Iain Weir

ABA‐induced NO generation and stomatal closure in Arabidopsis are dependent on H2O2 synthesis

Nitric oxide (NO) and hydrogen peroxide (H2 O2 ) are key signalling molecules produced in response to various stimuli and involved in a diverse range of plant signal transduction processes. Nitric oxide and H2 O2 have been identified as essential components of the complex signalling network inducing stomatal closure in response to the phytohormone abscisic acid (ABA). A close inter-relationship exists between ABA and the spatial and temporal production and action of both NO and H2 O2 in guard cells. This study shows that, in Arabidopsis thaliana guard cells, ABA-mediated NO generation is in fact dependent on ABA-induced H2 O2 production. Stomatal closure induced by H2 O2 is inhibited by the removal of NO with NO scavenger, and both ABA and H2 O2 stimulate guard cell NO synthesis. Conversely, NO-induced stomatal closure does not require H2 O2 synthesis nor does NO treatment induce H2 O2 production in guard cells. Tungstate inhibition of the NO-generating enzyme nitrate reductase (NR) attenuates NO production in response to nitrite in vitro and in response to H2 O2 and ABA in vivo. Genetic data demonstrate that NR is the major source of NO in guard cells in response to ABA-mediated H2 O2 synthesis. In the NR double mutant nia1, nia2 both ABA and H2 O2 fail to induce NO production or stomatal closure, but in the nitric oxide synthase deficient Atnos1 mutant, responses to H2 O2 are not impaired. Importantly, we show that in the NADPH oxidase deficient double mutant atrbohD/F, NO synthesis and stomatal closure to ABA are severely reduced, indicating that endogenous H2 O2 production induced by ABA is required for NO synthesis. In summary, our physiological and genetic data demonstrate a strong inter-relationship between ABA, endogenous H2 O2 and NO-induced stomatal closure.

A role for ETR1 in hydrogen peroxide signaling in stomatal guard cells

Signaling through the redox active molecule hydrogen peroxide (H2O2) is important for several processes in plants, such as stomatal closure, root growth, gravitropism, and responses to pathogen challenge ([Neill et al., 2002][1]; [Laloi et al., 2004][2]). Although oxidative modification of reactive

Fully Bayesian Reconstructions from Single-Photon Emission Computed Tomography Data

Abstract With suitably chosen priors, Bayesian models are useful in image reconstruction. I consider reconstructions from single-photon emission computerized tomography data using a Gibbs pairwise difference prior. A fully Bayesian approach is presented where the prior parameters are considered drawn from hyperpriors. The approach is problematical, because the normalization constant in the prior is an intractable function of its parameters. Here the constant is estimated off-line by reverse logistic regression. Markov chain Monte Carlo methods are used on simulated and real data to gain estimates of the posterior mean and pixelwise credibility bounds. The resulting reconstructions are compared to those obtained by filtered back-projection, maximum likelihood/EM, and the one-step-late solution to the fixed parameter posterior mode.

Binary probability maps using a hidden conditional autoregressive Gaussian process with an application to Finnish common toad data

The Finnish common toad data of Heikkinen and Hogmander are reanalysed using an alternative fully Bayesian model that does not require a pseudolikelihood approximation and an alternative prior distribution for the true presence or absence status of toads in each 10 km×10 km square. Markov chain Monte Carlo methods are used to obtain posterior probability estimates of the square‐specific presences of the common toad and these are presented as a map. The results are different from those of Heikkinen and Hogmander and we offer an explanation in terms of the prior used for square‐specific presence of the toads. We suggest that our approach is more faithful to the data and avoids unnecessary confounding of effects. We demonstrate how to extend our model efficiently with square‐specific covariates and illustrate this by introducing deterministic spatial changes.

Concentrations of Cd, Zn and Cu in sediments and brown shrimp (Crangon crangon L.) from the Severn Estuary and Bristol Channel, UK.

Cd, Zn and Cu levels were determined in sediments and Crangon crangon from 9 sites in the Severn Estuary/Bristol Channel during winter 1999. Metal levels in both shrimp and sediments varied significantly between sites and were related to proximity of input and/or sediment type. In the upper Estuary, Cd levels in shrimp were 100x higher than other reported values whereas sediment Cd contamination was comparable. It is suggested that high Cd levels in shrimp are due to the high inputs and enhanced bioavailability of metal during winter.

