bluuebunny/crossref_metadata_2025 huggingface dataset:
MMP‐21 is expressed by macrophages and fibroblasts in vivo and in culture
Authors: Skoog Tiina , Ahokas Katja , Orsmark Christina , Jeskanen Leila , Isaka Keiichi , Saarialho‐Kere Ulpu
Published: August 2006

Abstract:  Matrix metalloproteinase (MMP)‐21 and MMP‐26 (matrilysin‐2) are two recently cloned epithelial metalloproteases. Here we examined their expression in various benign skin disorders, in which macrophages and fibroblasts have been implicated as well as in cultures of these cells. Expression of MMP‐21 was detected by immunohistochemistry in a subset of macrophages of granulomatous skin lesions and in fibroblasts in dermatofibromas. MMP‐21 mRNA was found in THP‐1, U937, HEL 299 and Hs68 cells. Furthermore, MMP‐21 protein was detected by immunohistochemistry in cultures of the same cell lines. In culture MMP‐21 was upregulated by phorbol myristate acetate in THP‐1 cells and by retinoic acid (RA) in U937 cells, and downregulated by transforming growth factor beta 1 (TGF‐β1) in HEL 299 as assessed by Taqman quantitative polymerase chain reaction (PCR). Expression of MMP‐26 was detected by immunohistochemistry in granulomatous skin diseases and actinic elastosis. MMP‐26 at both mRNA and protein levels was only found in HEL 299 cells. In culture it was downregulated by TGF‐β1, RA and IL‐1β as assessed by Taqman quantitative PCR. Our results suggest these two novel MMPs are not only associated with cancer but may be important in connective tissue remodelling and pathobiology of various benign skin disorders.
Single amino acid residue changes in subsite − 1 of inulosucrase from Lactobacillus reuteri 121 strongly influence the size of products synthesized
Authors: Ozimek Lukasz K. , Kralj Slavko , Kaper Thijs , van der Maarel Marc J. E. C. , Dijkhuizen Lubbert
Published: August 2006

Bacterial fructansucrase enzymes belong to glycoside hydrolase family 68 and catalyze transglycosylation reactions with sucrose, resulting in the synthesis of fructooligosaccharides and/or a fructan polymer. Significant differences in fructansucrase enzyme product specificities can be observed, i.e. in the type of polymer (levan or inulin) synthesized, and in the ratio of polymer versus fructooligosaccharide synthesis. The Lactobacillus reuteri 121 inulosucrase enzyme produces a diverse range of fructooligosaccharide molecules and a minor amount of inulin polymer [with β(2–1) linkages]. The three‐dimensional structure of levansucrase (SacB) of Bacillus subtilis revealed eight amino acid residues interacting with sucrose. Sequence alignments showed that six of these eight amino acid residues, including the catalytic triad (D272, E523 and D424, inulosucrase numbering), are completely conserved in glycoside hydrolase family 68. The other three completely conserved residues are located at the − 1 subsite (W271, W340 and R423). Our aim was to investigate the roles of these conserved amino acid residues in inulosucrase mutant proteins with regard to activity and product profile. Inulosucrase mutants W340N and R423H were virtually inactive, confirming the essential role of these residues in the inulosucrase active site. Inulosucrase mutants R423K and W271N were less strongly affected in activity, and displayed an altered fructooligosaccharide product pattern from sucrose, synthesizing a much lower amount of oligosaccharide and significantly more polymer. Our data show that the − 1 subsite is not only important for substrate recognition and catalysis, but also plays an important role in determining the size of the products synthesized.
Karyotypes of parasitic Hymenoptera: Diversity, evolution and taxonomic significance
Authors: GOKHMAN VLADIMIR E.
Published: August 2006

Haploid chromosome numbers (n) of parasitic Hymenoptera (= traditional Parasitica + Chrysidoidea) vary from 2 to 23. However, this range can be subdivided into three intervals with n= 14–23 (less derived parasitic wasps, e.g., some Ichneumonidae and Braconidae as well as Gasteruptiidae), 8–13 (many other parasitic Hymenoptera) and 2–7 (Dryinidae, the majority of Chalcidoidea and some advanced Braconidae, e.g. Aphidiinae). The symmetric karyotype with a relatively high chromosome number (n= 14–17) and the prevalence of biarmed chromosomes must be considered as a groundplan feature of parasitic Hymenoptera. Independent reductions of chromosome numbers (n≤ 10–11) occurred in some groups of the superfamily Ichneumonoidea as well as in the common ancestor of the Proctotrupoidea sensu lato, Ceraphronoidea, Cynipoidea and Chalcidoidea. Further multiple decreases in chromosome numbers (n≤ 4–6) took place in some Braconidae, various lineages of the superfamily Chalcidoidea as well as in the family Dryinidae. Two main trends prevailed in the karyotype evolution of parasitic wasps: the reduction of chromosome numbers (mainly due to tandem fusions and less frequently due to centric ones) and karyotypic dissymmetrization (through an increase in size differentiation of chromosomes and/or in the share of acrocentrics in a chromosome set). Although karyotypic features of parasitic Hymenoptera can be used for solving taxonomic problems at various levels, this method is the most effective at the species level.
Enzymatic properties of phenoloxidase from Pieris rapae (Lepidoptera) larvae
Authors: XUE CHAO‐BIN , LUO WAN‐CHUN , CHEN QING‐XI , WANG QIN , KE LI‐NA
Published: August 2006

