bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of an inwardly rectifying K+ channel, Kir5.1, in specific types of fibrocytes in the cochlear lateral wall suggests its functional importance in the establishment of endocochlear potential
Authors: Hibino Hiroshi , Higashi‐Shingai Kayoko , Fujita Akikazu , Iwai Kaori , Ishii Masaru , Kurachi Yoshihisa 
Published: December 2004

AbstractCochlear endolymph contains 150 mm K+ and has a highly positive potential of ≈ +80 mV. The specialized ionic composition and high potential in endolymph are essential for hearing and maintained by circulation of K+ from perilymph to endolymph through the cochlear lateral wall. Various types of K+ channel such as Kir4.1 and KCNQ1/KCNE1 are expressed in stria vascularis of the lateral wall and play essential roles in K+ circulation. In this study, we examined a distribution of another K+ channel, Kir5.1, and found it specifically expressed in the spiral ligament of the cochlear lateral wall. Specific immunoreactivity for Kir5.1 was detected in type II, IV and V fibrocytes of the ligament and spiral limbus, all of which are directly involved in K+ circulation. Kir5.1 was not found in either type I or III fibrocytes. Although Kir5.1 assembles with Kir4.1 to form a functional Kir channel in renal epithelia and retinal Müller cells, double‐immunolabelling revealed that they were expressed in distinct regions in the cochlea lateral wall, i.e. Kir4.1 only in stria vascularis vs. Kir5.1 in spiral ligament. During development, the expression of Kir5.1 subunits started significantly later than Kir4.1 and was correlated with the ‘rapid’ phase of the elevation of endocochlear potential (EP). Kir5.1 and Kir4.1 channel‐subunits may therefore play distinct functional roles in K+ circulation in the cochlear lateral wall.
Lesions of dorsolateral striatum preserve outcome expectancy but disrupt habit formation in instrumental learning
Authors: Yin Henry H. , Knowlton Barbara J. , Balleine Bernard W. 
Published: December 2004

AbstractHabits are controlled by antecedent stimuli rather than by goal expectancy. Interval schedules of feedback have been shown to generate habits, as revealed by the insensitivity of behaviour acquired under this schedule to outcome devaluation treatments. Two experiments were conducted to assess the role of the dorsolateral striatum in habit learning. In Experiment 1, sham operated controls and rats with dorsolateral striatum lesions were trained to press a lever for sucrose under interval schedules. After training, the sucrose was devalued by inducing taste aversion to it using lithium chloride, whereas saline injections were given to the controls. Only rats given the devaluation treatment reduced their consumption of sucrose and this reduction was similar in both the sham and the lesioned groups. All rats were then returned to the instrumental chamber for an extinction test, in which the lever was extended but no sucrose was delivered. In contrast to sham operated controls, rats with dorsolateral striatum lesions refrained from pressing the lever if the outcome was devalued. To assess the specificity of the role of dorsolateral striatum in this effect a second experiment was conducted in which a group with lesions of dorsomedial striatum was added. In relation now to both the sham and the dorsomedial lesioned groups, only rats with lesions of dorsolateral striatum significantly reduced responding after outcome devaluation. In conclusion, this study provides direct evidence that the dorsolateral striatum is necessary for habit formation. Furthermore, it suggests that, when the habit system is disrupted, control over instrumental performance reverts to the system controlling the performance of goal‐directed instrumental actions.
Stimulus‐induced change in long‐range temporal correlations and scaling behaviour of sensorimotor oscillations
Authors: Linkenkaer‐Hansen Klaus , Nikulin Vadim V. , Palva J. Matias , Kaila Kai , Ilmoniemi Risto J. 
Published: December 2004

