bluuebunny/crossref_metadata_2025 huggingface dataset:
Summary of Weld Residual Stress Analyses for Dissimilar Metal Weld Nozzles
Authors: Brust F. W. , Zhang Tao , Shim Do-Jun , Kalyanam Sureshkumar , Wilkowski Gery , Smith Mike , Goodfellow Andrew
Published: January 2011

Flaw indications have been found in some dissimilar metal nozzle to stainless steel piping welds in pressurized water reactors (PWR) throughout the world. The nozzle welds usually involve welding ferritic (often A508) nozzles to 304/316 stainless steel pipe using Alloy 182/82 weld metal. Due to an unexpected aging issue with the weld metal, the weld becomes susceptible to a form of corrosion cracking referred to as primary water stress corrosion cracking (PWSCC). It can occur if the temperature is high enough (usually >300C) and the water chemistry in the PWR is typical of operating plants. This paper represents one of a series of papers which examine the propensity for cracking in a particular operating PWR in the UK. This paper represents an examination of the weld residual stress distributions which occur in four different size nozzles in the plant. Companion papers in this conference examine crack growth and PWSCC mitigation efforts related to this plant. British Energy (BE) has developed a work program to assess the possible impact of PWSCC on dissimilar metal welds in the primary circuit of the Sizewell ‘B’ pressurized water reactor. This effort has included the design and manufacture of representative PWR safety/relief valve nozzle welds both with and without a full structural weld overlay, multiple residual stress measurements on both mock-ups using the deep hole and incremental deep hole methods, and a number of finite element weld residual stress simulations of both the mock-ups and equivalent plant welds. This work is summarized in companion papers [1–3]. Here, the detailed weld residual stress predictions for these nozzles are summarized. The weld residual stresses in a PWR spray nozzle, safety/relief nozzle, surge nozzle, and finally a steam generator hot-leg nozzle are predicted here using an axis-symmetric computational weld solution process. The residual stresses are documented and these feed into a natural crack growth analysis provided in a companion PVP 2010-25162 paper [1]. The solutions are made using several different constitutive models: kinematic hardening, isotropic hardening, and a mixed hardening model. Discussion will be provided as to the appropriateness of the constitutive model for multi-pass DM weld modeling. In addition, the effect of including or neglecting the post-weld heat treatment process, which typically occurs after the buttering process in a DM weld, is presented. During operation the DM welds in a PWR experience temperatures in excess of 300°C. The coefficient of thermal expansion (CTE) mismatch between the three materials, particularly the higher CTE in the stainless steel, affects the stresses at operating temperature. The K-weld geometry used in the steam generator nozzles in this plant combines with CTE mis-match effects to result in service stresses somewhat different from V-weld groove cases.
Current Status of RRA Rules Development in JSME Fitness-for-Service Code
Authors: Dozaki Koji , Yamamoto Satoshi , Koyama Koji
Published: January 2011

Rules on Repair, Replacement Activities (RRA) in Fitness-For-Service (FFS) Code of the Japanese Society of Mechanical Engineers (JSME) have been under development since the 2004 Edition. The FFS of 2010 Addenda to the 2008 Edition is under preparation for publishing at present. However, Japanese regulatory authorities, the Nuclear and Industrial Safety Agency (NISA) and Japan Nuclear Energy Safety Organization (JNES) have not endorsed the RRA rules yet, even though the rest of the FFS Code, i.e. inspection and flaw evaluation rules have been already endorsed. NISA/JNES have not even begun technical assessment of RRA rules yet, because regulatory authorities do not consider that RRA rules of JSME FFS Code have a completed system of RRA, inspection and flaw evaluation rules, e.g. in-service inspection intervals after repair. Also, the regulatory authorities are concerned that no method has yet been established by NISA/JNES to confirm the conformity of RRA rules in FFS Code with the governmental technical standard. In order to solve the problem of developing the completed system of RRA and related rules and of providing information on the relationship between RRA rules and governmental technical standards so as to assist regulatory authorities’ understanding, the RRA part of the JSME FFS Code was modified in the 2010 addenda. This paper describes the major features of the code modification of RRA rules in the 2010 Addenda. Remaining issues to be solved in future addenda or editions are also discussed.
The 2009 Forum on Seismic Design of Piping Systems for the Year 2010
Authors: Slagis Gerry C.
Published: January 2011

A summary of The 2009 Forum on Seismic Design of Piping Systems for the Year 2010 is provided. This forum session was the thirteenth in a series that was started in 1992. Previously, the title was Appropriate Criteria and Methods for Seismic Design of Nuclear Piping. In this 2009 forum, the main topic of discussion was “Dynamic Response Behavior of Piping.” Test results from three experimental programs were reviewed. The Berkeley NL vibration tests, the University of Liverpool vibration tests, and the EPRI/NRC Piping and Fitting Dynamic Reliability Program. The self-limiting nature of piping response by inelastic energy absorption is obvious from the experimental data.
The Role of Environment on High Temperature Creep-Fatigue Behavior of Alloy 617
Authors: Carroll Laura , Cabet Celine , Wright Richard
Published: January 2011

Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) application of the Very High Temperature Nuclear Reactor (VHTR), expected to have an outlet temperature as high as 950°C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Initial creep-fatigue work on Alloy 617 suggests a more dominant role of environment with increasing temperature and/or hold times evidenced through changes in creep-fatigue crack growth mechanism/s and failure life. Furthermore, previous work on corrosion of nickel base alloys in impure helium has suggested that this environment is far from inert with respect to Alloy 617. Continuous cycle fatigue and creep-fatigue testing of Alloy 617 was conducted at 950°C and 0.3% and 0.6% total strain in air to simulate damage modes expected in a VHTR application. Continuous cycle and creep-fatigue specimens exhibited intergranular cracking, but did not show evidence of grain boundary cavitation. Despite the absence of grain boundary cavitation to accelerate crack propagation, the addition of a hold time at peak tensile strain was detrimental to cycle life. This suggests that creep-fatigue interaction may occur by a different mechanism or that the environment may be partially responsible for accelerating failure.
Ambient Temperature Temperbead Welding Using the Underwater Laser Beam Welding Process
Authors: Newton Bruce
Published: January 2011

Ambient temperature temperbead welding using the Machine Gas Tungsten Arc Welding (GTAW) process is widely accepted in the nuclear industry. GTAW machine ambient temperature temperbead welding, addressed in ASME Code Case N-638, has been used to repair ASME Class 1 components in numerous safety related applications. Underwater laser beam welding (ULBW) is gaining increasing industry recognition as a method for producing high quality welds in high radiation environments. Since ULBW enables high quality weld deposition in underwater environments, the process enables water to serve as a radiation moderator, reducing personnel exposure levels. ULBW’s advantages go beyond radiation exposure reductions, and this paper will provide the reader a better understanding of the ULBW process’s capabilities and properties. A recently formed ASME Task Group is preparing a new Code Case that will delineate specific requirements and essential variables governing use of ULBW to repair ASME Class 1 components. In addition, this Code Case will provide specific rules for use of the ULBW process for ambient temperature temperbead welding. Extensive testing has been performed to demonstrate ULBW’s capabilities with regard to ambient temperature temperbead welding in an underwater environment, and this paper summarizes testing and test results. It also provides a technical summary of the new Code Case, it’s requirements, and summarizes several of the bases for these requirements.
Initial Investigations Into the Development of Thin Film Voltammetric Sensors
Authors: Reich Alton , Teixeira Rodrigo , Cook Koy , Dykes Waite , Deaconu Stelu
Published: January 2011

Voltammetry is an electrochemical sensing technique that has been in use for almost a century using macro-scale electrodes. This paper discusses initial investigations into the development of a prototype voltammetric sensing system that uses electrodes with nano-scale features to reduce the size of the electrodes and increase performance. Modeling, fabrication, and testing are discussed.
Towards an Improved Understanding of Water-Hammer Column-Separation Due to Rapid Valve Closure
Authors: Warda H. A. , Elashry Y.
Published: January 2011

Column separation phenomenon occurring downstream of a closing valve, simulating the closure of non-return/check valve downstream of pumps due to pump trip is simulated. An improved understanding of how cavity is opened, grows and collapses is supported by comparing numerical results with measured values and analyzing video frames. In the present study two models, discrete vapor cavity and gas cavity models, of column separation are compared for the modeling of column separation. Both models showed considerable degree of stability with variation of number of sections into which the pipe is divided. An experimental setup was built to provide the means of obtaining reliable experimental data for transient flow in viscoelastic pipes to verify the numerical model. Two valve closure schemes were tested using solenoid globe and ball valves. Video photographs of column separation during the vapor cavity formation, growth and collapse were processed and video films are transformed into frames using computer software. The video frames representing the cavity development and pressure measurements downstream of the valve are compared with corresponding cavity and pressure traces predicted by the model at each time step of the framing process at the same location. It was also shown that the characteristic of check valve closure scheme seriously affects the cavity formation and the extent of pressure surges due to cavity collapse.
Shakedown Analysis Combined With the Problem of Heat Conduction
Authors: Simon Jaan-Willem , Chen Min , Weichert Dieter
Published: January 2011

This paper deals with the computation of the shakedown load of engineering systems subjected to varying loads. In particular, we focus on thermal loading and the resulting heat conduction problem in combination with shakedown analysis. The analysis is based on the lower bound shakedown theorem by Melan. The calculation is carried out by use of an interior-point algorithm. Emphasis is placed on the presentation of theoretical derivations whereas numerical aspects are out of scope and will be presented elsewhere. The methodology is illustrated by the application to a simplified model of a tube sheet in heat exchangers.
An Analysis of a Completed Temper Bead Weld Repair Performed on an Amine Tower
Authors: Mohr William C. , Boring Matt A. , Yang Yu-Ping
Published: January 2011

An amine tower was inspected and was shown to have wall loss over the majority of the circumference. A repair plan was developed which included welding onto the tower while the tower remained in operation. The two step repair plan first required welding two Inconel 625 rings to the SA516-70N steel tower and then welding a stainless steel sleeve to the Inconel 625 rings encapsulating the corroded area. Since the repair welds could be exposed to an amine environment if the steel tower corroded through, API Recommended Practice 945 (API RP 945) was used to aid in the qualification of the welding procedure. API RP 945 recommends a post-weld heat treatment (PWHT) to reduce hardness and relieve stress, but since the planned repair was to be made in-service, PWHT was not preferred. To address the hardness aspect a temper bead technique was used to successfully qualify a welding procedure, without PWHT, in accordance with 2006 NBIC and 2004 ASME Boiler and Pressure Vessel Code Section IX with hardness values below 200 Brinell. The temper bead welding procedure used Inconel 182 SMAW electrodes and required strict welding heat input control and weld bead placement. The heat input could be monitored by controlling the welding parameters or by using the run-out ratio diagram. The temper bead passes needed to be deposited in such a manner that the weld toe of the temper bead was no more than 3/32 in. (2.4 mm) away from the weld toe of the initial layer. To address the residual stress aspect the procedure qualification weld was thermo-mechanically modeled to predict the residual stress distribution on the inside surface of the amine tower. The repair procedure was performed on the operating vessel to emplace the straps and the sleeve. Shortly afterwards, the tower wall was breached and the internal environment reached the annulus inside the sleeve. Operation continued for several months until the replacement vessel was available. Once the vessel was removed from service, a section of the repaired area was examined for residual stresses and hardness in the carbon steel. The peak residual stresses were lower than predicted by the analysis from the qualification stage. However, the measured heat affected zone (HAZ) hardness was well above the desired level of 200 Brinnell. Analysis showed that the increased hardness level correlated with improper temper bead placement [i.e., temper bead to weld toe spacing greater than 3/32 in. (2.4 mm)] along with other indications of deviations from the qualified procedure.
Performance characteristics of GaN-based light-emitting diodes fabricated with AgNi, AgCu, and AgAl-alloy reflectors
Authors: Kim Hyunsoo , Lee Sung-Nam
Published: January 2011

