bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Hearing Loss Using 2f2-f1 and 2f1-f2 Distortion-Product Otoacoustic Emissions
Authors: Fitzgerald Tracy S. , Prieve Beth A.
Published: April 2006

Although many distortion-product otoacoustic emissions (DPOAEs) may be measured in the ear canal in response to 2 pure tone stimuli, the majority of clinical studies have focused exclusively on the DPOAE at the frequency 2f1-f2. This study investigated another DPOAE, 2f2-f1, in an attempt to determine the following: (a) the optimal stimulus parameters for its clinical measurement and (b) its utility in differentiating between normal-hearing and hearing-impaired ears at low-to-mid frequencies (≤2000 Hz) when measured either alone or in conjunction with the 2f1-f2 DPOAE. Two experiments were conducted. In Experiment 1, the effects of primary level, level separation, and frequency separation (f2/f1) on 2f2-f1 DPOAE level were evaluated in normal-hearing ears for low-to-mid f2 frequencies (700–2000 Hz). Moderately high-level primaries (60–70 dB SPL) presented at equal levels or with f2 slightly higher than f1 produced the highest 2f2-f1 DPOAE levels. When the f2/f1 ratio that produced the highest 2f2-f1 DPOAE levels was examined across participants, the mean optimal f2/f1 ratio across f2 frequencies and primary level separations was 1.08. In Experiment 2, the accuracy with which DPOAE level or signal-to-noise ratio identified hearing status at the f2 frequency as normal or impaired was evaluated using clinical decision analysis. The 2f2-f1 and 2f1-f2 DPOAEs were measured from both normal-hearing and hearing-impaired ears using 2 sets of stimulus parameters: (a) the traditional parameters for measuring the 2f1-f2 DPOAE (f2/f1 = 1.22; L1, L2 = 65, 55 dB SPL) and (b) the new parameters that were deemed optimal for the 2f2-f1 DPOAE in Experiment 1 (f2/f1 = 1.073, L1 and L2 = 65 dB SPL). Identification of hearing status using 2f2-f1 DPOAE level and signal-to-noise ratio was more accurate when the new stimulus parameters were used compared with the results achieved when the 2f2-f1 DPOAE was recorded using the traditional parameters. However, identification of hearing status was less accurate for the 2f2-f1 DPOAE measured using the new parameters than for the 2f1-f2 DPOAE measured using the traditional parameters. No statistically significant improvements in test performance were achieved when the information from the 2 DPOAEs was combined, either by summing the DPOAE levels or by using logistic regression analysis.
Velopharyngeal Port Status During Classical Singing
Authors: Tanner Kristine , Roy Nelson , Merrill Ray M. , Power David
Published: April 2006

Purpose:
This investigation was undertaken to examine the status of the velopharyngeal (VP) port during classical singing.

Method:
Using aeromechanical instrumentation, nasal airflow (mL/s), oral pressure (cm H
2
O), and VP orifice area estimates (cm
2
) were studied in 10 classically trained sopranos during singing and speaking. Each participant sang and spoke 3 nonsense words—/hampa/, /himpi/, and /humpu/—at 3 loudness levels (loud vs. comfortable vs. soft) and 3 pitches (high vs. comfortable vs. low), using a within-subject experimental design including all possible combinations.

Results:
In general, nasal airflow, oral pressure, and VP area estimates were significantly greater for singing as compared to speech, and nasal airflow was observed during non-nasal sounds in all participants. Anticipatory nasal airflow was observed in 9 of 10 participants for singing and speaking and was significantly greater during the first vowel in /hampa/ versus /himpi/ and /humpu/. The effect of vowel height on nasal airflow was also significantly influenced by loudness and pitch.

Conclusions:
The results from this investigation indicate that at least some trained singers experience regular VP opening during classical singing. Vowel height seems to influence this effect. Future research should consider the effects of voice type, gender, experience level, performance ability, and singing style on VP valving in singers.
Looking While Listening and Speaking
Authors: Turkstra Lyn S.
Published: April 2006

Purpose:The purpose of this study was to address the lack of quantitative data on eye-to-face gaze (also known as eye contact) in the literature on pragmatic communication. The study focused on adolescents and young adults with traumatic brain injury (TBI), as gaze often is included in social skills intervention in this population.

Method:Gaze times were calculated for participants with TBI (n= 16) and their typically developing (TD) peers (n= 16) engaged in 3-min extemporaneous conversations.

Results:The TD group members looked at the face of their conversation partner an average of 62% of the time while listening and 43% of the time while speaking, versus 67% and 51%, respectively, for the TBI group. There were no significant between-groups differences in average gaze times, but the within-group variability was significantly greater in the TBI group.

Implications:As there was no evidence of a uniform trend in gaze times among participants with TBI, general intervention to increase eye contact does not appear warranted. Instead, goals must consider that gaze is a highly complex behavior, not necessarily indicative of attention to one's partner, and that there are potential reasons for gaze aversion in individuals with cognitive limitations.
The Processing of Morphology in Old Age
Authors: Kavé Gitit , Levy Yonata
Published: April 2006

Purpose:Taking advantage of the rich morphological structure of Hebrew, the current article aims to examine whether age affects the processing of morphological forms through an investigation of 2 systematic morphological paradigms.

Method:Forty-eight young and 48 old Hebrew speakers completed 2 experiments: the 1st investigated sensitivity to subject-verb gender incongruity in a reading task, and the 2nd examined parsing of pseudoverbs containing existing and nonexisting consonantal roots in a lexical-decision task.

