Purpose: To investigate species differences in the distribution and localization of alpha B-crystallin (ABC) in the normal retina and optic nerve head region, and to describe changes during outer and inner retina degeneration. Material and methods: Animals studied included mice, rats, cats, pigs, cows, and monkeys. Sections of the optic nerve and central retina were labeled with antibodies against ABC and glial fibrillary acidic protein (GFAP). Results: ABC was located in astrocytes and Muller cells with different intensities. During outer retina degeneration (dystrophic rat and Abyssinian cat), only late stages showed an increase in ABC in the retina and optic nerve head. Inner retina degeneration in the glaucoma mouse model showed no increase of ABC. In the monkey glaucoma model, only the innermost layer of the optic nerve head showed increased labeling for ABC. Conclusions: The distribution of ABC is species dependent and is (excluding the mouse) present in the nerve fiber layer of the retina and in the optic nerve head (localization of astrocytes). Chronic retinal degeneration does not necessarily lead to an over-expression of ABC. While in outer retinal degeneration induction was predominantly present in late stages, pressure-induced glaucoma led to a specific increase in ABC already in early stages indicating a local stress-response in this region.

Loss or partial loss of eye sight can have major effect on quality of person's life. One of the most common diseases, which causes loss or partial loss of eye sight are diabetic retinopathy and age releated macular degeneration. Both of these diseases can be prevented or mediated by early detection and proper treatment. The fundus camera, which is used to capture eye retina, has had major effect on increasing quality and speed of early detection. Images captured by fundus camera can be automatically analyzed in order to detect any possible signs of retina damage. This thesis proposes one possible way of automating this process. First part of this thesis describes eye, its diseases and capturing technology. Second part then proposes way of automating detection process and its implementation. Lastly, the results are evaluated.

Photoreceptors are of prime importance for humans, since vision is one of the most important senses for us. In our daily life, where nearly every action is dependent on visual input, an impairment or a loss of eyesight leads to severe disability. With a non-syndromic prevalence of 1:4000, retinitis pigmentosa, a collective term for a group of inherited retinal eye diseases, represents, together with age-related macula degeneration, one of the main causes for visual impairment and blindness in industrialized countries. The dominant reason for vision loss is, in both cases, the irreversible loss of photoreceptor cells located in the outer nuclear layer of the retina. To date, no effective treatment is available to preserve or regain visual function in affected patients. Recent promising strategies for new retinal therapeutical approaches focus on one hand on the development of gene therapies, where an introduced wild-type allele compensates a mutated gene, and on the other hand on cell therapies, where stem or photoreceptor precursor cells (PPCs) are transplanted to the sub-retinal space to replace degenerated host photoreceptors. The current study is subdivided into three parts, addressing the issue of non-reversible photoreceptor cell loss due to retinal degenerative diseases by investigating in the first two parts new qualitative as well as quantitative approaches in the field of retinal cell therapy, while in the third part an ocular gene therapeutical approach targeting prominin-1, a gene involved in retinal degenerative disorders, was investigated. Briefly, this study shows in the first part, a significant enhancement of the integration rate of PPCs in wild-type host retinas, achieved by pre-transplantational sorting, using the recently discovered PPC - specific cell surface marker CD73. This sets another step further towards retinal cell therapy by increasing the effectiveness of such treatment. Next to this quantitative approach, it is also shown that the quality of transplanted photoreceptor precursor cells