51
|
Kume S, Shimomura T, Tateyama M, Kubo Y. Two mutations at different positions in the CNBH domain of the hERG channel accelerate deactivation and impair the interaction with the EAG domain. J Physiol 2018; 596:4629-4650. [PMID: 30086184 DOI: 10.1113/jp276208] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 08/06/2018] [Indexed: 12/24/2022] Open
Abstract
KEY POINTS In the human ether-a-go-go related gene (hERG) channel, both the ether-a-go-go (EAG) domain in the N-terminal and the cyclic nucleotide (CN) binding homology (CNBH) domain in the C-terminal cytoplasmic region are known to contribute to the characteristic slow deactivation. Mutations of Phe860 in the CNBH domain, reported to fill the CN binding pocket, accelerate the deactivation and decrease the fluorescence resonance energy transfer (FRET) efficiencies between the EAG and CNBH domains. An electrostatic interaction between Arg696 and Asp727 in the C-linker domain, critical for HCN and CNG channels, is not formed in the hERG channel. Mutations of newly identified electrostatically interacting pair, Asp727 in the C-linker and Arg752 in the CNBH domains, accelerate the deactivation and decrease FRET efficiency. Voltage-dependent changes in FRET efficiency were not detected. These results suggest that the acceleration of the deactivation by mutations of C-terminal domains is a result of the lack of interaction between the EAG and CNBH domains. ABSTRACT The human ether-a-go-go related gene (hERG) channel shows characteristic slow deactivation, and the contribution of both of the N-terminal cytoplasmic ether-a-go-go (EAG) domain and the C-terminal cytoplasmic cyclic nucleotide (CN) binding homology (CNBH) domain is well known. The interaction between these domains is known to be critical for slow deactivation. We analysed the effects of mutations in the CNBH domain and its upstream C-linker domain on slow deactivation and the interaction between the EAG and CNBH domains by electrophysiological and fluorescence resonance energy transfer (FRET) analyses using Xenopus oocyte and HEK293T cell expression systems. We first observed that mutations of Phe860 in the CNBH domain, which is reported to fill the CN binding pocket as an intrinsic ligand, accelerate deactivation and eliminate the inter-domain interaction. Next, we observed that the salt bridge between Arg696 and Asp727 in the C-linker domain, which is reported to be critical for the function of CN-regulated channels, is not formed. We newly identified an electrostatically interacting pair critical for slow deactivation: Asp727 and Arg752 in the CNBH domain. Their mutations also impaired the inter-domain interaction. Taking these results together, both mutations of the intrinsic ligand (Phe860) and a newly identified salt bridge pair (Asp727 and Arg752) in the hERG channel accelerated deactivation and also decreased the interaction between the EAG and CNBH domains. Voltage-dependent changes in FRET efficiency between the two domains were not detected. The results suggest that the CNBH domain contributes to slow deactivation of the hERG channel by a mechanism involving the EAG domain.
Collapse
Affiliation(s)
- Shinichiro Kume
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI, Hayama, Japan.,Present address: Department of Pathophysiology, Oita University School of Medicine, Yufu, Oita, Japan
| | - Takushi Shimomura
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI, Hayama, Japan
| | - Michihiro Tateyama
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI, Hayama, Japan
| | - Yoshihiro Kubo
- Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiological Sciences, School of Life Science, SOKENDAI, Hayama, Japan
| |
Collapse
|
52
|
Scholz D, Kröcher O, Vogel F. Deactivation and Regeneration of Sulfonated Carbon Catalysts in Hydrothermal Reaction Environments. ChemSusChem 2018; 11:2189-2201. [PMID: 29733550 DOI: 10.1002/cssc.201800678] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Indexed: 06/08/2023]
Abstract
The deactivation pathways of sulfonated carbon catalysts prepared from different carbons were studied during the aqueous-phase hydrolysis of cellobiose under continuous-flow conditions. The sulfonation of carbon materials with a low degree of graphitization introduced sulfonic acid groups that are partially stable even during prolonged exposure to harsh hydrothermal treatment conditions (180 °C). The physicochemical characterization of hydrothermally treated materials coupled with the treatment of model compounds for sulfonic acids demonstrated that the stability is related to the presence of activating and deactivating substituents on the aromatic system. Besides sulfonic acid group leaching, a hitherto unknown mode of deactivation was identified that proceeds by the ion exchange of cations contained in the aqueous feed and protons of the sulfonic acid groups. Proton leaching is a fully reversible mode of deactivation by the treatment of the spent catalysts with strong Brønsted acids. Through a combined approach of physicochemical characterization, catalytic testing, and hydrothermal treatment, a methodology for the preparation of catalytically stable carbon materials that bear sulfonic acid groups was established.
Collapse
Affiliation(s)
- David Scholz
- Bioenergy and Catalysis Laboratory, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
- Institute of Chemical Sciences and Engineering, Ecole polytechnique fédérale de Lausanne, EPFL SB ISIC-GE, 1015, Lausanne, Switzerland
| | - Oliver Kröcher
- Bioenergy and Catalysis Laboratory, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
- Institute of Chemical Sciences and Engineering, Ecole polytechnique fédérale de Lausanne, EPFL SB ISIC-GE, 1015, Lausanne, Switzerland
| | - Frédéric Vogel
- Bioenergy and Catalysis Laboratory, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland
- Institute of Biomass and Resource Efficiency, University of Applied Sciences and Arts Northwestern Switzerland, 5210, Windisch, Switzerland
| |
Collapse
|
53
|
Reinhold R, Stoeck U, Grafe HJ, Mikhailova D, Jaumann T, Oswald S, Kaskel S, Giebeler L. Surface and Electrochemical Studies on Silicon Diphosphide as Easy-to-Handle Anode Material for Lithium-Based Batteries-the Phosphorus Path. ACS Appl Mater Interfaces 2018; 10:7096-7106. [PMID: 29384653 DOI: 10.1021/acsami.7b18697] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The electrochemical characteristics of silicon diphosphide (SiP2) as a new anode material for future lithium-ion batteries (LIBs) are evaluated. The high theoretical capacity of about 3900 mA h g-1 (fully lithiated state: Li15Si4 + Li3P) renders silicon diphosphide as a highly promising candidate to replace graphite (372 mA h g-1) as the standard anode to significantly increase the specific energy density of LIBs. The proposed mechanism of SiP2 is divided into a conversion reaction of phosphorus species, followed by an alloying reaction forming lithium silicide phases. In this study, we focus on the conversion mechanism during cycling and report on the phase transitions of SiP2 during lithiation and delithiation. By using ex situ analysis techniques such as X-ray powder diffraction, formed reaction products are identified. Magic angle spinning nuclear magnetic resonance spectroscopy is applied for the characterization of long-range ordered compounds, whereas X-ray photoelectron spectroscopy gives information of the surface-layer species at the interface of active material and electrolyte. Our SiP2 anode material shows a high initial capacity of about 2700 mA h g-1, whereas a fast capacity fading during the first few cycles occurs which is not necessarily expected. On the basis of our results, we conclude that besides other degradation effects, such as electrolyte decomposition and electrical contact loss, the rapid capacity fading originates from the formation of a low ion-conductive layer of LiP. This insulating layer hinders lithium-ion diffusion during lithiation and thereby mainly contributes to fast capacity fading.
Collapse
Affiliation(s)
- Romy Reinhold
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
- Department of Inorganic Chemistry, Technische Universität Dresden , Bergstraße 66, D-01069 Dresden, Germany
| | - Ulrich Stoeck
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Hans-Joachim Grafe
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Daria Mikhailova
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Tony Jaumann
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Steffen Oswald
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
| | - Stefan Kaskel
- Department of Inorganic Chemistry, Technische Universität Dresden , Bergstraße 66, D-01069 Dresden, Germany
| | - Lars Giebeler
- Leibniz Institute for Solid State and Materials Research (IFW) Dresden e.V. , Helmholtzstraße 20, D-01069 Dresden, Germany
| |
Collapse
|
54
|
Steiner JM, Patton KK, Prutkin JM, Kirkpatrick JN. Moral Distress at the End of a Life: When Family and Clinicians Do Not Agree on Implantable Cardioverter-Defibrillator Deactivation. J Pain Symptom Manage 2018; 55:530-534. [PMID: 29191724 DOI: 10.1016/j.jpainsymman.2017.11.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/18/2017] [Accepted: 11/21/2017] [Indexed: 10/18/2022]
Abstract
A 63-year-old man with end-stage ischemic cardiomyopathy presented with incessant ventricular tachycardia. He had been hospitalized multiple times in the past year for severe heart failure. As he approached end of life and was regularly receiving defibrillator shocks, his care team recommended deactivation of his implantable cardioverter-defibrillator. However, his family did not wish to allow deactivation, reporting a religious obligation to prolong his life, regardless of the risk of suffering. The patient was unable to adequately participate in the decision-making process. An implantable cardioverter-defibrillator can serve to avoid sudden death but may lead to a prolonged death from heart failure. This possibility forces the examination of values regarding prolongation of life, sometimes producing disagreement among stakeholders. Although ethical consensus holds that defibrillator deactivation is legal and ethical, disagreements about life prolongation may complicate decision making. The ethical, technical, and medical complexity involved in this case speaks to the need for clear, prospective communication involving the patient, the patient's family, and members of the care team.
Collapse
Affiliation(s)
- Jill M Steiner
- Division of Cardiology, University of Washington, Seattle, Washington, USA.
| | - Kristen K Patton
- Division of Cardiology, University of Washington, Seattle, Washington, USA
| | - Jordan M Prutkin
- Division of Cardiology, University of Washington, Seattle, Washington, USA
| | - James N Kirkpatrick
- Division of Cardiology, University of Washington, Seattle, Washington, USA; Department of Bioethics and Humanities, University of Washington, Seattle, Washington, USA
| |
Collapse
|
55
|
Liu C, van Santen RA, Poursaeidesfahani A, Vlugt TJH, Pidko EA, Hensen EJM. Hydride Transfer versus Deprotonation Kinetics in the Isobutane-Propene Alkylation Reaction: A Computational Study. ACS Catal 2017; 7:8613-8627. [PMID: 29226012 PMCID: PMC5716443 DOI: 10.1021/acscatal.7b02877] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 11/01/2017] [Indexed: 12/04/2022]
Abstract
The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane-propene alkylation catalyzed by zeolitic solid acids. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate of hydride transfer in comparison to the competitive oligomerization and deprotonation reactions resulting in catalyst deactivation. Our calculations reveal that hydride transfer from isobutane to a carbenium ion occurs via a concerted C-C bond formation between a tert-butyl fragment and an additional olefin, or via deprotonation of the tert-butyl fragment to generate isobutene. A combination of high isobutane concentration and low propene concentration at the reaction center favor the selective alkylation. The key reaction step that has to be suppressed to increase the catalyst lifetime is the deprotonation of carbenium intermediates that are part of the hydride transfer reaction cycle.
