bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite-element analysis of middle-ear pressure effects on static and dynamic behavior of human ear
Authors: Wang Xuelin , Cheng Tao , Gan Rong Z.
Published: July 2007

A finite-element analysis for static behavior of middle ear under variation of the middle-ear pressure was conducted in a 3D model of human ear by combining the hyperelastic Mooney-Rivlin material model and geometry nonlinearity. An empirical formula was then developed to calculate material parameters of the middle-ear soft tissues as the stress-dependent elastic modulus relative to the middle-ear pressure. Dynamic behavior of the middle ear in response to sound pressure in the ear canal was predicted under various positive and negative middle-ear pressures. The results from static analysis indicate that a positive middle ear pressure produces the static displacements of the tympanic membrane (TM) and footplate more than a negative pressure. The dynamic analysis shows that the reductions of the TM and footplate vibration magnitudes under positive middle-ear pressure are mainly determined by stress dependence of elastic modulus. The reduction of the TM and footplate vibrations under negative pressure was caused by both the geometry changes of middle-ear structures and the stress dependence of elastic modulus.
Assessing temporary threshold shift in a bottlenose dolphin (Tursiops truncatus) using multiple simultaneous auditory evoked potentials
Authors: Finneran James J. , Schlundt Carolyn E. , Branstetter Brian , Dear Randall L.
Published: July 2007

Hearing sensitivity was measured in a bottlenose dolphin before and after exposure to an intense 20-kHz fatiguing tone in three different experiments. In each experiment, hearing was characterized using both the auditory steady-state response (ASSR) and behavioral methods. In experiments 1 and 2, ASSR stimuli consisted of seven frequency-modulated tones, each with a unique carrier and modulation frequency. The tones were simultaneously presented to the subject and the ASSR at each modulation rate measured to determine the effects of the sound exposure at the corresponding carrier frequency. In experiment 3 behavioral thresholds and ASSR input-output functions were measured at a single frequency before and after three exposures. Hearing loss was fre-quency-dependent, with the largest temporary threshold shifts occurring (in order) at 30, 40, and 20kHz. ASSR threshold shifts reached 40–45dB and were always larger than behavioral shifts (19–33dB). The ASSR input-output functions were represented as the sum of two processes: a low threshold, saturating process and a higher threshold, linear process, that react and recover to fatigue at different rates. The loss of the near-threshold saturating process after exposure may explain the discrepancies between the ASSR and behavioral threshold shifts.
Factors influencing glimpsing of speech in noise
Authors: Li Ning , Loizou Philipos C.
Published: July 2007

The idea that listeners are able to “glimpse” the target speech in the presence of competing noise has been supported by many studies, and is based on the assumption that listeners are able to glimpse pieces of the target speech occurring at different times and somehow patch them together to hear out the target speech. The factors influencing glimpsing in noise are not well understood and are examined in the present study. Specifically, the effects of the frequency location, spectral width, and duration of the glimpses are examined. Stimuli were constructed using an ideal time-frequency (T-F) masking technique that ensures that the target is stronger than the masker in certain T-F regions of the mixture, thereby rendering certain regions easier to glimpse than others. Sentences were synthesized using this technique with glimpse information placed in several frequency regions while varying the glimpse window duration and total duration of glimpsing. Results indicated that the frequency location and total duration of the glimpses had a significant effect on speech recognition, with the highest performance obtained when the listeners were able to glimpse information in the F1∕F2 frequency region (0–3kHz) for at least 60% of the utterance.
The hydrodynamic footprint of a benthic, sedentary fish in unidirectional flow
Authors: Coombs Sheryl , Anderson Erik , Braun Christopher B. , Grosenbaugh Mark
Published: July 2007

Mottled sculpin (Cottus bairdi) are small, benthic fish that avoid being swept downstream by orienting their bodies upstream and extending their large pectoral fins laterally to generate negative lift. Digital particle image velocimetry was used to determine the effects of these behaviors on the spatial and temporal characteristics of the near-body flow field as a function of current velocity. Flow around the fish’s head was typical for that around the leading end of a rigid body. Flow separated around the edges of pectoral fin, forming a wake similar to that observed for a flat plate perpendicular to the flow. A recirculation region formed behind the pectoral fin and extended caudally along the trunk to the approximate position of the caudal peduncle. In this region, the time-averaged velocity was approximately one order of magnitude lower than that in the freestream region and flow direction varied over time, resembling the periodic shedding of vortices from the edge of a flat plate. These results show that the mottled sculpin pectoral fin significantly alters the ambient flow noise in the vicinity of trunk lateral line sensors, while simultaneously creating a hydrodynamic footprint of the fish’s presence that may be detected by the lateral line of nearby fish.
Moderate cochlear hearing loss leads to a reduced ability to use temporal fine structure information
Authors: Hopkins Kathryn , Moore Brian C. J.
Published: July 2007

