bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear magnetohydrodynamic simulation of Tore Supra hollow current profile discharges
Authors: Maget P. , Huysmans G. T. A. , Garbet X. , Ottaviani M. , Lütjens H. , Luciani J.-F.
Published: May 2007

Magnetohydrodynamic (MHD) activity often undermines the realization of fully noninductive plasma discharges in the Tore Supra tokamak [J. Jacquinot, Nucl. Fusion 45, S118 (2005)], by producing large degradation of electron energy confinement in the plasma core and the bifurcation to a regime with permanent MHD activity. The nonlinear evolution of MHD modes in these hollow current density profile discharges is studied with the full-scale three-dimensional MHD code XTOR [K. Lerbinger and J.-F. Luciani, J. Comput. Phys. 97, 444 (1991)] and compared with experimental features. Large confinement degradation is predicted when q(0) is close to 2. This derives either from the full reconnection of an unstable double-tearing mode, or from the coupling between a single tearing mode and adjacent stable modes in a region with reduced magnetic shear.
Calculation of the mean first passage time tested on simple two-dimensional models
Authors: Kalinay Pavol
Published: May 2007

A particle diffusing in a two-dimensional (2D) container, shaped as a simplified configuration space of two passing 2D circular particles in a flat channel, is considered. The mean first passage time through one absorbing boundary is calculated using the one-dimensional Fick-Jacobs equation and its modification; both derived by mapping the 2D diffusion equation onto the longitudinal (“reaction”) coordinate. The obtained results are compared with the hopping time, defined as the inverted lowest eigenvalue of the full 2D problem. The comparison shows that the mapped equations give reliable results, in contrast to predictions of the simplest concept of the transition state theory.
Interstellar dust laser explorer: A new instrument for elemental and isotopic analysis and imaging of interstellar and interplanetary dust
Authors: Henkel Torsten , Tizard Julia , Blagburn David J. , Lyon Ian C.
Published: May 2007

We present the performance characteristics of a time-of-flight secondary ion mass spectrometer designed for 157nm laser postionization of sputtered neutrals for high sensitivity elemental and isotopic analyses. The instrument was built with the aim of analyzing rare element abundances in micron to submicron samples such as interstellar grains and cometary dust. Relative sensitivity factors have been determined for secondary ion mass spectrometry which show an exponential dependency against the first ionization potential. This allows elemental abundances to be measured with errors below 25% for most major elements. The accuracy for isotope ratios, where isotopes can be resolved from isobaric interferences, is usually limited only by counting statistics. In laser secondary neutral mass spectrometry, the spatial and temporal overlaps between the laser and sputtered neutral atoms are modeled and predictions of total detection efficiency and isotopic and elemental fractionation are compared with experimental data. Relative sensitivity factors for laser-ionized secondary neutrals from a stainless steel standard are found to vary less than 3% above saturation laser pulse energy enabling more accurate quantification.
The dielectric virial expansion and the models of dipolar hard-sphere fluid
Authors: Morozov Konstantin I.
Published: May 2007

The virial expansion technique to determine the dielectric constant ϵ of dipolar hard-sphere fluid is developed. It is shown that the formalism allows to bring into agreement the results of Debye’s, Onsager’s, and Langevin’s to the problem. The third virial coefficient of ϵ is considered as a series over dipolar parameter λ=m2∕d3kT. The terms up to O(λ11) are calculated analytically providing a correct description of the third virial coefficient for small and intermediate values of λ (0⩽λ⩽4). The results of the dielectric virial series are compared with the Monte Carlo data for ϵ found by Matyushov and Ladanyi [J. Chem. Phys. 110, 994 (1999)]. The theory is in agreement with simulations only at small values of λ⩽2. At higher polarities, the virial series diverges. Realization of the renormalization procedure permits to enlarge the range of applicability of the virial series. In this way, the new expression for the dielectric constant as a function of two dipolar parameters, λ and y=4πnm2∕9kT, has been found explicitly. The expression gives a perfect upper bound of the dielectric constant and is more reliable for determination of ϵ than the previously known ones.
Phytophthora cinnamomi invasion, a major threatening process to conservation of flora diversity in the South-west Botanical Province of Western Australia
Authors: Shearer B. L. , Crane C. E. , Barrett S. , Cochrane A.
Published: May 2007

