bluuebunny/crossref_metadata_2025 huggingface dataset:
Assimilation of water vapor sensitive infrared brightness temperature observations during a high impact weather event
Authors: Otkin Jason A.
Published: September 2012

A regional‐scale Observing System Simulation Experiment was used to examine the impact of water vapor (WV) sensitive infrared brightness temperature observations on the analysis and forecast accuracy during a high impact weather event across the central U.S. Ensemble data assimilation experiments were performed using the ensemble Kalman filter algorithm in the Data Assimilation Research Testbed system. Vertical error profiles at the end of the assimilation period showed that the wind and temperature fields were most accurate when observations sensitive to WV in the upper troposphere were assimilated; however, the largest improvements in the cloud and moisture analyses occurred after assimilating observations sensitive to WV in the lower and middle troposphere. The more accurate analyses at the end of these cases lead to improved short‐range precipitation forecasts compared to the Control case in which only conventional observations were assimilated. Equitable threat scores were consistently higher for all precipitation thresholds during the WV band forecasts. These results demonstrate that the ability of WV‐sensitive infrared brightness temperatures to improve not only the 3D moisture distribution, but also the temperature, cloud, and wind fields, enhances their utility within a data assimilation system.
Precipitation driving of droplet concentration variability in marine low clouds
Authors: Wood Robert , Leon David , Lebsock Matthew , Snider Jefferson , Clarke Antony D.
Published: September 2012

The concentration Nd of cloud droplets in marine low clouds is a primary determinant of their ability to reflect sunlight and modulates their ability to precipitate. Previous studies have focused upon aerosol source variability as the key driver of variability in Nd. Here, we use a highly simplified aerosol budget model to examine the impact of precipitation on Nd. This model considers: precipitation (coalescence) scavenging, constrained using new satellite measurements of light precipitation; entrainment of aerosol from above cloud combined with constant aerosol concentration based on recent field observations of aerosol particles in the free troposphere; and sea‐surface aerosol production estimated using a wind speed dependent source function. Despite the highly simplified nature of this model, it skillfully predicts the geographical variability ofNd in regions of extensive marine low clouds. Inclusion of precipitation results in reduction in Nd by factors of 2–3 over the remote oceans. Within 500 km of coastlines the reduction in Nd due to precipitation is weak but in these regions the model is not able to accurately predict Ndbecause of strong pollution sources. In general, neither free‐tropospheric nor surface CCN sources alone are sufficient to maintainNd against precipitation losses. The results demonstrate that even the light precipitation rates typical of marine stratocumulus profoundly impact the radiative properties of marine low clouds.
Upward lightning observations from towers in Rapid City, South Dakota and comparison with National Lightning Detection Network data, 2004–2010
Authors: Warner Tom A. , Cummins Kenneth L. , Orville Richard E.
Published: September 2012

We report on upward lightning observations from ten tall towers (91–191 m) in Rapid City, South Dakota, USA and compare with National Lightning Detection Network (NLDN) data. A total of 81 upward flashes were observed from 2004–2010 using GPS time‐stamped optical sensors, and in all but one case, visible flash activity preceded the development of the upward leaders. Time‐correlated analysis showed that the NLDN recorded an event within 50 km of towers and within 500 ms prior to upward leader development from the tower(s) for 83% (67/81) of the upward flashes. A preceding positive cloud‐to‐ground stroke (+CG) was detected in 57% (46/81) of the cases, and a preceding positive intracloud flash (+IC) in 23% (19/81) of the cases. However, 8 of the 19 NLDN‐indicated +IC events were actually +CG strokes based on optical observations. Preceding negative intracloud flashes (−IC) were recorded for 2% (2/81) of the cases. Analysis also showed that for 44% (36/81) of the upward flashes, the NLDN reported subsequent negative cloud‐to‐ground (−CG) strokes and/or −IC events at one or more tower locations. Of the 151 subsequent events, 70% (105/151) were −CG reports and 30% (46/151) were listed as −IC events. The geometric mean/median location accuracy and peak current for subsequent events were 194 m/206 m and −12.9 kA/−12.4 kA respectively. These correlated observations suggest that a majority of the upward lightning flashes were triggered by a preceding flash with the dominant triggering type being the +CG flash.
Large impact basins on Mercury: Global distribution, characteristics, and modification history from MESSENGER orbital data
Authors: Fassett Caleb I. , Head James W. , Baker David M. H. , Zuber Maria T. , Smith David E. , Neumann Gregory A. , Solomon Sean C. , Klimczak Christian , Strom Robert G. , Chapman Clark R. , Prockter Louise M. , Phillips Roger J. , Oberst Jürgen , Preusker Frank
Published: September 2012

The formation of large impact basins (diameter D ≥ 300 km) was an important process in the early geological evolution of Mercury and influenced the planet's topography, stratigraphy, and crustal structure. We catalog and characterize this basin population on Mercury from global observations by the MESSENGER spacecraft, and we use the new data to evaluate basins suggested on the basis of the Mariner 10 flybys. Forty‐six certain or probable impact basins are recognized; a few additional basins that may have been degraded to the point of ambiguity are plausible on the basis of new data but are classified as uncertain. The spatial density of large basins (D ≥ 500 km) on Mercury is lower than that on the Moon. Morphological characteristics of basins on Mercury suggest that on average they are more degraded than lunar basins. These observations are consistent with more efficient modification, degradation, and obliteration of the largest basins on Mercury than on the Moon. This distinction may be a result of differences in the basin formation process (producing fewer rings), relaxation of topography after basin formation (subduing relief), or rates of volcanism (burying basin rings and interiors) during the period of heavy bombardment on Mercury from those on the Moon.
Anik‐E1 and E2 satellite failures of January 1994 revisited
Authors: Lam H.‐L. , Boteler D. H. , Burlton B. , Evans J.
Published: September 2012

