bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitric oxide contributes both to papilla‐based resistance and the hypersensitive response in barley attacked by Blumeria graminis f. sp. hordei
Authors: PRATS ELENA , MUR LUIS A. J. , SANDERSON RUTH , CARVER TIMOTHY L. W. 
Published: February 2005

SUMMARYNonspecific penetration resistance due to papilla formation and race‐specific hypersensitive response (HR) can both contribute to Blumeria graminis resistance in barley. Some effective papillae form even in the susceptible cv. Pallas and the isoline P01 carries the additional Mla1 allele conditioning HR. The NO‐specific stain DAF‐2DA (4,5‐diaminofluorescein‐2‐diacetate) revealed a transient NO generation burst commencing 10 h after inoculation (h.a.i.) in close association with sites of papilla formation in both barley lines. In P01 a burst of NO production throughout some attacked cells was initiated around 10–12 h.a.i. and this preceded whole‐cell autofluorescence indicative of HR. The specificity of DAF‐2DA staining was demonstrated by the suppression of staining following application of the NO scavenger C‐PTIO (1H‐imidazol‐1‐yloxy‐2‐(4‐carboxyphenyl)‐4,5‐dihydro‐4,4,5,5‐tetramethyl‐3‐oxide). In addition, C‐PTIO application increased penetration frequencies in both barley lines, indicating a role for NO in papilla‐based resistance. Furthermore, C‐PTIO application slightly delayed HR in P01 whereas, conversely, application of an NO donor, sodium nitroprusside, slightly accelerated HR in P01 and increased cell death frequency in Pallas. Thus, NO generation is one of the earliest responses of barley epidermal cell defence against B. graminis attack and may be important in both the initiation and the development of effective papillae and cell death due to HR.
Prediction of haemorrhage in the early stage of acute myeloid leukaemia by flow cytometric analysis of platelet function
Authors: Leinoe Eva Birgitte , Hoffmann Marianne Hutchings , Kjaersgaard Erik , Nielsen Joern Dalsgaard , Bergmann Olav Jonas , Klausen Tobias Wirenfeldt , Johnsen Hans Erik 
Published: February 2005

SummaryHaemorrhage is often responsible for the lethal course of acute myeloid leukaemia (AML). Previously, multiple platelet function defects were identified by flow cytometric analysis of platelet activation markers in AML. The role of flow cytometric analysis of platelet function in characterization of prognostic markers of haemorrhage in AML patients has not been well elucidated. The objective of this prospective study was to analyse platelet function in 50 AML patients at diagnosis and to compare results with clinical bleeding score, graded by common toxicity criteria. Platelet activation markers CD62P, CD42b, CD63 and PAC‐1 were analysed following in vitro activation by thrombin receptor activating peptide. The following plasma haemostasis parameters were measured: soluble P‐selectin, activated partial thromboplastin time, thrombin time, prothrombin time, d‐dimer, fibrinogen, and von Willebrand factor antigen. In a multivariate analysis, P‐selectin (CD62P) <36 molecules of equivalent soluble fluorochrome × 103 (P < 0·0015) and platelet count <40 × 109/l (P = 0·01) were significant predictors of haemorrhage at diagnosis. Haemorrhage at diagnosis predicted grade 3–4 haemorrhage in the first 28 d following diagnosis (P = 0·018). The presented results indicate that low P‐selectin is a prognostic marker of haemorrhage in AML.
The effect of hypoxia and stem cell source on haemoglobin switching
Authors: Daisy Narayan A. , Ersek Adel , Campbell Thomas A. , Colón Donna M. , Pixley John S. , Zanjani Esmail D. 
Published: February 2005

