bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of model root exudates on structure and activity of a soil diazotroph community
Authors: Bürgmann Helmut , Meier Stefan , Bunge Michael , Widmer Franco , Zeyer Josef
Published: October 2005

Nitrogen fixation is often enhanced in the rhizosphere as compared with bulk soil, due to asymbiotic microorganisms utilizing root exudates as an energy source. We have studied the activity and composition of asymbiotic soil diazotrophs following pulse additions of artificial root exudates and single carbon sources, simulating the situation of bulk soil coming into contact with exudates from growing roots. Artificial root exudates and single sugars rapidly induced nitrogen fixation. The population of potential diazotrophs was studied using universal and group‐specific nifH polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analysis. Reverse transcription PCR of nifH mRNA confirmed that phylotypes with an apparently increasing population size also expressed the nitrogenase system. According to our results, the actively nitrogen‐fixing population represents only a fraction of the total diazotroph diversity, and the results of group‐specific nifH PCR and phylogenetic analysis of cloned nifH and 16S rRNA gene fragments identified active species that belonged to the genus Azotobacter. Rapid changes of transcriptional activity over time were observed, indicating different growth and activation strategies in different Azotobacter strains. Only sugar‐containing substrates were able to induce nitrogen fixation, but substrate concentration and the presence of organic acids may have additional selective effects on the active diazotroph population.
Influence of different Oryza cultivars on expression of nifH gene pools in roots of rice
Authors: Knauth Stefan , Hurek Thomas , Brar Darshan , Reinhold‐Hurek Barbara
Published: October 2005

Cultivation‐independent studies suggest that roots of rice (Oryza sativa) are colonized by a diverse community of nitrogen‐fixing bacteria. Here we report for the first time mRNA‐based profiling of nitrogenase (nifH) genes, to study the impact of lowland‐rice genotypes at the cultivar level on the functional diversity of root‐associated diazotrophs. Root RNA extracts from all plants contained nifH mRNA at levels detectable by reverse transcription polymerase chain reaction (RT‐PCR). Terminal restriction fragment length polymorphism (T‐RFLP) analysis of RT‐PCR products showed only small interplant variations. However, RNA‐ and DNA‐based profiles obtained from the same root extractions differed from each other, suggesting that presence of diazotrophs did not necessarily coincide with active transcription of nif genes. Application of N‐fertilizer at planting had a long‐term effect on the profile of expressed nitrogenase genes. Phylogenetic analysis of a clone library constructed for nifH fragments expressed in wild species of rice roots indicated that active diazotrophs were not related to cultured strains. The composition of active diazotrophic communities was compared for six related cultivars of O. sativa, wild species Oryza brachyantha, and a genetic cross between it and cv. IR56, grown under identical conditions in rice field soil in the Philippines without N‐fertilizer application. Remarkable varietal differences in root associated nifH‐gene expressing communities were detected. This underlines the importance of mRNA‐based approaches to study functional diversity and eventually identify key diazotrophs in a particular environment.
Establishment of DsRed.T3_S4T as an improved autofluorescent marker for microbial ecology applications
Authors: Dandie Catherine E. , Larrainzar Estibaliz , Mark G. Louise , O'Gara Fergal , Morrissey John P.
Published: October 2005

Autofluorescent proteins (AFPs), such as green fluorescent protein (GFP) and DsRed, are valuable tools for studying plant–microbe interactions. Nevertheless, because of some limitations, efforts are ongoing to generate improved AFP variants. Several groups have generated variants of GFP with altered spectral characteristics, and faster maturing and brighter variants of DsRed. In this study we used plasmid and chromosomal constructs to test the efficacy of a new variant of DsRed, DsRed.T3_S4T, in Pseudomonas fluorescens F113rif. In addition, we compared the ecological fitness of strains carrying chromosomal copies of EGFP, DsRed or DsRed.T3_S4T. Strains expressing DsRed.T3_S4T fluoresced significantly brighter than strains expressing DsRed. Furthermore, it was found that although all strains grew equally well in vitro, only strains carrying DsRed.T3_S4T functioned as well as wild type in a competitive rhizosphere colonization assay. In particular, it was observed that DsRed.T3_S4T is an improved marker over DsRed for microbial ecology studies in this strain.
Bacterial diversity in the rhizosphere of Proteaceae species
Authors: Stafford William H. L. , Baker Gillian C. , Brown Susan A. , Burton Stephanie G. , Cowan Don A.
Published: October 2005

