Living elasmobranchs occupy every major aquatic ecosystem throughout the world (Compagno 2003; Compagno et al. 2005). Sensory ecology can be a good determinant in comprehending the processes occurring between an organism and its natural environment (Weissburg and Browman 2005). By utilizing ecophysiological tools, insight into the adaptive responses of the sensory systems to their ever-changing ecological niche can help explain behavioral and life history characteristics (Hueter 1991; Litherland 2009). Aquatic animals show structural and physiological adaptations in their visual sense specific to the ecological requirements of their habitat (Hart et al. 2004), implying that vision is an important modality. The visual system of the smooth dogfish (Mustelus canis, family Triakidae) was examined using corneal electrophysiological methods to determine the visual spectral range, irradiance sensitivity, and speed of vision (flicker fusion frequency, FFF). The smooth dogfish, a shallow water bottom feeder inhabiting inshore waters along the eastern United States, was found to be extremely sensitive to dim light (-3.1- 0.1 log light intensity), and have a slow FFF (13 Hz), thus being well adapted to the scotopic conditions of the turbid coastal inshore waters. This prompted a second set of experiments focusing on the chromatic adaptations of the photoreceptor cells and retina function following light adaptation. Light adaptation increased the photopic threshold by 2.0 log light units of intensity (LLI). However, the temporal resolution was not dramatically increased (to 17 Hz), indicating that the retinal integration time is very slow for this species under all circumstances. The spectral sensitivity peak for M. canis (470 nm) was found to be significantly blue-shifted in comparison to other members of the Triakidae family (Crescitelli et al. 1995; Sillman et al. 1996). Smooth dogfish appear to forgo high spatial and temporal resolution for the enhancement of photon capture. The sandbar shark inhabits the same inshore estuaries during the summer months but has a visual system with a higher temporal resolution (FFF, 54 Hz) and a brighter photopic threshold (1.2 LLI-50% max) (Litherland 2009). Furthermore, other elasmobranch or telelost species inhabiting similar photic environments also exhibit faster temporal resolution; little skate (FFF, 30 Hz), weakfish (FFF, 40 Hz), red drum (FFF, 50 Hz), spotted sea trout (FFF, 60 Hz), and Atlantic croaker (FFF, 58 Hz) (Horodysky et al. 2008; McComb et al. 2010). Coastal seas tend to contain more dissolved organics and particulates than the clear oceanic waters of the epipelagic and pelagic zones (McFarland 1986), therefore the retina of smooth dogfish has adapted to be extremely sensitive to dim light, has a long integration time, a low flicker fusion frequency and temporal resolution, and retinal cells that are able to adjust to changing light conditions. All of these factors contribute to the visual system to provide optimal visual ability to enable smooth dogfish to accurately exploit its surroundings.

Le traitement de l’épilepsie chez le jeune enfant représente un enjeu majeur pour le développement de ce dernier. Chez la grande majorité des enfants atteints de spasmes infantiles et chez plusieurs atteints de crises partielles complexes réfractaires, le vigabatrin (VGB) représente un traitement incontournable. Cette médication, ayant démontré un haut taux d’efficacité chez cette population, semble toutefois mener à une atteinte du champ visuel périphérique souvent asymptomatique. L’évaluation clinique des champs visuels avec la périmétrie chez les patients de moins de neuf ans d’âge développemental est toutefois très difficile, voire impossible. Les études électrophysiologiques classiques menées auprès de la population épileptique pédiatrique suggèrent l’atteinte des structures liées aux cônes de la rétine. Les protocoles standards ne sont toutefois pas spécifiques aux champs visuels et les déficits soulignés ne concordent pas avec l’atteinte périphérique observée. Cette thèse vise donc à élaborer une tâche adaptée à l’évaluation des champs visuels chez les enfants en utilisant un protocole objectif, rapide et spécifique aux champs visuels à partir des potentiels évoqués visuels (PEVs) et à évaluer, à l’aide de cette méthode, les effets neurotoxiques à long terme du VGB chez des enfants épileptiques exposés en bas âge. La validation de la méthode est présentée dans le premier article. La stimulation est constituée de deux cercles concentriques faits de damiers à renversement de phase alternant à différentes fréquences temporelles. La passation de la tâche chez l’adulte permet de constater qu’une seule électrode corticale (Oz) est nécessaire à l’enregistrement simultané des réponses du champ visuel central et périphérique et qu’il est possible de recueillir les réponses électrophysiologiques très rapidement grâces l’utilisation de l’état-stationnaire (steady-state). La comparaison des données d’enfants et d’adultes normaux permet de constater