The consecutive failures of the geosynchronous Anik‐E1 communication satellite on January 20, 1994, and Anik‐E2 about nine hours later on January 21 (both incidents occurred on January 20 local time) received considerable publicity because the malfunctions of the satellites disrupted television and computer data transmissions across Canada, as well as telephone services to remote northern communities for hours. This often‐cited event is revisited here with materials not covered before. Using publicly available information, Anik‐E failure details, media coverage, recovery effort and cost incurred are first presented. This is then followed by scrutiny of space weather conditions pertinent to the occurrences of the Anik‐E upsets. We trace the space weather episode's inception on the Sun, propagation through interplanetary medium, and manifestation in magnetic field variations as well as in energetic electron flux increases, and its eventual impact on the Anik‐Es. The genesis of the energetic electron enhancements that have been blamed for the satellite malfunctions is thus traceable via high‐speed solar wind stream with Alfven wave fluctuations to a longitudinally wide coronal hole on the Sun. Furthermore, strong magnetic pulsations preceding electron flux peaks indicate Pc5 ULF (Ultra Low Frequency) waves as a probable acceleration mechanism for the energetic electron flux enhancement that resulted in the internal charging of the Anik‐Es. The magnetic fluctuations may even be possible triggers for the subsequent discharge that caused the satellites to malfunction. This incident illustrates that satellite operators should be on alert for elevated high‐energy electron environment that is above established thresholds, as specifications in satellite design may not render a satellite immune from internal charging.
Spatiotemporal reconstruction of gaps in multivariate fields using the direct sampling approach
Authors: Mariethoz Gregoire , McCabe Matthew F. , Renard Philippe
Published: September 2012

The development of spatially continuous fields from sparse observing networks is an outstanding problem in the environmental and Earth sciences. Here we explore an approach to produce spatially continuous fields from discontinuous data that focuses on reconstructing gaps routinely present in satellite‐based Earth observations. To assess the utility of the approach, we use synthetic imagery derived from a regional climate model of southeastern Australia. Orbital tracks, scan geometry influences, and atmospheric artifacts are artificially imposed upon these model simulations to examine the techniques' capacity to reproduce realistic and representative retrievals. The imposed discontinuities are reconstructed using a direct sampling technique and are compared against the original continuous model data: a synthetic simulation experiment. Results indicate that the multipoint geostatistical gap‐filling approach produces texturally realistic spatially continuous fields from otherwise discontinuous data sets. Reconstruction results are assessed through comparison of spatial distributions, as well as through visual assessment of fine‐scale features. Complex spatial patterns and fine‐scale structure can be resolved within the reconstructions, illustrating that the often nonlinear dependencies between variables can be maintained. The stochastic nature of the methodology makes it possible to expand the approach within a Monte Carlo framework in order to estimate the uncertainty related to subsequent reconstructions. From a practical perspective, the reconstruction method is straightforward and requires minimum user intervention for parameter adjustment. As such, it can be automated to systematically process real time remote sensing measurements.
Modeling stakeholder‐defined climate risk on the Upper Great Lakes
Authors: Moody Paul , Brown Casey
Published: September 2012

Climate change is believed to pose potential risks to the stakeholders of the Great Lakes due to changes in lake levels. This paper presents a model of stakeholder‐defined risk as a function of climate change. It describes the development of a statistical model that links water resources system performance and climate changes developed for the Great Lakes of North America. The function is used in a process that links bottom‐up water system vulnerability assessment to top‐down climate change information. Vulnerabilities are defined based on input from stakeholders and resource experts and are used to determine system performance thresholds. These thresholds are used to measure performance over a wide range of climate changes mined from a large (55,590 year) stochastic data set. The performance and climate conditions are used to create a climate response function, a statistical model to predict lake performance based on climate statistics. This function facilitates exploration and analysis of performance over a wide range of climate conditions. It can also be used to estimate risk associated with change in climate mean and variability resulting from climate change. Problematic changes in climate can be identified and the probability of those conditions estimated using climate projections or other sources of climate information. The function can also be used to evaluate the robustness of a regulation plan and to compare performance of alternate plans. This paper demonstrates the utility of the climate response function as applied within the context of the International Upper Great Lakes Study.
Glucan affinity of starch synthase IIa determines binding of starch synthase I and starch-branching enzyme IIb to starch granules
Authors: Liu Fushan , Romanova Nadya , Lee Elizabeth A. , Ahmed Regina , Evans Martin , Gilbert Elliot P. , Morell Matthew K. , Emes Michael J. , Tetlow Ian J.
Published: September 2012

