bluuebunny/crossref_metadata_2025_split huggingface dataset:
Association of beta2 toxin production with Clostridium perfringens type A human gastrointestinal disease isolates carrying a plasmid enterotoxin gene
Authors: Fisher Derek J. , Miyamoto Kazuaki , Harrison Benjamin , Akimoto Shigero , Sarker Mahfuzur R. , McClane Bruce A. 
Published: April 2005

Summary Clostridium perfringens type A isolates carrying an enterotoxin (cpe) gene are an important cause of human gastrointestinal diseases, including food poisoning, antibiotic‐associated diarrhoea (AAD) and sporadic diarrhoea (SD). Using polymerase chain reaction (PCR), the current study determined that the cpb2 gene encoding the recently discovered beta2 toxin is present in <15% of food poisoning isolates, which typically carry a chromosomal cpe gene. However, >75% of AAD/SD isolates, which usually carry a plasmid cpe gene, tested cpb2+ by PCR. Western blot analysis demonstrated that >97% of those cpb2+/cpe+ AAD/SD isolates can produce CPB2. Additional PCR analyses, sequencing studies and pulsed field gel electrophoresis experiments determined that AAD/SD isolates carry cpb2 and cpe on the same plasmid when IS1151 sequences are present downstream of cpe, but cpb2 and cpe are located on different plasmids in AAD/SD isolates where IS1470‐like sequences are present downstream of cpe. Those analyses also demonstrated that two different CPB2 variants (named CPB2h1 or CPB2h2) can be produced by AAD/SD isolates, dependent on whether IS1470‐like or IS1151 sequences are present downstream of their cpe gene. CPB2h1 is ∼10‐fold more cytotoxic for CaCo‐2 cells than is CPB2h2. Collectively, these results suggest that CPB2 could be an accessory toxin in C. perfringens enterotoxin (CPE)‐associated AAD/SD.
Broad analysis reveals a consistent pattern of var gene transcription in Plasmodium falciparum repeatedly selected for a defined adhesion phenotype
Authors: Duffy Michael F. , Byrne Timothy J. , Elliott Salenna R. , Wilson Danny W. , Rogerson Stephen J. , Beeson James G. , Noviyanti Rintis , Brown Graham V. 
Published: April 2005

SummaryTranscription of the majority of the members of the Plasmodium falciparum var multigene family were analysed in two isolates by a quantitative approach. Both of these isolates had been repeatedly selected for adhesion to chondroitin sulphate A (CSA) and one had also been selected for adhesion to hyaluronic acid (HA). These adhesion phenotypes are expressed by many parasites isolated from placentae and are associated with malaria disease in pregnancy. Increased transcription of the var gene var2csa, or its homologue IT4 var4, was associated with the CSA and HA adhesion phenotypes in all parasites suggesting that it was the dominant, if not the only, var gene that encoded adhesion to CSA in these allogeneic isolates. Some var genes were consistently transcribed at higher levels than others regardless of expressed adhesion phenotypes suggesting a transcriptional hierarchy. Unspliced or partial transcripts were detected for most var genes tested. These atypical var gene transcripts may have implications for the regulation of var gene transcription.
The alternative sigma factor σE is required for resistance of Salmonella enterica serovar Typhimurium to anti‐microbial peptides
Authors: Crouch Marie‐Laure , Becker Lynne A. , Bang Iel‐Soo , Tanabe Hiroki , Ouellette Andre J. , Fang Ferric C. 
Published: April 2005