is comparable to native photoreceptors by demonstrating, that an indispensable prerequisite of every photoreceptor cell, the outer segment, is developed by transplanted PPCs after proper integration. Importantly, transplanted PPCs develop native outer segments even when not integrated in the host tissue but located in the sub-retinal space, as it is predominantly observed after transplantation into severely degenerated retinas. These results substantiate the feasibility of cell therapeutical treatment of severely degenerated retinas. At the end of this part, it is demonstrated, that outer segments are not formed properly by PPCs transplanted to the vitreal side of the retina. This suggests an influence of signaling molecules, presumably secreted by retinal pigment epithelial cells into the sub-retinal space, on transplanted PPC final differentiation. Since intensive research is done to differentiate stem cells into PPCs for cell therapeutical transplantation, these results may contribute significantly to this research by demonstrating, that factors secreted by the retinal pigment epithelium might play a crucial role for successful stem cell to PPC differentiation. The last part of my work investigates a gene therapeutical approach to cure inherited retinal degenerative diseases. One gene, where reported mutations cause retinal degeneration in humans is prominin-1, a protein expressed at cell membrane evaginations in a variety of cell types. Interestingly, the prominin-1 knock-out mouse is characterized exclusively by disorganized photoreceptor outer segment formation and progressive retinal degeneration. Successful delivery of a wild-type form of mouse prominin-1 using adeno-associated viral vector transfer, into the photoreceptors of prominin-1 - deficient mice is demonstrated. The divergent results show on one hand a rescue of the thickness of the photoreceptor outer nuclear layer on a short time period (3 weeks post treatment), and on the other hand long-term data (8-10 weeks post treatment) suggests histologically as well as functionally a negative effect on treated photoreceptors. This might be due to effects caused by an over-expression of prominin-1 and will be investigated in future studies. In conclusion, distinct and important investigations were made which contribute significant puzzle pieces to new cell- as well as gene therapeutical approaches for the treatment of retinal degenerative disorders.

Das Vorkommen von über den Umgebungsdruck erhöhten Sauerstoffpartialdrucken in Geweben ist im Tierreich nur von der Schwimmblase und dem Auge von Knochenfischen bekannt. Die physiologischen Mechanismen dieser Sauerstoffkonzentrierung wurden an der Schwimmblase insbesondere des Aals intensiv untersucht, entsprechende Untersuchungen zu den Vorgängen im Auge der Knochenfische fehlen jedoch. In dieser Arbeit wurde daher eine Methode etabliert, mit der die Sauerstoffkonzentrierung im Auge der Knochenfische an isolierten Augen untersucht werden kann. 1. Das Gefäßsystem der Regenbogenforelle (Oncorhynchus mykiss, Walbaum 1792) wurde durch Gefäßausgüsse dargestellt. Das im Auge gelegene choroidale Rete mirabile wird über die Arteria ophthalmica, die gleichzeitig die efferente Pseudobranchienarterie darstellt, versorgt. Die Pseudobranchie selber empfängt das Blut aus der efferenten Arterie des ersten Kiemenbogens. Diese Gefäßtopologie, Versorgung der Pseudobranchie mit bereits im ersten Kiemenbogen oxygeniertem Blut und auschließliche Versorgung des choroidalen Rete mirabile mit Blut aus der Pseudobranchie, weist auf die Bedeutung der Pseudobranchie für die Prozesse im Auge hin. 2. Die Retina der Regenbogenforelle wurde mikroskopisch untersucht. Die einzelnen Schichten der Retina entsprechen denen anderer Wirbeltiere. Die Forellenretina ist mit 407 µm aber wesentlich dicker als z.B. die Retina von Mammaliern. Zusätzlich fehlt der Retina der Forelle die bei vielen Mammaliern vorhandene retinale Blutgefäßversorgung. Mit den der Retina am nächsten gelegenen Gefäßen in der Choroidea bestehen bei der Forelle wesentlich größere Diffusionsstrecken von den Blutgefäßen zum Ort des Sauerstoffverbrauchs in den Zellen der Retina als bei anderen Wirbeltieren. Dies wir durch den erhöhten Sauerstoffpartialdruck in den Choriokapillaren kompensiert. 