We report on the performance characteristics of GaN-based light-emitting diodes (LEDs) fabricated with Ag-alloy p-type reflectors including AgNi, AgCu, and AgAl. Compared to the reference LEDs fabricated with Ag, LEDs fabricated with AgNi and AgCu produced smaller forward voltages and higher light output power. Under optimized thermal annealing conditions, the forward voltages obtained were 3.56, 3.29, 3.28, and 3.44 V, the light output powers were 14.38, 15.73, 14.40, and 12.77 mW, and the power efficiencies were 20.2%, 23.91%, 21.95%, and 18.45% for LEDs fabricated with Ag, AgNi, AgCu, and AgAl, respectively. The surface morphology of Ag-alloy was also found to be smoother than that of Ag, suggesting that Ag-alloy reflectors, particularly AgNi, are very promising for practical applications.
Survival of
Escherichia coli
, Enterococci, and
Campylobacter
spp. in Sheep Feces on Pastures
Authors: Moriarty Elaine M. , Mackenzie Margaret L. , Karki Naveena , Sinton Lester W.
Published: January 2011

The survival of enteric bacteria in 10 freshly collected sheep fecal samples on pastures was measured in each of four seasons. Ten freshly collected feces were placed on pasture, and concentrations of
Escherichia coli
, enterococci, and
Campylobacter
spp. were monitored until exhaustion of the fecal samples. In all four seasons, there was an increase in enterococcal concentrations by up to 3 orders of magnitude, with peak concentrations recorded between 11 and 28 days after deposition.
E. coli
concentrations increased in three out of four seasons by up to 1.5 orders of magnitude, with peak concentrations recorded between 8 and 14 days after deposition. The apparent growth of
E. coli
and enterococci was strongly influenced by the initial water content of the feces and the moisture gained during periods of rehydration following rainfalls. Conversely, the results suggested that dehydration promoted inactivation.
Campylobacter
spp. did not grow and were rapidly inactivated at a rate that tended to be faster at higher temperatures. Pulsed-field gel electrophoresis (PFGE) of a selection of
Campylobacter
spp. suggested that these survival data are applicable to a range of
Campylobacter
spp., including the most frequently isolated PFGE genotype from sheep in New Zealand, and to genotypes previously observed to cause disease in humans. The results of this study are currently being incorporated into a fecal microbe reservoir model that is designed to assist water managers' abilities to estimate microbial loads on pastures grazed by sheep, including the influence of factors such as rainfall and temperature.
Differentiation of “
Candidatus
Liberibacter asiaticus” Isolates by Variable-Number Tandem-Repeat Analysis
Authors: Katoh Hiroshi , Subandiyah Siti , Tomimura Kenta , Okuda Mitsuru , Su Hong-Ji , Iwanami Toru
Published: January 2011

Four highly polymorphic simple sequence repeat (SSR) loci were selected and used to differentiate 84 Japanese isolates of “
Candidatus
Liberibacter asiaticus.” The Nei's measure of genetic diversity values for these four SSRs ranged from 0.60 to 0.86. The four SSR loci were also highly polymorphic in four isolates from Taiwan and 12 isolates from Indonesia.
Terminal Oxidase Diversity and Function in “
Metallosphaera yellowstonensis
”: Gene Expression and Protein Modeling Suggest Mechanisms of Fe(II) Oxidation in the
Sulfolobales
Authors: Kozubal M. A. , Dlakić M. , Macur R. E. , Inskeep W. P.
Published: January 2011

“
Metallosphaera yellowstonensis
” is a thermoacidophilic archaeon isolated from Yellowstone National Park that is capable of autotrophic growth using Fe(II), elemental S, or pyrite as electron donors. Analysis of the draft genome sequence from
M. yellowstonensis
strain MK1 revealed seven different copies of heme copper oxidases (subunit I) in a total of five different terminal oxidase complexes, including
doxBCEF
,
foxABCDEFGHIJ
,
soxABC
, and the
soxM
supercomplex, as well as a novel hypothetical two-protein
doxB
-like polyferredoxin complex. Other genes found in
M. yellowstonensis
with possible roles in S and or Fe cycling include a thiosulfate oxidase (
tqoAB
), a sulfite oxidase (
som
), a
cbsA
cytochrome
b
558/566
, several small blue copper proteins, and a novel gene sequence coding for a putative multicopper oxidase (Mco). Results from gene expression studies, including reverse transcriptase (RT) quantitative PCR (qPCR) of cultures grown autotrophically on either Fe(II), pyrite, or elemental S showed that the
fox
gene cluster and
mco
are highly expressed under conditions where Fe(II) is an electron donor. Metagenome sequence and gene expression studies of Fe-oxide mats confirmed the importance of
fox
genes (e.g.,
foxA
and
foxC
) and
mco
under Fe(II)-oxidizing conditions. Protein modeling of FoxC suggests a novel lysine-lysine or lysine-arginine heme B binding domain, indicating that it is likely the cytochrome component of a heterodimer complex with
foxG
as a ferredoxin subunit. Analysis of
mco
shows that it encodes a novel multicopper blue protein with two plastocyanin type I copper domains that may play a role in the transfer of electrons within the Fox protein complex. An understanding of metabolic pathways involved in aerobic iron and sulfur oxidation in
Sulfolobales
has broad implications for understanding the evolution and niche diversification of these thermophiles as well as practical applications in fields such as bioleaching of trace metals from pyritic ores.
Contribution of the
Klebsiella pneumoniae
Capsule to Bacterial Aggregate and Biofilm Microstructures
Authors: Dzul Stephen P. , Thornton Margaret M. , Hohne Danial N. , Stewart Elizabeth J. , Shah Aayush A. , Bortz David M. , Solomon Michael J. , Younger John G.
Published: January 2011

