bluuebunny/crossref_metadata_2025 huggingface dataset:
Chlorine activation near the midlatitude tropopause
Authors: Thornton Brett F. , Toohey Darin W. , Tuck A. F. , Elkins J. W. , Kelly K. K. , Hovde S. J. , Richard E. C. , Rosenlof K. H. , Thompson T. L. , Mahoney M. J. , Wilson J. C.
Published: September 2007

We report on substantial chlorine activation near the midlatitude tropopause over the central United States (39–42°N 102–105°W) during the WB‐57F Aerosol Mission (WAM) in April 1998. The extent of activation was determined by simultaneous in situ measurements of ClO and ozone and calculations of total inorganic chlorine (Cly) based on recently reported relationships between HCl, ozone, and halocarbons for similar latitudes. Levels of [ClO]/[Cly] approaching 50% occurred in a region of strong gravity wave activity, high particulate surface areas (5–20 μm2 cm−3), low ozone, and relatively high humidities (20–25 ppm of H2O, yet undersaturated with respect to ice), consistent with a heterogeneous mechanism on particles formed in recently lofted tropospheric air as it mixed into the lowermost stratosphere. These observations are similar to a previous one of chlorine activation on volcanic aerosol, suggesting a common heterogeneous chemical mechanism involving HCl, ClNO3, and HOCl that even in volcanically quiescent years can impact ozone photochemistry in regions of the lowermost stratosphere influenced by mixing from the tropopause region. Models not incorporating this chlorine activation process may be underestimating the impact on ozone in the midlatitude lowermost stratosphere by decomposition of very short lived halocarbon compounds, including substitutes for ozone‐depleting compounds.
Summer dust aerosols detected from CALIPSO over the Tibetan Plateau
Authors: Huang Jianping , Minnis Patrick , Yi Yuhong , Tang Qiang , Wang Xin , Hu Yongxiang , Liu Zhaoyan , Ayers Kirk , Trepte Charles , Winker David
Published: September 2007

Summertime Tibetan dust aerosol plumes are detected from the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. CALIPSO reveals that dust storms occur more frequently than previously found from Tibetan surface observations because few surface sites were available over remote northwestern Tibet due to high elevation and harsh climate. The Tibetan dust aerosol is characterized by column‐averaged volume depolarization and total volume color ratios around 21% and 0.83, respectively. The dust layers appear most frequently around 4–7 km above mean sea level. The volume depolarization ratio for about 90% of the dust particles is less than 10% at low altitudes (3–5 km), while only about 50% of the particles have a greater depolarization ratio at higher altitudes (7–10 km). The 4‐day back trajectory analyses show that these plumes probably originate from the nearby Taklamakan desert surface and accumulate over the northern slopes of the Tibetan Plateau. These dust outbreaks can affect the radiation balance of the atmosphere of Tibet because they both absorb and reflect solar radiation.
Water ice permafrost on Mars: Layering structure and subsurface distribution according to HEND/Odyssey and MOLA/MGS data
Authors: Mitrofanov I. G. , Zuber M. T. , Litvak M. L. , Demidov N. E. , Sanin A. B. , Boynton W. V. , Gilichinsky D. A. , Hamara D. , Kozyrev A. S. , Saunders R. D. , Smith D. E. , Tretyakov V. I.
Published: September 2007

To elucidate the nature of permafrost in the shallow subsurface of Mars, we analyze jointly neutron albedo from the High Energy Neutron Detector (HEND) on the Mars Odyssey spacecraft and near‐IR (1064‐nm) surface reflectance from the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor. The first dataset measures the content of hydrogen (in the form of water or hydroxyl) in the soil, and the second yields the flux of absorbed solar energy by the surface. We identify a statistically–significant negative cross‐correlation between these data at latitudes poleward of 40° latitude in the northern hemisphere and in the latitude band 40°–60° in the southern hemisphere, which we interpret as evidence for the presence of stable water ice under a dry equilibrium top layer (ETL). We deduce an empirical relation between near‐IR reflectance and thickness of this ETL, which allows the burial depth of the water ice table to be estimated with km‐scale spatial resolution. We observe no correlation between neutron and near‐IR albedo within the southern hemisphere poleward of 60° latitude. While it is known from previously analyzed neutron and gamma‐ray data that subsurface water ice is present within this region and is covered by a layer of dry regolith, the absence of a correlation indicates that the thickness of this layer is not controlled by an equilibrium condition between the ice table and atmosphere.
Correlations between optical, chemical and physical properties of biomass burn aerosols
Authors: Hopkins R. J. , Lewis K. , Desyaterik Y. , Wang Z. , Tivanski A. V. , Arnott W. P. , Laskin A. , Gilles M. K.
Published: September 2007

Aerosols generated from burning different plant fuels were characterized to determine relationships between chemical, optical and physical properties. Single scattering albedo (ω) and Angstrom absorption coefficients (αap) were measured using a photoacoustic technique combined with a reciprocal nephelometer. Carbon‐to‐oxygen atomic ratios, sp2 hybridization, elemental composition and morphology of individual particles were measured using scanning transmission X‐ray microscopy coupled with near‐edge X‐ray absorption fine structure spectroscopy (STXM/NEXAFS) and scanning electron microscopy with energy dispersion of X‐rays (SEM/EDX). Particles were grouped into three categories based on sp2 hybridization and chemical composition. Measured ω (0.4 − 1.0 at 405 nm) and αap (1.0 − 3.5) values displayed a fuel dependence. The category with sp2 hybridization >80% had values of ω (<0.5) and αap (∼1.25) characteristic of light absorbing soot. Other categories with lower sp2 hybridization (20 to 60%) exhibited higher ω (>0.8) and αap (1.0 to 3.5) values, indicating increased absorption spectral selectivity.
Transient electromagnetic S‐inversion in tunnel prediction
Authors: Xue G. Q. , Yan Y. J. , Li X. , Di Q. Y.
Published: September 2007

