No description available.

Les effets de la marijuana, un médicament utilisé par l’homme depuis des millénaires, sur le système visuel sont peu connus. Une meilleure connaissance de la distribution du système endocannabinoïde (eCB) de la rétine pourrait expliquer comment cette drogue affecte la vision. Cette étude vise à caractériser la distribution du récepteur cannabinoïde CB1 (CB1R) et de l’enzyme de dégradation FAAH (“fatty acid amide hydrolase”) des ligands du CB1R dans la rétine du singe Vert (Chlorocebus sabaeus). De plus, elle vise à déterminer quelles sous-populations cellulaires de la rétine expriment ces composantes. La plupart des études à ce jour ont été conduites surtout sur les rongeurs et peu de travaux ont été réalisés chez le singe. Notre étude vient donc combler cette carence. Par le biais de méthodes immunohistochimiques, nous avons investigué la localisation du CB1R et de l’enzyme FAAH à différentes excentricités rétiniennes, de la fovéa centralis vers la périphérie. Nos résultats, en accord avec notre hypothèse de travail, démontrent que CB1R et FAAH sont exprimés à travers toute la rétine mais avec, cependant, des différences notoires. Au niveau de la couche des photorécepteurs, CB1R est exprimé préférentiellement dans les cônes et ce patron d’expression suit la distribution des photorécepteurs centre-périphérie. De plus, CB1R se retrouve surtout dans les pédicules des cônes de la couche plexiforme externe. CB1R et FAAH sont abondants dans les cellules bipolaires tant au centre qu’en périphérie. Le soma et l’axone des cellules ganglionnaires expriment aussi CB1R et FAAH. Ces données suggèrent que le système eCB est présent à travers toute la rétine du primate et pourrait expliquer les perturbations visuelles entrainées par la marijuana, telles la photosensibilité et la vision des couleurs. / The effects of marijuana, a drug that has been used by men for millennia, on the visual system are poorly understood. A better understanding of the distribution of the endocannabinoid system in the retina will help us explain how this drug affects vision. This study aims at characterizing the distribution of the endocannabinoid receptor CB1 (CB1R) and the enzyme degrading CB1R ligands, fatty acid amide hydrolase (FAAH) throughout the Green monkey retina (Chlorocebus sabaeus). In addition, it seeks to determine which sub-population of neurons expresses CB1R and the degrading enzyme FAAH. Most data on the endocannabinoid system have been acquired in rodents and studies on monkeys are rather scarce. We attempted to fill this void by using immunohistochemical methods to locate CB1R and FAAH at various eccentricities of the monkey retina, from the center to the far periphery. Our results, in agreement with our hypothesis, demonstrate that CB1R and FAAH are expressed throughout the retina. At the level of the photoreceptors, CB1R is expressed preferentially in cones rather than in rods, and this expression pattern follows the photoreceptors distribution. In the outer plexiform layer, CB1R immunoreactivity is predominantly concentrated in the cone pedicles. Although foveal cones are the main expressers of both CB1R and FAAH, these are also found in rod bipolar cells. The ganglion cell axons strongly express the CB1 receptor and the enzyme FAAH. These data suggest that the presence of CB1R throughout the retina may be responsible for the visual effects commonly reported by cannabis users, such as the increase in photosensitivity and alterations in color discrimination.

The Nance-Horan syndrome gene (NHS) plays a role in lens, eye and brain development. To date, the function of NHS remains unclear. Recent evidence showed that p53 isoform, Δ113p53, inhibits abnormal cell growth during organogenesis. We show that NHS is expressed in the retinas of Danio rerio and Xenopus tropicalis during key stages of retinogenesis, and that knockdown of the gene resulted in a small eye phenotype in both species. Initially, knockdown of nhsb in zebrafish had no visible defects at 24hpf. But examination of the retina at 48hpf, we see a marked difference in size compared to control embryos. Cell proliferation is a major feature of the developing retina from 24 hpf to 48 hpf. Differentiation of neurons was delayed, while the total number of cells that makes up the volume of the retina was markedly reduced. Here we show that the small retina in nhsb knockdown embryos are due to p53-dependent cell cycle arrest with specific induction of p53 target gene, Δ113p53 and p21. Δ113p53 protects nhsb- knockdown cells from p53-mediated apoptosis. We hypothesize that nhsb overcomes a proliferation restriction in retina progenitor cells during retinogenesis, while knockdown of nhsb increases expression of Δ113p53 and p21, lengthening the cell cycle.

