bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extracellular nucleotides affect pericyte‐mediated regulation of rat in situ vasa recta diameter
Authors: Crawford C. , Kennedy‐Lydon T. M. , Callaghan H. , Sprott C. , Simmons R. L. , Sawbridge L. , Syme H. M. , Unwin R. J. , Wildman S. S. P. , Peppiatt‐Wildman C. M. 
Published: April 2011

AbstractAim:  We hypothesized that extracellular nucleotides, established as being released from renal tubular epithelial cells, act at pericytes to regulate vasa recta capillary diameter.Methods:  A rat live kidney slice model and video imaging techniques were used to investigate the effects of extracellular nucleotides on in situ (subsurface) vasa recta diameter at pericyte and non‐pericyte sites. In addition, RT‐qPCR was used to quantify P2 receptor mRNA expression in isolated vasa recta.Results:  Extracellular ATP, UTP, benzylbenzyl ATP (BzATP) or 2‐methylthioATP (2meSATP) evoked a significantly greater vasoconstriction of subsurface vasa recta at pericytes than at non‐pericyte sites. The rank order of agonist potency was BzATP = 2meSATP > ATP = UTP. The vasoconstriction evoked at pericyte sites by ATP was significantly attenuated by the P2 receptor antagonists suramin, pyridoxal phosphate‐6‐azo(benzene‐2,4‐disulfonic acid) (PPADS) or Reactive Blue‐2 (RB‐2). UTP‐evoked vasoconstriction at pericytes was attenuated by suramin or RB‐2 but not PPADS. Interestingly, suramin or PPADS, when applied in the absence of a P2 receptor agonist, evoked a weak but significant vasoconstriction of vasa recta at pericyte sites, suggesting tonic vasodilation by nucleotides. Significant levels of P2X1, 3 and 7 and P2Y4 and 6 receptor mRNA were detected in vasa recta.Conclusion:  Extracellular nucleotides act at pericytes to cause vasoconstriction of in situ vasa recta. Pharmacological characterization, supported by RT‐qPCR data, suggests that P2X1 and 7 and P2Y4 receptors mediate nucleotide‐evoked vasoconstriction of vasa recta by pericytes. We propose that nucleotides released from renal tubular epithelial cells, in close proximity to vasa recta capillaries, are key in regulating renal medullary blood flow.
Gas exchange in frogs and turtles: how ectothermic vertebrates contributed to solving the controversy of pulmonary oxygen secretion
Authors: Wang T. 
Published: April 2011

AbstractThe mechanisms governing pulmonary gas exchange were heavily debated at the start of the 20th century when Christian Bohr provided measurements of lung and blood gases as well as rational arguments in favour of oxygen being secreted actively from the lung gas to the blood within vertebrate lungs. The concept of active transport was studied by August Krogh in his doctoral dissertation on the partitioning of gas exchange in frogs. In later studies, where Marie and August Krogh provided conclusive evidence that pulmonary gas exchange occurs by diffusion and diffusion alone, the turtle lungs provided an important tool to investigate the role of perfusion in pulmonary gas exchange. Here, I review the early Bohr and Krogh studies on pulmonary and cutaneous gas exchange in frogs as well as the experimental studies on gas exchange and its possible autonomic regulation in turtles. The results are discussed within the context of recent studies on the cardiorespiratory physiology of frogs and turtles.
Myeloid‐Derived Suppressor Cells Limit the Inflammation by Promoting T Lymphocyte Apoptosis in the Spinal Cord of a Murine Model of Multiple Sclerosis
Authors: Moliné‐Velázquez Verónica , Cuervo Henar , Vila‐del Sol Virginia , Ortega María Cristina , Clemente Diego , de Castro Fernando 
Published: April 2011

