bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Pseudomonas proteins coordinately induced by acidic amino acids and their amides: a two-dimensional electrophoresis study
Authors: Sonawane Avinash , Klöppner Ute , Hövel Sven , Völker Uwe , Röhm Klaus-Heinrich
Published: October 2003

The acidic amino acids (Asp, Glu) and their amides (Asn, Gln) are excellent growth substrates for many pseudomonads. This paper presents proteomics data indicating that growth ofPseudomonas fluorescensATCC 13525 andPseudomonas putidaKT2440 on these amino acids as sole source of carbon and nitrogen leads to the induction of a defined set of proteins. Using mass spectrometry and N-terminal sequencing, a number of these proteins were identified as enzymes and transporters involved in amino acid uptake and metabolism. Most of them depended on the alternative sigma factorσ54for expression and were subject to strong carbon catabolite repression by glucose and citrate cycle intermediates. For a subset of the identified proteins, the observed regulatory effects were independently confirmed by RT-PCR. The authors propose that the respective genes (together with others still to be identified) make up a regulon that mediates uptake and utilization of the abovementioned amino acids.
Transcriptional regulation of drug efflux genes by EvgAS, a two-component system in Escherichia coli
Authors: Eguchi Yoko , Oshima Taku , Mori Hirotada , Aono Rikizo , Yamamoto Kaneyoshi , Ishihama Akira , Utsumi Ryutaro
Published: October 2003

A constitutively active mutant of histidine kinase sensor EvgS was found to confer multi-drug resistance (MDR) to an acrA-deficient Escherichia coli, indicating the relationship between the two-component system EvgAS and the expression of the MDR system. The observed MDR also depended on an outer-membrane channel, TolC. Microarray and S1 mapping assays indicated that, in the presence of this constitutive mutant EvgS, the level of transcription increased for some MDR genes, including the drug efflux genes emrKY, yhiUV, acrAB, mdfA and tolC. Transcription in vitro of emrK increased by the addition of phosphorylated EvgA. Transcription activation of tolC by the activated EvgS was, however, dependent on both EvgAS and PhoPQ (Mg2+-responsive two-component system), in agreement with the presence of the binding site (PhoP box) for the regulator PhoP in the tolC promoter region. Transcription in vitro of yhiUV also appears to require an as-yet-unidentified additional transcriptional factor besides EvgA. Taken together we propose that the expression of the MDR system is under a complex regulatory network, including the phosphorylated EvgA serving as the master regulator.
The adhesive and immunomodulating properties of the multifunctional Staphylococcus aureus protein Eap
Authors: Harraghy Niamh , Hussain Muzaffar , Haggar Axana , Chavakis Triantafyllos , Sinha Bhanu , Herrmann Mathias , Flock Jan-Ingmar
Published: October 2003

Adherence ofStaphylococcus aureusto the host tissue is an important step in the initiation of pathogenesis. At least 10 adhesins produced byS. aureushave been described and it is becoming clear that the expression of these adhesins and their interactions with eukaryotic cells involve complex processes. Some of these, such as the fibronectin-binding proteins (FnBPs) and Clumping Factor A, are well characterized. However, in the last 10 years a number of novelS. aureusadhesins have been described. Functional analyses of these proteins, one of which is Eap (extracellularadherenceprotein, also known as Map and p70), are revealing important information on the pathogenesis of staphylococcal disease. More than 10 years after the first report of Eap, we are beginning to understand that this protein, which has a broad spectrum of functions, may be a critical factor in the pathogenesis ofS. aureus. This review will focus on the interactions of Eap with eukaryotic cells, plasma proteins and the extracellular matrix as well as on the recently recognized role of Eap as an important mediator in the immune response to staphylococcal infection.
Disruption of the gene encoding the ChiB1 chitinase of Aspergillus fumigatus and characterization of a recombinant gene product
Authors: Jaques Alex K. , Fukamizo Tamo , Hall Diana , Barton Richard C. , Escott Gemma M. , Parkinson Tanya , Hitchcock Christopher A. , Adams David J.
Published: October 2003

The gene encoding a major, inducible 45 kDa chitinase ofAspergillus fumigatuswas cloned and analysis of the deduced amino acid sequence identified a chitinase of the fungal/bacterial class which was designated ChiB1. Recombinant ChiB1, expressed inPichia pastoris, was shown to function by a retaining mechanism of action. That is, theβ-conformation of the chitin substrate linkage was preserved in the product in a manner typical of family 18 chitinases. Cleavage patterns with theN-acetylglucosamine (GlcNAc) oligosaccharide substrates GlcNAc4, GlcNAc5and GlcNAc6indicated that the predominant reaction involved hydrolysis of GlcNAc2from the non-reducing end of each substrate. Products of transglycosylation were also identified in each incubation. Following disruption ofchiB1by gene replacement, growth and morphology of disruptants and of the wild-type strain were essentially identical. However, during the autolytic phase of batch cultures the level of chitinase activity in culture filtrate from a disruptant was much lower than the activity from the wild-type. The search for chitinases with morphogenetic roles in filamentous fungi should perhaps focus on chitinases of the fungal/plant class although such an investigation will be complicated by the identification of at least 11 putative active site domains for family 18 chitinases in theA. fumigatusTIGR database (http://www.tigr.org/).
The regulatory link between carbon and nitrogen metabolism in Bacillus subtilis: regulation of the gltAB operon by the catabolite control protein CcpA
Authors: Wacker Ingrid , Ludwig Holger , Reif Irene , Blencke Hans-Matti , Detsch Christian , Stülke Jörg
Published: October 2003

