bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of surface magnetism of Co2Cr0.6Fe0.4Al Heusler alloy films
Authors: Kallmayer M. , Schneider H. , Jakob G. , Elmers H. J. , Kroth K. , Kandpal H. C. , Stumm U. , Cramm S.
Published: February 2006

Element specific magnetization has been determined at the surface and in the bulk of Co2Cr0.6Fe0.4Al Heusler alloy films grown on α-Al2O3 and capped by Al, using x-ray magnetic circular dichroism both in transmission and total electron yield. The magnetic moments for Co and Fe are considerably reduced at the upper surface in comparison to their values in the bulk of the film. The large reduction at room temperature of 17% for thick films averaged along the electron escape depth implies an even larger reduction at the topmost layer which is crucial for spin-dependent transport. The surface magnetization decreases additionally with respect to the bulk value with decreasing film thickness below 20nm.
Length-scale dependence of the step bunch self-organization on patterned vicinal Si(111) surfaces
Authors: Kwon T. , Phaneuf R. J. , Kan H.-C.
Published: February 2006

We use lithographic patterning and high-temperature annealing to investigate the length-scale dependence of self-organization of step bunches on vicinal Si(111) surfaces due to the motion and interference of misorientation-derived straight steps and the circular steps which bound cylindrical pits. Annealing of patterns with small pit diameters produces a rapid relaxation to straight step bunches, while larger structures maintain significant in-plane corrugations for as long as the out-of-plane corrugations persist. This indicates the existence of a characteristic length scale, set by the competition between the Gibbs–Thomson effect and sublimation. Significantly, the eventual relaxation is to nearly uniform step trains indicating that the late stage evolution is dominated by repulsive step-step interactions.
Effects of Trichoderma harzianum on the yield and fruit quality of tomato plants (Lycopersicon esculentum) grown in an unheated greenhouse
Authors: Bal U. , Altintas S.
Published: February 2006

Trichoderma harzianum was applied to seedling growing media (a peat and soil-based mixture or greenhouse soil) at the time of sowing, at transplanting to vials and at planting. The factorial experiment using 2 seedling growing media, 2 cultivars and 4 dosages of T. harzianum at 0 (control), 4 g/m2, 10 g/m2 and 24 g/m2 showed that the Trichoderma dosage had no significant effect on the yield or fruit quality. None of the 3 factor interactions between the criteria studied, that is, total yield, marketable yield, early yield, individual fruit weight, total soluble solids and titratable acidity, were significant except for fruit diameter. The 3 factor combination of Peat × Belleveu F1 × 10 g/m2 resulted in the highest total yield, marketable yield and early yield with 1552, 1373 and 681 g/plant, respectively. The interaction between media and cultivars was significant for all the yield characteristics studied. However, the main effect of T. harzianum on early yield was the highest at 4 g/m2, producing 527 g/plant in comparison to the control with 374 g/plant. It was, therefore, hypothesised that the positive effect of T. harzianum, observed in the early yield, may be extended to the whole growing period by further applications, that is, by periodical renewal of the T. harzianum population at the root zone.
Effects of soil properties on variation in growth, grain yield and nutrient concentration of wheat and barley
Authors: McDonald G. K.
Published: February 2006

High spatial and temporal variability is an inherent feature of dryland cereal crops over much of the southern cereal zone. The potential limitations to crop growth and yield of the chemical properties of the subsoils in the region have been long recognised, but there is still an incomplete understanding of the relative importance of different traits and how they interact to affect grain yield. Measurements were taken in a paddock at the Minnipa Agriculture Centre, Upper Eyre Peninsula, South Australia, to describe the effects of properties in the topsoil and subsoil on plant dry matter production, grain yield and plant nutrient concentrations in two consecutive years. Wheat (Triticum aestivum L. cv. Worrakatta) was grown in the first year and barley (Hordeum vulgare L. cv. Barque) in the second.
All soil properties except pH showed a high degree of spatial variability. Variability in plant nutrient concentration, plant growth and grain yield was also high, but less than that of most of the soil properties. Variation in grain yield was more closely related to variation in dry matter at maturity and in harvest index than to dry matter production at tillering and anthesis.
Soil properties had a stronger relationship with dry matter production and grain yield in 1999, the drier of the two years. Colwell phosphorus concentration in the topsoil (0–0.15 m) was positively correlated with dry matter production at tillering but was not related to dry matter production at anthesis or with grain yield. Subsoil pH, extractable boron concentration and electrical conductivity (EC) were closely related. The importance of EC and soil extractable boron to grain yield variation increased with depth, but EC had a greater influence than the other soil properties. In a year with above-average rainfall, very little of the variation in yield could be described by any of the measured soil variables. The results suggest that variation in EC was more important to describing variation in yield than variation in pH, extractable boron or other chemical properties.
Wool production and quality of three strains of Merino in a semi-arid environment under different grazing strategies
Authors: Friend M. A. , Robards G. E.
Published: February 2006

