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La rupture de la barrière hémato-rétinienne interne (iBRB) se produit dans de nombreux troubles de la rétine et peut provoquer un œdème rétinien souvent responsable de la perte de vision. Le but de cette étude était de caractériser l'impact d'une rupture de l’iBRB sur les changements homéostatiques rétiniens de la dystrophine Dp71, AQP4 et Kir4.1 provoqués par les altérations les cellules gliales de Müller CGM. L'effet protecteur de la Dex a été étudié dans ce modèle. Par ailleurs, les explants rétiniens ont été utilisé pour étudier la formation et la résolution de l'œdème de CGM sans l'influence de l'inflammation du cristallin ainsi que l’effet de différentes doses de glucocorticoïdes (Dex, triamcinolone et fluocinolone) et des inhibiteurs de la voie de l'acide arachidonique. Nous avons observé que la chirurgie partielle du cristallin induit une rupture de l'iBRB et des changements moléculaires dans le CGM, une diminution de l’expression de la Dp71 et d’AQP4 et la délocalisation de Kir4.1. La Dex semble protéger la rétine par l’augmentation de l’expression du HSF1. Nous avons également observé que même si les glucocorticoides étudié ont des effets différents sur l’expression de la Dp71, AQP4 et Kir4.1 les trois sont capables de prévenir la formation de l’œdème de CGM. Nos résultats suggèrent que la formations d'œdème semblent être régulée par la voie des leucotriènes. Nous avons étudié le rôle des isoformes de la dystrophine Dp71 dans les processus d'adhésion intercellulaire des cellules PC12. Nos résultats suggèrent l’existence d’au moins deux mécanismes différents seraient impliqués dans l'adhésion intercellulaire associée à la Dp71, l'une impliquant Dp71dΔ71 et Cx43. / The breakdown of the internal blood-retinal barrier (iBRB) occurs in many retinal disorders and may cause retinal edema, often responsible for vision loss. The aim of this study was to characterize the impact of iBRB disruption on retinal homeostatic changes in Dp71 dystrophin, AQP4 and Kir4.1 caused by Müller glial cells (MGC) alterations. The protective effect of Dex has been studied in this model. In addition, retinal explants were used to study the formation and resolution of CGM edema without the influence of lens inflammation and the effect of different doses of glucocorticoids (Dex, triamcinolone and fluocinolone) and inhibitors of the arachidonic acid pathway. We observed that partial lens surgery induced iBRB breakdown and molecular changes in MGC, decreased expression of Dp71 and AQP4, and miss localization of Kir4.1. Dex seems to protect the retina by increasing the expression of HSF1. We also observed that although the glucocorticoids studied have different effects on the expression of Dp71, AQP4 and Kir4.1 all three can prevent the formation of MGC edema. Our results suggest that edema formation appears to be regulated by leukotrienes. We have studied the role of isoforms of dystrophin Dp71 in intercellular adhesion processes of PC12 cells. Our results suggest the existence of at least two different mechanisms involved in intercellular adhesion associated with Dp71, one involving Dp71dΔ71 and Cx43.

In this thesis the relationship between Gröbner bases and algebraic coding theory is investigated, and especially applications towards linear codes, with Reed-Müller codes as an illustrative example. We prove that each linear code can be described as a binomial ideal of a polynomial ring, and that a systematic encoding algorithm for such codes is given by the remainder of the information word computed with respect to the reduced Gröbner basis. Finally we show how to apply the representation of a code by its corresponding polynomial ring ideal to construct a class of codes containing the so called primitive Reed-Müller codes, with a few examples of this result.

