Development of Spontaneous Activity and Response Properties of Primary Lagenar Neurons in the Chick

Here, we report for the first time developmental changes in spontaneous activity and in response properties of single nerve fibers from the macular chick lagena. Such aspects are important in order to get insight into the functional role of the lagena which remains undetermined. For this purpose, we used intracellular and extracellular single-unit recording techniques in an isolated inner ear preparation from the chicken at ages E15 and P1. At E15, afferent fibers displayed a low irregular spontaneous discharge rate (41 ± 14 spikes/s, CV = 1.17 ± 0.1), which was replaced by regular high frequency spontaneous activity at P1 (CV = 0.48 ± 0.8, 89 ± 27 spikes/s). During the developmental period including E15, the percentage of silent neurons was 60% while that of P1 was 40%. The synaptic activity was higher at E15 than at P1. The action potential waveform generated at E15 had small amplitude and derivative depolarization, and consequently, a large duration in correlation with respect to action potential waveform at P1 (respectively: 53 ± 2 vs. 65 ± 3 mV, 60 ± 11 vs. 109 ± 20 mV/ms, 3.6 ± 0.4 vs. 1.1 ± 0.12 ms). In addition, we recognized two response dynamics to the injection of current steps: phasic, or rapidly adapting neurons and tonic, or slowly adapting neurons. Our results indicate similar developmental processes for the lagena as described for the vestibular system in other species, in agreement with the known morphological characteristics of this otholitic end organ. The presence of more than one subtype of afferent neuron also correlates with previous reports on vestibular afferents with analogous electrophysiological properties, strongly suggesting the vestibular nature of the lagena.     

Starch-based microspheres for sustained-release of curcumin: Preparation and cytotoxic effect on tumor cells

Curcumin (CUR) has been proved to be highly cytotoxic against different tumor cell lines. However, its poor solubility in aqueous medium and fast degradation in physiological pH are the common drawbacks preventing its efficient practical use. Herein, we report the development of original microspheres based on the biopolymer starch crosslinked with N,N-methylenebisacrylamide (MBA) to be applied as an efficient delivering system for CUR. The starch-based microspheres showed high loading efficiency even in loading solution with different CUR concentrations. In vitro release assays data showed that the CUR release is governed by anomalous transport (n = 0.73) and it is pH-dependent. Cytotoxicity assays showed that starch microspheres could improve the cytotoxicity of CUR toward Caco-2 and HCT-116 tumor cell lines up to 40 times than that found for pure CUR. This behavior was attributed to the slowly and sustained release of CUR from the microspheres.     

Ontogenetic and spatiotemporal variability in anchoveta Engraulis ringens diet off Peru

In this study, historical data available since 1954 were used to get new insight to ontogenetic and spatiotemporal variability in Peruvian anchovy or anchoveta Engraulis ringens diet. Whatever the period, E. ringens foraged mainly on macrozooplankton and the importance of euphausiids in E. ringens diet appears directly related to euphausiids abundance. This bottom‐up effect is also observed at smaller scale because the euphausiids fraction increased with E. ringens total length and euphausiids accessibility. Selecting the largest prey, the euphausiids, provides an energetic advantage for E. ringens in its ecosystem where oxygen depletion imposes strong metabolic constraints on pelagic fishes. This study illustrates the plasticity of E. ringens that allows it to cope with its highly variable environment.     

Phosphatidylinositol-specific phospholipase C induces biosynthesis of acetylcholinesterase via diacylglycerol in Schistosoma mansoni.