AbstractThe human brain spontaneously generates large‐scale network oscillations at around 10 and 20 Hz. The amplitude envelope of these oscillations fluctuates intermittently and was recently reported to exhibit power‐law decay of the autocorrelation for hundreds of seconds. This indicates that the underlying networks are in a dynamic state resembling the self‐organized critical state known to exist in many complex systems. Based on the mechanism of how correlations emerge in these systems, we hypothesized that the physiological basis of long‐range power‐law correlations is the buildup of a memory of past activity by a continuous modification of the network's functional connectivity by the ongoing oscillations. In this framework, exogenous perturbations of ongoing oscillations would degrade or abolish this dynamic network memory. We investigated the sensitivity of the temporal correlations in sensorimotor 10‐ and 20‐Hz oscillations to median nerve stimulation that is known to have immediate effects on ongoing oscillations. Our results show that the amplitude fluctuations of these oscillations were effectively modulated by the somatosensory stimuli but still exhibited long‐range temporal correlations and power‐law scaling behaviour. The magnitude of the temporal correlations was, however, attenuated and the power‐law exponents were decreased. This implies that the stimuli indeed degraded the network's memory of its past.
Cardiac arrest with cardiopulmonary resuscitation reduces dendritic spine density in CA1 pyramidal cells and selectively alters acquisition of spatial memory
Authors: Neigh Gretchen N. , Glasper Erica R. , Kofler Julia , Traystman Richard J. , Mervis Ronald F. , Bachstetter Adam , DeVries A. Courtney 
Published: December 2004

AbstractThe hippocampus is highly sensitive to ischemia and is one of the most extensively damaged regions of brain during cardiac arrest. Damage to hippocampus can subsequently lead to learning and memory deficits. The current study used the Morris water maze to characterize spatial learning and memory deficits elicited by 8 min of cardiac arrest with cardiopulmonary resuscitation (CA/CPR) in mice, which is associated with a 25–50% decrease in CA1 neurons. Mice were trained to navigate the water maze prior to CA/CPR or sham surgery (SHAM). They were retested in the water maze on days 7 and 8 postsurgery; both CA/CPR and SHAM groups were able to perform the task at presurgical levels. However, when the hidden platform was moved to a new location, the SHAM mice were able to adapt more quickly to the change and swam a shorter distance in search of the platform than did CA/CPR mice. Thus, CA/CPR did not affect the ability of mice to retain a previously learned platform location, but it did affect their ability to learn a new platform location. This behavioural impairment was correlated with dendritic spine density in the CA1 region of the hippocampus. Data presented here suggest that morphological changes, such as spine density, that occur in neurons that survive CA/CPR may be associated with cognitive impairments.
A meta‐analysis of biotic resistance to exotic plant invasions
Authors: Levine Jonathan M. , Adler Peter B. , Yelenik Stephanie G. 
Published: December 2004

AbstractBiotic resistance describes the ability of resident species in a community to reduce the success of exotic invasions. Although resistance is a well‐accepted phenomenon, less clear are the processes that contribute most to it, and whether those processes are strong enough to completely repel invaders. Current perceptions of strong, competition‐driven biotic resistance stem from classic ecological theory, Elton's formulation of ecological resistance, and the general acceptance of the enemies‐release hypothesis. We conducted a meta‐analysis of the plant invasions literature to quantify the contribution of resident competitors, diversity, herbivores and soil fungal communities to biotic resistance. Results indicated large negative effects of all factors except fungal communities on invader establishment and performance. Contrary to predictions derived from the natural enemies hypothesis, resident herbivores reduced invasion success as effectively as resident competitors. Although biotic resistance significantly reduced the establishment of individual invaders, we found little evidence that species interactions completely repelled invasions. We conclude that ecological interactions rarely enable communities to resist invasion, but instead constrain the abundance of invasive species once they have successfully established.
Hazardous duty pay and the foraging cost of predation
Authors: Brown Joel S. , Kotler Burt P. 
Published: December 2004

