bluuebunny/crossref_metadata_2025_split huggingface dataset:
I/St Mice Hypersusceptible toMycobacterium tuberculosisAre Resistant toM. avium
Authors: Kondratieva E. V. , Evstifeev V. V. , Kondratieva T. K. , Petrovskaya S. N. , Pichugin A. V. , Rubakova E. I. , Averbakh M. M. , Apt A. S. 
Published: July 2007

ABSTRACTWe previously demonstrated that mice of the I/St strain are extremely susceptible toMycobacterium tuberculosis, as well as to the taxonomically distant intracellular bacteriaChlamydia pneumoniaeandSalmonella enterica. To broaden our knowledge about the control of susceptibility to intracellular pathogens, we studied the infection caused byMycobacterium aviumvirulent strain 724 in a panel of inbred mouse strains and found that I/St mice are resistant toM. avium. By comparing I/St mice with B6 mice, we demonstrated that (i) B6 mice are much more susceptible to infection caused byM. aviumin terms of bacterial multiplication in the lung tissue and severity of lung pathology; (ii) in B6 mice but not in I/St mice infection leads to prolonged leukocyte infiltration of the lung tissue, development of necrotic lung granulomata, and lethality; and (iii) the unfavorable infectious course in B6 mice is accompanied by elevated production of gamma interferon, tumor necrosis factor alpha, and especially interleukin-12 in the lungs. Importantly,M. avium-resistant I/St mice carry a functionalrallele of theSlc11a1(formerlyNramp1) gene, while B6 mice have theSlc11a1sgenotype. Segregation genetic analysis of (I/St × B6) F2 hybrids demonstrated that susceptibility or resistance to infection caused byM. aviumlargely depended upon theSlc11a1genotype and that other genetic traits had a relatively weak influence. This close-to-monogenic pattern differs sharply from the host control of many other intracellular bacterial infections, for which the involvement of numerous quantitative trait loci has been ubiquitously observed.
c-Jun N-Terminal Kinase 1 Is Required for Toll-Like Receptor 1 Gene Expression in Macrophages
Authors: Izadi Hooman , Motameni Amirreza T. , Bates Tonya C. , Olivera Elias R. , Villar-Suarez Vega , Joshi Ila , Garg Renu , Osborne Barbara A. , Davis Roger J. , Rincón Mercedes , Anguita Juan 
Published: July 2007

ABSTRACTThe regulation of innate immune responses to pathogens occurs through the interaction of Toll-like receptors (TLRs) with pathogen-associated molecular patterns and the activation of several signaling pathways whose contribution to the overall innate immune response to pathogens is poorly understood. We demonstrate a mechanism of control of murine macrophage responses mediated by TLR1/2 heterodimers through c-Jun N-terminal kinase 1 (JNK1) activity. JNK controls tumor necrosis factor alpha production and TLR-mediated macrophage responses toBorrelia burgdorferi, the causative agent of Lyme disease, and the TLR1/TLR2-specific agonist PAM3CSK4. JNK1, but not JNK2, activity regulates the expression of thetlr1gene in the macrophage cell line RAW264.7, as well as in primary CD11b+cells. We also show that the proximal promoter region of the humantlr1gene contains an AP-1 binding site that is subjected to regulation by the kinase and binds two complexes that involve the JNK substrates c-Jun, JunD, and ATF-2. These results demonstrate that JNK1 regulates the response to TLR1/2 ligands and suggest a positive feedback loop that may serve to increase the innate immune response to the spirochete.
Impaired Expression of Perforin and Granulysin in CD8+T Cells at the Site of Infection in Human Chronic Pulmonary Tuberculosis
Authors: Andersson Jan , Samarina Arina , Fink Joshua , Rahman Sayma , Grundström Susanna 
Published: July 2007