Results:Older adults were slower relative to the young, but both groups were slower on incongruent relative to congruent targets and on a pseudoverb with a real root relative to a pseudoverb with a nonexistent root. In both experiments the interaction between condition and age was statistically significant.

Conclusions:While older adults demonstrate preserved morphological parsing abilities, possible explanations for the interaction effect include cognitive slowing or deficient inhibitory control.
Free energy of a trans-membrane pore calculated from atomistic molecular dynamics simulations
Authors: Wohlert J. , den Otter W. K. , Edholm O. , Briels W. J.
Published: April 2006

Atomistic molecular dynamics simulations of a lipid bilayer were performed to calculate the free energy of a trans-membrane pore as a function of its radius. The free energy was calculated as a function of a reaction coordinate using a potential of mean constraint force. The pore radius was then calculated from the reaction coordinate using Monte Carlo particle insertions. The main characteristics of the free energy that comes out of the simulations are a quadratic shape for a radius less than about 0.3nm, a linear shape for larger radii than this, and a rather abrupt change without local minima or maxima between the two regions. In the outer region, a line tension can be calculated, which is consistent with the experimentally measured values. Further, this line tension can be rationalized and understood in terms of the energetic cost for deforming a part of the lipid bilayer into a hydrophilic pore. The region with small radii can be described and understood in terms of statistical mechanics of density fluctuations. In the region of crossover between a quadratic and linear free energy there was some hysteresis associated with filling and evacuation of the pore with water. The metastable prepore state hypothesized to interpret the experiments was not observed in this region.
Multigraining: An algorithm for simultaneous fine-grained and coarse-grained simulation of molecular systems
Authors: Christen Markus , van Gunsteren Wilfred F.
Published: April 2006

A method to combine fine-grained and coarse-grained simulations is presented. The coarse-grained particles are described as virtual particles defined by the underlying fine-grained particles are described as virtual particles defined by the underlying fine-grained particles. The contribution of the two grain levels to the interaction between particles is specified by a grain-level parameter λ. Setting λ=0 results in a completely fine-grained simulation, whereas λ=1 yields a simulation governed by the coarse-grained potential energy surface with small contributions to keep the fine-grained covalently bound particles together. Simulations at different λ values may be coupled using the replica-exchange molecular dynamics method to achieve enhanced sampling at the fine-grained level.
Special stability of cationic MPb12+ clusters and superalkali character of neutral MPb12 clusters (M=B, Al, Ga, In, and Tl)
Authors: Chen De-Li , Tian Wei Quan , Lu Wen-Cai , Sun Chia-Chung
Published: April 2006

The electronic structures and stabilities of cationic MPb12+ clusters (M=B, Al, Ga, In, and Tl) with 50 valence electrons are investigated within density functional theory. It is shown that, at the B3LYP/cc-pVDZ(-PP) and BPW91/cc-pVDZ(-PP) levels of theory, the structures of MPb12+ with icosahedra (Ih) symmetry are energetically favorable, and their high stabilities may arise from the closed-shell nature of the π subsystems which are subject to the 2(Nπ+1)2 rule with Nπ=1. In addition, the possessing of large nucleus-independent chemical shifts of the five kinds of clusters reflects the common aromatic character of these clusters. From the comparison of our studies on the binding energies and the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy gaps, the cluster AlPb12+ has higher stability than the others and this is consistent with the recent mass-spectrometric discovery of Al-doped Pbn+ clusters, in which AlPb12+ is highly abundant. The same methods are used to search for the structures of the neutral MPb12 clusters. The calculations reveal that the most stable geometries of the BPb12 and GaPb12 clusters have Ih symmetry, the AlPb12 and InPb12 clusters have Th symmetry, and the TlPb12 cluster has C5v symmetry. Furthermore, the vertical ionization potentials of the neutral MPb12 clusters are smaller than that of some alkali atoms, indicating that the neutral MPb12 clusters possess superalkali character.
Quantitative analysis of the sensitivity of porous silicon optical biosensors
Authors: Ouyang Huimin , Striemer Christopher C. , Fauchet Philippe M.
Published: April 2006

The optical response of porous silicon affinity biosensors depends strongly on their nanomorphology because the sensing species does not completely fill the pores but is instead attached to the pore walls. The performance and sensitivity of porous silicon microcavity biosensors are calculated as a function of pore size using a simplified effective medium approximation. Excellent agreement is obtained between the model predictions and the experimental results after binding of aminopropyltriethoxysilane and glutaraldehyde in mesoporous and macroporous silicon microcavities. Detection of layers thinner than 0.01nm should be possible.
Imaging transport for the determination of minority carrier diffusion length
Authors: Luber D. R. , Bradley F. M. , Haegel N. M. , Talmadge M. C. , Coleman M. P. , Boone T. D.
Published: April 2006

A scanning electron microscope technique is used, in combination with an optical imaging system, to measure minority carrier diffusion length in a heavily doped GaAs double heterostructure. Diffusion and drift of charge are imaged. A diffusion length of 3.6μm is measured, corresponding to a minority carrier mobility of 1150cm2∕Vs in p-type material doped ∼5×1018cm−3. Measurements are made as a function of local electric field and sample temperature. The technique offers a flexible approach to direct measurement of transport properties and is applicable to a range of luminescent materials and multilayer devices.
InP-based two-dimensional photonic crystals filled with polymers
Authors: van der Heijden R. , Carlström C. F. , Snijders J. A. P. , van der Heijden R. W. , Karouta F. , Nötzel R. , Salemink H. W. M. , Kjellander B. K. C. , Bastiaansen C. W. M. , Broer D. J. , van der Drift E.
Published: April 2006

