Analysis of metabolic flux using dynamic labeling and metabolic modeling

Metabolic fluxes and the capacity to modulate them are a crucial component of the ability of the plant cell to react to environmental perturbations. Our ability to quantify them and to attain information concerning the regulatory mechanisms which control them is therefore essential to understand and influence metabolic networks. For all but the simplest of flux measurements labelling methods have proven to be the most informative. Both steady-state and dynamic labelling approaches having been adopted in the study of plant metabolism. Here the conceptual basis of these complementary approaches, as well as their historical application in microbial, mammalian and plant sciences are reviewed and an update on technical developments in label distribution analyses is provided. This is supported by illustrative cases studies involving the kinetic modelling of secondary metabolism. One issue that is particularly complex in the analysis of plant fluxes is the extensive compartmentation of the plant cell. This problem is discussed from both theoretical and experimental perspectives and the current approaches used to address it are assessed. Finally, current limitations and future perspectives of kinetic modelling of plant metabolism are discussed

Disempowerment and resistance in the print industry? Reactions to surveillance-capable technology

This article offers a critique of recent characterisations of the effects of electronic technologies in the workplace. It presents detailed case study evidence that calls into question a number of common theoretical assumptions about the character of surveillance at work and the responses of employees to it

UBVJHKLM photometry and modeling of R Coronae Borealis

We present the results of UBVJHKLM photometry of R CrB spanning the period from 1976 to 2001. Studies of the optical light curve have shown no evidence of any stable harmonics in the variations of the stellar emission. In the L band we found semi-regular oscillations with the two main periods of ~3.3 yr and 11.9 yr and the full amplitude of ~0.8 mag and ~0.6 mag, respectively. The colors of the warm dust shell (resolved by Ohnaka et al. 2001) are found to be remarkably stable in contrast to its brightness. This indicates that the inner radius is a constant, time-independent characteristic of the dust shell. The observed behavior of the IR light curve is mainly caused by the variation of the optical thickness of the dust shell within the interval \tau(V)= 0.2-0.4. Anticorrelated changes of the optical brightness (in particular with P ~ 3.3 yr) have not been found. Their absence suggests that the stellar wind of R CrB deviates from spherical symmetry. The light curves suggest that the stellar wind is variable. The variability of the stellar wind and the creation of dust clouds may be caused by some kind of activity on the stellar surface. With some time lag, periods of increased mass-loss cause an increase in the dust formation rate at the inner boundary of the extended dust shell and an increase in its IR brightness. We have derived the following parameters of the dust shell (at mean brightness) by radiative transfer modeling: inner dust shell radius r_in ~ 110 R_*, temperature T_dust(r_in) ~ 860 K, dust density \rho_dust(r_in) ~ 1.1x10^{-20} g cm^-3, optical depth \tau(V) ~ 0.32 at 0.55 micron, mean dust formation rate [dM/dt]_dust ~ 3.1x10^-9 M_sun / yr, mass-loss rate [dM/dt]_gas ~ 2.1x10^-7 M_sun / yr, size of the amorphous carbon grains <(~) 0.01 micron, and B-V ~ -0.28.Comment: 9 pages, 6 figures, accepted for publication in A&

Psychosocial impact of involvement in the special olympics

Existing evidence suggests that people with intellectual disabilities are vulnerable to low self-esteem leading to additional psychosocial issues such as social exclusion and stress. Previous research into the involvement of Special Olympics (SO) of people with intellectual disabilities has indicted positive psychosocial outcomes. Involvement in sport is known generally to have psychological and social benefits. This study aimed to compare the psychosocial impact of involvement in sport through the SO to no or limited sports involvement, for a sample of people with intellectual disabilities. A cross sectional design was employed comparing three groups, SO, Mencap Sports, and Mencap No Sports on the variables: Self-esteem, quality of life, stress levels and social networks. One hundred and one participants were recruited either through the SO or Mencap. Data were collected through the completion of validated questionnaires by one to one interviews with the participants. Analysis revealed that self-esteem, quality of life, and stress were all significantly associated with SO involvement. Logistic regression analysis was used to explore whether scores on these variables were able to predict group membership. Self-esteem was found to be a significant predictor of group membership, those in the SO having the highest self-esteem. The findings provide further evidence of a positive association between sport involvement and increased psychological wellbeing, especially for those involved in the SO. The implications of these findings for practice and future research into the relationship between sport and psychological wellbeing within the learning disabled population are considered

Learning on the IGT follows emergence of knowledge but not differential somatic activity

