The host metabolite D-serine contributes to bacterial niche specificity through gene selection

Escherichia coli comprise a diverse array of both commensals and niche-specific pathotypes. The ability to cause disease results from both carriage of specific virulence factors and regulatory control of these via environmental stimuli. Moreover, host metabolites further refine the response of bacteria to their environment and can dramatically affect the outcome of the host–pathogen interaction. Here, we demonstrate that the host metabolite, D-serine, selectively affects gene expression in E. coli O157:H7. Transcriptomic profiling showed exposure to D-serine results in activation of the SOS response and suppresses expression of the Type 3 Secretion System (T3SS) used to attach to host cells. We also show that concurrent carriage of both the D-serine tolerance locus (dsdCXA) and the locus of enterocyte effacement pathogenicity island encoding a T3SS is extremely rare, a genotype that we attribute to an ‘evolutionary incompatibility’ between the two loci. This study demonstrates the importance of co-operation between both core and pathogenic genetic elements in defining niche specificity

Adaptogenic and nootropic activities of aqueous extract of Vitis vinifera (grape seed): an experimental study in rat model

BACKGROUND: The aerial parts of Vitis vinifera (common grape or European grape) have been widely used in Ayurveda to treat a variety of common and stress related disorders. In the present investigation, the seed extract of V. vinifera was evaluated for antistress activity in normal and stress induced rats. Furthermore, the extract was studied for nootropic activity in rats and in-vitro antioxidant potential to correlate its antistress activity. METHODS: For the evaluation of antistress activity, groups of rats (n = 6) were subjected to forced swim stress one hour after daily treatment of V. vinifera extract. Urinary vanillylmandelic acid (VMA) and ascorbic acid were selected as non-invasive biomarkers to assess the antistress activity. The 24 h urinary excretion of vanillylmandelic acid (VMA) and ascorbic acid were determined by spectrophotometric methods in all groups under normal and stressed conditions. The nootropic activity of the extract as determined from acquisition, retention and retrieval in rats was studied by conditioned avoidance response using Cook's pole climbing apparatus. The in vitro antioxidant activity was determined based on the ability of V. vinifera to scavenge hydroxyl radicals. RESULTS: Daily administration of V. vinifera at doses of 100, 200 and 300 mg/kg body weight one hour prior to induction of stress inhibited the stress induced urinary biochemical changes in a dose dependent manner. However, no change in the urinary excretion of VMA and ascorbic acid was observed in normal animals at all the doses studied. The cognition, as determined by the acquisition, retention and recovery in rats was observed to be dose dependent. The extract also produced significant inhibition of hydroxyl radicals in comparison to ascorbic acid in a dose dependent manner. CONCLUSION: The present study provides scientific support for the antistress (adaptogenic), antioxidant and nootropic activities of V. vinifera seed extract and substantiate the traditional claims for the usage of grape fruits and seeds in stress induced disorders

Runge-Kutta residual distribution schemes

We are concerned with the solution of time-dependent non-linear hyperbolic partial differential equations. We investigate the combination of residual distribution methods with a consistent mass matrix (discretisation in space) and a Runge–Kutta-type time-stepping (discretisation in time). The introduced non-linear blending procedure allows us to retain the explicit character of the time-stepping procedure. The resulting methods are second order accurate provided that both spatial and temporal approximations are. The proposed approach results in a global linear system that has to be solved at each time-step. An efficient way of solving this system is also proposed. To test and validate this new framework, we perform extensive numerical experiments on a wide variety of classical problems. An extensive numerical comparison of our approach with other multi-stage residual distribution schemes is also given

On the Nonlinearity of Modern Shock-Capturing Schemes

The development is reviewed of shock capturing methods, paying special attention to the increasing nonlinearity in the design of numerical schemes. The nature is studies of this nonlinearity and its relation to upwind differencing is examined. This nonlinearity of the modern shock capturing methods is essential, in the sense that linear analysis is not justified and may lead to wrong conclusions. Examples to demonstrate this point are given

Compressive properties of min-mod-type limiters in modelling shockwave-containing flows

The long-ignored compressive properties of Min-mod-type limiter is investigated in this manuscript by demonstrating its potential in numerically modelling shockwave-containing flows, especially in shock wave/boundary layer interaction (SWBLI) problems. Theoretical studies were firstly performed based on Sweby’s total variation diminishing (TVD) limiter region and Spekreijse’s monotonicity-preserving limiter region to indicate Min-mod-type limiters’ compressive properties. The influence of limiters on the solution accuracy was evaluated using a hybrid-order analysis method based on the grid-independent study in three typical shockwave-containing flows. The conclusions are that, Min-mod-type limiter can be utilized as a dissipative and/or compressive limiter, but depending on the reasonable value of the compression parameter. The compressive Min-mod limiter tends to be more attractive in modelling shockwave-containing flows as compared to other commonly preferred limiters because of its stable computational process and its high-resolution predictions. However, the compressive Min-mod limiter may suffer from its slightly poor convergence, as that observed in other commonly accepted smooth limiters in modelling SWBLI problems. © 2020, The Author(s)

The genesis and development of landfall and its influence in relation to the culture of New Zealand and the Commonwealth

All the research and development of the following dissertation has been made possible by the award of a New Zealand Commonwealth Scholarship (1970-1972) tenable at the University of Canterbury in Christchurch. The spirit in which the Scholarship is awarded is one of mutual understanding between Commonwealth countries, as a first step to better international understanding among all countries, and it is sincerely hoped that this thesis will, in some small way, contribute to the spirit of friendship and cooperation that exists between Canada and New Zealand. It is my opinion that no two Western countries have greater common interests; in peacekeeping and peacemaking; in trade and non-alignment with military blocs; in standard of living and quality of life; in relations between ethnic minorities and powerful majorities in sovereign states: and I believe that our histories have led us in comparable cultural, social, and political directions. The original goal that led me to pursue doctoral studies was to present a major comparative study of "the social and literary mythology" (ideas discussed by Northrop Frye in Fables of Identity) of Canada, New Zealand and Australia. The comparative aspect of this goal is now planned for a future book. The extensive and rich documentation of the story of New Zealand, available in the many city, provincial, university and private libraries throughout the country, has made the confines of a Ph.D. thesis hard to determine. As a result, and in order to choose a suitable and original topic, the thesis has been confined to a discussion of post-war New Zealand literature and culture as presented in the quarterly Landfall under its first editor, Charles Brasch (1947-1966). The Introduction to the thesis explains the approach towards the topic: "The Genesis and Development of Landfall and its influence in Relation to the Culture of New Zealand and the Commonwealth." The term "Commonwealth" has been alluded to so that the thesis can be regarded in terms of the future comparative study. I believe that the term "Commonwealth literature", as accepted at the Conference on Commonwealth Literature held in Leeds (9-12 September 1964); can be used for the time being as a premise for comparative study. The chapter on historic influences on Landfall is a survey of intellectual periodicals that developed out of the radical years of the Depression. A discussion of Charles Brasch and editorial policy arose from the comment by E.H. McCormick that "the periodical is best approached through a consideration of its editor"