Journal articles on the topic 'Electrical compartmentalization'
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Wybo, Willem A. M., Benjamin Torben-Nielsen, Thomas Nevian, and Marc-Oliver Gewaltig. "Electrical Compartmentalization in Neurons." Cell Reports 26, no. 7 (February 2019): 1759–73. http://dx.doi.org/10.1016/j.celrep.2019.01.074.
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Yuste, Rafael. "Electrical Compartmentalization in Dendritic Spines." Annual Review of Neuroscience 36, no. 1 (July 8, 2013): 429–49. http://dx.doi.org/10.1146/annurev-neuro-062111-150455.
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Cornejo, Victor Hugo, Netanel Ofer, and Rafael Yuste. "Voltage compartmentalization in dendritic spines in vivo." Science 375, no. 6576 (January 7, 2022): 82–86. http://dx.doi.org/10.1126/science.abg0501.
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Dendritic spines’ electrical function? Dendritic spines are small protrusions that cover the dendrites of most neurons in the brain. Their electrical properties are still controversially discussed. Cornejo et al . used an array of techniques to investigate the degree of voltage attenuation by dendritic spine necks in pyramidal neurons of the mouse neocortex. Spines not only synchronously depolarized in response to backpropagating action potentials, but local and transient depolarization also occurred. Isolated depolarization in individual spines reflected localized synaptic activation. A significant voltage gradient between dendritic spine and dendrite indicated that spines may constitute elementary electric compartments. The spine neck resistance is thus not negligible and may substantially contribute to the regulation of synaptic efficacy in the central nervous system. —PRS
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Grunditz, A., N. Holbro, L. Tian, Y. Zuo, and T. G. Oertner. "Spine Neck Plasticity Controls Postsynaptic Calcium Signals through Electrical Compartmentalization." Journal of Neuroscience 28, no. 50 (December 10, 2008): 13457–66. http://dx.doi.org/10.1523/jneurosci.2702-08.2008.
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Koch, C., and A. Zador. "The function of dendritic spines: devices subserving biochemical rather than electrical compartmentalization." Journal of Neuroscience 13, no. 2 (February 1, 1993): 413–22. http://dx.doi.org/10.1523/jneurosci.13-02-00413.1993.
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Roessler, Nick, and André DeHon. "SCALPEL: Exploring the Limits of Tag-enforced Compartmentalization." ACM Journal on Emerging Technologies in Computing Systems 18, no. 1 (January 31, 2022): 1–28. http://dx.doi.org/10.1145/3461673.
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We present Secure Compartments Automatically Learned and Protected by Execution using Lightweight metadata (SCALPEL), a tool for automatically deriving compartmentalization policies and lowering them to a tagged architecture for hardware-accelerated enforcement. SCALPEL allows a designer to explore high-quality points in the privilege-reduction vs. performance overhead tradeoff space using analysis tools and a detailed knowledge of the target architecture to make best use of the available hardware. SCALPEL automatically implements hundreds of compartmentalization strategies across the privilege-performance tradeoff space, all without manual tagging or code restructuring. SCALPEL uses two novel optimizations for achieving highly performant policies: the first is an algorithm for packing policies into working sets of rules for favorable rule cache characteristics, and the second is a rule prefetching system that allows it to exploit the highly predictable nature of compartmentalization rules. To create policies, SCALPEL introduces a quantitative privilege metric (the Overprivilege Ratio) that is used to drive its algorithmic compartment generation. We implement SCALPEL on a FreeRTOS stack and target a tag-extended RISC-V core. Our results show that SCALPEL-created policies can reduce overprivilege by orders of magnitude with hundreds of logical compartments while imposing low overheads (<5%).
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Lee, Kevin F. H., Cary Soares, and Jean-Claude Béïque. "Examining Form and Function of Dendritic Spines." Neural Plasticity 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/704103.
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The majority of fast excitatory synaptic transmission in the central nervous system takes place at protrusions along dendrites called spines. Dendritic spines are highly heterogeneous, both morphologically and functionally. Not surprisingly, there has been much speculation and debate on the relationship between spine structure and function. The advent of multi-photon laser-scanning microscopy has greatly improved our ability to investigate the dynamic interplay between spine form and function. Regulated structural changes occur at spines undergoing plasticity, offering a mechanism to account for the well-described correlation between spine size and synapse strength. In turn, spine structure can influence the degree of biochemical and perhaps electrical compartmentalization at individual synapses. Here, we review the relationship between dendritic spine morphology, features of spine compartmentalization and synaptic plasticity. We highlight emerging molecular mechanisms that link structural and functional changes in spines during plasticity, and also consider circumstances that underscore some divergence from a tight structure-function coupling. Because of the intricate influence of spine structure on biochemical and electrical signalling, activity-dependent changes in spine morphology alone may thus contribute to the metaplastic potential of synapses. This possibility asserts a role for structural dynamics in neuronal information storage and aligns well with current computational models.
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Rabinowitch, Ithai, and Idan Segev. "The Interplay Between Homeostatic Synaptic Plasticity and Functional Dendritic Compartments." Journal of Neurophysiology 96, no. 1 (July 2006): 276–83. http://dx.doi.org/10.1152/jn.00074.2006.
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Homeostatic synaptic plasticity (HSP) is an important mechanism attributed with the slow regulation of the neuron's activity. Whenever activity is chronically enhanced, HSP weakens the weights of the synapses in the dendrites and vice versa. Because dendritic morphology and its electrical properties partition the dendritic tree into functional compartments, we set out to explore the interplay between HSP and dendritic compartmentalization. For this purpose, we used a detailed model of a CA1 pyramidal neuron receiving a large number of activity-dependent plastic synapses and developed a novel approach for specifying functional dendritic subunits. We found that the degree of dendritic compartmentalization and the location-specificity of HSP are strongly tied. A local HSP mechanism, operating at the level of the individual synapse, will regard the neuron as a multiunit distributed system, each unit consisting of many synapses, and will thus support dendritic compartmentalization, whereas a global HSP mechanism, modifying all synapses in unison, will treat the neuron as a single centralized unit. Both local and global HSP can successfully counterbalance persistent, cell-wide perturbations of dendritic activity. The spatial distribution of synaptic weights throughout the dendrites will markedly differ under the local versus global HSP mechanisms. We suggest an experimental paradigm to unravel which type of HSP mechanism operates in the dendritic tree. The answer to this question will have important implications to our understanding of the functional organization of the neuron.
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Verderio, C., S. Coco, G. Fumagalli, and M. Matteoli. "Spatial changes in calcium signaling during the establishment of neuronal polarity and synaptogenesis." Journal of Cell Biology 126, no. 6 (September 15, 1994): 1527–36. http://dx.doi.org/10.1083/jcb.126.6.1527.
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Calcium imaging techniques were used to obtain a clear although indirect evidence about the distribution of functional glutamate receptors of NMDA and non-NMDA type in cultured hippocampal neurons during establishment of polarity and synaptogenesis. Glutamate receptors were expressed and were already functional as early as one day after plating. At this stage NMDA and non-NMDA receptors were distributed in all plasmalemmal areas. During the establishment of neuronal polarity, responses to either types of glutamate receptors became restricted to the soma and dendrites. Compartmentalization of glutamate receptors occurred at stages of development when synaptic vesicles were already fully segregated to the axon. Formation of synapses was accompanied by a further redistribution of receptors, which segregated to synapse-enriched portions of dendrites. Receptor compartmentalization and dendritic redistribution as well as accumulation of synaptic vesicles at synaptic sites occurred also in neurons cultured in the presence of either the sodium channel blocker tetrodotoxin or glutamate receptor antagonists. These results indicate that signals generated by neuronal electrical activity or receptor activation are not involved in the establishment of neuronal polarity and synaptogenesis.
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Perrette, Guillaume, Sylvain Delagrange, and Christian Messier. "Optimizing Reduction Pruning of Trees Under Electrical Lines: The Influence of Intensity and Season of Pruning on Epicormic Branch Growth and Wound Compartmentalization." Arboriculture & Urban Forestry 46, no. 6 (November 1, 2020): 432–49. http://dx.doi.org/10.48044/jauf.2020.031.
