1,721,103 research outputs found
Immune dysfunction and childhood trauma in schizophrenia spectrum disorders
Get PDFSchizophrenia spectrum disorders (SSS) is a group of disorders in which patients suffer from various symptoms such as delusions and hallucinations, as well as cognitive symptoms, depressive symptoms and negative symptoms (such as social withdrawal behaviour and apathy). The cause and underlying mechanisms involved in SSS are not precisely known. One hypothesis is that dysfunction of the immune system of the brain plays a role in the onset or perpetuation of symptoms. Some studies suggest that antipsychotics may affect the immune system of the brain positively and that this mechanism contributes to their working mechanism. The first part of this thesis consists of animal studies in which the effects of antipsychotics on immune dysfunction in the brains of rats were investigated using positron emission tomography (PET) scans. We found no or small effects, but methodological limitations make it difficult to draw conclusions. The second part of the study investigated the association between childhood trauma, immune dysfunction and negative and depressive symptoms in SSS patients. We found that childhood trauma leads to more severe depressive and negative symptoms and that childhood sexual abuse is more common in women. Based on the studies conducted, necessary elements of follow-up research were identified. Existing PET tracers are not specific enough to investigate immune dysfunction of the brain. Therefore, research into new PET tracers is important. In addition, it is important to look at men and women with SSS separately, because of the male-female differences in SSS patients
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
PET methodology in rat models of Parkinson’s disease
Get PDFParkinson’s disease (PD) is one of the most common neurodegenerative diseases worldwide. The use of animal, especially rodent, models is of utmost importance to expand our understanding of the pathological features and treatments for the disease. Research in PD patients and rodent disease models has indicated that several neurotransmitter systems and inflammatory processes are involved in the brain of PD patients. A common method for the assessment of physiological processes in vivo is positron emission tomography (PET). Radiolabelled compounds specific for a certain biological process are administered to a subject and subsequently their distribution through the body, or brain is followed over time using a PET camera. The distribution and kinetics of the radiolabelled compound can be used to quantify the physiological process of interest using mathematical models.In this thesis, methodological aspects for the quantification of markers of the cholinergic neurotransmitter system using PET imaging were evaluated. The optimal quantification methods for the PET radiotracers [11C]-PMP, an acetylcholinesterase substrate, and [18F]-FEOBV, a ligand of the vesicular acetylcholine transporter, were determined in rats. Furthermore, the newly characterized as well as established radiotracers were applied to quantify changes in cholinergic activity, dopaminergic innervation, and neuroinflammation in rat models of PD. In the first study in a striatal 6-OHDA model of PD, no increase in cholinergic activity was found up to one month after the 6-OHDA injection. Additionally, no effect of exercise on cholinergic activity was seen. In the second study, a rat model carrying one of the most common genetic mutations in PD patients (LRRK2 p.G2019S) was subjected to a peripheral inflammatory trigger and followed over several months. Ten months after the inflammatory trigger no change in dopaminergic innervation but increased neuroinflammation in brain regions related to other neurotransmitters was found
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
Biological interactions in depression: Insights from preclinical studies
Get PDFMajor depressive disorder (MDD) is considered a major global health burden, being the single largest contributor to global disability and suicides. Because of its complex multifactorial nature and the variety of symptoms observed in this disorder, still around 50% of MDD patients show no or incomplete response to pharmacological therapies. In this regard, studying the molecular interactions and risk factors of MDD is a key step to improve our knowledge of the etiology and the differences in the treatment response between patients. This thesis aimed to investigate the contribution of several underlying biological processes on the development of depressive behavior in animal models, such as steroidal hormone and monoamine signaling and neuroinflammation. We found that PET imaging is a useful tool to study the effects of sex hormones in the brain in a menopausal animal model, but that chronic stress was not a strong risk factor for developing depressive symptoms in this model. In addition, we showed in a stress model of depression that repeated social defeat induced neuroinflammation, but that this effect was not counteracted by the fast antidepressant ketamine or caffeine. In this animal model, we also showed that social stress caused delayed changes in dopaminergic and serotonergic transmission when depressive symptoms had already resolved. Finally, we observed that antidepressant therapy during pregnancy had a detrimental effect on cognition in the offspring. In conclusion, this thesis provides insight in different interactions between systems and risk factors, contributing to the general knowledge of MDD
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