370 results on '"Nacher J"'
Search Results
2. Sex-specific differences in patients with significant aortic regurgitation
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Gonzalez Gomez, A, primary, Monteagudo, J M, additional, Garcia Martin, A, additional, Hinojar, R, additional, Casas, E, additional, Antonana-Ugalde, S, additional, Martinez-Vives, P, additional, Ramos, P, additional, Martinez-Moya, R, additional, Jimenez Nacher, J J, additional, Zamorano, J L, additional, and Fernandez-Golfin, C, additional
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- 2023
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3. Comparison of supine bicycle exercise versus treadmill exercise echocardiography in a cycling-naive population
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Monteagudo Ruiz, J M, primary, Gonzalez Gomez, A, additional, Garcia Martin, A, additional, Hinojar Baydes, R, additional, Casas Rojo, E, additional, Jimenez Nacher, J J, additional, Martin Vives, P, additional, Zamorano, J L, additional, and Fernandez-Golfin, C, additional
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- 2023
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4. Carpet cloaking and Laplace transformation
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Ochiai, T. and Nacher, J. C.
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Physics - Optics - Abstract
Recently, researchers have proposed several carpet cloaking designs that are able to hide a real object under a bump in a way that it is perceived as a flat ground plane. Here, we present a method to design two-dimensional isotropic carpet cloaking devices using Laplace transformation. We show that each functional form of a Laplace transformation corresponds to a different carpet cloaking design. Therefore, our approach allows us to systematically design a rich variety of cloaking devices. Our analysis includes several examples containing different bump geometries that illustrate the proposed methodology., Comment: 4 pages, 6 figures
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- 2012
5. Reflection-less device allows electromagnetic warp drive
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Ochiai, T. and Nacher, J. C.
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Physics - Optics - Abstract
One of the striking properties of artificially structured materials is the negative refraction, an optical feature that known natural materials do not exhibit. Here, we propose a simple design, composed of two parallel layers of materials with different refraction indices $n_1=-n_2$, that constructs perfect reflection-less devices. The electromagnetic waves can tunnel from one layer to the other, a feature that resembles a truncation of the physical space leading to an electromagnetic warp drive. Since the refractive indices do not require any large values, this method demonstrates for the first time the practical feasibility of guiding electromagnetic fields in complete absence of reflection phenomena and without degradation of transmission efficiency at all., Comment: 8 pages, 7 figures
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- 2010
6. Plus-minus construction leads to perfect invisibility
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Nacher, J. C. and Ochiai, T.
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Physics - Optics - Abstract
Recent theoretical advances applied to metamaterials have opened new avenues to design a coating that hides objects from electromagnetic radiation and even the sight. Here, we propose a new design of cloaking devices that creates perfect invisibility in isotropic media. A combination of positive and negative refractive indices, called plus-minus construction, is essential to achieve perfect invisibility (i.e., no time delay and total absence of reflection). Contrary to the common understanding that between two isotropic materials having different refractive indices the electromagnetic reflection is unavoidable, our method shows that surprisingly the reflection phenomena can be completely eliminated. The invented method, different from the classical impedance matching, may also find electromagnetic applications outside of cloaking devices, wherever distortions are present arising from reflections., Comment: 24 pages, 10 figures
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- 2010
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7. A Novel Design of Dielectric Perfect Invisibility Devices
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Ochiai, T., Leonhardt, U., and Nacher, J. C.
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Physics - Optics ,Physics - General Physics - Abstract
The aim of an invisibility device is to guide light around any object put inside, being able to hide objects from sight. In this work, we propose a novel design of dielectric invisibility media based on negative refraction and optical conformal mapping that seems to create perfect invisibility. This design has some advantages and more relaxed constraints compared with already proposed schemes. In particular, it represents an example where the time delay in a dielectric invisibility device is zero. Furthermore, due to impedance matching of negatively refracting materials, the reflection should be close to zero. These findings strongly indicate that perfect invisibility with optically isotropic materials is possible. Finally, the area of the invisible space is also discussed.
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- 2007
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8. ATLAS silicon module assembly and qualification tests at IFIC Valencia
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Bernabeu, J., Civera, J. V., Costa, M. J., Escobar, C., Fuster, J., Garcia, C., Garcia-Navarro, J. E., Gonzalez, F., Gonzalez-Sevilla, S., Lacasta, C., Llosa, G., Marti-Garcia, S., Minano, M., Mitsou, V. A., Modesto, P., Nacher, J., Rodriguez-Oliete, R., Sanchez, F. J., Sospedra, L., and Strachko, V.
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Physics - Instrumentation and Detectors - Abstract
ATLAS experiment, designed to probe the interactions of particles emerging out of proton proton collisions at energies of up to 14 TeV, will assume operation at the Large Hadron Collider (LHC) at CERN in 2007. This paper discusses the assembly and the quality control tests of forward detector modules for the ATLAS silicon microstrip detector assembled at the Instituto de Fisica Corpuscular (IFIC) in Valencia. The construction and testing procedures are outlined and the laboratory equipment is briefly described. Emphasis is given on the module quality achieved in terms of mechanical and electrical stability., Comment: 23 pages, 38 EPS figures, uses JINST LaTeX class
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- 2007
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9. Transcription and noise in negative feedback loops
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Nacher, J. C. and Ochiai, T.
