bluuebunny/crossref_metadata_2025 huggingface dataset:
Binaural technology for virtual reality
Authors: Lentz Tobias
Published: February 2009

The use of nonintrusive virtual environments is gaining more and more importance but was focused mainly on addressing the visual sense. However, the human perception consists not only of visual input and thus it would be worthwhile to create multimodal and interactive virtual environments. This thesis describes the techniques required to include the acoustic component into virtual environments and the implementation of a software system, which creates complex artificial acoustical scenes in real time. The system is based on the binaural technology. It features spatially distributed sound sources, which are utilized to create an environment that is as authentic as possible. This comprises a description of the source, including its relevant angle-, distance-, and time-dependent radiation, the sound distribution in the virtual scene, the perception-related consideration of all sound field components, and the exact reproduction at the ears of the user. In this context, an approach for dynamic crosstalk cancellation is presented, which enables a loudspeaker-based reproduction. The required filters are processed in real time on the basis of the position data and measured transfer functions of the outer ear. Furthermore the integration of this spatial audio system into a five-sided Virtual Reality display system is described and evaluated.
The Red Queen and the Court Jester: Species Diversity and the Role of Biotic and Abiotic Factors Through Time
Authors: Benton Michael J.
Published: February 2009

Evolution may be dominated by biotic factors, as in the Red Queen model, or abiotic factors, as in the Court Jester model, or a mixture of both. The two models appear to operate predominantly over different geographic and temporal scales: Competition, predation, and other biotic factors shape ecosystems locally and over short time spans, but extrinsic factors such as climate and oceanographic and tectonic events shape larger-scale patterns regionally and globally, and through thousands and millions of years. Paleobiological studies suggest that species diversity is driven largely by abiotic factors such as climate, landscape, or food supply, and comparative phylogenetic approaches offer new insights into clade dynamics.
Response to Comment on "Human-Specific Gain of Function in a Developmental Enhancer"
Authors: Prabhakar Shyam , Visel Axel , Akiyama Jennifer A. , Shoukry Malak , Lewis Keith D. , Holt Amy , Plajzer-Frick Ingrid , Morrison Harris , FitzPatrick David R. , Afzal Veena , Pennacchio Len A. , Rubin Edward M. , Noonan James P.
Published: February 2009

Duret and Galtier argue that human-specific sequence divergence and gain of function in the
HACNS1
enhancer result from deleterious biased gene conversion (BGC) with no contribution from positive selection. We reinforce our previous conclusion by analyzing hypothesized BGC events genomewide and assessing the effect of recombination rates on human-accelerated conserved noncoding sequence ascertainment. We also provide evidence that AT → GC substitution bias can coexist with positive selection.
Orc1 Controls Centriole and Centrosome Copy Number in Human Cells
Authors: Hemerly Adriana S. , Prasanth Supriya G. , Siddiqui Khalid , Stillman Bruce
Published: February 2009

Centrosomes, each containing a pair of centrioles, organize microtubules in animal cells, particularly during mitosis. DNA and centrosomes are normally duplicated once before cell division to maintain optimal genome integrity. We report a new role for the Orc1 protein, a subunit of the origin recognition complex (ORC) that is a key component of the DNA replication licensing machinery, in controlling centriole and centrosome copy number in human cells, independent of its role in DNA replication. Cyclin A promotes Orc1 localization to centrosomes where Orc1 prevents Cyclin E-dependent reduplication of both centrioles and centrosomes in a single cell division cycle. The data suggest that Orc1 is a regulator of centriole and centrosome reduplication as well as the initiation of DNA replication.
On the Metazoan Tree
Authors: Arthur Wallace
Published: February 2009

Perspectives in Animal Phylogeny and Evolution
.
By Alessandro Minelli
. Oxford University Press, Oxford, 2009. 360 pp. $150, £75. ISBN 9780198566205. Paper, $70, £34.95. ISBN 9780198566212. Oxford Biology.
Engineering a Synthetic Dual-Organism System for Hydrogen Production
Authors: Waks Zeev , Silver Pamela A.
Published: February 2009

Molecular hydrogen produced biologically from renewable biomass is an attractive replacement for fossil fuels. One potential route for biological hydrogen production is the conversion of biomass into formate, which can subsequently be processed into hydrogen by
Escherichia coli
. Formate is also a widely used commodity chemical, making its bioproduction even more attractive. Here we demonstrate the implementation of a formate-overproducing pathway in
Saccharomyces cerevisiae
, a well-established industrial organism. By expressing the anaerobic enzyme pyruvate formate lyase from
E. coli
, we engineered a strain of yeast that overproduced formate relative to undetectable levels in the wild type. The addition of a downstream enzyme, AdhE of
E. coli
, resulted in an additional 4.5-fold formate production increase as well as an increase in growth rate and biomass yield. Overall, an 18-fold formate increase was achieved in a strain background whose formate degradation pathway had been deleted. Finally, as a proof of concept, we were able to produce hydrogen from this formate-containing medium by using
E. coli
as a catalyst in a two-step process. With further optimizations, it may be feasible to use
S. cerevisiae
on a larger scale as the foundation for yeast-based biohydrogen.
Ecological Function of Myroilysin, a Novel Bacterial M12 Metalloprotease with Elastinolytic Activity and a Synergistic Role in Collagen Hydrolysis, in Biodegradation of Deep-Sea High-Molecular-Weight Organic Nitrogen
Authors: Chen Xiu-Lan , Xie Bin-Bin , Bian Fei , Zhao Guo-Yan , Zhao Hui-Lin , He Hai-Lun , Zhou Bai-Cheng , Zhang Yu-Zhong
Published: February 2009