The invasive soilborne plant pathogen Phytophthora cinnamomi Rands is a major threatening process in the South-west Botanical Province of Western Australia, an internationally recognised biodiversity hotspot. Comparatively recent introduction of P. cinnamomi into native plant communities of the South-west Botanical Province of Western Australia since the early 1900s has caused great irreversible damage and altered successional change to a wide range of unique, diverse and mainly susceptible plant communities. The cost of P. cinnamomi infestation to community values is illustrated by examination of direct (mortality curves, changes in vegetation cover) and indirect impacts on biodiversity and ecosystem dynamics, the proportion of Threatened Ecological Communities infested, Declared Rare Flora either directly or indirectly threatened by infestation and estimates of the proportion of the native flora of the South-west Botanical Province susceptible to the pathogen. While direct impacts of P. cinnamomi have been poorly documented in the South-west Botanical Province, even less attention has been given to indirect impact where destruction of the habitat by the pathogen affects taxa not directly affected by infection. Current poor understanding and quantification of indirect impacts of P. cinnamomi through habitat destruction results in an underestimation of the true impact of the pathogen on the flora of the South-west Botanical Province. Considerable variation of susceptibility to P. cinnamomi among and within families of threatened flora and responses of taxa within the genus Lambertia show how classification within family and genus are poor predictors of species susceptibility. Within apparently susceptible plant species, individuals are resistant to P. cinnamomi infection. Intra-specific variation in susceptibility can be utilised in the long-term management of threatened flora populations and needs to be a high research priority. Current control strategies for conservation of flora threatened by P. cinnamomi integrate hygiene and ex situ conservation with disease control using fungicide. Application of the fungicide phosphite has proven effective in slowing progress of P. cinnamomi in infested, threatened communities. However, variation in plant species responses to phosphite application is a major factor influencing effective control of P. cinnamomi in native communities. A greater understanding of the mechanisms of action of phosphite in plant species showing different responses to the fungicide may provide options for prescription modification to increase phosphite effectiveness in a range of plant species. The range of responses to P. cinnamomi infection and phosphite application described for Lambertia taxa suggests that the genus would make an ideal model system to elucidate the mechanisms of resistance to P. cinnamomi and the effectiveness of phosphite against the pathogen.
Optimum inclusion and replacement value of boiled Mucuna cochinchinensis for soybean meal in broiler diets
Authors: Ukachukwu S. N.
Published: May 2007

Optimum inclusion level of boiled Mucuna cochinchinensis and its replacement value for soybean meal in both starter and finisher broiler diets were assessed using 400 unsexed 7-day-old broiler chickens in a completely randomised experiment. The boiled Mucuna meal was used to replace soybean protein at five levels (0, 19, 38, 57 and 76%) in isonitrogenous and isocaloric diets. Feeding of the experimental diets lasted 4 weeks in each of the starter and finisher phases. During the last week of each phase, three birds per replicate were selected and used for metabolism (nutrient retention) studies. At the starter phase, only bodyweight and daily weight gain were significantly depressed (P < 0.05) by inclusion levels of 38% and above, whereas bodyweight, daily weight gain, feed conversion ratio and protein efficiency ratio were depressed (P < 0.05) by inclusion levels of 57 and 76% at the finisher phase. At both phases, the inclusion level had a cost sparing effect such that the highest inclusion level resulted in the production of the cheapest diet and lowest cost per unit weight gain. The replacement and inclusion levels produced no significant (P > 0.05) effects on the retention of all the proximate components and energy at both starter and finisher phases. Therefore, on the basis of bodyweight and weight gain, the replacement of soybean protein by boiled M. cochinchinensis at 19 and 38% for starter and finisher phases, respectively, is recommended. These translate to 9.36 and 14.4% inclusion levels of boiled M. cochinchinensis in starter and finisher broiler diets, respectively.
Long-term effects of NPK fertiliser and manure on soil fertility and a sorghum - wheat farming system
Authors: Manna M. C. , Swarup A. , Wanjari R. H. , Ravankar H. N.
Published: May 2007

Yield decline or stagnation under long-term cultivation and its relationship with soil organic matter fractions are rarely considered. To understand this phenomenon, soil organic matter fractions and soil aggregate size distribution were studied in a long-term experiment at Akola, in a Vertisol in a semiarid tropical environment. For 14 years, the following fertiliser treatments were compared with undisturbed fallow plots: unfertilised (control), 100% recommended rates of N, NP, NPK (N : P : K ratios of 100 : 21.8 : 18.2 and 120 : 26.2 : 50 kg/ha for sorghum and wheat, respectively) and 100% NPK plus farmyard manure (FYM) and continuous cropping with a sorghum (Sorghum bicolor L. Moench) and wheat (Triticum aestivum L.) system during 1988–2001. The significant negative yield trend was observed in unbalanced use of inorganic N application for both crops. However, yields were maintained when NPK and NPK + FYM were applied. Results showed that soil organic C and total N in the unfertilised plot decreased by 21.7 and 18.2%, compared to the initial value, at a depth of 0–15 cm. Depletion of large macroaggregates (>2 mm) accounted for 22–81% of the total mass of aggregates in N, NP and unfertilised control plots compared to fallow plots. Irrespective of treatments, small macroaggregates (0.25–2 mm) dominated aggregate size distribution (56–71%), followed by microaggregates (0.053–0.25 mm, 18–37%). Active fractions, such as microbial biomass C, microbial biomass N, hot water soluble C and N, and acid hydrolysable carbohydrates were greater in NPK and NPK + FYM treatments than in the control. Carbon and N mineralisation were greater in small macroaggregates than microaggregates. Particulate organic matter C (POMC) and N (POMN) were significantly correlated (P < 0.01) with water-stable aggregate C and N (0.25–2 mm size classes), respectively. It was further observed that POMC and POMN were significantly greater in NPK and NPK + FYM plots than N and NP treated plots. Microbial biomass C was positively correlated with acid-hydrolysable carbohydrates (r = 0.79, P < 0.05). Continuous cropping and fertiliser use also influenced humic acid C and fulvic acid C fractions of the soil organic matter. Acid-hydrolysable N proportion in humic acid was greater than fulvic acid and it was greatest in NPK + FYM treatments. Continuous application of 100% NPK + FYM could restore soil organic carbon (SOC) to a new equilibrium level much earlier (t = 1/k, 2.4 years) than N (t = 1/k, 25.7 years), NP (t = 1/k, 8.1 years) and NPK (t = 1/k, 5.02 years). In conclusion, integrated use of NPK with FYM would be vital to obtain sustainable yields without deteriorating soil quality.
Temperature and photoperiod effects on the growth and development of opium poppy (Papaver somniferum)
Authors: Lisson S. N.
Published: May 2007

