Synaptic Functions of Astroglial Hemichannels

In recent decades, astrocytes have gained ground in their protagonist role at the synapses, challenging the old-historic idea that neurons are the unique functional units in the nervous system. Although for a long time considered merely supportive elements, astrocytes are now recognized as a source of gliotransmitter release that regulates synaptic transmission and plasticity. Despite the initial evidence that supported gliotransmission depends on intracellular Ca2+-mediated vesicular release, recent data indicate that hemichannels may constitute an alternative non-vesicular route for gliotransmitter efflux. These channels are plasma membrane channels formed by the oligomerization of six connexins around a central pore. Hemichannels are permeable to ions and signaling molecules—such as ATP, glutamate, and Ca2+—constituting a pathway of diffusional interchange between the cytoplasm and the extracellular milieu. Connexin 43 is the main hemichannel-forming protein in astrocytes and is highly regulated under physiological and pathological conditions. In this chapter, the available data supporting the idea that hemichannels are chief components in tuning the synaptic gain in either resting or stimulated conditions is discussed

Glial connexin expression and function in the context of Alzheimer's disease

AbstractA hallmark of neurodegenerative diseases is the reactive gliosis characterized by a phenotypic change in astrocytes and microglia. This glial response is associated with modifications in the expression and function of connexins (Cxs), the proteins forming gap junction channels and hemichannels. Increased Cx expression is detected in most reactive astrocytes located at amyloid plaques, the histopathological lesions typically present in the brain of Alzheimer's patients and animal models of the disease. The activity of Cx channels analyzed in vivo as well as in vitro after treatment with the amyloid β peptide is also modified and, in particular, hemichannel activation may contribute to neuronal damage. In this review, we summarize and discuss recent data that suggest glial Cx channels participate in the neurodegenerative process of Alzheimer's disease. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics

Connexin and Pannexin-Based Channels in Oligodendrocytes: Implications in Brain Health and Disease

Oligodendrocytes are the myelin forming cells in the central nervous system (CNS). In addition to this main physiological function, these cells play key roles by providing energy substrates to neurons as well as information required to sustain proper synaptic transmission and plasticity at the CNS. The latter requires a fine coordinated intercellular communication with neurons and other glial cell types, including astrocytes. In mammals, tissue synchronization is mainly mediated by connexins and pannexins, two protein families that underpin the communication among neighboring cells through the formation of different plasma membrane channels. At one end, gap junction channels (GJCs; which are exclusively formed by connexins in vertebrates) connect the cytoplasm of contacting cells allowing electrical and metabolic coupling. At the other end, hemichannels and pannexons (which are formed by connexins and pannexins, respectively) communicate the intra- and extracellular compartments, serving as diffusion pathways of ions and small molecules. Here, we briefly review the current knowledge about the expression and function of hemichannels, pannexons and GJCs in oligodendrocytes, as well as the evidence regarding the possible role of these channels in metabolic and synaptic functions at the CNS. In particular, we focus on oligodendrocyte-astrocyte coupling during axon metabolic support and its implications in brain health and disease

Fascioliasis prevalence in livestock from abattoirs in southern Chile

Fascioliasis is a widely distributed parasitic zoonosis caused by the trematode Fasciola hepatica that affects livestock production and generates high economic losses. In Chilean authorised abattoirs, the infected livestock livers are condemned during the veterinary inspection. This study aims to evaluate the prevalence of fascioliasis in Chile from 2014 to 2016 and also monthly from 2002 to 2015 in livestock (cattle, pig, sheep, horse and goat) slaughtered in abattoirs of La Araucanía region, southern Chile. To do this, the available records on abattoirs provided by the sanitary authority were analysed. A descriptive statistics and trend analysis of the data by jointpoint regression was carried out. The Biobío and La Araucanía regions registered the highest levels of parasitosis in the country recording levels of 59.18 and 44.74%, respectively, and presented 50.03% of the liver condemnation rate in cattle. During the study period, a total of 2,239,164 animals were slaughtered and 40.59% infected livers with F. hepatica were condemned in the 9 existing abattoirs of La Araucanía region. The abattoirs located in the cities of Temuco (51.43%) and Angol (65.09%) recorded the highest percentages of fascioliasis. The cattle species recorded the highest number of slaughtered animals and liver condemnation (54.52%). The presence of the parasite was recorded annually and monthly and it was possible to observe a slight increase in fascioliasis over the years. This study provides updated information on the fascioliasis prevalence in the country and the dynamics of condemnation in endemic areas such as La Araucanía region, which could contribute to the control and prevention of this zoonosis

Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling

We consider the generation of a pure spin-current at zero bias voltage with a single time-dependent potential. To such end we study a device made of a mesoscopic ring connected to electrodes and clarify the interplay between a magnetic flux, spin-orbit coupling, and non-adiabatic driving in the production of a spin and electrical current. By using Floquet theory, we show that the generated spin to charge current ratio can be controlled by tuning the spin-orbit coupling.publishedVersionFil: Ramos Andrade, Juan Pablo. Universidad Católica del Norte. Departamento de Física; Chile.Fil: Foa Torres, Luis Eduardo Francisco. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Foa Torres, Luis Eduardo Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Orellana, P. A. Universidad Técnica Federico Santa María. Departamento de Física; Chile.Fil: Apel, Víctor Marcelo. Universidad Católica del Norte. Departamento de Física; Chile.Física de los Materiales Condensado

Restraint stress increases hemichannel activity in hippocampal glial cells and neurons

Stress affects brain areas involved in learning and emotional responses, which may contribute in the development of cognitive deficits associated with major depression. These effects have been linked to glial cell activation, glutamate release and changes in neuronal plasticity and survival including atrophy of hippocampal apical dendrites, loss of synapses and neuronal death. Under neuro-inflammatory conditions we recently unveiled a sequential activation of glial cells that release ATP and glutamate via hemichannels inducing neuronal death due to activation of neuronal NMDA/P2X7 receptors and pannexin1 hemichannels. In the present work, we studied if stress-induced glia activation is associated to changes in hemichannel activity. To this end, we compared hemichannel activity of brain cells after acute or chronic restraint stress in mice. Dye uptake experiments in hippocampal slices revealed that acute stress induces opening of both Cx43 and Panx1 hemichannels in astrocytes, which were further increased by chronic stress; whereas enhanced Panx1 hemichannel activity was detected in microglia and neurons after acute/chronic and chronic stress, respectively. Moreover, inhibition of NMDA/P2X7 receptors reduced the chronic stress-induced hemichannel opening, whereas blockade of Cx43 and Panx1 hemichannels fully reduced ATP and glutamate release in hippocampal slices from stressed mice. Thus, we propose that gliotransmitter release through hemichannels may participate in the pathogenesis of stress-associated psychiatric disorders and possibly depression

Building Suitable Datasets for Soft Computing and Machine Learning Techniques from Meteorological Data Integration: A Case Study for Predicting Significant Wave Height and Energy Flux

Meteorological data are extensively used to perform environmental learning. Soft Computing (SC) and Machine Learning (ML) techniques represent a valuable support in many research areas, but require datasets containing information related to the topic under study. Such datasets are not always available in an appropriate format and its preparation and pre-processing implies a lot of time and effort by researchers. This paper presents a novel software tool with a user-friendly GUI to create datasets by means of management and data integration of meteorological observations from two data sources: the National Data Buoy Center and the National Centers for Environmental Prediction and for Atmospheric Research Reanalysis Project. Such datasets can be created using buoys and reanalysis data through customisable procedures, in terms of temporal resolution, predictive and objective variables, and can be used by SC and ML methodologies for prediction tasks (classification or regression). The objective is providing the research community with an automated and versatile system for the casuistry that entails well-formed and quality data integration, potentially leading to better prediction models. The software tool can be used as a supporting tool for coastal and ocean engineering applications, sustainable energy production, or environmental modelling; as well as for decision-making in the design and building of coastal protection structures, marine transport, ocean energy converters, and well-planned running of offshore and coastal engineering activities. Finally, to illustrate the applicability of the proposed tool, a case study to classify waves depending on their significant height and to predict energy flux in the Gulf of Alaska is presented