AbstractMultiple Sclerosis (MS) is a demyelinating/inflammatory disease of the central nervous system. Relapsing‐remitting MS is characterized by a relapsing phase with clinical symptoms and the production of inflammatory cell infiltrates, and a period of remission during which patients recover partially. Myeloid‐derived suppressor cells (MDSCs) are immature cells capable of suppressing the inflammatory response through Arginase‐I (Arg‐I) activity, among other mechanisms. Here, we have identified Arg‐I+‐MDSCs in the spinal cord during experimental autoimmune encephalomyelitis (EAE), cells that were largely restricted to the demyelinating plaque and that always exhibited the characteristic MDSC surface markers Arg‐I/CD11b/Gr‐1/M‐CSF1R. The presence and density of Arg‐I+‐cells, and the proportion of apoptotic but not proliferative T cells, were correlated with the EAE time course: peaked in parallel with the clinical score, decreased significantly during the remitting phase and completely disappeared during the chronic phase. Spinal cord‐isolated MDSCs of EAE animals augmented the cell death when co‐cultured with stimulated control splenic CD3 T cells. These data point to an important role for MDSCs in limiting inflammatory damage in MS, favoring the relative recovery in the remitting phase of the disease. Thus, the MDSC population should be considered as a potential therapeutic target to accelerate the recovery of MS patients.
Towards a better understanding of the legibility bias in performance assessments: The case of gender‐based inferences
Authors: Greifeneder Rainer , Zelt Sarah , Seele Tim , Bottenberg Konstantin , Alt Alexander 
Published: April 2011

Background. Handwriting legibility systematically biases evaluations in that highly legible handwriting results in more positive evaluations than less legible handwriting. Because performance assessments in educational contexts are not only based on computerized or multiple choice tests but often include the evaluation of handwritten work samples, understanding the causes of this bias is critical.Aims. This research was designed to replicate and extend the legibility bias in two tightly controlled experiments and to explore whether gender‐based inferences contribute to its occurrence.Sample(s). A total of 132 students from a German university participated in one pre‐test and two independent experiments.Method. Participants were asked to read and evaluate several handwritten essays varying in content quality. Each essay was presented to some participants in highly legible handwriting and to other participants in less legible handwriting. In addition, the assignment of legibility to participant group was reversed from essay to essay, resulting in a mixed‐factor design.Results. The legibility bias was replicated in both experiments. Results suggest that gender‐based inferences do not account for its occurrence. Rather it appears that fluency from legibility exerts a biasing impact on evaluations of content and author abilities.Conclusions. The legibility bias was shown to be genuine and strong. By refuting a series of alternative explanations, this research contributes to a better understanding of what underlies the legibility bias. The present research may inform those who grade on what to focus and thus help to better allocate cognitive resources when trying to reduce this important source of error.
The effect of guiding questions on students’ performance and attitude towards statistics
Authors: Budé Luc , van de Wiel M. W. J. , Imbos Tjaart , Berger Martijn P. F. 
Published: April 2011

Background. In this study, the effect of guidance on students’ performance was investigated. This effect was hypothesized to be manifested through a reduction of cognitive load and enhancement of self‐explanations.Aim. The goal of this study was to investigate the effect of guiding questions on students’ understanding of statistics.Sample and Method. In an experimental setting, two randomly selected groups of students (N= 49) answered achievement and transfer questions on statistics as a measure of performance. Students in the intervention condition were given guiding questions to direct their way of reasoning before they answered the achievement questions. The students in the control condition were asked to write down their way of thinking before they answered the same achievement questions. In this way, both groups were stimulated to self‐explain, but only the reasoning processes of the students in the intervention condition were guided.Results and Conclusion.  It was found that students in the intervention condition performed significantly better on achievement and transfer questions and that this effect of guidance was mediated by self‐explanations. Attitude towards statistics was positively related to performance.
The Alperin Weight Conjecture and Dade's Conjecture for the Simple Group Fi′24
Authors: An Jianbei , Cannon John J. , O'Brien E. A. , Unger W. R. 
Published: April 2011

AbstractWe classify the radicalp-subgroups and chains of the Fischer simple group Fi′24and then verify the Alperin weight conjecture and the Uno reductive conjecture for Fi′24.
Computing Minimal Polynomials of Matrices
Authors: Neunhöffer Max , Praeger Cheryl E. 
Published: April 2011

AbstractWe present and analyse a Monte-Carlo algorithm to compute the minimal polynomial of ann × nmatrix over a finite field that requiresO(n3) field operations andO(n) random vectors, and is well suited for successful practical implementation. The algorithm, and its complexity analysis, use standard algorithms for polynomial and matrix operations. We compare features of the algorithm with several other algorithms in the literature. In addition we present a deterministic verification procedure which is similarly efficient in most cases but has a worst-case complexity ofO(n4). Finally, we report the results of practical experiments with an implementation of our algorithms in comparison with the current algorithms in the GAP library.
Relative Contributions of Ebp Pili and the Collagen Adhesin Ace to Host Extracellular Matrix Protein Adherence and Experimental Urinary Tract Infection by Enterococcus faecalis OG1RF
Authors: Nallapareddy Sreedhar R. , Singh Kavindra V. , Sillanpää Jouko , Zhao Meng , Murray Barbara E. 
Published: April 2011

