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Biomedical subjects

A M Soares

Publications and source records attributed to A M Soares.

At least 73 records · Page 4Linked to original sources
PubMed1999

Correlation between antigenemia of Paracoccidioides brasiliensis and inhibiting effects of plasma in patients with paracoccidioidomycosis.

Metabolites produced by pathogenic fungi may be involved in the pathogenesis of fungal infections consequently altering the defence mechanisms of the host. In this study the levels of Paracoccidioides brasiliensis antigens detected in the plasma of patients with paracoccidioidomycosis correlated with the suppression index detected by the low mitogenic response of peripheral blood mononuclear cells (PBMC) to phytohaemaglutinin (PHA). This inhibitory effect on lymphoproliferation was observed in the plasma of 58% of the patients, suggesting the presence of inhibitory factors. Plasma samples from paracoccidioidomycosis patients having or not having inhibitory factors showed no significant effect on chromosomes of lymphocytes from healthy individuals. However, these plasmas had a suppressive activity on the blastogenic response of these lymphocytes stimulated with PHA, that was independent of a cytotoxic effect. P. brasiliensis antigens added to the proliferative response of PBMC from healthy individuals stimulated or not stimulated with PHA showed a dose-dependent suppressor effect, reproducing the inhibitory effect of patients' plasma. We suggest that the antigens of P. brasiliensis present in the plasma of patients, even at low concentrations, can play an important role in the reduction of the cellular immune response and in the genesis of the immunoregulatory disturbances observed in paracoccidioidomycosis.

Adolescent↗
PubMed1998

Amino acid sequence of piratoxin-I, a myotoxin from Bothrops pirajai snake venom, and its biological activity after alkylation with p-bromophenacyl bromide.

The complete sequence of the 121 amino acid residues of piratoxin-I (PrTX-I), a phospholipase A2 (PLA2)-like myotoxin from Bothrops pirajai snake (Bahia jararacussu) venom, is reported. From the sequence, an M, of 13,825 and an approximate pI of 8.3 were calculated. PrTX-I shows a high sequence homology with Lys-49 myotoxins from other bothropic (approximately 95%) and nonbothropic (approximately 80%) venoms, but only 70-75% homology when aligned with the catalytically active Asp-49 PLA2s. When compared with bothropstoxin-I from Bothropsjararacussu, which is morphologically almost identical to B. pirajai, only two changes out of 121 total amino acid residues have been observed. The approximate minimal lethal dose LD50 (mice, i.p., 24 hr) of PrTX-I was 8 (6.8-9.1) mg/kg, and the minimal edematogenic dose (MED) in a rat paw model was 39.5+/-1.8 ug. After alkylation of His-48 with p-bromophenacyl bromide, the MED was 40.1+/-1.9 ug, but up to 4 LD50 were unable to cause death in any of a group of eight mice after 72 hr. Therefore the edematogenic activity was retained and apparently did not involve His-48, suggesting that at least two biologically active sites are present in PrTX-I.

Acetophenones↗
PubMed1998

A rapid procedure for the isolation of the Lys-49 myotoxin II from Bothrops moojeni (caissaca) venom: biochemical characterization, crystallization, myotoxic and edematogenic activity.

Bothtrops moojeni snake venom was fractionated on a CM-Sepharose column which was previously equilibrated with 0.05 M ammonium bicarbonate buffer at pH 8.0 and subsequently eluted with an ammonium bicarbonate concentration gradient from 0.05 to 0.5 M at constant pH (8.0) and temperature (25 degrees C). The fraction which eluted last (M-VI) showed, after direct lyophilization, a single band by polyacrylamide gel electrophoresis (PAGE) and SDS-PAGE, indicating an approximate Mr of 14000 and 27000, in the presence and absence of dithiothreitol, respectively. Its amino acid composition revealed a high level of hydrophobic and basic amino acids as well as 14 half-cystine residues. Its isoelectric point and extinction coefficient (E(1.0 mg/ml) (1.0 cm) at 278 nm and pH 7.0) were 8.2 and 1.170, respectively. M-VI was devoid of phospholipase A2 (PLA2) activity on egg yolk, as well as of hemorrhagic, anticoagulant and coagulant activities, but could induce drastic necrosis on skeletal muscle fibres as well as rapid and transient edema on the rat paw. Its N-terminal sequence: SLFELGKMILQETGKNPAKSYGVYGCNCGVGGRGKPKDATDRCCYVHKCCYK... revealed high homology with other Lys 49 PLA2-like myotoxins from other bothropic venoms. Orthorhombic crystals of M-VI, which diffracted to a maximal resolution of 1.6 A, were obtained and indicated the presence of a dimer in the asymmetrical unit.