The sugary-2 mutation in maize (Zea mays L.) is a result of the loss of catalytic activity of the endosperm-specific SS (starch synthase) IIa isoform causing major alterations to amylopectin architecture. The present study reports a biochemical and molecular analysis of an allelic variant of the sugary-2 mutation expressing a catalytically inactive form of SSIIa and sheds new light on its central role in protein–protein interactions and determination of the starch granule proteome. The mutant SSIIa revealed two amino acid substitutions, one being a highly conserved residue (Gly522→Arg) responsible for the loss of catalytic activity and the inability of the mutant SSIIa to bind to starch. Analysis of protein–protein interactions in sugary-2 amyloplasts revealed the same trimeric assembly of soluble SSI, SSIIa and SBE (starch-branching enzyme) IIb found in wild-type amyloplasts, but with greatly reduced activities of SSI and SBEIIb. Chemical cross-linking studies demonstrated that SSIIa is at the core of the complex, interacting with SSI and SBEIIb, which do not interact directly with each other. The sugary-2 mutant starch granules were devoid of amylopectin-synthesizing enzymes, despite the fact that the respective affinities of SSI and SBEIIb from sugary-2 for amylopectin were the same as observed in wild-type. The data support a model whereby granule-bound proteins involved in amylopectin synthesis are partitioned into the starch granule as a result of their association within protein complexes, and that SSIIa plays a crucial role in trafficking SSI and SBEIIb into the granule matrix.
Endogenous and induced angiogenic characteristics of human chorion‐derived stem cells
Authors: Fariha Mohd‐Manzor Nur , Chua Kien‐Hui , Tan Geok‐Chin , Lim Yun‐Hsuen , Hayati Abdul‐Rahman
Published: September 2012

Cell‐based therapy using stem cells has emerged as one of the pro‐angiogenic methods to enhance blood vessel growth and sprouting in ischaemic conditions. This study investigated the endogenous and induced angiogenic characteristics of hCDSC (human chorion‐derived stem cell) using QPCR (quantitative PCR) method, immunocytochemistry and fibrin‐matrigel migration assay. The results showed that cultured hCDSC endogenously expressed angiogenic–endogenic‐associated genes (VEGF, bFGF, PGF, HGF, Ang‐1, PECAM‐1, eNOS, Ve‐cad, CD34, VEGFR‐2 and vWF), with significant increase in mRNA levels of PGF, HGF, Ang‐1, eNOS, VEGFR‐2 and vWF following induction by bFGF (basic fibroblast growth factor) and VEGF (vascular endothelial growth factor). These enhanced angiogenic properties suggest that induced hCDSC provides a stronger angiogenic effect for the treatment of ischaemia. After angiogenic induction, hCDSC showed no reduction in the expression of the stemness genes, but had significantly higher levels of mRNA of Oct‐4, Nanog (3), FZD9, ABCG‐2 and BST‐1. The induced cells were positive for PECAM‐1 (platelet/endothelial cell adhesion molecule 1) and vWF (von Willebrand factor) with immunocytochemistry staining. hCDSC also showed endothelial migration behaviour when cultured in fibrin‐matrigel construct and were capable of forming vessels in vivo after implanting into nude mice. These data suggest that hCDSC could be the cells of choice in the cell‐based therapy for pro‐angiogenic purpose.
Effect of film thickness on structural, morphology, dielectric and electrical properties of parylene C films
Authors: Kahouli Abdelkader
Published: September 2012

Parylene C (C8H7Cl)n thin films were deposited along the Si(100) index on a p-type Si substrate at room temperature by a vapor deposition polymerization method. The effects of film thickness on the crystalline structure, roughness, dielectric and electrical properties of parylene C films were investigated. X-ray diffraction has confirmed an amorphous structure in thinner films (d < 40 nm ≈ Rg: gyration radius) and a semicrystalline structure in thicker films (d < 40 nm). The roughness (Rms) varied according to a power law depending on the thickness Rms ∼ dβ with β = 0.22 ± 0.05. The effect of the diffusion monomers and chains relaxations in volume are the main factors limiting the evolution of the surface roughness according to film thickness for d < 40 nm and the crystalline size effect for d > 40 nm due to surface energy minimization when the film gets thicker. The dielectric constant increases as a power law according to film thickness ε′ = dβ with β = 0.042 ± 0.04 for d < 1000 nm and 0.0138 ± 0.02 for d > 1000. This is interpreted as caused by the decreasing of voids and discontinuities of the material with increasing film thickness. The leakage current density J suddenly increases with decreasing film thickness especially for d < 1000 nm, referring to a more pronounced amorphous content, but it is practically thickness independent from d > 10 000 nm and it shows a value of a bout 4 × 10−8 A/m for an applied field of 20 MV/m.
Ozone-exposure and annealing effects on graphene-on-SiO2 transistors
Authors: Zhang E. X. , Newaz A. K. M. , Wang B. , Zhang C. X. , Fleetwood D. M. , Bolotin K. I. , Schrimpf R. D. , Pantelides S. T. , Alles M. L.
Published: September 2012

We employ resistance measurements and Raman spectroscopy to investigate the effects of UV ozone (UVO) exposure and Ar annealing on graphene-on-SiO2 transistors. Shorter UVO exposures lead to oxygen adsorption and doping; longer exposures lead to significant defect generation and then to etching. Elevated-temperature Ar annealing following UVO exposure leads to local defect healing, as shown by the evolution of the characteristic Raman D- and G-peaks. In striking contrast, the overall graphene transistor resistance increases significantly due to void formation. Density functional calculations show that carbon-oxygen reactions lead to efficient consumption and release of C atoms (as CO or CO2) under conditions of high surface oxygen concentration.
Phenotyping of wheat cultivars for heat tolerance using chlorophyll a fluorescence
Authors: Sharma Dew Kumari , Andersen Sven Bode , Ottosen Carl-Otto , Rosenqvist Eva
Published: September 2012