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Quantitative Biology - Molecular Networks - Abstract
Recently, several studies have investigated the transcription process associated to specific genetic regulatory networks. In this work, we present a stochastic approach for analyzing the dynamics and effect of negative feedback loops (FBL) on the transcriptional noise. First, our analysis allows us to identify a bimodal activity depending of the strength of self-repression coupling D. In the strong coupling region D>>1, the variance of the transcriptional noise is found to be reduced a 28 % more than described earlier. Secondly, the contribution of the noise effect to the abundance of regulating protein becomes manifest when the coefficient of variation is computed. In the strong coupling region, this coefficient is found to be independent of all parameters and in fair agreement with the experimentally observed values. Finally, our analysis reveals that the regulating protein is significantly induced by the intrinsic and external noise in the strong coupling region. In short, it indicates that the existence of inherent noise in FBL makes it possible to produce a basal amount of proteins even though the repression level D is very strong., Comment: Latex, 13 pages, 4 figures
- Published
- 2007
10. Universal collective fluctuations in gene expression dynamics from yeast to human
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Nacher, J. C., Ochiai, T., and Akutsu, T.
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Quantitative Biology - Biomolecules - Abstract
In this work, the dynamics of fluctuations in gene expression time series is investigated. By using collected data of gene expression from yeast and human organisms, we found that the fluctuations of gene expression level and its average value over time are strongly correlated and obey a scaling law. As this feature is found in yeast and human organisms, it suggests that probably this coupling is a common dynamical organizing property of all living systems. To understand these observations, we propose a stochastic model which can explain these collective fluctuations, and predict the scaling exponent. Interestingly, our results indicate that the observed scaling law emerges from the self-similarity symmetry embedded in gene expression fluctuations., Comment: 12 pages, 2 figures, LaTeX
- Published
- 2005
11. Symmetry and Dynamics in living organisms: The self-similarity principle governs gene expression dynamics
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Ochiai, T., Nacher, J. C., and Akutsu, T.
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Quantitative Biology - Biomolecules - Abstract
The ambitious and ultimate research purpose in Systems Biology is the understanding and modelling of the cell's system. Although a vast number of models have been developed in order to extract biological knowledge from complex systems composed of basic elements as proteins, genes and chemical compounds, a need remains for improving our understanding of dynamical features of the systems (i.e., temporal-dependence). In this article, we analyze the gene expression dynamics (i.e., how the genes expression fluctuates in time) by using a new constructive approach. This approach is based on only two fundamental ingredients: symmetry and the Markov property of dynamics. First, by using experimental data of human and yeast gene expression time series, we found a symmetry in short-time transition probability from time $t$ to time $t+1$. We call it self-similarity symmetry (i.e., surprisingly, the gene expression short-time fluctuations contain a repeating pattern of smaller and smaller parts that are like the whole, but different in size). Secondly, the Markov property of dynamics reflects that the short-time fluctuation governs the full-time behaviour of the system. Here, we succeed in reconstructing naturally the global behavior of the observed distribution of gene expression (i.e., scaling-law) and the local behaviour of the power-law tail of this distribution, by using only these two ingredients: symmetry and the Markov property of dynamics. This approach may represent a step forward toward an integrated image of the basic elements of the whole cell., Comment: 27 pages, 14 figures, Latex
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- 2005
12. A stochastic approach to multi-gene expression dynamics
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Ochiai, T., Nacher, J. C., and Akutsu, T.
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Quantitative Biology - Biomolecules - Abstract
In the last years, tens of thousands gene expression profiles for cells of several organisms have been monitored. Gene expression is a complex transcriptional process where mRNA molecules are translated into proteins, which control most of the cell functions. In this process, the correlation among genes is crucial to determine the specific functions of genes. Here, we propose a novel multi-dimensional stochastic approach to deal with the gene correlation phenomena. Interestingly, our stochastic framework suggests that the study of the gene correlation requires only one theoretical assumption -Markov property- and the experimental transition probability, which characterizes the gene correlation system. Finally, a gene expression experiment is proposed for future applications of the model., Comment: 17 pages, 2 figures, Latex, v2 includes minor modifications
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- 2005
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13. Flexible construction of hierarchical scale-free networks with general exponent
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Nacher, J. C., Ueda, N., Kanehisa, M., and Akutsu, T.
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Condensed Matter - Other Condensed Matter - Abstract
Extensive studies have been done to understand the principles behind architectures of real networks. Recently, evidences for hierarchical organization in many real networks have also been reported. Here, we present a new hierarchical model which reproduces the main experimental properties observed in real networks: scale-free of degree distribution $P(k)$ (frequency of the nodes that are connected to $k$ other nodes decays as a power-law $P(k)\sim k^{-\gamma}$) and power-law scaling of the clustering coefficient $C(k)\sim k^{-1}$. The major novelties of our model can be summarized as follows: {\it (a)} The model generates networks with scale-free distribution for the degree of nodes with general exponent $\gamma > 2$, and arbitrarily close to any specified value, being able to reproduce most of the observed hierarchical scale-free topologies. In contrast, previous models can not obtain values of $\gamma > 2.58$. {\it (b)} Our model has structural flexibility because {\it (i)} it can incorporate various types of basic building blocks (e.g., triangles, tetrahedrons and, in general, fully connected clusters of $n$ nodes) and {\it (ii)} it allows a large variety of configurations (i.e., the model can use more than $n-1$ copies of basic blocks of $n$ nodes). The structural features of our proposed model might lead to a better understanding of architectures of biological and non-biological networks., Comment: RevTeX, 5 pages, 4 figures
- Published
- 2004
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14. A Constructive Approach to Gene Expression Dynamics
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Ochiai, T., Nacher, J. C., and Akutsu, T.