Amino Acid Sequence↗
PubMed1998

The analgesic activity of crotamine, a neurotoxin from Crotalus durissus terrificus (South American rattlesnake) venom: a biochemical and pharmacological study.

Crotamine, a 4.88 kDa neurotoxic protein, has been purified to apparent homogeneity from Crotalus durissus venom by gel filtration on Sephadex G-75. When injected (i.p. or s.c.) in adult male Swiss mice (20-25 g), it induced a time-dose dependent analgesic effect which was inhibited by naloxone, thus suggesting an opioid action mechanism. When compared with morphine (4 mg/kg), crotamine, even in extremely low doses (133.4 microg/kg, i.p., about 0.4% of a LD50 is approximately 30-fold more potent than morphine (w/w) as an analgesic. On a molar basis it is more than 500-fold more potent than morphine. It is also much more potent than the lower molecular weight crude fractions of the same venom. The antinociceptive effects of crotamine and morphine were assayed by the hot plate test and by the acetic acid-induced writhing method. Therefore, both central and peripheral mechanisms should be involved. Histopathological analysis of the brain, liver, skeletal muscles, stomach, lungs, spleen, heart, kidneys and small intestine of the crotamine injected mice did not show any visible lesion in any of these organs by light microscopy. Since crotamine accounted for 22% (w/w) of the desiccated venom, it was identified as its major antinociceptive low molecular weight peptide component.

Analgesics↗
PubMed1998

The use of the mitochondrial transmembrane electric potential as an effective biosensor in ecotoxicological research.

In this work, the mitochondrial transmembrane electric potential (delta psi) of isolated mitochondria was used to evaluate the toxicity of some chemicals (endosulfan, 3,4-dichloroaniline, parathion, tributyltin and cadmium) and wastewater. Mitochondria were isolated from rat liver, and the delta psi measured in a suitable assay medium, using a sensitive tetraphenylphosphonium (TPP+) electrode. The test substance was pre-incubated in a rotenone-containing medium during 3 min with 1.0 mg of mitochondrial protein. Mitochondria were energised with succinate and after the establishment of a constant maximal potential ADP was added to induce the phosphorylative cycle. Chosen endpoints were the membrane potential from mitochondria oxidising succinate and the depolarisation induced by ADP. After the appropriate transformations the EC50 (effective concentration) was calculated for each toxicant. Even very low concentrations of a toxicant were able to affect the delta psi, thus showing its suitability as a biosensor in ecotoxicology and results were reproducible between tests. The utilisation of delta psi in screening tests of pure substances and wastewater seems to be very effective and can be carried out routinely.

Aniline Compounds↗
PubMed1998

Acute effects of 3,4-dichloroaniline on blood of male Wistar rats.

In this work we investigated the acute effects of 3,4-dichloroaniline (DCA) on the changes of specific biochemical and cellular blood parameters using male Wistar rats, 24 hours after the intraperitoneal administration of five different doses of DCA (0, 81, 162, 324, 486, and 568 mg/Kg of body weight). We also evaluated the dose-dependent toxicity of DCA on the ratio "organ weight:total body weight" for kidney, liver, spleen and thymus, and on the changes of morphological characteristics of the spleen. The LOEL (lowest observed effect level) value for spleen and thymus injury was 324 mg DCA/Kg. The cellular blood parameters affected by DCA include: methemoglobin concentration, the number of circulating leukocytes and the number and size of platelets. The relative sensitivity of all the analysis used to assess the acute toxicity of DCA was evaluated by comparing their ED50 values, which ranged from 224 to 837 mg DCA/Kg. We concluded that the most sensitive endpoint to measure the acute toxicity of DCA was the methemoglobin formation. Platelet counts, urea and creatinine showed ED50 values slightly higher than methemoglobin (329-367 mg/kg).

