The nightside cloud-top circulation of the atmosphere of Venus.

Although Venus is a terrestrial planet similar to Earth, its atmospheric circulation is much different and poorly characterized1. Winds at the cloud top have been measured predominantly on the dayside. Prominent poleward drifts have been observed with dayside cloud tracking and interpreted to be caused by thermal tides and a Hadley circulation2-4; however, the lack of nightside measurements over broad latitudes has prevented the unambiguous characterization of these components. Here we obtain cloud-tracked winds at all local times using thermal infrared images taken by the Venus orbiter Akatsuki, which is sensitive to an altitude of about 65 kilometres5. Prominent equatorward flows are found on the nightside, resulting in null meridional velocities when these are zonally averaged. The velocity structure of the thermal tides was determined without the influence of the Hadley circulation. The semidiurnal tide was found to have an amplitude large enough to contribute to the maintenance of the atmospheric superrotation. The weakness of the mean meridional flow at the cloud top implies that the poleward branch of the Hadley circulation exists above the cloud top and that the equatorward branch exists in the clouds. Our results should shed light on atmospheric superrotation in other celestial bodies.

Endocytosis-Like Vesicle Fission Mediated by a Membrane-Expanding Molecular Machine Enables Virus Encapsulation for In Vivo Delivery.

Biological membranes are functionalized by membrane-associated protein machinery. Membrane-associated transport processes, such as endocytosis, represent a fundamental and universal function mediated by membrane-deforming protein machines, by which small biomolecules and even micrometer-size substances can be transported via encapsulation into membrane vesicles. Although synthetic molecules that induce dynamic membrane deformation have been reported, a molecular approach enabling membrane transport in which membrane deformation is coupled with substance binding and transport remains critically lacking. Here, we developed an amphiphilic molecular machine containing a photoresponsive diazocine core (AzoMEx) that localizes in a phospholipid membrane. Upon photoirradiation, AzoMEx expands the liposomal membrane to bias vesicles toward outside-in fission in the membrane deformation process. Cargo components, including micrometer-size M13 bacteriophages that interact with AzoMEx, are efficiently incorporated into the vesicles through the outside-in fission. Encapsulated M13 bacteriophages are transiently protected from the external environment and therefore retain biological activity during distribution throughout the body via the blood following administration. This research developed a molecular approach using synthetic molecular machinery for membrane functionalization to transport micrometer-size substances and objects via vesicle encapsulation. The molecular design demonstrated in this study to expand the membrane for deformation and binding to a cargo component can lead to the development of drug delivery materials and chemical tools for controlling cellular activities.

Bromovalerylurea modulates GABAA receptor-mediated inhibitory neurotransmission while inducing sleep.

Bromovalerylurea (BU), an acyl urea derivative, was originally developed as a hypnotic/sedative. We recently reported that BU at a dose of 50 mg/kg ameliorates sepsis, Parkinson's disease, and traumatic brain injury in Wistar rat models through its anti-inflammatory actions on microglia and macrophages. However, since BU was developed more than 100 years ago, its hypnotic mechanism and characteristics are poorly understood. Herein, we conducted an electroencephalogram (EEG) study and found that BU, when administered at a dose of more than 125 mg/kg but not at a dose of 50 mg/kg in Wistar rats, significantly increased non-rapid eye movement (NREM) sleep duration and dose-dependently decreased rapid eye movement (REM) sleep duration. This characteristic of sleep induced by BU is similar to the effect of compounds such as barbiturate, benzodiazepine, and z-drugs, all of which require γ-aminobutyric acid A receptors (GABAAR) for hypnotic/sedative activity. To investigate whether BU could potentiate GABAAergic neurotransmission, we conducted a whole-cell patch-clamp recording from pyramidal neurons in rat cortical slices to detect spontaneous GABAAR-mediated inhibitory postsynaptic currents (IPSCs). We found that BU dose-dependently prolonged IPSCs. Importantly, the prolonged IPSCs were not attenuated by flumazenil, a benzodiazepine receptor antagonist, suggesting that modulation of IPSCs by BU is mediated by different mechanisms from that of benzodiazepine. Taken together, these data elucidate the basic characteristics of the hypnotic effects of BU and suggest that the enhancement of GABAAR-mediated Cl- flux may be a possible mechanism that contributes to its hypnotic/sedative activity.