Nearly all high-molecular-weight (HMW) dissolved organic nitrogen and part of the particulate organic nitrogen in the deep sea are present in hydrolysis-resistant amides, and so far the mechanisms of biodegradation of these types of nitrogen have not been resolved. The M12 family is the second largest family in subclan MA(M) of Zn-containing metalloproteases and includes most enzymes from animals and only one enzyme (flavastacin) from a human-pathogenic bacterium (
Flavobacterium meningosepticum
). Here, we characterized the novel M12 protease myroilysin with elastinolytic activity and collagen-swelling ability from the newly described deep-sea bacterium
Myroides profundi
D25. Myroilysin is a monomer enzyme with 205 amino acid residues and a molecular mass of 22,936 Da. It has the same conserved residues at the four zinc ligands as astacin and very low levels of identity (≤40%) to other metalloproteases, indicating that it is a novel metalloprotease belonging to subfamily M12A. Myroilysin had broad specificity and much higher elastinolytic activity than the bacterial elastinase pseudolysin. To our knowledge, it is the first reported elastase in the M12 family. Although it displayed very low activity with collagen, myroilysin had strong collagen-swelling ability and played a synergistic role with collagenase in collagen hydrolysis. It can be speculated that myroilysin synergistically interacts with other enzymes in its in situ biotic assemblage and that it may play an important role in the degradation of deep-sea HMW organic nitrogen.
Random Mutagenesis of the
Pm
Promoter as a Powerful Strategy for Improvement of Recombinant-Gene Expression
Authors: Bakke Ingrid , Berg Laila , Aune Trond Erik Vee , Brautaset Trygve , Sletta Håvard , Tøndervik Anne , Valla Svein
Published: February 2009

The inducible
Pm
-
xylS
promoter system has proven useful for production of recombinant proteins in several gram-negative species and in high-cell-density cultivations of
Escherichia coli
. In this study we subjected a 24-bp region of
Pm
(including the −10 element) to random mutagenesis, leading to large mutant libraries in
E. coli
. Low-frequency-occurring
Pm
mutants displaying strongly increased promoter activity (up-mutants) could be efficiently identified by using β-lactamase as a reporter. The up-mutants typically carried multiple point mutations positioned throughout the mutagenized region, combined with deletions around the transcription start site. Mutants displaying up to about a 14-fold increase in β-lactamase expression (relative to wild-type
Pm
) were identified without loss of the inducible phenotype. The mutants also strongly stimulated the expression of two other reporter genes,
luc
(encoding firefly luciferase) and
celB
(encoding phosphoglucomutase), and were found to significantly improve (twofold) a previously optimized process for high-level recombinant production of the medically important granulocyte-macrophage colony-stimulating factor in
E. coli
under high-cell-density conditions. These results demonstrate the potential of using random mutagenesis of promoters to improve protein expression at industrial levels and indicate that targeted modifications of individual functional elements are not sufficient to obtain optimized promoter sequences.
Effects of Biocides and Other Metal Removal Fluid Constituents on
Mycobacterium immunogenum
Authors: Falkinham Joseph O.
Published: February 2009

Cells of
Mycobacterium immunogenum
are significantly more resistant to biocides and antimicrobial compounds used for disinfection of metal removal fluids (MRFs) than cells of the gram-negative bacterium
Pseudomonas pseudoalcaligenes
. To ensure accurate measurement of
M. immunogenum
susceptibility, a biocide inactivation step must be included to prevent an overestimation of killing for short-term exposures. Cell suspensions in 5% MRF for 30 min rather than direct plating following biocide exposure increased the killing of
M. immunogenum
cells, suggesting a heretofore undiscovered interaction between MRF components and biocides. Biocide killing was reduced at high
M. immunogenum
cell densities (>10
6
/ml). Among the chemicals tested, only Synergex Premier, Preventol CMK, and dicyclohexylamine killed greater than 90% of
M. immunogenum
cells in 6 h.
M. immunogenum
cells adhered to and grew rapidly on glass, copper, and galvanized surfaces, forming biofilms of 10
6
cells/cm
2
within 2 weeks and suggesting it is likely that the majority of
M. immunogenum
cells in MRF systems are on surfaces.
M. immunogenum
cells grown on surfaces in biofilms were three- to 100-fold more resistant to the biocides Synergex Premier and Preventol CMK than cells grown in suspension, compounding the problem of eradication of
M. immunogenum
cells from MRF systems.
Enhanced Selenate Accumulation in
Cupriavidus metallidurans
CH34 Does Not Trigger a Detoxification Pathway
Authors: Avoscan Laure , Carrière Marie , Proux Olivier , Sarret Géraldine , Degrouard Jéril , Covès Jacques , Gouget Barbara
Published: February 2009

Cupriavidus metallidurans
CH34 cells grown under sulfate-limited conditions accumulated up to six times more selenate than cells grown in sulfate-rich medium. The products of selenate reduction detected by X-ray absorption spectroscopy, electron microscopy, and energy-dispersive X-ray analysis did not define this strain as being a good candidate for bioremediation of selenate-contaminated environments.
Antimicrobial Activity of the Iron-Sulfur Nitroso Compound Roussin's Black Salt [Fe4S3(NO)7] on the Hyperthermophilic ArchaeonPyrococcus furiosus
Authors: Hamilton-Brehm Scott D. , Schut Gerrit J. , Adams Michael W. W.
Published: February 2009

