The autoimmune regulator (AIRE) induces the transcription of thousands of peripheral tissue genes (PTGs) in thymic epithelial cells (TECs) to mediate immunological tolerance. The chromatin state ...required for optimal AIRE function in TECs and how this state is induced remains unclear. We tested the role of the histone acetyltransferase, KAT7 (also known as HBO1 or MYST2), which is essential for acetylation of histone 3 lysine 14, in TEC differentiation, AIRE-mediated PTG expression, and thymic tolerance. We find that KAT7 is required for optimal expansion of medullary TEC and has a major role in the expression of AIRE-dependent PTGs, associated with enhanced chromatin accessibility at these gene loci in TECs. Mice with TEC-specific
deletion develop organ-specific autoimmunity with features resembling those observed in
-deficient mice. These findings highlight critical roles for KAT7-mediated acetylation in promoting a chromatin state at PTG loci that enables AIRE function and the establishment of immunological tolerance.
We investigate the dynamics of large-scale interacting neural populations, composed of conductance based, spiking model neurons with modifiable synaptic connection strengths, which are possibly also ...subjected to external noisy currents. The network dynamics is controlled by a set of neural population probability distributions (PPD) which are constructed along the same lines as in the Klimontovich approach to the kinetic theory of plasmas. An exact non-closed, nonlinear, system of integro-partial differential equations is derived for the PPDs. As is customary, a closing procedure leads to a mean field limit. The equations we have obtained are of the same type as those which have been recently derived using rigorous techniques of probability theory. The numerical solutions of these so called McKean–Vlasov–Fokker–Planck equations, which are only valid in the limit of infinite size networks, actually shows that the statistical measures as obtained from PPDs are in good agreement with those obtained through direct integration of the stochastic dynamical system for large but finite size networks. Although numerical solutions have been obtained for networks of Fitzhugh–Nagumo model neurons, which are often used to approximate Hodgkin–Huxley model neurons, the theory can be readily applied to networks of general conductance-based model neurons of arbitrary dimension.
Adaptive Neural Compensator for Robotic Systems Control Gandolfo, Daniel Ceferino; Rossomando, Francisco Guido; Soria, Carlos Miguel ...
Revista IEEE América Latina,
2019-April, 2019-4-00, Letnik:
17, Številka:
4
Journal Article
In the area of robotics systems, there are numerous applications where robots are expected to move rapidly from one place to another, or follow desired trajectories while maintaining good dynamic ...behavior. However, certain non-linearities, uncertainties in dynamics and external perturbations make the design of ideal controllers a complicated task in many situations. In this paper, we propose a control scheme that combines a nominal feedback controller with a classical PD and a robust adaptive compensator based on artificial neural networks. Using this control scheme, it is possible to obtain a fully tuned compensation parameters and a strong robustness with respect to uncertain dynamics and different non-linearities, as well as to keep the output tracking error bounded to values close to zero. In order to show the performance of the proposed technique, a SCARA (Selective Compliant Articulated Robot Arm) type robot with two degrees of freedom is considered in this case; but this control proposal can be applied to different systems with dynamic variations. The efficiency and performance of the control law is demonstrated through simulation results and the stability analysis is carried out using Lyapunov's theory.
Divergence dating studies, which combine temporal data from the fossil record with branch length data from molecular phylogenetic trees, represent a rapidly expanding approach to understanding the ...history of life. National Evolutionary Synthesis Center hosted the first Fossil Calibrations Working Group (3–6 March, 2011, Durham, NC, USA), bringing together palaeontologists, molecular evolutionists and bioinformatics experts to present perspectives from disciplines that generate, model and use fossil calibration data. Presentations and discussions focused on channels for interdisciplinary collaboration, best practices for justifying, reporting and using fossil calibrations and roadblocks to synthesis of palaeontological and molecular data. Bioinformatics solutions were proposed, with the primary objective being a new database for vetted fossil calibrations with linkages to existing resources, targeted for a 2012 launch.