The kinetic parameters of partially purified phenoloxidase (PO, EC. 1.14.18.1) from the 5th instar larvae of Pieris rapae (Lepidoptera) were determined, using L‐3, 4‐dihydroxyphenylalanine (L‐DOPA) as substrate. The optimal pH and temperature of the enzyme for the oxidation of L‐DOPA were determined to be at pH 7.0 and at 42°C, respectively. The enzyme was stable between pH 6.5 and 7.4 and at temperatures lower than 37°C. At pH 6.8 and 37°C, the Michaelis constant (Km) and maximal velocity (Vm) of the enzyme for the oxidation of L‐DOPA were determined to be 0.80 μmol/L and 1.84 μmol/ L/min, respectively. Tetra‐hexylresorcinol and 4‐dodecylresorcinol effectively inhibited activity of phenoloxidase and this inhibition was reversible and competitive, with the IC50 of 1.50 and 1.12 μmol/L, respectively. The inhibition constants were estimated to be 0.50 and 0.47 μmol/L, respectively.
Female moths of cotton bollworm (Lepidoptera: Noctuidae) captured by waterbasin traps baited with synthetic female sex pheromone
Authors: SU JIAN‐WEI , WANG HONG‐TUO , GE FENG
Published: August 2006

Cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is one of the most important pest insects in cotton fields in China. Female moths were captured by waterbasin traps with a synthetic female sex pheromone blend in cotton fields over three years. The blend contained (Z)‐11‐hexadecenal and (Z)‐9‐hexadecenal with a ratio of 97:3. Each pheromone dispenser was impregnated with 2.0 mg of pheromone blend and 0.2 mg of antioxidant dissolved with 0.1 mL of hexane, and there was a control dispenser with a similar amount of antioxidant and solvent only. Waterbasin traps were deployed in three configurations in the fields. ‘A’ was pheromone traps only, ‘B’ was both pheromone and control traps, ‘C’ was control traps only. (i) In four plots of ‘A’, the average weekly female catch was 1.5, and more females were captured by centrally located pheromone traps, (ii) In three plots of ‘Brsquo;, control traps also captured female as well as male moths, but average weekly female catches of control traps was significantly lower than that in pheromone‐baited traps. (iii) There were significant linear relationships between the average weekly female catch and the corresponding layer in pheromone‐baited traps in both ‘A’ and ‘B’ plots, and in quadratic equations in control in ‘B’ plots. (iv) With the increase of the interval of traps, average weekly female catches per trap increased but average weekly female catches per hectare decreased. (v) Among the female moths captured by pheromone traps, 88.3% were mated female moths which each containing 1.46 spermatophores, while in control traps 86.9% of the mated female moths had 0.90 spermatophores. There was a significant difference between the average numbers of spermatophores of mated females in pheromone traps and in controls.
The discovery of the genus Indabracon van Achterberg (Hymenoptera: Braconidae: Braconinae) in China, with description of one new species
Authors: YANG JIAN‐QUAN , CHEN JIA‐HUA , LIU JUAN‐JUAN
Published: August 2006

The genus Indabracon van Achterberg, 1993 was discovered in China, and one new species (I. bicolor sp. nov.) of this genus is fully described and illustrated in the present paper. A key to the species of the genus is provided. The new species is similar to the Indian species I. trimaculatus (Cameron, 1900) structurally, but differs for example by: basal half of pterostigma yellow; apical half dark brown; smooth postero‐lateral area of the third tergite rather small; propodeum with belt of setae dorsally and lamelliform carinae posteriorly; ovipositor sheath approximately 0.60 times the forewing, somewhat longer than metasoma; the first tergite surface distinctly carinate and rugose, especially in its medial area and laterally. The type specimens are deposited in the Beneficial Insects Lab, College of Plant Protection, Fujian Agriculture & Forestry University, China.
Forearm plethysmography in the assessment of vascular tone and resistance vasculature design: new methodological insights
Authors: Mathiassen O. N. , Buus N. H. , Olsen H. W. , Larsen M. L. , Mulvany M. J. , Christensen K. L.
Published: August 2006

Aim:  High peripheral resistance and structural alteration in resistance arteries are central phenomena in essential hypertension and have been widely examined by forearm venous occlusion plethysmography; at rest for studying vascular tone, and during reactive hyperaemia for studying vascular structure. This work concerns the influence of venous pressure on hyperaemic vascular resistance (Rmin), the reproducibility of hyperaemic and resting vascular resistances (Rrest) and the relation between forearm and total peripheral vascular resistance (TPR).

Methods:  In four healthy subjects, intravenous and intra‐arterial blood pressures were measured simultaneously with plethysmographic recordings of hyperaemic and resting forearm blood flows. Reproducibility was examined in 15 young and 14 middle‐aged healthy subjects and in 21 untreated hypertensive patients.

Results:  R
min remained low in the first recorded cardiac cycle, but rose in the second, even though corrected for the venous pressure rise, suggesting vascular tone recovery along with venous congestion. Between‐day reproducibility of Rmin was high in middle‐aged normotensive (8.7%) and hypertensive subjects (10.6%), but Rmin fell significantly between successive days in the young subjects. Rrest correlated with TPR, but required up to 40 min to reach steady state and showed high day‐to‐day variation in young (21.8%) and hypertensive subjects (16.2%).

