Developmental and Nutritional Dynamics of Malpighian Tubule Autofluorescence in the Asian Tiger Mosquito Aedes albopictus.

Malpighian tubules (MTs) are arthropod excretory organs crucial for the osmoregulation, detoxification and excretion of xenobiotics and metabolic wastes, which include tryptophan degradation products along the kynurenine (KYN) pathway. Specifically, the toxic intermediate 3-hydroxy kynurenine (3-HK) is metabolized through transamination to xanthurenic acid or in the synthesis of ommochrome pigments. Early investigations in Drosophila larval fat bodies revealed an intracellular autofluorescence (AF) that depended on tryptophan administration. Subsequent observations documented AF changes in the MTs of Drosophila eye-color mutants genetically affecting the conversion of tryptophan to KYN or 3-HK and the intracellular availability of zinc ions. In the present study, the AF properties of the MTs in the Asian tiger mosquito, Aedes albopictus, were characterized in different stages of the insect's life cycle, tryptophan-administered larvae and blood-fed adult females. Confocal imaging and microspectroscopy showed AF changes in the distribution of intracellular, brilliant granules and in the emission spectral shape and amplitude between the proximal and distal segments of MTs across the different samples. The findings suggest AF can serve as a promising marker for investigating the functional status of MTs in response to metabolic alterations, contributing to the use of MTs as a potential research model in biomedicine.

Tryptophan regulates Drosophila zinc stores.

Zinc deficiency is commonly attributed to inadequate absorption of the metal. Instead, we show that body zinc stores in Drosophila melanogaster depend on tryptophan consumption. Hence, a dietary amino acid regulates zinc status of the whole insect­a finding consistent with the widespread requirement of zinc as a protein cofactor. Specifically, the tryptophan metabolite kynurenine is released from insect fat bodies and induces the formation of zinc storage granules in Malpighian tubules, where 3-hydroxykynurenine and xanthurenic acid act as endogenous zinc chelators. Kynurenine functions as a peripheral zinc-regulating hormone and is converted into a 3-hydroxykynurenine­zinc­chloride complex, precipitating within the storage granules. Thus, zinc and the kynurenine pathway­well-known modulators of immunity, blood pressure, aging, and neurodegeneration­are physiologically connected.

The adjustment of γ-aminobutyric acidA tonic subunits in Huntington's disease: from transcription to translation to synaptic levels into the neostriatum.

γ-Aminobutyric acid (GABA), plays a key role in all stages of life, also is considered the main inhibitory neurotransmitter. GABA activates two kind of membrane receptors known as GABAA and GABAB, the first one is responsible to render tonic inhibition by pentameric receptors containing α4-6, ß3, δ, or ρ1-3 subunits, they are located at perisynaptic and/or in extrasynaptic regions. The biophysical properties of GABAA tonic inhibition have been related with cellular protection against excitotoxic injury and cell death in presence of excessive excitation. On this basis, GABAA tonic inhibition has been proposed as a potential target for therapeutic intervention of Huntington's disease. Huntington's disease is a neurodegenerative disorder caused by a genetic mutation of the huntingtin protein. For experimental studies of Huntington's disease mouse models have been developed, such as R6/1, R6/2, HdhQ92, HdhQ150, as well as YAC128. In all of them, some key experimental reports are focused on neostriatum. The neostriatum is considered as the most important connection between cerebral cortex and basal ganglia structures, its cytology display two pathways called direct and indirect constituted by medium sized spiny neurons expressing dopamine D1 and D2 receptors respectively, they display strong expression of many types of GABAA receptors, including tonic subunits. The studies about of GABAA tonic subunits and Huntington's disease into the neostriatum are rising in recent years, suggesting interesting changes in their expression and localization which can be used as a strategy to delay the cellular damage caused by the imbalance between excitation and inhibition, a hallmark of Huntington's disease.

Erratum: Shrinking of Rapidly Evaporating Water Microdroplets Reveals their Extreme Supercooling [Phys. Rev. Lett. 120, 015501 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.120.015501.

Shrinking of Rapidly Evaporating Water Microdroplets Reveals their Extreme Supercooling.

The fast evaporative cooling of micrometer-sized water droplets in a vacuum offers the appealing possibility to investigate supercooled water-below the melting point but still a liquid-at temperatures far beyond the state of the art. However, it is challenging to obtain a reliable value of the droplet temperature under such extreme experimental conditions. Here, the observation of morphology-dependent resonances in the Raman scattering from a train of perfectly uniform water droplets allows us to measure the variation in droplet size resulting from evaporative mass losses with an absolute precision of better than 0.2%. This finding proves crucial to an unambiguous determination of the droplet temperature. In particular, we find that a fraction of water droplets with an initial diameter of 6379±12 nm remain liquid down to 230.6±0.6 K. Our results question temperature estimates reported recently for larger supercooled water droplets and provide valuable information on the hydrogen-bond network in liquid water in the hard-to-access deeply supercooled regime.

Biogenesis of zinc storage granules in Drosophila melanogaster.

