bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvements to the immunoassay for detection of Rathayibacter toxicus in hay
Authors: Masters A. M. , Samarasinghe B. , Kalkhoven M. J. , den Hollander G. L. , Palmer D. G.
Published: July 2011

An improved protocol for the previously described enzyme-linked immunosorbent assay for Rathayibacter toxicus in hay is described. The improvements were driven mainly by the export hay industry requirement of same-day turnaround for testing of hay extracts. The preparation of hay extracts was shortened by 8 h. The time for adding samples to the enzyme-linked immunosorbent assay plates was shortened by the use of sample tubes with penetrable stoppers combined with specially designed racks. The monoclonal antibody used in the original protocol was purified and conjugated to horseradish peroxidase. This eliminated the need for a secondary step with an anti-mouse horseradish peroxidase conjugate and thereby shortened the assay by over 1 h. Results with the improved assay protocol showed a very high correlation with results obtained with the original protocol (r = 0.98). The assay is still sensitive enough to detect antigen equivalent to less than 1 average gall per kg of hay. These cost-effective changes have streamlined the testing of large numbers of samples for the presence of R. toxicus, in support of the hay export industry.
Optical sensing estimation of leaf nitrogen concentration in maize across a range of water-stress levels
Authors: Wang Tong-Chao , Ma B. L. , Xiong You-Cai , Saleem M. Farrukh , Li Feng-Min
Published: July 2011

Optical sensing techniques offer an instant estimation of leaf nitrogen (N) concentration during the crop growing season. Differences in plant-moisture status, however, can obscure the detection of differences in N levels. This study presents a vegetation index that robustly measures differences in foliar N levels across a range of plant moisture levels. A controlled glasshouse study with maize (Zea mays L.) subjected to both water and N regimes was conducted in Ottawa, Canada. The purpose of the study was to identify spectral waveband(s), or indices derived from different wavebands, such as the normalised difference vegetation index (NDVI), that are capable of detecting variations in leaf N concentration in response to different water and N stresses. The experimental design includes three N rates and three water regimes in a factorial arrangement. Leaf chlorophyll content and spectral reflectance (400–1075 nm) were measured on the uppermost fully expanded leaves at the V6, V9 and V12 growth stages (6th, 9th and 12th leaves fully expanded). N concentrations of the same leaves were determined using destructive sampling. A quantitative relationship between leaf N concentration and the normalised chlorophyll index (normalised to well fertilised and well irrigated plants) was established. Leaf N concentration was also a linear function (R2 = 0.9, P < 0.01) of reflectance index (NDVI550, 760) at the V9 and V12 growth stages. Chlorophyll index increased with N nutrition, but decreased with water stress. Leaf reflectance at wavebands of 550 ± 5 nm and 760 ± 5 nm were able to separate water- and N-stressed plants from normal growing plants with sufficient water and N supply. Our results suggest that NDVI550, 760 and normalised chlorophyll index hold promise for the assessment of leaf N concentration at the leaf level of both normal and water-stressed maize plants.
Structural equation models and the quantification of behavior
Authors: Bollen Kenneth A. , Noble Mark D.
Published: July 2011

Quantifying behavior often involves using variables that contain measurement errors and formulating multiequations to capture the relationship among a set of variables. Structural equation models (SEMs) refer to modeling techniques popular in the social and behavioral sciences that are equipped to handle multiequation models, multiple measures of concepts, and measurement error. This work provides an overview of latent variable SEMs. We present the equations for SEMs and the steps in modeling, and we provide three illustrations of SEMs. We suggest that the general nature of the model is capable of handling a variety of problems in the quantification of behavior, where the researcher has sufficient knowledge to formulate hypotheses.
In vivo discovery of a peptide that prevents CUG–RNA hairpin formation and reverses RNA toxicity in myotonic dystrophy models
Authors: García-López Amparo , Llamusí Beatriz , Orzáez Mar , Pérez-Payá Enrique , Artero Ruben D.
Published: July 2011

Myotonic dystrophy type 1 (DM1) is caused by the expansion of noncoding CTG repeats in the
dystrophia myotonica-protein kinase
gene. Mutant transcripts form CUG hairpins that sequester RNA-binding factors into nuclear foci, including Muscleblind-like-1 protein (MBNL1), which regulate alternative splicing and gene expression. To identify molecules that target toxic CUG transcripts in vivo, we performed a positional scanning combinatorial peptide library screen using a
Drosophila
model of DM1. The screen identified a D-amino acid hexapeptide (ABP1) that reduced CUG foci formation and suppressed CUG-induced lethality and muscle degeneration when administered orally. Transgenic expression of natural, L-amino acid ABP1 analogues reduced CUG-induced toxicity in fly eyes and muscles. Furthermore, ABP1 reversed muscle histopathology and splicing misregulation of MBNL1 targets in DM1 model mice. In vitro, ABP1 bound to CUG hairpins and induced a switch to a single-stranded conformation. Our findings demonstrate that ABP1 shows antimyotonic dystrophy activity by targeting the core of CUG toxicity.
Smad6 promotes neuronal differentiation in the intermediate zone of the dorsal neural tube by inhibition of the Wnt/β-catenin pathway
Authors: Xie Zhihui , Chen Yongfeng , Li Zhenfei , Bai Ge , Zhu Yue , Yan Rui , Tan Fangzhi , Chen Ye-Guang , Guillemot Francois , Li Lin , Jing Naihe
Published: July 2011