This paper presents S‐inversion method to tunnel prediction to forecasting water‐filled faults or fracture zones ahead of the front wall of a tunnel during tunnel excavation. S‐inversion is an interpretation method of transient electromagnetic (TEM) data using the second derivative of the conductivity parameter based on the moving thin sheet approach. It is suggested for the technology of second derivative of vertical apparent conductivity, which is traditionally used in surface TEM data interpretation, the theoretical analyses and the method of numerical calculation in detail are also given. Finally, a real tunnel forecasting is studied for TEM surveys, and results show that the proposed method is effective and successful for exploring and predicting unfavorable geology during tunnel construction.
Sea surface slope statistics derived from Sun glint radiance measurements and their apparent dependence on sensor elevation
Authors: Ross Vincent , Dion Denis
Published: September 2007

Sea surface slope variances are obtained by inverting narrowband (444, 501, 677, and 864 nm) Sun glint radiance measurements using a detailed analytical specular sea surface bidirectional reflectance distribution function (BRDF) that includes mutual wave shadowing and hiding. The resulting data set spans a wide range of environmental conditions including wind speeds from 0.5 to 13.5 m s−1 and many different viewing and source geometries. Analysis against wind speed and atmospheric stability produces trends similar to those found in previous studies, as well as finer tendencies that were formerly difficult to detect. Furthermore, the detailed nature of the BRDF model used in the analysis permits an investigation of the correlation of the statistics with viewing geometry, revealing a strong relationship between sensor elevation and measured slope variance, especially at grazing angles.
In Vivo and In Vitro Characterization of a Novel Neuroprotective Strategy for Stroke: Ischemic Postconditioning
Authors: Pignataro Giuseppe , Meller Robert , Inoue Koichi , Ordonez Andrea N , Ashley Michelle D , Zhigang Xiong , Simon Roger P
Published: September 2007

As clinical trials of pharmacological neuroprotective strategies in stroke have been disappointing, attention has turned to the brain's own endogenous strategies for neuroprotection. Recently, a hypothesis has been offered that modified reperfusion subsequent to a prolonged ischemic episode may also confer ischemic neuroprotection, a phenomenon termed ‘postconditioning’. Here we characterize both in vivo and in vitro models of postconditioning in the brain and offer data suggesting a biological mechanism for protection. Postconditioning treatment reduced infarct volume by up to 50% in vivo and by ∼30% in vitro. A duration of 10 mins of postconditioning ischemia after 10 mins of reperfusion produced the most effective postconditioning condition both in vivo and in vitro. The degree of neuroprotection after postconditioning was equivalent to that observed in models of ischemic preconditioning. However, subjecting the brain to both preconditioning as well as postconditioning did not cause greater protection than each treatment alone. The prosurvival protein kinases extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), and Akt show prolonged phosphorylation in the cortex of postconditioned rats. Neuroprotection after postconditioning was inhibited only in the presence of LY294002, which blocks Akt activation, but not U0126 or SB203580, which block ERK and P38 MAP kinase activity. In contrast, preconditioning-induced protection was blocked by LY294002, U0126, and SB203580. Our data suggest that postconditioning may represent a novel neuroprotective approach for focal ischemia/reperfusion, and one that is mediated, at least in part, by the activation of the protein kinase Akt.
Genotype and age effects on sheep meat production. 1. Production and growth
Authors: Hopkins D. L. , Stanley D. F. , Martin L. C. , Gilmour A. R.
Published: September 2007