Bacillus subtilis assimilates ammonium by the concerted action of glutamine synthetase and glutamate synthase. The expression of the gltAB operon encoding the latter enzyme is impaired in B. subtilis ccpA mutant strains. CcpA is a pleiotropic transcriptional regulator that is the key factor in the regulation of carbon metabolism. However, in addition to their defect in catabolite repression ccpA mutants are unable to grow on minimal media with glucose and ammonium as the single sources of carbon and nitrogen, respectively. In this work, the expression of the gltAB operon was analysed and its role in growth on minimal sugar/ammonium media was studied. Expression of gltAB requires induction by glucose or other glycolytically catabolized carbon sources. In ccpA mutants, gltAB cannot be induced by glucose due to the low activity of the phosphotransferase sugar transport system in these mutants. A mutation that allowed phosphotransferase system activity in a ccpA background simultaneously restored glucose induction of gltAB and growth on glucose/ammonium medium. Moreover, artificial induction of the gltAB operon in the ccpA mutant allowed the mutant strain to grow on minimal medium with glucose and ammonium. It may be concluded that expression of the gltAB operon depends on the accumulation of glycolytic intermediates which cannot occur in the ccpA mutant. The lack of gltAB induction is the bottleneck that prevents growth of the ccpA mutant on glucose/ammonium media. The control of expression of the gltAB operon by CcpA provides a major regulatory link between carbon and amino acid metabolism.
Physical and gene maps of Agrobacterium biovar 2 strains and their relationship to biovar 1 chromosomes
Authors: Urbanczyk Henryk , Suzuki Katsunori , Yoshida Kazuo , Kondo Katsuhiko
Published: October 2003

Diverse types of genomic DNA organization have been found in Rhizobiaceae, especially among Agrobacterium species. Previous studies of Agrobacterium concentrated mainly on biovar 1 strains. Little attention has been given to biovar 2 strains. The biovar 2 genome consists of a large, circular chromosome and second megabase-sized replicon, as well as several plasmids. In this study two biovar 2 strains were analysed, A. rhizogenes (A. radiobacter) K84 and A. rhizogenes A4, by constructing physical maps of their chromosomes and mega-replicons. The maps revealed that in both strains their chromosomes consist of approximately 3·7 Mbp, while the mega-replicons are 2·6 Mbp circular DNAs. Gene mapping and comparative genomic analysis were performed based on the physical maps using Southern hybridization. It was found that rDNA, as well as analysed virulence and virulence-related genes, are present only on the chromosomes. The inter-chromosomal relationship between biovar 1 and biovar 2 strains was also analysed. Interestingly, there was a high similarity between the chromosomes of biovar 2 and the circular chromosomes of biovar 1, whereas similarity among the smaller megabase-sized replicons was restricted to each biovar. Based on these observations the possible relationship among large replicons in Agrobacterium biovars 1 and 2 is discussed.
Investigation of the role of a β(1–4) agarase produced by Pseudoalteromonas gracilis B9 in eliciting disease symptoms in the red alga Gracilaria gracilis
Authors: Schroeder Declan C. , Jaffer Mohamed A. , Coyne Vernon E.
Published: October 2003

Gracilariaspecies are an important source of agar. The South AfricanGracilariaindustry has experienced a number of setbacks over the last decade in the form of complete or partial die-offs of the agarophyte growing in Saldanha Bay, which may be attributed to bacterial infection. Since a positive correlation was observed between the presence of agarolytic epiphytes and bacterial pathogenicity, we investigated the role of an agarase in the virulence mechanism employed by a bacterium that elicits disease inGracilaria gracilis. The recombinant plasmid pDA1, isolated from aPseudoalteromonas gracilisB9 genomic library, was responsible for the agarolytic activity exhibited byEscherichia colitransformants when grown on solid medium. Ablastsearch of the GenBank database showed that an 873 bp ORF (aagA) located on pDA1 had 85 % identity to theβ-agarase (dagA) fromPseudoalteromonas atlanticaATCC 19262T(or IAM 12927T) at the amino acid level. AagA was purified from the extracellular medium of anE. colitransformant harbouring pDA1 by using a combination of gel filtration and ion-exchange chromatography. AagA has anMrof 30 000 on SDS-PAGE. TLC of the digestion products of AagA showed that the enzyme cleaves theβ-(1,4) linkages of agarose to yield predominately neoagarotetraose. Western hybridization confirmed that the cloned agarase was in fact the extracellularβ-agarase ofP. gracilisB9. The observed relationship between disease symptoms ofG. gracilisand the agarolytic phenotype ofP. gracilisB9 was confirmed. Transmission electron microscope examination of cross sections of both healthyG. gracilisandG. gracilisinfected withP. gracilis, revealed a weakening of the cell structure in the latter plants. Immunogold-labelled antibodies localized the agarasein situto the cell walls of bleachedG. gracilis. Thus, the weakening observed in the cell structure ofG. gracilisinfected withP. graciliscan be attributed to degradation of the mucilaginous component of the cell wall of the bleached thalli.
The cAMP phosphodiesterase encoded by CaPDE2 is required for hyphal development in Candida albicans
Authors: Jung Won Hee , Stateva Lubomira I.
Published: October 2003