Polymer filling of the air holes of indium-phosphide-based two-dimensional photonic crystals is reported. After infiltration of the holes with a liquid monomer and solidification of the infill in situ by thermal polymerization, complete filling is proven using scanning electron microscopy. Optical transmission measurements of a filled photonic crystal structure exhibit a redshift of the air band, confirming the complete filling.
Designing a nano-interface in a microfluidic chip to probe living cells: Challenges and perspectives
Authors: Helmke Brian P. , Minerick Adrienne R.
Published: April 2006

Nanotechnology-based materials are beginning to emerge as promising platforms for biomedical analysis, but measurement and control at the cell–chip interface remain challenging. This idea served as the basis for discussion in a focus group at the recent National Academies Keck
Futures Initiative
. In this Perspective, we first outline recent advances and limitations in measuring nanoscale mechanical, biochemical, and electrical interactions at the interface between biomaterials and living cells. Second, we present emerging experimental and conceptual platforms for probing living cells with nanotechnology-based tools in a microfluidic chip. Finally, we explore future directions and critical needs for engineering the cell–chip interface to create an integrated system capable of high-resolution analysis and control of cellular physiology.
Quantitative genetics of age at reproduction in wild swans: Support for antagonistic pleiotropy models of senescence
Authors: Charmantier Anne , Perrins Christopher , McCleery Robin H. , Sheldon Ben C.
Published: April 2006

Why do individuals stop reproducing after a certain age, and how is this age determined? The antagonistic pleiotropy theory for the evolution of senescence predicts that increased early-life performance should be accompanied by earlier (or faster) senescence. Hence, an individual that has started to breed early should also lose its reproductive capacities early. We investigate here the relationship between age at first reproduction (AFR) and age at last reproduction (ALR) in a free-ranging mute swan (Cygnus olor) population monitored for 36 years. Using multivariate analyses on the longitudinal data, we show that both traits are strongly selected in opposite directions. Analysis of the phenotypic covariance between these characters shows that individuals vary in their inherent quality, such that some individuals have earlier AFR and later ALR than expected. Quantitative genetic pedigree analyses show that both traits possess additive genetic variance but also that AFR and ALR are positively genetically correlated. Hence, although both traits display heritable variation and are under opposing directional selection, their evolution is constrained by a strong evolutionary tradeoff. These results are consistent with the theory that increased early-life performance comes with faster senescence because of genetic tradeoffs.
The decline of cross-species intersensory perception in human infants
Authors: Lewkowicz David J. , Ghazanfar Asif A.
Published: April 2006

Between 6 and 10 months of age, infants become better at discriminating among native voices and human faces and worse at discriminating among nonnative voices and other species’ faces. We tested whether these unisensory perceptual narrowing effects reflect a general ontogenetic feature of perceptual systems by testing across sensory modalities. We showed pairs of monkey faces producing two different vocalizations to 4-, 6-, 8-, and 10-month-old infants and asked whether they would prefer to look at the corresponding face when they heard one of the two vocalizations. Only the two youngest groups exhibited intersensory matching, indicating that perceptual narrowing is pan-sensory and a fundamental feature of perceptual development.
Synaptotagmin IV is necessary for the maturation of secretory granules in PC12 cells
Authors: Ahras Malika , Otto Grant P. , Tooze Sharon A.
Published: April 2006

In neuroendocrine PC12 cells, immature secretory granules (ISGs) mature through homotypic fusion and membrane remodeling. We present evidence that the ISG-localized synaptotagmin IV (Syt IV) is involved in ISG maturation. Using an in vitro homotypic fusion assay, we show that the cytoplasmic domain (CD) of Syt IV, but not of Syt I, VII, or IX, inhibits ISG homotypic fusion. Moreover, Syt IV CD binds specifically to ISGs and not to mature secretory granules (MSGs), and Syt IV binds to syntaxin 6, a SNARE protein that is involved in ISG maturation. ISG homotypic fusion was inhibited in vivo by small interfering RNA–mediated depletion of Syt IV. Furthermore, the Syt IV CD, as well as Syt IV depletion, reduces secretogranin II (SgII) processing by prohormone convertase 2 (PC2). PC2 is found mostly in the proform, suggesting that activation of PC2 is also inhibited. Granule formation, and the sorting of SgII and PC2 from the trans-Golgi network into ISGs and MSGs, however, is not affected. We conclude that Syt IV is an essential component for secretory granule maturation.
Spatial organization of the mammalian genome surveillance machinery in response to DNA strand breaks
Authors: Bekker-Jensen Simon , Lukas Claudia , Kitagawa Risa , Melander Fredrik , Kastan Michael B. , Bartek Jiri , Lukas Jiri
Published: April 2006