Three strains of Merino wethers (strong, medium and fine wool; n = 30 each; 3 years old) were grazed under 3 different management regimes (10 from each strain) in a semi-arid environment to test the hypothesis that attempting to keep liveweight stable at upper and lower levels would improve staple strength relative to sheep in which no attempt was made to limit liveweight fluctuations, and that strength and wool colour would not differ between strains. Sheep in the low grazing regime were managed in an attempt to keep liveweight stable at a level below that of sheep in the high grazing regime, which were managed in an attempt to keep liveweight stable at a level higher than sheep in the low grazing regime. For the control group, no attempt was made to limit liveweight fluctuations through grazing management. Sheep in the high grazing regime had greater liveweights throughout the experiment than sheep in the low grazing regime, while the liveweight of sheep in the control group was usually intermediate. Staple strength did not differ significantly between the strains, but was greater (P<0.05) for sheep in the high grazing regime (58.3 ± 2.2 N/ktex) than for sheep in the control (39.0 ± 2.3 N/ktex) and low (33.8 ± 2.3 N/ktex) grazing regimes, which did not differ significantly from each other. Wool yellowness was not affected by grazing regime, but was lower (P<0.05) in fine wool sheep (1.0 ± 0.1%) than medium wool sheep (1.4 ± 0.1%), which, in turn, was less (P<0.05) than in strong wool sheep (1.7 ± 0.1%). Staple strength was significantly (P<0.05) correlated with mean liveweight (0.27), mean fibre diameter (0.25), minimum fibre diameter (0.36), coefficient of variation of fibre diameter (–0.50), coefficient of variation of diameter along fibres (–0.48) and between fibres (–0.41). The results indicate staple strength was not adversely affected by the choice of strain in a semi-arid environment, and that nutritional management to limit fibre diameter variability can be an effective strategy to improve staple strength, regardless of strain.
Subsoil constraints to grain production in the cropping soils of the north-eastern region of Australia: an overview
Authors: Dang Y. P. , Dalal R. C. , Routley R. , Schwenke G. D. , Daniells I.
Published: February 2006

In dryland agricultural systems of the subtropical, semi-arid region of north-eastern Australia, water is the most limiting resource. Crop productivity depends on the efficient use of rainfall and available water stored in the soil during fallow. Agronomic management practices including a period of fallow, stubble retention, and reduced tillage enhance reserves of soil water. However, access to stored water in these soils may be restricted by the presence of growth-limiting conditions in the rooting zone of the crop. These have been termed as subsoil constraints. Subsoil constraints may include compacted or gravel layers (physical), sodicity, salinity, acidity, nutrient deficiencies, presence of toxic elements (chemical) and low microbial activity (biological). Several of these constraints may occur together in some soils.
Farmers have often not been able to obtain the potential yield determined by their prevailing climatic conditions in the marginal rainfall areas of the northern grains region. In the past, the adoption of soil management practices had been largely restricted to the top 100 mm soil layer. Exploitation of the subsoil as a source of water and nutrients has largely been overlooked. The key towards realising potential yields would be to gain better understanding of subsoils and their limitations, then develop options to manage them practically and economically. Due to the complex nature of the causal factors of these constraints, efforts are required for a combination of management approaches rather than individual options, with the aim to combat these constraints for sustainable crop production, managing natural resources and avoiding environmental damage.
Mineral nitrogen supply from pastures to cereals in three northern Victorian environments
Authors: Harris R. H. , Unkovich M. J. , Humphris J.
Published: February 2006

An experiment at 3 sites (Birchip, Elmore and Speed) in the northern Victorian cropping belt compared dry matter (DM) production of short-term (2 year) pastures and their contributions to soil mineral nitrogen (N) and subsequent wheat and barley production. The pastures included different varieties of subterranean clover, annual medic and lucerne, and these were compared with ryegrass-dominant pasture, which represented the experimental control.
More productive legume pastures generally resulted in greater accumulation of soil mineral N at sowing of the following cereal at both Elmore and Speed; however, at Birchip, soil mineral N remained high under all treatments. At Elmore and Speed, significant (P<0.10) positive relationships were observed between available N at sowing and subsequent wheat and barley production. Cereal grain yield at Birchip was not associated with available N at sowing.
The quantities of soil mineral N available at sowing (152 kg/ha) of the cereals were in excess of crop demand at Birchip. At Elmore, the soil mineral N supply (83 kg/ha) was below that required for wheat and barley to reach their water-limited potential yield (20 kg grain/mm of growing season rainfall). However, at Speed, the supply of soil mineral N (63 kg/ha) was sufficient to achieve the water-limited potential grain yield and to produce malting-grade barley, but not sufficient to elevate wheat grain protein concentrations above 11.5%.
In environments with low soil N levels, the amount of residual N following short-term pastures increased the availability of N to following cereals. Whether this is sufficient to satisfy subsequent crop demand is largely determined by water availability in the year of cropping. In cases where available N is already high, short-term pasture phases may have little effect on increasing crop production.
Growth and yield responses of apricot (cv. Moorpark) to soil-applied nitrogen
Authors: Rettke M. A. , Pitt T. R. , Maier N. A. , Jones J. A.
Published: February 2006