SummaryThis study investigated whether relative changes that accompany the naturally occurring shifts in haematopoietic sites during human development play a role in haemoglobin (Hb) switching or whether Hb switching is innately programmed into cells. CD34+/Lineage− haematopoietic stem/progenitor cells (HSCs) were isolated from human fetal liver (F‐LVR), cord blood (CB), and adult bone marrow (ABM), and the Hb was characterized by flow cytometry on cultures that generated enucleated red cells. All feeder layers (stroma from F‐LVR, ABM, and human fetal aorta) enhanced cell proliferation and erythropoiesis but did not affect Hb type. HSCs from CB and F‐LVR generated the same Hb profile under normoxia and hypoxia. HSCs from ABM had single‐positive HbA and double‐positive HbA and HbF cells at normoxia and almost entirely double‐positive cells at hypoxia. Further characterization of these ABM cultures was determined by following mRNA expression for the transcription factors erythroid Kruppel‐like factor (EKLF) and fetal Kruppel‐like factor (FKLF) as a function of time in cultures under hypoxia and normoxia. The erythroid‐specific isoform of 5‐amino‐levulinate synthase (ALAS2) was also expressed under hypoxic conditions. We conclude that Hb switching is affected by the environment but not all HSCs are preprogrammed to respond.
Childhood paroxysmal nocturnal haemoglobinuria (PNH), a report of 11 cases in the Netherlands
Authors: Van Den Heuvel‐Eibrink M. M. , Bredius R. G. M. , Te Winkel M. L. , Tamminga R. , de Kraker J. , Schouten‐van Meeteren A. Y. N. , Bruin M. , Korthof E. T. 
Published: February 2005

SummaryParoxysmal nocturnal haemoglobinuria (PNH) is characterized by intravascular haemolysis, nocturnal haemoglobinuria, thrombotic events, serious infections and bone marrow failure. This acquired disease, caused by a deficiency of glycosylphosphatidylinositol (GPI) anchored proteins on the haematopoietic cells, is rare in children. We describe 11 Dutch paediatric PNH patients (median age: 12 years, range 9–17 years) diagnosed since 1983, seven cases associated with aplastic anaemia (AA), four with myelodysplastic syndrome (MDS). Presenting symptoms were haemorrhagic diathesis (n = 10), palor/tiredness (n = 8), dark urine (n = 1), fever (n = 1) and serious weight loss (n = 1). Treatment consisted of prednisolone (n = 7), anti‐thymocyte globulin (n = 3) and/or androgens (n = 5). Eventually, five patients received a bone marrow transplantation (BMT) (three matched unrelated donors/two matched family donors), of whom four are still alive. PNH, diagnosed by immunophenotypic GPI‐linked anchor protein analysis, should be considered in all children with AA or MDS. BMT should be considered as a therapeutic option in every paediatric PNH patient with BM failure.
GATA1 mutation and trisomy 21 are required only in haematopoietic cells for development of transient myeloproliferative disorder
Authors: Carpenter Emily , Valverde‐Garduno Veronica , Sternberg Alex , Mitchell Chris , Roberts Irene , Vyas Paresh , Vora Ajay 
Published: February 2005

SummaryTrisomy 21 [Down's syndrome (DS)] and mutations in transcription factor GATA1 predispose neonates to a transient myeloproliferative disorder (TMD) and/or acute megakaryocytic leukaemia (AMKL). The role of trisomy 21 in their pathogenesis is unclear. We previously reported two rare neonates without DS who had TMD, one of whom progressed to AMKL. Trisomy 21 was detected only in blood cells at presentation with TMD/AMKL and disappeared with disease resolution. We now show that the blood cells at presentation of TMD harboured GATA1 genomic DNA mutations, suggesting a requirement for trisomy 21 in haematopoietic cells, rather than other cell types, for development of TMD/AMKL.
Estimating diurnal to annual ecosystem parameters by synthesis of a carbon flux model with eddy covariance net ecosystem exchange observations
Authors: Braswell Bobby H. , Sacks William J. , Linder Ernst , Schimel David S. 
Published: February 2005

AbstractWe performed a synthetic analysis of Harvard Forest net ecosystem exchange of CO2(NEE) time series and a simple ecosystem carbon flux model, the simplified Photosynthesis and Evapo‐Transpiration model (SIPNET). SIPNET runs at a half‐daily time step, and has two vegetation carbon pools, a single aggregated soil carbon pool, and a simple soil moisture sub‐model. We used a stochastic Bayesian parameter estimation technique that provided posterior distributions of the model parameters, conditioned on the observed fluxes and the model equations. In this analysis, we estimated the values of all quantities that govern model behavior, including both rate constants and initial conditions for carbon pools. The purpose of this analysis was not to calibrate the model to make predictions about future fluxes but rather to understand how much information about process controls can be derived directly from the NEE observations. A wavelet decomposition enabled us to assess model performance at multiple time scales from diurnal to decadal. The model parameters are most highly constrained by eddy flux data at daily to seasonal time scales, suggesting that this approach is not useful for calculating annual integrals. However, the ability of the model to fit both the diurnal and seasonal variability patterns in the data simultaneously, using the same parameter set, indicates the effectiveness of this parameter estimation method. Our results quantify the extent to which the eddy covariance data contain information about the ecosystem process parameters represented in the model, and suggest several next steps in model development and observations for improved synthesis of models with flux observations.
Soil microbial responses to experimental warming and clipping in a tallgrass prairie
Authors: Zhang W. , Parker K. M. , Luo Y. , Wan S. , Wallace L. L. , Hu S. 
Published: February 2005