We show that DNA double-strand breaks (DSBs) induce complex subcompartmentalization of genome surveillance regulators. Chromatin marked by γ-H2AX is occupied by ataxia telangiectasia–mutated (ATM) kinase, Mdc1, and 53BP1. In contrast, repair factors (Rad51, Rad52, BRCA2, and FANCD2), ATM and Rad-3–related (ATR) cascade (ATR, ATR interacting protein, and replication protein A), and the DNA clamp (Rad17 and -9) accumulate in subchromatin microcompartments delineated by single-stranded DNA (ssDNA). BRCA1 and the Mre11–Rad50–Nbs1 complex interact with both of these compartments. Importantly, some core DSB regulators do not form cytologically discernible foci. These are further subclassified to proteins that connect DSBs with the rest of the nucleus (Chk1 and -2), that assemble at unprocessed DSBs (DNA-PK/Ku70), and that exist on chromatin as preassembled complexes but become locally modified after DNA damage (Smc1/Smc3). Finally, checkpoint effectors such as p53 and Cdc25A do not accumulate at DSBs at all. We propose that subclassification of DSB regulators according to their residence sites provides a useful framework for understanding their involvement in diverse processes of genome surveillance.
Direct in vivo monitoring of sarcoplasmic reticulum Ca2+ and cytosolic cAMP dynamics in mouse skeletal muscle
Authors: Rudolf Rüdiger , Magalhães Paulo J. , Pozzan Tullio
Published: April 2006

Skeletal muscle contraction depends on the release of Ca2+ from the sarcoplasmic reticulum (SR), but the dynamics of the SR free Ca2+ concentration ([Ca2+]SR), its modulation by physiological stimuli such as catecholamines, and the concomitant changes in cAMP handling have never been directly determined. We used two-photon microscopy imaging of GFP-based probes expressed in mouse skeletal muscles to monitor, for the first time in a live animal, the dynamics of [Ca2+]SR and cAMP. Our data, which were obtained in highly physiological conditions, suggest that free [Ca2+]SR decreases by ∼50 μM during single twitches elicited through nerve stimulation. We also demonstrate that cAMP levels rise upon β-adrenergic stimulation, leading to an increased efficacy of the Ca2+ release/reuptake cycle during motor nerve stimulation.
A Norovirus Outbreak at a Long-Term-Care Facility: The Role of Environmental Surface Contamination
Authors: Wu Henry M. , Fornek Mary , Schwab Kellogg J. , Chapin Amy R. , Gibson Kristen , Schwab Edna , Spencer Charles , Henning Kelly
Published: April 2006

Background:

The role of environmental surface contamination in the propagation of norovirus outbreaks is unclear. An outbreak of acute gastroenteritis was reported among residents of a 240-bed veterans long-term-care facility.

Objectives:

To identify the likely mode of transmission, to characterize risk factors for illness, and to evaluate for environmental contamination in this norovirus outbreak.

Methods:

An outbreak investigation was conducted to identify risk factors for illness among residents and employees. Stool and vomitus samples were tested for norovirus by reverse transcription polymerase chain reaction (RT-PCR). Fourteen days after outbreak detection, ongoing cases among the residents prompted environmental surface testing for norovirus by RT-PCR.

Results:

One hundred twenty-seven (52%) of 246 residents and 84 (46%) of 181 surveyed employees had gastroenteritis. Case-residents did not differ from non-case-residents by comorbidities, diet, room type, or level of mobility. Index cases were among the nursing staff. Eight of 11 resident stool or vomitus samples tested positive for genogroup II norovirus. The all-cause mortality rate during the month of the outbreak peak was significantly higher than the expected rate. Environmental surface swabs from case-resident rooms, a dining room table, and an elevator button used only by employees were positive for norovirus. Environmental and clinical norovirus sequences were identical.

Conclusion:

Extensive contamination of environmental surfaces may play a role in prolonged norovirus outbreaks and should be addressed in control interventions.
Chimeras of the ABC drug transporter Cdr1p reveal functional indispensability of transmembrane domains and nucleotide-binding domains, but transmembrane segment 12 is replaceable with the corresponding homologous region of the non-drug transporter Cdr3p
Authors: Saini Preeti , Gaur Naseem Akhtar , Prasad Rajendra
Published: April 2006

The molecular basis of the broad substrate recognition and the transport of substrates by Cdr1p, a major drug efflux protein of Candida albicans, is not well understood. To investigate the role of transmembrane domains and nucleotide-binding domains (NBDs) of Cdr1p in drug transport, two sets of protein chimeras were constructed: one set between homologous regions of Cdr1p and the non-drug transporter Cdr3p, and another set consisting of Cdr1p variants comprising either two N- or two C-terminal NBDs of Cdr1p. The replacement of either the N- or the C-terminal half of Cdr1p by the homologous segments of Cdr3p resulted in non-functional recombinant strains expressing chimeric proteins. The results suggest that the chimeric protein could not reach the plasma membrane, probably because of misfolding and subsequent cellular trafficking problems, or the rapid degradation of the chimeras. As an exception, the replacement of transmembrane segment 12 (TMS12) of Cdr1p by the corresponding region of Cdr3p resulted in a functional chimera which displayed unaltered affinity for all the tested substrates. The variant protein comprising either two N-terminal or two C-terminal NBDs of Cdr1p also resulted in non-functional recombinant strains. However, the N-terminal NBD variant, which also showed poor cell surface localization, could be rescued to cell surface, if cells were grown in the presence of drug substrates. The rescued chimera remained non-functional, as was evident from impaired ATPase and efflux activities. Taken together, the results suggest that the two NBDs of Cdr1p are asymmetric and non-exchangeable and that the drug efflux by Cdr1p involves complex interactions between the two halves of the protein.
δ-Aminolaevulinic acid synthesis is required for virulence of the wheat pathogen Stagonospora nodorum
Authors: Solomon Peter S. , Jörgens Cordula I. , Oliver Richard P.
Published: April 2006