Collapse
Affiliation(s)
- Chong Liu
- Inorganic
Materials Chemistry Group, Schuit Institute of Catalysis, and Institute for
Complex Molecular Systems, Eindhoven University
of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Rutger A. van Santen
- Inorganic
Materials Chemistry Group, Schuit Institute of Catalysis, and Institute for
Complex Molecular Systems, Eindhoven University
of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Ali Poursaeidesfahani
- Process
& Energy Department, Delft University
of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - Thijs J. H. Vlugt
- Process
& Energy Department, Delft University
of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - Evgeny A. Pidko
- Inorganic
Materials Chemistry Group, Schuit Institute of Catalysis, and Institute for
Complex Molecular Systems, Eindhoven University
of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- TheoMAT
group, International Laboratory “Solution Chemistry of Advanced
Materials and Technologies”, ITMO
University, Lomonosova
9, St. Petersburg 191002, Russia
| | - Emiel J. M. Hensen
- Inorganic
Materials Chemistry Group, Schuit Institute of Catalysis, and Institute for
Complex Molecular Systems, Eindhoven University
of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| |
Collapse
|
56
|
Borodina E, Sharbini Harun Kamaluddin H, Meirer F, Mokhtar M, Asiri AM, Al-Thabaiti SA, Basahel SN, Ruiz-Martinez J, Weckhuysen BM. Influence of the Reaction Temperature on the Nature of the Active and Deactivating Species During Methanol-to-Olefins Conversion over H-SAPO-34. ACS Catal 2017; 7:5268-5281. [PMID: 28824823 PMCID: PMC5557614 DOI: 10.1021/acscatal.7b01497] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 06/21/2017] [Indexed: 11/29/2022]
Abstract
The selectivity toward lower olefins during the methanol-to-olefins conversion over H-SAPO-34 at reaction temperatures between 573 and 773 K has been studied with a combination of operando UV-vis diffuse reflectance spectroscopy and online gas chromatography. It was found that the selectivity toward propylene increases in the temperature range of 573-623 K, while it decreases in the temperature range of 623-773 K. The high degree of incorporation of olefins, mainly propylene, into the hydrocarbon pool affects the product selectivity at lower reaction temperatures. The nature and dynamics of the active and deactivating hydrocarbon species with increasing reaction temperature were revealed by a non-negative matrix factorization of the time-resolved operando UV-vis diffuse reflectance spectra. The active hydrocarbon pool species consist of mainly highly methylated benzene carbocations at temperatures between 573 and 598 K, of both highly methylated benzene carbocations and methylated naphthalene carbocations at 623 K, and of only methylated naphthalene carbocations at temperatures between 673 and 773 K. The operando spectroscopy results suggest that the nature of the active species also influences the olefin selectivity. In fact, monoenylic and highly methylated benzene carbocations are more selective to the formation of propylene, whereas the formation of the group of low methylated benzene carbocations and methylated naphthalene carbocations at higher reaction temperatures (i.e., 673 and 773 K) favors the formation of ethylene. At reaction temperatures between 573 and 623 K, catalyst deactivation is caused by the gradual filling of the micropores with methylated naphthalene carbocations, while between 623 and 773 K the formation of neutral poly aromatics and phenanthrene/anthracene carbocations are mainly responsible for catalyst deactivation, their respective contribution increasing with increasing reaction temperature. Methanol pulse experiments at different temperatures demonstrate the dynamics between methylated benzene and methylated naphthalene carbocations. It was found that methylated naphthalene carbocations species are deactivating and block the micropores at low reaction temperatures, while acting as the active species at higher reaction temperatures, although they give rise to the formation of extended hydrocarbon deposits.
Collapse
Affiliation(s)
- E. Borodina
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands
| | - H. Sharbini Harun Kamaluddin
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands
- Department
of Chemistry, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
| | - F. Meirer
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands
| | - M. Mokhtar
- Department
of Chemistry, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
| | - A. M. Asiri
- Department
of Chemistry, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
| | - S. A. Al-Thabaiti
- Department
of Chemistry, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
| | - S. N. Basahel
- Department
of Chemistry, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
| | - J. Ruiz-Martinez
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands
| | - B. M. Weckhuysen
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands
| |
Collapse
|
57
|
Vernon CG, Copits BA, Stolz JR, Guzmán YF, Swanson GT. N-glycan content modulates kainate receptor functional properties. J Physiol 2017; 595:5913-5930. [PMID: 28714086 DOI: 10.1113/jp274790] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 07/12/2017] [Indexed: 02/04/2023] Open
Abstract
KEY POINTS Ionotropic glutamate receptor (iGluR) subunits are N-glycosylated at 4-12 sites, and Golgi processing produces mature receptors that contain high-mannose, hybrid and complex oligosaccharides. N-glycosylation is crucial for receptor biogenesis, influences receptor trafficking and provides a binding site for carbohydrate binding proteins. Glycan moieties are large, polar and occasionally charged, and they are attached at sites along iGluRs that position them for involvement in the structural changes underlying gating. Altering glycan content on kainate receptors (KARs), a subfamily of iGluRs, changes functional properties of the receptor, such as desensitization, recovery from desensitization and deactivation. We report the first observation that the charged trisaccharide HNK-1 is conjugated to native KARs, and we find that it substantially alters recombinant KAR functional properties. Our results show that the molecular composition of N-glycans can influence KAR biophysical properties, revealing a potential mechanism for fine-tuning the function of these receptors. ABSTRACT Ionotropic glutamate receptors (iGluRs) are tetrameric proteins with between four and 12 consensus sites for N-glycosylation on each subunit, which potentially allows for a high degree of structural diversity conferred by this post-translational modification. N-glycosylation is required for proper folding of iGluRs in mammalian cells, although the impact of oligosaccharides on the function of successfully folded receptors is less clear. Glycan moieties are large, polar, occasionally charged and mediate many protein-protein interactions throughout the nervous system. Additionally, they are attached at sites along iGluR subunits that position them for involvement in the structural changes underlying gating. In the present study, we show that altering glycan content on kainate receptors (KARs) changes the functional properties of the receptors in a manner dependent on the identity of both the modified sugars and the subunit composition of the receptor to which they are attached. We also report that native KARs carry the complex capping oligosaccharide human natural killer-1. Glycosylation patterns probably differ between cell types, across development or with pathologies, and thus our findings reveal a potential mechanism for context-specific fine-tuning of KAR function through diversity in glycan structure.
Collapse
Affiliation(s)
- Claire G Vernon
- Northwestern University, Feinberg School of Medicine, Dept. of Pharmacology, Chicago, Illinois, 60611
| | - Bryan A Copits
- Northwestern University, Feinberg School of Medicine, Dept. of Pharmacology, Chicago, Illinois, 60611
| | - Jacob R Stolz
- Northwestern University, Feinberg School of Medicine, Dept. of Pharmacology, Chicago, Illinois, 60611
| | - Yomayra F Guzmán
- Northwestern University, Feinberg School of Medicine, Dept. of Pharmacology, Chicago, Illinois, 60611
| | - Geoffrey T Swanson
- Northwestern University, Feinberg School of Medicine, Dept. of Pharmacology, Chicago, Illinois, 60611
| |
Collapse
|
58
|
Goetze J, Meirer F, Yarulina I, Gascon J, Kapteijn F, Ruiz-Martínez J, Weckhuysen BM. Insights into the Activity and Deactivation of the Methanol-to-Olefins Process over Different Small-Pore Zeolites As Studied with Operando UV-vis Spectroscopy. ACS Catal 2017; 7:4033-4046. [PMID: 28603658 PMCID: PMC5460665 DOI: 10.1021/acscatal.6b03677] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 04/23/2017] [Indexed: 11/28/2022]
Abstract
The nature and evolution of the hydrocarbon pool (HP) species during the Methanol-to-Olefins (MTO) process for three small-pore zeolite catalysts, with a different framework consisting of large cages interconnected by small eight-ring windows (CHA, DDR, and LEV) was studied at reaction temperatures between 350 and 450 °C using a combination of operando UV-vis spectroscopy and online gas chromatography. It was found that small differences in cage size, shape, and pore structure of the zeolite frameworks result in the generation of different hydrocarbon pool species. More specifically, it was found that the large cage of CHA results in the formation of a wide variety of hydrocarbon pool species, mostly alkylated benzenes and naphthalenes. In the DDR cage, 1-methylnaphthalene is preferentially formed, while the small LEV cage generally contains fewer hydrocarbon pool species. The nature and evolution of these hydrocarbon pool species was linked with the stage of the reaction using a multivariate analysis of the operando UV-vis spectra. In the 3-D pore network of CHA, the reaction temperature has only a minor effect on the performance of the MTO catalyst. However, for the 2-D pore networks of DDR and LEV, an increase in the applied reaction temperature resulted in a dramatic increase in catalytic activity. For all zeolites in this study, the role of the hydrocarbon species changes with reaction temperature. This effect is most clear in DDR, in which diamantane and 1-methylnaphthalene are deactivating species at a reaction temperature of 350 °C, whereas at higher temperatures diamantane formation is not observed and 1-methylnaphthalene is an active species. This results in a different amount and nature of coke species in the deactivated catalyst, depending on zeolite framework and reaction temperature.
Collapse
Affiliation(s)
- Joris Goetze
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Florian Meirer
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Irina Yarulina
- Catalysis
Engineering, Chemical Engineering Department, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Jorge Gascon
- Catalysis
Engineering, Chemical Engineering Department, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Freek Kapteijn
- Catalysis
Engineering, Chemical Engineering Department, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Javier Ruiz-Martínez
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Bert M. Weckhuysen
- Inorganic
Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| |
Collapse
|
59
|
Abstract
Fe/ZSM-5 nanosheet zeolites of varying thickness were synthesized with di- and tetraquaternary ammonium structure directing agents and extensively characterized for their textural, structural, and catalytic properties. Introduction of Fe3+ ions in the framework of nanosheet zeolites was slightly less effective than in bulk ZSM-5 zeolite. Steaming was necessary to activate all catalysts for N2O decomposition and benzene oxidation. The higher the Fe content, the higher the degree of Fe aggregation was after catalyst activation. The degree of Fe aggregation was lower when the crystal domain size of the zeolite or the Fe content was decreased. These two parameters had a substantial influence on the catalytic performance. Decreasing the number of Fe sites along the b-direction strongly suppressed secondary reactions of phenol and, accordingly, catalyst deactivation. This together with the absence of diffusional limitations in nanosheet zeolites explains the much higher phenol productivity obtainable with nanostructured Fe/ZSM-5. Steamed Fe/ZSM-5 zeolite nanosheet synthesized using C22-6-3·Br2 (domain size in b-direction ∼3 nm) and containing 0.24 wt % Fe exhibited the highest catalytic performance. During the first 24 h on stream, this catalyst produced 185 mmolphenol g-1. Calcination to remove the coke deposits completely restored the initial activity.
Collapse
Affiliation(s)
- Lingqian Meng
- Inorganic Materials Chemistry,
Schuit Institute of Catalysis, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | | | - Emiel J. M. Hensen
- Inorganic Materials Chemistry,
Schuit Institute of Catalysis, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| |
Collapse
|
60
|
Chen Y, Liu Z, Zhang J, Chen K, Yao L, Li X, Gong G, Wang J, Zhang Z. Precuneus degeneration in nondemented elderly individuals with APOE ɛ4: Evidence from structural and functional MRI analyses. Hum Brain Mapp 2017; 38:271-282. [PMID: 27593520 PMCID: PMC6866889 DOI: 10.1002/hbm.23359] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/16/2016] [Accepted: 08/16/2016] [Indexed: 11/06/2022] Open
Abstract
Neurodegenerative diseases such as Alzheimer's disease (AD) have been recognized to exhibit disease-specific brain vulnerability patterns. Apolipoprotein E (APOE) ɛ4 allele imparts a high genetic risk of developing AD. Whether the APOE ɛ4 allele damages the brain when cognitive functions are still intact is important to understand, especially for possible early detection and intervention. This study aimed to examine the selective degeneration pattern associated with the APOE ɛ4 allele in the brains of cognitively normal elderly subjects. We enrolled 35 cognitively healthy ɛ4 carriers and 40 non-carriers (53 to 81 years old) to evaluate group differences in cortical thickness and brain activation during a memory-encoding task. We also assessed the functional connectivity of the brain regions with both structural and functional damages. The results from the neuropsychological tests showed that the performances of ɛ4 carriers and non-carriers were comparable. Primarily, we found that the precuneus exhibited thinner cortical thickness and decreased deactivation during memory encoding. Furthermore, the connectivity analyses show that carriers exhibited damaged connectivity of the precuneus to several regions in the default mode network and the attention/executive control network. Our study reveals the degeneration pattern of the ɛ4 allele, which could be used as a potential biomarker for early detection for possible interventions and treatments. Hum Brain Mapp 38:271-282, 2017. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Yaojing Chen
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Zhen Liu
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Junying Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Kewei Chen
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
- Banner Alzheimer's InstitutePhoenixArizona
| | - Li Yao
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- Information Processing Lab, College of Information Science and Technology, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Xin Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Gaolang Gong
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Jun Wang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| | - Zhanjun Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain ResearchBeijing Normal UniversityBeijingPeople's Republic of China
- BABRI Centre, Beijing Normal UniversityBeijingPeople's Republic of China
| |
Collapse
|
61
|
Song Y, Manian M, Fowler W, Korey A, Kumar Banga A. Activated Carbon-Based System for the Disposal of Psychoactive Medications. Pharmaceutics 2016; 8:pharmaceutics8040031. [PMID: 27827989 PMCID: PMC5198015 DOI: 10.3390/pharmaceutics8040031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Revised: 10/06/2016] [Accepted: 11/01/2016] [Indexed: 11/16/2022] Open
Abstract
The misuse and improper disposal of psychoactive medications is a major safety and environmental concern. Hence, the proper disposal of these medications is critically important. A drug deactivation system which contains activated carbon offers a unique disposal method. In the present study, deactivation efficiency of this system was tested by using three model psychoactive drugs. HPLC validation was performed for each drug to ensure that the analytical method employed was suitable for its intended use. The method was found to be specific, accurate and precise for analyzing the drugs. The extent and rate of deactivation of the drugs was determined at several time points. After 28 days in the presence of activated carbon, the extent of leaching out of the drugs was evaluated. Deactivation started immediately after addition of the medications into the disposal pouches. Within 8 h, around 47%, 70% and 97% of diazepam, lorazepam and buprenorphine were adsorbed by the activated carbon, respectively. By the end of 28 days, over 99% of all drugs were deactivated. The desorption/leaching study showed that less than 1% of the active ingredients leached out from the activated carbon. Thus, this deactivation system can be successfully used for the disposal of psychoactive medications.
