bluuebunny/crossref_metadata_2025_split huggingface dataset:
A type III effector protease NleC from enteropathogenic Escherichia coli targets NF‐κB for degradation
Authors: Pearson Jaclyn S. , Riedmaier Patrice , Marchès Olivier , Frankel Gad , Hartland Elizabeth L. 
Published: February 2011

SummaryMany bacterial pathogens utilize a type III secretion system (T3SS) to inject virulence effector proteins into host cells during infection. Previously, we found that enteropathogenic Escherichia coli (EPEC) uses the type III effector, NleE, to block the inflammatory response by inhibiting IκB degradation and nuclear translocation of the p65 subunit of NF‐κB. Here we screened further effectors with unknown function for their capacity to prevent p65 nuclear translocation. We observed that ectopic expression of GFP–NleC in HeLa cells led to the degradation of p65. Delivery of NleC by the T3SS of EPEC also induced degradation of p65 in infected cells as well as other NF‐κB components, c‐Rel and p50. Recombinant His6‐NleC induced p65 and p50 cleavage in HeLa cell lysates and mutation of a consensus zinc metalloprotease motif, HEIIH, abrogated NleC proteolytic activity. NleC inhibited IL‐8 production during prolonged EPEC infection of HeLa cells in a protease activity‐dependent manner. A double nleE/nleC mutant was further impaired for its ability to inhibit IL‐8 secretion than either a single nleE or a single nleC mutant. We conclude that NleC is a type III effector protease that degrades NF‐κB thereby contributing the arsenal of bacterial effectors that inhibit innate immune activation.
AlgW regulates multiple Pseudomonas syringae virulence strategies
Authors: Schreiber Karl J. , Desveaux Darrell 
Published: February 2011

SummaryGram‐negative bacterial pathogens have evolved a number of virulence‐promoting strategies including the production of extracellular polysaccharides such as alginate and the injection of effector proteins into host cells. The induction of these virulence mechanisms can be associated with concomitant downregulation of the abundance of proteins that trigger the host immune system, such as bacterial flagellin. In Pseudomonas syringae, we observed that bacterial motility and the abundance of flagellin were significantly reduced under conditions that induce the type III secretion system. To identify genes involved in this negative regulation, we conducted a forward genetic screen with P. syringae pv. maculicola ES4326 using motility as a screening phenotype. We identified the periplasmic protease AlgW as a key negative regulator of flagellin abundance that also positively regulates alginate biosynthesis and the type III secretion system. We also demonstrate that AlgW constitutes a major virulence determinant of P. syringae required to dampen plant immune responses. Our findings support the conclusion that P. syringae co‐ordinately regulates virulence strategies through AlgW in order to effectively suppress host immunity.
Heterochromatin formation in bistable chromatin domains controls the epigenetic repression of clonally variant Plasmodium falciparum genes linked to erythrocyte invasion
Authors: Crowley Valerie M. , Rovira‐Graells Núria , de Pouplana Lluís Ribas , Cortés Alfred 
Published: February 2011

SummaryClonally variant gene expression is a common survival strategy used by many pathogens, including the malaria parasite Plasmodium falciparum. Among the genes that show variant expression in this parasite are several members of small gene families linked to erythrocyte invasion, including the clag and eba families. The active or repressed state of these genes is clonally transmitted by epigenetic mechanisms. Here we characterized the promoters of clag3.1, clag3.2 and eba‐140, and compared nuclease accessibility and post‐translational histone modifications between their active and repressed states. Activity of these promoters in an episomal context is similar between parasite subclones characterized by different patterns of expression of the endogenous genes. Variant expression is controlled by the euchromatic or heterochromatic state of bistable chromatin domains. Repression is mediated by H3K9me3‐based heterochromatin, whereas the active state is characterized by H3K9ac. These marks are maintained throughout the asexual blood cycle to transmit the epigenetic memory. Furthermore, eba‐140 is organized in two distinct chromatin domains, probably separated by a barrier insulator located within its ORF. The 5′ chromatin domain controls expression of the gene, whereas the 3′ domain shares the chromatin conformation with the upstream region of the neighbouring phista family gene, which also shows variant expression.
Broad‐spectrum antimicrobial peptide resistance by MprF‐mediated aminoacylation and flipping of phospholipids
Authors: Ernst Christoph M. , Peschel Andreas 
Published: February 2011