We have previously shown that two ectoenzymes, acetylcholinesterase (AChE) and alkaline phosphatase, are released from the surface and from particulate fractions of the parasite Schistosoma mansoni, by a phosphatidylinositol-specific phospholipase C (PtdIns-PLC) of bacterial origin. Exposure to PtdIns-PLC not only removes large amounts of AChE from the surface of intact, viable Schistosoma in culture, but is accompanied by a concomitant increase in overall levels of AChE in the parasite. The same phenomenon is observed with PtdIns-PLC from two different bacterial sources; Staphylococcus aureus and Bacillus thuringiensis. The increase in AChE levels may be ascribed to de novo synthesis since exposure to PtdIns-PLC, in the presence of the protein-synthesis inhibitor cycloheximide, totally blocked the increase in AChE activity. Furthermore, PtdIns-PLC induced an increased incorporation of [35S]methionine into the AChE immunoprecipitated by a specific anti-AChE serum. This increase is selective for AChE, since total protein synthesis remained almost unchanged after PtdIns-PLC addition, and little or no effect was observed on the enzymatic activity of alkaline phosphatase, which is also glycophosphatidylinositol anchored. Since cleavage of the phosphatidylinositol anchor by PtdIns-PLC should liberate diacylglycerol, which may act as second messenger, we investigated the effect of exogenous diacylglycerols on the synthesis of AChE in S. mansoni. Three different diacylglycerols were tested as possible inducers of AChE activity in the parasite. Both 1-oleoyl-2-acetyl-sn-glycerol and 1,2-dimyristoyl-sn-glycerol were able to increase AChE activity by 35-40% at concentrations of 25 micrograms/ml. A higher concentration of 1,2-dioctanoyl-sn-glycerol (70 micrograms/ml) was needed to produce an equivalent effect. Moreover, addition of phorbol-12-myristate-13-acetate, together with the calcium ionophore A23187, produced a similar increase in AChE activity. Finally, polymixin B, a specific inhibitor of protein kinase C, partially blocked the increase in AChE activity induced by PtdIns-PLC. Our results suggest the involvement of glycophosphatidyl membrane-anchor breakdown products as putative second messengers in the parasite S. mansoni.     

Natural arbovirus infection rate and detectability of indoor female Aedes aegypti from Mérida,Yucatán,Mexico

Arbovirus infection in Aedes aegypti has historically been quantified from a sample of the adult population by pooling collected mosquitoes to increase detectability. However, there is a significant knowledge gap about the magnitude of natural arbovirus infection within areas of active transmission, as well as the sensitivity of detection of such an approach. We used indoor Ae. aegypti sequential sampling with Prokopack aspirators to collect all mosquitoes inside 200 houses with suspected active ABV transmission from the city of Mérida, Mexico, and tested all collected specimens by RT-PCR to quantify: a) the absolute arbovirus infection rate in individually tested Ae. aegypti females; b) the sensitivity of using Prokopack aspirators in detecting ABV-infected mosquitoes; and c) the sensitivity of entomological inoculation rate (EIR) and vectorial capacity (VC), two measures ABV transmission potential, to different estimates of indoor Ae. aegypti abundance. The total number of Ae. aegypti (total catch, the sum of all Ae. aegypti across all collection intervals) as well as the number on the first 10-min of collection (sample, equivalent to a routine adult aspiration session) were calculated. We individually tested by RT-PCR 2,161 Aedes aegypti females and found that 7.7% of them were positive to any ABV. Most infections were CHIKV (77.7%), followed by DENV (11.4%) and ZIKV (9.0%). The distribution of infected Aedes aegypti was overdispersed; 33% houses contributed 81% of the infected mosquitoes. A significant association between ABV infection and Ae. aegypti total catch indoors was found (binomial GLMM, Odds Ratio > 1). A 10-min indoor Prokopack collection led to a low sensitivity of detecting ABV infection (16.3% for detecting infected mosquitoes and 23.4% for detecting infected houses). When averaged across all infested houses, mean EIR ranged between 0.04 and 0.06 infective bites per person per day, and mean VC was 0.6 infectious vectors generated from a population feeding on a single infected host per house/day. Both measures were significantly and positively associated with Ae. aegypti total catch indoors. Our findings provide evidence that the accurate estimation and quantification of arbovirus infection rate and transmission risk is a function of the sampling effort, the local abundance of Aedes aegypti and the intensity of arbovirus circulation.     

Complete chloroplast genome of Myracrodruon urundeuva and its phylogenetics relationships in Anacardiaceae family

Continuous exploratory use of tree species is threatening the existence of several plants in South America. One of these threatened species is Myracroduron urundeuva, highly exploited due to the high quality and durability of its wood. The chloroplast (cp) has been used for several evolutionary studies as well traceability of timber origin, based on its gene sequences and simple sequence repeats (SSR) variability. Cp genome organization is usually consisting of a large single copy and a small single copy region separated by two inverted repeats regions. We sequenced the complete cp genome from M. urundeuva based on Illumina next-generation sequencing. Our results show that the cp genome is 159,883 bp in size. The 36 SSR identified ranging from mono- to hexanucleotides. Positive selection analysis revealed nine genes related to photosystem, protein synthesis, and DNA replication, and protease are under positive selection. Genome comparison a other Anacardiaceae chloroplast genomes showed great variability in the family. The phylogenetic analysis using complete chloroplast genome sequences of other Anacardiaceae family members showed a close relationship with two other economically important genera, Pistacia and Rhus. These results will help future investigations of timber monitoring and population and evolutionary studies. Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-00989-1.