The cAMP-dependent pathway, which regulates yeast-to-hypha morphogenesis inCandida albicans, is controlled by changes in cAMP levels determined by the processes of synthesis and hydrolysis. Both low- and high-affinity cAMP phosphodiesterases are encoded in theC. albicansgenome.CaPDE2, encoding the high-affinity cAMP phosphodiesterase, has been cloned and shown to be toxic inSaccharomyces cerevisiaeupon overexpression under pGAL1, but functional under the moderate pMET3. Deletion ofCaPDE2causes elevated cAMP levels and responsiveness to exogenous cAMP, higher sensitivity to heat shock, severe growth defects at 42 °C and highly reduced levels ofEFG1transcription.In vitroin hypha-inducing liquid mediumCaPDE2, deletion prohibits normal hyphal, but not pseudohyphal growth. On solid mediumcapde2mutants form aberrant hyphae, with fewer branches and almost no lateral buds, which are deficient in hypha-to-yeast reversion. The phenotypic defects ofcapde2mutants show that the cAMP-dependent pathway plays specific roles in hyphal and pseudohyphal development, its regulatory role however, being greater in liquid than on solid mediumin vitro. The increased expression ofCaPDE2after serum addition correlates well with a drop in cAMP levels following the initial rise in response to the hyphal inducer. These results suggest that Capde2p mediates a desensitization mechanism by lowering basal cAMP levels in response to environmental stimuli inC.albicans.
Identification and characterization of a novel autolysin (Aae) with adhesive properties from Staphylococcus epidermidis
Authors: Heilmann Christine , Thumm Günther , Chhatwal Gursharan S. , Hartleib Jörg , Uekötter Andreas , Peters Georg
Published: October 2003

Staphylococcus epidermidisbiofilm formation on polymer surfaces is considered a major pathogenicity factor in foreign-body-associated infections. Previously, the 148 kDa autolysin AtlE fromS.epidermidis, which is involved in the initial attachment of the cells to polymer surfaces and also binds to the extracellular matrix protein vitronectin, was characterized. Here, the characterization of a novel autolysin/adhesin (Aae) inS.epidermidis is described. Aae was identified as a 35 kDa surface-associated protein that has bacteriolytic activity and binds vitronectin. Its N-terminal amino acid sequence was determined and the respective gene,aae, was cloned. DNA-sequence analysis revealed thataaeencodes a deduced protein of 324 amino acids with a predicted molecular mass of 35 kDa. Aae contains three repetitive sequences in its N-terminal portion. These repeats comprise features of a putative peptidoglycan binding domain (LysM domain) found in a number of enzymes involved in cell-wall metabolism and also in some adhesins. Expression ofaaebyEscherichia coliand subsequent analysis revealed that Aae possesses bacteriolytic activity and adhesive properties. The interaction of Aae with fibrinogen, fibronectin and vitronectin was found to be dose-dependent and saturable and to occur with high affinity, by using the real-time Biomolecular Interaction Analysis (BIA). Aae binds to the Aα- and Bβ-chains of fibrinogen and to the 29 kDa N-terminal fragment of fibronectin. In conclusion, Aae is a surface-associated protein with bacteriolytic and adhesive properties representing a new member of the staphylococcal autolysin/adhesins potentially involved in colonization.
Proposed pathway for the biosynthesis of serovar-specific glycopeptidolipids in Mycobacterium avium serovar 2
Authors: Eckstein Torsten M. , Belisle John T. , Inamine Julia M.
Published: October 2003

Members of theMycobacterium aviumcomplex are distinguished by the presence of highly antigenic surface molecules called glycopeptidolipids (GPLs) and the oligosaccharide portion of the serovar-specific GPL defines the 28 serovars. Previously, the genomic region (ser2) encoding the enzymes responsible for the glycosylation of the lipopeptide core to generate the serovar-2-specific GPLs has been described. In this work, theser2gene clusters ofM. aviumserovar 2 strains 2151 and TMC 724 were fully sequenced and compared to the homologous regions ofM. aviumserovar 1 strain 104,M. aviumsubsp.paratuberculosisandM. aviumsubsp.silvaticum. It was also determined that 104Rg, a mutant of strain 104 that produces truncated GPLs, lost several GPL biosynthesis genes by deletion. This comparison, together with analysis of protein similarities, supports a biosynthetic model in which serovar-2-specific GPLs are synthesized from a serovar-1-specific GPL intermediate that is derived from a non-specific GPL precursor. We also identified a gene encoding an enzyme that is necessary for the biosynthesis of serovar-3- and 9-specific GPLs, but not serovar-2-specific GPLs, suggesting that the different serovars may have evolved from the acquisition or loss of genetic information. In addition, a subcluster of genes for the biosynthesis and transfer of fucose, which are needed to make serovar-specific GPLs such as those of serovar 2, is found in the non-GPL-producingM. aviumsubspeciesparatuberculosisandsilvaticum.
The staphylococcal saeRS system coordinates environmental signals with agr quorum sensing
Authors: Novick Richard P. , Jiang Dunrong
Published: October 2003