Collapse
Affiliation(s)
- Yang Song
- Department of Pharmaceutical Sciences, Mercer University, Atlanta, GA 30341, USA.
| | - Mahima Manian
- Department of Pharmaceutical Sciences, Mercer University, Atlanta, GA 30341, USA.
| | - William Fowler
- Verde Technologies, 12701 Whitewater Drive, Minnetonka, MN 55343, USA.
| | - Andrew Korey
- Verde Technologies, 12701 Whitewater Drive, Minnetonka, MN 55343, USA.
| | - Ajay Kumar Banga
- Department of Pharmaceutical Sciences, Mercer University, Atlanta, GA 30341, USA.
| |
Collapse
|
62
|
Mao X, Gu X, Lu W. GSG1L regulates the strength of AMPA receptor-mediated synaptic transmission but not AMPA receptor kinetics in hippocampal dentate granule neurons. J Neurophysiol 2016; 117:28-35. [PMID: 27707810 DOI: 10.1152/jn.00307.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 10/03/2016] [Indexed: 11/22/2022] Open
Abstract
GSG1L is an AMPA receptor (AMPAR) auxiliary subunit that regulates AMPAR trafficking and function in hippocampal CA1 pyramidal neurons. However, its physiological roles in other types of neurons remain to be characterized. Here, we investigated the role of GSG1L in hippocampal dentate granule cells and found that GSG1L is important for the regulation of synaptic strength but is not critical for the modulation of AMPAR deactivation and desensitization kinetics. These data demonstrate a neuronal type-specific role of GSG1L and suggest that physiological function of AMPAR auxiliary subunits may vary in different types of neurons. NEW & NOTEWORTHY GSG1L is a newly identified AMPA receptor (AMPAR) auxiliary subunit and plays a unique role in the regulation of AMPAR trafficking and function in hippocampal CA1 pyramidal neurons. However, its role in the regulation of AMPARs in hippocampal dentate granule cells remains to be characterized. The current work reveals that GSG1L regulates strength of AMPAR-mediated synaptic transmission but not the receptor kinetic properties in hippocampal dentate granule neurons.
Collapse
Affiliation(s)
- Xia Mao
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Xinglong Gu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Wei Lu
- Synapse and Neural Circuit Research Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| |
Collapse
|
63
|
Orton LD, Papasavvas CA, Rees A. Commissural Gain Control Enhances the Midbrain Representation of Sound Location. J Neurosci 2016; 36:4470-81. [PMID: 27098691 DOI: 10.1523/JNEUROSCI.3012-15.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 02/28/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Accurate localization of sound sources is essential for survival behavior in many species. The inferior colliculi (ICs) are the first point in the auditory pathway where cues used to locate sounds, ie, interaural time differences (ITDs), interaural level differences (ILDs), and pinna spectral cues, are all represented in the same location. These cues are first extracted separately on each side of the midline in brainstem nuclei that project to the ICs. Because of this segregation, each IC predominantly represents stimuli in the contralateral hemifield. We tested the hypothesis that commissural connections between the ICs mediate gain control that enhances sound localization acuity. We recorded IC neurons sensitive to either ITDs or ILDs in anesthetized guinea pig, before, during, and following recovery from deactivation of the contralateral IC by cryoloop cooling or microdialysis of procaine. During deactivation, responses were rescaled by divisive gain change and additive shifts, which reduced the dynamic range of ITD and ILD response functions and the ability of neurons to signal changes in sound location. These data suggest that each IC exerts multiplicative gain control and subtractive shifts over the other IC that enhances the neural representation of sound location. Furthermore, this gain control operates in a similar manner on both ITD- and ILD-sensitive neurons, suggesting a shared mechanism operates across localization cues. Our findings reveal a novel dependence of sound localization on commissural processing. SIGNIFICANCE STATEMENT Sound localization, a fundamental process in hearing, is dependent on bilateral computations in the brainstem. How this information is transmitted from the brainstem to the auditory cortex, through several stages of processing, without loss of signal fidelity, is not clear. We show that the ability of neurons in the auditory midbrain to encode azimuthal sound location is dependent on gain control mediated by the commissure of the inferior colliculi. This finding demonstrates that commissural processing between homologous auditory nuclei, on either side of the midline, enhances the precision of sound localization.
Collapse
|
64
|
Maillet D, Schacter DL. Default Network and Aging: Beyond the Task-Negative Perspective. Trends Cogn Sci 2016; 20:646-8. [PMID: 27282744 DOI: 10.1016/j.tics.2016.05.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/09/2016] [Accepted: 05/16/2016] [Indexed: 11/24/2022]
Abstract
During cognitive tasks requiring externally directed attention, activation in the default-network (DN) typically decreases below baseline levels ('deactivation'). Healthy aging is associated with reduced deactivation, which is usually attributed to a failure to suppress DN processes. Recent evidence instead suggests that older adults may be more reliant on DN than young adults when performing these tasks.
Collapse
|
65
|
Abstract
The goal of this research was to determine whether and how people deactivate prospective memory (PM) intentions after they have been completed. One view proposes that PM intentions can be deactivated after completion, such that they no longer come to mind and interfere with current tasks. Another view is that now irrelevant completed PM intentions exhibit persisting activation, and continue to be retrieved. In Experiment 1, participants were given a PM intention embedded within the ongoing task during Phase 1, after which participants were told either that the PM task had been completed or suspended until later. During Phase 2, participants were instructed to perform only the ongoing task and were periodically prompted to report their thoughts. Critically, the PM targets from Phase 1 reappeared in Phase 2. All of our measures, including thoughts reported about the PM task, supported the existence of persisting activation. In Experiment 2, we varied conditions that were expected to mitigate persisting activation. Despite our best attempts to promote deactivation, we found evidence for the persistence of spontaneous retrieval in all groups after intentions were completed. The theoretical and practical implications of this potential dark side to spontaneous retrieval are discussed.
Collapse
Affiliation(s)
- Francis T Anderson
- a Department of Psychological and Brain Sciences , Washington University , St. Louis , MO 63130 , USA
| | - Gilles O Einstein
- b Department of Psychology , Furman University , Greenville , SC , USA
| |
Collapse
|
66
|
Muller AM, Mérillat S, Jäncke L. Small Changes, But Huge Impact? The Right Anterior Insula's Loss of Connection Strength during the Transition of Old to Very Old Age. Front Aging Neurosci 2016; 8:86. [PMID: 27242508 PMCID: PMC4861722 DOI: 10.3389/fnagi.2016.00086] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 04/07/2016] [Indexed: 11/20/2022] Open
Abstract
A major contribution to our understanding of the aging brain comes either from studies comparing young with older adults or from studies investigating pathological aging and using the healthy aging older adults as control group. In consequence, we know relatively well, what distinguishes young from old brains or pathological aging from healthy but that does not mean that we really understand the structural and functional transformations characterizing the healthy aging brain. By analyzing task-free fMRI data from a large cross-sectional sample of 186 older adults (mean age = 70.4, 97 female), we aimed to elucidate age-related changes in the intrinsically active functional architecture of the brain in our study group covering an age range from 65 to 85 years. First, we conducted an intrinsic connectivity contrast analysis (ICC) in order to detect the brain regions whose degree of connectedness was significantly correlated with increasing age. Secondly, using connectivity analyses we investigated how the clusters highlighted by the ICC analysis functionally related to the other major resting-state networks. The most important finding was the right anterior insula's loss of connectedness in the older participants of the study group because of the region's causal role in the switching from the task-negative to the task-positive state of the brain. Further, we found a higher functional dedifferentiation of two of the brain's major intrinsic connectivity networks, the DMN, and the cingulo-opercular network, caused by a reduction of functional connection strength, especially in the frontal regions. At last, we showed that all these age-related changes have the potential to impair older adult's performance of working memory tasks.
Collapse
Affiliation(s)
- Angela M Muller
- University Research Priority Program, Dynamics of Healthy Aging, University of ZurichZurich, Switzerland; International Normal Aging and Plasticity Imaging Center, University of ZurichZurich, Switzerland
| | - Susan Mérillat
- University Research Priority Program, Dynamics of Healthy Aging, University of ZurichZurich, Switzerland; International Normal Aging and Plasticity Imaging Center, University of ZurichZurich, Switzerland
| | - Lutz Jäncke
- University Research Priority Program, Dynamics of Healthy Aging, University of ZurichZurich, Switzerland; International Normal Aging and Plasticity Imaging Center, University of ZurichZurich, Switzerland; Division Neuropsychology, Institute of Psychology, University of ZurichZurich, Switzerland; Center for Integrative Human Physiology, University of ZurichZurich, Switzerland
| |
Collapse
|
67
|
Johnston K, Lomber SG, Everling S. Unilateral deactivation of macaque dorsolateral prefrontal cortex induces biases in stimulus selection. J Neurophysiol 2016; 115:1468-76. [PMID: 26792881 DOI: 10.1152/jn.00563.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 01/11/2016] [Indexed: 11/22/2022] Open
Abstract
Following unilateral brain injury, patients are often unable to detect a stimulus presented in the contralesional field when another is presented simultaneously ipsilesionally. This phenomenon has been referred to as extinction and has been conceptualized as a deficit in selective attention. Although most commonly observed following damage to posterior parietal areas, extinction has been observed following lesions of prefrontal cortex (PFC) in both humans and nonhuman primates. To date, most studies in nonhuman primates have examined lesions of multiple PFC subregions, including the frontal eye fields (FEF). Theoretical accounts of attentional disturbances from human patients, however, also implicate other PFC areas, including the middle frontal gyrus. Here, we investigated the effects of deactivating PFC areas anterior to the FEF on stimulus selection using a free-choice task. Macaque monkeys were presented with two peripheral stimuli appearing either simultaneously, or at varying stimulus onset asynchronies, and their performance was evaluated during unilateral cryogenic deactivation of part of dorsolateral prefrontal cortex or the cortex lining the caudal principal sulcus, the likely homologue of the human middle frontal gyrus. A decreased proportion of saccades was made to stimuli presented in the hemifield contralateral to the deactivated PFC. We also observed increases in reaction times to contralateral stimuli and decreases for stimuli presented in the hemifield ipsilateral to the deactivated hemisphere. In both cases, these results were greatest when both PFC subregions were deactivated. These findings demonstrate that selection biases result from PFC deactivation and support a role of dorsolateral prefrontal subregions anterior to FEF in stimulus selection.