We studied the interaction between capsule production and hydrodynamic growth conditions on the internal and macroscopic structure of biofilms and spontaneously formed aggregates of
Klebsiella pneumoniae
. Wild-type and capsule-deficient strains were studied as biofilms and under strong and mild hydrodynamic conditions. Internal organization of multicellular structures was determined with a novel image-processing algorithm for feature extraction from high-resolution confocal microscopy. Measures included interbacterial spacing and local angular alignment of individual bacteria. Macroscopic organization was measured via the size distribution of aggregate populations forming under various conditions. Compared with wild-type organisms, unencapsulated mutant organisms formed more organized aggregates with less variability in interbacterial spacing and greater interbacterial angular alignment. Internal aggregate structure was not detectably affected by the severity of hydrodynamic growth conditions. However, hydrodynamic conditions affected both wild-type and mutant aggregate size distributions. Bacteria grown under high-speed shaking conditions (i.e., at Reynolds' numbers beyond the laminar-turbulent transition) formed few multicellular aggregates while clumpy growth was common in bacteria grown under milder conditions. Our results indicate that both capsule and environment contribute to the structure of communities of
K. pneumoniae
, with capsule exerting influence at an interbacterial length scale and fluid dynamic forces affecting overall particle size.
Persistence of Free-Living Protozoan Communities across Rearing Cycles in Commercial Poultry Houses
Authors: Baré Julie , Houf Kurt , Verstraete Tine , Vaerewijck Mario , Sabbe Koen
Published: January 2011

The introduction and survival of zoonotic bacterial pathogens in poultry farming have been linked to bacterial association with free-living protozoa. To date, however, no information is available on the persistence of protozoan communities in these environments across consecutive rearing cycles and how it is affected by farm- and habitat-specific characteristics and management strategies. We therefore investigated the spatial and temporal dynamics of free-living protozoa in three habitats (pipeline, water, and miscellaneous samples) in three commercial poultry houses across three rearing cycles by using the molecular fingerprinting technique denaturing gradient gel electrophoresis (DGGE). Our study provides strong evidence for the long-term (ca. 6-month) persistence of protozoa in broiler houses across consecutive rearing cycles. Various free-living protozoa (flagellates, ciliates, and amoebae), including known vectors of bacterial pathogens, were observed during the down periods in between rearing cycles. In addition, multivariate analysis and variation partitioning showed that the protozoan community structure in the broiler houses showed almost no change across rearing cycles and remained highly habitat and farm specific. Unlike in natural environments, protozoan communities inside broiler houses are therefore not seasonal. Our results imply that currently used biosecurity measures (cleaning and disinfection) applied during the down periods are not effective against many protozoans and therefore cannot prevent potential cross-contamination of bacterial pathogens via free-living protozoa between rearing cycles.
Entianin, a Novel Subtilin-Like Lantibiotic from
Bacillus subtilis
subsp.
spizizenii
DSM 15029
T
with High Antimicrobial Activity
Authors: Fuchs Sebastian W. , Jaskolla Thorsten W. , Bochmann Sophie , Kötter Peter , Wichelhaus Thomas , Karas Michael , Stein Torsten , Entian Karl-Dieter
Published: January 2011

Lantibiotics, such as nisin and subtilin, are lanthionine-containing peptides that exhibit antimicrobial as well as pheromone-like autoinducing activity. Autoinduction is specific for each lantibiotic, and reporter systems for nisin and subtilin autoinduction are available. In this report, we used the previously reported subtilin autoinduction bioassay in combination with mass spectrometric analyses to identify the novel subtilin-like lantibiotic entianin from
Bacillus subtilis
subsp.
spizizenii
DSM 15029
T
. Linearization of entianin using Raney nickel-catalyzed reductive cleavage enabled, for the first time, the use of tandem mass spectrometry for the fast and efficient determination of an entire lantibiotic primary structure, including posttranslational modifications. The amino acid sequence determined was verified by DNA sequencing of the
etnS
structural gene, which confirmed that entianin differs from subtilin at 3 amino acid positions. In contrast to
B. subtilis
ATCC 6633, which produces only small amounts of unsuccinylated subtilin,
B. subtilis
DSM 15029
T
secretes considerable amounts of unsuccinylated entianin. Entianin was very active against several Gram-positive pathogens, such as
Staphylococcus aureus
and
Enterococcus faecalis.
The growth-inhibiting activity of succinylated entianin (S-entianin) was much lower than that of unsuccinylated entianin: a 40-fold higher concentration was required for inhibition. For succinylated subtilin (S-subtilin), a concentration 100-fold higher than that of unsuccinylated entianin was required to inhibit the growth of a
B. subtilis
test strain. This finding was in accordance with a strongly reduced sensing of cellular envelope stress provided by S-entianin relative to that of entianin. Remarkably, S-entianin and S-subtilin showed considerable autoinduction activity, clearly demonstrating that autoinduction and antibiotic activity underlie different molecular mechanisms.
Stress Survival Islet 1 (SSI-1) Survey in
Listeria monocytogenes
Reveals an Insert Common to
Listeria innocua
in Sequence Type 121
L. monocytogenes
Strains
Authors: Hein Ingeborg , Klinger Sonja , Dooms Maxime , Flekna Gabriele , Stessl Beatrix , Leclercq Alexandre , Hill Colin , Allerberger Franz , Wagner Martin
Published: January 2011