The research described in this paper seeks to address knowledge gaps relating to leaf growth, flowering response to photoperiod and pre-emergent growth for opium poppy (Papaver somniferum), with a view to developing a new decision-support crop model. The pre-emergent growth phases of the commercial morphine cultivar CO58-34 were measured in 10 temperature treatments ranging between 1.5 and 34°C. Linear models fitted to the lag and linear phase growth rate v. temperature plots gave a thermal time duration for the lag phase of 32 degree days and 8.3 degree days per mm of hypocotyl growth for the linear hypocotyl elongation phase. In a second trial, two cultivars (CO58-34 and the thebaine cultivar WF01-1822) were grown in a range of photoperiods spanning 8 to 24 h. Data was also collected on leaf growth attributes. The response to photoperiod was typical for a long day plant. In photoperiods greater than ~18 h, floral initiation occurred in a minimum, constant thermal time. At shorter photoperiods, initiation was progressively delayed. A second plateau in initiation response to photoperiod occurred for daylengths less than ~12 h. The duration of the basic vegetative period was similar for the two cultivars at ~324 degree days from emergence. After an initial delay before the growth of the first fully expanded leaf, leaf appearance rates ranged between 45 and 50 day degrees per leaf. Leaf senescence rates varied between 56 and 84 day degrees per leaf. Leaf area profiles were typically parabolic in nature. Maximum leaf area occurred between nodes 13 and 16 at a value of 12 000–15 000 mm2.
The 'Landcare' approach to soil conservation in the Philippines: an assessment of farm-level impacts
Authors: Cramb R. A. , Catacutan D. , Culasero-Arellano Z. , Mariano K.
Published: May 2007

‘Landcare’ is a group-based approach to the promotion of conservation farming. A case study of the Landcare program in Lantapan in the southern Philippines is presented to assess the farm-level impacts of this approach. The program was successful in promoting the formation of Landcare groups and a municipal Landcare association, resulting in rapid and widespread adoption of conservation practices, particularly among maize farmers. This in turn significantly reduced soil erosion, though the impact on crop yield and income was somewhat delayed. Adoption was thus not motivated primarily by short-term returns but by a concern to reduce soil erosion and provide a basis for diversification into agroforestry.
Seed development in Malva parviflora: onset of germinability, dormancy and desiccation tolerance
Authors: Michael Pippa J. , Steadman Kathryn J. , Plummer Julie A.
Published: May 2007

Seed development was examined in Malva parviflora. The first flower opened 51 days after germination; flowers were tagged on the day that they opened and monitored for 33 days. Seeds were collected at 12 stages during this period and used to determine moisture content, germination of fresh seeds and desiccation tolerance (seeds dried to 10% moisture content followed by germination testing). Seed moisture content decreased as seeds developed, whereas fresh (max. 296 mg) and dry weight (max. 212 mg) increased to peak at 12–15 and ~21 days after flowering (DAF), respectively. Therefore, physiological maturity occurred at 21 DAF, when seed moisture content was 16–21%. Seeds were capable of germinating early in development, reaching a maximum of 63% at 9 DAF, but germination declined as development continued, presumably due to the imposition of physiological dormancy. Physical dormancy developed at or after physiological maturity, once seed moisture content declined below 20%. Seeds were able to tolerate desiccation from 18 DAF; desiccation hastened development of physical dormancy and improved germination. These results provide important information regarding M. parviflora seed development, which will ultimately improve weed control techniques aimed at preventing seed set and further additions to the seed bank.
Screening selected myrtaceous tree species for production of essential oils in northern Queensland
Authors: Doran J. C. , Drinnan J. E. , Macdonell P. F. , Aken K. M.
Published: May 2007

Trials to identify alternative cropping options to Melaleuca alternifolia for northern Queensland essential oil growers were established at Dimbulah and Innot Hot Springs in 2001. Seed sources of Asteromyrtus symphyocarpa (1,8-cineole form), Eucalyptus staigeriana (citral), Melaleuca cajuputi subsp. cajuputi (trans-nerolidol), M. ericifolia (d-linalool), M. quinquenervia (trans-nerolidol and viridiflorol forms) and M. viridiflora (methyl cinnamate) with potential to produce commercial foliar oils were evaluated. Information was gathered on their adaptability, growth and oil yields over 49 months and 52 months (two harvests) from planting at Dimbulah and Innot Hot Springs, respectively. Of the species and chemotypes evaluated, M. quinquenervia showed potential for commercial production of trans-nerolidol, a compound used in perfumery. It had a very high survival rate (96%) and yields could be expected to improve dramatically from the average 100 kg/ha per harvest achieved in these trials with further research into selection of seed source, control of insect damage and breeding for genetic improvement. M. cajuputi subsp. cajuputi gave a similar performance to M. quinquenervia. The rarity of the trans-nerolidol form of this species and remoteness of its natural occurrence are impediments to further planting and research. E. staigeriana, with second harvest yields of ~600 kg/ha, performed exceptionally well on both sites but potential for development is limited by the ready availability of competitively priced E. staigeriana oil produced in South America. Survival of M. ericifolia ranged from 62% to 82% at 32 months (second harvest) at Innot Hot Springs and was deemed a failure at Dimbulah with poor growth and low survival, raising a major question about the suitability of this species for cultivation in the seasonally dry tropics. Planting of this species on a wider scale in northern Queensland cannot be recommended until more is known about factors affecting its survival. A. symphyocarpa and M. viridiflora were too slow-growing to warrant further consideration as potential oil-producing species at this time.
Relative amounts of soluble and insoluble forms of phosphorus and other elements in intraradical hyphae and arbuscules of arbuscular mycorrhizas
Authors: Ryan Megan H. , McCully Margaret E. , Huang Cheng X.
Published: May 2007

