1,721,018 research outputs found
In vitro quantitative analysis of mesenchymal stromal cells migration towards tumours
No full textAnalysis of in vitro migration of cell populations plays a key role in studying a wide range of dynamic cell behaviours. Cell migration is dependent on a multitude of signals ranging from growth factors to chemokines secreted by injured cells and/or respondent immune cells. In the last decade, several studies were addressed to investigate tropism of Mesenchymal Stromal Cells (MSC) for some types of cancers. Understanding the factors involved in regulating MSC migration towards tumours is essential to ultimately develop novel clinical strategies aiming at using MSC as vehicles to deliver antitumor drugs. However, the mechanism behind MSC migration is still in its infancy, and the main cause is the lack of quantitative methods to analyse the MSC motion.
The analysis of objects motion relies on image-based tracking techniques and several methods have been recently proposed to track cells in vitro. However the vast majority of them are limited to fluorescently labelled cells. Very few tracking tools can analyze images taken using label-free microscopy techniques (e.g. phase contrast), that do not compromise the biological status of the cell and are the most common ways to observe living cells. However, to accurately track irregular-shaped, flat, and poor contrasted cells, such as MSC observed in phase-contrast, is really challenging. Furthermore, the majority of the tracking tools require relevant image processing skills, which strongly limits their practical usefulness within the biologist community. User-friendly and versatile open source software with track editing possibilities would boost live cell analysis research. In this work we introduced CellTracker, a user-friendly open-source software tool for tracking cells, including MSC. CellTracker is freely available at: http://celltracker.website/ and it works with Windows, Macintosh, and UNIX-based systems.
By using CellTracker and μ-Slide Chemotaxis2D (IBIDI, Madison, Wisconsin, USA) we performed experiments to analyse the motility of MSC when seeded near to cancer cells, simply seeding MSC in a chamber communicating to another one containing conditioned medium from MG-63 osteosarcoma cells. As negative and chemotaxis controls, we used respectively fresh culture medium and culture medium supplemented with serum.
From the CellTracker analysis we could not detect any significant change in MSC motility towards the culture medium with or without serum, whereas a different behaviour was observed by using culture conditioned medium taken from flasks previously containing MG-63 cells. We can therefore argue that MSC migration towards tumour cells is mediated by the presence of specific proteins (e.g. chemokines) secreted by cancer cells in the culture medium. These preliminary results pave the way for future applications such as the possibility to develop hybrid disposable diagnostic devices where biological fluids (e.g. blood) sampled from the area of interest are analysed by using the MSC motility as a cancer sensor
A new holistic 3D non-invasive analysis of cellular distribution and motility on fibroinalginate microcarriers using light sheet fluorescent microscopy
Full text linkCell interaction with biomaterials is one of the keystones to developing medical devices for tissue engineering applications. Biomaterials are the scaffolds that give three-dimensional support to the cells, and are vectors that deliver the cells to the injured tissue requiring repair. Features of biomaterials can influence the behaviour of the cells and consequently the efficacy of the tissue-engineered product. The adhesion, distribution and motility of the seeded cells onto the scaffold represent key aspects, and must be evaluated in vitro during the product development, especially when the efficacy of a specific tissue-engineered product depends on viable and functional cell loading. In this work, we propose a non-invasive and non-destructive imaging analysis for investigating motility, viability and distribution of Mesenchymal Stem Cells (MSCs) on silk fibroin-based alginate microcarriers, to test the adhesion capacity of the fibroin coating onto alginate which is known to be unsuitable for cell adhesion. However, in depth characterization of the biomaterial is beyond the scope of this paper. Scaffold-loaded MSCs were stained with Calcein-AM and Ethidium homodimer-1 to detect live and dead cells, respectively, and counterstained with Hoechst to label cell nuclei.
Time-lapse Light Sheet Fluorescent Microscopy (LSFM) was then used to produce three dimensional images of the entire cells-loaded fibroin/alginate microcarriers. In order to quantitatively track the cell motility over time, we also developed an open source user friendly software tool called Fluorescent Cell Tracker in Three-Dimensions (F-Tracker3D). Combining LSFM with F-Tracker3D we were able for the first time to assess the distribution and motility of stem cells in a non-invasive, non-destructive, quantitative, and three-dimensional analysis of the entire surface of the cell-loaded scaffold. We therefore propose this imaging technique as an innovative holistic tool for monitoring cell-biomaterial interactions, and as a tool for the design, fabrication and functionalization of a scaffold as a medical device
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
Notch signaling during development requires the function of awd, the Drosophila homolog of human metastasis suppressor gene Nm23
No full textBackground
The Drosophila abnormal wing discs (awd) belongs to a highly conserved family of genes implicated in metastasis suppression, metabolic homeostasis and epithelial morphogenesis. The cellular function of the mammalian members of this family, the Nm23 proteins, has not yet been clearly defined. Previous awd genetic analyses unraveled its endocytic role that is required for proper internalization of receptors controlling different signaling pathways. In this study, we analyzed the role of Awd in controlling Notch signaling during development.
Results
To study the awd gene function we used genetic mosaic approaches to obtain cells homozygous for a loss of function allele. In awd mutant follicle cells and wing disc cells, Notch accumulates in enlarged early endosomes, resulting in defective Notch signaling. Our results demonstrate that awd function is required before γ-secretase mediated cleavage since over-expression of the constitutively active form of the Notch receptor in awd mutant follicle cells allows rescue of the signaling. By using markers of different endosomal compartments we show that Notch receptor accumulates in early endosomes in awd mutant follicle cells. A trafficking assay in living wing discs also shows that Notch accumulates in early endosomes. Importantly, constitutively active Rab5 cannot rescue the awd phenotype, suggesting that awd is required for Rab5 function in early endosome maturation.
Conclusions
In this report we demonstrate that awd is essential for Notch signaling via its endocytic role. In addition, we identify the endocytic step at which Awd function is required for Notch signaling and we obtain evidence indicating that Awd is necessary for Rab5 function. These findings provide new insights into the developmental and pathophysiological function of this important gene family
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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