Influence of Autapses on Synchronization in Neural Networks With Chemical Synapses

A great deal of research has been devoted on the investigation of neural dynamics in various network topologies. However, only a few studies have focused on the influence of autapses, synapses from a neuron onto itself via closed loops, on neural synchronization. Here, we build a random network with adaptive exponential integrate-and-fire neurons coupled with chemical synapses, equipped with autapses, to study the effect of the latter on synchronous behavior. We consider time delay in the conductance of the pre-synaptic neuron for excitatory and inhibitory connections. Interestingly, in neural networks consisting of both excitatory and inhibitory neurons, we uncover that synchronous behavior depends on their synapse type. Our results provide evidence on the synchronous and desynchronous activities that emerge in random neural networks with chemical, inhibitory and excitatory synapses where neurons are equipped with autapses. © Copyright © 2020 Protachevicz, Iarosz, Caldas, Antonopoulos, Batista and Kurths

Hemoglobinopatias no Distrito Federal, Brasil

Em uma amostra de 3137 pessoas, residentes no Distrito Federal, foram detectadas as seguintes hemoglobinas: em 3009(95,92%) HbAA; em 91 (2,90%) HbAS; em 20(0,64%) HbAC; em 8 (0,26%) talassemia beta minor; em 5(0,16%) HbAJ alfa; em 3 (0,09%) HbAM e em 1 (0,03%) talassemia major associada com HbAS. A HbAS têm as seguintes freqüências, quanto ao grupo racial: branco - 1,84%; mulato claro 2,55%; mulato médio-3,68%; mulato escuro - 6,80%; negro -10,43% e mestiço de índio -3,85%.The hemoglobins of 3137 persons from the Federal District, Brazil was studied. The identified types of hemoglobins were: HbAA (3009 - 95,92%); HbAS (91 - 2,90%); HbAC (20 - 0,64%) beta thalassemia minor (8 - 0,26%); HbAJ alpha (5 - 0,16%); HbAM (3 - 0,09%) and beta thalassemia major/HbS (1 - 0,03%). The frequencies of sickle cell trait (HbAS) of each racial class were: white (1,84%); light mulatto (2,55%); medium mulatto (3,68%); dark mulatto(6,80%), negro (10,43%)and indian mestizo (3,85%)

Inferior petrosal sinus catheterization: technical aspects

OBJETIVO: O cateterismo dos seios petrosos inferiores (SPI) ajuda a diferenciar as formas hipofisária e ectópica na síndrome de Cushing (SC). O objetivo desse trabalho é descrever a técnica empregada em nosso serviço, discutir a solução de dificuldades e verificar o índice de sucesso atingido. CASUÍSTICA E MÉTODO: Foram submetidos a cateterismo bilateral dos SPI 42 pacientes com SC, entre setembro de 2000 e setembro de 2005. As dificuldades para o posicionamento do cateter foram correlacionadas com as soluções empregadas. RESULTADOS: As variações anatômicas, a semelhança entre o SPI e a veia emissária do plexo basilar e a dificuldade de contrastar as estruturas a contrafluxo para localizá-las foram os principais problemas. Foram utilizados cateter pré-moldado, fio-guia semicurvo e dirigível, road-maping e venografia por injeção contralateral, além de critérios para diferenciar o SPI da veia emissária. Dos 84 SPI abordados, um apresentava trombose, e dos 83 possíveis, 80 (96,4%) foram cateterizados. Não se observaram complicações. CONCLUSÃO: A cateterização dos SPI pode ser feita na maioria dos pacientes. A identificação da veia emissária do plexo basilar e o uso de flebografia por injeção contralateral melhoraram o desempenho do método.PURPOSE: Inferior petrosal sinus catheterization and sampling for corticotropin dosage helps to differentiate hypophisary and ectopic forms of Cushing syndrome. The aim of this paper is to describe the technique used in inferior petrosal sinus catheterization in our service, emphasizing the solution found for frequent difficulties, and verify the success rate achieved. PATIENTS AND METHODS: Between September/2000 and September/2005, forty-two (eighty-four sinuses) patients were submitted to inferior petrosal sinus sampling. The difficulties for correct catheter positioning were identified and correlated with their solutions. RESULTS: Anatomical variations, similarity between IPS and emissary vein of the basilar plexus and unfavorable flow to the contrastation of the structures (retrograde catheterization) were the main problems. Using pre-shaped catheters, curved, steerable guide-wires, road-maping and venography by contalateral injection, besides criteria to differentiate IPS from the emissary vein. Of the 84 sinuses approached, one was thrombosed, and 80 (96.4%) of 83 possible were selectively catheterized. No clinical complication occurred. CONCLUSION: IPSC can be safe and successfully performed in most cases. The identification of the emissary vein of the basilar plexus and use of venography by contralateral injection, improved the method performance

Unpredictability in seasonal infectious diseases spread

In this work, we study the unpredictability of seasonal infectious diseases considering a SEIRS model with seasonal forcing. To investigate the dynamical behaviour, we compute bifurcation diagrams type hysteresis and their respective Lyapunov exponents. Our results from bifurcations and the largest Lyapunov exponent show bistable dynamics for all the parameters of the model. Choosing the inverse of latent period as control parameter, over 70% of the interval comprises the coexistence of periodic and chaotic attractors, bistable dynamics. Despite the competition between these attractors, the chaotic ones are preferred. The bistability occurs in two wide regions. One of these regions is limited by periodic attractors, while periodic and chaotic attractors bound the other. As the boundary of the second bistable region is composed of periodic and chaotic attractors, it is possible to interpret these critical points as tipping points. In other words, depending on the latent period, a periodic attractor (predictability) can evolve to a chaotic attractor (unpredictability). Therefore, we show that unpredictability is associated with bistable dynamics preferably chaotic, and, furthermore, there is a tipping point associated with unpredictable dynamics

