1,720,964 research outputs found
Berberine exposure triggers developmental effects on planarian regeneration
No full textThe mechanisms of action underlying the pharmacological properties of the natural alkaloid berberine still
need investigation. Planarian regeneration is instrumental in deciphering developmental responses
following drug exposure. Here we report the effects of berberine on regeneration in the planarian Dugesia
japonica. Our findings demonstrate that this compound perturbs the regenerative pattern. By real-time
PCR screening for the effects of berberine exposure on gene expression, we identified alterations in the
transcriptional profile of genes representative of different tissues, as well as of genes involved in extracellular
matrix (ECM) remodeling. Although berberine does not influence cell proliferation/apoptosis, our
experiments prove that this compound causes abnormal regeneration of the planarian visual system.
Potential berberine-induced cytotoxic effects were noticed in the intestine. Although we were unable to
detect abnormalities in other structures, our findings, sustained by RNAi-based investigations, support the
possibility that berberine effects are critically linked to anomalous ECM remodeling in treated planarians
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
A cellular and molecular study of the effects of chelidonine and berberine alkaloids on planarian regeneration
No full textIn vivo effects of natural compounds present in Chelidonium majus on stem cells using a simple animal model
No full textPlanarians are a well-known model for regeneration and provide an excellent system to study the
behavior of stem cells in vivo. Despite the potential attractiveness of planarians these organisms
have not been used yet in large-scale chemical screenings to see the effects of compounds on
different key aspects of regeneration as, for instance, stem cell proliferation and differentiation.
Our work focuses on the analysis of the effects produced by the main alkaloids (chelidonine,
berberine, sanguinarine, chelerytrine, protopine and coptisine) present in Chelidonium majus
(Papaveraceae), an herb showing interesting therapeutical properties. We demonstrate that
chelidonine produces a significant anti-proliferative effect on planarian stem cells, supporting the
possibility that this alkaloid acts on cell cycle progression by inhibition of tubulin polymerization.
Berberine treatment perturbs the regenerative pattern. Although berberine does not influence
cell proliferation/apoptosis, this compound causes abnormal regeneration of the planarian
visual system. Our findings, sustained by RNAi-based investigations, support the possibility that
berberine effects are critically linked to anomalous extracellular matrix remodeling. Abnormal
head regeneration has also been observed following sanguinarine treatment. Preliminary results
provide evidence that sanguinarine induces apoptosis through a caspase-dependent mechanism,
but does not influence cell proliferation. The study presented here might become a good test to
determine the potentiality of planarians as a model to analyze drug effects. At the same time,
such screenings and experiments could help to better understand the process of planarian
regeneration itself by providing novel information about how proliferation, differentiation and/or
morphogenesis and patterning are regulated during this amazing process
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
La planaria come sistema modello per valutare in vivo il ruolo dei geni codificanti metalloproteasi di matrice durante l’omeostasi e la rigenerazione
No full textEffects of natural compounds present in Chelidonium majus on stem cells and embryo development
No full textDespite their potential attractiveness as model for regeneration, planarians have not been used yet in large-scale chemical screenings to test the effects of compounds on different key aspects of regeneration, such as stem cell proliferation and differentiation. Our work focuses on the analysis of the effects produced by the main alkaloids (chelidonine, berberine, sanguinarine) present in Chelidonium majus, an herb with therapeutical properties. The data obtained so far indicate that chelidonine generates anti-proliferative effects on planarian stem cells, possibly due to inhibition of tubulin polymerization, berberine induces a perturbation of the regenerative pattern and sanguinarine produces abnormal head regeneration. In particular, we find that berberine causes abnormal regeneration of the visual system, without affecting cell proliferation/apoptosis, while sanguinarine induces apoptosis through a caspase dependent mechanism. These results clearly indicate the potentiality of planarians as a model to analyze drug effects. We are currently exploiting the well-established zebrafish model to assess and compare the effects of the same compounds during vertebrate embryo development
A planarian kuzbanian-like gene is a key regulator during regeneration of the nervous system
No full textKuzbanian is a crucial member of the ADAM family of metalloproteinases. Kuzbanian-mediated
cleavage of Notch represents in fact one of the fundamental steps leading to activation of the
Notch pathway during early neurogenesis. This enzyme also plays important roles in later stages
of neural development, modulating axon guidance and extension. Planarians are a model system
well known for regenerative potential. These characteristics depend on a population of adult stem
cells that guarantees replacement of all differentiated cell types, including nerve cells. Here we
report the functional characterization of a planarian Kuzbanian-like gene (Smed-kuzbanian3).
Smed-kuzbanian3 is expressed in the mesenchyme and in the central nervous system (CNS) and
is overexpressed during regeneration of this structure. Functional ablation of Smed-kuzbanian3
by RNAi causes abnormal CNS regeneration. Anomalous eye morphogenesis, including atypical
axonal projections of the optic chiasm, is observed. The architecture of the regenerating cephalic
ganglia also appears unusual, with an aberrant number and distribution of nerve cells. We
speculate that Smed-Kuzbanian3, similarly to that observed in other organisms, plays different
roles during CNS regeneration. To test whether Smed-kuzbanian3 plays a conserved role during
neurogenesis we plan to use Xenopus laevis embryos as a model system. Gain of function
experiments will allow us to demonstrate the involvement of Smed-kuzbanian3 in modulating
early Notch-mediated lateral inhibition mechanisms and the guidance of axonal extensions at
later developmental stages
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