In view of the global climate change, heat stress is an increasing constraint for the productivity of wheat (Triticum aestivum L.). Our aim was to identify contrasting cultivars in terms of heat tolerance by mass screening of 1274 wheat cultivars of diverse origin, based on a physiological trait, the maximum quantum efficiency of PSII (Fv/Fm). A chlorophyll fluorescence protocol was standardised and used for repeated screening with increased selection pressure with a view to identifying a set of cultivars extreme for the trait. An initial mass screening of 1274 wheat cultivars with a milder heat stress of 38°C in 300 µmol m–2 s–1 for 2 h with preheating at 33–35°C for 19 h in 7–14 µmol m–2 s–1 light showed a genetic determination of 8.5 ± 2.7%. A heat treatment of 40°C in 300 µmol m–2 s–1 for 72 h in the second screening with 138 selected cultivars resulted in larger differentiation of cultivars with an increased genetic component (15.4 ± 3.6%), which was further increased to 27.9 ± 6.8% in the third screening with 41 contrasting cultivars. This contrasting set of cultivars was then used to compare the ability of chlorophyll fluorescence parameters to detect genetic difference in heat tolerance. The identification of a set of wheat cultivars contrasting for their inherent photochemical efficiency may aid future studies to understand the genetic and physiological nature of heat stress tolerance in order to dissect quantitative traits into simpler genetic factors.
Fire return intervals within the northern boundary of the larch forest in Central Siberia
Authors: Kharuk Vyacheslav I. , Dvinskaya Mariya L. , Ranson K. Jon
Published: September 2012

A fire history of northern larch forests was studied. These larch forests are found near the northern limit of their range at ~71°N, where fires are predominantly caused by lightning strikes rather than human activity. Fire-return intervals (FRIs) were calculated based on fire scars and dates of tree natality. Tree natality was used as an approximation of the date of the last fire. The average FRI was found to be 295±57 years, which is the longest reported for larch-dominated stands. Prior studies reported 80–90-year FRIs at 64°N and ~200 years near the latitude of the Arctic Circle. Comparing data from fires that occurred in 1700–1849 (end of the Little Ice Age, LIA) and 1850–1999 (post-LIA warming) indicates approximately twice as many fires occurred during the latter period. This agrees with the hypothesis that observed climatic warming will result in an increase in fire frequency. Our results also indicate that fires that did not leave visible fire scars on the tree stem may be identified based on the date of growth release revealed from dendrochronology.
Phylogenies reveal predictive power of traditional medicine in bioprospecting
Authors: Saslis-Lagoudakis C. Haris , Savolainen Vincent , Williamson Elizabeth M. , Forest Félix , Wagstaff Steven J. , Baral Sushim R. , Watson Mark F. , Pendry Colin A. , Hawkins Julie A.
Published: September 2012

There is controversy about whether traditional medicine can guide drug discovery, and investment in bioprospecting informed by ethnobotanical data has fluctuated. One view is that traditionally used medicinal plants are not necessarily efficacious and there are no robust methods for distinguishing those which are most likely to be bioactive when selecting species for further testing. Here, we reconstruct a genus-level molecular phylogenetic tree representing the 20,000 species found in the floras of three disparate biodiversity hotspots: Nepal, New Zealand, and the Cape of South Africa. Borrowing phylogenetic methods from community ecology, we reveal significant clustering of the 1,500 traditionally used species, and provide a direct measure of the relatedness of the three medicinal floras. We demonstrate shared phylogenetic patterns across the floras: related plants from these regions are used to treat medical conditions in the same therapeutic areas. This finding strongly indicates independent discovery of plant efficacy, an interpretation corroborated by the presence of a significantly greater proportion of known bioactive species in these plant groups than in random samples. We conclude that phylogenetic cross-cultural comparisons can focus screening efforts on a subset of traditionally used plants that are richer in bioactive compounds, and could revitalize the use of traditional knowledge in bioprospecting.
Conformational state of the MscS mechanosensitive channel in solution revealed by pulsed electron–electron double resonance (PELDOR) spectroscopy
Authors: Pliotas Christos , Ward Richard , Branigan Emma , Rasmussen Akiko , Hagelueken Gregor , Huang Hexian , Black Susan S. , Booth Ian R. , Schiemann Olav , Naismith James H.
Published: September 2012

The heptameric mechanosensitive channel of small conductance (MscS) provides a critical function in
Escherichia coli
where it opens in response to increased bilayer tension. Three approaches have defined different closed and open structures of the channel, resulting in mutually incompatible models of gating. We have attached spin labels to cysteine mutants on key secondary structural elements specifically chosen to discriminate between the competing models. The resulting pulsed electron–electron double resonance (PELDOR) spectra matched predicted distance distributions for the open crystal structure of MscS. The fit for the predictions by structural models of MscS derived by other techniques was not convincing. The assignment of MscS as open in detergent by PELDOR was unexpected but is supported by two crystal structures of spin-labeled MscS. PELDOR is therefore shown to be a powerful experimental tool to interrogate the conformation of transmembrane regions of integral membrane proteins.
Auditory perception at the root of language learning
Authors: Mueller Jutta L. , Friederici Angela D. , Männel Claudia
Published: September 2012