The importance of unconscious autonomic activity vs. knowledge in influencing behavior on the Iowa Gambling Task (IGT) has been the subject of debate. The task's developers, Bechara and colleagues, have claimed that behavior on the IGT is influenced by somatic activity and that this activity precedes the emergence of knowledge about the task contingencies sufficient to guide behavior. Since then others have claimed that this knowledge emerges much earlier on the task. However, it has yet to be established whether somatic activity which differentiates between advantageous and disadvantageous choices on the IGT is found before this point. This study describes an experiment to determine whether knowledge sufficient to guide behavior precedes differential autonomic activity or vice versa. This experiment used a computerized version of the IGT, knowledge probes after every 10 trials and skin conductance recording to measure somatic activity. Whereas in previous reports the majority of participants end the task with full conceptual knowledge of the IGT contingencies we found little evidence in support of this conclusion. However, full conceptual knowledge was not critical for advantageous deck selection to occur and most participants had knowledge sufficient to guide behavior after approximately 40 trials. We did not find anticipatory physiological activity sufficient to differentiate between deck types in the period prior to acquiring this knowledge. However, post-punishment physiological activity was found to be larger for the disadvantageous decks in the pre-knowledge period, but only for participants who displayed knowledge. Post-reward physiological activity distinguished between the advantageous and disadvantageous decks across the whole experiment but, again, only in participants who displayed knowledge and then only in later trials following their display of knowledge

Learning on the IGT follows emergence of knowledge but not differential somatic activity

The importance of unconscious autonomic activity vs. knowledge in influencing behavior on the Iowa Gambling Task (IGT) has been the subject of debate. The task's developers, Bechara and colleagues, have claimed that behavior on the IGT is influenced by somatic activity and that this activity precedes the emergence of knowledge about the task contingencies sufficient to guide behavior. Since then others have claimed that this knowledge emerges much earlier on the task. However, it has yet to be established whether somatic activity which differentiates between advantageous and disadvantageous choices on the IGT is found before this point. This study describes an experiment to determine whether knowledge sufficient to guide behavior precedes differential autonomic activity or vice versa. This experiment used a computerized version of the IGT, knowledge probes after every 10 trials and skin conductance recording to measure somatic activity. Whereas in previous reports the majority of participants end the task with full conceptual knowledge of the IGT contingencies we found little evidence in support of this conclusion. However, full conceptual knowledge was not critical for advantageous deck selection to occur and most participants had knowledge sufficient to guide behavior after approximately 40 trials. We did not find anticipatory physiological activity sufficient to differentiate between deck types in the period prior to acquiring this knowledge. However, post-punishment physiological activity was found to be larger for the disadvantageous decks in the pre-knowledge period, but only for participants who displayed knowledge. Post-reward physiological activity distinguished between the advantageous and disadvantageous decks across the whole experiment but, again, only in participants who displayed knowledge and then only in later trials following their display of knowledge

Repetition priming affects guessing not familiarity

<p>Abstract</p> <p>Background</p> <p>The claim that recollection and familiarity based memory processes have distinct retrieval mechanisms is based partly on the observation that masked repetition and semantic priming influence estimates of familiarity derived from <it>know </it>responses but have no effect on estimates of recollection derived from <it>remember </it>responses. Close inspection of the experiments on which this claim is based reveal the effect size to be small, potentially the result of a type-2 error, and/or inflated due to participants not having the opportunity to report <it>guesses</it>. This paper re-evaluates these claims by attempting a partial replication of two such Experiments.</p> <p>Methods</p> <p>In Experiment 1 participants made <it>remember</it>, <it>know</it>, and <it>guess </it>responses following primed and unprimed target words. In Experiment 2 participants made <it>sure</it>, <it>unsure</it>, and <it>guess </it>following primed and unprimed target words.</p> <p>Results</p> <p>In Experiment 1 the repetition priming effect occurred only for <it>guess </it>responses and only for unstudied items. In Experiment 2 the priming effect occurred for both <it>unsure </it>and <it>guess </it>responses, but again only for unstudied items.</p> <p>Conclusion</p> <p>The data are consistent with the view that <it>remembering </it>and <it>knowing </it>do not correspond to confidence ratings; and suggest that contrary to earlier findings, <it>recollection </it>and <it>familiarity </it>do not differ in retrieval mechanisms. As such the effects of repetition priming on subjective reports of remembering should not be cited as evidence for the distinction between recollection and familiarity based memory processes.</p

The Use of Natural Genetic Diversity in the Understanding of Metabolic Organization and Regulation

The study of metabolic regulation has traditionally focused on analysis of specific enzymes, emphasizing kinetic properties, and the influence of protein interactions and post-translational modifications. More recently, reverse genetic approaches permit researchers to directly determine the effects of a deficiency or a surplus of a given enzyme on the biochemistry and physiology of a plant. Furthermore, in many model species, gene expression atlases that give important spatial information concerning the quantitative expression level of metabolism-associated genes are being produced. In parallel, “top-down” approaches to understand metabolic regulation have recently been instigated whereby broad genetic diversity is screened for metabolic traits and the genetic basis of this diversity is defined thereafter. In this article we will review recent examples of this latter approach both in the model species Arabidopsis thaliana and the crop species tomato (Solanum lycopersicum). In addition to highlighting examples in which this genetic diversity approach has proven promising, we will discuss the challenges associated with this approach and provide a perspective for its future utility