We investigate the dynamics of large-scale interacting neural populations, composed of conductance based, spiking model neurons with modifiable synaptic connection strengths, which are possibly also ...subjected to external noisy currents. The network dynamics is controlled by a set of neural population probability distributions (\(\mathrm{PPD}\))which are constructed along the same lines as in the Klimontovich approach to the kinetic theory of plasmas. An exact non-closed, nonlinear, system of integro-partial differential equations is derived for the \(\mathrm{PPD}\)s. As is customary, a closing procedure leads to a mean field limit. The equations we have obtained are of the same type as those which have been recently derived using rigorous techniques of probability theory. The numerical solutions of these so called McKean-Vlasov-Fokker-Planck equations, which are only valid in the limit of infinite size networks, actually shows that the statistical measures as obtained from \(\mathrm{PPD}\)s are in good agreement with those obtained through direct integration of the stochastic dynamical system for large but finite size networks. Although numerical solutions have been obtained in the case of Fitzhugh-Nagumo model neurons, the theory can be readily applied to systems of Hodgkin-Huxley type model neurons of arbitrary dimension.
The octadecaneuropeptide (ODN; QATVGDVNTDRPGLLDLK) and its C-terminal octapeptide (OP; RPGLLDLK), which exert anxiogenic activity, have been previously shown to increase intracellular calcium ...concentration (Ca2+i) in cultured rat astrocytes through activation of a metabotropic receptor positively coupled to phospholipase C. It has also been found that the d-Leu5OP analog possesses a weak antagonistic activity. The aim of the present study was to synthesize and characterize cyclic analogs of OP and d-Leu5OP. On-resin homodetic backbone cyclization of OP yielded an analog, cyclo1-8 OP, which was three times more potent and 1.4-times more efficacious than OP to increase Ca2+i in cultured rat astrocytes. Cyclo1-8 OP also mimicked the effect of both OP and ODN on polyphosphoinositide turnover. Conversely, the cyclo1-8 d-Leu5OP analog was totally devoid of agonistic activity but suppressed the effect of OP and ODN on Ca2+i and phosphoinositide metabolism in astrocytes. The structure of these cyclic analogs has been determined by two-dimensional 1H-NMR and molecular dynamics. Cyclo1-8 OP exhibited a single conformation characterized by a gamma turn comprising residues Pro2-Leu4 and a type III beta turn encompassing residues Leu5-Lys8. Cyclo1-8 d-Leu5OP was present as two equimolar conformers resulting from cis/trans isomerization of the Arg-Pro peptide bond. These pharmacological and structural data should prove useful for the rational design of non peptidic ODN analogs.
Paracoprid scarabs (Scarabaeidae: Scarabaeinae) dig tunnels under or near various animals droppings, portions of which the beetles store to feed on or use to build nests for their larvae. These nests ...have been classified into 3 main patterns, based mainly on the structure of the nest, egg cell, and the existence of parental care. Pattern I nests are simple accumulations of feces at the end of a burrow, known as brood masses, with 1 or several eggs in individual cells built into the dung. Pattern II nests consist of spheroidal or pear-shaped food provisions plastered with a layer of soil (brood balls) loose in a subterranean chamber. Pattern III nests have several brood balls in one large chamber and receive parental care. The construction process of the brood masses and brood balls of 13 species of laboratory reared paracoprids from Argentina was studied by analyzing different stages of their construction. The species Dichotomius anaglypticus (Mannerheim), D. haroldi (Waterhouse), D. micans (Luederwaldt), D. semiaeneus (Germar), Onthophagus hirculus Mannerheim, Oruscatus davus (Erichson), and Gromphas lacordairei Brulle belong to the pattern I; Sulcophanaeus batesi (Harold), Sulcophanaeus menelas (Castelnau), S. imperator (Chevrolat), Bolbites onitoides Harold, Ontherus sulcator (F.), and O. appendiculatus (Mannerheim) to pattern II. The last pattern, which includes the Phanaeina, some Dichotomina (both subtribes of Coprini), and the Old World Catharsius, entails at least 4 different construction processes. Most brood masses and balls studied in this work are described for the first time. The building of spheroidal brood balls loose in a chamber could have evolved at least four times from the primitive brood masses, through four different convergent processes.
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