Collapse
Affiliation(s)
- Kevin Johnston
- Brain and Mind Institute, London, Ontario, Canada; Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada; Department of Psychology, University of Western Ontario, London, Ontario, Canada; Graduate Program in Neuroscience, University of Western Ontario, London, Ontario, Canada; and
| | - Stephen G Lomber
- Brain and Mind Institute, London, Ontario, Canada; Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada; Department of Psychology, University of Western Ontario, London, Ontario, Canada; Graduate Program in Neuroscience, University of Western Ontario, London, Ontario, Canada; and
| | - Stefan Everling
- Brain and Mind Institute, London, Ontario, Canada; Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada; Department of Psychology, University of Western Ontario, London, Ontario, Canada; Graduate Program in Neuroscience, University of Western Ontario, London, Ontario, Canada; and Robarts Research Institute, London, Ontario, Canada
| |
Collapse
|
68
|
Farrow P, Khodosevich K, Sapir Y, Schulmann A, Aslam M, Stern-Bach Y, Monyer H, von Engelhardt J. Auxiliary subunits of the CKAMP family differentially modulate AMPA receptor properties. eLife 2015; 4:e09693. [PMID: 26623514 PMCID: PMC4733035 DOI: 10.7554/elife.09693] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 11/30/2015] [Indexed: 01/01/2023] Open
Abstract
AMPA receptor (AMPAR) function is modulated by auxiliary subunits. Here, we report on three AMPAR interacting proteins—namely CKAMP39, CKAMP52 and CKAMP59—that, together with the previously characterized CKAMP44, constitute a novel family of auxiliary subunits distinct from other families of AMPAR interacting proteins. The new members of the CKAMP family display distinct regional and developmental expression profiles in the mouse brain. Notably, despite their structural similarities they exert diverse modulation on AMPAR gating by influencing deactivation, desensitization and recovery from desensitization, as well as glutamate and cyclothiazide potency to AMPARs. This study indicates that AMPAR function is very precisely controlled by the cell-type specific expression of the CKAMP family members. The brain processes and transmits information through large networks of cells called neurons. A neuron can pass the information it receives to other neurons by releasing chemicals called neurotransmitters across junctions known as synapses. These chemicals bind to receptor proteins on the surface of the neighboring neuron, which triggers changes that affect the activity of this neuron. Glutamate is the most commonly used neurotransmitter in the brain and binds to receptor proteins called AMPA receptors. If a neuron frequently sends glutamate across a particular synapse, the number of AMPA receptors in the second neuron will increase in response. This makes signaling across the synapse easier – a process known as synaptic strengthening. The ability to change the strength of synapses is important for learning and memory. Proteins called auxiliary subunits also bind to AMPA receptors and regulate their properties, and hence also affect the strength of the synapse. For instance, some auxiliary subunits increase the number of AMPA receptors at the synapse, while others have an effect on how the receptor protein works. In 2010, researchers identified a new auxiliary protein called CKAMP44 that modifies AMPA receptor activity. Now, Farrow, Khodosevich, Sapir, Schulmann et al. – including some of the researchers involved in the 2010 study – have identified three other auxiliary proteins that are similar to CKAMP44. Collectively, these four proteins are termed the CKAMP family. The sequences of all four proteins were found to share many common features, especially in the regions that bind to the AMPA receptors. Like CKAMP44, the new members of the CKAMP family are only present in the brain, although each protein is produced in different brain regions. Further investigation revealed that each member of the CKAMP family affects the AMPA receptor channels in a different way. Taken together, Farrow et al.’s results suggest that the different CKAMP family members allow the activity of the AMPA receptors to be precisely controlled. The next challenge is to understand in more detail how each CKAMP family member influences how AMPA receptors work.
Collapse
Affiliation(s)
- Paul Farrow
- Synaptic Signalling and Neurodegeneration, German Cancer Research Center, Heidelberg, Germany.,Synaptic Signalling and Neurodegeneration, German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Konstantin Khodosevich
- Department of Clinical Neurobiology, Medical Faculty of Heidelberg University, Heidelberg, Germany.,German Cancer Research Center, Heidelberg, Germany
| | - Yechiam Sapir
- Department of Biochemistry and Molecular Biology, Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Anton Schulmann
- Department of Clinical Neurobiology, Medical Faculty of Heidelberg University, Heidelberg, Germany.,German Cancer Research Center, Heidelberg, Germany
| | - Muhammad Aslam
- Synaptic Signalling and Neurodegeneration, German Cancer Research Center, Heidelberg, Germany.,Synaptic Signalling and Neurodegeneration, German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Yael Stern-Bach
- Department of Biochemistry and Molecular Biology, Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Hannah Monyer
- Department of Clinical Neurobiology, Medical Faculty of Heidelberg University, Heidelberg, Germany
| | - Jakob von Engelhardt
- Synaptic Signalling and Neurodegeneration, German Cancer Research Center, Heidelberg, Germany.,Synaptic Signalling and Neurodegeneration, German Center for Neurodegenerative Diseases, Bonn, Germany
| |
Collapse
|
69
|
Abstract
Much research has been carried out in the last decade to convert bio-based feedstock into fuels and chemicals. Most of the research focuses on developing active and selective catalysts, with much less attention devoted to their long-term stability. This Review considers the main challenges in long-term catalyst stability, discusses some fundamentals, and presents options for their mitigation. Three main challenges are discussed: catalyst fouling, catalyst poisoning, and catalyst destruction. Fouling is generally related to the deposition of insoluble components present in the feed or formed by degradation of the feed or intermediates. Poisoning is related to the deposition of electropositive contaminants (e.g. alkali and alkaline earth metals) on acid sites or of electronegative contaminants (e.g. N and S) at hydrogenation sites. Catalyst destruction results from the thermodynamic instability of most oxidic supports, solid acids/bases, and hydrogenation functions under hydrothermal conditions.
Collapse
Affiliation(s)
- Jean-Paul Lange
- Shell Research and Technology Center, Grasweg 10, HW 1031, Amsterdam (The Netherlands).
| |
Collapse
|
70
|
Brown CA, Hakun JG, Zhu Z, Johnson NF, Gold BT. White matter microstructure contributes to age-related declines in task-induced deactivation of the default mode network. Front Aging Neurosci 2015; 7:194. [PMID: 26500549 PMCID: PMC4598480 DOI: 10.3389/fnagi.2015.00194] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 09/25/2015] [Indexed: 12/24/2022] Open
Abstract
Task-induced deactivations within the brain's default mode network (DMN) are thought to reflect suppression of endogenous thought processes to support exogenous goal-directed task processes. Older adults are known to show reductions in deactivation of the DMN compared to younger adults. However, little is understood about the mechanisms contributing to functional dysregulation of the DMN in aging. Here, we explored the relationships between functional modulation of the DMN and age, task performance and white matter (WM) microstructure. Participants were 117 adults ranging from 25 to 83 years old who completed an fMRI task switching paradigm, including easy (single) and difficult (mixed) conditions, and underwent diffusion tensor imaging (DTI). The fMRI results revealed an age by condition interaction (β = -0.13, t = -3.16, p = 0.002) such that increasing age affected deactivation magnitude during the mixed condition (β = -0.29, t = -3.24 p = 0.002) but not the single condition (p = 0.58). Additionally, there was a WM by condition interaction (β = 0.10, t = 2.33, p = 0.02) such that decreasing WM microstructure affected deactivation magnitude during the mixed condition (β = 0.30, t = 3.42 p = 0.001) but not the single condition (p = 0.17). Critically, mediation analyses indicated that age-related reductions in WM microstructure accounted for the relationship between age and DMN deactivation in the more difficult mixed condition. These findings suggest that age-related declines in anatomical connectivity between DMN regions contribute to functional dysregulation within the DMN in older adults.
Collapse
Affiliation(s)
- Christopher A Brown
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Jonathan G Hakun
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Zude Zhu
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Nathan F Johnson
- Department of Rehabilitation Sciences, University of Kentucky Lexington, KY, USA
| | - Brian T Gold
- Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, Lexington, KY, USA ; Sanders-Brown Center on Aging, University of Kentucky Lexington, KY, USA ; Magnetic Resonance and Imaging and Spectroscopy Center, University of Kentucky Lexington, KY, USA
| |
Collapse
|
71
|
Herwadkar A, Singh N, Anderson C, Korey A, Fowler W, Banga AK. Development of Disposal Systems for Deactivation of Unused/Residual/Expired Medications. Pharm Res 2015; 33:110-24. [PMID: 26264512 DOI: 10.1007/s11095-015-1768-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 08/04/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE The objective of this work was to identify deactivation agents and develop a disposal system for unused/ residual/ expired medications. METHODS Deactivation agents screened included oxidizing agent-sodium percarbonate, hydrolysis agent- sodium carbonate and adsorbants- zeolite and activated carbon. Deactivation studies using these agents were performed on four active pharmaceutical agents (APIs) including ketoprofen, dexamethasone sodium phosphate, metformin hydrochloride and amoxicillin trihydrate. Disposal systems were also designed for deactivation studies on dexamethasone pills, amoxicillin trihydrate capsules and fentanyl transdermal patches (Duragesic®). Briefly, APIs/ dosage forms were allowed to be in close contact with deactivation agents for a specified period of time and percentage decrease in the amount of API from the initial amount was measured. RESULTS Sodium percarbonate and sodium carbonate were only successful in deactivation of amoxicillin trihydrate API. Adsorption agents resulted in more universal deactivation with activated carbon resulting in efficient deactivation of most APIs and all dosage forms tested. Also adsorption of oral dosage medications on activated carbons was maintained even on dilution and shaking and no desorption was observed. CONCLUSIONS Deactivation systems containing activated carbon are promising for efficient, safe and environment friendly disposal of unused/residual/expired medications.
Collapse
Affiliation(s)
- Anushree Herwadkar
- Department of Pharmaceutical Sciences, College of Pharmacy, Mercer University, Atlanta, Georgia, 30341, USA
| | - Neha Singh
- Department of Pharmaceutical Sciences, College of Pharmacy, Mercer University, Atlanta, Georgia, 30341, USA
| | - Carter Anderson
- Verde Environmental Technologies Inc., Burnsville, Minnesota, 55337, USA
| | - Andrew Korey
- Verde Environmental Technologies Inc., Burnsville, Minnesota, 55337, USA
| | - William Fowler
- Verde Environmental Technologies Inc., Burnsville, Minnesota, 55337, USA
| | - Ajay K Banga
- Department of Pharmaceutical Sciences, College of Pharmacy, Mercer University, Atlanta, Georgia, 30341, USA. .,Department of Pharmaceutical Sciences, College of Pharmacy, Mercer University, 3001 Mercer University , Atlanta, Georgia, 30341, USA.
| |
Collapse
|
72
|
Elvemo NA, Landrø NI, Borchgrevink PC, Håberg AK. A particular effect of sleep, but not pain or depression, on the blood-oxygen-level dependent response during working memory tasks in patients with chronic pain. J Pain Res 2015; 8:335-46. [PMID: 26185465 PMCID: PMC4500611 DOI: 10.2147/jpr.s83486] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Patients with chronic pain (CP) are often reported to have deficits in working memory. Pain impairs working memory, but so do depression and sleep problems, which are also common in CP. Depression has been linked to changes in brain activity in CP during working memory tasks, but the effect of sleep problems on working memory performance and brain activity remains to be investigated. Methods Fifteen CP patients and 17 age-, sex-, and education-matched controls underwent blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging at 3T while performing block design 0-back, 2-back, and paced visual serial addition test paradigms. Subjects also reported their level of pain (Brief Pain Inventory), depression (Beck Depression Inventory II), and sleep problems (Pittsburgh Sleep Quality Index) and were tested outside the scanner with neuropsychological tests of working memory. Results The CP group reported significantly higher levels of pain, depression, and sleep problems. No significant performance difference was found on the neuropsychological tests in or outside the scanner between the two groups. There were no correlations between level of pain, depression, and sleep problems or between these and the neuropsychological test scores. CP patients exhibited significantly less brain activation and deactivation than controls in parietal and frontal lobes, which are the brain areas that normally show activation and deactivation during working memory tasks. Sleep problems independently and significantly modulated the BOLD response to the complex working memory tasks and were associated with decreased brain activation in task-positive regions and decreased deactivation in the default mode network in the CP group compared to the control group. The pain and depression scores covaried with working memory activation. Discussion Sleep problems in CP patients had a significant impact on the BOLD response during working memory tasks, independent of pain level and depression, even when performance was shown not to be significantly affected.
Collapse
Affiliation(s)
- Nicolas A Elvemo
- Department of Neuroscience, Medical Faculty, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Nils I Landrø
- Clinical Neuroscience Research Group, Department of Psychology, University of Oslo, Oslo, Norway ; Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Petter C Borchgrevink
- Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; National Norwegian Advisory Unit for Complex Disorders, St Olav University Hospital, Trondheim, Norway
| | - Asta K Håberg
- Department of Neuroscience, Medical Faculty, Norwegian University of Science and Technology (NTNU), Trondheim, Norway ; Department of Medical Imaging, St Olav University Hospital, Trondheim, Norway
| |
Collapse
|
73
|
Osterbur ML, Zheng R, Marion R, Walsh C, McDonald TV. An Interdomain KCNH2 Mutation Produces an Intermediate Long QT Syndrome. Hum Mutat 2015; 36:764-73. [PMID: 25914329 DOI: 10.1002/humu.22805] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 04/08/2015] [Indexed: 12/19/2022]
Abstract
Hereditary long QT syndrome is caused by deleterious mutation in one of several genetic loci, including locus LQT2 that contains the KCNH2 gene (or hERG, human ether-a-go-go related gene), causing faulty cardiac repolarization. Here, we describe and characterize a novel mutation, p.Asp219Val in the hERG channel, identified in an 11-year-old male with syncope and prolonged QT interval. Genetic sequencing showed a nonsynonymous variation in KCNH2 (c.656A>T: amino acid p.Asp219Val). p.Asp219Val resides in a region of the channel predicted to be unstructured and flexible, located between the PAS (Per-Arnt-Sim) domain and its interaction sites in the transmembrane domain. The p.Asp219Val hERG channel produced K(+) current that activated with modest changes in voltage dependence. Mutant channels were also slower to inactivate, recovered from inactivation more readily and demonstrated a significantly accelerated deactivation rate compared with the slow deactivation of wild-type channels. The intermediate nature of the biophysical perturbation is consistent with the degree of severity in the clinical phenotype. The findings of this study demonstrate a previously unknown role of the proximal N-terminus in deactivation and support the hypothesis that the proximal N-terminal domain is essential in maintaining slow hERG deactivation.