Vision provides a critical interface with the physical world. This work examines visual development and vision loss in mice to glean the influence of the retinal state on visual connections. I first assessed the impact of retinal activity on the eye-specific segregation of retinal afferents in the lateral geniculate nucleus (LGN) of young Gβ5 -/- mice. Gβ5 is the fifth member of the β subfamily of heterotrimeric G proteins. Gβ5 binds and stabilizes the R7 family of regulators of G-protein signaling (RGS), which accelerate Gi/o GTP hydrolysis. Gβ5 -/- mice, which lack R7RGS activity, have malformed synapses in the outer plexiform layer (OPL) and impaired OPL transmission. Altered spontaneous retinal activity in Gβ5-/- mice at P7, P12, P14, and P28 correlates with impaired eye-specific segregation of retinal afferents in the LGN at corresponding timepoints. However, Gβ5-/- mice exhibit a normal transition from cholinergic to glutamatergic drive that corresponds with a temporary recovery of refinement at P10. Thus the abnormal-normal-abnormal pattern of activity in the retina is coupled with abnormal-normal-abnormal segregation. This activity-segregation profile suggests activity may instruct early retinogeniculate development. nob mice, which also exhibit impaired OPL transmission, have aberrant retinal waves that align with loss of segregation. nobxGβ5-/- mice have similar levels of segregation as Gβ5-/- at P21, but activity only similar P14 nobxGβ5-/- and Gβ5-/- RGCs. This suggests that the critical period of eye-specific segregation closes shortly after P14 and that R7RGS activity is critically important to postnatal RGCs. Next, I investigated the aged visual system via the retinofugal projections of mice with retinal remodeling after photoreceptor degeneration (PD). ΔCT mice, with mild remodeling, and TG9N mice, with aggressive remodeling, retain gross anatomical and physiological connectivity in the presence of attenuated visual activity compounded by organic remodeling. However, the magnitude of pupillary light responses in PD mice was diminished. Reduced melanopsin signal in the retina, not downstream anomalies, explains this functional deficiency. These observations suggest that changes to eye-specific segregation are limited once projections are established, regardless of retinal activity or remodeling. These observations bode well for future retina-based treatments of vision loss.

Le Syndrome métabolique (SMet) traduit le développement de désordres glucidiques et lipidiques résultant d’une balance énergétique positive. Par ses caractéristiques, le SMet est un facteur de risque de développer un diabète de type 2 qui se caractérise dans ses formes pathologiques par des altérations vasculaires, en particulier au niveau de la rétine, créant ainsi une rétinopathie diabétique (RD). Fortement vascularisée et bien que présentant une barrière hémato-rétinienne qui limite l’entrée de composés sanguins, la rétine subit les variations métaboliques. Les conséquences du SMet dans la rétine sont peu étudiées, alors même qu’une prise en charge précoce pourrait diminuer leur importance. A cet égard, une alimentation à la fois riche en acides gras polyinsaturés (AGPI) à longue chaîne de type oméga 3, comme l’acide docosahexaénoïque (DHA) et l’acide eicosapentaénoïque (EPA) et pauvre en oméga 6 participerait à la prévention de l’insulinorésistance, une composante du SMet, et serait protectrice vis-à-vis des premiers stades de la dégénérescence maculaire liée à l’âge (DMLA) et du vieillissement de la rétine. La biodisponibilité des AGPI oméga 3 dans la rétine, est un paramètre à prendre en compte pour bénéficier de leurs effets protecteurs. Pourtant, ces données, selon la source de provenance des AGPI, sont peu accessibles et méritent d’être étudiées. Nous voulions d’abord évaluer l’effet d’un régime diabétogène sur le métabolisme glucidique et lipidique chez le rat pour, de manière concomitante, en étudier les conséquences fonctionnelles et structurales sur la rétine. Notre second objectif était de comparer l’intégration de plusieurs formulations à base de phospholipides ou triglycérides, portant EPA ou DHA, dans la rétine.Ainsi, des rats Brown Norway ont été nourris avec un régime composé de 60% de fructose et 10% de lipides saturés (HFHF). L’étude du métabolisme glucidique a révélé une hyperglycémie à jeun, une intolérance au glucose et une résistance à l’insuline dès 8 jours de régime. D’autre part, nos analyses n’ont pas révélé de dyslipidémie. Ainsi, compte tenu de la résistance de ces rats à développer de manière précoce des altérations d’un mécanisme clé du syndrome métabolique comme la dyslipidémie, nous avons réalisé une étude comparative entre rats Brown Norway (BN) et Wistar (W) soumis au régime HFHF. Cette étude a révélé que les rats W étaient plus sensibles aux dérégulations lipidiques. Toutefois, les rats W n’ont pas développé d’insulinorésistance, et