The iron-sulfur nitroso compound [Fe4S3(NO)7]−is a broad-spectrum antimicrobial agent that has been used for more than 100 years to combat pathogenic anaerobes. Known as Roussin's black salt (RBS), it contains seven moles of nitric oxide, the release of which was always assumed to mediate its cytotoxicity. Using the hyperthermophilic archaeonPyrococcus furiosus, it is demonstrated through growth studies, membrane analyses, and scanning electron microscopy that nitric oxide does not play a role in RBS toxicity; rather, the mechanism involves membrane disruption leading to cell lysis. Moreover, insoluble elemental sulfur (S0), which is reduced byP. furiosusto hydrogen sulfide, prevents cell lysis by RBS. It is proposed that S0also directly interacts with the membranes ofP. furiosusduring its transfer into the cell, ultimately for reduction by a cytosolic NADPH sulfur reductase. RBS is proposed to be a new class of inorganic antimicrobial agent that also has potential use as an inert cell-lysing agent.
Catalytic Improvement and Evolution of Atrazine Chlorohydrolase
Authors: Scott Colin , Jackson Colin J. , Coppin Chris W. , Mourant Roslyn G. , Hilton Margaret E. , Sutherland Tara D. , Russell Robyn J. , Oakeshott John G.
Published: February 2009

The atrazine chlorohydrolase AtzA has evolved within the past 50 years to catalyze the hydrolytic dechlorination of the herbicide atrazine. It is of wide research interest for two reasons: first, catalytic improvement of the enzyme would facilitate its application in bioremediation, and second, because of its recent evolution, it presents a rare opportunity to examine the early stages in the acquisition of new catalytic activities. Using a structural model of the AtzA-atrazine complex, a region of the substrate-binding pocket was targeted for combinatorial randomization. Identification of improved variants through this process informed the construction of a variant AtzA enzyme with 20-fold improvement in its
k
cat
/

K
m

value compared with that of the wild-type enzyme. The reduction in

K
m

observed in the AtzA variants has allowed the full kinetic profile for the AtzA-catalyzed dechlorination of atrazine to be determined for the first time, revealing the hitherto-unreported substrate cooperativity in AtzA. Since substrate cooperativity is common among deaminases, which are the closest structural homologs of AtzA, it is possible that this phenomenon is a remnant of the catalytic activity of the evolutionary progenitor of AtzA. A catalytic mechanism that suggests a plausible mechanistic route for the evolution of dechlorinase activity in AtzA from an ancestral deaminase is proposed.
Cell Wall Polysaccharide Synthases Are Located in Detergent-Resistant Membrane Microdomains in Oomycetes
Authors: Briolay Anne , Bouzenzana Jamel , Guichardant Michel , Deshayes Christian , Sindt Nicolas , Bessueille Laurence , Bulone Vincent
Published: February 2009

The pathways responsible for cell wall polysaccharide biosynthesis are vital in eukaryotic microorganisms. The corresponding synthases are potential targets of inhibitors such as fungicides. Despite their fundamental and economical importance, most polysaccharide synthases are not well characterized, and their molecular mechanisms are poorly understood. With the example ofSaprolegnia monoicaas a model organism, we show that chitin and (1→3)-β-d-glucan synthases are located in detergent-resistant membrane microdomains (DRMs) in oomycetes, a phylum that comprises some of the most devastating microorganisms in the agriculture and aquaculture industries. Interestingly, no cellulose synthase activity was detected in the DRMs. The purified DRMs exhibited similar biochemical features as lipid rafts from animal, plant, and yeast cells, although they contained some species-specific lipids. This report sheds light on the lipid environment of the (1→3)-β-d-glucan and chitin synthases, as well as on the sterol biosynthetic pathways in oomycetes. The results presented here are consistent with a function of lipid rafts in cell polarization and as platforms for sorting specific sets of proteins targeted to the plasma membrane, such as carbohydrate synthases. The involvement of DRMs in the biosynthesis of major cell wall polysaccharides in eukaryotic microorganisms suggests a function of lipid rafts in hyphal morphogenesis and tip growth.
Role and Regulation of Fatty Acid Biosynthesis in the Response ofShewanella piezotoleransWP3 to Different Temperatures and Pressures
Authors: Wang Feng , Xiao Xiang , Ou Hong-Yu , Gai Yingbao , Wang Fengping
Published: February 2009

Members of the genusShewanellainhabit various environments; they are capable of synthesizing various types of low-melting-point fatty acids, including monounsaturated fatty acids (MUFA) and branched-chain fatty acids (BCFA) with and without eicosapentanoic acid (EPA). The genes involved in fatty acid synthesis in 15 whole-genome-sequencedShewanellastrains were identified and compared. A typical type II fatty acid synthesis pathway inShewanellawas constructed. A complete EPA synthesis gene cluster was found in all of theShewanellagenomes, although only a few of them were found to produce EPA. The roles and regulation of fatty acids synthesis inShewanellawere further elucidated in theShewanella piezotoleransWP3 response to different temperatures and pressures. The EPA and BCFA contents of WP3 significantly increased when it was grown at low temperature and/or under high pressure. EPA, but not MUFA, was determined to be crucial for its growth at low temperature and high pressure. A gene cluster for a branched-chain amino acid ABC transporter (LIV-I) was found to be upregulated at low temperature. Combined approaches, including mutagenesis and an isotopic-tracer method, revealed that the LIV-I transporter played an important role in the regulation of BCFA synthesis in WP3. The LIV-I transporter was identified only in the cold-adaptedShewanellaspecies and was assumed to supply an important strategy forShewanellacold adaptation. This is the first time the molecular mechanism of BCFA regulation in bacteria has been elucidated.
Crystal Structure of Butyrate Kinase 2 from
Thermotoga maritima
, a Member of the ASKHA Superfamily of Phosphotransferases
Authors: Diao Jiasheng , Hasson Miriam S.
Published: February 2009