3. Für die Messung des intraretinalen Sauerstoffpartialdrucks wurden im Rahmen dieser Arbeit Sauerstoffmikroelektroden inklusive der zur Betreibung der Elektroden notwendigen Elektronik entwickelt. Die Elektroden waren vom Recess-Typ: die reaktive Oberfläche schloss nicht mit dem Ende der Glaskapillare ab, sondern war unter Belassung eines Hohlraumes in der Elektrodenspitze (Recess) in das innere der Glaskapillare verlagert. Dadurch waren die Elektroden unempfindlich gegenüber Rühreffekten. Die Mikroelektroden hatten eine Spitzendurchmesser von < 10 µm und eine mittlere Empfindlichkeit von 172 fA Torr-1 O2. Die Linearität der Elektroden über eine Partialdruckbereich von 0 bis 760 Torr O2 war besser als r = 0,9998. 4. Zur Überprüfung des normale Sauerstoffpartialdrucks in der Retina wurden Regenbogenforellen betäubt und künstlich ventiliert. Die systemischen Parameter wie arterieller PO2-Wert, Blutdruck und Herzschlag entsprachen dabei im Mittel mit 99 Torr (arterieller PO2), 28 Torr (Blutdruck) und 1,23 Hz (Herzschlag) den Werten unbetäubter, freischwimmender Forellen. Lediglich der arterielle pH-Wert war mit 8,02 während der künstlichen Ventilation durch eine ungenügende Kompensation einer respiratorischen Alkalose leicht gegenüber dem normalen Wert von 7,9 erhöht. 5. Die Auswirkungen der Präparation des Auges zur Messung des intraretinalen Sauerstoffpartialdrucks auf den Augeninnendruck wurde überprüft. Der Augeninnendruck betrug 4,9 Torr. Die Einbringung der Sauerstoffmikroelektrode hatte keine Auswirkung auf den Augeninnendruck. Erst das Entfernen der Elektrode nach der Messung führte zu einer deutlichen Verringerung des Augeninnendrucks. 6. Zum ersten Mal wurde in der vorliegenden Arbeit die Durchblutungsrate des Auges eines Knochenfisches bestimmt. Aus präparatorischen Gründen wurde die Messung an der afferenten Pseudobranchienarterie durchgeführt. Der mittlere Blutfluss in dem Gefäß betrug 745 µl min-1 kg-1. Durch Verschluss des kontralateralen Gefäßes stieg der Fluss auf 135% des ursprünglichen Wertes, da jetzt durch das ipsilaterale Gefäß und über die zwischen den beiden Gefäßen bestehende Anastomose beide Augen durch das ipsilaterale Gefäß mit Blut versorgt wurden. 7. Die Funktion der Retina während der intraretinalen Sauerstoffmessung wurde durch Ableitung des Elektroretinogramms kontrolliert. Trotz der während der Versuche fortbestehenden Betäubung mit dem Betäubungsmittel MS222, welches sich negativ auf das Elektroretinogramm auswirken soll, konnten normale Elektroretinogramme aufgezeichnet werde. Die invasive Messung des intraretinalen PO2 wirkte sich nicht negativ auf die Funktionalität der Retina aus. 8. Der intraretinale Sauerstoffpartialdruck wurde an betäubten, künstlich ventilierten Forellen überprüft. Der mittlere maximale PO2 im Bereich der Bruch´schen Membran betrug 382 Torr. An der Innenseite der Retina wurde ein PO2 von 10 Torr gemessen. Der Bereich des O2-Partialdruckgradienten in der Retina, gemessen über den Vorschub der Sauerstoffmikroelektrode vom niedrigsten bis zum höchsten PO2, betrug 433 µm, ein Wert der gut mit der mikroskopisch bestimmten Dicke der Retina (407 µm) übereinstimmt. 9. Zur Untersuchung der Einflüsse von Blutparametern auf die Sauerstoffkonzentrierung im Auge der Forelle wurden isolierte Augen künstlich mit verschiedenen Erythrozytensuspensionen perfundiert. Dazu wurde zum einen eine Suspension von Forellenerythrozyten eingesetzt, bei der erst der Root-Effekt in Abhängigkeit vom pH-Wert der Suspension bestimmt wurde. Bei basischem pH-Werten war das Hämoglobin der Erythrozyten vollständig gesättigt. Bei einem pH-Wert von 7,68 war noch eine Sättigung von 90% vorhanden, die bis zu einem pH-Wert von 7,31 auf 50% abnahm. 10% Sättigung wurden bei einem pH-Wert von 6,94 erreicht. Für die Perfusion wurde die Suspension der Forellenerythrozyten mit einem pH-Wert von 7,48 eingesetzt. Bei diesem pH-Wert liegt die Sättigung bei ca. 82% und eine Änderung des pH hat in diesem Bereich eine deutliche Änderung der Sättigung zur Folge, was die Freisetzung von O2 von Hämoglobin erleichtert. Als alternative Perfusionslösung wurde eine Suspension von Humanerythrozyten eingesetzt. Humanhämoglobin weist keinen Root-Effekt auf, es kann also durch die im Auge der Knochenfische vorhandenen Mechanismen kein Sauerstoff freigesetzt werden. 