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Cardiac autonomic dysfunction expressed by reduced baroreflex bradycardia was detected in rats chronically infected with T cruzi, as in human Chagas' disease. The disturbance, shown for the first time in an animal model of chagasic infection, resulted primarily from impaired efferent parasympathetic activity caused by intrinsic neuroganglionar lesions.

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Ten male Wistar rats, chronically infected with Colombian, São Felipe (12SF) and Y strains of Trypanosoma cruzi and ten non-infected control animals were submitted to the bradycardia responsiveness test, an assessment of heart parasympathetic function, after phenylephrine injection. Six chagasic animals showed heart parasympathetic dysfunction characterized by reduction in the index of bradycardia baroreflex responsiveness, as compared with the control group. Microscopic examination of the atrial heart ganglia of chagasic rats showed ganglionitis, but no statistically significant reduction in the number of neurons.

The Griess assay is widely used by regulation agencies as an official method for nitrite quantification in water and food samples. In Brazil, the official method, which has been used to determine nitrite in food, was described by Instituto Adolfo Lutz (283/IV) in 1984. It uses 8 mL of reactants and provides 50 mL (reactants plus sample) of waste per sample analyzed. Here, students scaled down the official method 50 times and quantified nitrite in water and food samples by using just 0.2 mL of the Griess reactant and 1 mL of sample. Quantitative analysis was carried out using absorbance measured at 540 nm (standard method) and 96-well-plate images (proposed method) obtained with a desktop scanner. The nitrite was extracted from solid food samples by heating it in a water bath. After heating, sample color and turbidity were eliminated by addition of K4[Fe­(CN)6] and ZnSO4 solutions and filtering. During samples preparation, students evaluate the heating time effect in nitrite extraction from sausage samples using hypothesis tests. Students did a series of matrix matched samples to observe the matrix effect. Students also calculated the detection limit (DL) and the quantification limit (QL) for the proposed method (1.35 and 4.1 μmol/L nitrite, respectively) and for the standard method (1.1 and 3.4 μmol/L nitrite, respectively). DL and QL were determined using the standard deviation of the lowest concentration point on the standard curve. The major pedagogical value of this laboratory class was to scale down the official method and use it to prepare and analyze a solid food sample. As a learning model, finding real water samples, which have nitrite concentrations larger than method QL, was a hard task, but all sausage samples analyzed had larger nitrate concentrations than the method QL and nitrite quantification in sausages was a good learning model.

In the present work, the ester synthesis in organic media catalyzed by lipases immobilized on chrysotile was studied. Lipases of different sources (Mucor javanicus, Pseudomonas cepacia, Rhizopus oryzae, Aspergillus niger and Candida rugosa) were immobilized on chrysotile, an inexpensive magnesium silicate, and used for esterification of hexanoic, octanoic and lauric acid with methanol, ethanol, 1-butanol and 1-octanol at 25 • C in hexane as solvent. The best results were obtained with Mucor javanicus lipase and lauric acid giving yields of 62-97% of ester.