The ability of normally hearing and hearing-impaired subjects to use temporal fine structure information in complex tones was measured. Subjects were required to discriminate a harmonic complex tone from a tone in which all components were shifted upwards by the same amount in Hz, in a three-alternative, forced-choice task. The tones either contained five equal-amplitude components (non-shaped stimuli) or contained many components, but were passed through a fixed bandpass filter to reduce excitation pattern changes (shaped stimuli). Components were centered at nominal harmonic numbers (N) 7, 11, and 18. For the shaped stimuli, hearing-impaired subjects performed much more poorly than normally hearing subjects, with most of the former scoring no better than chance when N=11 or 18, suggesting that they could not access the temporal fine structure information. Performance for the hearing-impaired subjects was significantly improved for the non-shaped stimuli, presumably because they could benefit from spectral cues. It is proposed that normal-hearing subjects can use temporal fine structure information provided the spacing between fine structure peaks is not too small relative to the envelope period, but subjects with moderate cochlear hearing loss make little use of temporal fine structure information for unresolved components.
A two-layer composite model of the vocal fold lamina propria for fundamental frequency regulation
Authors: Zhang Kai , Siegmund Thomas , Chan Roger W.
Published: July 2007

The mechanical properties of the vocal fold lamina propria, including the vocal fold cover and the vocal ligament, play an important role in regulating the fundamental frequency of human phonation. This study examines the equilibrium hyperelastic tensile deformation behavior of cover and ligament specimens isolated from excised human larynges. Ogden’s hyperelastic model is used to characterize the tensile stress-stretch behaviors at equilibrium. Several statistically significant differences in the mechanical response differentiating cover and ligament, as well as gender are found. Fundamental frequencies are predicted from a string model and a beam model, both accounting for the cover and the ligament. The beam model predicts nonzero F0 for the unstretched state of the vocal fold. It is demonstrated that bending stiffness significantly contributes to the predicted F0, with the ligament contributing to a higher F0, especially in females. Despite the availability of only a small data set, the model predicts an age dependence of F0 in males in agreement with experimental findings. Accounting for two mechanisms of fundamental frequency regulation—vocal fold posturing (stretching) and extended clamping—brings predicted F0 close to the lower bound of the human phonatory range. Advantages and limitations of the current model are discussed.
Dynamic response of an insonified sonar window interacting with a Tonpilz transducer array
Authors: Hull Andrew J.
Published: July 2007

This paper derives and evaluates an analytical model of an insonified sonar window in contact with an array of Tonpilz transducers operating in receive mode. The window is fully elastic so that all wave components are present in the analysis. The output of the model is a transfer function of a transducer element output voltage divided by input pressure versus arrival angle and frequency. This model is intended for analysis of sonar systems that are to be built or modified for broadband processing. The model is validated at low frequency with a comparison to a previously derived thin plate model. Once this is done, an example problem is studied so that the effects of higher order wave interaction with acoustic reception can be understood. It was found that these higher order waves cause multiple nulls in the region where the array detects acoustic energy and that their locations in the arrival angle-frequency plane can be determined. The effects of these nulls in the beam patterns of the array are demonstrated.
Acoustic variability within and across German, French, and American English vowels: Phonetic context effects
Authors: Strange Winifred , Weber Andrea , Levy Erika S. , Shafiro Valeriy , Hisagi Miwako , Nishi Kanae
Published: July 2007

Cross-language perception studies report influences of speech style and consonantal context on perceived similarity and discrimination of non-native vowels by inexperienced and experienced listeners. Detailed acoustic comparisons of distributions of vowels produced by native speakers of North German (NG), Parisian French (PF) and New York English (AE) in citation (di)syllables and in sentences (surrounded by labial and alveolar stops) are reported here. Results of within- and cross-language discriminant analyses reveal striking dissimilarities across languages in the spectral/temporal variation of coarticulated vowels. As expected, vocalic duration was most important in differentiating NG vowels; it did not contribute to PF vowel classification. Spectrally, NG long vowels showed little coarticulatory change, but back/low short vowels were fronted/raised in alveolar context. PF vowels showed greater coarticulatory effects overall; back and front rounded vowels were fronted, low and mid-low vowels were raised in both sentence contexts. AE mid to high back vowels were extremely fronted in alveolar contexts, with little change in mid-low and low long vowels. Cross-language discriminant analyses revealed varying patterns of spectral (dis)similarity across speech styles and consonantal contexts that could, in part, account for AE listeners’ perception of German and French front rounded vowels, and “similar” mid-high to mid-low vowels.
Listeners’ identification and discrimination of digitally manipulated sounds as prolongations
Authors: Kawai Norimune , Healey E. Charles , Carrell Thomas D.
Published: July 2007

The present study had two main purposes. One was to examine if listeners perceive gradually increasing durations of a voiceless fricative categorically (“fluent” versus “stuttered”) or continuously (gradient perception from fluent to stuttered). The second purpose was to investigate whether there are gender differences in how listeners perceive various duration of sounds as “prolongations.” Forty-four listeners were instructed to rate the duration of the /ʃ/ in the word “shape” produced by a normally fluent speaker. The target word was embedded in the middle of an experimental phrase and the initial /ʃ/ sound was digitally manipulated to create a range of fluent to stuttered sounds. This was accomplished by creating 20ms stepwise increments for sounds ranging from 120to500ms in duration. Listeners were instructed to give a rating of 1 for a fluent word and a rating of 100 for a stuttered word. The results showed listeners perceived the range of sounds continuously. Also, there was a significant gender difference in that males rated fluent sounds higher than females but female listeners rated stuttered sounds higher than males. The implications of these results are discussed.
Spectral modulation masking patterns reveal tuning to spectral envelope frequency
Authors: Saoji Aniket A. , Eddins David A.
Published: July 2007