Transport of phosphorus (P) into host plants and its release to root cells is an important function of arbuscular mycorrhizal fungi (AMF). However, relatively little is known about the forms and water solubilities of P compounds in specific locations in the intraradical fungal structures. We determined concentrations and solubility of P components in these structures in white clover (Trifolium repens L.). Plants were grown in the field (colonised by indigenous AMF) or in the glasshouse (inoculated with Glomus intraradices). Mycorrhizas were cryo-fixed in liquid nitrogen immediately (control) or after treatments designed to destroy cell membranes and extract solubles. Thirty to 70% of total P in hyphae and 100% in arbuscules was not extracted. The unextracted proportion of P was higher in the inoculated plants suggesting an environmental effect. It is proposed that the large component of non-extractable P in the arbuscules is involved in the tight regulation of inorganic P release to the host cells. In control roots magnesium, potassium and P were present in hyphae in molar ratios 1 : 2 : 4, further evidence that this relationship may be universal for AMF, and that other P-balancing cations are present but undetectable by the analytical technique.
Impact of defoliation frequency on regrowth and carbohydrate metabolism in contrasting varieties of Lolium perenne
Authors: Lasseur Bertrand , Lothier Jérémy , Morvan-Bertrand Annette , Escobar-Guttiérez Abraham , Humphreys Mervyn O. , Prud'homme Marie-Pascale
Published: May 2007

The aims of the study were to gain a better understanding of fructan metabolism regulation during regrowth of Lolium perenne, and to evaluate the role of fructans of remaining tissues as well as carbon assimilation of new leaf tissues in refoliation. Two varieties that contrast for carbohydrate metabolism, Aurora and Perma, were subject to severe and frequent or infrequent defoliations before regrowth. Aurora, which had a greater content of fructans in leaf sheaths than Perma before defoliation, produced more leaf biomass within the 4 days following the first cut. At the end of the regrowth period, Aurora produced more leaf biomass than Perma. Photosynthetic parameters, which were barely affected by defoliation frequency, could not explain these differences. Fructan synthesising activities [sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan:fructan 6G-fructosyltransferase (6G-FFT)], declined after defoliation. In elongating leaf bases, corresponding transcript levels did not decline concomitantly, suggesting a post-transcriptional regulation of expression, while in leaf sheaths the gene expression pattern mostly followed the time-course of the enzyme activities. Regulation of Lp1-SST and Lp6G-FFT gene expression depends, therefore, on the sink–source status of the tissue after defoliation. During the phase of reserve accumulation, fructosyltransferase activities together with corresponding transcripts increased more in frequently defoliated plants than in infrequently defoliated plants.
Nitrogen resorption and protein degradation during leaf senescence in Chenopodium album grown in different light and nitrogen conditions
Authors: Yasumura Yuko , Hikosaka Kouki , Hirose Tadaki
Published: May 2007

The extent of nitrogen (N) resorption and the degradability of different protein pools were examined in senescing leaves of an annual herb, Chenopodium album L., grown in two light and N conditions. Both N resorption efficiency (REFF; the proportion of green-leaf N resorbed) and proficiency (RPROF; the level to which leaf N content is reduced by resorption) varied among different growth conditions. During leaf senescence, the majority of soluble and membrane proteins was degraded in all growth conditions. Structural proteins were also highly degradable, implying that no particular protein pool constitutes a non-retranslocatable N pool in the leaf. Leaf carbon/N ratio affected the timing and duration of senescing processes, but it did not regulate the extent of protein degradation or N resorption. Sink–source relationships for N in the plant exerted a more direct influence, depressing N resorption when N sink strength was weakened in the low-light and high-N condition. N resorption was, however, not enhanced in high-light and low-N plants with the strongest N sinks, possibly because it reached an upper limit at some point. We conclude that a combination of several physiological factors determines the extent of N resorption in different growth conditions.
Growth of Eucalyptus species in a Brown Kandosol, and changes in soil phosphorus fractionation following fertilisation
Authors: Short Terrence A. , Kopittke Peter M. , Mulligan David R. , Menzies Neal W.
Published: May 2007

As observed with many soils, much of the P in the Brown Kandosol soils of Weipa (Australia) is associated with organic matter. However, following bauxite mining, much of this organic matter is either lost due to mineralisation, or is ‘diluted’ by the mixing of the soil profile. Using a sequential P extraction, the partitioning of P following fertiliser application was examined in an ‘undisturbed’ (Surface) soil and a Mixed soil. In addition, the effect of split-P applications on the growth of 2 native Eucalyptus species was examined. Following its addition to the soil, much of the P was converted comparatively rapidly to forms with reduced availability; by the time of the first measurement (4 weeks) only approximately 10% of the added P remained as the readily available AER-P. For the Surface soil, much of this added P was initially converted to organic P (Po) (measured as hydroxide-Po), before progressively moving into the hydroxide-Pi fraction. In comparison, in the mixed soil, competition for P from microbial biomass was lower (due to a lower organic matter content) and the P was rapidly converted to the hydroxide-Pi fraction before moving to unavailable forms (residual P). Although the use of split-P applications was expected to increase plant growth, maximum growth of Eucalyptus tetrodonta and Eucalyptus leptophleba was generally achieved when all P fertiliser was applied in the first few weeks of growth. Indeed, splitting the P application beyond 16 weeks caused a significant reduction in growth.
Field calibration of ThetaProbe (ML2x) and ECHO probe (EC-20) soil water sensors in a Black Vertosol
Authors: Foley J. L. , Harris E.
Published: May 2007

