bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian hierarchical modelling of maturity-at-length for rock lobsters, Jasus edwardsii, off Victoria, Australia
Authors: Punt André E. , Hobday David K. , Flint Rhonda
Published: July 2006

Maturity-at-length is a key input to stock assessments when the management objectives are expressed in terms of the size of the spawning output relative to some reference level. Data for rock lobsters, Jasus edwardsii (Hutton, 1875), off Victoria, Australia, are used to estimate logistic relationships between carapace length and the probability of being mature. The analyses are based primarily on mixed-effects models in which the parameters governing maturity-at-length depend on year and region, fitted using a Bayesian hierarchical approach. Maturity-at-length differs among years and regions, and the length-at-50%-maturity increases from west to east and then remains relatively constant. However, the estimates for all years and regions are not equally precise, so there is value in using a mixed-effects approach to allow the years for which the dataset is large to ‘provide support’ for the years for which the data are sparse. The results provide the input needed to conduct assessments of rock lobster populations off Victoria and to form the basis for conducting population projections.
MAGE-A tumor antigens target p53 transactivation function through histone deacetylase recruitment and confer resistance to chemotherapeutic agents
Authors: Monte Martin , Simonatto Marta , Peche Leticia Y. , Bublik Debora R. , Gobessi Stefania , Pierotti Marco A. , Rodolfo Monica , Schneider Claudio
Published: July 2006

The MAGE gene family is characterized by a conserved domain (MAGE Homology Domain). A subset of highly homologous MAGE genes (group A; MAGE-A) belong to the chromosome X-clustered cancer/testis antigens. MAGE-A genes are normally expressed in the human germ line and overexpressed in various tumor types; however, their biological function is largely unknown. Here we present evidence indicating that MageA2 protein, belonging to the MAGE-A subfamily, confers wild-type-p53-sensitive resistance to etoposide (ET) by inducing a novel p53 inhibitory loop involving recruitment of histone deacetylase 3 (HDAC3) to MageA2/p53 complex, thus strongly down-regulating p53 transactivation function. In fact, enhanced MageA2 protein levels, in addition to ET resistance, correlate with impaired acetylation of both p53 and histones surrounding p53-binding sites. Association between MAGE-A expression levels and resistance to ET treatment is clearly shown in short-term cell lines obtained from melanoma biopsies harboring wild-type-p53, whereas cells naturally, or siRNA-mediated expressing low MAGE-A levels, correlate with enhanced p53-dependent sensitivity to ET. In addition, combined trichostatin A/ET treatment in melanoma cells expressing high MAGE-A levels reestablishes p53 response and reverts the chemoresistance.
Acid-sensitive ionic channels in midbrain dopamine neurons are sensitive to ammonium, which may contribute to hyperammonemia damage
Authors: Pidoplichko Volodymyr I. , Dani John A.
Published: July 2006

Acid-sensitive ion channels (ASICs) are proton-gated and belong to the family of degenerin channels. In the mammalian nervous system, ASICs are most well known in sensory neurons, where they are involved in nociception, occurring when injury or inflammation causes acidification. ASICs also are widely expressed in the CNS, and some synaptic roles have been revealed. Because neuronal activity can produce pH changes, ASICs may respond to local acidic transients and alter the excitability of neuronal circuits more widely than is presently appreciated. Furthermore, ASICs have been found to underlie calcium transients that contribute to neuronal death. Degeneration of midbrain dopamine neurons is characteristic of advanced idiopathic Parkinson’s disease. Therefore, we tested for functional ASICs in midbrain dopamine neurons of the ventral tegmental area and substantia nigra compacta. Patch-clamp electrophysiology applied to murine midbrain slices revealed abundant acid-sensitive channels. The ASICs were gated and desensitized by extracellular application of millimolar concentrations of NH
4
Cl. Although the NH
4
Cl solution contains micromolar concentrations of NH
3
at pH 7.4, our evidence indicates that NH
4
+
gates the ASICs. The proton-gated and the ammonium-gated currents were inhibited by tarantula venom (psalmotoxin), which is specific for the ASIC1a subtype. The results show that acid-sensitive channels are expressed in midbrain dopamine neurons and suggest that ammonium sensitivity is a widely distributed ASIC characteristic in the CNS, including the hippocampus. The ammonium sensitivity suggests a role for ASIC1s in hepatic encephalopathy, cirrhosis, and other neuronal disorders that are associated with hyperammonemia.
Transgenic mice rich in endogenous omega-3 fatty acids are protected from colitis
Authors: Hudert Christian A. , Weylandt Karsten H. , Lu Yan , Wang Jingdong , Hong Song , Dignass Axel , Serhan Charles N. , Kang Jing X.
Published: July 2006

Omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFA) are the precursors of potent lipid mediators and play an important role in regulation of inflammation. Generally, n-6 PUFA promote inflammation whereas n-3 PUFA have antiinflammatory properties, traditionally attributed to their ability to inhibit the formation of n-6 PUFA-derived proinflammatory eicosanoids. Newly discovered resolvins and protectins are potent antiinflammatory lipid mediators derived directly from n-3 PUFA with distinct pathways of action. However, the role of the n-3 PUFA tissue status in the formation of these antiinflammatory mediators has not been addressed. Here we show that an increased n-3 PUFA tissue status in transgenic mice that endogenously biosynthesize n-3 PUFA from n-6 PUFA leads to significant formation of antiinflammatory resolvins and effective reduction in inflammation and tissue injury in colitis. The endogenous increase in n-3 PUFA and related products did not decrease n-6 PUFA-derived lipid mediators such as leukotriene B4 and prostaglandin E2. The observed inflammation protection might result from decreased NF-κB activity and expression of TNFα, inducible NO synthase, and IL-1β, with enhanced mucoprotection probably because of the higher expression of trefoil factor 3, Toll-interacting protein, and zonula occludens-1. These results thus establish the
fat-1
transgenic mouse as a new experimental model for the study of n-3 PUFA-derived lipid mediators. They add insight into the molecular mechanisms of inflammation protection afforded by n-3 PUFA through formation of resolvins and protectins other than inhibition of n-6 PUFA-derived eicosanoid formation.
Consequences of receptor editing at the λ locus: Multireactivity and light chain secretion
Authors: Doyle Colleen M. , Han Jiong , Weigert Martin G. , Prak Eline T. Luning
Published: July 2006

To investigate the manner in which B cells with λ light (L) chains undergo receptor editing, we have studied hybridoma panels from 56R/κ-deleted (kdel) mice. 56R/kdel mice only produce four L chains (λ1, λ2, λ3, and λX). They also have a simplified heavy (H) chain repertoire: All B cells start out with a 56R anti-DNA H chain. A few frankly autoreactive 56R λ1 cells appear to escape into the periphery, but the majority of the peripheral B cell repertoire in 56R/kdel is made up of B cells expressing the 56R H chain with the λX L chain. Surprisingly, 56R λX B cells are multireactive, binding to a variety of self and nonself antigens, including dsDNA (albeit at reduced affinity compared with the other λ L chains). Another significant population in the 56R/kdel mouse consists of allelically included B cells that express λX along with another L chain. The multireactivity of both 56R λX and 56R λX/λ1 receptors could contribute to autoimmunity if these B cells were to become activated. Also found among 56R/kdel hybridomas are clones that have inactivated the H chain and secrete only L chains. These clones may represent products of exhaustive rearrangement. Multireactivity, allelic inclusion, and L chain secretion are three consequences of editing at the λ locus that may predispose toward the development of autoimmunity.
Phenotypic effects of membrane protein overexpression in
Saccharomyces cerevisiae
Authors: Österberg Marie , Kim Hyun , Warringer Jonas , Melén Karin , Blomberg Anders , von Heijne Gunnar
Published: July 2006

Large-scale protein overexpression phenotype screens provide an important complement to the more common gene knockout screens. Here, we have targeted the so far poorly understood
Saccharomyces cerevisiae
membrane proteome and report growth phenotypes for a strain collection overexpressing ≈600 C-terminally tagged integral membrane proteins grown both under normal and three different stress conditions. Although overexpression of most membrane proteins reduce the growth rate in synthetic defined medium, we identify a large number of proteins that, when overexpressed, confer specific resistance to various stress conditions. Our data suggest that regulation of glycosylphosphatidylinositol anchor biosynthesis and the Na
+
/K
+
homeostasis system constitute major downstream targets of the yeast PKA/RAS pathway and point to a possible connection between the early secretory pathway and the cells’ response to oxidative stress. We also have quantified the expression levels for >550 membrane proteins, facilitating the choice of well expressing proteins for future functional and structural studies.
A threshold of
GATA4
and
GATA6
expression is required for cardiovascular development
Authors: Xin Mei , Davis Christopher A. , Molkentin Jeffery D. , Lien Ching-Ling , Duncan Stephen A. , Richardson James A. , Olson Eric N.
Published: July 2006

The zinc-finger transcription factors GATA4 and GATA6 play critical roles in embryonic development. Mouse embryos lacking
GATA4
die at embryonic day (E) 8.5 because of failure of ventral foregut closure and cardiac bifida, whereas GATA6 is essential for development of the visceral endoderm. Although mice that are heterozygous for either a
GATA4
or
GATA6
null allele are normal, we show that compound heterozygosity of
GATA4
and
GATA6
results in embryonic lethality by E13.5 accompanied by a spectrum of cardiovascular defects, including thin-walled myocardium, ventricular and aortopulmonary septal defects, and abnormal smooth muscle development. Myocardial hypoplasia in
GATA4/GATA6
double heterozygous mutant embryos is associated with reduced proliferation of cardiomyocytes, diminished expression of the myogenic transcription factor MEF2C (myocyte enhancer factor 2C), and down-regulation of β-myosin heavy chain expression, a key determinant of cardiac contractility. These findings reveal a threshold of GATA4 and GATA6 activity that is required for gene expression in the developing cardiovascular system and underscore the potential of recessive mutations to perturb the delicate regulation of cardiovascular development.
Adoptive immunotherapy induces CNS dendritic cell recruitment and antigen presentation during clearance of a persistent viral infection
Authors: Lauterbach Henning , Zuniga Elina I. , Truong Phi , Oldstone Michael B.A. , McGavern Dorian B.
Published: July 2006