Membrane transporters and sequestration mechanisms concentrate metal ions differentially into discrete subcellular microenvironments for use in protein cofactors, signalling, storage or excretion. Here we identify zinc storage granules as the insect's major zinc reservoir in principal Malpighian tubule epithelial cells of Drosophila melanogaster The concerted action of Adaptor Protein-3, Rab32, HOPS and BLOC complexes as well as of the white-scarlet (ABCG2-like) and ZnT35C (ZnT2/ZnT3/ZnT8-like) transporters is required for zinc storage granule biogenesis. Due to lysosome-related organelle defects caused by mutations in the homologous human genes, patients with Hermansky-Pudlak syndrome may lack zinc granules in beta pancreatic cells, intestinal paneth cells and presynaptic vesicles of hippocampal mossy fibers.

Huntington's disease leads to decrease of GABA-A tonic subunits in the D2 neostriatal pathway and their relocalization into the synaptic cleft.

GABA is a widely distributed inhibitory neurotransmitter. GABA-A receptors are hetero-pentameric channels assembled in multiple combinations from 19 available subunits; this diversity mediates phasic and tonic inhibitory synaptic potentials. Whereas GABA-A phasic receptors are located within the synaptic cleft, GABA-A tonic receptors are found peri- or extra-synaptically, where they are activated by diffusion of synaptic GABA release. In the neostriatum, GABA-A tonic subunits are present in the D2 medium-size spiny neurons. Since early impairment of these neurons is observed in Huntington's disease, we determined the ultrastructural localization of GABA-A-α5, -ß3, -δ, -ρ2 and, for the first time, of GABA-A-ρ3 subunits, in the D2 pathway of the YAC128 murine model of Huntington's disease at various stages of disease progression. We report mislocalization of all five subunits from peri- and extra-synaptic spaces into the synaptic clefts of YAC128 mice, present in diseased mice as early as 6 months-old. The synaptic localization of GABA-A tonic receptors correlated with increased sensitivity to pharmacologic antagonists during extracellular electrophysiological recordings in neostriatal slices. Finally, the association of GABA-A tonic receptors with the D2 pathway in 6-month-old mice was largely lost at 12 months of age.

Raman Vibrational Shifts of Small Clusters of Hydrogen Isotopologues.

Raman vibrational shifts of small parahydrogen (pH2), orthodeuterium (oD2), and paratritium (pT2) clusters with respect to the free molecules are calculated by combining a first order perturbation theory approach with Langevin equation Path Integral Ground State (LePIGS) simulations [ J. Phys. Chem. A 2013 , 117 , 7461 ]. Our theoretical predictions are compared to existing cryogenic free jet expansion results for pure (pH2)N clusters [ Phys. Rev. Lett. 2004 , 92 , 223401 ] and to new measurements for (oD2)N clusters reported here. This method has been successfully used before to predict the Raman vibrational shifts of (pH2)N clusters [ J. Chem. Phys. 2014 , 141 , 014310 ]. The 6-D interaction potential of Hinde [ J. Chem. Phys. 2008 , 128 , 154308 ] is reduced to 1-D using the Adiabatic Hindered Rotor approximation to yield effective pair potentials for both molecules being in the ground vibrational state, and for one of them carrying one quantum of vibrational excitation. These reduced 1-D potentials are fitted to a Morse Long Range analytic form for later convenience. Good agreement between experiment and theory is found for the smaller clusters, but significant deviations remain for the larger ones.

The role of swelling-activated chloride currents (I(CL,swell)) in the regulatory volume decrease response of freshly dissociated rat articular chondrocytes.

BACKGROUND/AIMS: Articular chondrocytes dwell in an environment that is continuously changing its osmolarity as a consequence of mechanical loading, yet their volume regulation capabilities (RVD) are not fully understood. This work aimed to determine the osmotic sensitivity of freshly isolated rat chondrocytes, their RVD capabilities and to study the properties of any anion currents associated. METHODS: Cell volume responses were determined by microscopy. Whole cell patch clamp was used to record ion currents. RESULTS: Chondrocytes showed to be osmotically sensitive and capable of RVD in a size-dependent manner. RVD was accompanied by activation of outwardly rectifying chloride currents, featuring time and voltage independent activation and inactivation at most depolarizing voltage levels, with an anion selectivity sequence of: SCN->I-≅NO3->Br->Cl->F->> Gluconate-> Methanesulphonate-, corresponding to Eisenman's sequence I. They were also permeable to taurine. These currents were blocked by DIDS, SITS, 9-AC and NPPB and by drugs that block ICl,swell such as fluoxetine, phloretin, DCPIB and tamoxifen. RT-PCR assays show the presence of mRNA for CLC-3 and TMEM16A, that had been proposed as molecular determinants of ICl,swell currents. CONCLUSIONS: These findings indicate that freshly isolated rat articular chondrocytes have ICl,swell. The further finding that ICl,swell blockers alter the RVD response suggest that ICl,swell is involved in the RVD response of rat articular chondrocytes.

Time-resolved study of crystallization in deeply cooled liquid parahydrogen.

We present real-time measurements of the crystallization process occurring in liquid para-hydrogen (para-H(2)) quenched to ≈0.65T(m) (T(m)=13.8   K is the melting point of bulk liquid para-H(2)). The combination of high spatial resolution Raman spectroscopy and liquid microjet generation allows, in situ, capturing structural changes with ∼10(-8) s time resolution. Our results provide a crystal growth rate that rules out a thermally activated freezing process and reveal that the quenched melt freezes into a metastable polymorph, which undergoes a structural transition. The achieved temporal control offers new opportunities for exploring the elementary processes of nonequilibrium phase transformations in supercooled liquids.