Past studies have shown that soil-specific calibrations are required to attain a higher level of accuracy when measuring soil water content with ThetaProbe and ECHO probe soil water sensors, particularly in swelling clay soils. Both probes were assessed for their capacity to accurately monitor soil water in a deep drainage study on a Black Vertosol. Probes were trialled in situ and calibrated against hand-sampled volumetric measurements. The generic calibrations given by the manufacturers resulted in significant errors in water content estimates for both probes. Using the generic calibration, ECHO probes under-estimated water content by 0.10–0.2 m3/m3, whereas ThetaProbes under-estimated by 0.04 m3/m3 at the wet end and over-estimated by 0.08 m3/m3 at the dry end. The soil-specific calibrations significantly improved the accuracy of both probes. ThetaProbes were chosen for the drainage study. The calibration allowed for accuracy across the full wet–dry range to within 0.001–0.004 m3/m3 of volumetric measurements. ECHO probes were less accurate at the wet end, but still determined soil water content to within 0.02–0.05 m3/m3 of volumetric measurements.
Scattered native trees and soil patterns in grazing land on the Northern Tablelands of New South Wales, Australia
Authors: Wilson Brian R. , Growns Ivor , Lemon John
Published: May 2007

Over large areas of south-eastern Australia, the original cover of native woodland has been extensively cleared or modified, and what remains is often characterised by scattered trees beneath which the ground-storey vegetation is largely grazed or otherwise managed. This study investigated the influence of scattered Blakely’s red gum (Eucalyptus blakelyi) trees on both near-surface and deeper soil layers in temperate grazed pastures on the Northern Tablelands of New South Wales, Australia. A significant canopy effect was observed with elevated soil pH, carbon, and nutrient status inside the tree canopy indicating soil enrichment in a zone around the tree. This effect, however, was largely restricted to the surface (0–0.20 m) soil layers. Chloride concentrations were elevated near to trees but only in the deeper soil layers, suggesting that a modified water use and deep drainage mechanism occurred near the trees. Close to the tree, however, a significant acidification was observed between 0.40–0.60 m depth in the soil, without any obvious depletion in other soil element concentrations. It is concluded that this acidification provides strong evidence in support of a ‘biological pumping’ mechanism that has been proposed elsewhere. Key questions remain as to the management implications of these results, whether the subsurface acidification that was observed is common among native Australian trees, if it might be persistent through time, and if this might be a soil issue that requires management.
Multimerized T cell epitopes protect from experimental autoimmune diabetes by inducing dominant tolerance
Authors: Piaggio Eliane , Mars Lennart T. , Cassan Cécile , Cabarrocas Julie , Hofstätter Maria , Desbois Sabine , Bergereau Emilie , Rötzschke Olaf , Falk Kirsten , Liblau Roland S.
Published: May 2007

Immunotherapy by using multimerized self-peptides has demonstrated a clear protective effect on experimental models of autoimmune diseases. However, the mechanisms involved remain ill-defined. Here we have evaluated the therapeutic efficacy of multimerized self-peptides at the effector phase of autoimmune diabetes and examined their mechanisms of action. Diabetes was induced in rat insulin promoter-hemagglutinin (HA) mice expressing HA in pancreatic β-cells by adoptive transfer of HA
110–119
-specific T helper 1 cells. Complete protection was provided by low doses of the HA 4-mer consisting of four covalently linked linear HA
107–119
peptides.
In vivo
, the 4-mer appeared to act directly on the pathogenic HA-specific T helper 1 cells and indirectly by activation/recruitment of lymphocytes with regulatory properties so that mice became resistant to a second transfer of diabetogenic T cells. This effect was associated with a recruitment of Foxp3
+
CD4 T cells around islets. Moreover, we show that dominant protection from autoimmunity was transferable by spleen cells, and that development of this regulatory population was crucially dependent on the lymphocytes from treated rat insulin promoter-HA mice. Thus, immunotherapy using multimerized epitopes emerges as a promising strategy in view of the current identification of self-epitopes that are major targets of the pathogenic CD4 T cell response in autoimmune diseases.
Structure of the Munc18c/Syntaxin4 N-peptide complex defines universal features of the N-peptide binding mode of Sec1/Munc18 proteins
Authors: Hu Shu-Hong , Latham Catherine F. , Gee Christine L. , James David E. , Martin Jennifer L.
Published: May 2007