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Quantitative Biology - Biomolecules - Abstract
The advent of new experimental genomic technologies and the massive increase of DNA sequence information is helping researchers better understand how our genes work. Recently, experiments on mRNA abundance (gene expression) have revealed that gene expression shows a stationary organization described by a power-law distribution (scale-free organization) (i.e., gene expression $k$ decays as $k^{-\gamma}$), which is highly conserved in all the major five kingdoms of life, from Bacteria to Human. An underlying gene expression dynamics "rich-travel-more" was suggested to recover that evolutional conservation of transcriptional organization. Here we propose a constructive approach to gene expression dynamics with larger scope. Our gene expression construction restores the stationary state, predicts the power-law exponent for different organisms with natural explanation for small correction at high and low expression levels, describes the intermediate state dynamics (time finite) and elucidates the gene expression stability. This approach requires only one assumption: Markov property., Comment: 14 pages, 4 figures
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- 2004
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15. Clustering under the line graph transformation: Application to reaction network
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Nacher, J. C., Ueda, N., Yamada, T., Kanehisa, M., and Akutsu, T.
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Quantitative Biology - Molecular Networks - Abstract
Many real networks can be understood as two complementary networks with two kind of nodes. This is the case of metabolic networks where the first network has chemical compounds as nodes and the second one has nodes as reactions. The second network can be related to the first one by a technique called line graph transformation (i.e., edges in an initial network are transformed into nodes). Recently, the main topological properties of the metabolic networks have been properly described by means of a hierarchical model. In our work, we apply the line graph transformation to a hierarchical network and the clustering coefficient $C(k)$ is calculated for the transformed network, where $k$ is the node degree. While $C(k)$ follows the scaling law $C(k)\sim k^{-1.1}$ for the initial hierarchical network, $C(k)$ scales weakly as $k^{0.08}$ for the transformed network. These results indicate that the reaction network can be identified as a degree-independent clustering network., Comment: 20 pages, 12 figures, REVTeX 4 style
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- 2004
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16. Two complementary representations of a scale-free network
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Nacher, J. C., Yamada, T., Goto, S., Kanehisa, M., and Akutsu, T.
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Physics - Biological Physics ,Condensed Matter - Disordered Systems and Neural Networks ,Condensed Matter - Statistical Mechanics ,Physics - Data Analysis, Statistics and Probability - Abstract
Several studies on real complex networks from different fields as biology, economy, or sociology have shown that the degree of nodes (number of edges connected to each node) follows a scale-free power-law distribution like $P(k)\approx k^{-\gamma}$, where $P(k)$ denotes the frequency of the nodes that are connected to $k$ other nodes. Here we have carried out a study on scale-free networks, where a line graph transformation (i.e., edges in an initial network are transformed into nodes) is applied to a power-law distribution. Our results indicate that a power-law distribution as $P(k)\approx k^{-\gamma +1}$ is found for the transformed network together with a peak for low-degree nodes. In the present work we show a parametrization of this behaviour and discuss its application to real networks as metabolic networks, protein-protein interaction network and World Wide Web., Comment: 18 pages, 8 figures. Minor changes. One figure added
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- 2004
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17. Magnetic moments of the Lambda(1405) and Lambda(1670) resonances
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Jido, D., Hosaka, A., Nacher, J. C., Oset, E., and Ramos, A.
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High Energy Physics - Phenomenology ,Nuclear Theory - Abstract
By using techniques of unitarized chiral perturbation theory, where the $\Lambda(1405)$ and $\Lambda(1670)$ resonances are dynamically generated, we evaluate the magnetic moments of these resonances and their transition magnetic moment. The results obtained here differ appreciably from those obtained with existing quark models. The width for the $\Lambda(1670) \to \Lambda(1405) \gamma$ transition is also evaluated leading to a branching ratio of the order of $2 \times 10^{-6}$., Comment: 19 pags., 8 figs
- Published
- 2002
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18. Two pion photoproduction on nucleons and nuclei in the rho and sigma regions
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Oset, E., Roca, L., Vacas, M. J. Vicente, and Nacher, J. C.
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Nuclear Theory - Abstract
In this talk we report on two physical processes, the photoproduction of $\rho$ mesons in nuclei and the $\pi^0 \pi^0$ photoproduction in nuclei at low energies. In the first case the aim is to observe experimentally the theoretically predicted changes on the $\rho $ properties in the nuclear medium. In the second case one wishes to investigate the modifications of the $\pi \pi$ interaction in the nuclear medium in the region of the $\sigma$ meson. In the first case we observe that it is quite difficult to see large effects due to the $\rho$ modification in the medium because the detection of the $\rho $ is done through the two pions which are produced in the $\Delta$ region and are largely distorted in the medium. In the second case, when the I=0 part of the $\pi \pi$ interaction is substituted by the in medium $\pi \pi$ amplitude, we observe a very large shift of strength in the invariant mass distribution to small values of the mass in $^{12}C$ and $^{208}Pb$ with respect to the distribution of the elementary reaction. This spectacular shift appears to be corroborated by recent experiments at Mainz reported in this same Workshop., Comment: 16 pags., 19 figs., Contribution to the Workshop on chiral fluctuations in hadronic matter, Orsay, Sep. 2001
- Published
- 2001
19. Chiral dynamics and pion-nucleon scattering around the N*(1535) resonance
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Inoue, T., Nacher, J. C., Vacas, M. J. Vicente, and Oset, E.