Epigenetic reprogramming by TET enzymes impacts co-transcriptional R-loops

PTDC/BIA-MOL/30438/2017 PTDC/MED-OUT/4301/2020 RiboMed 857119 PD/BD/128292/2017 LCF/PR/HP21/52310016 PTDC/BIA-MOL/6624/2020 PTDC/MED-ONC/7864/2020DNA oxidation by ten-eleven translocation (TET) family enzymes is essential for epigenetic reprogramming. The conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC) initiates developmental and cell-type-specific transcriptional programs through mechanisms that include changes in the chromatin structure. Here, we show that the presence of 5hmC in the transcribed gene promotes the annealing of the nascent RNA to the template DNA strand, leading to the formation of an R-loop. Depletion of TET enzymes reduced global R-loops in the absence of gene expression changes, whereas CRISPR-mediated tethering of TET to an active gene promoted the formation of R-loops. The genome-wide distribution of 5hmC and R-loops shows a positive correlation in mouse and human stem cells and overlap in half of all active genes. Moreover, R-loop resolution leads to differential expression of a subset of genes that are involved in crucial events during stem cell proliferation. Altogether, our data reveal that epigenetic reprogramming via TET activity promotes co-transcriptional R-loop formation, disclosing new mechanisms of gene expression regulation.publishersversionpublishe

Spike-burst chimera states in an adaptive exponential integrate-and-fire neuronal network

We wish to acknowledge the support from Fundação Araucária, CNPq (Grant No. 150701/2018-7), CAPES, and FAPESP (Grant Nos. 2015/07311-7, 2018/03211-6, and 2017/18977-1).Peer reviewedPublisher PD

Influence of Delayed Conductance on Neuronal Synchronization

In the brain, the excitation-inhibition balance prevents abnormal synchronous behavior. However, known synaptic conductance intensity can be insufficient to account for the undesired synchronization. Due to this fact, we consider time delay in excitatory and inhibitory conductances and study its effect on the neuronal synchronization. In this work, we build a neuronal network composed of adaptive integrate-and-fire neurons coupled by means of delayed conductances. We observe that the time delay in the excitatory and inhibitory conductivities can alter both the state of the collective behavior (synchronous or desynchronous) and its type (spike or burst). For the weak coupling regime, we find that synchronization appears associated with neurons behaving with extremes highest and lowest mean firing frequency, in contrast to when desynchronization is present when neurons do not exhibit extreme values for the firing frequency. Synchronization can also be characterized by neurons presenting either the highest or the lowest levels in the mean synaptic current. For the strong coupling, synchronous burst activities can occur for delays in the inhibitory conductivity. For approximately equal-length delays in the excitatory and inhibitory conductances, desynchronous spikes activities are identified for both weak and strong coupling regimes. Therefore, our results show that not only the conductance intensity, but also short delays in the inhibitory conductance are relevant to avoid abnormal neuronal synchronization.Peer Reviewe

Spiral wave dynamics in a neuronal network model

Spiral waves are spatial-temporal patterns that can emerge in different systems as heart tissues, chemical oscillators, ecological networks and the brain. These waves have been identified in the neocortex of turtles, rats, and humans, particularly during sleep-like states. Although their functions in cognitive activities remain until now poorly understood, these patterns are related to cortical activity modulation and contribute to cortical processing. In this work, we construct a neuronal network layer based on the spatial distribution of pyramidal neurons. Our main goal is to investigate how local connectivity and coupling strength are associated with the emergence of spiral waves. Therefore, we propose a trustworthy method capable of detecting different wave patterns, based on local and global phase order parameters. As a result, we find that the range of connection radius (R) plays a crucial role in the appearance of spiral waves. For R < 20 {\mu}m, only asynchronous activity is observed due to small number of connections. The coupling strength (gsyn ) greatly influences the pattern transitions for higher R, where spikes and bursts firing patterns can be observed in spiral and non-spiral waves. Finally, we show that for some values of R and gsyn bistable states of wave patterns are obtained

Inference of topology and the nature of synapses, and the flow of information in neuronal networks

ACKNOWLEDGEMENTS CAPES, DFG-IRTG 1740/2, Fundacao Araucaria, Newton Fund, CNPq (154705/2016-0, 311467/2014-8), FAPESP (2011/19296-1, 2015/07311-7, 2016/16148-5, 2016/23398-8, 2015/50122-0), EPSRC-EP/I032606.Peer reviewedPublisher PD

Effects of drug resistance in the tumour-immune system with chemotherapy treatment

Acknowledgement This study was possible by partial financial support from the following Brazilian government agencies: Fundaao Araucaria, National Council for Scientific and Technological Development, Coordination for the Improvement of Higher Education Personnel, and Sao Paulo Research Foundation (2015/07311-7, 2017/18977- 1, 2018/03211-6, 2020/04624-2)Peer reviewedPostprin