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High-Level Adaptation and Aftereffects

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889451470 Year: Pages: 98 DOI: 10.3389/978-2-88945-147-0 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Psychology --- Science (General)
Added to DOAB on : 2017-08-28 14:01:09
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Abstract

Aftereffects generally occur after a prolonged exposure (adaptation) to a first stimulus possessing one given property followed by presentation of a stimulus bearing a neutral value of that property. The aftereffect consists in a change in appearance of the neutral stimulus following the adapter, compared to the appearance of the neutral stimulus when it is perceived without any previous exposure to the adapter. The transient phenomena of perceptual aftereffects are believed to depend on the activation of neuron populations that respond selectively to a given property of the stimuli. Studying how adaptation occurs (which stimulus properties are sensitive to it, which timings are necessary, whether individual differences modulate its occurrence) has thus become an indirect way to probe the plasticity of sensory functions in the nervous system, recently extending to more cognitive and representational aspects of neural coding. In the last two decades, indeed, it has been demonstrated that aftereffects occur not only for low-level properties of stimuli (such as motion, color, or orientation) but also for high-level properties. Many studies have proven that high-level proprieties of the stimuli, e.g. gender, identity, ethnicity, or age of a face or a voice, are sensitive to this phenomenon. It has been shown, for example, that the prolonged exposure to a female or male face produces a gender misperception in the opposite direction when an androgynous face is shown after the adapter. Furthermore, recent studies have also shown that aftereffects are not strictly contingent upon the physical features that make up stimuli, but they seem to run across the high-level proprieties subjects are adapted to. These evidences are supported by cross-category adaptation studies, which underlie how aftereffects occur even across stimuli that do not share physical features (e.g. bodies and faces) but that instead, share common higher-level properties, such as gender. Given the growing body of research focused on adaptation and aftereffects in high-level perception at the boundaries with perceptual learning, attention and cognition, the purpose of this topic is to provide a picture of the state of the art relative to the specific phenomena of adaptation in high-level perceptual processing.

Keywords

adaptation --- Aftereffects --- High-level --- faces --- bodies --- emotion --- Perception

Recombinant protein expression in microbial systems

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889192946 Year: Pages: 102 DOI: 10.3389/978-2-88919-294-6 Language: English
Publisher: Frontiers Media SA
Subject: Environmental Sciences --- Biotechnology --- General and Civil Engineering --- Microbiology --- Science (General)
Added to DOAB on : 2015-12-10 11:59:07
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With the advent of recombinant DNA technology, expressing heterologous proteins in microorganisms rapidly became the method of choice for their production at laboratory and industrial scale. Bacteria, yeasts and other hosts can be grown to high biomass levels efficiently and inexpensively. Obtaining high yields of recombinant proteins from this material was only feasible thanks to constant research on microbial genetics and physiology that led to novel strains, plasmids and cultivation strategies. Despite the spectacular expansion of the field, there is still much room for progress. Improving the levels of expression and the solubility of a recombinant protein can be quite challenging. Accumulation of the product in the cell can lead to stress responses which affect cell growth. Buildup of insoluble and biologically inactive aggregates (inclusion bodies) lowers the yield of production. This is particularly true for obtaining membrane proteins or high-molecular weight and multi-domain proteins. Also, obtaining eukaryotic proteins in a prokaryotic background (for example, plant or animal proteins in bacteria) results in a product that lack post-translational modifications, often required for functionality. Changing to a eukaryotic host (yeasts or filamentous fungi) may not be a proper solution since the pattern of sugar modifications is different than in higher eukaryotes. Still, many advances in the last couple of decades have provided to researchers a wide variety of strategies to maximize the production of their recombinant protein of choice. Everything starts with the careful selection of the host. Be it bacteria or yeast, a broad list of strains is available for overcoming codon use bias, incorrect disulfide bond formation, protein toxicity and lack of post-translational modifications. Also, a huge catalog of plasmids allows choosing for different fusion partners for improving solubility, protein secretion, chaperone co-expression, antibiotic resistance and promoter strength. Next, controlling culture conditions like temperature, inducer and media composition can bolster recombinant protein production. With this Research Topic, we aim to provide an encyclopedic account of the existing approaches to the expression of recombinant proteins in microorganisms, highlight recent discoveries and analyze the future prospects of this exciting and ever-growing field.