Given the global impact of persistent infections on the human population, it is of the utmost importance to devise strategies to noncytopathically purge tissues of infectious agents. The central nervous system (CNS) poses a unique challenge when considering such strategies, as it is an immunologically specialized compartment that contains a nonreplicative cell population. Administration of exogenously derived pathogen-specific memory T cells (referred to as adoptive immunotherapy) to mice burdened with a persistent lymphocytic choriomeningitis virus (LCMV) infection from birth results in eradication of the pathogen from all tissues, including the CNS. In this study, we sought mechanistic insights into this highly successful therapeutic approach. By monitoring the migration of traceable LCMV-specific memory CD8+ T cells after immunotherapy, it was revealed that cytotoxic T lymphocytes (CTLs) distributed widely throughout the CNS compartment early after immunotherapy, which resulted in a dramatic elevation in the activity of CNS antigen-presenting cells (APCs). Immunotherapy induced microglia activation as well as the recruitment of macrophages and dendritic cells (DCs) into the brain parenchyma. However, DCs emerged as the only CNS APC population capable of inducing memory CTLs to preferentially produce the antiviral cytokine tumor necrosis factor-α, a cytokine demonstrated to be required for successful immunotherapeutic clearance. DCs were also found to be an essential element of the immunotherapeutic process because in their absence, memory T cells failed to undergo secondary expansion, and viral clearance was not attained in the CNS. These experiments underscore the importance of DCs in the immunotherapeutic clearance of a persistent viral infection and suggest that strategies to elevate the activation/migration of DCs (especially within the CNS) may facilitate pathogen clearance.
Ring of Negative Charge in BK Channels Facilitates Block by Intracellular Mg2+ and Polyamines through Electrostatics
Authors: Zhang Yaxia , Niu Xiaowei , Brelidze Tinatin I. , Magleby Karl L.
Published: July 2006

Intracellular Mg2+ and natural polyamines block outward currents in BK channels in a highly voltage-dependent manner. Here we investigate the contribution of the ring of eight negatively charged residues (4 x E321/E324) at the entrance to the inner vestibule of BK channels to this block. Channels with or without (E321N/E324N) the ring of negative charge were expressed in oocytes and unitary currents were recorded from inside-out patches over a range of intracellular Mg2+ and polyamine concentrations. Removing the ring of charge greatly decreased the block, increasing KBap (0 mV) for Mg2+ block from 48.3 ± 3.0 to 143 ± 8 mM, and for spermine block from 8.0 ± 1.0 to 721 ± 9 mM (150 mM symmetrical KCl). Polyamines with fewer amine groups blocked less: putrescine < spermidine < spermine. An equation that combined an empirical Hill function for block together with a Boltzmann function for the voltage dependence of KBap described the voltage and concentration dependence of the block for channels with and without the ring of charge. The Hill coefficients for these descriptions were <1 for both Mg2+ and spermine block, and were unchanged by removing the ring of charge. When KCli was increased from 150 mM to 3 M, the ring of charge no longer facilitated block, Mg2+ block was reduced, spermine block became negligible, and the Hill coefficients became ∼1.0. BK channels in cell-attached oocyte patches displayed inward rectification, which was reduced for channels without the ring of charge. Taken together, these observations suggest that the ring of negative charge facilitates block through a preferential electrostatic attraction of Mg2+ and polyamine over K+. This preferential attraction of multivalent blockers over monovalent K+ would decrease the K+ available at the inner vestibule to carry outward current in the presence of Mg2+ or polyamines, while increasing the concentration of blocker available to enter and block the conduction pathway.
Open archives and their impact on journal cancellations
Authors: Ware Mark
Published: July 2006

We report on a research study commissioned by ALPSP into the factors affecting journal cancellations and, in particular, on the impact of the free availability of journal articles via open access repositories.
A Wel(l)come development: research funders and open access
Authors: Pinfield Stephen
Published: July 2006

This paper discusses the implications of the Wellcome Trust agreement with Blackwell, OUP, and Springer in which authors of accepted papers are able to pay an open‐access publication charge to make their article freely available online. In bringing together flexible licence terms and clear funding streams, the agreement has the potential to be used as a way of migrating towards possible new business models for journal publishing. It also has the potential, if implemented more widely, to deliver greater open access in such a way as to work in the interests of a broad range of stakeholders.
The first comprehensive Chinese university journal published in English: the Tsing Hua Journal
Authors: Li Zhang , Yuan Yao , Fenglian Zhang , Wentao Du
Published: July 2006