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High Energy Physics - Phenomenology ,Nuclear Theory - Abstract
We study the S-wave interaction of mesons with baryons in the strangeness S=0 sector in a coupled channel unitary approach. The basic dynamics is drawn from the lowest order meson baryon chiral Lagrangians. Small modifications inspired by models with explicit vector meson exchange in the t-channel are also considered. In addition the pi pi N channel is included and shown to have an important repercussion in the results, particularly in the isospin 3/2 sector., Comment: 3 pages, 2 figues, Talk given by T. Inoue at 9th International Conference on Meson-Nucleon Physics and the Structure of Nucleon (MENU2001), Washington, DC, July 2001
- Published
- 2001
20. Dynamical meson-baryon resonances with chiral Lagrangians
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Ramos, A., Parreno, A., Nacher, J. C., Oset, E., and Bennhold, C.
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Nuclear Theory - Abstract
The s-wave meson-baryon interaction is studied using the lowest-order chiral Lagrangian in a unitary coupled-channels Bethe-Salpeter equation. In the strangeness $S=-1$ sector the low-energy $K^- p$ dynamics leads to the dynamical generation of the $\Lambda(1405)$ as a ${\bar K}N$ state, along with a good description of the $K^- p$ scattering observables. At higher energies, the $\Lambda(1670)$ is also found to be generated dynamically as a $K \Xi$ quasibound state for the first time. For strangeness S=0, it is the $S_{11}(1535)$ resonance that emerges from the coupled-channels equations, leading to a satisfactory description of meson-baryon scattering observables in the energy region around the $S_{11}(1535)$. We speculate on the possible dynamical generation of $\Xi$ resonances within the chiral $S=-2$ sector as ${\bar K} \Lambda$ or ${\bar K} \Sigma$ quasibound states., Comment: 8 pages, 5 figures, Talk given at NSTAR2001, Workshop on the Physics of Excited Nucleons, Mainz (Germany), March 7-10, to be published in World Scientific
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- 2001
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21. Study of polarization observables in double pion photoproduction on the proton
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Nacher, J. C. and Oset, E.
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Nuclear Theory - Abstract
Using a model for two pion photoproduction on the proton previously tested in total cross sections and invariant mass distributions, we evaluate here polarization observables on which recent experiments are providing new information. We evaluate cross sections for spin 1/2 and 3/2, which are measured at Mainz and play an important role in tests of the GHD sum rule. We also evaluate the proton polarization asymmetry $\Sigma$ which is currently under investigation at GRAAL in Grenoble., Comment: 23 pages, 14 ps figures
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- 2001
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22. The role of Delta(1700) excitation and rho production in double pion photoproduction
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Nacher, J. C., Oset, E., Vacas, M. J. Vicente, and Roca, L.
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Nuclear Theory - Abstract
Recent information on invariant mass distributions of the $\gamma p\to\pi^+\pi^0 n$ reaction, where previous theoretical models had shown deficiencies, have made more evident the need for new mechanisms, so far neglected or inaccurately included. We have updated a previous model to include new necessary mechanisms. We find that the production of the $\rho$ meson, and the $\Delta(1700)$ excitation, through interference with the dominant terms, are important mechanisms that solve the puzzle of the $\gamma p\to\pi^+\pi^0 n$ reaction without spoiling the early agreement with the $\gamma p\to\pi^+\pi^- p$ and $\gamma p\to\pi^0\pi^0 p$ reactions., Comment: 39 pages, 13 figures (ps files). Final version. To be published in Nucl. Phys. A
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- 2000
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23. Two pion electroproduction
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Nacher, J. C. and Oset, E.
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Nuclear Theory - Abstract
We have extended a model for the $\gamma N\to \pi\pi N$ reaction to virtual photons and selected the diagrams which have a $\Delta$ in the final state. The agreement found with the $\gamma_v p\to\Delta^0\pi^+$ and $\gamma_v p\to\Delta^{++}\pi^-$ reactions is good. The sensitivity of the results to $N\Delta$ transition form factors is also studied. The present reaction, selecting a particular final state, is an extra test for models of the $\gamma_{v} N\to \pi\pi N$ amplitude., Comment: 4 pages, 2 figures, Talk given at Meson 2000 Workshop, Krakow, Poland, 19-23 May 2000
- Published
- 2000
24. Photoproduction of meson and baryon resonances in a chiral unitary approach
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Oset, E., Marco, E., Nacher, J. C., Oller, J. A., Pelaez, J. R., Ramos, A., and Toki, H.
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Nuclear Theory - Abstract
By means of a coupled channel non-perturbative unitary approach, it is possible to extend the strong constrains of Chiral Perturbation Theory to higher energies. In particular, it is possible to reproduce the lowest lying resonances in meson-meson scattering up to 1.2 GeV using the parameters of the O(p^2) and O(p^4) Chiral Lagrangian. The meson baryon sector can also be tackled along similar lines. We report on an update of these results showing some examples of photon induced reactions where the techniques have been recently applied., Comment: Contribution to the Erice Summer School of Nuclear Physics, 21th course: Electromagnetic Probes and the Structure of Hadrons and Nuclei September 17th - 25th, 1999, Erice/Sicily/Italy
- Published
- 1999
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25. SU(3) Chiral approach to meson and baryon dynamics
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Oset, E., Hosaka, A., Nacher, J. C., Oka, M., Oller, J. A., Parreno, A., Pelaez, J. R., Ramos, A., and Toki, H.
