bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ralstonia solanacearum genes induced during growth in tomato: an inside view of bacterial wilt
Authors: Brown Darby G. , Allen Caitilyn 
Published: September 2004

SummaryThe phytopathogen Ralstonia solanacearum has over 5000 genes, many of which probably facilitate bacterial wilt disease development. Using in vivo expression technology (IVET), we screened a library of 133 200 R. solanacearum strain K60 promoter fusions and isolated ≈ 900 fusions expressed during bacterial growth in tomato plants. Sequence analysis of 307 fusions revealed 153 unique in planta‐expressed (ipx) genes. These genes included seven previously identified virulence genes (pehR, vsrB, vsrD, rpoS, hrcC, pme and gspK) as well as seven additional putative virulence factors. A significant number of ipx genes may reflect adaptation to the host xylem environment; 19.6%ipx genes are predicted to encode proteins with metabolic and/or transport functions, and 9.8%ipx genes encode proteins possibly involved in stress responses. Many ipx genes (18%) encode putative transmembrane proteins. A majority of ipx genes isolated encode proteins of unknown function, and 13% were unique to R. solanacearum. The ipx genes were variably induced in planta; β‐glucuronidase reporter gene expression analysis of a subset of 44 ipx fusions revealed that in planta expression levels were between two‐ and 37‐fold higher than in culture. The expression of many ipx genes was subject to known R. solanacearum virulence regulators. Of 32 fusions tested, 28 were affected by at least one virulence regulator; several fusions were controlled by multiple regulators. Two ipx fusion strains isolated in this screen were reduced in virulence on tomato, indicating that gene(s) important for bacterial wilt pathogenesis were interrupted by the IVET insertion; mutations in other ipx genes are necessary to determine their roles in virulence and in planta growth. Collectively, this profile of ipx genes suggests that in its host, R. solanacearum confronts and overcomes a stressful and nutrient‐poor environment.
Complex spatial distribution and dynamics of an abundant Escherichia coli outer membrane protein, LamB
Authors: Gibbs Karine A. , Isaac Daniel D. , Xu Jun , Hendrix Roger W. , Silhavy Thomas J. , Theriot Julie A. 
Published: September 2004

SummaryAdvanced techniques for observing protein localization in live bacteria show that the distributions are dynamic. For technical reasons, most such techniques have not been applied to outer membrane proteins in Gram‐negative bacteria. We have developed two novel live‐cell imaging techniques to observe the surface distribution of LamB, an abundant integral outer membrane protein in Escherichia coli responsible for maltose uptake and for attachment of bacteriophage lambda. Using fluorescently labelled bacteriophage lambda tails, we quantitatively des‐cribed the spatial distribution and dynamic movement of LamB in the outer membrane. LamB accumulated in spiral patterns. The distribution depended on cell length and changed rapidly. The majority of the protein diffused along spirals extending across the cell body. Tracking single particles, we found that there are two populations of LamB – one shows very restricted diffusion and the other shows greater mobility. The presence of two populations recalls the partitioning of eukaryotic membrane proteins between ‘mobile’ and ‘immobile’ populations. In this study, we have demonstrated that LamB moves along the bacterial surface and that these movements are restricted by an underlying dynamic spiral pattern.
Fungicide activity through activation of a fungal signalling pathway
Authors: Kojima Kaihei , Takano Yoshitaka , Yoshimi Akira , Tanaka Chihiro , Kikuchi Taisei , Okuno Tetsuro 
Published: September 2004

