Determinação de parâmetros cinéticos em fluxo com câmara de gradiente e deteção espectrofotométrica: aplicação à reação entre o violeta de cristal e o ião hidróxido

A didactic experiment is proposed aimed to extend the Flow Injection Analysis (FIA) based methodology to the area of physical chemistry/chemical reactors for undergraduate labs. Our prime objective was to describe the use of a gradient chamber for determination of the rate constant for the reaction between crystal violet and the hydroxide ion. The study was complemented by determining the effect of temperature on the rate constant. The kinetic parameters, activation energy and reaction rate constant are determined based on an assumption of rate orders. The main didactic advantages of the proposed experimental set-up are the use of less reagents, contributing to a more environmental friendly experiment. The experiment illustrates also the reduction of associated errors and time by using automated analysis owing to decreased operator manipulation.

Propriedades estruturais e eletrônicas de nanofilmes de TiO2 anatase: cálculos B3LYP-D* em sistemas periódicos bidimensionais

Structural and electronic properties of titanium dioxide (TiO2) thin films, in anatase phase, were investigated using periodic 2D calculations at density functional theory (DFT) level with B3LYP hybrid functional. The Grimme dispersion correction (DFT/B3LYP-D*) was included to better reproduce structural features. The electronic properties were discussed based on the band gap energy, and proved dependent on surface termination. Surface energies ranged from 0.80 to 2.07 J/m², with the stability orders: (101) > (100) > (112) > (110) ~ (103) > (001) >> (111), and crystal shape by Wulff construction in accordance with experimental data.

Resolução multivariada de curvas com mínimos quadrados alternantes: descrição, funcionamento e aplicações

Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS) is a resolution method that has been efficiently applied in many different fields, such as process analysis, environmental data and, more recently, hyperspectral image analysis. When applied to second order data (or to three-way data) arrays, recovery of the underlying basis vectors in both measurement orders (i.e. signal and concentration orders) from the data matrix can be achieved without ambiguities if the trilinear model constraint is considered during the ALS optimization. This work summarizes different protocols of MCR-ALS application, presenting a case study: near-infrared image spectroscopy.

Uncertainties of the 137Cs technique for validation of soil redistribution modelling in a semiarid meso-scale watershed

Scarcity of long-term series of sediment-related variables has led watershed managers to apply mathematical models to simulate sediment fluxes. Due to the high efforts for installation and maintenance of sedimentological gauges, tracers have been pointed out as an alternative to validate soil redistribution modelling. In this study, the 137Cs technique was used to assess the WASA-SED model performance at the Benguê watershed (933 km²), in the Brazilian semiarid. Qualitatively, good agreement was found among the 137Cs technique and the WASA-SED model results. Nonetheless, quantitatively great differences, up to two orders of magnitude, were found between the two methods. Among the uncertainties inherent to the 137Cs technique, definition of the reference inventory seems to be a major source of imprecision. In addition, estimations of water and sediment fluxes with mathematical models usually also present high uncertainty, contributing to the quantitative differences of the soil redistribution estimates with the two methods.

Bariatric surgery: impact on sexuality of the obese person

Objective: To assess the impact of surgical treatment in the sexuality of the obese.Methods: We conducted a qualitative / quantitative research with 30 patients who had undergone Fobi-Capella Roux-Y gastric bypass for at least one year. We collected data through individual interviews using a questionnaire with 10 mixed questions and one open, between May and June 2011. The objective data were quantified in absolute numbers and percentages, and the subjective ones were analyzed using the Discourse of the Collective Subject (DCS) and discussed in view of reference published on the subject.Results: 30 patients were enrolled, with a mean age 44 ± 12 years, 24 (80%) were female and six (20%) were male, 23 (77%) were married, 23 (96%) were hypertensive and eight (33%) were diagnosed with Diabetes Mellitus. After the operation, 11 (37%) individuals reported no change in the number sexual intercourses, but 19 (63%) reported that this number was altered, 16 (53%) informed increased frequency, one (3%) reported a decrease in frequency, one (3%) did not practice sexual intercourse anymore and one (3%) did not report the frequency. The central ideas (CI) raised originated four DCSs: Experience of female sexuality; No experience of female sexuality; Experience of male sexuality; and improvements of comorbidities and psychological factor.Conclusion: there are positive repercussions of physical and emotional orders of the surgical treatment of obesity, favoring the quality of life, including sexuality.