Endoplasmic reticulum - shape and function in stress translation

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193448 Year: Pages: 110 DOI: 10.3389/978-2-88919-344-8 Language: English
Publisher: Frontiers Media SA
Subject: Botany --- Science (General)
Added to DOAB on : 2016-03-10 08:14:32
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The endoplasmic reticulum (ER) is a manufacturing unit in eukaryotic cells required for the synthesis of proteins, lipids, metabolites and hormones. Besides supporting cellular signalling networks by its anabolic function, the ER on its own or in communication with other organelles directly initiates signalling processes of physiological significance. Based on the intimate and immediate involvement in stress signalling the ER is considered as sensory organelle on which cells strongly rely to effectively translate environmental cues into adaptive stress responses. The transcellular distribution of the ER providing comprehensive cell-to-cell connections in multicellular organisms probably allows a concerted action of cell alliances and tissue areas towards environmental constraints. At the cellular level, stress adaptation correlates with the capability of the ER machinery to synthesise proteins participating in stress signalling as well as in the activation of ER membrane localised proteins to start cell-protective signalling processes. Importantly, depending on the stress insult, the ER either supports protective strategies or initiates cell death programmes. Recent, genetic, molecular and cell biological studies have drawn an initial picture of underlying signalling events activated by ER membrane localised proteins. In this Research Topic, we provided a platform for articles describing research on ER morphology and metabolism with a focus on stress translation. The Research Topic is sub-divided into the following sections: 1. ER in stress signalling and adaptation 2. ER structure and biosynthetic functions 3. Regulation of protein processing 4. Regulation of programmed cell death

Mitochondria: Hubs of Cellular Signaling, Energetics and Redox Balance

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889452392 Year: Pages: 228 DOI: 10.3389/978-2-88945-239-2 Language: English
Publisher: Frontiers Media SA
Subject: Physiology --- Science (General)
Added to DOAB on : 2017-10-13 14:57:01
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Poised at the convergence of most catabolic and anabolic pathways, mitochondria are the center of heterotrophic aerobic life, representing a hub in the overall metabolic network of cells. The energetic functions performed by mitochondria face the unavoidable redox hurdle of handling huge amounts of oxygen while keeping its own as well as the cellular redox environment under control. Reactive oxygen species (ROS) are produced in the respiratory chain as a result of the energy supplying function of mitochondria. Originally considered an unavoidable by-product of oxidative phosphorylation, ROS have become crucial signaling molecules when their levels are kept within physiological range. This occurs when their production and scavenging are balanced within mitochondria and cells. Mitochondria-generated hydrogen peroxide can act as a signaling molecule within mitochondria or in the cytoplasm, affecting multiple networks that control, for example, cell cycle, stress response, cell migration and adhesion, energy metabolism, redox balance, cell contraction, and ion channels. However, under pathophysiological conditions, excessive ROS levels can happen due to either overproduction, overwhelming of antioxidant defenses, or both. Under oxidative stress, detrimental effects of ROS include oxidation of protein, lipids, and nucleic acids; mitochondrial depolarization and calcium overload; and cell-wide oscillations mediated by ROS-induced ROS release mechanisms. Mitochondrial dysfunction is central in the pathogenesis of numerous human maladies including cardiomyopathies and neurodegeneration. Diseases characterized by altered nutrient metabolism, such as diabetes and cancer, exhibit elevated ROS levels. These may contribute to pathogenesis by increasing DNA mutation, affecting regulatory signaling and transcription, and promoting inflammation. Under metabolic stress, several ionic channels present in the inner and outer mitochondrial membranes can have pro-life and -death effects. In the present E-book, based on the Frontiers Research Topic entitled: "Mitochondria: Hubs of cellular signaling, energetics and redox balance", we address one of the fundamental questions that the field of ROS biology faces today: how do mitochondria accomplish a reliable energy provision and at the same time keep ROS levels within physiological, non-harming, limits but crucial for cellular signaling function? Additionally, and within the perspective of mitochondria as signaling-energetic hubs in the extensive cellular metabolic network, we ask how can their collective dynamics scale from the subcellular to the cellular, tissue and organ levels to affect function in health and disease.

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