Proliferation of the neural/neuronal progenitor cells (NPCs) at the ventricular zone of the dorsal spinal cord requires the stimuli of Wnt and bone morphogenic protein (BMP). However, how these two signaling pathways are regulated to initiate differentiation in the NPCs as they enter the intermediate zone is not known. Here, we show that Smad6, a negative regulator of BMP signaling, is expressed in the intermediate zone of the chick dorsal spinal cord. Knockdown experiments show that Smad6 is required for promoting NPCs to exit the cell cycle and differentiate into neurons. Although we find that Smad6 inhibits BMP signaling, as expected, we also find that Smad6 unexpectedly inhibits the Wnt/β-catenin pathway. The inhibition of the Wnt/β-catenin pathway by Smad6 is independent of its effect on the BMP pathway. Rather, Smad6 through its N-terminal domain and link region enhances the interaction of C-terminal binding protein with the β-catenin/T cell factor (TCF) complex and the TCF-binding element to inhibit β-catenin–mediated transcriptional activation. Our study provides evidence that transition of NPCs from a proliferative state to a differentiating state is controlled by the dual inhibitory role of Smad6 to both BMP and Wnt signaling at the level of transcription.
Predicting human blood viscosity in silico
Authors: Fedosov Dmitry A. , Pan Wenxiao , Caswell Bruce , Gompper Gerhard , Karniadakis George E.
Published: July 2011

The viscosity of blood has long been used as an indicator in the understanding and treatment of disease, and the advent of modern viscometers allows its measurement with ever-improving clinical convenience. However, these advances have not been matched by theoretical developments that can yield a quantitative understanding of blood’s microrheology and its possible connection to relevant biomolecules (e.g., fibrinogen). Using coarse-grained molecular dynamics and two different red blood cell models, we accurately predict the dependence of blood viscosity on shear rate and hematocrit. We explicitly represent cell–cell interactions and identify the types and sizes of reversible rouleaux structures that yield a tremendous increase of blood viscosity at low shear rates. We also present the first quantitative estimates of the magnitude of adhesive forces between red cells. In addition, our simulations support the hypothesis, previously deduced from experiments, of yield stress as an indicator of cell aggregation. This non-Newtonian behavior is analyzed and related to the suspension’s microstructure, deformation, and dynamics of single red blood cells. The most complex cell dynamics occurs in the intermediate shear rate regime, where individual cells experience severe deformation and transient folded conformations. The generality of these cell models together with single-cell measurements points to the future prediction of blood-viscosity anomalies and the corresponding microstructures associated with various diseases (e.g., malaria, AIDS, and diabetes mellitus). The models can easily be adapted to tune the properties of a much wider class of complex fluids including capsule and vesicle suspensions.
Transcriptome transfer provides a model for understanding the phenotype of cardiomyocytes
Authors: Kim Tae Kyung , Sul Jai-Yoon , Peternko Nataliya B. , Lee Jae Hee , Lee Miler , Patel Vickas V. , Kim Junhyong , Eberwine James H.
Published: July 2011

We show that the transfer of the adult ventricular myocyte (AVM) transcriptome into either a fibroblast or an astrocyte converts the host cell into a cardiomyocyte. Transcriptome-effected cardiomyocytes (tCardiomyocytes) display morphologies, immunocytochemical properties, and expression profiles of postnatal cardiomyocytes. Cell morphology analysis shows that tCardiomyoctes are elongated and have a similar length-to-width ratio as AVMs. These global phenotypic changes occur in a time-dependent manner and confer electroexcitability to the tCardiomyocytes. tCardiomyocyte generation does not require continuous overexpression of specific transcription factors; for example, the expression level of transcription factor Mef2c is higher in tCardiomyocytes than in fibroblasts, but similar in tCardiomyocytes and AVMs. These data highlight the dominant role of the gene expression profile in developing and maintaining cellular phenotype. The transcriptome-induced phenotype remodeling–generated tCardiomyocyte has significant implications for understanding and modulating cardiac disease development.
The microRNA-21−PDCD4 axis prevents type 1 diabetes by blocking pancreatic β cell death
Authors: Ruan Qingguo , Wang Ting , Kameswaran Vasumathi , Wei Qin , Johnson Derek S. , Matschinsky Franz , Shi Weiyun , Chen Youhai H.
Published: July 2011

Death of pancreatic β cells is a pathological hallmark of type 1 diabetes (T1D). However, the molecular mechanisms of β cell death and its regulation are poorly understood. Here we describe a unique regulatory pathway of β cell death that comprises microRNA-21, its target tumor suppressor PDCD4, and its upstream transcriptional activator nuclear factor-κB (NF-κB). In pancreatic β cells, c-Rel and p65 of the NF-κB family activated the
mir21
gene promoter and increased miR-21 RNA levels; miR-21 in turn decreased the level of PDCD4, which is able to induce cell death through the Bax family of apoptotic proteins. Consequently, PDCD4 deficiency in pancreatic β cells renders them resistant to death, and PDCD4 deficiency in NOD or C57BL/6 mice conferred resistance to spontaneous diabetes and diabetes induced by autoimmune T cells or the β cell toxin streptozotocin (STZ). Thus, the NF-κB−microRNA-21−PDCD4 axis plays a crucial role in T1D and represents a unique therapeutic target for treating the disease.
Single-molecule investigations of the stringent response machinery in living bacterial cells
Authors: English Brian P. , Hauryliuk Vasili , Sanamrad Arash , Tankov Stoyan , Dekker Nynke H. , Elf Johan
Published: July 2011

