1,721,061 research outputs found
Molekulare Analyse der Nogo Expression und der Myelinisierung im Hippocampus während der Entwicklung und nach Läsion
Full text linkIm Gegensatz zum peripheren Nervensystem (PNS) ist die Regenerationsfähigkeit im adulten zentralen Nervensystem (ZNS) von Vertebraten sehr eingeschränkt. Diese eingeschrängte Regenerationsfähigkeit wird im Wesentlichen durch das Vorhandensein von Myelin im adulten ZNS determiniert. Einerseits ist dieses Lipid für die Stabilisierung und Ernährung von Axonen sowie für die schnelle Reizweiterleitung unbedingt notwendig, andererseits stellt es den größten Inhibitor axonaler Regeneration dar. Myelin ist außerdem Zielstruktur diverser ZNS Pathologien, wie z.B. der Multiplen Sklerose. Für das Verständnis dieser Pathologien sowie der auswachsinhibitorischen Wirkung von Myelin wurde der Hippocampus als eine der plastischten ZNS Regionen gewählt. Dazu waren genaue Kenntnisse der Myeloarchitektur dieses Gebietes notwendig. Nach Etablierung einer zuverlässigen Detektierung für Myelin konnten in der vorliegenden Arbeit detailliert Myelinisierungsvorgänge im sich entwickelnden, im adulten und im deafferenzierten Hippocampus der Ratte analysiert werden. Während der Entwicklung erreichen die ersten entorhinale Axone den Hippocampus bereits am embryonal Tag 17 (E17); Myelin kann jedoch erst am postnatal Tag 17 (P17) lichtmikrokopisch nachgewiesen werden. Die Anzahl myelinisierter Fasern erreicht um den P25 ein Verteilungsmuster, welches dem von adulten Tieren gleicht. Nach Entorhinaler Cortex Läsion (ECL), bei der die Durchtrennung des Tractus perforans (PP) eine Denervation des Hippocampus bewirkt, kommt es zu einem langanhaltenden Verlust von Myelin. Zehn Tage nach Läsion (10 dal), also zum Zeitpunkt maximaler Aussprossung (Sprouting), kommt es zu einem Wiederkehren myelinisierter Fasern. Mehrere myelin-assoziierte Proteine, mit wachstumshemmenden Eigenschaften sind bekannt, wie z.B. die Familie der Nogo Gene (Nogo; englisch, kein Durchkommen). Diese werden ganz entschieden für den Verlust der Regenerationsfähigkeit des adulten ZNS verantwortlich gemacht. In der vorliegenden Arbeit wird die Expression der drei Nogo Gene (Nogo-A, -B, - C) und deren Rezeptor (Ng66R) während der postnatalen Entwicklung, im adulten ZNS sowie nach Läsion beschrieben. Ein erster überraschender Befund war die neuronale Expression der Nogos, die bisher nur in Oligodendrocyten nachgewiesen worden war. Zu einem Zeitpunkt, an dem entorhinale Fasern bereits in den Hippocampus eingewachsen, aber noch nicht myelinisiert sind (P0), wird Nogo-A, -B und Ng66R mRNA mit Ausnahme der Körnerzellschicht des Gyrus dentatus in allen Zellschichten des sich entwickelnden Hippocampus detektiert. Nogo-C und myelin basic protein (MBP) mRNA, werden erst am P15 expremiert, zu einem Zeitpunkt also, an dem myelinisierte Fasern erstmalig im Hippocampus auftreten. MBP wird ausschließlich in glialen, Nogo-C hingegen hauptsächlich in neuronalen Zellen exprimiert. Nach Deafferenzierung zeigt sich eine dynamische und Isoform- spezifische Regulation aller Nogo Transkripte. So zeigen die als erste von der Deafferenzierung betroffenen Körnerzellen zu Beginn der Waller`schen Degeneration sowie der neuronalen und glialen Antwort, eine starke Erhöhung aller Nogo Transkripte. Zum Zeitpunkt der maximalen Aussprossung kam es zu einem signifikanten Abfall der Nogo-C und Ng66R mRNA Expression, währendessen Nogo-A und Nogo-B bereits wieder das Kontrollniveau erreicht hatten. Vor allem im contralateralen Hippocampus, dem Hauptquellgebiet sproutender Fasern, imponierte die Runterregulation von Ng66R mRNA und zeigte erst nach Abschluß von axonalen Sproutingprozessen und der Synapsenformation wieder vergleichbare Werte mit den Kontrolltieren. Diese Korrelation der erniedrigten Ng66R Expression im contralateralen Hippocampus und dem axonalen Einwachsen in den deafferenzierten Hippocampus, läßt eine reduzierte axonale Ansprechbarkeit auf den Neuriten-Auswachshemmer Nogo-A vermuten, da bekannt ist, dass Axone, die kein Ng66R exprimieren, nicht durch die Nogo Gene im Wachstum gehemmt werden. Zusammenfassend kommt es während der Entwicklung und in der Reorganisationsphase zu einer spezifischen und geordneten Myelinisierung im Hippocampus. Die neuronale Expression von Nogo- A, -B und -C in einer so plastischen ZNS- Region unterstützt die Hypothese, dass den Nogo- Genen neben der reinen Hemmung von axonalen Auswachsen weitere Funktionen zuzuordnen sind. So scheinen sie vor allem während der Entwicklung und während der Stabilisierungsphase der hippocampalen Reorganisation eine wichtige Rolle einzunehmen. Die hier dargestellten Daten zeigen auf, dass vor einem therapeutischen Einsatz von Nogo- Antagonisten nach Schädigung deren Verträglichkeit bzw. unerwünschte Nebeneffekte