δ-Aminolaevulinic acid (ALA) is synthesized in fungi by ALA synthase, a key enzyme in the synthesis of haem. The requirement for ALA synthase inStagonospora nodorumto cause disease in wheat was investigated. The single gene encoding ALA synthase (Als1) was cloned and characterized. Expression analysis determined thatAls1transcription was up-regulated during germination and also towards the latter stages of the infection. TheAls1gene was further characterized by homologous gene replacement. The inactivation ofAls1resulted in strains producing severely stunted germ tubes leading quickly to death. The strains could be recovered by supplementation with 33 μM ALA. Pathogenicity assays revealed theals1strains were essentially non-pathogenic, inferring a key role for the synthesis of ALA duringin plantagrowth. Supplementing the strains with ALA restored growthin vitroand also pathogenicity for up to 5 days after inoculation. Further examination by inoculating theals1strains onto wounded leaves found that pathogenicity was only partially restored, suggesting that host-derivedin plantalevels of ALA are not sufficient to support growth. This study has identified a key role for fungal ALA synthesis during infection and revealed its potential as an antifungal target.
Genes involved in the methyl tert-butyl ether (MTBE) metabolic pathway of Mycobacterium austroafricanum IFP 2012
Authors: Ferreira Nicolas Lopes , Labbé Diane , Monot Frédéric , Fayolle-Guichard Françoise , Greer Charles W.
Published: April 2006

Methyltert-butyl ether (MTBE) is a persistent pollutant of surface and groundwater, and the reasons for its low biodegradability are poorly documented. Using one of the rare bacterial strains able to grow in the presence of MTBE,Mycobacterium austroafricanumIFP 2012, the protein profiles of crude extracts after growth in the presence of MTBE and glucose were compared by SDS-PAGE. Ten proteins with molecular masses of 67, 64, 63, 55, 50, 27, 24, 17, 14 and 11 kDa were induced after growth in the presence of MTBE. Partial amino acid sequences of N-terminal and internal peptide fragments of the 64 kDa protein were used to design degenerate oligonucleotide primers to amplify total DNA by PCR, yielding a DNA fragment that was used as a probe for cloning. A two-step cloning procedure was performed to obtain a 10 327 bp genomic DNA fragment containing seven ORFs, including a putative regulator,mpdR, and four genes,mpdC,orf1,mpdBandorf2, in the same cluster. The MpdB protein (64 kDa) was related to a flavoprotein of the glucose–methanol–choline oxidoreductase family, and the MpdC protein (55 kDa) showed a high similarity with NAD(P) aldehyde dehydrogenases. Heterologous expression of these gene products was performed inMycobacterium smegmatismc2 155. The recombinant strain was able to degrade an intermediate of MTBE biodegradation, 2-methyl 1,2-propanediol, to hydroxyisobutyric acid. This is believed to be the first report of the cloning and characterization of a cluster of genes specifically involved in the MTBE biodegradation pathway ofM. austroafricanumIFP 2012.
Phospholipase A in Gram-negative bacteria and its role in pathogenesis
Authors: Istivan Taghrid S. , Coloe Peter J.
Published: April 2006

Phospholipase A (PLA) is one of the few enzymes present in the outer membrane of Gram-negative bacteria, and is likely to be involved in the membrane disruption processes that occur during host cell invasion. Both secreted and membrane-bound phospholipase A2 activities have been described in bacteria, fungi and protozoa. Recently there have been increasing reports on the involvement of PLA in bacterial invasion and pathogenesis. This review highlights the latest findings on PLA as a virulence factor in Gram-negative bacteria.
The phylogeny of Staphylococcus aureus – which genes make the best intra-species markers?
Authors: Cooper Jessica E. , Feil Edward J.
Published: April 2006

The ability to make informed decisions on the suitability of alternative marker loci is central for population and epidemiological investigations. This issue was addressed usingStaphylococcus aureusas a model population by generating nucleotide sequence data from 33 gene fragments in a representative sample of 30 strains. Supplementing the data with pre-existing multilocus sequence typing data, an intra-species tree based on ∼17·8 kb of sequence was reconstructed and the goodness of fit of each individual gene tree was computed. No strong association was noted between gene function per se and phylogenetic reliability, but it is suggested that candidate loci should possess at least the average degree of nucleotide diversity for all genes in the genome. In the case ofS. aureusthis threshold is >1 % mean pairwise diversity.
Biofilm formation by Pseudomonas fluorescens WCS365: a role for LapD
Authors: Hinsa Shannon M. , O'Toole George A.
Published: April 2006

A role for the outer-membrane-associated LapA protein in early biofilm formation by Pseudomonas fluorescens WCS365 has previously been shown. This paper reports that lapD, a gene located adjacent to the lapA gene, also plays a role in biofilm formation. A mutation in lapD results in a conditional biofilm defect in a static assay – this biofilm phenotype is exacerbated when biofilm formation is assayed in a flow-cell system. Furthermore, a lapD mutation shows a partial defect in the transition from reversible to irreversible attachment, consistent with an early role for the lapD gene product in biofilm formation. LapD is shown to be localized to the inner membrane of P. fluorescens. The data show decreased LapA associated with the cell surface, but no apparent change in cytoplasmic levels of this protein or lapA transcription, in a lapD mutant. A model is proposed wherein the role of LapD in biofilm formation is modulating the secretion of the LapA adhesin.
Flagellar glycosylation – a new component of the motility repertoire?
Authors: Logan Susan M.
Published: April 2006

