bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple Genetic Selection Protocol for Isolation of Overexpressed Genes That Enhance Accumulation of Membrane-Integrated Human G Protein-Coupled Receptors inEscherichia coli
Authors: Skretas Georgios , Georgiou George
Published: July 2010

The efficient production of membrane proteins in bacteria remains a major challenge. In this work, we sought to identify overexpressed genes that enhance the yields of recombinant membrane proteins inEscherichia coli. We developed a genetic selection system for bacterial membrane protein production, consisting of membrane protein fusions with the enzyme β-lactamase and facile selection of high-production strains on ampicillin-containing media. This system was used to screen the ASKA library, an ordered library of plasmids encoding all the knownE. coliopen reading frames (ORFs), and several clones with the ability to accumulate enhanced amounts of recombinant membrane proteins were selected. Notably, coexpression ofybaB, a gene encoding a putative DNA-binding protein of unknown function, was found to enhance the accumulation of a variety of membrane-integrated human G protein-coupled receptors and other integral membrane proteins inE. coliby up to 10-fold. The results of this study highlight the power of genetic approaches for identifying factors that impact membrane protein biogenesis and for generating engineered microbial hosts for membrane protein production.
Survival of
Campylobacter jejuni
under Conditions of Atmospheric Oxygen Tension with the Support of
Pseudomonas
spp
Authors: Hilbert Friederike , Scherwitzel Manuela , Paulsen Peter , Szostak Michael P.
Published: July 2010

Campylobacter jejuni
is a major food-borne pathogen. Despite causing enteritis in humans, it is a well-adapted intestinal microorganism in animals, hardly ever generating disease symptoms. Nevertheless, as a true microaerophilic microorganism it is still puzzling how
Campylobacter
cells can survive on chicken meat, the main source of human infection. In this study, we demonstrate that
C. jejuni
is able to withstand conditions of atmospheric oxygen tension when cocultured with
Pseudomonas
species, major food-spoiling bacteria that are frequently found on chicken meat in rather high numbers. Using an
in vitro
survival assay, interactions of 145
C. jejuni
wild-type strains and field isolates from chicken meat, broiler feces, and human clinical samples with type strains and food isolates of
Pseudomonas
spp.,
Proteus mirabilis
,
Citrobacter freundii
,
Micrococcus luteus
, and
Enterococcus faecalis
were studied. When inoculated alone or in coculture with
Proteus mirabilis
,
Citrobacter freundii
,
Micrococcus luteus
, or
Enterococcus faecalis
type strains,
Campylobacter
cells were able to survive ambient oxygen levels for no more than 18 h. In contrast,
Campylobacter
bacteria inoculated with type strains or wild-type isolates of
Pseudomonas
showed a prolonged aerobic survival of up to >48 h. This microbial commensalism was diverse in
C. jejuni
isolates from different sources; isolates from chicken meat and humans in coculture with
P
seudomonas
putida
were able to use this survival support better than fecal isolates from broilers. Scanning electron microscopy revealed the development of fiberlike structures braiding
P. putida
and
C. jejuni
cells. Hence, it seems that microaerophilic
C. jejuni
is able to survive ambient atmospheric oxygen tension by metabolic commensalism with
Pseudomonas
spp. This bacterium-bacterium interaction might set the basis for survival of
C. jejuni
on chicken meat and thus be the prerequisite step in the pathway toward human infection.
Differential Filamentation of Candida albicans and Candida dubliniensis Is Governed by Nutrient Regulation of
UME6
Expression
Authors: O'Connor Leanne , Caplice Nicole , Coleman David C. , Sullivan Derek J. , Moran Gary P.
Published: July 2010

Candida dubliniensis
is closely related to
Candida albicans
; however, it is responsible for fewer infections in humans and is less virulent in animal models of infection.
C. dubliniensis
forms fewer hyphae
in vivo
, and this may contribute to its reduced virulence. In this study we show that, unlike
C. albicans
,
C. dubliniensis
fails to form hyphae in yeast extract-peptone-dextrose (YPD) medium supplemented with 10% (vol/vol) fetal calf serum (YPDS medium). However,
C. dubliniensis
filaments in water plus 10% (vol/vol) fetal calf serum (WS), and this filamentation is inhibited by the addition of peptone and glucose. Repression of filamentation in YPDS medium could be partly overcome by preculture in synthetic Lee's medium. Unlike
C. albicans
, inoculation of
C. dubliniensis
in YPDS medium did not result in increased
UME6
transcription. However, >100-fold induction of
UME6
was observed when
C. dubliniensis
was inoculated in nutrient-poor WS medium. The addition of increasing concentrations of peptone to WS medium had a dose-dependent effect on reducing
UME6
expression. Transcript profiling of
C. dubliniensis
hyphae in WS medium identified a starvation response involving expression of genes in the glyoxylate cycle and fatty acid oxidation. In addition, a core, shared transcriptional response with
C. albicans
could be identified, including expression of virulence-associated genes including
SAP456
,
SAP7
,
HWP1
, and
SOD5
. Preculture in nutrient-limiting medium enhanced adherence of
C. dubliniensis
, epithelial invasion, and survival following coculture with murine macrophages. In conclusion,
C. albicans
, unlike
C. dubliniensis
, appears to form hyphae in liquid medium regardless of nutrient availability, which may account for its increased capacity to cause disease in humans.
Roles of Minor Pilin Subunits Spy0125 and Spy0130 in the Serotype M1
Streptococcus pyogenes
Strain SF370
Authors: Smith Wendy D. , Pointon Jonathan A. , Abbot Emily , Kang Hae Joo , Baker Edward N. , Hirst Barry H. , Wilson Janet A. , Banfield Mark J. , Kehoe Michael A.
Published: July 2010