sae is a two-component signal transduction system in Staphylococcus aureus that regulates the expression of many virulence factors at the transcriptional level and appears to act synergistically with agr in some cases. In this study, the interactions between sae and agr have been characterized in some detail. It was found that the sae locus is larger and more complex than originally envisioned, in that it is expressed from several promoters, giving rise to four or five transcripts, at least three of which are initiated upstream of saeRS and contain two additional reading frames, here designated saeP and saeQ, which are likely to have important roles in sae function. The upstream transcripts are induced during exponential phase concomitantly with the onset of RNAIII synthesis and their induction requires the agr effector, RNAIII, but is blocked by several environmental signals that override the effects of RNAIII. saeR is also required for the induction of these transcripts, so that the sae locus contains an autoinduction circuit. It is suggested that sae is downstream of agr in the exoprotein activation pathway (and also epistatic with agr), that it coordinates the effects of environmental signals with the agr quorum-sensing system, and therefore that it is a key intermediary in the overall regulatory strategy by which S. aureus senses and responds to its environment.
mSin3-associated protein, mSds3, is essential for pericentric heterochromatin formation and chromosome segregation in mammalian cells
Authors: David Gregory , Turner Garth M. , Yao Yao , Protopopov Alexei , DePinho Ronald A.
Published: October 2003

The histone code guides many aspects of chromosome biology including the equal distribution of chromosomes during cell division. In the chromatin domains surrounding the centromere, known as pericentric heterochromatin, histone modifications, particularly deacetylation and methylation, appear to be essential for proper chromosome segregation. However, the specific factors and their precise roles in this highly orchestrated process remain under active investigation. Here, we report that germ-line or somatic deletion of mSds3, an essential component of the functional mSin3/HDAC corepressor complex, generates a cell-lethal condition associated with rampant aneuploidy, defective karyokinesis, and consequently, a failure of cytokinesis. mSds3-deficient cells fail to deacetylate and methylate pericentric heterochromatin histones and to recruit essential heterochromatin-associated proteins, resulting in aberrant associations among heterologous chromosomes via centromeric regions and consequent failure to properly segregate chromosomes. Mutant mSds3 molecules that are defective in mSin3 binding fail to rescue the mSds3 null phenotypes. On the basis of these findings, we propose that mSds3 and its associated mSin3/HDAC components play a central role in initiating the cascade of pericentric heterochromatin-specific modifications necessary for the proper distribution of chromosomes during cell division in mammalian cells.
Local regulation of fat metabolism in peripheral nerves
Authors: Verheijen Mark H.G. , Chrast Roman , Burrola Patrick , Lemke Greg
Published: October 2003

We comprehensively analyzed gene expression during peripheral nerve development by performing microarray analyses of premyelinating, myelinating, and postmyelinating mouse sciatic nerves, and we generated a database of candidate genes to be tested in mapped peripheral neuropathies. Unexpectedly, we identified a large cluster of genes that are (1) maximally expressed only in the mature nerve, after myelination is complete, and (2) tied to the metabolism of storage (energy) lipids. Many of these late-onset genes are expressed by adipocytes, which we find constitute the bulk of the epineurial compartment of the adult nerve. However, several such genes, includingSREBP-1, SREBP-2, andLpin1, are also expressed in the endoneurium. We find thatLpin1null mutations lead to lipoatrophy of the epineurium, and to the dysregulation of a battery of genes required for the regulation of storage lipid metabolism in both the endoneurium and peri/epineurium. Together with the observation that these mutations also result in peripheral neuropathy, our findings demonstrate a crucial role for local storage lipid metabolism in mature peripheral nerve function, and have important implications for the understanding and treatment of peripheral neuropathies that are commonly associated with metabolic diseases such as lipodystrophy and diabetes.
KNL-1 directs assembly of the microtubule-binding interface of the kinetochore in C. elegans
Authors: Desai Arshad , Rybina Sonja , Müller-Reichert Thomas , Shevchenko Andrej , Shevchenko Anna , Hyman Anthony , Oegema Karen
Published: October 2003

Segregation of the replicated genome during cell division requires kinetochores, mechanochemical organelles that assemble on mitotic chromosomes to connect them to spindle microtubules. CENP-A, a histone H3 variant, and CENP-C, a conserved structural protein, form the DNA-proximal foundation for kinetochore assembly. Using RNA interference-based genomics in Caenorhabditis elegans, we identified KNL-1, a novel kinetochore protein whose depletion, like that of CeCENP-A or CeCENP-C, leads to a “kinetochore-null” phenotype. KNL-1 is downstream of CeCENP-A and CeCENP-C in a linear assembly hierarchy. In embryonic extracts, KNL-1 exhibits substoichiometric interactions with CeCENP-C and forms a near-stoichiometric complex with CeNDC-80 and HIM-10, the C. elegans homologs of Ndc80p/HEC1p and Nuf2p—two widely conserved outer kinetochore components. However, CeNDC-80 and HIM-10 are not functionally equivalent to KNL-1 because their inhibition, although preventing formation of a mechanically stable kinetochore-microtubule interface and causing chromosome missegregation, does not result in a kinetochore-null phenotype. The greater functional importance of KNL-1 may be due to its requirement for targeting multiple components of the outer kinetochore, including CeNDC-80 and HIM-10. Thus, KNL-1 plays a central role in translating the initiation of kinetochore assembly by CeCENP-A and CeCENP-C into the formation of a functional microtubule-binding interface.
Inheritance of Polycomb-dependent chromosomal interactions in Drosophila
Authors: Bantignies Frédéric , Grimaud Charlotte , Lavrov Sergey , Gabut Mathieu , Cavalli Giacomo
Published: October 2003