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Reduction pruning of the main stem is commonly used during the maintenance of power lines to encourage the establishment and development of scaffold limbs away from wires. Understanding the physiology of epicormic branch initiation and growth as well as wound compartmentalization following reduction pruning are important for optimizing the pruning cycle and maintaining healthy and safe trees. In this study, the influence of both intensity and time of year of pruning on epicormic branch response and wound compartmentalization was investigated on 56 11-year-old Pennsylvania ash trees (Fraxinus pennsylvanica Marsh.) about 5 to 7 m in height within a controlled nursery environment. During the second growing season following reduction of the main stem, the number, height, and volume of epicormic branches, as well as tallest epicormic branches and the area of discolored wood, increased with pruning intensity. Pruning during the leaf-on season compared to the leaf-off season limited the establishment and development of epicormic branches without affecting wound-closure rate or the area of wood discoloration at the cutting point. Results are consistent with the known seasonal fluctuation of carbohydrates reserves. In the context of the electrical distribution network, where trees are subjected to pruning throughout the year, trees pruned in summer during a maintenance cycle could be pruned during the next cycle, in winter, and so on, to optimize the return interval of the pruning cycle.
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Strumpf, H. J., V. Avanessian, and R. Ghafourian. "Design Analysis and Containment Canister Life Prediction for a Brayton Engine Solar Receiver for Space Station." Journal of Solar Energy Engineering 116, no. 3 (August 1, 1994): 142–47. http://dx.doi.org/10.1115/1.2930073.
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A study has been conducted on the design and development of a solar receiver to be used for electrical power production for Space Station. The receiver incorporates integral thermal storage, using a eutectic mixture of LiF and CaF2 as a solid-to-liquid phase-change material (PCM). The design comprises a cylindrical receiver cavity. The walls of the cavity are lined with a series of working fluid tubes running the length of the cavity. The PCM is enclosed in individual, sealed metallic containment canisters which are stacked and brazed to the tubes. The compartmentalization of the PCM localizes void formation upon freezing. An additional attribute of compartmentalization is that a containment canister failure affects only that canister; the receiver continues to operate with only a minute loss of capacity. Nevertheless, a considerable effort has been expended to ensure that the containment canisters will survive a 30-year life. A detailed analytical procedure was developed to evaluate the canister creep strain accumulated in 30 years. This accumulated creep strain, which is in the range of 0.03 to 0.79 percent, compares favorably with the preliminary value of four percent for the canister material allowable 30-year creep rupture ductility.
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Sorensen, Dane W., Elisha R. Injeti, Luisa Mejia-Aguilar, James M. Williams, and William J. Pearce. "Postnatal development alters functional compartmentalization of myosin light chain kinase in ovine carotid arteries." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 321, no. 3 (September 1, 2021): R441—R453. http://dx.doi.org/10.1152/ajpregu.00293.2020.
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The rate-limiting enzyme for vascular contraction, myosin light chain kinase (MLCK), phosphorylates regulatory myosin light chain (MLC20) at rates that appear faster despite lower MLCK abundance in fetal compared with adult arteries. This study explores the hypothesis that greater apparent tissue activity of MLCK in fetal arteries is due to age-dependent differences in intracellular distribution of MLCK in relation to MLC20. Under optimal conditions, common carotid artery homogenates from nonpregnant adult female sheep and near-term fetuses exhibited similar values of Vmax and Km for MLCK. A custom-designed, computer-controlled apparatus enabled electrical stimulation and high-speed freezing of arterial segments at exactly 0, 1, 2, and 3 s, calculation of in situ rates of MLC20 phosphorylation, and measurement of time-dependent colocalization between MLCK and MLC20. The in situ rate of MLC20 phosphorylation divided by total MLCK abundance averaged to values 147% greater in fetal (1.06 ± 0.28) than adult (0.43 ± 0.08) arteries, which corresponded, respectively, to 43 ± 10% and 31 ± 3% of the Vmax values measured in homogenates. Confocal colocalization analysis revealed in fetal and adult arteries that 33 ± 6% and 20 ± 5% of total MLCK colocalized with pMLC20, and that MLCK activation was greater in periluminal than periadventitial regions over the time course of electrical stimulation in both age groups. Together, these results demonstrate that the catalytic activity of MLCK is similar in fetal and adult arteries, but that the fraction of total MLCK in the functional compartment involved in contraction is significantly greater in fetal than adult arteries.
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Yang, Sung Min, María Eugenia Vilarchao, Lorena Rela, and Lidia Szczupak. "Wide propagation of graded signals in nonspiking neurons." Journal of Neurophysiology 109, no. 3 (February 1, 2013): 711–20. http://dx.doi.org/10.1152/jn.00934.2012.
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Signal processing in neuritic trees is ruled by the concerted action of passive and active membrane properties that, together, determine the degree of electrical compartmentalization of these trees. We analyzed how active properties modulate spatial propagation of graded signals in a pair of nonspiking (NS) neurons of the leech. NS neurons present a very extensive neuritic tree that mediates the interaction with all the excitatory motoneurons in leech ganglia. NS cells express voltage-activated Ca2+ conductances (VACCs) that, under certain experimental conditions, evoke low-threshold spikes. We studied the distribution of calcium transients in NS neurons loaded with fluorescent calcium probes in response to low-threshold spikes, electrical depolarizing pulses, and synaptic inputs. The three types of stimuli evoked calcium transients of similar characteristics in the four main branches of the neuron. The magnitude of the calcium transients evoked by electrical pulses was a graded function of the change in NS membrane potential and depended on the baseline potential level. The underlying VACCs were partially inactivated at rest and strongly inactivated at −20 mV. Stimulation of mechanosensory pressure cells evoked calcium transients in NS neurons whose amplitude was a linear function of the amplitude of the postsynaptic response. The results evidenced that VACCs aid an efficient propagation of graded signals, turning the vast neuritic tree of NS cells into an electrically compact structure.
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Campbell, Evan P., Ahmed A. Abushawish, Lauren A. Valdez, Miriam K. Bell, Melita Haryono, Padmini Rangamani, and Brenda L. Bloodgood. "Electrical signals in the ER are cell type and stimulus specific with extreme spatial compartmentalization in neurons." Cell Reports 42, no. 1 (January 2023): 111943. http://dx.doi.org/10.1016/j.celrep.2022.111943.
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Gonzalez, Juan M. Carlos, Kenneth M. Hopkinson, Gabriel H. Greve, Matthew D. Compton, Joseph Wilhelm, Stuart H. Kurkowski, and Ryan W. Thomas. "Optimization of Trust System Placement for Power Grid Security and Compartmentalization." IEEE Transactions on Power Systems 26, no. 2 (May 2011): 550–63. http://dx.doi.org/10.1109/tpwrs.2010.2053725.
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Healy, Mae W., Shelley N. Dolitsky, Maria Villancio-Wolter, Meera Raghavan, Alexandra R. Tillman, Nicole Y. Morgan, Alan H. DeCherney, Solji Park, and Erin F. Wolff. "Creating an Artificial 3-Dimensional Ovarian Follicle Culture System Using a Microfluidic System." Micromachines 12, no. 3 (March 4, 2021): 261. http://dx.doi.org/10.3390/mi12030261.
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We hypothesized that the creation of a 3-dimensional ovarian follicle, with embedded granulosa and theca cells, would better mimic the environment necessary to support early oocytes, both structurally and hormonally. Using a microfluidic system with controlled flow rates, 3-dimensional two-layer (core and shell) capsules were created. The core consists of murine granulosa cells in 0.8 mg/mL collagen + 0.05% alginate, while the shell is composed of murine theca cells suspended in 2% alginate. Somatic cell viability tests and hormonal assessments (estradiol, progesterone, and androstenedione) were performed on days 1, 6, 13, 20, and 27. Confocal microscopy confirmed appropriate compartmentalization of fluorescently-labeled murine granulosa cells to the inner capsule and theca cells to the outer shell. Greater than 78% of cells present in capsules were alive up to 27 days after collection. Artificially constructed ovarian follicles exhibited intact endocrine function as evidenced by the production of estradiol, progesterone, and androstenedione. Oocytes from primary and early secondary follicles were successfully encapsulated, which maintained size and cellular compartmentalization. This novel microfluidic system successfully encapsulated oocytes from primary and secondary follicles, recapitulating the two-compartment system necessary for the development of the mammalian oocyte. Importantly, this microfluidic system can be easily adapted for sterile, high throughput applications.
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Zhou, Quan, Mohammad Shahidehpour, Zhiyi Li, Liang Che, Ahmed Alabdulwahab, and Abdullah Abusorrah. "Compartmentalization Strategy for the Optimal Economic Operation of a Hybrid AC/DC Microgrid." IEEE Transactions on Power Systems 35, no. 2 (March 2020): 1294–304. http://dx.doi.org/10.1109/tpwrs.2019.2942273.