ausgeschlossen werden müssen.Compared to the peripheral neuronal system (PNS) the reorganisation capacity in the adult central neuronal system (CNS) is highly restricted. One important reason for the lack of reorganisation is the existence of myelin in the CNS. Myelin is crucial for the stabilization of axonal projections in the developing and adult mammalian brain. However, myelin components also act as a non-permissive and repellent substrate of outgrowing axons. In these thesis the appearance of mature, fully myelinated axons during hippocampal development and following entorhinal cortex lesion with the myelin-specific marker Black Gold is reported. Althrough entorhinal axons enter the hippocampal formation at the embryonic day 17, light and ultrastructural analysis revealed that mature myelinated fibres in the hippocampus occur in the second postnatal week. During postnatal development, increasing numbers of myelinated fibers appear and the distribution of myelinated fibers at postnatal day 25 was similar to that found in the adult. After entorhinal cortex lesion, a specific anterograde denervation in the hippocampus takes place, accompanied by a long- lasting loss of myelin. Quantitative analysis of myelin and myelin breakdown products at different time points after lesion revealed a temporally close correlation to the degeneration and reorganisation phases in the hippocampus. In conclusion, it could be shown that the appearance of mature axons in the hippocampus is temporally regulated during development. Reappearing mature axons were found in the hippocampus following axonal sprouting. Various myelin-associated proteins, with neurite inhibition properties are known. One is the family of Nogo genes (no go). They are distinctly responsible for the lack of reorganisation. In these thesis the expression pattern of Nogo-A, Nogo-B, Nogo-C and Nogo-66 receptor (Ng66R) mRNA during hippocampal development and lesion induced axonal sprouting is reported. The first surprising result was the neuronal expression of all Nogos, who were supposed to be only expressed by oligodendrocytes. Nogo-A, Nogo-B and Ng66R transcrips preceded the process of myelination and were highly expressed at postnatal day zero (P0) in all principal hippocampal cell layers, with the exception of dentate granule cells. Only a slight Nogo-C expression was found at P0 in the principal cell layers of the hippocampus. During adulthood, all Nogo splice variants and their receptor were expressed in the neuronal cell layers of the hippocampus, in contrast to the myelin basic protein mRNA expression pattern, which revealed a neuronal source of Nogo gene expression in addition to oligodendrocytes. After hippocampal denervation, the Nogo genes showed an isoform-specific temporal regulation. All Nogo genes were strongly regulated in the hippocampal cell layers, wheras the Ng66R transcrips showed a significant increase in the contralateral cortex. These data could be confirmed on protein levels. Futhermore, Nogo-A expression was up-regulated after kainat- induced seizure. These data show that neurons express Nogo genes with a clearly distinguishable pattern during development. This expression is further dynamically and isoform-specifically altered after lesioning during the early phase of structural rearrangements. Thus, these results indicate a role for Nogo-A, -B and –C during development and during stabilisation phase of hippocampal reorganization. Taken together with these data, the findings that neurons in a highly plastic brain region express Nogo genes supports the hypothesis that Nogo may function beyond its known neuronal growth inhibition activity in shaping neuronal circuits
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
Language, selfhood and otherness in the works of D. H. Lawrence
No full textThe aim of this dissertation is to trace the development of Lawrence’s thought about the interdependence between language, selfhood and otherness in the period between the composition of Women in Love and the closing years of his literary career. Around the time of Women in Love’s inception, Lawrence saw the relationship between self and language in terms of the gap separating the speaker’s experience from his utterance. This gap, Lawrence believed, could be bridged through a type of verbal expression that was qualitatively different from the static language of representation on which Western rationalism was predicated. In “Foreword to Women in Love” this authentic mode of expression is referred to as “the new idea” arising out of the individual’s “struggle for verbal consciousness” (276). However, the complexity of linguistic signification, revealed on the dramatic plane of the novel itself, proves the one-to-one correspondence between expression and experience impossible to achieve.
