| 1. |
- Abbas, Abdul-Karim, 1959, et al.
(författare)
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Temporal phases of long-term potentiation (LTP): myth or fact?
- 2015
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Ingår i: Reviews in the Neurosciences. - : Walter de Gruyter GmbH. - 0334-1763 .- 2191-0200. ; 26:5, s. 507-546
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Tidskriftsartikel (refereegranskat)abstract
- Long-term potentiation (LTP) remains the most widely accepted model for learning and memory. In accordance with this belief, the temporal differentiation of LTP into early and late phases is accepted as reflecting the differentiation of short-term and long-term memory. Moreover, during the past 30 years, protein synthesis inhibitors have been used to separate the early, protein synthesis-independent (E-LTP) phase and the late, protein synthesis-dependent (L-LTP) phase. However, the role of these proteins has not been formally identified. Additionally, several reports failed to show an effect of protein synthesis inhibitors on LTP. In this review, a detailed analysis of extensive behavioral and electrophysiological data reveals that the presumed correspondence of LTP temporal phases to memory phases is neither experimentally nor theoretically consistent. Moreover, an overview of the time courses of E-LTP in hippocampal slices reveals a wide variability ranging from <1 h to more than 5 h. The existence of all these conflictual findings should lead to a new vision of LTP. We believe that the E-LTP vs. L-LTP distinction, established with protein synthesis inhibitor studies, reflects a false dichotomy. We suggest that the duration of LTP and its dependency on protein synthesis are related to the availability of a set of proteins at synapses and not to the de novo synthesis of plasticity-related proteins. This availability is determined by protein turnover kinetics, which is regulated by previous and ongoing electrical activities and by energy store availability. RAHAM WC, 1991, MOLECULAR NEUROBIOLOGYSATELLITE MEETING ON MOLECULAR MECHANISMS RAHAM WC, 1995, MOLECULAR BRAIN RESEARCH, V30, P367 RAHAM WC, 1993, NEUROSCIENCE, V56, P717
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| 2. |
- Agnati, LF, et al.
(författare)
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Role of iso-receptors in receptor-receptor interactions with a focus on dopamine iso-receptor complexes
- 2016
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Ingår i: Reviews in the neurosciences. - : Walter de Gruyter GmbH. - 2191-0200 .- 0334-1763. ; 27:1, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Intercellular and intracellular communication processes consist of signals and recognition/decoding apparatuses of these signals. In humans, the G protein-coupled receptor (GPCR) family represents the largest family of cell surface receptors. More than 30 years ago, it has been proposed that GPCR could form dimers or higher-order oligomers (receptor mosaics [RMs] at the plasma membrane level and receptor-receptor interactions [RRIs] have been proposed as a new integrative mechanism for chemical signals impinging on cell plasma membranes). The basic phenomena involved in RRIs are allostery and cooperativity of membrane receptors, and the present paper provides basic information concerning their relevance for the integrative functions of RMs. In this context, the possible role of iso-receptor RM is discussed (with a special focus on dopamine receptor subtypes and on some of the RMs they form with other dopamine iso-receptors), and it is proposed that two types of cooperativity, namely, homotropic and heterotropic cooperativity, could allow distinguishing two types of functionally different RMs. From a general point of view, the presence of iso-receptors and their topological organization within RMs allow the use of a reduced number of signals for the intercellular communication processes, since the target cells can recognize and decode the same signal in different ways. This theoretical aspect is further analyzed here by means of an analogy with artificial information systems. Thus, it is suggested that the ‘multiplexer’ and ‘demultiplexer’ concepts could, at least in part, model the role of RMs formed by iso-receptors in the information handling by the cell.
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| 3. |
- Agnati, LF, et al.
(författare)
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The multi-facet aspects of cell sentience and their relevance for the integrative brain actions: role of membrane protein energy landscape
- 2016
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Ingår i: Reviews in the neurosciences. - : Walter de Gruyter GmbH. - 2191-0200 .- 0334-1763. ; 27:4, s. 347-363
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Tidskriftsartikel (refereegranskat)abstract
- Several ion channels can be randomly and spontaneously in an open state, allowing the exchange of ion fluxes between extracellular and intracellular environments. We propose that the random changes in the state of ion channels could be also due to proteins exploring their energy landscapes. Indeed, proteins can modify their steric conformation under the effects of the physicochemical parameters of the environments with which they are in contact, namely, the extracellular, intramembrane and intracellular environments. In particular, it is proposed that the random walk of proteins in their energy landscape is towards attractors that can favor the open or close condition of the ion channels and/or intrinsic activity of G-protein-coupled receptors. The main aspect of the present proposal is that some relevant physicochemical parameters of the environments (e.g. molecular composition, temperature, electrical fields) with which some signaling-involved plasma membrane proteins are in contact alter their conformations. In turn, these changes can modify their information handling via a modulatory action on their random walk towards suitable attractors of their energy landscape. Thus, spontaneous and/or signal-triggered electrical activities of neurons occur that can have emergent properties capable of influencing the integrative actions of brain networks. Against this background, Cook’s hypothesis on ‘cell sentience’ is developed by proposing that physicochemical parameters of the environments with which the plasma-membrane proteins of complex cellular networks are in contact fulfill a fundamental role in their spontaneous and/or signal-triggered activity. Furthermore, it is proposed that a specialized organelle, the primary cilium, which is present in most cells (also neurons and astrocytes), could be of peculiar importance to pick up chemical signals such as ions and transmitters and to detect physical signals such as pressure waves, thermal gradients, and local field potentials.