The enzymatic transfer of phosphoryl groups is central to the control of many cellular processes. One of the phosphoryl transfer mechanisms, that of acetate kinase, is not completely understood. Besides better understanding of the mechanism of acetate kinase, knowledge of the structure of butyrate kinase 2 (Buk2) will aid in the interpretation of active-site structure and provide information on the structural basis of substrate specificity. The gene
buk2
from
Thermotoga maritima
encodes a member of the ASKHA (acetate and sugar kinases/heat shock cognate/actin) superfamily of phosphotransferases. The encoded protein Buk2 catalyzes the phosphorylation of butyrate and isobutyrate. We have determined the 2.5-Å crystal structure of Buk2 complexed with (β,γ-methylene) adenosine 5′-triphosphate. Buk2 folds like an open-shelled clam, with each of the two domains representing one of the two shells. In the open active-site cleft between the N- and C-terminal domains, the active-site residues consist of two histidines, two arginines, and a cluster of hydrophobic residues. The ATP binding region of Buk2 in the C-terminal domain consists of abundant glycines for nucleotide binding, and the ATP binding motif is similar to those of other members of the ASKHA superfamily. The enzyme exists as an octamer, in which four disulfide bonds form between intermolecular cysteines. Sequence alignment and structure superposition identify the simplicity of the monomeric Buk2 structure, a probable substrate binding site, the key residues in catalyzing phosphoryl transfer, and the substrate specificity differences among Buk2, acetate, and propionate kinases. The possible enzyme mechanisms are discussed.
The Core Oligosaccharide and Thioredoxin of
Vibrio cholerae
Are Necessary for Binding and Propagation of Its Typing Phage VP3
Authors: Zhang Jingyun , Li Wei , Zhang Qian , Wang Hongxia , Xu Xiao , Diao Baowei , Zhang Lijuan , Kan Biao
Published: February 2009

VP3 is a T7-like phage and was used as one of the typing phages in a phage-biotyping scheme that has been used for the typing of
Vibrio cholerae
O1 biotype El Tor. Here, we studied the receptor and other host genes of
V. cholerae
necessary for the lytic propagation of VP3. Six mutants resistant to VP3 infection were obtained from the random transposon insertion mutant bank of the sensitive strain N16961. The genes VC0229 and VC0231, which belong to the
wav
gene cluster encoding the core oligosaccharide (OS) region of lipopolysaccharide, were found to be interrupted by the transposon in five mutants, and the sixth mutant had the transposon inserted between the genes
rhlB
and
trxA
, which encode the ATP-dependent RNA helicase RhlB and thioredoxin, respectively. Gene complementation, transcription analysis, and the loss of VP3 sensitivity by the gene deletion mutants confirmed the relationship between VP3 resistance and VC0229, VC0231, and
trxA
mutation. The product of VP3 gene 44 (gp44) was predicted to be a tail fiber protein. gp44 could bind to the sensitive wild-type strain and the
trxA
mutant, but not to VC0229 and VC0231 mutants. The results showed that OS is a VP3 receptor on the surface of N16961, thioredoxin of the host strain is involved in the propagation of the phage, and gp44 is the tail fiber protein of VP3. This revealed the first step in the infection mechanism of the T7-like phage VP3 in
V. cholerae
.
Identification of anrshGene from aNovosphingobiumsp. Necessary for Quorum-Sensing Signal Accumulation
Authors: Gan Han Ming , Buckley Larry , Szegedi Ernő , Hudson André O. , Savka Michael A.
Published: February 2009

The stringent response is a mechanism by which bacteria adapt to environmental stresses and nutritional deficiencies through the synthesis and hydrolysis of (p)ppGpp by RelA/SpoT enzymes. Alphaproteobacteria and plants contain a single Rsh enzyme (named forRelA/SpoThomolog) that is bifunctional. Here we report the identification of a new species of bacteria belonging to the genusNovosphingobiumand characterization of anrshmutation in this plant tumor-associated isolate. Isolate Rr 2-17, from a grapevine crown gall tumor, is a member of theNovosphingobiumgenus that produces theN-acyl-homoserine lactone (AHL) quorum-sensing (QS) signals. A Tn5mutant, Hx 699, deficient in AHL production was found to have an insertion in anrshgene. The Rsh protein showed significant percent sequence identity to Rsh proteins of alphaproteobacteria. TheNovosphingobiumsp.rshgene (rshNsp) complemented the multiple amino acid requirements of theEscherichia coli relA spoTdouble mutant by restoring the growth on selection media. Besides QS signal production, thershmutation also affects soluble polysaccharide production and cell aggregation. Genetic complementation of the Hx 699 mutant with thershNspgene restored these phenotypes. This is the first discovery of a functionalrshgene in a member of theNovosphingobiumgenus.
BldG and SCO3548 Interact Antagonistically To Control Key Developmental Processes inStreptomyces coelicolor
Authors: Parashar Archana , Colvin Kimberley R. , Bignell Dawn R. D. , Leskiw Brenda K.
Published: February 2009

The similarity of BldG and the downstream coexpressed protein SCO3548 to anti-anti-sigma and anti-sigma factors, respectively, together with the phenotype of abldGmutant, suggests that BldG and SCO3548 interact as part of a regulatory system to control both antibiotic production and morphological differentiation inStreptomyces coelicolor. A combination of bacterial two-hybrid, affinity purification, and far-Western analyses demonstrated that there was self-interaction of both BldG and SCO3548, as well as a direct interaction between the two proteins. Furthermore, a genetic complementation experiment demonstrated that SCO3548 antagonizes the function of BldG, similar to other anti-anti-sigma/anti-sigma factor pairs. It is therefore proposed that BldG and SCO3548 form a partner-switching pair that regulates the function of one or more sigma factors inS. coelicolor. The conservation ofbldGand sco3548 in other streptomycetes demonstrates that this system is likely a key regulatory switch controlling developmental processes throughout the genusStreptomyces.
A
Burkholderia cenocepacia
Orphan LuxR Homolog Is Involved in Quorum-Sensing Regulation
Authors: Malott Rebecca J. , O'Grady Eoin P. , Toller Jessica , Inhülsen Silja , Eberl Leo , Sokol Pamela A.
Published: February 2009