The growth, wool production and teeth eruption of animals from five genotypes [Poll Dorsetgrowth (PD) × Border Leicester × Merino (BLM); PDg × Merino (M); Poll Dorsetmuscling (PDm) × M; M × M; BL × M] were evaluated over the age span of 4 to 22 months of age. In total, 16 sires were used to generate the animals and these were selected for growth based on estimated breeding values (EBVs), apart from one group (PDm) which was selected for muscling based on EBVs. In total, 595 animals were slaughtered at 4, 8, 14 or 22 months of age. The birthweight of lambs born to BLM ewes was 0.6 kg heavier (P < 0.001) than those born to Merino ewes, and wether lambs were 0.2 kg heavier than ewe lambs (P < 0.001). The yearling weight (YWT) EBV had no effect on birthweight. There were significant (P < 0.001) differences between genotypes for predicted weaning weight at 4 months of age, with a range of 10.6 kg among the groups. The PDg × BLM were the heaviest (37.8 ± 0.7 kg) and the Merino the lightest (27.3 ± 0.8 kg). Wether lambs were 2.0 kg heavier (P < 0.001) than ewe lambs at weaning. The YWT EBV had no effect on weaning weight. There was a significant (P < 0.001) interaction between the age at slaughter and genotype for final liveweight of each age group. The PDg × BLM were the heaviest at each age and the Merinos the lightest, and for the oldest animals, the BLM were significantly (P < 0.05) heavier than PDm × M, whereas at younger ages this was not the case. The significant interaction (P < 0.001) between sex and age at slaughter reflected the increasing difference in liveweight between the sexes as age at slaughter increased. There was also a significant (P < 0.05) interaction between the YWT EBV and age at slaughter. The overall coefficients were –0.01, 0.14, 0.34 and 0.65 for slaughter ages 4, 8, 14 and 22 months, respectively, indicating that in young animals there was no effect of sire YWT EBV on liveweight, but as the animals aged there was an increasing effect such that progeny of sires with high sire YWT EBV were heavier. This effect was evident within all genotypes. There was a sire breed effect on fleece weight and total wool weight (P < 0.001) with Merino-sired hoggets producing 0.4 kg more wool than Border Leicester-sired hoggets and 1.5 kg more than Poll Dorset-sired hoggets. There was a weak genotype effect on time to erupt the first permanent incisor, which if modelled as a proportion of Border Leicester (0, 1/4, 1/2) was significant (–34 ± 12 days, P < 0.05), Border Leicester earlier than not Border Leicester. Ewe lambs took 9 days longer (P < 0.05) to erupt their first permanent incisor compared with wether lambs.
Myofibre characteristics of ovine longissimus and semitendinosus muscles are influenced by sire breed, gender, rearing type, age and carcass weight
Authors: Greenwood P. L. , Harden S. , Hopkins D. L.
Published: September 2007

The objective of this study was to determine the extent to which sire breed (Merino, primarily a wool-producing breed, and Poll Dorset, primarily a meat-producing breed), gender (castrate and ewe), rearing type (single- or multiple-reared), age (4, 8, 14 and 22 months) and carcass weight influence ovine (n = 204) myofibre characteristics. In Merino-sired sheep, the relative area (% of total myofibre area) of type 2X myofibres was lower and of type 2A myofibres higher in the longissimus lumborum (longissimus) muscle than in Poll Dorset-sired sheep. Female sheep had a higher relative area of type 2X and a lower relative area of type 2A myofibres than castrate sheep in the longissimus muscle. The percentage of type 2A myofibres increased and of type 2X myofibres decreased in the longissimus between 4 and 22 months of age. Type 1 myofibres in the semitendinosus muscle were more prevalent and type 2X myofibres less prevalent in Merino than in Poll Dorset-sired sheep. The percentage of type 1 myofibres was lower in female than in castrate sheep. Age-related effects on semitendinosus myofibre characteristics varied with gender, sire breed and rearing type. Influences of rearing type on myofibre characteristics were evident in the semitendinosus muscle at younger ages, but did not persist to 22 months of age. The greatest increases in myofibre cross-sectional areas occurred between 8 and 14 months of age in the longissimus muscle, and between 14 and 22 months of age in the semitendinosus muscle. Carcass weight significantly influenced cross-sectional area of type 2A, 2AX and 2X myofibres in longissimus and semitendinosus muscles. It is concluded that influences of sire breed, gender, rearing type, age and carcass weight on ovine myofibre percentages varies between longissimus and semitendinosus muscles. Furthermore, the pattern of postnatal myofibre growth differs between these muscles.
Genotype and age effects on sheep meat production. 2. Carcass quality traits
Authors: Ponnampalam E. N. , Hopkins D. L. , Butler K. L. , Dunshea F. R. , Warner R. D.
Published: September 2007

The present study examines carcass quality traits in different genotypes of Australian sheep slaughtered at 4, 8, 14 and 22 months of age. Poll Dorsetgrowth × Border Leicester Merino (PDg × BLM), Poll Dorsetgrowth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Merino × Merino (M × M) and Border Leicester × Merino (BL × M) genotypes were compared. Sires were selected on the basis of growth (PDg, M and BL) and muscle (PDm) using estimated breeding values (EBVs). Approximately 150 mixed sex animals were slaughtered at each age (595 in total for the four slaughters) and carcass quality traits, including hot carcass weight, loin and semitendinosus (ST) muscle weights, GR fat, fat C, rump fat depth and eye muscle area (EMA), were determined at 45 min to 3 days postslaughter. With age, all carcass quality traits increased in magnitude. Merinos produced the lightest and leanest carcasses (P < 0.01) with lowest values in nearly all the carcass quality traits. At 4 and 8 months of age carcass and loin weights, EMA and GR fat measures were greater (P < 0.01) in second-cross PDg × BLM sheep than all other genotypes. However, traits related to muscle content were similar between first- and second-cross Poll Dorset genotypes at 14 and 22 months of age. The BL × M genotype had lower values than the PD × M genotypes for these traits, at all ages. Traits related to carcass fatness showed that sheep with Border Leicester genetics tend to deposit more fat (P < 0.001) in the carcass than those with Merino or Poll Dorset genetics from 14 months of age onwards. Most carcass quality traits did not differ (P > 0.05) between first-cross Poll Dorset genotypes selected for growth or muscling (PDg × M v. PDm × M). Sires with high muscling EBVs are associated more with shorter carcass length than low muscling EBVs. From ~8 months of age, wethers had greater values (P < 0.05) than ewes of the same age for most carcass quality traits related to size and muscle development, but no effect was present for carcass quality traits that were related to fat deposition. It was clear that the carcass weight of M × M at 8 and 14 months were similar to that observed in PDg × BLM at 4 and 8 months, respectively. Loin weights of M × M and BL × M at 13 and 8 months were similar to that weights observed in PDg × BLM at 8 and 4 months of age, respectively. Animals slaughtered to a muscle weight specification will reach the target at a younger age when they have more Poll Dorset than Border Leicester background genetics. Alternatively animals slaughtered at a specified fat score (using fat C or rump fat depth) will reach the specification at a younger age when they have more Border Leicester than Poll Dorset genetics.
Sheep genotype, age and muscle type affect the expression of metabolic enzyme markers
Authors: Gardner G. E. , Hopkins D. L. , Greenwood P. L. , Cake M. A. , Boyce M. D. , Pethick D. W.
Published: September 2007