The Cape Floral Kingdom is an area of unique plant biodiversity in South Africa with exceptional concentrations of rare and endemic species and experiencing drastic habitat loss. Here we present the first molecular study of the microbial diversity associated with the rhizosphere soil of endemic plants of the Proteaceae family (Leucospermum truncatulum and Leucadendron xanthoconus). Genomic DNA was extracted from L. truncatulum rhizosphere soil, L. xanthoconus rhizosphere and non‐rhizosphere soil and used as a template for the polymerase chain reaction (PCR) amplification of the 16S ribosomal RNA gene (rDNA). Construction and sequencing of 16S rDNA libraries revealed a high level of biodiversity and led to the identification of several novel bacterial phylotypes. The bacterial community profiles were compared by 16S rDNA denaturing gradient gel electrophoresis (DGGE). Cluster analysis and biodiversity indices revealed that the rhizosphere soil samples were more similar to each other than to non‐rhizosphere soil and the rhizosphere soil contained a bacterial diversity that was richer and more equitable compared with non‐rhizosphere soil. A Chloroflexus and an Azospirillum genospecies were restricted to the L. xanthoconus rhizosphere soil and Stenotrophomonas genospecies was identified in all rhizosphere soil samples but was not present in the non‐rhizosphere soil. Taxon‐specific nested PCR and DGGE‐identified differences between the Proteaceae plant rhizosphere soil with a Frankia genospecies restricted the L. truncatulum rhizosphere. Archaea‐specific rDNA PCR, DGGE and DNA sequencing revealed that Crenarcheote genospecies were excluded from the plant rhizosphere soil and only present in non‐rhizosphere soil.
Thermal Properties Measurement of Micro‐electromechanical System Sensors by Digital Moiré Method
Authors: Shang H. , Xie H. , Wang X. , Jiang S. , Dai F. , Wang W. , Fang Y. , Zhao Y.
Published: October 2005

Abstract:  The thermal properties of a micro‐electromechanical system sensor were analysed by a novel digital moiré method. A double‐layer micro‐cantilever sensor (60 μm long, 10 μm width and 2 μm thick) was prepared by focused ion beam milling. A grating with frequency of 5000 lines mm−1 was etched on the cantilever. The sensor was placed into a scanning electron microscope system with a high temperature device. The observation and recording of the thermal deformation of the grating were realised in real‐time as the temperature rose from room temperature to 300 °C at intervals of 50 °C. Digital moiré was generated by interference of the deformed grating and a digital virtual grating. The thermal properties including strain distribution of the sensor and the linear expansion coefficient of polysilicon were accurately measured by the phase‐shifted moiré patterns.
An Evaluation of Digital Image Correlation Criteria for Strain Mapping Applications
Authors: Tong W.
Published: October 2005

Abstract:  The performance of four digital image correlation criteria widely used in strain mapping applications has been critically examined using three sets of digital images with various whole‐field deformation characteristics. The deformed images in these image sets are digitally modified to simulate the less‐than‐ideal image acquisition conditions in an actual experiment, such as variable brightness, contrast, uneven local lighting and blurring. The relative robustness, computational cost and reliability of each criterion are assessed for precision strain mapping applications. Recommendations are given for selecting a proper image correlation criterion to efficiently extract reliable deformation data from a given set of digital images.
An Analysis of the Factors Influencing the Data Derived from a Plug Type Three‐Dimensional Strain Rosette under Compression and Torsion
Authors: Little E. G. , Tocher D. , Colgan D. , O'Donnell P.
Published: October 2005

Abstract:  The embedding of three‐dimensional strain rosettes embedded into epoxy models provides an experimental technique for analysing complex structures; however, this technique has been known to produce data that were difficult to explain in terms of their physical significance. To gain a greater insight into the behaviour of a three‐dimensional strain rosette used in this way, a three‐dimensional strain rosette was embedded into each of two separate prismatic bars of square cross‐section and subjected to fundamental tests of compression and torsion in standard commercial testing machines. In initial tests on a bar containing a three‐dimensional strain rosette (Bar A) the data derived from the individual gauges sometimes departed from the theoretical values by more that 30 μe. After critical evaluation of the procedures used for making and testing Bar A, further tests were carried out on Bar B, which led to a reduction in the difference between theoretical and experimental data to 14 μe, acceptable for most practical purposes. The use of square plugs containing three‐dimensional strain rosettes which are embedded into square cavities in the model, and the measurement of the actual direction cosines of the gauges on the square plug prior to embedment is a distinct advantage over the use of cylindrical plugs. In addition, the use of testing machines with a fixed base as opposed to a floating lower platen is recommended.
Fracture‐induced Physical Phenomena and Memory Effects in Rocks: A Review
Authors: Lavrov A.
Published: October 2005

Losing stability, the earth split;
Losing strength, the mountains sank. Tao De Ching

Abstract:  Fracture‐induced physical phenomena allow a real‐time monitoring of damage evolution in rocks induced by mechanical loading. Some of these phenomena, e.g. plastic deformation, changes in permeability and electric resistivity, provide an overall estimate of damage as a function of stress. Others, such as acoustic emission or electromagnetic emission, allow an exact location of cracks in space and time. Being nondestructive, monitoring techniques based on fracture‐induced physical phenomena, are a basis for prediction of earthquakes and rockbursts in underground mines. They are also crucial for a fundamental understanding of rock fracture mechanisms and for developing constitutive models of rock behaviour. Memory effects take place in rocks subjected to cyclic loading with the peak stress (strain) value increasing from cycle to cycle. The effects are represented by certain characteristic changes in rock properties and parameters that are observed when the stress (strain) reaches its previous peak value. Potential applications of memory effects range from stress measurement techniques to earthquake prediction to damage surface scanning. Essential experimental and theoretical results on fracture‐induced physical phenomena and memory effects in rocks are considered in the article. Possible applications as well as not‐yet‐clear points are discussed.
Application of the Time‐Dependent ROC Curves for Prognostic Accuracy with Multiple Biomarkers
Authors: Zheng Yingye , Cai Tianxi , Feng Ziding
Published: October 2005