Collapse
Affiliation(s)
- Marika L Osterbur
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY
| | - Renjian Zheng
- Wilf Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY
| | - Robert Marion
- Department of Pediatrics, Division of Genetics, Children's Hospital at Montefiore, Bronx, NY
| | - Christine Walsh
- Department of Pediatrics, Division of Cardiology, Children's Hospital at Montefiore, Bronx, NY
| | - Thomas V McDonald
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY.,Wilf Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY.,Department of Medicine, Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY
| |
Collapse
|
74
|
Liu K, Jounaidi Y, Forman SA, Feng HJ. Etomidate uniquely modulates the desensitization of recombinant α1β3δ GABA(A) receptors. Neuroscience 2015; 300:307-13. [PMID: 26028470 DOI: 10.1016/j.neuroscience.2015.05.051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 05/18/2015] [Accepted: 05/20/2015] [Indexed: 11/24/2022]
Abstract
Central GABA(A) receptors mediate GABAergic phasic and tonic inhibition. While synaptic αβγ GABA(A) receptors primarily mediate phasic inhibition, extrasynaptic αβδ receptors play an important role in mediating tonic inhibition. Etomidate is a general anesthetic that produces its effects by enhancing GABA(A) receptor activity. We previously showed that etomidate modulates the gating of oocyte-expressed αβγ and αβδ receptors with similar overall allosteric impact, but different pharmacological patterns. In αβγ receptors, etomidate enhances apparent GABA sensitivity (reduces GABA EC50), modestly increases maximal GABA efficacy, and slows current deactivation without affecting desensitization (Zhong et al., 2008). In αβδ receptors characterized by low GABA efficacy, etomidate dramatically increases responses to both low and maximal GABA. The effects of etomidate on desensitization and deactivation of αβδ receptors are unknown. To investigate the kinetic effects of etomidate on α1β3δ receptors of defined subunit arrangement, we expressed concatenated trimer (β3-α1-δ) and dimer (β3-α1) GABA(A) receptor subunit assemblies in human embryonic kidney (HEK)293T cells and recorded whole-cell voltage-clamp currents during rapid external solution exchanges. As expected, etomidate substantially increased maximal GABA-induced currents and prolonged deactivation. Moreover, desensitization was significantly decreased by etomidate. During prolonged GABA applications, etomidate enhanced steady-state currents more than peak currents. Thus, etomidate enhances tonic GABAergic inhibition through extrasynaptic αβδ receptors by both augmenting gating and reducing desensitization.
Collapse
Affiliation(s)
- K Liu
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Anesthesia, China-Japan Friendship Hospital, Beijing, China
| | - Y Jounaidi
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - S A Forman
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
| | - H-J Feng
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
| |
Collapse
|
75
|
Inagaki S, Sato K, Hayashi S, Tatami J, Kubota Y, Wakihara T. Mechanochemical approach for selective deactivation of external surface acidity of ZSM-5 zeolite catalyst. ACS Appl Mater Interfaces 2015; 7:4488-4493. [PMID: 25654542 DOI: 10.1021/am507982n] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The acid sites associated with the external surface of zeolite particles are responsible for undesirable consecutive reactions, such as isomerization, alkylation, and oligomerization, resulting in a lower selectivity to a target product; therefore, the selective modification (deactivation) of the external surface of zeolite particles has been an important issue in zeolite science. Here, a new method for surface deactivation of zeolite catalyst was tested via a mechanochemical approach using powder composer. Postsynthetic mechanochemical treatment of ZSM-5 zeolite causes a selective deactivation of catalytically active sites existing only on the external surface, as a potentially useful catalyst for highly selective production of p-xylene.
Collapse
Affiliation(s)
- Satoshi Inagaki
- Division of Materials Science and Chemical Engineering, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
| | | | | | | | | | | |
Collapse
|
76
|
Guo K, Wang YP, Zhou ZW, Jiang YB, Li W, Chen XM, Li YG. Impact of phosphomimetic and non-phosphorylatable mutations of phospholemman on L-type calcium channels gating in HEK 293T cells. J Cell Mol Med 2015; 19:642-50. [PMID: 25656605 PMCID: PMC4369820 DOI: 10.1111/jcmm.12484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Accepted: 10/10/2014] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Phospholemman (PLM) is an important phosphorylation substrate for protein kinases A and C in the heart. Until now, the association between PLM phosphorylation status and L-type calcium channels (LTCCs) gating has not been fully understood. We investigated the kinetics of LTCCs in HEK 293T cells expressing phosphomimetic or nonphosphorylatable PLM mutants. METHODS The LTCCs gating was measured in HEK 293T cells transfected with LTCC and wild-type (WT) PLM, phosphomimetic or nonphosphorylatable PLM mutants: 6263AA, 6869AA, AAAA, 6263DD, 6869DD or DDDD. RESULTS WT PLM significantly slowed LTCCs activation and deactivation while enhanced voltage-dependent inactivation (VDI). PLM mutants 6869DD and DDDD significantly increased the peak of the currents. 6263DD accelerated channel activation, while 6263AA slowed it more than WT PLM. 6869DD significantly enhanced PLM-induced increase of VDI. AAAA slowed the channel activation more than 6263AA, and DDDD accelerated the channel VDI more than 6869DD. CONCLUSIONS Our results demonstrate that phosphomimetic PLM could stimulate LTCCs and alter their dynamics, while PLM nonphosphorylatable mutant produced the opposite effects.
Collapse
Affiliation(s)
- Kai Guo
- Department of Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | | | | | | | | | | | | |
Collapse
|
77
|
Orton LD, Rees A. Intercollicular commissural connections refine the representation of sound frequency and level in the auditory midbrain. eLife 2014; 3. [PMID: 25406067 PMCID: PMC4235006 DOI: 10.7554/elife.03764] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 10/15/2014] [Indexed: 11/13/2022] Open
Abstract
Connections unifying hemispheric sensory representations of vision and touch occur in cortex, but for hearing, commissural connections earlier in the pathway may be important. The brainstem auditory pathways course bilaterally to the inferior colliculi (ICs). Each IC represents one side of auditory space but they are interconnected by a commissure. By deactivating one IC in guinea pig with cooling or microdialysis of procaine, and recording neural activity to sound in the other, we found that commissural input influences fundamental aspects of auditory processing. The areas of nonV frequency response areas (FRAs) were modulated, but the areas of almost all V-shaped FRAs were not. The supra-threshold sensitivity of rate level functions decreased during deactivation and the ability to signal changes in sound level was decremented. This commissural enhancement suggests the ICs should be viewed as a single entity in which the representation of sound in each is governed by the other. DOI:http://dx.doi.org/10.7554/eLife.03764.001 The bilateral arrangement of our eyes and ears enables us to receive information from both sides of our body. This information is conveyed via various sensory pathways that take different routes through the brain to culminate in the cerebral hemispheres. The information is then processed in the brain's outer layer, which is called the cortex. In the visual system, information from both eyes is kept separate until it reaches the cortex. A similar arrangement exists for touch. However, hearing is unusual among our senses in that sounds undergo much more processing in the brainstem, which is located at the base of the brain, than other types of stimuli. Orton and Rees now show that, in contrast to vision and touch, information about sounds occurring to our left or right is refined by interactions between the two sides of the midbrain. To test for sideward interactions between the two limbs of the auditory pathway, electrodes were lowered into the brains of anesthetized guinea pigs so that neuronal responses to tones could be recorded. The electrodes were placed in the region of the midbrain that contains two structures called the inferior colliculi (meaning ‘lower hills’ in Latin). Each inferior colliculus predominantly receives inputs from the opposite ear. However, recordings made in one colliculus when the other was deactivated revealed that one colliculus normally alters the response of the other. This shows that there is an important sideward interaction between the two halves of the auditory pathway in the midbrain that refines how fundamental aspects of sound, such as its frequency and intensity, are processed. This represents a marked departure from our previous understanding of auditory processing in the mammalian brain, and opens up new lines of investigation into the functioning of the auditory system in health and disease. DOI:http://dx.doi.org/10.7554/eLife.03764.002
Collapse
Affiliation(s)
- Llwyd David Orton
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Adrian Rees
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| |
Collapse
|
78
|
Gordon BA, Tse CY, Gratton G, Fabiani M. Spread of activation and deactivation in the brain: does age matter? Front Aging Neurosci 2014; 6:288. [PMID: 25360115 PMCID: PMC4199281 DOI: 10.3389/fnagi.2014.00288] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 09/29/2014] [Indexed: 11/30/2022] Open
Abstract
Cross-sectional aging functional MRI results are sometimes difficult to interpret, as standard measures of activation and deactivation may confound variations in signal amplitude and spread, which however, may be differentially affected by age-related changes in various anatomical and physiological factors. To disentangle these two types of measures, here we propose a novel method to obtain independent estimates of the peak amplitude and spread of the BOLD signal in areas activated (task-positive) and deactivated (task-negative) by a Sternberg task, in 14 younger and 28 older adults. The peak measures indicated that, compared to younger adults, older adults had increased activation of the task-positive network, but similar levels of deactivation in the task-negative network. Measures of signal spread revealed that older adults had an increased spread of activation in task-positive areas, but a starkly reduced spread of deactivation in task-negative areas. These effects were consistent across regions within each network. Further, there was greater variability in the anatomical localization of peak points in older adults, leading to reduced cross-subject overlap. These results reveal factors that may confound the interpretation of studies of aging. Additionally, spread measures may be linked to local connectivity phenomena and could be particularly useful to analyze age-related deactivation patterns, complementing the results obtained with standard peak and region of interest analyses.
Collapse
Affiliation(s)
- Brian A. Gordon
- Department of Radiology, Washington University in St. LouisSt. Louis, MO, USA
| | - Chun-Yu Tse
- Department of Psychology, Chinese University of Hong KongShatin, Hong Kong
| | - Gabriele Gratton
- Department of Psychology and Beckman Institute, University of IllinoisUrbana, IL, USA
| | - Monica Fabiani
- Department of Psychology and Beckman Institute, University of IllinoisUrbana, IL, USA
| |
Collapse
|
79
|
Kraynik SE, Casarett DJ, Corcoran AM. Implantable cardioverter defibrillator deactivation: a hospice quality improvement initiative. J Pain Symptom Manage 2014; 48:471-7. [PMID: 24480530 DOI: 10.1016/j.jpainsymman.2013.09.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 09/24/2013] [Accepted: 10/04/2013] [Indexed: 11/16/2022]
Abstract
BACKGROUND Dying patients whose implantable cardioverter defibrillators (ICDs) continue to deliver shocks may experience significant pain, and the National Quality Forum has endorsed routine deactivation of ICDs when patients near the end of life. The overarching goal of this quality improvement project was to increase rates of ICD deactivation among hospice patients. MEASURES ICD deactivation rates pre- vs. post-intervention; and clinicians' knowledge and confidence regarding ICD management. INTERVENTION A multifaceted intervention included clinical tools, education, and standardized documentation templates in the electronic medical record. OUTCOMES The proportion of patients whose ICD was deactivated increased after the intervention (pre- vs. post-intervention: 39/68, 57% vs. 47/56, 84%; odds ratio 3.88; 95% confidence interval 1.54-10.37; P = 0.001). Clinicians' knowledge and confidence regarding ICD management improved (pre- vs. post-intervention median questionnaire scores: 5 vs. 9 on a scale of 0 to 10; Wilcoxon signed-rank test Z = -5.01; P < 0.001). CONCLUSIONS/LESSONS LEARNED A multifaceted intervention can increase rates of ICD deactivation among patients near the end of life.