Auditory processing appears to include a series of domain-specific filtering operations that include tuning in the audio-frequency domain, followed by tuning in the temporal modulation domain, and perhaps tuning in the spectral modulation domain. To explore the possibility of tuning in the spectral modulation domain, a masking experiment was designed to measure masking patterns in the spectral modulation domain. Spectral modulation transfer functions (SMTFs) were measured for modulation frequencies from 0.25 to 14 cycles/octave superimposed on noise carriers either one octave (800–1600Hz, 6400–12800Hz) or six octaves wide (200–12800Hz). The resulting SMTFs showed maximum sensitivity to modulation between 1 and 3 cycles/octave with reduced sensitivity above and below this region. Masked spectral modulation detection thresholds were measured for masker modulation frequencies of 1, 3, and 5 cycles/octave with a fixed modulation depth of 15dB. The masking patterns obtained for each masker frequency and carrier band revealed tuning (maximum masking) near the masker frequency, which is consistent with the theory that spectral envelope perception is governed by a series of spectral modulation channels tuned to different spectral modulation frequencies.
Effects of noise and distortion on speech quality judgments in normal-hearing and hearing-impaired listeners
Authors: Arehart Kathryn H. , Kates James M. , Anderson Melinda C. , Harvey Lewis O.
Published: July 2007

Noise and distortion reduce speech intelligibility and quality in audio devices such as hearing aids. This study investigates the perception and prediction of sound quality by both normal-hearing and hearing-impaired subjects for conditions of noise and distortion related to those found in hearing aids. Stimuli were sentences subjected to three kinds of distortion (additive noise, peak clipping, and center clipping), with eight levels of degradation for each distortion type. The subjects performed paired comparisons for all possible pairs of 24 conditions. A one-dimensional coherence-based metric was used to analyze the quality judgments. This metric was an extension of a speech intelligibility metric presented in Kates and Arehart (2005) [J. Acoust. Soc. Am. 117, 2224–2237] and is based on dividing the speech signal into three amplitude regions, computing the coherence for each region, and then combining the three coherence values across frequency in a calculation based on the speech intelligibility index. The one-dimensional metric accurately predicted the quality judgments of normal-hearing listeners and listeners with mild-to-moderate hearing loss, although some systematic errors were present. A multidimensional analysis indicates that several dimensions are needed to describe the factors used by subjects to judge the effects of the three distortion types.
Impact of Empirical-Therapy Selection on Outcomes of Intravenous Drug Users with Infective Endocarditis Caused by Methicillin-Susceptible
Staphylococcus aureus
Authors: Lodise Thomas P. , McKinnon Peggy S. , Levine Donald P. , Rybak Michael J.
Published: July 2007

This study compares beta-lactam and vancomycin among intravenous drug users with infective endocarditis caused by methicillin-susceptible
Staphylococcus aureus
. Patients who received vancomycin had higher infection-related mortality, even if they were switched to beta-lactam once culture results became available; this relationship persisted after logistic regression analysis controlling for clinical characteristics.
Negamycin Binds to the Wall of the Nascent Chain Exit Tunnel of the 50S Ribosomal Subunit
Authors: Schroeder Susan J. , Blaha Gregor , Moore Peter B.
Published: July 2007

Negamycin, a small-molecule inhibitor of protein synthesis, binds the
Haloarcula marismortui
50S ribosomal subunit at a single site formed by highly conserved RNA nucleotides near the cytosolic end of the nascent chain exit tunnel. The mechanism of antibiotic action and the function of this unexplored tunnel region remain intriguingly elusive.
Targeting the Calcineurin Pathway Enhances Ergosterol Biosynthesis Inhibitors against
Trichophyton mentagrophytes
In Vitro and in a Human Skin Infection Model
Authors: Onyewu Chiatogu , Eads Emily , Schell Wiley A. , Perfect John R. , Ullmann Yehuda , Kaufman Gil , Horwitz Benjamin A. , Berdicevsky Israela , Heitman Joseph
Published: July 2007

Fluconazole-FK506 or fluconazole-cyclosporine drug combinations were tested in an ex vivo
Trichophyton mentagrophytes
human skin infection model. Conidia colonization was monitored by scanning electron microscopy over a 7-day treatment period. The fluconazole-FK506 combination demonstrated the most obvious advantage over single-drug therapy by clearing conidia and protecting skin from damage at low drug concentrations.
Role of the
rapA
Gene in Controlling Antibiotic Resistance of
Escherichia coli
Biofilms
Authors: Lynch S. V. , Dixon L. , Benoit M. R. , Brodie E. L. , Keyhan M. , Hu P. , Ackerley D. F. , Andersen G. L. , Matin A.
Published: July 2007

