1,720,984 research outputs found
Image Descriptors of Transformed Foci in BALB/c 3T3 Cell transformation Assay: a Statistical Analysis
No full textThe prediction of the carcinogenic potential for humans still relies, at regulatory level, on life-time bioassays in rodents, extremely costly in terms of time, animal used and trained personnel hours. Among the proposed alternatives to the animal bioassay for human carcinogenicity prediction, the in vitro cell transformation assays (CTAs) have shown to model important stages of in vivo carcinogenesis and have the potential to predict carcinogenicity in humans. The endpoint of the CTA is focus formation (colony of transformed cells), and requires classification under light microscopy based on morphology.
Thus current limitations for the wide adoption of the assay partially depend on a fair degree of subjectivity in foci scoring.
Following the suggestion by EURL ECVAM (ECVAM, 2012), the aim of this study was to develop statistical descriptors which represent eye-scored morphological features adopted to classify transformed foci of BALB/c 3T3 CTA in a quantitative way through digital image processing
Objective scoring of transformed foci in BALB/c 3T3 cell transformation assay by statistical image descriptors
No full textIn vitro cell transformation assays (CTAs) have been shown to model important stages of in vivo carcinogenesis and have the potential to predict carcinogenicity in humans.
Advantages of CTAs are their ability of revealing both genotoxic and non-genotoxic carcinogens while reducing both experimental costs and the number of animals used. The endpoint of the CTA is foci formation, and requires classification under light microscopy based on morphology. Thus current limitations for the wide adoption of the assay partially depend on a fair degree of subjectivity in foci scoring. An objective evaluation may be obtained after separating foci from background monolayer in the digital image, and quantifying values of statistical descriptors which are selected to capture eye-scored morphological features. The aim of this study was to develop statistical descriptors to be applied to transformed foci of BALB/c 3T3, which cover foci size, multilayering and invasive cell growth into the background monolayer. Proposed descriptors were applied to a database of 407 foci images to explore the numerical features, and to illustrate open problems and potential solutions
Image analysis and automatic classification of transformed foci
No full textCarcinogenesis is a multi-step process involving genetic
alterations and non-genotoxic mechanisms. The in vitro cell
transformation assay allows the monitoring of the neoplastic
phenotype by foci formation in suitable cells (e.g. C3H10T1/2
mouse embryo fibroblasts) showing aberrant morphology of
massive build-up, polar and multi-layered densely stained
cells. The classification of transformed foci in C3H cells relies
on light microscopy scoring by a trained human expert
based on standard rules. This procedure is time-consuming
and prone, in some cases, to subjectivity, thereby leading
to possible over- or under-estimation of the carcinogenic
potential of tested compounds. Herewith we describe the in
vitro neoplastic transformation induced by B[a]P and CdCl 2 ,
and the development of a foci classifier based on image analysis
and statistical classification. The image analysis system,
which relies on ‘spectrum enhancement’, is quantitative
and extracts descriptors of foci texture and structure. The
statistical classification method is based on the Random Forest
algorithm. We obtained a classifier trained by using expert’s
supervision with a 20% classification error. The proposed
method could serve as a basis to automate the in vitro cell
transformation assay
Image classifiers for the cell transformation assay: a progress report
No full textThe human carcinogenicity evaluation of chemicals has a great impact on public health. In vitro methods, such as the cell transformation assay (CTA), allow for a fast and reliable assessment of the carcinogenic potential of a chemical compound in comparison with the standard two-year bioassay. The scoring and classification of foci in selected cell lines is performed, after staining, by light microscopy. Foci can be separated into three classes: type I, which are scored as non-transformed, and types II and III that are considered to include fully transformed foci. However, in a number of cases, even an expert is uncertain about the attribution of a focus to a given class, due to its mixed or intermediate nature. Here, we suggest a simple approach to classifying mixed or intermediate foci by exploiting the quantitative information available from images, which is captured by statistical descriptors. A quantitative index is proposed, to describe the degree of dissimilarity of mixed and intermediate images to the three well-distinguished classes
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
Image analysis applied to Cell Transformation Assay to advance carcinogenicity testing : morphology evaluation of transformed foci and mitochondria
No full textDigital image analysis has demonstrated to be a very promising tool to promote toxicity testing and advancements in the comprehension of olecular mechanisms underlying toxicity outcomes. Cell and tissue imaging allow quantitative detection and measurement of cellular structures and components including organelles, and is supported by microscopes, digitized cameras, and image analysis algorithms (Xu, 2015). We developed methods of image analysis to improve carcinogenicity testing, as the phenotype can be informative of many underlying mechanisms and pathways of in vitro transformation. We foster the adoption of an integrated approach, where functional assays can be coupled with morphology studies in order to understand mechanisms of toxicity. Our work supports the idea that form follows function
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