AbstractWe review the concepts and research associated with measuring fear and its consequences for foraging. When foraging, animals should and do demand hazardous duty pay. They assess a foraging cost of predation to compensate for the risk of predation or the risk of catastrophic injury. Similarly, in weighing foraging options, animals tradeoff food and safety. The foraging cost of predation can be modelled, and it can be quantitatively and qualitatively measured using risk titrations. Giving‐up densities (GUDs) in depletable food patches and the distribution of foragers across safe and risky feeding opportunities are two frequent experimental tools for titrating food and safety. A growing body of literature shows that: (i) the cost of predation can be big and comprise the forager's largest foraging cost, (ii) seemingly small changes in habitat or microhabitat characteristics can lead to large changes in the cost of predation, and (iii) a forager's cost of predation rises with risk of mortality, the forager's energy state and a decrease in its marginal value of energy. In titrating for the cost of predation, researchers have investigated spatial and temporal variation in risk, scale‐dependent variation in risk, and the role of predation risk in a forager's ecology. A risk titration from a feeding animal often provides a more accurate behavioural indicator of predation risk than direct observations of predator‐inflicted mortality. Titrating for fear responses in foragers has some well‐established applications and holds promise for novel methodologies, concepts and applications. Future directions for expanding conceptual and empirical tools include: what are the consequences of foraging costs arising from interference behaviours and other sources of catastrophic loss? Are there alternative routes by which organisms can respond to tradeoffs of food and safety? What does an animal's landscape of fear look like as a spatially explicit map, and how do various environmental factors affect it? Behavioural titrations will help to illuminate these issues and more.
The σ54 regulon (sigmulon) of Pseudomonas putida
Authors: Cases Ildefonso , Ussery David W. , De Lorenzo Víctor 
Published: December 2004

Summaryσ54 is unique among the bacterial sigma factors. Besides not being related in sequence with the rest of such factors, its mechanism of transcription initiation is completely different and requires the participation of a transcription activator. In addition, whereas the rest of the alternative sigma factors use to be involved in transcription of somehow related biological functions, this is not the case for σ54 and many different and unrelated genes have been shown to be transcribed from σ54‐dependent promoters, ranging from flagellation, to utilization of several different carbon and nitrogen sources, or alginate biosynthesis. These genes have been characterized in many different bacterial species and, only until recently with the arrival of complete genome sequences, we have been able to look at the σ54 functional role from a genomic perspective. Aided by computational methods, the σ54 regulon has been studied both in Escherichia coli, Salmonella typhimurium and several species of the Rhizobiaceae. Here we present the analysis of the σ54 regulon (sigmulon) in the complete genome of Pseudomonas putida KT2440. We have developed an improved method for the prediction of σ54‐dependent promoters which combines the scores of σ54‐RNAP target sequences and those of activator binding sites. In combination with other evidence obtained from the chromosomal context and the similarity with closely related bacteria, we have been able to predict more than 80% of the σ54‐dependent promoters of P. putida with high confidence. Our analysis has revealed new functions for σ54 and, by means of comparative analysis with the previous studies, we have drawn a potential mechanism for the evolution of this regulatory system.
Influence of maize mucilage on the diversity and activity of the denitrifying community
Authors: Mounier E. , Hallet S. , Chèneby D. , Benizri E. , Gruet Y. , Nguyen C. , Piutti S. , Robin C. , Slezack‐Deschaumes S. , Martin‐Laurent F. , Germon J.C. , Philippot L. 
Published: December 2004

SummaryIn order to understand the effect of the maize rhizosphere on denitrification, the diversity and the activity of the denitrifying community were studied in soil amended with maize mucilage. Diversity of the denitrifying community was investigated by polymerase chain reaction (PCR) amplification of total community DNA extracted from soils using gene fragments, encoding the nitrate reductase (narG) and the nitrous oxide reductase (nosZ), as molecular markers. To assess the underlying diversity, PCR products were cloned and 10 gene libraries were obtained for each targeted gene. Libraries containing 738 and 713 narG and nosZ clones, respectively, were screened by restriction fragment analysis, and grouped based on their RFLP (restriction fragment length polymorphism) patterns. In all, 117 and 171 different clone families have been identified for narG and nosZ and representatives of RFLP families containing at least two clones were sequenced. Rarefaction curves of both genes did not reach a clear saturation, indicating that analysis of an increasing number of clones would have revealed further diversity. Recovered NarG sequences were related to NarG from Actinomycetales and from Proteobacteria but most of them are not related to NarG from known bacteria. In contrast, most of the NosZ sequences were related to NosZ from α, β, and γProteobacteria. Denitrifying activity was monitored by incubating the control and amended soils anaerobically in presence of acetylene. The N2O production rates revealed denitrifying activity to be greater in amended soil than in control soil. Altogether, our results revealed that mucilage addition to the soil results in a strong impact on the activity of the denitrifying community and minor changes on its diversity.
Environmental regulation of the anaerobic oxidation of methane: a comparison of ANME‐I and ANME‐II communities
Authors: Nauhaus Katja , Treude Tina , Boetius Antje , Krüger Martin 
Published: December 2004

