Development of an Alcohol Dehydrogenase Biosensor for Ethanol Determination with Toluidine Blue O Covalently Attached to a Cellulose Acetate Modified Electrode

In this work, a novel voltammetric ethanol biosensor was constructed using alcohol dehydrogenase (ADH). Firstly, alcohol dehydrogenase was immobilized on the surface of a glassy carbon electrode modified by cellulose acetate (CA) bonded to toluidine blue O (TBO). Secondly, the surface was covered by a glutaraldehyde/bovine serum albumin (BSA) cross-linking procedure to provide a new voltammetric sensor for the ethanol determination. In order to fabricate the biosensor, a new electrode matrix containing insoluble Toluidine Blue O (TBO) was obtained from the process, and enzyme/coenzyme was combined on the biosensor surface. The influence of various experimental conditions was examined for the characterization of the optimum analytical performance. The developed biosensor exhibited sensitive and selective determination of ethanol and showed a linear response between 1 × 10−5 M and 4 × 10−4 M ethanol. A detection limit calculated as three times the signal-to-noise ratio was 5.0 × 10−6 M. At the end of the 20th day, the biosensor still retained 50% of its initial activity

Allopregnanolone-induced rise in intracellular calcium in embryonic hippocampal neurons parallels their proliferative potential

<p>Abstract</p> <p>Background</p> <p>Factors that regulate intracellular calcium concentration are known to play a critical role in brain function and neural development, including neural plasticity and neurogenesis. We previously demonstrated that the neurosteroid allopregnanolone (APα; 5α-pregnan-3α-ol-20-one) promotes neural progenitor proliferation <it>in vitro </it>in cultures of rodent hippocampal and human cortical neural progenitors, and <it>in vivo </it>in triple transgenic Alzheimer's disease mice dentate gyrus. We also found that APα-induced proliferation of neural progenitors is abolished by a calcium channel blocker, nifedipine, indicating a calcium dependent mechanism for the proliferation.</p> <p>Methods</p> <p>In the present study, we investigated the effect of APα on the regulation of intracellular calcium concentration in E18 rat hippocampal neurons using ratiometric Fura2-AM imaging.</p> <p>Results</p> <p>Results indicate that APα rapidly increased intracellular calcium concentration in a dose-dependent and developmentally regulated manner, with an EC₅₀of 110 ± 15 nM and a maximal response occurring at three days <it>in vitro</it>. The stereoisomers 3β-hydroxy-5α-hydroxy-pregnan-20-one, and 3β-hydroxy-5β-hydroxy-pregnan-20-one, as well as progesterone, were without significant effect. APα-induced intracellular calcium concentration increase was not observed in calcium depleted medium and was blocked in the presence of the broad spectrum calcium channel blocker La³⁺, or the L-type calcium channel blocker nifedipine. Furthermore, the GABA_Areceptor blockers bicuculline and picrotoxin abolished APα-induced intracellular calcium concentration rise.</p> <p>Conclusion</p> <p>Collectively, these data indicate that APα promotes a rapid, dose-dependent, stereo-specific, and developmentally regulated increase of intracellular calcium concentration in rat embryonic hippocampal neurons via a mechanism that requires both the GABA_Areceptor and L-type calcium channel. These data suggest that APα-induced intracellular calcium concentration increase serves as the initiation mechanism whereby APα promotes neurogenesis.</p

Contrasting physiological responses to future ocean acidification among Arctic copepod populations