ABSTRACTProtective immunity in tuberculosis is dependent on the coordinated release of cytolytic effector molecules from effector T cells and the subsequent granule-associated killing of infected target cells. In this study, we investigated the expression of cytolytic (perforin and granzyme A) and antimicrobial (granulysin) molecules at the single-cell level in cryopreserved lung tissue from patients with chronic, progressive tuberculosis disease. Quantification of protein-expressing cells was performed by in situ imaging, while mRNA levels in the infected tissue were analyzed by real-time PCR. Persistent inflammation, including excessive expression of inducible nitric oxide synthase in CD68+macrophages and significant infiltration of CD3+, CD8+and CD4+T cells, was evident in tuberculosis lesions in all patients. However, despite the accumulation of CD3+T cells, perforin- and granulysin-expressing CD3+T cells were detected at two- to threefold-lower ratios in the tuberculosis lesions than in distal lung parenchyma and uninfected control lungs, respectively. This was evident at both the protein and mRNA levels. Moreover, perforin- and granulysin-expressing CD8+T cells were scarce in individual granulomas within the tuberculosis lesions. In contrast, significant up-regulation of granzyme A-expressing CD3+T cells was evident in the lesions from all patients. Confocal microscopy revealed coexpression of perforin and granulysin, primarily in CD8+T cells; however, this expression was lower in the tuberculosis lesions. These findings suggest that symptomatic, chronic tuberculosis disease is associated with insufficient up-regulation of perforin and granulysin coexpression in CD8+T cells at the local site of infection.
T-Cell-Independent Humoral Immunity Is Sufficient for Protection against Fatal Intracellular Ehrlichia Infection
Authors: Bitsaktsis Constantine , Nandi Bisweswar , Racine Rachael , MacNamara Katherine C. , Winslow Gary 
Published: July 2007

ABSTRACTAlthough humoral immunity has been shown to contribute to host defense during intracellular bacterial infections, its role has generally been ancillary. Instead, CD4 T cells are often considered to play the dominant role in protective immunity via their production of type I cytokines. Our studies of highly pathogenicEhrlichiabacteria isolated fromIxodes ovatus(IOE) reveal, however, that this paradigm is not always correct. Immunity to IOE infection can be induced by infection with a closely related weakly pathogenic ehrlichia,Ehrlichia muris.Type I cytokines (i.e., gamma interferon, tumor necrosis factor alpha, and interleukin-12) were not necessary forE. muris-induced immunity. In contrast, humoral immunity was essential, as shown by the fact thatE. muris-infected B-cell-deficient mice were not protected from IOE challenge and becauseE. murisimmunization was effective in CD4-, CD8-, and major histocompatibility complex (MHC) class II-deficient mice. Immunity was unlikely due to nonspecific inflammation, as prior infection withListeria monocytogenesdid not induce immunity to IOE. Antisera from both wild-type and MHC-II-deficient mice provided at least partial resistance to challenge infection, and protection could also be achieved following transfer of total, but not B-cell-depleted, splenocytes obtained fromE. muris-immunized mice. The titers of class-switched antibodies in immunized CD4 T-cell- and MHC class II-deficient mice, although lower than those observed in immunized wild-type mice, were significant, indicating thatE. muriscan induce class switch recombination in the absence of classical T-cell-mediated help. These studies highlight a major protective role for classical T-cell-independent humoral immunity during an intracellular bacterial infection.
Genetic Alteration ofMycobacterium smegmatisTo Improve Mycobacterium-Mediated Transfer of Plasmid DNA into Mammalian Cells and DNA Immunization
Authors: Mo Yongkai , Quanquin Natalie M. , Vecino William H. , Ranganathan Uma Devi , Tesfa Lydia , Bourn William , Derbyshire Keith M. , Letvin Norman L. , Jacobs William R. , Fennelly Glenn J. 
Published: July 2007

ABSTRACTMycobacteria target and persist within phagocytic monocytes and are strong adjuvants, making them attractive candidate vectors for DNA vaccines. We characterized the ability of mycobacteria to deliver transgenes to mammalian cells and the effects of various bacterial chromosomal mutations on the efficiency of transfer in vivo and in vitro. First, we observed green fluorescent protein expression via microscopy and fluorescence-activated cell sorting analysis after infection of phagocytic and nonphagocytic cell lines byMycobacterium smegmatisorM. bovisBCG harboring a plasmid encoding the fluorescence gene under the control of a eukaryotic promoter. Next, we compared the efficiencies of gene transfer usingM. smegmatisor BCG containing chromosomal insertions or deletions that cause early lysis, hyperconjugation, or an increased plasmid copy number. We observed a significant—albeit only 1.7-fold—increase in the level of plasmid transfer to eukaryotic cells infected withM. smegmatishyperconjugation mutants.M. smegmatisstrains that overexpressed replication proteins (Rep) of pAL5000, a plasmid whose replicon is incorporated in many mycobacterial constructs, generated a 10-fold increase in plasmid copy number and 3.5-fold and 3-fold increases in gene transfer efficiency to HeLa cells and J774 cells, respectively. Although BCG strains overexpressing Rep could not be recovered, BCG harboring a plasmid with a copy-up mutation inoriMresulted in a threefold increase in gene transfer to J774 cells. Moreover,M. smegmatisstrains overexpressing Rep enhanced gene transfer in vivo compared with a wild-type control. Immunization of mice with mycobacteria harboring a plasmid (pgp120hE) encoding human immunodeficiency virus gp120 elicited gp120-specific CD8 T-cell responses among splenocytes and peripheral blood mononuclear cells that were up to twofold (P< 0.05) and threefold (P< 0.001) higher, respectively, in strains supporting higher copy numbers. The magnitude of these responses was approximately one-half of that observed after intramuscular immunization with pgp120hE.M. smegmatisand other nonpathogenic mycobacteria are promising candidate vectors for DNA vaccine delivery.
Effects of elevated carbon dioxide and sucrose concentrations onArabidopsis thalianaroot architecture and anatomy
Authors: Lee-Ho Elaine , Walton Linda J. , Reid David M. , Yeung Edward C. , Kurepin Leonid V. 
Published: July 2007