SummaryThe anaerobic oxidation of methane (AOM) is one of the major sinks for methane on earth and is known to be mediated by at least two phylogenetically different groups of anaerobic methanotrophic Archaea (ANME‐I and ANME‐II). We present the first comparative in vitro study of the environmental regulation and physiology of these two methane‐oxidizing communities, which occur naturally enriched in the anoxic Black Sea (ANME‐I) and at Hydrate Ridge (ANME‐II). Both types of methanotrophic communities are associated with sulfate‐reducing‐bacteria (SRB) and oxidize methane anaerobically in a 1:1 ratio to sulfate reduction (SR). They responded sensitively to elevated methane partial pressures with increased substrate turnover. The ANME‐II‐dominated community showed significantly higher cell‐specific AOM rates. Besides sulfate, no other electron acceptor was used for AOM. The processes of AOM and SR could not be uncoupled by feeding the SRB with electron donors such as acetate, formate or molecular hydrogen. AOM was completely inhibited by the addition of bromoethanesulfonate in both communities, indicating the participation of methanogenic enzymes in the process. Temperature influenced the intensity of AOM, with ANME‐II being more adapted to cold temperatures than ANME‐I. The variation of other environmental parameters, such as sulfate concentration, pH and salinity, did not influence the activity of both communities. In conclusion, the ecological niches of methanotrophic Archaea seem to be mainly defined by the availability of methane and sulfate, but it remains open which additional factors lead to the dominance of ANME‐I or ‐II in the environment.
Isolation and characterization of Tn‐Dha1, a transposon containing the tetrachloroethene reductive dehalogenase of Desulfitobacterium hafniense strain TCE1
Authors: Maillard Julien , Regeard Christophe , Holliger Christof 
Published: December 2004

SummaryA new 9.9 kb catabolic transposon, Tn‐Dha1, containing the gene responsible for tetrachloroethene (PCE) reductive dechlorination activity, was isolated from Desulfitobacterium hafniense strain TCE1. Two fully identical copies of the insertion sequence ISDha1, a new member of the IS256 family, surround the gene cluster pceABCT, a truncated gene for another transposase and a short open reading frame with homology to a member of the twin‐arginine transport system (tatA). Evidence was obtained by Southern blot for an alternative form of the transposon element as a circular molecule containing only one copy of ISDha1. This latter structure most probably represents a dead‐end product of the transposition of Tn‐Dha1. Strong indications for the transposition activity of ISDha1 were given by polymerase chain reaction (PCR) amplification and sequencing of the intervening sequence located between both inverted repeats (IR) of ISDha1 (IR junction). A stable genomic ISDha1 tandem was excluded by quantitative real‐time PCR. Promoter mapping of the pceA gene, encoding the reductive dehalogenase, revealed the presence of a strong promoter partially encoded in the right inverted repeat of ISDha1. A sequence comparison with pce gene clusters from Desulfitobacterium sp. strains PCE‐S and Y51 and from Dehalobacter restrictus, all of which show 100% identity for the pceAB genes, indicated that both Desulfitobacterium strains seem to possess the same transposon structure, whereas only the pceABCT gene cluster is conserved in D. restrictus.
Diversity of functional genes of methanogens, methanotrophs and sulfate reducers in deep‐sea hydrothermal environments
Authors: Nercessian Olivier , Bienvenu Nadège , Moreira David , Prieur Daniel , Jeanthon Christian 
Published: December 2004