La manière dont la diversité neuronale du système nerveux central est établie au cours du développement est une question d'un grand intérêt depuis plus d'un siècle. Les progéniteurs neuronaux sont contrôlés dans l'espace et dans le temps afin de générer un ensemble diversifié de neurones. Les composants moléculaires du contrôle spatial chez les vertébrés soient bien compris, mais le cadre moléculaire du contrôle temporel chez les vertébrés n’a été que peu exploré. Les travaux réalisés, au cours de la dernière décennie, sur le développement de la rétine chez la souris ont révélé l'existence de deux importants facteurs de transcription temporels (tTF). Ikzf1 confère une compétence temporelle précoce alors que Casz1 confère une compétence temporelle tardive aux cellules progénitrices de la rétine (RPC) des mammifères. Cependant, sur les sept types cellulaires présents dans la rétine, ces tTFs ne régulent pas la capacité de générer les cônes nés précocement ni pour les cellules gliales de Müller nées tardivement, suggérant la présence d'autres tTFs non identifiés. L'objectif principal de cette thèse a été de découvrir les mécanismes moléculaires contrôlant la production des cônes au cours de la rétinogenèse précoce ainsi que la production tardive des cellules gliales de Müller. Dans cette thèse, Pou2f1 a été découvert comme un tTF qui confère aux RPCs une compétence temporelle à générer des cônes. Pou2f1 active l'expression de Pou2f2, qui permet ensuite de favoriser la production de cônes en réprimant l’expression du facteur de transcription Nrl. Ikzf1 active l'expression de Pou2f1 dans les RPC alors que Pou2f1 réprime le tTF tardif Casz1, suggérant une boucle d'autorégulation transcriptionnelle entre ces différents tTF. De plus, Ikzf4, un autre membre de la famille Ikzf, s'est avéré important pour la spécification des cônes et des cellules gliales de Müller. Ikzf4 active l’expression de Pou2f1/Pou2f2 lorsqu'il est surexprimé dans des RPC tardifs, suggérant qu’il permet la production de cônes en activant directement l’expression de Pou2f1/Pou2f2. Ikzf4 était également lié à de nombreux gènes de la voie de signalisation de Notch, qui sont impliqués dans la production de cellules gliales de Müller au cours de la rétinogenèse. Ce travail établi des bases pouvant inspirer de futures études dans d'autres parties du SNC, où des tTF similaires pourraient aussi contrôler la production de différents types cellulaires en fonction du temps. Enfin, cette thèse propose de nouveaux tTF comme outils thérapeutiques pour améliorer l’efficacité de production des cônes à partir de cellules souches. / How neural diversity is established in the developing central nervous system has been a question of great interest for more than a century. Neural progenitors are spatially and temporally patterned to generate a diverse set of neurons. Although molecular components of spatial patterning in vertebrates are well understood, the molecular framework behind temporal patterning in vertebrates has been largely unexplored. Work done in the past decade on mouse retinal development has revealed insights on how temporal patterning could be established in the CNS. Retinal neurons and glia are born in a sequential but overlapping manner from a pool of multipotent retinal progenitor cells (RPCs), consisting of an early embryonic and late post-natal window of cell birth. Two temporal transcription factors (tTFs), Ikzf1 and Casz1, confer early and late temporal competence to retinal progenitor cells (RPCs), respectively. However, out of the seven cell types in the retina, these tTFs do not regulate the competence for early born cones and late born Müller glia, suggesting the presence of other unidentified tTFs. The prime goal of this thesis was to uncover the molecular mechanisms controlling cone specification during early, and Müller glia specification during late retinal development. In this thesis, Pou2f1 was discovered as a novel tTF that confers temporal competence to RPCs to generate cones. Pou2f1 activates Pou2f2, which binds to the promoter of Nrl, a key rod specification gene, and represses its expression. Early tTF Ikzf1 activates Pou2f1, whereas Pou2f1 represses late tTF Casz1 in RPCs. Additionally, Ikzf4 was discovered as an important regulator of cone specification early, and Müller glia specification late during retinal development. Ikzf4 binds to genomic regions near Pou2f1/Pou2f2 gene bodies and activates their expression during early retinogenesis. During late retinogenesis, Ikzf4 binds to promoters of Notch signaling genes and activates their expression to promote Müller glia differentiation. Taken together, these results reveal important insights on how cone and Müller glia production is temporally controlled during early and late retinogenesis. This work lays the groundwork for future studies in other parts of the developing CNS that could employ similar tTFs for temporal patterning. Finally, this thesis proposes novel tTFs as therapeutic tools to efficiently generate cones from ESC-derived retinal organoids and sheets.