Widespread ocean acidification (OA) is modifying the chemistry of the global ocean, and the Arctic is recognized as the region where the changes will progress at the fastest rate. Moreover, Arctic species show lower capacity for cellular homeostasis and acid‐base regulation rendering them particularly vulnerable to OA. In the present study, we found physiological differences in OA response across geographically separated populations of the keystone Arctic copepod Calanus glacialis. In copepodites stage CIV, measured reaction norms of ingestion rate and metabolic rate showed severe reductions in ingestion and increased metabolic expenses in two populations from Svalbard (Kongsfjord and Billefjord) whereas no effects were observed in a population from the Disko Bay, West Greenland. At pHT 7.87, which has been predicted for the Svalbard west coast by year 2100, these changes resulted in reductions in scope for growth of 19% in the Kongsfjord and a staggering 50% in the Billefjord. Interestingly, these effects were not observed in stage CV copepodites from any of the three locations. It seems that CVs may be more tolerant to OA perhaps due to a general physiological reorganization to meet low intracellular pH during hibernation. Needless to say, the observed changes in the CIV stage will have serious implications for the C. glacialis population health status and growth around Svalbard. However, OA tolerant populations such as the one in the Disko Bay could help to alleviate severe effects in C. glacialis as a species

Urbanizing economics

Action space, Urban, Trust, B25, B41, R11, Z13,

The Role of "Social Capital" in the Market Process

From the standpoint of modern economics, the marvel of the price system is the way in which contextual knowledge is discovered and utilized without requiring individuals to articulate and transmit any great part of it to a central planner. While extremely valuable, this insight has tended to draw attention away from the actual contextual knowledge possessed by agents in a particular time and place that can over time promote the utilization of the market and its related institutions, including the price system, private property, and the rule of law. Examining forms of contextual knowledge such as social capital and trust can deepen our understanding of some of the conditions that promote the entrepreneurial discovery of profit opportunities in complex market processes, in which in the vast majority of trades very few of the actors involved ever know one another or meet face-to-face.Du point de vue de la science économique moderne, le miracle du système de prix est la manière à travers laquelle la connaissance contextuelle est découverte et utilisée sans que les individus aient à en articuler et en transmettre une grande partie à un planificateur central. Bien quextrêmement utile, cette idée a eu tendance à détourner lattention de la connaissance contextuelle actuelle possédée par les agents à un moment donné et dans un lieu donné qui peut, à travers le temps, promouvoir lutilisation du marché et de ses institutions telles que le système des prix, le droit de propriété et la règle de droit. Lexamen des formes que peut revêtir la connaissance contextuelle à linstar du capital social et de la confiance, peut améliorer notre compréhension de certaines conditions qui promeuvent la découverte des opportunités de profit par lentrepreneur dans des processus marchands complexes, une des caractéristiques de ces derniers étant que peu déchanges ont lieu entre des agents qui se connaissent ou lors de rencontre en face à face.

Deterministic coastal morphological and sediment transport modeling: a review and discussion

Modern coastal ocean modeling systems are now capable of numerically simulating a variety of coastal and estuarine problems and can thus provide useful information for managing coastal zones. Here we review state-of-the-art Eulerian implementations of bottom-up sediment transport and morphological change in coastal ocean hydrodynamic models. In order to investigate the fate of suspended sediment in coastal and estuarine waters as well as the evolution of sea or river beds, sediment dynamics need to be represented at a scale relevant to the numerical discretized solution, and significant effort is devoted to parameterize sediment processes. We discuss boundary layer hydrodynamics and the computation of the bed shear stress. We also focus on approaches used to represent near-bed processes such as bed load transport and sediment erosion and deposition. Sediment diffusivities, settling velocities, and cohesive processes such as flocculation all have an impact on suspended sediment throughout the water column. We then describe the implementation of process parameterizations in coastal hydrodynamic models, explicitly reviewing five widely used systems. The approaches implemented in these coastal models may present distinct strengths and shortcomings with regard to some important issues for coastal zones, both numerical and physical. While these detailed limitations need to be considered as part of model assessment, more general issues also hinder present state-of-the-art models. In particular, sediment transport is inherently highly empirical, which is further compounded by issues arising from turbulence closure schemes. We conclude by suggesting some possible directions toward improving sediment dynamics understanding and coastal-scale predictive abilit