The effect of soil-applied nitrogen on the growth and yield of 12-year-old apricot Prunus armeniaca cultivar Moorpark trees growing on an orthic Tenosol in the Riverland region of South Australia was studied over 3 years. The experiment was set up in a randomised complete block design with 6 annual rates of nitrogen (0, 250, 500, 750, 1000 and 1250 g/tree.year) applied in the form of ammonium nitrate. Application was split into 30% at budburst, 30% 6 weeks after budburst and 40% after harvest. Growth in trunk circumference was significantly greater at 750 and 1000 g/tree.year than at the other rates of nitrogen. In years 1 and 2, the weight of water shoot growth removed at pruning was significantly higher at nitrogen rates of 750–1250 g/tree.year than from trees that received no nitrogen. It is suggested that for Moorpark apricots growing on an orthic Tenosol, applying nitrogen at rates of 750 g/tree.year and above produces levels of water shoot growth that are undesirable for tree management. Nitrogen application resulted in darker and more vivid green leaves as measured with a Minolta Chroma Meter. Concentration of nitrogen in mid-shoot leaves was increased with increase in applied nitrogen. Fruit size was significantly increased by applied nitrogen in year 1, but fruit size was not significantly affected in years 2 and 3. Nitrogen application increased fruit set in the second and third year. Yield of fresh fruit was not significantly affected in the first year, but was in subsequent years with the maximum yield obtained at a rate of 1000 g/tree.year of nitrogen in both years. Yield of dried fruit followed similar trends to that of fresh fruit. Fruit maturation was delayed by 4 to 8 days by nitrogen application. After 3 years, applying nitrogen at 1250 g/tree.year the pH of soil in the top 15 cm was 4.7 compared with 6.7 where no nitrogen was applied.
Genotypic variation in metribuzin tolerance in narrow-leafed lupin (Lupinus angustifolius L.)
Authors: Si P. , Sweetingham M. W. , Buirchell B. J. , Bowran D. G. , Piper T.
Published: February 2006

Tolerance to metribuzin herbicide is an essential agronomic trait for narrow-leafed lupin (L. angustifolius L.) grown in Western Australia (WA), however, metribuzin causes up to 30% yield loss in cv. Tanjil. Tanjil is widely used as a parent in the WA lupin breeding programme to provide anthracnose resistance. Hence, identification of genotypes tolerant to metribuzin and incorporation of this tolerance into the disease-resistant cultivar is necessary for maintaining lupin production. This study identified tolerance to metribuzin among lupin cultivars and advanced breeding lines under both controlled temperature and natural winter conditions. Differences in dose responses between cultivars revealed that cv. Gungurru was tolerant and cv. Tanjil susceptible to metribuzin. Gungurru seedlings survived metribuzin applications of up to 1600 g/ha, whereas Tanjil seedlings exhibited zero survival at 800 g/ha. The rate of herbicide application that caused a 50% growth reduction (GR50, excluding dead plants) for Gungurru was 2 times greater than that for Tanjil. The level of tolerance in Gungurru is adequate to protect plants against metribuzin damage in the field. Large and consistent differences in tolerance between genotypes were identified among cultivars and advanced breeding lines across controlled temperatures (20°C during the day and 12°C at night) and in natural winter conditions. One breeding line (95L208–13–13) showed marginally better tolerance than Gungurru. A number of advanced breeding lines were as susceptible to metribuzin as Tanjil, indicating that it is very important to select for metribuzin tolerance concurrently with disease resistance in the breeding programme. Of the 6 measures of tolerance used in this study, leaf score proved to be the simplest and most effective measure and could be used for the selection of individual tolerant plants in segregating populations. Tolerance was independent of early vigour, suggesting that it is possible to combine both early vigour and tolerance into a cultivar for better weed management. In conclusion, breeding for metribuzin tolerance in lupin is feasible, and the screening method tested here was simple and consistent, which would assist a breeding programme in making rapid progress towards herbicide-tolerant plants.
The interactive effects of phosphorus, sulfur and cultivar on the early growth and condensed tannin content of greater lotus (Lotus uliginosus) and birdsfoot trefoil (L. corniculatus)
Authors: Kelman W. M.
Published: February 2006

Although soil phosphorus and sulfur influence the establishment and condensed tannin (CT) content of perennial Lotus species, previous field responses to superphosphate fertiliser applications have been confounded by moisture stress and weed competition, and the association of CT content with soil fertility has not been consistent between sites and species. In a glasshouse experiment, 2 cultivars of L. uliginosus (Grasslands Maku and Sharnae) and 1 cultivar of L. corniculatus (Grasslands Goldie) were grown in sand culture under 3 levels of phosphorus (0.1, 0.2 and 0.7 mmol/L) and 3 levels of sulfur (2.6, 6.4 and 92.4 mmol/L), applied as nutrient solutions, to examine the interaction of cultivar, phosphorus and sulfur on dry weight, CT content and mineral nutrient concentrations. Dry weight of the Lotus cultivars 68 days after sowing was significantly increased by increasing levels of phosphorus and sulfur, and there was a significant phosphorus × sulfur interaction, characterised by a much smaller response to increasing phosphorus at low levels of sulfur compared with the response at intermediate and high levels. Results indicated that positive responses to superphosphate applications at establishment can be expected if weed competition is controlled and that both soil phosphorus and sulfur should be monitored in order to predict responses to superphosphate applications at sowing. In L. corniculatus cv. Grasslands Goldie, low levels of CT were maintained at increasing phosphorus and sulfur treatment levels, whereas the CT content of the L. uliginosus cultivars increased with increasing levels of phosphorus and sulfur and was positively correlated with dry weight accumulation. This result, allied to measurements of CT in grazed swards, suggests that a management strategy of frequent cutting or grazing during the active growth phase will maintain optimal CT levels for grazing in L. uliginosus cultivars.
Genetic alternatives to mulesing and tail docking in sheep: a review
Authors: James P. J.
Published: February 2006