10. Der mittlere intraretinale Sauerstoffpartialdruck isolierter Augen betrug bei Perfusion mit der Suspension von Forellenerythrozyten 99 Torr. Nach dem Wechsel auf die Suspension mit Humanerythrozyten fiel der intraretinale Sauerstoffpartialdruck sofort auf 30 Torr ab. Der Perfusionsdruck änderte sich bei dieser Umstellung nicht. Bei Perfusion mit Ringerlösung fiel der intraretinale PO2 auf 20 Torr, gleichzeitig fiel jetzt auch der Perfusionsdruck ab. 11. Eine Konzentrierung des Sauerstoffs konnte bei der künstlichen Perfusion isolierter Augen nicht nachgewiesen werden. Die Notwendigkeit des Root-Effekts für einen hohen Sauerstoffpartialdruck im Auge wird trotzdem deutlich, da bei Perfusion mit einer Suspension von Humanerythrozyten, die einen höheren Sauerstoffgehalt aufwies als die Suspension der Forellenerythrozyten, der intraretinale Sauerstoffpartialdruck deutlich geringer war. 12. Das Modell des isoliert perfundierten Auges ist zur physiologischen Untersuchung des choroidalen Rete mirabile und Sauerstoffkonzentrierung besser geeignet als in vivo - Experimente, da systemische Einflüsse vermieden und die Auswirkungen der Pseudobranchie auf die Blutchemie ausgeschaltet werden können. / Oxygen partial pressures (Po2) above ambient levels are found only in the swimbladder and the eye of teleost fish species. The mechanisms related to the involved oxygen concentration processes have been investigated to some detail in eel swimbladder, but little attention has been paid to analogous mechanisms of the teleost eye. This thesis has accordingly concentrated on developing a method promoting investigation of oxygen concentrating mechanisms in teleost eyes by application of an isolated perfused eye preparation. 1. The vascular supply of eye and pseudobranch in rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) was depicted by corrosion casts of the vascular system. The choroid rete mirabile is supplied with blood by the ophthalmic artery as the efferent blood vessel of the pseudobranch, with a small anastomosis to the contralateral vessel. The pseudobranch in turn is fed by the efferent artery of the first gill arch. This pattern of serial vascular connection suggests a role for the pseudobranch in the process of providing high oxygen tensions required for the high metabolic demand of the visual perception in the retina. 2. Eyes of various fish species were sectioned after paraffin embedding and examined microscopically. The organisation of teleost fish retinae is characterised by the same features and organisation well known from other vertebrates. However, the total thickness of 407 µm found for the retina of the rainbow is much larger than that observed in other animals such as mammals. The conditions of diffusive oxygen supply of retinal nerve cells is further hampered by the complete lack of intraretinal blood vessels commonly found in mammals. In trout, blood is supplied to only the choroid layer, leaving large diffusion distances to the retinal nerve cells to be spanned by oxygen partial pressures, elevated as compared to the bulk arterial system in the choroid capillaries. 3. Intraretinal oxygen partial pressure was determined in long-term anaesthetised specimens of Oncorhynchus mykiss, using specially developed oxygen microelectrodes and required electronic circuitry. Characteristic features of the electrodes include insensitivity of the signal to stirring, achieved by a recess of the reactive metal surface in a glass capillary, an average tip diameter of less than 10 µm and a characteristic sensitivity to oxygen of 172 fA Torr-1. The response of the electrodes to oxygen was linear over a range of partial pressures from 0 to 760 Torr O2 (r= 0,9998). 4. Normal oxygen partial pressures in trout retina were measured in long-term anaesthetised and artificially ventilated specimens of Oncorhynchus mykiss. In order to conduct the experiments under conditions as close as possible to normal homoiostasis, several systemic valuables were monitored continuously. During experimentation arterial Po2 averaged 99 Torr, mean blood pressure was 28 Torr and heart frequency was on the average 74 bpm, respectively, data in the range of values determined in unanesthetized, freely swimming trout. As the one exception, arterial pH (8,02) was slightly elevated during artificial ventilation as compared to control values (7,89), a shift induced by an inadequately high rate of artificial ventilation. 