bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of the gut microbiota on host adiposity are modulated by the short-chain fatty-acid binding G protein-coupled receptor, Gpr41
Authors: Samuel Buck S. , Shaito Abdullah , Motoike Toshiyuki , Rey Federico E. , Backhed Fredrik , Manchester Jill K. , Hammer Robert E. , Williams S. Clay , Crowley Jan , Yanagisawa Masashi , Gordon Jeffrey I.
Published: October 2008

The distal human intestine harbors trillions of microbes that allow us to extract calories from otherwise indigestible dietary polysaccharides. The products of polysaccharide fermentation include short-chain fatty acids that are ligands for Gpr41, a G protein-coupled receptor expressed by a subset of enteroendocrine cells in the gut epithelium. To examine the contribution of Gpr41 to energy balance, we compared
Gpr41
−/− and
Gpr41
+/+ mice that were either conventionally-raised with a complete gut microbiota or were reared germ-free and then cocolonized as young adults with two prominent members of the human distal gut microbial community: the saccharolytic bacterium,
Bacteroides thetaiotaomicron
and the methanogenic archaeon,
Methanobrevibacter smithii
. Both conventionally-raised and gnotobiotic
Gpr41
−/− mice colonized with the model fermentative community are significantly leaner and weigh less than their WT (+/+) littermates, despite similar levels of chow consumption. These differences are not evident when germ-free WT and germ-free Gpr41 knockout animals are compared. Functional genomic, biochemical, and physiologic studies of germ-free and cocolonized
Gpr41
−/− and +/+ littermates disclosed that Gpr41-deficiency is associated with reduced expression of PYY, an enteroendocrine cell-derived hormone that normally inhibits gut motility, increased intestinal transit rate, and reduced harvest of energy (short-chain fatty acids) from the diet. These results reveal that Gpr41 is a regulator of host energy balance through effects that are dependent upon the gut microbiota.
The potential of desferrioxamine-gallium as an anti-
Pseudomonas
therapeutic agent
Authors: Banin Ehud , Lozinski Alina , Brady Keith M. , Berenshtein Eduard , Butterfield Phillip W. , Moshe Maya , Chevion Mordechai , Greenberg Everett Peter , Banin Eyal
Published: October 2008

The opportunistic pathogen
Pseudomonas aeruginosa
causes infections that are difficult to treat by antibiotic therapy. This bacterium can cause biofilm infections where it shows tolerance to antibiotics. Here we report the novel use of a metallo-complex, desferrioxamine-gallium (DFO-Ga) that targets
P. aeruginosa
iron metabolism. This complex kills free-living bacteria and blocks biofilm formation. A combination of DFO-Ga and the anti-
Pseudomonas
antibiotic gentamicin caused massive killing of
P. aeruginosa
cells in mature biofilms. In a
P. aeruginosa
rabbit corneal infection, topical administration of DFO-Ga together with gentamicin decreased both infiltrate and final scar size by about 50% compared to topical application of gentamicin alone. The use of DFO-Ga as a Trojan horse delivery system that interferes with iron metabolism shows promise as a treatment for
P. aeruginosa
infections.
Functional recognition of a distinct receptor preferential for leukotriene E4in mice lacking the cysteinyl leukotriene 1 and 2 receptors
Authors: Maekawa Akiko , Kanaoka Yoshihide , Xing Wei , Austen K. Frank
Published: October 2008

The cysteinyl leukotrienes (cys-LTs) are a family of potent lipid mediators of inflammation derived from arachidonic acid. Activation of certain cell types results in the biosynthesis and export of leukotriene (LT) C4, which then undergoes extracellular metabolism to LTD4and LTE4. LTE4, the most stable cys-LT, is only a weak agonist for the defined type 1 and type 2 cys-LT receptors (CysLT1R and CysLT2R, respectively). We had recognized a greater potency for LTE4than LTC4or LTD4in constricting guinea pig tracheain vitroand comparable activity in eliciting a cutaneous wheal and flare response in humans. Thus, we hypothesized that a vascular permeability response to LTE4in mice lacking both the CysLT1R and CysLT2R could establish the existence of a separate LTE4receptor. We now report that the intradermal injection of LTE4into the ear of mice deficient in both CysLT1R and CysLT2R elicits a vascular leak that exceeds the response to intradermal injection of LTC4or LTD4, and that this response is inhibited by pretreatment of the mice with pertussis toxin or a Rho kinase inhibitor. LTE4is ≈64-fold more potent in the CysLT1R/CysLT2R double-deficient mice than in sufficient mice. The administration of a CysLT1R antagonist augmented the permeability response of the CysLT1R/CysLT2R double-deficient mice to LTC4, LTD4, and LTE4. Our findings establish the existence of a third receptor, CysLTER, that responds preferentially to LTE4, the most abundant cys-LT in biologic fluids, and thus reveal a new target for therapeutic intervention.
Abnormal mammography and sonography associated with foreign-body giant-cell reaction after stereotactic vacuum-assisted breast biopsy with carbon marking
Authors: Ruiz-Delgado M. L. , López-Ruiz J. A. , Sáiz-López A.
Published: October 2008

Background: Carbon marking of the biopsy site and needle track following stereotactic breast biopsy in nonpalpable mammography-detected lesions provides for safe and accurate localization for subsequent surgical excision. No significant complications of carbon marking have been reported to date.