Adhesive pili on the surface of the serotype M1
Streptococcus pyogenes
strain SF370 are composed of a major backbone subunit (Spy0128) and two minor subunits (Spy0125 and Spy0130), joined covalently by a pilin polymerase (Spy0129). Previous studies using recombinant proteins showed that both minor subunits bind to human pharyngeal (Detroit) cells (A. G. Manetti et al., Mol. Microbiol. 64:968-983, 2007), suggesting both may act as pilus-presented adhesins. While confirming these binding properties, studies described here indicate that Spy0125 is the pilus-presented adhesin and that Spy0130 has a distinct role as a wall linker. Pili were localized predominantly to cell wall fractions of the wild-type
S. pyogenes
parent strain and a
spy0125
deletion mutant. In contrast, they were found almost exclusively in culture supernatants in both
spy0130
and
srtA
deletion mutants, indicating that the housekeeping sortase (SrtA) attaches pili to the cell wall by using Spy0130 as a linker protein. Adhesion assays with antisera specific for individual subunits showed that only anti-rSpy0125 serum inhibited adhesion of wild-type
S. pyogenes
to human keratinocytes and tonsil epithelium to a significant extent. Spy0125 was localized to the tip of pili, based on a combination of mutant analysis and liquid chromatography-tandem mass spectrometry analysis of purified pili. Assays comparing parent and mutant strains confirmed its role as the adhesin. Unexpectedly, apparent spontaneous cleavage of a labile, proline-rich (8 of 14 residues) sequence separating the N-terminal ∼1/3 and C-terminal ∼2/3 of Spy0125 leads to loss of the N-terminal region, but analysis of internal
spy0125
deletion mutants confirmed that this has no significant effect on adhesion.
A Putrescine-Inducible Pathway Comprising PuuE-YneI in Which γ-Aminobutyrate Is Degraded into Succinate in
Escherichia coli
K-12
Authors: Kurihara Shin , Kato Kenji , Asada Kei , Kumagai Hidehiko , Suzuki Hideyuki
Published: July 2010

γ-Aminobutyrate (GABA) is metabolized to succinic semialdehyde by GABA aminotransferase (GABA-AT), and the succinic semialdehyde is subsequently oxidized to succinate by succinic semialdehyde dehydrogenase (SSADH). In
E
scherichia
coli
, there are duplicate GABA-ATs (GabT and PuuE) and duplicate SSADHs (GabD and YneI). While GabT and GabD have been well studied previously, the characterization and expression analysis of PuuE and YneI are yet to be investigated. By analyzing the amino acid profiles in cells of Δ
puuE
and/or Δ
gabT
mutants, this study demonstrated that PuuE plays an important role in GABA metabolism in
E. coli
cells. The similarity of the amino acid sequences of PuuE and GabT is 67.4%, and it was biochemically demonstrated that the catalytic center of GabT is conserved as an amino acid residue important for the enzymatic activity in PuuE as Lys-247. However, the regulation of expression of PuuE is significantly different from that of GabT. PuuE is induced by the addition of putrescine to the medium and is repressed by succinate and low aeration conditions; in contrast, GabT is almost constitutive. Similarly, YneI is induced by putrescine, while GabD is not. For
E. coli
, PuuE is important for utilization of putrescine as a sole nitrogen source and both PuuE and YneI are important for utilization of putrescine as a sole carbon source. The results demonstrate that the PuuE-YneI pathway was a putrescine-inducible GABA degradation pathway for utilizing putrescine as a nutrient source.
Genetic and Functional Analyses of the
mob
Operon on Conjugative Transposon CTn
341
from
Bacteroides
spp
Authors: Peed Lindsay , Parker Anita C. , Smith C. Jeffrey
Published: July 2010

Bacteroides
are Gram-negative anaerobes indigenous to the intestinal tract of humans, and they are important opportunistic pathogens. Mobile genetic elements, such as conjugative transposons (CTns), have contributed to an increase in antibiotic resistance in these organisms. CTns are self-transmissible elements that belong to the superfamily of
i
ntegrative and
c
onjugative
e
lements (ICEs). CTn
341
is 52 kb; it encodes tetracycline resistance and its transfer is induced by tetracycline. The mobilization region of CTn
341
was shown to be comprised of a three-gene operon,
mobABC
, and the transfer origin,
oriT
. The three genes code for a nicking accessory protein, a relaxase, and a VirD4-like coupling protein, respectively. The Mob proteins were predicted to mediate the formation of the relaxosome complex, nick DNA at the
oriT
, and shuttle the DNA/protein complex to the mating-pore apparatus. The results of mutational studies indicated that the three genes are required for maximal transfer of CTn
341
. Mob gene transcription was induced by tetracycline, and this regulation was mediated through the two-component regulatory system, RteAB. The
oriT
region of CTn
341
was located within 100 bp of
mobA
, and a putative
Bacteroides
consensus nicking site was observed within this region. Mutation of the putative nick site resulted in a loss of transfer. This study demonstrated a role of the mobilization region for transfer of
Bacteroides
CTns and that tetracycline induction occurs for the
mob
gene operon, as for the
tra
gene operon(s), as shown previously.
The Paralogous MarR/DUF24-Family Repressors YodB and CatR Control Expression of the Catechol Dioxygenase CatE inBacillus subtilis
Authors: Chi Bui Khanh , Kobayashi Kazuo , Albrecht Dirk , Hecker Michael , Antelmann Haike
Published: July 2010