Collapse
Affiliation(s)
- Sally E Kraynik
- University of Pennsylvania School of Nursing, Philadelphia, Pennsylvania, USA.
| | | | - Amy M Corcoran
- Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| |
Collapse
|
80
|
Liu PW, Bean BP. Kv2 channel regulation of action potential repolarization and firing patterns in superior cervical ganglion neurons and hippocampal CA1 pyramidal neurons. J Neurosci 2014; 34:4991-5002. [PMID: 24695716 DOI: 10.1523/JNEUROSCI.1925-13.2014] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Kv2 family "delayed-rectifier" potassium channels are widely expressed in mammalian neurons. Kv2 channels activate relatively slowly and their contribution to action potential repolarization under physiological conditions has been unclear. We explored the function of Kv2 channels using a Kv2-selective blocker, Guangxitoxin-1E (GxTX-1E). Using acutely isolated neurons, mixed voltage-clamp and current-clamp experiments were done at 37°C to study the physiological kinetics of channel gating and action potentials. In both rat superior cervical ganglion (SCG) neurons and mouse hippocampal CA1 pyramidal neurons, 100 nm GxTX-1E produced near-saturating block of a component of current typically constituting ∼60-80% of the total delayed-rectifier current. GxTX-1E also reduced A-type potassium current (IA), but much more weakly. In SCG neurons, 100 nm GxTX-1E broadened spikes and voltage clamp experiments using action potential waveforms showed that Kv2 channels carry ∼55% of the total outward current during action potential repolarization despite activating relatively late in the spike. In CA1 neurons, 100 nm GxTX-1E broadened spikes evoked from -70 mV, but not -80 mV, likely reflecting a greater role of Kv2 when other potassium channels were partially inactivated at -70 mV. In both CA1 and SCG neurons, inhibition of Kv2 channels produced dramatic depolarization of interspike voltages during repetitive firing. In CA1 neurons and some SCG neurons, this was associated with increased initial firing frequency. In all neurons, inhibition of Kv2 channels depressed maintained firing because neurons entered depolarization block more readily. Therefore, Kv2 channels can either decrease or increase neuronal excitability depending on the time scale of excitation.
Collapse
|
81
|
Tüdös Z, Hok P, Hrdina L, Hluštík P. Modality effects in paced serial addition task: differential responses to auditory and visual stimuli. Neuroscience 2014; 272:10-20. [PMID: 24802163 DOI: 10.1016/j.neuroscience.2014.04.057] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 04/24/2014] [Accepted: 04/26/2014] [Indexed: 12/22/2022]
Abstract
Paced Auditory Serial-Addition Task (PASAT) is a complex task commonly used to examine patients with diffuse brain damage. A visual version of the neuropsychological test (Paced Visual Serial-Addition Task, PVSAT) has also been introduced to clinical practice, and both versions were adapted to be used in neuroimaging, namely functional magnetic resonance imaging (fMRI). The aim of our work was direct comparison of auditory and visual versions of the paced serial addition test (PASAT/PVSAT) in a within-subject and within-session study and description of the commonalities and differences in both activated and deactivated brain regions. Twenty young adult right-handed healthy volunteers participated in the study and underwent whole-brain fMRI examination during PASAT and PVSAT performance. Higher-level statistical analysis was performed to generate group mean activation and deactivation maps for both tasks, their conjunctions and differences across modalities. In PASAT/PVSAT activation conjunction analysis, we confirmed the existence of a modality-independent neural network similar to working memory tasks and to previous PASAT or PVSAT studies. In PASAT/PVSAT deactivation conjunction analysis, we observed a rather symmetrical extensive pattern of deactivated regions, overlapping the default mode network. Significant differences between PASAT and PVSAT were found in the right frontal eye field (FEF) and bilaterally in the striate and extrastriate cortices. Activation in one task and deactivation in the other jointly contributed to significant differences in all occipital and occipitotemporal regions. Both tasks activated right FEF, but activation during PASAT was significantly stronger than during PVSAT. Between-modality differences should be considered when preparing and interpreting neuroimaging experiments.
Collapse
Affiliation(s)
- Z Tüdös
- Department of Radiology, Faculty of Medicine and Dentistry, Palacky University and University Hospital, I.P. Pavlova 6, Olomouc, Czech Republic.
| | - P Hok
- Department of Neurology, Faculty of Medicine and Dentistry, Palacky University and University Hospital, I.P. Pavlova 6, Olomouc, Czech Republic.
| | - L Hrdina
- Department of Radiology, Faculty of Medicine and Dentistry, Palacky University and University Hospital, I.P. Pavlova 6, Olomouc, Czech Republic.
| | - P Hluštík
- Department of Radiology, Faculty of Medicine and Dentistry, Palacky University and University Hospital, I.P. Pavlova 6, Olomouc, Czech Republic; Department of Neurology, Faculty of Medicine and Dentistry, Palacky University and University Hospital, I.P. Pavlova 6, Olomouc, Czech Republic.
| |
Collapse
|
82
|
Soares JM, Sampaio A, Marques P, Ferreira LM, Santos NC, Marques F, Palha JA, Cerqueira JJ, Sousa N. Plasticity of resting state brain networks in recovery from stress. Front Hum Neurosci 2013; 7:919. [PMID: 24416009 PMCID: PMC3873630 DOI: 10.3389/fnhum.2013.00919] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 12/15/2013] [Indexed: 01/19/2023] Open
Abstract
Chronic stress has been widely reported to have deleterious impact in multiple biological systems. Specifically, structural and functional remodeling of several brain regions following prolonged stress exposure have been described; importantly, some of these changes are eventually reversible. Recently, we showed the impact of stress on resting state networks (RSNs), but nothing is known about the plasticity of RSNs after recovery from stress. Herein, we examined the “plasticity” of RSNs, both at functional and structural levels, by comparing the same individuals before and after recovery from the exposure to chronic stress; results were also contrasted with a control group. Here we show that the stressed individuals after recovery displayed a decreased resting functional connectivity in the default mode network (DMN), ventral attention network (VAN), and sensorimotor network (SMN) when compared to themselves immediately after stress; however, this functional plastic recovery was only partial as when compared with the control group, as there were still areas of increased connectivity in dorsal attention network (DAN), SMN and primary visual network (VN) in participants recovered from stress. Data also shows that participants after recovery from stress displayed increased deactivations in DMN, SMN, and auditory network (AN), to levels similar to those of controls, showing a normalization of the deactivation pattern in RSNs after recovery from stress. In contrast, structural changes (volumetry) of the brain areas involving these networks are absent after the recovery period. These results reveal plastic phenomena in specific RSNs and a functional remodeling of the activation-deactivation pattern following recovery from chronic-stress, which is not accompanied by significant structural plasticity.
Collapse
Affiliation(s)
- José M Soares
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - Adriana Sampaio
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; Neuropsychophysiology Lab, CIPsi, School of Psychology, University of Minho Braga, Portugal
| | - Paulo Marques
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - Luís M Ferreira
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - Nadine C Santos
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - Fernanda Marques
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - Joana A Palha
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - João J Cerqueira
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho Braga, Portugal ; ICVS/3B's - PT Government Associate Laboratory Braga/Guimarães, Portugal ; Clinical Academic Center Braga, Portugal
| |
Collapse
|
83
|
Fluur C, Bolse K, Strömberg A, Thylén I. Spouses' reflections on implantable cardioverter defibrillator treatment with focus on the future and the end-of-life: a qualitative content analysis. J Adv Nurs 2013; 70:1758-69. [PMID: 24321029 DOI: 10.1111/jan.12330] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2013] [Indexed: 12/01/2022]
Abstract
AIM To explore future reflections of spouses living with an implantable cardioverter defibrillator recipient with focus on the end-of-life phase in an anticipated palliative phase. BACKGROUND A history of or risk for life-threatening arrhythmias may require an implantable cardioverter defibrillator. Despite the life-saving capacity of the device, eventually life will come to an end. As discussion about preferences of shock therapy at end-of-life phase seldom takes place in advance, the implantable cardioverter defibrillator recipients may face defibrillating shocks in the final weeks of their lives, adding to stress and anxiety in patients and their families. DESIGN Qualitative study with in-depth interviews analysed with a content analysis. METHODS Interviews were performed with 18 spouses of medically stable implantable cardioverter defibrillator recipients during 2011-2012. RESULTS The spouses described how they dealt with changes in life and an uncertain future following the implantable cardioverter defibrillator implantation. Six subcategories conceptualized the spouses' concerns: Aspiring for involvement; Managing an altered relationship; Being attentive to warning signs; Worries for deterioration in the partner's health; Waiting for the defibrillating shock; and Death is veiled in silence. CONCLUSION Despite the partner's serious state of health; terminal illness or death and the role of the device was seldom discussed with healthcare professionals or the implantable cardioverter defibrillator recipient. Open and honest communication was requested as important to support coping with an unpredictable life situation and to reduce worries and uncertainty about the future and end-of-life.
Collapse
Affiliation(s)
- Christina Fluur
- Department of Cardiology UHL, County Council of Östergötland, Linköping, Sweden
| | | | | | | |
Collapse
|
84
|
O'Hanlon E, Newell FN, Mitchell KJ. Combined structural and functional imaging reveals cortical deactivations in grapheme-color synaesthesia. Front Psychol 2013; 4:755. [PMID: 24198794 PMCID: PMC3812565 DOI: 10.3389/fpsyg.2013.00755] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 09/27/2013] [Indexed: 12/02/2022] Open
Abstract
Synaesthesia is a heritable condition in which particular stimuli generate specific and consistent sensory percepts or associations in another modality or processing stream. Functional neuroimaging studies have identified potential correlates of these experiences, including, in some but not all cases, the hyperactivation of visuotemporal areas and of parietal areas thought to be involved in perceptual binding. Structural studies have identified a similarly variable spectrum of differences between synaesthetes and controls. However, it remains unclear the extent to which these neural correlates reflect the synaesthetic experience itself or additional phenotypes associated with the condition. Here, we acquired both structural and functional neuroimaging data comparing thirteen grapheme-color synaesthetes with eleven non-synaesthetes. Using voxel-based morphometry and diffusion tensor imaging, we identify a number of clusters of increased volume of gray matter, of white matter or of increased fractional anisotropy in synaesthetes vs. controls. To assess the possible involvement of these areas in the synaesthetic experience, we used nine areas of increased gray matter volume as regions of interest in an fMRI experiment that characterized the contrast in response to stimuli which induced synaesthesia (i.e., letters) vs. those which did not (non-meaningful symbols). Four of these areas showed sensitivity to this contrast in synaesthetes but not controls. Unexpectedly, in two of them, in left lateral occipital cortex and in postcentral gyrus, the letter stimuli produced a strong negative BOLD signal in synaesthetes. An additional whole-brain fMRI analysis identified 14 areas, three of which were driven mainly by a negative BOLD response to letters in synaesthetes. Our findings suggest that cortical deactivations may be involved in the conscious experience of internally generated synaesthetic percepts.
Collapse
Affiliation(s)
- Erik O'Hanlon
- School of Psychology and Institute of Neuroscience, Trinity College Dublin Dublin, Ireland
| | | | | |
Collapse
|
85
|
Dick LJ, Gray A, Ram A, Hume A, Parris C, Hogg PJ, Elliott MA, Ford SJ, Halbert GW. Elimination of the antimicrobial action of the organoarsenical cancer therapeutic, 4-(N-(S-glutathionylacetyl)amino) phenylarsonous acid, before finished product sterility testing. J Pharm Pharmacol 2013; 65:1664-9. [PMID: 24102542 DOI: 10.1111/jphp.12143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 08/20/2013] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Arsenical compounds have been used therapeutically for over 2000 years finding particular relevance as antimicrobials. After being replaced by more selective and consequently less toxic antibiotics in the last century, arsenicals have recently made a resurgence as anticancer drugs (specifically arsenic trioxide and its derivatives). Arsenical parenteral formulations require post-manufacture sterility testing; however, their intrinsic antimicrobial activity must be neutralised before testing to eliminate the possibility of false (no-growth) test results. METHODS A range of thiol-containing compounds was screened to establish a suitable deactivation agent for the novel organoarsenical compound, 4-(N-(S-glutathionylacetyl)amino) phenylarsonous acid (GSAO). Dimercatopropanol (DMP) was found to successful deactivate GSAO and was validated according to pharmacopoeial sterility test guidelines (specifically the method suitability test/sterility validation test). KEY FINDINGS DMP is an effective way of deactivating GSAO before sterility testing and can be used for pharmacopoeial sterility tests. Our results affirm previous research highlighting the sensitivity of Staphylococcus aureus to arsenical compounds CONCLUSIONS A method of deactivating the arsenical drug GSAO before the post-manufacture sterility test was established and validated. DMP is a commonly used chelator/deactivation agent so this work may have implications for other inorganic therapeutic agents.