AbstractGlobal surface temperature is predicted to increase by 1.4–5.8°C by the end of this century. However, the impacts of this projected warming on soil C balance and the C budget of terrestrial ecosystems are not clear. One major source of uncertainty stems from warming effects on soil microbes, which exert a dominant influence on the net C balance of terrestrial ecosystems by controlling organic matter decomposition and plant nutrient availability. We, therefore, conducted an experiment in a tallgrass prairie ecosystem at the Great Plain Apiaries (near Norman, OK) to study soil microbial responses to temperature elevation of about 2°C through artificial heating in clipped and unclipped field plots. While warming did not induce significant changes in net N mineralization, soil microbial biomass and respiration rate, it tended to reduce extractable inorganic N during the second and third warming years, likely through increasing plant uptake. In addition, microbial substrate utilization patterns and the profiles of microbial phospholipid fatty acids (PLFAs) showed that warming caused a shift in the soil microbial community structure in unclipped subplots, leading to the relative dominance of fungi as evidenced by the increased ratio of fungal to bacterial PLFAs. However, no warming effect on soil microbial community structure was found in clipped subplots where a similar scale of temperature increase occurred. Clipping also significantly reduced soil microbial biomass and respiration rate in both warmed and unwarmed plots. These results indicated that warming‐led enhancement of plant growth rather than the temperature increase itself may primarily regulate soil microbial response. Our observations show that warming may increase the relative contribution of fungi to the soil microbial community, suggesting that shifts in the microbial community structure may constitute a major mechanism underlying warming acclimatization of soil respiration.
Plant and microbial N acquisition under elevated atmospheric CO2 in two mesocosm experiments with annual grasses
Authors: Hu Shuijin , Wu Jiansheng , Burkey Kent O. , Firestone Mary K. 
Published: February 2005

AbstractThe impact of elevated CO2 on terrestrial ecosystem C balance, both in sign or magnitude, is not clear because the resulting alterations in C input, plant nutrient demand and water use efficiency often have contrasting impacts on microbial decomposition processes. One major source of uncertainty stems from the impact of elevated CO2 on N availability to plants and microbes. We examined the effects of atmospheric CO2 enrichment (ambient+370 μmol mol−1) on plant and microbial N acquisition in two different mesocosm experiments, using model plant species of annual grasses of Avena barbata and A. fatua, respectively. The A. barbata experiment was conducted in a N‐poor sandy loam and the A. fatua experiment was on a N‐rich clayey loam. Plant–microbial N partitioning was examined through determining the distribution of a 15N tracer. In the A. barbata experiment, 15N tracer was introduced to a field labeling experiment in the previous year so that 15N predominantly existed in nonextractable soil pools. In the A. fatua experiment, 15N was introduced in a mineral solution [(15NH4)2SO4 solution] during the growing season of A. fatua. Results of both N budget and 15N tracer analyses indicated that elevated CO2 increased plant N acquisition from the soil. In the A. barbata experiment, elevated CO2 increased plant biomass N by ca. 10% but there was no corresponding decrease in soil extractable N, suggesting that plants might have obtained N from the nonextractable organic N pool because of enhanced microbial activity. In the A. fatua experiment, however, the CO2‐led increase in plant biomass N was statistically equal to the reduction in soil extractable N. Although atmospheric CO2 enrichment enhanced microbial biomass C under A. barbata or microbial activity (respiration) under A. fatua, it had no significant effect on microbial biomass N in either experiment. Elevated CO2 increased the colonization of A. fatua roots by arbuscular mycorrhizal fungi, which coincided with the enhancement of plant competitiveness for soluble soil N. Together, these results suggest that elevated CO2 may tighten N cycling through facilitating plant N acquisition. However, it is unknown to what degree results from these short‐term microcosm experiments can be extrapolated to field conditions. Long‐term studies in less‐disturbed soils are needed to determine whether CO2‐enhancement of plant N acquisition can significantly relieve N limitation over plant growth in an elevated CO2 environment.
Linking microbial activity and soil organic matter transformations in forest soils under elevated CO2
Authors: Billings S. A. , Ziegler S. E. 
Published: February 2005