ABSTRACT

Previous studies have demonstrated that the
ebp
operon and the
ace
gene of
Enterococcus faecalis
, encoding
e
ndocarditis- and
b
iofilm-associated
p
ili and an
a
dhesin to
c
ollagen of

E

. faecalis
, respectively, are both important in experimental urinary tract infections (UTI) and endocarditis. We have also shown that growth of
E. faecalis
in brain heart infusion (BHI) serum enhances Ebp pilus and Ace production and increases adherence to several host extracellular matrix proteins. Here, we report that deletion of
ebpABC
almost eliminated serum-elicited adherence to fibrinogen (
P
< 0.0001), resulted in moderate reduction in adherence to collagen (
P
< 0.05), and had no effect on fibronectin adherence relative to that of wild-type OG1RF. An OG1RFΔ
ace
Δ
ebpABC
double mutant showed further reduced collagen adherence versus that of the OG1RFΔ
ace
or OG1RFΔ
ebpABC
mutants (
P
< 0.001). These results were corroborated by complementation and/or studies with native pilus-enriched surface extracts and a collagen-secreting 3T6 fibroblast cell line, as well as antibody inhibition. In the UTI model, both the OG1RFΔ
ace
and OG1RFΔ
ace
Δ
ebpABC
mutants were found to be significantly attenuated compared to the wild type; however, no significant differences were observed between individual
ace
or
ebp
mutants and the OG1RFΔ
ace
Δ
ebpABC
mutant. In summary, these data implicate the Ebp pili as having some role in collagen adherence, albeit less than that of Ace, and a very major role in fibrinogen adherence, which may explain in part the importance of these pili in experimental endocarditis. The OG1RFΔ
ace
Δ
ebpABC
mutant was attenuated in the UTI model, although not significantly more so than the Δ
ace
or Δ
ebpABC
mutants, suggesting involvement of other
E. faecalis
factors in urinary tract colonization or infection.
Transcriptome of Proteus mirabilis in the Murine Urinary Tract: Virulence and Nitrogen Assimilation Gene Expression
Authors: Pearson Melanie M. , Yep Alejandra , Smith Sara N. , Mobley Harry L. T. 
Published: April 2011

ABSTRACTThe enteric bacteriumProteus mirabilisis a common cause of complicated urinary tract infections. In this study, microarrays were used to analyzeP. mirabilisgene expressionin vivofrom experimentally infected mice. Urine was collected at 1, 3, and 7 days postinfection, and RNA was isolated from bacteria in the urine for transcriptional analysis. Across nine microarrays, 471 genes were upregulated and 82 were downregulatedin vivocompared toin vitrobroth culture. Genes upregulatedin vivoencoded mannose-resistantProteus-like (MR/P) fimbriae, urease, iron uptake systems, amino acid and peptide transporters, pyruvate metabolism enzymes, and a portion of the tricarboxylic acid (TCA) cycle enzymes. Flagella were downregulated. Ammonia assimilation geneglnA(glutamine synthetase) was repressedin vivo, whilegdhA(glutamate dehydrogenase) was upregulatedin vivo. Contrary to our expectations, ammonia availability due to urease activity inP. mirabilisdid not drive this gene expression. AgdhAmutant was growth deficient in minimal medium with citrate as the sole carbon source, and loss ofgdhAresulted in a significant fitness defect in the mouse model of urinary tract infection. UnlikeEscherichia coli, which repressesgdhAand upregulatesglnAin vivoand cannot utilize citrate, the data suggest thatP. mirabilisuses glutamate dehydrogenase to monitor carbon-nitrogen balance, and this ability contributes to the pathogenic potential ofP. mirabilisin the urinary tract.
Mua (HP0868) Is a Nickel-Binding Protein That Modulates Urease Activity in Helicobacter pylori
Authors: Benoit Stéphane L. , Maier Robert J. 
Published: April 2011