The RelA-mediated stringent response is at the heart of bacterial adaptation to starvation and stress, playing a major role in the bacterial cell cycle and virulence. RelA integrates several environmental cues and synthesizes the alarmone ppGpp, which globally reprograms transcription, translation, and replication. We have developed and implemented novel single-molecule tracking methodology to characterize the intracellular catalytic cycle of RelA. Our single-molecule experiments show that RelA is on the ribosome under nonstarved conditions and that the individual enzyme molecule stays off the ribosome for an extended period of time after activation. This suggests that the catalytically active part of the RelA cycle is performed off, rather than on, the ribosome, and that rebinding to the ribosome is not necessary to trigger each ppGpp synthesis event. Furthermore, we find fast activation of RelA in response to heat stress followed by RelA rapidly being reset to its inactive state, which makes the system sensitive to new environmental cues and hints at an underlying excitable response mechanism.
The p53 inhibitors MDM2/MDMX complex is required for control of p53 activity in vivo
Authors: Huang Lei , Yan Zheng , Liao Xiaodong , Li Yuan , Yang Jie , Wang Zhu-Gang , Zuo Yong , Kawai Hidehiko , Shadfan Miriam , Ganapathy Suthakar , Yuan Zhi-Min
Published: July 2011

There are currently two distinct models proposed to explain why both MDM2 and MDMX are required in p53 control, with a key difference centered on whether these two p53 inhibitors work together or independently. To test these two competing models, we generated knockin mice expressing a point mutation MDMX mutant (C462A) that is defective in MDM2 binding. This approach allowed a targeted disassociation of the MDM2/MDMX heterocomplex without affecting the ability of MDMX to bind to p53, and while leaving the MDM2 protein itself completely untouched. Significantly,
Mdmx
C462A/C462A
homozygous mice died at approximately day 9.5 of embryonic development, as the result of a combination of apoptosis and decreased cell proliferation, as shown by TUNEL and BrdU incorporation assays, respectively. Interestingly, even though the MDMX mutant protein abundance was found slightly elevated in the
Mdmx
C462A/C462A
homozygous embryos, both the abundance and activity of p53 were markedly increased. A p53-dependent death was demonstrated by the finding that concomitant deletion of p53 completely rescued the embryonic lethality in
Mdmx
C462A/C462A
homozygous mice. Our data demonstrate that MDM2 and MDMX function as an integral complex in p53 control, providing insights into the nonredundant nature of the function of MDM2 and MDMX.
E-cadherin mediates contact inhibition of proliferation through Hippo signaling-pathway components
Authors: Kim Nam-Gyun , Koh Eunjin , Chen Xiao , Gumbiner Barry M.
Published: July 2011

Contact inhibition of cell growth is essential for embryonic development and maintenance of tissue architecture in adult organisms, and the growth of tumors is characterized by a loss of contact inhibition of proliferation. The recently identified Hippo signaling pathway has been implicated in contact inhibition of proliferation as well as organ size control. The modulation of the phosphorylation and nuclear localization of Yes-associated protein (YAP) by the highly conserved kinase cascade of the Hippo signaling pathway has been intensively studied. However, cell-surface receptors regulating the Hippo signaling pathway in mammals are not well understood. In this study, we show that Hippo signaling pathway components are required for E-cadherin–dependent contact inhibition of proliferation. Knockdown of the Hippo signaling components or overexpression of YAP inhibits the decrease in cell proliferation caused by E-cadherin homophilic binding at the cell surface, independent of other cell–cell interactions. We also demonstrate that the E-cadherin/catenin complex functions as an upstream regulator of the Hippo signaling pathway in mammalian cells. Expression of E-cadherin in MDA-MB-231 cells restores the density-dependent regulation of YAP nuclear exclusion. Knockdown of β-catenin in densely cultured MCF10A cells, which mainly depletes E-cadherin–bound β-catenin, induces a decrease in the phosphorylation of S127 residue of YAP and its nuclear accumulation. Moreover, E-cadherin homophilic binding independent of other cell interactions is sufficient to control the subcellular localization of YAP. Therefore, Our results indicate that, in addition to its role in cell–cell adhesion, E-cadherin-mediated cell–cell contact directly regulates the Hippo signaling pathway to control cell proliferation.
Ezrin-mediated apical integrity is required for intestinal homeostasis
Authors: Casaletto Jessica B. , Saotome Ichiko , Curto Marcello , McClatchey Andrea I.
Published: July 2011

Individual cell types are defined by architecturally and functionally specialized cortical domains. The Ezrin, Radixin, and Moesin (ERM) proteins play a major role in organizing cortical domains by assembling membrane protein complexes and linking them to the cortical actin cytoskeleton. Many studies have focused on the individual roles of the ERM proteins in stabilizing the membrane–cytoskeleton interface, controlling the distribution and function of apical membrane complexes, regulating the small GTPase Rho, or establishing cell–cell junctions. We previously found that deletion of the mouse
Ezrin
gene yields severe defects in apical integrity throughout the developing intestinal epithelium, resulting in incomplete villus morphogenesis and neonatal death. However, the molecular function of Ezrin in building the apical surface of the intestinal epithelium was not clear. By deleting
Ezrin
in the adult mouse intestinal epithelium, we provide evidence that Ezrin performs multiple molecular functions that collaborate to build the functional apical surface of the intestinal epithelium in vivo. The loss of Ezrin-mediated apical integrity in the adult intestine yields severe morphological consequences during intestinal homeostasis, including defects in cell geometry, extrusion, junctional remodeling, and spindle orientation. Surprisingly, deletion of Ezrin either before or after villus morphogenesis yields villus fusion, revealing a previously unrecognized step in intestinal homeostasis. Our studies indicate that the function of Ezrin in building and maintaining the apical domain is essential not only for intestinal morphogenesis but also for homeostasis in the mature intestine.
Cysteine scanning and modification reveal major differences between BK channels and Kv channels in the inner pore region
Authors: Zhou Yu , Xia Xiao-Ming , Lingle Christopher J.
Published: July 2011