The redox-sensing MarR/DUF24-type repressor YodB controls expression of the azoreductase AzoR1 and the nitroreductase YodC that are involved in detoxification of quinones and diamide inBacillus subtilis. In the present paper, we identified YodB and its paralog YvaP (CatR) as repressors of theyfiDE(catDE) operon encoding a catechol-2,3-dioxygenase that also contributes to quinone resistance. Inactivation of both CatR and YodB is required for full derepression ofcatDEtranscription. DNA-binding assays and promoter mutagenesis studies showed that CatR protects two inverted repeats with the consensus sequence TTAC-N5-GTAA overlapping the −35 promoter region (BS1) and the transcriptional start site (TSS) (BS2). The BS1 operator was required for binding of YodBin vitro. CatR and YodB share the conserved N-terminal Cys residue, which is required for redox sensing of CatRin vivoas shown by Cys-to-Ser mutagenesis. Our data suggest that CatR is modified by intermolecular disulfide formation in response to diamide and quinonesin vitroandin vivo. Redox regulation of CatR occurs independently of YodB, and no protein interaction was detected between CatR and YodBin vivousing protein cross-linking and mass spectrometry.
The Heat Shock Protein YbeY Is Required for Optimal Activity of the 30S Ribosomal Subunit
Authors: Rasouly Aviram , Davidovich Chen , Ron Eliora Z.
Published: July 2010

The highly conserved bacterial
ybeY
gene is a heat shock gene whose function is not fully understood. Previously, we showed that the YbeY protein is involved in protein synthesis, as
Escherichia coli
mutants with
ybeY
deleted exhibit severe translational defects
in vivo
. Here we show that the
in vitro
activity of the translation machinery of
ybeY
deletion mutants is significantly lower than that of the wild type. We also show that the lower efficiency of the translation machinery is due to impaired 30S small ribosomal subunits.
The Omptins ofYersinia pestisandSalmonella entericaCleave the Reactive Center Loop of Plasminogen Activator Inhibitor 1
Authors: Haiko Johanna , Laakkonen Liisa , Juuti Katri , Kalkkinen Nisse , Korhonen Timo K.
Published: July 2010

Plasminogen activator inhibitor 1 (PAI-1) is a serine protease inhibitor (serpin) and a key molecule that regulates fibrinolysis by inactivating human plasminogen activators. Here we show that two important human pathogens, the plague bacteriumYersinia pestisand the enteropathogenSalmonella entericaserovar Typhimurium, inactivate PAI-1 by cleaving the R346-M347 bait peptide bond in the reactive center loop. No cleavage of PAI-1 was detected withYersinia pseudotuberculosis, an oral/fecal pathogen from whichY. pestishas evolved, or withEscherichia coli. The cleavage and inactivation of PAI-1 were mediated by the outer membrane proteases plasminogen activator Pla ofY. pestisand PgtE protease ofS. enterica, which belong to the omptin family of transmembrane endopeptidases identified in Gram-negative bacteria. Cleavage of PAI-1 was also detected with the omptins Epo ofErwinia pyrifoliaeand Kop ofKlebsiella pneumoniae, which both belong to the same omptin subfamily as Pla and PgtE, whereas no cleavage of PAI-1 was detected with omptins ofShigella flexneriorE. colior theYersiniachromosomal omptins, which belong to other omptin subfamilies. The results reveal a novel serpinolytic mechanism by which enterobacterial species expressing omptins of the Pla subfamily bypass normal control of host proteolysis.
H-NS Silences
gfp
, the Green Fluorescent Protein Gene:
gfp
TCD
Is a Genetically Remastered
gfp
Gene with Reduced Susceptibility to H-NS-Mediated Transcription Silencing and with Enhanced Translation
Authors: Corcoran Colin P. , Cameron Andrew D. S. , Dorman Charles J.
Published: July 2010

The bacterial nucleoid-associated protein H-NS, which preferentially targets and silences A+T-rich genes, binds the ubiquitous reporter gene
gfp
and dramatically reduces local transcription. We have redesigned
gfp
to reduce H-NS-mediated transcription silencing and simultaneously improve translation
in vivo
without altering the amino acid sequence of the GFP protein.
Genome Sequences of
Lactococcus lactis
MG1363 (Revised) and NZ9000 and Comparative Physiological Studies
Authors: Linares Daniel M. , Kok Jan , Poolman Bert
Published: July 2010

Lactococcus lactis
NZ9000 and its parent MG1363 are the most commonly used lactic acid bacteria for expression and physiological studies. We noted unexpected but significant differences in the growth behaviors of both strains. We sequenced the entire genomes of the original NZ9000 and MG1363 strains using an ultradeep sequencing strategy. The analysis of the
L. lactis
NZ9000 genome yielded 79 differences, mostly point mutations, with the annotated genome sequence of
L. lactis
MG1363. Resequencing of the MG1363 strain revealed that 73 out of the 79 differences were due to errors in the published sequence. Comparative transcriptomic studies revealed several differences in the regulation of genes involved in sugar fermentation, which can be explained by two specific mutations in a region of the
ptcC
promoter with a key role in the regulation of cellobiose and glucose uptake.
Regulation of
ciaXRH
Operon Expression and Identification of the CiaR Regulon in
Streptococcus mutans
Authors: Wu Chenggang , Ayala Eduardo A. , Downey Jennifer S. , Merritt Justin , Goodman Steven D. , Qi Fengxia
Published: July 2010

