1,721,042 research outputs found
A FOX Binding Site is Necessary for the Activation of Pl-Tuba1a Gene in the neurogenic domains
No full textAll echinoderm larvae possess a nervous system consisting of a ciliary band and associated sensory ganglia
(apical, oral and lateral ganglia) that controls swimming and feeding. Neurons of the larval nervous system
first appear as neuroblasts in the thickened ectoderm of the animal plate (anterior neuroectoderm, ANE) at
the late blastula – early gastrula stage and then also in the ciliary band. The neural differentiation process of
sea urchin embryos has been analysed and the Gene Regulatory Network involved in the differentiation
processes is extensively studied. We have previously isolated an alpha tubulin family member of the sea
urchin Paracentrotus lividus (Pl-Tuba1a, formerly known as Pl-Talpha2) that is specifically expressed in the
neurogenic territory of embryo (1). In order to identify cis-regulatory elements controlling its spatiotemporal
expression, we conducted gene transfer experiments, transgene deletions and site specific
mutagenesis. Thus, a genomic region of about 2.6 Kb of Pl-Tuba1a, containing four Interspecifically
Conserved Regions (ICRs), was identified as responsible for proper gene expression. An enhancer role was
ascribed to ICR1 and ICR2, while ICR3 exerted a pivotal role in basal expression, restricting Tuba1a
expression to the neurogenic territory of the embryo. The functional analysis of the ICR3 showed that 10 bp
(corresponding to a putative forkhead box consensus sequence binding site) are necessary for the gene
activation. Additionally, the point mutation of this site in ICR3 prevents Pl-Tuba1a expression
GENE STRUCTURE, DIFFERENTIAL EXPRESSION AND PHYLOGENETIC ANALYSIS OF THE METALLOTHIONEIN GENE FAMILY OF THE SEA URCHIN PARACENTROTUS LIVIDUS
No full textMetallothioneins (MT) are small and cysteine-rich proteins that bind metal ions such as zinc, copper, cadmium, and nickel1. Several functions were proposed for these peptides, ranging from toxic metal protection to physiological metal homeostasis, free radical scavenging, oxidative stress protection, antiapoptotic defense, control of the redox status of the cell and also roles during development. Previously, we reported the identification of five different MT homologues (PlMT4-8) from the Mediterranean sea urchin species P. lividus2. In order to shed some light on MT gene structure and evolution, we cloned seven P. lividus MT genes, comparing them to Echinodermata and Chordata genes3. Moreover, we performed a phylogenetic analysis of newly identified MTs from different classes of echinoderms and from the most ancient chordates, highlighting the relationships between them. Since MTs have multiple roles in the cells, we performed RT-qPCR and in situ hybridization experiments to understand better MT functions in sea urchin embryos. Results showed that the expression of MTs is regulated throughout development in a cell type-specific manner and in response to various metals3. The MT7 transcript is expressed in all tissues, especially in the stomach and in the intestine of the larva, but it is less metal-responsive. In contrast, MT8 is ectodermic and rises only at relatively high metal doses. MT5 and MT6 expression is highly stimulated by metals in the mesenchyme cells. Our results suggest that the P. lividus MT family originated by gene duplications and evolved developmental and environmental sub-functionalization. A preliminary in silico promoter analysis showed interesting similarities and differences among these genes
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
Effects of cadmium exposure on sea urchin development assessed by SSH and RT-qPCR: metallothionein genes and their differential induction
No full textIn order to study the defense strategies activated by Paracentrotus lividus embryos in response to sublethal
doses of CdCl2, we compared the induced transcripts to that of control embryos by suppression subtractive
hybridization technique. We isolated five metallothionein (MT) cDNAs and other genes related to detoxification, to signaling pathway components, to oxidative, reductive and conjugative biotransformation, to RNA maturation and protein synthesis. RT-qPCR analysis revealed that two of the five P. lividus MT (PlMT7 and PlMT8) genes appeared to be constitutively expressed and upregulated following cadmium treatment, whereas the other three genes (PlMT4, PlMT5, PlMT6) are specifically switched-on in response to cadmium treatment. Moreover, we found that this transcriptional induction is concentration dependent and that the cadmium concentration threshold for the gene activation is distinct for every gene. RT-qPCR experiments showed in fact that, among induced genes, PlMT5 gene is activated at a very low cadmium concentration (0.1 lM) whereas PlMT4 and PlMT6 are activated at intermediate doses (1–10 lM). Differently, PlMT7 and PlMT8 genes increase significantly their expression only in embryos treated with the highest dose (100 lM CdCl2). We found also that, in response to a lethal dose of cadmium (1 lM), only PlMT5 and PlMT6 mRNA levels increased further.
These data suggest a hierarchical and orchestrated response of the P. lividus embryo to overcome differential environmental stressors that could interfere with a normal
development
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
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
Caracterization of a 4.6 Kb upstream region necessary for the specific a2 neural tubulin gene expression in P. lividus embryos.
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