fibrinogen was purified from Bothrops moojeni venom using a single step chromatography on a CM-Sepharose fast flow column. The enzyme, MOO3, was not hemorrhagic and presented only a trace of blood-clotting activity. Synthetic chromogenic substrates (azoacasein and azoalbumin) where not hydrolyzed by MOO3. Using polyacrylamide gel electrophoresis at pH 4.3, MOO3 showed as a single protein band. Using sodium dodecyl sulfate-polyacrylamide electrophoresis, MOO3 behaved as a single-chain protein with an approximate mol. weight of 27,000, both in the presence and absence of beta-mercaptoethanol. Its pI was 7.8 by electrofocusing. The enzyme did not contain neutral carbohydrates and its N-terminal amino acid was alanine. The amino acid composition showed 249 residues/mole, a high content of hydrophilic amino acids and 14 half-cystine residues, which should account for 7 disulfide bonds. The protease cleaved the A-alpha chain faster than the B-beta of bovine fibrinogen and showed no effect on the delta-chain. Specific esterolytic activity of MOO3 on alpha-N-tosyl-l-arginine methyl ester was 29.64 mumol min-1 x mg-1. MOO3 represented 1.42% (w/w) of the initial desiccated venom. Its proteolytic activity was inhibited by beta-mercaptoethanol, leupeptin, phenylmethylsulphonyl fluoride and ethylenediamine tetraacetate.

Animals↗
PubMed1999

Crystallization and preliminary X-ray diffraction studies of piratoxin III, a D-49 phospholipase A2 from the venom of Bothrops pirajai.

Piratoxin III (PrTX-III) is a phospholipase A2 (PLA2, E.C. 3.1.1.4, phosphatide sn-2 acylhydrolase) isolated from Bothrops pirajai. Crystals of PrTX-III were obtained using the vapour-diffusion technique and X-ray diffraction data have been collected to 2.7 A resolution. The enzyme was crystallized in the space group C2 with unit-cell parameters a = 60.88, b = 100.75, c = 48.19 A, beta = 123. 89 degrees. A molecular-replacement solution of the structure has been found using bothropstoxin I from the venom of B. jararacussu as a search model.

Animals↗
PubMed1999

Immunological alterations in patients with primary tumors in central nervous system.

Natural killer (NK) cells play an important role in immune surveillance against tumors. The present work aimed to study the cytotoxic activity of NK cells and T cell subsets in peripheral blood of 13 patients with primary tumors in central nervous system (CNS). As controls 29 healthy subjects with the age range equivalent to the patients were studied. The methods employed were: a) determination of cytotoxic activity of NK cells towards K562 target cells, evaluated by single cell-assay; b) enumeration of CD3+ lymphocytes and their CD4+ and CD8+ subsets defined by monoclonal antibodies; c) the identification of tumors were done by histologic and immunochemistry studies. The results indicated that adults and children with tumor in CNS display reduced percentage of total T cells, helper/inducer subset and low helper/suppressor ratio. The cytotoxic activity of NK cells was decreased in patients with CNS tumors due mainly to a decrease in the proportion of target-binding lymphocytes. These results suggest that cytotoxic activity of NK cells may be affected by the immunoregulatory disturbances observed in patients with primary tumors in CNS.

Adolescent↗
PubMed1999

Aortopulmonary window. Clinical and surgical assessment of 18 cases.

OBJECTIVE: Aortopulmonary window (APW) is an uncommon congenital malformation. Its clinical presentation is dependent on the size of the defect and on the associated lesions. We evaluated our experience with this anomaly and compared it with 296 cases reported in the literature. METHODS: Retrospective study of 18 patients diagnosed as having APW (age range from 13 days to 31 years, 13 (72.2%) females), divided into two groups: Group A (GA): 10 patients with isolated APW, and Group B (GB): 8 patients with associated lesions. RESULTS: Heart failure occurred in 14 patients, and cyanosis in 3:2 from GB (tetralogy of Fallot--TF, and double outlet right ventricle--DORV), and one from GA with pulmonary hypertension. In 5 patients from GA the diagnosis of mitral regurgitation was made based on a systolic murmur and LV hypertrophy on the EKG. In GB, clinical findings were determined by the associated defect. Diagnosis was established by echocardiography in 11 (61.2%) of the patients. In 3 patients, a wrong diagnosis of mitral regurgitation was made, in 1 a patent ductus arteriosus was diagnosed and in 3 others, the diagnosis of APW was masked by other important associated defects (2 cases of DORV and 1 case of TF). The diagnosis was made by catheterization in 3 (16.6%) patients, by surgery in 3 (16.6%) and by necropsy in 1 (5.5%). Corrective surgery was performed in 14 (77.7%) patients, with one immediate death and good long-term follow-up in the remaining patients. CONCLUSION: APW can be confused with other defects. Clinical findings, associated with an adequate echocardiogram can provide the information for the correct diagnosis.

Adolescent↗