SummaryBacteria are frequently exposed to cationic antimicrobial peptides (CAMPs) from eukaryotic hosts (host defence peptides) or from prokaryotic competitors (bacteriocins). However, many bacteria, among them most of the major human pathogens, achieve CAMP resistance by MprF, a unique enzyme that modifies anionic phospholipids with l‐lysine or l‐alanine thereby introducing positive charges into the membrane surface and reducing the affinity for CAMPs. The lysyl or alanyl groups are derived from aminoacyl tRNAs and are usually transferred to phosphatidylglycerol (PG). Recent studies with MprF from Staphylococcus aureus demonstrated that production of Lys‐PG only leads to CAMP resistance when an additional flippase domain of MprF is present that translocates Lys‐PG and exposes it at the outer leaflet of the membrane. Thus, MprF exerts two specific functions that have hardly been found in other bacterial proteins. MprF proteins are crucial virulence factors of many human pathogens, which recommends them as targets for new anti‐virulence drugs. Intriguingly, specific point mutations in mprF cause resistance to the CAMP‐like antibiotic daptomycin in a yet unclear way that may involve altered Lys‐PG synthesis and/or Lys‐PG flipping capacities. Thus, a thorough characterization of MprF domains and functions will help to unravel how bacteria maintain and protect their cytoplasmic membranes.
Dickeya species: an emerging problem for potato production in Europe
Authors: Toth I. K. , van der Wolf J. M. , Saddler G. , Lojkowska E. , Hélias V. , Pirhonen M. , Tsror (Lahkim) L. , Elphinstone J. G. 
Published: February 2011

Dickeya species (formerly Erwinia chrysanthemi) cause diseases on numerous crop and ornamental plants world‐wide. Dickeya spp. (probably D. dianthicola) were first reported on potato in the Netherlands in the 1970s and have since been detected in many other European countries. However, since 2004–5 a new pathogen, with the proposed name ‘D. solani’, has been spreading across Europe via trade in seed tubers and is causing increasing economic losses. Although disease symptoms are often indistinguishable from those of the more established blackleg pathogen Pectobacterium spp., Dickeya spp. can initiate disease from lower inoculum levels, have a greater ability to spread through the plant’s vascular tissue, are considerably more aggressive, and have higher optimal temperatures for disease development (the latter potentially leading to increased disease problems as Europe’s climate warms). However, they also appear to be less hardy than Pectobacterium spp. in soil and other environments outside the plant. Scotland is currently the only country in Europe to enforce zero tolerance for Dickeya spp. in its potato crop in an attempt to keep its seed tuber industry free from disease. However, there are a number of other ways to control the disease, including seed tuber certification, on‐farm methods and the use of diagnostics. For diagnostics, new genomics‐based approaches are now being employed to develop D. dianthicola‐ and ‘D. solani’‐specific PCR‐based tests for rapid detection and identification. It is hoped that these diagnostics, together with other aspects of ongoing research, will provide invaluable tools and information for controlling this serious threat to potato production.
COMT and ALDH2 polymorphisms moderate associations of implicit drinking motives with alcohol use
Authors: Hendershot Christian S. , Lindgren Kristen P. , Liang Tiebing , Hutchison Kent E. 
Published: February 2011

