1,720,958 research outputs found
Cellular localization of GDNF and its GFRalpha1/RET receptor complex in the developing pancreas of cat
Full text linkGlial cell line-derived neurotrophic factor (GDNF) acts through RET receptor tyrosine kinase and its co-receptor
GFRalpha1. In an effort to better understand the possible biological contribution of the GDNF and GFRalpha1/RET
complex in pancreatic development, in this study we report the cellular localization of these proteins in the
pancreas of domestic cat embryos and fetuses by immunocytochemical methods. In early embryos, GDNF, GFRalpha
and RET immunoreactivity (IR) was localized in closely intermingled cells. GDNF and RET immunoreactive cells
displayed chromogranin (an endocrine marker) and PGP 9.5 (a neuronal marker) IR, respectively. GFRalpha IR was
present in both a few GDNF/chromogranin and RET/PGP 9.5 immunoreactive cells. In elderly fetuses, GDNF and
GFRalpha IR were co-localized in glucagon cells and RET IR was detected in few neurons and never co-localized with
GFRalpha or GDNF IR. In early embryos, the presence of GDNF IR in chromogranin immunoreactive cells and
GFRalpha1/RET complex IR in PGP9.5 immunoreactive cells seems to suggest a paracrine action of GDNF contained
in endocrine cell precursors on neuronal cell precursors expressing its receptor complex. The presence in different
cell populations of RET and its co-receptor GFRalpha1 IR could be due to independent signaling of GRFalpha1. Thus,
the co-presence of GDNF and GFRalpha1 in chromogranin and glucagon cells could lead to the hypothesis that
GDNF can act in an autocrinal manner. In fetuses, RET IR was detected only in intrapancreatic ganglia. Because of
the lack of GFRalpha1 IR in pancreatic innervation, RET receptor could be activated by other GFR alphas and ligands
of GDNF family. In conclusion, these findings suggest that in differently aged embryos and fetuses the GDNF signal
is differently mediated by RET and GFRalpha1
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
Distribution of glial cell line-derived neurotrophic factor receptor alpha-1 in the brain of adult zebrafish.
No full textAbstract
Glial cell line-derived neurotrophic factor (GDNF) is a potent trophic factor for several types of neurons in the central and peripheral nervous systems. The biological activity of GDNF is mediated by a multicomponent receptor complex that includes a common transmembrane signaling component (the rearranged during transfection (RET) proto-oncogene product, a tyrosine kinase receptor) as well as a GDNF family receptor alpha (GFRalpha) subunit, a high-affinity glycosyl phosphatidylinositol (GPI)-linked binding element. Among the four known GFRalpha subunits, GFRalpha1 preferentially binds to GDNF. In zebrafish (Danio rerio) embryos, the expression of the GFRalpha1a and GFRalpha1b genes has been shown in primary motor neurons, the kidney, and the enteric nervous system. To examine the activity of GFRalpha in the adult brain of a lower vertebrate, we have investigated the localization of GFRalpha1a and GFRalpha1b mRNA and the GFRalpha1 protein in zebrafish. GFRalpha1a and GFRalpha1b transcripts were observed in brain extracts by reverse transcription-polymerase chain reaction. Whole-mount in-situ hybridization experiments revealed a wide distribution of GFRalpha1a and GFRalpha1b mRNAs in various regions of the adult zebrafish brain. These included the olfactory bulbs, dorsal and ventral telencephalic area (telencephalon), preoptic area, dorsal and ventral thalamus, posterior tuberculum and hypothalamus (diencephalon), optic tectum (mesencephalon), cerebellum, and medulla oblongata (rhombencephalon). Finally, expression patterns of the GFRalpha1 protein, detected immunohistochemically, correlated well with the mRNA expression and provided further insights into translational activity at the neuroanatomical level. In conclusion, the current study demonstrated that the presence of GFRalpha1 persists beyond the embryonic development of the zebrafish brain and, together with the GDNF ligand, is probably implicated in the brain physiology of an adult teleost fish.
PMID: 20572899 [PubMed - indexed for MEDLINE
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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