Collapse
Affiliation(s)
- Lindsay J Dick
- Cancer Research UK Formulation Unit, Strathclyde Institute for Pharmacy and Biomedical Sciences, Robertson Wing, University of Strathclyde, Glasgow, Scotland, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
86
|
Spier E, Hermans I. Enhancing the deperoxidation activity of cobalt(II)acetylacetonate by the addition of octanoic acid. Chemphyschem 2013; 14:3384-8. [PMID: 23881854 DOI: 10.1002/cphc.201300460] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 07/09/2013] [Indexed: 11/11/2022]
Abstract
The homolytic scission of peroxides with catalytic amounts of cobalt(II) complexes is used in several industrial oxidation processes. In this contribution, we report that addition of small amounts of octanoic acid significantly enhances the catalytic deperoxidation activity of the cobalt(II)acetylacetonate complex. We attribute this to the stabilization of the Co--OOR bond upon coordination of octanoic acid, preventing the unimolecular scission. As such, the cobalt peroxo intermediate is forced to enter an alternative catalytic cycle which causes its rapid conversion to the highly reactive cobalt hydroxy. This shift in catalytic cycle results in a higher pre-exponential rate factor, over-compensating the higher barrier of the new rate-determining step.
Collapse
Affiliation(s)
- Eyal Spier
- Department of Chemistry and Applied Bio-Sciences, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich (Switzerland)
| | | |
Collapse
|
87
|
Huang Y, Zeng T, Zhang G, Li G, Lu N, Lai X, Lu Y, Chen J. Activated and deactivated functional brain areas in the Deqi state: A functional MRI study. Neural Regen Res 2012; 7:2362-9. [PMID: 25538761 PMCID: PMC4268742 DOI: 10.3969/j.issn.1673-5374.2012.30.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 07/10/2012] [Indexed: 11/28/2022] Open
Abstract
We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects during acupuncture. Twelve healthy volunteers received sham and true needling at the Waiguan (TE5) acupoint. Real-time cerebral functional MRI showed that compared with non-sensation after sham needling, true needling activated Brodmann areas 3, 6, 8, 9, 10, 11, 13, 20, 21, 37, 39, 40, 43, and 47, the head of the caudate nucleus, the parahippocampal gyrus, thalamus and red nucleus. True needling also deactivated Brodmann areas 1, 2, 3, 4, 5, 6, 7, 9, 10, 18, 24, 31, 40 and 46.
Collapse
Affiliation(s)
- Yong Huang
- Traditional Chinese Medicine School, Southern Medical University, Guangzhou 510515, Guangdong Province, China
| | - Tongjun Zeng
- Rehabilitation Department, First People's Hospital, Shunde District, Foshan 528300, Guangdong Province, China
| | - Guifeng Zhang
- Academic Affairs Department, Xinxing Chinese Medicine School, Xinxing 527400, Guangdong Province, China
| | - Ganlong Li
- Traditional Chinese Medicine Department, Huarui Hospital, Southern Medical University, Guangzhou 510360, Guangdong Province, China
| | - Na Lu
- Medicophysics Department, Guangzhou Medical University, Guangzhou 510182, Guangdong Province, China
| | - Xinsheng Lai
- Acupuncture and Massage College, Guangzhou Traditional Chinese Medicine University, Guangzhou 510405, Guangdong Province, China
| | - Yangjia Lu
- Traditional Chinese Medicine Department, Guangdong Medical College, Dongguan 523808, Guangdong Province, China
| | - Jiarong Chen
- First School of Clinical Medicine, Southern Medical University, Guangzhou 510515, Guangdong Province, China
| |
Collapse
|
88
|
Takeuchi H, Taki Y, Nouchi R, Hashizume H, Sassa Y, Sekuguchi A, Kotozaki Y, Nakagawa S, Nagase T, Miyauchi CM, Kawashima R. Associations among imaging measures (2): the association between gray matter concentration and task-induced activation changes. Hum Brain Mapp 2012; 35:185-98. [PMID: 22965755 DOI: 10.1002/hbm.22167] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 06/04/2012] [Accepted: 06/27/2012] [Indexed: 11/10/2022] Open
Abstract
The association between functional activation and gray matter (GM) structure has been revealed in clinical studies and studies of aging involving a small number of subjects. The purpose of this study was to investigate the association between functional activation maps and GM structures in young adults who do not show apparent GM atrophy and to investigate in detail the nature of this association using a large number of subjects. We used voxel-by-voxel regression analyses to investigate voxel-by-voxel associations between GM concentration (GMC) and contrast estimate images of brain activity during n-back working memory tasks. Associations were assessed for each voxel after regressing out the effects of age, sex, and mean signal intensity during functional magnetic resonance imaging scanning at each voxel using data from 248 normal, right-handed, young adult subjects. In our study, the concept of "the greater the GMC, the greater the task-related activation increase/task-related activation decrease (or the greater the task-related activation change from baseline)" was true for a wide range of activated and deactivated areas. However, in some minor regions, the other pattern of "the greater the GMC, the smaller the task-related activation increase" was observed. The first pattern is often observed at the borders of GM structures. These findings may have to be taken into consideration when group/individual differences in functional activation are investigated.
Collapse
Affiliation(s)
- Hikaru Takeuchi
- Department of Advanced Brain Science, Smart Ageing International Research Center, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
89
|
Bejanin A, Viard A, Chételat G, Clarys D, Bernard F, Pélerin A, de La Sayette V, Eustache F, Desgranges B. When Higher Activations Reflect Lower Deactivations: A PET Study in Alzheimer's Disease during Encoding and Retrieval in Episodic Memory. Front Hum Neurosci 2012; 6:107. [PMID: 22557957 PMCID: PMC3340943 DOI: 10.3389/fnhum.2012.00107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 04/10/2012] [Indexed: 11/18/2022] Open
Abstract
The aim of the present study was to explore the cerebral substrates of episodic memory disorders in Alzheimer’s disease (AD) and investigate patients’ hyperactivations frequently reported in the functional imaging literature. It remains unclear whether some of these hyperactivations reflect real increased activity or deactivation disturbances in the default mode network (DMN). Using positron emission tomography (15O-H2O), cerebral blood flow was measured in 11 AD patients and 12 healthy elderly controls at rest and during encoding and stem-cued recall of verbal items. Subtractions analyses between the target and control conditions were performed and compared between groups. The average signal was extracted in regions showing hyperactivation in AD patients versus controls in both contrasts. To determine whether hyperactivations occurred in regions that were activated or deactivated during the memory tasks, we compared signal intensities between the target conditions versus rest. Our results showed reduced activation in AD patients compared to controls in several core episodic memory regions, including the medial temporal structures, during both encoding and retrieval. Patients also showed hyperactivations compared to controls in a set of brain areas. Further analyses conducted on the signal extracted in these areas indicated that most of these hyperactivations actually reflected a failure of deactivation. Indeed, whereas almost all of these regions were significantly more activated at rest than during the target conditions in controls, only one region presented a similar pattern of deactivation in patients. Altogether, our findings suggest that hyperactivations in AD must be interpreted with caution and may not systematically reflect increased activity. Although there has been evidence supporting the existence of genuine compensatory mechanisms, dysfunction within the DMN may be responsible for part of the apparent hyperactivations reported in the literature on AD.
Collapse
|
90
|
Park DC, Polk TA, Hebrank AC, Jenkins LJ. Age differences in default mode activity on easy and difficult spatial judgment tasks. Front Hum Neurosci 2010; 3:75. [PMID: 20126437 PMCID: PMC2814559 DOI: 10.3389/neuro.09.075.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 12/22/2009] [Indexed: 11/13/2022] Open
Abstract
The default network is a system of brain areas that are engaged when the mind is not involved in goal-directed activity. Most previous studies of age-related changes in default mode processing have used verbal tasks. We studied non-verbal spatial tasks that vary in difficulty. We presented old and young participants with two spatial judgment tasks: an easy categorical judgment and a more demanding coordinate judgment. We report that (a) Older adults show markedly less default network modulation than young on the demanding spatial task, but there is age equivalence on the easy task; (b) This Age × Task interaction is restricted to the default network: Brain areas that are deactivated by the tasks, but that are outside the default network, show no interaction; (c) Young adults exhibit significantly stronger functional connectivity among posterior regions of the default network compared with older adults, whereas older adults exhibit stronger connectivity between medial prefrontal cortex and other sites; and (d) The relationship of default activity to reaction time performance on the spatial tasks is mediated by age: in old adults, those who deactivate the default network most also perform best, whereas the opposite is true in younger adults. These results extend the findings of age-related changes in default mode processing and connectivity to visuo-spatial tasks and demonstrate that the results are specific to the default network.
Collapse
Affiliation(s)
- Denise C Park
- Center for Vital Longevity, University of Texas at Dallas Dallas, TX, USA
| | | | | | | |
Collapse
|
91
|
Mayer JS, Roebroeck A, Maurer K, Linden DEJ. Specialization in the default mode: Task-induced brain deactivations dissociate between visual working memory and attention. Hum Brain Mapp 2010; 31:126-39. [PMID: 19639552 PMCID: PMC6870780 DOI: 10.1002/hbm.20850] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 05/08/2009] [Accepted: 06/07/2009] [Indexed: 11/09/2022] Open
Abstract
The idea of an organized mode of brain function that is present as default state and suspended during goal-directed behaviors has recently gained much interest in the study of human brain function. The default mode hypothesis is based on the repeated observation that certain brain areas show task-induced deactivations across a wide range of cognitive tasks. In this event-related functional resonance imaging study we tested the default mode hypothesis by comparing common and selective patterns of BOLD deactivation in response to the demands on visual attention and working memory (WM) that were independently modulated within one task. The results revealed task-induced deactivations within regions of the default mode network (DMN) with a segregation of areas that were additively deactivated by an increase in the demands on both attention and WM, and areas that were selectively deactivated by either high attentional demand or WM load. Attention-selective deactivations appeared in the left ventrolateral and medial prefrontal cortex and the left lateral temporal cortex. Conversely, WM-selective deactivations were found predominantly in the right hemisphere including the medial-parietal, the lateral temporo-parietal, and the medial prefrontal cortex. Moreover, during WM encoding deactivated regions showed task-specific functional connectivity. These findings demonstrate that task-induced deactivations within parts of the DMN depend on the specific characteristics of the attention and WM components of the task. The DMN can thus be subdivided into a set of brain regions that deactivate indiscriminately in response to cognitive demand ("the core DMN") and a part whose deactivation depends on the specific task.
Collapse
Affiliation(s)
- Jutta S Mayer
- Department of Psychiatry, Goethe-University, Frankfurt, Germany.
| | | | | | | |
Collapse
|
92
|
Shen L, Ji HF. Theoretical study on reactions of triplet excited state thioxanthone with indole. Int J Mol Sci 2009; 10:4284-9. [PMID: 20057945 DOI: 10.3390/ijms10104284] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 09/10/2009] [Accepted: 09/25/2009] [Indexed: 11/24/2022] Open
Abstract
In the present work, a theoretical study on the deactivation of triplet excited (T1) state thioxanthone (TX) by indole (INH) was performed, based on density functional theory calculations. Three feasible pathways, namely direct electron transfer from INH to T1 state TX, electron transfer followed by proton transfer from INH.+ to TX.−, and H-atom transfer from nitrogen of INH to keto oxygen of T1 state TX, were proposed theoretically to be involved in T1 state TX deactivation by INH.
Collapse
|
93
|
Feng HJ, Botzolakis EJ, Macdonald RL. Context-dependent modulation of alphabetagamma and alphabetadelta GABA A receptors by penicillin: implications for phasic and tonic inhibition. Neuropharmacology 2009; 56:161-73. [PMID: 18775733 PMCID: PMC2661208 DOI: 10.1016/j.neuropharm.2008.08.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 08/11/2008] [Accepted: 08/12/2008] [Indexed: 01/25/2023]
Abstract
Penicillin, an open-channel blocker of GABA(A) receptors, was recently reported to inhibit phasic, but not tonic, currents in hippocampal neurons. To distinguish between isoform-specific and context-dependent modulation as possible explanations for this selectivity, the effects of penicillin were evaluated on recombinant GABA(A) receptors expressed in HEK293T cells. When co-applied with saturating GABA, penicillin decreased peak amplitude, induced rebound, and prolonged deactivation of currents evoked from both synaptic and extrasynaptic receptor isoforms. However, penicillin had isoform-specific effects on the extent of desensitization, reflecting its ability to differentially modulate peak (non-equilibrium) and residual (near-equilibrium) currents. This suggested that the context of activation could determine the apparent sensitivity of a given receptor isoform to penicillin. To test this hypothesis, we explored the ability of penicillin to modulate synaptic and extrasynaptic isoform currents that were activated under more physiologically relevant conditions. Interestingly, while currents evoked from synaptic isoforms under phasic conditions (transient activation by a saturating concentration of GABA) were substantially inhibited by penicillin, currents evoked from extrasynaptic isoforms under tonic conditions (prolonged application by a sub-saturating concentration of GABA) were minimally affected. We therefore concluded that the reported inability of penicillin to modulate tonic currents could not simply be attributed to insensitivity of extrasynaptic receptors, but rather, reflected an inability to modulate these receptors in their native context of activation.