ABSTRACTDual process models of addiction emphasize the importance of implicit (automatic) cognitive processes in the development and maintenance of substance use behavior. Although genetic influences are presumed to be relevant for dual process models, few studies have evaluated this possibility. The current study examined two polymorphisms with functional significance for alcohol use behavior (COMT Val158Met and ALDH2*2) in relation to automatic alcohol cognitions and tested additive and interactive effects of genotype and implicit cognitions on drinking behavior. Participants were college students (n = 69) who completed Implicit Association Tasks (IATs) designed to assess two classes of automatic drinking motives (enhancement motives and coping motives). Genetic factors did not show direct associations with IAT measures; however, COMT and ALDH2 moderated associations of implicit coping motives with drinking outcomes. Interaction effects indicated that associations of implicit motives with drinking outcomes were strongest in the context of genetic variants associated with relatively higher risk for alcohol use (COMT Met and ALDH2*1). Associations of genotype with drinking behavior were observed for ALDH2 but not COMT. These findings are consistent with the possibility that genetic risk or protective factors could potentiate or mitigate the influence of reflexive cognitive processes on drinking behavior, providing support for the evaluation of genetic influences in the context of dual process models of addiction.
Quantitative genetic variation for thermal performance curves within and among natural populations ofDrosophila serrata
Authors: LATIMER C. A. L. , WILSON R. S. , CHENOWETH S. F. 
Published: February 2011

AbstractThermal performance curves (TPCs) provide a powerful framework for studying the evolution of continuous reaction norms and for testing hypotheses of thermal adaptation. Although featured heavily in comparative studies, the framework has been comparatively underutilized for quantitative genetic tests of thermal adaptation. We assayed the distribution of genetic (co)variance for TPC (locomotor activity) within and among three natural populations ofDrosophila serrataand performed replicated tests of two hypotheses of thermal adaptation – that ‘hotter is better’ and that a generalist‐specialist trade‐off underpins the evolution of thermal sensitivity. We detected significant genetic variance within, and divergence among, populations. The ‘hotter is better’ hypothesis was not supported as the genetic correlations between optimal temperature (Topt) and maximum performance (zmax) were consistently negative. A pattern of variation consistent with a generalist‐specialist trade‐off was detected within populations and divergence among populations indicated that performance curves were narrower and had higher optimal temperatures in the warmer, but less variable tropical population.
Testicular melanization has evolved in birds with high mtDNA mutation rates
Authors: GALVÁN I. , MØLLER A. P. , ERRITZØE J. 
Published: February 2011

AbstractMelanin is mainly found in the integument of animals, but it also appears in several extracutaneous tissues. The presence of melanin in testes has been anecdotally reported in all vertebrate groups, but the causes and functions of this melanin remain unknown. Similar to other extracutaneous melanins, testicular melanin may protect male germ cells from oxidative stress. Given the high respiratory activity of spermatozoa, oxidative stress generated by mitochondrial dysfunction as a consequence of mtDNA mutations directly affects sperm viability. Thus, natural selection may favour testicular melanization in males of species with high historical mutation rates in the mitochondrial genome. Here, we tested this hypothesis using information on occurrence of testicular melanization and mutation accumulation as reflected by cytochromebmtDNA base pair substitution rates in a large set of 134 species of birds, controlling for the confounding effects of body mass, reproductive activity and phylogeny. We found that testicular melanization has evolved in species with high rates of accumulated mitochondrial mutations and propose that this is an adaptive response related to the protective capacity of melanin against oxidative stress. In support of this hypothesis, testicular melanization was more frequently observed during the breeding season of birds (i.e. when spermatogenesis is likely to occur) than during reproductive inactivity. In contrast to other extracutaneous melanins whose abundance seems to reflect skin and coat colour, we did not find a correlation between the proportion of plumage coloured by melanins and occurrence of testicular melanization. Whereas future experimental studies should test these hypotheses, our study highlights for the first time that melanization patterns in animals may evolve as a response to historical mutation rates.
Gene expression profiling of Arabidopsis meiocytes
Authors: Libeau P. , Durandet M. , Granier F. , Marquis C. , Berthomé R. , Renou J. P. , Taconnat‐Soubirou L. , Horlow C. 
Published: February 2011