Learning a spoken language presupposes efficient auditory functions. In the present event-related potential study, we tested whether and how basic auditory processes are related to online learning of a linguistic rule in infants and adults. Participants listened to frequent standard stimuli, which were interspersed with infrequent pitch deviants and rule deviants, violating a nonadjacent dependency between two syllables. Only infants who showed the more mature mismatch response for the pitch deviants (i.e., a negativity) showed a mismatch response to the rule deviants. Concordantly, the small group of adults who showed evidence of rule learning showed larger mismatch effects for pitch processing. We conclude that the ability to extract linguistic rules develops in early infancy and is tightly linked to functional aspects of basic auditory mechanisms.
Virulence and transmissibility of H1N2 influenza virus in ferrets imply the continuing threat of triple-reassortant swine viruses
Authors: Pascua Philippe Noriel Q. , Song Min-Suk , Lee Jun Han , Baek Yun Hee , Kwon Hyeok-il , Park Su-Jin , Choi Eun Hye , Lim Gyo-Jin , Lee Ok-Jun , Kim Si-Wook , Kim Chul-Joong , Sung Moon Hee , Kim Myung Hee , Yoon Sun-Woo , Govorkova Elena A. , Webby Richard J. , Webster Robert G. , Choi Young-Ki
Published: September 2012

Efficient worldwide swine surveillance for influenza A viruses is urgently needed; the emergence of a novel reassortant pandemic H1N1 (pH1N1) virus in 2009 demonstrated that swine can be the direct source of pandemic influenza and that the pandemic potential of viruses prevalent in swine populations must be monitored. We used the ferret model to assess the pathogenicity and transmissibility of predominant Korean triple-reassortant swine (TRSw) H1N2 and H3N2 influenza viruses genetically related to North American strains. Although most of the TRSw viruses were moderately pathogenic, one [A/Swine/Korea/1204/2009; Sw/1204 (H1N2)] was virulent in ferrets, causing death within 10 d of inoculation, and was efficiently transmitted to naive contact ferrets via respiratory droplets. Although molecular analysis did not reveal known virulence markers, the Sw/1204 virus acquired mutations in hemagglutinin (HA) (Asp-225-Gly) and neuraminidase (NA) (Ser-315-Asn) proteins during the single ferret passage. The contact-Sw/1204 virus became more virulent in mice, replicated efficiently in vitro, extensively infected human lung tissues ex vivo, and maintained its ability to replicate and transmit in swine. Reverse-genetics studies further indicated that the HA
225G
and NA
315N
substitutions contributed substantially in altering virulence and transmissibility. These findings support the continuing threat of some field TRSw viruses to human and animal health, reviving concerns on the capacity of pigs to create future pandemic viruses. Apart from warranting continued and enhanced global surveillance, this study also provides evidence on the emerging roles of HA
225G
and NA
315N
as potential virulence markers in mammals.
Cannabinoid receptor 1-expressing neurons in the nucleus accumbens
Authors: Winters Bradley D. , Krüger Juliane M. , Huang Xiaojie , Gallaher Zachary R. , Ishikawa Masago , Czaja Krzysztof , Krueger James M. , Huang Yanhua H. , Schlüter Oliver M. , Dong Yan
Published: September 2012

Endocannabinoid signaling critically regulates emotional and motivational states via activation of cannabinoid receptor 1 (CB1) in the brain. The nucleus accumbens (NAc) functions to gate emotional and motivational responses. Although expression of CB1 in the NAc is low, manipulation of CB1 signaling within the NAc triggers robust emotional/motivational alterations related to drug addiction and other psychiatric disorders, and these effects cannot be exclusively attributed to CB1 located at afferents to the NAc. Rather, CB1-expressing neurons in the NAc, although sparse, appear to be critical for emotional and motivational responses. However, the cellular properties of these neurons remain largely unknown. Here, we generated a knock-in mouse line in which CB1-expressing neurons expressed the fluorescent protein td-Tomato (tdT). Using these mice, we demonstrated that tdT-positive neurons within the NAc were exclusively fast-spiking interneurons (FSIs). These FSIs were electrically coupled with each other, and thus may help synchronize populations/ensembles of NAc neurons. CB1-expressing FSIs also form GABAergic synapses on adjacent medium spiny neurons (MSNs), providing feed-forward inhibition of NAc output. Furthermore, the membrane excitability of tdT-positive FSIs in the NAc was up-regulated after withdrawal from cocaine exposure, an effect that might increase FSI-to-MSN inhibition. Taken together with our previous findings that the membrane excitability of NAc MSNs is decreased during cocaine withdrawal, the present findings suggest that the basal functional output of the NAc is inhibited during cocaine withdrawal by multiple mechanisms. As such, CB1-expressing FSIs are targeted by cocaine exposure to influence the overall functional output of the NAc.
Rice phytochrome-interacting factor-like protein OsPIL1 functions as a key regulator of internode elongation and induces a morphological response to drought stress
Authors: Todaka Daisuke , Nakashima Kazuo , Maruyama Kyonoshin , Kidokoro Satoshi , Osakabe Yuriko , Ito Yusuke , Matsukura Satoko , Fujita Yasunari , Yoshiwara Kyouko , Ohme-Takagi Masaru , Kojima Mikiko , Sakakibara Hitoshi , Shinozaki Kazuo , Yamaguchi-Shinozaki Kazuko
Published: September 2012