BK channels are regulated by two distinct physiological signals, transmembrane potential and intracellular Ca
2+
, each acting through independent modular sensor domains. However, despite a presumably central role in the coupling of sensor activation to channel gating, the pore-lining S6 transmembrane segment has not been systematically studied. Here, cysteine substitution and modification studies of the BK S6 point to substantial differences between BK and Kv channels in the structure and function of the S6-lined inner pore. Gating shifts caused by introduction of cysteines define a pattern and direction of free energy changes in BK S6 distinct from
Shaker
. Modification of BK S6 residues identifies pore-facing residues that occur at different linear positions along aligned BK and Kv S6 segments. Periodicity analysis suggests that one factor contributing to these differences may be a disruption of the BK S6 α-helix from the unique diglycine motif at the position of the Kv hinge glycine. State-dependent MTS accessibility reveals that, even in closed states, modification can occur. Furthermore, the inner pore of BK channels is much larger than that of K
+
channels with solved crystal structures. The results suggest caution in the use of Kv channel structures as templates for BK homology models, at least in the pore-gate domain.
Endocannabinoid signal in the gut controls dietary fat intake
Authors: DiPatrizio Nicholas V. , Astarita Giuseppe , Schwartz Gary , Li Xiaosong , Piomelli Daniele
Published: July 2011

Oral sensory signals drive dietary fat intake, but the neural mechanisms underlying this process are largely unknown. The endocannabinoid system has gained recent attention for its central and peripheral roles in regulating food intake, energy balance, and reward. Here, we used a sham-feeding paradigm, which isolates orosensory from postingestive influences of foods, to examine whether endocannabinoid signaling participates in the positive feedback control of fat intake. Sham feeding a lipid-based meal stimulated endocannabinoid mobilization in the rat proximal small intestine by altering enzymatic activities that control endocannabinoid metabolism. This effect was abolished by surgical transection of the vagus nerve and was not observed in other peripheral organs or in brain regions that control feeding. Sham feeding of a nutritionally complete liquid meal produced a similar response to that of fat, whereas protein or carbohydrate alone had no such effect. Local infusion of the CB
1
-cannabinoid receptor antagonist, rimonabant, into the duodenum markedly reduced fat sham feeding. Similarly to rimonabant, systemic administration of the peripherally restricted CB
1
-receptor antagonist, URB 447, attenuated sham feeding of lipid. Collectively, the results suggest that the endocannabinoid system in the gut exerts a powerful regulatory control over fat intake and might be a target for antiobesity drugs.
Evolution of the V, D, and J gene segments used in the primate γδ T-cell receptor reveals a dichotomy of conservation and diversity
Authors: Kazen Allison R. , Adams Erin J.
Published: July 2011

γδ T cells are an immunological enigma in that both their function in the immune response and the molecular mechanisms behind their activation remain unclear. These cells predominate in the epithelia and can be rapidly activated to provide an array of responses. However, no homologous γδ T-cell populations have been identified between humans and mice, and our understanding of what these cells recognize as ligands is limited. Here we take an alternative approach to understanding human γδ T-cell ligand recognition by studying the evolutionary forces that have shaped the V, D, and J gene segments that are used during somatic rearrangement to generate the γδ T-cell receptor. We find that distinctly different forces have shaped the γ and δ loci. The Vδ and Jδ genes are highly conserved, some even through to mouse. In contrast, the γ-locus is split: the Vγ9, Vγ10, and Vγ11 genes represent the conserved region of the Vγ gene locus whereas the remaining Vγ genes have been evolving rapidly, such that orthology throughout the primate lineage is unclear. We have also analyzed the coding versus silent substitutions between species within the V and J gene segments and find a preference for coding substitutions in the complementarity determining region loops of many of the V gene segments. Our results provide a different perspective on investigating human γδ T-cell recognition, demonstrating that diversification at particular γδ gene loci has been favored during primate evolution, suggesting adaptation of particular V domains to a changing ligand environment.
Mechanism of activation gating in the full-length KcsA K
+
channel
Authors: Uysal Serdar , Cuello Luis G. , Cortes D. Marien , Koide Shohei , Kossiakoff Anthony A. , Perozo Eduardo
Published: July 2011