A genetic solution to breech strike control is attractive, as it is potentially permanent, cumulative, would not involve increased use of chemicals and may ultimately reduce labour inputs. There appears to be significant opportunity to reduce the susceptibility of Merinos to breech strike by genetic means although it is unlikely that in the short term breeding alone will be able to confer the degree of protection provided by mulesing and tail docking. Breeding programmes that aim to replace surgical techniques of flystrike prevention could potentially: reduce breech wrinkle; increase the area of bare skin in the perineal area; reduce tail length and wool cover on and near the tail; increase shedding of breech wool; reduce susceptibility to internal parasites and diarrhoea; and increase immunological resistance to flystrike. The likely effectiveness of these approaches is reviewed and assessed here. Any breeding programme that seeks to replace surgical mulesing and tail docking will need to make sheep sufficiently resistant that the increased requirement for other strike management procedures remains within practically acceptable bounds and that levels of strike can be contained to ethically acceptable levels.
RETRACTED: Flexible bilayers with spontaneous curvature lead to lamellar gels and spontaneous vesicles
Authors: Coldren Bret A. , Warriner Heidi , van Zanten Ryan , Zasadzinski Joseph A. , Sirota Eric B.
Published: February 2006

Mixtures of cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzene sulfonate (SDBS) in water form a fluid lamellar phase at ≤40 wt % water but surprisingly turn into viscous gels at higher water fractions. The gels are characterized by spherulite and other bilayer defects consistent with a low bending elasticity, κ ∼
k
B
T
, and a nonzero spontaneous curvature. Caillé analysis of the small-angle x-ray line shape confirms that for 7:3 wt:wt CTAT:SDBS bilayers at 50% water, κ = 0.62 ± 0.09
k
B
T
and κ̄ = −0.9 ± 0.2
k
B
T
. For 13:7 wt:wt CTAT:SDBS bilayers, the measured bending elasticity decreases with increasing water dilution in good agreement with predictions based on renormalization theory, giving κ
o
= 0.28
k
B
T
. These results show that surfactant mixing is sufficient to make κ ∼
k
B
T
, which promotes strong, Helfrich-type repulsion between bilayers that can dominate the van der Waals attraction. These are necessary conditions for spontaneous vesicles formed at even higher water fractions to be equilibrium structures.
In search of rat stem Leydig cells: Identification, isolation, and lineage-specific development
Authors: Ge Ren-Shan , Dong Qiang , Sottas Chantal M. , Papadopoulos Vassilios , Zirkin Barry R. , Hardy Matthew P.
Published: February 2006

Leydig cells (LCs) are thought to differentiate from spindle-shaped precursor cells that exhibit some aspects of differentiated function, including 3β-hydroxysteroid dehydrogenase (3βHSD) activity. The precursor cells ultimately derive from undifferentiated stem LCs (SLCs), which are postulated to be present in testes before the onset of precursor cell differentiation. We searched for cells in the neonatal rat testis with the abilities to: (
i
) proliferate and expand indefinitely
in vitro
(self renew); (
ii
) differentiate (i.e., 3βHSD and ultimately synthesize testosterone); and (
iii
) when transplanted into host rat testes, colonize the interstitium and subsequently differentiate
in vivo
. At 1 week postpartum, spindle-shaped cells were seen in the testicular interstitium that differed from the precursor cells in that they were 3βHSD-negative, luteinizing hormone (LH) receptor (LHR)-negative, and platelet-derived growth factor receptor α (PDGFRα)-positive. These cells were purified from the testes of 1-week-old rats. The cells contained proteins known to be involved in LC development, including GATA4, c-kit receptor, and leukemia inhibitory factor receptor. The putative SLCs expanded over the course of 6 months while remaining undifferentiated. When treated in media that contained thyroid hormone, insulin-like growth factor I, and LH, 40% of the putative SLCs came to express 3βHSD and to synthesize testosterone. When transplanted into host rat testes from which LCs had been eliminated, the putative SLCs colonized the interstitium and subsequently expressed 3βHSD, demonstrating their ability to differentiate
in vivo
. We conclude that these cells are likely to be the sought-after SLCs.
Molecular structure of EmbR, a response element of Ser/Thr kinase signaling in
Mycobacterium
tuberculosis
Authors: Alderwick Luke J. , Molle Virginie , Kremer Laurent , Cozzone Alain J. , Dafforn Timothy R. , Besra Gurdyal S. , Fütterer Klaus
Published: February 2006

Ser/Thr phosphorylation has emerged as a critical regulatory mechanism in a number of bacteria, including
Mycobacterium tuberculosis
. This problematic pathogen encodes 11 eukaryotic-like Ser/Thr kinases, yet few substrates or signaling targets have been characterized. Here, we report the structure of EmbR (2.0 Å), a putative transcriptional regulator of key arabinosyltransferases (EmbC, -A, and -B), and an endogenous substrate of the Ser/Thr-kinase PknH. EmbR presents a unique domain architecture: the N-terminal winged-helix DNA-binding domain forms an extensive interface with the all-helical central bacterial transcriptional activation domain and is positioned adjacent to the regulatory C-terminal forkhead-associated (FHA) domain, which mediates binding to a Thr-phosphorylated site in PknH. The structure in complex with a phospho-peptide (1.9 Å) reveals a conserved mode of phospho-threonine recognition by the FHA domain and evidence for specific recognition of the cognate kinase. The present structures suggest hypotheses as to how EmbR might propagate the phospho-relay signal from its cognate kinase, while serving as a template for the structurally uncharacterized
Streptomyces
antibiotic regulatory protein family of transcription factors.
Buffering of crucial functions by paleologous duplicated genes may contribute cyclicality to angiosperm genome duplication
Authors: Chapman Brad A. , Bowers John E. , Feltus Frank A. , Paterson Andrew H.
Published: February 2006

