A Dynamic Model of Interactions of Ca^(2+), Calmodulin, and Catalytic Subunits of Ca^(2+)/Calmodulin-Dependent Protein Kinase II

During the acquisition of memories, influx of Ca^(2+) into the postsynaptic spine through the pores of activated N-methyl-D-aspartate-type glutamate receptors triggers processes that change the strength of excitatory synapses. The pattern of Ca^(2+) influx during the first few seconds of activity is interpreted within the Ca^(2+)-dependent signaling network such that synaptic strength is eventually either potentiated or depressed. Many of the critical signaling enzymes that control synaptic plasticity, including Ca^(2+)/calmodulin-dependent protein kinase II (CaMKII), are regulated by calmodulin, a small protein that can bind up to 4 Ca^(2+) ions. As a first step toward clarifying how the Ca^(2+)-signaling network decides between potentiation or depression, we have created a kinetic model of the interactions of Ca^(2+), calmodulin, and CaMKII that represents our best understanding of the dynamics of these interactions under conditions that resemble those in a postsynaptic spine. We constrained parameters of the model from data in the literature, or from our own measurements, and then predicted time courses of activation and autophosphorylation of CaMKII under a variety of conditions. Simulations showed that species of calmodulin with fewer than four bound Ca^(2+) play a significant role in activation of CaMKII in the physiological regime, supporting the notion that processing ofCa^(2+) signals in a spine involves competition among target enzymes for binding to unsaturated species of CaM in an environment in which the concentration of Ca^(2+) is fluctuating rapidly. Indeed, we showed that dependence of activation on the frequency of Ca^(2+) transients arises from the kinetics of interaction of fluctuating Ca^(2+) with calmodulin/CaMKII complexes. We used parameter sensitivity analysis to identify which parameters will be most beneficial to measure more carefully to improve the accuracy of predictions. This model provides a quantitative base from which to build more complex dynamic models of postsynaptic signal transduction during learning

Physical activity of Estonian family doctors and their counselling for a healthy lifestyle: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Physical activity offers major health benefits and counselling for it should be integrated into the medical consultation. Based on the literature, the personal health behaviour of the physician (including physical activity) is associated with his/her approach to counselling patients. Our hypothesis is that family doctors (FD) in Estonia are physically active and their recommendation to counsel patients with chronic diseases to use physical activity is high. The study was also interested in how FDs value physical activity among other important determinants of a healthy lifestyle, e.g. nutrition, non-consumption of alcohol, and non-smoking.</p> <p>Methods</p> <p>Physicians on the electronic list were contacted by e-mail and sent a questionnaire. The first part assessed physical activity by the International Physical Activity Questionnaire (IPAQ) short form. Self-reported physical activity during one week was calculated as total physical activity in minutes per week (MET min/week). The second part of the questionnaire included questions about the counselling of patients with chronic disease concerning their physical activity and a healthy lifestyle. The study focused on female FDs because 95% of the FDs in Estonia are women and to avoid bias related to gender.</p> <p>Results</p> <p>198 female FDs completed the questionnaire. 92% reported that they exercised over the past 7 days to a moderate or high level of physical activity. Analysis revealed no statistically significant relationship between the level of physical activity and general characteristics (age, living area, body mass index [BMI], time spent sitting). FDs reported that patients with heart problems, diabetes, and obesity seek their advice on physical activity more often than patients with depression. Over 94% of the FDs claimed that they counsel their patients with chronic diseases about exercising. According to the FDs' reports, the most important topic in counselling patients for a healthy lifestyle was physical activity.</p> <p>Conclusion</p> <p>This study showed that female FDs are physically active. The level of physical activity is not related to their age, BMI, living area, or time spent sitting. Also, FDs reported that promotion of physical activity is part of their everyday work.</p

Biological Invasions and Ecological Restoration in South Africa

This chapter provides an overview of the researchers and research initiatives relevant to invasion science in South Africa over the past 130 years, profiling some of the more recent personalities, particularly those who are today regarded as international leaders in the field. A number of key points arise from this review. Since 1913, South Africa has been one of a few countries that have investigated and implemented alien plant biological control on a large scale, and is regarded as a leader in this field. South Africa was also prominent in the conceptualisation and execution of the international SCOPE project on the ecology of biological invasions in the 1980s, during which South African scientists established themselves as valuable contributors to the field. The development of invasion science benefitted from a deliberate strategy to promote multi-organisational, interdisciplinary research in the 1980s. Since 1995, the Working for Water programme has provided funding for research and a host of practical questions that required research solutions. Finally, the establishment of a national centre of excellence with a focus on biological invasions has made a considerable contribution to building human capacity in the field, resulting in advances in all aspects of invasion science—primarily in terms of biology and ecology, but also in history, sociology, economics and management. South Africa has punched well above its weight in developing the field of invasion science, possibly because of the remarkable biodiversity that provided a rich template on which to carry out research, and a small, well-connected research community that was encouraged to operate in a collaborative manner

Genetic interactions contribute less than additive effects to quantitative trait variation in yeast

Genetic mapping studies of quantitative traits typically focus on detecting loci that contribute additively to trait variation. Genetic interactions are often proposed as a contributing factor to trait variation, but the relative contribution of interactions to trait variation is a subject of debate. Here we use a very large cross between two yeast strains to accurately estimate the fraction of phenotypic variance due to pairwise QTL–QTL interactions for 20 quantitative traits. We find that this fraction is 9% on average, substantially less than the contribution of additive QTL (43%). Statistically significant QTL–QTL pairs typically have small individual effect sizes, but collectively explain 40% of the pairwise interaction variance. We show that pairwise interaction variance is largely explained by pairs of loci at least one of which has a significant additive effect. These results refine our understanding of the genetic architecture of quantitative traits and help guide future mapping studies

Social identity theory

According to social identity theory, people derive part of their identity – their social identity – from the groups to which they belong (e.g., an identity as “student,” “woman,” “left-hander,” or “Barcelona supporter”). Social identities differ in strength and content. The strength component is conceptualized in terms of social identification (e.g., “I identity strongly with Europeans”), while the content of social identity is determined by the group’s features (e.g., colors associated with a soccer team) and norms (e.g., “real men don’t cry”). Social identity determines emotions (e.g., depression after a team loss) and behavior (e.g., discrimination against out-groups or effort on behalf of one’s in-group). In this chapter we outline the basic features of social identity theory – from social categorization to coping with a negative social identity – and then discuss two important domains of application: health and organizations. We conclude by describing a social identity-based intervention for improving intergroup relations in an educational setting.Social decision makin

Social identity theory

According to social identity theory people derive part of their identity—their social identity—from the groups to which they belong (e.g., an identity as “student”, “woman”, “left-hander”, or “Barcelona supporter”). Social identities differ in strength and content. The strength component is conceptualized in terms of social identification (e.g., “I identity strongly with Europeans”), while the content of social identity is determined by the group’s features (e.g., colors associated with a soccer team) and norms (e.g., “real men don’t cry”). Social identity determines emotions (e.g., depression after a team loss) and behavior (e.g., discrimination against out-groups, or effort on behalf of one’s in-group). In this chapter we outline the basic features of social identity theory—from social categorization to coping with a negative social identity—and then discuss two important domains of application: health and organizations. We conclude by describing a social identity based intervention for improving inter-group relations in an educational setting