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Kirschner Peretz, Noa, Sofia Segal, Ido Weiser-Bitoun, and Yael Yaniv. "Distinct PKA Signaling in Cytosolic and Mitochondrial Compartments in Electrically Paced Atrial Myocytes." Cells 11, no. 14 (July 21, 2022): 2261. http://dx.doi.org/10.3390/cells11142261.
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Protein kinase A (PKA) is a key nodal signaling molecule that regulates a wide range of cellular functions in the cytosol and mitochondria. The distribution of A-kinase anchoring proteins that tether PKA, the local interaction with degradation molecules, and regulation by Ca2+, may lead to distinct spatiotemporal cAMP/PKA signaling in these compartments. In this work, FRET-based sensors were used to investigate PKA signaling in the cytosol, outer mitochondrial membrane (OMM), and mitochondrial matrix (MM) and its crosstalk with Ca2+ in response to electrical stimulation of cultured rabbit atrial cells. A gradual decrease in PKA activity eliminating the ability of the atrial cells to respond to physiological electrical stimulation, was observed upon treatment of cells with H-89. Chelation of intracellular Ca2+ by BAPTA reduced PKA activity and diminished its response to forskolin, an AC stimulator. Under basal conditions, PKA activity in response to forskolin was lower in the OMM compared to the cytosol and MM. In response to electrical stimulation in the presence of ISO, distinct compartmentalization of PKA activity was observed, with higher activity in the cytosol and MM than in the OMM. Thus, distinct Ca2+-dependent spatiotemporal cAMP/PKA signaling exists in atrial cells, likely mediating its excitation and mitochondrial function.
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Rajabi, Fatemeh, Christian Gusbeth, Wolfgang Frey, Jan Maisch, and Peter Nick. "Nanosecond pulsed electrical fields enhance product recovery in plant cell fermentation." Protoplasma 257, no. 6 (July 10, 2020): 1585–94. http://dx.doi.org/10.1007/s00709-020-01534-9.
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Abstract The potential of pharmacologically active secondary plant metabolites is limited by the low yield from often rare plants, and the lack of economically feasible chemical synthesis of these complex compounds. Plant cell fermentation offers an alternative strategy to overcome these constraints. However, the efficiency of this approach is limited by intracellular sequestration of the products, such that continuous bioprocessing is not possible. As a precondition for such a, more attractive, continuous process, it is of great importance to stimulate the export of the product into the medium without impairing viability and, thus, the productivity of the cells. Using nicotine alkaloids of tobacco as a case study, an alternative strategy is explored, where nanosecond pulsed electric fields (nsPEFs) are applied for the efficient downstream recovery of the products. To maintain cell viability and allow for the further use of biomass, cells were exposed to strong (1–20 kV·cm−1), but very short (10–100 ns) electric pulses, which leads to a temporary permeabilisation of cell membranes. Using two transgenic cell lines, where two key genes involved in the metabolism of the anti-Alzheimer compound nornicotine were overexpressed, we could show that this nsPEF treatment improved the partitioning of some nicotine alkaloids to the culture medium without impairing viability, nor the synthesis of alkaloids. However, this release was only partial and did not work for nornicotine. Thus, nsPEFs produced a fractionation of alkaloids. We explain this electrofractionation by a working model considering the differential intracellular compartmentalization of nicotineic alkaloids.
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Rezende Filho, A. T., S. Furian, R. L. Victoria, C. Mascré, V. Valles, and L. Barbiero. "Hydrochemical variability at the Upper Paraguay Basin and Pantanal wetland." Hydrology and Earth System Sciences 16, no. 8 (August 14, 2012): 2723–37. http://dx.doi.org/10.5194/hess-16-2723-2012.
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Abstract. Compartmentalization is a prerequisite to understand large wetlands that receive water from several sources. However, it faces the heterogeneity in space and time, resulting from physical, chemical and biological processes that are specific to wetlands. The Pantanal is a vast seasonally flooded continental wetland located in the centre of South America. The chemical composition of the waters that supply the Pantanal (70 rivers) has been studied in order to establish a compartmentalization of the wetland based on soil-water interactions. A PCA-based EMMA (End-Members Mixing Analysis) procedure shows that the chemistry of the rivers can be viewed as a mixture of 3 end-members, influenced by lithology and land use, and delimiting large regions. Although the chemical composition of the end-members changed between dry and wet seasons, their spatial distribution was maintained. The results were extended to the floodplain by simple tributary mixing calculation according to the hydrographical network and to the areas of influence for each river when in overflow conditions. The resulting map highlights areas of high geochemical contrast on either side of the river Cuiaba in the north, and of the rivers Aquidauana and Abobral in the south. The PCA-based treatment on a sampling conducted in the Nhecolândia, a large sub region of the Pantanal, allowed the identification and ordering of the processes that control the geochemical variability of the surface waters. Despite an enormous variability in electrical conductivity and pH, all data collected were in agreement with an evaporation process of the Taquari River water, which supplies the region. Evaporation and associated saline precipitations (Mg-calcite, Mg-silicates K-silicates) explained more than 77% of the total variability in the chemistry of the regional surface water sampling.
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Rezende Filho, A. T., S. Furian, R. L. Victoria, C. Mascré, V. Valles, and L. Barbiero. "Hydrochemical variability at the Upper Paraguay Basin and Pantanal wetland." Hydrology and Earth System Sciences Discussions 9, no. 3 (March 12, 2012): 3129–63. http://dx.doi.org/10.5194/hessd-9-3129-2012.
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Abstract. Compartmentalization is a prerequisite to understand large wetlands that receive water from several sources. However, it faces the heterogeneity in space and time, resulting from physical, chemical and biological processes that are specific to wetlands. The Pantanal is a vast seasonally flooded continental wetland located in the centre of South America. The chemical makeup of the waters that supply the Pantanal (70 rivers) has been studied in order to establish a compartmentalization of the wetland based on soil-water interactions. A PCA-based EMMA (End-Members Mixing Analysis) procedure shows that the chemistry of the rivers can be regarded as a mixture of 3 end-members, influenced by lithology and land use, and delimiting large regions. Although the chemical composition of the end-members changed between dry and wet seasons, their spatial distribution was maintained. The results were extended to the floodplain by simple tributary mixing calculation according to the hydrographical network and to the areas of influence for each river when in overflow conditions. The resulting document highlights areas of high geochemical contrast on either side of the river Cuiaba in the north, and of the rivers Aquidauana and Abobral located in the south. The PCA-based treatment on a sampling conducted in the Nhecolândia, a large sub region of the Pantanal floodplain, allowed for the identification and prioritization of the processes that control the geochemical variability of the surface waters. Despite an enormous variability in Electrical Conductivity and pH, all data collected were in agreement with an evaporation process of the Taquari River water, which supplies the region. Evaporation and associated saline precipitations (Mg-calcite, Mg-silicates K-silicates) explained more than 77% of the total variability in the chemistry of the regional surface water sampling.
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Minlebaev, Marat, Yehezkel Ben-Ari, and Rustem Khazipov. "Network Mechanisms of Spindle-Burst Oscillations in the Neonatal Rat Barrel Cortex In Vivo." Journal of Neurophysiology 97, no. 1 (January 2007): 692–700. http://dx.doi.org/10.1152/jn.00759.2006.
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Early in development, cortical networks generate particular patterns of activity that participate in cortical development. The dominant pattern of electrical activity in the neonatal rat neocortex in vivo is a spatially confined spindle-burst. Here, we studied network mechanisms of generation of spindle-bursts in the barrel cortex of neonatal rats using a superfused cortex preparation in vivo. Both spontaneous and sensory-evoked spindle-bursts were present in the superfused barrel cortex. Pharmacological analysis revealed that spindle-bursts are driven by glutamatergic synapses with a major contribution of AMPA/kainate receptors, but slight participation of NMDA receptors and gap junctions. Although GABAergic synapses contributed minimally to the pacing the rhythm of spindle-burst oscillations, surround GABAergic inhibition appeared to be crucial for their compartmentalization. We propose that local spindle-burst oscillations, driven by glutamatergic synapses and spatially confined by GABAergic synapses, contribute to the development of barrel cortex during the critical period of developmental plasticity.