Purpose: To report follow-up imaging findings and histological changes (foreign-body giant-cell reaction) attributable to the use of carbon marking after vacuum breast biopsies.

Material and Methods: This was a retrospective study of 130 patients in a mammographic screening program with nonpalpable suspicious breast lesions that were referred for stereotactic directional vacuum-assisted breast biopsy with carbon marking. Histological diagnosis was benign in all cases, but 1-year follow-up mammograms demonstrated suspect findings in four of them.

Results: For all four patients, the results of the initial stereotactic vacuum-assisted biopsy were benign, but mammographic follow-up and ultrasound findings revealed suspicious changes that, in all cases, were histologically shown to be foreign-body giant-cell reactions attributable to the use of carbon.

Conclusion: In four of 130 lesions (3%) that were carbon marked following stereotactic vacuum-assisted breast biopsy, and in which surgical excision was not required, the mammographic and ultrasound follow-up appearance of the breast simulated malignancy. The abnormality was attributable to the use of carbon, which represents a potential source of misdiagnosis.
Theorizing Visual Representation in Children's Literature
Authors: Albers Peggy
Published: October 2008

Children's literature has been analyzed through a number of different theoretical lenses, including critical literacy, feminism, and multiculturalism. Yet, given the prominence that image plays in such literature, little if any work in literacy has analyzed children's literature from the perspective of art theory. This study first theorized how and why artists render visual representations as they do. It then used this theory to analyze images in Caldecott award-winning literature. Three findings emerged from the analysis: (a) image types cut across time, culture, and artists' rendering; (b) images embody stable representations of culture; and (c) images tend to render visual binaries and invite oppositional readings. Implications are discussed for developing and using a theory for the close reading of visual imagery in children's literature.
The Information Text Gap: The Mismatch between Non-Narrative Text Types in Basal Readers and 2009 NAEP Recommended Guidelines
Authors: Moss Barbara
Published: October 2008

The purpose of this study was to compare the text genres represented in two recent California-adopted basal readers (grades 1 through 6) with the guidelines for informational text types in the 2009 NAEP framework. Phase 1 of data collection involved the use of two measures to determine the presence of each text genre: number of pages and number of selections. The researchers assigned pages and selections to one of four categories: narrative, poetry, play, or nonfiction. The second phase of data collection involved classification of nonfiction selections according to one of four categories: literary nonfiction, or one of three types of informational text: expository, argumentation and persuasive, or procedural and documents. The researchers computed percentages of pages and selections devoted to each genre and each type of nonfiction across grade levels and series. Results overall indicated that 40% of pages/selections in both series were devoted to nonfiction text, and that 50% of nonfiction text selections were expository and 33% were literary nonfiction. The findings indicate that these basal readers expose students to more nonfiction text than in the past, but that the exposure to informational text is still less than recommended by the 2009 NAEP and limited mainly to exposition.
Participatory Dialogue and Participatory Learning in a Discussion-Based Graduate Seminar
Authors: Ma Wen
Published: October 2008

This study investigated the participatory learning experiences of mainstream U.S. and Korean international students in a discussion-based doctoral seminar. The author examined the multilayered and complex nature of these experiences by collecting and analyzing data from class discussions, multiple interviews, written artifacts, and field observations. Findings indicated that students' participatory learning varied with regard to discussion, reading, and writing; changed as the activity and context changed; and embodied a “dialogic spirit” for acquiring a disciplinary discourse at the doctoral level. The discussion of these findings provides insights for university faculty to better understand the nature of participatory learning at the doctoral level.
Age Differences in what is Viewed and Remembered in Complex Conjunction Search
Authors: Williams Carrick C. , Zacks Rose T. , Henderson John M.
Published: October 2008

Older and younger adults searched arrays of 12 unique real-world photographs for a specified object (e.g., a yellow drill) among distractors (e.g., yellow telephone, red drill, and green door). Eye-tracking data from 24 of 48 participants in each age group showed generally similar search patterns for the younger and older adults but there were some interesting differences. Older adults processed all the items in the arrays more slowly than the younger adults (e.g., they had longer fixation durations, gaze durations, and total times), but this difference was exaggerated for target items. We also found that older and younger adults differed in the sequence in which objects were searched, with younger adults fixating the target objects earlier in the trial than older adults. Despite the relatively longer fixation times on the targets (in comparison to the distractors) for older adults, a surprise visual recognition test revealed a sizeable age deficit for target memory but, importantly, no age differences for distractor memory.
The Effectiveness of Feedback in Multiple-Cue Probability Learning
Authors: Newell Ben R. , Weston Nicola J. , Tunney Richard J. , Shanks David R.
Published: October 2008

How effective are different types of feedback in helping us to learn multiple contingencies? This article attempts to resolve a paradox whereby, in comparison to simple outcome feedback, additional feedback either fails to enhance or is actually detrimental to performance in nonmetric multiple-cue probability learning (MCPL), while in contrast the majority of studies of metric MCPL reveal improvements at least with some forms of feedback. In three experiments we demonstrate that if feedback assists participants to infer cue polarity then it can in fact be effective in nonmetric MCPL. Participants appeared to use cue polarity information to adopt a linear judgement strategy, even though the environment was nonlinear. The results reconcile the paradoxical contrast between metric and nonmetric MCPL and support previous findings of people's tendency to assume linearity and additivity in probabilistic cue learning.
Short Article: Intention and attention in ideomotor learning
Authors: Herwig Arvid , Waszak Florian
Published: October 2008