The objective of this study was to determine whether genotype, age (4, 8, 14 and 22 months), sex (ewe and wether) and muscle type influence ovine (n = 587) muscle metabolic characteristics. The genotypes represented were Poll Dorsetgrowth × Border Leicester Merino, Poll Dorsetgrowth × Merino, Poll Dorsetmuscling × Merino, Merino × Merino and Border Leicester × Merino. Between 4 and 22 months of age, myoglobin concentration within all muscles and all genotypes doubled, with the bulk of this response occurring between 4 and 8 months of age. Levels in the longissimus thoracis et lumborum (LT) and semimembranosus muscles were double those seen in the semitendinosus (ST) muscle, and Merinos had the lowest myoglobin concentrations of all genotypes. The other aerobic indicator, isocitrate dehydrogenase, had lower activity in the ST compared with the LT, was lower in 22-month-old sheep compared with all other ages, and decreased as selection for leanness increased. Both phosphofructokinase and lactate dehydrogenase activity tended to increase with age, were lower in the ST compared with the LT, and had higher activity in the Border Leicester × Merino sheep. The correlation between the percentage of total myofibre area comprising type 2X myofibres and metabolic markers was far higher for the oxidative indicators isocitrate dehydrogenase and myoglobin, which both decreased as relative area of type 2X fibres increased. However, the strongest correlations were with the relative area of type 2A myofibres, which were consistently high for both oxidative and glycolytic metabolic markers implying positive coregulation with both energy producing pathways.
Unravelling the complex interactions between genetics, animal age and nutrition as they impact on tissue deposition, muscle characteristics and quality of Australian sheep meat
Authors: Warner R. D. , Pethick D. W. , Greenwood P. L. , Ponnampalam E. N. , Banks R. G. , Hopkins D. L.
Published: September 2007

The combined effects of age and genetics and Poll Dorset sire and growth path were studied in two separate experiments (n = 595 and 627, respectively). In the first experiment, containing genotype crosses typically used in Australia (Merino, Poll Dorset, Border Leicester) and sires selected for growth or muscling, sheep were slaughtered at 4, 8, 14 and 22 months. The second experiment used Poll Dorset sires selected for high muscling, fat or growth with progeny having two levels of nutrition postweaning. Border Leicesters expressed higher levels of carcass fat percentage and intramuscular fat and produced the heaviest carcass. Merinos had the lowest subcutaneous fat depth and highest carcass lean percentage when compared at the same age. The progeny of Poll Dorset sires selected for high muscling (PDm) expressed a shift toward glycolytic fibres relative to those from Merino sires, and PDm sires produced progeny with reduced spine and limb length and higher carcass muscle : mineral ratios, suggesting skeletal stunting. Genotype meat quality differences were minimal except that PDm sire topsides were tougher and Merinos produced higher pH meat. With age (4–22 months), lambs became heavier and fatter, fibres shifted towards oxidative and away from glycolytic, muscle myoglobin increased, the meat became darker and redder and tenderness declined. Early weaning had no effect on the time to reach slaughter weight, provided nutrition was not restricted. The sire genetics influence on the carcass composition far outweighed the effect of nutrition postweaning. Lambs on a restricted diet tended to have less acceptable meat quality but this was not evident in lambs from sires selected for high fatness. Sensory tenderness was improved and intramuscular fat was higher in lamb progeny from sires selected for high fatness.
Systematics, phylogeny and historical biogeography of the Pentagonaster clade (Asteroidea:Valvatida:Goniasteridae)
Authors: Mah Christopher
Published: September 2007

Morphology-based phylogenetic hypotheses developed for living and fossil goniasterid asteroids have provided several unique opportunities to study bathymetric and biogeographic shifts for an ecologically important group of prominent, megafaunal invertebrates. A cladistic analysis of 18 ingroup taxa employing 65 morphological characters resulted in a single most parsimonious tree. The tree supports assignment of the Atlantic Tosia parva (Perrier, 1881) and the Pacific Tosia queenslandensis Livingstone, 1932 to new, separate genera. The phylogenetic tree supports offshore to onshore bathymetric shifts between basal and derived taxa. The phylogeny is also consistent with historical events surrounding the separation of Antarctica from Australia and South Africa. Buterminaster Blake & Zinsmeister, 1988 from the Eocene La Meseta Formation, Antarctic Peninsula, was included in the phylogenetic analysis and is now supported as the only fossil species in the genus Pentagonaster Gray, 1840. Pentagonaster stibarus H. L. Clark, 1914 is separated from synonymy with P. dubeni Gray, 1847 and resurrected as a valid species. The new genus, Akelbaster, gen. nov., shows unusual new structures that resemble cribiform organs, although their function has not been determined. One specific ingroup lineage, including Tosia and Pentagonaster, attains a much larger adult size than those of its sister-taxa, suggesting that Cope’s rule may apply to asteroids within this clade. Pentagonaster and related genera are revised. Descriptions of four new genera and three new species are presented, including: Akelbaster novaecaledoniae, gen. nov., sp. nov., Ryukuaster onnae, gen. nov., sp. nov., Eknomiaster beccae, sp. nov., Pawsonaster parvus, gen. nov., comb. nov. and Anchitosia queenslandensis, gen. nov., comb. nov.
Copper release characteristics in selected soils from southern and northern Iran
Authors: Ghasemi-Fasaei R. , Tavajjoh M. , Olama V. , Molazem B. , Maftoun M. , Ronaghi A. , Karimian N. , Adhami E.
Published: September 2007

