1,720,966 research outputs found
Calcium bursts allow rapid reorganization of EFhD2/Swip-1 cross-linked actin networks in epithelial wound closure
No full textChanges in cell morphology require the dynamic remodeling of the actin cytoskeleton. Calcium fluxes have been suggested as an important signal to rapidly relay information to the actin cytoskeleton, but the underlying mechanisms remain poorly understood. Here, we identify the EF-hand domain containing protein EFhD2/Swip-1 as a conserved lamellipodial protein strongly upregulated in Drosophila macrophages at the onset of metamorphosis when macrophage behavior shifts from quiescent to migratory state. Loss- and gain-of-function analysis confirm a critical function of EFhD2/Swip-1 in lamellipodial cell migration in fly and mouse melanoma cells. Contrary to previous assumptions, TIRF-analyses unambiguously demonstrate that EFhD2/Swip-1 proteins efficiently cross-link actin filaments in a calcium-dependent manner. Using a single-cell wounding model, we show that EFhD2/Swip-1 promotes wound closure in a calcium-dependent manner. Mechanistically, our data suggest that transient calcium bursts reduce EFhD2/Swip-1 cross-linking activity and thereby promote rapid reorganization of existing actin networks to drive epithelial wound closure
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
Myc and the Tip60 chromatin remodeling complex control neuroblast maintenance and polarity in Drosophila
No full textreleased at the onset of metamorphosis
No full textABSTRACT Drosophila blood cells called hemocytes form an efficient barrier against infections and tissue damage. During metamorphosis, hemocytes undergo tremendous changes in their shape and behavior, preparing them for tissue clearance. Yet, the diversity and functional plasticity of pupal blood cells have not been explored. Here, we combine single-cell transcriptomics and high-resolution microscopy to dissect the heterogeneity and plasticity of pupal hemocytes. We identified undifferentiated and specified hemocytes with different molecular signatures associated with distinct functions such as antimicrobial, antifungal immune defense, cell adhesion or secretion. Strikingly, we identified a highly migratory and immune-responsive pupal cell population expressing typical markers of the posterior signaling center (PSC), which is known to be an important niche in the larval lymph gland. PSC-like cells become restricted to the abdominal segments and are morphologically very distinct from typical Hemolectin (Hml)-positive plasmatocytes. G-TRACE lineage experiments further suggest that PSC-like cells can transdifferentiate to lamellocytes triggered by parasitoid wasp infestation. In summary, we present the first molecular description of pupal Drosophila blood cells, providing insights into blood cell functional diversification and plasticity during pupal metamorphosis
Characterization of stem cell niche interaction and analysis of non-occluding functions of septate junction components in regulating follicle epithelium development in the Drosophila ovary
No full textEpithelial development relies on coordinated stem cell niche interactions. In this
study I characterize the stem cell niche interaction of escort cells and follicle stem
cells. I found a consistent number of 1 to 4 follicle stem cells per ovariole, with
the stem cell number being synchronized to the germline cell development.
Follicle stem cells and escort cells both exhibit an active and actin dependent
nuclear movement. Additionally, follicle stem cells display a specific lateral
nuclear movement which timely correlates with the rounding of germline cysts.
The inhibition of the actin cytoskeleton dynamics strongly reduces the nuclear
movements of escort cells and follicle stem cells and resulted in a loss of stem
cells and a reduced proliferation of the early follicle cell lineage. Moreover, follicle
stem cells and nearby escort cells exhibit long actin-rich filopodia-like structures,
which potentially fulfill functions in signal transduction.
During epithelial development, cellular junctions are essential components for
tissue integrity. Specifically, occluding junctions like septate junctions fulfill an
important function as paracellular barrier in epithelial tissues. In this study I
identified several non-occluding functions of septate junction components in the
early follicle cell development. Septate junction proteins cell-autonomously
contribute to the stalk formation process by regulating an apical-basal polarity,
cell adhesion and actin cytoskeleton distribution. In addition, I found that septate
junction components regulate signaling pathways in a cell-type specific fashion.
In undifferentiated follicle stem cells and prefollicle cells, septate junction
components regulate Wnt signaling to control proliferation. Further, in polar cells
septate junction components restrict Jak-Stat signaling activity to limit the number
of stalk cells.
Together, this study provides new insights into the mechanisms of epithelial
development by characterizing the stem cell niche interaction of escort cells and
follicle stem cells and by analyzing non-occluding functions of septate junction
components in the Drosophila ovary.Follikelstammzellen stark
und führt zu einem Verlust von Stammzellen und einer verringerten Proliferation
der frühen Follikelzelllinie. Darüber hinaus weisen Follikelstammzellen und nahe
gelegene Nischenzellen lange Aktin-reiche Filopodien-ähnliche Strukturen auf,
die möglicherweise Funktionen bei der Signalübertragung erfüllen.
Während der epithelialen Entwicklung sind Zelladhäsionen wesentliche
Komponenten für die Integrität des Gewebes. Insbesondere verschließende
Adhäsionen wie Septate Junction erfüllen eine wichtige Funktion als
parazelluläre Barriere in Epithelgeweben. In dieser Arbeit habe ich mehrere
Barriere-unabhängige Funktionen von Komponenten der Septate Junctions in
der frühen Follikelzellentwicklung identifiziert. Die Septate Junctions tragen
zellautonom zur Bildung der Stielzellen bei, indem sie apikal-basale Polarität,
Zelladhäsion und die Verteilung des Aktinzytoskeletts regulieren. Darüber hinaus
regulieren die Komponenten der Septate Junctions Signalwege auf
zelltypspezifische Weise. In undifferenzierten Follikelstammzellen und
Präfollikelzellen regulieren die Komponenten der Septate Junctions die Wnt-
Signalübertragung zur Steuerung der Proliferation. In Polarzellen hingegen
schränken Komponenten der Septate Junctions die Jak-Stat-Signalaktivität ein,
um die Anzahl der Stielzellen zu begrenzen.
Insgesamt liefert diese Arbeit neue Einblicke in die Mechanismen der
Epithelentwicklung, indem sie die Interaktion zwischen Nischenzellen und
Follikelstammzellen charakterisiert und die Barriere-unabhängige Funktionen der
Komponenten von Septate Junctions analysiert im Ovar von Drosophila
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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