5. The impact of insertion of electrodes required for intraretinal Po2 measurement into the eye was found to have little effect. The intraocular pressure remained unaffected by opening the eye by puncture with leading cannula and inserted micro-Po2-electrode. The intraocular pressure fell only after removing the electrode after completion of the experiment. 6. Normal function of the retina during experimentation in vivo was checked by repeatedly measuring electroretinograms provoked by light flashes under dark ambient conditions. Although extended anaesthesia with MS222 is expected to affect the electroretinogram in fish, there was no indication of abnormal or reduced electroretinograms during experimentation. Also puncture of the eye with insertion of electrodes did not affect the electroretinogram. 7. Intraretinal Po2 was measured in anaesthetised and artificially ventilated trout. Oxygen profiles were recorded during advancement of the electrode tip though the retina, from the lowest Po2 at the inner surface with about 10 Torr to the highest Po2 in the region of Bruch´s membrane with about 382 Torr, travelling a total distance of 433 µm. This distance closely corresponds to the thickness of the retina measured by microscopic sectioning. 8. Blood flow to the eye as an important parameter for the establishment of an isolated eye preparation was measured in the afferent artery of the pseudobranch. Due to the anatomical situation this represents the closest possible approximation to measurement of flow in the ophthalmic artery. The blood flow was estimated by ultrasonic Doppler techniques with in situ calibration to be 216 µl min-1. Occlusion of the contralateral vessel resulted in an increase of the blood flow in the ipsilateral vessel to 135% of the original as a result of flow through the small anastomosis between the two ophthalmic arteries. This estimate is the first performed for blood flow to the eye of a fish. 9. An isolated eye preparation was used to investigate the influence of specific blood parameters on oxygen concentrating processes in the eye of Oncorhynchus mykiss. Eyes were perfused with suspensions of trout erythrocytes, human erythrocytes and Ringer´s solution. The Root Effect of trout haemoglobin was confirmed in suspension of erythrocytes. The haemoglobin was fully saturated at pH 8.45, still 90% saturated at 7.68, 50% at 7.31 and 10% at pH 6.94. In order to provide optimal starting conditions for the release of oxygen by relatively small changes in pH, pH 7.48 (resulting in 82 % saturation) was chosen for the perfusion of isolated eyes. As a control perfusion, suspensions of human erythrocytes provided a perfusate lacking any Root effect, thus not supporting the oxygen concentrating processes in fish eyes. 10. Perfusion of isolated trout eyes with pH 7.48 trout erythrocyte suspension resulted in an average intraretinal Po2 of 99 Torr, whereas perfusion with human erythrocytes resulted in an immediate decrease of Po2 to (of) 30 Torr, with a further drop to 20 Torr during perfusion with Ringer´s solution. Changes in perfusion between erythrocyte suspensions were performed without any changes in perfusion pressure, but the switch to control perfusion with Ringer´s solution exhibited a drop in perfusion pressure due to the reduced viscosity of the medium. 11. Although perfusion of isolated eyes did not exhibit Po2 above ambient values, the effect of oxygen concentrating processes were clearly indicated by comparison with Root effect-lacking human erythrocyte perfusate (Po2´s of 99 vs. 30 Torr, respectively). 12. It is concluded that studies of oxygen concentrating mechanisms are to be performed preferably on isolated eye preparations. For closer analysis of the involved mechanisms this preparation allows for isolated control of individual parameter of the perfusate. In particular, uncontrolled effects of the pseudobranch on the perfusate can be eliminated.

