1,720,959 research outputs found
Calcium and mitochondria: mechanisms and functions of a troubled relationship.
No full textMitochondria promptly respond to Ca2+-mediated cell stimulations with a rapid accumulation of the cation into the matrix. In this article, we review (i) the basic principles of mitochondrial Ca2+ transport, (ii) the physiological/pathological role of mitochondrial Ca2+ uptake, (iii) the regulatory mechanisms that may operate in vivo, and (iv) the new targeted Ca2+ probes that allowed the “rediscovery” of these organelles in calcium signalling
Ca2+ homeostasis of intracellular compartments: measurements using the jellyfish photo-protein aequorin
No full textThe development of molecular biology techniques (which enable the modification and expression of exogenous cDNA in heterologous cell types), has been responsible in recent years for the widespread use of protein probes by cell biologists, for the measurement of biological parameters. To this end, two main types of proteins are used, isolated from a wide variety of luminescent organisms.
The first group consists of chemiluminescent proteins. These are proteins that emit light, often associated to physiological parameters of interest, such as changes in ATP or Ca2+ concentration. Since mammalian cells do not possess endogenous lumiunescent molecules, the use of these proteins is normally associated to an excellent signal-to-noise ratio, as exemplified by aequorin, a photoprotein isolated from Aequorea victoria.
The second group consists of fluorescent proteins. Among these, Aequorea victoria's "Green Fluorescent Protein" (GFP) has attracted much attention, since its expression (or that of fusion products with proteins of interest) generates an intense signal, which enables complex phenomena (such as organelle structure and their dynamic changes, protein targeting, etc) to be followed in real time in living cells.
This review presents some of the results obtained using aequorin for studying intracellular Ca2+ homeostasis
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
Biosensors for the Detection of Calcium and pH
No full textThe wide diffusion of molecular biology techniques, with the possibility of modifying and expressing in virtually all cell types exogenous cDNAs, has been responsible for the large expansion in the use of protein probes in cell biology.
Two groups of reporter proteins are currently employed: the chemiluminescent proteins (e.g. aequorin of Aequorea victoria), and the fluorescent proteins (e.g. green fluorescent protein GFP of Aequorea victoria).
The study of isolated mitochondria, dating back to the 60ties, has provided a wealth of information on the biochemical routes allowing these organelles, deriving from the adaptation of primordial symbionts, to couple oxidation of substrates to the production of ATP. Moreover, recent work highlighted the role of signals reaching the mitochondria in the activation of apoptosis.
In this context, it is an exciting task to study mitochondrial function in living cells. For this purpose, new tools are needed, that combine a specific mitochondrial distribution to the sensitivity to the parameter of interest. Recombinant reporter proteins are emerging as the tools of choice, as targeting sequences can be appended that direct them to the compartment of interest.
In particular, we will describe the development, and use, of protein chimeras (deriving from proteins naturally present in the medusa Aequorea victoria) specifically targeted to the mitochondria, either to the matrix or to the intermembrane space. Aequorin, the pioneer of the targeted recombinant probes, is a Ca2+-sensitive photoprotein, that emits light upon binding of Ca2+ to three high affinity binding sites. Then, we will describe the use of mutants of GFP as Ca2+ and pH probes
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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