The
ciaRH
operon in
Streptococcus mutans
contains 3 contiguous genes,
ciaXRH
. Unlike the CiaRH system in other streptococci, only the
ciaH
-null mutant displays defective phenotypes, while the
ciaR
-null mutant behaves like the wild type. The objective of this study was to determine the mechanism of this unusual property. We demonstrate that the
ciaH
mutation caused a >20-fold increase in
ciaR
transcript synthesis. A
ciaRH
double deletion reversed the
ciaH
phenotype, suggesting that overexpressed
ciaR
might be responsible for the observed
ciaH
phenotypes. When
ciaR
was forced to be overexpressed by a transcriptional fusion to the
ldh
promoter in the wild-type background, the same
ciaH
phenotypes were restored, confirming the involvement of overexpressed
ciaR
in the
ciaH
phenotypes. The
ciaH
mutation and
ciaR
overexpression also caused transcriptional alterations in 100 genes, with 15 genes upregulated >5-fold. Bioinformatics analysis identified a putative CiaR regulon consisting of 8 genes/operons, including the
ciaXRH
operon itself, all of which were upregulated.
In vitro
footprinting on 4 of the 8 promoters revealed a protected region of 26 to 28 bp encompassing two direct repeats, NTTAAG-n5-WTTAAG, 10 bp upstream of the −10 region, indicating direct binding of the CiaR protein to these promoters. Taken together, we conclude that overexpressed CiaR, as a result of either
ciaH
deletion or forced expression from a constitutive promoter, is a mediator in the CiaH-regulated phenotypes.
Pmr, a Histone-Like Protein H1 (H-NS) Family Protein Encoded by the IncP-7 Plasmid pCAR1, Is a Key Global Regulator That Alters Host Function
Authors: Yun Choong-Soo , Suzuki Chiho , Naito Kunihiko , Takeda Toshiharu , Takahashi Yurika , Sai Fumiya , Terabayashi Tsuguno , Miyakoshi Masatoshi , Shintani Masaki , Nishida Hiromi , Yamane Hisakazu , Nojiri Hideaki
Published: July 2010

Histone-like protein H1 (H-NS) family proteins are nucleoid-associated proteins (NAPs) conserved among many bacterial species. The IncP-7 plasmid pCAR1 is transmissible among variousPseudomonasstrains and carries a gene encoding the H-NS family protein, Pmr.Pseudomonas putidaKT2440 is a host of pCAR1, which harbors five genes encoding the H-NS family proteins PP_1366 (TurA), PP_3765 (TurB), PP_0017 (TurC), PP_3693 (TurD), and PP_2947 (TurE). Quantitative reverse transcription-PCR (qRT-PCR) demonstrated that the presence of pCAR1 does not affect the transcription of these five genes and that onlypmr,turA, andturBwere primarily transcribed in KT2440(pCAR1).In vitropull-down assays revealed that Pmr strongly interacted with itself and with TurA, TurB, and TurE. Transcriptome comparisons of thepmrdisruptant, KT2440, and KT2440(pCAR1) strains indicated thatpmrdisruption had greater effects on the host transcriptome than did pCAR1 carriage. The transcriptional levels of some genes that increased with pCAR1 carriage, such as themexEF-oprNefflux pump genes andparI, reverted withpmrdisruption to levels in pCAR1-free KT2440. Transcriptional levels of putative horizontally acquired host genes were not altered by pCAR1 carriage but were altered bypmrdisruption. Identification of genome-wide Pmr binding sites by ChAP-chip (chromatin affinity purification coupled with high-density tiling chip) analysis demonstrated that Pmr preferentially binds to horizontally acquired DNA regions. The Pmr binding sites overlapped well with the location of the genes differentially transcribed followingpmrdisruption on both the plasmid and the chromosome. Our findings indicate that Pmr is a key factor in optimizing gene transcription on pCAR1 and the host chromosome.
NtcA Regulates
patA
Expression in
Anabaena
sp. Strain PCC 7120
Authors: Bastet Laurène , Boileau Céline , Bédu Sylvie , Janicki Annick , Latifi Amel , Zhang Cheng-Cai
Published: July 2010

patA
expression is induced 3 to 6 h after nitrogen step-down. We establish that the transcription of
patA
is under the positive control of NtcA. The
patA
promoter region shows two conserved NtcA-binding boxes. These NtcA-binding sites and their interaction with NtcA are key elements for
patA
expression in heterocysts.
Complete Genome Sequence of the Diesel-Degrading
Acinetobacter
sp. Strain DR1
Authors: Jung Jaejoon , Baek Jeong-Hun , Park Woojun
Published: July 2010

The genus
Acinetobacter
is ubiquitous in soil, aquatic, and sediment environments and includes pathogenic strains, such as
A. baumannii
. Many
Acinetobacter
species isolated from various environments have biotechnological potential since they are capable of degrading a variety of pollutants.
Acinetobacter
sp. strain DR1 has been identified as a diesel degrader. Here we report the complete genome sequence of
Acinetobacter
sp. DR1 isolated from the soil of a rice paddy.
Genome Sequence of
Fulvimarina pelagi
HTCC2506
T
, a Mn(II)-Oxidizing Alphaproteobacterium Possessing an Aerobic Anoxygenic Photosynthetic Gene Cluster and Xanthorhodopsin
Authors: Kang Ilnam , Oh Hyun-Myung , Lim Seung-Il , Ferriera Steve , Giovannoni Stephen J. , Cho Jang-Cheon
Published: July 2010

Fulvimarina pelagi
is a Mn(II)-oxidizing marine heterotrophic bacterium in the order
Rhizobiales
. Here we announce the draft genome sequence of
F. pelagi
HTCC2506
T
, which was isolated from the Sargasso Sea by using dilution-to-extinction culturing. The genome sequence contained a xanthorhodopsin gene as well as a photosynthetic gene cluster, which suggests the coexistence of two different phototrophic mechanisms in a single microorganism.
Evaluation of Corrosion Inhibiting Pigments
Authors: Kendig Martin
Published: July 2010

A review of the electrochemical methods used to evaluate the effectiveness of corrosion inhibiting pigments for paint illustrates the importance of considering tests specific for both anodic and cathodic inhibition, and the importance of considering the mechanism of corrosions for the target application.
Characterization of Nano-structured UV Cured Acrylic Coatings
Authors: Fedel Michele , Deflorian Flavio , Diré Sandra , Tagliazucca Valeria , Bongiovanni Roberta , Vescovo Lorenzo
Published: July 2010