The Tsing Hua Journal sponsored by Tsing Hua University is investigated by reading, comparing, and analysing original literature about it. It is concluded that it was the first English‐language journal of natural science and social science published by a Chinese university. The early establishment of an editorial department, of exchange with European and American journals, and of its inclusion of abstracts of foreign papers, demonstrate its international aims. Through its parallel Chinese‐ and English‐language versions it aimed to achieve an exchange of knowledge between China and the West.
Insects from the grazing food web favoured the evolutionary habitat shift to bright environments in araneoid spiders
Authors: Miyashita Tadashi , Shimazaki Aya
Published: July 2006

The Araneoidea comprises a diverse group of web-building spiders, and part of this diversity is believed attributable to habitat expansion to bright environments. We clarified the fitness-related advantages of living in such environments by examining prey availability and the growth rates of 10 species in three families inhabiting grassland (bright) and forest understory (dim) habitats. Spiders in the grassland habitat captured more prey, derived mainly from the grazing food web, than those in the forest-floor environment, and this difference was manifested in their growth rate. Independent contrasts indicated that increased utilization of insects from the grazing food web led to an evolutionary increase in adult body size. These results suggest that the shift to bright environments enabled araneoid spiders to evolve diverse life-history traits, including rapid growth and large size, which were not possible in dim environments.
Historical processes enhance patterns of diversity along latitudinal gradients
Authors: Stevens Richard D
Published: July 2006

One of the more vexing issues in ecology is how historical processes affect contemporary patterns of biodiversity. Accordingly, few models have been presented. Two corollary models (centre of origin, time-for-speciation) can be used to make quantitative predictions characterizing the tropical niche conservatism hypothesis and describe diversification as diffusion and subsequent cladogenesis of species away from the place of origin of a higher taxon in the tropics. Predictions derived from such models are: (i) species richness declines toward the periphery of the range of a higher taxon; (ii) taxa are more derived toward the periphery than the centre; (iii) ages of taxa are lower toward the periphery than the centre; and (iv) ages and measures of derivedness are less variable toward the periphery of the range of a higher taxon. I tested these predictions to better understand the formation of one of the most ubiquitous patterns of biodiversity—the latitudinal gradient in species richness. Results indicate well-supported predictions for New World leaf-nosed bats and that diversification has had strong influences on latitudinal gradients of species richness. A better understanding of how evolutionary diversification of taxa contributes to formation of patterns of species richness along environmental gradients is necessary to fully understand spatial variation in biodiversity.
Deep-sea food bonanzas: early Cenozoic whale-fall communities resemble wood-fall rather than seep communities
Authors: Kiel Steffen , Goedert James L
Published: July 2006

The evolutionary history of invertebrate communities utilizing whale carcasses and sunken wood in the deep-sea is explored using fossil evidence. Compared to modern whale-fall communities, the Eo-Oligocene examples lack those vent-type taxa that most heavily rely on sulphide produced by anaerobic breakdown of bone lipids, but are very similar in their trophic structure to contemporaneous wood-falls. This sheds doubt on the hypothesis that whale-falls were evolutionary stepping stones for taxa that now inhabit hydrothermal vents and seeps. We suggest that the whale-fall communities reported here represent a new ecologic stage among whale-falls, which we have coined the ‘chemosymbiotic opportunist stage’ and that the ‘sulphophilic stage’ of modern whale-falls developed during the Early Miocene, resulting from a significant increase in both body size and/or oil content of bones among cetaceans during this time.
Exploring biomolecular machines: energy landscape control of biological reactions
Authors: Onuchic José N , Kobayashi Chigusa , Miyashita Osamu , Jennings Patricia , Baldridge Kim K
Published: July 2006

For almost 15 years, our Pathway model has been the most powerful model in terms of predicting the tunnelling mechanism for electron transfer (ET) in biological systems, particularly proteins. Going beyond the conventional Pathway models, we have generalized our method to understand how protein dynamics modulate not only the Franck–Condon factor, but also the tunnelling matrix element. We have demonstrated that when interference among pathways modulates the electron tunnelling interactions in proteins (particularly destructive interference), dynamical effects are of critical importance. Tunnelling can be controlled by protein conformations that lie far from equilibrium—those that minimize the effect of destructive interference during tunnelling, for example. In the opposite regime, electron tunnelling is mediated by one (or a few) constructively interfering pathway tubes and dynamical effects are modest. This new mechanism for dynamical modulation of the ET rate has been able to explain and/or predict several rates that were later confirmed by experiment. However, thermal fluctuations can also affect these molecular machines in many other ways. For example, we show how global transformations, which control protein functions such as allostery, may involve large-scale motion and possibly partial unfolding during the reaction event.
Distribution of 19 major virulence genes in Legionella pneumophila serogroup 1 isolates from patients and water in Queensland, Australia
Authors: Huang Bixing , Yuan Zheng , Heron Brett A. , Gray Bruce R. , Eglezos Sofroni , Bates John R. , Savill John
Published: July 2006

