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Search Results: 1 - 10 of 8466 matches for " Vladimir Parpura "
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SNAREs: Could They be the Answer to an Energy Landscape Riddle in Exocytosis?
Wei Liu,Vladimir Parpura
The Scientific World Journal , 2010, DOI: 10.1100/tsw.2010.137
Neuroglia at the crossroads of homoeostasis, metabolism and signalling: evolution of the concept
Vladimir Parpura,Alexei Verkhratsky
ASN Neuro , 2012, DOI: 10.1042/an20120019
Abstract: Ever since Rudolf Virchow in 1858 publicly announced his apprehension of neuroglia being a true connective substance, this concept has been evolving to encompass a heterogeneous population of cells with various forms and functions. We briefly compare the 19th–20th century perspectives on neuroglia with the up-to-date view of these cells as an integral, and possibly integrating, component of brain metabolism and signalling in heath and disease. We conclude that the unifying property of otherwise diverse functions of various neuroglial cell sub-types is to maintain brain homoeostasis at different levels, from whole organ to molecular.
Data and model tango to aid the understanding of astrocyte-neuron signaling
Shivendra Tewari,Vladimir Parpura
Frontiers in Computational Neuroscience , 2014, DOI: 10.3389/fncom.2014.00003
Plasmalemmal Na+/Ca2+ exchanger modulates Ca2+-dependent exocytotic release of glutamate from rat cortical astrocytes
Reno C Reyes,Alexei Verkhratsky,Vladimir Parpura
ASN Neuro , 2012, DOI: 10.1042/an20110059
Abstract: Astroglial excitability operates through increases in Ca2+cyt (cytosolic Ca2+), which can lead to glutamatergic gliotransmission. In parallel fluctuations in astrocytic Na+cyt (cytosolic Na+) control metabolic neuronal-glial signalling, most notably through stimulation of lactate production, which on release from astrocytes can be taken up and utilized by nearby neurons, a process referred to as lactate shuttle. Both gliotransmission and lactate shuttle play a role in modulation of synaptic transmission and plasticity. Consequently, we studied the role of the PMCA (plasma membrane Ca2+-ATPase), NCX (plasma membrane Na+/Ca2+ exchanger) and NKA (Na+/K+-ATPase) in complex and coordinated regulation of Ca2+cyt and Na+cyt in astrocytes at rest and upon mechanical stimulation. Our data support the notion that NKA and PMCA are the major Na+ and Ca2+ extruders in resting astrocytes. Surprisingly, the blockade of NKA or PMCA appeared less important during times of Ca2+ and Na+ cytosolic loads caused by mechanical stimulation. Unexpectedly, NCX in reverse mode appeared as a major contributor to overall Ca2+ and Na+ homoeostasis in astrocytes both at rest and when these glial cells were mechanically stimulated. In addition, NCX facilitated mechanically induced Ca2+-dependent exocytotic release of glutamate from astrocytes. These findings help better understanding of astrocyte-neuron bidirectional signalling at the tripartite synapse and/or microvasculature. We propose that NCX operating in reverse mode could be involved in fast and spatially localized Ca2+-dependent gliotransmission, that would operate in parallel to a slower and more widely distributed gliotransmission pathway that requires metabotropically controlled Ca2+ release from the ER (endoplasmic reticulum).
A Caenorhabditis elegans Locomotion Phenotype Caused by Transgenic Repeats of the hlh-17 Promoter Sequence
Randy F. Stout Jr, Vladimir Grubi?i?, Vladimir Parpura
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081771
Abstract: Transgene technology is one of the most heavily relied upon tools in modern biological research. Expression of an exogenous gene within cells, for research and therapeutic applications, nearly always includes promoters and other regulatory sequences. We found that repeats of a non-protein coding transgenic sequence produced profound changes to the behavior of the nematode Caenorhabditis elegans. These changes were produced by a glial promoter sequence but, unexpectedly, major deficits were observed specifically in backward locomotion, a neuron-driven behavior. We also present evidence that this behavioral phenotype is transpromoter copy number-dependent and manifests early in development and is maintained into adulthood of the worm.
