1,720,960 research outputs found
Muscle growth in response to changing demands in the teleost Sparus aurata (L) during development from hatching to juvenile.
No full textGrowth of laterarl muscle in the teleost fish
Sparus aurata (L.) was examined from hatching to juvenile
by a basic morphofunctional approach that takes into
account structural and ecophysiological aspects and
combines in vivo observations and LM and TEM microscopic
analysis. As shown in most teleost fishes, muscle
growth proceeds by a double mechanism of hyperplasia
and hypertrophy that contribute differentially to the overall
development of the lateral muscle, giving rise in each
myomere to a typical pattern of structurally and functionally
different fibre types (slow-red and fast-white fibres,
plus pink intermediate fibres) in a nerve-dependent
process. During larval life the muscle growth takes place
mainly due to hyperplastic growth at the level of specific
proliferative zones of the myomeres, from which slow,
pink and white muscle fibres are derived. In those species
that reach a large adult size a new typical hyperplastic
process disseminated throughout the fast white muscle
layer takes place during post-larval life. In contrast,
hypertrophic growth occurs in all stages, but is the dominant
mechanism of muscle growth only in juvenile and
adult. The suitable recruitment of the different fibre
types enables the fish to optimize its performances according
to specific functional and metabolic requirements
related to the swimming behaviour and hydrodynamic
regimes. The different mechanisms of growth are
here analysed in their detailed structural and ultrastructural
aspects in order to interpret their adaptive significance
in the light of the fish life cycle, with particular
reference to locomotion and feeding behaviou
Cellular and molecular mechanisms of arm regeneration in Crinoid Echinoderms.
No full textCrinoid echinoderms can provide a valuable
experimental model for studying all aspects of regenerative
processes from molecular to macroscopic level. Recently
we carried out a detailed study into the overall
process of arm regeneration in the crinoid Antedon mediterranea
and provided an interpretation of its basic
mechanisms. However, the problem of the subsequent
fate of the amputated arm segment (explant) once isolated
from the animal body and of its possible regenerative
potential have never been investigated before. The arm
explant in fact represents a simplified and controlled regenerating
system which may be very useful in regeneration
experiments by providing a valuable test of our hypotheses
in terms of mechanisms and processes. In the
present study we carried out a comprehensive analysis of
double-amputated arm explants (i.e. explants reamputated
at their distal end immediately after the first proximal
amputation) subjected to the same experimental conditions
as the regenerating donor animals. Our results
showed that the explants undergo similar regenerative
processes but with some significant differences to those
mechanisms described for normal regenerating arms. For
example, whilst the proximal-distal axis of arm growth is
maintained, there are differences in terms of the recruitment
of cells which contribute to the regenerating tissue.
As with normal regenerating arms, the present work focuses
on (1) timing and modality of regeneration in the
explant; (2) proliferation, migration and contribution of
undifferentiated and/or dedifferentiated/transdifferentiated
cells; (3) putative role of neural growth factors. These
problems were addressed by employing a combination of
conventional microscopy and immunocytochemistry.
Comparison between arm explants and regenerating
arms of normal donor adults indicates an extraordinary
potential and regenerative autonomy of crinoid tissues
and the cellular plasticity of the phenomenon.
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
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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