1,721,079 research outputs found
Free magnesium concentration in human brain
No full textThe cytosolic free magnesium concentration can be assessed in vivo in human brain by phosphorus magnetic resonance spectroscopy. This technique has been employed in human brain providing new hints on the Mg2+ homeostasis and on its involvement on the cellular bioenergetics. The free cytosolic [Mg2+] measured in the human brain is about half of that assessed in the human skeletal muscle. This result is likely related to the lower ATP concentration of brain tissue. The possibility to assess the cytosolic [Mg2+] in human brain opened the chance to study the involvement of Mg2+ in different neurological pathologies, and particularly in those where the defective mitochondrial energy production represents the primary causative factor in pathogenesis. The results obtained, studying patients affected by different types of mitochondrial cytopathies, helped to clarify the functional relationship between the energy metabolism and free [Mg2+], providing evidences that the cytosolic [Mg2+] is a function of the energy charge of brain cells and a defective mitochondrial respiration causes a derangement of cytosolic [Mg2+] homeostasis. A reduced cytosolic [Mg2+] has been also found in the occipital lobes of patients with different types of migraine and cluster headache, showing among migraine patients, a trend in keeping with the severity of clinical phenotype. In addition, the assessment by phosphorus magnetic resonance spectroscopy of brain [Mg2+] can help in the differential diagnosis of Multiple System Atrophy and Parkinson's disease, offering a new diagnostic tool that may help to differentiate neurodegenerative diseases sharing common clinical features
Implementation of an iterative approach to optimize synchrotron X-ray fluorescence quantification of light elements in single cell
No full textA new approach for elemental quantification and error estimation in single cells, named Single Cell Elemental Quantification Iterative Approach (SCEQIA), has been performed merging two analytical approaches conceptually different. The first one is a multimodal approach designed to identify and quantify the concentration of light elements in biological samples and to calculate errors following error propagation law. The second one is an iterative algorithm conceived to quantify heavy elements in terms of mass fraction in mineral samples and to evaluate errors using an iterative Monte Carlo-based procedure. The fluorescence data and scanning transmission data, provided by synchrotron X-ray microscopic techniques, together with the volumetric data from Atomic Force Microscopy (AFM) of two colon carcinoma cells have been analyzed following SCEQIA approach. The mass fraction and the molar concentration of the elements C, N, O, Na, and Mg have been mapped. The obtained results have been compared with those previously provided with the original multimodal approach above mentioned. The outputs of the two approaches are comparable in terms of elemental quantification (mass fraction and concentration) for both the analyzed samples. On the contrary, the two approaches differ in error estimation: the newly developed SCEQIA approach results less influenced by the uncertainties of AFM measurements
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
Fluorescence lifetime imaging of intracellular magnesium content in live cells
Full text linkThe first detailed analysis of FLIM applications for Mg cell imaging is presented. We employed the Mg-sensitive fluorescent dye named DCHQ5, a derivative of diaza-18-crown-6 ethers appended with two 8-hydroxyquinoline groups, to perform fluorescence lifetime imaging in control and Mg deprived SaOS-2 live cells, which contain different concentrations of magnesium. We found that the lifetime maps are almost uniform all over the cells and, most relevantly, we showed that the ratio of the amplitude terms is related to the magnesium intracellular concentration
Where is it and how much? Mapping and quantifying elements in single cells
No full textThe biological function of a chemical element in cells not only requires the determination of its intracellular quantity, but also the spatial distribution of its concentration. Different strategies can be employed to quantify and map the intracellular concentration of elements in single cells. The assessment of the intracellular elemental concentration, which is the relevant information, requires the measurement of cell volume. This challenging and demanding task requires combining different techniques allowing gathering of both morphological and compositional information on the same cell. Moreover, the need to analyse samples more similar to their natural state requires complex hardware equipment, and supplementary efforts in preparation protocols. Nevertheless, the response to the question: "where is it and how much?" is worth all these efforts. This review aims at providing an insight into the recent and most advanced techniques and strategies for quantifying and mapping chemical elements in single cells. We describe and discuss indirect detection techniques (label based) which make use of fluorescent dyes, and direct ones (label free), such as particle induced X-ray emission, proton backscattering spectrometry, scanning transmission ion spectrometry, nano-secondary ion mass spectrometry, X-ray fluorescence microscopy, complemented by X-ray imaging
Nutrients and Nutraceuticals from Vitis vinifera L. Pomace: Biological Activities, Valorization, and Potential Applications
Full text linkGrape pomace, also known as wine pomace, is a by-product of winemaking that has traditionally been discarded. However, recent studies have highlighted its rich nutritional and bioactive potential, positioning it as a promising resource for various applications in the functional food, pharmaceutical, and cosmetic sectors. This review explores the nutrient and nutraceutical contents of grape pomace, including its high levels of polyphenols, dietary fiber, vitamins, minerals, and melatonin. The biological activities of grape pomace, such as antioxidant, anti-inflammatory, antimicrobial, and anticancer effects, are also discussed, emphasizing its potential as raw material endowed with multifunctional properties. Additionally, the valorization of grape pomace as a food supplement and for the development of cosmetics is examined, focusing on its incorporation into dietary products and skincare formulations. The growing interest in the sustainable utilization of grape pomace is underscored, highlighting its significant role in promoting human health and contributing to a circular economy
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
Analysis of Intracellular Zn-Hydroxyapatite Nucleation in the Early Stages of Human Osteogenic Differentiation Combining Synchrotron-Based and Diffraction Techniques
Full text linkThe core knowledge about biomineralization is provided by studies on the advanced phases of the process mainly occurring in the extracellular matrix. This PhD project is based on the analysis of the early stages of biomineralization by evaluating the chemical fingerprint of the initial mineral nuclei deposition in the intracellular milieu and their evolution toward hexagonal hydroxyapatite. The study is conducted on human bone mesenchymal stem cells (bMSC) exposed to an osteogenic cocktail for 4 and 10 days, exploiting laboratory X-ray diffraction techniques and cutting-edge developments of synchrotron based 2D and 3D cryo X-ray microscopy. The synchrotron-based phase contrast imaging revealed few small intracellular depositions @4th day of differentiation and a lot of extracellular and intracellular mineral nuclei @10th day. The 3D reconstructions of phase-contrast images of bMSC at 10 days allowed browsing the entire cell along its thickness to explore the three-dimensional localization of the mineral depositions. Several spots are localized in the cytoplasm of the cell, indicating that the biomineralization starts in the intracellular environment. Synchrotron X-ray Fluorescence Microscopy was carried out to determine the chemical composition of mineral nuclei formation at nanoscale, confirming that mineral accumulation starts early during the osteogenic differentiation of bMSC and providing experimental evidence about the Zn role in HA nucleation. The X-ray fluorescence tomography was performed to obtain the 3D visualization of Ca, P and Zn elemental distribution.
Wide/Small Angle X-ray Scattering and X-ray Absorption Near-Edge Spectroscopy revealed the hexagonal HA as the unique crystalline structure present in differentiating bMSC.
In conclusion, thanks to the combination of 3D high-resolution synchrotron-based X-ray techniques, it has been demonstrated that biomineralization starts with hydroxyapatite nucleation in the intracellular environment, rapidly evolving toward a hexagonal hydroxyapatite crystal very similar to the one present in human bone as detected after just ten days of osteogenic induction
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