Human actions may be carried out in response to exogenous stimuli (stimulus based) or they may be selected endogenously on the basis of the agent's intentions (intention based). We studied the functional differences between these two types of action during action–effect (ideomotor) learning. Participants underwent an acquisition phase, in which each key-press (left/right) triggered a specific tone (low pitch/high pitch) either in a stimulus-based or in an intention-based action mode. Consistent with previous findings, we demonstrate that auditory action effects gain the ability to prime their associated responses in a later test phase only if the actions were selected endogenously during acquisition phase. Furthermore, we show that this difference in ideomotor learning is not due to different attentional demands for stimulus-based and intention-based actions. Our results suggest that ideomotor learning depends on whether or not the action is selected in the intention-based action mode, whereas the amount of attention devoted to the action–effect is less important.
Inflammation and oxidative stress in vertebrate host–parasite systems
Authors: Sorci Gabriele , Faivre Bruno
Published: October 2008

Innate, inflammation-based immunity is the first line of vertebrate defence against micro-organisms. Inflammation relies on a number of cellular and molecular effectors that can strike invading pathogens very shortly after the encounter between inflammatory cells and the intruder, but in a non-specific way. Owing to this non-specific response, inflammation can generate substantial costs for the host if the inflammatory response, and the associated oxygen-based damage, get out of control. This imposes strong selection pressure that acts to optimize two key features of the inflammatory response: the timing of activation and resolution (the process of downregulation of the response). In this paper, we review the benefits and costs of inflammation-driven immunity. Our aim is to emphasize the importance of resolution of inflammation as a way of maintaining homeostasis against oxidative stress and to prevent the ‘horror autotoxicus’ of chronic inflammation. Nevertheless, host immune regulation also opens the way to pathogens to subvert host defences. Therefore, quantifying inflammatory costs requires assessing (i) short-term negative effects, (ii) delayed inflammation-driven diseases, and (iii) parasitic strategies to subvert inflammation.
Immune defence, parasite evasion strategies and their relevance for ‘macroscopic phenomena’ such as virulence
Authors: Schmid-Hempel Paul
Published: October 2008

The discussion of host–parasite interactions, and of parasite virulence more specifically, has so far, with a few exceptions, not focused much attention on the accumulating evidence that immune evasion by parasites is not only almost universal but also often linked to pathogenesis, i.e. the appearance of virulence. Now, the immune evasion hypothesis offers a deeper insight into the evolution of virulence than previous hypotheses. Sensitivity analysis for parasite fitness and life-history theory shows promise to generate a more general evolutionary theory of virulence by including a major element, immune evasion to prevent parasite clearance from the host. Also, the study of dose–response relationships and multiple infections should be particularly illuminating to understand the evolution of virulence. Taking into account immune evasion brings immunological processes to the core of understanding the evolution of parasite virulence and for a range of related issues such as dose, host specificity or immunopathology. The aim of this review is to highlight the mechanism underlying immune evasion and to discuss possible consequences for the evolutionary ecology analysis of host–parasite interactions.
The role of ecological feedbacks in the evolution of host defence: what does theory tell us?
Authors: Boots Michael , Best Alex , Miller Martin R , White Andrew
Published: October 2008

Hosts have evolved a diverse range of defence mechanisms in response to challenge by infectious organisms (parasites and pathogens). Whether defence is through avoidance of infection, control of the growth of the parasite once infected, clearance of the infection, tolerance to the disease caused by infection or innate and/or acquired immunity, it will have important implications for the population ecology (epidemiology) of the host–parasite interaction. As a consequence, it is important to understand the evolutionary dynamics of defence in the light of the ecological feedbacks that are intrinsic to the interaction. Here, we review the theoretical models that examine how these feedbacks influence the nature and extent of the defence that will evolve. We begin by briefly comparing different evolutionary modelling approaches and discuss in detail the modern game theoretical approach (adaptive dynamics) that allows ecological feedbacks to be taken into account. Next, we discuss a number of models of host defence in detail and, in particular, make a distinction between ‘resistance’ and ‘tolerance’. Finally, we discuss coevolutionary models and the potential use of models that include genetic and game theoretical approaches. Our aim is to review theoretical approaches that investigate the evolution of defence and to explain how the type of defence and the costs associated with its acquisition are important in determining the level of defence that evolves.
Mechanism of Infection Thread Elongation in Root Hairs ofMedicago truncatulaand Dynamic Interplay with Associated Rhizobial Colonization
Authors: Fournier Joëlle , Timmers Antonius C.J. , Sieberer Björn J. , Jauneau Alain , Chabaud Mireille , Barker David G.
Published: October 2008