Les altérations de la barrière hémato-rétinienne (BRB) sont associées à des maladies rétiniennes telles que la rétinopathie diabétique et la dégénérescence maculaire liée à l’âge (DMLA). L’intégrité de la BRB est cruciale pour maintenir un microenvironnement rétinien en homéostasie et est étroitement régulé grâce à la régulation du transport transcellulaire et paracellulaire. Ici, nous décrirons brièvement la BRB interne, en mettant davantage l’accent sur la structure et la fonction de la BRB externe dans les états sains et malades. Nous avons hypothétisé que le dysfonctionnement des aquaporines exprimées dans des composantes de la BRB est suffisant pour générer un oedème diabétique dans une rétine diabétique. Bien que les résultats indiquent qu’aucune des aquaporines ciblées n’est suffisante pour générer un oedème cystoïde dans un modèle murin - et ce même en l’exacerbant en augmentant la perméabilité vasculaire rétinienne, nous mettons à l’avant un outil de segmentation semi-automatisé ainsi que deux modèles de recherches engageants. Le modèle murin de DT1 induit via STZ a été étudié de façon longitudinale sur un intervalle de temps modéré et pourra être ajusté pour des expériences futures en mettant à profit un outil de quantification semi-automatique performant. D’autre part, le modèle in vitro de la sénescence de l’ÉPR est conceptuellement établi et partiellement mis sur pied. Finalement, les résultats sont prometteurs et incitent à approfondir des cibles alternatives dans un modèle conceptuellement similaire, mais soit exacerbé ou plus anatomiquement près de l’humain. / Alterations in the blood-retina barrier (BRB) are associated with retinal diseases such as diabetic retinopathy and age-related macular degeneration (AMD). The integrity of the BRB is crucial for maintaining a tightly regulated and retinal microenvironment in homeostasis through the regulation of transcellular and paracellular transport. Here, we will briefly describe the inner BRB, with a greater emphasis on the structure and function of the outer BRB in both healthy and diseased states. We hypothesized that dysfunction of aquaporins expressed in components of the BRB is sufficient to generate diabetic edema in a diabetic retina. Although the results indicate that none of the targeted aquaporin are sufficient to generate a cystoid edema in a murine model, even when exacerbated by increasing retinal vascular permeability, we present a semi-automated segmentation tool and two engaging research models. A murine model and a programmation tool were developped to efficiently assess semi-automated quantitation of retinal edema. On the other hand, the in vitro model of RPE senescence is conceptually established and partially implemented. Ultimately, the results are promising and encourage further exploration of alternative targets in a conceptually similar model, either exacerbated or more anatomically close to humans.

Müllerzellen - die dominierenden Gliazellen der Netzhaut - üben vielfältige Funktionen und Aufgaben im retinalen „Zellnetzwerk“ aus. Ihre wohl wichtigste Funktion ist die Aufrechterhaltung der Volumen- und Ionenhomöostase der Retina. Forschungsergebnisse der letzten Jahre deuten darauf hin, dass pathologische Veränderungen in der Volumenregulation von Müllerzellen bei vielen Erkrankungen der Netzhaut eine bedeutende Rolle spielen. Diese Promotionsarbeit befasst sich mit morphologischen Veränderungen in der Netzhaut von Wildtypmäusen sowie von drei Mausstämmen mit genetischen Veränderungen (Überexpression von dnSNARE, P2Y1-defizient, IP3-R2-defizient) unter pathologischen Bedingungen. In den experimentellen Untersuchungen fand das in Vorarbeiten bereits etablierte Ischämie-Reperfusions-Modell Anwendung. Es ist bekannt, dass Müllerzellen nach retinaler Ischämie Veränderungen durchmachen, die als reaktive Gliose bezeichnet werden. Reaktive Müllerzellen sind nicht mehr in der Lage, bestimmte Funktionen zu erfüllen, die sie in der gesunden Netzhaut haben, dazu gehört eine Einschränkung der Fähigkeit zur Volumenregulation. Ziel der Arbeit war es erstens, eine Charakterisierung der Mausnetzhäute hinsichtlich der zellulären Zusammensetzung der Retina vorzunehmen und zweitens zu untersuchen, inwiefern sich eine Störung der Müllerzellfunktion – wie sie bei allen drei genetisch veränderten Mauslinien vorliegt – auf das Überleben der Nervenzellen unter extremen Stressbedingungen wie z.B. einer Ischämie auswirkt. Denn gerade unter den mit einer Ischämie einhergehenden Bedingungen sollte die Funktion der Müllerzellen zum Erhalt der retinalen Ionen- und Volumenhomöostase von entscheidender Bedeutung sein.