Sec1/Munc18 proteins (SM proteins) bind to soluble NSF attachment protein receptors (SNAREs) and play an essential role in membrane fusion. Divergent modes of regulation have been proposed for different SM proteins indicating that they can either promote or inhibit SNARE assembly. This is in part because of discrete modes of binding that have been described for various SM/SNARE complexes. One mode suggests that SM proteins bind only to Syntaxins (Stx) preventing SNARE assembly, whereas in another they facilitate SNARE assembly and bind to SNARE complexes. The mammalian cell surface SM protein Munc18c binds to an N-peptide in Stx4, and this is compatible with its interaction with SNARE complexes. Here we describe the crystal structure of Munc18c in complex with the Stx4 N-peptide. This structure shows remarkable similarity with a yeast complex indicating that the mode of binding, which can accommodate SNARE complexes, is highly conserved throughout evolution. Modeling reveals the presence of the N-peptide binding mode in most but not all yeast and mammalian SM/Stx pairs, suggesting that it has coevolved to fulfill a specific regulatory function. It is unlikely that the N-peptide interaction alone accounts for the specificity in SM/SNARE binding, implicating other contact surfaces in this function. Together with other data, our results support a sequential two-state model for SM/SNARE binding involving an initial interaction via the Stx N-peptide, which somehow facilitates a second, more comprehensive interaction comprising other contact surfaces in both proteins.
Cultural hitchhiking on the wave of advance of beneficial technologies
Authors: Ackland Graeme J. , Signitzer Markus , Stratford Kevin , Cohen Morrel H.
Published: May 2007

The wave-of-advance model was introduced to describe the spread of advantageous genes in a population. It can be adapted to model the uptake of any advantageous technology through a population, such as the arrival of neolithic farmers in Europe, the domestication of the horse, and the development of the wheel, iron tools, political organization, or advanced weaponry. Any trait that preexists alongside the advantageous one could be carried along with it, such as genetics or language, regardless of any intrinsic superiority. Decoupling of the advantageous trait from other “hitchhiking” traits depends on its adoption by the preexisting population. Here, we adopt a similar wave-of-advance model based on food production on a heterogeneous landscape with multiple populations. Two key results arise from geographic inhomogeneity: the “subsistence boundary,” land so poor that the wave of advance is halted, and the temporary “diffusion boundary” where the wave cannot move into poorer areas until its gradient becomes sufficiently large. At diffusion boundaries, farming technology may pass to indigenous people already in those poorer lands, allowing their population to grow and resist encroachment by farmers. Ultimately, this adoption of technology leads to the halt in spread of the hitchhiking trait and establishment of a permanent “cultural boundary” between distinct cultures with equivalent technology.
Evaluation of the Microbiology of Soft-Tissue Abscesses in the Era of Community-Associated Strains of Methicillin-ResistantStaphylococcus aureus: An Argument for Empirical Contact Precautions
Authors: Talbot Thomas R. , Nania Joseph J. , Wright Patty W. , Jones Ian , Aronsky Dominik
Published: May 2007

To ascertain the microbiology of skin abscesses, emergency department records were reviewed to identify patients with debrided skin abscesses. Methicillin-resistantStaphylococcus aureuswas isolated from 255 (67.6%) of 377 culture samples from episodes in the adult cohort and from 145 (79.7%) of 182 culture samples from episodes in the pediatric cohort. Thus, empirical use of contact precautions for patients with skin abscesses should be strongly considered.
Increased Rate of Catheter-Related Bloodstream Infection Associated With Use of a Needleless Mechanical Valve Device at a Long-Term Acute Care Hospital
Authors: Salgado Cassandra D. , Chinnes Libby , Paczesny Tammy H. , Cantey J. Robert
Published: May 2007

Objective.

To determine whether introduction of a needleless mechanical valve device (NMVD) at a long-term acute care hospital was associated with an increased frequency of catheter-related bloodstream infection (BSI).

Design.

For patients with a central venous catheter in place, the catheter-related BSI rate during the 24-month period before introduction of the NMVD, a period in which a needleless split-septum device (NSSD) was being used (hereafter, the NSSD period), was compared with the catheter-related BSI rate during the 24-month period after introduction of the NMVD (hereafter, the NMVD period). The microbiological characteristics of catheter-related BSIs during each period were also compared. Comparisons and calculations of relative risks (RRs) with 95% confidence intervals (CIs) were performed using χ2 analysis.

Results.

Eighty-six catheter-related BSIs (3.86 infections per 1,000 catheter-days) occurred during the study period. The rate of catheter-related BSI during the NMVD period was significantly higher than that during the NSSD period (5.95 vs 1.79 infections per 1,000 catheter-days; RR, 3.32 [95% CI, 2.88–3.83]; P < .001). A significantly greater percentage of catheter-related BSIs during the NMVD period were caused by gram-negative organisms, compared with the percentage recorded during the NSSD period (39.5% vs 8%; P = .007). Among catheter-related BSIs due to gram-positive organisms, the percentage caused by enterococci was significantly greater during the NMVD period, compared with the NSSD period (54.8% vs 13.6%; P = .004). The catheter-related BSI rate remained high during the NMVD period despite several educational sessions regarding proper use of the NMVD.

Conclusions.

An increased catheter-related BSI rate was temporally associated with use of a NMVD at the study hospital, despite several educational sessions regarding proper NMVD use. The current design of the NMVD may be unsafe for use in certain patient populations.
Clinical and Economic Impact of Multidrug Resistance in Nosocomial Acinetobacter baumannii Bacteremia
Authors: Lee Nan-Yao , Lee Hsin-Chun , Ko Nai-Ying , Chang Chia-Ming , Shih Hsin-I , Wu Chi-Jung , Ko Wen-Chien
Published: May 2007

Objective.

To investigate the impact of antimicrobial resistance on clinical and economic outcomes among hospitalized patients with multidrug-resistant (MDR) Acinetobacter baumannii bacteremia.

Design.

A retrospective, matched-cohort study.

Setting.

A tertiary care university teaching hospital

Methods.