The aim of this research was to study and compare release characteristics of copper (Cu) in 2 groups of soils from Guilan province in northern (SNI) and Fars province in southern Iran (SSI) with significant differences in Cu availability and other soil properties. The patterns of Cu release from the soils by ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) were studied using 5 kinetic models. Results showed that the power function, simple Elovich, and parabolic diffusion in SSI, and the power function and simple Elovich in SNI, were the best fitted models. The greater rates and magnitude of Cu released from SNI compared with SSI could be interpreted as the greater capability of the former in maintaining Cu concentration in the sufficient range. The difference in Cu release rates was considerable during initial times. Mean initial Cu release rate from SNI was ~3 times higher than that of SSI. The results reveal that the cation exchange capacity (CEC) and pH were the most influential soil factors causing differences in Cu release patterns between these 2 groups of soils. Greater CEC and lower pH in SNI compared with SSI, are mainly responsible for greater initial rates of Cu release in the former. Difference in CEC and pH of these 2 groups of soils was mainly attributed to different soil organic matter, carbonate content, and clay mineralogy.
Burning crop residues under no-till in semi-arid land, Northern Spain—effects on soil organic matter, aggregation, and earthworm populations
Authors: Virto Iñigo , Imaz Maria José , Enrique Alberto , Hoogmoed Willem , Bescansa Paloma
Published: September 2007

Stubble burning has traditionally been used in semi-arid land for pest and weed control, and to remove the excess of crop residues before seeding in no-tillage systems. We compared differences in soil properties in a long-term (10 years) tillage trial on a carbonated soil in semi-arid north-east Spain under no-tillage with stubble returned and stubble burnt, with the conventional tillage system (mouldboard plough, stubble returned) as a reference.
Differences in total soil organic C and C in particulate organic matter, mineralisation potential, soil physical properties (bulk density, penetration resistance, and aggregate size distribution and stability), and earthworm populations were quantified. The effect of stubble burning was absent or insignificant compared with that of tillage in most of the parameters studied. The most significant effect of stubble burning was the change in soil organic matter quality in the topsoil and penetration resistance. No-till plus stubble burning stocked an amount of organic C in the soil similar to no-till without burning, but the particulate organic matter content and mineralisation potential were smaller. Earthworm activity was similar under the 2 no-till systems, although a trend towards bigger earthworms with increasing penetration resistance was observed under the system with burning.
Our results indicate that the role of burnt plant residues and earthworms in organic matter accumulation and soil aggregation in Mediterranean carbonated soils under no tillage is of major importance, meriting further attention and research.
Principal component analysis of the pH-dependent conformational transitions of bovine β-lactoglobulin monitored by heteronuclear NMR
Authors: Sakurai Kazumasa , Goto Yuji
Published: September 2007

To clarify the pH-dependent conformational transitions of proteins, we propose an approach in which structural changes monitored by heteronuclear sequential quantum correlation (HSQC) spectroscopy were analyzed by using a principal component analysis (PCA). We use bovine β-lactoglobulin, a protein widely used in protein folding studies, as a target. First, we measured HSQC spectra at various pH values and subjected them to a PCA. The analysis revealed three apparent transitions with p
K
a
values of 2.9, 4.9, and 6.8, consistent with previous reports using different methods. Next, Gdn-HCl-induced unfolding was examined by measuring tryptophan fluorescence at various pH values. Between pH 2 and 8, β-lactoglobulin exhibited a number of structural transitions as well as changes in stability represented by the free energy change of unfolding, Δ
G
U
. By combining the NMR and fluorescence results, the change in Δ
G
U
was suggested to result from the decreased p
K
a
of some acidic residues. Notably, the native state at neutral pH is destabilized by deprotonation of Glu-89, leading to an increase in the relative population of the intermediate. Thus, the PCA of pH-dependent HSQC spectra provides a more comprehensive understanding of the stability and function of proteins.
Viral targeting of fibroblastic reticular cells contributes to immunosuppression and persistence during chronic infection
Authors: Mueller Scott N. , Matloubian Mehrdad , Clemens Daniel M. , Sharpe Arlene H. , Freeman Gordon J. , Gangappa Shivaprakash , Larsen Christian P. , Ahmed Rafi
Published: September 2007