The mechanisms for plant growth restriction during stress conditions remains unclear. Here, we demonstrate that a phytochrome-interacting factor-like protein, OsPIL1/OsPIL13, acts as a key regulator of reduced internode elongation in rice under drought conditions. The level of
OsPIL1
mRNA in rice seedlings grown under nonstressed conditions with light/dark cycles oscillated in a circadian manner with peaks in the middle of the light period. Under drought stress conditions,
OsPIL1
expression was inhibited during the light period. We found that
OsPIL1
was highly expressed in the node portions of the stem using promoter-glucuronidase analysis. Overexpression of
OsPIL1
in transgenic rice plants promoted internode elongation. In contrast, transgenic rice plants with a chimeric repressor resulted in short internode sections. Alteration of internode cell size was observed in
OsPIL1
transgenic plants, indicating that differences in cell size cause the change in internode length. Oligoarray analysis revealed
OsPIL1
downstream genes, which were enriched for cell wall-related genes responsible for cell elongation. These data suggest that
OsPIL1
functions as a key regulatory factor of reduced plant height via cell wall-related genes in response to drought stress. This regulatory system may be important for morphological stress adaptation in rice under drought conditions.
Role of pro-brain-derived neurotrophic factor (proBDNF) to mature BDNF conversion in activity-dependent competition at developing neuromuscular synapses
Authors: Je H. Shawn , Yang Feng , Ji Yuanyuan , Nagappan Guhan , Hempstead Barbara L. , Lu Bai
Published: September 2012

Formation of specific neuronal connections often involves competition between adjacent axons, leading to stabilization of the active terminal, while retraction of the less active ones. The underlying molecular mechanisms remain unknown. We show that activity-dependent conversion of pro–brain-derived neurotrophic factor (proBDNF) to mature (m)BDNF mediates synaptic competition. Stimulation of motoneurons triggers proteolytic conversion of proBDNF to mBDNF at nerve terminals. In
Xenopus
nerve–muscle cocultures, in which two motoneurons innervate one myocyte, proBDNF-p75
NTR
signaling promotes retraction of the less active terminal, whereas mBDNF–tyrosine-related kinase B (TrkB) p75NTR (p75 neurotrophin receptor) facilitates stabilization of the active one. Thus, proBDNF and mBDNF may serve as potential “punishment” and “reward” signals for inactive and active terminals, respectively, and activity-dependent conversion of proBDNF to mBDNF may regulate synapse elimination.
Reversible cycling between cysteine persulfide-ligated [2Fe-2S] and cysteine-ligated [4Fe-4S] clusters in the FNR regulatory protein
Authors: Zhang Bo , Crack Jason C. , Subramanian Sowmya , Green Jeffrey , Thomson Andrew J. , Le Brun Nick E. , Johnson Michael K.
Published: September 2012

Fumarate and nitrate reduction (FNR) regulatory proteins are O
2
-sensing bacterial transcription factors that control the switch between aerobic and anaerobic metabolism. Under anaerobic conditions [4Fe-4S]
2+
-FNR exists as a DNA-binding homodimer. In response to elevated oxygen levels, the [4Fe-4S]
2+
cluster undergoes a rapid conversion to a [2Fe-2S]
2+
cluster, resulting in a dimer-to-monomer transition and loss of site-specific DNA binding. In this work, resonance Raman and UV-visible absorption/CD spectroscopies and MS were used to characterize the interconversion between [4Fe-4S]
2+
and [2Fe-2S]
2+
clusters in
Escherichia coli
FNR. Selective
34
S labeling of the bridging sulfides in the [4Fe-4S]
2+
cluster-bound form of FNR facilitated identification of resonantly enhanced Cys
32
S-
34
S stretching modes in the resonance Raman spectrum of the O
2
-exposed [2Fe-2S]
2+
cluster-bound form of FNR. This result indicates O
2
-induced oxidation and retention of bridging sulfides in the form of [2Fe-2S]
2+
cluster-bound cysteine persulfides. MS also demonstrates that multiple cysteine persulfides are formed on O
2
exposure of [4Fe-4S]
2+
-FNR. The [4Fe-4S]
2+
cluster in FNR can also be regenerated from the cysteine persulfide-coordinated [2Fe-2S]
2+
cluster by anaerobic incubation with DTT and Fe
2+
ion in the absence of exogenous sulfide. Resonance Raman data indicate that this type of cluster conversion involving sulfide oxidation is not unique to FNR, because it also occurs in O
2
-exposed forms of O
2
-sensitive [4Fe-4S] clusters in radical S-adenosylmethionine enzymes. The results provide fresh insight into the molecular mechanism of O
2
sensing by FNR and iron-sulfur cluster conversion reactions in general, and suggest unique mechanisms for the assembly or repair of biological [4Fe-4S] clusters.
Degradation of the antiviral component ARGONAUTE1 by the autophagy pathway
Authors: Derrien Benoît , Baumberger Nicolas , Schepetilnikov Mikhail , Viotti Corrado , De Cillia Julia , Ziegler-Graff Véronique , Isono Erika , Schumacher Karin , Genschik Pascal
Published: September 2012

