Profiling molecular and behavioral circadian rhythms in the non-symbiotic sea anemone Nematostella vectensis

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 5 (2015): 11418, doi:10.1038/srep11418.Endogenous circadian clocks are poorly understood within early-diverging animal lineages. We have characterized circadian behavioral patterns and identified potential components of the circadian clock in the starlet sea anemone, Nematostella vectensis: a model cnidarian which lacks algal symbionts. Using automatic video tracking we showed that Nematostella exhibits rhythmic circadian locomotor activity, which is persistent in constant dark, shifted or disrupted by external dark/light cues and maintained the same rate at two different temperatures. This activity was inhibited by a casein kinase 1δ/ε inhibitor, suggesting a role for CK1 homologue(s) in Nematostella clock. Using high-throughput sequencing we profiled Nematostella transcriptomes over 48 hours under a light-dark cycle. We identified 180 Nematostella diurnally-oscillated transcripts and compared them with previously established databases of adult and larvae of the symbiotic coral Acropora millepora, revealing both shared homologues and unique rhythmic genes. Taken together, this study further establishes Nematostella as a non-symbiotic model organism to study circadian rhythms and increases our understanding about the fundamental elements of circadian regulation and their evolution within the Metazoa.This work was supported by the Israel-US Binational Science Foundation to OL and AMT (Award 2011187). Additional support was provided by the WHOI Early Career Scientist Award to AMT

Hypocretin neuron-specific transcriptome profiling identifies the sleep modulator Kcnh4a

Sleep has been conserved throughout evolution; however, the molecular and neuronal mechanisms of sleep are largely unknown. The hypothalamic hypocretin/orexin (Hcrt) neurons regulate sleep/wake states, feeding, stress, and reward. To elucidate the mechanism that enables these various functions and to identify sleep regulators, we combined fluorescence cell sorting and RNA-seq in hcrt:EGFP zebrafish. Dozens of Hcrt-neuron-specific transcripts were identified and comprehensive high-resolution imaging revealed gene-specific localization in all or subsets of Hcrt neurons. Clusters of Hcrt-neuron-specific genes are predicted to be regulated by shared transcription factors. These findings show that Hcrt neurons are heterogeneous and that integrative molecular mechanisms orchestrate their diverse functions. The voltage-gated potassium channel Kcnh4a, which is expressed in all Hcrt neurons, was silenced by the CRISPR-mediated gene inactivation system. The mutant kcnh4a(kcnh4a-/-) larvae showed reduced sleep time and consolidation, specifically during the night, suggesting that Kcnh4a regulates sleep.United States-Israel Binational Science Foundation (Grant 2011335)Israel Science Foundation (Grant 366/11)Israel Science Foundation (Legacy Heritage Biomedical Program Grant 398/11)Israel Science Foundation (Legacy Heritage Biomedical Program Grant 992/14)European Community. Marie-Curie Research Networks (International Reintegration Grant FP7-PEOPLE-2010-RG274333

Neuronal noise as an origin of sleep arousals and its role in sudden infant death syndrome

In addition to regular sleep/wake cycles, humans and animals exhibit brief arousals from sleep. Although much is known about consolidated sleep and wakefulness, the mechanism that triggers arousals remains enigmatic. Here, we argue that arousals are caused by the intrinsic neuronal noise of wake-promoting neurons. We propose a model that simulates the superposition of the noise from a group of neurons, and show that, occasionally, the superposed noise exceeds the excitability threshold and provokes an arousal. Because neuronal noise decreases with increasing temperature, our model predicts arousal frequency to decrease as well. To test this prediction, we perform experiments on the sleep/wake behavior of zebrafish larvae and find that increasing water temperatures lead to fewer and shorter arousals, as predicted by our analytic derivations and model simulations. Our findings indicate a previously unrecognized neurophysiological mechanism that links sleep arousals with temperature regulation, and may explain the origin of the clinically observed higher risk for sudden infant death syndrome with increased ambient temperature

Comparison of new metal organic framework-based catalysts for oxygen reduction reaction

In this article, we collected the most significant and recent data in brief in the field of metal organic frameworks oxygen reduction reaction catalysts, obtained from some of the most recent research papers in the field. We present lists of materials and their key parameters that are relevant to the cathode catalysts in polymer electrolyte membrane fuel cells. All the materials listed in this paper are composed of metal organic frameworks, zeolitic imidazolate frameworks, or their derivatives. These are divided into two main groups: pristine MOFs and MOF-derived materials. The data in this article is a summary of more extensive review (Gonen and Elbaz, 2018) [1]