Burkholderia cenocepacia
utilizes quorum sensing to control gene expression, including the expression of genes involved in virulence. In addition to CepR and CciR, a third LuxR homolog, CepR2, was found to regulate gene expression and virulence factor production. All
B. cenocepacia
strains examined contained this orphan LuxR homolog, which was not associated with an adjacent
N
-acyl-homoserine lactone synthase gene. Expression of
cepR2
was negatively autoregulated and was negatively regulated by CciR in strain K56-2. Microarray analysis and quantitative reverse transcription-PCR determined that CepR2 did not influence expression of
cepIR
or
cciIR
. However, in strain K56-2, CepR2 negatively regulated expression of several known quorum-sensing-controlled genes, including genes encoding zinc metalloproteases. CepR2 exerted positive and negative regulation on genes on three chromosomes, including strong negative regulation of a gene cluster located adjacent to
cepR2
. In strain H111, which lacks the CciIR quorum-sensing system, CepR2 positively regulated pyochelin production by controlling transcription of one of the operons required for the biosynthesis of the siderophore in an
N
-acyl-homoserine lactone-independent manner. CepR2 activation of a
luxI
promoter was demonstrated in a heterologous
Escherichia coli
host, providing further evidence that CepR2 can function in the absence of signaling molecules. This study demonstrates that the orphan LuxR homolog CepR2 contributes to the quorum-sensing regulatory network in two distinct strains of
B. cenocepacia
.
Combinatorial Regulation by a Novel Arrangement of FruA and MrpC2 Transcription Factors during
Myxococcus xanthus
Development
Authors: Mittal Sheenu , Kroos Lee
Published: February 2009

Myxococcus xanthus
is a gram-negative soil bacterium that undergoes multicellular development upon nutrient limitation. Intercellular signals control cell movements and regulate gene expression during the developmental process. C-signal is a short-range signal essential for aggregation and sporulation. C-signaling regulates the
fmgA
gene by a novel mechanism involving cooperative binding of the response regulator FruA and the transcription factor/antitoxin MrpC2. Here, we demonstrate that regulation of the C-signal-dependent
fmgBC
operon is under similar combinatorial control by FruA and MrpC2, but the arrangement of binding sites is different than in the
fmgA
promoter region. MrpC2 was shown to bind to a crucial
cis
-regulatory sequence in the
fmgBC
promoter region. FruA was required for MrpC and/or MrpC2 to associate with the
fmgBC
promoter region in vivo, and expression of an
fmgB-lacZ
fusion was abolished in a
fruA
mutant. Recombinant FruA was shown to bind to an essential regulatory sequence located slightly downstream of the MrpC2-binding site in the
fmgBC
promoter region. Full-length FruA, but not its C-terminal DNA-binding domain, enhanced the formation of complexes with
fmgBC
promoter region DNA, when combined with MrpC2. This effect was nearly abolished with
fmgBC
DNA fragments having a mutation in either the MrpC2- or FruA-binding site, indicating that binding of both proteins to DNA is important for enhancement of complex formation. These results are similar to those observed for
fmgA
, where FruA and MrpC2 bind cooperatively upstream of the promoter, except that in the
fmgA
promoter region the FruA-binding site is located slightly upstream of the MrpC2-binding site. Cooperative binding of FruA and MrpC2 appears to be a conserved mechanism of gene regulation that allows a flexible arrangement of binding sites and coordinates multiple signaling pathways.
Are asthma-like symptoms in elite athletes associated with classical features of asthma?
Authors: Lund T K , Pedersen L , Anderson S D , Sverrild A , Backer V
Published: February 2009

Background:

Asthma is frequent in elite athletes and clinical studies in athletes have found increased airway inflammation.

Objective:

To investigate asthma-like symptoms, airway inflammation, airway reactivity (AR) to mannitol and use of asthma medication in Danish elite athletes.

Methods:

The study group consisted of 54 elite athletes (19 with doctor-diagnosed asthma), 22 non-athletes with doctor-diagnosed asthma (steroid naive for 4 weeks before the examination) and 35 non-athletes without asthma; all aged 18–35 years. Examinations (1 day): questionnaires, exhaled nitric oxide (eNO) in parts per billion, spirometry, skin prick test, AR to mannitol and blood samples. Induced sputum was done in subjects with asthma.

Results:

No significant difference was found in values for eNO, AR and atopy between 42 elite athletes with and 12 without asthma-like symptoms. Elite athletes with doctor-diagnosed asthma had less AR (response dose ratio 0.02 (0.004) vs 0.08 (0.018) p<0.01) and fewer sputum eosinophils (0.8% (0–4.8) vs 6.0% (0–18.5), p<0.01) than non-athletes with doctor-diagnosed asthma. Use of inhaled corticosteroids was similar in the two groups (not significant). In all, 42 elite athletes had asthma-like symptoms but only 12 had evidence of current asthma. Elite athletes without asthma had asthma-like symptoms more frequently than non-athletes without asthma (68.6% vs 25.7%, p<0.001).

Conclusion:

Asthma-like symptoms in elite athletes are not necessarily associated with classic features of asthma and alone should not give a diagnosis of asthma. More studies are needed to further investigate if and how the asthma phenotype of elite athletes differs from that of classical asthma.
Medical education on fitness to drive: a survey of all UK medical schools
Authors: Hawley C A , Galbraith N D , deSouza V A
Published: February 2009

Aim

To identify the extent to which medical aspects of fitness to drive (FTD) are taught within UK medical schools.