Using a constitutively active channel mutant, we solved the structure of full-length KcsA in the open conformation at 3.9 Å. The structure reveals that the activation gate expands about 20 Å, exerting a strain on the bulge helices in the C-terminal domain and generating side windows large enough to accommodate hydrated K
+
ions. Functional and spectroscopic analysis of the gating transition provides direct insight into the allosteric coupling between the activation gate and the selectivity filter. We show that the movement of the inner gate helix is transmitted to the C-terminus as a straightforward expansion, leading to an upward movement and the insertion of the top third of the bulge helix into the membrane. We suggest that by limiting the extent to which the inner gate can open, the cytoplasmic domain also modulates the level of inactivation occurring at the selectivity filter.
Targeting the regulation of androgen receptor signaling by the heat shock protein 90 cochaperone FKBP52 in prostate cancer cells
Authors: De Leon Johanny Tonos , Iwai Aki , Feau Clementine , Garcia Yenni , Balsiger Heather A. , Storer Cheryl L. , Suro Raquel M. , Garza Kristine M. , Lee Sunmin , Sang Kim Yeong , Chen Yu , Ning Yang-Min , Riggs Daniel L. , Fletterick Robert J. , Guy R. Kiplin , Trepel Jane B. , Neckers Leonard M. , Cox Marc B.
Published: July 2011

Drugs that target novel surfaces on the androgen receptor (AR) and/or novel AR regulatory mechanisms are promising alternatives for the treatment of castrate-resistant prostate cancer. The 52 kDa FK506 binding protein (FKBP52) is an important positive regulator of AR in cellular and whole animal models and represents an attractive target for the treatment of prostate cancer. We used a modified receptor-mediated reporter assay in yeast to screen a diversified natural compound library for inhibitors of FKBP52-enhanced AR function. The lead compound, termed MJC13, inhibits AR function by preventing hormone-dependent dissociation of the Hsp90-FKBP52-AR complex, which results in less hormone-bound receptor in the nucleus. Assays in early and late stage human prostate cancer cells demonstrated that MJC13 inhibits AR-dependent gene expression and androgen-stimulated prostate cancer cell proliferation.
A key mechanism underlying sensory experience-dependent maturation of neocortical GABAergic circuits in vivo
Authors: Jiao Yuanyuan , Zhang Zhi , Zhang Chunzhao , Wang Xinjun , Sakata Kazuko , Lu Bai , Sun Qian-Quan
Published: July 2011

Mechanisms underlying experience-dependent refinement of cortical connections, especially GABAergic inhibitory circuits, are unknown. By using a line of mutant mice that lack activity-dependent BDNF expression (
bdnf
-KIV), we show that experience regulation of cortical GABAergic network is mediated by activity-driven BDNF expression. Levels of endogenous BDNF protein in the barrel cortex are strongly regulated by sensory inputs from whiskers. There is a severe alteration of excitation and inhibition balance in the barrel cortex of
bdnf
-KIV mice as a result of reduced inhibitory but not excitatory conductance. Within the inhibitory circuits, the mutant barrel cortex exhibits significantly reduced levels of GABA release only from the parvalbumin-expressing fast-spiking (FS) interneurons, but not other interneuron subtypes. Postnatal deprivation of sensory inputs markedly decreased perisomatic inhibition selectively from FS cells in wild-type but not
bdnf
-KIV mice. These results suggest that postnatal experience, through activity-driven BDNF expression, controls cortical development by regulating FS cell-mediated perisomatic inhibition in vivo.
MicroRNA regulation of the paired-box transcription factor Pax3 confers robustness to developmental timing of myogenesis
Authors: Goljanek-Whysall Katarzyna , Sweetman Dylan , Abu-Elmagd Muhammad , Chapnik Elik , Dalmay Tamas , Hornstein Eran , Münsterberg Andrea
Published: July 2011

Commitment of progenitors in the dermomyotome to myoblast fate is the first step in establishing the body musculature. Pax3 is a crucial transcription factor, important for skeletal muscle development and expressed in myogenic progenitors in the dermomyotome of developing somites and in migratory muscle progenitors that populate the limb buds. Down-regulation of Pax3 is essential to ignite the myogenic program, including up-regulation of myogenic regulators, Myf-5 and MyoD. MicroRNAs (miRNAs) confer robustness to developmental timing by posttranscriptional repression of genetic programs that are related to previous developmental stages or to alternative cell fates. Here we demonstrate that the muscle-specific miRNAs miR-1 and miR-206 directly target Pax3. Antagomir-mediated inhibition of miR-1/miR-206 led to delayed myogenic differentiation in developing somites, as shown by transient loss of myogenin expression. This correlated with increased Pax3 and was phenocopied using Pax3-specific target protectors. Loss of myogenin after antagomir injection was rescued by Pax3 knockdown using a splice morpholino, suggesting that miR-1/miR-206 control somite myogenesis primarily through interactions with Pax3. Our studies reveal an important role for miR-1/miR-206 in providing precision to the timing of somite myogenesis. We propose that posttranscriptional control of Pax3 downstream of miR-1/miR-206 is required to stabilize myoblast commitment and subsequent differentiation. Given that mutually exclusive expression of miRNAs and their targets is a prevailing theme in development, our findings suggest that miRNA may provide a general mechanism for the unequivocal commitment underlying stem cell differentiation.
Structure and function of the interacting domains of Spire and Fmn-family formins
Authors: Vizcarra Christina L. , Kreutz Barry , Rodal Avital A. , Toms Angela V. , Lu Jun , Zheng Wei , Quinlan Margot E. , Eck Michael J.
Published: July 2011