This paper deals with the production and characterization of nano-structured UV curable acrylic coatings applied on mild steel substrates for corrosion protection purposes. UV curable acrylic coatings were modified in two ways: by adding pre-formed silica nanoparticles modified with MEMO molecules and by promoting an in situ formation of silica domains functionalized with MEMO molecules. The coatings were characterized by means of both chemical (FT-IR, DSC, UV-Vis absorbance, Gloss) and electrochemical techniques (EIS, Potential vs Time). The coatings showed different thermal stability as revealed by the DSC measurements. The coatings showed also different barrier properties depending on the presence of the nanoparticles or of the silica domains. It was proved that a convenient functionalization of the silica domains (or particles) lead to noticeable improvements of the barrier properties of the coating respect to the pure UV curable polymer.
Critical Factors in the Inhibition of Filiform Corrosion by in-Coating Ion-Exchange Pigments
Authors: Williams Geraint
Published: July 2010

In-coating cation and anion exchange pigments are studied with respect to their ability to inhibit filiform corrosion (FFC) on AA2024 aluminium alloy substrates. Smart-release cerium (III) and yttrium (III)-exchanged bentonite pigments are shown to be largely ineffective in reducing rates of FFC propagation. The reasons for this are discussed in terms of the chemistry of the filiform localised corrosion cell. In contrast, anion-exchange hydrotalcite based pigments are highly effective inhibitors of FFC. The efficiency is greatly improved by exchanging the native carbonate ions with anionic species which act as complexing agents for copper ions. The implication of these findings with respect to the mechanism of FFC on copper containing aluminium alloys is considered.
Coupling Interactions between Active Particulates and Aluminum Substrates
Authors: Vetter C A. , Hoge S. , Yan M. , Gelling Victoria J.
Published: July 2010

PPy/aluminum flake composite pigment was synthesized in an aqueous chemical deposition reaction with catechol, phloroglucide, pyrrole, and ammonium persulfate. The pigment was then incorporated into an epoxy binder and was sprayed applied to sand blasted and degreased aluminum 2024 T3 panels. The panels were then exposed to ASTM B117 salt spray to determine how the PPy/Al flake composite would perform as a corrosion inhibitor. The panels were monitored using linear polarization (LP), scanning vibrating electrode (SVET), and coupling current measurements. From the results, it is apparent that the aluminum flake synthesized without polypyrrole afforded some cathodic protection to aluminum 2024 T3; however, the polypyrrole further activates the aluminum flake surface.
The Influence of UV Light on Performance of Poly(methyl Methacrylate) in Regard to Dye-Sensitised Solar Cells
Authors: Darowicki Kazimierz , Szociński Michał , Schaefer Katarzyna , Mills Douglas J.
Published: July 2010

Low - cost production and simplicity of the process as well as comparable efficiencies make Dye - Sensitised Solar Cells (DSSC) competitive among commercial solar technologies. Excellent transparency and weatherability make the poly(methyl methacrylate) (PMMA) polymer a possible substitute of transparent, conductive glass commonly used in Dye-Sensitised Solar Cells. In the presented investigation thin PMMA film was applied. UV-C irradiation in range of 200-280nm was used to accelerate polymer degradation. Combination of Electrochemical Impedance Spectroscopy (EIS) and Atomic Force Microscopy (AFM) were used in order to provide information about photodegradation of the polymer coating as well as durability of PMMA film. AFM allowed evaluation of the photodegradation of PMMA coating and indicated possible local defects. The data gained using EIS technique confirmed that the PMMA deteriorated over a period of 141 hours of irradiation with UV-C.
The Prediction of Long-term Coating Performance from Short-term Electrochemical Data, Part I. Inhibited Aerospace Coating Systems - Comparison to Salt Spray Data
Authors: Taylor S. R. , Contu Francesco , Hunter C. N. , Fenzy L.
Published: July 2010

This study examines the role of short-term changes in the coating-substrate interface as a means to predict the long-term coating performance. A through-coating defect is introduced and interfacial changes are quantified using EIS testing over short times of exposure to aqueous environments. The ability of these short-term measurements to predict long-term performance was examined through a blind comaprison to 300h h salt spray results using 44 coating systems. EIS data acquired after the introduction of the defect was essential and the dominate factor in the prediction of 3000 h salt spray results. The high correlation of short-term to long-term results show the important role of interfacial stability and demonstrate a quantitative method to rapidly predict long-term coating performance for these materials.
The Prediction of Long-term Coating Performance from Short-term Electrochemical Data, Part II. Comparison of Electrochemical Data to Field Exposure Results for Coatings on Steel
Authors: Contu Francesco , Taylor S. R. , Calle L. M. , Hintze P. E. , Curran J. P. , Li W.
Published: July 2010

The pace of coatings development is limited by the time required to assess their corrosion protection properties. This study takes a step forward from Part I of this series and correlates the corrosion performance of organic coatings assessed by a series of short-term electrochemical measurement with 18-month beachside exposure results of duplicate panels. A series of 19 coating systems on A36 steel substrates were tested in a blind study using the damage tolerance test (DTT). In the DTT, a through-film pinhole defect is created, and the electrochemical characteristics of the defect are then monitored over the next 4 to 7 days while immersed in 0.5M NaCl. The results from open circuit potential, anodic potentiostatic polarization, and electrochemical impedance spectroscopy were used to characterize the corrosion behavior of the coating systems. The beachside exposure tests were conducted at the Kennedy Space Center according to ASTM D610-01. It was found that for 79% of the coatings systems examined, the 18 month beachside exposure results could be predicted by two independent laboratory tests obtained within 7 days.
Cathodic Corrosion Protection Performance of Mg-Rich Primers: Effect of Pigment Shape and Pigment Volume Concentration
Authors: Nie Jun , Yan Mao C. , Wang Jinhai , Tallman Dennis E. , Battocchi Dante , Bierwagen Gordon P.
Published: July 2010

