1,721,077 research outputs found
A Genomic Approach to the Shade Avoidance Response in Arabidopsis
No full textEssendo organismi sessili, le piante hanno evoluto strategie molto sofisticate per la percezione dell’ambiente che le circonda nel loro habitat naturale, allo scopo di adattarvisi con il massimo profitto per la loro sopravvivenza e riproduzione. Le piante ottengono la loro energia dalla radiazione luminosa mediante il processo fotosintetico, e sono quindi particolarmente sensibili alla qualità e quantità della luce che le circonda, percependo in particolar modo la presenza della vegetazione circostante come un segnale di competizione per l’approvvigionamento luminoso. Infatti, crescendo in condizioni di ombreggiatura le piante percepiscono una luce filtrata nella sua componente più fotosinteticamente attiva, caratterizzata da una riduzione nel rapporto tra la radiazione nel rosso (R) e nel rosso lontano (FR) (basso R/FR), a cui reagiscono molto rapidamente aumentando la crescita in allungamento degli organi di sostegno della parte aerea (ipocotile, piccioli) a spese dello sviluppo di foglie e radici (risposta di “fuga dall’ombra”). Se la pianta ha successo nel suo tentativo di crescere al di sopra della vegetazione che la circonda, questa risposta va incontro ad una rapida reversione. D’altra parte, se il segnale persiste la pianta attenua la risposta attraverso l’azione del fattore di trascrizione bHLH HFR1/SICS1. In questo lavoro sono stati integrati studi globali di espressione genica mediante microarray ed analisi genetiche allo scopo di individuare molecole regolative implicate nel controllo della risposta di fuga dall’ombra. I nostri risultati hanno evidenziato che un numero significativo di regolatori trascrizionali sono rapidamente e transientemente indotti dalla luce con basso R/FR (fattori di trascrizione bHLH e HD-Zip). Le analisi condotte hanno anche messo in evidenza un nuovo meccanismo di controllo negativo della risposta di fuga dall’ombra che sembra agire attraverso il fattore di trascrizione bZip HY5. Analisi filogenetiche su alcuni dei regolatori trascrizionali della risposta di fuga dall’ombra (bHLH e HD-Zip II) ci hanno condotto alla loro classificazione in diverse sottofamiglie, caratterizzate da proteine con differenti capacità di legame al DNA e profili di espressione. I nostri risultati hanno identificato diversi cladi contenenti un piccolo numero di molecole molto simili tra loro regolate dalla qualità della luce ambientale. Ulteriori analisi saranno condotte per approfondire il ruolo di questi fattori e identificare i loro target molecolari durante la risposta di fuga dall’ombra
The emerging role of MicroRNA in schizophrenia
No full textMicroRNAs (miRNAs) are ~22 nucleotide non-coding RNAs that control gene expression post-transcriptionally by base pairing to mRNAs. MiRNAs are predicted to target ~50% of all protein-coding genes and functional studies indicate that they participate in the regulation of almost every cellular process. They also play a key role in pathogenetic mechanisms underlying several diseases, e.g. cancer, cardiovascular diseases, autoimmune diseases, and neurodegenerative diseases. Several miRNAs are expressed in the human brain where they contribute to equilibrium between maintenance and differentiation of neural stem cells. MiRNAs specific mechanisms of action and their roles in brain development and synaptic plasticity resulted in a great interest in the analysis of their potential role in the pathogenesis and pathophysiology of neuropsychiatric disorders. Currently, schizophrenia is one of the fields in psychiatry where miRNAs have been most widely investigated. The understanding of miRNAs role in schizophrenia has been achieved through association, functional and expression profiling studies on post mortem brain and peripheral tissues. Several studies identified association between neuropsychiatric disorders and variants in miRNAs including variations in miRNA/primary-/precursor-miRNAs sequences, in miRNAs biogenesis machinery genes, in the 3'UTR of target genes and in miRNAs expression. In summary, there is growing evidence that miRNAs exert a crucial role in gene expression regulation in the central nervous system and are altered in the development, presentation and response to treatment of psychiatric disorders. In this review we summarize the most significant results of experimental studies aimed at highlighting the involvement of human miRNAs in schizophrenia
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
Plant adaptation to dynamically changing environment: the shade avoidance response.
No full textThe success of competitive interactions between plants determines the chance of survival of individuals and eventually of whole plant species. Shade-tolerant plants have adapted their photosynthesis to function optimally under low-light conditions. These plants are therefore capable of long-term survival under a canopy shade. In contrast, shade-avoiding plants adapt their growth to perceive maximum sunlight and therefore rapidly dominate gaps in a canopy. Daylight contains roughly equal proportions of red and far-red light, but within vegetation that ratio is lowered as a result of red absorption by photosynthetic pigments. This light quality change is perceived through the phytochrome system as an unambiguous signal of the proximity of neighbors resulting in a suite of developmental responses (termed the shade avoidance response) that, when successful, result in the overgrowth of those neighbors. Shoot elongation induced by low red/far-red light may confer high relative fitness in natural dense communities. However, since elongation is often achieved at the expense of leaf and root growth, shade avoidance may lead to reduction in crop plant productivity. Over the past decade, major progresses have been achieved in the understanding of the molecular basis of shade avoidance. However, uncovering the mechanisms underpinning plant response and adaptation to changes in the ratio of red to far-red light is key to design new strategies to precise modulate shade avoidance in time and space without impairing the overall crop ability to compete for light
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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