The distribution of 19 major virulence genes and the presence of plasmids were surveyed in 141 Legionella pneumophila serogroup (SG) 1 isolates from patients and water in Queensland, Australia. The results showed that 16 of the virulence genes examined were present in all isolates, suggesting that they are life-essential genes for isolates in the environment and host cells. The 65 kb pathogenicity island identified originally in strain Philadelphia-1T was detected more frequently in isolates from water (44.2 %) than in those from patients (2.7 %), indicating that the 65 kb DNA fragment may aid the survival of L. pneumophila in the sampled environment. However, the low frequency of the 65 kb fragment in isolates from patients suggests that the pathogenicity island may not be necessary for L. pneumophila to cause disease. Plasmids were not detected in the L. pneumophila SG1 isolates from patients or water studied. There was an association of both lvh and rtxA with the virulent and predominant genotype detected by amplified fragment length polymorphism, termed AF1, whereas the avirulent common isolate from water termed AF16 did not have lvh or rtxA genes, with the exception of one isolate with rtxA. It was found that a PCR detection test strategy with lvh and rtxA as pathogenesis markers would be useful for determining the infection potential of an isolate.
Biofilm matrix of Candida albicans and Candida tropicalis: chemical composition and role in drug resistance
Authors: Al-Fattani Mohammed A. , Douglas L. Julia
Published: July 2006

Matrix material was extracted from biofilms of Candida albicans and Candida tropicalis and analysed chemically. Both preparations contained carbohydrate, protein, hexosamine, phosphorus and uronic acid. However, the major component in C. albicans matrix was glucose (32 %), whereas in C. tropicalis matrix it was hexosamine (27 %). Biofilms of C. albicans were more easily detached from plastic surfaces by treatment with the enzyme lyticase (β-1,3-glucanase) than were those of C. tropicalis. Biofilms of C. albicans were also partially detached by treatment with proteinase K, chitinase, DNase I, or β-N-acetylglucosaminidase, whereas C. tropicalis biofilms were only affected by lipase type VII or chitinase. To investigate a possible role for the matrix in biofilm resistance to antifungal agents, biofilms of C. albicans were grown under conditions of continuous flow in a modified Robbins device (MRD). These biofilms produced more matrix material than those grown statically, and were significantly more resistant to amphotericin B. Biofilms of C. tropicalis synthesized large amounts of matrix material even when grown statically, and such biofilms were completely resistant to both amphotericin B and fluconazole. Mixed-species biofilms of C. albicans and a slime-producing strain of Staphylococcus epidermidis (RP62A), when grown statically or in the MRD, were also completely resistant to amphotericin B and fluconazole. Mixed-species biofilms of C. albicans and a slime-negative mutant of S. epidermidis (M7), on the other hand, were completely drug resistant only when grown under flow conditions. These results demonstrate that the matrix can make a significant contribution to drug resistance in Candida biofilms, especially under conditions similar to those found in catheter infections in vivo, and that the composition of the matrix material is an important determinant in resistance.
Characterization of proteinase–adhesin complexes of Porphyromonas gingivalis
Authors: Pathirana Rishi D. , O'Brien-Simpson Neil M. , Veith Paul D. , Riley Peter F. , Reynolds Eric C.
Published: July 2006

Proteinase–adhesin complexes ofPorphyromonas gingivaliswild-type and RgpA and Kgp mutants were extracted using a Triton X-114 procedure and purified using arginine-affinity chromatography. The complexes were then characterized by peptide mass fingerprinting (PMF) and their equilibrium binding constants, immunogenicity and ability to induce protection as vaccines in the murine lesion model determined. The Triton X-114 procedure resulted in consistently higher yield and specific activity of the wild-type (wt) complex compared with that produced by the previously published sonication method. PMF and N-terminal sequencing of the purified wt complex showed that it consisted of the previously identified Arg-specific proteinase RgpAcat, the Lys-specific proteinase Kgpcatand adhesin domains RgpAA1, RgpAA2, RgpAA3, KgpA1and KgpA2. However, analysis of the 30 kDa band in the wt complex, previously suggested to be RgpAA4, indicated that this band contained C-terminally truncated KgpA1(which has an identical N-terminus to RgpAA4) as well as the HagAA1* adhesin. Analysis of the Triton X-114 extracted complexes from theP. gingivalisisogenic mutantskgp(RgpA complex) andrgpA(Kgp complex) suggested that the Kgp complex consisted of Kgpcat, KgpA1and KgpA2/HagAA2and that the RgpA complex consisted of RgpAcat, RgpAA1, HagAA1*, RgpAA2and RgpAA3. Each of the complexes was found to have equilibrium binding constants (KD) in the nanomolar range for fibrinogen, fibronectin, haemoglobin, collagen type V and laminin. However, the Triton-wt complex exhibited significantly lowerKDvalues for binding to each host protein compared with the sonication-wt complex, or the Triton-RgpA complex and Triton-Kgp complex. Furthermore, the Triton-wt complex induced a stronger antibody response to the A1 adhesins and tended to be more effective in providing protection in the mouse lesion model compared with the sonication-wt complex.
Biosynthesis of the unusual 5,5-gem-dimethyl-deoxysugar noviose: investigation of the C-methyltransferase gene cloU
Authors: Freitag Anja , Li Shu-Ming , Heide Lutz
Published: July 2006