Many chronic viral infections are marked by pathogen persistence and a generalized immunosuppression. The exact mechanisms by which this occurs are still unknown. Using a mouse model of persistent lymphocytic choriomeningitis virus (LCMV) infection, we demonstrate viral targeting of fibroblastic reticular cells (FRC) in the lymphoid organs. The FRC stromal networks are critical for proper lymphoid architecture and function. High numbers of FRC were infected by LCMV clone 13, which causes a chronic infection, whereas few were infected by the acute strain, LCMV Armstrong. The function of the FRC conduit network was altered after clone 13 infection by the action of CD8+T cells. Importantly, expression of the inhibitory programmed death ligand 1, which was up-regulated on FRC after infection, reduced early CD8+T cell-mediated immunopathology and prevented destruction of the FRC architecture in the spleen. Together, this reveals an important tropism during a persistent viral infection. These data also suggest that the inhibitory PD-1 pathway, which likely evolved to prevent excessive immunopathology, may contribute to viral persistence in FRC during chronic infection.
Notch1 engagement by Delta-like-1 promotes differentiation of B lymphocytes to antibody-secreting cells
Authors: Santos Margarida Almeida , Sarmento Leonor Morais , Rebelo Manuel , Doce Ana Agua , Maillard Ivan , Dumortier Alexis , Neves Helia , Radtke Freddy , Pear Warren S. , Parreira Leonor , Demengeot Jocelyne
Published: September 2007

Notch signaling regulates B and T lymphocyte development and T cell effector class decision. In this work, we tested whether Notch activity affects mature B cell activation and differentiation to antibody-secreting cells (ASC). We show increased frequency of ASC in cultures of splenic B cells activated with LPS or anti-CD40 when provided exogenous Notch ligand Delta-like-1 (Dll1). Our results indicate that Notch–Dll1 interaction releases a default pathway that otherwise inhibits Ig secretion upon B cell activation. Thus, Dll1 enhanced spontaneous Ig secretion by naturally activated marginal zone B and B1 cells and reversed the inhibition of ASC differentiation mediated by B cell receptor crosslinking during LPS. Moreover, suppression of Notch signaling in B cell expression of either a dominant-negative mutant form of Mastermind-like 1 or a null mutation of Notch1 not only prevented Dll1-mediated enhancement of ASC differentiation but also reduced dramatically LPS-induced Ig secretion. Finally, we show that Dll1 and Jagged-1 are differentially expressed in discrete areas of the spleen, and that the effect of Notch engagement on Ig secretion is ligand-specific. These results indicate that Notch ligands participate in the definition of the mature B cell microenvironment that influences their terminal differentiation.
Phospholipase Cε is a nexus for Rho and Rap-mediated G protein-coupled receptor-induced astrocyte proliferation
Authors: Citro Simona , Malik Sundeep , Oestreich Emily A. , Radeff-Huang Julie , Kelley Grant G. , Smrcka Alan V. , Brown Joan Heller
Published: September 2007

Phospholipase Cε (PLCε) has been suggested to transduce signals from small GTPases, but its biological function has not yet been clarified. Using astrocytes from PLCε-deficient mice, we demonstrate that endogenous G protein-coupled receptors (GPCRs) for lysophosphatidic acid, sphingosine 1-phosphate, and thrombin regulate phosphoinositide hydrolysis primarily through PLCε. Stimulation by lysophospholipids occurs through Gi, whereas thrombin activates PLC through Rho. Further studies reveal that PLCε is required for thrombin- but not LPA-induced sustained ERK activation and DNA synthesis, providing a novel mechanism for GPCR and Rho signaling to cell proliferation. The requirement for PLCε in this pathway can be explained by its role as a guanine nucleotide exchange factor for Rap1. Thus, PLCε serves to transduce mitogenic signals through a mechanism distinct from its role in generation of PLC-derived second messengers.
Yeast screens show aromatic residues at the end of the sixth helix anchor transient receptor potential channel gate
Authors: Zhou Xinliang , Su Zhenwei , Anishkin Andriy , Haynes W. John , Friske Eric M. , Loukin Stephen H. , Kung Ching , Saimi Yoshiro
Published: September 2007

Transient receptor potential (TRP) channels are first elements in sensing chemicals, heat, and force and are widespread among protists and fungi as well as animals. Despite their importance, the arrangement and roles of the amino acids that constitute the TRP channel gate are unknown. The yeast TRPY1 is activated
in vivo
by osmotically induced vacuolar membrane deformation and by cytoplasmic Ca
2+
. After a random mutagenesis, we isolated TRPY1 mutants that responded more strongly to mild osmotic upshocks. One such gain-of-function mutant has a Y458H substitution at the C terminus of the predicted sixth transmembrane helix. Direct patch-clamp examination of vacuolar membranes showed that Y458H channels were already active with little stimulus and showed marked flickers between the open and intraburst closed states. They remained responsive to membrane stretch force and to Ca
2+
, indicating primary defects in the gate region but not in the sensing of gating principles. None of the other 18 amino acid replacements engineered here showed normal channel kinetics except the two aromatic substitutions, Y458F and Y458W. The Y458 of TRPY1 has its aromatic counterpart in mammalian TRPM. Furthermore, conserved aromatics one α-helical turn downstream from this point are also found in animal TRPC, TRPN, TRPP, and TRPML, suggesting that gate anchoring with aromatics may be common among many TRP channels. The possible roles of aromatics at the end of the sixth transmembrane helix are discussed.
Resting-state networks in the infant brain
Authors: Fransson Peter , Skiöld Beatrice , Horsch Sandra , Nordell Anders , Blennow Mats , Lagercrantz Hugo , Åden Ulrika
Published: September 2007