Divergent mechanisms of reduced growth performance in Betula ermanii saplings from high-altitude and low-latitude range edges.

The reduced growth performance of individuals from range edges is a common phenomenon in various taxa, and considered to be an evolutionary factor that limits the species' range. However, most studies did not distinguish between two mechanisms that can lead to this reduction: genetic load and adaptive selection to harsh conditions. To address this lack of understanding, we investigated the climatic and genetic factors underlying the growth performance of Betula ermanii saplings transplanted from 11 populations including high-altitude edge and low-latitude edge population. We estimated the climatic position of the populations within the overall B. ermanii's distribution, and the genetic composition and diversity using restriction-site associated DNA sequencing, and measured survival, growth rates and individual size of the saplings. The high-altitude edge population (APW) was located below the 95% significance interval for the mean annual temperature range, but did not show any distinctive genetic characteristics. In contrast, the low-latitude edge population (SHK) exhibited a high level of linkage disequilibrium, low genetic diversity, a distinct genetic composition from the other populations, and a high relatedness coefficient. Both APW and SHK saplings displayed lower survival rates, heights and diameters, while SHK saplings also exhibited lower growth rates than the other populations' saplings. The low heights and diameters of APW saplings was likely the result of adaptive selection to harsh conditions, while the low survival and growth rates of SHK saplings was likely the result of genetic load. Our findings shed light on the mechanisms underlying the reduced growth performance of range-edge populations.

Artificial Palmitoylation of Proteins Controls the Lipid Domain-Selective Anchoring on Biomembranes and the Raft-Dependent Cellular Internalization.

Protein palmitoylation, a post-translational modification, is universally observed in eukaryotic cells. The localization of palmitoylated proteins to highly dynamic, sphingolipid- and cholesterol-rich microdomains (called lipid rafts) on the plasma membrane has been shown to play an important role in signal transduction in cells. However, this complex biological system is not yet completely understood. Here, we used a combined approach where an artificial lipidated protein was applied to biomimetic model membranes and plasma membranes in cells to illuminate chemical and physiological properties of the rafts. Using cell-sized giant unilamellar vesicles, we demonstrated the selective partitioning of enhanced green fluorescent protein modified with a C-terminal palmitoyl moiety (EGFP-Pal) into the liquid-ordered phase consisting of saturated phospholipids and cholesterol. Using Jurkat T cells treated with an immunostimulant (concanavalin A), we observed the vesicular transport of EGFP-Pal. Further cellular studies with the treatment of methyl ß-cyclodextrin revealed the cholesterol-dependent internalization of EGFP-Pal, which can be explained by a raft-dependent, caveolae-mediated endocytic pathway. The present synthetic approach using artificial and natural membrane systems can be further extended to explore the potential utility of artificially lipidated proteins at biological and artificial interfaces.

Developmental Phase Transitions in Spatial Organization of Spontaneous Activity in Postnatal Barrel Cortex Layer 4.

Spatially-organized spontaneous activity is a characteristic feature of developing mammalian sensory systems. However, the transitions of spontaneous-activity spatial organization during development and related mechanisms remain largely unknown. We reported previously that layer 4 (L4) glutamatergic neurons in the mouse barrel cortex exhibit spontaneous activity with a patchwork-type pattern at postnatal day (P)5, which is during barrel formation. In the current work, we revealed that spontaneous activity in mouse barrel-cortex L4 glutamatergic neurons exhibits at least three phases during the first two weeks of postnatal development. Phase I activity has a patchwork-type pattern and is observed not only at P5, but also P1, before barrel formation. Phase II is found at P9, by which time barrel formation is completed, and exhibits broadly synchronized activity across barrel borders. Phase III emerges around P11 when L4-neuron activity is desynchronized. The Phase I activity, but not Phase II or III activity, is blocked by thalamic inhibition, demonstrating that the Phase I to II transition is associated with loss of thalamic dependency. Dominant-negative (DN)-Rac1 expression in L4 neurons hampers the Phase II to III transition. It also suppresses developmental increases in spine density and excitatory synapses of L4 neurons in the second postnatal week, suggesting that Rac1-mediated synapse maturation could underlie the Phase II to III transition. Our findings revealed the presence of distinct mechanisms for Phase I to II and Phase II to III transition. They also highlighted the role of a small GTPase in the developmental desynchronization of cortical spontaneous activity.SIGNIFICANCE STATEMENT Developing neocortex exhibits spatially-organized spontaneous activity, which plays a critical role in cortical circuit development. The features of spontaneous-activity spatial organization and the mechanisms underlying its changes during development remain largely unknown. In the present study, using two-photon in vivo imaging, we revealed three phases (Phases I, II, and III) of spontaneous activity in barrel-cortex layer 4 (L4) glutamatergic neurons during the first two postnatal weeks. We also demonstrated the presence of distinct mechanisms underlying phase transitions. Phase I to II shift arose from the switch in the L4-neuron driving source, and Phase II to III transition relied on L4-neuron Rac1 activity. These results provide new insights into the principles of developmental transitions of neocortical spontaneous-activity spatial patterns.