In temperate legumes, endosymbiotic nitrogen-fixing rhizobia gain access to inner root tissues via a specialized transcellular apoplastic compartment known as the infection thread (IT). To study IT development in living root hairs, a protocol has been established for Medicago truncatula that allows confocal microscopic observations of the intracellular dynamics associated with IT growth. Fluorescent labeling of both the IT envelope (AtPIP2;1-green fluorescent protein) and the host endoplasmic reticulum (green fluorescent protein-HDEL) has revealed that IT growth is a fundamentally discontinuous process and that the variable rate of root hair invagination is reflected in changes in the host cell cytoarchitecture. The concomitant use of fluorescently labeled Sinorhizobium meliloti has further revealed that a bacteria-free zone is frequently present at the growing tip of the IT, thus indicating that bacterial contact is not essential for thread progression. Finally, these in vivo studies have shown that gaps within the bacterial file are a common feature during the early stages of IT development, and that segments of the file are able to slide collectively down the thread. Taken together, these observations lead us to propose that (1) IT growth involves a host-driven cellular mechanism analogous to that described for intracellular infection by arbuscular mycorrhizal fungi; (2) the non-regular growth of the thread is a consequence of the rate-limiting colonization by the infecting rhizobia; and (3) bacterial colonization involves a combination of bacterial cell division and sliding movement within the extracellular matrix of the apoplastic compartment.
Characterization of OsbZIP23 as a Key Player of the Basic Leucine Zipper Transcription Factor Family for Conferring Abscisic Acid Sensitivity and Salinity and Drought Tolerance in Rice
Authors: Xiang Yong , Tang Ning , Du Hao , Ye Haiyan , Xiong Lizhong
Published: October 2008

OsbZIP23 is a member of the basic leucine zipper (bZIP) transcription factor family in rice (Oryza sativa). Expression of OsbZIP23 is strongly induced by a wide spectrum of stresses, including drought, salt, abscisic acid (ABA), and polyethylene glycol treatments, while other stress-responsive genes of this family are slightly induced only by one or two of the stresses. Transactivation assay in yeast demonstrated that OsbZIP23 functions as a transcriptional activator, and the sequences at the N terminus (amino acids 1–59) and a region close to the C terminus (amino acids 210–240) are required for the transactivation activity. Transient expression of OsbZIP23-green fluorescent protein in onion (Allium cepa) cells revealed a nuclear localization of the protein. Transgenic rice overexpressing OsbZIP23 showed significantly improved tolerance to drought and high-salinity stresses and sensitivity to ABA. On the other hand, a null mutant of this gene showed significantly decreased sensitivity to a high concentration of ABA and decreased tolerance to high-salinity and drought stress, and this phenotype can be complemented by transforming the OsbZIP23 back into the mutant. GeneChip and real-time polymerase chain reaction analyses revealed that hundreds of genes were up- or down-regulated in the rice plants overexpressing OsbZIP23. More than half of these genes have been annotated or evidenced for their diverse functions in stress response or tolerance. In addition, more than 30 genes that are possible OsbZIP23-specific target genes were identified based on the comparison of the expression profiles in the overexpressor and the mutant of OsbZIP23. Collectively, these results indicate that OsbZIP23 functions as a transcriptional regulator that can regulate the expression of a wide spectrum of stress-related genes in response to abiotic stresses through an ABA-dependent regulation pathway. We propose that OsbZIP23 is a major player of the bZIP family in rice for conferring ABA-dependent drought and salinity tolerance and has high potential usefulness in genetic improvement of stress tolerance.
Novel Proteins, Putative Membrane Transporters, and an Integrated Metabolic Network Are Revealed by Quantitative Proteomic Analysis of Arabidopsis Cell Culture Peroxisomes
Authors: Eubel Holger , Meyer Etienne H. , Taylor Nicolas L. , Bussell John D. , O'Toole Nicholas , Heazlewood Joshua L. , Castleden Ian , Small Ian D. , Smith Steven M. , Millar A. Harvey
Published: October 2008

Peroxisomes play key roles in energy metabolism, cell signaling, and plant development. A better understanding of these important functions will be achieved with a more complete definition of the peroxisome proteome. The isolation of peroxisomes and their separation from mitochondria and other major membrane systems have been significant challenges in the Arabidopsis (Arabidopsis thaliana) model system. In this study, we present new data on the Arabidopsis peroxisome proteome obtained using two new technical advances that have not previously been applied to studies of plant peroxisomes. First, we followed density gradient centrifugation with free-flow electrophoresis to improve the separation of peroxisomes from mitochondria. Second, we used quantitative proteomics to identify proteins enriched in the peroxisome fractions relative to mitochondrial fractions. We provide evidence for peroxisomal localization of 89 proteins, 36 of which have not previously been identified in other analyses of Arabidopsis peroxisomes. Chimeric green fluorescent protein constructs of 35 proteins have been used to confirm their localization in peroxisomes or to identify endoplasmic reticulum contaminants. The distribution of many of these peroxisomal proteins between soluble, membrane-associated, and integral membrane locations has also been determined. This core peroxisomal proteome from nonphotosynthetic cultured cells contains a proportion of proteins that cannot be predicted to be peroxisomal due to the lack of recognizable peroxisomal targeting sequence 1 (PTS1) or PTS2 signals. Proteins identified are likely to be components in peroxisome biogenesis, β-oxidation for fatty acid degradation and hormone biosynthesis, photorespiration, and metabolite transport. A considerable number of the proteins found in peroxisomes have no known function, and potential roles of these proteins in peroxisomal metabolism are discussed. This is aided by a metabolic network analysis that reveals a tight integration of functions and highlights specific metabolite nodes that most probably represent entry and exit metabolites that could require transport across the peroxisomal membrane.
A Genome-Wide and Metabolic Analysis Determined the Adaptive Response of Arabidopsis Cells to Folate Depletion Induced by Methotrexate
Authors: Loizeau Karen , De Brouwer Veerle , Gambonnet Bernadette , Yu Agnès , Renou Jean-Pierre , Van Der Straeten Dominique , Lambert Willy E. , Rébeillé Fabrice , Ravanel Stéphane
Published: October 2008

