1,720,958 research outputs found
An Integrated Analytical Approach for the Characterization of Probiotic Strains in Food Supplements
Full text linkResearch surrounding health benefits from probiotics is becoming popular because of the increasing demand for safer products with protective and therapeutic effects. Proven benefits are species- or genus-specific; however, no certified assays are available for their characterization and quantification at the strain level in the food supplement industry. The objective of this study was to develop a strain-specific Real-time quantitative polymerase chain reaction (RT-qPCR)-based method to be implemented in routine tests for the identification and quantification of Bifidobacterium longum, Bifidobacterium animalis spp. lactis, Lactobacillus paracasei, Lactobacillus rhamnosus, Lactobacillus casei, Bifidobacterium breve, Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus helveticus, starting from a powder mixture of food supplements. The method optimization was carried out in combination with flow cytometry to compare results between the two strategies and implement the analytical workflow with the information also regarding cell viability. These assays were validated in accordance with the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) criteria using the plate count enumeration as the gold standard reference. Briefly, probiotic DNAs were extracted from two powder food supplements. Strain-specific primers targeting unique sequence regions of 16S RNA were identified and amplified by RT-qPCR. Primers were tested for specificity, sensitivity, and efficiency. Both RT-qPCR and flow-cytometry methods described in our work for the quantification and identification of Lactobacillus and Bifidobacterium strains were specific, sensitive, and precise, showing better performances with respect to the morphological colony identification. This work demonstrated that RT-qPCR can be implemented in the quality control workflow of commercial probiotic products giving more standardized and effective results regarding species discrimination
A streamlined workflow for a fast and cost-effective count of tyndallized probiotics using flow cytometry
Full text linkThe use of dead probiotics and their cellular metabolites seems to exhibit immunomodulatory and anti-inflammatory properties, providing protection against pathogens. These inanimate microorganisms, often referred to as tyndallized or heat-killed bacteria, are a new class of probiotics employed in clinical practice. Safety concerns regarding the extensive use of live microbial cells have increased interest in inactivated bacteria, as they could eliminate shelf-life problems and reduce the risks of microbial translocation and infection. Culture-dependent methods are not suitable for the quality assessment of these products, and alternative methods are needed for their quantification. To date, bacterial counting chambers and microscopy have been used for tyndallized bacteria enumeration, but no alternative validated methods are now available for commercial release. The aim of the present study is to design a new method for the qualitative and quantitative determination of tyndallized bacterial cells using flow cytometric technology. Using a live/dead viability assay based on two nucleic acid stains, thiazole orange (TO) and propidium iodide (PI), we optimized a workflow to evaluate bacterial viability beyond the reproduction capacity that provides information about the structural properties and metabolic activities of probiotics on FACSVerse without using beads as a reference. The data obtained in this study represent the first analytical application that works effectively both on viable and non-viable cells. The results provided consistent evidence, and different samples were analyzed using the same staining protocol and acquisition settings. No significant discrepancies were highlighted between the declared specification of commercial strain and the analytical data obtained. For the first time, flow cytometry was used for counting tyndallized bacterial cells as a quality control assessment in probiotic production. This aspect becomes important if applied to medical devices where we cannot boast metabolic but only mechanical activities
Exploring the Adsorption Properties of Zeolite in a New Skin Care Formulation
Full text linkIntroduction: Zeolites are natural or synthetic aluminosilicates, characterized by a regular and microporous crystalline structure that plays a particularly active role in neutralizing free radicals, screening UV rays and in the adsorption of toxins and heavy metals. Skin is one of the main areas for the accumulation of toxic substances released by environmental pollutants. The biological scavenger activity of zeolite opens a wide spectrum of applications in cosmetics and dermatology. Up to now, there is little evidence related to the use of natural zeolite in cosmetics. Aim: The purpose of this work was to evaluate the ability of zeolite to retain heavy metals in a new skin care formulation, in order to provide a proof of principle of its employment in the field of cosmetics. Materials and Methods: Taking the advantages of spiked samples, we studied the in vitro adsorption properties of zeolite in a new skin care formulation. The removal capacities of Cadmium, Lead, Chromium, Nickel and Cobalt were studied, using the inductively coupled plasma optical emission spectrometry (ICP-OES). First of all, the better concentration of zeolite was defined, testing two different proportions of zeolite, from 1% to 3%, keeping all other components constant. Then, on the 3% formulation, the adsorption properties of each single metal were measured. Results and Conclusions: Our preliminary study demonstrated the selectivity of zeolite in retaining Cadmium (p < 0.0001), Nickel (p = 0.026), in a 3% zeolite-based formulation. This work provides a proof of principle of zeolite employment in the field of cosmetics. Based on the data collected, our work provides a scientific proof of principle of zeolite employment in the field of cosmetics. New and extensive research will be needed to explore all the potential benefits of zeolite
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
Friction drag measurements in turbulent wall flows
Full text linkResults of an experimental investigation devoted to the assessment of methodologies aimed at the friction drag measurement in turbulent wall flows are presented. Two techniques for local measurements have been developed. Namely, different versions of the velocity profile method have been used for a turbulent boundary layer developing on a flat plate. The oil flow interferometer has been arranged and results related with measurements performed in a fully developed turbulent channel flow and in the turbulent boundary layer are presented. Moreover a balance based on a floating-buoyancy system finalized to the integral measurement of the friction force acting on the flat plate is presented. The results of the three techniques are compared considering as a reference a well assessed empirical law. Good level of measurement accuracy using the balance has been evidenced highlighting the capability of the balance or the characterization of micro-grooved surfaces addressed for friction drag reduction applications
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
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