Inner retinal inhibition shapes the receptive field of retinal ganglion cells in primate

The centre-surround organisation of receptive fields is a feature of most retinal ganglion cells (RGCs) and is critical for spatial discrimination and contrast detection. Although lateral inhibitory processes are known to be important in generating the receptive field surround, the contribution of each of the two synaptic layers in the primate retina remains unclear. Here we studied the spatial organisation of excitatory and inhibitory synaptic inputs onto ON and OFF ganglion cells in the primate retina. All RGCs showed an increase in excitation in response to stimulus of preferred polarity. Inhibition onto RGCs comprised two types of responses to preferred polarity: some RGCs showed an increase in inhibition whilst others showed removal of tonic inhibition. Excitatory inputs were strongly spatially tuned but inhibitory inputs showed more variable organisation: in some neurons they were as strongly tuned as excitation, and in others inhibitory inputs showed no spatial tuning. We targeted one source of inner retinal inhibition by functionally ablating spiking amacrine cells with bath application of tetrodotoxin (TTX). TTX significantly reduced the spatial tuning of excitatory inputs. In addition, TTX reduced inhibition onto those RGCs where a stimulus of preferred polarity increased inhibition. Reconstruction of the spatial tuning properties by somatic injection of excitatory and inhibitory synaptic conductances verified that TTX-mediated inhibition onto bipolar cells increases the strength of the surround in RGC spiking output. These results indicate that in the primate retina inhibitory mechanisms in the inner plexiform layer sharpen the spatial tuning of ganglion cells. © 2013 The Physiological Society

DNA-cellulose: an economical, fully recyclable and highly effective chiral biomaterial for asymmetric catalysis

similarity_check: This document is Similarity Check deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal peer_review_method: Single-blind history: Received 20 December 2014; Accepted 11 January 2015; Accepted Manuscript published 14 January 2015; Advance Article published 23 January 2015; Version of Record published 24 March 2015This research was supported by the Ministe`re de l’Enseignement Supe´rieur et de la Recherche and the Agence Nationale de la Recherche (NCiS; ANR-2010-JCJC-715-1)

Expanding biohybrid-mediated asymmetric catalysis into the realm of RNA

crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 2016crosscheck: This document is CrossCheck deposited related_data: Supplementary Information identifier: Stellios Arseniyadis (ResearcherID) copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal history: Received 27 April 2016; Accepted 10 June 2016; Accepted Manuscript published 10 June 2016; Advance Article published 21 June 2016; Version of Record published 30 June 201

Methods for L-ribooligonucleotide sequence determination using LCMS

The ability to verify the sequence of a nucleic acid-based therapeutic is an essential step in the drug development process. The challenge associated with sequence identification increases with the length and nuclease resistance of the nucleic acid molecule, the latter being an important attribute of therapeutic oligonucleotides. We describe methods for the sequence determination of Spiegelmers, which are enantiomers of naturally occurring RNA with high resistance to enzymatic degradation. Spiegelmer sequencing is effected by affixing a label or hapten to the 5′-end of the oligonucleotide and chemically degrading the molecule in a controlled fashion to generate fragments that are then resolved and identified using liquid chromatography-mass spectrometry. The Spiegelmer sequence is then derived from these fragments. Examples are shown for two different Spiegelmers (NOX-E36 and NOX-A12), and the specificity of the method is shown using a NOX-E36 mismatch control