Aniline Compounds↗
PubMed1998

Correlation between whole blood cholinesterase activity and cerebral cortex cholinesterase activity in rats treated with parathion.

Organophosphate and carbamate insecticides are inhibitors of cholinesterases (ChE). The depression of blood ChE activity is frequently used as indicative of exposure to these chemicals. However, it is not known whether the inhibition of blood ChE activity reflects the inhibition of ChE in target tissues (e.g. brain and muscle). In this study we investigated the possibility of using whole blood ChE activity to predict frontal cerebral cortex ChE activity in rats treated with parathion. Twenty four hours after the intraperitoneal administration of several doses of parathion, the activity of ChE in whole blood and the activity of ChE in frontal cerebral cortex were determined in each animal. A high correlation between the two parameters was found (r = 0.96, p < 0.05) and the model of linear regression fitted to the data accounted for 93% of its variability. Thus, these results seem to indicate that 24 hours after the treatment with parathion the effects induced on whole blood ChE activity may be used to predict the effects caused on frontal cerebral cortex ChE activity.

Animals↗
PubMed1998

Geographic variations in the composition of myotoxins from Bothrops neuwiedi snake venoms: biochemical characterization and biological activity.

(1) Venom pools from Bothrops neuwiedi (Bn) and from two subspecies, namely Bothrops neuwiedi pauloensis (Bnp) and Bothrops neuwiedi urutu (Bnu), collected in the States of São Paulo (SP) and Minas Gerais (MG), Brazil, were electrophoretically examined. Basic toxins with different isoelectric points were identified in the venom collected in São Paulo (BnSP). These toxins were absent in the corresponding pools from Minas Gerais (BnMG, BnpMG and BnuMG). (2) BnSP, but not BnMG, BnpMG or BnuMG, showed two myotoxins (pI approximately equal to 8.6 and 8.8, respectively) which were isolated by ion-exchange chromatography on CM-Sepharose. (3) From BnMG, three myotoxic isoforms (pI approximately equal to 8.2 and M(r) = 13,600) were isolated by chromatography on CM-Sepharose followed by reversed-phase high-performance liquid chromatography. (4) The chemical and biological characterization of these toxins showed a high similarity with the Lys-49 myotoxins from other bothropic venoms. (5) Doses up to 5 LD50 (i.p.) of p-bromophenacyl bromide alkylated BnSP-7 caused a total loss of lethality in 18-22-g mice, thus indicating that the LD50 was increased by greater than 5-fold. At this dose myotoxicity was also not detectable, but the edematogenic activity on the rat paw apparently did not change.

Alkylation↗
PubMed1998

Efficacy of a glutamine-based oral rehydration solution on the electrolyte and water absorption in a rabbit model of secretory diarrhea induced by cholera toxin.