The aminocoumarin antibiotic clorobiocin contains an unusual branched deoxysugar with a 5,5-gem-dimethyl structure. Inactivation of the putativeC-methyltransferase genecloUwas carried out, which led to the loss of the axial methyl group at C-5 of this deoxysugar moiety. This result establishes the function ofcloU, and at the same time it proves that the biosynthesis of the deoxysugar moiety of clorobiocin proceeds via a 3,5-epimerization of the dTDP-4-keto-6-deoxyglucose intermediate. The inactivation was carried out on a cosmid which contained the entire clorobiocin biosynthetic gene cluster. Expression of the modified cluster in a heterologous host led to the formation of desmethyl-clorobiocin and a structural isomer thereof. Both compounds were isolated on a preparative scale, their structures were elucidated by1H-NMR and mass spectroscopy and their antibacterial activity was assayed.
pSM19035-encoded ζ toxin induces stasis followed by death in a subpopulation of cells
Authors: Lioy Virginia S. , Martín M. Teresa , Camacho Ana G. , Lurz Rudi , Antelmann Haike , Hecker Michael , Hitchin Ed , Ridge Yvonne , Wells Jerry M. , Alonso Juan C.
Published: July 2006

The toxin–antitoxin operon of pSM19035 encodes three proteins: the ω global regulator, the ε labile antitoxin and the stable ζ toxin. Accumulation of ζ toxin free of ε antitoxin induced loss of cell proliferation in both Bacillus subtilis and Escherichia coli cells. Induction of a ζ variant (ζY83C) triggered stasis, in which B. subtilis cells were viable but unable to proliferate, without selectively affecting protein translation. In E. coli cells, accumulation of free ζ toxin induced stasis, but this was fully reversed by expression of the ε antitoxin within a defined time window. The time window for reversion of ζ toxicity by expression of ε antitoxin was dependent on the initial cellular level of ζ. After 240 min of constitutive expression, or inducible expression of high levels of ζ toxin for 30 min, expression of ε failed to reverse the toxic effect exerted by ζ in cells growing in minimal medium. Under the latter conditions, ζ inhibited replication, transcription and translation and finally induced death in a fraction (∼50 %) of the cell population. These results support the view that ζ interacts with its specific target and reversibly inhibits cell proliferation, but accumulation of ζ might lead to cell death due to pleiotropic effects.
Peptidyl-tRNA hydrolase and its critical role in protein biosynthesis
Authors: Das Gautam , Varshney Umesh
Published: July 2006

Peptidyl-tRNA hydrolase (Pth) releases tRNA from peptidyl-tRNA by cleaving the ester bond between the peptide and the tRNA. Genetic analyses usingEscherichia coliharbouring temperature-sensitive Pth have identified a number of translation factors involved in peptidyl-tRNA release. Accumulation of peptidyl-tRNA in the cells leads to depletion of aminoacyl-tRNA pools and halts protein biosynthesis. Thus, it is vital for cells to maintain Pth activity to deal with the pollution of peptidyl-tRNAs generated during the initiation, elongation and termination steps of protein biosynthesis. Interestingly, while eubacteria possess a single class of peptidyl-tRNA hydrolase, eukaryotes possess several such activities, making Pth a potential drug target to control eubacterial infections. This review discusses the aspects of Pth that relate to its history and biochemistry and its physiological connections with various cellular factors.
Adult but not aged C57BL/6 male mice are capable of using geometry for orientation
Authors: Fellini Laetitia , Schachner Melitta , Morellini Fabio
Published: July 2006

Geometry, e.g., the shape of the environment, can be used by numerous animal species to orientate, but data concerning the mouse are lacking. We addressed the question of whether mice are capable of using geometry for navigating. To test whether aging could affect searching strategies, we compared adult (3- to 5-mo old) and aged (20- to 21-mo old) C57BL/6 male mice. We established a water maze task in which spatial information is provided by one landmark proximal to the target (featural information) and by the rectangular shape of the maze (geometric information). By means of probe trials in which we manipulated the presence of these two kinds of information, we show that adult mice can use both geometry and landmark to orientate. By contrast, aged mice do not use geometry and rely exclusively on the landmark to locate the platform. This study provides the first evidence that mice are capable of using geometric information for orientation and that this ability declines in aged animals.
“Free lessons” in aviation safety
Authors: Rose Andrew
Published: July 2006

The aviation industry has traditionally been good at learning from its accidents: a global network of government run accident investigation organizations and the high media profile given to any major aviation disaster helps to ensure this. As commercial aviation successfully reduces its accident rate the opportunity for learning from accidents diminishes and learning from potential accidents becomes more important. Ironically, however, this success can generate a culture that minimises the perceived potential of incidents and becomes less likely to learn from them. The key to overcoming this is in generating a culture that has the desire to maximize the lessons for safety from any opportunity and openly share that learning. To succeed, this culture has to overcome the human and organizational desire to find a single cause and attribute blame. Invariably any accident is a chain of events and occurrences that come together in a tragic way and there are often many solutions to even the simplest incident. An incident that doesn't lead to a loss of life or significant financial burden should be seen as a “free lesson”, simply an opportunity to see how the system and its components broke down to allow the event, or more importantly one worse, to happen. Any system and ultimately any person is prone to failure and hence blame is of no value, understanding where the failures are likely to occur and how to minimise their potential is important.
Effect of deformation‐induced martensite on the pit propagation behavior of 304 stainless steel
Authors: Chunchun Xu , Gang Hu
Published: July 2006

