Stress and Memory: Behavioral Effects and Neurobiological Mechanisms

Stress is a potent modulator of learning and memory processes. Although there have been a few attempts in the literature to explain the diversity of effects (including facilitating, impairing, and lack of effects) described for the impact of stress on memory function according to single classification criterion, they have proved insufficient to explain the whole complexity of effects. Here, we review the literature in the field of stress and memory interactions according to five selected classifying factors (source of stress, stressor duration, stressor intensity, stressor timing with regard to memory phase, and learning type) in an attempt to develop an integrative model to understand how stress affects memory function. Summarizing on those conditions in which there was enough information, we conclude that high stress levels, whether intrinsic (triggered by the cognitive challenge) or extrinsic (induced by conditions completely unrelated to the cognitive task), tend to facilitate Pavlovian conditioning (in a linear-asymptotic manner), while being deleterious for spatial/explicit information processing (which with regard to intrinsic stress levels follows an inverted U-shape effect). Moreover, after reviewing the literature, we conclude that all selected factors are essential to develop an integrative model that defines the outcome of stress effects in memory processes. In parallel, we provide a brief review of the main neurobiological mechanisms proposed to account for the different effects of stress in memory function. Glucocorticoids were found as a common mediating mechanism for both the facilitating and impairing actions of stress in different memory processes and phases. Among the brain regions implicated, the hippocampus, amygdala, and prefrontal cortex were highlighted as critical for the mediation of stress effects

The response surface methodology for optimization of tyrosinase immobilization onto electrospun polycaprolactone-chitosan fibers for use in bisphenol A removal.

Composite polycaprolactone-chitosan material was produced by an electrospinning method and used as a support for immobilization of tyrosinase by mixed ionic interactions and hydrogen bonds formation. The morphology of the fibers and enzyme deposition were confirmed by SEM images. Further, multivariate polynomial regression was used to model the experimental data and to determine optimal conditions for immobilization process, which were found to be pH 7, temperature 25 °C and 16 h process duration. Under these conditions, novel type of biocatalytic system was produced with immobilization yield of 93% and expressed activity of 95%. Furthermore, as prepared system was applied in batch experiments related to biodegradation of bisphenol A under various remediation conditions. It was found that over 80% of the pollutant was removed after 120 min of the process, in the temperature range 15-45 °C and pH 6-9, using solutions at concentration up to 3 mg/L. Experimental data collected proved that the stability and reusability of the tyrosinase were significantly improved upon immobilization: the immobilized biomolecule retained around 90% of its initial activity after 30 days of storage, and was still capable to remove over 80% of bisphenol A even after 10 repeated uses. By contrast, free enzyme was able to remove over 80% of bisphenol A at pH 7-8 and temperature range 15-35 °C, and retained less than 60% of its initial activity after 30 days of storage

Bonchoalveolar lavage fluid sample preparation for diverse proteomic approaches in pulmonary diseases

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The effect of ultrasound pretreatment on some selected physicochemical properties of black cumin (Nigella Sativa)

Background In the present study, the effects of ultrasound pretreatment parameters including irradiation time and power on the quantity of the extracted phenolic compounds quantity as well as on some selected physicochemical properties of the extracted oils including oil extraction efficiency, acidity and peroxide values, color, and refractive index of the extracted oil of black cumin seeds with the use of cold press have been studied. Methods For each parameter, three different levels (30, 60, and 90 W) for the ultrasound power and (30, 45, and 60 min) and for the ultrasound irradiation time were studied. Each experiment was performed in three replications. Results The achieved results revealed that, with enhancements in the applied ultrasound power, the oil extraction efficiency, acidity value, total phenolic content, peroxide value, and color parameters increased significantly (P 0.05). Conclusions In summary, it could be mentioned that the application of ultrasound pretreatment in the oil extraction might improve the oil extraction efficiency, the extracted oil’s quality, and the extracted phenolic compounds content.info:eu-repo/semantics/publishedVersio

Effect of Charge on Membrane Rejection During Ultrafiltration: Comparison of Dextran and Carboxymethilcellulose (CMC) Solutions

BaCeO3-based proton conductor BaCe0.5Zr 0.3Y0.16Zn0.04O3-δ (BCZYZn) was adopted as a part of the oxide-carbonate composite electrolyte. The total ionic conductivity of BCZYZn-carbonate composite is 0.28 S cm-1 at 500 C. Perovskite oxide SrFe0.7Mn0.2Mo0.1O 3-δ was developed and used as cathode. It was found that SrFe0.7Mn0.2Mo0.1O3-δ exhibits a primitive cubic structure with space group Pm3m(221); a = 3.8790(1) Å, V = 58.364(1) Å3. The electrical conductivity of SrFe 0.7Mn0.2Mo0.1O3-δ is 15-26 S cm-1 in the temperature range 400-700 C measured by d.c. method. Single cell with BCZYZn-carbonate composite electrolyte and SrFe 0.7Mn0.2Mo0.1O3-δ cathode was fabricated and tested with humidified H2 (∼3 vol% H2O) as fuel and air as oxidant. A similar configuration cell with lithiated NiO cathode was also constructed for comparison. It was found that neither BaCe 0.5Zr0.3Y0.16Zn0.04O 3-δ nor SrFe0.7Mn0.2Mo 0.1O3-δ is chemically compatible with (Li,Na) 2CO3. The fuel cell performance is not as good as those based on doped ceria-carbonate electrolytes

Continuous ethanol production via ultrasound-enhanced yeast sedimentation

Continuous glucose fermentation produces bioethanol at higher volumetric rates than conventional batch or fed-batch systems. The retention of yeast cells via ultrasonic sedimentation in a lab-scale fermenter allowed for shearless, continuous cell upconcentration, and consequently process intensification. The cell separation efficiency of the ultrasonic system was predicted with a Response Surface Model (RSM) developed for yeast cells based on the linear, mixed, and quadratic effects of the operating variables and flow rates (3 levels, 5 variables). The experiments for the RSM calibration were designed via a central composite design. The efficiency model was validated and showed dependency to the Biomass concentration, Power input, and Harvest rate (R2calibration = 0.92, R2prediction = 0.83). A lab-scale fermenter fed with yeast growth medium was operated at varying dilution rates (0.1 – 0.6 h−1) based on the RSM to maximize the cell retention efficiency (23%−90%). Yeast cell concentration in the fermenter reached up to 31.5 ± 0.7 g/L while it remained at around 3 g/L in the harvest stream for all the dilution rates tested. The ethanol concentration ranged between 17 and 23 g/L and reached high volumetric productivity (8.8 g/L/h). A control run without ultrasonic sedimentation led to the washout of biomass at a dilution rate of 0.6 h−1. Ultrasonic yeast sedimentation is a promising technology for cell retention and enhanced productivity in continuous fermentation processes