Posttranscriptional gene silencing (PTGS) mediated by siRNAs is an evolutionarily conserved antiviral defense mechanism in higher plants and invertebrates. In this mechanism, viral-derived siRNAs are incorporated into the RNA-induced silencing complex (RISC) to guide degradation of the corresponding viral RNAs. In
Arabidopsis
, a key component of RISC is ARGONAUTE1 (AGO1), which not only binds to siRNAs but also carries the RNA slicer activity. At present little is known about posttranslational mechanisms regulating AGO1 turnover. Here we report that the viral suppressor of RNA silencing protein P0 triggers AGO1 degradation by the autophagy pathway. Using a P0-inducible transgenic line, we observed that AGO1 degradation is blocked by inhibition of autophagy. The engineering of a functional AGO1 fluorescent reporter protein further indicated that AGO1 colocalizes with autophagy-related (ATG) protein 8a (ATG8a) positive bodies when degradation is impaired. Moreover, this pathway also degrades AGO1 in a nonviral context, especially when the production of miRNAs is impaired. Our results demonstrate that a selective process such as ubiquitylation can lead to the degradation of a key regulatory protein such as AGO1 by a degradation process generally believed to be unspecific. We anticipate that this mechanism will not only lead to degradation of AGO1 but also of its associated proteins and eventually small RNAs.
Frequency-invariant temporal ordering of interneuronal discharges during hippocampal oscillations in awake mice
Authors: Varga Csaba , Golshani Peyman , Soltesz Ivan
Published: September 2012

Endogenous brain rhythms occurring at various frequencies and associated with distinct behavioral states provide multiscale temporal windows that enable cells to time their spiking activity with high precision, which is thought to be important for the coding of information in neuronal circuits. However, although the selective timing of GABAergic inputs to specific spatial domains of principal cells are known to play key roles in network oscillations, the in vivo firing patterns of distinct hippocampal interneurons in awake animals are not known. Here we used a combination of juxtacellular labeling techniques with recordings from anesthesia-free, head-fixed mice running or resting on a spherical treadmill to study the oscillation-dependent discharges by two major interneuronal subtypes, the perisomatically projecting parvalbumin-positive basket cells (PVBCs) and distal dendritically projecting oriens lacunosum moleculare (OLM) cells. Recordings of the spiking activity of post hoc-identified CA1 interneurons during theta (5–10 Hz), gamma (25–90Hz), epsilon (“high-gamma”; 90–130 Hz), and ripple (130–200 Hz) oscillations revealed both cell type- and behavioral state-dependent entrainments of PVBC and OLM cell discharges in awake mice. Our results in awake mice differed in several respects from previous data on interneuronal discharge patterns in anesthetized animals. In addition, our results demonstrate a form of frequency-invariant, cell type-specific temporal ordering of inhibitory inputs in which PVBC-derived perisomatic inhibition is followed by OLM cell-generated distal dendritic inhibition during each of the network oscillation bands studied, spanning more than an order of magnitude in frequencies.
Positive bias is a defining characteristic of aging to the same extent as declining performance
Authors: Simón Teresa , Suengas Aurora G. , Ruiz‐Gallego‐Largo Trinidad , Bandrés Javier
Published: September 2012

The aim of this study was to analyze whether one of the supposed gains of aging—positive bias—discriminates between young and older participants to the same extent as some of the losses in cognitive performance—recall and source monitoring—that come with age. Two age groups (N = 120)—young (M = 22.08, SD = 3.30) and older (M = 72.78, SD = 6.57)—carried out three tasks with varying levels of difficulty that included recall, recognition, and source monitoring using pictures, faces, and personal descriptors exchanged in a conversation as stimuli. The results of the discriminant analysis performed on 20 dependent variables indicated that six of them were key in discriminating between young and older participants. Younger participants outperformed older participants in recalling pictures, and in recognizing the descriptors exchanged in a conversation, as well as in monitoring their source. Just as important in discriminating between the two groups were the ability to recognize previously seen pictures, the likability rating they produced, and the recognition of faces with positive expressions—all superior in older participants. Thus, variables related to a positive bias—likability ratings and recognition of positive expressions—characterize the differences as a function of age as well as variables related to cognitive performance, such as recall and source monitoring. In addition, the likability ratings evoked by both pictures and faces were also significantly higher in the older participants with better cognitive performance than in those who performed poorly. This effect was not present in younger participants. The results are interpreted within the framework of socioemotional selectivity theory as evidence for a positive bias in old age. The connection between a positive bias and the maintenance of cognitive performance is also discussed.
Evidence of Female Heterogamety in Largemouth Bass, Based on Sex Ratio of Gynogenetic Progeny
Authors: Glennon Robert P , Gomelsky Boris , Schneider Kyle J , Kelly Anita M , Haukenes Alf
Published: September 2012

Meiotic gynogenetic progeny in largemouth bass Micropterus salmoides have been obtained by inseminating largemouth bass eggs with UV-irradiated sperm from white bass Morone chrysops or striped bass Morone saxatilis and suppressing the second meiotic division by hydrostatic pressure. The sex composition of gynogenetic progeny was determined by dissection or ultrasound investigation of 1-year-old fish. Among the 21 fish analyzed, 7 fish (33.3%) were male and 14 fish (66.7%) were female. The presence of males in meiotic gynogenetic progeny suggests the existence of female heterogamety (WZ females, ZZ males) in largemouth bass.
On avoiding framing effects in experienced decision makers
Authors: Garcia-Retamero Rocio , Dhami Mandeep K.
Published: September 2012