The objective of this study was to evaluate the effects of elevated carbon dioxide and sucrose concentrations on Arabidopsis thaliana L. Heynh root growth, morphology, and architecture. Two levels of CO2, 360 (ambient) and 900 (elevated) μmol·mol–1, and various sucrose concentrations were used. A. thaliana plants grown on a phytagar medium in small chambers with elevated CO2had longer roots, more lateral root growth and a more dichotomous branching pattern than plants grown in ambient CO2. Roots in elevated CO2had wider root diameters, and showed considerably more secondary growth such as larger diameter vascular cylinders and better-developed periderm. Addition of sucrose to the media closely resembled the effects of elevated CO2. Further, the increase in sucrose concentration had a more pronounced effect on root morphology under ambient, than elevated CO2. Thus, both elevated CO2and increased sucrose concentrations promote root growth by increasing their number, length, and diameter, and by changing the branching pattern from herringbone to dichotomous.
Trametes gibbosa (Basidiomycetes, Polyporales) in the USA and Canada
Authors: Kout J. , Vlasák J. 
Published: July 2007

The polypore Trametes gibbosa (Pers.) Fries, common in Europe and Asia, is reported from eastern North America for the first time. Single basidiospore cultures from Pennsylvania, United States, and Quebec, Canada, were paired with each other and with cultures from the Czech Republic. The North American intercollection crosses were 60% compatible and 100% compatible with the Czech cultures. All the crosses among the Czech cultures were 100% compatible. The recent introduction of T. gibbosa to North America is suggested as a possible explanation for the limited number of mating-type alleles and subsequent incompatibility among the North American cultures.
Vegetation responses to conifer encroachment in a western Cascade meadow: a chronosequence approach
Authors: Haugo Ryan D. , Halpern Charles B. 
Published: July 2007

Conifer invasion of mountain meadows is pervasive in western North America, but its consequences for plant composition and diversity have not been studied. We used a chronosequence approach to reconstruct temporal patterns of vegetation change in response to ~200 years of conifer encroachment of a dry, montane meadow in the western Cascade Range, Oregon. Tree age distributions, forest structure, light, and vegetation composition were determined for three hundred and fifty-six 10 m × 10 m samples representing a gradient from open meadow to old forest (>90 years). Nonmetric multidimensional scaling revealed strong turnover in species composition from open meadow to old forest. Ordination axes were highly correlated with light availability and density/basal area of encroaching grand fir, Abies grandis (Dougl. ex D. Don) Lindl., and lodgepole pine, Pinus contorta Dougl. ex Loud. Cover of meadow species declined steeply with establishment of A. grandis ; richness declined more gradually and extirpations of meadow species were rare. Forest herbs colonized within two decades of tree establishment and within 60–80 years dominated the understory flora. In contrast with meadow species, changes in richness and cover of forest herbs were weakly related to changes in forest structure. Rapid replacement of meadow by forest species and long-term effects of trees on soils may limit potential for restoration of these unique habitats.
The association between floral longevity and pollen removal, pollen receipt, and fruit production in flame azalea (Rhododendron calendulaceum)
Authors: Blair Amy C. , Wolfe Lorne M. 
Published: July 2007