AbstractSoil organic matter (SOM) dynamics ultimately govern the ability of soil to provide long‐term C sequestration and the nutrients required for ecosystem productivity. Predicting belowground responses to elevated CO2 requires an integrated understanding of SOM transformations and the microbial activity that governs them. It remains unclear how the microorganisms upon which these transformations depend will function in an elevated CO2 world. This study examines SOM transformations and microbial metabolism in soils from the Duke Free Air Carbon Enrichment site in North Carolina, USA. We assessed microbial respiration and net nitrogen (N) mineralization in soils with and without elevated CO2 exposure during a 100‐day incubation. We also traced the depleted C isotopic signature of the supplemental CO2 into SOM and the soils' phospholipid fatty acids (PLFA), which serve as biomarkers for living cells. Cumulative net N mineralization in elevated CO2 soils was 50% that in control soils after a 100‐day incubation. Respiration was not altered with elevated CO2. C : N ratios of bulk SOM did not change with elevated CO2, but incubation data suggest that the C : N ratios of mineralized organic matter increased with elevated CO2. Values of SOM δ13C were depleted with elevated CO2 (−26.7±0.2 vs. −30.2±0.3‰), reflecting the depleted signature of the supplemental CO2. We compared δ13C of individual PLFA with the δ13C of SOM to discern incorporation of the depleted C isotopic signature into soil microbial groups in elevated CO2 plots. PLFA i15:0, a15:0, and 10Met18:0 reflected significant incorporation of recently produced photosynthate, suggesting that the bacterial groups defined by these biomarkers are active metabolizers in elevated CO2 soils. At least one of these groups (actinomycetes, 10Met18:0) specializes in metabolizing less labile substrates. Because control plots did not receive an equivalent 13C tracer, we cannot determine from these data whether this group of organisms was stimulated by elevated CO2 compared with these organisms in control soils. Stimulation of this group, if it occurred in the elevated CO2 plot, would be consistent with a decline in the availability of mineralizable organic matter with elevated CO2, which incubation data suggest may be the case in these soils.
A membrane metalloprotease participates in the sequential degradation of a Caulobacter polarity determinant
Authors: Chen Joseph C. , Viollier Patrick H. , Shapiro Lucy 
Published: February 2005

Summary Caulobacter crescentus assembles many of its cellular machines at distinct times and locations during the cell cycle. PodJ provides the spatial cues for the biogenesis of several polar organelles, including the pili, adhesive holdfast and chemotactic apparatus, by recruiting structural and regulatory proteins, such as CpaE and PleC, to a specific cell pole. PodJ is a protein with a single transmembrane domain that exists in two forms, full‐length (PodJL) and truncated (PodJS), each appearing during a specific time period of the cell cycle to control different aspects of polar organelle development. PodJL is synthesized in the early predivisional cell and is later proteolytically converted to PodJS. During the swarmer‐to‐stalked transition, PodJS must be degraded to preserve asymmetry in the next cell cycle. We found that MmpA facilitates the degradation of PodJS. MmpA belongs to the site‐2 protease (S2P) family of membrane‐embedded zinc metalloproteases, which includes SpoIVFB and YluC of Bacillus subtilis and YaeL of Escherichia coli. MmpA appears to cleave within or near the transmembrane segment of PodJS, releasing it into the cytoplasm for complete proteolysis. While PodJS has a specific temporal and spatial address, MmpA is present throughout the cell cycle; furthermore, periplasmic fusion to mRFP1 suggested that MmpA is uniformly distributed around the cell. We also determined that mmpA and yaeL can complement each other in C. crescentus and E. coli, indicating functional conservation. Thus, the sequential degradation of PodJ appears to involve regulated intramembrane proteolysis (Rip) by MmpA.
A PrfA‐regulated bile exclusion system (BilE) is a novel virulence factor in Listeria monocytogenes
Authors: Sleator Roy D. , Wemekamp‐Kamphuis Henrike H. , Gahan Cormac G. M. , Abee Tjakko , Hill Colin 
Published: February 2005