Conclusions:  During hyperaemia, vascular resistance should be measured in the first cardiac cycle following venous occlusion to minimize influences of venous pressure rise and possible tone recovery. Rrest seems to reflect TPR. About 20 subjects may be needed to detect 15% changes between days in Rrest, fewer when concerning Rmin and TPR.
Effects of hearing loss and spectral shaping on identification and neural response patterns of stop-consonant stimuli
Authors: Harkrider Ashley W. , Plyler Patrick N. , Hedrick Mark S.
Published: August 2006

In order to determine the effects of hearing loss and spectral shaping on a dynamic spectral speech cue, behavioral identification and neural response patterns of stop-consonant stimuli varying along the /b-d-g/ place-of-articulation continuum were measured from 11 young adults (mean age=27 years) and 10 older adults (mean age=55.2 years) with normal hearing, and compared to those from 10 older adults (mean age=61.3 years) with mild-to-moderate hearing impairment. Psychometric functions and N1-P2 cortical evoked responses were obtained using consonant-vowel (CV) stimuli with frequency-independent (unshaped) amplification as well as with frequency-dependent (shaped) amplification that enhanced F2 relative to the rest of the stimulus. Results indicated that behavioral identification and neural response patterns of stop-consonant CVs were affected primarily by aging and secondarily by age-related hearing loss. Further, enhancing the audibility of the F2 transition cue with spectrally shaped amplification partially reduced the effects of age-related hearing loss on categorization ability but not neural response patterns of stop-consonant CVs. These findings suggest that aging affects excitatory and inhibitory processes and may contribute to the perceptual differences of dynamic spectral cues seen in older versus young adults. Additionally, age and age-related hearing loss may have separate influences on neural function.
Effect of noise on the detectability and fundamental frequency discrimination of complex tones
Authors: Gockel Hedwig , Moore Brian C. J. , Plack Christopher J. , Carlyon Robert P.
Published: August 2006

Percent correct performance for discrimination of the fundamental frequency (F0) of a complex tone was measured as a function of the level of a background pink noise (using fixed values of the difference in F0, ΔF0) and compared with percent correct performance for detection of the complex tone in noise, again as a function of noise level. The tone included some low, resolvable components, but not the fundamental component. The results were used to test the hypothesis that the worsening in F0 discrimination with increasing noise level was caused by the reduced detectability of the tone rather than by reduced precision of the internal representation of F0. For small values of ΔF0, the hypothesis was rejected because measured performance fell below that predicted by the hypothesis. However, this was true only for high noise levels, within 2–4.5dB of the level required for masked threshold. The results indicate that the mechanism for extracting the F0 of a complex tone with resolved harmonics is remarkably robust. They also indicate that adding a background noise to a complex tone containing resolved harmonics is not a good means for equating its pitch salience with that of a complex tone containing only unresolved harmonics.
Frame bulk modulus of porous granular marine sediments
Authors: Kimura Masao
Published: August 2006

Frame bulk modulus is important for analyzing the acoustic wave propagation in porous water-saturated marine sediments such as sands. Previous measurements of the longitudinal wave velocities in air-saturated glass beads of uniform grain size showed that the longitudinal wave velocity increased with the grain size. This result cannot be explained by using a classical contact theory such as the Hertz-Mindlin model. It was speculated that this phenomenon is due to the effect of air elasticity between the grains. In this study, the longitudinal and shear wave velocities in samples of vacuum-, air-, and water-saturated glass beads as well as beach sands at a lower stress were measured. The results obtained were used to estimate the corresponding values of the frame bulk modulus. In the water-saturated samples, these values are about 109Pa at a frequency of 500kHz and about ten times greater than those in air-saturated samples at a frequency of 11.8kHz. The grain size dependence was also observed. These measurements are explained in terms of the effect of fluid elasticity at the grain-to-grain contact in the context of a modified gap stiffness model.
Improved theory of acoustic elementary edge waves
Authors: Ufimtsev Pyotr Ya.
Published: August 2006

The high-frequency asymptotic theory of acoustic edge waves [P. Ya. Ufimtsev, J. Acoust. Soc. Am. 86, 463–74 (1989)] is well suited for investigation of backscattering from perfectly reflecting (soft or hard) three-dimensional objects with edges. However, it needs to be improved for calculation of forward scattering, especially in the directions grazing to the edge faces, where it predicts infinite values. The present paper removes this singularity by the appropriate choice of the so-called uniform component of the surface field. It is defined here as the field induced on the half-plane tangential to the illuminated face of the scattering edge (and to the edge itself). An improved theory of elementary edge waves is proposed, which is valid for all directions of scattering, including the forward grazing directions.
Classification of communication signals of the little brown bat
Authors: Melendez Karla V. , Jones Douglas L. , Feng Albert S.
Published: August 2006

Little brown bats, Myotis lucifugus, are known for their ability to echolocate and utilize their echolocation system to navigate, and locate and identify prey. Their echolocation signals have been characterized in detail but their communication signals are less well understood despite their widespread use during social interactions. The goal of this study was to develop an automatic classification algorithm for characterizing the communication signals of little brown bats. Sound recordings were made overnight on five individual male bats (housed separately from a large group of captive bats) for 7 nights, using a bat detector and a digital recorder. The spectral and temporal characteristics of recorded sounds were first analyzed and classified by visual observation of a call’s temporal pattern and spectral composition. Sounds were later classified using an automatic classification scheme based on multivariate statistical parameters in MATLAB. Human- and machine-based analysis revealed five discrete classes of bat’s communication signals: downward frequency-modulated calls, steep frequency-modulated calls, constant frequency calls, broadband noise bursts, and broadband click trains.
Lexical frequency and voice assimilation
Authors: Ernestus Mirjam , Lahey Mybeth , Verhees Femke , Baayen R. Harald
Published: August 2006