Control of folate homeostasis is essential to sustain the demand for one-carbon (C1) units that are necessary for major biological functions, including nucleotide synthesis and methylation reactions. In this study, we analyzed the genome-wide and metabolic adaptive response of Arabidopsis (Arabidopsis thaliana) cells to folate depletion induced by the antifolate methotrexate. Drug treatment induced a response typical to xenobiotic stress and important changes in folate content and composition. This resulted in a reduction of cell division and primary energy metabolism that was likely associated with perturbation of nucleotide homeostasis. Through a modification of serine metabolism, folate depletion also induced O-acetylserine accumulation and mimicked sulfur deficiency response. The major adaptive response to folate limitation concerned the composition of the folate pool rather than the intracellular level of cofactors. Thus, no significant change in the expression of genes involved in cofactor synthesis, degradation, or trafficking was observed. However, changes in the distribution of C1 derivative pools and increased expression levels for transcripts coding enzymes manipulating C1 moieties in plastids suggested a reorientation of C1 units toward the synthesis of purine and thymidylate. Also, no genomic or metabolic adaptation was built up to counterbalance the major impairment of the methyl index, which controls the efficiency of methylation reactions in the cell. Together, these data suggested that the metabolic priority of Arabidopsis cells in response to folate limitation was to shuttle the available folate derivatives to the synthesis of nucleotides at the expense of methylation reactions.
Interaction of the WD40 Domain of a Myoinositol Polyphosphate 5-Phosphatase with SnRK1 Links Inositol, Sugar, and Stress Signaling
Authors: Ananieva Elitsa A. , Gillaspy Glenda E. , Ely Amanda , Burnette Ryan N. , Erickson F. Les
Published: October 2008

In plants, myoinositol signaling pathways have been associated with several stress, developmental, and physiological processes, but the regulation of these pathways is largely unknown. In our efforts to better understand myoinositol signaling pathways in plants, we have found that the WD40 repeat region of a myoinositol polyphosphate 5-phosphatase (5PTase13; At1g05630) interacts with the sucrose nonfermenting-1-related kinase (SnRK1.1) in the yeast two-hybrid system and in vitro. Plant SnRK1 proteins (also known as AKIN10/11) have been described as central integrators of sugar, metabolic, stress, and developmental signals. Using mutants defective in 5PTase13, we show that 5PTase13 can act as a regulator of SnRK1 activity and that regulation differs with different nutrient availability. Specifically, we show that under low-nutrient or -sugar conditions, 5PTase13 acts as a positive regulator of SnRK1 activity. In contrast, under severe starvation conditions, 5PTase13 acts as a negative regulator of SnRK1 activity. To delineate the regulatory interaction that occurs between 5PTase13 and SnRK1.1, we used a cell-free degradation assay and found that 5PTase13 is required to reduce the amount of SnRK1.1 targeted for proteasomal destruction under low-nutrient conditions. This regulation most likely involves a 5PTase13-SnRK1.1 interaction within the nucleus, as a 5PTase13:green fluorescent protein was localized to the nucleus. We also show that a loss of function in 5PTase13 leads to nutrient level-dependent reduction of root growth, along with abscisic acid (ABA) and sugar insensitivity. 5ptase13 mutants accumulate less inositol 1,4,5-trisphosphate in response to sugar stress and have alterations in ABA-regulated gene expression, both of which are consistent with the known role of inositol 1,4,5-trisphosphate in ABA-mediated signaling. We propose that by forming a protein complex with SnRK1.1 protein, 5PTase13 plays a regulatory role linking inositol, sugar, and stress signaling.
F-Actin Organization and Pollen Tube Tip Growth inArabidopsisAre Dependent on the Gametophyte-Specific Armadillo Repeat Protein ARO1
Authors: Gebert Marina , Dresselhaus Thomas , Sprunck Stefanie
Published: October 2008

The signal-mediated and spatially controlled assembly and dynamics of actin are crucial for maintaining shape, motility, and tip growth of eukaryotic cells. We report that a novel Armadillo repeat protein in Arabidopsis thaliana, ARMADILLO REPEAT ONLY1 (ARO1), is of fundamental importance for polar growth and F-actin organization in tip-growing pollen tubes. ARO1 is specifically expressed in the vegetative cell of pollen as well as in the egg cell. ARO1-GFP (for green fluorescent protein) fusion proteins accumulate most notably in pollen tube tips and partially colocalize with F-actin in the shank of pollen tubes. ARO1 knockout results in a highly disorganized actin cytoskeleton, growth depolarization, and ultimately tube growth arrest. Tip-localized ARO1-GFP is spatially shifted toward the future site of tip growth, indicating a role of ARO1 in the signaling network controlling tip growth and regulating actin organization. After the pollen tube discharges its contents into the receptive synergid, ARO1-GFP colocalizes with emerging F-actin structures near the site of sperm cell fusion, suggesting additional participation in the mechanism of sperm cell tracking toward the female gametes. The variable localization of ARO1 in the cytoplasm, the nucleus, and at the plasma membrane, however, indicates a multifunctional role like that of β-catenin/Armadillo and the p120 catenins.
Mechanisms of endothelial senescence
Authors: Erusalimsky Jorge D. , Skene Chris
Published: October 2008