Floral longevity is an important feature of a plant’s reproductive strategy. The goal of this study was to examine flower life span in the shrub flame azalea ( Rhododendron calendulaceum (Michx.) Torr.) to determine if it is fixed or plastic and to evaluate its association with pollen removal and receipt. Unmanipulated flowers remained open for ~10 days, while hand-pollinated flowers closed earlier (~7 days), indicating that these flowers are subject to pollination-induced senescence. In 2002, pollen removal was rapid (~70% of pollen was removed in the first 2 h of anthesis), while female function was a slower process (pollen accumulated on stigmas for up to 4 days). Fruit set was pollen limited, as 80% of hand-outcrossed flowers set fruit versus 35% of naturally pollinated flowers. This is likely the result of the pollen-collecting behavior of a common solitary bee, which did not contact stigmas. In sharp contrast, 2003 was a cooler and wetter spring, few flower visitors were observed, and virtually no pollen was removed from or deposited on stigmas after 48 h. These results suggest that the flower life span of flame azalea is a result of selection for increasing the probability of pollen receipt rather than pollen dispersal.
Seasonal variation in plant nutritive quality for Greater Snow Goose goslings in mesic tundra
Authors: Audet Benoît , Lévesque Esther , Gauthier Gilles 
Published: July 2007

Variation in nutritive quality over time and among forage plants is important for herbivores such as geese. We examined the seasonal variation of some nutritive attributes (nitrogen, neutral detergent fibre, and phenolic compounds) of five plant species consumed by Greater Snow Geese ( Chen caerulescens atlantica ) L. in mesic tundra, a habitat where goose feeding ecology has been little studied compared with wetlands. We sampled ungrazed, aboveground plant tissues five times at 10–14 d intervals between 1 July and 15 August 2003 on Bylot Island, Nunavut. The species were Arctagrostis latifolia (R. Br.) Griseb. (Gramineae), Luzula nivalis (Laest.) Beurl. (Juncaceae), Oxytropis maydelliana Trautv. (Leguminosae), Oxyria digyna (L.) Hill, and Polygonum viviparum L. (both Polygonaceae). All species showed a seasonal decline in nitrogen content in both leaves and flowering heads (includes flowers and fruits) but the amplitude was variable among species (from 10% to 62% decline depending on the species). Neutral detergent fibre concentration in leaves remained stable or increased slightly over time in contrast to flowering heads where it increased in all species (from 7% to 94%). Fibre content was higher in flowering heads than in leaves. The total content of phenolic compounds varied throughout the summer. In some cases, the content of phenolic compounds remained stable but in others it initially increased and then decreased later on, or it increased throughout the summer. Seasonal variations in plant nutritive quality were smaller than interspecific differences. The nitrogen content of forbs (especially Oxytropis ) was high and their fibre content low compared with the grass and rush species (Luzula), particularly during the early summer.
Macromolecular dynamics of the photosynthetic system over a seasonal developmental progression in Spartina alterniflora
Authors: Morash Andrea J. , Campbell Douglas A. , Ireland Robert J. 
Published: July 2007

Spartina alterniflora Loisel. is a dominant primary producer in salt marsh intertidal zones along the Bay of Fundy of New Brunswick and Nova Scotia, Canada, where it has a 5-month growing season from May to September. We quantified key subunits of the S. alterniflora photosynthetic system (chlorophyll, PsbA, PsaC, AtpB, RbcL) over a seasonal developmental progression to determine resource allocations and estimate capacities for key subprocesses of photosynthesis catalyzed by light-harvesting antennae, photosystems I and II (PSI and PSII, respectively), ATP (adenosine triphosphate) synthase, and RuBisCO (ribulose bisphosphate carboxylase–oxygenase). Early in the season, all of the macromolecules peaked in concentration around day 159, but then declined as leaves elongated. Later in the season, just after flowering, chlorophyll b, PsbA, PsaC, and AtpB peaked again before declining at the end of the season. RbcL, however, did not exhibit a second late-season peak, but continually declined from the early-season peak. Estimates of metabolic flux per PSII and per RuBisCO were closely parallel until late in the season, indicating coordinated regulation of catalytic turnover per complex. Early in the season, carbon fixation per RuBisCO peaked near the expected turnover rate (kcat) for a C4 plant, but then declined. The effective absorbance cross sections of PSII varied seasonally, reflecting significant regulation of antenna performance across the season.
Environmental and biotic controls on bryophyte productivity along forest to peatland ecotones
Authors: Bauer Ilka E. , Tirlea Diana , Bhatti Jagtar S. , Errington Ruth C. 
Published: July 2007