SummaryTo contribute to the identification of methanogens, methanotrophs and sulfate‐reducing bacteria (SRB) in microbial communities from the 13°N (East Pacific Rise) and Rainbow (Mid‐Atlantic Ridge) hydrothermal vent fields, we investigated the diversity of mcrA, pmoA and dsrAB genes sequences. Clone libraries were obtained using DNA isolated from fragments of diffuse vents, sediment and in situ samplers. The clones were categorized by restriction fragment length polymorphism, and representatives of each group were sequenced. Sequences were related to that of hyperthermophilic (order Methanopyrales and family Methanocaldococcaceae), thermophilic and mesophilic (family Methanococcaceae) methanogens, thermophilic (proposed genus ‘Methylothermus’) and mesophilic type I methanotrophs, and hyperthermophilic (order Archaeoglobales), thermophilic (order Thermodesulfobacteriales) and mesophilic (family Desulfobulbaceae) SRB. Several of the obtained sequences were distantly related to the genes of cultivated organisms, providing evidence of the existence of novel lineages in the three functional groups. This study provides for the first time an insight into the diversity of several functional genes of deep‐sea hydrothermal system microorganisms.
Modelling potential impacts of climate change on the bioclimatic envelope of species in Britain and Ireland
Authors: Berry P. M. , Dawson T. P. , Harrison P. A. , Pearson R. G. 
Published: December 2004

ABSTRACTAim Climate change has the potential to have significant impacts on the distribution of species and on the composition of habitats. This paper identifies the potential changes in the future distribution of species under the UKCIP98 climate change scenarios, in order that such changes can be taken into account in conservation management.Location The model was applied to Britain and Ireland.Methods A model based on an artificial neural network was used to predict the changing bioclimate envelopes of species in Britain and Ireland. Fifty‐four species representing 15 habitats were modelled.Results The modelled species could be placed into three categories: those losing suitable climate space, those gaining it, and those showing little or no change. When the species were associated with habitats it was found that Arctic–Alpine/montane heath communities were the most sensitive to climate change, followed by pine woodland and beech woodland in southern England. In lowland heath, wet heath, cereal field margins, coastal grazing marsh, drought‐prone acid grassland and calcareous grassland, the species either showed little change or an increase in suitable climate space. The other eight habitats showed a mixed response.Conclusions The species show a variety of responses to climate change and thus their current habitat associations may alter. The uncertain future of some species and habitats is highlighted. Conservation policy and practice will need to be revised in the face of climate change.
Effect of Promoter Region Mutations and
mgrA
Overexpression on Transcription of
norA
, Which Encodes a
Staphylococcus aureus
Multidrug Efflux Transporter
Authors: Kaatz Glenn W. , Thyagarajan Rama V. , Seo Susan M. 
Published: December 2004

ABSTRACT

NorA is a
Staphylococcus aureus
multidrug transporter that confers resistance to structurally distinct compounds. The MgrA global regulatory protein is reported to augment
norA
expression when
mgrA
is overexpressed from an undefined plasmid-based promoter. Further details about
norA
regulatory mechanisms are scant. A chromosomal
norA
::
lacZ
transcriptional fusion was constructed in different
S. aureus
strains, and allele replacement was used to define the relevance of promoter region sequences to
norA
expression. The effect of
mgrA
overexpression in wild-type and mutant backgrounds was also determined. Contrary to existing data, overexpression of
mgrA
repressed
norA
transcription in all parent and selected
norA
promoter mutant strains in a dose-dependent fashion. Disruption of a near-perfect inverted repeat or other putative regulatory protein binding sites did not affect
norA
transcription, but the repressive effect of
mgrA
overexpression was blunted in these mutants. This result, and the conservation of all of these motifs in
S. aureus
, suggests that their presence is required for the full effect of MgrA, or other regulatory proteins, on
norA
expression. Mutations at the +5 nucleotide of
norA
mRNA (
flqB
mutations) had a major impact; all resulted in markedly increased
norA
expression that was significantly reversed by
mgrA
overexpression. The
flqB
position of
norA
mRNA is part of a conserved imperfect inverted repeat; it is feasible that this motif could be a binding site for a
norA
regulatory protein.