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Search Results: 1 - 10 of 222783 matches for " Lisa C. Crossman "
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The complete genome, comparative and functional analysis of Stenotrophomonas maltophilia reveals an organism heavily shielded by drug resistance determinants
Lisa C Crossman, Virginia C Gould, J Maxwell Dow, Georgios S Vernikos, Aki Okazaki, Mohammed Sebaihia, David Saunders, Claire Arrowsmith, Tim Carver, Nicholas Peters, Ellen Adlem, Arnaud Kerhornou, Angela Lord, Lee Murphy, Katharine Seeger, Robert Squares, Simon Rutter, Michael A Quail, Mari-Adele Rajandream, David Harris, Carol Churcher, Stephen D Bentley, Julian Parkhill, Nicholas R Thomson, Matthew B Avison
Genome Biology , 2008, DOI: 10.1186/gb-2008-9-4-r74
Abstract: The genome of the bacteremia-associated isolate S. maltophilia K279a is 4,851,126 bp and of high G+C content. The sequence reveals an organism with a remarkable capacity for drug and heavy metal resistance. In addition to a number of genes conferring resistance to antimicrobial drugs of different classes via alternative mechanisms, nine resistance-nodulation-division (RND)-type putative antimicrobial efflux systems are present. Functional genomic analysis confirms a role in drug resistance for several of the novel RND efflux pumps. S. maltophilia possesses potentially mobile regions of DNA and encodes a number of pili and fimbriae likely to be involved in adhesion and biofilm formation that may also contribute to increased antimicrobial drug resistance.The panoply of antimicrobial drug resistance genes and mobile genetic elements found suggests that the organism can act as a reservoir of antimicrobial drug resistance determinants in a clinical environment, which is an issue of considerable concern.The rise of antimicrobial drug resistance in bacteria is one of the biggest threats to healthcare provision in the developed world. Few new antimicrobial drugs are undergoing clinical trials, and almost none are effective against Gram-negative multi-drug resistant (MDR) pathogens [1]. A return to the pre-antibiotic era is a possibility, and for some infections is the current reality [2].Antimicrobial resistance in historically common pathogens is usually either acquired on a mobile genetic element or results from a mutation [3]. However, some opportunistic pathogens are intrinsically resistant to the actions of a number of antimicrobial classes. These tend to be of environmental origin, and their intrinsic drug resistance determinants either provide resistance to antibiotics produced by competitors, or represent broad-spectrum methods for removing toxic compounds or waste products that, by chance, protect against antimicrobials [3,4]. It is known that established opportuni
A Common Genomic Framework for a Diverse Assembly of Plasmids in the Symbiotic Nitrogen Fixing Bacteria
Lisa C. Crossman, Santiago Castillo-Ramírez, Craig McAnnula, Luis Lozano, Georgios S. Vernikos, José L. Acosta, Zara F. Ghazoui, Ismael Hernández-González, Georgina Meakin, Alan W. Walker, Michael F. Hynes, J. Peter W. Young, J. Allan Downie, David Romero, Andrew W. B. Johnston, Guillermo Dávila, Julian Parkhill, Víctor González
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002567
Abstract: This work centres on the genomic comparisons of two closely-related nitrogen-fixing symbiotic bacteria, Rhizobium leguminosarum biovar viciae 3841 and Rhizobium etli CFN42. These strains maintain a stable genomic core that is also common to other rhizobia species plus a very variable and significant accessory component. The chromosomes are highly syntenic, whereas plasmids are related by fewer syntenic blocks and have mosaic structures. The pairs of plasmids p42f-pRL12, p42e-pRL11 and p42b-pRL9 as well large parts of p42c with pRL10 are shown to be similar, whereas the symbiotic plasmids (p42d and pRL10) are structurally unrelated and seem to follow distinct evolutionary paths. Even though purifying selection is acting on the whole genome, the accessory component is evolving more rapidly. This component is constituted largely for proteins for transport of diverse metabolites and elements of external origin. The present analysis allows us to conclude that a heterogeneous and quickly diversifying group of plasmids co-exists in a common genomic framework.