In 1985, the East German playwright Heiner Müller (1929-95) spoke of the importance of a ‘democratic’ theatre: for Müller, the theatre was to be a space in which audience members are free to produce their own interpretations of the material presented on stage. In turn, the audience is encouraged to question the composition of its material reality but is not presented with a solution. Müller explicitly related this practice to his own production of his three texts Der Lohndrücker (1956-57), Der Horatier (1968), and Wolokolamsker Chaussee IV: Kentauren (1986) together at the Deutsches Theater in 1988-91. As this thesis demonstrates, Müller foregrounds instigating audience participation and the means of creating ‘democratic’ theatre from the very beginning of his career. In studying the composition of Müller’s texts, the historical contexts in which they were written, and their premières we gain new perspectives on the ways in which the possibility for political theatre is anchored in Müller’s texts and just how this political theatre aims to engage its contemporary, implied audiences; indeed, this thesis argues that the politics of Müller’s theatre can be best defined as ‘democratic’. In the introduction, I establish how Müller understands the term ‘democratic’ and how his understanding differs from interpretations of democracy contemporary to him; in doing so, I borrow critical vocabulary from the contemporary French philosopher Jacques Rancière. The introduction also elaborates a methodology for studying both implied and real audiences. While each of the prevalent semiological, phenomenological, or materialist theories of audience response has its strengths, in order to pay sufficient attention to the multiple influences upon and aspects of audience interaction, we must take a more holistic approach to audience research. I therefore articulate a new materialist phenomenological approach to audiences, drawing on Martin Heidegger’s phenomenology. In the following chapters, I study Der Lohndrücker, Der Horatier, and Kentauren in their historical contexts and consider how they were both composed with their contemporary audiences in mind and staged in their premières. This approach sheds new light on each text in question: not only do all three texts demonstrate a concern for a lack of democracy in material reality, but each also contains strategies for engaging audience involvement in a piece of ‘democratic’ theatre. My final chapter analyses Müller’s own staging techniques in Der Lohndrücker in 1988, arguing that they enhance the production’s democratic political potential and contribute to our understanding of Müller’s political theatre. While the productions discussed in Chapters 2 and 3 have largely been overlooked by theatre scholarship to date, they provide important insights into the politics of Müller’s texts and the possible limits of writing political theatre texts. This thesis draws on a wide range of both published and unpublished materials, including rehearsal notes, stage manuscripts, audience letters, newspaper reviews, theatre programmes, records of reactions to Müller’s works within the GDR’s statecraft, and Müller’s own notes for writing his texts. Through this wealth of material we not only gain an insight into the ways in which Müller’s texts were written for his audiences but we also recognise the parameters for his audiences’ responses. In offering a fresh perspective on Müller’s works, this thesis demonstrates both a compelling model for audience research and that a synthesis of textual/performance analysis, historical contextualisation, and audience research provides us with a very adept tool for analysing the making of political theatre and the politics of making theatre.