Listeria monocytogenes
strains (
n
= 117) were screened for the presence of stress survival islet 1 (SSI-1). SSI-1
+
strains (32.5%) belonged mainly to serotypes 1/2c, 3b, and 3c. All sequence type 121 (ST-121) strains included (
n
= 7) possessed homologues to
Listeria innocua
genes
lin0464
and
lin0465
instead of SSI-1.
A New Wine
Saccharomyces cerevisiae
Killer Toxin (Klus), Encoded by a Double-Stranded RNA Virus, with Broad Antifungal Activity Is Evolutionarily Related to a Chromosomal Host Gene
Authors: Rodríguez-Cousiño Nieves , Maqueda Matilde , Ambrona Jesús , Zamora Emiliano , Esteban Rosa , Ramírez Manuel
Published: January 2011

Wine
Saccharomyces cerevisiae
strains producing a new killer toxin (Klus) were isolated. They killed all the previously known
S. cerevisiae
killer strains, in addition to other yeast species, including
Kluyveromyces lactis
and
Candida albicans
. The Klus phenotype is conferred by a medium-size double-stranded RNA (dsRNA) virus,
Saccharomyces
cerevisiae
virus Mlus (ScV-Mlus), whose genome size ranged from 2.1 to 2.3 kb. ScV-Mlus depends on ScV-L-A for stable maintenance and replication. We cloned and sequenced Mlus. Its genome structure is similar to that of M1, M2, or M28 dsRNA, with a 5′-terminal coding region followed by two internal A-rich sequences and a 3′-terminal region without coding capacity. Mlus positive strands carry
cis
-acting signals at their 5′ and 3′ termini for transcription and replication similar to those of killer viruses. The open reading frame (ORF) at the 5′ portion codes for a putative preprotoxin with an N-terminal secretion signal, potential Kex2p/Kexlp processing sites, and N-glycosylation sites. No sequence homology was found either between the Mlus dsRNA and M1, M2, or M28 dsRNA or between Klus and the K1, K2, or K28 toxin. The Klus amino acid sequence, however, showed a significant degree of conservation with that of the product of the host chromosomally encoded ORF YFR020W of unknown function, thus suggesting an evolutionary relationship.
Autoregulation of Nodulation Interferes with Impacts of Nitrogen Fertilization Levels on the Leaf-Associated Bacterial Community in Soybeans
Authors: Ikeda Seishi , Anda Mizue , Inaba Shoko , Eda Shima , Sato Shusei , Sasaki Kazuhiro , Tabata Satoshi , Mitsui Hisayuki , Sato Tadashi , Shinano Takuro , Minamisawa Kiwamu
Published: January 2011

The diversities leaf-associated bacteria on nonnodulated (Nod
−
), wild-type nodulated (Nod
+
), and hypernodulated (Nod
++
) soybeans were evaluated by clone library analyses of the 16S rRNA gene. To analyze the impact of nitrogen fertilization on the bacterial leaf community, soybeans were treated with standard nitrogen (SN) (15 kg N ha
−1
) or heavy nitrogen (HN) (615 kg N ha
−1
) fertilization. Under SN fertilization, the relative abundance of
Alphaproteobacteria
was significantly higher in Nod
−
and Nod
++
soybeans (82% to 96%) than in Nod
+
soybeans (54%). The community structure of leaf-associated bacteria in Nod
+
soybeans was almost unaffected by the levels of nitrogen fertilization. However, differences were visible in Nod
−
and Nod
++
soybeans. HN fertilization drastically decreased the relative abundance of
Alphaproteobacteria
in Nod
−
and Nod
++
soybeans (46% to 76%) and, conversely, increased those of
Gammaproteobacteria
and
Firmicutes
in these mutant soybeans. In the
Alphaproteobacteria
, cluster analyses identified two operational taxonomic units (OTUs) (
Aurantimonas
sp. and
Methylobacterium
sp.) that were especially sensitive to nodulation phenotypes under SN fertilization and to nitrogen fertilization levels. Arbuscular mycorrhizal infection was not observed on the root tissues examined, presumably due to the rotation of paddy and upland fields. These results suggest that a subpopulation of leaf-associated bacteria in wild-type Nod
+
soybeans is controlled in similar ways through the systemic regulation of autoregulation of nodulation, which interferes with the impacts of N levels on the bacterial community of soybean leaves.
Tracking Glideosome-Associated Protein 50 Reveals the Development and Organization of the Inner Membrane Complex of Plasmodium falciparum
Authors: Yeoman Jeffrey A. , Hanssen Eric , Maier Alexander G. , Klonis Nectarios , Maco Bohumil , Baum Jake , Turnbull Lynne , Whitchurch Cynthia B. , Dixon Matthew W. A. , Tilley Leann
Published: January 2011