Acoustic duration and degree of vowel reduction are known to correlate with a word’s frequency of occurrence. The present study broadens the research on the role of frequency in speech production to voice assimilation. The test case was regressive voice assimilation in Dutch. Clusters from a corpus of read speech were more often perceived as unassimilated in lower-frequency words and as either completely voiced (regressive assimilation) or, unexpectedly, as completely voiceless (progressive assimilation) in higher-frequency words. Frequency did not predict the voice classifications over and above important acoustic cues to voicing, suggesting that the frequency effects on the classifications were carried exclusively by the acoustic signal. The duration of the cluster and the period of glottal vibration during the cluster decreased while the duration of the release noises increased with frequency. This indicates that speakers reduce articulatory effort for higher-frequency words, with some acoustic cues signaling more voicing and others less voicing. A higher frequency leads not only to acoustic reduction but also to more assimilation.
Vibroacoustic analysis of rectangular plates with elastic rotational edge restraints
Authors: Li W. L.
Published: August 2006

This investigation deals with the vibration of and the acoustic radiation from a simply supported rectangular plate with elastic restraints against edge rotations. The displacement of the plate is first sought as a series expansion in terms of the beam functions. Each of the beam functions is then expressed as the linear combination of a Fourier sine series and a complementary sufficiently smooth function that is introduced to ensure and improve the convergence of the Fourier series expansion. To facilitate the acoustic analysis, the plate displacement is eventually simplified to a standard Fourier sine series. The modal and acoustic characteristics of square plates are studied for different restraining stiffnesses and configurations. It is shown that the modes of the restrained plates can be considerably different from those in the simply supported case, so are the corresponding modal radiation efficiencies. The proposed method is generally applicable to rectangular plates elastically restrained along any edge(s), and the acoustic calculations are valid for an arbitrary acoustic or structural (modal) wave number.
Wideband multichannel time-reversal processing for acoustic communications in highly reverberant environments
Authors: Candy James V. , Chambers David H. , Robbins Christopher L. , Guidry Brian L. , Poggio Andrew J. , Dowla Farid , Hertzog Claudia A.
Published: August 2006

The development of multichannel time-reversal (T/R) processing techniques continues to progress rapidly especially when the need to communicate in a reverberant environment is critical. The underlying T/R concept is based on time-reversing the Green’s function characterizing the uncertain communications channel mitigating the deleterious dispersion and multipath effects. In this paper, attention is focused on two major objectives: (1) wideband communications leading to a time-reference modulation technique; and (2) multichannel acoustic communications in two waveguides: a stairwell and building corridors with many obstructions, multipath returns, severe background noise, disturbances, and long propagation paths (∼180ft) including disruptions (bends). It is shown that T/R receivers are easily extended to wideband designs. Acoustic information signals are transmitted with an eight-element array to two receivers with a significant loss in signal levels due to the propagation environment. The results of the new wideband T/R processor and modulation scheme demonstrate that the overall performance for both high (24-bit) and low (1-bit) bit level analog-to-digital converter designs. These results are validated by performing proof-of-principle acoustic communications experiments in air. It is shown that the resulting T/R receivers are capable of extracting the transmitted coded sequence from noisy microphone array measurements with zero-bit error.
Source localization in the presence of gross sediment uncertainties
Authors: Baer Ralph N. , Collins Michael D.
Published: August 2006

The possibility of determining the location of an acoustic source in the presence of gross sediment uncertainties is investigated. Promising results are obtained using focalization, which involves constructing ambiguity surfaces corresponding to randomly selected realizations of the sediment parameters. Due to a parameter hierarchy in which the source location is more important than environmental parameters, it is often possible to reliably determine the source position without determining the correct sediment parameters. The examples involve multiple sediment layers, with sound speeds and range-dependent thicknesses that are unknown. An example that includes both sediment uncertainties and internal waves is also included.
Comment on “Auditory-nerve first-spike latency and auditory absolute threshold: A computer model” [J. Acoust. Soc. Am.119, 406–417 (2006)]
Authors: Krishna B. Suresh
Published: August 2006

A recent paper by Meddis [J. Acoust. Soc. Am. 119, 406–417 (2006)] shows that an existing model of the auditory nerve [Meddis and O’Mard, J. Acoust. Soc. Am. 117, 3787–3798 (2005)] is consistent with experimentally-measured first-spike latencies in the auditory nerve [Heil and Neubauer, J. Neurosci. 21, 7404–7415 (2001)]. The paper states that this consistency emerges because in the model, the calcium concentration inside the inner hair cell builds up over long periods of time (up to at least 200ms) during tone presentation. It further states that integration over long time-scales happens despite the very short time constants (<1ms) used for the calcium dynamics. This letter demonstrates that these statements are incorrect. It is shown by simulation that calcium concentration inside the hair cell stage of the Meddis model rapidly reaches a steady state within a few milliseconds of a stimulus onset, exactly as expected from the short time-constant in the simple first-order differential equation used to model the calcium concentration. The success of the Meddis model in fitting experimental data actually confirms earlier results [Krishna, J. Comput. Neurosci. 13, 71–91 (2002a)] that show that the experimental data are a natural result of stochasticity in the synaptic events leading up to spike-generation in the auditory nerve; integration over long time scales is not necessary to model the experimental data.
Image-source method and truncation of a series expansion of the integral solution—Case of an angular sector in two dimensions
Authors: Martin Vincent , Guignard Thomas
Published: August 2006

