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81.
Matthieu Gilson Anthony N. Burkitt David B. Grayden Doreen A. Thomas J. Leo van Hemmen 《Biological cybernetics》2009,101(2):103-114
Spike-timing-dependent plasticity (STDP) is believed to structure neuronal networks by slowly changing the strengths (or weights)
of the synaptic connections between neurons depending upon their spiking activity, which in turn modifies the neuronal firing
dynamics. In this paper, we investigate the change in synaptic weights induced by STDP in a recurrently connected network
in which the input weights are plastic but the recurrent weights are fixed. The inputs are divided into two pools with identical
constant firing rates and equal within-pool spike-time correlations, but with no between-pool correlations. Our analysis uses
the Poisson neuron model in order to predict the evolution of the input synaptic weights and focuses on the asymptotic weight
distribution that emerges due to STDP. The learning dynamics induces a symmetry breaking for the individual neurons, namely
for sufficiently strong within-pool spike-time correlation each neuron specializes to one of the input pools. We show that
the presence of fixed excitatory recurrent connections between neurons induces a group symmetry-breaking effect, in which
neurons tend to specialize to the same input pool. Consequently STDP generates a functional structure on the input connections
of the network. 相似文献
82.
Matthieu Gilson Anthony N. Burkitt David B. Grayden Doreen A. Thomas J. Leo van Hemmen 《Biological cybernetics》2009,101(2):81-102
Spike-timing-dependent plasticity (STDP) determines the evolution of the synaptic weights according to their pre- and post-synaptic
activity, which in turn changes the neuronal activity. In this paper, we extend previous studies of input selectivity induced
by (STDP) for single neurons to the biologically interesting case of a neuronal network with fixed recurrent connections and
plastic connections from external pools of input neurons. We use a theoretical framework based on the Poisson neuron model
to analytically describe the network dynamics (firing rates and spike-time correlations) and thus the evolution of the synaptic
weights. This framework incorporates the time course of the post-synaptic potentials and synaptic delays. Our analysis focuses
on the asymptotic states of a network stimulated by two homogeneous pools of “steady” inputs, namely Poisson spike trains
which have fixed firing rates and spike-time correlations. The (STDP) model extends rate-based learning in that it can implement,
at the same time, both a stabilization of the individual neuron firing rates and a slower weight specialization depending
on the input spike-time correlations. When one input pathway has stronger within-pool correlations, the resulting synaptic
dynamics induced by (STDP) are shown to be similar to those arising in the case of a purely feed-forward network: the weights
from the more correlated inputs are potentiated at the expense of the remaining input connections. 相似文献
83.
William Matlock Kevin K. Chau Manal AbuOun Emma Stubberfield Leanne Barker James Kavanagh Hayleah Pickford Daniel Gilson Richard P. Smith H. Soon Gweon Sarah J. Hoosdally Jeremy Swann Robert Sebra Mark J. Bailey Timothy E. A. Peto Derrick W. Crook Muna F. Anjum Daniel S. Read A. Sarah Walker Nicole Stoesser Liam P. Shaw REHAB consortium 《The ISME journal》2021,15(8):2322
F-type plasmids are diverse and of great clinical significance, often carrying genes conferring antimicrobial resistance (AMR) such as extended-spectrum β-lactamases, particularly in Enterobacterales. Organising this plasmid diversity is challenging, and current knowledge is largely based on plasmids from clinical settings. Here, we present a network community analysis of a large survey of F-type plasmids from environmental (influent, effluent and upstream/downstream waterways surrounding wastewater treatment works) and livestock settings. We use a tractable and scalable methodology to examine the relationship between plasmid metadata and network communities. This reveals how niche (sampling compartment and host genera) partition and shape plasmid diversity. We also perform pangenome-style analyses on network communities. We show that such communities define unique combinations of core genes, with limited overlap. Building plasmid phylogenies based on alignments of these core genes, we demonstrate that plasmid accessory function is closely linked to core gene content. Taken together, our results suggest that stable F-type plasmid backbone structures can persist in environmental settings while allowing dramatic variation in accessory gene content that may be linked to niche adaptation. The association of F-type plasmids with AMR may reflect their suitability for rapid niche adaptation.Subject terms: Environmental microbiology, Genomics 相似文献
84.