The present study aimed to (a) demonstrate the effect of positive–negative framing on experienced criminal justice decision makers, (b) examine the debiasing effect of visually structured risk messages, and (c) investigate whether risk perceptions mediate the debiasing effect of visual aids on decision making. In two phases, 60 senior police officers estimated the accuracy of a counterterrorism technique in identifying whether a known terror suspect poses an imminent danger and decided whether they would recommend the technique to policy makers. Officers also rated their confidence in this recommendation. When information about the effectiveness of the counterterrorism technique was presented in a numerical format, officers' perceptions of accuracy and recommendation decisions were susceptible to the framing effect: The technique was perceived to be more accurate and was more likely to be recommended when its effectiveness was presented in a positive than in a negative frame. However, when the information was represented visually using icon arrays, there were no such framing effects. Finally, perceptions of accuracy mediated the debiasing effect of visual aids on recommendation decisions. We offer potential explanations for the debiasing effect of visual aids and implications for communicating risk to experienced, professional decision makers.
Cell confinement controls centrosome positioning and lumen initiation during epithelial morphogenesis
Authors: Rodríguez-Fraticelli Alejo E. , Auzan Muriel , Alonso Miguel A. , Bornens Michel , Martín-Belmonte Fernando
Published: September 2012

Epithelial organ morphogenesis involves sequential acquisition of apicobasal polarity by epithelial cells and development of a functional lumen. In vivo, cells perceive signals from components of the extracellular matrix (ECM), such as laminin and collagens, as well as sense physical conditions, such as matrix stiffness and cell confinement. Alteration of the mechanical properties of the ECM has been shown to promote cell migration and invasion in cancer cells, but the effects on epithelial morphogenesis have not been characterized. We analyzed the effects of cell confinement on lumen morphogenesis using a novel, micropatterned, three-dimensional (3D) Madin-Darby canine kidney cell culture method. We show that cell confinement, by controlling cell spreading, limits peripheral actin contractility and promotes centrosome positioning and lumen initiation after the first cell division. In addition, peripheral actin contractility is mediated by master kinase Par-4/LKB1 via the RhoA–Rho kinase–myosin II pathway, and inhibition of this pathway restores lumen initiation in minimally confined cells. We conclude that cell confinement controls nuclear–centrosomal orientation and lumen initiation during 3D epithelial morphogenesis.
Crumbs limits oxidase-dependent signaling to maintain epithelial integrity and prevent photoreceptor cell death
Authors: Chartier François J.-M. , Hardy Émilie J.-L. , Laprise Patrick
Published: September 2012

Drosophila melanogaster Crumbs (Crb) and its mammalian orthologues (CRB1–3) share evolutionarily conserved but poorly defined roles in regulating epithelial polarity and, in photoreceptor cells, morphogenesis and stability. Elucidating the molecular mechanisms of Crb function is vital, as mutations in the human CRB1 gene cause retinal dystrophies. Here, we report that Crb restricts Rac1–NADPH oxidase-dependent superoxide production in epithelia and photoreceptor cells. Reduction of superoxide levels rescued epithelial defects in crb mutant embryos, demonstrating that limitation of superoxide production is a crucial function of Crb and that NADPH oxidase and superoxide contribute to the molecular network regulating epithelial tissue organization. We further show that reduction of Rac1 or NADPH oxidase activity or quenching of reactive oxygen species prevented degeneration of Crb-deficient retinas. Thus, Crb fulfills a protective role during light exposure by limiting oxidative damage resulting from Rac1–NADPH oxidase complex activity. Collectively, our results elucidate an important mechanism by which Crb functions in epithelial organization and the prevention of retinal degeneration.
Mitotic lamin disassembly is triggered by lipid-mediated signaling
Authors: Mall Moritz , Walter Thomas , Gorjánácz Mátyás , Davidson Iain F. , Nga Ly-Hartig Thi Bach , Ellenberg Jan , Mattaj Iain W.
Published: September 2012

Disassembly of the nuclear lamina is a key step during open mitosis in higher eukaryotes. The activity of several kinases, including CDK1 (cyclin-dependent kinase 1) and protein kinase C (PKC), has been shown to trigger mitotic lamin disassembly, yet their precise contributions are unclear. In this study, we develop a quantitative imaging assay to study mitotic lamin B1 disassembly in living cells. We find that CDK1 and PKC act in concert to mediate phosphorylation-dependent lamin B1 disassembly during mitosis. Using ribonucleic acid interference (RNAi), we showed that diacylglycerol (DAG)-dependent PKCs triggered rate-limiting steps of lamin disassembly. RNAi-mediated depletion or chemical inhibition of lipins, enzymes that produce DAG, delayed lamin disassembly to a similar extent as does PKC inhibition/depletion. Furthermore, the delay of lamin B1 disassembly after lipin depletion could be rescued by the addition of DAG. These findings suggest that lipins activate a PKC-dependent pathway during mitotic lamin disassembly and provide evidence for a lipid-mediated mitotic signaling event.