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Circuital modelling for electroporation
No full textThe application of intense, short-duration pulsed electric fields to biological membranes induces an increase of their conductivity to external molecules, an effect termed electroporation (EP), which is currently exploited in several biomedical, industrial and environmental applications. The study of interaction mechanisms between pulsed electric fields and biological structures is addressed by experiments and modelling. In the latter case, analytical, circuital, numerical and molecular dynamics approaches have been proposed in the literature, providing complementary information on the EP phenomenon. In this paper, an overview on circuital modelling of EP is presented. In spite of the simplifications adopted from both a physical and electrical point of view, this approach is useful to perform rapid analysis on broad ranges of electrical parameters and provides aid to the optimization of the experimental design
Phytoremediation of Zn: Identify the Diverging Resistance, Uptake and Biomass Production Behaviours of Poplar Clones Under High Zinc Stress
No full textLeaves position in Populus alba Villafranca clone reveals a strategy towards cadmium uptake response
No full textAbstract: The aim of this study was to investigate Cd uptake of Populus alba Villafranca clone applying 0, 0.5 and 1 mg kg−1 soil DW of Cd (Cdc, Cdl and Cdh respectively) for 6 weeks. Cd allocation in the leaves, as a function of their position along the stem, was studied before its toxicity may alter physiological, biochemical and molecular biology of plants. Significant growth stimulation of roots (2.5 and 2.2 times more than control at Cdl and Cdh, respectively) and basal leaves (+79 and +55 % at Cdl and Cdh, respectively) was recorded when Cd was accumulated in a relatively higher concentration compared to other organs. In these experimental conditions, Villafranca clone can be considered a ‘‘root accumulator’’; in fact Translocation factor (Tf) calculated at leaves and stem levels were below 1. Even if Cd distribution among leaves did not change in function of their position, only apical leaves of Villafranca clone didn’t show changes in AsA and GSH concentration after Cd exposure as indication of different mechanism of Cd scavenge ability. A different expression of the genes related to antioxidant machinery such as GST, GPX and cAPX was observed in apical leaves, indicating that a strict regulation of the antioxidant defence system is required by poplar plant under Cd. All these energy consuming mechanisms were not found in more aged median and basal leaves. This could be a strategy adopted by Villafranca clone to avoid Cd effect in apical leaves, allowing plants to continue their growth without damages. Graphical Abstract: [Figure not available: see fulltext.
Comparative epigenomic and transcriptomic analysis of Populus roots under excess Zn
No full textEpigenetic modifications of chromatin structure are extremely important in mediating stress responses in plants. Epigenetic modifications are especially important in perennial species such as trees, where they contribute to phenotypic plasticity and adaptation to unfavourable environments. Populus is a model for physiological studies of trees, and is suitable for phytoremediation of Zn-contaminated soils. Currently, epigenetic modifications involved in Zn stress response are poorly characterized for Populus. Here, we compared changes in epigenetic modifications under excess Zn using chromatin immunoprecipitation sequencing (Chip-Seq) for two histone modifications associated with highly expressed genes (H3K4me3) and repressed genes (H3K27me3) in roots of Populus × canadensis I-214. Chip-Seq data were integrated with RNA-Seq transcript abundance data to examine how epigenetic modifications affect gene expression. These analyses showed that genes with a H3K4me3 modification are generally high-expressed, while genes with a H3K27me3 modification on the 5′-UTR are mainly low-expressed. H3K4me3 modifications in roots under excess Zn condition were enriched in genes involved in carbon (C) catabolism, nitrogen (N) metabolism, and in regulation of sub-cellular vesicular trafficking. These results are consistent with Zn redistribution at a sub-cellular level to buffer Zn-induced nutrient imbalance and osmotic stress in Zn-stressed roots. In contrast H3K27me3 modifications were enriched primarily in genes involved in photosynthetic processes. Together our results provide a useful resource for understanding epigenetic modifications in response to excess Zn in Populus roots, and constitute a starting point for the identification of epigenetic markers and improving phytoremediation potential in this species
ns Pulsed Electric Field-Induced Action Potentials in the Circuital Model of an Axon
No full textPulsed electric fields with duration in the sub- μs and ns time scale (nsPEFs) increase the permeability of cell membranes, enabling the transport of normally impermeant molecules into or out of the cell (electroporation). Such effect is associated to intracellular alterations and indicates nsPEFs as a new stimulus to modulate cell functions. In particular, studies dealing with the application of nsPEFs to excitable cells suggest their use for the stimulation/inhibition of cell excitation. In this paper, the circuital model per surface unit of the plasma membrane of an axon was developed to implement the Hodgkin and Huxley equations, describing the action potential activation process. For the first time, a power electronics circuital simulator was adopted. The model was first validated with conventional microsecond stimuli, and then it was employed to identify the conditions for cell excitation by nsPEFs. The results demonstrated the possibility of electrostimulation by nsPEFs at depolarization levels far below those required for inducing electroporation, and with ionic current dynamics similar to that induced by conventional stimuli, confirming recent experimental findings. Moreover, by using a power electronics tool, easier integration of the cell modeling with the design and optimization of pulse generation systems can be gained
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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