Genome duplication followed by massive gene loss has permanently shaped the genomes of many higher eukaryotes, particularly angiosperms. It has long been believed that a primary advantage of genome duplication is the opportunity for the evolution of genes with new functions by modification of duplicated genes. If so, then patterns of genetic diversity among strains within taxa might reveal footprints of selection that are consistent with this advantage. Contrary to classical predictions that duplicated genes may be relatively free to acquire unique functionality, we find among both
Arabidopsis
ecotypes and
Oryza
subspecies that SNPs encode less radical amino acid changes in genes for which there exists a duplicated copy at a “paleologous” locus than in “singleton” genes. Preferential retention of duplicated genes encoding long complex proteins and their unexpectedly slow divergence (perhaps because of homogenization) suggest that a primary advantage of retaining duplicated paleologs may be the buffering of crucial functions. Functional buffering and functional divergence may represent extremes in the spectrum of duplicated gene fates. Functional buffering may be especially important during “genomic turmoil” immediately after genome duplication but continues to act ≈60 million years later, and its gradual deterioration may contribute cyclicality to genome duplication in some lineages.
Type III effector AvrPtoB requires intrinsic E3 ubiquitin ligase activity to suppress plant cell death and immunity
Authors: Abramovitch Robert B. , Janjusevic Radmila , Stebbins C. Erec , Martin Gregory B.
Published: February 2006

Microbial pathogens of both plants and animals employ virulence factors that suppress the host immune response. The tomato pathogen
Pseudomonas syringae
injects the AvrPtoB type III effector protein into the plant cell to suppress programmed cell death (PCD) associated with plant immunity. AvrPtoB also inhibits PCD in yeast, indicating that AvrPtoB manipulates a conserved component of eukaryotic PCD. To identify host targets of AvrPtoB, we performed a yeast two-hybrid screen and identified tomato ubiquitin (Ub) as a strong AvrPtoB interactor. AvrPtoB is ubiquitinated
in vitro
and exhibits E3 Ub ligase activity in the presence of recombinant E1 activating enzyme and specific E2 Ub-conjugating enzymes. The C terminus of AvrPtoB is sufficient for both anti-PCD and E3 Ub ligase activities, suggesting the two functions are associated. Indeed, mutation of AvrPtoB lysine residues in the C terminus, between K512 and K529, disrupts AvrPtoB–Ub interactions, decreases AvrPtoB-mediated anti-PCD activity, and abrogates
P. syringae
pathogenesis of susceptible tomato plants. Remarkably, quantitative decreases in AvrPtoB anti-PCD activity are correlated with decreases in AvrPtoB ubiquitination and E3 Ub ligase activity. Overall, these data reveal a unique bacterial pathogenesis strategy, where AvrPtoB manipulates the host Ub system and requires intrinsic E3 Ub ligase activity to suppress plant immunity.
Direct structural observation of a molecular junction by high-energy x-ray reflectometry
Authors: Lefenfeld Michael , Baumert Julian , Sloutskin Eli , Kuzmenko Ivan , Pershan Peter , Deutsch Moshe , Nuckolls Colin , Ocko Benjamin M.
Published: February 2006

We report a direct angstrom resolution measurement of the structure of a molecular-size electronic junction comprising a single (or a double) layer of alkyl-thiol and alkyl-silane molecules at the buried interface between solid silicon and liquid mercury. The high-energy synchrotron x-ray measurements reveal densely packed layers comprising roughly interface-normal molecules. The monolayer’s thickness is found to be 3–4 Å larger than that of similar layers at the free surfaces of both mercury and silicon. The origins of this and the other unusual features detected are discussed in this article. Measurements of the bilayer junction with an applied potential did not show visible changes in the surface normal structure.
Protein tyrosine phosphatase 1B negatively regulates macrophage development through CSF-1 signaling
Authors: Heinonen Krista M. , Dubé Nadia , Bourdeau Annie , Lapp Wayne S. , Tremblay Michel L.
Published: February 2006