Doctor of Philosophy / Department of History / Robert D. Linder / George Müller of Bristol (1805-1898) was widely celebrated in the nineteenth century as the founder of the Ashley Down Orphan Homes in Bristol, England. He was a German immigrant to Great Britain who was at the vanguard of evangelical philanthropic care of children. The object of his charitable work, orphans, influenced the establishment of Christian orphanages in Great Britain, North America, Asia, Africa, Latin America, and Europe. However, what brought Müller widespread public acclaim was his assertion that he supported his orphan homes solely by relying on faith and prayer. According to Müller, he prayed to God for the material needs of the orphans and he believed, in faith, that those needs were supplied by God, without resort to direct solicitation, through donations given to him. He employed his method as a means to strengthen the faith of his fellow Christians and published an ongoing chronicle of his answered prayers that served as evidence. Müller’s method of financial support brought him to the forefront of public debate in the nineteenth century about the efficacy of prayer and the supernatural claims of Christianity. His use of prayer to provide for the orphans made his name a “household word the world round.” This dissertation is a study of Müller’s influence on evangelicals that analyzes Müller’s enduring legacy as a hero of the faith among evangelicals around the world. For evangelicals Müller was an exemplary Christian—a Protestant saint—who embodied a simple but pure form of biblical piety. To explore his influence from the nineteenth century through the twentieth century, this study, as a social biography, investigates how evangelicals remember individuals and how that memory, in this case Müller, influenced the practice of prayer in evangelical piety. The dissertation affirms a link between evangelicals and eighteenth-century German Pietism, while also showing that evangelicals used publications to celebrate and to informally canonize individuals esteemed for their piety. The dissertation, ultimately, is concerned with how evangelicals identified heroes of the faith and why these heroes were and are widely used as models for edification and for emulation in everyday life.

A conquista do ambiente terrestre por caranguejos Brachyura é dependente da obtenção e reserva de água na câmara branquial durante o período de emersão. Uma maneira de se obter água do meio é através de tufos de cerdas hidrofílicas, capazes de captar água do solo por capilaridade. Sabe-se que essas cerdas hidrofílicas estão associadas à abertura de Müller e que a água captada é admitida na câmara branquial graças à diferença de pressão entre a câmara branquial e o meio externo, produzida pelos batimentos do escafognatito. Contudo, as modificações morfológicas esqueletais e apendiculares para a formação da abertura de Müller e a composição das cerdas do tufo não são conhecidos. Com o intuito de elucidar tais lacunas, foram estudados o esqueleto axial, apendicular e a quetotaxia de 22 espécies de caranguejos semiterrestres pertencentes às superfamílias Grapsoidea (Grapsidae, Sesarmidae, Varunidae e Gecarcinidae) e Ocypoidea (Ocypodidae e Ucididae). O estudo do esqueleto axial e apendicular revelou que a abertura de Müller é, na verdade, um canal complexo que pode ser composto por três componentes: o canal pleural, a calha apendicular e o tufo de cerdas. A água presente no substrato é captada pelo tufo de cerdas, é conduzida pela calha apendicular, passa pelo canal pleural para, enfim, ser admitida na câmara branquial. O tufo de cerdas é formado entre a face posterior do coxopodito do pereópode 3 e a face anterior do coxopodito do pereópode 4. Em Sesarmidae, o tufo também ocorre entre os coxopoditos dos pereópodes 2 e 3. Os representantes das superfamílias Grapsoidea e Ocypodoidea diferem quanto à formação do canal de Müller. Os tipos de cerdas presentes nos tufos de cerda associados ao canal de Müller são os mesmos encontrados em outros pereópodes e no bordo da região branquiostegal (cerdas simples, paposas e papo-serradas). A única exceção são as cerdas constritas presentes, exclusivamente, nos tufos de cerdas das espécies da família Ocypodidae. Nos tufos de Grapsoidea, a inserção de cerdas no coxopodito do pereópode 4 ocorre somente na sua porção ventral enquanto, em Ocypodoidea, as cerdas do coxopodito do pereópode 4 se inserem tanto na porção ventral como na porção distal. A calha apendicular pode ser formada entre as coxas dos pereópodes 5/6 ou 6/7, de formato cilíndrico ou semicilíndrico. A função da calha apendicular está associada com a condução