Methods

A survey of all 32 UK medical schools. In-depth interviews with a range of staff at two medical schools; telephone survey of 30 schools.

Results

Two thirds of schools reported specific teaching on medical aspects of FTD but few covered it in any depth or in relation to specific medical conditions. Only one school taught FTD in relation to elderly medicine. FTD was an examination topic at only 12 schools.

Conclusion

Teaching on FTD is inconsistent across UK medical schools. Many new doctors will graduate with limited knowledge of medical aspects of FTD.
From mountain to bedside: understanding the clinical relevance of human acclimatisation to high-altitude hypoxia
Authors: Martin D , Windsor J
Published: February 2009

For centuries man has strived to reach the greatest heights on earth. In order to explain the physiological changes that are needed to achieve this, physiologists have tended to focus on the improvements made in oxygen delivery to the body's tissues. Although this explains much of the acclimatisation process, it has not been able to address the large interindividual variations seen in human performance at altitude. In recent years, attention has shifted and now focuses on microvascular and cellular responses in an attempt to explain these differences. Investigating these processes not only helps to unravel the process of acclimatising to altitude, but it may also improve our understanding of the body's response to hypoxia in those with critical illness.
Attenuation of experimental hepatopulmonary syndrome in endothelin B receptor-deficient rats
Authors: Zhang Junlan , Ling Yiqun , Tang Liping , Luo Bao , Pollock David M. , Fallon Michael B.
Published: February 2009

Experimental hepatopulmonary syndrome (HPS) after common bile duct ligation (CBDL) in rat is accompanied by increased lung vascular endothelial endothelin B (ETB) receptor expression and increased circulating levels of endothelin-1 (ET-1). The onset of HPS is hypothesized to be triggered by ET-1/ETBreceptor activation of endothelial nitric oxide synthase (eNOS)-derived NO production in the pulmonary endothelium. However, whether functional pulmonary vascular ETBreceptors are required for the development of experimental HPS is not defined. We evaluated the effects of vascular ETBreceptor deficiency on the development of experimental HPS. The molecular and physiological alterations of HPS were compared in 2-wk CBDL wild-type and ETBreceptor-deficient (transgenic sl/sl) rats. Relative to wild-type rats, basal hepatic and plasma ET-1 levels were elevated in sl/sl controls although, unlike wild-type animals circulating ET-1 levels, did not increase further after CBDL in sl/sl animals. In contrast to wild-type animals, ETBreceptor-deficient rats did not develop increased Akt and eNOS expression and activation and did not develop gas exchange abnormalities of HPS after CBDL. There was a similar degree of pulmonary intravascular monocyte accumulation in both 2-wk CBDL sl/sl and wild-type animals. In conclusion, ETBreceptor deficiency inhibits lung Akt/eNOS activation and prevents the onset of experimental HPS after CBDL. This effect is independent of inhibition of pulmonary intravascular monocyte accumulation. These results demonstrate that ET-1/ETBreceptor signaling plays a key role in the initiation of experimental HPS.
Transient opening of mitochondrial permeability transition pore by reactive oxygen species protects myocardium from ischemia-reperfusion injury
Authors: Saotome Masao , Katoh Hideki , Yaguchi Yasuhiro , Tanaka Takamitsu , Urushida Tsuyoshi , Satoh Hiroshi , Hayashi Hideharu
Published: February 2009

Reactive oxygen species (ROS) production during ischemia-reperfusion (I/R) is thought to be a critical factor for myocardial injury. However, a small amount of ROS during the ischemic preconditioning (IPC) may provide a signal for cardioprotection. We have previously reported that the repetitive pretreatment of a small amount of ROS [hydrogen peroxide (H2O2), 2 μM] mimicked the IPC-induced cardioprotection in the Langendorff-perfused rat hearts. We further investigated the mechanisms of the ROS-induced cardioprotection against I/R injury and tested the hypothesis whether it could mediate the mitochondrial permeability transition pore (mPTP) opening. The Langendorff-perfused rat hearts were subjected to 35 min ischemia and 40 min reperfusion, and the pretreatment of H2O2(2 μM) significantly improved the postischemic recoveries in left ventricular developed pressure, intracellular phosphocreatine, and ATP levels. A specific mPTP inhibitor cyclosporin A (CsA; 0.2 μM) canceled these H2O2-induced effects. In isolated permeabilized myocytes, H2O2(1 μM) accelerated the calcein leakage from mitochondria in a CsA-sensitive manner, indicating the opening of mPTP by H2O2. However, H2O2did not depolarize mitochondrial membrane potential (ΔΨm) even in the presence of oligomycin (F1/F0ATPase inhibitor; 1 μM) and decreased mitochondrial Ca2+concentration ([Ca2+]m) by accelerating the mitochondrial Ca2+extrusion via an mPTP. We conclude that the transient mPTP opening could be involved in the H2O2-induced cardioprotection against reperfusion injury, and the reduction of [Ca2+]mwithout the change in ΔΨmmight be a possible mechanism for the protection.
Activation of NTS A2aadenosine receptors differentially resets baroreflex control of renal vs. adrenal sympathetic nerve activity
Authors: Ichinose Tomoko K. , O'Leary Donal S. , Scislo Tadeusz J.
Published: February 2009