Protein tyrosine phosphatase 1B (PTP-1B) is a ubiquitously expressed cytosolic phosphatase with the ability to dephosphorylate JAK2 and TYK2, and thereby down-regulate cytokine receptor signaling. Furthermore, PTP-1B levels are up-regulated in certain chronic myelogenous leukemia patients, which points to a potential role for PTP-1B in myeloid development. The results presented here show that the absence of PTP-1B affects murine myelopoiesis by modifying the ratio of monocytes to granulocytesin vivo. This bias toward monocytic development is at least in part due to a decreased threshold of response to CSF-1, because the PTP-1B −/− bone marrow presents no abnormalities at the granulocyte–monocyte progenitor level but produces significantly more monocytic colonies in the presence of CSF-1. This phenomenon is not due to an increase in receptor levels but rather to enhanced phosphorylation of the activation loop tyrosine. PTP-1B −/− cells display increased inflammatory activityin vitroandin vivothrough the constitutive up-regulation of activation markers as well as increased sensitivity to endotoxin. Collectively, our data indicate that PTP-1B is an important modulator of myeloid differentiation and macrophage activationin vivoand provide a demonstration of a physiological role for PTP-1B in immune regulation.
Effect of protein kinase A on accumulation of brefeldin A-inhibited guanine nucleotide-exchange protein 1 (BIG1) in HepG2 cell nuclei
Authors: Citterio Carmen , Jones Heather D. , Pacheco-Rodriguez Gustavo , Islam Aminul , Moss Joel , Vaughan Martha
Published: February 2006

Brefeldin A-inhibited guanine nucleotide-exchange proteins, BIG1 and BIG2, are activators of ADP-ribosylation factor GTPases that are essential for regulating vesicular traffic among intracellular organelles. Biochemical analyses and immunofluorescence microscopy demonstrated BIG1 in nuclei as well as membranes and cytosol of serum-starved HepG2 cells. Within 20 min after addition of 8-Br-cAMP, BIG1 accumulated in nuclei, and this effect was blocked by protein kinase A (PKA) inhibitors H-89 and PKI, suggesting a dependence on PKA-catalyzed phosphorylation. BIG2 localization was not altered by cAMP, nor did BIG2 small interfering RNA influence nuclear accumulation of BIG1 induced by cAMP. Mutant BIG1 (S883A) in which Ala replaced Ser-883, a putative PKA phosphorylation site, did not move to the nucleus with cAMP addition, whereas replacement with Asp (S883D) resulted in nuclear accumulation of BIG1 without or with cAMP exposure, consistent with the mechanistic importance of a negative charge at that site. Mutation (712KPK714) of the nuclear localization signal inhibited BIG1 accumulation in nuclei, and PKA-catalyzed phosphorylation of S883, although necessary, was not sufficient for nuclear accumulation, as shown by the double mutation S883D/nuclear localization signal. A role for microtubules in cAMP-induced translocation of BIG1 is inferred from its inhibition by nocodazole. Thus, two more critical elements of BIG1 molecular structure were identified, as well as the potential function of microtubules in a novel PKA effect on BIG1 translocation.
Multiconformation continuum electrostatics analysis of the NhaA Na
+
/H
+
antiporter of
Escherichia coli
with functional implications
Authors: Olkhova Elena , Hunte Carola , Screpanti Emanuela , Padan Etana , Michel Hartmut
Published: February 2006

Sodium proton antiporters are essential enzymes that catalyze the exchange of sodium ions for protons across biological membranes. Protonations and deprotonations of individual amino acid residues and of clusters formed by these residues play an important role in activating these enzymes and in the mechanism of transport. We have used multiconformation continuum electrostatics method to investigate the protonation states of residues in the sodium proton exchanger NhaA from
Escherichia coli
, the structure of which has been determined recently by x-ray crystallography. Our calculations identify four clusters of electrostatically tightly interacting residues as well as long-range interactions between residues required for activation. The importance of many of these residues has been demonstrated by the characterization of site-directed mutants. A number of residues with extreme pK
a
values, including several of the “pH sensor,” can only undergo protonation/deprotonation reactions subsequent to conformational changes. The results of the calculations provide valuable information on the activation of the antiporter and the role of individual amino acid residues, and provide a solid framework for further experiments.
Ceramide mediates the rapid phase of febrile response to IL-1β
Authors: Sanchez-Alavez Manuel , Tabarean Iustin V. , Behrens M. Margarita , Bartfai Tamas
Published: February 2006

IL-1β was identified after a long search for the endogenous pyrogen. It acts by inducing synthesis of prostaglandin E
2
, which mediates the late phase of IL-1β-induced fever. Here we show by radiotelemetry that the early phase of the fever response to IL-1β is mediated by ceramide. Hypothalamic application of the cell-penetrating C2-ceramide mimics the rapid phase of the IL-1β-induced fever. Inhibition of ceramide synthesis blocks the rapid phase of fever but does not affect the slower prostaglandin E
2
-dependent phase, which is blocked by indomethacin or by null mutation of the EP3 prostanoid receptor. Electrophysiological experiments on preoptic area/anterior hypothalamic neurons show that C2-ceramide, but not dihydroceramide, mimics the rapid hyperpolarizing effects of IL-1β on the activity of warm-sensitive hypothalamic neurons. IL-1β-mediated hyperpolarization is blocked by PP2, the selective inhibitor of the protein tyrosine kinase Src, which is known to be activated by ceramide. These
in vivo
and
in vitro
data suggest that ceramide fulfills the criteria for an endogenous pyrogen.
NMDA receptor mediates tau-induced neurotoxicity by calpain and ERK/MAPK activation
Authors: Amadoro Giuseppina , Ciotti Maria Teresa , Costanzi Marco , Cestari Vincenzo , Calissano Pietro , Canu Nadia
Published: February 2006