ABSTRACT

A novel mechanism aimed at controlling urease expression in
Helicobacter pylori
in the presence of ample nickel is described. Higher urease activities were observed in an
hp0868
mutant (than in the wild type) in cells supplemented with nickel, suggesting that the HP0868 protein (herein named Mua for
m
odulator of
u
rease
a
ctivity) represses urease activity when nickel concentrations are ample. The increase in urease activity in the Δ
mua
mutant was linked to an increase in urease transcription and synthesis, as shown by quantitative real-time PCR, SDS-PAGE, and immunoblotting against UreAB. Increased urease synthesis was also detected in a Δ
mua
Δ
nikR
double mutant strain. The Δ
mua
mutant was more sensitive to nickel toxicity but more resistant to acid challenge than was the wild-type strain. Pure Mua protein binds 2 moles of Ni
2+
per mole of dimer. Electrophoretic mobility shift assays did not reveal any binding of Mua to the
ureA
promoter or other selected promoters (
nikR
,
arsRS
,
5′ ureB
-sRNAp). Previous yeast two-hybrid studies indicated that Mua and RpoD may interact; however, only a weak interaction was detected via cross-linking with pure components and this could not be verified by another approach. There was no significant difference in the intracellular nickel level between wild-type and
mua
mutant cells. Taken together, our results suggest the HP0868 gene product represses urease transcription when nickel levels are high through an as-yet-uncharacterized mechanism, thus counterbalancing the well-described NikR-mediated activation.

IMPORTANCE
Urease is a nickel-containing enzyme that buffers both the cytoplasm and the periplasm of
Helicobacter pylori
by converting urea into ammonia and carbon dioxide. The enzyme is the most abundant protein in
H. pylori
, accounting for an estimated 10% of the total protein content of the cell, and it is essential for early colonization and virulence. Numerous studies have focused on the transcription of the structural
ureAB
genes and its control by the regulatory proteins NikR and ArsR. Here we propose that urease transcription is under the control of another Ni-binding protein besides NikR, the Mua (HP0868) protein. Our results suggest that the Mua protein represses urease transcription when nickel levels are high. This mechanism would counterbalance the NikR-mediated activation of urease and ensure that, in the presence of a high nickel concentration, urease activation is limited and does not lead to massive production of detrimental ammonia.
Concussion information online: evaluation of information quality, content and readability of concussion-related websites
Authors: Ahmed Osman H , Sullivan S John , Schneiders Anthony G , McCrory Paul R 
Published: April 2011

BackgroundThe internet plays an important role in the dissemination of health information to the general public. Information on orthopaedic sports medicine websites has been shown to be of a varying standard, and to date there has been no evaluation of the overall quality of concussion-related websites.MethodsA four-stage methodological sampling technique was used to identify concussion-related websites. Websites were assessed for the presence of a quality standard (theHONcode), their adherence to current expert concussion knowledge using a custom-developed concussion checklist ('CONcheck'), and their readability using the established Flesch Reading Ease (FRE) and Flesch–Kincaid Grade Level (FKGL).Results43 Websites were identified from the search strategy with the majority (70%) notHONcodecertified. A wide distribution of scores was seen for the CONcheck (0–22), FRE (16.3–77.4) and FKGL (6–17.8). Statistical analysis using independent t tests between websites with theHONcodeand websites without theHONcodeshowed no significant differences between the two groups for CONcheck (t41=0.571, p=0.571), FRE (t41=0.808, p=0.424) and FKGL(t41=−0.964, p=0.341) scores.ConclusionsThe variability in the standard of concussion-related websites highlights the need for sports medicine website providers to consider the delivery, content and readability of information to the public.
Social responsibility in tobacco production? Tobacco companies' use of green supply chains to obscure the real costs of tobacco farming
Authors: Otañez Marty , Glantz Stanton A 
Published: April 2011