A goal in human embryonic stem cell (hESC) research is the faithful differentiation to given cell types such as neural lineages. During embryonic development, a basement membrane surrounds the neural plate that forms a tight, apico-basolaterally polarized epithelium before closing to form a neural tube with a single lumen. Here we show that the three-dimensional epithelial cyst culture of hESCs in Matrigel combined with neural induction results in a quantitative conversion into neuroepithelial cysts containing a single lumen. Cells attain a defined neuroepithelial identity by 5 days. The neuroepithelial cysts naturally generate retinal epithelium, in part due to IGF-1/insulin signaling. We demonstrate the utility of this epithelial culture approach by achieving a quantitative production of retinal pigment epithelial (RPE) cells from hESCs within 30 days. Direct transplantation of this RPE into a rat model of retinal degeneration without any selection or expansion of the cells results in the formation of a donor-derived RPE monolayer that rescues photoreceptor cells. The cyst method for neuroepithelial differentiation of pluripotent stem cells is not only of importance for RPE generation but will also be relevant to the production of other neuronal cell types and for reconstituting complex patterning events from three-dimensional neuroepithelia.

Les nétrines sont une petite famille de protéines de guidage axonal qui peuvent attirer des axones ou en repousser d’autres lors du développement neuronal. Lors du développement de la rétine, les axones des cellules ganglionnaires de la rétine (CGR) sont attirés vers une source de nétrines au niveau du disque optique leur permettant de quitter la rétine et de former le nerf optique. Afin de pouvoir caractériser le rôle des nétrines dans le système visuel adulte, nous avons investigué l’expression des nétrines et leurs récepteurs dans la rétine de souris adulte. Alors qu’aucune expression de la nétrine-1 n’a été détectée dans la rétine adulte, l’expression de la nétrine-3 a été abondamment détectée au niveau des CGR et des cellules amacrines. Nous démontrons aussi que les récepteurs des nétrines sont exprimés dans la rétine adulte. Alors que DCC semble être confiné au niveau des axones des CGR, néogénine est retrouvé dans les dendrites des CGR et des cellules horizontales. Quant aux protéines de la famille des récepteurs homologues à UNC-5, UNC5B a été détecté dans les somas des CGR et UNC5C dans les cellules de Müller. La découverte que nétrine-3 et ses récepteurs sont abondamment exprimés dans plusieurs types cellulaires de la rétine adulte leur suggère un rôle dans le fonctionnement du système visuel mature. / The netrins are a small family of axonal guidance proteins that can attract or repulse growing axons during neural development. During development of the retina, retinal ganglion cells (RGCs) axons are attracted by a netrin source at the optic disc that permits them to exit the retina and form the optic nerve. To characterise the role of netrins in the adult visual system, we investigated the expression of netrins and their receptors in the adult mouse retina. While expression of netrin-1 has not been detected in the adult retina, netrin- 3 has been abundantly found in RGCs amacrine cells. We also demonstrate that netrin receptors are expressed in the adult retina. DCC was found to be restricted in RGCs axons and neogenin in dendrites of RGCs and horizontal cells. UNC5B proteins were detected at RGC soma and UNC5C proteins in the Müller cells. The finding that netrin-3 and its receptors are abundantly expressed in many cell types of the adult retina suggests a funtional role for them in the mature visual system.