Maintenance of cell identity is a complex task that involves multiple layers of regulation, acting at all levels of chromatin packaging, from nucleosomes to folding of chromosomal domains in the cell nucleus. Polycomb-group (PcG) and trithorax-group (trxG) proteins maintain memory of chromatin states through binding at cis-regulatory elements named PcG response elements or cellular memory modules. Fab-7 is a well-defined cellular memory module involved in regulation of the homeotic gene Abdominal-B (Abd-B). In addition to its action in cis, we show here by three-dimensional FISH that the Fab-7 element leads to association of transgenes with each other or with the endogenous Fab-7, even when inserted in different chromosomes. These long-distance interactions enhance PcG-mediated silencing. They depend on PcG proteins, on DNA sequence homology, and on developmental progression. Once long-distance pairing is abolished by removal of the endogenous Fab-7, the derepressed chromatin state induced at the transgene locus can be transmitted through meiosis into a large fraction of the progeny, even after reintroduction of the endogenous Fab-7. Strikingly, meiotic inheritance of the derepressed state involves loss of pairing between endogenous and transgenic Fab-7. This suggests that transmission of nuclear architecture through cell division might contribute to inheritance of chromatin states in eukaryotes.
β1 integrins regulate chondrocyte rotation, G1 progression, and cytokinesis
Authors: Aszodi Attila , Hunziker Ernst B. , Brakebusch Cord , Fässler Reinhard
Published: October 2003

β1 integrins are highly expressed on chondrocytes, where they mediate adhesion to cartilage matrix proteins. To assess the functions of β1 integrin during skeletogenesis, we inactivated the β1 integrin gene in chondrocytes. We show here that these mutant mice develop a chondrodysplasia of various severity. β1-deficient chondrocytes had an abnormal shape and failed to arrange into columns in the growth plate. This is caused by a lack of motility, which is in turn caused by a loss of adhesion to collagen type II, reduced binding to and impaired spreading on fibronectin, and an abnormal F-actin organization. In addition, mutant chondrocytes show decreased proliferation caused by a defect in G1/S transition and cytokinesis. The G1/S defect is, at least partially, caused by overexpression of Fgfr3, nuclear translocation of Stat1/Stat5a, and up-regulation of the cell cycle inhibitors p16 and p21. Altogether these findings establish that β1-integrin-dependent motility and proliferation of chondrocytes are mandatory events for endochondral bone formation to occur.
The Transport of Prolamine RNAs to Prolamine Protein Bodies in Living Rice Endosperm Cells[W]
Authors: Hamada Shigeki , Ishiyama Keiki , Choi Sang-Bong , Wang Changlin , Singh Salvinder , Kawai Naoko , Franceschi Vincent R. , Okita Thomas W.
Published: October 2003

RNAs that code for the major rice storage proteins are localized to specific subdomains of the cortical endoplasmic reticulum (ER) in developing endosperm. Prolamine RNAs are localized to the ER and delimit the prolamine intracisternal inclusion granules (PB-ER), whereas glutelin RNAs are targeted to the cisternal ER. To study the transport of prolamine RNAs to the surface of the prolamine protein bodies in living endosperm cells, we adapted a two-gene system consisting of green fluorescent protein (GFP) fused to the viral RNA binding protein MS2 and a hybrid prolamine RNA containing tandem MS2 RNA binding sites. Using laser scanning confocal microscopy, we show that the GFP-labeled prolamine RNAs are transported as particles that move at an average speed of 0.3 to 0.4 μm/s. These prolamine RNA transport particles generally move unidirectionally in a stop-and-go manner, although nonlinear bidirectional, restricted, and nearly random movement patterns also were observed. Transport is dependent on intact microfilaments, because particle movement is inhibited rapidly by the actin filament–disrupting drugs cytochalasin D and latrunculin B. Direct evidence was obtained that these prolamine RNA-containing particles are transported to the prolamine protein bodies. The significance of these results with regard to protein synthesis in plants is discussed.
Rapid Induction of Distinct Stress Responses after the Release of Singlet Oxygen in Arabidopsis[W]
Authors: op den Camp Roel G. L. , Przybyla Dominika , Ochsenbein Christian , Laloi Christophe , Kim Chanhong , Danon Antoine , Wagner Daniela , Hideg Éva , Göbel Cornelia , Feussner Ivo , Nater Mena , Apel Klaus
Published: October 2003

