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Einflussfaktoren der linksventrikulären Myokarddeformation: Pathophysiologische Grundlagen und praktischer Nutzen
Get PDFKardiovaskuläre Erkrankungen stellen die weltweit führende Todesursache dar, weshalb ihrer Früherkennung eine übergeordnete Rolle zukommt. In dieser kumulativen Habilitationsschrift wurde experimentell untersucht, wie sich verschiedene Pathologien in ihren Frühphasen auf die Deformationseigenschaften ("Strain") des linken Ventrikels auswirken, und wie dies für diagnostische Zwecke genutzt werden könnte. Am Beispiel von Subendokardfibrose, Adipositas-Kardiomyopathie und Anthrazyklin-induzierter Kardiotoxizität wurden verschiedene Mechanismen identifiziert, die zu einer eingeschränkten linksventrikulären Myokarddeformation führen. Dabei wurde insbesondere der Stellenwert des longitudinalen Strains als sensitiver Parameter mit diagnostischem Potenzial in der Früherkennung kardiovaskulärer Erkrankungen herausgearbeitet
Verwendung von Speckle-tracking Echokardiographie für die Evaluation der subendokardialen Funktion im Kleintiermodell
Get PDFHintergrund: Aufgrund seiner hohen Vulnerabilität ist das Subendokard bereits in subklinischen Phasen von kardiovaskulären Erkrankungen betroffen. Methoden zur Beurteilung der subendokardialen Funktion kommt daher eine große klinische Relevanz in Hinblick auf Früherkennung kardialer Schädigungen und Prävention funktioneller Einschränkungen zu. Die vorliegende Arbeit untersucht das Potential von myokardialen Strain-Parametern, Veränderungen innerhalb des Subendokards zu evaluieren.
Methodik: Männliche 129/Sv Mäuse wurden zur Induktion isolierter subendokardialer Fibrose mit Isoproterenol behandelt (ISO; n = 32), eine Kontrollgruppe erhielt stattdessen Kochsalzlösung (n = 15). Die transthorakale Echokardiographie der Tiere erfolgte mit einem 30-MHz Linearschallkopf und einem hochauflösenden System für Kleintierbildgebung; in den anschließenden Auswertungen des akquirierten Bildmaterials wurden sowohl konventionelle- als auch myokardiale Strain-Parameter erhoben. Der Kollagengehalt innerhalb der verschiedenen myokardialen Schichten wurde histologisch bestimmt, und die Serumkonzentration des Tissue Inhibitor of Metalloproteinase-1, einem Biomarker für Fibrose, erhoben.
Ergebnisse: Die Gabe von ISO führte als Reaktion auf Zelluntergang zu einem deutlichen Anstieg des subendokardialen Kollagengehaltes (Kontrollgruppe: 0,6 ± 0,3% vs. ISO: 5,8 ± 0,9%, P < 0,001) und resultierte in einem moderaten Anstieg der linksventrikulären Wanddicken bei erhaltener systolischer Funktion. Global Longitudinal Peak Strain (LS) und -Strain Rate waren in den ISO-behandelten Tieren deutlich erniedrigt (LS: –15,49% vs. –11,49% [P = 0,001]; Longitudinal Strain Rate: –4,81 vs. –3,88 sec-1 [P < 0,05]), während die radialen und circumferentiellen Strain-Parameter unverändert blieben. Global LS korrelierte mit dem subendokardialen Kollagengehalt (r = 0,46; P = 0,01) und der Serumkonzentration von Tissue Inhibitor of Metalloproteinase-1 (r = 0,52; P < 0,05). Anschließende Analysen identifizierten den global LS als überlegenden Prädiktor für das Vorhandensein von subendokardialer Fibrose (Sensitivität: 84 %, Spezifität: 80 %; Cut-off: –14,4%).
Schlussfolgerung: Die Erhebung des LS könnte eine nicht-invasive Methode zur Detektion subendokardialer Schäden darstellen und folglich die frühzeitige Diagnose kardialer Erkrankungen verbessern.Background: The subendocardium is highly vulnerable to damage and is thus affected even in subclinical disease stages. Therefore, methods reflecting subendocardial status are of great clinical relevance for the early detection of cardiac damage and the prevention of functional impairment. The aim of this study was to investigate the potential ability of myocardial strain parameters to evaluate changes within the subendocardium.
Methods: Male 129/Sv mice were injected with isoproterenol (ISO; n = 32) to induce isolated subendocardial fibrotic lesions or saline as appropriate control (n = 15). Transthoracic echocardiography was performed using a 30-MHz linear-frequency transducer coupled to a high-resolution imaging system, and acquired images were analyzed for conventional and strain parameters. The degree of collagen content within the different cardiac layers was quantified by histologic analysis and serum levels of tissue inhibitor of metalloproteinase-1, a biomarker for fibrosis, were assessed.
Results: ISO treatment induced a marked increase in subendocardial collagen content in response to cell loss (control vs ISO, 0.6 ± 0.3% vs 5.8 ± 0.9%; P < .001) and resulted in a moderate increase in left ventricular wall thickness with preserved systolic function. Global longitudinal peak strain (LS) and longitudinal strain rate were significantly decreased in ISO-treated animals (LS, –15.49% vs –11.49% [P = .001]; longitudinal strain rate, –4.81 vs –3.88 sec-1 [P < .05]), whereas radial and circumferential strain values remained unchanged. Global LS was associated with subendocardial collagen content (r = 0.46, P = .01) and tissue inhibitor of metalloproteinase–1 serum level (r = 0.52, P < .05). Further statistical analyses identified global LS as a superior predictor for the presence of subendocardial fibrosis (sensitivity, 84%; specificity, 80%; cutoff value, –14.4%).
Conclusion: Assessment of LS may provide a noninvasive method for the detection of subendocardial damage and may consequently improve early diagnosis of cardiac diseases
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
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
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