Epidemiology of leptospirosis at Sorocaba Zoo, São Paulo state, Southeastern Brazil

Leptospirosis is considered a worldwide distributed zoonosis, caused by the bacteria Leptospira spp. Since several species of wildlife animals are reportedly reservoirs, the aim of the present study was to know the epidemiology of leptospirosis at the Sorocaba Zoo, Southern Brazil. Serum samples of wild mammals from Artiodactyla, Carnivora, Didelphimorphia, Diprotodontia, Perissodactyla, Pilosa, Primates, Proboscidea and Rodentia orders, kept in captivity as well as from zoological staff were assayed by microscopic agglutination test (MAT). Whole blood, urine and tissue samples from wild mammals and synanthropic animals were assayed by polymerase chain reaction (PCR). An epidemiological survey was applied to evaluate the risk factors for animal infection and staff level of knowledge on leptospirosis. A total of 13/229 (5.68%; CI95% 3.37-9.47%) serum samples from wild mammals were reagent on MAT. Serology from synanthropic animals, zoo staff and molecular analysis of animal samples were all negative. Leptospirosis knowledge of zoo park staff was considered medium. In conclusion, leptospiral infection occurs at the studied zoo but due to the low occurrence found, the lowest reported in literature, wild captive mammals do not act as source of infection of leptospirosis to other animals and human beings.

Planktic Cyanobacteria from upper Tietê basin reservoirs, SP, Brazil

Considering the great ecological and sanitary importance of the cyanobacteria and the need of detailed information about these organisms in Brazilian water bodies, the present study aims at contributing towards the knowledge of the cyanobacterial flora of five reservoirs belonging to the upper Tietê Basin, São Paulo: Billings, Guarapiranga, Jundiaí, Pirapora, Ponte Nova and Taiaçupeba. In the past several years, these reservoirs have been submitted to severe environmental deterioration and have repeatedly presented cyanobacterial blooms, including those of toxic species. The samples were collected between 1997 and 2003 either with plankton net (20 µm mesh) or van Dorn's bottle, and preserved with lugol solution or formaldehyde. Some species were isolated and maintained in culture. Forty-eight species of cyanobacteria were identified, with predominance of the order Chroococcales (58%), followed by the orders Oscillatoriales (21%) and Nostocales (21%). Among the 48 studied species, 17 (35%) were considered potentially toxic. The occurrence and biodiversity of the cyanobacteria in each reservoir depend on the environmental conditions. Among the five water bodies, Billings Reservoir presented the most adequate situation for the development of a greater number of species (34), probably due to its high pH values (around 8). Pirapora Reservoir on the other hand, with highest conductivity (445.0 µS cm-1) and lowest Secchi depth values (0.2 m), presented the lowest cyanobacterial biodiversity (14 species).

Proliferation of differentiated glial cells in the brain stem

Classical studies of macroglial proliferation in muride rodents have provided conflicting evidence concerning the proliferating capabilities of oligodendrocytes and microglia. Furthermore, little information has been obtained in other mammalian orders and very little is known about glial cell proliferation and differentiation in the subclass Metatheria although valuable knowledge may be obtained from the protracted period of central nervous system maturation in these forms. Thus, we have studied the proliferative capacity of phenotypically identified brain stem oligodendrocytes by tritiated thymidine radioautography and have compared it with known features of oligodendroglial differentiation as well as with proliferation of microglia in the opossum Didelphis marsupialis. We have detected a previously undescribed ephemeral, regionally heterogeneous proliferation of oligodendrocytes expressing the actin-binding, ensheathment-related protein 2'3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), that is not necessarily related to the known regional and temporal heterogeneity of expression of CNPase in cell bodies. On the other hand, proliferation of microglia tagged by the binding of Griffonia simplicifolia B4 isolectin, which recognizes an alpha-D-galactosyl-bearing glycoprotein of the plasma membrane of macrophages/microglia, is known to be long lasting, showing no regional heterogeneity and being found amongst both ameboid and differentiated ramified cells, although at different rates. The functional significance of the proliferative behavior of these differentiated cells is unknown but may provide a low-grade cell renewal in the normal brain and may be augmented under pathological conditions.