The conditional fluorescent (flu) mutant of Arabidopsis accumulates the photosensitizer protochlorophyllide in the dark. After a dark-to-light shift, the generation of singlet oxygen, a nonradical reactive oxygen species, starts within the first minute of illumination and was shown to be confined to plastids. Immediately after the shift, plants stopped growing and developed necrotic lesions. These early stress responses of the flu mutant do not seem to result merely from physicochemical damage. Peroxidation of chloroplast membrane lipids in these plants started rapidly and led to the transient and selective accumulation of a stereospecific and regiospecific isomer of hydroxyoctadecatrieonic acid, free (13S)-HOTE, that could be attributed almost exclusively to the enzymatic oxidation of linolenic acid. Within the first 15 min of reillumination, distinct sets of genes were activated that were different from those induced by superoxide/hydrogen peroxide. Collectively, these results demonstrate that singlet oxygen does not act primarily as a toxin but rather as a signal that activates several stress-response pathways. Its biological activity in Arabidopsis exhibits a high degree of specificity that seems to be derived from the chemical identity of this reactive oxygen species and/or the intracellular location at which it is generated.
How one European community embraces a growing Muslim minority
Authors: Richardson Jacques
Published: October 2003

In a Europe whose social make‐up is being significantly transformed by a shifting religious presence, responses to unaccustomed pressure and new needs must be met by the processes of governance and orderly administration. First affected are neighbourhoods, then entire communities. Here we take a look at the situation in France, whose experience may be emulated elsewhere.
Technological forecasting and scenarios matter
Authors: Bouwman H. , van der Duin P.
Published: October 2003

Information and communication technology (ICT) is increasingly being used in the home environment, making it a very important and interesting research topic for communication scientists. Future developments will influence the way and the extent to which ICT will be used in the home environment and therefore the way people look for information, communicate, make use of entertainment services and carry out transactions. However, it is still very difficult to make meaningful and accurate forecasts with regard to the possible future use and acceptance of ICT in people’s homes. Important reasons are, for example, that more and more market parties are involved in the development of innovative ICT products and services. This makes developments more complex and the outcomes more uncertain. Furthermore, consumers play an important role in the development of new ICT‐based information, communication, transaction and entertainment services. Since a precise prediction of the possible use of ICT in domestic environments in 2010 is hard to make, other methods of futures research must be used. Combining technological forecasting with scenario thinking is such a research method, whereon, technological forecasting shows the major trends in the specific technology domain, while scenarios cover the possible future worlds. By giving end‐users a central place in these scenarios, the diversity of the use and acceptance of innovative products and services is captured. Thus, the addition of scenarios to the technology trends gives insight into the possibilities (and impossibilities) of new ICT‐technologies and the way they may be used in the home environment.
The futures of futures: a scenario salon
Authors: Hines Andy
Published: October 2003

The Association of Professional Futurists (APF) recently held a scenario salon that explored the “Futures of futures.” The centerpiece of the findings was the identification and implications of four critical uncertainties affecting futurists and the futures field. First, is addressing the extremely fragmented nature of the field. Futurists must get better at working together more closely as a field to be successful. Second, is the need to confront our aging tool kit. It is not as if methodological innovation has stopped, but it is seen as largely incremental. Third, is the need for futures to create a unique value proposition that distinguishes futurists from mainstream consultants. Finally, there is the poor public image of the field. This suggests that there is a long‐term task ahead of careful rebuilding the brand of futures through a more sophisticated engagement with the public, especially the media. The APF has formed working teams around these issues. The APF sees a generation task ahead, but is confident that together with our futurist colleagues, we can achieve our goal of a “credible profession, thriving professionals.”
Baby Boomers, Generation X and Generation Y?
Authors: Jorgensen Bradley
Published: October 2003

In recent years there has been discussion in the management and organisational literature on generational differences and how they may impact on the design of workforce strategies. However, much of the discussion appears to be based on observation rather than large empirical work. Indeed, I would argue that wider support for the requirement to manage the workforce around X and Y issues is absent. For example, employers of choice are looking to win talent by tailoring employment policy to capture the dynamism of the modern era rather than discrete generational values. Significantly, the bulk of generational data cited by popular writers is subjective, non‐representative, makes use of single‐point‐of‐time data and uses retrospective comparisons. Importantly, scholarly literature does not draw arbitrary and abrupt lines between generations. In seeking to determine a preferred workforce strategy organisations would be better served by acknowledging the technical, economic, political and social dynamism of modern life rather than the flawed conclusions of popular generational literature.
Manipulating the governance characteristics of code
Authors: Shah Rajiv C. , Kesan Jay P.
Published: October 2003

Regulation through “code,” i.e. the hardware and software of communication technologies, is growing in importance. Policymakers are addressing societal concerns such as privacy, freedom of speech, and intellectual property protection with code‐based solutions. While scholars have noted the role of code, there is little analysis of the various features or characteristics of code that have significance in regulating behavior. This paper examines three universal governance characteristics that policymakers may use to ensure code comports with societal concerns. The characteristics are transparency, defaults, and standards. For each characteristic, the paper discusses the salient regulatory issues for manipulating code. Additionally, the paper provides normative proposals for modifying some characteristics, such as defaults. In sum, our analysis should aid policymakers seeking to manipulate code to ensure that code comports with our societal values and addresses our societal concerns.
Deploying e‐government programs: the strategic importance of “I” before “E”
Authors: Schware Robert , Deane Arsala
Published: October 2003