présentaient une hyperglycémie à jeun plus tardive que les rats BN. En complément de ces données, les analyses fonctionnelles de la rétine des rats BN par électrorétinographie ont révélé une diminution de sensibilité des photorécepteurs de type cône, après 4 semaines de régime HFHF. De plis, nos résultats indiquent que le régime HFHF constitue un terrain favorable au développement néovasculaire dans la rétine, avec une exacerbation de l’activation des cellules de Müller.Dans l’objectif d’optimiser la forme d’apport en acides gras à effets protecteurs de la rétine, nous souhaitions comparer l’intégration du DHA dans la rétine apporté par différentes sources de lipides intégrées dans l’alimentation de rats Wistar. L’apport consistait principalement en EPA ou en DHA, soit sous forme de phospholipides, soit sous forme de triglycérides. Nos données mettent principalement en évidence un enrichissement de la couche des photorécepteurs dans une zone à proximité du nerf optique, ceci quelle que soit la formule lipidique considérée. Nos données quantitatives révèlent quant à elles une meilleure intégration du DHA, estérifié sur les phosphatidylcholines de la rétine lorsque l’EPA est apporté sous forme de phospholipides, et que le DHA est apporté par les phospholipides ou les triglycérides. L’ensemble des régimes permettent d’augmenter la teneur en AGPI à très longue chaîne dans la rétine. / Metabolic syndrome (MetS) results from carbohydrate and lipid disorders that originate from misbalanced energy metabolism. MetS is a risk factor for type 2 diabetes that, in pathophysiological conditions, is characterized by vascular alterations, particularly in the retina, creating the diabetic retinopathy (DR). Despite it presents a barrier limiting the input of blood factors, the retina is under metabolic variations. The consequences of MetS in the retina have not been characterized. MetS would be responsible for the inflammation and microvascular alterations in the retina and could participate to the development of age-related macular degeneration (AMD). A diet rich in omega-3 long chain polyunsaturated fatty acids (LC-PUFA) i.e. docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and low omega-6 fatty acid, should participate to the prevention of insulin resistance, a feature of MetS. Such diet would be protective against AMD, the leading cause of visual impairment after the age of 55 years in Western populations. Meanwhile, the bioavailability of omega-3 in the retina, is a parameter to consider to fully take advantages of their protective effects. Yet, data on the bioavailability of fatty acids from different origins are sparse and need to be studied.Our first goal was to associate metabolic and retinal disturbances in the context of MetS. For that purpose, we evaluated the impact of a pro diabetic diet on carbohydrate and lipid metabolism in the rat, and further analyzed the function and structure of the retina. Our second objective was to compare the efficacy of phospholipids and triglycerides to improve the incorporation of omega-3 LC-PUFA in the retina and others tissues in the rat.Brown Norway (BN) rats were fed with a 60% fructose and 10% saturated lipid diet (HFHF). The results revealed fasted hyperglycaemia, glucose intolerance and insulin resistance at 8 days and afterwards, without dyslipidaemia. Thus, considering the resistance of BN rats to develop dyslipidaemia, we performed a comparative study with BN and W rats by feeding them with HFHF. Our results showed that W rats were more sensitive to lipid deregulations. However, they did not develop insulin resistance, and developed hyperglycaemia later than BN. Regarding these data, functional analyses of retina by electroretinography was performed in BN. Electroretinograms revealed a loss of cone photoreceptor sensitivity after 4 weeks of HFHF diet without other functional dysfunction.In one independent group of BN rats, choroidal neovascularization was induced by rupture of Bruch’s membrane with impact lasers in eye fundus. Retinal angiography revealed that feeding HFHF diet during 4 weeks favoured neovascular development in the retina, and activated Müller cells. Then, we wanted to compare omega-3 LC-PUFA integration in the retina by feeding Wistar rats with 6 different lipid sources. The strength of this work was to use either phospholipids, triglycerides or a mix of both, that contained either EPA or DHA as the prominent omega-3 fatty acid. Our qualitative data revealed an increase of DHA in the retina, particularly in the photoreceptor layer, around the optic nerve, regardless lipid formula. Our quantitative data revealed a better integration of DHA, particularly DHA-containing phosphatidylcholine, in the retina, when EPA is provided esterified on phospholipids, and DHA is provided on both, phospholipids and triglycerides. All the supplemented diets allowed an increase in very long chain-PUFAs in the retina.

