Biology subjects

Peixoto, J.

Publications and source records attributed to Peixoto, J..

5 recordsLinked to original sources

bioRxiv2021

An unconventional GABAergic circuit differently controls pyramidal neuron activity in two visual cortical areas via endocannabinoids

Perisomatic inhibition of neocortical pyramidal neurons (PNs) coordinates cortical network activity during sensory processing, and it has been mainly attributed to parvalbumin-expressing basket cells (BCs). However, cannabinoid receptor type 1 (CB1)-expressing interneurons also inhibit the perisomatic region of PNs but the connectivity and function of these elusive - yet prominent - neocortical GABAergic cells is unknown. We found that the connectivity pattern of CB1-positive BCs strongly differs between primary and high-order cortical visual areas. Moreover, persistently active CB1 signaling suppresses GABA release from CB1 BCs in the medial secondary visual cortex (V2M), but not in the primary (V1) visual area. Accordingly, in vivo, tonic CB1 signaling is responsible for higher but less coordinated PN activity in V2M than in V1. Our results indicate a differential CB1-mediated mechanism controlling PN activity, and suggest an alternative connectivity schemes of a specific GABAergic circuit in different cortical areas

neuroscience↗

bioRxiv2021

Large-scale deployment and establishment of Wolbachia into the Aedes aegypti population in Rio de Janeiro, Brazil.

Traditional methods of vector control have proven insufficient to reduce the alarming incidence of Dengue, Zika and chikungunya in endemic countries. The bacterium symbiont Wolbachia has emerged as an efficient pathogen-blocking and self-dispersing agent that reduces the vectorial potential of Aedes aegypti populations and potentially impairs arboviral disease transmission. In this work, we report the results of a large-scale Wolbachia intervention in Ilha do Governador, Rio de Janeiro, Brazil. wMel-infected adults were released across residential areas between August 2017 and March 2020. Over 131 weeks, including release and post-release phases, we monitored the wMel prevalence in field specimens, and analyzed introgression profiles of two assigned intervention areas, RJ1 and RJ2. Our results revealed that wMel successfully invaded both areas, reaching overall infection rates of 50-70% in RJ1, and 30-60% in RJ2 by the end of the monitoring period. At the neighborhood-level, wMel introgression was heterogeneous in both RJ1 and RJ2, with some profiles sustaining a consistent increase in infection rates and others failing to elicit the same. Correlation analysis revealed a weak overall association between RJ1 and RJ2 (r = 0.2849, P = 0.0236), and an association at a higher degree when comparing different deployment strategies, vehicle or backpack-assisted, within RJ1 (r = 0.4676, P < 0.0001) or RJ2 (r = 0.6263, P < 0.0001). The frequency knockdown resistance (kdr) alleles in wMel-infected specimens from both areas was consistently high over this study. Altogether, these findings corroborate that wMel can be successfully deployed at large-scale as part of vector control intervention strategies, and provide the basis for imminent disease impact studies in Southeastern Brazil.

ecology↗

bioRxiv2020

Reduced competence to arboviruses following the sustainable invasion of Wolbachia into native Aedes aegypti from Niteroi, Southeastern Brazil

Field release of Wolbachia-infected Aedes aegypti has emerged as a promising solution to manage the transmission of dengue, Zika and chikungunya in endemic areas across the globe. Through an efficient self-dispersing mechanism, and the ability to induce virus-blocking properties, Wolbachia offers an unmatched potential to gradually modify wild Ae. aegypti populations turning them unsuitable disease vectors. Here in this work, a proof-of-concept field trial was carried out in a small community of Niteroi, greater Rio de Janeiro. Following the release of Wolbachia-infected eggs, we reported a successful invasion and long-term establishment of the bacterium across the territory, as denoted by stable high-infection indexes (>80%). We have also demonstrated that refractoriness to dengue and Zika viruses, either thorough oral-feeding or intra-thoracic saliva challenging assays, were maintained over the adaptation to the natural environment of Southeastern Brazil. These findings further support Wolbachias ability to invade local Ae. aegypti populations and impair disease transmission, and shall pave the way for future epidemiological and economic impact assessments.

microbiology↗

bioRxiv2020

Alterations of specific inhibitory circuits of the prefrontal cortex underlie abnormal network activity in a mouse model of Down syndrome

Down syndrome (DS) results in various degrees of cognitive deficits. In DS mouse models, recovery of behavioral and neurophysiological deficits using GABAAR antagonists led to hypothesize an excessive activity of inhibitory circuits in this condition. Nonetheless, whether over-inhibition is present in DS and whether this is due to specific alterations of distinct GABAergic circuits is unknown. In the prefrontal cortex of Ts65Dn mice (a well-established DS model), we found that the dendritic synaptic inhibitory loop formed by somatostatin-positive Martinotti cells (MCs) and pyramidal neurons (PNs) was strongly enhanced, with no alteration of their excitability. Conversely, perisomatic inhibition from parvalbumin-positive (PV) interneurons was unaltered, but PV cells of DS mice lost their classical fast-spiking phenotype and exhibited increased excitability. These microcircuit alterations resulted in reduced pyramidal-neuron firing and increased phase locking to cognitive-relevant network oscillations in vivo. These results define important synaptic and circuit mechanisms underlying of cognitive dysfunctions in DS.

neuroscience↗

bioRxiv2019

Microscale interactions between immigrant bacteria and plant leaf microbiota as revealed by live imaging

The phyllosphere - the aerial parts of plants - is an important microbial habitat that is home to diverse microbial communities. The spatial organization of bacterial cells on leaf surfaces is non-random, and correlates with leaf microscopic features. Yet, the role of microscale interactions between bacterial cells therein is not well understood. Here, we ask how interactions between immigrant bacteria and resident microbiota affect the spatial organization of the combined community. By means of live imaging in a simplified in vitro system, we studied the spatial organization, at the micrometer scale, of the bio-control agent Pseudomonas fluorescens A506 and the plant pathogen P. syringae B728a when introduced to pear and bean leaf microbiota (the corresponding native plants of these strains). We found significant co-localization of immigrant and resident microbial cells at distances of a few micrometers, for both strains. Interestingly, this co-localization was in part due to preferential attachment of microbiota cells near newly formed P. fluorescens aggregates. Our results indicate that two-way immigrant bacteria - resident microbiota interactions affect the leafs microscale spatial organization, and possibly that of other surface-related microbial communities.

microbiology↗