SummaryFungicides generally inhibit enzymatic reactions involved in fungal cellular biosynthesis. Here we report, for the first time, an example of fungicidal effects through hyperactivation of a fungal signal transduction pathway. The OSC1 gene, encoding a MAP kinase (MAPK) related to yeast Hog1, was isolated from the fungal pathogen Colletotrichum lagenarium that causes cucumber anthracnose. The osc1 knockout mutants were sensitive to high osmotic stress and showed increased resistance to the fungicide fludioxonil, indicating that Osc1 is involved in responses to hyperosmotic stress and sensitivity to fludioxonil. The Osc1 MAPK is phosphorylated under high osmotic conditions, indicating activation of Osc1 by high osmotic stress. Importantly, fludioxonil treatment also activates phosphorylation of Osc1, suggesting that improper activation of Osc1 by fludioxonil has negative effects on fungal growth. In the presence of fludioxonil, the wild‐type fungus was not able to infect the host plant because of a failure of appressorium‐mediated penetration, whereas osc1 mutants successfully infected plants. Analysis using a OSC1‐GFP fusion gene indicated that Osc1 is rapidly translocated to the nucleus in appressorial cells after the addition of fludioxonil, suggesting that fludioxonil impairs the function of infection structures by activation of Osc1. Furthermore, fludioxonil activates Hog1‐type MAPKs in the plant pathogenic fungi Cochliobolus heterostrophus and Botrytis cinerea. These results strongly suggest that fludioxonil acts as a fungicide, in part, through activation of the MAPK cascade in fungal pathogens.
Hydraulic responses to height growth in maritime pine trees
Authors: DELZON S. , SARTORE M. , BURLETT R. , DEWAR R. , LOUSTAU D. 
Published: September 2004

ABSTRACTAs trees grow taller, decreased xylem path conductance imposes a major constraint on plant water and carbon balance, and is thus a key factor underlying forest productivity decline with age. The responses of stomatal conductance, leaf area: sapwood area ratio (AL : AS) and soil–leaf water potential gradient (ΔΨS–L) to height growth were investigated in maritime pine trees. Extensive measurements ofin situsap flow, stomatal conductance and (non‐gravitational) needle water potential (L = ΨL − ρwgh) were made during 2 years in a chronosequence of four even‐aged stands, under both wet and dry soil conditions. Under wet soil conditions,Lwas systematically lower in taller trees on account of differences in gravitational potential. In contrast, under dry soil conditions, our measurements clearly showed thatLwas maintained above a minimum threshold value of −2.0 MPa independently of tree height, thus limiting the range of compensatory change in ΔΨS–L. Although a decrease in theAL : ASratio occurred with tree height, this compensation was not sufficient to prevent a decline in leaf‐specific hydraulic conductance,KL(50% lower in 30 m trees than in 10 m trees). An associated decline in stomatal conductance with tree height thus occurred to maintain a balance between water supply and demand. Both the increased investment in non‐productive versus productive tissues (AS : AL) and stomatal closure may have contributed to the observed decrease in tree growth efficiency with increasing tree height (by a factor of three from smallest to tallest trees), although other growth‐limiting responses (e.g. soil nutrient sequestration, increased respiratory costs) cannot be excluded.
Characterization of the Saccharomyces cerevisiae ARG7 Gene Encoding Ornithine Acetyltransferase, An Enzyme also Endowed with Acetylglutamate Synthase Activity
Authors: Crabeel Marjolaine , Abadjieva Agnes , Hilven Pierre , Desimpelaere Joke , Soetens Oriane 
Published: September 2004

We have cloned by functional complementation and characterized the yeast ARG7 gene encoding mitochondrial ornithine acetyltransferase, the enzyme catalyzing the fifth step in arginine biosynthesis. While forming ornithine, this enzyme regenerates acetylglutamate, also produced in the first step by the ARG2‐encoded acetylglutamate synthase. Interestingly, total deletion of the genomic ARG7 ORF resulted in an arginine‐leaky phenotype, indicating that yeast cells possess an alternative route for generating ornithine from acetylornithine.Yeast ornithine acetyltransferase has been purified and characterized previously as a heterodimer of two subunits proposed to derive from a single precursor protein [Liu, Y.‐S., Van Heeswijck R., Hoj, P. & Hoogenraad, N. (1995) Eur. J. Biochem. 228, 291–296]; those authors further suggested that the internal processing of Arg7p, which is a mitochondrial enzyme, might occur in the matrix, while the leader peptide would be of the non‐cleavable‐type. The characterization of the gene (a) establishes that Arg7p is indeed encoded by a single gene, (b) demonstrates the existence of a cleaved mitochondrial prepeptide of eight residues, and (c) shows that the predicted internal processing site is unlike the mitochondrial proteolytic peptidase target sequence.Yeast Arg7p shares between 32–43% identity in pairwise comparisons with the ten analogous bacterial ArgJ enzymes characterized. Among these evolutionarily related enzymes, some but not all appear bifunctional, being able to produce acetylglutamate not only from acetylornithine but also from acetyl‐CoA, thus catalyzing the same reaction as the apparently unrelated acetylglutamate synthase. We have addressed the question of the bifunctionality of the eucaryotic enzyme, showing the overexpressed ARG7 can complement yeast arg2 and Escherichia coli argA mutations (affecting acetylglutamate synthase). Furthermore, Arg7p‐linked acetylglutamate synthase activity was measurable in an assay. The yeast enzyme is thus clearly, albeit modestly, bifunctional.As with several bacterial ornithine acetyltransferases, the activity of Arg7p was practically insensitive to arginine but strongly inhibited by ornithine, which behaved as a competitive inhibitor.
Functional Properties of the Quinol Oxidase from Acidianus ambivalens and the Possible Catalytic Role of its Electron Donor
Authors: Giuffrè Alessandro , Gomes Cláudio M. , Antonini Giovanni , D'itri Emilio , Teixeira Miguel , Brunori Maurizio 
Published: September 2004