SummaryThe enteric pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) encounters a variety of anti‐microbial peptides during the course of infection. We report here that the extracytoplasmic sigma factor σE (RpoE) is required for Salmonella resistance to killing by the bactericidal/permeability‐increasing protein (BPI)‐derived peptide P2 and the murine α‐defensin cryptdin‐4 (Crp4). Moreover, σE‐deficient S. Typhimurium is attenuated for virulence after oral infection of immunocompromised gp91phox–/– mice that lack a functional NADPH phagocyte oxidase, suggesting that σE plays an important role in resistance to non‐oxidative mucosal host defences such as anti‐microbial peptides. Although both P2 and Crp4 target the cell envelope, bacterial killing by these peptides appears to occur by distinct mechanisms. Formate enhances bacterial resistance to P2, as previously demonstrated, but not to Crp4. Both σE and cytoplasmic membrane‐associated formate dehydrogenase are required for the protective effect of formate against P2. In contrast to P2, Crp4 does not inhibit bacterial respiration at lethal concentrations. However, both peptides induce expression of rpoE, suggesting that they trigger a common mechanism for sensing extracytoplasmic stress.
The initial step of glycerolipid metabolism in Leishmania major promastigotes involves a single glycerol‐3‐phosphate acyltransferase enzyme important for the synthesis of triacylglycerol but not essential for virulence
Authors: Zufferey Rachel , Mamoun Choukri Ben 
Published: April 2005

SummaryThe synthesis of the major phospholipids, including those that play an essential role in Leishmania virulence, initiates with the acylation of glycerol‐3‐phosphate and dihydroxyacetonephosphate at the sn‐1 position by glycerol‐3‐phosphate and dihydroxyacetonephosphate acyltransferases respectively. In this study, we show that Leishmania major promastigotes express a single glycerol‐3‐phosphate acyltransferase activity important for triacylglycerol synthesis but not essential for virulence. The encoding gene, LmGAT, expressed in yeast results in full complementation of the lethality of a mutant, gat1Δgat2Δ, lacking glycerol‐3‐phosphate activity. Biochemical analyses revealed that LmGAT is a low‐affinity glycerol‐3‐phosphate acyltransferase and exhibits higher specific activity with unsaturated long fatty acyl‐CoA donors. A L. major null mutant, Δlmgat/Δlmgat, was created and a thorough analysis of its lipid composition was performed. Deletion of LmGAT resulted in a complete loss of Leishmania glycerol‐3‐phosphate acyltransferase activity and a major reduction in triacylglycerol synthesis. Consistent with the specificity of LmGAT for glycerol‐3‐phosphate but not dihydroxyacetonephosphate, Δlmgat/Δlmgat mutant expressed normal levels of the ether‐lipid derivatives and virulence factors, lipophosphoglycan and GPI‐anchored proteins, gp63, and its virulence was not affected in mice.
Alternative sigma factor interactions in Salmonella: σE and σH promote antioxidant defences by enhancing σS levels
Authors: Bang Iel‐Soo , Frye Jonathan G. , McClelland Michael , Velayudhan Jyoti , Fang Ferric C. 
Published: April 2005

SummaryHierarchical interactions between alternative sigma factors control sequential gene expression in Gram‐positive bacteria, whereas alternative sigma factors in Gram‐negative bacteria are generally regarded to direct expression of discrete gene subsets. In Salmonella enterica serovar Typhimurium (S. Typhimurium), σE responds to extracytoplasmic stress, whereas σH responds to heat shock and σS is induced during nutrient limitation. Deficiency of σE, σH or σS increases S. Typhimurium susceptibility to oxidative stress, but an analysis of double and triple mutants suggested that antioxidant actions of σE and σH might be dependent on σS. Transcriptional profiling of mutant Salmonella lacking σE revealed reduced expression of genes dependent on σH and σS in addition to σE. Further investigation demonstrated that σE augments σS levels during stationary phase via enhanced expression of σH and the RNA‐binding protein Hfq, leading to increased expression of σS‐dependent genes and enhanced resistance to oxidative stress. Maximal expression of the σS‐regulated gene katE required σE in Salmonella‐infected macrophages as well as stationary‐phase cultures. Interactions between alternative sigma factors permit the integration of diverse stress signals to produce coordinated genetic responses.
Budding yeast PDS5 plays an important role in meiosis and is required for sister chromatid cohesion
Authors: Zhang Zhaojie , Ren Qun , Yang Hui , Conrad Michael N. , Guacci Vincent , Kateneva Anna , Dresser Michael E. 
Published: April 2005