When endothelial cells from different vascular beds are grown in culture they show a limited capacity to divide, eventually entering into a permanent and phenotypically distinctive non‐dividing state referred to as ‘replicative senescence’. Replicative senescence is thought to result from progressive shortening of telomeric DNA and consequent telomere dysfunction. More recently, it has been realised that senescence can also be induced by a variety of insults, including those causing intracellular oxidative stress. In this report, we review evidence for the occurrence of endothelial cell senescence in vivo. We will also examine the causes, mechanisms and regulation of this process as they emerge from our studies in cell culture, focusing in particular on the roles of oxidative stress, telomerase, growth factors and nitric oxide.
Sympathetic neurogenic Ca2+ signalling in rat arteries: ATP, noradrenaline and neuropeptide Y
Authors: Wier W. Gil , Zang Wei‐jin , Lamont Christine , Raina Hema
Published: October 2008

The sympathetic nervous system (SNS) plays an essential role in the control of total peripheral vascular resistance by controlling the contraction of small arteries. The SNS also exerts long‐term trophic influences in health and disease; SNS hyperactivity accompanies most forms of human essential hypertension, obesity and heart failure. At their junctions with smooth muscle cells, the peri‐arterial sympathetic nerves release ATP, noradrenaline (NA) and neuropeptide Y (NPY) onto smooth muscle cells. Confocal Ca2+ imaging studies reveal that ATP and NA each produce unique types of postjunctional Ca2+ signals and consequent smooth muscle cell contractions. Neurally released ATP activates postjunctional P2X1 receptors to produce local, non‐propagating Ca2+ transients, termed ‘junctional Ca2+ transients’, or ‘jCaTs’. Neurally released NA binds to α1‐adrenoceptors and can activate Ca2+ waves or more uniform global changes in [Ca2+]. Neurally released NPY does not appear to produce Ca2+ transients directly, but significantly modulates NA‐induced Ca2+ signalling. The neural release of ATP and NA, as judged by postjunctional Ca2+ signals, electrical recording of excitatory junction potentials and carbon fibre amperometry to measure NA, varies markedly with the pattern of nerve activity. This probably reflects both pre‐ and postjunctional mechanisms, which are not yet fully understood. These phenomena, together with different temporal patterns of sympathetic nerve activity in different regional circulations, are probably an important mechanistic basis of the important selective regulation of regional vascular resistance and blood flow by the sympathetic nervous system.
Dexamethasone differentially regulates renal and duodenal calcium‐processing genes in calbindin‐D9k and ‐D28k knockout mice
Authors: Kim Man‐Hee , Lee Geun‐Shik , Jung Eui‐Man , Choi Kyung‐Chul , Oh Goo‐Taeg , Jeung Eui‐Bae
Published: October 2008

Glucocorticoids (GCs) appear to downregulate active calcium‐transporting genes in the duodenum, resulting in GC‐induced calcium‐absorbing disorder. In this study, we examined the effects of GCs on calcium‐processing genes in the duodenum and kidney and the compensatory mechanism in calbindin‐D9k (CaBP‐9k) and calbindin‐D28k (CaBP‐28k) knockout (KO) mice. In the duodenum, we observed compensatory increases in transient receptor potential vanilloid 6 (TRPV6) mRNAs in both calbindin KO mice and CaBP‐9k transcripts in CaBP‐28k KO mice, and their expressions were decreased by addition of a synthetic GC, dexamethasone (Dex, 10 mg kg−1). In addition, the expression of plasma membrane calcium ATPase 1b (PMCA1b) underwent a compensatory increase in CaBP‐9k KO mice, and was blocked by Dex, while the mRNA level of duodenal sodium‐calcium exchanger 1 was not altered by KO status or Dex. The renal transcriptional levels of TRPV5 in CaBP‐9k KO and CaBP‐9k in CaBP‐28k KO mice were upregulated in a compensatory manner, while the TRPV6 gene was downregulated following treatment with Dex in the kidney of CaBP‐28k KO mice. The immunological location of these duodenal proteins as a primary target of Dex‐involved regulation was not altered by Dex or KO status. To elucidate potential mechanism(s) of Dex‐induced compensatory gene expression, the levels of GC receptor (GR), vitamin D receptor (VDR) and parathyroid hormone receptor (PTHR) mRNA was also measured in these tissues. Duodenal VDR transcripts were induced in a compensatory manner in both types of KO mice, and were decreased by Dex. In addition, serum corticosterone levels in both KO mice were lower than in wild‐type mice. In conclusion, these results suggest that duodenal TRPV6 and CaBP‐9k genes appear to be a primary target for GC‐induced calcium‐absorbing disorder, through direct regulation of duodenal VDR transcription.
Can we generate new hypotheses about Dent's disease from gene analysis of a mouse model?
Authors: Guggino Sandra E.
Published: October 2008