The aa3 quinol oxidase has been purified from the thermoacidophilic archaea Acidianus ambivalens as a three‐redox‐centers enzyme. The functional properties of this oxidase both as purified and in its most integral form (i.e. in native membranes and in intact cells) were investigated by stopped‐flow spectrophotometry. The results suggest that the enzyme interacts in vivo with a redox‐active molecule, which favours the electron entry via heme a and provides the fourth electron demanded for catalysis.We observe that the purified enzyme has two hemes with apparent redox potentials 215 ± 20 mV and 415 ± 20 mV at pH 5.4, showing redox‐Bohr effect, and a heme a3‐CuB center with an affinity for carbon monoxide (Ka= 5.7 × 104 M−1 at 35°C) much lower than that reported for the mammalian enzyme (Ka= 4 × 106 M−1 at 20deg;C). The reduction by dithionite is fast and monophasic when the quinol oxidase is in the native membranes, whereas it is slow and biphasic in the purified enzyme (with heme a3 being reduced faster than heme a). The oxygen reaction of the reduced purified enzyme is fast (few milliseconds), but yields an intermediate (likely ferryl) clearly different from the fully oxidized enzyme. In contrast, the same reaction performed in intact cells leads to the fully oxidized enzyme.We postulate that caldariella quinol, the physiological electron donor, is in vivo tightly bound to the enzyme, providing the fourth redox active center lacking in the purified enzyme.
Identification of Stat 5B as a Substrate of the Insulin Receptor
Authors: Sawka‐Verhelle Dominique , Filloux Chantal , Tartare‐Deckert Sophie , Mothe Isabelle , Van Obberghen Emmanuel 
Published: September 2004

We have screened a human placenta library using the yeast two‐hybrid system to identify proteins that interact with the cytoplasmic domain of the insulin receptor. Doing so, we trapped a cDNA clone which encodes the Stat 5B region comprising amino acids 469 to 786. We show that interaction between Stat 5B and the receptor requires a functional insulin‐receptor Kinase, Tyr960 of insulin receptor is implicated in the interaction with Stat 5B, whereas asparagine and proline forming the NPEY960‐motif are not, and Stat 5B mutated at Thr684, a potential phosphorylation site of mitogen‐activated protein Kinase, loses its ability to interact with the insulin receptor. Further, we found that insulin promotes rapid tyrosine phosphorylation of endogenous Stat 5B in 293 EBNA cells overexpressing insulin receptor and in NHIR cells.Taken together, our finding suggest that Stat 5B corresponds to a substrate for the insulin‐receptor Kinase, and this widens the repertoire of insulin‐signaling pathways.
Thermomechanical design in the automotive industry
Authors: THOMAS J. J. , VERGER L. , BIGNONNET A. , CHARKALUK E. 
Published: September 2004

ABSTRACTIn this paper thermomechanical fatigue assessment in the automotive industry is discussed. The design strategy is based upon a consistent approach of the thermomechanical loading, the mechanical constitutive law of the material, the damage parameters and the fatigue strength criteria. The good understanding of these different steps allows one to perform predictive calculations of automotive parts subjected to thermomechanical loading. The main hypotheses and modelling choices are presented and results are illustrated by a series of computations on real 3D structures. Cracked area and lifetime prediction are described in the case of aluminium alloy cylinder heads subjected to transient thermal loadings.
A simple model for the prediction of the fatigue delamination growth of impacted composite panels
Authors: KATERELOS D. G. , PAIPETIS A. , KOSTOPOULOS V. 
Published: September 2004