In the absence of any overt task performance, it has been shown that spontaneous, intrinsic brain activity is expressed as systemwide, resting-state networks in the adult brain. However, the route to adult patterns of resting-state activity through neuronal development in the human brain is currently unknown. Therefore, we used functional MRI to map patterns of resting-state activity in infants during sleep. We found five unique resting-states networks in the infant brain that encompassed the primary visual cortex, bilateral sensorimotor areas, bilateral auditory cortex, a network including the precuneus area, lateral parietal cortex, and the cerebellum as well as an anterior network that incorporated the medial and dorsolateral prefrontal cortex. These results suggest that resting-state networks driven by spontaneous signal fluctuations are present already in the infant brain. The potential link between the emergence of behavior and patterns of resting-state activity in the infant brain is discussed.
Global transcriptional responses to cisplatin in
Dictyostelium discoideum
identify potential drug targets
Authors: Van Driessche Nancy , Alexander Hannah , Min Junxia , Kuspa Adam , Alexander Stephen , Shaulsky Gad
Published: September 2007

Dictyostelium discoideum
is a useful model for studying mechanisms of cisplatin drug sensitivity. Our previous findings, that mutations in sphingolipid metabolism genes confer cisplatin resistance in
D. discoideum
and in human cells, raised interest in the resistance mechanisms and their implications for cisplatin chemotherapy. Here we used expression microarrays to monitor physiological changes and to identify pathways that are affected by cisplatin treatment of
D. discoideum
. We found >400 genes whose regulation was altered by cisplatin treatment of wild-type cells, including groups of genes that participate in cell proliferation and in nucleotide and protein metabolism, showing that the cisplatin response is orderly and multifaceted. Transcriptional profiling of two isogenic cisplatin-resistant mutants, impaired in different sphingolipid metabolism steps, showed that the effect of cisplatin treatment was greater than the effect of the mutations, indicating that cisplatin resistance in the mutants is due to specific abilities to overcome the drug effects rather than to general drug insensitivity. Nevertheless, the mutants exhibited significantly different responses to cisplatin compared with the parent, and >200 genes accounted for that difference. Mutations in five cisplatin response genes (
sgkB
,
csbA
,
acbA
,
smlA
, and
atg8
) resulted in altered drug sensitivity, implicating novel pathways in cisplatin response. Our data illustrate how modeling complex cellular responses to drugs in genetically stable and tractable systems can uncover new targets with the potential for improving chemotherapy.
Myosin V stepping mechanism
Authors: Cappello Giovanni , Pierobon Paolo , Symonds Clémentine , Busoni Lorenzo , Christof J. , Gebhardt M. , Rief Matthias , Prost Jacques
Published: September 2007

We observe the myosin V stepping mechanism by traveling wave tracking. This technique, associated with optical tweezers, allows one to follow a scattering particle in a two-dimensional plane, with nanometer accuracy and a temporal resolution in the microsecond range. We have observed that, at the millisecond time scale, the myosin V combines longitudinal and vertical motions during the step. Because at this time scale the steps appear heterogeneous, we deduce their general features by aligning and averaging a large number of them. Our data show that the 36-nm step occurs in three main stages. First, the myosin center of mass moves forward 5 nm; the duration of this short prestep depends on the ATP concentration. Second, the motor performs a fast motion over 23 nm; this motion is associated to a vertical movement of the myosin center of mass, whose distance from the actin filament increases by 6 nm. Third, the myosin head freely diffuses toward the next binding site and the vertical position is recovered. We propose a simple model to describe the step mechanism of the dimeric myosin V.
Thousand-year-long Chinese time series reveals climatic forcing of decadal locust dynamics
Authors: Stige Leif Christian , Chan Kung-Sik , Zhang Zhibin , Frank David , Stenseth Nils C.
Published: September 2007

For >1,000 years, Chinese officials have recorded the annual abundance of the oriental migratory locust
Locusta migratoria manilensis
, with the ultimate aim of predicting locust outbreaks. Linking these records with temperature and precipitation reconstructions for the period 957-1956, we show that decadal mean locust abundance is highest during cold and wet periods. These periods coincide with above-average frequencies of both floods and droughts in the lower Yangtze River, phenomena that are associated with locust outbreaks. Our results imply differential ecological responses to interdecadal and interannual climatic variability. Such frequency-dependent effects deserve increased attention in global warming studies.
Wiskott–Aldrich syndrome protein (WASP) and N-WASP are critical for T cell development
Authors: Cotta-de-Almeida Vinicius , Westerberg Lisa , Maillard Michel H. , Onaldi Dilek , Wachtel Heather , Meelu Parool , Chung Ung-il , Xavier Ramnik , Alt Frederick W. , Snapper Scott B.
Published: September 2007

