Plants' responses to novel environmental pressures

Plants have been exposed to multiple environmental stressors on long-term (seasonal) and short-term (daily) basis since their appearance on land. During the last decades, however, plants have been frequently exposed to sudden changes in their environment (imposed by global change) which indeed involves the acclimation/adaptation syndrome of living organisms. The frequency of these unpredictable \u2018stress\u2019 events is expected to increase further in the near future. Such severe, even transient alterations in environmental stimuli (variables) represent new challenges to plants, which do not possess the \u2018flight\u2019 strategy usually displayed by other organisms. Plants have developed, however, a multiplicity of highly integrated adjustments, involving morpho-anatomical, physiological and biochemical traits, to cope with challenges imposed by novel, harsher environments: these constitute the \u2018flight strategy of sessile organisms\u2019. Interestingly, several habitats threatened by the novel stresses are biodiversity hotspots. For example, Mediterranean basin, in which high light growing plants face heat waves coupled with the scarcity of rainfall of increasing frequency and severity, represents just 2% of the earth\u2019s land area, but account for 16% of the world\u2019s plant species. This implies that plants have been and are capable to display a wide range of acclimation/adaptation strategies to cope with most unfavorable environments. Nonetheless, the unpreceded rate at which climate changes may exceed the capacity of plants to acclimate and adapt successfully to the novel environmental pressures, further exacerbated by an increase in anthropogenic pressure. Understanding the mechanisms through which plants respond to new challenges posed by the concurrent effect of different stress agents is crucial, as obvious, to develop strategies of biodiversity conservation and ecosystem functionality. This is exactly the focus of this Research Topic. Review, Opinion as well as Original Research articles are welcome covering basic and applied research on plant functioning under adverse environmental conditions. The frequency of extreme stress events, mostly due to the concurrent effects of different stressors, is increasing particularly in the arid and semi-arid regions, which represent indeed among the most fragile ecosystems worldwide. Papers dealing with the effects of multiple stress agents on plant functioning are, therefore, particularly welcome. We are, however, also interested to receive contributions dissecting response mechanisms (from molecular to organism and whole-plant levels) of plants to a wide range of individual stressors, with a view to a rapidly changing climate, covering plant responses from other regions of the world. These include, but are not limited to drought and heat stress, excess light stress (including UV radiation), cold, ozone and rising CO2 concentration, and their combinations. Theories that predict the plant behavior, acclimation and plant plasticity are also inside the scope of this topi

El arrepentimiento de los alzados en armas y su influencia en el desarrollo de la cultura política de la región San Martin 1993-2016

This research was concluded in 2018 and the objective was to investigate the contrition of the rebels and the effect of this phenomenon on the political culture of the region of San Martin. The study covers the 1993-2016 period, in which a sector of the armed rebels take on the benefits of the repentance law -part of the government's anti-subversive strategy- and a new political culture emerges that includes new forms of political party organization. It is also the period in which Alberto Fujimori’s dictatorship falls, and the process of democratic transition takes place, in which the repentant participate in the political arena by joining new organizations that emerge in this period and they recycle themselves and recycle the political system built by the Fujimori dictatorship and which is based on the 1993 constitution. The research topic is relevant because in the San Martín Region a significant number of those who were members of subversive organizations and participated in the subversive conflict of the 1980s actively participate in politics. Therefore, it is important to know if this participation strengthens the democratic system or rather enhances conservative positions. The data processed are the result of the application of surveys that provide information on the context in which the repentant form their ideology, which leads them to take up armed action, the reasons for their repentance and the way they currently see and participate in politics.La investigación se concluyó en el año 2018 y tuvo como propósito investigar sobre el arrepentimiento de los alzados en armas y el efecto de este fenómeno en la cultura política de la Región San Martín. El estudio comprende el periodo 1993-2016, en el cual se un sector de los alzados en armas se acoge a los beneficios de la ley del arrepentimiento -como parte de la estrategia gubernamental antisubversiva- y surge una nueva cultura política que incluyen nuevas formas de organización político partidaria. También es el periodo en el cual se produce la caída de la dictadura de Alberto Fujimori y el proceso de la transición democrática en el cual los arrepentido van a participar en la vida política vinculados a las nuevas organizaciones que emergen, reciclándose el sistema político construido por la dictadura fujimorista y que se sustenta en la constitución del 93. El tema de investigación es relevante porque, en la Región San Martín, un número significativa de que militaron en organizaciones subversivas y participaron en el conflicto subversivo de la década del 80, participan activamente en política, por lo cual es importante saber si esta participación fortalece el sistema democrático o más bien posiciones conservadoras. Los datos son el resultado de la aplicación de encuestas que arrojan información del contexto en que los arrepentidos forman sus ideologías, que los lleva a asumir la acción armada, las razones de su arrepentimiento y la forma en que ven y participan en política en la actualidad

Serotonin synthesis, release and reuptake in terminals: a mathematical model

<p>Abstract</p> <p>Background</p> <p>Serotonin is a neurotransmitter that has been linked to a wide variety of behaviors including feeding and body-weight regulation, social hierarchies, aggression and suicidality, obsessive compulsive disorder, alcoholism, anxiety, and affective disorders. Full understanding of serotonergic systems in the central nervous system involves genomics, neurochemistry, electrophysiology, and behavior. Though associations have been found between functions at these different levels, in most cases the causal mechanisms are unknown. The scientific issues are daunting but important for human health because of the use of selective serotonin reuptake inhibitors and other pharmacological agents to treat disorders in the serotonergic signaling system.</p> <p>Methods</p> <p>We construct a mathematical model of serotonin synthesis, release, and reuptake in a single serotonergic neuron terminal. The model includes the effects of autoreceptors, the transport of tryptophan into the terminal, and the metabolism of serotonin, as well as the dependence of release on the firing rate. The model is based on real physiology determined experimentally and is compared to experimental data.</p> <p>Results</p> <p>We compare the variations in serotonin and dopamine synthesis due to meals and find that dopamine synthesis is insensitive to the availability of tyrosine but serotonin synthesis is sensitive to the availability of tryptophan. We conduct <it>in silico </it>experiments on the clearance of extracellular serotonin, normally and in the presence of fluoxetine, and compare to experimental data. We study the effects of various polymorphisms in the genes for the serotonin transporter and for tryptophan hydroxylase on synthesis, release, and reuptake. We find that, because of the homeostatic feedback mechanisms of the autoreceptors, the polymorphisms have smaller effects than one expects. We compute the expected steady concentrations of serotonin transporter knockout mice and compare to experimental data. Finally, we study how the properties of the the serotonin transporter and the autoreceptors give rise to the time courses of extracellular serotonin in various projection regions after a dose of fluoxetine.</p> <p>Conclusions</p> <p>Serotonergic systems must respond robustly to important biological signals, while at the same time maintaining homeostasis in the face of normal biological fluctuations in inputs, expression levels, and firing rates. This is accomplished through the cooperative effect of many different homeostatic mechanisms including special properties of the serotonin transporters and the serotonin autoreceptors. Many difficult questions remain in order to fully understand how serotonin biochemistry affects serotonin electrophysiology and vice versa, and how both are changed in the presence of selective serotonin reuptake inhibitors. Mathematical models are useful tools for investigating some of these questions.</p