SummaryThe ability to colonize the gall bladder has recently been shown to be an important feature of virulent Listeria monocytogenes (J. Hardy, K. P. Francis, M. DeBoer, P. Chu, K. Gibbs, C. H. Contag. Science 303: 851–853, 2004). We suggest that the cytotoxic effects of bile may be increased upon release from the gall bladder into the upper small intestine, and report the identification of a novel bile exclusion system which plays an essential role in intestinal colonization and virulence of L. monocytogenes. In silico analysis of the L. monocytogenes EGDe genome revealed a two‐gene operon (formerly opuB) exhibiting significant sequence similarity to members of the betaine carnitine choline transporter (BCCT) family. The operon, herein designated bilE (bile Exclusion) is preceded by consensus σA‐ and σB‐dependent promoter‐binding sites and is transcriptionally upregulated at elevated osmolarities and reduced temperatures (stresses known to induce sigB). Furthermore, a significant reduction in the level of bilE transcription was observed in the absence of σB. In addition, we demonstrate an important role for PrfA, the master regulator of virulence potential in L. monocytogenes, in coordinating bilE expression. Computational structural analysis suggests that, rather than functioning as a compatible solute uptake system as was previously believed, BilE is more likely to be an exclusion system, a conclusion substantiated by radiolabelled bile accumulation studies. In addition, functionally inactivating BilE resulted in a five‐log reduction in the ability of the bacterium to tolerate lethal concentrations of bovine bile (oxgall) and also significantly increased sensitivity to physiological concentrations of human bile, a phenotype which translates to a significant reduction in virulence potential when administered to a murine model by the oral route. Thus, this novel bile exclusion locus bilE, coordinately regulated by σB and PrfA, represents a new and important virulence factor in L. monocytogenes.
A large, mobile pathogenicity island confers plant pathogenicity on Streptomyces species
Authors: Kers Johan A. , Cameron Kimberly D. , Joshi Madhumita V. , Bukhalid Raghida A. , Morello Joanne E. , Wach Michael J. , Gibson Donna M. , Loria Rosemary 
Published: February 2005

SummaryPotato scab is a globally important disease caused by polyphyletic plant pathogenic Streptomyces species. Streptomyces acidiscabies, Streptomyces scabies and Streptomyces turgidiscabies possess a conserved biosynthetic pathway for the nitrated dipeptide phytotoxin thaxtomin. These pathogens also possess the nec1 gene which encodes a necrogenic protein that is an independent virulence factor. In this article we describe a large (325–660 kb) pathogenicity island (PAI) conserved among these three plant pathogenic Streptomyces species. A partial DNA sequence of this PAI revealed the thaxtomin biosynthetic pathway, nec1, a putative tomatinase gene, and many mobile genetic elements. In addition, the PAI from S. turgidiscabies contains a plant fasciation (fas) operon homologous to and colinear with the fas operon in the plant pathogen Rhodococcus fascians. The PAI was mobilized during mating from S. turgidiscabies to the non‐pathogens Streptomyces coelicolor and Streptomyces diastatochromogenes on a 660 kb DNA element and integrated site‐specifically into a putative integral membrane lipid kinase. Acquisition of the PAI conferred a pathogenic phenotype on S. diastatochromogenes but not on S. coelicolor. This PAI is the first to be described in a Gram‐positive plant pathogenic bacterium and is responsible for the emergence of new plant pathogenic Streptomyces species in agricultural systems.
Genetic rescue of a Toxoplasma gondii conditional cell cycle mutant
Authors: White Michael W. , Jerome Maria E. , Vaishnava Shipra , Guerini Michael , Behnke Michael , Striepen Boris 
Published: February 2005

SummaryGrowth rate is a major pathogenesis factor in the parasite Toxoplasma gondii; however, how cell division is controlled in this protozoan is poorly understood. Herein, we show that centrosomal duplication is an indicator of S phase entry while centrosome migration marks mitotic entry. Using the pattern of centrosomal replication, we confirmed that mutant ts11C9 undergoes a bimodal cell cycle arrest that is characterized by two subpopulations containing either single or duplicated centrosomes which correlate with the bipartite genome distribution observed at the non‐permissive temperature. Genetic rescue of ts11C9 was performed using a parental RH strain cDNA library, and the cDNA responsible for conferring temperature resistance (growth at 40°C) was recovered by recombination cloning. A single T. gondii gene encoding the protein homologue of XPMC2 was responsible for genetic rescue of the temperature‐sensitive defect in ts11C9 parasites. This protein is a known suppressor of mitotic defects, and in tachyzoites, TgXPMC2–YFP localized to the parasite nucleus and nucleolus which is consistent with the expected subcellular localization of critical mitotic factors. Altogether, these results demonstrate that ts11C9 is a conditional mitotic mutant containing a single defect which influences two distinct control points in the T. gondii tachyzoite cell cycle.