Bryophyte growth and production can be critical measurements in quantifying carbon input into peatlands. For any species, total biomass produced in a given year is determined by three main factors: abundance of the species, bulk density, and annual (length) increment. We examined the relationship of these parameters to environmental factors (water table depth, tree canopy cover) and biotic interactions (presence of other species) in seven common peatland bryophytes. Correlations suggest that bulk density changed in response to environmental variation in Sphagnum angustifolium (C. Jens. ex Russ.) C. Jens. in Tolf, Sphagnum fuscum (Schimp.) Klinggr., and Aulacomnium palustre (Hedw.) Schwaegr., and it remained constant in Pleurozium schreberi (Brid.) Mitt., Hylocomium splendens (Hedw.) Schimp. in B.S.G., Tomenthypnum nitens (Hedw.) Loeske, and Hamatocaulis vernicosus (Mitt.) Hedenäs. Length increment was dependent on water table depth in S. angustifolium, P. schreberi, and Hamatocaulis vernicosus, and changed with canopy cover in H. splendens at one of two sites examined. Overall, our results suggest that (i) in some species, changes in bulk density are likely to be an important component of changes in productivity in response to environmental variation; (ii) local vigour tends to increase with abundance, but may not do so in all cases; and (iii) phenomena such as biotic interactions and environmental extremes may lead to non-linearity of productivity responses to environmental change.
Fractal fits to Riemann zeros
Authors: Slater P B 
Published: July 2007

Wu and Sprung (Phys. Rev. E, 48, 2595 (1993)) reproduced the first 500 nontrivial Riemann zeros, using a one-dimensional local potential model. They concluded — as did van Zyl and Hutchinson (Phys. Rev. E, 67, 066211 (2003)) — that the potential possesses a fractal structure of dimension d = 3/2. We model the nonsmooth fluctuating part of the potential by the alternating-sign sine series fractal of Berry and Lewis A(x,γ). Setting d = 3/2, we estimate the frequency parameter (γ), plus an overall scaling parameter (σ) that we introduce. We search for that pair of parameters (γ,σ) that minimizes the least-squares fit Sn(γ,σ) of the lowest n eigenvalues — obtained by solving the one-dimensional stationary (nonfractal) Schrodinger equation with the trial potential (smooth plus nonsmooth parts) — to the lowest n Riemann zeros for n = 25. For the additional cases, we study, n = 50 and 75, we simply set σ = 1. The fits obtained are compared to those found by using just the smooth part of the Wu–Sprung potential without any fractal supplementation. Some limited improvement — 5.7261 versus 6.392 07 (n = 25), 11.2672 versus 11.7002 (n = 50), and 16.3119 versus 16.6809 (n = 75) — is found in our (nonoptimized, computationally bound) search procedures. The improvements are relatively strong in the vicinities of γ = 3 and (its square) 9. Further, we extend the Wu-Sprung semiclassical framework to include higher order corrections from the Riemann–von Mangoldt formula (beyond the leading, dominant term) into the smooth potential. PACS Nos.: 02.10.De, 03.65.Sq, 05.45.Df, 05.45.Mt
Gauging Newton's law
Authors: Wheeler James T 
Published: July 2007

We derive both Lagrangian and Hamiltonian mechanics as gauge theories of Newtonian mechanics. Systematic development of the distinct symmetries of dynamics and measurement suggest that gauge theory may be motivated as a reconciliation of dynamics with measurement. Applying this principle to Newton's law with the simplest measurement theory leads to Lagrangian mechanics, while use of conformal measurement theory leads to Hamiltonian mechanics. PACS Nos.: 45.20.Jj, 11.25.Hf, 45.10.–b
D-branes behind the horizon
Authors: Rozali M 
Published: July 2007

We review the study of D-particles in the two-dimensional black-hole background, concentrating on aspects of the dynamics that are sensitive to the region behind the horizon. Surprisingly, the portion of the trajectory behind the horizon appears to an asymptotic observer as ghost D-particle. This suggests a way of constructing a matrix model for the Lorentzian black-hole background. PACS No.: 11.25.Uv
Formation of antihydrogen in the ground state
Authors: Kulhar V S 
Published: July 2007

Cross sections for antihydrogen formation in the ground state for the process [Formula: see text] + Ps(nlm) → [Formula: see text](1s) + e– have been calculated using charge conjugation and time reversal invariance. Calculations are based on a two-state approximation method, used by the author earlier for positron–hydrogen charge -exchange process (e+ – H → Ps(nlm) + p). Cross-section results are reported in the intermediate- and high-energy region (20 keV – 500 keV). PACS No.: 36.10.Dr