da água entre o tufo de cerdas e o canal pleural, embora existam casos de formação do canal de Müller sem a presença da calha apendicular. O canal pleural pode ser aberto ou semitubular, ocorrendo, sempre, entre os pleuritos torácicos 6 e 7 e, em algumas espécies, também entre os pleuritos torácicos 5 e 6. O canal pleural aberto é formado pelo afastamento de dois pleuritos torácicos adjacentes; o canal semitubular é formado pela projeção do pleurito 7 sobre o pleurito torácico 6. Foram encontrados, pelo menos, sete padrões de organização do canal de Müller que variam entre a ausência completa da estrutura até a formação de um canal completo (que apresente tufo de cerdas, calha apendicular e canal pleural, concomitantemente). Ucides cordatus (Ucididae) apresentou modificações esqueletais singulares, bastante diferentes dos demais Ocypodoidea e também de Grapsoidea. As espécies que apresentam maior nível de terrestrialidade (família Gecarcinidae) foram as únicas que não apresentaram canal de Müller ou qualquer adaptação para captação de água do substrato. / The conquest of terrestrial environment by brachyuran crabs depends on the attainment and maintainability of water in the branchial chamber during the emersion period. One way to get environmental water is through tufts of hydrophilic setae, capable of picking up water from the soil by capillarity. It is known that these hydrophilic setae are attached to the Müllers opening and the collected water is admitted into the branchial chamber due to the pressure difference between the branchial chamber and the external environment, produced by the scaphognathite beating. However, the morphological modifications of the axial and appendicular skeleton to form the Müllers opening and the composition of the seta tuft are not known. In order to elucidate such gaps, the axial skeleton, the appendicular skeleton and the chaetotaxy of 22 species of semiterrestrial crabs belonging to superfamilies Grapsoidea (Grapsidae, Sesarmidae, Varunidae and Gecarcinidae) and Ocypodoidea (Ocypodidae and Ucididae) were studied. The study of the axial and appendicular skeleton revealed that the Müllers opening is actually a complex channel that may be comprised of three components: the pleural channel, the appendicular gutter and the setal tuft. The water is collected from the substrate by the setal tuft and carried through the appendicular gutter. Then it passes through the pleural channel to be finally admitted into the branchial chamber. The setal tuft is formed between the posterior face of the coxopodite of pereopod 3 and the anterior face of the coxopodite of pereopod 4. In Sesarmidae species, a second tuft also occurs between the coxopodites of pereopods 2 and 3. Representatives of the superfamilies Grapsoidea and Ocypoidea differ in the formation of Müllers channel. In Grapsoidea tuft, the setal insertion occurs only in the ventral portion of coxopodite of pereopod 4 while in Ocypodoidea, the insertion of these seta occurs both in the ventral and distal portions of coxopodite of pereopod 4. The types of seta which are present in setal tufts associated with the Müllers channel are the same found in other pereopods and in the edge of branchiostegal region (simple, paposes and paposerrate seta). The only exception is the constricted seta which is present exclusively in the setal tufts of Ocypodidae species. The appendicular gutter may be formed between the coxopodites of the 5/6 or 6/7 pereopods, in cylindrical or semi-cylindrical shape. The function of the appendicular gutter is associated with the water conduction between the setal tuft and the pleural channel, although there are cases in which the formation of Müllers channel happens without the presence of the appendicular gutter. Pleural channel can be opened or semitubular. They always occur between thoracic pleurites 6/7 and, in some species, between the thoracic pleurites 5 and 6 as well. The open pleural channel is formed by the spacing of two adjacent thoracic pleurites; the semitubular pleural channel is formed by the projection of pleurite 7 above pleurite 6. At least seven patterns of organization of the Müllers channel were found, ranging from the complete absence of the structure to the formation of a full channel (presenting setal tuft, appendicular gutter and pleural channel concurrently). Ucides cordatus (Ucididae) showed quite unique skeletal modifications, different from the others Ocypodoidea and also from the Grapsoidea. The species with the highest level of terrestriality (Gecarcinidae family) were the only ones who did not have Müllers channel or any adaptation to water abstraction from the substrate.

