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

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

Formal institutions, ICSID arbitration and firm performance: evidence from Latin America

This paper analyzes how a country’s formal institutional quality impacts the performance of listed companies across different Latin American countries (namely, Argentina, Brazil, Colombia, Mexico, Peru, and Chile) and industries. Latin America provides a unique setting to address this question due to the region’s high institutional instability. The sample consists of 571 large listed companies, with a total of 8576 observations, for the period 2004–2019. Results show that the quality of a country’s formal institutions is positively related to firm performance, measured through two alternative variables (ROA and Tobin’s Q). Additionally, countries that are signatories of the ICSID agreement provide companies with a more stable environment in which to do business, which ultimately has a positive impact on their performance. However, as the number of cases recorded before the ICSID increases, the relationship turns negative. The paper provides a more comprehensive understanding of formal institutions by considering six alternative governance dimensions. Moreover, international arbitration is found to be a substitute for formal institutions in Latin American countries

Orbital involvement in Pott's puffy tumor: a systematic review of published cases

Pott's puffy tumor (PPT) is a frontal subperiosteal abscess associated with underlying frontal bone osteomyelitis. It represents a well-known source of sinogenic intracranial infection, but the orbital complications related to this entity are rarely reported. The goal of this study was to characterize the orbital involvement in PPT

Cardiotoxicity of anthracycline agents for the treatment of cancer: systematic review and meta-analysis of randomised controlled trials

Background: We conducted a systematic review and meta-analysis to clarify the risk of early and late cardiotoxicity of anthracycline agents in patients treated for breast or ovarian cancer, lymphoma, myeloma or sarcoma.Methods: Randomized controlled trials were sought using comprehensive searches of electronic databases in June 2008. Reference lists of retrieved articles were also scanned for additional articles. Outcomes investigated were early or late clinical and sub-clinical cardiotoxicity. Trial quality was assessed, and data were pooled through meta-analysis where appropriate.Results: Fifty-five published RCTs were included; the majority were on women with advanced breast cancer. A significantly greater risk of clinical cardiotoxicity was found with anthracycline compared with non-anthracycline regimens (OR 5.43 95% confidence interval: 2.34, 12.62), anthracycline versus mitoxantrone (OR 2.88 95% confidence interval: 1.29, 6.44), and bolus versus continuous anthracycline infusions (OR 4.13 95% confidence interval: 1.75, 9.72). Risk of clinical cardiotoxicity was significantly lower with epirubicin versus doxorubicin (OR 0.39 95% confidence interval: 0.20, 0.78), liposomal versus non-liposomal doxorubicin (OR 0.18 95% confidence interval: 0.08, 0.38) and with a concomitant cardioprotective agent (OR 0.21 95% confidence interval: 0.13, 0.33). No statistical heterogeneity was found for these pooled analyses. A similar pattern of results were found for subclinical cardiotoxicity; with risk significantly greater with anthracycline containing regimens and bolus administration; and significantly lower risk with epirubicin, liposomal doxorubicin versus doxorubicin but not epirubicin, and with concomitant use of a cardioprotective agent. Low to moderate statistical heterogeneity was found for two of the five pooled analyses, perhaps due to the different criteria used for reduction in Left Ventricular Ejection Fraction. Meta-analyses of any cardiotoxicity (clinical and subclinical) showed moderate to high statistical heterogeneity for four of five pooled analyses; criteria for any cardiotoxic event differed between studies. Nonetheless the pattern of results was similar to those for clinical or subclinical cardiotoxicity described above.Conclusions: Evidence is not sufficiently robust to support clear evidence-based recommendations on different anthracycline treatment regimens, or for routine use of cardiac protective agents or liposomal formulations. There is a need to improve cardiac monitoring in oncology trials.<br/