A matched case-control (1:1) study was conducted to compare the differences in clinical and economic outcomes of patients with MDR A. baumannii bacteremia and patients with non-MDR A. baumannii bacteremia. Case patients were matched to control patients on the basis of sex, age, severity of underlying and acute illness, and length of hospital stay before onset of bacteremia.

Results.

Forty-six (95.8%) of 48 cases with MDR A. baumannii bacteremia were eligible for the study and matched with appropriate controls. The sepsis-related mortality rate was 34.8% among cases and 13.0% among controls, for an attributable mortality rate of 21.8% (adjusted odds ratio, 4.1 [95% confidence interval, 1.1-15.7]; P = .036). After the onset of bacteremia, cases and controls had a significantly different length of hospital stay (54.2 vs 34.1 days; P = .006), hospitalization cost (US$9,349 vs US$4,865; P = .001 ), and antibiotic therapy cost (US$2,257 vs US$1,610; P = .014). Thus, bacteremia due to MDR A. baumannii resulted in 13.4 days of additional hospitalization and US$3,758 of additional costs, compared with bacteremia due to non-MDR A. baumannii.

Conclusions.

Patients with MDR A. baumannii bacteremia had a higher mortality rate and incurred greater medical costs than patients with non-MDR A. baumannii bacteremia.
Importation ofAcinetobacter baumanniiInto a Burn Unit: A Recurrent Outbreak of Infection Associated With Widespread Environmental Contamination
Authors: Zanetti Giorgio , Blanc Dominique S. , Federli Isabelle , Raffoul Wassim , Petignat Christiane , Maravic Philippe , Francioli Patrick , Berger Mette M.
Published: May 2007

A burn patient was infected withAcinetobacter baumanniion transfer to the hospital after a terrorist attack. Two patients experienced cross-infection. Environmental swab samples were negative forA. baumannii. Six months later, the bacteria reemerged in 6 Patients. Environmental swab samples obtained at this time were inoculated into a minimal mineral broth, and culture results showed widespread contamination. No case of infection occurred after closure of the unit for disinfection.
Colonization With Multidrug-Resistant Organisms in Evacuees After Hurricane Katrina
Authors: Seybold Ulrich , White Nancy , Wang Yun F. , Halvosa J. Sue , Blumberg Henry M.
Published: May 2007

After Hurricane Katrina, 50 patients were evacuated to Grady Memorial Hospital in Atlanta, Georgia, with limited medical records. The infection control department ordered contact precautions for 16 Patients. Surveillance cultures performed on admission identified colonization with multidrug-resistant (MDR) bacteria in 9 patients (18%). Presence of a wound was the strongest predictor for MDR colonization. More data are needed to reliably predict MDR bacterial colonization.
Impact of Bordetella pertussis Exposures on a Massachusetts Tertiary Care Medical System
Authors: Zivna Iva , Bergin Diana , Casavant Joanne , Fontecchio Sally , Nelson Susan , Kelley Anita , Mathis Sandra , Melvin Zita , Erlichman Rosemarie , Ellison Richard T.
Published: May 2007

Objective.

To assess the impact of outbreaks of Bordetella pertussis infection on a tertiary care medical system.

Design.

Retrospective study.

Setting.

Academic tertiary care medical center and affiliated ambulatory care settings.

Subjects.

All patients and healthcare workers (HCWs) who were in close contact with patients with laboratory-confirmed cases of B. pertussis infection from October 1, 2003, through September 30, 2004.

Intervention.

Direct and indirect medical center costs were determined, including low and high estimates of time expended in the evaluation and management of exposed patients and HCWs during outbreak investigations of laboratory-confirmed cases of B. pertussis infection.

Results.

During this period, 20 primary and 3 secondary laboratory-confirmed cases of B. pertussis infection occurred, with 2 primary pertussis cases and 1 secondary case occurring in HCWs. Outbreak investigations prompted screening of 353 medical center employees. Probable or definitive exposure was identified for 296 HCWs, and 287 subsequently received treatment or prophylaxis for B. pertussis infection. Direct medical center costs for treatment and prophylaxis were $13,416 and costs for personnel time were $19,500-$31,190. Indirect medical center costs for time lost from work were $51,300-$52,300. The total cost of these investigations was estimated to be $85,066-$98,456.

Conclusions.

Frequent B. pertussis exposures had a major impact on our facility. Given the impact of exposures on healthcare institutions, routine vaccination for HCWs may be beneficial.
E-Cadherin Inhibits Cell Surface Localization of the Pro-Migratory 5T4 Oncofetal Antigen in Mouse Embryonic Stem Cells
Authors: Spencer Helen L. , Eastham Angela M. , Merry Catherine L.R. , Southgate Thomas D. , Perez-Campo Flor , Soncin Francesca , Ritson Sarah , Kemler Rolf , Stern Peter L. , Ward Christopher M.
Published: May 2007