Specimens of 304 stainless steel with various martensite contents were prepared by a low temperature (−70°C) elongation method. Optical microscopy and transmission electron micrography were used to study the phase structure of the samples. A simulated occluded cell (OC) and electrochemical impedance spectroscopy were used to study the chemical and the electrochemical changes within pits on 304 stainless steel containing the different martensite contents. The EIS results showed that the martensite phase decreased not only the solution resistance in pit, but also the polarization resistance value between metal and solution in pit. The composition of the passive film in OC solution was studied by X‐ray photoelectron spectroscopy. It was observed that martensite transformation was a very important factor in changing the composition of the passive film. The martensite phase destroyed the integrality and compactness of the passive film. For these reasons, pit propagation in Type 304 stainless steel was accelerated with increasing martensite content.
A statistical interpretation of term specificity and its application in retrieval
Authors: Spärck Jones Karen
Published: July 2006

The exhaustivity of document descriptions and the specificity of index terms are usually regarded as independent. It is suggested that specificity should be interpreted statistically, as a function of term use rather than of term meaning. The effects on retrieval of variations in term specificity are examined, experiments with three test collections showing, in particular, that frequently‐occurring terms are required for good overall performance. It is argued that terms should be weighted according to collection frequency, so that matches on less frequent, more specific, terms are of greater value than matches on frequent terms. Results for the test collections show that considerable improvements in performance are obtained with this very simple procedure.
Employee commitment and organizational policies
Authors: Foote David A. , Seipel Scott J. , Johnson Nancy B. , Duffy Michelle K.
Published: July 2006

Purpose

To propose new commitment construct‐policy commitment, and to examine the influence of attitude, role clarity, and role conflict on policy commitment, as well as the influence of policy commitment on citizenship behavior.

Design/methodology/approach

Using a self‐report questionnaire and a sample of 148 workers in a rural manufacturing plant, we use structural equation modeling (SEM) techniques to examine the effects of attitude, role clarity, and role conflict on policy commitment, as well as the effect of policy commitment on the conscientiousness and civic virtue dimensions of citizenship behavior.

Findings

SEM revealed that attitudes and role clarity positively influenced policy commitment, and that policy commitment positively influenced conscientiousness and civic virtue.

Research limitations/implications

Our sample is relatively small (N=148) and largely homogeneous, which may limit its generalizability. A number of additional research opportunities are suggested in the study, including those designed to further explore the nature of the policy commitment construct and those designed to examine its relationship with other known commitment antecedents and outcomes. Implications for practitioners and researchers are suggested.

Originality/value

Commitment in organizations has long been conceptualized as acceptance of organizational goals and dedicated effort on behalf of the organization itself. However, we believe this conceptualization of commitment may be considerably less salient in today's highly mobile work environment. This study introduces the construct of policy commitment, a conceptualization of commitment as belief in and proactive endorsement of specific courses of action (i.e. policies) that embody the values resident within organizations.
John Seely Brown
Authors: Powell Sarah
Published: July 2006

Purpose

To determine the views of a prominent speaker, author and teacher on his views on nurturing invention and managing innovation.

Design/methodology/approach

The article is an interview with John Seely Brown, a visiting scholar at the Annenberg Center at the University of Southern California.

Findings

The interview covers Brown's opinions on a range of issues about invention, innovation and information technology.

Originality/value

Provides insights into the thinking of a prominent researcher in organizational and individual learning.
Does diet protect against Parkinson's disease? Part 3 – fruit, vegetables and grains
Authors: Brown Isabella
Published: July 2006

Parkinson's disease is an age‐related brain disease which is currently incurable. The long period during which damage occurs but symptoms are not evident is a focus of research with an aim to finding ways of reducing damage. This paper is the third in a series of diet and PD and covers the evidence for a role of fruit, vegetables and grains in the development of PD. Evidence is not conclusive but suggests that increasing the consumption of fruit, vegetables and grains may reduce the incidence of PD. A small number of studies have found a positive association between fruit and vegetables and PD but this may be due to chemical contamination. There is a need for further research to be carried out, preferably as part of a large ongoing study, rather than using retospective data, with its inherent bias.
A survey of hygiene practices among food vendors in rural areas in Mauritius
Authors: Subratty A.H. , Beeharry P. , Chan Sun M.
Published: July 2006