The altered function and/or structure of tau protein is postulated to cause cell death in tauopathies and Alzheimer’s disease. However, the mechanisms by which tau induces neuronal death remain unclear. Here we show that overexpression of human tau and of some of its N-terminal fragments in primary neuronal cultures leads to an
N
-methyl-
d
-aspartate receptor (NMDAR)-mediated and caspase-independent cell death. Death signaling likely originates from stimulation of extrasynaptic NR2B-subunit-containing NMDARs because it is accompanied by dephosphorylation of cAMP-response-element-binding protein (CREB) and it is inhibited by ifenprodil. Interestingly, activation of NMDAR leads to a crucial, sustained, and delayed phosphorylation of extracellular-regulated kinases 1 and 2, whose inhibition largely prevents tau-induced neuronal death. Moreover, NMDAR involvement causes the fatal activation of calpain, which, in turn, degrades tau protein into a 17-kDa peptide and possibly other highly toxic N-terminal peptides. Some of these peptides are hypothesized, on the basis of our
in vitro
experiments, to initiate a negative loop, ultimately leading to cell death. Thus, inhibition of calpain largely prevents tau degradation and cell death. Our findings unravel a cellular mechanism linking tau toxicity to NMDAR activation and might be relevant to Alzheimer’s disease and tauopathies where NMDAR-mediated toxicity is postulated to play a pivotal role.
Crystal structure of obelin after Ca2+-triggered bioluminescence suggests neutral coelenteramide as the primary excited state
Authors: Liu Zhi-Jie , Stepanyuk Galina A. , Vysotski Eugene S. , Lee John , Markova Svetlana V. , Malikova Natalia P. , Wang Bi-Cheng
Published: February 2006

The crystal structure at 1.93-Å resolution is determined for the Ca2+-discharged obelin containing three bound calcium ions as well as the product of the bioluminescence reaction, coelenteramide. This finding extends the series of available spatial structures of the ligand-dependent conformations of the protein to four, the obelin itself, and those after the bioluminescence reaction with or without bound Ca2+and/or coelenteramide. Among these structures, global conformational changes are small, typical of the class of “calcium signal modulators” within the EF-hand protein superfamily. Nevertheless, in the active site there are significant repositions of two residues. The His-175 imidazole ring flips becoming almost perpendicular to the original orientation corroborating the crucial importance of this residue for triggering bioluminescence. Tyr-138 hydrogen bonded to the coelenterazine N1-atom in unreacted obelin is moved away from the binding cavity after reaction. However, this Tyr is displaced by a water molecule from within the cavity, which now forms a hydrogen bond to the same atom, the amide N of coelenteramide. From this observation, a reaction scheme is proposed that would result in the neutral coelenteramide as the primary excited state product in photoprotein bioluminescence. From such a higher energy state it is now energetically feasible to account for the shorter wavelength bioluminescence spectra obtained from some photoprotein mutants or to populate the lower energy state of the phenolate anion to yield the blue bioluminescence ordinarily observed from native photoproteins.
Self-fulfilling cavitands: Packing alkyl chains into small spaces
Authors: Purse Byron W. , Rebek Julius
Published: February 2006

The present research was undertaken to determine the conformations of alkyl groups that are forced into small spaces. Unbranched alkyl groups assume fully extended conformations in the free space of solutions, because any bends in the structure create steric clashes between hydrogens along the chain. We synthesized a series of alkyl esters of a carboxylic acid attached to the inner surface of a vase-shaped container structure. The shorter esters (ethyl and propyl) can be accommodated in extended conformations, and even small solvent molecules can share the container’s space. Longer (butyl-octyl) esters adopt increasingly coiled conformations that writhe rapidly in the limited space of the cavity. Even longer esters (nonyl and decyl) can be synthesized, but their containers become distorted, and their spectra indicate slowed internal motions of the alkyl groups within the space. In general, alkyl groups are readily contorted when their internal strains are compensated by attraction with the inner surfaces and the proper filling of space.
Polyamines in sow colostrum and milk at different stages of lactation
Authors: Cheng Z. B. , Li D. F. , Ge C. R. , Xing J. J.
Published: February 2006

The objective of this study was to determine the effect of stage of lactation on the concentration of polyamines (spermine, spermidine, and putrescine) in sow colostrum and milk. Ten, third parity sows (Landrace×Yorkshire) were sampled throughout a 28-day lactation. Litter size for all sows was standardized at 10 sucking piglets immediately after farrowing. Colostrum collection began at the birth of the first piglet (0 h), and colostrum was subsequently collected 6, 12, 18, and 24 h after farrowing. Sow milk was sampled on days 3, 7, 10, 14, 17, 21, 24 and 28 of lactation. Spermine concentration in sow colostrum was relatively constant for the first 12 h after farrowing and then rapidly increased to 10·26 μmol/l 24 h after farrowing (linear and quadratic effect; P<0·01). In contrast, the concentrations of spermidine and putrescine showed little change during the first 24 h with spermidine concentration in colostrum ranging from 3·76 to 4·54 μmol/l, and putrescine concentration ranging from 1·15 to 1·52 μmol/l. The highest concentration of spermine in sow milk was 18·82 μmol/l, observed on day 7, with levels gradually declining to 4·28 μmol/l by day 28 of lactation (linear and quadratic effect; P<0·01). In contrast, the concentration of spermidine increased during lactation ranging from a low of 4·32 μmol/l on day 7 to a high of 9·01 μmol/l on day 28 of lactation (linear effect P<0·01; quadratic effect P=0·03). Putrescine concentration ranged from 1·53 μmol/l on day 3 to 1·84 μmol/l on day 28 (linear effect P=0·07; quadratic effect P>0·05). The results of this study show sow colostrum and milk provide polyamines for sucking piglets before weaning, which could potentially modulate intestinal maturation.
Correlations between sport performance and different radiographic findings in the limbs of Hanoverian Warmblood horses
Authors: Stock K. F. , Distl O.
Published: February 2006