Lawrence’s exploration of the interdependence between selfhood and language continued with his essays on psychology, which followed chronologically Women in
Love. In both Psychoanalysis and the Unconscious and Fantasia of the Unconscious, Lawrence describes the ego as a rational construct analogous to the static language of representation. This structural homology allows the full verbal representability of the ego whilst rendering un-signifyable all those facets of subjectivity which transcend reason. The argument of Lawrence’s psychology essays can therefore be said to introduce an important twist in his earlier views on the interrelation between self and language. If the “Foreword to Women in Love” envisaged at least the possibility for an absolute coincidence between experience and verbal expression, the psychology essays reveal this at-oneness as virtually unattainable. With the hindsight of the late twentieth century developments in psychoanalytic thought, the argument put forth in Psychoanalysis and Fantasia can be said to foreshadow certain aspects of Jacques Lacan’s and Julia Kristeva’s views on subjectivity.
The completion of the psychology essays left Lawrence undeterred in his quest for a new mode of signification able to reveal the entirety of the human self. Since all his attempts to elicit a solution from within Western ontology proved futile, he turned his attention to a variety of non-European civilisations, which the science of the time believed to share a mode of being different from the one engendered by rationalism. This essentially primitivist image of the non-European other had a profound impact on Lawrence who was fascinated to discover that societies so radically different from his own were predicated on the same state of at-oneness between experience and language which he himself hoped to achieve in the present. It was with these thoughts that Lawrence departed to the United States to familiarise himself with the traditional, non-European culture of the Native Americans and find inspiration therein.
In other words, Lawrence’s impulse to travel to the New World was rooted in preconceived ideas which tend to transform the other into a projection issuing from the self. These ideas influenced in varying degrees Lawrence’s account of the indigenous people throughout his stay in North America, yet, in time, he began to develop a more authentic sense of their otherness which was reflected in his narrative technique.
The Native American essays included in the collection Mornings in Mexico demonstrate how Lawrence began to, literally, write himself out of his own projections by creating what can be referred to as a self-conscious discourse on alterity. The specificity of this discourse lies in its capacity to foreground its very own cultural bias and thus bracket off, as it were, the truth that it ostensibly affirms. In this sense it prefigures the methodological adjustments that Jacques Derrida prescribed to late twentieth-century science of ethnology.
The signifying logic of Lawrence’s discourse on alterity is applied further in some of his later works which examine cultural otherness in terms of a particular mode of expression epitomised by the symbol. The symbol, conceived of as a particular type of language, functions in accordance with the same logic of transcendence that we found in the discourse of the Native American essays in Mornings in Mexico, in the sense that it simultaneously affirms and subverts a particular meaning. However, if the essays’ narrative leaves an unbridgeable gap between the European observer and the indigenous people, the symbol creates a signifying space where self and other can genuinely interact. Thus the collection of Places elaborates a social model allowing culturally diverse communities to co-exist without infringing upon each other’s difference.
Using Julia Kristeva’s theory of inter-subjective relations across a cultural divide, put forth in her work Strangers to Ourselves, I will try to demonstrate that the social model Lawrence develops in Sketches of Etruscan Places is based on a fundamental re-conceptualisation of the correspondence between selfhood and language, conceived as symbolic discourse.
Since the symbol contains its own undoing in the dynamic flux of experience, its meaning is characterised with a semantic surplus, an otherness, that can never be
fully explicated. Symbolic discourse can therefore signify the ever changing and ultimately unknowable dimension of the self, which Lawrence calls variously dynamic consciousness or the unconscious, and which the static language of representation is unable to express. In other words, the symbol can accommodate both the self-sameness of the ego and the otherness of the non-cerebral self.
By positing in language the decentred human subject, never at one with itself, the symbol renders hollow the idea of a homogenous society based on individual selfsameness. Since the subject is always at variance with itself, social cohesion begins to appear possible only if predicated on difference, a difference that all the members of society share. This sameness in difference creates an open and inclusive social framework able to integrate people irrespective of their cultural background.
In this sense, the essays included in Sketches of Etruscan Places create a new balance between the notions of language, selfhood and otherness that is both similar and different from the one we described in Part I of this thesis. The correspondence between self and language, i.e. the speaker and his utterance has been regenerated at the cost of a radical redefinition of the notion of language. This redefinition, in turn, has been made possible by Lawrence’s recourse to cultural otherness and has led to the development of a model of self-other interrelation whereby self and other can coexist in difference
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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