Using a questionnaire, assesses the hygienic practices of a group of 50 street food vendors in Mauritius. The findings showed that generally, food vendors were quite aware of hygienic conditions, which have to be respected while handling and preparing foods. However, it was found that the majority of them were not implementing their knowledge into practice and still perceived that their products were of relatively low risk to the consumers. It was also found that for more than half of the vending households, street food vending was the main income provider. Despite the role of health inspectors in promoting awareness of the risks which poor hygiene practices may lead to, findings from the present study highlight the need for further health education of food vendors.
Empowered self‐management and the design of work teams
Authors: Cooney Richard
Published: July 2006

This paper explores the theoretical implications of empowered self‐management as a teamwork design concept. It explores the multiple definitions of empowerment and self‐management that have been used in the design of work teams and it attempts to locate empowered self‐management within the relevant traditions of work design. The paper provides a critical appraisal of empowered self‐management as a team design concept arguing that its unique contribution to the work design literature, has been the development of concepts that focus upon task enlargement as the basis of enhanced role accountabilities within teams. Empowered self‐management as a team design concept has little to say about employee or group autonomy but in fact reflects the design of teams to provide for the normative self‐regulation of employees within management directed systems of control.
Impediments to promoting access to global knowledge in sub‐Saharan Africa
Authors: Ondari‐Okemwa Ezra
Published: July 2006

Knowledge‐based societies have come to be identified with the advanced economies. Knowledge is now looked on as a new source of competitive advantage. Those economies where knowledge is created and used in large quantities may be said to enjoy a competitive advantage over those that do not create and use knowledge in large quantities. Sub‐Saharan Africa is one region which needs to have access to global knowledge for its economic development. However, there are several impediments to promoting access to global knowledge in sub‐Saharan Africa. The impediments are identified in the study and solutions to the impediments proposed. Research methods used are highlighted.
Influence of contextual factors on health‐care leadership
Authors: Kay Brazier Davina
Published: July 2006

Purpose

To extend understanding of the influence of contextual factors on: power and influence; creativity and innovation; and leadership behaviour.

Design/methodology/approach

The review has been compiled following a search of seven electronic databases from 1999 to 2004. The author also uses her experience as a physiotherapy manager within a children's hospital NHS Trust to reflect on some of the theories in the workplace.

Findings

While the literature is contradictory in places, some trends do emerge. Bureaucratic organizations can inhibit an empowering environment, as can those that are poor at disseminating information or communicating a vision. Hierarchical structures, high staff turnover and lack of resources are likely to stifle creativity and innovation. Organic structures tend to facilitate a more transformational leadership style, whereas bureaucratic structures encourage a more transactional style. The quality of leader‐member exchange is thought to be related to work group size, work group cohesiveness and organizational climate.

Research limitations/implications

Care is needed in applying these findings to the National Health Service as theory that is developed in one organisation or culture may not be transferable to another. The author suggests that an empirical investigation should be undertaken in different National Health Service units.

Originality/value

This paper explores an aspect of leadership that is often neglected. Organizations that wish to nurture and develop their leaders and managers will need to be mindful of the environmental context within which this takes place.
Teamwork by swarms of all terrain mobile robots
Authors: Pettinaro Giovanni C.
Published: July 2006

The classic monolithic design of robot agents shows all its limits when tasks require capabilities which go beyond those initially planned. Robot collaboration seems to be a possible answer to the otherwise ever increasing complexity of mechanical and electrical design. Swarm robotics, by exploiting the power of interaction among members, offers such an answer. Simple units can in fact collaborate in achieving their common goal without the need of being aware at all of the rest of the group. The resilience achieved in this way makes the paradigm very appealing in all those applications, where mechanical or software failure may jeopardise the success of the overall mission. The present work summarizes the ongoing research which is being carried out by the author and his team. The hardware and software employed as well as some application experiments are described and discussed.
The OmniTread serpentine robot for industrial inspection and surveillance
Authors: Granosik Grzegorz , Hansen Malik G. , Borenstein Johann
Published: July 2006

Purpose

Describes the design, construction, and performance of the OmniTread serpentine robot. Provides a review of other designs in this new area of mobile robotics. Presents innovative and unique mechanical and control solutions.

Design/methodology/approach

A theoretical analysis of key aspects of the mechanical design and their implications on the performance of the robot is presented. Extensive experimentation and testing helped optimize choices of materials for the critical components: tracks and pneumatic bellows. Performance was evaluated by an independent third party: the Southwest Research Institute.

Findings

It was found that pneumatic bellows are optimal joint actuators for serpentine robots. They can provide both strength and compliance, depending on the task, at minimal volume and weight.

Research limitations/implications

The described prototype is tethered to external sources of electrical and pneumatic power. A smaller and fully self‐contained version of the OmniTread is currently under development.

Practical implications

A fully functional OmniTread serpentine robot will provide unprecedented mobility on rough terrain, such as the rubble of a collapsed building. The ability to climb over high obstacles and span large gaps, while still fitting through small openings suggests use of this robot in urban search and rescue, industrial inspection, and military reconnaissance tasks.

Originality/value

The OmniTread serpentine robot incorporates multiple original features, which resulted in three recent patents. Most notably are the Integrated pneumatic joint actuator with proportional position and stiffness control system and the “Tracks all Around” design. These features provide dramatic performance improvements in serpentine robots.