The biosynthesis, assembly and regulation of the flagellar apparatus has been the subject of extensive studies over many decades, with considerable attention devoted to the peritrichous flagella ofEscherichia coliandSalmonella enterica. The characterization of flagellar systems from many other bacterial species has revealed subtle yet distinct differences in composition, regulation and mode of assembly of this important subcellular structure. Glycosylation of the major structural protein, the flagellin, has been shown most recently to be an important component of numerous flagellar systems in both Archaea and Bacteria, playing either an integral role in assembly or for a number of bacterial pathogens a role in virulence. This review focuses on the structural diversity in flagellar glycosylation systems and demonstrates that as a consequence of the unique assembly processes, the type of glycosidic linkage found on archaeal and bacterial flagellins is distinctive.
Exploring the role of the CTL epitope region of listeriolysin O in the pathogenesis of Listeria monocytogenes
Authors: Lety Marie-Annick , Frehel Claude , Raynaud Catherine , Dupuis Marion , Charbit Alain
Published: April 2006

Listeria monocytogenesis a facultative intracellular bacterial pathogen responsible for severe opportunistic infections in humans and animals. The secreted cholesterol-dependent cytolysin, listeriolysin O (LLO), mediates phagosomal escape and allows bacterial growth in the cytosol of infected cells. In order to identify new LLO determinants participating in bacterial pathogenesis, this study focused on a major target of LLO proteolytic cleavagein vitro, the CTL epitope region (residues 91–99). Mutations were generated by site-directed mutagenesis in the epitope or in the two clusters of positive charges flanking the epitope. Two LLO mutants (a single mutation K103A and a double mutation R89G, K90G) were normally and stably secreted byL. monocytogenes. In contrast, a mutant carrying four amino acid substitutions in the epitope itself (Y92K, D94A, E97K, Y98F) was highly susceptible to proteolytic degradation. While these three LLO mutant proteins showed a reduced haemolytic activity, they all promoted efficient phagosomal escape and intracellular multiplication in different cell types, and were non-cytotoxic. The deletion of the epitope (Δ91–99), as well as the substitution of two, three or four of the four lysine residues (K103 to K106) by alanine residues did not lead to the production of a detectable protein. These results confirm the lack of correlation between haemolytic activity and phagosomal membrane disruption. They reveal the importance of the 91–99 region in the production of a stable and functional LLO. LD50determinations in the mouse model suggest a possible link between LLO stability and virulence.
Mammalian Sir2 homolog SIRT7 is an activator of RNA polymerase I transcription
Authors: Ford Ethan , Voit Renate , Liszt Gregory , Magin Cornelia , Grummt Ingrid , Guarente Leonard
Published: April 2006

We investigated the role of SIRT7, one of the seven members of the mammalian sirtuin family. We show that SIRT7 is a widely expressed nucleolar protein that is associated with active rRNA genes (rDNA), where it interacts with RNA polymerase I (Pol I) as well as with histones. Overexpression of SIRT7 increases Pol I-mediated transcription, whereas knockdown of SIRT7 or inhibition of the catalytic activity results in decreased association of Pol I with rDNA and a reduction of Pol I transcription. Depletion of SIRT7 stops cell proliferation and triggers apoptosis. Our findings suggest that SIRT7 is a positive regulator of Pol I transcription and is required for cell viability in mammals.
Feedback control of morphogenesis in fungi by aromatic alcohols
Authors: Chen Hao , Fink Gerald R.
Published: April 2006

Many fungi undergo a developmental transition from a unicellular yeast form to an invasive filamentous form in response to environmental cues. Here we describe a quorum signaling pathway that links environmental sensing to morphogenesis in Saccharomyces cerevisiae. Saccharomyces cells secrete aromatic alcohols that stimulate morphogenesis by inducing the expression of FLO11 through a Tpk2p-dependent mechanism. Mutants defective in synthesis of these alcohols show reduced filamentous growth, which is partially suppressed by the addition of these aromatic alcohols. The production of these autosignaling alcohols is regulated by nitrogen: High ammonia restricts it by repressing the expression of their biosynthetic pathway, whereas nitrogen-poor conditions activate it. Moreover, the production of these aromatic alcohols is controlled by cell density and subjected to positive feedback regulation, which requires the transcription factor Aro80p. These interactions define a quorum-sensing circuit that allows Saccharomyces to respond to both cell density and the nutritional state of the environment. These same autoregulatory molecules do not evoke the morphological switch in Candida albicans, suggesting that these molecular signals are species-specific.
Ecological models of alcohol outlets and violent assaults: crime potentials and geospatial analysis
Authors: Gruenewald Paul J. , Freisthler Bridget , Remer Lillian , LaScala Elizabeth A. , Treno Andrew
Published: April 2006

Aims  Empirical tests of relationships between alcohol outlets and violence are generally conducted with statistical controls for correlates related to characteristics of people and the places in which they live. Crime potentials theory asserts that certain subpopulations are disposed to participate in criminal activities (population potentials) and certain neighborhoods are more likely to be places where crimes occur (place potentials). The current study assesses the degree to which measures of the different geographic distributions of these potentials contribute to violent crime.