SummaryThe rapid advancement in molecule technology has led to the discovery of many markers that have potential applications in disease diagnosis and prognosis. In a prospective cohort study, information on a panel of biomarkers as well as the disease status for a patient are routinely collected over time. Such information is useful to predict patients' prognosis and select patients for targeted therapy. In this article, we develop procedures for constructing a composite test with optimal discrimination power when there are multiple markers available to assist in prediction and characterize the accuracy of the resulting test by extending the time‐dependent receiver operating characteristic (ROC) curve methodology (Heagerty, Lumley, and Pepe, 2000,Biometrics56,337–344). We employ a modified logistic regression model to derive optimal linear composite scores such that their corresponding ROC curves are maximized at every false positive rate. We provide theoretical justification for using such a model for prognostic accuracy. The proposed method allows for time‐varying marker effects and accommodates censored failure time outcome. When the effects of markers are approximately constant over time, we propose a more efficient estimating procedure under such models. We conduct numerical studies to evaluate the performance of the proposed procedures. Our results indicate the proposed methods are both flexible and efficient. We contrast these methods with an application concerning the prognostic accuracies of expression levels of six genes.
Random Changepoint Model for Joint Modeling of Cognitive Decline and Dementia
Authors: Jacqmin‐Gadda Hélène , Commenges Daniel , Dartigues Jean‐François
Published: October 2005

Summary We propose a joint model for cognitive decline and risk of dementia to describe the pre‐diagnosis phase of dementia. We aim to estimate the time when the cognitive evolution of subjects in the pre‐dementia phase becomes distinguishable from normal evolution and to study whether the shape of cognitive decline depends on educational level. The model combines a piecewise polynomial mixed model with a random changepoint for the evolution of the cognitive test and a log‐normal model depending on the random changepoint for the time to dementia. Parameters are estimated by maximum likelihood using a Newton–Raphson‐like algorithm. The expected cognitive evolution given age to dementia is then derived and the marginal distribution of dementia is estimated to check the log‐normal assumption.
Structural Inference in Transition Measurement Error Models for Longitudinal Data
Authors: Pan Wenqin , Lin Xihong , Zeng Donglin
Published: October 2005

SummaryWe propose a new class of models, transition measurement error models, to study the effects of covariates and the past responses on the current response in longitudinal studies when one of the covariates is measured with error. We show that the response variable conditional on the error‐prone covariate follows a complex transition mixed effects model. The naive model obtained by ignoring the measurement error correctly specifies the transition part of the model, but misspecifies the covariate effect structure and ignores the random effects. We next study the asymptotic bias in naive estimator obtained by ignoring the measurement error for both continuous and discrete outcomes. We show that the naive estimator of the regression coefficient of the error‐prone covariate is attenuated, while the naive estimators of the regression coefficients of the past responses are generally inflated. We then develop a structural modeling approach for parameter estimation using the maximum likelihood estimation method. In view of the multidimensional integration required by full maximum likelihood estimation, an EM algorithm is developed to calculate maximum likelihood estimators, in which Monte Carlo simulations are used to evaluate the conditional expectations in the E‐step. We evaluate the performance of the proposed method through a simulation study and apply it to a longitudinal social support study for elderly women with heart disease. An additional simulation study shows that the Bayesian information criterion (BIC) performs well in choosing the correct transition orders of the models.
Joint Models for Multivariate Longitudinal and Multivariate Survival Data
Authors: Chi Yueh‐Yun , Ibrahim Joseph G.
Published: October 2005

SummaryJoint modeling of longitudinal and survival data is becoming increasingly essential in most cancer and AIDS clinical trials. We propose a likelihood approach to extend both longitudinal and survival components to be multidimensional. A multivariate mixed effects model is presented to explicitly capture two different sources of dependence among longitudinal measures over time as well as dependence between different variables. For the survival component of the joint model, we introduce a shared frailty, which is assumed to have a positive stable distribution, to induce correlation between failure times. The proposed marginal univariate survival model, which accommodatesbothzero and nonzero cure fractions for the time to event, is then applied to each marginal survival function. The proposed multivariate survival model has a proportional hazards structure for the population hazard, conditionally as well as marginally, when the baseline covariates are specified through a specific mechanism. In addition, the model is capable of dealing with survival functions with different cure rate structures. The methodology is specifically applied to the International Breast Cancer Study Group (IBCSG) trial to investigate the relationship between quality of life, disease‐free survival, and overall survival.
Neighbor effects on germination, survival, and growth in two arctic tundra plant communities
Authors: Gough Laura
Published: October 2005