By using a high-throughput screening method, a mutant of a uropathogenic
Escherichia coli
strain affected in the
rapA
gene was isolated. The mutant formed normal-architecture biofilms but showed decreased penicillin G resistance, although the mutation did not affect planktonic cell resistance. Transcriptome analysis showed that 22 genes were down-regulated in the mutant biofilm. One of these genes was
yhcQ
, which encodes a putative multidrug resistance pump. Mutants with mutations in this gene also formed biofilms with decreased resistance, although the effect was less pronounced than that of the
rapA
mutation. Thus, an additional mechanism(s) controlled by a
rapA
-regulated gene(s) was involved in wild-type biofilm resistance. The search for this mechanism was guided by the fact that another down-regulated gene in
rapA
biofilms,
yeeZ
, is suspected to be involved in extra cell wall-related functions. A comparison of the biofilm matrix of the wild-type and
rapA
strains revealed decreased polysaccharide quantities and coverage in the mutant biofilms. Furthermore, the (fluorescent) functional penicillin G homologue Bocillin FL penetrated the mutant biofilms more readily. The results strongly suggest a dual mechanism for the wild-type biofilm penicillin G resistance, retarded penetration, and effective efflux. The results of studies with an
E. coli
K-12 strain pointed to the same conclusion. Since efflux and penetration can be general resistance mechanisms, tests were conducted with other antibiotics. The
rapA
biofilm was also more sensitive to norfloxacin, chloramphenicol, and gentamicin.
Influence of TEM-1 β-Lactamase on the Pharmacodynamic Activity of Simulated Total versus Free-Drug Serum Concentrations of Cefditoren (400 Milligrams) versus Amoxicillin-Clavulanic Acid (2,000/125 Milligrams) against
Haemophilus influenzae
Strains Exhibiting an N526K Mutation in the
ftsI
Gene
Authors: Torrico M. , Aguilar L. , González N. , Giménez M. J. , Echeverría O. , Cafini F. , Sevillano D. , Alou L. , Coronel P. , Prieto J.
Published: July 2007

The aim of this study was to explore bactericidal activity of total and free serum simulated concentrations after the oral administration of cefditoren (400 mg, twice daily [bid]) versus the oral administration of amoxicillin-clavulanic acid extended release formulation (2,000/125 mg bid) against
Haemophilus influenzae
. A computerized pharmacodynamic simulation was performed, and colony counts and β-lactamase activity were determined over 48 h. Three strains were used: ampicillin-susceptible, β-lactamase-negative ampicillin-resistant (BLNAR) (also resistant to amoxicillin-clavulanic acid) and β-lactamase-positive amoxicillin-clavulanic acid-resistant (BLPACR) strains, with cefditoren MICs of ≤0.12 μg/ml and amoxicillin-clavulanic acid MICs of 2, 8, and 8 μg/ml, respectively. Against the ampicillin-susceptible and BLNAR strains, bactericidal activity (≥3 log
10
reduction) was obtained from 6 h on with either total and free cefditoren or amoxicillin-clavulanic acid. Against the BLPACR strain, free cefditoren showed bactericidal activity from 8 h on. In amoxicillin-clavulanic acid simulations the increase in colony counts from 4 h on occurred in parallel with the increase in β-lactamase activity for the BLPACR strain. Since both BLNAR and BLPACR strains exhibited the same MIC, this was due to the significantly lower (
P
≤ 0.012) amoxicillin concentrations from 4 h on in simulations with β-lactamase positive versus negative strains, thus decreasing the time above MIC (T>MIC). From a pharmacodynamic point of view, the theoretical amoxicillin T>MIC against strains with elevated ampicillin/amoxicillin-clavulanic acid MICs should be considered with caution since the presence of β-lactamase inactivates the antibiotic, thus rendering inaccurate theoretical calculations. The experimental bactericidal activity of cefditoren is maintained over the dosing interval regardless of the presence of a mutation in the
ftsI
gene or β-lactamase production.
Interleukin 18 Participates in the Early Inflammatory Response and Bacterial Clearance during Pneumonia Caused by Nontypeable
Haemophilus influenzae
Authors: Wieland Catharina W. , Florquin Sandrine , van der Poll Tom
Published: July 2007

Nontypeable
Haemophilus influenzae
(NTHi) is a common gram-negative respiratory pathogen. To determine the role of the proinflammatory cytokine interleukin 18 (IL-18) during NTHi pneumonia, normal wild-type (WT) and IL-18 knockout (KO) mice were intranasally infected with NTHi. IL-18 KO mice displayed a delayed clearance of NTHi from the respiratory tract, resulting in >20-fold higher bacterial loads in their lungs at 24 h after infection, preceded by a strongly attenuated pulmonary innate immune response as determined by cytokine and chemokine induction and histopathology. These data identify IL-18 as part of an adequate innate immune response during NTHi pneumonia.
Passively Released Heme from Hemoglobin and Myoglobin Is a Potential Source of Nutrient Iron for
Bordetella bronchiseptica
Authors: Mocny Jeffrey C. , Olson John S. , Connell Terry D.
Published: July 2007

Colonization by
Bordetella bronchiseptica
results in a variety of inflammatory respiratory infections, including canine kennel cough, porcine atrophic rhinitis, and a whooping cough-like disease in humans. For successful colonization,
B. bronchiseptica
must acquire iron (Fe) from the infected host. A vast amount of Fe within the host is sequestered within heme, a metalloporphyrin which is coordinately bound in hemoglobin and myoglobin. Utilization of hemoglobin and myoglobin as sources of nutrient Fe by
B. bronchiseptica
requires expression of BhuR, an outer membrane protein. We hypothesize that hemin is acquired by
B. bronchiseptica
in a BhuR-dependent manner after spontaneous loss of the metalloporphyrin from hemoglobin and/or myoglobin. Sequestration experiments demonstrated that direct contact with hemoglobin or myoglobin was not required to support growth of
B. bronchiseptica
in an Fe-limiting environment. Mutant myoglobins, each exhibiting a different affinity for heme, were employed to demonstrate that the rate of growth of
B. bronchiseptica
was directly correlated with the rate at which heme was lost from the hemoprotein. Finally,
Escherichia coli
cells expressing recombinant BhuR had the capacity to remove hemin from solution. Collectively, these experiments provided strong experimental support for the model that BhuR is a hemin receptor and
B. bronchiseptica
likely acquires heme during infection after passive loss of the metalloporphyrin from hemoglobin and/or myoglobin. These results also suggest that spontaneous hemin loss by hemoglobin and myoglobin may be a common mechanism by which many pathogenic bacteria acquire heme and heme-bound Fe.
Additive and Synergistic Bactericidal Activity of Antibodies Directed against Minor Outer Membrane Proteins of
Neisseria meningitidis
Authors: Weynants Vincent E. , Feron Christiane M. , Goraj Karine K. , Bos Martine P. , Denoël Philippe A. , Verlant Vincent G. , Tommassen Jan , Peak Ian R. A. , Judd Ralph C. , Jennings Michael P. , Poolman Jan T.
Published: July 2007