In humans, Dent's disease, an X‐linked renal tubular disorder, is characterized by low molecular weight proteinuria, aminoaciduria, glycosuria, hyperphosphaturia, hypercalciuria, nephrolithiasis, progressive renal failure and sometimes rickets or osteomalacia. The aetiology of X‐linked Dent's disease is established to be caused by mutations of the CLCN5 gene. The protein product of this gene is the voltage‐gated chloride–proton exchanger CLC‐5. Previous studies by the Johns Hopkins group (Guggino) and the Hamburg group (Jentsch) have established that the Clcn5 knockout mouse recapitulates the renal attributes of Dent's disease. In order to understand the changes in kidney function that accompany the knockout of the Clcn5 gene, we examined gene expression profiles from dissected proximal segment 1 (S1) and segment 2 (S2) tubules of mouse kidneys. Overall, 725 genes are expressed differentially in the proximal tubules of the Dent Clcn5 knockout mouse model compared with those of control wild‐type mice. A major finding is the change in the cholesterol synthesis pathway. Some interesting changes also occur in genes encoding transport proteins. One of these transport proteins, the sodium bile cotransporter gene, Slc10a2, has transcripts increased by 17‐fold in the Clcn5 knockout mouse. The Clc‐3 protein encoded by Clcn3, a chloride–proton exchanger related to Clc‐5, has a 1.9‐fold increase in transcripts. The Npt2c protein, a proximal tubule sodium phosphate cotransporter encoded by Slc34a3, has a 0.6‐fold decrease in the number of transcripts. The sodium–proton exchanger‐like protein, Nhe10/sperm, encoded by Slc9a10, has a 0.5‐fold decrease in transcript number. These genes are discussed with regard to the possible physiological outcomes of their transcript or protein changes.
Increased temperature and protein oxidation lead to HSP72 mRNA and protein accumulation in the in vivo exercised rat heart
Authors: Staib Jessica L. , Tümer Nihal , Powers Scott K.
Published: October 2008

Expression of myocardial heat shock protein 72 (HSP72), mediated by its transcription factor, heat shock factor 1 (HSF1), increases following exercise. However, the upstream stimuli governing exercise‐induced HSF1 activation and subsequent Hsp72 gene expression in the whole animal remain unclear. Exercise‐induced increases in body temperature may promote myocardial radical production, leading to protein oxidation. Conceivably, myocardial protein oxidation during exercise may serve as an important signal to promote nuclear HSF1 migration and activation of Hsp72 expression. Therefore, these experiments tested the hypothesis that prevention of exercise‐induced increases in body temperature attenuates cardiac protein oxidation, diminishes HSF1 activation and decreases HSP72 expression in vivo. To test this hypothesis, in vivo exercise‐induced changes in body temperature were manipulated by exercising male rats in either cold (4°C) or warm ambient conditions (22°C). Warm exercise increased both body temperature (+3°C) and myocardial protein oxidation, whereas these changes were attenuated by cold exercise. Interestingly, exercise in both conditions did not significantly increase myocardial nuclear localized phosphorylated HSF1. Nonetheless, warm exercise elevated left‐ventricular HSP72 mRNA by ninefold and increased myocardial HSP72 protein levels by threefold compared with cold‐exercised animals. Collectively, these data indicate that elevated body temperature and myocardial protein oxidation promoted exercise‐induced cardiac HSP72 mRNA expression and protein accumulation following in vivo exercise. However, these results suggest that exercise‐induced myocardial HSP72 protein accumulation is not a result of nuclear‐localized, phosphorylated HSF1, indicating that other transcriptional or post‐transcriptional regulatory mechanisms are involved in exercise‐induced HSP72 expression.
Effect of Permeate Drag Force on the Development of a Biofouling Layer in a Pressure-Driven Membrane Separation System
Authors: Eshed L. , Yaron S. , Dosoretz C. G.
Published: October 2008

The effect of permeate flux on the development of a biofouling layer on cross-flow separation membranes was studied by using a bench-scale system consisting of two replicate 100-molecular-weight-cutoff tubular ultrafiltration membrane modules, one that allowed flow of permeate and one that did not (control). The system was inoculated with
Pseudomonas putida
S-12 tagged with a red fluorescent protein and was operated using a laminar flow regimen under sterile conditions with a constant feed of diluted (1:75) Luria-Bertani medium. Biofilm development was studied by using field emission scanning electron microscopy and confocal scanning laser microscopy and was subsequently quantified by image analysis, as well as by determining live counts and by permeate flux monitoring. Biofilm development was highly enhanced in the presence of permeate flow, which resulted in the buildup of complex three-dimensional structures on the membrane. Bacterial transport toward the membrane by permeate drag was found to be a mechanism by which cross-flow filtration contributes to the buildup of a biofouling layer that was more dominant than transport of nutrients. Cellular viability was found to be not essential for transport and adhesion under cross-flow conditions, since the permeate drag overcame the effect of bacterial motility.
Random Mutagenesis Identifies Novel Genes Involved in the Secretion of Antimicrobial, Cell Wall-Lytic Enzymes by
Lactococcus lactis
Authors: Tan Yu Pei , Giffard Philip M. , Barry Daniel G. , Huston Wilhelmina M. , Turner Mark S.
Published: October 2008