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Bertero, Alessandro, Paul A. Fields, Alec S. T. Smith, Andrea Leonard, Kevin Beussman, Nathan J. Sniadecki, Deok-Ho Kim, et al. "Chromatin compartment dynamics in a haploinsufficient model of cardiac laminopathy." Journal of Cell Biology 218, no. 9 (August 8, 2019): 2919–44. http://dx.doi.org/10.1083/jcb.201902117.
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Mutations in A-type nuclear lamins cause dilated cardiomyopathy, which is postulated to result from dysregulated gene expression due to changes in chromatin organization into active and inactive compartments. To test this, we performed genome-wide chromosome conformation analyses in human induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) with a haploinsufficient mutation for lamin A/C. Compared with gene-corrected cells, mutant hiPSC-CMs have marked electrophysiological and contractile alterations, with modest gene expression changes. While large-scale changes in chromosomal topology are evident, differences in chromatin compartmentalization are limited to a few hotspots that escape segregation to the nuclear lamina and inactivation during cardiogenesis. These regions exhibit up-regulation of multiple noncardiac genes including CACNA1A, encoding for neuronal P/Q-type calcium channels. Pharmacological inhibition of the resulting current partially mitigates the electrical alterations. However, chromatin compartment changes do not explain most gene expression alterations in mutant hiPSC-CMs. Thus, global errors in chromosomal compartmentation are not the primary pathogenic mechanism in heart failure due to lamin A/C haploinsufficiency.
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Thomas, Jean-Luc, Vincent Moncollin, Aymeric Ravel-Chapuis, Carmen Valente, Daniela Corda, Alexandre Méjat, and Laurent Schaeffer. "PAK1 and CtBP1 Regulate the Coupling of Neuronal Activity to Muscle Chromatin and Gene Expression." Molecular and Cellular Biology 35, no. 24 (September 28, 2015): 4110–20. http://dx.doi.org/10.1128/mcb.00354-15.
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Acetylcholine receptor (AChR) expression in innervated muscle is limited to the synaptic region. Neuron-induced electrical activity participates in this compartmentalization by promoting the repression of AChR expression in the extrasynaptic regions. Here, we show that the corepressor CtBP1 (C-terminal binding protein 1) is present on the myogenin promoter together with repressive histone marks. shRNA-mediated downregulation of CtBP1 expression is sufficient to derepress myogenin and AChR expression in innervated muscle. Upon denervation, CtBP1 is displaced from the myogenin promoter and relocates to the cytoplasm, while repressive histone marks are replaced by activating ones concomitantly to the activation of myogenin expression. We also observed that upon denervation the p21-activated kinase 1 (PAK1) expression is upregulated, suggesting that phosphorylation by PAK1 may be involved in the relocation of CtBP1. Indeed, preventing CtBP1 Ser158 phosphorylation induces CtBP1 accumulation in the nuclei and abrogates the activation of myogenin and AChR expression. Altogether, these findings reveal a molecular mechanism to account for the coordinated control of chromatin modifications and muscle gene expression by presynaptic neurons via a PAK1/CtBP1 pathway.
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Chávez, Jorge L., Hui Jiang, and Randolph S. Duran. "A study of the compartmentalization of core–shell nanoparticles through fluorescence energy transfer of dopants." Nanotechnology 21, no. 5 (December 21, 2009): 055703. http://dx.doi.org/10.1088/0957-4484/21/5/055703.
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Mangia, Silvia, Federico Giove, Ivan Tkáč, Nikos K. Logothetis, Pierre-Gilles Henry, Cheryl A. Olman, Bruno Maraviglia, Francesco Di Salle, and Kâmil Uğurbil. "Metabolic and Hemodynamic Events after Changes in Neuronal Activity: Current Hypotheses, Theoretical Predictions and in vivo NMR Experimental Findings." Journal of Cerebral Blood Flow & Metabolism 29, no. 3 (November 12, 2008): 441–63. http://dx.doi.org/10.1038/jcbfm.2008.134.
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Unraveling the energy metabolism and the hemodynamic outcomes of excitatory and inhibitory neuronal activity is critical not only for our basic understanding of overall brain function, but also for the understanding of many brain disorders. Methodologies of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are powerful tools for the noninvasive investigation of brain metabolism and physiology. However, the temporal and spatial resolution of in vivo MRS and MRI is not suitable to provide direct evidence for hypotheses that involve metabolic compartmentalization between different cell types, or to untangle the complex neuronal microcircuitry, which results in changes of electrical activity. This review aims at describing how the current models of brain metabolism, mainly built on the basis of in vitro evidence, relate to experimental findings recently obtained in vivo by 1H MRS, 13C MRS, and MRI. The hypotheses related to the role of different metabolic substrates, the metabolic neuron—glia interactions, along with the available theoretical predictions of the energy budget of neurotransmission will be discussed. In addition, the cellular and network mechanisms that characterize different types of increased and suppressed neuronal activity will be considered within the sensitivity-constraints of MRS and MRI.
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Ioannidis, Panagiotis, Theodoros Zografos, Evangelia Christoforatou, Konstantinos Kouvelas, Andreas Tsoumeleas, and Charalambos Vassilopoulos. "The Electrophysiology of Atrial Fibrillation: From Basic Mechanisms to Catheter Ablation." Cardiology Research and Practice 2021 (June 5, 2021): 1–14. http://dx.doi.org/10.1155/2021/4109269.
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The electrophysiology of atrial fibrillation (AF) has always been a deep mystery in understanding this complex arrhythmia. The pathophysiological mechanisms of AF are complex and often remain unclear despite extensive research. Therefore, the implementation of basic science knowledge to clinical practice is challenging. After more than 20 years, pulmonary vein isolation (PVI) remains the cornerstone ablation strategy for maintaining the sinus rhythm (SR). However, there is no doubt that, in many cases, especially in persistent and long-standing persistent AF, PVI is not enough, and eventually, the restoration of SR occurs after additional intervention in the rest of the atrial myocardium. Substrate mapping is a modern challenge as it can reveal focal sources or rotational activities that may be responsible for maintaining AF. Whether these areas are actually the cause of the AF maintenance is unknown. If this really happens, then the targeted ablation may be the solution; otherwise, more rough techniques such as atrial compartmentalization may prove to be more effective. In this article, we attempt a broad review of the known pathophysiological mechanisms of AF, and we present the recent efforts of advanced technology initially to reveal the electrical impulse during AF and then to intervene effectively with ablation.
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Nadim, Farzan, and Jorge Golowasch. "Signal Transmission Between Gap-Junctionally Coupled Passive Cables Is Most Effective at an Optimal Diameter." Journal of Neurophysiology 95, no. 6 (June 2006): 3831–43. http://dx.doi.org/10.1152/jn.00033.2006.
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We analyze simple morphological configurations that represent gap-junctional coupling between neuronal processes or between muscle fibers. Specifically, we use cable theory and simulations to examine the consequences of current flow from one cable to other gap-junctionally coupled passive cables. When the proximal end of the first cable is voltage clamped, the amplitude of the electrical signal in distal portions of the second cable depends on the cable diameter. However, this amplitude does not simply increase if cable diameter is increased, as expected from the larger length constant; instead, an optimal diameter exists. The optimal diameter arises because the dependency of voltage attenuation along the second cable on cable diameter follows two opposing rules. As cable diameter increases, the attenuation decreases because of a larger length constant yet increases because of a reduction in current density arising from the limiting effect of the gap junction on current flow into the second cable. The optimal diameter depends on the gap junction resistance and cable parameters. In branched cables, dependency on diameter is local and thus may serve to functionally compartmentalize branches that are coupled to other cells. Such compartmentalization may be important when periodic signals or action potentials cause the current flow across gap junctions.
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Paz, Maria, Francisco Alcalá, Ana Medeiros, Pedro Martínez-Pagán, Jaruselsky Pérez-Cuevas, and Luís Ribeiro. "Integrated MASW and ERT Imaging for Geological Definition of an Unconfined Alluvial Aquifer Sustaining a Coastal Groundwater-Dependent Ecosystem in Southwest Portugal." Applied Sciences 10, no. 17 (August 26, 2020): 5905. http://dx.doi.org/10.3390/app10175905.