The acoustic ray method rests upon specular reflection, an intuition that gives access only to an approximation of the solution by not taking into account the parts of the field called diffusion and diffraction. In trying to understand rationally the roots of the approximation, it has appeared that the image source could be generalized and also that errors may be partially due to missing generalized sources, already in elementary geometries such as obtuse angles. Indeed, it is shown that the exact integral solution of a two dimensional acoustic problem, expressed as a series of terms, could be seen as the contribution of the different image sources, via a partial use of the Huygens’ principle. With the correspondence between the terms and the image sources shown, the missing sources would appear and the method would thereby be refined.
Beam pattern calculation for optimization of broadband array transducers
Authors: Wang Qiongbo , Guo Ningqun , Du Hejun , Huang Weimin
Published: August 2006

Broadband array transducers are widely used in medical imaging systems, and their beam patterns determine the imaging quality. The characteristics of the beam patterns such as mainlobe beamwidth and sidelobe levels are the major criteria for designing and optimizing sparse array systems. The spatial impulse response approach can be used to calculate the beam patterns rigorously in both near field and far field. However, it is time consuming due to the high sampling frequency required, and thus not suitable for array optimization. On the other hand, assuming the array elements to be omnidirectional point sources the field calculation can be much simplified and fast but at the expense of poor accuracy. This paper presents a modified model that has the accuracy comparable to that from the impulse response model while keeping the efficiency close to that of the simple point source model. The developed algorithm is particularly suitable for stochastic methods for two-dimensional (2D) sparse arrays design and optimization such as genetic algorithms (GA), in which the iterative beam pattern calculation dominates the optimization program running time.
Efficient array beam forming by spatial filtering for ultrasound B-mode imaging
Authors: Kim Kang-Sik , Liu Jie , Insana Michael F.
Published: August 2006

This paper proposes an efficient array beam-forming method using spatial matched filtering (SMF) for ultrasonic imaging. In the proposed method, ultrasonic waves are transmitted from an array subaperture with fixed transmit focus as in conventional array imaging. At receive, radio frequency echo signals from each receive channel are passed through a spatial matched filter that is constructed based on the system transmit-receive spatial impulse response. The filtered echo signals are then summed without time delays. The filter concentrates and spatially registers the echo energy from each element so that the pulse-echo impulse response of the summed output is focused with acceptably low side lobes. Analytical beam pattern analysis and simulation results using a linear array show that this spatial filtering method can improve lateral resolution and contrast-to-noise ratio as compared with conventional dynamic receive focusing (DRF) methods. Experimental results with a linear array are consistent but point out the need to address additional practical issues. Spatial filtering is equivalent to synthetic aperture methods that dynamically focus on both transmit and receive throughout the field of view. In one common example of phase aberrations, the SMF method was degraded to a degree comparable to conventional DRF methods.
Spectral-peak selection in spectral-shape discrimination by normal-hearing and hearing-impaired listeners
Authors: Lentz Jennifer J.
Published: August 2006

Spectral-shape discrimination thresholds were measured in the presence and absence of noise to determine whether normal-hearing and hearing-impaired listeners rely primarily on spectral peaks in the excitation pattern when discriminating between stimuli with different spectral shapes. Standard stimuli were the sum of 2, 4, 6, 8, 10, 20, or 30 equal-amplitude tones with frequencies fixed between 200 and 4000Hz. Signal stimuli were generated by increasing and decreasing the levels of every other standard component. The function relating the spectral-shape discrimination threshold to the number of components (N) showed an initial decrease in threshold with increasing N and then an increase in threshold when the number of components reached 10 and 6, for normal-hearing and hearing-impaired listeners, respectively. The presence of a 50-dB SPL/Hz noise led to a 1.7dB increase in threshold for normal-hearing listeners and a 3.5dB increase for hearing-impaired listeners. Multichannel modeling and the relatively small influence of noise suggest that both normal-hearing and hearing-impaired listeners rely on the peaks in the excitation pattern for spectral-shape discrimination. The greater influence of noise in the data from hearing-impaired listeners is attributed to a poorer representation of spectral peaks.
Increases in deep ocean ambient noise in the Northeast Pacific west of San Nicolas Island, California
Authors: McDonald Mark A. , Hildebrand John A. , Wiggins Sean M.
Published: August 2006

Recent measurement at a previously studied location illustrates the magnitude of increases in ocean ambient noise in the Northeast Pacific over the past four decades. Continuous measurements west of San Nicolas Island, California, over 138days, spanning 2003–2004 are compared to measurements made during the 1960s at the same site. Ambient noise levels at 30–50Hz were 10–12dB higher (95% CI=2.6dB) in 2003–2004 than in 1964–1966, suggesting an average noise increase rate of 2.5–3dB per decade. Above 50Hz the noise level differences between recording periods gradually diminished to only 1–3dB at 100–300Hz. Above 300Hz the 1964–1966 ambient noise levels were higher than in 2003–2004, owing to a diel component which was absent in the more recent data. Low frequency (10–50Hz) ocean ambient noise levels are closely related to shipping vessel traffic. The number of commercial vessels plying the world’s oceans approximately doubled between 1965 and 2003 and the gross tonnage quadrupled, with a corresponding increase in horsepower. Increases in commercial shipping are believed to account for the observed low-frequency ambient noise increase.
Analysis of Mitogen-Activated Protein Kinase Signaling Specificity in Response to Hyperosmotic Stress: Use of an Analog-Sensitive
HOG1
Allele
Authors: Westfall Patrick J. , Thorner Jeremy
Published: August 2006