Many developing countries are in the initial phases of adopting electronic government (e‐government) programs to improve public services and deliver them as efficiently and conveniently as possible. Our experience with a variety of governments throughout the developing world at different stages of implementing e‐government programs with citizens (G2C), businesses (G2B), and other entities of government (G2G) suggests that a major reason behind the success or failure of e‐government projects is the extent to which, first, the governments address technological infrastructure encouraged by appropriate telecommunications policies; and second, the legal and regulatory instruments required for e‐government. Information and communication technology (ICT) infrastructure (the “I”) development is at the heart of successful deployment and sustainability of e‐government programs.
Has the telecommunications meltdown finally come to an end?
Authors: Curwen Peter
Published: October 2003

This article is the fourth in a series that analyses the constantly changing structure of the TMT sector. It covers the period 28 March 2002 to 28 March 2003. Prior to March 2002, the sector had already spent two years in the doldrums, and this update reveals that the overall trend continued to be broadly negative during the ensuing year, partly driven by the implosions at the likes of WorldCom. However, there are signs that the worst is now over and that, albeit slowly, the sector will be in better shape by the end of the year.
Regulatory peripheries: Using prepaid to extend the network
Authors: Mahan Amy
Published: October 2003

Telecom network roll‐out is crucial for economic development, and with the advent of mobile telephony, it is increasingly achievable. Mobile adoption in many countries has surpassed fixed line connections. This paper, however, proposes that regulators need to look beyond teledensity to anticipate future access to information infrastructure. Prepaid mobile especially does not provide a solid foundation for future information services. Different stages of regulatory and network development determine the conditions for mobile (and prepaid mobile) adoption at a national level. Likewise, access to further or future information services will be affected by the kind of network now being established and by regulatory conditions which either recognise or ignore national and regional differences.
Exercise‐Induced Expression of Vascular Endothelial Growth Factor mRNA in Rat Skeletal Muscle is Dependent on Fibre Type
Authors: Birot Olivier J. G. , Koulmann Nathalie , Peinnequin André , Bigard Xavier A.
Published: October 2003

In this study, we quantified the expression of the vascular endothelial growth factor (VEGF) gene in individual muscle fibres at the end of a single 90 min run of 20−25 m min−1, at 10 % incline. In addition, we evaluated the co‐ordinated expression of several hypoxia‐sensitive genes, including the ORP‐150 gene. Individual fibres were taken from rat plantaris muscle, either at the end of a single bout of exercise or at rest, and classified as Type I, IIa, IIx or IIb, according to the expression of myosin heavy chain (MHC) isoforms. VEGF mRNA levels increased by 90 % in exercising whole plantaris in comparison with those in control muscle (P < 0.001), while the VEGF protein content increased by 72 % (P < 0.05). Using real‐time PCR analysis, an accurate and reproducible method for quantification of mRNA levels, a marked rise in VEGF transcript levels was observed at the end of exercise in individual myofibres (P < 0.05), providing the first direct evidence that VEGF transcripts increase in muscle cells after a single bout of exercise. This exercise‐induced increase in VEGF transcript levels was specifically observed in type IIb myofibres, which are predominantly glycolytic and more susceptible to local hypoxia than oxidative myofibres such as type I or IIa fibres (110 %, P < 0.05). Moreover, treadmill exercise increased the expression of two hypoxia‐sensitive genes. The levels of mRNA for Flt‐1, a VEGF‐specific receptor, and those for ORP‐150, a chaperone essential for the secretion of mature VEGF, increased in whole plantaris muscles (108 and 92 %, respectively, P < 0.05). Taken together, these findings are consistent with the suggestion that hypoxia could be one of the mechanisms involved in exercise‐induced capillary growth.
A Single Course of Prenatal Betamethasone in the Rat Alters Postnatal Brain Cell Proliferation but not Apoptosis
Authors: Scheepens Arjan , van de Waarenburg Marjo , van den Hove Daniël , Blanco Carlos E.
Published: October 2003

The aim of this study was to determine the effects of a clinically relevant single course of prenatal betamethasone in the rat on growth parameters with particular reference to brain cell proliferation and apoptosis. We report that administration of 170 μg kg−1 betamethasone twice within 4 h to E20 pregnant rats conveys moderate somatic growth retardation. Further, using a measure of brain cell proliferation independent of blood‐brain barrier (BBB) permeability, we demonstrate for the first time that betamethasone is chronically anti‐proliferative to brain cells without inducing caspase‐3‐mediated apoptosis. More importantly we show that there is a significant and sexually divergent rebound of neural proliferation which occurs earlier in males than in females and continues until at least 21 days of postnatal life. BBB permeability to [3H]thymidine was significantly increased by steroid treatment re‐iterating the fact that tracer studies not correcting for BBB permeability, such as bromodeoxyuridine (BrdU), may be questionable in this type of study. Further, prenatal steroid treatment did not alter postnatal corticosterone levels. In summary we show that prenatal betamethasone conveys significant and long‐lasting side effects and that its human clinical application in preterm labour needs more careful consideration as compared to the relative ease with which it is prescribed today.
Single Muscle Fibre Contractile Properties in Young and Old Men and Women
Authors: Trappe Scott , Gallagher Philip , Harber Matthew , Carrithers John , Fluckey James , Trappe Todd
Published: October 2003