Neisseria meningitidis
serogroup B is a major cause of bacterial meningitis in younger populations. The available vaccines are based on outer membrane vesicles obtained from wild-type strains. In children less than 2 years old they confer protection only against strains expressing homologous PorA, a major, variable outer membrane protein (OMP). We genetically modified a strain in order to eliminate PorA and to overproduce one or several minor and conserved OMPs. Using a mouse model mimicking children's PorA-specific bactericidal activity, it was demonstrated that overproduction of more than one minor OMP is required to elicit antibodies able to induce complement-mediated killing of strains expressing heterologous PorA. It is concluded that a critical density of bactericidal antibodies needs to be reached at the surface of meningococci to induce complement-mediated killing. With minor OMPs, this threshold is reached when more than one antigen is targeted, and this allows cross-protection.
BvrR/BvrS-Controlled Outer Membrane Proteins Omp3a and Omp3b Are Not Essential forBrucella abortusVirulence
Authors: Manterola Lorea , Guzmán-Verri Caterina , Chaves-Olarte Esteban , Barquero-Calvo Elías , de Miguel María-Jesús , Moriyón Ignacio , Grilló María-Jesús , López-Goñi Ignacio , Moreno Edgardo
Published: July 2007

TheBrucella abortustwo-component regulatory system BvrR/BvrS controls the expression of outer membrane proteins (Omp) Omp3a (Omp25) and Omp3b (Omp22). Disruption ofbvrSorbvrRgenerates avirulent mutants with altered cell permeability, higher sensitivity to microbicidal peptides, and complement. Consequently, the role of Omp3a and Omp3b in virulence was examined. Similar tobvrSorbvrRmutants,omp3aandomp3bmutants displayed increased attachment to cells, indicating surface alterations. However, they showed unaltered permeability; normal expression of Omp10, Omp16, Omp19, Omp2b, and Omp1; native hapten polysaccharide; and lipopolysaccharide and were resistant to complement and polymyxin B at ranges similar to those of the wild-type (WT) counterpart. Likewise,omp3aandomp3bmutants were able to replicate in murine macrophages and in HeLa cells, were resistant to the killing action of human neutrophils, and persisted in mice, like the WT strain. Murine macrophages infected with theomp3amutant generated slightly higher levels of tumor necrosis factor alpha than the WT, whereas thebvrSmutant induced lower levels of this cytokine. Since the absence of Omp3a or Omp3b does not result in attenuation, it can be concluded that BvrR/BvrS influences additionalBrucellaproperties involved in virulence. Our results are discussed in the light of previous works suggesting that disruption ofomp3agenerates attenuatedBrucellastrains, and we speculate on the role of group 3 Omps.
Shigella flexneri
Phagosomal Escape Is Independent of Invasion
Authors: Paetzold Susanne , Lourido Sebastian , Raupach Bärbel , Zychlinsky Arturo
Published: July 2007

Infections with
Salmonella enterica
serovar Typhimurium and
Shigella flexneri
result in mucosal inflammation in response to epithelial cell invasion and macrophage cytotoxicity. These processes are mediated by type III secretion systems encoded in homologous virulence loci in the two species, namely,
Salmonella
pathogenicity island 1 (SPI-1), carried in the genome, and the
Shigella
entry region (SER), carried in a large virulence plasmid. Here we show that SPI-1 can functionally complement a deletion of SER in
S. flexneri
, restoring invasion of epithelial cells, macrophage cytotoxicity, and phagosomal escape. Furthermore,
S. flexneri
phagosomal escape requires the SER and another gene(s) carried on the large virulence plasmid. We demonstrate that the processes of invasion and phagosomal escape can be uncoupled in
S. flexneri
.
Depletion of Alveolar Macrophages Decreases the Dissemination of a Glucosylceramide-Deficient Mutant ofCryptococcus neoformansin Immunodeficient Mice
Authors: Kechichian Talar B. , Shea John , Del Poeta Maurizio
Published: July 2007