When confronted with a marked increase in external osmolarity, budding yeast (
Saccharomyces cerevisiae
) cells utilize a conserved mitogen-activated protein kinase (MAPK) signaling cascade (the high-osmolarity glycerol or HOG pathway) to elicit cellular responses necessary to permit continued growth. One input that stimulates the HOG pathway requires the integral membrane protein and putative osmosensor Sho1, which recruits and enables activation of the MAPK kinase kinase Ste11. In mutants that lack the downstream MAPK kinase (
pbs2
Δ) or the MAPK (
hog1
Δ) of the HOG pathway, Ste11 activated by hyperosmotic stress is able to inappropriately stimulate the pheromone response pathway. This loss of signaling specificity is known as cross talk. To determine whether it is the Hog1 polypeptide per se or its kinase activity that is necessary to prevent cross talk, we constructed a fully functional analog-sensitive allele of
HOG1
to permit acute inhibition of this enzyme without other detectable perturbations of the cell. We found that the catalytic activity of Hog1 is required continuously to prevent cross talk between the HOG pathway and both the pheromone response and invasive growth pathways. Moreover, contrary to previous reports, we found that the kinase activity of Hog1 is necessary for its stress-induced nuclear import. Finally, our results demonstrate a role for active Hog1 in maintaining signaling specificity under conditions of persistently high external osmolarity.
Antagonism between Two Mechanisms of Antifungal Drug Resistance
Authors: Anderson James B. , Ricker Nicole , Sirjusingh Caroline
Published: August 2006

This study tested for interaction between two independently evolved mechanisms of fluconazole resistance in
Saccharomyces cerevisiae
. One set of strains was from a 400-generation evolution experiment, during which the concentration of fluconazole was increased from 16 to 256 μg/ml in four increments. At 100 generations, populations became fixed for resistance mutations in either of two transcriptional regulators,
PDR1
or
PDR3
. At 400 generations, replicate populations became fixed for another resistance mutation in
UNK1
, an unmapped gene further increasing resistance. Another genotype used in this study came from a population placed initially in 128 μg/ml of fluconazole; this environment selects for resistance through loss of function at
ERG3
, resulting in altered sterol metabolism. Mutant strains carrying
PDR1
r
or
PDR3
r
were crossed with the
erg3
r
mutant strain, and the doubly mutant, haploid offspring were identified. The double-mutant strains grew less well than the parent strains at all concentrations of fluconazole tested. In genome-wide assays of gene expression, several ABC transporter genes that were overexpressed in one parent and several
ERG
genes that were overexpressed in the other parent were also overexpressed in the double mutants. Of the 43 genes that were consistently overexpressed in the
PDR1
r
parents at generation 100, however, 31 were not consistently overexpressed in the double mutants. Of these 31 genes, 30 were also not consistently overexpressed after a further 300 generations of evolution in the
PDR1
r
parent populations. The two independently evolved mechanisms of fluconazole resistance are strongly antagonistic to one another.
Eukaryotic Release Factor 1 Phosphorylation by CK2 Protein Kinase Is Dynamic but Has Little Effect on the Efficiency of Translation Termination inSaccharomyces cerevisiae
Authors: Kallmeyer Adam K. , Keeling Kim M. , Bedwell David M.
Published: August 2006

Protein synthesis requires a large commitment of cellular resources and is highly regulated. Previous studies have shown that a number of factors that mediate the initiation and elongation steps of translation are regulated by phosphorylation. In this report, we show that a factor involved in the termination step of protein synthesis is also subject to phosphorylation. Our results indicate that eukaryotic release factor 1 (eRF1) is phosphorylated in vivo at serine 421 and serine 432 by the CK2 protein kinase (previously casein kinase II) in the budding yeastSaccharomyces cerevisiae. Phosphorylation of eRF1 has little effect on the efficiency of stop codon recognition or nonsense-mediated mRNA decay. Also, phosphorylation is not required for eRF1 binding to the other translation termination factor, eRF3. In addition, we provide evidence that the putative phosphatase Sal6p does not dephosphorylate eRF1 and that the state of eRF1 phosphorylation does not influence the allosuppressor phenotype associated with asal6Δ mutation. Finally, we show that phosphorylation of eRF1 is a dynamic process that is dependent upon carbon source availability. Since many other proteins involved in protein synthesis have a CK2 protein kinase motif near their extreme C termini, we propose that this represents a common regulatory mechanism that is shared by factors involved in all three stages of protein synthesis.
Characterization and Developmentally Regulated Localization of the Mitochondrial Carrier Protein Homologue MCP6 from
Trypanosoma brucei
Authors: Colasante Claudia , Alibu Vincent P. , Kirchberger Simon , Tjaden Joachim , Clayton Christine , Voncken Frank
Published: August 2006