Two research paths for probing the roles of oxygen in metabolic regulation

Tissues such as skeletal and cardiac muscles must sustain very large-scale changes in ATP turnover rate during equally large changes in work. In many skeletal muscles these changes can exceed 100-fold. Examination of a number of cell and whole-organism level systems identifies ATP concentration as a key parameter of the interior milieu that is nearly universally 'homeostatic'; it is common to observe no change in ATP concentration even while change in its turnover rate can increase or decrease by two orders of magnitude or more. A large number of other intermediates of cellular metabolism are also regulated within narrow concentration ranges, but none seemingly as precisely as is [ATP]. In fact, the only other metabolite in aerobic energy metabolism that is seemingly as 'homeostatic' is oxygen - at least in working muscles where myoglobin serves to buffer oxygen concentrations at stable and constant values at work rates up to the aerobic maximum. In contrast to intracellular oxygen concentration, a 1:1 relationship between oxygen delivery and metabolic rate is observed over biologically realistic and large-magnitude changes in work. The central regulatory question is how the oxygen delivery signal is transmitted to the intracellular metabolic machinery. Traditional explanations assume diffusion as the dominant mechanism, while proponents of an ultrastructurally dominated view of the cell assume an intracellular perfusion system to account for the data which have been most perplexing to metabolic biochemistry so far: the striking lack of correlation between changes in pathway reaction rates and changes in concentrations of pathway substrates, including oxygen and pathway intermediates.

Brain ischemia alters platelet ATP diphosphohydrolase and 5'-nucleotidase activities in naive and preconditioned rats

The effects of transient forebrain ischemia, reperfusion and ischemic preconditioning on rat blood platelet ATP diphosphohydrolase and 5'-nucleotidase activities were evaluated. Adult Wistar rats were submitted to 2 or 10 min of single ischemic episodes, or to 10 min of ischemia 1 day after a 2-min ischemic episode (ischemic preconditioning) by the four-vessel occlusion method. Rats submitted to single ischemic insults were reperfused for 60 min and for 1, 2, 5, 10 and 30 days after ischemia; preconditioned rats were reperfused for 60 min 1 and 2 days after the long ischemic episode. Brain ischemia (2 or 10 min) inhibited ATP and ADP hydrolysis by platelet ATP diphosphohydrolase. On the other hand, AMP hydrolysis by 5'-nucleotidase was increased after 2, but not 10, min of ischemia. Ischemic preconditioning followed by 10 min of ischemia caused activation of both enzymes. Variable periods of reperfusion distinctly affected each experimental group. Enzyme activities returned to control levels in the 2-min group. However, the decrease in ATP diphosphohydrolase activity was maintained up to 30 days of reperfusion after 10-min ischemia. 5'-Nucleotidase activity was decreased 60 min and 1 day following 10-min ischemia; interestingly, enzymatic activity was increased after 2 and 5 days of reperfusion, and returned to control levels after 10 days. Ischemic preconditioning cancelled the effects of 10-min ischemia on the enzymatic activities. These results indicate that brain ischemia and ischemic preconditioning induce peripheral effects on ecto-enzymes from rat platelets involved in nucleotide metabolism. Thus, ATP, ADP and AMP degradation and probably the generation of adenosine in the circulation may be altered, leading to regulation of microthrombus formation since ADP aggregates platelets and adenosine is an inhibitor of platelet aggregation.

Meningoencephalitis caused by a zygomycete fungus (Basidiobolus) associated with septic shock in an immunocompetent patient: 1-year follow-up after treatment

Zygomycosis is an infection caused by opportunistic fungi of the Zygomycetes class, specifically those from the Mucorales and Entomophthorales orders. It is an uncommon disease, mainly restricted to immunocompromised patients. We report a case of a 73-year-old male patient with a history of fever (39°C) lasting for 1 day, accompanied by shivering, trembling, and intense asthenia. The patient was admitted to the intensive care unit with complex partial seizures, and submitted to orotracheal intubation and mechanical ventilation under sedation with midazolam. The electroencephalogram showed evidence of non-convulsive status epilepticus. There is no fast specific laboratory test that permits confirmation of invasive fungal disease. Unless the physician suspects this condition, the disease may progress rapidly while the patient is treated with broad-spectrum antibiotics. Differential diagnosis between fungal and bacterial infection is often difficult. The clinical presentation is sometimes atypical, and etiological investigation is not always successful. In the present case, the histopathological examination of the biopsy obtained from the right temporal lobe indicated the presence of irregular, round, thick-walled fungi forming papillae and elongated structures of irregular diameter, with no septa, indicative of zygomycete (Basidiobolus). Treatment with liposomal amphotericin B and fluconazole was initiated after diagnosis of meningoencephalitis by zygomycete, with a successful outcome.