Light Activates Output from Evening Neurons and Inhibits Output from Morning Neurons in the Drosophila Circadian Clock

Animal circadian clocks are based on multiple oscillators whose interactions allow the daily control of complex behaviors. The Drosophila brain contains a circadian clock that controls rest–activity rhythms and relies upon different groups of PERIOD (PER)–expressing neurons. Two distinct oscillators have been functionally characterized under light-dark cycles. Lateral neurons (LNs) that express the pigment-dispersing factor (PDF) drive morning activity, whereas PDF-negative LNs are required for the evening activity. In constant darkness, several lines of evidence indicate that the LN morning oscillator (LN-MO) drives the activity rhythms, whereas the LN evening oscillator (LN-EO) does not. Since mutants devoid of functional CRYPTOCHROME (CRY), as opposed to wild-type flies, are rhythmic in constant light, we analyzed transgenic flies expressing PER or CRY in the LN-MO or LN-EO. We show that, under constant light conditions and reduced CRY function, the LN evening oscillator drives robust activity rhythms, whereas the LN morning oscillator does not. Remarkably, light acts by inhibiting the LN-MO behavioral output and activating the LN-EO behavioral output. Finally, we show that PDF signaling is not required for robust activity rhythms in constant light as opposed to its requirement in constant darkness, further supporting the minor contribution of the morning cells to the behavior in the presence of light. We therefore propose that day–night cycles alternatively activate behavioral outputs of the Drosophila evening and morning lateral neurons

Global perturbation of stratospheric water and aerosol burden by Hunga eruption

The eruption of the submarine Hunga volcano in January 2022 was associated with a powerful blast that injected volcanic material to altitudes up to 58 km. From a combination of various types of satellite and ground-based observations supported by transport modeling, we show evidence for an unprecedented increase in the global stratospheric water mass by 13% relative to climatological levels, and a 5-fold increase of stratospheric aerosol load, the highest in the last three decades. Owing to the extreme injection altitude, the volcanic plume circumnavigated the Earth in only 1 week and dispersed nearly pole-to-pole in three months. The unique nature and magnitude of the global stratospheric perturbation by the Hunga eruption ranks it among the most remarkable climatic events in the modern observation era, with a range of potential long-lasting repercussions for stratospheric composition and climate

Spéciation de l'arsenic dans la salive et l'urine humaines après exposition professionnelle

La surveillance biologique des personnes exposées professionnellement aux composés de l'arsenic (As) est basée sur la mesure de la concentration urinaire de cet élément. Toutefois, l'utilisation de l'arsenic urinaire comme indicateur biologique d'exposition, nécessite que soit faite la distinction entre, d'une part les composés organiques, non toxiques, d'origine alimentaire, tels que l'arsénobétaïne et l'arsénocholine et d'autre part, les formes inorganiques et organiques toxiques, à savoir, arsénites (As3+), arsénates (As5+), monométhylarsonate (MMA) et diméthylarsinate (DMA), d'origine iatrogène, professionnelle ou environnementale. La pratique actuelle consiste à distinguer les composés d'origine alimentaire ou non alimentaire. La méthode élaborée a pour objectif d'individualiser, à des fins de recherche, les composés inorganiques (As3+, As5+), les métabolites organiques (MMA, DMA) et les composés d'origine alimentaire (arsénobétaïne, arsénocholine). Cela a été réalisé par chromatographie d'échange d'ions pour l'urine et la salive, en combinant deux résines, une cationique et une anionique. La méthode est directe, sans prétraitement pour les échantillons d'urine et de salive. Quatre élutions successives permettent d'individualiser 5 fractions, As3+, As5+, MMA, DMA et As alimentaire. Après séparation des différentes espèces d'arsenic, l'analyse des fractions a été réalisée par spectrophotométrie d'absorption atomique électrothermique avec correction de fond par effet Zeeman et modifieur de matrice. Les méthodes décrites ont été adaptées à l'urine et à la salive à partir d'une méthode développée par Grabinski (1981) pour la spéciation dans l'eau. Elles ont été validées par l'évaluation de leurs critères de qualité sur l'eau surchargée en espèces chimiques et sur l'urine et la salive humaines, natives et surchargées des mêmes espèces chimiques. La technologie analytique utilisée, permet d'atteindre des sensibilités voisines de 9 µg/l pour 0,0044 unités d'absorbance.sec-1. Les limites de détection (définies à 3 écarts-types de la mesure du blanc), sont de 20,3, de 18,3, 20,4 et 13,0 µg/l, respectivement pour As total urinaire, As total salivaire, As urinaire non alimentaire et As dans les fractions éluées par chromatographie. Ces limites de détection sont inférieures aux valeurs de référence moyennes, et comparées à la valeur limite biologique urinaire de 50 µg/g de créatinine, elles permettent le suivi biologique des personnes exposées

Loop-stabilized BAB triblock copolymer morphologies by PISA in water

International audienceA straightforward strategy to synthesize in water, loop-stabilized particles via PISA is developed. These particular structures can in theory be obtained through the synthesis of amphiphilic BAB triblock copolymers, starting from a hydrophilic middle block A, which is chain extended in an aqueous PISA process by two hydrophobic external blocks B. For that purpose, symmetrical bifunctional poly(N,N-dimethylacrylamide) macroRAFT agents with a central benzoic acid group and an alkyl chain as Z group are used in the aqueous dispersion polymerization of diacetone acrylamide. For the first time, stable BAB flower-like particles are formed via PISA in pure water. It is shown that the colloidal stability and the resulting particle morphology (spheres, worms, vesicles) strongly depend on the degree of ionization of the central charge in the stabilizer loop, thus on the pH at which PISA is performed. Moreover, the influence of the length of the alkyl Z group (dodecyl and butyl alkyl chains) on the colloidal stability is studied

Templated-PISA: Driving Polymerization-Induced Self-Assembly towards the Fibre Morphology

International audienceDispersions of block-copolymer fibres in water have many potential applications and can be obtained by polymerization-induced self-assembly (PISA), but only in very restricted experimental conditions. In order to enlarge this experimental window, we introduced a supramolecular moiety, a hydrogen-bonded bis-urea sticker, in the macromolecular reversible addition-fragmentation chain transfer agent to drive the morphology of the nano-objects produced by RAFT-mediated PISA towards the fibre morphology. This novel concept is tested in the synthesis of a series of poly(N,N-dimethylacrylamide)-b-poly(2-methoxyethyl acrylate) (PDMAc-b-PMEA) diblock copolymers prepared by dispersion polymerization in water. The results prove that the introduction of the templating bis-urea stickers into PISA greatly promotes the formation of fibres in a large experimental window