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This paper integrates multichannel analysis of surface waves (MASW) and time-lapse electrical resistivity tomography (ERT) to define aquifer geometry and identify transient groundwater features of the Cascalheira Stream Basin Holocene alluvial aquifer (aquifer H), which contributes to the Santo André Lagoon, part of a coastal groundwater-dependent ecosystem (GDE), located in southwest Portugal. MASW measures shear-wave velocity (VS), allowing one to obtain steady geological models of the subsurface, and ERT measures subsurface electrical resistivity (ER), being subjected to ambient changes. MASW enables disambiguation of geological structures in low ER environments, such as coastal areas. This research covered one natural year and involved one MASW campaign, four ERT campaigns, and additional geological field surveys and groundwater monitoring to assist interpretation of results. In the area, the conjugate NW–SE and NE–SW strike-slip fault systems determine compartmentalization of geological structures and subsequent accommodation space for Holocene sedimentation. MASW and ERT surveys show how the NW–SE system deepens these structures toward the coast, whereas the NE–SW system generates small horsts and grabens, being one of these occupied by aquifer H. From upstream to downstream, aquifer H thickness and width increase from 10 m to 12 m and from 140 m to 240 m, respectively. Performance of VS and ER models was satisfactory, with a normalized error of the VR and ER models in the 0.01–0.09 range, meaning that a quantitative quota of uncertainty can be segregated from the overall uncertainty of groundwater models without substantially affecting its simulations accuracy. This methodology seeks to improve the design of shallow groundwater research in GDE preservation policies.
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Hurwitz, I., R. S. Goldstein, and A. J. Susswein. "Compartmentalization of pattern-initiation and motor functions in the B31 and B32 neurons of the buccal ganglia of Aplysia californica." Journal of Neurophysiology 71, no. 4 (April 1, 1994): 1514–27. http://dx.doi.org/10.1152/jn.1994.71.4.1514.
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1. The B31 and B32 cells in the buccal ganglia of Aplysia californica have unusual electrophysiological features. The somata of these strongly coupled cells do not sustain conventional action potentials. Brief depolarization of the soma produces a complex, sustained regenerative slow depolarization that is followed by a hyperpolarization. This activity in B31/B32 is correlated with a patterned burst of activity expressed in many of the neurons of the buccal ganglia. 2. Intracellular fills of B31/B32 showed that they have many neurites adjacent to the soma, as well as peripheral axons leaving the buccal ganglia via the radular nerve and innervating the Intrinsic-2 (I2) muscle of the buccal mass. Varicosities of B31/B32 axons are seen within the muscle. Backfills from I2 filled two adjacent B31/B32 cells as well as two newly identified neurons: B61 and B62. 3. Intracellular recording from the B31/B32 axons shows that they sustain conventional action potentials. These are recorded in the soma as approximately 10-mV fast depolarizations. Failed spikes in B31/B32, and conventional spikes in B61/B62, are correlated one for one with end-junction potentials (EJPs) in the I2 muscle. The EJPs are present even when the ganglia and muscles are bathed in high-divalent cations seawater. Thus B31/B32 and B61/B62 are motor neurons to the I2 muscle. 4. To determine whether the ability of B31/B32 to initiate patterned bursts is mediated by spikes in the axon or by slow potentials in the soma, the B31/B32 axon was stimulated directly while recording from the B31/B32 soma. Patterned bursts were never seen in the absence of slow potentials in the soma. Thus the ability of B31/B32 to initiate patterned bursts is localized to the soma and adjacent neurites. Slow potentials influence and cause spiking in adjacent neurons even in the absence of axon spikes. 5. These data show that the B31/B32 cells serve two functions that are compartmentalized in different regions of the cell and are mediated via different electrical signaling mechanisms. The B31/B32 somata utilize slow, sustained potentials as part of a network initiating patterned activity in the buccal ganglia. The B31/B32 axons utilize conventional action potentials, and act as motor neurons to the I2 muscle.
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May, Michael T., and Thomas B. Brackman. "Geophysical characterization of karst landscapes in Kentucky as modern analogs for paleokarst reservoirs." Interpretation 2, no. 3 (August 1, 2014): SF51—SF63. http://dx.doi.org/10.1190/int-2013-0179.1.
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Subsurface interpretation of paleokarst reservoirs is greatly aided by 3D seismic and other modern modeling tools and the inherent complexity of productive reservoirs requires an understanding of reservoir heterogeneities and compartmentalization. Such complexity also requires a review of karst processes and development, which can be beneficially captured via geophysical characterization of near-surface karst landscape features that certainly equate to our better understanding of high-side oil productive areas. Both electrical resistivity tomography (ERT) and refraction microtremor (ReMi) geophysical surveys at the Green River Preserve adjacent to Mammoth Cave National Park in the Mississippian Ste. Genevieve and Girkin Limestones are providing details of karst features, including horizontal passages, uvulas or karst valleys, sinkholes (dolines), vertical pits or dome caves, and associated karst system infill. Geophysical anomalies include reversals of shear-wave velocities in a domal (pit) cave, and an inferred bedding-plane controlled conduit system associated with a drained sinkhole basin. Other anomalies detected in the shallow subsurface include large contrasts in geoelectrical measurements near the sinkhole basin interpreted also as a cave or conduit system. In contrast to anomalies, a mappable continuity of ERT and ReMi transects along the Green River suggests bedrock joints controlling the linear nature of bedrock highs and lows, similar to a series of grikes and clints that typify the south-central Kentucky karst.
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Ambatkar, Mugdha, and Kevin D’cruz. "Aluminium Accumulation Potential of Alstonia scholaris." INTERNATIONAL JOURNAL OF PLANT AND ENVIRONMENT 6, no. 03 (July 25, 2020): 194–97. http://dx.doi.org/10.18811/ijpen.v6i03.06.
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Aluminium toxicity commonly affects plants and considerably reduces crop production. However, some plants, particularly tropical trees, have adapted to high aluminium concentrations by using strategies such as aluminium accumulation. The present study is the first report of aluminium hyperaccumulation in Alstonia scholaris, which is a common tree in Mumbai. Aluminium was accidently detected in the inflorescence tissue of A. scholaris. Volumetric analysis and atomic absorption spectrometry revealed that the aluminium concentration exceeded 1000 μg/g (dry weight). Notably, aluminium appeared to be stored in the fresh inflorescence stalks but not in the flowers. The aluminium concentration in the stalks determined through volumetric analysis was 10689.7±846.8 μg/g dry weight. Furthermore, the aluminium concentration in oven-dried stalks determined through atomic absorption spectrometry was 4080.36±11.60 μg/g. Because A. scholaris accumulates aluminium in its aerial parts at a concentration exceeding 1000 ppm, it can be considered a hyperaccumulator of aluminium. The high concentration of organic acids in the flowers indicated the possible role of organic acids in compartmentalization or sequestration of aluminium in the inflorescence stalks. Investigating the molecular and genetic basis of the mechanism(s) underlying aluminium sequestration in A. scholaris can provide important information for the development of crop varieties that are minimally affected by aluminium toxicity.
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Carlsson, Matt, Marianne Touchie, and Russell Richman. "Investigating the potential impact of a compartmentalization and ventilation system retrofit strategy on energy use in high-rise residential buildings." Energy and Buildings 199 (September 2019): 20–28. http://dx.doi.org/10.1016/j.enbuild.2019.06.035.
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Sasaki, Kosei, Michael R. Due, Jian Jing, and Klaudiusz R. Weiss. "Feeding CPG in Aplysia Directly Controls Two Distinct Outputs of a Compartmentalized Interneuron That Functions as a CPG Element." Journal of Neurophysiology 98, no. 6 (December 2007): 3796–801. http://dx.doi.org/10.1152/jn.00965.2007.
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In the context of motor program generation in Aplysia, we characterize several functional aspects of intraneuronal compartmentalization in an interganglionic interneuron, CBI-5/6. CBI-5/6 was shown previously to have a cerebral compartment (CC) that includes a soma that does not generate full-size action potentials and a buccal compartment (BC) that does. We find that the synaptic connections made by the BC of CBI-5/6 in the buccal ganglion counter the activity of protraction-phase neurons and reinforce the activity of retraction-phase neurons. In buccal motor programs, the BC of CBI-5/6 fires phasically, and its premature activation can phase advance protraction termination and retraction initiation. Thus the BC of CBI-5/6 can act as an element of the central pattern generator (CPG). During protraction, the CC of CBI-5/6 receives direct excitatory inputs from the CPG elements, B34 and B63, and during retraction, it receives antidromically propagating action potentials that originate in the BC of CBI-5/6. Consequently, in its CC, CBI-5/6 receives depolarizing inputs during both protraction and retraction, and these depolarizations can be transmitted via electrical coupling to other neurons. In contrast, in its BC, CBI-5/6 uses spike-dependent synaptic transmission. Thus the CPG directly and differentially controls the program phases in which the two compartments of CBI-5/6 may transmit information to its targets.