The relationship between teenage ‘binge’ drinking, age of first alcohol consumption and intoxication

This paper is an investigation into the relationships between ‘binge’ drinking in adolescence, and ages of first drinking alcohol (beer, wine, spirits) and of first intoxication. These relationships are examined using data collected as part of the UK component of the European School Project on Alcohol and Other Drugs (ESPAD). This single phase cross sectional survey elicited self‐report data from a national sample of 1710 school students aged 15 and 16 years. It has been suggested that the early onset of alcohol consumption is predictive of heavy drinking and/or alcohol‐related problems in later life. This possibility is examined by estimating within‐gender effects of earlier age of first drinking alcohol (beer, wine, spirits)/first intoxication on the likelihood of (more frequent) recent ‘binge’ drinking (i.e. ‘binge’ drinking in the last 30 days). Another line of enquiry is examination of between‐gender effects of first drinking alcohol (beer, wine, spirits)/first intoxication at a particular age on the likelihood of (more frequent) recent ‘binge’ drinking. Proportional odds logistic regression has been used to investigate relationships of interest. There was no evidence to suggest statistical associations between ‘binge’ drinking and the ages of first drinking beer or of first intoxication. Even so, ‘binge’ drinking was found to be associated with the age of first drinking wine and the age of first drinking spirits. Furthermore, these associations were significantly different for girls and boys. Nearly two‐thirds of the within‐gender effects of earlier age of first drinking wine or spirits on ‘binge’ drinking examined were statistically non‐significant. Those results that were significant revealed that, with one exception, boys/girls who first drank wine or spirits earlier in life were more likely to ‘binge’ drink than individuals of the same gender who first drank wine or spirits later in life or who have never consumed wine or spirits. The exception was boys who first drank wine at 15–16 years of age; they were less likely to drink in ‘binges’ than boys who have never drunk wine. This exploration suggests that early first drinking experience with any type of alcoholic beverage is not necessarily a risk factor for ‘binge’ drinking amongst UK teenagers.

Observation and modelling of magnetization reversal in multilayers supporting perpendicular magnetization

Lorentz electron microscopy and micromagnetic modelling have been used to gain insight into the magnetization reversal of CoNi/Pt multilayers supporting perpendicular magnetization. Experimental observations were made in a highly modified transmission electron microscope as a function of the field magnitude and elapsed time. With appropriate selection of parameters, in particular the domain-wall energy and the activation volume, Monte Carlo simulations were able to reproduce most of the experimental results. Both of these quantities are difficult to measure directly. Finally, we note that pinning sites had to be introduced into the model to account for the very irregular manner in which the magnetization reversal proceeded.

Clinical Evaluation of a Prototype Underwear Designed to Detect Urine Leakage From Continence Pads.

PURPOSE: We evaluated the performance of prototype underwear designed to detect urine leakage from continence pads, their acceptability to users, and their effect on health-related quality of life and psychosocial factors. DESIGN: Prototype product evaluation. SUBJECTS AND SETTING: Participants were 81 women with an average age of 67 years (range, 32-98 years) recruited between October 2010 and February 2012 from outpatient clinics, general practice surgeries, community continence services, and through charities and networks. METHODS: The TACT3 project developed and manufactured a prototype undergarment designed to alert the wearer to a pad leak before it reaches outer clothing or furniture. The study was conducted in 2 stages: a pilot/feasibility study to assess general performance and a larger study to measure performance, acceptability to users, health-related quality of life, and psychosocial impact. Participants were asked to wear the prototype underwear for a period of 2 weeks, keeping a daily diary of leakage events for the first 7 days. They also completed validated instruments measuring lower urinary tract symptoms, health-related quality of life, and psychosocial impact. RESULTS: On average, 86% of the time participants were alerted to pad leakage events. More than 90% thought the prototype underwear was “good” or “OK” and that it would or could give them more confidence. Mean scores for the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form indicated no change in the level of symptoms reported before or after the intervention, and no significant changes in health-related quality of life status occurred, except improvement in for travel restrictions. Evaluation via the Psychosocial Impact of Assistive Devices Scale also indicated a positive impact. CONCLUSION: The prototype underwear evaluated in this study was effective and acceptable for 5 out of every 10 wearers. Findings also suggest that the prototype underwear is suitable for women of all ages, dress sizes, and continence severity.

OPEN ACCESS STATISTICS RESOURCES

In this paper we illustrate an open access statistics resource related to the statistical activities involved in choosing and carrying out an appropriate one sample test for location (mean or median) on a randomly generated data set. The development of the resource was funded through a sigma Resource Development Grant and is freely available from the UK national statstutor site. Five e-Assessment modules are available and these may be accessed independently or can be taken sequentially mimicking the flow of a full statistical analysis using the SPSS software package. On accessing the resource a new statistical data set may be generated or an existing data set used. Each module requires the data to have been downloaded to the SPSS statistical package, relevant analysis output obtained and a few questions answered to demonstrate understanding of the results. On submission, the e-Assessment system marks the responses immediately and provides full bespoke feedback for inappropriate test choices as well as other incorrect analysis. Videos and instruction pamphlets are accessible as links from each e-Assessment, which give clear instructions as to how to carry out the analyses and interpret results using SPSS. These additional resources, together with repeated use of the e-Assessment modules, facilitates learning how to identify and employ the correct test on a variety of data sets.