Evidence for cooperation between actin nucleators is growing. The WH2-containing nucleator Spire and the formin Cappuccino interact directly, and both are essential for assembly of an actin mesh during
Drosophila
oogenesis. Their interaction requires the kinase noncatalytic C-lobe domain (KIND) domain of Spire and the C-terminal tail of the formin. Here we describe the crystal structure of the KIND domain of human Spir1 alone and in complex with the tail of Fmn2, a mammalian ortholog of Cappuccino. The KIND domain is structurally similar to the C-lobe of protein kinases. The Fmn2 tail is coordinated in an acidic cleft at the base of the domain that appears to have evolved via deletion of a helix from the canonical kinase fold. Our functional analysis of Cappuccino reveals an unexpected requirement for its tail in actin assembly. In addition, we find that the KIND/tail interaction blocks nucleation by Cappuccino and promotes its displacement from filament barbed ends providing insight into possible modes of cooperation between Spire and Cappuccino.
Speciation with gene flow on Lord Howe Island
Authors: Papadopulos Alexander S. T. , Baker William J. , Crayn Darren , Butlin Roger K. , Kynast Ralf G. , Hutton Ian , Savolainen Vincent
Published: July 2011

Understanding the processes underlying the origin of species is a fundamental goal of biology. It is widely accepted that speciation requires an interruption of gene flow between populations: ongoing gene exchange is considered a major hindrance to population divergence and, ultimately, to the evolution of new species. Where a geographic barrier to reproductive isolation is lacking, a biological mechanism for speciation is required to counterbalance the homogenizing effect of gene flow. Speciation with initially strong gene flow is thought to be extremely rare, and few convincing empirical examples have been published. However, using phylogenetic, karyological, and ecological data for the flora of a minute oceanic island (Lord Howe Island, LHI), we demonstrate that speciation with gene flow may, in fact, be frequent in some instances and could account for one in five of the endemic plant species of LHI. We present 11 potential instances of species divergence with gene flow, including an in situ radiation of five species ofCoprosma(Rubiaceae, the coffee family). These results, together with the speciation ofHoweapalms on LHI, challenge current views on the origin of species diversity.
Dissection of the
Burkholderia
intracellular life cycle using a photothermal nanoblade
Authors: French Christopher T. , Toesca Isabelle J. , Wu Ting-Hsiang , Teslaa Tara , Beaty Shannon M. , Wong Wayne , Liu Minghsun , Schröder Imke , Chiou Pei-Yu , Teitell Michael A. , Miller Jeff F.
Published: July 2011

Burkholderia pseudomallei
and
Burkholderia thailandensis
are related pathogens that invade a variety of cell types, replicate in the cytoplasm, and spread to nearby cells. We have investigated temporal and spatial requirements for virulence determinants in the intracellular life cycle, using genetic dissection and photothermal nanoblade delivery, which allows efficient placement of bacterium-sized cargo into the cytoplasm of mammalian cells. The conserved Bsa type III secretion system (T3SS
Bsa
) is dispensable for invasion, but is essential for escape from primary endosomes. By nanoblade delivery of
B. thailandensis
we demonstrate that all subsequent events in intercellular spread occur independently of T3SS
Bsa
activity. Although intracellular movement was essential for cell–cell spread by
B. pseudomallei
and
B. thailandensis
, neither BimA-mediated actin polymerization nor the formation of membrane protrusions containing bacteria was required for
B. thailandensis
. Surprisingly, the cryptic (
fla2
) flagellar system encoded on chromosome 2 of
B. thailandensis
supported rapid intracellular motility and efficient cell–cell spread. Plaque formation by both pathogens was dependent on the activity of a type VI secretion system (T6SS-1) that functions downstream from T3SS
Bsa
-mediated endosome escape. A remarkable feature of
Burkholderia
is their ability to induce the formation of multinucleate giant cells (MNGCs) in multiple cell types. By infection and nanoblade delivery, we observed complete correspondence between mutant phenotypes in assays for cell fusion and plaque formation, and time-course studies showed that plaque formation represents MNGC death. Our data suggest that the primary means for intercellular spread involves cell fusion, as opposed to pseudopod engulfment and bacterial escape from double-membrane vacuoles.
Protein self-diffusion in crowded solutions
Authors: Roosen-Runge Felix , Hennig Marcus , Zhang Fajun , Jacobs Robert M. J. , Sztucki Michael , Schober Helmut , Seydel Tilo , Schreiber Frank
Published: July 2011

Macromolecular crowding in biological media is an essential factor for cellular function. The interplay of intermolecular interactions at multiple time and length scales governs a fine-tuned system of reaction and transport processes, including particularly protein diffusion as a limiting or driving factor. Using quasielastic neutron backscattering, we probe the protein self-diffusion in crowded aqueous solutions of
bovine serum albumin
on nanosecond time and nanometer length scales employing the same protein as crowding agent. The measured diffusion coefficient
D
(
φ
) strongly decreases with increasing protein volume fraction
φ
explored within 7% ≤ 
φ
 ≤ 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational
D

r

(
φ
) and translational
D

t

(
φ
) contributions to
D
(
φ
). The resulting
D

t

(
φ
) is described by short-time self-diffusion of effective spheres. Protein self-diffusion at biological volume fractions is found to be slowed down to 20% of the dilute limit solely due to hydrodynamic interactions.
Moiré bands in twisted double-layer graphene
Authors: Bistritzer Rafi , MacDonald Allan H.
Published: July 2011

