Biological deterioration of alginate beads containing immobilized microalgae and bacteria during tertiary wastewater treatment.

Secondary treatment of municipal wastewater affects the mechanical stability of polymer Ca-alginate beads containing the microalgae Chlorella vulgaris that are jointly immobilized with Azospirillum brasilense as treating agents whose presence do not affect bead stability. Nine strains of potential alginate-degrading bacteria were isolated from wastewater and identified, based on their nearly complete 16S rDNA sequence. Still, their population was relatively low. Attempts to enhance the strength of the beads, using different concentrations of alginate and CaCl2 or addition of either of three polymers (polyvinylpyrrolidone, polyvinyl alcohol, carboxymethylcellulose), CaCO3, or SrCl2, failed. Beads lost their mechanical strength after 24 h of incubation but not the integrity of their shape for at least 96 h, a fact that sustained successful tertiary wastewater treatment for 48 h. In small bioreactors, removal of phosphorus was low under sterile conditions but high in unsterile wastewater. Alginate beads did not absorb PO4 (-3) in sterile wastewater, but in natural wastewater, they contained PO4 (-3). Consequently, PO4 (-3) content declined in the wastewater. A supplement of 10 % beads (w/v) was significantly more efficient in removing nutrients than 4 %, especially in a jointly immobilized treatment where >90 % of PO4 (-3) and >50 % ammonium were removed. Tertiary wastewater treatment in 25-L triangular, airlift, autotrophic bioreactors showed, as in small bioreactors, very similar nutrient removal patterns, decline in bead strength phenomena, and increase in total bacteria during the wastewater treatment only in the presence of the immobilized treatment agents. This study demonstrates that partial biological degradation of alginate beads occurred during tertiary wastewater treatment, but the beads survive long enough to permit efficient nutrient removal.

Adsorption and corrosion inhibition behaviour of new theophylline-triazole-based derivatives for steel in acidic medium.

The design and synthesis of a series of theophylline derivatives containing 1,2,3-triazole moieties are presented. The corrosion inhibition activities of these new triazole-theophylline compounds were evaluated by studying the corrosion of API 5 L X52 steel in 1 M HCl medium. The results showed that an increase in the concentration of the theophylline-triazole derivatives also increases the charge transference resistance (R ct) value, enhancing inhibition efficiency and decreasing the corrosion process. The electrochemical impedance spectroscopy under static conditions studies revealed that the best inhibition efficiencies (approx. 90%) at 50 ppm are presented by the all-substituted compounds. According to the Langmuir isotherm, the compounds 4 and 5 analysed exhibit physisorption-chemisorption process, with exception of the hydrogen 3, bromo 6 and iodo 7 substituted compounds, which exhibit chemisorption process. The corrosion when submerging a steel bar in 1 M HCl was studied using SEM-EDS. This experiment showed that the corrosion process decreases considerably in the presence of 50 ppm of the organic inhibitors. Finally, the theoretical study showed a correlation between EHOMO, hardness (η), electrophilicity (W), atomic charge and the inhibition efficiency in which the iodo 7 substituted compound presents the best inhibitor behaviour.

Differential effects on natural reward processing in rats after repeated heroin.

RATIONALE: Heroin users report reward deficits as well as reward enhancements (to drug stimuli). To better understand the causal relation between chronic heroin and alterations in natural reward processing, we used experimental techniques in animal models. METHODS: Separate groups of rats were trained in several food reward paradigms: conditioned place preference (CPP), food-reinforced lever pressing under a progressive ratio schedule of reinforcement, free feeding, and lever pressing with conditioned reinforcement. After training, the rats were subjected to 10 daily heroin (2 mg/kg) or saline vehicle injections and tested at 3, 15, and 30 days post-treatment. RESULTS: Repeated heroin treatment abolished the CPP and significantly reduced break points for food reward at 3, 15, and 30 days post-treatment. Repeated heroin did not affect free feeding. Finally, repeated heroin significantly enhanced responding for a food-based conditioned reinforcer. CONCLUSIONS: Repeated heroin decreases the attractiveness of food-associated cues and reduces motivation to work for natural reward. However, it appears to enhance natural conditioned reward processes that involve the acquisition of novel responding. Thus, repeated heroin appears to produce differential effects on natural reward processing depending on the nature of the reward-directed behavior.

A food-associated CS activates c-Fos in VTA DA neurons and elicits conditioned approach.

Neutral stimuli associated with unconditioned stimuli (USs) acquire the ability to act as conditioned stimuli (CSs), which can elicit behaviors similar to the US with which they are associated. The neural mechanisms by which this occurs are not fully known. We have previously proposed a model stipulating CSs function as such because they acquire the capacity to activate dopamine (DA) neurons at the level of the ventral tegmental area (VTA). In the present experiments we hypothesized that a food-associated CS (light), which demonstrably functions as such by eliciting conditioned responses (CRs), comes to acquire the capacity to activate VTA DA neurons. In Experiment 1, rats were allowed to eat or not eat food (food being the US). In Experiment 2, rats were trained to retrieve food pellets after light presentations (the CS) and then tested for the expression of the food checking response (the CR) with only CS presentations. In Experiment 1, eating food (exposure to the US) caused a significantly greater number of VTA DA (TH-labeled) cells to express c-Fos than not eating. In Experiment 2, CS (light) presentations caused a significant amount of conditioned approach and a significantly greater number of VTA TH-labeled (DA) cells to express c-Fos. These findings support our model stipulating that conditioned approach learning occurs when CSs acquire the capacity to cause conditioned activation of VTA DA neurons.

Efecto de la furazolidona sobre el glutatión sanguíneo del pollo de engorda / Effec of furazolidone on chicks blood glutathione

El objetivo de este trabajo fue establecer si la furazolidona utiliza el sistema detoxificante de glutatión en el organismo, mediante la determinación de la cantidad (µmol/ml de sangre) de glutatión total (GT), glutatión oxidado (GSSG), y glutatión reducido (GSH) durante las 5 semanas de vida del pollo de engorda que no consumió aditivos (testigo), comparado con los niveles de GT, GSSG y GSH sanguíneo de las aves que consumieron furazolidona durante las 5 primeras semanas de vida. Hubo diferencia significativa entre el GT (µmol/ml de sangre) y el peso corporal de pollos del grupo testigo y el que consumió furazolidona (55 ppm en el alimento) (R²= -0.709; P< 0.05, y = 2.15 - 0.607x y R²=-0.820 P< 0.05, y = 2.17 -0.61x respectivamente) hubo diferencia significativa (P< 0.05) entre el peso de los pollos del grupo testigo y el de los que consumieron furazolidona (751.3 vs 884.35 g respectivamente)