In relatively harsh environments such as arctic tundra, abiotic factors have traditionally been considered the primary determinants of community structure, overwhelming any effects of biotic interactions such as competition. Two common low arctic tundra types that differ in soil properties, moist acidic and moist non‐acidic tussock tundra (MAT and MNT, respectively), occur in close proximity in northern Alaska. Several plant species occur in both communities with different relative abundance, while others are restricted to one. This study experimentally examined how neighboring vegetation affects germination, survival, and growth of species in these two communities that differ in soil pH, cation availability, and other characteristics.  Germination of sown seeds was greater than background levels suggesting seed limitation may restrict recruitment of these clonal, perennial species. Germination of sown seeds was greater at both sites when both mosses and vascular plants had been removed compared to plots with intact vegetation. However, neighbors had almost no effect on survival and growth of adult transplants. Patterns of germination, survival and growth of several species differed depending on the community of origin and the community of destination of the seeds or transplanted adults. For example, transplants of the sedge Eriophorum vaginatum grew better if they were from MAT, and this species germinated better when sown at MNT. Although of relatively short duration (three growing seasons), this study suggests that biotic interactions may affect local species composition by restricting germination and establishment in these two communities, but have less of an effect on adult plants. Not surprisingly, site‐specific abiotic conditions also exhibit control over species occurrence and relative abundance. Without disturbance to clear bare ground for recruitment of new individuals, these populations for the most part must rely on clonal growth to persist.
The structure of food webs along river networks
Authors: Romanuk Tamara N. , Jackson Leland J. , Post John R. , McCauley Ed , Martinez Neo D.
Published: October 2005

Do changes in the species composition of riverine fish assemblages along river networks lead to predictable changes in food‐web structure? We assembled empirical “fish‐centered” river food webs for three rivers located along a latitudinal gradient in the South Saskatchewan River Basin (SSRB) that differ in land‐use impacts and geomorphology but flow through similar mountain, foothill, and prairie physiographic regions. We then calculated 17 food‐web properties to determine whether the nine river food webs differed according to physiographic region or river sub‐basin. There were no statistically significant differences in the 17 food‐web properties calculated among the rivers. In contrast, fish species richness, connectance, the proportion of herbivores, and the proportion of cannibals changed longitudinally along the river network. Our results suggest that regional changes in river geomorphology and physicochemistry play an important role in determining longitudinal variation in food‐web properties such as fish species richness and connectance. In contrast, the overall structure of river food webs may be relatively similar and insensitive to regional influences such as zoogeography. Further explorations of river and other food webs would greatly illuminate this suggestion.
Life history variation in an annual plant under two opposing environmental constraints along an aridity gradient
Authors: Petrů Martina , Tielbörger Katja , Belkin Ruthie , Sternberg Marcelo , Jeltsch Florian
Published: October 2005

Environmental gradients represent an ideal framework for studying adaptive variation in the life history of plant species. However, on very steep gradients, largely contrasting conditions at the two gradient ends often limit the distribution of the same species across the whole range of environmental conditions. Here, we study phenotypic variation in a winter annual crucifer Biscutella didyma persisting along a steep gradient of increasing rainfall in Israel. In particular, we explored whether the life history at the arid end of the gradient indicates adaptations to drought and unpredictable conditions, while adaptations to the highly competitive environment prevail at the mesic Mediterranean end. We examined several morphological and reproductive traits in four natural populations and in populations cultivated in standard common environment. Plants from arid environments were faster in phenological development, more branched in architecture and tended to maximize reproduction, while the Mediterranean plants invested mainly in vertical vegetative growth. Differences between cultivation and field in diaspore production were very large for arid populations as opposed to Mediterranean ones, indicating a larger potential to increase reproduction under favorable conditions. Our overall findings indicate two strongly opposing selective forces at the two extremes of the aridity gradient, which result in contrasting strategies within the studied annual plant species.
Regulation of lactate production at the onset of ischaemia is independent of mitochondrial NADH/NAD+: insights from in silico studies
Authors: Zhou Lufang , Stanley William C. , Saidel Gerald M. , Yu Xin , Cabrera Marco E.
Published: October 2005

Ischaemia decreases mitochondrial NADH oxidation, activates glycolysis, increases the NADH/NAD+ ratio, and causes lactate production. The mechanisms that regulate anaerobic glycolysis and the NADH/NAD+ ratio during ischaemia are unclear. Although continuous measurements of metabolic fluxes and NADH/NAD+ in cytosol and mitochondria are not possible in vivo with current experimental techniques, computational models can be used to predict these variables by simulations with in silico experiments. Such predictions were obtained using a mathematical model of cellular metabolism in perfused myocardium. This model, which distinguishes cytosolic and mitochondrial domains, incorporates key metabolic species and processes associated with energy transfer. Simulation of metabolic responses to mild, moderate and severe ischaemia in large animals showed that mitochondrial NADH/NAD+ was rapidly reset to higher values in proportion to the reduced O2 delivery and myocardial oxygen consumption . Cytosolic NADH/NAD+, however, showed a biphasic response, with a sharp initial increase that was due to activation of glycogen breakdown and glycolysis, and corresponded with lactate production. Whereas the rate of glycolysis and the malate–aspartate shuttle had a significant effect on the cytosolic NADH/NAD+, their effects on the mitochondrial NADH/NAD+ were minimal. In summary, model simulations of the metabolic response to ischaemia showed that mitochondrial NADH/NAD+ is primarily determined by O2 consumption, while cytosolic NADH/NAD+ is largely a function of glycolytic flux during the initial phase, and is determined by mitochondrial NADH/NAD+ and the malate–aspartate shuttle during the steady state.
Nitric oxide blunts myogenic autoregulation in rat renal but not skeletal muscle circulation via tubuloglomerular feedback
Authors: Just Armin , Arendshorst William J.
Published: October 2005