Three-Phase Coexistence in Binary Charged Lipid Membranes in a Hypotonic Solution.

We investigated the phase separation of dioleoylphosphatidylserine (DOPS) and dipalmitoylphosphatidylcholine (DPPC) in giant unilamellar vesicles in a hypotonic solution using fluorescence and confocal laser scanning microscopy. Although phase separation in charged lipid membranes is generally suppressed by the electrostatic repulsion between the charged headgroups, osmotic stress can promote the formation of charged lipid domains. Interestingly, we observed a three-phase coexistence even in the DOPS/DPPC binary lipid mixtures. The three phases were DPPC-rich, dissociated DOPS-rich, and nondissociated DOPS-rich phases. The two forms of DOPS were found to coexist owing to the ionization of the DOPS headgroup, such that the system could be regarded as quasi-ternary. The three formed phases with differently ionized DOPS domains were successfully identified experimentally by monitoring the adsorption of positively charged particles. In addition, coarse-grained molecular dynamics simulations confirmed the stability of the three-phase coexistence. Attraction mediated by hydrogen bonding between protonated DOPS molecules and reduction of the electrostatic interactions at the domain boundaries stabilized the three-phase coexistence.

Osmotic-Tension-Induced Membrane Lateral Organization.

Alteration of lipid raft organization manifesting as phase separation is important for cellular processes, such as signaling and trafficking. Such behaviors and dynamics of lipid membranes can be affected by external stimuli including both physical and chemical stimuli. In this study, we focused on osmotic-tension-induced phase separation. The effects of osmotic tension on the phase behaviors of vesicles consisting of dioleoylphosphocholine (DOPC)/dipalmitoylphosphocholine (DPPC)/cholesterol (Chol) were quantitatively studied at different temperatures by fluorescence microscopy. We determined the ternary phase diagrams and found that tension leads to a shift in the miscibility temperature. Cholesterol plays a key role in determining the extent of this shift. In addition, we found that osmotic tension can enhance the line tension. The physicochemical mechanism of osmotic-pressure-induced phase separation is discussed.

Localization of transmembrane multiblock amphiphilic molecules in phase-separated vesicles.

A series of triblock amphiphilic molecules bearing hydrophilic PEG chains at both ends of the long aromatic hydrophobic moieties were obtained serendipitously. The molecules involve linearly connected diarylethyne and diarylbutadiyne units, which show characteristic emissions upon excitation by UV light. These emissions showed red-shifts upon an increase in the solvent polarity, where the shifts are larger for the molecules with longer aromatic moieties. The distribution of these molecules in phase-separated membranes consisting of DOPC/DPPC/cholesterol was studied by fluorescence microscopy. It was found that most compounds, except for that with the longest hydrophobic unit, were selectively distributed in the Ld phase consisting mainly of DOPC. Interestingly, some of them were suggested to encourage delocalization of cholesterol in both the Lo and Ld phases.

[Examination about the Direction for Uses of the Radiation Exposure Reduction Mechanism (Organ Effective Modulation) in Consideration of Organ Sensitivity].