que les réponses recueillies au sein des deux régions visuelles ne dépendent ni de l’âge ni du sexe. Les réponses centrales sont aussi corrélées à l’acuité visuelle. De plus, la validité de cette méthode est corroborée auprès d’adolescents ayant reçu un diagnostic clinique d’un déficit visuel central ou périphérique. En somme, la méthode validée permet d’évaluer adéquatement les champs visuels corticaux central et périphérique simultanément et rapidement, tant chez les adultes que chez les enfants. Le second article de cette thèse porte sur l’évaluation des champs visuels, grâce à la méthode préalablement validée, d’enfants épileptiques exposés au VGB en jeune âge en comparaison avec des enfants épileptiques exposés à d’autres antiépileptiques et à des enfants neurologiquement sains. La méthode a été bonifiée grâce à la variation du contraste et à l’enregistrement simultané de la réponse rétinienne. On trouve que la réponse corticale centrale est diminuée à haut et à moyen contrastes chez les enfants exposés au VGB et à haut contraste chez les enfants exposés à d’autres antiépileptiques. Le gain de contraste est altéré au sein des deux groupes d’enfants épileptiques. Par contre, l’absence de différences entre les deux groupes neurologiquement atteints ne permet pas de faire la distinction entre l’effet de la médication et celui de la maladie. De plus, la réponse rétinienne périphérique est atteinte chez les enfants épileptiques exposés au Sabril® en comparaison avec les enfants neurologiquement sains. La réponse rétinienne périphérique semble liée à la durée d’exposition à la médication. Ces résultats corroborent ceux rapportés dans la littérature. En somme, les résultats de cette thèse offrent une méthode complémentaire, rapide, fiable, objective à celles connues pour l’évaluation des champs visuels chez les enfants. Ils apportent aussi un éclairage nouveau sur les impacts à long terme possibles chez les enfants exposés au VGB dans la petite enfance. / Epilepsy control is a major issue for the normal development in children. For the vast majority of children with infantile spasms and for some with refractory complex partial seizures, vigabatrin (VGB) represents the main treatment. VGB, which have shown high efficiency rate in this population, may, however, induce a peripheral visual field deficit, often asymptomatic. Clinical visual field assessment with perimetry is practically impossible in patients less than nine years of developmental age. Electrophysiological studies in epileptic children suggest an impact on the retinal structures related to the cones. However, standard protocols are not field-specific and the deficits reported in the literature are not coherent with the peripheral deficit observed. Thus, this thesis aims to develop a fast and efficient electrophysiological protocol to examine the visual field’s integrity, which would be useful in pediatric testing and to assess the visual field long-term effects of the VGB in school-aged epileptic children exposed early in life. The first article concerns the method’s validation. The stimulation is made of two high-contrast radial checks reversing at two different temporal frequencies. Adult testing reveals that only one electrode (Oz) is needed to record simultaneously both central and peripheral visual fields and that steady-state use allows fast gathering of both electrophysiological responses. No effect of age or sex was found in the comparison of adult and child’ responses. Moreover, the visual acuity, as calculated by the binocular visual acuity index, was related to the central signal when comparing healthy participants with central visual impaired adolescents. Our method presents several advantages in evaluating visual fields integrity, as it is fast, reliable and efficient, and applicable in children. The aim of the second article of the thesis is the assessment of the long term visual effect on the visual field in children exposed to VGB in infancy in comparison to epileptic children exposed to other antiepileptics and with healthy children using the previously validated electrophysiology method with the addition of contrast variation and simultaneous recording of electroretinograms. Results reveal a cortical central deficit at high and mid-range contrast in VGB exposed-children and at high contrast in other antiepileptic exposed group. The contrast gain is also affected in both epileptic groups. The absence of difference between both epileptic groups does not allow distinguishing the impact of medication and/or seizure disorder. The peripheral retinal response is also altered in the VGB-exposed group in comparison to the healthy group. The peripheral retinal response is related to the exposition duration. This result concurs with previous studies in the literature. Finally, the results of the thesis offer an objective, fast, efficient and alternative method to assess visual fields in children. They also bring a new point of view on the likely long term impacts of the VGB in children exposed in infancy.