The purpose of this work was to quantify the additive genetic correlations between prevalent radiographic findings in the limbs of Warmblood riding horses and performance parameters. Data on 3725 Hanoverian Warmblood horses selected for sale at auctions in the period 1991 to 1998 were used. The numbers of annual entries (TE) and placings (TP) in tournament competitions in the period 1991 to 2002 served as measures of performance in riding sports. Multivariate genetic analyses were performed in linear animal models using restricted maximum likelihood (REML). The four most prevalent radiographic findings, i.e. osseous fragments in fetlock (OFF) and hock joints (OFH), deforming arthropathy in hock joints (DAH) and pathologic changes in navicular bones (PCN) were analysed jointly with the performance parameters, i.e. TE and TP. Additive genetic correlations between the radiographic findings and the performance in sports were in many cases close to zero. There were some indications for significantly negative, but few indications for significantly positive additive genetic correlations between radiological conditions in the equine limbs and the performance of Warmblood riding horses in dressage, show-jumping and basic build-up competitions. Breeding measures that allow for orthopaedic health traits could therefore contribute to maximize the breeding progress in terms of sport performance.
Genetic analysis of weight, fat and muscle depth in growing lambs using random regression models
Authors: Fischer T. M. , Werf J. H. J. van der , Banks R. G. , Ball A. J. , Gilmour A. R.
Published: February 2006

Genetic parameters were estimated using uni- and bi-variate random regression models for weight, eye-muscle depth and fat depth measures between 60 and 360 days of age. Each trait was measured up to five times in 50-day intervals following weaning on approximately 4000 Australian Poll Dorset Sheep. The model accounted for rearing type, dam age, management group and age of recording. The model used for analysing weight included quadratic, orthogonal polynomials for direct genetic and environmental effects, a linear polynomial for maternal genetic effects and heterogeneous error variance across ages. The fat and muscle analysis used linear orthogonal polynomials for direct genetic and environmental effects and heterogeneous error variance. Throughout the 300-day trajectory heritability for weight traits ranged from 0·20 to 0·31, while heritability for fat depth ranged from 0·24 to 0·34 and heritability for eye-muscle depth ranged from 0·24 to 0·40. Genetic correlations between repeated measures of the same trait at different ages were positive and declined as the age interval increased, to minimum values of 0·60, 0·31 and 0·50 for weight, fat and muscle respectively between 60 and 360 days of age. Genetic correlations between weight and fat and weight and eye muscle were moderate to high (0·6 to 0·8) and positive but decreased slightly with age. The genetic correlations between fat and muscle were moderate to high (0·5 to 0·7) throughout the 300-day trajectory. In all cases, the estimates produced in this study were reasonably consistent with the limited number of studies that exist in the reported literature. This study demonstrated the relationships that exist between repeated measures of weight, fat and muscle measures over time, which is of interest to prime lamb producers looking to select for specific breeding objectives or market end points requiring precise weight, fat and muscle combinations at certain ages.
Digestion, rumen fermentation and circulating concentrations of insulin, growth hormone and IGF-1 in steers given maize silages harvested at three stages of maturity
Authors: Juniper D. T. , Browne E. M. , Bryant M. J. , Beever D. E.
Published: February 2006

Advancing maturity of forage maize is associated with increases in the proportion of dry matter (DM) and starch and decreases in the proportions of structural carbohydrates in the ensiled crop. Three maize silages (286 (low, L), 329 (medium, M) and 379 (high, H) g DM per kg fresh weight) plus a concentrate formulated to give isonitrogenous intakes were offered to Holstein-Friesian steers fitted with a cannula in the dorsal sac of the rumen and a ‘T’ piece cannula in the proximal duodenum in an experiment with a cross-over design that allowed four collection periods. Nutrient flow to the duodenum was estimated using chromium-EDTA. Steers consumed approximately 0·6 kg DM per day less of diet L compared with the other two diets (P=0·026), resulting in less DM being digested (P=0·005) but digestibility did not differ between diets. Similar results were obtained for organic matter. There were no differences between diets in the intake or digestibility of neutral-detergent fibre. Intake, duodenal flow and faecal output of starch were greater for steers offered diets M and H compared with those given diet L (P<0·05). In all diets rumen digestion contributed to over 90% of total digestion of starch, although rumen digestibility declined significantly with advancing maize maturity (P=0·002). Molar proportions of acetic acid were higher in diet H (P<0·05) whilst proportions of propionic acid and n-butyric acid were higher in diets M and L. There were no significant differences between diets in mean rumen pH or ammonia concentrations. Mean circulating concentrations of insulin were higher (P=0·009) in cattle given diets L and M compared with diet H. There were no differences between diets in the mean circulating concentration of growth hormone, or the frequency, amplitude and duration of growth hormone pulses, or the mean circulating concentrations of IGF-1. Changes in forage composition that accompany advancing maize maturity affect overall silage digestion and circulating concentrations of insulin.