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Localizzazione immunochimica di regioni ricche in 5-metilcitosina su cromosomi politenici del sospensore di Phaseolus coccineus in differenti stadi dell'embriogenesi.
No full text
Immunogold localization of 5-methylcytosine rich regions and RNA synthesis in polytene chromosomes of Phaseolus coccineus L. embryo suspensor at two stages of embryogenesis.
No full textDevelopmental stages and gibberellin activity in ovules of abscission-affected fruits of Malus domestica Borkh
No full textArsenic-induced morphogenic response in roots of arsenic hyperaccumulator fern Pteris vittata.
No full textOn the assumption that arsenic induces stress morphogenetic responses involved in As tolerance and hyperaccumulation in the Pteris vittata fern, we analyzed the root system of young sporophytes grown in 250, 334, and 500 M As for five days and for 14 days. Anatomical and histological analyses were performed in plants grown for five days to evaluate the number, position, length and differentiation pattern of root hairs. AgNOR staining, employed to study nucleolus behavior in root apices, showed that arsenic influences nucleolar activity (evaluated by nucleolus size, number and absorbance) in the root meristem. In plants treated with 250 and 334 M As an acropetal shift of root hair development and an increase in hair length and density were observed, linked to an ectopic pattern of differentiation. The opposite trend was recorded in plants treated with 500 M As. It is worth noting the presence of living border-like cells, not yet observed in ferns, and their increase following As treatments. Analysis and vitality of border-like cells were surveyed after 14 days of treatments. In conclusion As treatments elicited a stress-induced morphogenic response which, by modifying the differentiation pattern, number and length of root hairs, modulating nucleolar activity and interacting with the rhizosphere by inducing border-like cell production, may adjust the rate of root uptake and its metabolic activity
RNA-SYNTHESIS IN THE EMBRYO SUSPENSOR OF PHASEOLUS-COCCINEUS AT 2 STAGES OF EMBRYOGENESIS, AND THE EFFECT OF SUPPLIED GIBBERELLIC-ACID
No full textRNA synthesis in giant cells containing polytene chromosomes in the embryo suspensor of Phaseolus coccineus was analyzed by autoradiography after [ 3H]-uridine treatment. Embryos at the heart-shaped stage of development and at a cotyledonary stage were studied. Discontinuous labelling of the polytene chromosomes was always observed. The chromosomes were subdivided into segments (chromosome regions) which behaved as functional units, since discontinuous labelling was never seen within any of the regions. It was found that most chromosome regions were engaged in RNA synthesis to different degrees at the two embryo developmental stages. Regions showing identical labelling patterns tended to lie close together in the chromosome arms and to keep their functional activity coordinated at both stages of embryo development. The chromosome regions bearing 18 S+25 S ribosomal genes were never simultaneously active in RNA synthesis and different regions were preferentially transcribed at each stage of embryo development. However, at both stages, all the chromosome regions bearing 5 S ribosomal genes showed comparable labelling frequencies. The effect on transcription of gibberellic acid (GA 3) treatments was also studied. At both embryo developmental stages, GA 3 enhanced the rate of RNA synthesis in the polytene suspensor cells. The frequency with which certain chromosome regions were transcribed was also increased significantly (P≤0.001) and this stimulatory effect was greater in embryos at the cotyledonary stage than in heart-shaped embryos. At the latter developmental stage, RNA synthesis was repressed by GA 3 in a few chromosome regions. These results are discussed briefly in relation to previous findings using different methods of studying the organization of polytene chromosomes and the functional activity of the embryo suspensor of Phaseolus coccineus
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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