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Search Results: 1 - 10 of 3016 matches for " Arthur Bikbaev "
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Hippocampal network activity is transiently altered by induction of long-term potentiation in the dentate gyrus of freely behaving rats
Arthur Bikbaev,Denise Manahan-Vaughan
Frontiers in Behavioral Neuroscience , 2007, DOI: 10.3389/neuro.08.007.2007
Abstract: A role for oscillatory activity in hippocampal neuronal networks has been proposed in sensory encoding, cognitive functions and synaptic plasticity. In the hippocampus, theta (5–10?Hz) and gamma (30–100?Hz) oscillations may provide a mechanism for temporal encoding of information, and the basis for formation and retrieval of memory traces. Long-term potentiation (LTP) of synaptic transmission, a candidate cellular model of synaptic information storage, is typically induced by high-frequency tetanisation (HFT) of afferent pathways. Taking into account the role of oscillatory activity in the processing of information, dynamic changes may occur in hippocampal network activity in the period during HFT and/or soon after it. These changes in rhythmic activity may determine or, at least, contribute to successful potentiation and, in general, to formation of memory. We have found that short-term potentiation (STP) and LTP as well LTP-failure are characterised with different profiles of changes in theta and gamma frequencies. Potentiation of synaptic transmission was associated with a significant increase in the relative theta power and mean amplitude of theta cycles in the period encompassing 300?seconds after HFT. Where LTP or STP, but not failure of potentiation, occurred, this facilitation of theta was accompanied by transient increases in gamma power and in the mean amplitude of gamma oscillations within a single theta cycle. Our data support that specific, correlated changes in these parameters are associated with successful synaptic potentiation. These findings suggest that changes in theta-gamma activity associated with induction of LTP may enable synaptic information storage in the hippocampus.
MGluR5 Mediates the Interaction between Late-LTP, Network Activity, and Learning
Arthur Bikbaev, Sergey Neyman, Richard Teke Ngomba, Jeffrey Conn, Ferdinando Nicoletti, Denise Manahan-Vaughan
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002155
Abstract: Hippocampal synaptic plasticity and learning are strongly regulated by metabotropic glutamate receptors (mGluRs) and particularly by mGluR5. Here, we investigated the mechanisms underlying mGluR5-modulation of these phenomena. Prolonged pharmacological blockade of mGluR5 with MPEP produced a profound impairment of spatial memory. Effects were associated with 1) a reduction of mGluR1a-expression in the dentate gyrus; 2) impaired dentate gyrus LTP; 3) enhanced CA1-LTP and 4) suppressed theta (5–10 Hz) and gamma (30–100 Hz) oscillations in the dentate gyrus. Allosteric potentiation of mGluR1 after mGluR5 blockade significantly ameliorated dentate gyrus LTP, as well as suppression of gamma oscillatory activity. CA3-lesioning prevented MPEP effects on CA1-LTP, suggesting that plasticity levels in CA1 are driven by mGluR5-dependent synaptic and network activity in the dentate gyrus. These data support the hypothesis that prolonged mGluR5-inactivation causes altered hippocampal LTP levels and network activity, which is mediated in part by impaired mGluR1-expression in the dentate gyrus. The consequence is impairment of long-term learning.
Synaptically Released Matrix Metalloproteinase Activity in Control of Structural Plasticity and the Cell Surface Distribution of GluA1-AMPA Receptors
Zsuzsanna Szepesi, Eric Hosy, Blazej Ruszczycki, Monika Bijata, Marta Pyskaty, Arthur Bikbaev, Martin Heine, Daniel Choquet, Leszek Kaczmarek, Jakub Wlodarczyk
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098274
Abstract: Synapses are particularly prone to dynamic alterations and thus play a major role in neuronal plasticity. Dynamic excitatory synapses are located at the membranous neuronal protrusions called dendritic spines. The ability to change synaptic connections involves both alterations at the morphological level and changes in postsynaptic receptor composition. We report that endogenous matrix metalloproteinase (MMP) activity promotes the structural and functional plasticity of local synapses by its effect on glutamate receptor mobility and content. We used live imaging of cultured hippocampal neurons and quantitative morphological analysis to show that chemical long-term potentiation (cLTP) induces the permanent enlargement of a subset of small dendritic spines in an MMP-dependent manner. We also used a superresolution microscopy approach and found that spine expansion induced by cLTP was accompanied by MMP-dependent immobilization and synaptic accumulation as well as the clustering of GluA1-containing AMPA receptors. Altogether, our results reveal novel molecular and cellular mechanisms of synaptic plasticity.
Example of shock wave in unstaible medium: The focusing nonlinear Schrodinger equation
Ramil' F. Bikbaev,Vadim R. Kudashev
Physics , 1994, DOI: 10.1016/0375-9601(94)90751-X
Abstract: Dissipationless shock waves in modulational unstable one-dimensional medium are investigated on the simplest example of integrable focusing nonlinear Schr\''odinger (NS) equation. Our approach is based on the construction of special exact solution of the Whitham-NS system, which ''partially saturates'' the modulational instability.
Whitham deformations partially saturating the modulational instability in the nonlinear Schrodinger equation
Ramil' F. Bikbaev,Vadim R. Kudashev
Physics , 1994,
Abstract: In the framework of Gurevich and Pitaevskii approach [1] we construct modulated by Whitham [2] solution of nonlinear Shrodinger (NS) equation partially saturating the modulational instability. This solution describes new scenario of monochromatic wave evolution in NS equation which leads to generation of new phase and oscillation region.
Magnetization waves in Landau-Lifshitz Model
R. F. Bikbaev,R. A. Sharipov
Physics , 1999, DOI: 10.1016/0375-9601(88)90943-7
Abstract: The solutions of the Landau-Lifshitz equation with finite-gap behavior at infinity are considered. By means of the inverse scattering method the large-time asymptotics is obtained.
Optimal Recovery of Holomorphic Functions from Inaccurate Information about Radial Integration  [PDF]
Arthur DeGraw
American Journal of Computational Mathematics (AJCM) , 2012, DOI: 10.4236/ajcm.2012.24035
Abstract: This paper addresses the optimal recovery of functions from Hilbert spaces of functions on the unit disc. The estimation, or recovery, is performed from inaccurate information given by integration along radial paths. For a holomorphic function expressed as a series, three distinct situations are considered: where the information error in L2 norm is bound by δ>0 or for a finite number of terms the error in l2N norm is bound by δ>0 or lastly the error in the jth coefficient is bound by δj>0. The results are applied to the Hardy-Sobolev and Bergman-Sobolev spaces.
The rationale for pre-race aspirin to protect susceptible runners from sudden cardiac death during marathons: Deconstructing the Pheidippides conundrum  [PDF]
Arthur J. Siegel
World Journal of Cardiovascular Diseases (WJCD) , 2013, DOI: 10.4236/wjcd.2013.35A003
Abstract: Objectives: While endurance exercise such as training for marathons is cardioprotective, cardiac arrests and sudden death occur in previously healthy runners during races predominantly in middle-aged males due to atherosclerotic heart disease. Recent evidence related to this problem is reviewed herein including epidemiologic studies and findings related to acute cardiac risk in asymptomatic middle-aged male runners during races. Method: Literature review related to the above. Findings: The risks of cardiac arrest and sudden death were 1 in 57,002 and 1 in 171,005 respectively in runners with a mean age of 49.7 years among 1,710,052 participants in marathons in the United States since 1980. Atherosclerotic heart disease was the cause of death in over 90% of cases in two retrospective studies and a greater than two-fold increase in cardiac arrests was observed in middle-aged men in the latter half of a 10-year prospective registry beginning in the year 2000. Asymptomatic middle-aged male runners showed elevated biomarkers of inflammation such as interleukin-6, C-reactive protein together with procoagulant effects including in vivo platelet activation, indicating susceptibility to atherothrombosis. Conclusions: Antithrombotic prophylaxis is evidence-based by validated clinical paradigms to prevent cardiac arrest and sudden death in susceptibile marathon runners at high risk for atherothrombosis during races.

