1,720,955 research outputs found
Developmental expression of protein kinase C immunoreactivity in rod bipolar cells of the rabbit retina
No full textRod bipolar cells constitute the second-order neuron in the rod pathway. Previous investigations of the rabbit retina have evaluated the development of other components of the rod pathway, namely the dopaminergic and AII amacrine cell populations. To gain further insights into the maturation of this retinal circuitry, we studied the development of rod bipolar cells, identified with antibodies directed to the alpha isoform of protein kinase C (PKC), in the rabbit retina. Lightly immunostained PKC-immunoreactive (IR) somata are first observed at postnatal day (PND) 6 in the distal inner nuclear layer (INI.). Immunostaining is also observed in the outer plexiform layer (OPL), indicating the presence of PKC-IR dendrites. PKC-IR axons are present in the INL oriented toward the inner plexiform layer (IPL). Several of them terminate with enlarged structures resembling growth cones. At PND 8, some immunostained terminal bulbs, characteristic of rod bipolar cells, are detected in the proximal IPL. PKC-IR cells at PND 11 (cye opening) display stronger immunostaining and more mature characteristics than at earlier ages. The dendritic arborizations of these cells in the OPL and their axon terminals in the IPL attain mature morphology at later ages (PND 30 or older). The density of PKC-IR cells shows a peak at PND 11 followed by a drastic decrease up to adulthood. The total number of PKC-IR cells increases from PND 6 to PND 11 and then it remains almost unchanged until adulthood. The mosaic of PKC-IR cells is nonrandom in some retinal locations at PND 6, but the overall regularity index at PND 6 is lower than at older ages. The present data provide a comprehensive evaluation of the development of rod bipolar cells in the postnatal rabbit retina and are consistent with those previously reported for dopaminergic and AII amacrine cell populations, indicating that different components of the rod pathway follow a similar pattern of maturation, presumably allowing the rod pathway to be functional at eye opening
Postnatal development of parvalbumin-immunoreactive amacrine cells in the rabbit retina
No full textIn the adult rabbit, rat and cat retina, parvalbumin PV. immunoreactivity is primarily localized to a population of narrow-field, bistratified amacrine cells, the AII amacrine cells–major interneurons of the rod pathway. This investigation examines the postnatal
development of PV immunoreactivity in order to better understand the ontogeny of the AII amacrine cell population and the formation of the rod pathway. Rabbit retinas at various postnatal ages were processed for immunohistochemistry using a monoclonal antibody directed
to PV and analyzed morphometrically. On the day of birth, PV immunoreactive cell bodies are numerous in the proximal inner nuclear
layer INL. in all retinal regions. These cells have a primary process directed towards the inner plexiform layer IPL.. At postnatal day PND. 2, a few faint immunoreactive processes are observed in the IPL. At PND 4, well-stained processes are observed to ramify mainly in the proximal IPL. At PND 6, strongly immunoreactive processes are present in both the distal and proximal IPL, and at PND 10 they
form a continuous, dense plexus in both levels of the IPL. By PND 10, the morphology of PV immunoreactive cells is similar to PV immunoreactive cells in adult retinas. The density of PV immunoreactive cells in the proximal INL increases from PND 2 to PND 5, then it gradually decreases to adult values, while the total number of PV immunoreactive cell bodies increases until PND 10. PV
immunoreactive amacrine cells at PND 2, as in the adult, are nonrandomly distributed across the retinal surface. These studies show that
PV immunoreactive amacrine cells have a developmental profile that is similar to several other amacrine cell types. This includes the elaboration of processes in the IPL during the first postnatal week and a mature appearance towards the end of the second week of life,
about the time of eye opening. These observations indicate that the AII amacrine cell may participate in the processing of visual information at eye opening
Morphologic maturation of tachykinin peptide-expressing cells in the postnatal rabbit retina
No full textTachykinin TK. peptides, which include substance P, neurokinin A, two neurokinin A-related peptides and neurokinin B, are widely
present in the nervous system, including the retina, where they act as neurotransmittersrmodulators as well as growth factors. In the
present study, we investigated the maturation of TK-immunoreactive IR. cells in the rabbit retina with the aim of further contributing to
the knowledge of the development of transmitter-identified retinal cell populations. In the adult retina, the pattern of TK immunostaining
is consistent with the presence of TK peptides in amacrine, displaced amacrine, interplexiform and ganglion cells. In the newborn retina,
intensely immunostained TK-IR somata are located in the ganglion cell layer GCL. and in the inner nuclear layer INL. adjacent to the
inner plexiform layer IPL.. They are characterized by an oval-shaped cell body originating a single process without ramifications. TK-IR
processes are occasionally observed in the IPL and in the outer plexiform layer OPL.. Long TK-IR fiber bundles are observed in the
ganglion cell axon layer. TK-IR profiles resembling small somata are rarely observed in the INL adjacent to the OPL. At postnatal day
PND. 2, some TK-IR cells display more complex morphologic features, including processes with secondary ramifications. Long TK-IR
processes in the IPL are often seen to terminate with growth cones. Between PND 6 and PND 11 eye opening., there is a dramatic
increase in the number of immunolabeled processes with growth cones both in the IPL and in the OPL and the mature lamination of
TK-IR fibers in laminae 1, 3 and 5 of the IPL is established. TK-IR cells attain mature morphological characteristics and the rare, putative
TK-IR somata in the distal INL are no longer observed. After eye opening, growth cones are not present and the pattern typical of the
adult is reached. These observations indicate that the development of TK-IR cells can be divided into an early phase from birth to PND
6. in which these cells establish their morphological characteristics, and a later phase from PND 6 to eye opening. in which they are
involved in active growth of their processes and likely in synapse formation. Since TK peptides are thought to play neurotrophic actions
in the developing nervous system and they are consistently present in the retina throughout postnatal development, they may also act as
growth factors during retinal maturation
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
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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