Les hallucinations visuelles (HV) sont un symptôme psychotique commun retrouvé de manière transdiagnostique dans les troubles de la vision, les troubles neurologiques et les troubles psychiatriques. Les différents modèles cognitifs des HV s’accordent sur la présence d’une perturbation du traitement de l’information visuelle bottom-up et des processus tardifs top-down pour expliquer la survenue des HV. Dans un première partie de notre travail, nous avons étudié les caractéristiques communes entre les pathologies caractérisées par la présence d’HV et avons constaté que toutes présentent des anomalies structurales ou fonctionnelles de la rétine mais que peu d’études ont exploré le lien entre anomalies fonctionnelles de la rétine et HV. Nous avons ensuite étudié le fonctionnement de la rétine chez des patients souffrant de schizophrénie présentant ou non des HV. Nos résultats ont montré la présence d’anomalies fonctionnelles touchant le système des photorécepteurs et les cellules ganglionnaires de la rétine chez les patients souffrant de schizophrénie et des anomalies fonctionnelles du système des bâtonnets spécifiquement chez les patients présentant des HV. Les anomalies du traitement sensoriel sont une condition nécessaire mais insuffisante pour expliquer la survenue des HV. Ainsi nous avons exploré l’influence du traitement des émotions dans les HV, par une tâche d’amorçage émotionnel sur le traitement de stimuli ambigus chez des sujets sains prônes aux hallucinations et des patients souffrant de schizophrénie. Les premiers résultats intermédiaires présentés montrent en partie que la manipulation d'une amorce émotionnelle pourrait influencer la perception de stimuli ambigus chez les sujets sains prônes aux hallucinations. Ces arguments sont à confirmer par un nouveau protocole de recherche à adapter. Nos résultats nous permettent de discuter l’adaptation d’un modèle des HV dans la schizophrénie. / Visual hallucinations (VH) are a common psychotic symptom present in eye disease, neurological disorders and psychiatric disorders. Cognitive models of VH postulate the disruption of both bottom-up visual information processing and late top-down processes to explain the emergence of VH. In the first part of our work, we have reviewed the common characteristics between pathologies characterized by VH. We have found that structural or functional abnormalities of the retina were systematically present, but few studies have explored the link between these abnormalities and VH. Hence, we have explored the retinal functions in schizophrenia patients with or without VH. We have found photoreceptors and retinal ganglion cells abnormalities in patients with schizophrenia and abnormalities of the rod system specifically in patients with VH. Abnormalities of sensory processing are a necessary but insufficient condition to explain the occurrence of VH. Thus, we have explored the influence of emotion processing in healthy hallucinations prone subjects and schizophrenia patients in an emotional priming task requiring the treatment of ambiguous stimuli. We expose intermediate results which show that the manipulation of an emotional primer can influence the perception of ambiguous stimuli in healthy hallucinations prone subjects. These results need replications in a new research protocol. Our results allow us to discuss the adaptation of a model of VH in schizophrenia.

A presente dissertação aborda o processo de identificação por biometria das estruturas oculares, analisando suas bases biológicas e tecnológicas e sua aplicabilidade e confiabilidade para utilização jurídica. Está dividida em três partes. Na primeira, são analisados aspectos do conceito de identidade em suas diversas acepções e do processo de identificação médico legal por meio da utilização de diferentes métodos. Na segunda, passa-se a estudar a biometria da íris e da retina, abordando suas bases biológicas e tecnológicas. Na terceira e última parte, estuda-se a aplicabilidade e confiabilidade da biometria ocular para finalidades jurídicas, como método de perícia da identidade. / The purpose of this work is to study the identification process by ocular biometrics, from its biological and technological basis to its forensic and legal system applications. It is divided into three sections. The first section discusses the concept of identity and the identification methods used by forensic professionals. The second section discusses the ocular biometrics methods using iris and retinal traits, emphasizing their biological as well as their technological basis. The third and last section discusses the reliability and applicability of these biometrics modalities as identification methods in legal and forensic issues.