SummaryBudding yeast PDS5 is an essential gene in mitosis and is required for chromosome condensation and sister chromatid cohesion. Here we report that PDS also is required in meiosis. Pds5p localizes on chromosomes at all stages during meiotic cycle, except anaphase I. PDS5 plays an important role at first meiotic prophase. Failure in function of PDS5 causes premature separation of chromosomes. The loading of Pds5p onto chromosome requires the function of REC8, but the association of Rec8p with chromosome is independent of PDS5. Mutant analysis and live cell imaging indicate that PDS5 play a role in meiosis II as well.
Antibiotic‐induced SOS response promotes horizontal dissemination of pathogenicity island‐encoded virulence factors in staphylococci
Authors: Úbeda Carles , Maiques Elisa , Knecht Erwin , Lasa Íñigo , Novick Richard P. , Penadés José R. 
Published: April 2005

SummaryAlthough mobile genetic elements have a crucial role in spreading pathogenicity‐determining genes among bacterial populations, environmental and genetic factors involved in the horizontal transfer of these genes are largely unknown. Here we show that SaPIbov1, a Staphylococcus aureus pathogenicity island that belongs to the growing family of these elements that are found in many strains, is induced to excise and replicate after SOS induction of at least three different temperate phages, 80α, φ11 and φ147, and is then packaged into phage‐like particles and transferred at high frequency. SOS induction by commonly used fluoroquinolone antibiotics, such as ciprofloxacin, also results in replication and high‐frequency transfer of this element, as well as of SaPI1, the prototypical island of S. aureus, suggesting that such antibiotics may have the unintended consequence of promoting the spread of bacterial virulence factors. Although the strains containing these prophages do not normally contain SaPIs, we have found that RF122‐1, the original SaPIbov1‐containing clinical isolate, contains a putative second pathogenicity island that is replicated after SOS induction, by antibiotic treatment, of the prophage(s) present in the strain. Although SaPIbov1 is not induced to replicate after SOS induction in this strain, it is transferred by the antibiotic‐activated phages. We conclude that SOS induction by therapeutic agents can promote the spread of staphylococcal virulence genes.
Bistability in the Bacillus subtilis K‐state (competence) system requires a positive feedback loop
Authors: Maamar Hédia , Dubnau David 
Published: April 2005

SummaryHigh expression of the transcriptional activator ComK occurs in 10–20% of the cells in stationary phase cultures of Bacillus subtilis strain 168. ComK drives the expression of more than 100 genes constituting the semidormant K‐state, distinct from sporulation and vegetative growth. Among the genes so activated are those that permit competence for genetic transformation. We have addressed the origin of bistability in expression of ComK. We show that bistability requires positive autoregulation at the promoter of comK, but not a potential toggle switch, in which ComK represses the promoter of rok and Rok represses the promoter of comK. We further address the source of the noise that results in the stochastic selection of cells that will express comK. A revised model for the regulation of comK expression is proposed that partially explains bistability.
Diversity within cyanobacterial mat communities in variable salinity meltwater ponds of McMurdo Ice Shelf, Antarctica
Authors: Jungblut Anne‐Dorothee , Hawes Ian , Mountfort Doug , Hitzfeld Bettina , Dietrich Daniel R. , Burns Brendan P. , Neilan Brett A. 
Published: April 2005

SummaryThis study investigated the diversity of cyanobacterial mat communities of three meltwater ponds – Fresh, Orange and Salt Ponds, south of Bratina Island, McMurdo Ice Shelf, Antarctica. A combined morphological and genetic approach using clone libraries was used to investigate the influence of salinity on cyanobacterial diversity within these ecosystems without prior cultivation or isolation of cyanobacteria. We were able to identify 22 phylotypes belonging to Phormidium sp., Oscillatoria sp. and Lyngbya sp. In addition, we identified Antarctic Nostoc sp., Nodularia sp. and Anabaena sp. from the clone libraries. Fresh (17 phylotypes) and Orange (nine phylotypes) Ponds showed a similar diversity in contrast to that of the hypersaline Salt Pond (five phylotypes), where the diversity within cyanobacterial mats was reduced. Using the comparison of identified phylotypes with existing Antarctic sequence data, it was possible to gain further insight into the different levels of distribution of phylotypes identified in the investigated cyanobacterial mat communities of McMurdo Ice Shelf.
Flux and turnover of fixed carbon in soil microbial biomass of limed and unlimed plots of an upland grassland ecosystem
Authors: Rangel‐Castro J. Ignacio , Prosser Jim I. , Ostle Nick , Scrimgeour Charlie M. , Killham Ken , Meharg Andy A. 
Published: April 2005