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High Energy Physics - Phenomenology - Abstract
We report on recent progress on the chiral unitary approach, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV and meson baryon interaction up to the first baryonic resonances. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, concretely the K^- p\to\Lambda(1405)\gamma reaction and the N^\ast (1535)N^\ast(1535)\pi and \eta couplings., Comment: 4 pages,3 figures, LaTeX, Talk given at PANIC99, Uppsala (Sweden), June 10-16, 1999
- Published
- 1999
- Full Text
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26. Chiral symmetry in electromagnetically induced resonant two hadron production
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Oset, E., Ramos, A., Marco, E., Nacher, J. C., and Toki, H.
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Nuclear Theory - Abstract
We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented, in which two hadrons, either two mesons or a meson and a baryon, in a resonant state are produced in photoproduction processes., Comment: 10 pages, 2 ps figures. Talk given at the IVth Workshop on "Electromagnetically Induced Two Hadron Emission", Granada (Spain), May 26-29, 1999
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- 1999
27. Chiral Unitary Approach To The N*N*pi, N*N*eta Couplings For The N*(1535) Resonance
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Nacher, J. C., Parreno, A., Oset, E., Ramos, A., Hosaka, A., and Oka, M.
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Nuclear Theory - Abstract
Using a chiral unitary model in which the negative parity nucleon resonance $N^\ast \equiv N^\ast(1535)$ is generated dynamically by means of the Bethe Salpeter equation with coupled meson baryon channels in the $S = 0$ sector, we have obtained the $\pi^0 N^\ast N^\ast$ and $\eta N^\ast N^\ast$ couplings. The $\pi^0 N^\ast N^\ast$ coupling has smaller strength and the same sign as the $\pi^0 N N$ coupling. This rules out the mirror assignment of chiral symmetry where the ground state nucleon $N$ and the negative parity resonance $N^\ast$ are envisaged as chiral partners in the baryon sector., Comment: 30 pages, 15 figures (ps files). The new version discusses pi-N scattering around the N*(1535) resonance
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- 1999
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28. Radiative production of the Lambda(1405) resonance in K collisions on protons and nuclei
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Nacher, J. C., Oset, E., Toki, H., and Ramos, A.
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Nuclear Theory - Abstract
We have carried a theoretical study of the K^- p\to M B \gamma reaction with M B = K^-p, \bar{K}^0 n, \pi^- \Sigma^+, \pi^+ \Sigma^-, \pi^0 \Sigma^0, \pi^0 \Lambda, for K^- lab. momenta between 200 and 500 MeV/c, using a chiral unitary approach for the strong K^-p interaction with its coupled channels. The \Lambda(1405) resonance, which is generated dynamically in this approach, shows up clearly in the d\sigma/dM_I spectrum, providing new tests for chiral symmetry and the unitary approach, as well as information regarding the nature of the resonance. The photon detection alone, summing all channels, is shown to reproduce quite accurately the strength and shape of the \Lambda(1405) resonance. Analogous reactions in nuclei can provide much information on the properties of this resonance in a nuclear medium., Comment: 11 pages, 3 postscripts figures
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- 1999
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29. Recent progress on the chiral unitary approach to meson meson and meson baryon interactions
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Oset, E., Oller, J. A., Pelaez, J. R., Ramos, A., Chiang, H. C., Guerrero, F., Hirenzaki, S., Lee, T. S. H., Marco, E., Nacher, J. C., Okumura, Y., Parreno, A., Toki, H., and Vicente-Vacas, M.
- Subjects
Nuclear Theory - Abstract
We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and $K^-$ atoms., Comment: Contribution to the KEK Tanashi Symposium on Physics of Hadrons and Nuclei, Tokyo, December 1998, 10 pages, 3 postscript figures. To be published as a special issue of Nuclear Physics A
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- 1999
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30. Photoproduction of the Lambda(1405) on the proton and nuclei
- Author
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Nacher, J. C., Oset, E., Toki, H., and Ramos, A.
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Nuclear Theory - Abstract
We study the gamma p ---> K^+ Lambda(1405) reaction at energies close to threshold using a chiral unitary model where the resonance is generated dynamically from K^-p interaction with other channels constructed from the octets of baryons and mesons. Predictions are made for cross sections into several channels and it is shown that the detection of the K^+ is sufficient to determine the shape and strength of the Lambda(1405) resonance. The determination of the resonance properties in nuclei requires instead the detection of the resonance decay channels. Pauli blocking effects on the resonance, which have been shown to be very important for the resonance at rest in the nucleus, are irrelevant here where the resonance is produced with a large momentum. The nuclear modifications here would thus offer information on the resonance and K^- nucleus dynamics complementary to the one offered so far by K^- atoms., Comment: 9 pages, 4 postscripts figures
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- 1998
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31. Double Pion Production Reactions
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Oset, E., Tejedor, J. A. Gomez, Cano, F., Nacher, J. C., Kamalov, S., Alvarez-Ruso, L., and Hernandez, E.
- Subjects
Nuclear Theory - Abstract
We report on reactions producing two pions induced by real and virtual photons or nucleons. The role of different resonances in these reactions is emphasized. Novel results on coherent two pion photoproduction in nuclei are also reported., Comment: Contribution to the conference on N* physics and non-perturbative QCD, Trento, Italy, May 18 - 29, 1998. 9 pages and 7 postscript figures. To be published in Few-Body Systems Suppl
- Published
- 1998
32. A model for pion Delta electroproduction on the proton
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Nacher, J. C. and Oset, E.