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| 4. |
- Anisimov, Sergey, et al.
(författare)
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Genetic aspects of melatonin biology.
- 2004
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Ingår i: Reviews in the Neurosciences. - 0334-1763. ; 15:3, s. 209-230
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Forskningsöversikt (refereegranskat)
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| 5. |
- Egonsson, Dan
(författare)
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Death and irreversibility.
- 2009
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Ingår i: Reviews in the Neurosciences. - 0334-1763. ; 20:3-4, s. 275-281
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Tidskriftsartikel (refereegranskat)abstract
- The concept of irreversibility plays a central role in most discussions of how to understand and determine human death. This seems to relativize death, since the possibilities of reversal will always depend on circumstance. I discuss the conceptual problems created by this fact, arguing that their seriousness depends on whether we take our conception of death to be a definition or criterion. Relativity is probably not fatal in a definition of death; it might even be desirable in a policy criterion. The concept of permanence is no less philosophically problematic in this context than irreversibility.
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| 6. |
- Guidolin, D, et al.
(författare)
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G protein-coupled receptor-receptor interactions give integrative dynamics to intercellular communication
- 2018
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Ingår i: Reviews in the neurosciences. - : Walter de Gruyter GmbH. - 2191-0200 .- 0334-1763. ; 29:7, s. 703-726
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Tidskriftsartikel (refereegranskat)abstract
- The proposal of receptor-receptor interactions (RRIs) in the early 1980s broadened the view on the role of G protein-coupled receptors (GPCR) in the dynamics of the intercellular communication. RRIs, indeed, allow GPCR to operate not only as monomers but also as receptor complexes, in which the integration of the incoming signals depends on the number, spatial arrangement, and order of activation of the protomers forming the complex. The main biochemical mechanisms controlling the functional interplay of GPCR in the receptor complexes are direct allosteric interactions between protomer domains. The formation of these macromolecular assemblies has several physiologic implications in terms of the modulation of the signaling pathways and interaction with other membrane proteins. It also impacts on the emerging field of connectomics, as it contributes to set and tune the synaptic strength. Furthermore, recent evidence suggests that the transfer of GPCR and GPCR complexes between cells via the exosome pathway could enable the target cells to recognize/decode transmitters and/or modulators for which they did not express the pertinent receptors. Thus, this process may also open the possibility of a new type of redeployment of neural circuits. The fundamental aspects of GPCR complex formation and function are the focus of the present review article.
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| 7. |
- Guidolin, D, et al.
(författare)
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New dimensions of connectomics and network plasticity in the central nervous system
- 2017
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Ingår i: Reviews in the neurosciences. - : Walter de Gruyter GmbH. - 2191-0200 .- 0334-1763. ; 28:2, s. 113-132
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Tidskriftsartikel (refereegranskat)abstract
- Cellular network architecture plays a crucial role as the structural substrate for the brain functions. Therefore, it represents the main rationale for the emerging field of connectomics, defined as the comprehensive study of all aspects of central nervous system connectivity. Accordingly, in the present paper the main emphasis will be on the communication processes in the brain, namely wiring transmission (WT), i.e. the mapping of the communication channels made by cell components such as axons and synapses, and volume transmission (VT), i.e. the chemical signal diffusion along the interstitial brain fluid pathways. Considering both processes can further expand the connectomics concept, since both WT-connectomics and VT-connectomics contribute to the structure of the brain connectome. A consensus exists that such a structure follows a hierarchical or nested architecture, and macro-, meso- and microscales have been defined. In this respect, however, several lines of evidence indicate that a nanoscale (nano-connectomics) should also be considered to capture direct protein-protein allosteric interactions such as those occurring, for example, in receptor-receptor interactions at the plasma membrane level. In addition, emerging evidence points to novel mechanisms likely playing a significant role in the modulation of intercellular connectivity, increasing the plasticity of the system and adding complexity to its structure. In particular, the roamer type of VT (i.e. the intercellular transfer of RNA, proteins and receptors by extracellular vesicles) will be discussed since it allowed us to introduce a new concept of ‘transient changes of cell phenotype’, that is the transient acquisition of new signal release capabilities and/or new recognition/decoding apparatuses.
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