ABSTRACTThe fatigue behaviour of composite panels that have been subjected to low‐velocity impact was studied. Impacted specimens were tested under compression–compression fatigue. A delamination propagation model based on the derivation of the strain energy release rate was used. The stress distribution around the initially induced delamination was derived analytically. The shape of the delamination was experimentally monitored by c‐scan imaging and is assumed to be an ellipse. The orientation and aspect ratio of the ellipse were used to calculate the corresponding strain energy‐release rates, which were subsequently used to predict the direction of delamination propagation.
A local approach to cleavage fracture in ferritic steels following warm pre‐stressing
Authors: HADIDI‐MOUD S. , MIRZAEE‐SISAN A. , TRUMAN C. E. , SMITH D. J. 
Published: September 2004

ABSTRACTQuantification of the enhancement in cleavage fracture toughness of ferritic steels following warm pre‐stressing has received great interest in light of its significance in the integrity assessment of such structures as pressure vessels. A Beremin type probability distribution model, i.e., a local stress‐based approach to cleavage fracture, has been developed and used for estimating cleavage fracture following prior loading (or warm pre‐stressing, WPS) in two ferritic steels with different geometry configurations. Firstly, the Weibull parameters required to match the experimental scatter in lower shelf toughness of the candidate steels are identified. These parameters are then used in two‐ and three‐dimensional finite element simulations of prior loading on the upper shelf followed by unloading and cooling to lower shelf temperatures (WPS) to determine the probability of failure. Using both isotropic hardening and kinematic hardening material models, the effect of hardening response on the predictions obtained from the suggested approach has been examined. The predictions are consistent with experimental scatter in toughness following WPS and provide a means of determining the importance of the crack tip residual stresses. We demonstrate that for our steels the crack tip residual stress is the pivotal feature in improving the fracture toughness following WPS. Predictions are compared with the available experimental data. The paper finally discusses the results in the context of the non‐uniqueness of the Weibull parameters and investigates the sensitivity of predictions to the Weibull exponent, m, and the relevance of m to the stress triaxiality factor as suggested in the literature.
A new model for describing a stable cyclic stress–strain relationship under non‐proportional loading based on activation state of slip systems
Authors: ITOH T. , KAMEOKA M. , OBATAYA Y. 
Published: September 2004

ABSTRACTThis paper proposes a new simple model for cyclic incremental plasticity based on activation states of slip systems describing stable cyclic stress–strain relationships under non‐proportional loading. In the model, the magnitude and the direction of incremental plastic strain are estimated by (1+αfNP) and Q, respectively. Here, α is the constant related to the dependence of material on additional hardening and fNP the intensity factor expressing the severity of non‐proportional loading. Q is the second‐order tensor describing the activation states of slip systems in polycrystalline metals and is given by the calculation using a virtual specimen. The model was examined by application to the prediction of the stable cyclic stress–strain relationship in extensive non‐proportional low cycle fatigue tests for type 304 stainless steel and 6061 aluminium alloy. The simulated results showed that the model gave a satisfactory prediction of the stable cyclic stress–strain relationship under complex non‐proportional multiaxial loadings for the two materials.
The use of multiaxial fatigue models to predict fretting fatigue life of components subjected to different contact stress fields
Authors: ARAÚJO J. A. , NOWELL D. , VIVACQUA R. C. 
Published: September 2004

ABSTRACTThis work describes the application of multiaxial fatigue criteria based on critical plane and mesoscopic (Dang Van, 1973, Sciences et Techniques de lÁrmement,47, 647—722) approaches to predict the fatigue initiation life of fretted components. To validate the analysis, several tests under closely controlled laboratory conditions are carried out in a Ti‐6Al‐4V alloy. These classical Hertzian tests reveal a size effect where fretting fatigue lives vary with contact size. Experimentally available data for fretting fatigue of an Al‐4Cu alloy are also used to assess the models. Neither the critical plane models nor the mesoscopic criterion considered can account for the effects of different contact stress fields on the initiation life, if the calculation is based only on highly stressed points on the surface. It is shown, however, that satisfactory results can be achieved if high values of the fatigue parameters are sustained over a critical volume.
Plasmolysis induced by toluene in a cyoB mutant of Pseudomonas putida
Authors: Duque Estrella , García Vanina , De La Torre Jesús , Godoy Patricia , Bernal Patricia , Ramos Juan‐Luis 
Published: September 2004