BACKGROUND: Glutamine is absorbed in the intestinal tract coupled with sodium and is the principal metabolic substrate for the enterocyte. Therefore, an oral rehydration solution containing this substance might provide an effective oral means of restoring electrolyte losses as well as speeding repair of mucosal damage. The objective of this work was to investigate the use of an oral rehydration solution based on glutamine in vivo in the perfused rabbit ileal loop model of secretory diarrhea induced by choleratoxin. METHODS: Phenolsulfonphthalein (PSP, 50 mg/l) was used as a nonabsorbable marker for calculations of net water and electrolyte transport. Solutions tested included: (a) a glutamine-based oral rehydration solution with 111 mmol/l glutamine, (Gln-ORS); (b) the oral rehydration solution recommended by the World Health Organization; (c) modified Ringer's solution. Choleratoxin (1 microg/ml) was injected into the lumen of the ileal rabbit segments for 30 minutes prior to the initiation of the perfusion. RESULTS: Choleratoxin induced significant secretion of sodium in the control modified Ringer's solution (10.8 +/- 2.95 vs -14.05 +/- 5.95 microEq/g/min, n = 10; p < 0.01) and of water (0.06 +/- 0.03 vs -0.15 +/- 0.06 ml/g/min, n = 10; p < 0.01) with a maximum effect at 60 minutes after initiation of perfusion. World Health Organization oral rehydration solution was able to significantly reduce the intestinal secretion of sodium (control with cholera = -14.34 +/- 2.18 vs oral rehydration solution with cholera = -0.50 +/- 0.48 microEq/g/min, n = 10; p < 0.01) and water (-0.15 +/- 0.02 vs -0.012 +/- 0.005 ml/g/min, n = 10; p < 0.01). For comparison, glutamine-based oral rehydration solution had an even greater effect on sodium and water absorption (glutamine-based oral rehydration solution with choleratoxin = 10.31 +/- 1.21 microEq/g/min, n = 5; p < 0.01 for sodium and 0.08 +/- 0.008 ml water/g/min; n = 5; p < 0.01). Choleratoxin did not change the effect of glutamine-based oral rehydration solution on sodium and water absorption (12.90 +/- -1.09 microEq sodium/g/min, n = 5; and 0.11 +/- 0.01 ml water/g/min; n = 5). In addition glutamine-based oral rehydration solution also induced a greater absorption of potassium and chloride in the intestinal ileal segments treated with choleratoxin compared with World Health Organization glutamine-based oral rehydration solution. CONCLUSIONS: These results demonstrate the superior efficacy of glutamine-based oral rehydration solution in electrolyte and water absorption compared with modified Ringer's control solution or even with World Health Organization-recommended oral rehydration solution.

Animals↗
PubMed1998

Intestinal secretory factor released by macrophages stimulated with Clostridium difficile toxin A: role of interleukin 1beta.

Clostridium difficile toxin A is associated with enterocolitis in animals and humans. However, the mechanisms of its secretory and damaging effects are not totally understood. In this work, we examined the intestinal secretion of electrolytes and water caused by supernatants from macrophages stimulated with toxin A in rabbit ileal mucosa mounted in Ussing chambers. We also investigated the mechanism by which the intestinal secretory factor (ISF) is released from stimulated macrophages. Supernatants from macrophages stimulated with toxin A caused potent intestinal secretion (change in short-circuit current [DeltaIsc], 76 microA x cm-2; P < 0.01). The release of the ISF was pertussis toxin sensitive (reduction, 61%; P < 0.01) and was also reduced (P < 0.05) by a protein synthesis inhibitor (67%), protease inhibitors (57%), a phospholipase A2 inhibitor (54%), a cyclo-oxygenase inhibitor (62%), a dual cyclo- and lipoxygenase inhibitor (48%), a platelet-activating factor (PAF) receptor antagonist (55%), and tumor necrosis factor alpha (TNF-alpha) synthesis inhibitors (48%). However, this release was not inhibited by a lipo-oxygenase inhibitor. Monoclonal anti-interleukin 1beta (IL-1beta) but not anti-IL-1alpha antibody blocked (72%; P < 0.01) the secretory action of the ISF, as did recombinant human IL-1 receptor antagonist (80%; P < 0.01). High levels of IL-1beta (3,476 pg/ml) were detected by an enzyme-linked immunosorbent assay in the above supernatants. Furthermore, the addition of IL-1beta to the serosal side caused a potent secretory effect (DeltaIsc, 80 microA x cm-2; P < 0.01). These results show that macrophages stimulated with toxin A release an ISF capable of provoking intestinal secretion. The regulation of this factor is dependent upon the activation of the G protein. In addition, prostaglandins, PAF, and TNF-alpha are involved in the release of the ISF. We conclude that IL-1beta is probably the ISF released by macrophages in response to toxin A.

Animals↗
PubMed1997

Suitability of test media containing EDTA for the evaluation of acute metal toxicity to Daphnia magna straus.