The most deadly of the human malaria parasites,
Plasmodium falciparum
, has different stages specialized for invasion of hepatocytes, erythrocytes, and the mosquito gut wall. In each case, host cell invasion is powered by an actin-myosin motor complex that is linked to an inner membrane complex (IMC) via a membrane anchor called the glideosome-associated protein 50 (PfGAP50). We generated
P. falciparum
transfectants expressing green fluorescent protein (GFP) chimeras of PfGAP50 (PfGAP50-GFP). Using immunoprecipitation and fluorescence photobleaching, we show that C-terminally tagged PfGAP50-GFP can form a complex with endogenous copies of the linker protein PfGAP45 and the myosin A tail domain-interacting protein (MTIP). Full-length PfGAP50-GFP is located in the endoplasmic reticulum in early-stage parasites and then redistributes to apical caps during the formation of daughter merozoites. In the final stage of schizogony, the PfGAP50-GFP profile extends further around the merozoite surface. Three-dimensional (3D) structured illumination microscopy reveals the early-stage IMC as a doubly punctured flat ellipsoid that separates to form claw-shaped apposed structures. A GFP fusion of PfGAP50 lacking the C-terminal membrane anchor is misdirected to the parasitophorous vacuole. Replacement of the acid phosphatase homology domain of PfGAP50 with GFP appears to allow correct trafficking of the chimera but confers a growth disadvantage.
Depletion of Mitochondrial Acyl Carrier Protein in Bloodstream-Form Trypanosoma brucei Causes a Kinetoplast Segregation Defect
Authors: Clayton April M. , Guler Jennifer L. , Povelones Megan L. , Gluenz Eva , Gull Keith , Smith Terry K. , Jensen Robert E. , Englund Paul T.
Published: January 2011

Like other eukaryotes, trypanosomes have an essential type II fatty acid synthase in their mitochondrion. We have investigated the function of this synthase in bloodstream-form parasites by studying the effect of a conditional knockout of acyl carrier protein (ACP), a key player in this fatty acid synthase pathway. We found that ACP depletion not only caused small changes in cellular phospholipids but also, surprisingly, caused changes in the kinetoplast. This structure, which contains the mitochondrial genome in the form of a giant network of several thousand interlocked DNA rings (kinetoplast DNA [kDNA]), became larger in some cells and smaller or absent in others. We observed the same pattern in isolated networks viewed by either fluorescence or electron microscopy. We found that the changes in kDNA size were not due to the disruption of replication but, instead, to a defect in segregation. kDNA segregation is mediated by the tripartite attachment complex (TAC), and we hypothesize that one of the TAC components, a differentiated region of the mitochondrial double membrane, has an altered phospholipid composition when ACP is depleted. We further speculate that this compositional change affects TAC function, and thus kDNA segregation.
A Processive Glycosyltransferase Involved in Glycolipid Synthesis during Phosphate Deprivation in
Mesorhizobium loti
Authors: Devers Emanuel A. , Wewer Vera , Dombrink Isabel , Dörmann Peter , Hölzl Georg
Published: January 2011

Natural habitats are often characterized by a low availability of phosphate. In plants and many bacteria, phosphate deficiency causes different physiological responses, including the replacement of phosphoglycerolipids in the membranes with nonphosphorous lipids. We describe here a processive glycosyltransferase (Pgt) in
Mesorhizobium loti
(
Rhizobiales
) involved in the synthesis of di- and triglycosyldiacylglycerols (DGlycD and TGlycD) during phosphate deprivation. Cells of the corresponding Δ
pgt
deletion mutant are deficient in DGlycD and TGlycD. Additional Pgt-independent lipids accumulate in
Mesorhizobium
after phosphate starvation, including diacylglyceryl trimethylhomoserine (DGTS) and ornithine lipid (OL). The accumulation of the nonphosphorous lipids during phosphate deprivation leads to the reduction of phosphoglycerolipids from 90 to 50%. Nodulation experiments of
Mesorhizobium
wild type and the Δ
pgt
mutant with its host plant,
Lotus japonicus
, revealed that DGlycD and TGlycD are not essential for nodulation under phosphate-replete or -deficient conditions. Lipid measurements showed that the Pgt-independent lipids including OL and DGTS accumulate to higher proportions in the Δ
pgt
mutant and therefore might functionally replace DGlycD and TGlycD during phosphate deprivation.
Mesenchymal stem cells in infantile haemangioma
Authors: Itinteang Tinte , Vishvanath Anasuya , Day Darren J , Tan Swee T
Published: January 2011

Background

Fibro-fatty deposition commonly occurs during involution of infantile haemangioma (IH). Mesenchymal stem cells have been identified in this tumour and have been proposed to be recruited from the bone marrow and/or adjacent niches, and then give rise to the fibro-fatty tissue. The authors have recently demonstrated that the capillary endothelium of proliferating IH co-expresses primitive mesodermal, mesenchymal and neural crest markers and proposed that this same endothelium has the ability to give rise to cells of mesenchymal lineage that constitute the fibro-fatty deposition.

Methods

Immunohistochemistry and real-time RT-PCR were used to further characterise proliferating IHs and haemangioma explant-derived cells (HaemEDCs).

Results

The authors have further confirmed expression of the mesenchymal-associated proteins including preadipocyte factor-1, a mesenchymal differentiation inhibition-associated cytokine. The HaemEDCs could be differentiated into osteoblasts and adipocytes, indicating their functional potential for terminal differentiation.