The genome of Rhizobium leguminosarum has recognizable core and accessory components
J Peter W Young, Lisa C Crossman, Andrew WB Johnston, Nicholas R Thomson, Zara F Ghazoui, Katherine H Hull, Margaret Wexler, Andrew RJ Curson, Jonathan D Todd, Philip S Poole, Tim H Mauchline, Alison K East, Michael A Quail, Carol Churcher, Claire Arrowsmith, Inna Cherevach, Tracey Chillingworth, Kay Clarke, Ann Cronin, Paul Davis, Audrey Fraser, Zahra Hance, Heidi Hauser, Kay Jagels, Sharon Moule, Karen Mungall, Halina Norbertczak, Ester Rabbinowitsch, Mandy Sanders, Mark Simmonds, Sally Whitehead, Julian Parkhill
Genome Biology , 2006, DOI: 10.1186/gb-2006-7-4-r34
Abstract: The 7.75 Mb genome comprises a circular chromosome and six circular plasmids, with 61% G+C overall. All three rRNA operons and 52 tRNA genes are on the chromosome; essential protein-encoding genes are largely chromosomal, but most functional classes occur on plasmids as well. Of the 7,263 protein-encoding genes, 2,056 had orthologs in each of three related genomes (Agrobacterium tumefaciens, Sinorhizobium meliloti, and Mesorhizobium loti), and these genes were over-represented in the chromosome and had above average G+C. Most supported the rRNA-based phylogeny, confirming A. tumefaciens to be the closest among these relatives, but 347 genes were incompatible with this phylogeny; these were scattered throughout the genome but were over-represented on the plasmids. An unexpectedly large number of genes were shared by all three rhizobia but were missing from A. tumefaciens.Overall, the genome can be considered to have two main components: a 'core', which is higher in G+C, is mostly chromosomal, is shared with related organisms, and has a consistent phylogeny; and an 'accessory' component, which is sporadic in distribution, lower in G+C, and located on the plasmids and chromosomal islands. The accessory genome has a different nucleotide composition from the core despite a long history of coexistence.The symbiosis between legumes and N2-fixing bacteria (rhizobia) is of huge agronomic benefit, allowing many crops to be grown without N fertilizer. It is a sophisticated example of coupled development between bacteria and higher plants, culminating in the organogenesis of root nodules [1]. There have been many genetic analyses of rhizobia, notably of Sinorhizobium meliloti (the symbiont of alfalfa), Bradyrhizobium japonicum (soybean), and Rhizobium leguminosarum, which has biovars that nodulate peas and broad beans (biovar viciae), clovers (biovar trifolii), or kidney beans (biovar phaseoli).The Rhizobiales, an α-proteobacterial order that also includes mammalian pathogens B
Study protocol: a randomised controlled trial investigating the effect of exercise training on peripheral blood gene expression in patients with stable angina
Liam Bourke, Garry A Tew, Marta Milo, David C Crossman, John M Saxton, Timothy JA Chico
BMC Public Health , 2010, DOI: 10.1186/1471-2458-10-620
Abstract: Sixty patients with stable angina will be recruited and randomised 1:1 to exercise training or conventional care. Patients randomised to exercise training will attend an exercise physiology laboratory up to three times weekly for supervised aerobic interval training sessions of one hour in total duration. Patients will undergo assessments of angina, anxiety, depression, and peripheral blood gene expression at baseline, after six and twelve weeks of training, and twelve weeks after formal exercise training ceases.This study will provide comprehensive data on the effect of exercise training on peripheral blood gene expression in patients with angina. By correlating this with improvement in angina status we will identify candidate peripheral blood transcriptional markers predictive of improvements in angina level in response to exercise training.Clinicaltrials.gov identifier: NCT01147952Regular exercise protects against cardiovascular disease [1] and has beneficial effects on coronary perfusion and ventricular function in patients with established coronary artery disease [2]. However, the exact mechanism whereby exercise training exerts these effects is unclear. Meta-analyses have concluded that exercise based cardiac rehabilitation reduces cardiac mortality in patients with coronary artery disease (prior myocardial infarction, angina, bypass grafting or angioplasty) by 26%-31% [3,4]. Although exercise favourably influences serum lipids and blood pressure, the biological pathway whereby it protects against cardiovascular death remains unclear, though there is substantial evidence that exercise improves myocardial oxygenation. Exercise-induced improvement in myocardial perfusion has been demonstrated in a number of studies [2,5] suggesting exercise training increases absolute myocardial blood flow, rather than by altering myocardial efficiency. Exercise training has also been shown to improve coronary artery endothelial function (even after only 4 weeks training) [6].So
Hiroko Noma,Joanna Crossman
Asian Academy of Management Journal , 2012,
Abstract: Globalising forces have given rise to new relationships between organisations operating in Eastern and Western cultural contexts. Despite the rich opportunities presented by globalisation, the literature indicates that managers are challenged by the complexity of intercultural communication. This scholarly paper discusses some implications of analogue and digital mindsets for the managers of organisations in which effective inter- cultural communication across Eastern and Western contexts is crucial. We do so by adopting a multidisciplinary approach to the phenomenon and suggesting how managers may capitalise on knowledge related to analogue and digital mindsets to foster creative and holistic approaches to communication.