SummaryThe cyoABCDE gene cluster of Pseudomonas putida DOT‐T1E encodes a terminal cytochrome oxidase. A 500‐bp ‘cyoB’ DNA fragment was cloned in pCHESIΩKm and used to generate a cyoB knock‐out mutant in vivo. The mutant strain was not limited in the generation of proton‐motif force, although when grown on minimal medium with glucose or citrate, the CyoB mutant exhibited a slight increase in duplication time with respect to the wild‐type strain. This effect was even more pronounced when toluene was supplied in the gas phase. In consonance with the negative effect of toluene on the growth was the finding that the CyoB mutant was hypersensitive to sudden 0.3% (v/v) toluene shocks, in contrast with the wild‐type strain. This effect was particularly exacerbated in cells that reached the stationary phase. The increased sensitivity to solvents of the CyoB mutant did not appear to be related to the inability of the cells to strengthen the membrane package or to induce the efflux pumps in response to the solvent, but rather to solvent‐induced plasmolysis that may be triggered by wrinkles in the cytoplasmic membrane at the poles of the mutant cells, and invagination of the outer membranes, which eventually lead to cell death.
Promoting Effective Task Interpretation as an Important Work Habit: A Key to Successful Teaching and Learning
Authors: Butler Deborah L. , Cartier Sylvie C. 
Published: September 2004

In this article we argue that to be successful in an academic arena, students must adopt a consistent approach to completing academic work (i.e., a work habit) that includes very carefully interpreting the demands of tasks that are presented to them in schools. To clarify why task interpretation is so critical to student success, and is thus an important instructional objective for teachers, we begin by presenting two vignettes illustrating links between task interpretation and students’ successful engagement in academic work. Then, we take a step back to describe what we mean by academic work and engagement and to explain how and why students’ knowledge about, conceptions of, and interpretations of tasks are so foundational to performance. We also describe how students’ task interpretation breaks down and why such breakdowns often occur. Finally, we close by advancing practical suggestions for teachers regarding how to structure activities, instruction, and evaluation to promote students’ adoption of task interpretation as an important work habit in the pursuit of effective learning. Sally is teaching a ninth grade English class. Her goal is for students to learn how to write various kinds of paragraphs. After showing some examples and talking with the class about the structure of a narrative paragraph, Sally asks the students to write one themselves. She writes the assignment on the chalkboard as she explains it to the class but notices that quite a number of students start talking to each other while her back is turned. As students work on the assignment, Sally circulates around the room. She reexplains the task to some students and reminds others to focus on their work. She notices that many students seem lost and that only a few students are doing a good job of following her very detailed instructions. Amy is an eighth grade student taking science. One day, Amy arrives home with her science textbook and instructions to answer the questions at the end of Chapter 6. Amy sits down, turns her book to the end of the chapter, finds the first question and looks for key words. She then searches for those key words in the chapter to find information relevant to the question. She copies the information word for word onto a piece of paper, then moves onto the remaining questions. When she is challenged by her teacher the next day, who asks if she has answered the questions in her own words, Amy replies that she does not need to understand the information. She shows her teacher how she has received 100% on each of her previous homework assignments, which she completed in the same way.
Tests for Cycling in a Signalling Pathway
Authors: Müller T. G. , Faller D. , Timmer J. , Swameye I. , Sandra O. , Klingmüller U. 
Published: September 2004

SummaryCellular signalling pathways, mediating receptor activity to nuclear gene activation, are generally regarded as feed forward cascades. We analyse measured data of a partially observed signalling pathway and address the question of possible feed-back cycling of involved biochemical components between the nucleus and cytoplasm. First we address the question of cycling in general, starting from basic assumptions about the system. We reformulate the problem as a statistical test leading to likelihood ratio tests under non-standard conditions. We find that the modelling approach without cycling is rejected. Afterwards, to differentiate two different transport mechanisms within the nucleus, we derive the appropriate dynamical models which lead to two systems of ordinary differential equations. To compare both models we apply a statistical testing procedure that is based on bootstrap distributions. We find that one of both transport mechanisms leads to a dynamical model which is rejected whereas the other model is satisfactory.