Automatic exposure control technology can reduce the radiation dose during CT. The purpose of this study is to reveal the important points regarding the usage of organ effective modulation (OEM), by evaluating the characteristics of OEM, an automatic exposure control technology. An analysis of the dosage profiles revealed that OEM may not work with the first rotation of the X-ray tube in the helical method and wide volume method. This phenomenon can be avoided by using the orbital synchronism helical method. This was also demonstrated upon measurement of the integrated absorption dose at the imaging start position. An analysis of standard deviation measurement revealed that with the combined use of OEM and x-y modulation, the reduction in dose may significantly vary depending on the presence or absence of the gantry tilt. Based on the above results, when using OEM to reduce the dose at the imaging start position, the combined use of x-y modulation should be avoided and the orbital synchronism helical method should be used.

Formation of modulated phases and domain rigidification in fatty acid-containing lipid membranes.

We investigated the phase behavior of lipid membranes containing fatty acids (FAs) by microscopy and differential scanning calorimetry. We used palmitic acid (saturated FA), oleic acid (cis-isomer of unsaturated FA), elaidic acid (trans-isomer of unsaturated FA), and phytanic acid (branched FA) and examined the effects of FAs on phase-separated structures in lipid bilayer membranes consisting of dioleolylphosphocholine (DOPC)/dipalmitoylphosphocholine (DPPC)/cholesterol (Chol). Palmitic acid and elaidic acid exclude Chol from the DPPC-rich phase. As a result, the liquid-ordered phase formed by DPPC and Chol transforms into a solid-ordered phase. Oleic acid and phytanic acid significantly reduce the line tension at the liquid domain boundary. This decrease in line tension leads to the formation of modulated phases, such as striped, hexagonal, and polygonal domains. We measured the line tension and the interdomain interaction in these specific domains by an image analysis. The result showed that oleic acid and phytanic acid-containing vesicles as well as palmitic acid-containing vesicles are not spherical, and this domain-induced deformation is explained theoretically.

Multiple QTL Determine Dorsal Abdominal Scale Patterns in the Mosquito Aedes aegypti.

The mosquito, Aedes aegypti (L.) originated in Sub-Saharan Africa as a dark form sylvan species (A. aegypti formosus). Evolution of A. aegypti aegypti type form as a human commensal facilitated its colonization of most semitropical and tropical areas. We investigated the genetic basis for abdominal white scale presence that represents the diagnostic for sylvan A. aegypti formosus (scales absent), from type form (scales present) and A. aegypti queenslandensis form (dense scaling). We performed quantitative trait locus (QTL) mapping using 3 criteria for scale patterns among 192 F1 intercross progeny from matings between a queenslandensis type and an aegypti type form. Results identified 3 QTL determining scale patterns and indicated that classification criteria impact robustness of QTL LOD support. Dark- and light-colored forms exist in sympatry, but vary in multiple phenotypic characteristics, including preferences for vertebrate host, oviposition container, house-entering behavior, and dengue vector competence. Markers associated with 2 QTL regions reflected major reductions in recombination frequencies compared with the standard type form linkage map, suggestive of inversion polymorphisms associated with observed linkage disequilibrium between type-specific characteristics. Understanding the genic basis for differences in A. aegypti forms could inform efforts to develop new mosquito and arboviral disease control strategies.

Structure-dependent interactions of polyphenols with a biomimetic membrane system.

Polyphenols are naturally-occurring compounds, reported to be biologically active, and through their interactions with cell membranes. Although association of the polyphenols with the bilayer has been reported, the detailed mechanism of interaction is not yet well elucidated. We report on spatio-temporal real-time membrane dynamics observed in the presence of polyphenols. Two distinct membrane dynamics, corresponding to the two classes of polyphenols used, were observed. Flavonoids (epi-gallocatechin-3-gallate, gallocatechin, theaflavin and theaflavin-3-gallate) caused lipid membrane aggregation and rigidification. As simple structural modification through opening of the aromatic C-ring into an olefin bond, present in trans-stilbenes (resveratrol and picead), completely changed the membrane properties, increasing fluidity and inducing fluctuation. There were differences in the membrane transformations within the same class of polyphenols. Structure-dependent classification of membrane dynamics may contribute to a better understanding of the physicochemical mechanism involved in the bioactivity of polyphenols. In general, an increase in the number of hydrophilic side chains (galloyl, hydroxyl, glucoside, gallate) increased the reactivity of the polyphenols. Most notable was the difference observed through a simple addition of the gallate group. Unraveling the importance of these polyphenols, at a functional group level further opens the key to tailored design of bioactive compounds as potential drug candidates.