Ventilation rates indicate stress-coping styles in Nile tilapia 总被引:2,自引:0,他引:2
Behavioural responses to stress can form distinct profiles in a wide range of animals: proactive and reactive profiles or
coping styles. Stress responsiveness can also differentiate between the behavioural profiles. The tendency to regain feed
intake following transfer to a novel social-isolation tank (the speed of acclimation) can discriminate between proactive or
reactive profiles. Consequently, differential stress responsiveness can be linked to this feeding behaviour trait. This study
shows that ventilation rates of Nile tilapia, Oreochromis niloticus (L.), correlate with the rate of feeding resumption, following transfer to a novel social-isolation aquarium. Therefore,
ventilation rate (VR) indicates coping styles; consequently, VR is a proxy for the way fish will deal with environmental challenges. 相似文献
85.
86.
Alessandra Galati Emanuela Micheli Claudia Alicata Tiziano Ingegnere Alessandro Cicconi Miriam Caroline Pusch Marie-Josèphe Giraud-Panis Eric Gilson Stefano Cacchione 《Nucleic acids research》2015,43(12):5824-5837
The ends of eukaryotic chromosomes need to be protected from the activation of a DNA damage response that leads the cell to replicative senescence or apoptosis. In mammals, protection is accomplished by a six-factor complex named shelterin, which organizes the terminal TTAGGG repeats in a still ill-defined structure, the telomere. The stable interaction of shelterin with telomeres mainly depends on the binding of two of its components, TRF1 and TRF2, to double-stranded telomeric repeats. Tethering of TRF proteins to telomeres occurs in a chromatin environment characterized by a very compact nucleosomal organization. In this work we show that binding of TRF1 and TRF2 to telomeric sequences is modulated by the histone octamer. By means of in vitro models, we found that TRF2 binding is strongly hampered by the presence of telomeric nucleosomes, whereas TRF1 binds efficiently to telomeric DNA in a nucleosomal context and is able to remodel telomeric nucleosomal arrays. Our results indicate that the different behavior of TRF proteins partly depends on the interaction with histone tails of their divergent N-terminal domains. We propose that the interplay between the histone octamer and TRF proteins plays a role in the steps leading to telomere deprotection. 相似文献
87.
Degang Yang Tiejun Shui Jake W. Miranda Danny J. Gilson Zhengyu Song Jia Chen Chao Shi Jianyu Zhu Jun Yang Zhichun Jing 《PLoS neglected tropical diseases》2016,10(1)
Background
The persistence of Mycobacterium leprae (M. leprae) infection is largely dependent on the types of host immune responses being induced. Macrophage, a crucial modulator of innate and adaptive immune responses, could be directly infected by M. leprae. We therefore postulated that M. leprae-infected macrophages might have altered immune functions.Methodology/Principal Findings
Here, we treated monocyte-derived macrophages with live or killed M. leprae, and examined their activation status and antigen presentation. We found that macrophages treated with live M. leprae showed committed M2-like function, with decreased interleukin 1 beta (IL-1beta), IL-6, tumor necrosis factor alpha (TNF-alpha) and MHC class II molecule expression and elevated IL-10 and CD163 expression. When incubating with naive T cells, macrophages treated with live M. leprae preferentially primed regulatory T (Treg) cell responses with elevated FoxP3 and IL-10 expression, while interferon gamma (IFN-gamma) expression and CD8+ T cell cytotoxicity were reduced. Chromium release assay also found that live M. leprae-treated macrophages were more resistant to CD8+ T cell-mediated cytotoxicity than sonicated M. leprae-treated monocytes. Ex vivo studies showed that the phenotype and function of monocytes and macrophages had clear differences between L-lep and T-lep patients, consistent with the in vitro findings.Conclusions/Significance
Together, our data demonstrate that M. leprae could utilize infected macrophages by two mechanisms: firstly, M. leprae-infected macrophages preferentially primed Treg but not Th1 or cytotoxic T cell responses; secondly, M. leprae-infected macrophages were more effective at evading CD8+ T cell-mediated cytotoxicity. 相似文献88.