Design  Cross‐sectional data on hospital discharges for violent assaults were obtained for residents of 1637 zip code areas in California. Assault rates were related to measures of population and place characteristics using spatial statistical models corrected for spatial autocorrelated error.

Findings  Rates of assault were related to population and place characteristics within zip code areas, and with characteristics of populations living in adjacent zip code areas. Assault rates were greater in densely populated, poor minority urban areas with greater residential instability. Assault rates were also greater in zip code areas adjacent to densely populated urban areas. Assault rates were related significantly to local densities of off‐premise alcohol retail establishments, not bars. However, densities of bars moderated substantially effects related to local population characteristics. Bars were related significantly to violence in unstable poor minority areas and in rural middle‐income areas of the state.

Conclusion  Population and place characteristics are associated with rates of violence across spatial areas. Alcohol outlets directly affect and moderate potentials for violence associated with socio‐demographic groups.
An outbreak of hepatitis B virus infection among methamphetamine injectors: the role of sharing injection drug equipment
Authors: Vogt Tara M. , Perz Joseph F. , Van Houten Clayton K. , Harrington Robert , Hansuld Tia , Bialek Stephanie R. , Johnston Robert , Bratlie Rachel , Williams Ian T.
Published: April 2006

Aim  To identify risk factors for acute hepatitis B virus (HBV) infection among Wyoming methamphetamine injectors.

Design  A case–control study conducted in the setting of an outbreak.

Setting  A county in central Wyoming, United States.

Participants  Cases were identified through surveillance and contact tracing and were defined as Natrona County, Wyoming, residents who were either symptomatic or confirmed serologically to be acutely infected with HBV during January–August, 2003. Controls were susceptible to HBV infection. All participants identified themselves as methamphetamine injectors.

Measurements  Participants were administered a survey that inquired about risk factors for HBV infection, including drug use practices and sexual behaviors. Controls were also tested serologically for acute HBV infection.

Findings  Among the 18 case‐patients and 49 controls who participated in the study, sharing water used to prepare injections and/or rinse syringes was associated with HBV infection (94% of case‐participants versus 44% of controls; OR = 21.9, 95% CI: 2.7, 177.8), as was sharing cotton filters (89% of case‐participants versus 52% of controls; OR = 7.4, 95% CI: 1.5, 35.6); sharing syringes was not statistically associated. In logistic regression models adjusted for age, sex, and interview site, sharing rinse water and sharing cotton remained statistically associated.

Conclusions  Methamphetamine use has become increasingly prevalent in the United States. Our findings highlight the need for awareness of risks associated with injection drug use and sharing behaviors. Enhanced hepatitis B vaccination programs and educational campaigns that target methamphetamine injectors specifically, including those living in rural areas, should be developed and implemented.
Subjective responses to initial experience with cocaine: an exploration of the incentive–sensitization theory of drug abuse
Authors: Lambert Nadine M. , McLeod Marsha , Schenk Susan
Published: April 2006

Aims  This study investigated the relationship between positive and negative subjective responses at the time of initial cocaine use with adult cocaine dependence and life‐time use rates. Psychostimulant pre‐exposure, regular smoking or stimulant treatment before initiation were examined to explore the incentive sensitization theory of addiction.

Participants  A total of 202 adult participants who had tried cocaine on at least one occasion were studied prospectively from childhood into adulthood. The cocaine‐initiated group included 89 who met Diagnostic and Statistical Manual version IV (DSM‐IV) criteria for attention deficit hyperactive disorder (ADHD) and 113 age‐matched controls.

Design  Five childhood and three adulthood interviews provided data on ages of initiation into cocaine and life‐time use of cocaine from ages 16–40 years. Correlations of each subjective response and analyses of variance (ANOVAs) of cocaine ‘liking’ and ‘wanting’ with DSM‐III‐R cocaine dependence and life‐time use provided support for the validity of the measures. ANOVA provided evidence of the effect of psychostimulant pre‐exposure on ‘liking’ and ‘wanting’. Logistic regression modeled the prediction of dependence and life‐time use with the independent variables of ‘liking’ and ‘wanting’, psychostimulant pre‐exposure and participant characteristics.

Results  When cocaine was first tried, ‘liking’ and ‘wanting’ were significant predictors of cocaine dependence and life‐time use. Mean ‘liking’ or ‘wanting’ responses did not differ by participant characteristics. Those who were pre‐exposed by regular smoking or stimulant treatment had higher ‘liking’ and ‘wanting’ scores; but participants who were pre‐exposed by both stimulant treatment and regular smoking reported the lowest liking and the highest wanting responses, consistent with the incentive sensitization theory. Logistic regression showed that the ‘liking’ and ‘wanting’ responses increased significantly the odds of DSM‐III‐R cocaine dependence and life‐time use.