Aid to a Declining Matriarch in the Giant Otter (Pteronura brasiliensis)
Lisa C. Davenport
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011385
Abstract: Scientists are increasingly revealing the commonalities between the intellectual, emotional and moral capacities of animals and humans. Providing assistance to elderly and ailing family members is a human trait rarely documented for wild animals, other than anecdotal accounts. Here I report observations of multiple forms of assistance to the declining matriarch of a habituated group of giant otters (Pteronura brasiliensis) in Manu National Park, Peru. The otter group had been observed annually for several years and all members were known individually. In 2007, the breeding female of the group failed to reproduce and appeared to be in physical decline. She begged from other family members 43 times over 41 contact hours and received food 11 times. Comparisons with 2004–2006 demonstrate that the family's behavior in 2007 constitutes a role-reversal, in which the majority of assistance and prey transfers accrued from young-to-old rather than from old-to-young. As in human societies, both non-adaptive and adaptive hypotheses could explain the family members' aid to their declining matriarch. I suggest that giant otter families may benefit from the knowledge and experience of an elderly matriarch and “grandparent helper,” consistent with the “Grandmother Hypothesis” of adaptive menopause in women.
Critical role of the circadian clock in memory formation: lessons from Aplysia
Lisa C. Lyons
Frontiers in Molecular Neuroscience , 2011, DOI: 10.3389/fnmol.2011.00052
Abstract: Unraveling the complexities of learning and the formation of memory requires identification of the cellular and molecular processes through which neural plasticity arises as well as recognition of the conditions or factors through which those processes are modulated. With its relatively simple nervous system, the marine mollusk Aplysia californica has proven an outstanding model system for studies of memory formation and identification of the molecular mechanisms underlying learned behaviors, including classical and operant associative learning paradigms and non-associative behaviors. In vivo behavioral studies in Aplysia have significantly furthered our understanding of how the endogenous circadian clock modulates memory formation. Sensitization of the tail-siphon withdrawal reflex represents a defensive non-associative learned behavior for which the circadian clock strongly modulates intermediate and long-term memory formation. Likewise, Aplysia exhibit circadian rhythms in long-term memory, but not short-term memory, for an operant associative learning paradigm. This review focuses on circadian modulation of intermediate and long-term memory and the putative mechanisms through which this modulation occurs. Additionally, potential functions and the adaptive advantages of time of day pressure on memory formation are considered. The influence of the circadian clock on learning and memory crosses distant phylogeny highlighting the evolutionary importance of the circadian clock on metabolic, physiological, and behavioral processes. Thus, studies in a simple invertebrate model system have and will continue to provide critical mechanistic insights to complementary processes in higher organisms.
Group cohomology construction of the cohomology of moduli spaces of flat connections on 2-manifolds
Lisa C. Jeffrey
Physics , 1994,
Abstract: We use group cohomology and the de Rham complex on simplicial manifolds to give explicit differential forms representing generators of the cohomology rings of moduli spaces of representations of fundamental groups of 2-manifolds. These generators are constructed using the de Rham representatives for the cohomology of classifying spaces $BK$ where $K$ is a compact Lie group; such representatives (universal characteristic classes) were found by Bott and Shulman. Thus our representatives for the generators of the cohomology of moduli spaces are given explicitly in terms of the Maurer-Cartan form. This work solves a problem posed by Weinstein, who gave a corresponding construction (following Karshon and Goldman) of the symplectic forms on these moduli spaces. We also give a corresponding construction of equivariant differential forms on the extended moduli space $X$, which is a finite dimensional symplectic space equipped with a Hamiltonian action of $K$ for which the symplectic reduced space is the moduli space of representations of the 2-manifold fundamental group in $K$. (This paper is in press in Duke Math. J. The substance of the text is unaltered; inor changes and corrections have been made to the file to correspond to the version that will be published.)
Symplectic Forms on Moduli Spaces of Flat Connections on 2-manifolds
Lisa C. Jeffrey
Physics , 1994,
Abstract: Let $G$ be a compact connected semisimple Lie group. We extend the techniques of Weinstein [W] to give a construction in group cohomology of symplectic forms $\omega$ on \lq twisted' moduli spaces of representations of the fundamental group $\pi$ of a 2-manifold $\Sigma$ (the smooth analogues of ${\rm Hom} (\pi_1(\Sigma), G)/G$) and on relative character varieties of fundamental groups of 2-manifolds. We extend this construction to exhibit a symplectic form on the extended moduli space [J1] (a Hamiltonian $G$-space from which these moduli spaces may be obtained by symplectic reduction), and compute the moment map for the action of $G$ on the extended moduli space.
Symplectic Quantum Mechanics and Chern-Simons Gauge Theory II: Mapping Tori of Tori
Lisa C. Jeffrey
Mathematics , 2012, DOI: 10.1063/1.4804154
Abstract: We compute the semiclassical formulas for the partition functions obtained using two different Lagrangians: the Chern-Simons functional and the symplectic action functional.
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