In previous studies we showed that aCryptococcus neoformansmutant lacking glucosylceramide (Δgcs1) is avirulent and unable to reach the brain when it is administered intranasally into an immunocompetent mouse and is contained in a lung granuloma. To determine whether granuloma formation is key for containment ofC. neoformansΔgcs1, we studied the role ofC. neoformansglucosylceramide in a T- and NK-cell-immunodeficient mouse model (Tgε26) in which alveolar macrophages (AMs) are not activated and granuloma formation is not expected. The results show that Tgε26 mice infected with Δgcs1do not produce a lung granuloma and that the Δgcs1mutant proliferates in the lungs and does disseminate to the brain, although its virulence phenotype is dramatically reduced. Since Δgcs1can grow only in acidic niches, such as the phagolysosome of AMs, and not in neutral or alkaline environments, such as the extracellular spaces, we hypothesize that in immunodeficient mice Δgcs1proliferates inside AMs. Indeed, we found that depletion of AMs significantly improved Tgε26 mouse survival and decreased the dissemination of Δgcs1cells to the central nervous system. Thus, these results suggest that the growth of Δgcs1in immunodeficient mice is maintained within AMs. This study highlights the hypothesis that AMs may exacerbateC. neoformansinfection in conditions in which there is severe host immunodeficiency.
Occupation and adult onset of rhinitis in the general population
Authors: Radon K , Gerhardinger U , Schulze A , Zock J-P , Norback D , Toren K , Jarvis D , Held L , Heinrich J , Leynaert B , Nowak D , Kogevinas M ,   for the occupational group of the ECRHS study
Published: July 2007

Objectives:

Occupational exposures have been associated with an increased risk of new-onset rhinitis in apprentices. However, population-based prospective data are scarce and do not cover new onset of rhinitis later in life. The authors studied the association between occupational exposure and adult onset of rhinitis prospectively.

Methods:

The data of 4994 participants (age at follow-up 28–57 years) from 27 centres of the European Community Respiratory Health Survey II who were symptom-free at baseline were analysed. As outcome at follow-up self-reported (a) nasal allergies (“allergic rhinitis”) and (b) runny, blocked nose for 12 months a year (“perennial rhinitis”) were used. Occupational exposures at any time during follow-up were defined by job title.

Results:

The cumulative incidence of allergic rhinitis, perennial rhinitis and both conditions was 12%, 11% and 3%, respectively. Compared to office workers, male medical professionals were at increased risk of new onset of allergic rhinitis (OR 3.0; 95% CI 1.4 to 6.4). Odds ratios were reduced in metal workers not involved in metal making or treating (0.3; 95% CI 0.1 to 0.7). For perennial rhinitis ORs were significantly increased in cleaners (1.4; 95% CI 1.0 to 2.1).

Conclusions:

Cleaners and medical professionals may be at increased risk for adult-onset rhinitis.
Mountain pine beetle associated blue-stain fungi cause lesions on jack pine, lodgepole pine, and lodgepole × jack pine hybrids in Alberta
Authors: Rice Adrianne V. , Thormann Markus N. , Langor David W.
Published: July 2007

Mountain pine beetles ( Dendroctonus ponderosae Hopkins; (MPB)) have spread into lodgepole × jack pine hybrid ( Pinus contorta Douglas × Pinus banksiana Lambert) forests in Alberta and are predicted to spread into jack pine forests. Their success in these forests is uncertain but will be influenced by multiple factors, including the ability of their associated blue-stain fungi to colonize the trees and the health of the encountered trees. Healthy and dwarf mistletoe infected pines at three sites across Alberta (one site per pine species) were inoculated with three isolates each of Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel, de Beer and Wingfield and Ophiostoma montium (Rumbold) von Arx. Both fungi grew and caused lesions on all hosts, suggesting that MPB will not be limited by a lack of fungal growth. Both fungi caused longer lesions in jack and hybrid pines than in lodgepole pines, indicating that susceptibility varies among hosts and is greater in the novel systems than in the co-evolved one. G. clavigera caused longer lesions than O. montium in hybrids and lodgepole pines, while the two species caused similar-sized lesions on jack pine. Intraspecific variation was high in G. clavigera, with one isolate producing much shorter lesions than the other two. Dwarf mistletoe infestation had little effect on infection lesion length.
An altered root exudation pattern through mycorrhization affecting microconidia germination of the highly specialized tomato pathogen Fusarium oxysporum f. sp. lycopersici (Fol) is not tomato specific but also occurs in Fol nonhost plants
Authors: Scheffknecht Stephan , St-Arnaud Marc , Khaosaad Thanasan , Steinkellner Siegrid , Vierheilig Horst
Published: July 2007

The effect of root exudates from plants colonized or noncolonized by the arbuscular mycorrhizal fungus Glomus mosseae on microconidia germination of Fusarium oxysporum f. sp. lycopersici (Fol) was studied. Root exudates from the Fol-host tomato and root exudates from Fol nonhost plants were tested. Root exudates from all tested plants stimulated microconidia germination. Mycorrhization increased the stimulatory effect exhibited by the root exudates from the Fol host tomato and from all Fol nonhost plants, showing that similar changes occur in the root exudates of all plants after mycorrhization.
Engineering nitrogen use efficiency with alanine aminotransferase
Authors: Good Allen G. , Johnson Susan J. , De Pauw Mary , Carroll Rebecka T. , Savidov Nic , Vidmar John , Lu Zhongjin , Taylor Gregory , Stroeher Virginia
Published: July 2007

Nitrogen (N) is the most important factor limiting crop productivity worldwide. The ability of plants to acquire N from applied fertilizers is one of the critical steps limiting the efficient use of nitrogen. To improve N use efficiency, genetically modified plants that overexpress alanine aminotransferase (AlaAT) were engineered by introducing a barley AlaAT cDNA driven by a canola root specific promoter (btg26). Compared with wild-type canola, transgenic plants had increased biomass and seed yield both in the laboratory and field under low N conditions, whereas no differences were observed under high N. The transgenics also had increased nitrate influx. These changes resulted in a 40% decrease in the amount of applied nitrogen fertilizer required under field conditions to achieve yields equivalent to wild-type plants.
Calcium oxalate crystals in tribe Galegeae (Leguminosae) including foliar crystal macropattern development in Caragana frutex
Authors: Lersten Nels R. , Horner Harry T.
Published: July 2007

