1,720,972 research outputs found
Advancing Vibrational Spectroscopy for Cellular and Sub Cellular Analysis: Raman Spectroscopy as a Novel In Vitro Nanotoxicological Assessment Protocol
Get PDFThis work is designed to establish a ‘High content Nanotoxicological Screening method’ using in vitro Raman microspectroscopy. The undeniable increase of nanotechnology based products has brought challenges in terms of determining their toxicological properties. Considering the total time and cost of screening nanomaterials by conventional methods, the need for a rapid, label-free technique which will provide a wide range of information on multiple parameters is unquestionable. This study investigated the applicability of Raman microspectroscopy as a High Content Screening technique to clarify cell-nanoparticle interaction by determining the localisation of the nanoparticles and consequent effects in these localised areas in terms of cyto- and geno- toxicity. For this purpose, in the first part of the study, the potential of Raman spectroscopy has been explored to monitor sequential trafficking of nanoparticles in cellular organelles and to determine the differing spectral signatures of the organelles. Human lung carcinoma cells (A549) were exposed to non-toxic carboxylate-modified and fluorescently-labelled polystyrene nanoparticles for 4, 12 and 24 hours and Raman spectral maps were acquired from the subcellular regions to determine their localisation. With the aid of multivariate analysis techniques, the study demonstrated the applicability of Raman microspectroscopy to provide information regarding localisation and to determine the local environment based on differing signatures of intracellular compartments such as endosomes, lysosomes and endoplasmic reticulum, in a completely label free manner. Aminated polystyrene nanoparticles (PS-NH2) and polyamidoamine (PAMAM) dendrimers are known to show acute toxicity and in order to observe this toxicity and corresponding responses, time and dose dependant Raman spectroscopic markers of
cellular toxic events were systematically monitored upon nanoparticle exposure to A549 cells. Alamar Blue (AB) and 3-(4,5-Dimethylthiazol-2-yl)-2,5diphenyltetrazoliumbromid (MTT) assays were employed to determine the mean effective concentration, EC50 and Raman spectroscopy was used to acquire multiple point spectra from the cytoplasm, nucleus and nucleolus. The most significant changes were observed in the cytoplasm for both time and dose dependent cases. The Raman spectral markers for lipidosis and oxidative stress were determined as a function of dose and time, and the responses were correlated with conventional cytotoxicity assays. With the aid of multivariate analysis techniques, the study showed the ability of Raman spectroscopy to provide information about cellular responses at different particle concentrations and exposure times. Following this, the potential of Raman microspectroscopy was analysed by comparing spectral marker evolution in non-cancerous cells (immortalized human bronchial epithelium) with cancerous cells (A549 and human lung epidermoid). Spectral markers of oxidative stress, cytoplasmic RNA aberrations and liposomal rupture were identified and cell-line dependent variations in these spectral markers were observed, and were correlated with cellular assays and imaging techniques. The findings from the comparison of spectral markers, especially in the low wavenumber region, have shown the applicability of Raman spectroscopy to identify different cell death pathways in cancerous and non-cancerous cell lines. Different cell death mechanisms were also identified based on common and/or differing spectral markers of cyto- and geno- toxicity upon PS-NH2 and PAMAM exposure. The results were correlated with flow cytometry and cytotoxicity assays. The study further demonstrated the potential of Raman microspectroscopy to
iii differentiate apoptotic and necrotic cell death mechanisms, as a function of time (from 4 to 72 h) and applied dose (sub-lethal/lethal). Finally, in order to establish a toxicological assessment protocol based on Raman microspectroscopy, 3D graphs of biomarker intensities are plotted as a function of time and dose and also intensities are correlated with % viability values. The established 3D models can be used to predict nanotoxicity, which can also be applied to nanomedicine
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
In Situ Monitoring of Biofilm Formation by Using Surface-Enhanced Raman Scattering
No full textA biofilm is a complex biochemical structure composed of microorganisms and extracellular polymeric substances used by microorganisms to adhere to each other and to surfaces. The monitoring of molecular changes during biofilm formation in situ can provide valuable insights in medicine, microbiology, and industrial processes. In this study, we investigated the characterization of biofilm produced by two model bacteria by using surface-enhanced Raman scattering (SERS) with the use of core silver (AgNPs)-shell chitosan nanoparticles (c-AgNPs), which are prepared by coating citrate-reduced AgNPs with a thin layer of chitosan averaging 10 nm. The chitosan thin film acts as porous layer and prevents the excess interactions of biological media secreted by bacteria. The two model bacteria, Escherichia colt and Staphylococcus cohnii, gram positive and gram negative, respectively, were chosen for the study. The SERS spectra were acquired directly from the growth culture by simply placing c-AgNPs substrate on the biofilm formed during the growth of the bacteria for in situ monitoring. It was found that c-AgNPs are effective SERS substrates to monitor molecular changes in the biofilm during the biofilm formation
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Surface-Enhanced Raman Scattering for Biofilm Characterization
No full textMicroorganisms are known as the predominant life form on Earth because of their variability and high metabolic activity. Most of the organisms require protection during their growth after their adhesion onto a surface. The protection layers are known as extracellular polymeric substances (EPS), which include organic based materials such as proteins, carbohydrates, lipids, nucleic acids, and humic-like substances. Microorganisms are found in an embedded form in an EPS matrix, and this whole structure is referred to as a biofilm. The identification and characterization of microorganisms and their growth dynamics based on produced metabolites are very important in fields ranging from the accurate and rapid diagnosis of bacterial infections to industrial processes. Surface-enhanced Raman scattering (SERS) is a powerful technique for identification and characterization of biological molecules and biomolecular organizations. In this review, the effort to use SERS for in situ molecular characterization of biofilms is discussed
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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