This rat renal blood flow (RBF) study quantified the impact of nitric oxide synthase (NOS) inhibition on the myogenic response and the balance of autoregulatory mechanisms in the time domain following a 20 mmHg‐step increase or decrease in renal arterial pressure (RAP). When RAP was increased, the myogenic component of renal vascular resistance (RVR) rapidly rose within the initial 7–10 s, exhibiting an ∼5 s time constant and providing ∼36% of perfect autoregulation. A secondary rise between 10 and 40 s brought RVR to 95% total autoregulatory efficiency, reflecting tubuloglomerular feedback (TGF) and possibly one or two additional mechanisms. The kinetics were similar after the RAP decrease. Inhibition of NOS (by l‐NAME) increased RAP, enhanced the strength (79% autoregulation) and doubled the speed of the myogenic response, and promoted the emergence of RVR oscillations (∼0.2 Hz); the strength (52%) was lower at control RAP. An equi‐pressor dose of angiotensin II had no effect on myogenic or total autoregulation. Inhibition of TGF (by furosemide) abolished the l‐NAME effect on the myogenic response. RVR responses during furosemide treatment, assuming complete inhibition of TGF, suggest a third mechanism that contributes 10–20% and is independent of TGF, slower than the myogenic response, and abolished by NOS inhibition. The hindlimb circulation displayed a solitary myogenic response similar to the kidney (35% autoregulation) that was not enhanced by l‐NAME. We conclude that NO normally restrains the strength and speed of the myogenic response in RBF but not hindlimb autoregulation, an action dependent on TGF, thereby allowing more and slow RAP fluctuations to reach glomerular capillaries.
High affinity ATP/ADP analogues as new tools for studying CFTR gating
Authors: Zhou Zhen , Wang Xiaohui , Li Min , Sohma Yoshiro , Zou Xiaoqin , Hwang Tzyh‐Chang
Published: October 2005

Previous studies using non‐hydrolysable ATP analogues and hydrolysis‐deficient cystic fibrosis transmembrane conductance regulator (CFTR) mutants have indicated that ATP hydrolysis precedes channel closing. Our recent data suggest that ATP binding is also important in modulating the closing rate. This latter hypothesis predicts that ATP analogues with higher binding affinities should stabilize the open state more than ATP. Here we explore the possibility of using N6‐modified ATP/ADP analogues as high‐affinity ligands for CFTR gating, since these analogues have been shown to be more potent than native ATP/ADP in other ATP‐binding proteins. Among the three N6‐modified ATP analogues tested, N6‐(2‐phenylethyl)‐ATP (P‐ATP) was the most potent, with a K½ of 1.6 ± 0.4 μm (>50‐fold more potent than ATP). The maximal open probability (Po) in the presence of P‐ATP was ∼30% higher than that of ATP, indicating that P‐ATP also has a higher efficacy than ATP. Single‐channel kinetic analysis showed that as [P‐ATP] was increased, the opening rate increased, whereas the closing rate decreased. The fact that these two kinetic parameters have different sensitivities to changes of [P‐ATP] suggests an involvement of two different ATP‐binding sites, a high‐affinity site modulating channel closing and a low affinity site controlling channel opening. The effect of P‐ATP on the stability of open states was more evident when ATP hydrolysis was abolished, either by mutating the nucleotide‐binding domain 2 (NBD2) Walker B glutamate (i.e. E1371) or by using the non‐hydrolysable ATP analogue AMP‐PNP. Similar strategies to develop nucleotide analogues with a modified adenine ring could be valuable for future studies of CFTR gating.
Maximum likelihood fitting of single channel NMDA activity with a mechanism composed of independent dimers of subunits
Authors: Schorge Stephanie , Elenes Sergio , Colquhoun David
Published: October 2005

Steady‐state single channel activity from NMDA receptors was recorded at a range of concentrations of both glutamate and glycine. The results were fitted with several plausible mechanisms that describe both binding and gating. The mechanisms we have tested were based on our present understanding of receptor structure, or based on previously proposed mechanisms for these receptors. The steady‐state channel properties appear to have virtually no dependence on the concentration of either ligand, other than the frequency of channel activations. This limited the ability to discriminate detail in the mechanism, and, along with the persistence of open–shut correlations in high agonist concentrations, suggests that NMDA channels, unlike other neurotransmitter receptors, cannot open unless all binding sites are occupied. As usual for analyses of NMDA channels, the applicability of our results to physiological observations is limited by uncertainties in synaptic zinc and hydrogen ion concentrations, both of these being known to affect the receptor. The mechanism that we propose, on the basis of steady‐state single channel recordings, predicts with fair accuracy the apparent open and shut‐time distributions in different concentrations of agonists, correlations between open and shut times, and both the rising and falling phases of the macroscopic response to concentration jumps, and can therefore account for the main features of synaptic currents.
Cardioprotection afforded by chronic exercise is mediated by the sarcolemmal, and not the mitochondrial, isoform of the KATPchannel in the rat
Authors: Brown David A. , Chicco Adam J. , Jew Korinne N. , Johnson Micah S. , Lynch Joshua M. , Watson Peter A. , Moore Russell L.
Published: October 2005