The role of nucleus of solitary tract (NTS) A2aadenosine receptors in baroreflex mechanisms is controversial. Stimulation of these receptors releases glutamate within the NTS and elicits baroreflex-like decreases in mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA), whereas inhibition of these receptors attenuates HR baroreflex responses. In contrast, stimulation of NTS A2aadenosine receptors increases preganglionic adrenal sympathetic nerve activity (pre-ASNA), and the depressor and sympathoinhibitory responses are not markedly affected by sinoaortic denervation and blockade of NTS glutamatergic transmission. To elucidate the role of NTS A2aadenosine receptors in baroreflex function, we compared full baroreflex stimulus-response curves for HR, RSNA, and pre-ASNA (intravenous nitroprusside/phenylephrine) before and after bilateral NTS microinjections of selective adenosine A2areceptor agonist (CGS-21680; 2.0, 20 pmol/50 nl), selective A2areceptor antagonist (ZM-241385; 40 pmol/100 nl), and nonselective A1+ A2areceptor antagonist (8-SPT; 1 nmol/100 nl) in urethane/α-chloralose anesthetized rats. Activation of A2areceptors decreased the range, upper plateau, and gain of baroreflex-response curves for RSNA, whereas these parameters all increased for pre-ASNA, consistent with direct effects of the agonist on regional sympathetic activity. However, no resetting of baroreflex-response curves along the MAP axis occurred despite the marked decreases in baseline MAP. The antagonists had no marked effects on baseline variables or baroreflex-response functions. We conclude that the activation of NTS A2aadenosine receptors differentially alters baroreflex control of HR, RSNA, and pre-ASNA mostly via non-baroreflex mechanism(s), and these receptors have virtually no tonic action on baroreflex control of these sympathetic outputs.
Reversal of cardiac myocyte dysfunction as a unique mechanism of rescue by P2X4receptors in cardiomyopathy
Authors: Shen Jian-Bing , Shutt Robin , Agosto Mariela , Pappano Achilles , Liang Bruce T.
Published: February 2009

Binary cardiac transgenic (Tg) overexpression of P2X4receptors (P2X4R) improved the survival of the cardiomyopathic calsequestrin (CSQ) mice. Here we studied the mechanism of rescue using binary P2X4R/CSQ Tg and CSQ Tg mice as models. Cellular and intact heart properties were determined by simultaneous sarcomere shortening (SS) and Ca2+transients in vitro and echocardiography in vivo. Similar to a delay in death, binary mice exhibited a slowed heart failure progression with a greater left ventricular (LV) fractional shortening (FS) and thickness and a concomitant lesser degree of LV dilatation in both systole and diastole at 8 or 12 wk. By 16 wk, binary hearts showed similarly depressed FS and thinned out LV and equal enlargement of LV as did 12-wk-old CSQ hearts. Binary cardiac myocytes showed higher peak basal cell shortening (CS) and SS as well as greater basal rates of shortening and relaxation than did the CSQ myocytes at either 8 or 12 wk. Similar data were obtained in comparing the Ca2+transient. At 16 wk, binary myocytes were like the 12-wk-old CSQ myocytes with equally depressed CS, SS, and Ca2+transient. CSQ myocytes were longer than myocytes from wild-type and binary mice at 12 wk of age. At 16 wk, the binary myocyte length increased to that of the 12-wk-old CSQ myocyte, parallel to LV dilatation. The data suggest a unique mechanism, which involves a reversal of cardiac myocyte dysfunction and a delay in heart failure progression. It represents an example of targeting the abnormal failing myocyte in treating heart failure.
Protective effect of beraprost sodium, a stable prostacyclin analog, in the development of cigarette smoke extract-induced emphysema
Authors: Chen Yan , Hanaoka Masayuki , Chen Ping , Droma Yunden , Voelkel Norbert F. , Kubo Keishi
Published: February 2009

Chronic inflammation, imbalance of proteolytic and anti-proteolytic activities, oxidative stress, and apoptosis of lung structural cells contribute to the pathogenesis of COPD. Prostacyclin protects cells against apoptosis, has anti-inflammatory properties, partially prevents cigarette smoke extract (CSE)-induced apoptosis of the pulmonary endothelium, and thus may be relevant in the pathogenesis of emphysema. We determined whether a synthetic stable prostacyclin analog, beraprost sodium (BPS), attenuates the development of CSE-induced emphysema and elucidated the molecular mechanisms involved in its effect. Sprague-Dawley rats were treated with BPS and injected with CSE once a week for 3 wk. We measured the DNA damage of cells, the expression of caspase-3, and the activity of matrix metalloproteinase (MMP)-2 and MMP-9. We also analyzed TNFα and IL-1β concentrations and the serum antioxidant activity. BPS prevented the development of CSE-induced emphysema, resulting in significant attenuation in alveolar enlargement and pulmonary parenchymal destruction. BPS inhibited pulmonary apoptosis and induction of MMP-2 and MMP-9 activity. Moreover, the protective effect of BPS was associated with a reduction of the expression of proinflammatory cytokines including TNFα and IL-1β and a normalized biological oxidant activity. BPS introduces all these events, probably by activating cAMP signaling through acting specific prostacyclin receptors. In conclusion, BPS protects against the development of CSE-induced emphysema by attenuating apoptosis, inhibiting proteolytic enzyme activity, reducing inflammatory cytokine levels, and augmenting antioxidant activity. BPS may potentially represent a new therapeutic option in the prevention of emphysema in humans in prospect.
Ozone modulates IL-6 secretion in human airway epithelial and smooth muscle cells
Authors: Damera Gautam , Zhao Hengjiang , Wang Miao , Smith Michael , Kirby Christopher , Jester William F. , Lawson John A. , Panettieri Reynold A.
Published: February 2009