Galegeae was reported in 1987 to be unique among papilionoid tribes because calcium oxalate crystals were shown to be mostly lacking. We surveyed leaves of 45 species from 20 genera, mostly from herbarium specimens. A living species ( Caragana frutex (L.) K. Koch) with crystals was also studied developmentally, important because only three other species have been similarly studied. Herbarium specimens and various stages of C. frutex leaflets were bleached, dehydrated, cleared in alcohol–xylol, and made permanent. Freehand sections of C. frutex were mounted in glycerine. Crystals were detected microscopically and are generally lacking among Galegeae genera. This supports tentative contemporary opinion that the tribe is unnatural. Crystals provide new, potentially useful systematic data. Variously differing unicellular trichomes were also described in the survey. Caragana frutex leaflets have a previously undescribed macropattern development: crystals form only along veins, except for late-season prisms in scattered palisade parenchyma. Crystals form progressively base to apex, first following along successive major veins from midvein to margin and then in later-developing smaller veins, progressing acropetally. The midvein remains almost crystal-free until leaflets are at or near full size. Crystal macropattern development in C. frutex leaflets suggests that crystallization may be influenced by the whole organ, as well as by individual cells.
Plant glutathione transferases — a decade falls short
Authors: Basantani Mahesh , Srivastava Alka
Published: July 2007

The glutathione transferase (GST) superfamily in plants has been subdivided into eight classes, seven of which (phi, tau, zeta, theta, lambda, dehydroascorbate reductase, and tetrachlorohydroquinone dehalogenase) are soluble and one is microsomal. Since their identification in plants in 1970, these enzymes have been well established as phase II detoxification enzymes that perform several other essential functions in plant growth and development. These enzymes catalyze nucleophilic conjugation of the reduced form of the tripeptide glutathione to a wide variety of hydrophobic, electrophilic, and usually cytotoxic substrates. In plants, the conjugated product is either sequestered in the vacuole or transferred to the apoplast. The GSTs of phi and tau classes, which are plant-specific and the most abundant, are chiefly involved in xenobiotic metabolism. Zeta- and theta-class GSTs have very restricted activities towards xenobiotics. Theta-class GSTs are glutathione peroxidases and are involved in oxidative-stress metabolism, whereas zeta-class GSTs act as glutathione-dependent isomerases and catalyze the glutathione-dependent conversion of maleylacetoacetate to fumarylacetoacetate. Zeta-class GSTs participate in tyrosine catabolism. Dehydroascorbate reductase- and lambda-class GSTs function as thioltransferases. Microsomal-class GSTs are members of the MAPEG (membrane-associated proteins in eicosanoid and glutathione metabolism) superfamily. A plethora of studies utilizing both proteomics and genomics approaches have greatly helped in revealing the functional diversity exhibited by these enzymes. The three-dimensional structure of some of the members of the family has been described and this has helped in elucidating the mechanism of action and active-site amino-acid residues of these enzymes. Although a large amount of information is available on this complex enzyme superfamily, more research is necessary to answer additional questions such as, why are phi- and tau-class GSTs more abundant than GSTs from other classes? What functions do phi- and tau-class GSTs perform in plant taxa other than angiosperms? Do more GST classes exist? Future studies on GSTs should focus on these aspects.
Morphological and molecular studies on Resinicium s. str.
Authors: Nakasone Karen K.
Published: July 2007

Resinicium Parmasto is typified by Resinicium bicolor (Alb. & Schwein.: Fr.) Parm., (Hymenochaetales, Basidiomycota), a readily recognized and widely distributed corticioid, lignicolous species in the northern hemisphere. Five new species of Resinicium closely allied to R. bicolor from the Caribbean region are described and illustrated: Resinicium confertum Nakasone, sp. nov., Resinicium monticola Nakasone, sp. nov., Resinicium mutabile Nakasone, sp. nov., Resinicium rimulosum Nakasone, sp. nov., and Resinicium tenue Nakasone, sp. nov. In addition, R. bicolor and Resinicium friabile Hjortstam & Melo are redescribed and illustrated. Sequence analyses of the internal transcribed spacer region support the recognition of the new taxa. Further, nuclear small subunit ribosomal RNA sequence data support the recognition of two groups of Resinicium species: the Resinicium s. str. group, including R. bicolor, and the Resinicium s.l. group that includes Resinicium furfuraceum (Bres.) Parm. The genus Resinicium is redefined and a key to the Resinicium s. str. species is provided.
Identification of the full-length Hs1pro-1 coding sequence and preliminary evaluation of soybean cyst nematode resistance in soybean transformed with Hs1pro-1 cDNA
Authors: McLean Michael D. , Hoover Gordon J. , Bancroft Bonnie , Makhmoudova Amina , Clark Shawn M. , Welacky Tom , Simmonds Daina H. , Shelp Barry J.
Published: July 2007