Advances in Ceramic Supports for Polymer Electrolyte Fuel Cells

Durability of catalyst supports is a technical barrier for both stationary and transportation applications of polymer-electrolyte-membrane fuel cells. New classes of non-carbon-based materials were developed in order to overcome the current limitations of the state-of-the-art carbon supports. Some of these materials are designed and tested to exceed the US DOE lifetime goals of 5000 or 40,000 hrs for transportation and stationary applications, respectively. In addition to their increased durability, the interactions between some new support materials and metal catalysts such as Pt result in increased catalyst activity. In this review, we will cover the latest studies conducted with ceramic supports based on carbides, oxides, nitrides, borides, and some composite materials

Heteroatom-Doped Carbon Supports with Enhanced Corrosion Resistance in Polymer Electrolyte Membrane Fuel Cells

Polymer Electrolyte Membrane Fuel Cells (PEMFC) are currently considered the most advanced fuel cell technology. However, the industrial implementation of PEMFCs is strongly hindered by deficient durability, especially that of the carbonaceous materials commonly used to support the platinum-based catalyst nanoparticles, which are prone to electrochemical corrosion at the cathode, resulting in a serious performance loss of the entire cell. In the attempt to overcome this issue, many research groups have tried to introduce heteroatoms (N, S, B, P) into the carbon lattice, thus trying to make the electrode corrosion-resistant. Newly developed heteroatom-doped carbons were subjected to corrosion tests in half-cell and single-cell systems to evaluate their stability. This paper reviews the recent studies devoted to corrosion research of heteroatom-doped carbon supports for Pt-based catalysts in PEMFCs. In particular, an overview on N, B, and S dopants and their effects on carbon corrosion is provided

Evidence of High Electrocatalytic Activity of Molybdenum Carbide Supported Platinum Nanorafts

The article of record as published may be found at http://dx.doi.org/10.1149/2.0991509jesThis was Paper 614 presented at the Orlando, Florida, Meeting of the Society, May 11–15, 2014.A remarkable new supported metal catalyst structure on Mo₂C substrates, ‘rafts’ of platinum consisting of less than 6 atoms, was synthesized and found to be catalytically active electrocatalyst for oxygen reduction. A novel catalytic synthesis method: Reduction- Expansion-Synthesis of Catalysts (RES-C), from rapid heating of dry mixture of solid precursors of molybdenum, platinum and urea in an inert gas environment, led to the creation of unique platinum Nanorafts on Mo₂C. The Pt Nanorafts offer a complete utilization of the Pt atoms for electrocatalysis with no “hidden” atoms. This structure is strongly affected by its interaction with the substrate as was observed by XPS. In this work, we show for the first time, evidence of electrocatalytic activity with such small clusters of non-crystalline Pt atoms as catalysts for oxygen reduction. Electrochemical half-cell characterization shows that this structure permit more efficient utilization of platinum, with mass activity conservatively measured to be 50% that of platinum particles generated using traditional approaches. Moreover, as cathode fuel cell catalysts, these novel material may dramatically enhance stability, relative to the commercial Pt/carbon catalysts.U.S. Department of Energy Fuel Cell Technologies OfficeIsrael Ministry of Defense (MAFAT

Electrocatalysis of Oxygen Reduction with in-Situ formed Pt Nano-Rafts on Molybdenum Carbide Support

Proton exchange membrane fuel cell (PEMFC), is a technology that has the potential to economically replace combustion engines for transport with high efficiency, and clean (only water emission) energy. The US department of energy (DOE) identifies two remaining major hurdles to the deployment of this alternative: cost and durability of the cathode. Reducing the amount of platinum, still the only material with the needed catalytic activity for oxygen reduction reaction on the cathode, and the most expensive component, will help overcome the first problem and the creation of a new, ‘non-carbon’, more oxidation-resistant catalyst support material could overcome the second.US Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technology and Fuel Cell Technology Program

Identification of a Durability Descriptor for Molecular Oxygen Reduction Reaction Catalysts

The development of durable platinum-group-metal-free oxygen reduction reaction (ORR) catalysts is a key research direction for enabling the wide use of fuel cells. Here, we use a combination of experimental measurements and density functional theory calculations to study the activity and durability of seven iron-based metallophthalocyanine (MPc) ORR catalysts that differ only in the identity of the substituent groups on the MPcs. While the MPcs show similar ORR activity, their durabilities as measured by the current decay half-life differ greatly. We find that the energy difference between the hydrogenated intermediate structure and the final demetalated structure (ΔEdemetalation) of the MPcs is linearly related to the degradation reaction barrier energy. Comparison to the degradation data for the previously studied metallocorrole systems suggested that ΔEdemetalation also serves as a descriptor for the corrole systems and that the high availability of protons at the active site due to the COOH group of the o-corrole decreases the durability