Le cannabis produit de nombreux effets psychologiques et physiologiques sur le corps humain. Les molécules contenues dans cette plante, désignées comme « phytocannabinoïdes », activent un système endogène qu’on appelle le système endocannabinoïde (eCB). Les effets de la consommation de cannabis sur la vision ont déjà été décrits sans cependant de formulation sur les mécanismes sous-jacents. Ces résultats comportementaux suggèrent, malgré tout, la présence de ce système eCB dans le système visuel, et particulièrement dans la rétine. Cette thèse vise donc à caractériser l’expression, la localisation et le rôle du système eCB dans la rétine du singe vervet, une espèce animale ayant un système visuel semblable à celui de l’humain. Nous avons mis au point un protocole expérimental d’immunohistochimie décrit dans l’article apparaissant dans l’Annexe I que nous avons utilisé pour répondre à notre objectif principal. Dans une première série de quatre articles, nous avons ainsi caractérisé l’expression et la localisation de deux récepteurs eCBs reconnus, les récepteurs cannabinoïdes de type 1 (CB1R) et de type 2 (CB2R), et d’un 3e présumé récepteur aux cannabinoïdes, le récepteur GPR55. Dans l’article 1, nous avons démontré que CB1R et une enzyme clé de ce système, la fatty acid amide hydrolase (FAAH), sont exprimés dans les parties centrale et périphérique de la rétine, et abondamment présents dans la fovéa, une région où l’acuité visuelle est maximale. Dans l’article 2, nous avons localisé le CB2R dans des cellules gliales de la rétine : les cellules de Müller et nous avons proposé un modèle sur l’action de cette protéine dans la fonction rétinienne faisant appel à une cascade chimique impliquant les canaux potassiques. Dans l’article 3, nous avons observé le GPR55 exclusivement dans les bâtonnets qui sont responsables de la vision scotopique et nous avons soumis un deuxième modèle de fonctionnement de ce récepteur par le biais d'une modulation des canaux calciques et sodiques des bâtonnets. Vu que ces 3 récepteurs se retrouvent dans des cellules distinctes, nous avons suggéré leur rôle primordial dans l’analyse de l’information visuelle au niveau rétinien. Dans l’article 4, nous avons effectué une analyse comparative de l’expression du système eCB dans la rétine de souris, de toupayes (petits mammifères insectivores qui sont sont considérés comme l’étape intermédiaire entre les rongeurs et les primates) et de deux espèces de singe (le vervet et le rhésus). Ces résultats nous ont menés à présenter une hypothèse évolutionniste quant à l’apparition et à la fonction précise de ces récepteurs. Dans les articles subséquents, nous avons confirmé notre hypothèse sur le rôle spécifique de ces trois récepteurs par l’utilisation de l’électrorétinographie (ERG) après injection intravitréenne d’agonistes et d’antagonistes de ces récepteurs. Nous avons conclu sur leur influence indéniable dans le processus visuel rétinien chez le primate. Dans l’article 5, nous avons établi le protocole d’enregistrement ERG normalisé sur le singe vervet, et nous avons produit un atlas d’ondes ERG spécifique à cette espèce, selon les règles de l’International Society for Clinical Electrophysiology of Vision (ISCEV). Les patrons électrorétinographiques se sont avérés semblables à ceux de l’humain et ont confirmé la similarité entre ces deux espèces. Dans l’article 6, nous avons démontré que le blocage de CB1R ou CB2R entraine une modification de l’électrorétinogramme, tant au niveau photopique que scotopique, ce qui supporte l’implication de ces récepteurs dans la modulation des ondes de l’ERG. Finalement, dans l’article 7, nous avons confirmé le modèle neurochimique proposé dans l’article 3 pour expliquer le rôle fonctionnel de GPR55, en montrant que l’activation ou le blocage de ce récepteur, respectivement par un agoniste (lysophosphatidylglucoside, LPG) ou un antagoniste (CID16020046), entraine soit une augmentation ou une baisse significative de l’ERG scotopique seulement. Ces données, prises ensemble, démontrent que les récepteurs CB1R, CB2R et GPR55 sont exprimés dans des types cellulaires bien distincts