Physical properties of the hybrid lipid POPC on micrometer-sized domains in mixed lipid membranes.

Macro-phase separation in mixed lipid membranes containing the hybrid lipid palmitoyloleoylphosphatidylcholine (POPC) was observed by fluorescent and confocal laser scanning microscopy. In a binary system consisting of the saturated lipid dipalmitoylphosphatidylcholine (DPPC) and the hybrid lipid POPC, the hybrid lipid forms a liquid-disordered (Ld) phase. In a ternary system consisting of this binary system and an unsaturated lipid dioleoylphosphatidylcholine (DOPC), three-phase coexistence is observed. The POPC-rich phase appears around DPPC-rich domains, and the hybrid lipid is expected to behave like a line-active agent (linactant). Finally, phase separation in a four-component system, composed of this ternary system and cholesterol, was examined. Domains with a size that is smaller than 1 µm are found, and domain-induced budding is also observed. To explain small domain formation and domain-induced budding, chain ordering was evaluated based on Laurdan generalized polarization measurements. Our observations revealed that the hybrid lipid acted like a linactant to solid domains and disturbed chain ordering in liquid-ordered (Lo) domains. In both cases, the hybrid lipid reduced line tension at the domain boundary.

Winter Activity and Diapause of Aedes albopictus (Diptera: Culicidae) in Hanoi, Northern Vietnam.

We studied the winter activity of Aedes albopictus (Skuse) from November 2008 to April 2009 in Bat Trang village of Hanoi, Vietnam. We selected 12 houses and collected: 1) adults with BG sentinel traps, 2) pupae from household water containers, and 3) eggs with ovitraps. Aedes albopictus adults, pupae, and eggs were not collected from early January to early February. Though the egg hatching probability tended to be initially high at longer day length, the maximum probability gradually shifted to shorter day length, as the observation period elapsed. When females were reared under long day length and their eggs were immersed 1 or 5 wk after oviposition, >50% of eggs hatched within 20 days. However, when females were reared under short day length and their eggs were immersed after 1 wk, hatching was suppressed for 60 days. When females were reared under short day length, the median hatching day occurred earlier in eggs kept dry for 5 and 10 wk after oviposition than in those dried for only 1 wk. This indicates that the extended dry periods accelerate egg hatching. Our results showed that hatchability gradually changed with day length, suggesting that selection for overwintering is not as strong relative to Ae. albopictus living in the temperate zone, where winter conditions are less favorable than in tropical and subtropical areas.

Membrane fusion and vesicular transformation induced by Alzheimer's amyloid beta.

Amyloid beta (Aß) peptides, produced through endo-proteolytic cleavage of amyloid precursor protein, are thought to be involved in the death of neural cells in Alzheimer's disease (AD). Although the mechanisms are not fully known, it has been suggested that disruption of cellular activity due to Aß interactions with the cell membrane may be one of the underlying causes. Here in, we have investigated the interaction between Aß-42 and biomimetic lipid membranes and the resulting perturbations in the lipid vesicles. We have shown that Aß oligomeric species localized closer to the membrane surface. Localization of the fibrillar species of Aß-42, although varied, was not as closely associated with the membrane surface. We have demonstrated that the presence of Aß-42 leads to an increase in membrane surface area, inducing lipid temporal vesicular transformation. Furthermore, we have unequivocally shown that Aß-peptides mediate membrane fusion. Although membrane fusion induced by Aß has been hypothesized/proposed, this is the first time it has been visually captured. This fusion may be one of the mechanisms behind the membrane increase in surface area and the resulting vesicular transformation. We have shown that the longer 'amyloidogenic' isoform causes vesicular transformation more readily, and has a higher membrane fusogenic potential than Aß-40. Although not core to this study, it is hugely interesting to observe the high agreement between membrane dynamics and the reported amyloidogenicity of the peptides and aggregation species opening up the potential role of vesicular dynamics for profiling and biosensing of Aß-induced neuro-toxicity.