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Stoddard, J. S., E. Jakobsson, and S. I. Helman. "Basolateral membrane chloride transport in isolated epithelia of frog skin." American Journal of Physiology-Cell Physiology 249, no. 3 (September 1, 1985): C318—C329. http://dx.doi.org/10.1152/ajpcell.1985.249.3.c318.
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Isotopic methodology was used to characterize Cl- transport in isolated epithelia of frog skin (northern Rana pipiens) bathed in Cl--rich Ringer solution and short-circuited. Cl- content of epithelia measured when loaded to 36Cl specific activity equilibrium averaged 139.6 neq/mg dry wt. The kinetics of 36Cl efflux was biexponential and consistent with binding or compartmentalization of approximately 30% of tissue Cl- within the intracellular pool. Because efflux of 36Cl to the apical solution was immeasurable, it was concluded that apical membranes were virtually impermeable to Cl- and that basolateral membranes were highly permeable to Cl- with a mean unidirectional Cl- efflux of 21.7 microA/cm2. Both furosemide (1 mM) and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (5 X 10(-4) M) inhibited markedly the basolateral membrane chloride fluxes within seconds, as measured in chamber experiments. As inhibition of Cl- flux occurred in the absence of a change of the electrical parameters of apical and basolateral membranes, the mechanisms of Cl- transport appeared to be electroneutral and, for the most part at least, not coupled to the fluxes of Na+ and K+. Transepithelial Cl- fluxes averaged near 1 microA/cm2, proceeding via transport routes in parallel to the cells of the stratified epithelium. No correlation existed between the "shunt" resistance measured in the presence of 100 microM amiloride (greater than 1,000 omega X cm2) and the partial conductance to Cl-.
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De Santis, Ilaria, Luca Lorenzini, Marzia Moretti, Elisa Martella, Enrico Lucarelli, Laura Calzà, and Alessandro Bevilacqua. "Co-Density Distribution Maps for Advanced Molecule Colocalization and Co-Distribution Analysis." Sensors 21, no. 19 (September 24, 2021): 6385. http://dx.doi.org/10.3390/s21196385.
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Cellular and subcellular spatial colocalization of structures and molecules in biological specimens is an important indicator of their co-compartmentalization and interaction. Presently, colocalization in biomedical images is addressed with visual inspection and quantified by co-occurrence and correlation coefficients. However, such measures alone cannot capture the complexity of the interactions, which does not limit itself to signal intensity. On top of the previously developed density distribution maps (DDMs), here, we present a method for advancing current colocalization analysis by introducing co-density distribution maps (cDDMs), which, uniquely, provide information about molecules absolute and relative position and local abundance. We exemplify the benefits of our method by developing cDDMs-integrated pipelines for the analysis of molecules pairs co-distribution in three different real-case image datasets. First, cDDMs are shown to be indicators of colocalization and degree, able to increase the reliability of correlation coefficients currently used to detect the presence of colocalization. In addition, they provide a simultaneously visual and quantitative support, which opens for new investigation paths and biomedical considerations. Finally, thanks to the coDDMaker software we developed, cDDMs become an enabling tool for the quasi real time monitoring of experiments and a potential improvement for a large number of biomedical studies.
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Midtgaard, J., N. Lasser-Ross, and W. N. Ross. "Spatial distribution of Ca2+ influx in turtle Purkinje cell dendrites in vitro: role of a transient outward current." Journal of Neurophysiology 70, no. 6 (December 1, 1993): 2455–69. http://dx.doi.org/10.1152/jn.1993.70.6.2455.
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1. Intracellular recordings were made from Purkinje cells in a slice preparation of the turtle cerebellum. Simultaneously, changes in [Ca2+]i in all regions of the cell were detected with high-speed fluorescence imaging of injected fura-2. Cells were stimulated either intrasomatically or synaptically. In addition, the cells were polarized locally with an external electrical field aligned parallel to the soma-dendritic axis. 2. The soma, smooth dendrites, and spiny dendrites displayed voltage-dependent changes in [Ca2+]i. Changes in the somatic region were correlated with Na+ spike firing and local depolarization. Small [Ca2+]i changes in the spiny dendrites were correlated with graded potentials and larger changes with Ca2+ action potentials. Individual Ca2+ spike transients sometimes occurred separately in different dendritic regions demonstrating localized firing. 3. The amplitude and spatial extent of spike-related [Ca2+]i transients were increased with intrasomatic depolarizing prestimulus membrane potentials and reduced by hyperpolarizing prestimulus potentials. This dependence and the latency to Ca2+ spike activation were strongly reduced by 4-aminopyridine (4-AP). These results suggest that a transient A-like current regulates the generation of Ca2+ spikes and the localization of Ca2+ influx in turtle Purkinje cell dendrites. 4. Both electric field depolarization and intrasomatic depolarization affected the generation of Ca2+ spikes and [Ca2+]i signals in a similar manner. Strong field stimulation could evoke focal depolarization at the tips of the spiny dendrites and cause local Ca2+ spike generation near the pial surface. When both stimuli were used, their effects were additive. 5. Climbing fiber (CF) or parallel fiber (PF) stimulation were associated with the generation of dendritic Ca2+ transients. In some experiments the PF-induced Ca2+ transients were confined to a small part of the spiny dendrites. The spatial distribution and the amplitude of these transients were influenced by somatic depolarization or field stimulation in a manner similar to their effect on directly evoked Ca2+ spikes and consistent with the involvement of a transient outward current in the control of the synaptically induced Ca2+ influx. 6. These results suggest that the intrinsic potassium conductances dynamically modulate spatial integration and influence the compartmentalization of Ca2+ spikes and [Ca2+]i changes in the dendrites.
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Bird, G. S. J., K. G. Oliver, D. A. Horstman, J. Obie, and J. W. Putney. "Relationship between the calcium-mobilizing action of inositol 1,4,5-trisphosphate in permeable AR4-2J cells and the estimated levels of inositol 1,4,5-trisphosphate in intact AR4-2J cells." Biochemical Journal 273, no. 3 (February 1, 1991): 541–46. http://dx.doi.org/10.1042/bj2730541.
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Various experimental strategies were employed in an effort to explain the previously reported [Horstman, Takemura & Putney (1988) J. Biol. Chem. 263, 15297-15303] paradoxically high levels of inositol 1,4,5-trisphosphate [(1,4,5)IP3] in resting and substance-P-stimulated AR4-2J cells. The concentration-effect curves for substance-P-induced [3H](1,4,5)IP3 formation in [3H]inositol-labelled cells and substance-P-induced increase in intracellular [Ca2+] were essentially superimposable, suggesting that formation of (1,4,5)IP3 is limiting for cellular Ca2+ mobilization. In electrically permeabilized AR4-2J cells, (1,4,5)IP3 and other inositol polyphosphates stimulated Ca2+ release with potencies similar to those reported for other cell types, including the parent pancreatic acinar cell. Compartmentalization of basal (1,4,5)IP3 was suggested by the fact that this material was stable in the presence of antimycin A, although this toxin completely blocked agonist stimulation of phospholipase C. However, subcellular fractionation as well as permeabilization of the cells with Staphylococcus aureus alpha-toxin failed to provide evidence for binding or sequestration of [3H](1,4,5)IP3 in AR4-2J cells. The density of (1,4,5)IP3 receptors in AR4-2J cells was not sufficiently large to impose non-linearity in the relationship between (1,4,5)IP3 concentration and (1,4,5)IP3-induced Ca2+ release. Thus the apparent high concentrations of (1,4,5)IP3 in resting and stimulated AR4-2J cells are not indicative of atypically low sensitivity or high concentration of (1,4,5)IP3 receptors, nor is there evidence for compartmentalization of (1,4,5)IP3 outside of the cytoplasm in these cells. It is possible that soluble factors in the cytoplasm of AR4-2J cells regulate the free concentration of (1,4,5)IP3 or the sensitivity of receptors to (1,4,5)IP3.
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Roy, Debjit, Zehavit Shapira, and Shimon Weiss. "Membrane potential sensing: Material design and method development for single particle optical electrophysiology." Journal of Chemical Physics 156, no. 8 (February 28, 2022): 084201. http://dx.doi.org/10.1063/5.0076522.