Cell-type specific mechanisms of D-serine uptake and release in the brain
Magalie Martineau,Vladimir Parpura,Jean-Pierre Mothet
Frontiers in Synaptic Neuroscience , 2014, DOI: 10.3389/fnsyn.2014.00012
Abstract: Accumulating evidence during the last decade established that D-serine is a key signaling molecule utilized by neurons and astroglia in the mammalian central nervous system. D-serine is increasingly appreciated as the main physiological endogenous coagonist for synaptic NMDA receptors at central excitatory synapses; it is mandatory for long-term changes in synaptic strength, memory, learning, and social interactions. Alterations in the extracellular levels of D-serine leading to disrupted cell-cell signaling are a trademark of many chronic or acute neurological (i.e., Alzheimer disease, epilepsy, stroke) and psychiatric (i.e., schizophrenia) disorders, and are associated with addictive behavior (i.e., cocaine addiction). Indeed, fine tuning of the extracellular levels of D-serine, achieved by various molecular machineries and signaling pathways, is necessary for maintenance of accurate NMDA receptor functions. Here, we review the experimental data supporting the notion that astroglia and neurons use different pathways to regulate levels of extracellular D-serine.
Computational quest for understanding the role of astrocyte signaling in synaptic transmission and plasticity
Maurizio De Pittà,Vladislav Volman,Hugues Berry,Vladimir Parpura,Andrea Volterra,Eshel Ben-Jacob
Frontiers in Computational Neuroscience , 2012, DOI: 10.3389/fncom.2012.00098
Abstract: The complexity of the signaling network that underlies astrocyte-synapse interactions may seem discouraging when tackled from a theoretical perspective. Computational modeling is challenged by the fact that many details remain hitherto unknown and conventional approaches to describe synaptic function are unsuitable to explain experimental observations when astrocytic signaling is taken into account. Supported by experimental evidence is the possibility that astrocytes perform genuine information processing by means of their calcium signaling and are players in the physiological setting of the basal tone of synaptic transmission. Here we consider the plausibility of this scenario from a theoretical perspective, focusing on the modulation of synaptic release probability by the astrocyte and its implications on synaptic plasticity. The analysis of the signaling pathways underlying such modulation refines our notion of tripartite synapse and has profound implications on our understanding of brain function.
Weak Interaction and the Nature of Virtual Particles  [PDF]
Vladimir Konushko
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.22009
Abstract: The granular structure of space, the nature of virtual particles and the unity of physical interactions are under study. The mass of an elementary cell in the Universe is determined, as a whole, with the physical meaning of the renormalization procedure changing in this case.
Granular Space and the Problem of Large Numbers  [PDF]
Vladimir Konushko
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.25038
Abstract: Two and a half thousand years ago the ancient atomists made a suggestion that space has a cellular structure, is material and consists of elementary cells. In 1900 Plank found the elementary length L*=10-33 cm. This notion has been widely used in modern physics ever since. The properties of granular space are studied in this article on the assumption that a three-dimensional material cell with the size of Planck’s elementary length is the only material for the construction of the whole Universe. This approach allows one to account for such mysterious phenomena as inertia, ultimate velocity of transfer of material body interactions and huge difference between gravitational and Coulomb forces - the so called “Large Numbers Problem”, as well essence of electric charge and Pauli exclusions principle.
Gravitational Energy Level and the Nature of Microwave Background of Universe  [PDF]
Vladimir Konushko
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.24026
Abstract: In 1965, Penzias and Wilson discovered thermal radiation with T0 ~ 2.7 K further on called “relict”. This article is concerned with the new phenomenon, i.e. the formation of gravitational energy levels by any body, with the result that photons are produced whose spectrum close to the Earth is similar to that of a blackbody with T0 ~ 2.7 K. The critical analysis of the experiments performed with the cosmic observatories COBE and WMAP completely confirms this prediction.
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