Heterogeneity and Convergence of Olfactory First-Order Neurons Account for the High Speed and Sensitivity of Second-Order Neurons

In the olfactory system of male moths, a specialized subset of neurons detects and processes the main component of the sex pheromone emitted by females. It is composed of several thousand first-order olfactory receptor neurons (ORNs), all expressing the same pheromone receptor, that contact synaptically a few tens of second-order projection neurons (PNs) within a single restricted brain area. The functional simplicity of this system makes it a favorable model for studying the factors that contribute to its exquisite sensitivity and speed. Sensory information—primarily the identity and intensity of the stimulus—is encoded as the firing rate of the action potentials, and possibly as the latency of the neuron response. We found that over all their dynamic range, PNs respond with a shorter latency and a higher firing rate than most ORNs. Modelling showed that the increased sensitivity of PNs can be explained by the ORN-to-PN convergent architecture alone, whereas their faster response also requires cell-to-cell heterogeneity of the ORN population. So, far from being detrimental to signal detection, the ORN heterogeneity is exploited by PNs, and results in two different schemes of population coding based either on the response of a few extreme neurons (latency) or on the average response of many (firing rate). Moreover, ORN-to-PN transformations are linear for latency and nonlinear for firing rate, suggesting that latency could be involved in concentration-invariant coding of the pheromone blend and that sensitivity at low concentrations is achieved at the expense of precise encoding at high concentrations.     

Renal Function in Hepatosplenic Schistosomiasis – An Assessment of Renal Tubular Disorders

Background

Renal involvement in Schistosoma mansoni infection is not well studied. The aim of this study is to investigate the occurrence of renal abnormalities in patients with hepatosplenic schistosomiasis (HSS), especially renal tubular disorders.

Methods

This is a cross-sectional study with 20 consecutive patients with HSS followed in a medical center in Maceió, Alagoas, Brazil. Urinary acidification and concentration tests were performed using calcium chloride (CaCl₂) after a 12-h period of water and food deprivation. The biomarker monocyte chemoattractant protein 1 (MCP-1) was quantified in urine. Fractional excretion of sodium (FE_Na+), transtubular potassium gradient (TTKG) and solute-free water reabsorption (TcH₂O) were calculated. The HSS group was compared to a group of 17 healthy volunteers.

Results

Patients'' mean age and gender were similar to controls. Urinary acidification deficit was found in 45% of HSS patients. Urinary osmolality was significantly lower in HSS patients (588±112 vs. 764±165 mOsm/kg, p = 0,001) after a 12-h period of water deprivation. TcH₂O was lower in HSS patients (0.72±0.5 vs. 1.1±0.3, p = 0.04). Urinary concentration deficit was found in 85% of HSS patients. The values of MCP-1 were higher in HSS group than in control group (122±134 vs. 40±28 pg/mg-Cr, p = 0.01) and positively correlated with the values of microalbuminuria and proteinuria.

Conclusions

HSS is associated with important kidney dysfunction. The main abnormalities found were urinary concentrating ability and incomplete distal acidification defect, demonstrating the occurrence of tubular dysfunction. There was also an increase in urinary MCP-1, which appears to be a more sensitive marker of renal damage than urinary albumin excretion rate.     

Melanophore appearance in wild and red tilapia embryos

Red tilapia has aroused interest in many countries for its commercial potential. This tilapia strain combines a desirable coloration and appearance with other advantageous farming characteristics. To study the early appearance of melanophore pigmentation in tilapia, a red tilapia strain originating from Thailand and a wild type coloration of Oreochromis niloticus were used as broodstock to produce artificially wild x wild and red x red progenies. The larvae were assessed periodically up to the first feeding and were recorded. Wild type fish showed a regular appearance of stellate melanophores. In the red strain, the pattern of chromatophores varies from total absence of black spotting to different degrees of macromelanophore distribution. Comparison between red and wild types showed that these two tilapia can be easily scored at day 7. Further, we present indications that the pigmentation over the body develops independently of the initial degree of pigmentation.     

The Psychedelic State Induced by Ayahuasca Modulates the Activity and Connectivity of the Default Mode Network

The experiences induced by psychedelics share a wide variety of subjective features, related to the complex changes in perception and cognition induced by this class of drugs. A remarkable increase in introspection is at the core of these altered states of consciousness. Self-oriented mental activity has been consistently linked to the Default Mode Network (DMN), a set of brain regions more active during rest than during the execution of a goal-directed task. Here we used fMRI technique to inspect the DMN during the psychedelic state induced by Ayahuasca in ten experienced subjects. Ayahuasca is a potion traditionally used by Amazonian Amerindians composed by a mixture of compounds that increase monoaminergic transmission. In particular, we examined whether Ayahuasca changes the activity and connectivity of the DMN and the connection between the DMN and the task-positive network (TPN). Ayahuasca caused a significant decrease in activity through most parts of the DMN, including its most consistent hubs: the Posterior Cingulate Cortex (PCC)/Precuneus and the medial Prefrontal Cortex (mPFC). Functional connectivity within the PCC/Precuneus decreased after Ayahuasca intake. No significant change was observed in the DMN-TPN orthogonality. Altogether, our results support the notion that the altered state of consciousness induced by Ayahuasca, like those induced by psilocybin (another serotonergic psychedelic), meditation and sleep, is linked to the modulation of the activity and the connectivity of the DMN.     

Anthranilic acid-based Thumb Pocket 2 HCV NS5B polymerase inhibitors with sub-micromolar potency in the cell-based replicon assay

Optimization efforts on the anthranilic acid-based Thumb Pocket 2 HCV NS5B polymerase inhibitors 1 and 2 resulted in the identification of multiple structural elements that contributed to improved cell culture potency. The additive effect of these elements resulted in compound 46, an inhibitor with enzymatic (IC₅₀) and cell culture (EC₅₀) potencies of less than 100 nanomolar.     

Theoretical Study of the Anchoring Influence on Plasmonic Resonance Tunability of Metallic Nanoparticles Embedded in a Liquid Crystal Cell

In this paper, the localized surface plasmon resonance (LSPR) peak position of an ordered gold nanoparticles array embedded in a nematic liquid crystal (LC) media is investigated using finite-difference time-domain method. The influence of the anchoring effects between nematic LC molecules and glass substrate on the shift of LSPR wavelength is taken into account, and results are compared with the case of a perfect alignment of the LC molecules.