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Nuclear Theory - Abstract
We have extended a model for the $\gamma N\to \pi\pi N$ reaction to virtual photons and selected the diagrams which have a $\Delta$ in the final state. With this model we have evaluated cross sections for the virtual photon cross section as a function of $Q^2$ for different energies. The agreement found with the $\gamma_v p\to\Delta^0\pi^+$ and $\gamma_v p\to\Delta^{++}\pi^-$ reactions is good. The sensitivity of the results to $N\Delta$ transition form factors is also studied. The present reaction, selecting a particular final state, is an extra test for models of the $\gamma_{v} N\to \pi\pi N$ amplitude. The experimental measurement of the different isospin channels for this reaction are encouraged as a means to unravel the dynamics of the two pions photoproduction processes., Comment: 30 pages, 10 figures (ps files). Major changes added. To be published in Nucl. Phys. A
- Published
- 1998
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33. Clinical utility and prognostic value of right atrial function in severe tricuspid regurgitation. One more piece of the puzzle
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Hinojar Baydes, R, primary, Gonzalez-Gomez, A, additional, Garcia-Martin, A, additional, Monteagudo, J M, additional, Garcia-Lunar, I, additional, Rivas, S, additional, Sanroman, M A, additional, Pardo, A, additional, Jimenez-Nacher, J J, additional, Sanchez-Recalde, A, additional, Zamorano, J L, additional, and Fernandez-Golfin, C, additional
- Published
- 2022
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34. A Bipartite Graph Based Model of Protein Domain Networks
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Nacher, J. C., Ochiai, T., Hayashida, M., Akutsu, T., Akan, Ozgur, Series editor, Bellavista, Paolo, Series editor, Cao, Jiannong, Series editor, Dressler, Falko, Series editor, Ferrari, Domenico, Series editor, Gerla, Mario, Series editor, Kobayashi, Hisashi, Series editor, Palazzo, Sergio, Series editor, Sahni, Sartaj, Series editor, Shen, Xuemin (Sherman), Series editor, Stan, Mircea, Series editor, Xiaohua, Jia, Series editor, Zomaya, Albert, Series editor, Coulson, Geoffrey, Series editor, and Zhou, Jie, editor
- Published
- 2009
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35. Incremental value of cardiac deformation analysis in patients severe tricuspid regurgitation and normal right ventricular function: a cardiovascular magnetic resonance imaging study: P718
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Gomez, Gonzalez A., Hinojar, R., Esteban, A., Fernandez Mendez, M A., Carbonell, A., Garcia, A., Marco, A., Monteagudo Ruiz, J M., Jimenez Nacher, J J., Zamorano, J L., and Fernandez-Golfin, C.
- Published
- 2017
36. Topological aspects of protein networks
- Author
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Nacher, J. C., Hayashida, M., Akutsu, T., Kacprzyk, Janusz, editor, Namatame, Akira, editor, Kurihara, Satoshi, editor, and Nakashima, Hideyuki, editor
- Published
- 2007
- Full Text
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37. Postnatal Neurogenesis and Neuronal Regeneration
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López-García, C., Nacher, J., Herdegen, T., editor, and Delgado-García, J., editor
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- 2004
- Full Text
- View/download PDF
38. Long term effects of 24-h-restraint stress on the connectivity and structure of interneurons in the basolateral amygdala
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Pesarico A, Carceller H, Guirado R, Coviello S, and Nacher J
- Abstract
The effects of intense stressors can last a long time and may lead to the development of psychiatric disorders, including posttraumatic stress disorder. The basolateral amygdala (BLA) plays a critical role in these diseases and is extremely sensitive to stress. Here, we explored in male and female mice the long-term (35days) impact of a 24-h restraint stress on BLA circuitry. We used Thy1-YFP mice to discriminate 2 subpopulations of excitatory neurons, which participate in "Fear-On" (Thy1-) and "Fear-Off" (Thy1+) circuits. The stress decreased the density of parvalbumin (PV)+inhibitory neurons in both sexes but did not alter their dendritic complexity. We also analyzed the perisomatic input of basket interneurons on Thy1+ and Thy1- neurons, finding sex dependent effects. In males, we did not find alterations in the density of PV+ puncta or in that of cannabinoid receptor 1 (CB1R)+puncta from cholecystokinin+ basket cells. By contrast, in females we found increased the density of PV+ puncta on Thy1+ neurons and reduced on the Thy1- neurons. This adverse experience also reduced in the long term the density of CB1R+ puncta both on Thy1+ and Thy1- cells in females. The expression of the activity marker FosB was not altered in PV+ interneurons and in Thy1+ neurons of stressed animals. The density of perineuronal nets, a specialized region of the extracellular matrix, which covers particularly PV+ interneurons and regulates their connectivity, was increased by stress in male mice. Our findings indicate that a single stressful event can produce long-term alterations in the inhibitory circuits of the BLA, especially on PV+ neurons and their plasticity, and that there is a differential impact depending on the sex and the fear-related circuits involved. Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.
- Published
- 2022
39. The Parietal Lobe in Alzheimer's Disease and Blindness
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Ahullo-Fuster M, Ortiz T, Varela-Donoso E, Nacher J, and Sanchez-Sanchez M
- Abstract
The progressive aging of the population will notably increase the burden of those diseases which leads to a disabling situation, such as Alzheimer's disease (AD) and ophthalmological diseases that cause a visual impairment (VI). Eye diseases that cause a VI raise neuroplastic processes in the parietal lobe. Meanwhile, the aforementioned lobe suffers a severe decline throughout AD. From this perspective, diving deeper into the particularities of the parietal lobe is of paramount importance. In this article, we discuss the functions of the parietal lobe, review the parietal anatomical and pathophysiological peculiarities in AD, and also describe some of the changes in the parietal region that occur after VI. Although the alterations in the hippocampus and the temporal lobe have been well documented in AD, the alterations of the parietal lobe have been less thoroughly explored. Recent neuroimaging studies have revealed that some metabolic and perfusion impairments along with a reduction of the white and grey matter could take place in the parietal lobe during AD. Conversely, it has been speculated that blinding ocular diseases induce a remodeling of the parietal region which is observable through the improvement of the integration of multimodal stimuli and in the increase of the volume of this cortical region. Based on current findings concerning the parietal lobe in both pathologies, we hypothesize that the increased activity of the parietal lobe in people with VI may diminish the neurodegeneration of this brain region in those who are visually impaired by oculardiseases.