Proteins of the mitochondrial carrier family (MCF) are located mainly in the inner mitochondrial membrane and mediate the transport of a large range of metabolic intermediates. The genome of
Trypanosoma brucei
harbors 29 genes encoding different MCF proteins. We describe here the characterization of MCP6, a novel
T. brucei
MCF protein. Sequence comparison and phylogenetic reconstruction revealed that MCP6 is closely related to different mitochondrial ADP/ATP and calcium-dependent solute carriers, including the ATP-Mg/Pi carrier of
Homo sapiens
. However, MCP6 lacks essential amino acids and sequence motifs conserved in these metabolite transporters, and functional reconstitution and transport assays with
E. coli
suggested that this protein indeed does not function as an ADP/ATP or ATP-Mg/Pi carrier. The subcellular localization of MCP6 is developmentally regulated: in bloodstream-form trypanosomes, the protein is predominantly glycosomal, whereas in the procyclic form, it is found mainly in the mitochondria. Depletion of MCP6 in procyclic trypanosomes resulted in growth inhibition, an increased cell size, aberrant numbers of nuclei and kinetoplasts, and abnormal kinetoplast morphology, suggesting that depletion of MCP6 inhibits division of the kinetoplast.
Spo5/Mug12, a Putative Meiosis-Specific RNA-Binding Protein, Is Essential for Meiotic Progression and Forms Mei2 Dot-Like Nuclear Foci
Authors: Kasama Takashi , Shigehisa Akira , Hirata Aiko , Saito Takamune T. , Tougan Takahiro , Okuzaki Daisuke , Nojima Hiroshi
Published: August 2006

We report here a functional analysis of
spo5
+
(
mug12
+
)
of
Schizosaccharomyces pombe
, which encodes a putative RNA-binding protein. The disruption of
spo5
+
caused abnormal sporulation, generating inviable spores due to failed forespore membrane formation and the absence of a spore wall, as determined by electron microscopy. Spo5 regulates the progression of meiosis I because
spo5
mutant cells display normal premeiotic DNA synthesis and the timely initiation of meiosis I but they show a delay in the peaking of cells with two nuclei, abnormal tyrosine 15 dephosphorylation of Cdc2, incomplete degradation of Cdc13, retarded formation and repair of double strand breaks, and a reduced frequency of intragenic recombination. Immunostaining showed that Spo5-green fluorescent protein (GFP) appeared in the cytoplasm at the horsetail phase, peaked around the metaphase I to anaphase I transition, and suddenly disappeared after anaphase II. Images of Spo5-GFP in living cells revealed that Spo5 forms a dot in the nucleus at prophase I that colocalized with the Mei2 dot. Unlike the Mei2 dot, however, the Spo5 dot was observed even in
sme2Δ
cells. Taken together, we conclude that Spo5 is a novel regulator of meiosis I and that it may function in the vicinity of the Mei2 dot.
Effects of Depleting the Essential Central Metabolic Enzyme Fructose-1,6-Bisphosphate Aldolase on the Growth and Viability of
Candida albicans
: Implications for Antifungal Drug Target Discovery
Authors: Rodaki Alexandra , Young Tim , Brown Alistair J. P.
Published: August 2006

The central metabolic enzyme fructose-1,6-bisphosphate aldolase (Fba1p) catalyzes a reversible reaction required for both glycolysis and gluconeogenesis. Fba1p is a potential antifungal target because it is essential in yeast and because fungal and human aldolases differ significantly. To test the validity of Fba1p as an antifungal target, we have examined the effects of depleting this enzyme in the major fungal pathogen
Candida albicans
. Using a methionine/cysteine-conditional mutant (
MET3-FBA1/fba1
), we have shown that Fba1p is required for the growth of
C. albicans
. However, Fba1p must be depleted to below 5% of wild-type levels before growth is blocked. Furthermore, Fba1p depletion exerts static rather than cidal effects upon
C. albicans
. Fba1p is a relatively abundant and stable protein in
C. albicans
, and hence, Fba1p levels decay relatively slowly following
MET3-FBA1
shutoff. Taken together, our observations can account for our observation that the virulence of
MET3-FBA1/fba1
cells is only partially attenuated in the mouse model of systemic candidiasis. We conclude that an antifungal drug directed against Fba1p would have to be potent to be effective.
Heterologous Expression Implicates a GATA Factor in Regulation of Nitrogen Metabolic Genes and Ion Homeostasis in the Halotolerant Yeast
Debaryomyces hansenii
Authors: García-Salcedo Raúl , Casamayor Antonio , Ruiz Amparo , González Asier , Prista Catarina , Loureiro-Dias Maria C. , Ramos José , Ariño Joaquín
Published: August 2006

The yeast
Debaryomyces hansenii
has a remarkable capacity to proliferate in salty and alkaline environments such as seawater. A screen for
D. hansenii
genes able to confer increased tolerance to high pH when overexpressed in
Saccharomyces cerevisiae
yielded a single gene, named here Dh
GZF3
, encoding a putative negative GATA transcription factor related to
S. cerevisiae
Dal80 and Gzf3. Overexpression of this gene in wild-type
S. cerevisiae
increased caffeine and rapamycin tolerance, blocked growth in low glucose concentrations and nonfermentable carbon sources, and resulted in lithium- and sodium-sensitive cells. Sensitivity to salt could be attributed to a reduced cation efflux, most likely because of a decrease in expression of the
ENA1
Na
+
-ATPase gene. Overexpression of Dh
GZF3
did not affect cell growth in a
gat1
mutant but was lethal in the absence of Gln3. These are positive factors that oppose both Gzf3 and Dal80. Genome-wide transcriptional profiling of wild-type cells overexpressing Dh
GZF3
shows decreased expression of a number of genes that are usually induced in poor nitrogen sources. In addition, the entire pathway leading to Lys biosynthesis was repressed, probably as a result of a decrease in the expression of the specific Lys14 transcription factor. In conclusion, our results demonstrate that DhGzf3 can play a role as a negative GATA transcription factor when expressed in
S. cerevisiae
and that it most probably represents the only member of this family in
D. hansenii
. These findings also point to the GATA transcription factors as relevant elements for alkaline-pH tolerance.
Import-Associated Translational Inhibition: Novel In Vivo Evidence for Cotranslational Protein Import intoDictyostelium discoideumMitochondria
Authors: Ahmed Afsar U. , Beech Peter L. , Lay Sui T. , Gilson Paul R. , Fisher Paul R.
Published: August 2006