This study was conducted to examine the role of myocardial ATP‐sensitive potassium (KATP) channels in exercise‐induced protection from ischaemia–reperfusion (I–R) injury. Female rats were either sedentary (Sed) or exercised for 12 weeks (Tr). Hearts were excised and underwent a 1–2 h regional I–R protocol. Prior to ischaemia, hearts were subjected to pharmacological blockade of the sarcolemmal KATPchannel with HMR 1098 (SedHMR and TrHMR), mitochondrial blockade with 5‐hydroxydecanoic acid (5HD; Sed5HD and Tr5HD), or perfused with buffer containing no drug (Sed and Tr). Infarct size was significantly smaller in hearts from Tr animals (35.4 ± 2.3versus44.7 ± 3.0% of the zone at risk for Tr and Sed, respectively). Mitochondrial KATPblockade did not abolish the training‐induced infarct size reduction (30.0 ± 3.4versus38.0 ± 2.6 in Tr5HD and Sed5HD, respectively); however, sarcolemmal KATPblockade completely eradicated the training‐induced cardioprotection. Infarct size was 71.2 ± 3.3 and 64.0 ± 2.4% of the zone at risk for TrHMR and Sed HMR. The role of sarcolemmal KATPchannels in Tr‐induced protection was also supported by significant increases in both subunits of the sarcolemmal KATPchannel following training. LV developed pressure was better preserved in hearts from Tr animals, and was not influenced by addition of HMR 1098. 5HD decreased pressure development regardless of training status, from 15 min of ischaemia through the duration of the protocol. This mechanical dysfunction was likely to be due to a 5HD‐induced increase in myocardial Ca2+content following I–R. The major findings of the present study are: (1) unlike all other known forms of delayed cardioprotection, infarct sparing following chronic exercise was not abolished by 5HD; (2) pharmacological blockade of the sarcolemmal KATPchannel nullified the cardioprotective benefits of exercise training; and (3) increased expression of sarcolemmal KATPchannels was observed following chronic training.
Excitation–transcription coupling in smooth muscle
Authors: Barlow Christy A. , Rose Patricia , Pulver‐Kaste Renee A. , Lounsbury Karen M.
Published: October 2005

Calcium (Ca2+) signals affect virtually every biological process, including both contraction and gene transcription in smooth muscle. Ca2+‐regulated gene transcription is known to be important for both physiological and pathological responses in smooth muscle. The aim of this review is to discuss the current understanding of gene transcription regulated by excitation through Ca2+signalling using a comparison of the two most characterized Ca2+‐regulated transcription factors in smooth muscle, Ca2+–cyclic AMP response element binding protein (CREB) and nuclear factor of activated T‐cells (NFAT). Recent studies have shown commonalities and differences in the regulation of CREB and NFAT through both voltage‐ and non‐voltage‐gated Ca2+channels that lead to expression of smooth muscle cell specific differentiation markers as well as markers of proliferation. New insights into the regulation of specific genes through companion elements on the promoters of Ca2+‐regulated genes have led to new models for transcriptional regulation by Ca2+that are defined both by the source and duration of the Ca2+signal and the composition of enhancer elements found within the regulatory regions of specific genes. Thus the combination of signalling pathways elicited by particular Ca2+signals affect selective promoter elements that are key to the ultimate pattern of gene transcription.
The neurotransmitters glycine and GABA stimulate glucagon‐like peptide‐1 release from the GLUTag cell line
Authors: Gameiro A. , Reimann F. , Habib A. M. , O'Malley D. , Williams L. , Simpson A. K. , Gribble F. M.
Published: October 2005

The incretin hormone, glucagon‐like peptide‐1 (GLP‐1) is released from intestinal L‐cells following food ingestion. Its secretion is triggered by a range of nutrients, including fats, carbohydrates and proteins. We reported previously that Na+‐dependent glutamine uptake triggered electrical activity and GLP‐1 release from the L‐cell model line GLUTag. However, whereas alanine also triggered membrane depolarization and GLP‐1 secretion, the response was Na+independent. A range of alanine analogues, includingd‐alanine, β‐alanine, glycine andl‐serine, but notd‐serine, triggered similar depolarizing currents and elevation of intracellular [Ca2+], a sensitivity profile suggesting the involvement of glycine receptors. In support of this idea, glycine‐induced currents and GLP‐1 release were blocked by strychnine, and currents showed a 58.5 mV shift in reversal potential per 10‐fold change in [Cl−], consistent with the activation of a Cl−‐selective current. GABA, an agonist of related Cl−channels, also triggered Cl−currents and secretion, which were sensitive to picrotoxin. GABA‐triggered [Ca2+]iincrements were abolished by bicuculline and partially impaired by (1,2,5,6‐tetrahydropyridine‐4‐yl)methylphosphinic acid (TPMPA), suggesting the involvement of both GABAAand GABACreceptors. Expression of GABAA, GABACand glycine receptor subunits was confirmed by RT‐PCR. Glycine‐triggered GLP‐1 secretion was impaired by bumetanide but not bendrofluazide, suggesting that a high intracellular [Cl−] maintained by Na+–K+–2Cl−cotransporters is necessary for the depolarizing response to glycine receptor ligands. Our results suggest that GABA and glycine stimulate electrical activity and GLP‐1 release from GLUTag cells by ligand‐gated ion channel activation, a mechanism that might be important in responses to endogenous ligands from the enteric nervous system or dietary sources.
Acoustic harmonic radiation from fluid-loaded spherical shells using elasticity theory
Authors: Pathak Ardhendu G. , Stepanishen Peter R.
Published: October 2005