Discussion

The collective expression of neural crest, mesenchymal and mesenchymal differentiation inhibition-associated proteins on the endothelium of proliferating IH suggests that the cells in the capillary endothelium within the lesion possess the ability to undergo terminal mesenchymal differentiation during the proliferating phase, but are inhibited from doing so.
Active tension adaptation at a shortened arterial muscle length: inhibition by cytochalasin-D
Authors: Bednarek Melissa L. , Speich John E. , Miner Amy S. , Ratz Paul H.
Published: January 2011

Unlike the static length-tension curve of striated muscle, airway and urinary bladder smooth muscles display a dynamic length-tension curve. Much less is known about the plasticity of the length-tension curve of vascular smooth muscle. The present study demonstrates that there were significant increases of ∼15% in the phasic phase and ∼10% in the tonic phase of a third KCl-induced contraction of a rabbit femoral artery ring relative to the first contraction after a 20% decrease in length from an optimal muscle length ( L0) to 0.8-fold L0. Typically, three repeated contractions were necessary for full length adaptation to occur. The tonic phase of a third KCl-induced contraction was increased by ∼50% after the release of tissues from 1.25-fold to 0.75-fold Lo. The mechanism for this phenomenon did not appear to lie in thick filament regulation because there was no increase in myosin light chain (MLC) phosphorylation to support the increase in tension nor was length adaptation abolished when Ca2+entry was limited by nifedipine and when Rho kinase (ROCK) was blocked by H-1152. However, length adaptation of both the phasic and tonic phases was abolished when actin polymerization was inhibited through blockade of the plus end of actin by cytochalasin-D. Interestingly, inhibition of actin polymerization when G-actin monomers were sequestered by latrunculin-B increased the phasic phase and had no effect on the tonic phase of contraction during length adaptation. These data suggest that for a given level of cytosolic free Ca2+, active tension in the femoral artery can be sensitized not only by regulation of MLC phosphatase via ROCK and protein kinase C, as has been reported by others, but also by a nonmyosin regulatory mechanism involving actin polymerization. Dysregulation of this form of active tension modulation may provide insight into alterations of large artery stiffness in hypertension.
Endothelial ischemia-reperfusion injury in humans: association with age and habitual exercise
Authors: DeVan Allison E. , Umpierre Daniel , Harrison Michelle L. , Lin Hsin-Fu , Tarumi Takashi , Renzi Christopher P. , Dhindsa Mandeep , Hunter Stacy D. , Tanaka Hirofumi
Published: January 2011

Advancing age is a major risk factor for coronary artery disease. Endothelial dysfunction accompanied by increased oxidative stress and inflammation with aging may predispose older arteries to greater ischemia-reperfusion (I/R) injury. Because coronary artery ischemia cannot be induced safely, the effects of age and habitual endurance exercise on endothelial I/R injury have not been determined in humans. Using the brachial artery as a surrogate model of the coronary arteries, endothelial function, assessed by brachial artery flow-mediated dilation (FMD), was measured before and after 20 min of continuous forearm occlusion in young sedentary ( n = 10, 24 ± 2 yr) and middle-aged ( n = 9, 48 ± 2 yr) sedentary adults to gain insight into the effects of primary aging on endothelial I/R injury. Young ( n = 9, 25 ± 1 yr) and middle-aged endurance-trained ( n = 9, 50 ± 2 yr) adults were also studied to determine whether habitual exercise provides protection from I/R injury. Fifteen minutes after ischemic injury, FMD decreased significantly by 37% in young sedentary, 35% in young endurance-trained, 68% in middle-aged sedentary, and 50% in middle-aged endurance-trained subjects. FMD returned to baseline levels within 30 min in young sedentary and endurance-trained subjects but remained depressed in middle-aged sedentary and endurance-trained subjects. Circulating markers of antioxidant capacity and inflammation were not related to FMD. In conclusion, advancing age is associated with a greater magnitude and delayed recovery from endothelial I/R injury in humans. Habitual endurance exercise may provide partial protection to the endothelium against this form of I/R injury with advancing age.
Isoform-selective 5′-AMP-activated protein kinase-dependent preconditioning mechanisms to prevent postischemic leukocyte-endothelial cell adhesive interactions
Authors: Spencer Gaskin F. , Kamada Kazuhiro , Zuidema Mozow (Yusof) , Jones Allan W. , Rubin Leona J. , Korthuis Ronald J.
Published: January 2011

We previously demonstrated that preconditioning induced by ethanol consumption at low levels [ethanol preconditioning (EPC)] or with 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR-PC) 24 h before ischemia-reperfusion prevents postischemic leukocyte-endothelial cell adhesive interactions (LEI) by a mechanism that is initiated by nitric oxide formed by endothelial nitric oxide synthase. Recent work indicates that 1) ethanol increases the activity of AMP-activated protein kinase (AMPK) and 2) AMPK phosphorylates endothelial nitric oxide synthase at the same activation site seen following EPC (Ser1177). In light of these observations, we postulated that the heterotrimeric serine/threonine kinase, AMPK, may play a role in triggering the development of the anti-inflammatory phenotype induced by EPC. Ethanol was administered to C57BL/6J mice by gavage in the presence or absence of AMPK inhibition. Twenty-four hours later, the numbers of rolling and adherent leukocytes in postcapillary venules of the small intestine were recorded using an intravital microscopic approach. Following 45 min of ischemia, LEI were recorded after 30 and 60 min of reperfusion or at equivalent time points in control animals. Ischemia-reperfusion induced a marked increase in LEI relative to sham-operated control mice. The increase in LEI was prevented by EPC, an effect that was lost with AMPK inhibition during the period of ethanol exposure. Studies conducted in AMPK α1- and α2-knockout mice suggest that the anti-inflammatory effects of AICAR are not dependent on which isoform of the catalytic α-subunit is present because a deficiency of either isoform results in a loss of protection. In sharp contrast, EPC appears to be triggered by an AMPK α2-isoform-dependent mechanism.
Mineralocorticoid receptor blockade improves diastolic function independent of blood pressure reduction in a transgenic model of RAAS overexpression
Authors: Habibi Javad , DeMarco Vincent G. , Ma Lixin , Pulakat Lakshmi , Rainey William E. , Whaley-Connell Adam T. , Sowers James R.
Published: January 2011