Collapse
Affiliation(s)
- Hua-Jun Feng
- Department of Neurology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | | | - Robert L. Macdonald
- Department of Neurology, Vanderbilt University School of Medicine, Nashville, TN 37232
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232
| |
Collapse
|
94
|
Ji HF, Shen L. A DFT study on deactivation of triplet excited state riboflavin by polyphenols. Int J Mol Sci 2008; 9:1908-1914. [PMID: 19325725 PMCID: PMC2635615 DOI: 10.3390/ijms9101908] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Revised: 09/07/2008] [Accepted: 09/27/2008] [Indexed: 11/16/2022] Open
Abstract
The deactivation of triplet excited state riboflavin by polyphenols, e.g. rutin and catechin, was studied on the basis of density functional theory calculations. The results show that the H-atom transfer pathway is more feasible on thermodynamic grounds in comparison with the direct energy transfer or direct electron transfer pathways involved in the triplet excited state riboflavin deactivation by rutin/catechin. The findings are helpful to understand the protective effect of polyphenols against the riboflavin induced photosensitizing damage.
Collapse
Affiliation(s)
| | - Liang Shen
- Author to whom correspondence should be addressed; E-mail:
| |
Collapse
|
95
|
Harrison BJ, Pujol J, López-Solà M, Hernández-Ribas R, Deus J, Ortiz H, Soriano-Mas C, Yücel M, Pantelis C, Cardoner N. Consistency and functional specialization in the default mode brain network. Proc Natl Acad Sci U S A 2008; 105:9781-6. [PMID: 18621692 PMCID: PMC2474491 DOI: 10.1073/pnas.0711791105] [Citation(s) in RCA: 260] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Indexed: 11/18/2022] Open
Abstract
The notion of a "default mode of brain function" has taken on certain relevance in human neuroimaging studies and in relation to a network of lateral parietal and midline cortical regions that show prominent activity fluctuations during passive imaging states, such as rest. In this study, we perform three fMRI experiments that demonstrate consistency and specialization in the default mode network. Correlated activity fluctuations of default mode network regions are identified during (i) eyes-closed spontaneous rest, (ii) activation by moral dilemma, and (iii) deactivation by Stroop task performance. Across these imaging states, striking uniformity is shown in the basic anatomy of the default mode network, but with both tasks clearly and differentially modulating this activity compared with spontaneous fluctuations of the network at rest. Against rest, moral dilemma is further shown to evoke regionally specific activity increases of hypothesized functional relevance. Mapping spontaneous and task-related brain activity will help to constrain the meaning of the default mode network. These findings are discussed in relation to recent debate on the topic of default modes of brain function.
Collapse
Affiliation(s)
- Ben J Harrison
- Institut d'Alta Tecnologia-Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitària, 08003 Barcelona, Spain.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
96
|
Abstract
A consistent finding from functional neuroimaging studies of cognitive aging is an age-related reduction in occipital activity coupled with increased frontal activity. This posterior-anterior shift in aging (PASA) has been typically attributed to functional compensation. The present functional magnetic resonance imaging sought to 1) confirm that PASA reflects the effects of aging rather than differences in task difficulty; 2) test the compensation hypothesis; and 3) investigate whether PASA generalizes to deactivations. Young and older participants were scanned during episodic retrieval and visual perceptual tasks, and age-related changes in brain activity common to both tasks were identified. The study yielded 3 main findings. First, inconsistent with a difficulty account, the PASA pattern was found across task and confidence levels when matching performance among groups. Second, supporting the compensatory hypothesis, age-related increases in frontal activity were positively correlated with performance and negatively correlated with the age-related occipital decreases. Age-related increases and correlations with parietal activity were also found. Finally, supporting the generalizability of the PASA pattern to deactivations, aging reduced deactivations in posterior midline cortex but increased deactivations in medial frontal cortex. Taken together, these findings demonstrate the validity, function, and generalizability of PASA, as well as its importance for the cognitive neuroscience of aging.
Collapse
Affiliation(s)
- Simon W. Davis
- Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Nancy A. Dennis
- Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Sander M. Daselaar
- Faculty of Science, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Mathias S. Fleck
- Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Roberto Cabeza
- Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| |
Collapse
|
97
|
Abstract
We measured frequency-dependent functional MRI (fMRI) activations (at 11.7 T) in the somatosensory cortex with whisker and forepaw stimuli in the same alpha-chloralose anesthetized rats. Whisker and forepaw stimuli were attained by computer-controlled pulses of air puffs and electrical currents, respectively. Air puffs deflected (+/-2 mm) the chosen whisker(s) in the right snout in the rostral to caudal direction, and electrical currents (2 mA amplitude, 0.3 ms duration) stimulated the left forepaw with subcutaneous copper electrodes placed between the second and fourth digits. In the same subject, unimodal stimulation of whisker and forepaw gave rise to significant blood oxygen level-dependent (BOLD) signal increases in corresponding contralateral somatosensory areas of whisker barrel field (S1BF) and forelimb (S1FL), respectively, with no significant spatial overlap between these regions. The BOLD responses in S1(BF) and S1(FL) regions were found to be differentially variable with frequency of each stimulus type. In the S1BF, a linear increase in the BOLD response was observed with whisker stimulation frequency of up to approximately 12 Hz, beyond which the response seemed to saturate (and/or slightly attenuate) up to the maximum frequency studied (i.e. 30 Hz). In the S1FL, the magnitude of the BOLD response was largest at forepaw stimulation frequency between 1.5 and 3 Hz, beyond which the response diminished with little or no activity at frequencies higher than 20 Hz. The volume of tissue activated by each stimulus type followed a similar pattern to that of the stimulation frequency dependence. These results of bimodal whisker and forepaw stimuli in the same subject may provide a framework to study interactions of different tactile modules, with both fMRI and neurophysiology (i.e. inside and outside the magnet).
Collapse
Affiliation(s)
- Basavaraju G. Sanganahalli
- Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT 06520, USA
- Quantitative Neuroscience with Magnetic Resonance (QNMR), Yale University, New Haven, CT 06520, USA
- Department of Diagnostic Radiology, Yale University, New Haven, CT 06520, USA
| | - Peter Herman
- Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT 06520, USA
- Quantitative Neuroscience with Magnetic Resonance (QNMR), Yale University, New Haven, CT 06520, USA
- Department of Diagnostic Radiology, Yale University, New Haven, CT 06520, USA
- Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary
| | - Fahmeed Hyder
- Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT 06520, USA
- Quantitative Neuroscience with Magnetic Resonance (QNMR), Yale University, New Haven, CT 06520, USA
- Department of Diagnostic Radiology, Yale University, New Haven, CT 06520, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| |
Collapse
|
98
|
Abstract
It is not easy to determine the location of the cerebral generators and the other brain regions that may be involved at the time of an epileptic spike seen in the scalp EEG. The possibility to combine EEG recording with functional MRI scanning (fMRI) opens the opportunity to uncover the regions of the brain showing changes in metabolism and blood flow in response to epileptic spikes seen in the EEG. These regions are presumably involved in the abnormal neuronal activity at the origin of epileptic discharges. This paper reviews the methodology involved in performing such studies, including the special techniques required for recording the EEG inside the scanner and the statistical issues in analyzing the fMRI signal. We then discuss the results obtained in patients with different types of focal epileptic disorders and in patients with primary generalized epilepsy. The results in general indicate that interictal epileptic discharges may affect brain areas well beyond the presumed region in which they are generated. The noninvasive nature of this method opens new horizons in the investigation of brain regions involved and affected by epileptic discharges.
Collapse
Affiliation(s)
- Jean Gotman
- Montreal Neurological Institute, McGill University, Montréal, Québec, Canada.
| |
Collapse
|
99
|
Iannetti GD, Zambreanu L, Wise RG, Buchanan TJ, Huggins JP, Smart TS, Vennart W, Tracey I. Pharmacological modulation of pain-related brain activity during normal and central sensitization states in humans. Proc Natl Acad Sci U S A 2005; 102:18195-200. [PMID: 16330766 PMCID: PMC1306794 DOI: 10.1073/pnas.0506624102] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 10/13/2005] [Indexed: 11/18/2022] Open
Abstract
Abnormal processing of somatosensory inputs in the central nervous system (central sensitization) is the mechanism accounting for the enhanced pain sensitivity in the skin surrounding tissue injury (secondary hyperalgesia). Secondary hyperalgesia shares clinical characteristics with neurogenic hyperalgesia in patients with neuropathic pain. Abnormal brain responses to somatosensory stimuli have been found in patients with hyperalgesia as well as in normal subjects during experimental central sensitization. The aim of this study was to assess the effects of gabapentin, a drug effective in neuropathic pain patients, on brain processing of nociceptive information in normal and central sensitization states. Using functional magnetic resonance imaging (fMRI) in normal volunteers, we studied the gabapentin-induced modulation of brain activity in response to nociceptive mechanical stimulation of normal skin and capsaicin-induced secondary hyperalgesia. The dose of gabapentin was 1,800 mg per os, in a single administration. We found that (i) gabapentin reduced the activations in the bilateral operculoinsular cortex, independently of the presence of central sensitization; (ii) gabapentin reduced the activation in the brainstem, only during central sensitization; (iii) gabapentin suppressed stimulus-induced deactivations, only during central sensitization; this effect was more robust than the effect on brain activation. The observed drug-induced effects were not due to changes in the baseline fMRI signal. These findings indicate that gabapentin has a measurable antinociceptive effect and a stronger antihyperalgesic effect most evident in the brain areas undergoing deactivation, thus supporting the concept that gabapentin is more effective in modulating nociceptive transmission when central sensitization is present.
Collapse
Affiliation(s)
- G D Iannetti
- Department of Human Anatomy and Genetics, and Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, UK.
| | | | | | | | | | | | | | | |
Collapse
|
100
|
Wagner DA, Goldschen-Ohm MP, Hales TG, Jones MV. Kinetics and spontaneous open probability conferred by the epsilon subunit of the GABAA receptor. J Neurosci 2005; 25:10462-8. [PMID: 16280584 PMCID: PMC6725813 DOI: 10.1523/jneurosci.1658-05.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 09/28/2005] [Accepted: 10/02/2005] [Indexed: 12/26/2022] Open
Abstract
GABAA receptors mediate synaptic and extrasynaptic inhibition. Native receptors consist of alpha and beta subunits, which are required for function, and another "modulatory" subunit, for example, gamma, delta, or epsilon. Of these, the epsilon subunit has the most restricted distribution, confers resistance to neurosteroid and anesthetic modulation, and causes spontaneous channel opening. Little is known, however, about how epsilon affects receptor kinetics, which in turn shape responses to both ambient and synaptic GABA exposure. Here, we expressed human alpha2beta1, alpha2beta1gamma2, or alpha2beta1epsilon subunit combinations in human embryonic kidney 293 cells and used rapid solution exchange to study receptor kinetics in outside-out patches. The epsilon subunit greatly slowed deactivation and recovery after brief GABA pulses. During long, saturating GABA pulses, the rate of desensitization was slower for alpha2beta1epsilon and alpha2beta1gamma2 than for alpha2beta1. However, in alpha2beta1epsilon, the final extent of desensitization was large compared with that of alpha2beta1gamma2. Responses in alpha2beta1epsilon, but not the others, were often followed by an "overshoot" above the baseline, suggesting that a fraction of channels are spontaneously open and are transiently silenced by receptor activation and subsequent desensitization. The baseline current and associated noise were reduced by picrotoxin, revealing that epsilon-containing channels are open approximately 4% of the time in the absence of GABA. These results suggest that, if epsilon-containing receptors are expressed at synapses, the synaptic currents would be long-lasting but may rundown quickly under high-frequency activation. In addition, silencing of spontaneous openings by desensitization raises the possibility that tonic inhibition mediated by epsilon-containing receptors may be regulated by phasic inhibition.
Collapse
Affiliation(s)
- David A Wagner
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201, USA.
| | | | | | | |
Collapse
|