The purpose of this study was to determine whether there was an age‐related decline in the isometric and isotonic contractile function of permeabilized slow (MHC I) and fast (MHC IIa) single muscle fibres. Vastus lateralis muscle fibres from six young men (YM; 25 ± 1 years), six young women (YW; 25 ± 1 years), six old men (OM; 80 ± 4 years) and six old women (OW; 78 ± 2 years) were studied at 15 °C for in vitro force‐velocity properties, peak force and contractile velocity. Peak power was 23‐28 % lower (P < 0.05) in MHC I fibres of YW compared to the other three groups. MHC IIa peak power was 25–40 % lower (P < 0.05) in OW compared to the other three groups. No difference was found in MHC I and IIa normalized peak power among any of the groups. Peak force was lower (P < 0.05) in the YW (MHC I fibres) and OW (MHC IIa fibres) compared to the other groups. Differences in peak force with ageing were negated when normalized to cell size. No age‐related differences were observed in single fibre contractile velocity of MHC I and IIa fibres. These data show that YW (MHC I) and OW (MHC IIa) have lower single fibre absolute peak power and peak force compared to men; however, these differences are negated when normalized to cell size. General muscle protein concentrations (i.e. total, sarcoplasmic and myofibrillar) from the same biopsies were lower (4–9 %, P < 0.05) in the OM and OW. However, myosin and actin concentrations were not different (P > 0.05) among the four groups. These data suggest that differences in whole muscle strength and function that are often observed with ageing appear to be regulated by quantitative rather than qualitative parameters of single muscle fibre contractile function.
Synaptogenesis in the CNS: An Odyssey from Wiring Together to Firing Together
Authors: Munno David W. , Syed Naweed I.
Published: October 2003

To acquire a better comprehension of nervous system function, it is imperative to understand how synapses are assembled during development and subsequently altered throughout life. Despite recent advances in the fields of neurodevelopment and synaptic plasticity, relatively little is known about the mechanisms that guide synapse formation in the central nervous system (CNS). Although many structural components of the synaptic machinery are pre‐assembled prior to the arrival of growth cones at the site of their potential targets, innumerable changes, central to the proper wiring of the brain, must subsequently take place through contact‐mediated cell‐cell communications. Identification of such signalling molecules and a characterization of various events underlying synaptogenesis are pivotal to our understanding of how a brain cell completes its odyssey from ‘wiring together to firing together’. Here we attempt to provide a comprehensive overview that pertains directly to the cellular and molecular mechanisms of selection, formation and refinement of synapses during the development of the CNS in both vertebrates and invertebrates.
Purinergic Signalling in the Medullary Mechanisms of Respiratory Control in the Rat: Respiratory Neurones Express the P2X2 Receptor Subunit
Authors: Gourine Alexander V. , Atkinson Lucy , Deuchars Jim , Spyer K. Michael
Published: October 2003

ATP is involved in central respiratory control and may mediate changes in the activity of medullary respiratory neurones during hypercapnia, thus playing an important role in central chemoreception. The main objective of this study was to explore further the role of ATP‐mediated signalling in respiratory control and central chemoreception by characterising the profile of the P2X receptors expressed by physiologically identified respiratory neurones. In particular we determined whether respiratory neurones in the rostral ventrolateral medulla (VLM) express P2X2 receptor subunits of the ATP‐gated ion channel, since ATP currents evoked at recombinant P2X2 receptors are potentiated by lowering extracellular pH. Experiments were performed on anaesthetised (pentobarbitone sodium 60 mg kg−1 I.P., then 10 mg kg−1 I.V. as required), gallamine‐triethiodide‐treated (10 mg kg−1 I.V., then 2‐4 mg kg−1 h−1 I.V.) and artificially ventilated rats. The VLM respiratory neurones were classified according to the timing of their discharge pattern in relation to that of the phrenic nerve and by the exclusion of pump cells from the study population; these were labelled with Neurobiotin using the juxtacellular method, and visualised with fluorescence microscopy. It was found that a substantial proportion of the VLM respiratory neurones express the P2X2 receptor subunit. P2X2 receptor subunit immunoreactivity was detected in ≈50 % (six out of 12) of expiratory neurones and in ≈20 % (two out of 11) of neurones with inspiratory‐related discharge (pre‐inspiratory and inspiratory). In contrast, no Neurobiotin‐labelled VLM respiratory neurones (n= 19) were detectably immunoreactive for the P2X1 receptor subunit. Microionophoretic application of ATP (0.2 m, 20−80 nA for 40 s) increased the activity of ≈80 % (13 out of 16) of expiratory neurones and of ≈30 % (five out of 18) of VLM neurones with inspiratory‐related discharge. These effects were abolished by the P2 receptor blocker suramin (0.02 M, 80 nA), which also reduced the baseline firing in some expiratory neurones. These data indicate that modulation of P2X2 receptor function, such as that evoked by acidification of the extracellular environment during hypercapnia, may contribute to the changes in activity of the VLM respiratory neurones that express these receptors.