Lactococcus lactis
is a gram-positive bacterium that is widely used in the food industry and is therefore desirable as a candidate for the production and secretion of recombinant proteins. Previously, we generated a
L. lactis
strain that expressed and secreted the antimicrobial cell wall-lytic enzyme lysostaphin. To identify lactococcal gene products that affect the production of lysostaphin, we isolated and characterized mutants generated by random transposon mutagenesis that had altered lysostaphin activity. Out of 35,000 mutants screened, only one with no lysostaphin activity was identified, and it was found to contain an insertion in the lysostaphin expression cassette. Ten mutants with higher lysostaphin activity contained insertions in only four different genes, which encode an uncharacterized putative transmembrane protein (llmg_0609) (three mutants), an enzyme catalyzing the first step in peptidoglycan biosynthesis (
murA2
) (five mutants), a putative regulator of peptidoglycan modification (
trmA
) (one mutant), and an uncharacterized enzyme possibly involved in ubiquinone biosynthesis (llmg_2148) (one mutant). These mutants were found to secrete larger amounts of lysostaphin than the control strain (MG1363[
lss
]), and the greatest increase in secretion was 9.8- to 16.1-fold, for the llmg_0609 mutants. The lysostaphin-oversecreting llmg_0609,
murA2
, and
trmA
mutants were also found to secrete larger amounts of another cell wall-lytic enzyme (the
Listeria monocytogenes
bacteriophage endolysin Ply511) than the control strain, indicating that the phenotype is not limited to lysostaphin.
Multilocus Sequence Typing, Pulsed-Field Gel Electrophoresis, and
fla
Short Variable Region Typing of Clonal Complexes of
Campylobacter jejuni
Strains of Human, Bovine, and Poultry Origins in Luxembourg
Authors: Ragimbeau Catherine , Schneider François , Losch Serge , Even Jos , Mossong Joël
Published: October 2008

Campylobacter jejuni
is the most common cause of bacterial gastroenteritis in Luxembourg, with a marked seasonal peak during summer. The majority of these infections are thought to be sporadic, and the relative contribution of potential sources and reservoirs is still poorly understood. We monitored human cases from June to September 2006 (
n
= 124) by molecular characterization of isolates with the aim of rapidly detecting temporally related cases. In addition, isolates from poultry meat (
n
= 36) and cattle cecal contents (
n
= 48) were genotyped for comparison and identification of common clusters between veterinary and human
C. jejuni
populations. A total of 208 isolates were typed by sequencing the
fla
short variable region, macrorestriction analysis resolved by pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). We observed a high diversity of human strains during a given summer season. Poultry and human isolates had a higher diversity of sequence types than isolates of bovine origin, for which clonal complexes CC21 (41.6%) and CC61 (18.7%) were predominant. CC21 was also the most common complex found among human isolates (21.8%). The substantial concordance between PFGE and MLST results for this last group of strains suggests that they are clonally related. Our study indicates that while poultry remains an important source, cattle could be an underestimated reservoir of human
C. jejuni
cases. Transmission mechanisms of cattle-specific strains warrant further investigation.
Metabolic Function of
Corynebacterium glutamicum
Aminotransferases AlaT and AvtA and Impact on
l
-Valine Production
Authors: Marienhagen Jan , Eggeling Lothar
Published: October 2008

Aminotransferases (ATs) interacting with
l
-alanine are the least studied bacterial ATs. Whereas AlaT converts pyruvate to
l
-alanine in a glutamate-dependent reaction, AvtA is able to convert pyruvate to
l
-alanine in an
l
-valine-dependent manner. We show here that the wild type of
Corynebacterium glutamicum
with a deletion of either of the corresponding genes does not exhibit an explicit growth deficiency. However, a double mutant was auxotrophic for
l
-alanine, showing that both ATs can provide
l
-alanine and that they are the only ATs involved. Kinetic studies with isolated enzymes demonstrate that the catalytic efficiency,
k
cat
/
K

m

, of AlaT is higher than 1 order of magnitude in the direction of
l
-alanine formation (3.5 × 10
4
M
−1
s
−1
), but no preference was apparent for AvtA, suggesting that AlaT is the principal
l
-alanine-supplying enzyme. This is in line with the cytosolic
l
-alanine concentration, which is reduced in the exponential growth phase from 95 mM to 18 mM by a deletion of
alaT
, whereas
avtA
deletion decreases the
l
-alanine concentration only to 76 mM. The combined data show that the presence of both ATs has subtle but obvious consequences on balancing intracellular amino acid pools in the wild type. The consequences are more obvious in an
l
-valine production strain where a high intracellular drain-off of the
l
-alanine precursor pyruvate prevails. We therefore used deletion of
alaT
to successfully reduce the contaminating
l
-alanine in extracellular accumulated
l
-valine by 80%.
Genetic Diversity and Abundance of Flavobacterial Proteorhodopsin in China Seas
Authors: Zhao Meiru , Chen Feng , Jiao Nianzhi
Published: October 2008

Proteorhodopsin (PR) genes related toFlavobacteriawere found to be highly diverse in the East and South China seas and displayed a distinct geographic pattern, which appeared to reflect cold versus warm adaptation when Global Oceanic Sampling database metagenomic data were included. Flavobacterial PR genes were more abundant offshore than nearshore, implying that inheritance of the PR gene could be important forFlavobacterialiving in the oligotrophic environment.