There is emerging evidence that aldosterone can promote diastolic dysfunction and cardiac fibrosis independent of blood pressure effects, perhaps through increased oxidative stress and inflammation. Accordingly, this investigation was designed to ascertain if mineralocorticoid receptor blockade improves diastolic dysfunction independently of changes in blood pressure through actions on myocardial oxidative stress and fibrosis. We used young transgenic (mRen2)27 [TG(mRen2)27] rats with increases in both tissue ANG II and circulating aldosterone, which manifests age-related increases in hypertension and cardiac dysfunction. Male TG(mRen2)27 and age-matched Sprague-Dawley rats were treated with either a low dose (∼1 mg·kg−1·day−1) or a vasodilatory, conventional dose (∼30 mg·kg−1·day−1) of spironolactone or placebo for 3 wk. TG(mRen2)27 rats displayed increases in systolic blood pressure and plasma aldosterone levels as well as impairments in left ventricular diastolic relaxation without changes in systolic function on cine MRI. TG(mRen2)27 hearts also displayed hypertrophy (left ventricular weight, cardiomyoctye hypertrophy, and septal wall thickness) as well as fibrosis (interstitial and perivascular). There were increases in oxidative stress in TG(mRen2)27 hearts, as evidenced by increases in NADPH oxidase activity and subunits as well as ROS formation. Low-dose spironolactone had no effect on systolic blood pressure but improved diastolic dysfunction comparable to a conventional dose. Both doses of spironolactone caused comparable reductions in ROS/3-nitrotryosine immunostaining and perivascular and interstitial fibrosis. These data support the notion mineralocorticoid receptor blockade improves diastolic dysfunction through improvements in oxidative stress and fibrosis independent of changes in systolic blood pressure.
Neuregulin-1β regulation of embryonic endothelial progenitor cell survival
Authors: Safa Radwan N. , Peng Xu-Yang , Pentassuglia Laura , Lim Chee Chew , Lamparter Mathias , Silverstein Cheri , Walker Jeremy , Chen Billy , Geisberg Carrie , Hatzopoulos Antonis K. , Sawyer Douglas B.
Published: January 2011

Endothelial progenitor cells (EPCs) are mobilized into the vascular space and home to damaged tissues, where they promote repair in part through a process of angiogenesis. Neuregulins (NRGs) are ligands in the epidermal growth factor family that signal through type I receptor tyrosine kinases in the erbB family (erbB2, erbB3, and erbB4) and regulate endothelial cell biology, promoting angiogenesis. Stimuli such as ischemia and exercise that promote EPC mobilization also induce cleavage and release of transmembrane NRG from cardiac microvascular endothelial cells (CMECs). We hypothesized that NRG/erbB signaling may regulate EPC biology. Using an embryonic (e)EPC cell line that homes to and repairs injured myocardium, we were able to detect erbB2 and erbB3 transcripts. Identical receptor expression was found in EPCs isolated from rat bone marrow and human whole blood. NRG treatment of eEPCs induces phosphorylation of kinases including Akt, GSK-3β, and Erk1/2 and the nuclear accumulation and transcriptional activation of β-catenin. NRG does not induce eEPC proliferation or migration but does protect eEPCs against serum deprivation-induced apoptosis. These results suggest a role for tissue-derived NRG in the regulation of EPC survival.
High-fat diet is associated with blunted splanchnic sympathoinhibitory responses to gastric leptin and cholecystokinin: implications for circulatory control
Authors: How Jackie M. Y. , Fam Barbara C. , Verberne Anthony J. M. , Sartor Daniela M.
Published: January 2011

Gastric leptin and cholecystokinin (CCK) act on vagal afferents to induce cardiovascular effects and reflex inhibition of splanchnic sympathetic nerve discharge (SSND) and may act cooperatively in these responses. We sought to determine whether these effects are altered in animals that developed obesity in response to a medium high-fat diet (MHFD). Male Sprague-Dawley rats were placed on a low-fat diet (LFD; n = 8) or a MHFD ( n = 24) for 13 wk, after which the animals were anesthetized and artificially ventilated. Arterial pressure was monitored and blood was collected for the determination of plasma leptin and CCK. SSND responses to leptin (15 μg/kg) and CCK (2 μg/kg) administered close to the coeliac artery were evaluated. Collectively, MHFD animals had significantly higher plasma leptin but lower plasma CCK levels than LFD rats ( P < 0.05), and this corresponded to attenuated or reversed SSND responses to CCK (LFD, −21 ± 2%; and MHFD, −12 ± 2%; P < 0.05) and leptin (LFD, −6 ± 2%; and MHFD, 4 ± 1%; P < 0.001). Alternatively, animals on the MHFD were stratified into obesity-prone (OP; n = 8) or obesity-resistant (OR; n = 8) groups according to their weight gain falling within the upper or lower tertile, respectively. OP rats had significantly higher resting arterial pressure, adiposity, and plasma leptin but lower plasma CCK compared with LFD rats ( P < 0.05). The SSND responses to CCK or leptin were not significantly different between OP and OR animals. These results demonstrate that a high-fat diet is associated with blunted splanchnic sympathoinhibitory responses to gastric leptin and CCK and may impact on sympathetic vasomotor mechanisms involved in circulatory control.