The finite Legendre transform technique is used to address the problem of acoustic harmonic radiation from fluid-loaded elastic spherical shells subjected to axisymmetric force excitations. The partial wave series for the response parameters such as the normal velocity of the shell surface, the pressure on the outer surface of the shell, and the far-field pressure are obtained using the mathematical theory of elasticity. Expressions for the input admittance and the transfer admittances for a ring force are also derived. Numerical results are presented for the velocity of the shell, the pressure on the shell, and the far-field pressure directionality patterns as a function of frequency, the relative thickness of the shell, and the location of the force. For low frequencies, the results are compared to those obtained by using a thin shell theory. The convergence properties of the partial wave series as a function of the frequency are also discussed.
Formant frequencies of Hindi vowels in /hVḍ/ and C1VC2 contexts
Authors: Khan I. , Gupta S. K. , Rizvi S. H. S.
Published: October 2005

Formant frequencies of Hindi vowels in /hVḍ/ and C1VC2 contexts for words spoken in isolation have been measured from sonagrams for two male and one female adult speakers and a spectrographic normalized coefficient of variance (C.V.) for F0 to F4 has been presented in a tabular form.
Comment on ‘‘Modulation of the hair cell motor: A possible source of odd-order distortion’’ [J. Acoust. Soc. Am. 96, 2210–2215 (1994)]
Authors: Nuttall A. L. , Dolan D. F.
Published: October 2005

This reply to the response by Brown [J. Acoust. Soc. Am. 96, 2210–2215 (1994) on the report ‘‘Intermodulation distortion (F2−F1) in inner hair cell and basilar membrane responses [J. Acoust. Soc. Am. 93, 2061–2068 (1993)]’’ by Nuttall and Dolan is for the purpose of adding additional data concerning the nature and origin of the round window (RW)-recorded quadratic distortion tone (QDT) signal. It is shown that a major portion of the RW electrical signal originates from the activity of auditory neurons since tetrodotoxin (TTX) applied to the cochlea diminishes the distortion product by about 75%. The neural component is also responsible for the characteristic 900-Hz optimal frequency separation of the primaries in producing the response. These data support our earlier suggestion [Nuttall and Dolan, J. Acoust. Soc. Am. 93, 2061–2068 (1993)] that the level of intracellular receptor potential at the QDT frequency would be a stimulus for afferent fibers at low sound levels. These new data do not force a reinterpretation of Brown’s hypothesis on the relationship of quadratic and cubic intermodulation distortion.
Implications of noise on the reference signal in feedforward control of harmonic disturbances
Authors: Clark Robert L. , Gibbs Gary P.
Published: October 2005

The purpose of this Letter is to detail the effect of random (zero-mean) noise on the reference input of an adaptive feedforward filter in the control of single-frequency disturbance inputs. Results from this study indicate that if system identification is required to execute the adaptive algorithm (as is the case with the filtered-x LMS algorithm), then the sample rate should be set at 4 samples per period to minimize the number of finite impulse response filter coefficients needed to compute an accurate estimate of the filtered reference signal for multi-channel control. However, results from this study demonstrate that the sample rate has very little effect on the minimum mean-squared error that can be achieved with the adaptive control filter, owing to the reverberant characteristics of the dynamics system.
Recording of sound emission and propagation in air using TV holography
Authors: Lo/kberg Ole J.
Published: October 2005

The pressure variations caused by sound waves propagating in air result in corresponding changes in the refractive index. Using TV holography, the refractive index variations caused by single-frequency sound waves in a volume surrounding the sound emitter were recorded. The recording represents a two-dimensional mapping of the integrated sound fields where the magnitude and direction of the integrated field are found by phase stepping and image processing. For a complete description of the three-dimensional field recordings of several cross sections are needed, but in many cases valuable information can be obtained by two-dimensional projections. It is demonstrated how the technique can be used to study spatial variations in the sound emission from extended sources.
An acoustics measurement program for evaluating auditoriums based on the early/late sound energy ratio
Authors: Marshall L. Gerald
Published: October 2005

The importance of the early reflection portion of a sound decay process in an auditorium is well established. Curves showing early/late sound energy ratios (ELR) in the early reflection period comprise a useful way of examining energy-time data within that period. An auditorium measurement and analysis procedure using ELR data in the period between 20 and 200 ms after the arrival of the initial signal is presented.
Localization of helical flexural waves by irregularity
Authors: Photiadis Douglas M.
Published: October 2005