Epithelial-mesenchymal transition (EMT) events occur during embryonic development and are important for the metastatic spread of epithelial tumors. We show here that spontaneous differentiation of mouse embryonic stem (ES) cells is associated with an E- to N-cadherin switch, up-regulation of E-cadherin repressor molecules (Snail and Slug proteins), gelatinase activity (matrix metalloproteinase [MMP]-2 and -9), and increased cellular motility, all characteristic EMT events. The 5T4 oncofetal antigen, previously shown to be associated with very early ES cell differentiation and altered motility, is also a part of this coordinated process. E- and N-cadherin and 5T4 proteins are independently regulated during ES cell differentiation and are not required for induction of EMT-associated transcripts and proteins, as judged from the study of the respective knockout ES cells. Further, abrogation of E-cadherin–mediated cell–cell contact in undifferentiated ES cells using neutralizing antibody results in a reversible mesenchymal phenotype and actin cytoskeleton rearrangement that is concomitant with translocation of the 5T4 antigen from the cytoplasm to the cell surface in an energy-dependent manner. E-cadherin null ES cells are constitutively cell surface 5T4 positive, and although forced expression of E-cadherin cDNA in these cells is sufficient to restore cell–cell contact, cell surface expression of 5T4 antigen is unchanged. 5T4 and N-cadherin knockout ES cells exhibit significantly decreased motility during EMT, demonstrating a functional role for these proteins in this process. We conclude that E-cadherin protein stabilizes cortical actin cytoskeletal arrangement in ES cells, and this can prevent cell surface localization of the promigratory 5T4 antigen.
Spc24 and Stu2 Promote Spindle Integrity When DNA Replication Is Stalled
Authors: Ma Lina , McQueen Jennifer , Cuschieri Lara , Vogel Jackie , Measday Vivien
Published: May 2007

The kinetochore, a protein complex that links chromosomes to microtubules (MTs), is required to prevent spindle expansion during S phase in budding yeast, but the mechanism of how the kinetochore maintains integrity of the bipolar spindle before mitosis is not well understood. Here, we demonstrate that a mutation of Spc24, a component of the conserved Ndc80 kinetochore complex, causes lethality when cells are exposed to the DNA replication inhibitor hydroxyurea (HU) due to premature spindle expansion and segregation of incompletely replicated DNA. Overexpression of Stu1, a CLASP-related MT-associated protein or a truncated form of the XMAP215 orthologue Stu2 rescues spc24-9 HU lethality and prevents spindle expansion. Truncated Stu2 likely acts in a dominant-negative manner, because overexpression of full-length STU2 does not rescue spc24-9 HU lethality, and spindle expansion in spc24-9 HU-treated cells requires active Stu2. Stu1 and Stu2 localize to the kinetochore early in the cell cycle and Stu2 kinetochore localization depends on Spc24. We propose that mislocalization of Stu2 results in premature spindle expansion in S phase stalled spc24-9 mutants. Identifying factors that restrain spindle expansion upon inhibition of DNA replication is likely applicable to the mechanism by which spindle elongation is regulated during a normal cell cycle.
Cytotoxic Necrotizing Factor 1 Prevents Apoptosis via the Akt/IκB Kinase Pathway: Role of Nuclear Factor-κB and Bcl-2
Authors: Miraglia Alessandro Giamboi , Travaglione Sara , Meschini Stefania , Falzano Loredana , Matarrese Paola , Quaranta Maria Giovanna , Viora Marina , Fiorentini Carla , Fabbri Alessia
Published: May 2007

Cytotoxic necrotizing factor 1 (CNF1) is a protein toxin produced by some pathogenic strains of Escherichia coli that specifically activates Rho, Rac, and Cdc42 GTPases. We previously reported that this toxin prevents the ultraviolet-B–induced apoptosis in epithelial cells, with a mechanism that remained to be defined. In this work, we show that the proteasomal degradation of the Rho GTPase is necessary to achieve cell death protection, because inhibition of Rho degradation abolishes the prosurvival activity of CNF1. We hypothesize that Rho inactivation allows the activity of Rac to become dominant. This in turn leads to stimulation of the phosphoinositide 3-kinase/Akt/IκB kinase/nuclear factor-κB prosurvival pathway and to a remarkable modification in the architecture of the mitochondrial network, mainly consisting in the appearance of elongated and interconnected mitochondria. Importantly, we found that Bcl-2 silencing reduces the ability of CNF1 to protect cells against apoptosis and that it also prevents the CNF1-induced mitochondrial changes. It is worth noting that the ability of a bacterial toxin to induce such a remodeling of the mitochondrial network is herein reported for the first time. The possible pathophysiological relevance of this finding is discussed.
Bsr, a Nuclear-retained RNA with Monoallelic Expression
Authors: Royo Hélène , Basyuk Eugenia , Marty Virginie , Marques Maud , Bertrand Edouard , Cavaillé Jérôme
Published: May 2007

The imprinted Dlk1-Gtl2 and Prader-Willi syndrome (PWS) regions are characterized by a complex noncoding transcription unit spanning arrays of tandemly repeated C/D RNA genes. These noncoding RNAs (ncRNAs) are thought to play an essential but still poorly understood role. To better understand the intracellular fate of these large ncRNAs, fluorescence in situ hybridization was carried out at the rat Dlk1-Gtl2 domain. This locus contains a ∼100-kb-long gene cluster comprising 86 homologous RBII-36 C/D RNA gene copies, all of them intron-encoded within the ncRNA gene Bsr. Here, we demonstrate that the Bsr gene is monoallelically expressed in primary rat embryonic fibroblasts as well as in hypothalamic neurons and yields a large amount of unspliced and spliced RNAs at the transcription site, mostly as elongated RNA signals. Surprisingly, spliced Bsr RNAs released from the transcription site mainly concentrate as numerous, stable nuclear foci that do not colocalize with any known subnuclear structures. On drug treatments, a fraction of Bsr RNA relocalizes to the cytoplasm and associates with stress granules (SGs), but not with P-bodies, pointing to a potential link between SGs and the metabolism of ncRNA. Thus, Bsr might represent a novel type of nuclear-retained transcript.