AbstractMeiosis is a special type of cell division present in all organisms that reproduce by sexual reproduction. It ensures the transition between the sporophytic and gametophytic state and allows gamete production through meiotic recombination and chromosome number reduction. In this paper, we describe a technique for the isolation of Arabidopsis thaliana male meiocytes. From this cellular material, it was then possible to develop large‐scale transcriptome studies using CATMA microarrays and thus to obtain an overview of genes expressed during Arabidopsis meiosis. The expression profiles were studied with either stringent statistical criteria or by performing clustering. Both methods resulted in gene clusters enriched in meiosis‐specific genes (from 14‐ to 55‐fold). Analysis of these data provided a unique set of genes that will be pivotal to further analysis aimed at understanding the meiotic process.
Consumer complaint channel choice in online and offline purchases
Authors: Lee Seul , Cude Brenda J. 
Published: February 2011

AbstractThis research explored the influence of the purchase environment on the choice of complaint channel. The study was based on responses from 480 undergraduate students who participated in a 2 (purchase environment: offline vs. online) × 2 (the degree of dissatisfaction: weak vs. strong) online experiment. Consumers who purchased online were more likely to complain online than those who made their purchase offline. Online complaining among online purchasers increased with the degree of dissatisfaction. The research suggests that future researchers should include consumer complaint channel choices when examining consumer complaining behaviour.
Effect of near adds on the variability of accommodative response in myopic children
Authors: Sreenivasan Vidhyapriya , Irving Elizabeth L , Bobier William R 
Published: February 2011

Citation information: Sreenivasan V, Irving EL & Bobier WR. Effect of near adds on the variability of accommodative response in myopic children. Ophthalmic Physiol Opt 2011, 31, 145–154. doi: 10.1111/j.1475‐1313.2010.00818.xAbstractPurpose:  Higher variability of accommodative response (VAR) has been reported in myopes and speculated to be a possible risk factor for the progression of myopia. We investigated whether near adds of +2D and −2D were capable of altering accommodative variability and also determined the influence of near phoria and viewing condition (binocular vs monocular) on the VAR in myopic and emmetropic children.Methods:  Twenty‐seven myopic and 25 emmetropic children between 7 and 14 years were examined. All children were classified into ‘normophores’ (0 to 4 exo), exophores (>6 exo) or esophores (>2 eso) based on their near phoria. Binocular and monocular steady‐state measures of accommodation were obtained for 5 s using a PowerRefractor (Multichannel Co) while children fixated a high contrast target (33 cm) with distance correction, and then with +2D add and −2D add over the corrective lenses. The variation in accommodative responses (VAR) was defined as the standard deviation of the accommodative response during the 5 s period.Results:  Myopic children showed higher VAR through their distance spectacle corrections compared to emmetropes (emmetropes = 0.23 ± 0.03D, myopes = 0.37 ± 0.07D, p < 0.001). Plus adds significantly reduced the VAR in myopic children to the level of emmetropes (emmetropes = 0.2 ± 0.03D, myopes = 0.19 ± 0.02D, p > 0.9). Introduction of a −2D add significantly increased the VAR in both refractive groups; however, myopes showed greater VAR compared to emmetropes (emmetropes = 0.39 ± 0.03D, myopes = 0.53 ± 0.07D, p < 0.001). Near phoria or binocular viewing did not alter the magnitude of fluctuations in either refractive group. VAR significantly correlated with the monocular accommodative error in both refractive groups (emmetropes r2 = 0.34; p < 0.0001; myopes: r2 = 0.35; p < 0.001). Pupil size, while varying with add type, did not confound the VAR.Conclusions:  The near steady state accommodative response of young myopes shows greater variability than non‐myopes. This difference is maintained when accommodative responses are increased beyond the vergence plane using − 2D adds. However, accommodative fluctuations were reduced to emmetropic levels when the stimulus to accommodation is reduced using a +2D add. The resulting VAR through adds appear to follow that expected from variations in accommodative demands and hence properties of the accommodative controller. Vergence postures (eso and exo phoria) do not appear to influence the VAR with and without near adds.
Potential hazards of viewing 3‐D stereoscopic television, cinema and computer games: a review
Authors: Howarth Peter A 
Published: February 2011