Motivating Generation Y and Virtual Teams  [PDF]
Arthur M. Baldonado
Open Journal of Business and Management (OJBM) , 2013, DOI: 10.4236/ojbm.2013.12006
Abstract: How can team members remain effective if members cannot engage in face-to-face interactions? Although the concept of global virtual teams has been a relatively new phenomenon, their use by organizations is a growing trend. The growth of globalization and the explosion of new technology have led to a new paradigm—a workplace that has no walls or boundaries. The purpose of the qualitative, descriptive study was to explore the motivational needs of Gen Y virtual team members and their impact in the workplace based on Herzberg’s two-factor theory of motivation. The participants consisted of Gen Y members at the Lakeland,Florida. The author used a researcher-developed, written survey as research methodology. The findings of the study revealed that Gen Y cohort placed great importance to both hygiene and motivator factors in their motivational needs. Advancement and personal life were both important to Gen Y participants. Managers must be flexible in their managerial approach to Gen Y workers.
A Hypothesis Concerning the Effect of Schedule on the Pattern of 5-Fluorouracil Toxicity  [PDF]
Arthur J. Weiss
Journal of Cancer Therapy (JCT) , 2015, DOI: 10.4236/jct.2015.63028
Abstract:

The significant effect that scheduling has upon the severity and types of drug toxicity has been known for many years. Evidence is available demonstrating that the schedule chosen will substantially effect the relative distribution of drug to various target organs. It has been shown that a likely cause for this with doxorubicin is that the efficiency of the various enzyme complexes responsible for disposing of the drug can be affected by scheduling. We believe a similar process can explain the marked effect that scheduling has on the pattern of 5-fluorouracil toxicity and present both clinical and computer data to illustrate this.

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