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We review the development of “single” nanoparticle-based inorganic and organic voltage sensors, which can eventually become a viable tool for “non-genetic optogenetics.” The voltage sensing is accomplished with optical imaging at the fast temporal response and high spatial resolutions in a large field of view. Inorganic voltage nanosensors utilize the Quantum Confined Stark Effect (QCSE) to sense local electric fields. Engineered nanoparticles achieve substantial single-particle voltage sensitivity (∼2% Δλ spectral Stark shift up to ∼30% ΔF/F per 160 mV) at room temperature due to enhanced charge separation. A dedicated home-built fluorescence microscope records spectrally resolved images to measure the QCSE induced spectral shift at the single-particle level. Biomaterial based surface ligands are designed and developed based on theoretical simulations. The hybrid nanobiomaterials satisfy anisotropic facet-selective coating, enabling effective compartmentalization beyond non-specific staining. Self-spiking- and patched-HEK293 cells and cortical neurons, when stained with hybrid nanobiomaterials, show clear photoluminescence intensity changes in response to membrane potential (MP) changes. Organic voltage nanosensors based on polystyrene beads and nanodisk technology utilize Fluorescence (Förster) Resonance Energy Transfer (FRET) to sense local electric fields. Voltage sensing FRET pairs achieve voltage sensitivity up to ∼35% ΔF/F per 120 mV in cultures. Non-invasive MP recording from individual targeted sites (synapses and spines) with nanodisks has been realized. However, both of these QCSE- and FRET-based voltage nanosensors yet need to reach the milestone of recording individual action potentials from individual targeted sites.
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van Kessel, Onno. "Champion East: Low-Cost Redevelopment of Shallow, Stacked, and Faulted Heavy-Oil Reservoirs." SPE Reservoir Evaluation & Engineering 5, no. 04 (August 1, 2002): 295–301. http://dx.doi.org/10.2118/78674-pa.
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Summary The Champion East area offshore Brunei Darussalam consists of approximately 50 stacked, shallow, and intensely faulted heavy oil reservoirs. These reservoirs have been under development since 1975 and have to date produced just 9% of the oil initially in place. Over the period 1998-2003, Brunei Shell Petroleum (BSP) is embarking on a major redevelopment with the aim of converting a further 30 million m3 of oil-in-place volume into commercial reserves. An overview will be given of how new technology is adding value to the total redevelopment, supported by actual application results and learning points. The primary development of Champion East is now nearing completion. The use of existing facilities and ultra shallow, long reach horizontal wells - with innovative sand exclusion and downhole intelligence - has achieved a 60% unit cost reduction over previous drilling campaigns in the area. The only way to unlock another 5 to 15% of the oil-in-place volume is to start secondary recovery through water injection, in combination with the use of electric submersible pumps (ESPs). Introduction The Champion Asset comprises the Champion Field offshore Brunei Darussalam (Fig. 1) and all associated facilities and infrastructure, which also serve as an export hub for BSP's entire Offshore East production division. Oil production from the Champion Field averages approximately one-third of total BSP production. A large scope for recovery, mostly technology-driven, remains, even at low oil prices. Subsurface, the area comprises a hydrostatic, heterolithic sequence of interbedded thin sandstones and mudstones (with reservoir flow units no more than 15 m thick and permeabilities ranging from 0.01 to 0.2 µm2 in lower shoreface sands to 0.5 to 5 µm2 in tidal channels) deposited in environments spanning a systems tract that extends from the outer shelf into the lower coastal plain. Other key features are significant lateral thickness variations, compartmentalization caused by syndepositional tectonics, and the presence of multiple growth faults. The Champion field can be divided into two distinct parts (Fig. 2): Champion East, spanning a depth of approximately 200 to 1200 m, with hydrocarbons in some places seeping through the seabed and feeding a coral reef; and Champion Main, which encompasses a depth of approximately 1000 to 2000 m. Champion Main contains the mature core of the Champion field, where both primary and secondary (water-injection) recovery processes are well advanced and 28% of the oil initially in place has been produced. The main focus in Champion Main is on water-injection maintenance, production-system optimization, and scope for recompleting or sidetracking existing wells-all aimed at slowing the decline in oil production. Most efforts in the area are, however, focused on the growth potential offered by shallow reservoirs. The Champion East area is much less mature than Champion Main, with a cumulative oil production to date of just 9% of the oil initially in place. Historically, Champion East is underdeveloped because of its subsurface complexity and heterogeneity (leading to erratic well performance), less favorable reservoir and oil properties [density of 930 g/cm3 (20° API) and viscosity between 5 and 15 mPa's], and a perceived lack of spare conductor slots, which would necessitate large investments in new infrastructure. In 1995, it was estimated that an upfront investment in excess of U.S. $400 million would be required to advance the development of Champion East by accessing another 30 million m3 of undeveloped reserves. Out of this total, 40% would be required for new facilities, and the remaining 60% would be for drilling new wells. This hurdle essentially halted further developments (between 1992 and 1997, just one well was drilled in the area), and it was obvious that major changes were required to all the fundamentals (average reserves and rates per well, well costs, and facilities costs) to break this deadlock. The case for change, together with plans for possible solutions, is further described in Ref. 1. Reservoir Modeling Technology Traditionally, Champion East had been modeled with 2D methods of mapping gross interval properties for groups of reservoirs ranging in thickness from 20 to 40 m, using the previous 3D seismic survey shot in 1983 (relatively poor resolution) and well correlation methods based on lithostratigraphy. However, these methods often can prove unreliable in deltaic reservoirs that have undergone synsedimentary tectonics. The previous major Champion East infill drilling campaign (1990-92) was relatively unsuccessful because approximately 35% of all target reservoirs were found to be either nonexistent, water-bearing, or depleted. It then became clear that it was necessary to understand the structure, sequence stratigraphy, and fluid distribution of these reservoirs in greater detail. Two key data acquisition activities occurred in 1994: a high-resolution 3D seismic survey and the retrieval of some 350 m of continuous cores to review the sedimentology and high-resolution sequence stratigraphy, as described in Ref. 2. After screening studies to establish the correct priority and level of detail required, Shell's proprietary reservoir modeling software (GEOCAP-MoReS) was used to provide detailed 3D reservoir models for reservoir simulation. A total of 16 models were built and history matched (with approximately 50,000 grid cells each) between 1996 and 1999; together, they covered the entire area, with boundaries positioned (generally at sealing faults) to minimize crossflow effects. This allowed fast optimization of reservoir development plans by identifying connected oil in place and transmissibility for individual reservoir flow units, such as an upper shoreface sandbody or a tidal channel, which have remained undrained from previous development.
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Francioni, Valerio, and Mark T. Harnett. "Rethinking Single Neuron Electrical Compartmentalization: Dendritic Contributions to Network Computation In Vivo." Neuroscience, June 2021. http://dx.doi.org/10.1016/j.neuroscience.2021.05.038.
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Effertz, Thomas, Tobias Moser, and Dominik Oliver. "Recent advances in cochlear hair cell nanophysiology: subcellular compartmentalization of electrical signaling in compact sensory cells." Faculty Reviews 9 (December 21, 2020). http://dx.doi.org/10.12703/r/9-24.
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Pan, Ting, Islam E. Khalil, Zhiling Xu, Hongfeng Li, Xinglong Zhang, Gengwu Xiao, Weina Zhang, Yu Shen, and Fengwei Huo. "Spatial compartmentalization of metal nanoparticles within metal-organic frameworks for tandem reaction." Nano Research, August 17, 2021. http://dx.doi.org/10.1007/s12274-021-3621-7.
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Tamada, Hiromi, Jerome Blanc, Natalya Korogod, Carl CH Petersen, and Graham W. Knott. "Ultrastructural comparison of dendritic spine morphology preserved with cryo and chemical fixation." eLife 9 (December 4, 2020). http://dx.doi.org/10.7554/elife.56384.
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Previously, we showed that cryo fixation of adult mouse brain tissue gave a truer representation of brain ultrastructure in comparison with a standard chemical fixation method (Korogod et al., 2015). Extracellular space matched physiological measurements, there were larger numbers of docked vesicles and less glial coverage of synapses and blood capillaries. Here, using the same preservation approaches, we compared the morphology of dendritic spines. We show that the length of the spine and the volume of its head is unchanged; however, the spine neck width is thinner by more than 30% after cryo fixation. In addition, the weak correlation between spine neck width and head volume seen after chemical fixation was not present in cryo-fixed spines. Our data suggest that spine neck geometry is independent of the spine head volume, with cryo fixation showing enhanced spine head compartmentalization and a higher predicted electrical resistance between spine head and parent dendrite.