A moiré pattern is formed when two copies of a periodic pattern are overlaid with a relative twist. We address the electronic structure of a twisted two-layer graphene system, showing that in its continuum Dirac model the moiré pattern periodicity leads to moiré Bloch bands. The two layers become more strongly coupled and the Dirac velocity crosses zero several times as the twist angle is reduced. For a discrete set of magic angles the velocity vanishes, the lowest moiré band flattens, and the Dirac-point density-of-states and the counterflow conductivity are strongly enhanced.
Rational growth of branched nanowire heterostructures with synthetically encoded properties and function
Authors: Jiang Xiaocheng , Tian Bozhi , Xiang Jie , Qian Fang , Zheng Gengfeng , Wang Hongtao , Mai Liqiang , Lieber Charles M.
Published: July 2011

Branched nanostructures represent unique, 3D building blocks for the “bottom-up” paradigm of nanoscale science and technology. Here, we report a rational, multistep approach toward the general synthesis of 3D branched nanowire (NW) heterostructures. Single-crystalline semiconductor, including groups IV, III–V, and II–VI, and metal branches have been selectively grown on core or core/shell NW backbones, with the composition, morphology, and doping of core (core/shell) NWs and branch NWs well controlled during synthesis. Measurements made on the different composition branched NW structures demonstrate encoding of functional p-type/n-type diodes and light-emitting diodes (LEDs) as well as field effect transistors with device function localized at the branch/backbone NW junctions. In addition, multibranch/backbone NW structures were synthesized and used to demonstrate capability to create addressable nanoscale LED arrays, logic circuits, and biological sensors. Our work demonstrates a previously undescribed level of structural and functional complexity in NW materials, and more generally, highlights the potential of bottom-up synthesis to yield increasingly complex functional systems in the future.
Biodiversity hotspots house most undiscovered plant species
Authors: Joppa Lucas N. , Roberts David L. , Myers Norman , Pimm Stuart L.
Published: July 2011

For most organisms, the number of described species considerably underestimates how many exist. This is itself a problem and causes secondary complications given present high rates of species extinction. Known numbers of flowering plants form the basis of biodiversity “hotspots”—places where high levels of endemism and habitat loss coincide to produce high extinction rates. How different would conservation priorities be if the catalog were complete? Approximately 15% more species of flowering plant are likely still undiscovered. They are almost certainly rare, and depending on where they live, suffer high risks of extinction from habitat loss and global climate disruption. By using a model that incorporates taxonomic effort over time, regions predicted to contain large numbers of undiscovered species are already conservation priorities. Our results leave global conservation priorities more or less intact, but suggest considerably higher levels of species imperilment than previously acknowledged.
D2 receptor overexpression in the striatum leads to a deficit in inhibitory transmission and dopamine sensitivity in mouse prefrontal cortex
Authors: Li Yan-Chun , Kellendonk Christoph , Simpson Eleanor H. , Kandel Eric R. , Gao Wen-Jun
Published: July 2011

Two distinct defects are thought to be important for the pathophysiology of schizophrenia. One is an increase of D2 receptors (D2Rs) in the striatum and another is a decrease in the GABAergic function in the prefrontal cortex (PFC). Whether these two defects are functionally linked is not known. We previously reported that selective overexpression of D2Rs in the striatum of the mouse causes behavioral abnormality associated with PFC functions. Using patch-clamp recording, we find that overexpression of D2Rs in the striatum affects inhibitory transmission in the PFC and dopamine (DA) sensitivity. The overexpression of D2Rs in the striatum caused an increase in frequency of spontaneous excitatory postsynaptic currents (EPSCs) in layer V pyramidal neurons, whereas their neuronal excitability was unaffected. In contrast, both the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) were significantly decreased in these mice, indicating a reduced inhibitory transmission. Furthermore, in D2R transgenic mice the dopaminergic modulation of evoked IPSCs was shifted, with reduced sensitivity. The change in dopamine sensitivity in the PFC of D2R transgenic mice appears specific for D2Rs because in D2R transgenic mice the effects of D2 agonist but not D1 agonist, on both evoked IPSCs and EPSCs, were reduced. Together, these results indicate that overexpression of D2Rs in the striatum leads to a functional deficit in the GABAergic system. These results provide a functional link between D2R overexpression and GABAergic inhibition in the PFC and suggest that the postulated deficit in GABAergic function in schizophrenia could be secondary to alterations in the striatal dopamine system.
INTENTIONS TO MIGRATE WITHIN THE EUROPEAN UNION: A CHALLENGE FOR SIMPLE ECONOMIC MACRO-LEVEL EXPLANATIONS
Authors: Hadler Markus
Published: July 2011

Individual mobility within the European Union has remained rather low, in spite of large socio-economical differences and the lack of political restrictions for citizens of member states. Taking this as a starting point, this paper sets out to develop a more appropriate view by combing aspects of economic and sociological migration theories both at the macro and micro levels. For this purpose, the Eurobarometer survey 54.2 of 2001 is analysed by applying a three-level regression. Therefore, different characteristics of 15 European countries, 196 nuts-2-regions and about 7,000 respondents aged younger than 45 years are considered. Analyses show that the assumption of push-and-pull models – namely, that people leave less developed places – applies only within countries. In fact, the highest migration intentions can be observed in regions with a developmental gap compared to the overall level of a country. But between countries, the effect is quite the opposite – the highest intentions can be found in highly developed countries. However, the explanatory power of macro-level variables is rather low compared to that of individual characteristics. Therefore, research should place more emphasis on individual characteristics, to estimate a migration potential more accurately.
THE IMPACT OF UNEMPLOYMENT BENEFIT SYSTEM ON THE MENTAL WELL-BEING OF THE UNEMPLOYED IN SWEDEN, IRELAND AND GREAT BRITAIN
Authors: Nordenmark Mikael , Strandh Mattias , Layte Richard
Published: July 2011

