1,720,992 research outputs found
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
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
Endoplasmic reticulum stress signalling in myelination
No full textDemyelinating conditions such as multiple sclerosis have a continued unmet need for remyelinating therapies. Myelin is a multi-lamellar membrane structure made by oligodendrocyte progenitor cells (OPCs) that is critical for saltatory conduction and neuronal health. The simultaneous ensheathment of multiple axons with myelin confers a radically increased load on the endoplasmic reticulum (ER) from which membrane proteins and lipids are made. ER stress signalling triggers a conserved, homeostatic signalling system known as the Unfolded Protein Response (UPR) which can increase ER capacity or initiate apoptosis according to stress severity. Despite recognition of the substantial synthetic demands placed on oligodendrocytes, the role of ER stress signalling and the UPR has not previously been fully investigated. In this work, cerebellar tracts were used to exemplify the temporal dynamics of myelination. The cerebellum is an eloquent anatomical region of high clinical relevance to MS and a widely-used model of myelination, however the majority of studies do not take into account the well-established heterogeneity of its parasagittal domains. Therefore this work has combined a comprehensive profile of ER stress and UPR-associated markers with respect to the developing and adult cerebellum in the cortex as well as in white matter tracts. It then investigated the function of these pathways during oligodendrocyte differentiation in vitro. UPR signalling was found to be unaltered between parasagittal domains of the cerebellum, suggesting it is not an intrinsic factor in patterned neurodegeneration as previously indicated. Distinct UPR profiles were associated with specific cell-types during development and highlighted transient, proliferative subpopulations in germinal niches of the cerebellum. Actively myelinating cerebellar tracts showed selective upregulation of ATF6 and IRE1 signalling in the absence of PERK activation. In addition, high basal expression of ATF6 and ER-resident chaperones was observed in mature oligodendrocytes, indicating the usage of a nuanced UPR. Modulators of UPR signalling were tested on differentiating OPCs in vitro and impairments to oligodendrocyte maturation were observed. Changes in myelin gene expression, however, did not correlate with UPR markers. This work supports the activation of the UPR during myelination and highlights how approaches to the study of the UPR may be challenging in current models. This work draws attention to how myelin synthesis is facilitated by the ER of oligodendrocytes which merits further study.2018-06-0
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Impact of B cell secreted factors on myelin in progressive multiple sclerosis
No full textEx vivo organotypic slice models present several advantages over conventional cell culture systems by enabling the investigation of multiple cell types within their native 3D architecture, while preserving intrinsic cell-cell interactions and signalling pathways. In approximately 40% of individuals with progressive multiple sclerosis (PMS), B cell niches, referred to as ectopic lymphoid follicles (ELF), are observed in cortical sulci and are associated with cortical demyelination. This PhD thesis focused on developing a novel hybrid human-rat ex vivo platform to assess the cytotoxicity of B cells from individuals with PMS, hypothesizing that co-culture with brain slices may induce PMS-like cortical demyelination.
Coronal organotypic brain slice (OBS) cultures were optimized using both neonatal and adult rat brains. Initially, evaluation of the metabolic activity of slice cultures from neonatal rats (P10/11) was investigated. The data indicated that caudal slices (Bregma -1.10mm to -3.50mm) exhibited 29.6% higher metabolic activity than rostral slices (p<0.001, n=50). Furthermore, cortical slices without structural connections exhibited 38.5% lower metabolic activity than those with intact connections (p<0.001, n=26). Severing these connections resulted in a 25.5% reduction in metabolic activity (p<0.02, n=20), emphasizing the necessity of maintaining anatomical integrity and connectivity for ex vivo cortical studies. The caudal brain regions provided optimal metabolic activity and extended viability, making them ideal for mimicking cortical physiology under healthy and diseased conditions.
Adult rat brain slices typically exhibit limited viability in ex vivo cultures (often not exceeding 7 days, so fetal bovine serum (FBS) concentrations (0-10%) in growth media were tested. Cortical slices cultured in 10% FBS demonstrated significantly higher metabolic activity (p<0.001, N=4) compared to those cultured with reduced FBS concentrations, prolonging viability to 21 days. Caudal slices (~Bregma -1.33mm) remained more metabolically active (p<0.05) than rostral slices.
Since hybrid human-rat models, using LPC to induce demyelination, were being developed, culture conditions compatible with both neonatal rat OBS and human B cells had to be optimised. In the absence of FBS, slices treated with 0.5mg/ml LPC exhibited an 88% reduction in metabolic activity at T2 (p<0.001), and a 67% reduction at T4 (p<0.01) compared to untreated controls. The addition of 10% FBS improved metabolic activity, reducing cytotoxicity at T2 and T4, but tissue integrity was lost. The optimal FBS concentration for
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culturing both neonatal OBS and B cells was found to be 2%, which preserved tissue integrity and prevented cytotoxic effects.
Coronal OBS cultures were then treated with B cell supernatant, from cultures of peripheral blood from PMS+ and PMS- individuals. Proteome Profiler Rat XL Cytokine Array analyses demonstrated that OBS cultures treated with PMS+ supernatant exhibited cytokine expression patterns consistent with clinical PMS, including upregulation of IL-1, IL-17, and IL-22. PMS+ samples also showed the highest cytotoxicity at T2 (p<0.001, N=5) and significantly reduced myelin thickness (quantified on Image J using anti-MOG staining) at T2 (p<0.05) and T4 (p<0.01), disappearing by day T7 (N=5, n= 360). These findings suggest that factors released by PMS+ B cells are cytotoxic to myelin, inducing cortical demyelination in the OBS model.
Next, a series of pilot studies were carried out to further examine the potential of rodent models of MS. Firstly, a study of activated mouse B cell migration in the brain demonstrated that a cuprizone-induced inflammatory environment promotes B cell retention in brain sections, particularly when treated with chemokine ligand 13 (CXCL13), compared to LPC or untreated controls (~30.6% and ~57.4% cells less, respectively). This highlights the necessity of developing an ex vivo model of PMS-like pathology and reinforces the role of B cells in MS-associated cortical myelin toxicity. Injecting B cells into an inflamed brain milieu facilitates their retention despite active glymphatic and cerebrospinal fluid flow. Secondly, further understanding of an inflamed brain milieu was sought by experimenting with biomaterials that could potentially be used to model ELF-like structures. For that purpose, hydrogel (HG) formulations were tested to obtain the storage modulus most closely resembling the malignant human lymph node, as that of ELFs has not yet been documented, and a non-adherent cell line (THP1) was successfully embedded within the hydrogel's 3D structure, showing proof-of-concept. Thirdly, attempts were made to mimic ELFs by promoting extracellular matrix (ECM) deposition in meningeal cultures, using the macromolecular crowder (MMC) carrageenan (CG). Unfortunately, at higher concentrations, cells treated with CG exhibited significant cell death, and no acceleration of collagen deposition was observed.
Finally, the established ex vivo model was used to test the effect on remyelination of a peptide previously shown to be immunomodulatory in vivo. Peptide FhHDM, and its truncated version, were tested on demyelinated cerebellar slices (0.5mg/ml LPC). Treatment with full-length FhHDM resulted in improved metabolic activity and reduced cytotoxicity, suggesting a
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protective effect on myelin. However, further tests and quantification of the myelin area are required to confirm the peptide’s myelin-rescuing potential.
Overall, this model has been extensively optimised and tested and introduces a novel platform for using adult OBS cultures to study neurodegenerative diseases, including drug screening and cortical pathology analysis, particularly in conditions like MS
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