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Scheffer, Louis K., C. Shan Xu, Michal Januszewski, Zhiyuan Lu, Shin-ya Takemura, Kenneth J. Hayworth, Gary B. Huang, et al. "A connectome and analysis of the adult Drosophila central brain." eLife 9 (September 7, 2020). http://dx.doi.org/10.7554/elife.57443.
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The neural circuits responsible for animal behavior remain largely unknown. We summarize new methods and present the circuitry of a large fraction of the brain of the fruit fly Drosophila melanogaster. Improved methods include new procedures to prepare, image, align, segment, find synapses in, and proofread such large data sets. We define cell types, refine computational compartments, and provide an exhaustive atlas of cell examples and types, many of them novel. We provide detailed circuits consisting of neurons and their chemical synapses for most of the central brain. We make the data public and simplify access, reducing the effort needed to answer circuit questions, and provide procedures linking the neurons defined by our analysis with genetic reagents. Biologically, we examine distributions of connection strengths, neural motifs on different scales, electrical consequences of compartmentalization, and evidence that maximizing packing density is an important criterion in the evolution of the fly’s brain.
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Vinokurova, Daria, Andrey Zakharov, Kseniya Chernova, Gulshat Burkhanova-Zakirova, Viktor Horst, Coline L. Lemale, Jens P. Dreier, and Roustem Khazipov. "Depth-profile of impairments in endothelin-1 – induced focal cortical ischemia." Journal of Cerebral Blood Flow & Metabolism, June 14, 2022, 0271678X2211074. http://dx.doi.org/10.1177/0271678x221107422.
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The development of ischemic lesions has primarily been studied in horizontal cortical space. However, how ischemic lesions develop through the cortical depth remains largely unknown. We explored this question using direct current coupled recordings at different cortical depths using linear arrays of iridium electrodes in the focal epipial endothelin-1 (ET1) ischemia model in the rat barrel cortex. ET1-induced impairments were characterized by a vertical gradient with (i) rapid suppression of the spontaneous activity in the superficial cortical layers at the onset of ischemia, (ii) compartmentalization of spreading depolarizations (SDs) to the deep layers during progression of ischemia, and (iii) deeper suppression of activity and larger histological lesion size in superficial cortical layers. The level of impairments correlated strongly with the rate of spontaneous activity suppression, the rate of SD onset after ET1 application, and the amplitude of giant negative ultraslow potentials (∼−70 mV), which developed during ET1 application and were similar to the tent-shaped ultraslow potentials observed during focal ischemia in the human cortex. Thus, in the epipial ET1 ischemia model, ischemic lesions develop progressively from the surface to the cortical depth, and early changes in electrical activity at the onset of ET1-induced ischemia reliably predict the severity of ischemic damage.
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Juresa, Jelena, and Asa Mendelsohn. "On social practices which Donna Haraway calls "Teddy Bear Patriarchy"." Documenta 37, no. 1 (January 14, 2019). http://dx.doi.org/10.21825/documenta.81903.
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Jelena Jureša’s video installation Aphasia consists of three chapters, each focusing on the absurdity arising from the collective silence surrounding crime and the compartmentalization of historical events, tracing the line between Belgian colonialism, Austrian antisemitism and the war in Yugoslavia. The film borrows the term 'aphasia' not exclusively from medical vocabulary—where it refers to trouble finding words or losing the ability to speak—but also from the writing of scholar Ann L. Stoler, who coined the term 'colonial aphasia', referring to the occlusion of knowledge in addition to collective amnesia, and the difficulty of generating a vocabulary that associates appropriate words, or concepts with appropriate things. Aphasia brings together compartmentalized historical events, through the history of racism and eugenics, focusing on the blind spots of history and the difficulty of speaking about the troubled past. The film charts the line starting with museum dioramas through photography to film, and sees them as deeply interwoven with imperialism and colonialism, used in order to produce a template for the blooming science of biological or physical anthropology.
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Gonzalez-Gonzalez, Maria A., Geetanjali S. Bendale, Kezhong Wang, Gordon G. Wallace, and Mario Romero-Ortega. "Platinized graphene fiber electrodes uncover direct spleen-vagus communication." Communications Biology 4, no. 1 (September 17, 2021). http://dx.doi.org/10.1038/s42003-021-02628-7.
Full textAbstract:
AbstractNeural interfacing nerve fascicles along the splenic neurovascular plexus (SNVP) is needed to better understand the spleen physiology, and for selective neuromodulation of this major organ. However, their small size and anatomical location have proven to be a significant challenge. Here, we use a reduced liquid crystalline graphene oxide (rGO) fiber coated with platinum (Pt) as a super-flexible suture-like electrode to interface multiple SNVP. The Pt-rGO fibers work as a handover knot electrodes over the small SNVP, allowing sensitive recording from four splenic nerve terminal branches (SN 1–4), to uncover differential activity and axon composition among them. Here, the asymmetric defasciculation of the SN branches is revealed by electron microscopy, and the functional compartmentalization in spleen innervation is evidenced in response to hypoxia and pharmacological modulation of mean arterial pressure. We demonstrate that electrical stimulation of cervical and sub-diaphragmatic vagus nerve (VN), evokes activity in a subset of SN terminal branches, providing evidence for a direct VN control over the spleen. This notion is supported by adenoviral tract-tracing of SN branches, revealing an unconventional direct brain-spleen projection. High-performance Pt-rGO fiber electrodes, may be used for the fine neural modulation of other small neurovascular plexus at the point of entry of major organs as a bioelectronic medical alternative.
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Sutrsino, Himawan Hadi. "The Active Fire Protection Prototype for Household-Scale Kitchen Based on Silica Gel from Rice Husk Ash." International Journal of Integrated Engineering 14, no. 3 (June 20, 2022). http://dx.doi.org/10.30880/ijie.2022.14.03.005.
Full textAbstract:
This study aims to create a fire protection design in the kitchen with technology that is easily applied along with inexpensive extinguishing media using silica gel from rice husk ash. By using an experimental method, the active design of fire protection in the kitchen area uses compartmentalization equipped with a gas stove, kitchen equipment, as well as specially designed fire equipment components. The composition of the air in the compartment is calculated based on the volume of the compartment so that it can represent the coverage of oxygen and fuel in accordance with the conditions of free air, while the silica used as an extinguishing media from the extraction of rice husk ash using KOH 0,5M solvent. From the results of this study, the design of fire protection for silica gel-based kitchens made from rice husk ash is effectively used and easy to install in the kitchen area.
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Bossink, Elsbeth G. B. M., Anke R. Vollertsen, Joshua T. Loessberg-Zahl, Andries D. van der Meer, Loes I. Segerink, and Mathieu Odijk. "Systematic characterization of cleanroom-free fabricated macrovalves, demonstrating pumps and mixers for automated fluid handling tuned for organ-on-chip applications." Microsystems & Nanoengineering 8, no. 1 (May 23, 2022). http://dx.doi.org/10.1038/s41378-022-00378-y.
Full textAbstract:
AbstractIntegrated valves enable automated control in microfluidic systems, as they can be applied for mixing, pumping and compartmentalization purposes. Such automation would be highly valuable for applications in organ-on-chip (OoC) systems. However, OoC systems typically have channel dimensions in the range of hundreds of micrometers, which is an order of magnitude larger than those of typical microfluidic valves. The most-used fabrication process for integrated, normally open polydimethylsiloxane (PDMS) valves requires a reflow photoresist that limits the achievable channel height. In addition, the low stroke volumes of these valves make it challenging to achieve flow rates of microliters per minute, which are typically required in OoC systems. Herein, we present a mechanical ‘macrovalve’ fabricated by multilayer soft lithography using micromilled direct molds. We demonstrate that these valves can close off rounded channels of up to 700 µm high and 1000 µm wide. Furthermore, we used these macrovalves to create a peristaltic pump with a pumping rate of up to 48 µL/min and a mixing and metering device that can achieve the complete mixing of a volume of 6.4 µL within only 17 s. An initial cell culture experiment demonstrated that a device with integrated macrovalves is biocompatible and allows the cell culture of endothelial cells over multiple days under continuous perfusion and automated medium refreshment.