The acute toxicity of six metals [Hg, Cd, Cu, Zn, Cr(II), and Cr(VI)] to Daphnia magna neonates was evaluated using three different test media (Elendt M7, a complex medium containing EDTA; ASTM hard water and EEC, two simple media free of chelators). The EC50 values, at both 24 and 48 h, obtained for Zn, Cr(II), and Cr(VI) were similar in all of the media tested. Hg was more toxic in ASTM than in M7 and in EEC media. The toxicity of Cd and Cu was similar in ASTM and EEC media and higher when evaluated in M7 medium. Thus, M7 should be used only carefully for the toxicity evaluation of mixtures and effluents containing metals. It is recommended, however, that it be excluded from use in tests evaluating samples of unknown composition, or those known to contain Cu and Cd. For the metals tested in this study, a factor of five applied to each 48-h EC50 would be sufficient in order to attain the respective acute NOECs for immobility.

Animals↗
PubMed1997

The histamine releasers crotamine, protamine and compound 48/80 activate specific proteases and phospholipases A2.

Crotamine, a basic, myonecrotic, histamine-releasing neurotoxin, was isolated from Crotalus durissus terrificus venom. Carboxypeptidase A was shown to be activated by crotamine when acting upon N-carbobenzoxyglycil-L-phenylalanine. However the activity of carboxypeptidase B upon the substrate hippuryl-L-arginine was not enhanced by this toxin. Teh basic histamine releasers protamine and compound 48/80 also activated carboxypeptidase A. These three agents activated both alpha-chymotrypsin when acting upon acetyl-L-tyrosine ethyl ester and also five snake venom phospholipase-like myotoxins acting upon egg yolk phosphatidylcholine. These findings suggest that the action of these agents during histamine release may involve the participation of specific intermediary hydrolases which, upon activation, would enhance their cytolytic effects on the sequence of events which lead to granule extrusion and histamine release from mast cells.

Carboxypeptidases↗
PubMed1997

Inhibition of proteases, myotoxins and phospholipases A2 from Bothrops venoms by the heteromeric protein complex of Didelphis albiventris opossum serum.

The antibothropic complex (ABC) from opossum (species Didelphis albiventris) serum was purified by chromatography on DEAE-Sephacel. It showed an acidic character and two polypeptide chains of ca. 45 kDa and 48 kDa, respectively. Lyophilized opossum serum or the ABC (100 micrograms), as well as ethylenediamine tetraacetate (0.25 mumoles) were able to completely neutralise the hemorrhagic effect of 50 micrograms of the desiccated venoms of Bothrops moojeni, Bothrops pirajai and Bothrops jararacussu. The myotoxic (100 micrograms venom in mice) and edematogenic (90 micrograms venom in rats) activities of Bothrops moojeni and Bothrops jararacussu venoms, as well as of the major myonecrotic protein (myotoxin-I) isolated from Bothrops moojeni venom, were also totally inhibited by the ABC (200 micrograms and 270 micrograms, respectively). The lyophilized opossum serum (30 micrograms) and the ABC (30 micrograms) reduced to 50% the phospholipase A2 activity of Bothrops moojeni venom (10 micrograms). The clotting activity of Bothrops alternatus and Bothrops moojeni (20 micrograms) on bovine plasma was also significantly inhibited by the ABC (60 micrograms).

Animals↗
PubMed1997

Alterations of cell-mediated immune response in children with febrile seizures.

The aim of the present investigation was to study the distribution of T-cell subsets in peripheral blood defined by monoclonal antibodies and by the lymphocyte proliferative response to phytohemagglutinin (PHA) in 30 children with febrile seizures and in 14 age-matched control subjects. Frequent respiratory, urinary and dermatologic infections were observed in 22 patients. The immunologic parameters showed that 64% of the patients presented an increased number of CD8+ cells and a low helper/suppressor ratio was observed in 60% of the patients. In addition, the proliferative response of lymphocytes to PHA was impaired in the patients. It was observed the presence of inhibitory activity on lymphocyte function in the plasma of 33% of children with febrile seizures. These results suggest that patients with febrile seizures have an impairment of cellular immunity that may be connected with this epileptic syndrome and explain the infections observed.

CD4-CD8 Ratio↗