Citation information: Howarth PA. Potential hazards of viewing 3‐D stereoscopic television and cinema: a review. Ophthalmic Physiol Opt 2011, 31, 111–122. doi: 10.1111/j.1475‐1313.2011.00822.xAbstractThe visual stimulus provided by a 3‐D stereoscopic display differs from that of the real world because the image provided to each eye is produced on a flat surface. The distance from the screen to the eye remains fixed, providing a single focal distance, but the introduction of disparity between the images allows objects to be located geometrically in front of, or behind, the screen. Unlike in the real world, the stimulus to accommodation and the stimulus to convergence do not match. Although this mismatch is used positively in some forms of Orthoptic treatment, a number of authors have suggested that it could negatively lead to the development of asthenopic symptoms. From knowledge of the zone of clear, comfortable, single binocular vision one can predict that, for people with normal binocular vision, adverse symptoms will not be present if the discrepancy is small, but are likely if it is large, and that what constitutes ‘large’ and ‘small’ are idiosyncratic to the individual. The accommodation‐convergence mismatch is not, however, the only difference between the natural and the artificial stimuli. In the former case, an object located in front of, or behind, a fixated object will not only be perceived as double if the images fall outside Panum’s fusional areas, but it will also be defocused and blurred. In the latter case, however, it is usual for the producers of cinema, TV or computer game content to provide an image that is in focus over the whole of the display, and as a consequence diplopic images will be sharply in focus. The size of Panum’s fusional area is spatial frequency‐dependent, and because of this the high spatial frequencies present in the diplopic 3‐D image will provide a different stimulus to the fusion system from that found naturally.
Repealing Federal Oversight of State Health Policy: Lessons from the Boren Amendment
Authors: Miller Edward Alan 
Published: February 2011

AbstractThe Boren Amendment is frequently cited as an example where judicial involvement markedly shaped the implementation of federal legislation. Unlike other controversial health policies, Boren was eventually rescinded by Congress. Results indicate that the Amendment was repealed because changing socioeconomic, political, and programmatic conditions combined with policy‐oriented learning to facilitate a shift in policy venue away from the judiciary toward the President and Congress. This is because during the devolutionary climate of the mid‐to‐late 1990s, both the executive and legislature proved more conducive to the policy image promulgated by state officials that the Amendment unnecessarily restricted state discretion, than the policy image promulgated by providers that without the Amendment, low reimbursement levels would compromise access and quality. Data for this analysis derive from archival documents, secondary sources, and 101 interviews with state and federal experts.
Confronting the Governance Challenges of Developing Nigeria's Extractive Industry: Policy and Performance in the Oil and Gas Sector1
Authors: Okpanachi Eyene 
Published: February 2011

AbstractThe issue of economic growth and human development has been a central concern in the oil and gas sector of Nigeria's extractive industry, and this has featured prominently in the agitations and generalized restiveness in the Niger Delta, the oil‐producing region. While many studies have focused on these problems, policies aimed at confronting them have not received much broad attention. This article bridges this research gap by holistically focusing on the solution to the problem. In doing this, the article examines the policies during the Obasanjo administration from 1999 to 2007 in order to critically assess the efficacy or inefficiency of the policies in reversing the general problem now known as the “resource curse,” and to offer a better understanding of the deeper political, social, and economic issues that drive outcomes. The article finds that while significant efforts were made to avoid the boom and bust cycle of oil and lower volatility by de‐linking public expenditure from oil revenue through the “oil‐price‐based fiscal rule,” generally, progress in this area was not matched by improvement in the other areas examined by this study, notably peace and safety of lives and oil/gas installations, the development of the oil‐producing region, environmental security and sustainability, and the transparent and accountable use of oil/gas revenues.
Modelling recombinations during cosmological reionization
Authors: Raičević Milan , Theuns Tom 
Published: February 2011

Abstract
An ionization front expanding into a neutral medium can be slowed down significantly by recombinations. In cosmological numerical simulations the recombination rate is often computed using a ‘clumping factor’ that takes into account that not all scales in the simulated density field are resolved. Here we demonstrate that using a single value of the clumping factor significantly overestimates the recombination rate, and how a local estimate of the clumping factor is both easy to compute, and gives significantly better numerical convergence. We argue that this lower value of the recombination rate is more relevant during the reionization process and hence that the importance of recombinations during reionization has been overestimated.