The Hs1pro-1 gene reportedly confers resistance to the beet cyst nematode in wild beet and sugar beet. Here, we tested the hypothesis that Hs1pro-1 confers resistance in soybean against the soybean cyst nematode (SCN). The full-length Hs1pro-1 coding sequence, which encodes a predicted polypeptide of 490 amino acids, was first acquired then expressed in ‘Westag’ soybean using a constitutive octopine synthase – mannopine synthase promoter. Thirty T0 lines that successfully expressed the Hs1pro-1 gene, as indicated by both polymerase chain reaction and reverse transcriptase – polymerase chain reaction analyses, were generated. Bioassay of the T1 progeny from these lines revealed that only five T0 lines grew normally and exhibited a high degree of SCN resistance. On average, these T1 transgenic progeny were about 70% more resistant to SCN than susceptible control cultivars. These preliminary data suggest that Hs1pro-1 is a promising candidate for genetically engineering SCN resistance in elite, locally adapted soybean cultivars.
Diversity of calcium oxalate crystals in Cactaceae
Authors: Hartl Walter P. , Klapper Helmut , Barbier Bruno , Ensikat Hans Jürgen , Dronskowski Richard , Müller Paul , Ostendorp Gertrud , Tye Alan , Bauer Ralf , Barthlott Wilhelm
Published: July 2007

The occurrence of various types of calcium oxalate crystals was studied in 251 species and subspecies of Cactaceae to determine whether they are useful characters for Cactaceae systematics. Crystal hydration states were identified by X-ray powder diffraction and polarizing microscopy as monoclinic calcium oxalate monohydrate (COM) and tetragonal calcium oxalate dihydrate (COD). Ninety-eight percent of taxa studied contained either COM or COD crystals, or both. Different morphologies of crystals were further defined by light microscopy and scanning electron microscopy as druses, raphides, styloids (prisms), and crystal sand. In particular, the preponderance of one of the hydration states (COM or COD) was characteristic for certain Cactus subfamilies. Data showed that in Pereskioideae, Maihuenioideae, and Opuntioideae COM is predominant, while in Cactoideae COD prevails. In the remainder of Cactoideae, the crystals were quite variable. In tribe Hylocereeae, many species form both COM and COD as well. In the genera Hylocereus , Epiphyllum , Selenicereus , and Weberocereus , COM forms were almost exclusively represented by raphides together with different crystal forms in their epidermal cells. In the remainder of the Cactoideae, crystals did not follow any observable patterns. Development of crystallographic standards for identifying crystal forms microscopically is proposed for future crystal studies.
Magnetic fabric studies of the Nipissing sill province and Senneterre dykes, Canadian Shield, and implications for emplacement
Authors: Palmer H C , Ernst R E , Buchan K L
Published: July 2007

The 2.21 Ga Nipissing diabase sills intrude the Huronian Supergroup of the Southern Province. Coeval Senneterre dykes in the adjacent portion of the Superior Province are potential feeders for the sills. Anisotropy of magnetic susceptibility (AMS) data were obtained from both of these units to study flow patterns and test emplacement models. The sills exhibit three distinct paleomagnetic directions that are likely primary and represent a time-correlation tool within the magmatic event. Two of the three directions are also found in Senneterre dykes. Sites in the northern Cobalt Embayment carry an N1 (reverse) paleomagnetic signature. They possess maximum AMS axes that trend north-northwest–south-southeast, interpreted as the direction of magma emplacement. In one area, the data rule out a cone sheet emplacement mechanism. The N3 paleomagnetic signature is restricted to a sill and (or) dyke-like bodies near Lake Timiskaming, where the AMS axes are dominantly north-northwest–south-southeast, similar to that of the nearby N1 (reverse) sites. Sites in a geographically restricted area farther south carry an N1 (normal) paleomagnetic direction. The AMS patterns in these sites exhibit very poor within- and between-site consistency, compatible with the magma having crystallized statically in this volumetrically minor magmatic pulse. In the Sudbury – Elliot Lake area, the Nipissing diabase is deformed, and outcrops exhibit east–west elongation parallel to the fold axes of the enclosing Huronian sedimentary rocks. AMS fabrics are interpreted as reflecting this deformation rather than primary magmatic flow. Three of eight Senneterre dyke sites show horizontal flow patterns, whereas the remainder have more complicated AMS patterns.
Tectonic evolution of the Yaoundé segment of the Neoproterozoic Central African Orogenic Belt in southern Cameroon
Authors: Mvondo Hubert , Owona Sébastien , Ondoa Joseph Mvondo , Essono Jean
Published: July 2007

The deformation history of the Neoproterozoic Central African Orogenic Belt in southern Cameroon is well recorded in the low- to high-grade rocks outcropping in the area around Yaoundé. The fabrics in these rocks are consistent with two main ductile deformation events D1 and D2. D1 predated emplacement of calc-alkaline dioritic bodies and caused the formation of nappes that resulted in high-pressure granulite metamorphism of soft sediments. A strong overprinting of these nappes during D2 symmetric extension, probably associated with large-scale foliation boudinage and (or) gneissic doming and intense magmatic underplating, gave rise to regional flat-lying fabrics. The latter were further buckled by D3 and D4 folding phases defining a vertical constriction occurring with a major east–west to NW–SE shortening direction. The corresponding F3 and F4 folds trend north–south to NE–SW and east–west to NW–SE, respectively, and represent the main regional strain patterns. Based on the east–west to NW–SE maximum shortening orientation indicated by F3 folds, it is proposed that the nappe-stacking phase D1 occurred in the same direction. The deformation history in the area can thus be described as corresponding principally to alternating east–west to NW–SE contractions and north–south to NE–SW orogenic-parallel extensions. At the regional scale, this could be due to the Transaharan east–west collisional system.