Un des obstacles majeurs de la recherche en neurosciences est la difficulté d’accéder de manière directe au fonctionnement du cerveau afin de comprendre les mécanismes biologiques à l’origine des dysfonctionnements cérébraux dans les troubles psychiatriques. En tant qu’extension anatomique et développementale du système nerveux central, la rétine pourrait permettre d’offrir un accès indirect aux fonctions neurologiques cérébrales. Ainsi, l’investigation de la fonction rétinienne apporte l’unique opportunité d’étudier de manière objective un réseau neuronal complexe présentant des similarités avec celui du cerveau. Le cannabis est une substance neurotoxique identifiée comme modulant la transmission synaptique cérébrale par l’intermédiaire du système cannabinoïde mais les mécanismes précis à l’origine de ces anomalies sont peu connus. La première partie de ce travail consiste à présenter les bases neurobiologiques et les hypothèses physiopathologiques justifiant l’étude de la fonction rétinienne chez les usagers de cannabis, en se basant sur la présence du système cannabinoïde dans la rétine et son implication dans la régulation de la libération synaptique de neurotransmetteurs. La seconde partie discute l’intérêt de l’étude de la fonction rétinienne dans la recherche en psychiatrie avec des méthodes électrophysiologiques. Enfin, la dernière partie présente les dysfonctions rétiniennes présentes chez les usagers de cannabis, après un usage aigu ou régulier, évaluées par les techniques électrophysiologiques comme l’électrorétinogramme. Toutes ces données renforcent la pertinence de la rétine comme site d’investigation du cerveau et ouvrent éventuellement la perspective au développement de marqueurs fonctionnels / One of major obstacles in neuroscience research is the difficulty of directly accessing the brain function to understand the biological mechanisms underlying brain dysfunctions in psychiatric disorders. As an anatomical and developmental extension of the central nervous system, the retina could afford to offer an indirect access to brain neurological functions. Investigating the retinal function provides the unique opportunity to study in an objective way a complex neuronal network which shares similar properties with the brain. Cannabis is a neurotoxic substance identified as modulating brain synaptic transmission through the cannabinoid system, but the precise mechanisms underpinning these anomalies are poorly understood. The first part of this work is dedicated to present the neurobiological basis and pathophysiological hypotheses justifying the study of retinal function in cannabis users and is based on the presence of the cannabinoid system in the retina and its involvement in the regulation of synaptic neurotransmission. The second part discusses the interest of the study of retinal function with electrophysiological methods in psychiatric research. The last part presents the retinal dysfunctions detected in cannabis users, after acute or regular use, and assessed by electrophysiological techniques such as electroretinogram. All these data reinforce the relevance of the retina as a site of brain investigation and possibly open the prospect for the development of functional markers

No description available.

Neurons are able to maintain membrane potential and synaptic integrity by an intricate equilibrium of membrane transporter proteins and ion channels. Two membrane proteins of particular importance in the vertebrate retina are the excitatory amino acid transporters (EAATs) which are responsible for the reuptake of glutamate into both glial and neuronal cells and the sodium potassium chloride cotransporters (NKCCs) that are responsible for the uptake of chloride ions into the cell. NKCCs are electro-neutral with the uptake of 2 Cl- coupled to an exchange of a potassium and Na+ ion into the cells. Therefore, there is little change of cell membrane potential in the action of NKCCs. In this study the localization and function of EAATs in the distal retina is investigated. Whole cell patch clamp recordings in lower vertebrate retina have demonstrated that EAAT2 is the main synaptic EAATs in rod photoreceptors and it is localized to the axon terminals. Furthermore, the action of the transporter seems to be modified by intracellular calcium concentration. There is also evidence that EAAT2 might be regulated by feedback from the neuron network by glycinergic and GABAergic mechanisms. The second half of this study investigates expression of NKCCs in the retina by western blot analysis and quantitative polymerase chain reaction. There are two forms of NKCCs, NKCC1 and NKCC2. NKCC1 is mostly expressed in the central nervous system and NKCC2 was thought to only be expressed in the kidneys. NKCC1 is responsible for the majority of chloride uptake into neuronal and epithelial cells and NKCC1 is expressed in the distal retina where photoreceptors synapse on second order horizontal and bipolar cells. This study found the expression of NKCC1 in the distal retina to be regulated by temporal light and dark adaptation. Light adaptation increased phosphorylated NKCC1 expression (the active form of the cotransporter). The increase in NKCC1 expression during light adaptation was modulated by dopamine. Specifically, a D1 receptor agonist increased phosphorylated NKCC1 expression. Dopamine is an essential chemical and receptor known for initiating light adaptation in retina. Finally, an NKCC1 knockout mouse model was examined and it revealed that both forms of NKCC are expressed in the vertebrate retina. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Made available in DSpace on 2015-04-14T13:56:31Z (GMT). No. of bitstreams: 1 458958.pdf: 7355419 bytes, checksum: 8a2fa20967c4240f1bb187644d3207a4 (MD5) Previous issue date: 2013-12-19 / Vision is one of the most important senses of man. Many diseases that affect the sense of vision are related to the retina. Some of these diseases specifically affecting the photoreceptors, light-sensitive cells that is the first stage of vision. The examinations of dark adaptation have motivated interest in the study of mechanisms of retinal diseases. This exam directly accesses the functions of the photoreceptors by noninvasive methods. The technique consists in measuring the time to recovery of sensitivity of the retina after exposing the retina to a controlled amount of light. The dark adaptometry equipment is used to monitor the response of these cells to a light stimulus and then reveal some deficiency in the operation. This work describes the procedures, calculations, measurements and verifications necessary for the calibration of an existing dark adaptometer. This equipment was developed in the Image Laboratory at PUCRS, led by Professor Dario Azevedo, Ph.D. from a modified fundus camera. This dark adaptometer is able to test localized regions of the retina, while visualizing the regions of interest, and therefore compensating for any eye movements. For calibration of dark adaptometer, various calculations based on literature review was conducted. After using instruments such as spectrometer, radiometer, and light meter luminometer dark adaptometer was calibrated. The operation of each block that makes up this instrument was checked. Measurements of illuminance values of the light stimulus, retinal luminance attenuation of dark adaptometer, attenuation imposed by optical fiber, was observed throughout the range of attenuation filters (0 dB to 60 dB), also checked the operation of the wheels were made and a shutter that filters are controlled by the motor steps. The dark adaptometer met all specifications, i.e., the values set in the calculations in this work has been achieved. / A vis?o ? um dos mais importantes sentidos do homem. Muitas doen?as que afetam o sentido da vis?o est?o relacionadas com a retina. Algumas dessas doen?as afetam especificamente os fotorreceptores, c?lulas sens?veis ? luz, que ? o primeiro est?gio da vis?o. Os exames de adapta??o ao escuro t?m motivado o interesse no estudo de mecanismos de doen?as de retina. Esse exame acessa diretamente as fun??es dos fotorreceptores por m?todos n?o invasivos. A t?cnica consiste, em medir o tempo de recupera??o da sensitividade da retina, depois de expor a retina a uma quantidade controlada de luz. Um equipamento de adaptometria ao escuro ? utilizado para monitorar a resposta destas c?lulas a um est?mulo luminoso e ent?o revelar alguma defici?ncia no funcionamento. Neste trabalho, est?o descritos os procedimentos, c?lculos, medidas e verifica??es necess?rias para a calibra??o de um adapt?metro de escuro j? existente. Este equipamento foi desenvolvido no Laborat?rio de Imagens da PUCRS, liderado pelo professor Dario Azevedo Ph.D. a partir de uma c?mera de fundus modificada. Este adapt?metro de escuro ? capaz de testar, de forma localizada, regi?es da retina permitindo, a crit?rio do examinador testar e mapear exclusivamente as regi?es que forem do seu interesse e compensar eventuais movimentos oculares. Para a calibra??o do adapt?metro de escuro, foi realizados diversos c?lculos com base na revis?o bibliogr?fica. Ap?s, utilizando instrumentos como espectrofot?metro, espectroradi?metro, lux?metro e luminanc?metro o adapt?metro de escuro foi calibrado. Foi verificado o funcionamento de cada bloco que comp?e este instrumento. Foram realizadas as medidas dos valores de ilumin?ncia do est?mulo luminoso, lumin?ncia retinal, atenua??es do adapt?metro de escuro, atenua??o impostas pela fibra ?ptica, foi verificado toda a faixa de atenua??o dos filtros (0 dB at? 60 dB), tamb?m verificado o funcionamento das rodas de filtros e do shutter que s?o comandados pelos motores de passos. O adapt?metro de escuro atendeu todas as especifica??es, ou seja, os valores definidos nos c?lculos neste trabalho foram atingidos.

Sun Qiang. / "December 1999." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (p. 119-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.