SummaryThe influence of liming on rhizosphere microbial biomass C and incorporation of root exudates was studied in the field by in situ pulse labelling of temperate grassland vegetation with 13CO2 for a 3‐day period. In plots that had been limed (CaCO3 amended) annually for 3 years, incorporation into shoots and roots was, respectively, greater and lower than in unlimed plots. Analysis of chloroform‐labile C demonstrated lower levels of 13C incorporation into microbial biomass in limed soils compared to unlimed soils. The turnover of the recently assimilated 13C compounds was faster in microbial biomass from limed than that from unlimed soils, suggesting that liming increases incorporation by microbial communities of root exudates. An exponential decay model of 13C in total microbial biomass in limed soils indicated that the half‐life of the tracer within this carbon pool was 4.7 days. Results are presented and discussed in relation to the absolute values of 13C fixed and allocated within the plant–soil system.
Three‐dimensional virtual worlds and distance learning: two case studies of Active Worlds as a medium for distance education
Authors: Dickey Michele D. 
Published: April 2005

AbstractOnline three‐dimensional (3D) virtual worlds are emerging technologies that offer unique learning opportunities for traditional and distributed education. One of the more popular 3D virtual worlds, Active Worlds, is currently being used as a medium for synchronous and asynchronous distance learning. This investigation presents two exploratory case studies of different, but exemplary educational activities using Active Worlds for formal and informal education. The focus of each case study is to investigate how Active Worlds is being used for distance learning and to determine the type of learning experiences afforded  by  this  3D  virtual  environment.  Whilst  more  research  is  necessary to explore fully the potential of 3D virtual worlds for learning, this initial investigation illustrates how Active Worlds affords opportunities for experiential learning and situated learning within a collaboration learning environment.
Managing content in e‐learning environments
Authors: Mwanza Daisy , Engeström Yrjö 
Published: April 2005

AbstractThe use of e‐learning environments to support teaching and learning has had great impact on the way content is developed and managed. In most cases, both teachers and students have had to re‐adapt the way they prepare, access and engage with educational matter. The adjustment in human mechanisms for organising and interacting with educational content has become necessary due to the re‐mediation of established practices through the introduction of software‐based techniques to structure content, for example, using metadata. Whilst metadata standards provide effective guidelines for organising content in web‐based e‐learning environments, technology‐based approaches to managing educational resources do not fully address social‐cultural and pedagogical aspects of users in the context in which teaching and learning takes place. In this regard, the effectiveness of using metadata to structure the discovery and access to educational content should be considered in relation to the extent by which metadata descriptors are associated with established socio‐cultural and pedagogical practices. Towards this end, we reflect on potential contributions of social‐cultural and learning theories to the task of managing content in e‐learning environments. The paper presents an activity‐centred approach to abstracting contextually and pedagogically enriched metadata descriptions of educational content and interactions with learning objects.
Evolution of a laptop university: a case study
Authors: McVay Gloria J. , Snyder Kimberlee D. , Graetz Kenneth A. 
Published: April 2005

AbstractTechnology is integral to carrying out many types of business transactions and has become entwined in the very fabric of everyday life. In the educational environment—particularly higher education—technology is underutilised as a pedagogical tool and in many cases remains largely untapped. Winona State University and its laptop programme learned some valuable lessons from the marriage between the application of the Seven Principles of Good Practice in Undergraduate Education and technology. The transformation into a leading laptop university was neither smooth nor easy, but it is a successful case about principle‐centred technological change and improved student learning outcomes.
Ring fenced research: the case of computer‐assisted learning in health sciences
Authors: Jacobs Gabriel , Ip Barry 
Published: April 2005