Although ozone enhances leukocyte function and recruitment in airways, the direct effect of ozone in modulating structural cell-derived inflammatory mediators remains unknown. Using a coculture model comprised of differentiated human airway epithelial cells (NHBE) and smooth muscle cells (ASM), we postulate that ozone regulates IL-6 secretion in basal and cytokine-primed structural cells. Air-liquid interface (ALI) cultures of NHBE cells underwent differentiation as determined by mucin secretion, transepithelial electrical resistance (TEER), and ultrastructure parameters. Whereas TNF enhanced basal secretion of IL-6 (57 ± 3%), ozone exposure at 0.6 ppm for 6 h augmented IL-6 levels in basal (41 ± 3%) and TNF- (50 ± 5%) primed cocultures compared with that derived from NHBE or ASM monolayers alone. Levels of PGE2, 6-keto-PGF1α, PGF2α, and thromboxane B2(TxB2) levels in basal and TNF-primed cocultures revealed that ozone selectively enhanced PGE2production in TNF- (6 ± 3-fold) primed cocultures, with little effect ( P > 0.05) on diluent-treated cultures. In accordance with ozone-induced increases in PGE2levels, cyclooxygenase inhibition with indomethacin partially abolished IL-6 secretion. Surprisingly, indomethacin had little effect on constitutive secretion of IL-6 in cocultures, whereas indomethacin completely restored ozone-mediated TEER reduction in TNF-primed cocultures. Collectively, our data for the first time suggest a dual role of ozone in modulating IL-6 secretion and TEER outcomes in a PGE2-dependent (in presence of TNF stimulus) and -independent manner (in absence of cytokine stimulus).
Systematic analysis of adaptations in aerobic capacity and submaximal energy metabolism provides a unique insight into determinants of human aerobic performance
Authors: Vollaard Niels B. J. , Constantin-Teodosiu Dimitru , Fredriksson Katarina , Rooyackers Olav , Jansson Eva , Greenhaff Paul L. , Timmons James A. , Sundberg Carl Johan
Published: February 2009

It has not been established which physiological processes contribute to endurance training-related changes (Δ) in aerobic performance. For example, the relationship between intramuscular metabolic responses at the intensity used during training and improved human functional capacity has not been examined in a longitudinal study. In the present study we hypothesized that improvements in aerobic capacity (V̇o2max) and metabolic control would combine equally to explain enhanced aerobic performance. Twenty-four sedentary males (24 ± 2 yr; 1.81 ± 0.08 m; 76.6 ± 11.3 kg) undertook supervised cycling training (45 min at 70% of pretraining V̇o2max) 4 times/wk for 6 wk. Performance was determined using a 15-min cycling time trial, and muscle biopsies were taken before and after a 10-min cycle at 70% of pretraining V̇o2maxto quantify substrate metabolism. Substantial interindividual variability in training-induced adaptations was observed for most parameters, yet “low responders” for ΔV̇o2maxwere not consistently low responders for other variables. While V̇o2maxand time trial performance were related at baseline ( r2= 0.80, P < 0.001), the change in V̇o2maxwas completely unrelated to the change in aerobic performance. The maximal parameters ΔV̇emaxand ΔVeqmax(ΔV̇e/V̇o2max) accounted for 64% of the variance in ΔV̇o2max( P < 0.001), whereas Δperformance was related to changes in the submaximal parameters Veqsubmax( r2= 0.33; P < 0.01), muscle Δlactate ( r2= 0.32; P < 0.01), and Δacetyl-carnitine ( r2= 0.29; P < 0.05). This study demonstrates that improvements in high-intensity aerobic performance in humans are not related to altered maximal oxygen transport capacity. Altered muscle metabolism may provide the link between training stimulus and improved performance, but metabolic parameters do not change in a manner that relates to aerobic capacity changes.
Intrauterine Programmierung reproduktiver Funktionen – ein tragfähiges Konzept?
Authors: Schleussner Ekkehard
Published: February 2009

Eine frühe intrauterine fetale (Fehl-)Programmierung hat nicht nur Auswirkungen auf die kardiovaskuläre und metabolische Regulation im späteren Leben, auch die reproduktive Funktion kann dadurch beeinflusst werden. Eine intrauterine Wachstumsretardierung kann mit einer vorzeitigen Reifung der gonadalen Funktion und einer Vorverlegung der Pubertät und des Menarchealters verbunden sein. Sowohl die Entwicklung von Ovarien und äusseren Genitalien selbst als auch die neurodendokrine Regulation der hypothalamisch-hypophysär-ovariellen Achse werden insbesondere durch pränatale Androgeneffekte ungünstig beeinflusst, sodass im späteren Leben häufiger ein polyzystisches Ovarsyndrom mit Hyperandrogenämie und Ovulationsstörungen auftritt. Diese tierexperimentell klar nachweisbaren Zusammenhänge bedürfen jedoch noch weiterer Belege durch epidemiologische und klinische Untersuchungen am Menschen.
Brusterhaltende Therapie des Mammakarzinoms nach Augmentation mit injiziertem hydrophilem Polyacrylamidgel und Literaturübersicht
Authors: Abdallah Abdallah , Wesemann Alena , Saklaoui Omar , Stückle Christoph , Sommerer Florian , Zink Matthias , Papadopoulos Sarantos
Published: February 2009

Wir berichten über den Fall einer 33-jährigen Patientin mit invasiv duktalem Mammakarzinom. Bei Zustand nach Brustaugmentation mit injiziertem hydrophilem Polyacrylamidgel wurde erfolgreich brusterhaltend therapiert. Ausgeprägte Migration der Gelkonglomerate erschwerte zunächst die Bildgebung in der Karzinomdiagnostik sowie die anschliessende operative Therapie und Tumornachsorge. Nach aufwendiger Entfernung des Gels konnte brusterhaltend operiert werden, die Wundheilung verlief regelrecht und komplikationslos. Nach adjuvanter Hormon-, Chemo- und Radiotherapie ist die Patientin seitdem tumorfrei bei zufriedenstellendem kosmetischem Ergebnis.