To investigate protein import into the mitochondria ofDictyostelium discoideum, green fluorescent protein (GFP) was fused as a reporter protein either to variable lengths of the N-terminal region of chaperonin 60 (the first 23, 40, 80, 97, and 150 amino acids) or to the mitochondrial targeting sequence of DNA topoisomerase II. The fusion proteins were expressed in AX2 cells under the actin-15 promoter. Fluorescence images of GFP transformants confirmed thatDictyosteliumchaperonin 60 is a mitochondrial protein. The level of the mitochondrially targeted GFP fusion proteins was unexpectedly much lower than the nontargeted (cytoplasmic) forms. The distinction between targeted and nontargeted protein activities was investigated at both the transcriptional and translational levels in vivo. We found that targeting GFP to the mitochondria results in reduced levels of the fusion protein even though transcription of the fusion gene and the stability of the protein are unaffected. [35S]methionine labeling and GFP immunoprecipitation confirmed that mitochondrially targeted GFP is translated at much slower rates than nontargeted GFP. The results indicate a novel phenomenon, import-associated translational inhibition, whereby protein import into the mitochondria limits the rate of translation. The simplest explanation for this is that import of the GFP fusion proteins occurs cotranslationally, i.e., protein synthesis and import into mitochondria are coupled events. Consistent with cotranslational import, Northern analysis showed that the GFP mRNA is associated with isolated mitochondria. This association occurred regardless of whether the GFP was fused to a mitochondrial leader peptide. However, the presence of an import-competent leader peptide stabilized the mRNA-mitochondria association, rendering it more resistant to extensive EDTA washing. In contrast with GFP, the mRNA of another test protein, aequorin, did not associate with the mitochondria, and its translation was unaffected by import of the encoded polypeptide into the mitochondria.
Is the VO2 slow component in heavy arm-cranking exercise associated with recruitment of type II muscle fibers as assessed by an increase in surface EMG?
Authors: Bernasconi Sylvain , Tordi Nicolas , Perrey Stéphane , Parratte Bernard , Monnier Guy
Published: August 2006

The recruitment of additional type II muscle fibers is one mechanism often suggested to be responsible for the slow component of oxygen uptake (VO2 SC). We hypothesized that surface electromyogram (EMG) of the biceps brachii, triceps brachii, anterior deltoid, and infraspinatus muscles could be related to the VO2 SC amplitude during arm-cranking exercises above ventilatory threshold (VT). Eight healthy subjects performed transitions from rest to 6-min heavy exercise at a constant power output of approximately 40% between VT and peak VO2. A 2-component exponential model was used to fit the VO2 response. EMG were recorded the last 15 s of each minute to obtain root mean square (RMS) and mean power frequency (MPF). Mean EMG responses for RMS and MPF were calculated by averaging EMG responses of the 4 muscles. The VO2 SC amplitude was of 530 ± 166 mL/min and occurred after 134 ± 31 s of exercise onset. Significant correlations were found for most of the subjects between EMG parameters and the VO2 SC amplitude as determined between the 2nd and the 6th minute. For all muscles, RMS values significantly increased over time during the VO2 SC, whereas MPF decreased significantly. These results suggest a relation between the recruitment of additional type II muscle fibers and the VO2 SC in arm-cranking exercises.
Roles of Ca2+and protein kinase C in the excitatory response to serotonin in embryonic molluscan ciliary cells
Authors: Doran Shandra A. , Goldberg Jeffrey I.
Published: August 2006

We examined the roles of Ca2+and protein kinase C (PKC) in the cilio-excitatory response to serotonin in pedal ciliary cells from Helisoma trivolvis embryos. Serotonin (5-hydroxytryptamine; 5-HT; 100 µmol/L) induced an increase in ciliary beat frequency (CBF) was abolished by microinjected BAPTA (50 mmol/L), but was only partially inhibited by the phospholipase C inhibitor U-73122 (10 µmol/L). The diacylglycerol analogs 1-oleoyl-2-acetyl-sn-glycerol (100 µmol/L) and 1,2-dioctanoyl-sn-glycerol (100 µmol/L) caused increases in [Ca2+]ithat were smaller than those induced by serotonin. In the absence of extracellular Ca2+, 1,2-dioctanoyl-sn-glycerol (100 µmol/L) failed to elicit an increase in both CBF and [Ca2+]i. In contrast, the serotonin-induced increase in CBF persisted in the absence of extracellular Ca2+, although the increase in [Ca2+]iwas abolished. PKC inhibitors bisindolylmaleimide (10 and 100 nmol/L) and calphostin C (10 nmol/L) partially inhibited the serotonin-induced increase in CBF, but didn’t affect the serotonin-induced change in [Ca2+]i. These findings suggest that an intracellular store-dependent increase in [Ca2+]imediates the cilio-excitatory response to serotonin. Furthermore, although PKC is able to cause an increase in [Ca2+]ithrough calcium influx, it contributes to the cilio-excitatory response to 5-HT through a different mechanism.