Small amounts of irregularity are known to produce vibration localization in one-dimensional chains, but the effects in two- and three-dimensional systems are typically much weaker. Here, a system with both one- and two-dimensional aspects, an axisymmetric, irregularly ribbed fluid-loaded cylindrical shell has been considered. A new formulation of this problem is given and each mode of the system is shown to be approximately equivalent to a nearest-neighbor coupled chain with six degrees of freedom corresponding to three left-going and three right-going traveling waves. An important theoretical ingredient of this investigation is the Green’s function of the infinite fluid-loaded cylindrical shell. A new representation of the Green’s function is given and it is shown that the long range coupling due to the adjoining fluid becomes very weak, falling off as z−(n+1) as the azimuthal mode number increases. Neglecting this weak coupling all the azimuthal modes are shown to be localized simultaneously by irregularity. The slow flexural waves have been shown to localize separately from the fast waves provided the helical angle of the flexural wave is greater than about (2Ωβ)1/2. As the helical angle increases the effects of irregularity become much more important and very short localization lengths of the order of a single rib spacing can occur.
Orthogonality relation for Rayleigh–Lamb modes of vibration of an arbitrarily layered elastic plate with and without fluid loading
Authors: Murphy Joseph E. , Li Gongqin , Chin-Bing Stanley A.
Published: October 2005

An orthogonality relation for the Rayleigh–Lamb modes of vibration of an isotropic, vertically layered elastic plate is derived. The derivation allows arbitrary variation of the plate properties in the vertical direction and includes the effects of fluid loading.
The Heard Island Feasibility Test
Authors: Munk Walter H. , Spindel Robert C. , Baggeroer Arthur , Birdsall Theodore G.
Published: October 2005

In January 1991, the Heard Island Feasibility Test (HIFT) was carried out to establish the limits of usable, long-range acoustic transmissions. Coded acoustic signals transmitted from a source near Heard Island in the southern Indian Ocean were monitored at 16 sites in the North and South Atlantic, the North and South Pacific, the Indian Ocean, and the Southern Ocean. The question posed by HIFT, whether at such global ranges the signals would permit phase-coherent processing and thus yield favorable signal-to-noise levels, was answered in the affirmative. There was no evidence of distress by the local marine mammal population in response to the acoustic transmissions. HIFT was prerequisite to a program for Acoustic Thermometry of Ocean Climate (ATOC). The principal challenges to such a program are discussed.
A ray variability analysis of sound transmission from Heard Island to California
Authors: Chiu Ching-Sang , Semtner Albert J. , Ort Coenraad M. , Miller James H. , Ehret Laura L.
Published: October 2005

The influence of mesoscale and seasonal ocean variability on three-dimensional acoustic ray paths from Heard Island through the Southern and Pacific Oceans to the California coast is investigated. For the simulation of these global acoustic ray paths, a three-dimensional Hamiltonian ray-tracing code was used. The input sound-speed fields to the acoustic ray model were interpolated from gridded temperature and salinity output data from the Semtner–Chervin eddy-resolving, global, general circulation model. The ray-tracing results have provided input to experimental planners for receiver placement off the California coast in the Heard Island Feasibility Test and shed light on the variability of the acoustic paths, insonified locations, arrival azimuthal angles, and travel times.
Doppler-inferred launch angles of global acoustic ray paths
Authors: Forbes Andrew , Munk Walter
Published: October 2005

Doppler measured at Ascension Island from a moving acoustic source at Heard Island is used to compute the azimuth of the acoustic path at the source. This method yields a launch angle of 268.06±0.1° as compared to the geodesically derived launch angle (allowing for Earth flattening and horizontal refraction) of 268.05°. Although the Doppler-derived launch azimuths should theoretically be able to resolve the small angular differences between acoustic paths to hydrophones to the West and East of Ascension, this proved not to be the case.
The Tasman blockage—An acoustic sink for the Heard Island feasibility test?
Authors: Forbes A. M. G.
Published: October 2005

Low-frequency (57-Hz) signals from the Heard Island Feasibility Test, conducted in January 1991 were received on many hydrophones around the globe. The Atlantic and Indian Ocean paths were relatively clear and unimpeded, so received signal-to-noise ratios (after some averaging) were generally high. The Pacific paths were not as clear and considerable interaction with bathymetric features attenuated the signals received off the west coast of the U.S. A New Zealand-manned receiver in the Tasman Sea received the transmissions strongly, but a Japanese ship, placed strategically northeast of the south Fiji (Lau) Ridge did not detect any signals. There is good evidence from U.S. west coast receivers with beam forming capability, that the signals arrived from 20 deg further south (i.e., south of New Zealand, then through the Polynesian window) than if they had passed through the Tasman Sea window. Doppler-derived matching of transmitted and received azimuths further indicates that all U.S. west coast signals traveled south of New Zealand. A series of transverse ridges lying between northern New Zealand and New Caledonia and Fiji appears to have effectively blocked the transmissions from exiting the Tasman Sea. An adiabatic modal model of refracted geodesic raypaths sheds some light on the reasons for such effective blockage.