AbstractInterdisciplinary research is being promoted in many quarters as the way forward, but “research islands” still persist. Taking computer‐assisted learning (CAL) within health sciences as a case in point, this paper describes a detailed study of the references to source material within papers published in general medical, specific nursing and general information and communications technology journals as pointing to papers published either in the same category of journal or journals of other categories. The results show that research within this area exhibits a disquieting inbred approach. Furthermore, there is clear evidence of a tendency amongst the papers examined to cite research published in journals with broadly the same impact factors as the journal in which the papers themselves are published. A discussion of the value of journal impact factors, which are a crude but useful index of the quality of journal, and their possible effect on the future of research in CAL within health sciences is embedded in the paper.
Issues in the adoption of broadband‐enabled learning
Authors: Murphy Elizabeth 
Published: April 2005

AbstractThis paper presents one case of broadband‐enabled learning (BEL) involving geo‐culturally and organisationally diverse collaboration using music as the vehicle. Findings from five evaluations over a 15‐month period were considered in relation to issues of relative advantage, compatibility, complexity, trialability, and observability. Advantages included access to mentors, peers, and experts; support for cross‐cultural and linguistic collaboration, interaction, and exchanges; promotion of a more open classroom; and exposure to alternative and new experiences. Compatibility with existing practices was evident, however, cross‐cultural interaction presented difficulties as did synchronous communication across time zones and between institutions. BEL technologies are complex, however, users can develop a capacity to use the tools if provided with adequate support. Trialability is dependent on access to a high‐speed connection and equipment, multiple partners, development of technical expertise, and support. Use of videoconferencing and choice of subject area can enhance observability.
A knowledge management technology architecture for educational research organisations: Scaffolding research projects and workflow processing
Authors: Muthukumar  , Hedberg John G. 
Published: April 2005

AbstractThere is growing recognition that the economic climate of the world is shifting towards a knowledge‐based economy where knowledge will be cherished as the most prized asset. In this regard, technology can be leveraged as a useful tool in effectually managing the knowledge capital of an organisation. Although several research studies have advanced knowledge management frameworks catering to the requirements of organisations specialising in diverse fields of expertise, no comprehensive knowledge‐management architecture has been found that is technology mediated and orientated towards the emergent needs of an educational research organisation. In this paper, we review a knowledge management technology approach modeled as a web portal that was developed to create a repository and to facilitate shared resources in a research organisation. This technology‐based framework encapsulates the knowledge management processes that capture and augment the explicit knowledge resources of the research organisation. The framework also supports social networks that enable the sharing and encoding of tacit knowledge by facilitating online exchanges and feedback.
Implementation and evaluation of computer‐aided Mandarin phonemes training system for hearing‐impaired students
Authors: Yang Hui‐Jen , Lay Yun‐Long 
Published: April 2005

AbstractA computer‐aided Mandarin phonemes training (CAMPT) system was developed and evaluated for training hearing‐impaired students in their pronunciation of Mandarin phonemes. Deaf or hearing‐impaired people have difficulty hearing their own voice, hence most of them cannot learn how to speak. Phonemes are the basis for learning to read and speak in Mandarin. Thus, the main purpose of this study is to use voice‐recognition techniques to develop a Mandarin phoneme training system for the self‐training of hearing‐impaired people. The system analyses the spoken Mandarin phoneme of a hearing‐impaired person, compares it with the phonemes database, and shows the results on the computer monitor. Our CAMPT system helps hearing‐impaired people pronounce Mandarin phonemes, and the system automatically gives the learner a percentage score for each phoneme. In other words, learners can receive instant feedback from the system. Experiments conducted among high school students diagnosed with hearing impairment revealed that our system can help students learn the Mandarin phonemes with a neural net recognition algorithm for different users. After five months, most learners can pronounce 95% of the phonemes correctly.