- Published
- 2022
40. Phenotype and Distribution of Immature Neurons in the Human Cerebral Cortex Layer II
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Coviello S, Gramuntell Y, Klimczak P, Varea E, Blasco-Ibanez J, Crespo C, Gutierrez A, and Nacher J
- Subjects
neurogenesis ,immature neurons ,doublecortin ,cerebral cortex ,human brain - Abstract
This work provides evidence of the presence of immature neurons in the human brain, specifically in the layer II of the cerebral cortex. Using surgical samples from epileptic patients and post-mortem tissue, we have found cells with different levels of dendritic complexity (type I and type II cells) expressing DCX and PSA-NCAM and lacking expression of the mature neuronal marker NeuN. These immature cells belonged to the excitatory lineage, as demonstrated both by the expression of CUX1, CTIP2, and TBR1 transcription factors and by the lack of the inhibitory marker GAD67. The type II cells had some puncta expressing inhibitory and excitatory synaptic markers apposed to their perisomatic and peridendritic regions and ultrastructural analysis suggest the presence of synaptic contacts. These cells did not present glial cell markers, although astroglial and microglial processes were found in close apposition to their somata and dendrites, particularly on type I cells. Our findings confirm the presence of immature neurons in several regions of the cerebral cortex of humans of different ages and define their lineage. The presence of some mature features in some of these cells suggests the possibility of a progressively integration as excitatory neurons, as described in the olfactory cortex of rodents.
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- 2022
41. Perineuronal Nets: Subtle Structures with Large Implications
- Author
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Carceller H, Gramuntell Y, Klimczak P, and Nacher J
- Subjects
brain evolution, extracellular matrix, interneuron, perineuronal net, psychiatric disorders - Abstract
Perineuronal nets (PNNs) are specialized structures of the extracellular matrix that surround the soma and proximal dendrites of certain neurons in the central nervous system, particularly parvalbumin-expressing interneurons. Their appearance overlaps the maturation of neuronal circuits and the closure of critical periods in different regions of the brain, setting their connectivity and abruptly reducing their plasticity. As a consequence, the digestion of PNNs, as well as the removal or manipulation of their components, leads to a boost in this plasticity and can play a key role in the functional recovery from different insults and in the etiopathology of certain neurologic and psychiatric disorders. Here we review the structure, composition, and distribution of PNNs and their variation throughout the evolutive scale. We also discuss methodological approaches to study these structures. The function of PNNs during neurodevelopment and adulthood is discussed, as well as the influence of intrinsic and extrinsic factors on these specialized regions of the extracellular matrix. Finally, we review current data on alterations in PNNs described in diseases of the central nervous system (CNS), focusing on psychiatric disorders. Together, all the data available point to the PNNs as a promising target to understand the physiology and pathologic conditions of the CNS.
- Published
- 2022
42. Altered expression of vesicular glutamate transporter-2 and cleaved caspase-3 in the locus coeruleus of nerve-injured rats
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Bravo L, Mariscal P, Llorca-Torralba M, Lopez-Cepero J, Nacher J, and Berrocoso E
- Subjects
neuropathic pain ,locus coeruleus ,vesicular glutamate transporter 2 ,cleaved caspase 3 ,vesicular glutamate transporter 1 - Abstract
Neuropathic pain is a debilitating chronic condition provoked by a lesion in the nervous system and it induces functional alterations to the noradrenergic locus coeruleus (LC), affecting distinct dimensions of pain, like sensorial hypersensitivity, pain-induced depression, and anxiety. However, the neurobiological changes induced by nerve damage in the LC remain unclear. Here, we analyzed excitatory and inhibitory inputs to the LC, as well as the possible damage that noradrenergic neurons suffer after the induction of neuropathic pain through chronic constriction injury (CCI). Neuropathic pain was induced in male Sprague-Dawley rats, and the expression of the vesicular glutamate transporter 1 or 2 (VGLUT1 or VGLUT2), vesicular GABA transporter (VGAT), and cleaved caspase-3 (CC3) was analyzed by immunofluorescence 7 (CCI7d) or 28 days after the original lesion (CCI28d). While no significant differences in the density of VGLUT1 puncta were evident, CCI7d induced a significant increase in the perisomatic VGLUT2/VGAT ratio relative to Sham-operated and CCI28d animals. By contrast, when the entire region of LC is evaluated, there was a significant reduction in the density of VGLUT2 puncta in CCI28d animals, without changes in VGLUT2/VGAT ratio relative to the CCI7d animals. Additionally, changes in the noradrenergic soma size, and a lower density of mitochondria and lysosomes were evident in CCI28d animals. Interestingly, enhanced expression of the apoptotic marker CC3 was also evident in the CCI28d rats, mainly co-localizing with glial fibrillary acidic protein but not with any neuronal or noradrenergic marker. Overall, short-term pain appears to lead to an increase of markers of excitatory synapses in the perisomatic region of noradrenergic cells in the LC, an effect that is lost after long-term pain, which appears to activate apoptosis.