In analogy to Zinc-rich coatings technology, Mg-rich primers (MgRPs) have been developed to protect Al alloys, particularly Al 2024-T3. Pigment shape and pigment volume concentration are two important parameters for metal rich coatings and their role in Mg-rich coatings was examined in this report. Two magnesium pigments, spherical Mg 1-11 and irregular shape Mg 3820, were formulated in Mg-rich coatings at different PVC levels. Pigment shape and particle size and were characterized by scanning electron microscopy (SEM), and particle size distribution (Accusizer 780a), respectively. Critical pigment volume concentration (CPVC) values were predicted by the methods of Bierwagen & Johnson(1, 2) , and were experimentally verified via fluorescence microscopy and SEM. Polarization curves, open circuit potential (OCP) and scanning vibrating electrode technique (SVET) were applied to characterize cathodic protection properties of MgRPs. It has been found that most MgRPs provided cathodic protection to Al alloys except for some low PVC MgRPs. These MgRPs were topcoated and then placed in Neutral Salt Spray chamber, and it is seen that Mg 1-11 coatings had less blistering than Mg 3820 coatings.
Roles of cytosolic Ca2+concentration and myofilament Ca2+sensitization in age-dependent cerebrovascular myogenic tone
Authors: Charles Shelton M. , Zhang Lubo , Cipolla Marilyn J. , Buchholz John N. , Pearce William J.
Published: July 2010

In light of evidence that immature arteries contain a higher proportion of noncontractile smooth muscle cells than found in fully differentiated mature arteries, the present study explored the hypothesis that age-related differences in the smooth muscle phenotype contribute to age-related differences in contractility. Because Ca2+handling differs markedly between contractile and noncontractile smooth muscle, the present study specifically tested the hypothesis that the relative contributions of Ca2+influx and myofilament sensitization to myogenic tone are upregulated, whereas Ca2+release is downregulated, in immature [14 days postnatal (P14)] compared with mature (6 mo old) rat middle cerebral arteries (MCAs). Myofilament Ca2+sensitivity measured in β-escin-permeabilized arteries increased with pressure in P14 but not adult MCAs. Cyclopiazonic acid (an inhibitor of Ca2+release from the sarcoplasmic reticulum) increased diameter and reduced Ca2+in adult MCAs but increased diameter with no apparent change in Ca2+in P14 MCAs. La3+(Ca2+influx inhibitor) increased diameter and decreased Ca2+in adult MCAs, but in P14 MCAs, La3+increased diameter with no apparent change in Ca2+. After treatment with both La3+and CPA, diameters were passive in both adult and P14 MCAs, but Ca2+was decreased only in adult MCAs. To quantify the fraction of smooth muscle cells in the fully differentiated contractile phenotype, extents of colocalization between smooth muscle α-actin and SM2 myosin heavy chain were determined and found to be at least twofold greater in adult than pup MCAs. These data suggest that compared with adult MCAs, pup MCAs contain a greater proportion of noncontractile smooth muscle and, as a consequence, rely more on myofilament Ca2+sensitization and Ca2+influx to maintain myogenic reactivity. The inability of La3+to reduce cytosolic Ca2+in the pup MCA appears due to La3+-insensitive noncontractile smooth muscle cells, which contribute to the spatially averaged measurements of Ca2+but not contraction.
Pulmonary and systemic vasodilator responses to the soluble guanylyl cyclase stimulator, BAY 41-8543, are modulated by nitric oxide
Authors: Badejo Adeleke M. , Nossaman Vaughn E. , Pankey Edward A. , Bhartiya Manish , Kannadka Chandrika B. , Murthy Subramanyam N. , Nossaman Bobby D. , Kadowitz Philip J.
Published: July 2010

BAY 41-8543 is a nitric oxide (NO)-independent stimulator of soluble guanylyl cyclase (sGC). Responses to intravenous injections of BAY 41-8543 were investigated under baseline and elevated tone conditions and when NO synthase (NOS) was inhibited with Nω-nitro-l-arginine methyl ester (l-NAME). Under baseline conditions, intravenous injections of BAY 41-8543 caused small decreases in pulmonary arterial pressure, larger decreases in systemic arterial pressure, and increases in cardiac output. When pulmonary arterial pressure was increased to ∼30 mmHg with an intravenous infusion of U-46619, intravenous injections of BAY 41-8543 produced larger dose-dependent decreases in pulmonary arterial pressure, and the relative decreases in pulmonary and systemic arterial pressure in response to the sGC stimulator were similar. Treatment with l-NAME markedly decreased responses to BAY 41-8543 when pulmonary arterial pressure was increased to similar values (∼30 mmHg) in U-46619-infused and in U-46619-infused plus l-NAME-treated animals. The intravenous injection of a small dose of sodium nitroprusside (SNP) when combined with BAY 41-8543 enhanced pulmonary and systemic vasodilator responses to the sGC stimulator in l-NAME-treated animals. The present results indicate that BAY 41-8543 has similar vasodilator activity in the systemic and pulmonary vascular beds when pulmonary vasoconstrictor tone is increased with U-46619. These results demonstrate that pulmonary and systemic vasodilator responses to BAY 41-8543 are significantly attenuated when NOS is inhibited by l-NAME and show that vasodilator responses to BAY 41-8543 are enhanced when combined with a small dose of SNP in l-NAME-treated animals. The present results are consistent with the concept that pulmonary and systemic vasodilator responses to the sGC stimulator are NO-independent; however, the vasodilator activity of the compound is greatly diminished when endogenous NO production is inhibited with l-NAME. These data show that BAY 41-8543 has similar vasodilator activity in the pulmonary and systemic vascular beds in the rat.
Adenosine receptor A3is a critical mediator in LPS-induced pulmonary inflammation
Authors: Wagner Rosalyn , Ngamsri Kristian-Christos , Stark Stefanie , Vollmer Irene , Reutershan Jörg
Published: July 2010