BackgroundTobacco companies have come under increased criticism because of environmental and labour practices related to growing tobacco in developing countries.MethodsAnalysis of tobacco industry documents, industry websites and interviews with tobacco farmers in Tanzania and tobacco farm workers, farm authorities, trade unionists, government officials and corporate executives from global tobacco leaf companies in Malawi.ResultsBritish American Tobacco and Philip Morris created supply chains in the 1990s to improve production efficiency, control, access to markets and profits. In the 2000s, the companies used their supply chains in an attempt to legitimise their portrayals of tobacco farming as socially and environmentally friendly, rather than take meaningful steps to eliminate child labour and reduce deforestation in developing countries. The tobacco companies used nominal self-evaluation (not truly independent evaluators) and public relations to create the impression of social responsibility. The companies benefit from $1.2 billion in unpaid labour costs because of child labour and more than $64 million annually in costs that would have been made to avoid tobacco-related deforestation in the top 12 tobacco growing developing countries, far exceeding the money they spend nominally working to change these practices.ConclusionsThe tobacco industry uses green supply chains to make tobacco farming in developing countries appear sustainable while continuing to purchase leaf produced with child labour and high rates of deforestation. Strategies to counter green supply chain schemes include securing implementing protocols for the WHO Framework Convention on Tobacco Control to regulate the companies' practices at the farm level.
Population study of electrophoretic polymorphisms of red cell enzymes and plasma proteins in Caucasian Canadians
Authors: Philipps Sylvia , Giblett Eloise R. , Anderson Jeanne E. , Lewis Marion , Kaita Hiroko 
Published: April 2011

Blood samples from a random series of Canadian Caucasians were phenotyped for 28 red cell enzyme systems and eight plasma protein systems. Polymorphism was found in 17 and rare variants in 11 of the systems. Allele frequencies are presented for these; distribution of phenotypes is in accordance with the Hardy–Weinberg equilibrium theory. In a complementary study of families there was no evidence of de novo mutation in any of the 36 systems and they allowed a minimum estimate of the frequency of null alleles in the ADA, C2, and GPT systems. Key words: polymorphism, red cell enzyme, plasma protein, phenotype, allele frequency, population.
A DNA cytophotometric and chromosome banding study in Hedera helix (Araliaceae), with reference to differential DNA replication associated with juvenile–adult phase change
Authors: König C. , Ebert I. , Greilhuber J. 
Published: April 2011

The present DNA cytophotometric and chromosome banding comparison of the juvenile and the adult developmental phase in the common ivy, Hedera helix, was undertaken as an attempt to verify or refute the asserted phase-correlated differential DNA replication in this plant. No statistically significant differences between the two developmental phases were found in genome size (as determined from mitotic nuclei), nuclear DNA content in resting meristems and somatic leaf tissues, and content of constitutive heterochromatin as measured from C-banded metaphase plates. There is no evidence for differential DNA replication in Hedera helix. Key words: Hedera helix, differential DNA replication, morphogenesis, genome size, chromosome structure.
Chromosome organization in meiosis revealed by light microscope analysis of silver-stained cores
Authors: Rufas J. S. , Gimenez-Abian J. , Suja J. A. , Vega C. Garcia De La 
Published: April 2011

Three species of grasshoppers have been analyzed by means of a modified silver impregnation technique that reveals the presence of a chromatid core that identifies chiasmata at first meiotic metaphase. In terms of the behaviour of the chromatid core most of the configurations observed at diplotene with orcein are easily recognized in metaphase I silver-stained bivalents. Some "hidden" configurations, as well as simple chromatin associations, that do not appear to represent chiasmata have also been detected. The disposition and behaviour of the chromatid cores in metaphase I and anaphase I provide grounds to support a reorganization of half-bivalents between first and second division. Key words: chromatid core, meiotic chromosome organization, chiasma formation, insect cytogenetics.
Progenies of Thinopyrum elongatum × Agropyron mongolicum
Authors: Wang Richard R-C. 
Published: April 2011

With the aid of embryo rescue, both a monoploid and several hybrids were obtained from the cross Thinopyrum elongatum × Agropyron mongolicum. The monoploid was a result of gradual and eventually complete elimination of A. mongolicum chromosomes in the hybrid. About 95% of the root-tip cells, and nearly all of the pollen mother cells, had only the seven chromosomes of the Je genome of the maternal parent. Very little autosyndesis occurred between chromosomes within the Je genome. Extensive chromosome pairings were observed in one headed hybrid, averaging 6.42 I + 2.53 rod II + 0.85 ring II + 0.25 III + 0.02 IV at metaphase I in pollen mother cells, which revealed a high degree of chromosome homology between the two genomes and thus justifying the close phylogenetic relationship between the two species. All plants died from hybrid necrosis, some as seedlings and some after heading. The Je and P genomes in the accessions used in this study carry complementary genes for hybrid necrosis. Key words: hybrid (intergeneric), haploid, genome, chromosome elimination, meiosis.