Gaia Nebbia Dimitra Peppa Anna Schurich Pooja Khanna Harsimran D. Singh Yang Cheng William Rosenberg Geoffrey Dusheiko Richard Gilson Joanne ChinAleong Patrick Kennedy Mala K. Maini 《PloS one》2012,7(10)
The S-type lectin galectin-9 binds to the negative regulatory molecule Tim-3 on T cells and induces their apoptotic deletion or functional inactivation. We investigated whether galectin-9/Tim-3 interactions contribute to the deletion and exhaustion of the antiviral T cell response in chronic hepatitis B virus infection (CHB). We found Tim-3 to be expressed on a higher percentage of CD4 and CD8 T cells from patients with CHB than healthy controls (p<0.0001) and to be enriched on activated T cells and those infiltrating the HBV-infected liver. Direct ex vivo examination of virus-specific CD8 T cells binding HLA-A2/peptide multimers revealed that Tim-3 was more highly upregulated on HBV-specific CD8 T cells than CMV-specific CD8 T cells or the global CD8 T cell population in patients with CHB (p<0.001) or than on HBV-specific CD8 after resolution of infection. T cells expressing Tim-3 had an impaired ability to produce IFN-γ and TNF-α upon recognition of HBV-peptides and were susceptible to galectin-9-triggered cell death in vitro. Galectin-9 was detectable at increased concentrations in the sera of patients with active CHB-related liver inflammation (p = 0.02) and was strongly expressed by Kupffer cells within the liver sinusoidal network. Tim-3 blockade resulted in enhanced expansion of HBV-specific CD8 T cells able to produce cytokines and mediate cytotoxicity in vitro. Blocking PD-1 in combination with Tim-3 enhanced the number of patients from whom functional antiviral responses could be recovered and/or the strength of responses, indicating that these co-inhibitory molecules play a non-redundant role in driving T cell exhaustion in CHB. Patients taking antivirals able to potently suppress HBV viraemia continued to express Tim-3 on their T cells and respond to Tim-3 blockade. In summary, both Tim-3 and galectin-9 are increased in CHB and may contribute to the inhibition and deletion of T cells as they infiltrate the HBV-infected liver. 相似文献
89.
Caroline Marques Maia Gilson Luiz Volpato 《Journal of applied animal welfare science : JAAWS》2018,21(4):316-324
Preference tests have usually been used to identify nonhuman animal preferences for welfare purposes (environmental enrichment), but they are mostly at the group level—that is, group preferences for resources or environmental conditions. However, a more robust method was developed to analyze animal preference, and this method detected clear individual variation in preferences of Nile tilapia fish (Oreochromis niloticus) selecting different background colors. Here, a clear individual variability of preference was found for another type of enrichment—the sizes of substrate. Despite this variability, a consistent response was detected at the group level: Small gravel was less frequently preferred than avoided, and the more decided fish (those who preferred only one substrate size) never preferred gravel over sand-size substrate. That is, Nile tilapia avoided gravel and preferred smaller substrate, and this finding was possibly associated with their mouth gap. Considering that small gravel is a substrate often used for fish rearing, these findings highlight fish keepers’ incorrect perception of fish needs, based mostly on arbitrary criteria instead of actual fish preferences and without considering individual needs. 相似文献
90.
Fenofibrate reverses changes induced by high‐fat diet on metabolism in mice muscle and visceral adipocytes 下载免费PDF全文