Recentes estudos sugerem a existência de sinapses elétricas mediadas por junções gap entre fotorreceptores na retina de vertebrados. Neste trabalho, descrevemos um modelo computacional dos circuitos primário e secundário mediados pelos bastonetes da retina de vertebrados. O modelo é composto pelas seguintes populações de células: bastonetes, cones, células bipolares dos bastonetes, células bipolares dos cones, células amácrinas do tipo AII e células ganglionares. As células do modelo estão acopladas entre si por sinapses químicas e elétricas segundo padrões realísticos de convergência e divergência. As sinapses elétricas ocorrem entre os bastonetes, entre os bastonetes e os cones, entre as células amácrinas AII e entre as células bipolares dos cones e a células amácrinas AII. O modelo assume que um estímulo luminoso de baixa intensidade, simulando condições escotópicas, atinge todos os bastonetes da camada receptora, porém menos da metade deles é excitada. A resposta dos bastonetes excitados é controlada por uma fotocorrente cuja amplitude pode ser alterada para simular estímulos de diferentes intensidades dentro da faixa escotópica. O modelo é utilizado para investigar os efeitos dos diferentes graus de acoplamento elétrico entre as células receptoras e entre as células amácrinas AII, além do efeito de diferentes valores de condutância do canal Ih ativado pela hiperpolarização nos bastonetes, sobre a faixa dinâmica da retina. Os resultados das simulações mostram que, para valores realísticos da condutância do canal Ih, a faixa dinâmica medida na camada receptora é maximizada para o índice de conectividade crítico para que haja percolação de ligação. No entanto, quando a faixa dinâmica é medida para as células bipolares ou ganglionares o valor máximo é obtido para um índice de conectividade subcrítico. Este resultado é conseqüência da alta convergência de sinapses químicas entre os bastonetes e células bipolares. / Recent studies suggest the existence of electrical synapses (gap junctions) connecting photoreceptors in the vertebrate retina. In this work we describe a computer model of the primary and secondary rod pathways in the vertebrate retina. The model is composed of the following cell populations: rods, cones, rod bipolar cells, cone bipolar cells, AII amacrine cells and ganglion cells. Cells of the model are connected via chemical as well as electrical synapses according to realistic convergence and divergence factors. There are electrical synapses between rods, rods and cones, AII amacrine cells, and cone bipolar cells and AII amacrine cells. The model assumes that low intensity stimuli simulating scotopic conditions reach all rods in the receptor array but less than half of them are excited. The excited rods response is controlled by a photocurrent waveform whose amplitude can be manipulated to simulate stimuli of different intensities within the scotopic range. The model is used to investigate the effects of different degrees of coupling among photoreceptors and among AII amacrine cells, as well as values of rod hyperpolarization activated current Ih on the dynamic range of the retina. Results show that for realistic values of Ih conductance the dynamic range of the rod array is maximized at the critical connectivity degree for bond percolation. However, the dynamic range of the rod bipolar and ganglion cells is maximized for a photoreceptor connectivity degree below the critical value. The latter result is a consequence of the high convergence of chemical synapses from rods to rod bipolar cells.

Diabetic retinopathy is an ischemic retinal neovascular disease causing vision loss among adults. The studies presented involve the design and testing of a gene therapy vector to inhibit retinal revascularization, similar to that found in diabetic retinopathy. Gene therapy has proven to be an effective method to introduce therapeutic proteins to treat retinal diseases. Targeting a specific cell type and expression of therapeutic proteins according to the tissue microenvironment should have an advantage over traditional gene therapy by avoiding unwanted transgene expression. Hypoxia plays a significant role in the pathophysiology of many retinal ischemic diseases. Retinal Mèuller cells provide structural and functional support to retinal neurons, as well as playing a significant role in retinal neovascularization. Targeting Mèuller cells may be an effective strategy to prevent retinal neovascularization under pathological conditions. ... The hypoxia regulated, glial specific vector successfully reduced the abnormal neovascularization in the periphery by 93% and reduced the central vasobliterated area by 90%. A substantial amount of exogenous endostatin was produced in the retinas of P17 OIR mice. A significant increase in human endostatin protein and reduced vascular endothelial growth factor (VEGF) were identified by Western blot and ELISA, respectively. These findings suggest hypoxia-regulated, glial cell-specific scAAV mediated gene expression may be useful to prevent blindness found in devastating retinal diseases involving neovascularization. / by Manas Ranjan Biswal. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.