Die Funktionsweise des invertierten Aufbaus der Netzhaut im Wirbeltierauge ist ein altes Rätsel der Wissenschaft. Das beim Sehvorgang auf die Netzhaut einfallende Licht muss erst alle Netzhautschichten durchdringen, bevor es die Photorezeptorzellen erreicht, welche sich auf der lichtabgewandten Seite des Gewebes befinden. Die vorgelagerten Gewebsschichten enthalten zahlreiche lichtstreuende Bestandteile und müssten den Sehvorgang der Wirbeltiere theoretisch negativ beeinflussen. Diese Annahme steht jedoch im Widerspruch zu dem beeindruckenden Sehvermögen der meisten Wirbeltiere. Die Müllerschen Radialgliazellen stellen eine Lösung für diesen scheinbaren Widerspruch dar. Aufgrund der auffälligen morphologischen Struktur dieser Gliazellen, welche die gesamte Dicke der Netzhaut säulenförmig durchspannen, wurde die Hypothese aufgestellt, dass Müllerzellen nach dem Prinzip der Lichtleitung arbeiten und so das Licht zu den Photorezeptoren transportieren. Diese Theorie konnte jedoch bisher noch nicht bewiesen werden, da die bisherigen experimentellen Messmethoden auf der Basis von isolierten Müllerzellen ungeeignet sind, um diese Funktion im lebenden Gewebe nachzuweisen. Die vorliegende Arbeit beweist erstmalig, dass die Müllerschen Gliazellen als lebende Lichtleiter im Netzhautgewebe funktionieren. Um diese Aufgabe den Müllerzellen eindeutig zuzuordnen, wurde eine neuartige Methode entwickelt, welche gleichzeitig mehrere für den Nachweis unverzichtbare Parameter erfassen kann. Aufgrund einer fluoreszenzbasierten Visualisierung der Müllerzellen in der intakten Netzhaut konnte mit Hilfe eines auf Glasfaseroptik basierenden Aufbaus die Beleuchtung einzelner Müllerzellen erfolgen. Zeitgleich war es möglich, sowohl den Weg des Lichtes von der lichtzugewandten Seite bis zu den Photorezeptoren als auch die Transmission hinter dem Gewebe zu detektieren. Die Komplexität dieses Messverfahrens erlaubte eine detaillierte Charakterisierung des Einflusses der Müllerzelle auf die Streueigenschaften der verschiedenen retinalen Schichten sowie des sich ergebenden Lichtsignals an den Rezeptorzellen. Mittels eines speziellen Analyseverfahrens konnte umfassendes Datenmaterial erhoben und so die Müllerzelle eindeutig als Lichtleiter identifiziert werden. Darauf aufbauend wird in dieser Arbeit außerdem gezeigt, dass alle Müllerzellen gemeinsam und damit in ihrer Gesamtheit mittels ihrer Lichtleitfunktion das an den Photorezeptoren ankommende Lichtmuster beeinflussen, was zu einer verbesserten Bildqualität führt. Dies wird zusätzlich durch morphologische Untersuchungen gestützt, die zeigen, dass die für das Kontrastsehen verantwortlichen Zapfen-Photorezeptorzellen lokal hinter den Müllerzellen angeordnet sind. Demnach ist jeder Zapfen mit einem ihm vorgelagerten Lichtleiter ausgestattet. Zusammenfassend liefert diese Arbeit eine Erklärung, wie trotz des invertierten Aufbaus der Netzhaut die visuelle Information als Grundlage für das Sehen der Wirbeltiere erhalten bleibt.