[Microbial interactions with heavy metals]. / Interacciones microbianas con metales pesados.

Living organisms are exposed in nature to heavy metals, commonly present in their ionized species. These ions exert diverse toxic effects on microorganisms. Metal exposure both selects and maintains microbial variants able to tolerate their harmful effects. Varied and efficient metal resistance mechanisms have been identified in diverse species of bacteria, fungi and protists. The study of the interactions between microorganisms and metals may be helpful to understand the relations of toxic metals with higher organisms such as mammals and plants. Some microbial systems of metal tolerance have the potential to be used in biotechnological processes, such as the bioremediation of environmental metal pollution or the recovery of valuable metals. In this work we analyze several examples of the interactions of different types of microbes with heavy metals; these cases are related either with basic research or with possible practical applications.

Perceived psychological stress in diabetes mellitus type 2.

We studied the factors associated with perceived psychosocial stress in patients with diabetes mellitus type 2. A cross-sectional study was carried out in 105 patients (27 men and 78 women) with a mean age of 51.6 (50.2-52.5, 95% CI) years and 8.6 (7.3-9.8, 95% CI) years since diagnosis. The patients were overweight with body mass index (BMI) of 27.6, and most of them had deficient metabolic control (mean glucose of 10.6 nmol/L and HbA1c of 9.2%). Glycated hemoglobin was associated with BMI (negatively, p = 0.002), with adherence to diet (negatively, p = 0.027) and with years since diagnosis (p = 0.031). The association with BMI was found only in women. It was explained by the fact that obese women had fewer years since diagnosis, and recently diagnosed patients have a better metabolic control. A stepwise multiple regression analysis showed perceived stress associated with percent body fat and blood glucose in the total group, with years since diagnosis in women (p = 0.02), and with BMI in men (p = 0.03). No association was found between perceived stress and adherence to treatment. We concluded that in our group, perceived stress was associated with obesity and metabolic control.

Application of internal standard for derivative-spectrophotometric determination of azinphos-methyl in commercial formulations.

The use of an internal standard is proposed in this work for first derivative spectrophotometric determination of azinphos in formulations. Generally, the spectrophotometric procedure is simpler and less expensive than chromatographic techniques recommended for the analysis of pesticides. However, while determining the pesticide in commercial formulations the, many-fold dilution required for such sensitive detection is a serious source of analytical error. It is known that an internal standard (IS), if properly chosen, can help eliminate this type of problem. A mixture of acetophenone (used as an IS in the high performance liquid chromatography (HPLC) procedure) and the blue dye Erioglaucine (A) was applied for the determination of azinphos-methyl in commercial formulations. To ensure the best conditions for the zero-crossing technique, the composition of the mixture was optimized to obtain the zero value of the first derivative absorbance of the IS at a minimum of the azinphos-methyl first derivative absorbance. Also, at the maximum of the first derivative spectrum of the IS, the differential absorption signal of the analyte was negligible. Analytical characteristics for the first derivative spectrophotometric procedure proposed were evaluated (r(2) = 0.9998, detection limit = 0.043 mg, quantification limit = 0.143 mg) and the analytical results obtained (35.02 +/- 0.20% of azinphos-methyl in the formulation) were in good agreement with the results obtained using the official HPLC method (35.44 +/- 0.32%).