Conclusion  In this sample, subjective ‘liking’ and ‘wanting’ measured risk for cocaine abuse.
Nasopharyngeal oxygen insufflation following pre‐oxygenation using the four deep breath technique
Authors: Taha S. K. , Siddik‐Sayyid S. M. , El‐Khatib M. F. , Dagher C. M. , Hakki M. A. , Baraka A. S.
Published: April 2006

This paper evaluates the effectiveness of nasopharyngeal oxygen insufflation following preoxygenation using the four deep breath technique within 30 s, on the onset of haemoglobin desaturation during the subsequent apnoea. Thirty ASA I or II patients were randomly allocated to one of two groups. In the study group (n = 15), pre‐oxygenation was followed by insufflation of oxygen at a flow of 5 l.min−1 via a nasopharyngeal catheter commenced at the onset of apnoea. In the control group, pre‐oxygenation was not followed by nasopharyngeal oxygen insufflation (n = 15). In the control group, Spo2 fell to 95% within a mean (SD) apnoea time of 3.65 (1.15) min, whereas in the study group, Spo2 was maintained in all patients at 100% throughout the 6 min of apnoea, at which point apnoea was terminated and positive pressure ventilation commenced. We conclude that nasopharyngeal oxygen insufflation following pre‐oxygenation using the four deep breath technique can delay the onset of haemoglobin desaturation for a significant period of time during the subsequent apnoea.
The effect of fundal pressure at Caesarean section on maternal haemodynamics
Authors: Kim T. Y. , Ryu D. H.
Published: April 2006

In 20 women undergoing Caesarean section, we determined brachial arterial blood pressure, heart rate and cardiac output (using an oesophageal Doppler probe) just after uterine incision and during the application of extra‐abdominal uterine fundal pressure to facilitate delivery. Mean (SD) systolic aortic flow time (354.3 (35.4) ms), cardiac output (3.85 (0.68) l.min−1), heart rate (80.6 (14.2) beats.min−1) and blood pressure (84.7 (12.1) mmHg) decreased when fundal pressure was applied compared with after uterine incision (397.6 (31.6) ms, 4.69 (0.78) l.min−1, 95.1 (14.0) beats.min−1and 100.3 (12.0) mmHg, respectively; p < 0.05). Peak velocity and stroke distance of the aortic flow when fundal pressure was applied was similar to after uterine incision. The mothers and babies were not observed to be clinically compromised. The results suggest that applying fundal pressure to facilitate Caesarean delivery produces significant haemodynamic effects but the impact of these effects may be clinically insignificant.
Effects of a cinnamon extract on plasma glucose, HbA1c, and serum lipids in diabetes mellitus type 2
Authors: Mang B. , Wolters M. , Schmitt B. , Kelb K. , Lichtinghagen R. , Stichtenoth D. O. , Hahn A.
Published: April 2006

Background  According to previous studies, cinnamon may have a positive effect on the glycaemic control and the lipid profile in patients with diabetes mellitus type 2. The aim of this trial was to determine whether an aqueous cinnamon purified extract improves glycated haemoglobin A1c (HbA1c), fasting plasma glucose, total cholesterol, low‐density lipoprotein (LDL), high‐density lipoprotein (HDL) and triacylglycerol concentrations in patients with type 2 diabetes.

Methods  A total of 79 patients with diagnosed diabetes mellitus type 2 not on insulin therapy but treated with oral antidiabetics or diet were randomly assigned to take either a cinnamon extract or a placebo capsule three times a day for 4 months in a double‐blind study. The amount of aqueous cinnamon extract corresponded to 3 g of cinnamon powder per day.

Results  The mean absolute and percentage differences between the pre‐ and post‐intervention fasting plasma glucose level of the cinnamon and placebo groups were significantly different. There was a significantly higher reduction in the cinnamon group (10·3%) than in the placebo group (3·4%). No significant intragroup or intergroup differences were observed regarding HbA1c, lipid profiles or differences between the pre‐ and postintervention levels of these variables. The decrease in plasma glucose correlated significantly with the baseline concentrations, indicating that subjects with a higher initial plasma glucose level may benefit more from cinnamon intake. No adverse effects were observed.

Conclusions  The cinnamon extract seems to have a moderate effect in reducing fasting plasma glucose concentrations in diabetic patients with poor glycaemic control.
Exhaled markers of oxidative stress in idiopathic pulmonary fibrosis
Authors: Psathakis K. , Mermigkis D. , Papatheodorou G. , Loukides S. , Panagou P. , Polychronopoulos V. , Siafakas N. M. , Bouros D.
Published: April 2006

Background Expired breath condensate (EBC) has never been used to explore the level of oxidative stress in idiopathic pulmonary fibrosis (IPF). Therefore, the aim of this study was to measure the levels of H2O2and 8‐isoprostane, as biomarkers of oxidative stress, in the EBC of patients with IPF.

Materials and methods We investigated 16 patients with IPF and 15 healthy subjects as the control group. The levels of H2O2 and8‐isoprostane were measured in the EBC of all subjects and were compared between the IPF and control groups. In patients with IPF, H2O2 and8‐isoprostane were further correlated with pulmonary function tests (PFTs), the resting pO2and the differential cell count from the bronchoalveolar lavage fluid (BALF).

Results The mean (95%CI) concentration of H2O2was increased in the patients with IPF compared with the normal subjects (0·36, 0·24–0·47 µM vs. 0·16, 0·10–0·23 µM,P = 0·003).The mean (95%CI) concentration of 8‐isoprostane was also increased in the patients with IPF compared with the controls (74, 38–110 pg mL−1vs. 33, 28–39 pg mL−1,P = 0·02). In the patients with IPF, the diffusing capacity of the lung for carbon monoxide was negatively correlated with the levels of H2O2in EBC (P = 0·03,r = −0·58). No other correlation was found between the oxidative stress markers in the EBC and PFT values, pO2or BALF cell count.

Conclusions Our data suggest that H2O2 and8‐isoprostane are increased in the EBC of patients with IPF. H2O2may be correlated with the severity of the disease in IPF.