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- 2022
43. Impact of stress on inhibitory neuronal circuits, our tribute to Bruce McEwen
- Author
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Perez-Rando M, Carceller H, Castillo-Gomez E, Bueno-Fernandez C, Garcia-Mompo C, Gilabert-Juan J, Guirado R, Pesarico A, and Nacher J
- Abstract
This manuscript is dedicated to the memory of Bruce S. McEwen, to commemorate the impact he had on how we understand stress and neuronal plasticity, and the profound influence he exerted on our scientific careers. The focus of this review is the impact of stressors on inhibitory circuits, particularly those of the limbic system, but we also consider other regions affected by these adverse experiences. We revise the effects of acute and chronic stress during different stages of development and lifespan, taking into account the influence of the sex of the animals. We review first the influence of stress on the physiology of inhibitory neurons and on the expression of molecules related directly to GABAergic neurotransmission, and then focus on specific interneuron subpopulations, particularly on parvalbumin and somatostatin expressing cells. Then we analyze the effects of stress on molecules and structures related to the plasticity of inhibitory neurons: the polysialylated form of the neural cell adhesion molecule and perineuronal nets. Finally, we review the potential of antidepressants or environmental manipulations to revert the effects of stress on inhibitory circuits. © 2022 The Authors.
- Published
- 2022
44. Estradiol Regulates Polysialylated Form of the Neural Cell Adhesion Molecule Expression and Connectivity of O-LM Interneurons in the Hippocampus of Adult Female Mice
- Author
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Perez-Rando M, Guirado R, Tellez-Merlo G, Carceller H, and Nacher J
- Subjects
Structural plasticity ,17 beta-Estradiol ,nervous system ,Polysialylated form of the neural cell adhesion molecule ,O-LM interneurons ,Somatostatin - Abstract
The estrous cycle is caused by the changing concentration of ovarian hormones, particularly 17 beta-estradiol, a hormone whose effect on excitatory circuits has been extensively reported. However, fewer studies have tried to elucidate how this cycle, or this hormone, affects the plasticity of inhibitory networks and the structure of interneurons. Among these cells, somatostatin-expressing O-LM neurons of the hippocampus are especially interesting. They have a role in the modulation of theta oscillations, and they receive direct input from the entorhinal cortex, which place them in the center of hippocampal function. In this study, we report that the expression of polysialylated form of the neural cell adhesion molecule (PSA-NCAM) in the hippocampus, a molecule involved in the plasticity of somatostatin-expressing interneurons in the adult brain, fluctuated through the different stages of the estrous cycle. Likewise, these stages and the expression of PSA-NCAM affected the density of dendritic spines of O-LM cells. We also describe that 17 beta-estradiol replacement of adult ovariectomized female mice caused an increase in the perisomatic inhibitory puncta in O-LM interneurons as well as an increase in their axonal bouton density. Interestingly, this treatment also induced a decrease in their dendritic spine density, specifically in O-LM interneurons lacking PSA-NCAM expression. Finally, using an ex vivo real-time assay with entorhinal-hippocampal organotypic cultures, we show that this hormone decreased the dynamics in spinogenesis, altogether highlighting the modulatory effect that 17 beta-estradiol has on inhibitory circuits. (C) 2021 S. Karger AG, Basel
- Published
- 2022
45. Double Pion Production Reactions
- Author
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Oset, E., Gómez Tejedor, J. A., Cano, F., Nacher, J. C., Kamalov, S., Alvarez-Ruso, L., Hernández, E., Plessas, W., editor, Simula, Silvano, editor, Saghai, Bijan, editor, Mukhopadhyay, Nimai C., editor, and Burkert, Volker D., editor
- Published
- 1999
- Full Text
- View/download PDF
46. Alterations in the volume of thalamic nuclei in patients with schizophrenia and persistent auditory hallucinations
- Author
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Perez-Rando, M., Elvira, U., and Nacher, J.
- Published
- 2022
- Full Text
- View/download PDF
47. Effects of a double hit model for schizophrenia on the thalamic reticular nucleus
- Author
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Klimczak, P., Gramuntell, Y., Pérez-Rando, M., Alcaide, J., and Nacher, J.
- Published
- 2022
- Full Text
- View/download PDF
48. Perineuronal nets regulate synaptic transmission in the thalamic reticular nucleus
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Gramuntell, Y., Klimczak, P., Carceller, H., Beltran, M., and Nacher, J.
- Published
- 2022
- Full Text
- View/download PDF
49. Prognostic value of atrial fibrillation in COVID-19 admitted patients
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Santos Sanchez, A, primary, Gonzalez-Recio, P E, additional, Sanchez-Corral, E, additional, and Jimenez-Nacher, J J, additional
- Published
- 2021
- Full Text
- View/download PDF
50. Mortality and heart failure in patients with severe tricuspid regurgitation. Risk stratification based on TR severity by CMR
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Hinojar Baydes, R, primary, Gonzalez-Gomez, A, additional, Garcia-Martin, A, additional, Monteagudo, J M, additional, Alonso-Salinas, G, additional, Hernandez-Jimenez, S, additional, Fernandez-Mendez, M A, additional, Garcia De Vicente, A, additional, Jimenez-Nacher, J J, additional, Zamorano, J L, additional, and Fernandez-Golfin, C, additional
- Published
- 2021
- Full Text
- View/download PDF
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