Drosophila as a Model for MECP2 Gain of Function in Neurons

Methyl-CpG-binding protein 2 (MECP2) is a multi-functional regulator of gene expression. In humans loss of MECP2 function causes classic Rett syndrome, but gain of MECP2 function also causes mental retardation. Although mouse models provide valuable insight into Mecp2 gain and loss of function, the identification of MECP2 genetic targets and interactors remains time intensive and complicated. This study takes a step toward utilizing Drosophila as a model to identify genetic targets and cellular consequences of MECP2 gain-of function mutations in neurons, the principle cell type affected in patients with Rett-related mental retardation. We show that heterologous expression of human MECP2 in Drosophila motoneurons causes distinct defects in dendritic structure and motor behavior, as reported with MECP2 gain of function in humans and mice. Multiple lines of evidence suggest that these defects arise from specific MECP2 function. First, neurons with MECP2-induced dendrite loss show normal membrane currents. Second, dendritic phenotypes require an intact methyl-CpG-binding domain. Third, dendritic defects are amended by reducing the dose of the chromatin remodeling protein, osa, indicating that MECP2 may act via chromatin remodeling in Drosophila. MECP2-induced motoneuron dendritic defects cause specific motor behavior defects that are easy to score in genetic screening. In sum, our data show that some aspects of MECP2 function can be studied in the Drosophila model, thus expanding the repertoire of genetic reagents that can be used to unravel specific neural functions of MECP2. However, additional genes and signaling pathways identified through such approaches in Drosophila will require careful validation in the mouse model

Nicotine exposure and transgenerational impact: a prospective study on small regulatory microRNAs

Early developmental stages are highly sensitive to stress and it has been reported that pre-conditioning with tobacco smoking during adolescence predisposes those youngsters to become smokers as adults. However, the molecular mechanisms of nicotine-induced transgenerational consequences are unknown. In this study, we genome-widely investigated the impact of nicotine exposure on small regulatory microRNAs (miRNAs) and its implication on health disorders at a transgenerational aspect. Our results demonstrate that nicotine exposure, even at the low dose, affected the global expression profiles of miRNAs not only in the treated worms (F0 parent generation) but also in two subsequent generations (F1 and F2, children and grandchildren). Some miRNAs were commonly affected by nicotine across two or more generations while others were specific to one. The general miRNA patterns followed a “two-hit� model as a function of nicotine exposure and abstinence. Target prediction and pathway enrichment analyses showed daf-4, daf-1, fos-1, cmk-1, and unc-30 to be potential effectors of nicotine addiction. These genes are involved in physiological states and phenotypes that paralleled previously published nicotine induced behavior. Our study offered new insights and further awareness on the transgenerational effects of nicotine exposed during the vulnerable post-embryonic stages, and identified new biomarkers for nicotine addiction.ECU Open Access Publishing Support Fun

Mapping the melatonin receptor. 4. Comparison of the binding affinities of a series of substituted phenylalkyl amides

A series of 2-, 3-, and 4-substituted phenylalkyl amides were prepared as potential melatonin analogs in order to investigate the nature of the binding site of the melatonin receptor in chicken brain. The length of the alkyl chain was systematically varied from n = 1 to 4, and methoxyl substituents were incorporated into the phenyl ring at the 2-, 3-, and 4-positions. The maximum binding affinity was found to occur when n = 3 and when the methoxyl substituent was in the 3-position, the direct analog of the carbon framework of melatonin in which the 1,2-atoms of the indole ring have been removed. Whereas there was only a relatively small decrease in binding affinity for the corresponding 2-methoxy derivatives, 4-methoxyl substitution led to a large decrease in binding affinity, suggesting that the binding sites for the side chain and methoxyl group could not now be occupied at the same time. As in the indole analogs of melatonin, replacement of the methyl group of the amide by a longer alkyl chain led to an increase in binding affinity for ethyl and propyl with a subsequent decrease in binding affinity for butyl chains. Thus N-propanoyl-3-(3-methoxyphenyl)propanamine (6f) has a binding affinity of 5.6 nM, a remarkably high affinity for so simple a compound. Substitution of halogen for 3-methoxyl in the prepanamide series gave a series of compounds with lower, but still substantial, binding affinities, the 3-chloro derivative 7e showing the highest affinity, 113 nM. In the case of the 3-fluoro propanamides, a maximum in the binding affinity was not observed in the series synthesized, and these derivatives will merit further exploration. These results demonstrate the utility of simple, readily modified phenylalkylamines as a 'framework' for studying the effect of changes in the nature and position of substituents on the melatonin receptor binding affinity