1,721,260 research outputs found
The interaction between astrocytes and excitatory synapses in health and disease
No full textSynaptic transmission forms the basis of neuronal activity and astrocytes play an integral part in this process. Glutamate is the major excitatory neurotransmitter in the brain and an important function of astrocyte during excitatory synaptic activity involves the uptake of glutamate through astrocyte glutamate transporters (EAATs) and hence shaping the excitatory neurotransmission. Recently astrocytes have also been shown to affect a sustained form of inhibition. In this thesis, we study these aspects of astrocyte functions and their role in affecting the excitatory synapse. In addition, using animal models of diseases we describe how the astrocyte synapse interaction is affected in diseased conditions.In the Paper I, we confirmed previous studies showing that astrocytes respond by a longlasting depolarization upon synaptic stimulation, mediated by an increase in extracellular potassium ions. We found that this long-lasting depolarization is enhanced when astrocytic glutamate transporters are blocked, whereas the neuronal EPSC is reduced under these conditions. Blocking the glutamate transporters reduces the AMPA receptor response whereas the NMDA receptor activation is increased, causing the enhancement seen in the astrocytic long-lasting depolarization. Since astrocyte glutamate transporters are impaired in many neurodegenerative diseases, this study gives us an idea about how the impairment of astrocytic glutamate transporters can influence synapse activity.In the Paper II and III we used animal models of depression and AD respectively to understand the role of astrocytes in affecting synaptic transmission. In Paper II we used the well characterized FSL rat model of depression and investigated how reactive astrocytes affect inhibition by producing and releasing GABA. We found that tonic inhibition of pyramidal neurons is increased in the FSL rat while the synaptic plasticity is impaired. We also found that this tonic inhibition was reduced by blocking the astrocytic GABA synthesis or by chelating intracellular Ca[superscript2+] in astrocytes in slices from the FSL rat, giving evidence for increased astrocytic involvement in tonic inhibition in an animal model of depression. Furthermore, blocking of astrocytic GABA synthesis restored the impaired synaptic plasticity seen in FSL rats. In the Paper III, we explored the astrocyte mediated glutamate uptake in Alzheimer’s disease model using a knock in AD mouse model App[superscript NL-G-F]. Astrocytes displayed a reactive morphology, with swollen cell bodies and increased number of processes. We found that though there was an increase in the protein expression levels of astrocytic glutamate transporters (EAATs), they were functionally impaired as reflected by the glutamate transporter current recordings.List of scientific papersI. Ipsit Srivastava, Erika Vazquez-Juarez, Maria Lindskog. Reducing glutamate uptake in rat hippocampal slices enhances astrocytic membrane depolarization while down- regulating CA3-CA1 synaptic response. Frontiers in Synaptic Neuroscience. 2020 Aug 18;12:37. https://doi.org/10.3389/fnsyn.2020.00037 II. Ipsit Srivastava, Erika Vazquez-Juarez, Lukas Henning, Marta Gómez-Galán and Maria Lindskog. Blocking Astrocytic GABA Restores Synaptic Plasticity in Prefrontal Cortex of Rat Model of Depression. Cells. 2020 Jul 16;9(7):1705. https://doi.org/10.3390/cells9071705 III. Ipsit Srivastava, Marta Pereira Iglesias, Tamer Ayberk Kaya, Luis Enrique Arroyo-García, Per Nilsson, André Fisahn, Maria Lindskog, Silvia Maioli and Raúl Loera-Valencia. Increased levels but reduced function of astrocytic glutamate transporters in the hippocampus of the App[superscript NL-G-F] knock-in mice. [Manuscript]</p
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
Preclinical amyloid pathology is associated with anxiety but not depression in cognitively normal older adults: Evidence for differential neuropsychiatric pathways
No full textIntroduction: Neuropsychiatric symptoms may represent early Alzheimer's disease (AD) manifestations, but their relationship with amyloid pathology in cognitively unimpaired individuals remains unclear. Methods: We analyzed 4,492 cognitively unimpaired adults (aged 65-85) from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Study. Participants completed amyloid-PET imaging and assessments of anxiety, depression, memory complaints, and AD concerns. Results: 1,231 participants (27.4%) were amyloid-positive. While anxiety and depression scores remained within normal ranges, amyloid-positive participants reported higher memory complaints (p = 0.008) and AD concerns (p < 0.001) before status disclosure. Regression analyses showed amyloid burden associated with anxiety (β = 0.04, standardized, p = 0.003) but not depression (p = 0.68). Mediation analyses revealed anxiety was directly associated with amyloid, while depression was mediated through subjective cognitive concerns. Discussion: Preclinical amyloid pathology directly associates with subclinical anxiety but only indirectly with depression through subjective stress, suggesting distinct neuropsychiatric pathways in early AD that could inform detection strategies
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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