Adenosine receptor A3(A3) regulates directed movement of polymorphonuclear cells (PMNs) to sites of inflammation and has been implicated as a relevant mediator in models of inflammatory diseases. Here, we sought to characterize the role of A3in a murine model of lung inflammation. Initial studies revealed that pulmonary A3transcript levels were elevated following LPS exposure in vivo. In addition, inhalation of LPS increased the accumulation of PMNs in wild-type and A3−/−mice in all lung compartments. Pretreatment with the specific A3-agonist Cl-IB-MECA significantly decreased migration of PMNs into lung interstitium and alveolar air space of wild-type mice but not of A3−/−mice. Lower PMN counts were associated with reduced levels of TNF-α and IL-6 in the alveolar space of wild-type mice that received Cl-IB-MECA. In addition, Cl-IB-MECA attenuated LPS-induced microvascular permeability in wild-type mice as assessed by the extravasation of Evans blue. In pulmonary microvascular endothelial cells, Cl-IB-MECA reduced LPS-induced cytoskeletal remodeling and cell retraction, consistent with a specific role of A3for maintaining endothelial integrity. Migratory activity of human PMNs across an endothelial or epithelial monolayer was reduced when A3was activated on PMNs. Studies in chimeric mice, however, revealed that Cl-IB-MECA required A3on both hematopoietic and nonhematopoietic cells to reduce transmigration in vivo. Together, our results shed new light on the role of A3in LPS-induced PMN trafficking in the lung and suggest pharmacological modulation of A3-dependent pathways as a promising approach in lung inflammation.
Calcium transient evoked by TRPV1 activators is enhanced by tumor necrosis factor-α in rat pulmonary sensory neurons
Authors: Hu Youmin , Gu Qihai , Lin Ruei-Lung , Kryscio Richard , Lee Lu-Yuan
Published: July 2010

TNFα, a proinflammatory cytokine known to be involved in the pathogenesis of allergic asthma, has been shown to induce hyperalgesia in somatic tissue via a sensitizing effect on dorsal root ganglion neurons expressing transient receptor potential vanilloid type 1 receptor (TRPV1). Because TRPV1-expressing pulmonary sensory neurons play an important role in regulating airway function, this study was carried out to determine whether TNFα alters the sensitivity of these neurons to chemical activators. Responses of isolated nodose and jugular ganglion neurons innervating the rat lungs were determined by measuring the transient increase in intracellular Ca2+concentration ([Ca2+]i). Our results showed the following. 1) A pretreatment with TNFα (50 ng/ml) for ∼24 h increased significantly the peak Δ[Ca2+]ievoked by capsaicin (Cap) in these neurons. A pretreatment with the same concentration of TNFα for a longer duration (∼48 h) did not further increase the response, but pretreatment for a shorter duration (1 h) or with a lower concentration (25 ng/ml, 24 h) failed to enhance the Cap sensitivity. 2) The same TNFα pretreatment also induced similar but less pronounced and less uniform increases in the responses to acid (pH 6.5–5.5), 2-aminoethoxydiphenyl borate (2-APB), a common activator of TRPV1, V2, and V3 channels, and allyl isothiocyanate (AITC), a selective activator of TRPA1 channel. 3) In sharp contrast, the responses to ATP, ACh, and KCl were not affected by TNFα. 4) The TNFα-induced hypersensitivity to Cap was not prevented by pretreatment with indomethacin (30 μM). 5) The immunoreactivity to both TNF receptor types 1 and 2 were detected in rat vagal pulmonary sensory neurons. In conclusion, prolonged treatment with TNFα induces a pronounced potentiating effect on the responses of isolated pulmonary sensory neurons to TRPV1 activators. This action of TNFα may contribute in part to the airway hyperresponsiveness induced by this cytokine.
Lipopolysaccharide hyperpolarizes guinea pig airway epithelium by increasing the activities of the epithelial Na+channel and the Na+-K+pump
Authors: Dodrill Michael W. , Fedan Jeffrey S.
Published: July 2010

Earlier, we found that systemic administration of lipopolysaccharide (LPS; 4 mg/kg) hyperpolarized the transepithelial potential difference (Vt) of tracheal epithelium in the isolated, perfused trachea (IPT) of the guinea pig 18 h after injection. As well, LPS increased the hyperpolarization component of the response to basolateral methacholine, and potentiated the epithelium-derived relaxing factor-mediated relaxation responses to hyperosmolar solutions applied to the apical membrane. We hypothesized that LPS stimulates the transepithelial movement of Na+via the epithelial sodium channel (ENaC)/Na+-K+pump axis, leading to hyperpolarization of Vt. LPS increased the Vt-depolarizing response to amiloride (10 μM), i.e., offset the effect of LPS, indicating that Na+transport activity was increased. The functional activity of ENaC was measured in the IPT after short-circuiting the Na+-K+pump with basolateral amphotericin B (7.5 μM). LPS had no effect on the hyperpolarization response to apical trypsin (100 U/ml) in the Ussing chamber, indicating that channel-activating proteases are not involved in the LPS-induced activation of ENaC. To assess Na+-K+pump activity in the IPT, ENaC was short-circuited with apical amphotericin B. The greater Vtin the presence of amphotericin B in tracheas from LPS-treated animals compared with controls revealed that LPS increased Na+-K+pump activity. This finding was confirmed in the Ussing chamber by inhibiting the Na+-K+pump via extracellular K+removal, loading the epithelium with Na+, and observing a greater hyperpolarization response to K+restoration. Together, the findings of this study reveal that LPS hyperpolarizes the airway epithelium by increasing the activities of ENaC and the Na+-K+pump.
Teacher Ratings of Children’s Behavior Problems and Functional Impairment Across Gender and Ethnicity: Construct Equivalence of the Strengths and Difficulties Questionnaire
Authors: Zwirs Barbara , Burger Huibert , Schulpen Tom , Vermulst A.A. , HiraSing R.A. , Buitelaar Jan
Published: July 2010