Although T cell dysfunction and lymphopenia are key features of immunodeficient patients with the Wiskott–Aldrich syndrome and Wiskott–Aldrich syndrome protein (WASP)-deficient mice, T cell development appears relatively normal. We hypothesized that N-WASP, a ubiquitously expressed homologue of WASP, may serve a redundant function with WASP. To examine the unique and redundant activities of WASP and N-WASP, we generated ES cells devoid of WASP and N-WASP [double knockout (DKO)] and used the RAG-2-deficient blastocyst complementation system to generate DKO lymphocytes. Moreover, we mated WASP KO mice with mice containing a conditionally targeted N-WASP allele and used the Cre-loxP system to generate mice lacking WASP and N-WASP in T cells [conditional DKO (cDKO)]. In both systems, N-WASP-deficient cells were indistinguishable from WT cells. In contrast, T cell development in DKO and cDKO mice was markedly altered, as shown by thymic hypocellularity and reduced numbers of peripheral T cells. We found that the combined activity of WASP and N-WASP was important for CD4−CD8−double-negative (DN)-to-CD4+CD8+double-positive (DP) cell transition, and this may be partly explained by reduced cycling DN3 cells. In addition, decreased migratory responses of CD4+CD8−and CD4−CD8+single-positive (SP) cells and increased percentage of CD69lowCD24lowand CD62LlowSP cells in cDKO cells imply retention of SP cells in the thymus. In summary, this study suggests that, although WASP serves a unique role for peripheral T cell function, T cell development depends on the combined activity of WASP and N-WASP.
Changes in climate and land use have a larger direct impact than rising CO
2
on global river runoff trends
Authors: Piao Shilong , Friedlingstein Pierre , Ciais Philippe , de Noblet-Ducoudré Nathalie , Labat David , Zaehle Sönke
Published: September 2007

The significant worldwide increase in observed river runoff has been tentatively attributed to the stomatal “antitranspirant” response of plants to rising atmospheric CO
2
[Gedney N, Cox PM, Betts RA, Boucher O, Huntingford C, Stott PA (2006)
Nature
439: 835–838]. However, CO
2
also is a plant fertilizer. When allowing for the increase in foliage area that results from increasing atmospheric CO
2
levels in a global vegetation model, we find a decrease in global runoff from 1901 to 1999. This finding highlights the importance of vegetation structure feedback on the water balance of the land surface. Therefore, the elevated atmospheric CO
2
concentration does not explain the estimated increase in global runoff over the last century. In contrast, we find that changes in mean climate, as well as its variability, do contribute to the global runoff increase. Using historic land-use data, we show that land-use change plays an additional important role in controlling regional runoff values, particularly in the tropics. Land-use change has been strongest in tropical regions, and its contribution is substantially larger than that of climate change. On average, land-use change has increased global runoff by 0.08 mm/year
2
and accounts for ≈50% of the reconstructed global runoff trend over the last century. Therefore, we emphasize the importance of land-cover change in forecasting future freshwater availability and climate.
IL-20 is an arteriogenic cytokine that remodels collateral networks and improves functions of ischemic hind limbs
Authors: Tritsaris Katerina , Myren Maja , Ditlev Sisse B. , Hübschmann Martin V. , van der Blom Ida , Hansen Anker Jon , Olsen Uffe B. , Cao Renhai , Zhang Junhang , Jia Tanghong , Wahlberg Eric , Dissing Steen , Cao Yihai
Published: September 2007

Successful therapeutic angiogenesis for the treatment of ischemic disorders relies on selection of optimal proangiogenic or arteriogenic agents that are able to promote establishment of functional collateral networks. Here, we show that IL-20, a pleiotropic inflammatory cytokine, displays an imperative effect on vascular remodeling. Stimulation of both large and microvascular endothelial cells with IL-20 leads to activation of receptor-dependent multiple intracellular signaling components, including increased phosphorylation levels of JAK2/STAT5, Erk1/2, and Akt; activation of small GTP-binding proteins Rac and Rho; and intracellular release of calcium. Surprisingly, IL-20 significantly promotes endothelial cell tube formation without affecting their proliferation and motility. These findings suggest that the vascular function of IL-20 involves endothelial cell organization, vessel maturation, and remodeling. Consistent with this notion, delivery of IL-20 to the ischemic muscle tissue significantly improves arteriogenesis and blood perfusion in a rat hind-limb model. Our findings provide mechanistic insights on vascular functions of IL-20 and define therapeutic implication of this cytokine for the treatment of ischemic disorders.
Species-specific positive selection of the male-specific lethal complex that participates in dosage compensation in
Drosophila
Authors: Rodriguez Monica A. , Vermaak Danielle , Bayes Joshua J. , Malik Harmit S.
Published: September 2007

In many taxa, males and females have unequal ratios of sex chromosomes to autosomes, which has resulted in the invention of diverse mechanisms to equilibrate gene expression between the sexes (dosage compensation). Failure to compensate for sex chromosome dosage results in male lethality in
Drosophila
. In
Drosophila
, a male-specific lethal (MSL) complex of proteins and noncoding RNAs binds to hundreds of sites on the single male X chromosome and up-regulates gene expression. Here we use population genetics of two closely related
Drosophila
species to show that adaptive evolution has occurred in all five protein-coding genes of the MSL complex. This positive selection is asymmetric between closely related species, with a very strong signature apparent in
Drosophila melanogaster
but not in
Drosophila simulans
. In particular, the MSL1 and MSL2 proteins have undergone dramatic positive selection in
D. melanogaster
, in domains previously shown to be responsible for their specific targeting to the X chromosome. This signature of positive selection at an essential protein–DNA interface of the complex is unexpected and suggests that X chromosomal MSL-binding DNA segments may themselves be changing rapidly. This highly asymmetric, rapid evolution of the MSL genes further suggests that misregulated dosage compensation may represent one of the underlying causes of male hybrid inviability in
Drosophila
, wherein the fate of hybrid males depends on which species' X chromosome is inherited.