Although the availability of social support and psychological attachment to work have been shown to influence mental well-being in unemployment, the main determinant suggested in research is economic strain. Yet, though the level of state support in unemployment is the most crucial determinant of economic strain, there has been little research on the impact of welfare benefit regime on mental well-being among the unemployed. In this paper we compare the impact of benefit regime by comparing the unemployed in Britain, Ireland and Sweden. We find that the type of benefit received is an important determinant of mental distress with income replacement benefits being more beneficial than flat rate benefits. Results also show that different systems differentially impact on different groups with income replacement benefits tending to maintain pre-unemployment differences in distress and flat rate benefits equalising these differences.
INFORMATION SOCIETY FOR ALL? STRUCTURAL CHARACTERISTICS OF INTERNET USE IN 15 EUROPEAN COUNTRIES
Authors: Räsänen Pekka
Published: July 2011

The article examines the patterns of Internet use in 15 European Union countries. In the theoretical part, it is discussed how the social scientists have addressed the consequences of the diffusion of the new information and communication technologies (ICT). It is asked whether there is a potential in the use of ICT for increasing social inequalities within and between the affluent societies. In the empirical part, it is examined whether the 15 European countries selected have qualitatively different patterns of Internet use from each other. Results from Eurobarometer 56.0 survey data collected in 2001 (N=16,200) show that the basic socio-demographic factors explain the use of the Internet rather similarly in the then EU area. However, it is also revealed that the institutional differences between European countries affect the strengths of socio-demographic factors.
The spatially resolved measurements of the atomic densities in argon Paschen 1s levels by OES in a capacitively coupled plasma
Authors: Li Jiang , Liu Fei-Xiang , Zhu Xi-Ming , Pu Yi-Kang
Published: July 2011

Spatially resolved atomic densities of argon 1s levels in a capacitively coupled plasma are measured by using an OES branching fraction method with the mono-directional escape factor. Different spatial profiles of the densities of the metastable and resonance levels are observed. The resonance levels increase more drastically than the metastable levels with the distance from the power electrode in the sheath, while in the bulk plasma, both resonance and metastable levels are more uniform. The relationship between the distribution of the electron density and those of the metastable and the resonance levels is also discussed.
Type-II heterojunction organic/inorganic hybrid non-volatile memory based on FeS2 nanocrystals embedded in poly(3-hexylthiophene)
Authors: Lin C W , Wang D Y , Tai Y , Jiang Y T , Chen M C , Chen C C , Yang Y J , Chen Y F
Published: July 2011

Electrical bistable behaviour was demonstrated in memory devices based on n-type FeS2 nanocrystals (NCs) embedded in a p-type poly(3-hexylthiophene) (P3HT) matrix. An organic/inorganic hybrid non-volatile memory device with a type-II band alignment, fabricated by a spin-coating process, exhibited electrical bistable characteristics. The bistable behaviour of carrier transport can be well described through the space-charge-limited current model. The small amount of FeS2 NCs in this device serve as an excellent charge trapping medium arising from the type-II band alignment between FeS2 and P3HT. Our study suggests a new way to integrate non-volatile memory with other devices such as transistor or photovoltaic since the presented FeS2/P3HT offers a type-II band alignment.
Tunable cut-off frequency by in-plane uniaxial anisotropy in (Fe66.9Co33.1)86.8Sm13.2 films
Authors: Xi L , Zhou J J , Sun Q J , Li X Y , Ma J H , Zuo Y L , Xue D S
Published: July 2011

(Fe66.9Co33.1)86.8Sm13.2 (FeCoSm) thin films with thickness from 110 to 330 nm are fabricated on silicon (1 1 1) substrates by magnetron co-sputtering under ambient condition. The as-deposited FeCoSm thin film is amorphous when the thickness is less than 150 nm. When the thickness increases further, the film becomes partially crystallized. The maximum in-plane uniaxial anisotropy field is up to 1200 Oe. After the films are heat treated in vacuum with a magnetic field, the in-plane uniaxial anisotropy field decreases with an increase in annealing temperature and becomes zero after annealing at 500 °C. The dynamic magnetic properties of the FeCoSm films are also investigated in the range 0.1–9 GHz. Based on the one-terminal micro-strip transmission-line perturbation method and an analysis by the Landau–Lifshitz equation, the anisotropy field and the resonance frequency of the FeCoSm_films are in the range 50–1200 Oe and 1.8–12.1 GHz, respectively. The anisotropy field and resonance frequency of the film can be controlled by varying the film thickness or annealing temperature, this means that FeCoSm films have great potential in high-frequency applications.
Hydrophobic self-cleaning surfaces of ZnO thin films synthesized by sol–gel technique
Authors: Patra S , Sarkar S , Bera S K , Ghosh R , Paul G K
Published: July 2011

This paper reported on highly transparent self-cleaning surfaces of zinc oxide synthesized via the sol–gel route. The results, including the x-ray diffraction, optical transmittance spectra, atomic force microscopy and the contact angles, were also reported in the paper, along with a discussion on the hydrophobic properties of zinc oxide. However, upon further investigation of the hydrophobicity of zinc oxide thin films, we found that the contact angles originally reported were not reproducible, and hence this might have led to incorrect and ambiguous analysis of the properties of zinc oxide thin films. The inconsistency in the data and the ambiguities oblige the authors to retract the above article.