The present study examined construct equivalence of the teacher Strengths and Difficulties Questionnaire and compared mean scores in an ethnically diverse sample of children living in the Netherlands. Elementary schoolteachers completed the Strengths and Difficulties Questionnaire for 2,185 children aged 6 to 10 years of the four largest ethnic groups in the Netherlands, namely native Dutch ( n = 684) and Moroccan ( n = 702), Turkish ( n = 434), and Surinamese ( n = 365) immigrant children. Multigroup confirmatory factor analysis suggested the factor structure of the Strengths and Difficulties Questionnaire to be invariant across children’s ethnicity and gender. Additionally, the factor structure appeared to be similar for Dutch and Surinamese teachers. However, mean scores on emotional problems, hyperactivity, conduct problems, prosocial behavior, and impairment varied significantly according to ethnicity and gender. Mean scores on peer problems differed significantly for boys and girls, but not across ethnicity. Whether mean differences reflect a method bias or actual differences in classroom behaviors is discussed and needs further research.
Cytokine Expression and Accelerated Tooth Movement
Authors: Teixeira C.C. , Khoo E. , Tran J. , Chartres I. , Liu Y. , Thant L.M. , Khabensky I. , Gart L.P. , Cisneros G. , Alikhani M.
Published: July 2010

It has been shown that inhibiting the expression of certain cytokines decreases the rate of tooth movement. Here, we hypothesized that stimulating the expression of inflammatory cytokines, through small perforations of cortical bone, increases the rate of bone remodeling and tooth movement. Forty-eight rats were divided into 4 groups: 50-cN force applied to the maxillary first molar (O), force application plus soft tissue flap (OF), force application plus flap plus 3 small perforations of the cortical plate (OFP), and a control group (C). From the 92 cytokines studied, the expression of 37 cytokines increased significantly in all experimental groups, with 21 cytokines showing the highest levels in the OFP group. After 28 days, micro-computed tomography, light and fluorescent microscopy, and immunohistochemistry demonstrated higher numbers of osteoclasts and bone remodeling activity in the OFP group, accompanied by generalized osteoporosity and increased rate of tooth movement.
Optimisation of City Size
Authors: Laurila Hannu
Published: July 2010

Club theoretical analysis of migration between asymmetrical cities shows that centralised policy intervention is necessary to ensure the efficient allocation of people between cities. Administrative and economic measures are compared as policy instruments of central government. These instruments are found to differ in their effects on residential allocation and welfare. In particular, a lump-sum tax-transfer programme pools the welfare-creating potentials of cities, thus affecting the efficiency condition. Therefore, lump-sum tax-transfers are superior to both quantity rationing and Pigouvian taxes, and they also activate, rather than stabilise, migration.
Constructing Legitimacy in the New Community Governance
Authors: Connelly Steve
Published: July 2010

What is the legitimacy of new forms of governance at community level? This paper addresses the important yet little understood issue of how this is established, developing a constructivist approach to the concept of ‘legitimacy’ and presenting an analysis of how the legitimacy of community-based organisations is understood and constructed in a northern English city. This shows how their legitimacy draws on a range of pre-existing norms as well as new ones, only some of which are recognisably democratic, and is more a product of informal practices than formal structures. It is consequently fragile and open to challenge, and weak according to the norms of legitimacy derived from the representative democratic tradition or the standpoint of modern deliberative democracy. What could appropriately replace such norms remains unclear, although it is suggested that a way forward may be through reintroducing the value of activism as an acceptable grounding for political legitimacy.
Rethinking Systems
Authors: Crozier Michael P.
Published: July 2010

New governance patterns in Western democracies pose challenges to political analysis. Key here is the relationship of politics and policy. This article examines how this relationship is changing in terms of a communication systems shift. From this perspective, the adequacy of current frameworks of political analysis is called into question. The article applies this critical review to the rise of policy-politics modes of behavior as distinct from older politics-policy forms. This contrast draws attention to the emergent qualities of interactive policy processes and asks how open generative modes of organization operate in fluid conditions while nonetheless exercising political authority.
Ant colony optimization-based bio-inspired hardware: survey and prospect
Authors: Duan Haibin , Yu Yaxiang , Zou Jie , Feng Xing
Published: July 2010

Bio-inspired hardware (BHW) refers to hardware that can change its architecture and behaviour dynamically and autonomously by interacting with its environment, and ant colony optimization is a meta-heuristic algorithm for the approximate solution of combinatorial optimization problems that has been inspired by the foraging behaviour of real ant colonies. In this paper, we take a broad survey on the recent progresses of ant colony optimization-based BHW, which includes ant colony optimization-based fuzzy controller, ant colony optimization-based hardware for the Travelling Salesman Problem (TSP), digital circuits, digital infinite impulse-response (IIR) filters, hardware-oriented ant colony optimization with look-up table and hardware/software partition. Some important issues of the challenges of ant colony optimization-based BHW are also presented. Online realization, robustness, generalization, disaster problems, theoretical analysis, implementation, swarm robotics, applications and hybrid approaches are eight key challenging issues for the ant colony optimization-based BHW.
Detecting Halo Effects in Performance-Based Examinations
Authors: Bechger Timo M. , Maris Gunter , Hsiao Ya Ping
Published: July 2010

The main purpose of this article is to demonstrate how halo effects may be detected and quantified using two independent ratings of the same person. A practical illustration is given to show how halo effects can be avoided.