The effect of oxysterols on the interaction of Alzheimer's amyloid beta with model membranes.

The interaction of amyloid beta (Aß) peptide with cell membranes has been shown to be influenced by Aß conformation, membrane physicochemical properties and lipid composition. However, the effect of cholesterol and its oxidized derivatives, oxysterols, on Aß-induced neurotoxicity to membranes is not fully understood. We employed here model membranes to investigate the localization of Aß in membranes and the peptide-induced membrane dynamics in the presence of cholesterol and 7-ketocholesterol (7keto) or 25-hydroxycholesterol (25OH). Our results have indicated that oxysterols rendered membranes more sensitive to Aß, in contrast to role of cholesterol in inhibiting Aß/membrane interaction. We have demonstrated that two oxysterols had different impacts owing to distinct positions of the additional oxygen group in their structures. 7keto-containing cell-sized liposomes exhibited a high propensity toward association with Aß, while 25OH systems were more capable of morphological changes in response to the peptide. Furthermore, we have shown that 42-amino acid Aß (Aß-42) pre-fibril species had higher association with membranes, and caused membrane fluctuation faster than 40-residue isoform (Aß-40). These findings suggest the enhancing effect of oxysterols on interaction of Aß with membranes and contribute to clarify the harmful impact of cholesterol on Aß-induced neurotoxicity by means of its oxidation.

Micrometer-size vesicle formation triggered by UV light.

Vesicle formation is a fundamental kinetic process related to the vesicle budding and endocytosis in a cell. In the vesicle formation by artificial means, transformation of lamellar lipid aggregates into spherical architectures is a key process and known to be prompted by e.g. heat, infrared irradiation, and alternating electric field induction. Here we report UV-light-driven formation of vesicles from particles consisting of crumpled phospholipid multilayer membranes involving a photoactive amphiphilic compound composed of 1,4-bis(4-phenylethynyl)benzene (BPEB) units. The particles can readily be prepared from a mixture of these components, which is casted on the glass surface followed by addition of water under ultrasonic radiation. Interestingly, upon irradiation with UV light, micrometer-size vesicles were generated from the particles. Neither infrared light irradiation nor heating prompted the vesicle formation. Taking advantage of the benefits of light, we successfully demonstrated micrometer-scale spatiotemporal control of single vesicle formation. It is also revealed that the BPEB units in the amphiphile are essential for this phenomenon.

Charge-induced phase separation in lipid membranes.

Phase separation in lipid bilayers that include negatively charged lipids is examined experimentally. We observed phase-separated structures and determined the membrane miscibility temperatures in several binary and ternary lipid mixtures of unsaturated neutral lipid, dioleoylphosphatidylcholine (DOPC), saturated neutral lipid, dipalmitoylphosphatidylcholine (DPPC), unsaturated charged lipid, dioleoylphosphatidylglycerol (DOPG((-))), saturated charged lipid, dipalmitoylphosphatidylglycerol (DPPG((-))), and cholesterol. In binary mixtures of saturated and unsaturated charged lipids, the combination of the charged head with the saturation of the hydrocarbon tail is a dominant factor in the stability of membrane phase separation. DPPG((-)) enhances phase separation, while DOPG((-)) suppresses it. Furthermore, the addition of DPPG((-)) to a binary mixture of DPPC/cholesterol induces phase separation between DPPG((-))-rich and cholesterol-rich phases. This indicates that cholesterol localization depends strongly on the electric charge on the hydrophilic head group rather than on the ordering of the hydrocarbon tails. Finally, when DPPG((-)) was added to a neutral ternary system of DOPC/DPPC/cholesterol (a conventional model of membrane rafts), a three-phase coexistence was produced. We conclude by discussing some qualitative features of the phase behaviour in charged membranes using a free energy approach.

Endo- and exocytic budding transformation of slow-diffusing membrane domains induced by Alzheimer's amyloid beta.

Cell-sized liposomes are a powerful tool for clarifying physicochemical mechanisms that govern molecular interactions. Herein, budding transformation of membrane domains was induced by amyloid beta peptides. The peptides increased the membrane viscosity as demonstrated by the Brownian motion of membrane domains. These results could aid in understanding the physicochemical mechanism of Alzheimer's disease.