de la rétine du singe et ont chacun un rôle spécifique. L’importance de notre travail se manifeste aussi par des applications cliniques en permettant le développement de cibles pharmacologiques potentielles dans le traitement des maladies de la rétine. / Cannabis produces a range of psychological and physiological effects on the human body. Cannabinoids are the chemical compounds found in cannabis that activate an endogenous system, termed the endocannabinoid (eCB) system. Reports made in the 1970s have noted that cannabis consumption affects vision. It is therefore suggested that the eCB system is present in the visual system, particularly in the retina. This thesis aims at characterizing the expression, localization, and role of the eCB system in the vervet monkey retina. This animal model has a similar visual system as humans. Using immunohistochemistry methods presented in the article of Annexe I, we have established an experimental protocol to answer our goal. In the first series of four articles, we have characterized the expression and localization of the cannabinoid receptor 1 (CB1R), cannabinoid receptor 2 (CB2R), and the putative cannabinoid receptor GPR55. In Article 1, we have demonstrated that CB1R and a key enzyme of this system, FAAH (fatty acid amide hydrolase), are expressed in the central and peripheral retina, but heavily present in the fovea, the retinal region responsible for high acuity vision. In Article 2, we have localized CB2R in the glial Müller cells and hypothesized a possible mechanism of action of CB2R involving potassium buffering. In Article 3, we found that GPR55 is exclusively expressed in rods and have proposed its role through the modulation of calcium and sodium channels in rods. Given that these three receptors are segregated in the vervet monkey retina, we suggested that they might have distinct roles in retinal physiology. In Article 4, we reported a comparative analysis of the expression of the eCB system components in the retina of rodents, tree shrews (small mammals considered as early primates), and monkeys. This paper provides evidence that the eCB system is differently expressed in the retina of these mammals and suggests a distinctive role of eCBs in visual processing. In the subsequent series of three articles, we confirmed their suggested roles in the retina by using electroretinography (ERG) and intravitreal injections of agonist and antagonist of these receptors. We concluded that they indeed play important roles in the retina. In Article 5, we developed a standard protocol for ERG testing in our animal model and have published an ERG atlas with normalized amplitudes and latency values similar to that of humans, following the guidelines of the International Society for Clinical Electrophysiology of Vision. In Article 6, we showed that blockade of CB1R or CB2R with specific antagonists modifies the ERG, both in photopic and scotopic conditions, which confirms the implication of these receptors in normal retinal function. Finally, in Article 7 (expression of GPR55 in rods only), we confirmed the suggest role of GPR55 in rods by showing that activation or blockade of GPR55 with a specific agonist (lysophosphatidylglucoside) or antagonist (CID16020046) increases or decreases the amplitude of the scotopic ERG waveforms. Taken together, these articles demonstrate that CB1R, CB2R, and GPR55 are differentially expressed in the vervet monkey retina and have distinct roles. This work has also clinical relevance in the way that we have discovered new pharmacological targets that can be used for treatment of many retinal diseases.

Submitted by Ana Lúcia Torres (bfmhuap@gmail.com) on 2017-09-19T15:20:57Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) COMPARAÇÃO ENTRE O PEVP E O PERG DE CRIANÇAS COM AMBLIOPIA ESTRÁBICA E ANISOMETROPICA 1_3 V5.pdf: 3334834 bytes, checksum: f21a6dfb6b0e7fbc0eb2ef6452f3f4c0 (MD5) / Approved for entry into archive by Ana Lúcia Torres (bfmhuap@gmail.com) on 2017-09-19T15:21:17Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) COMPARAÇÃO ENTRE O PEVP E O PERG DE CRIANÇAS COM AMBLIOPIA ESTRÁBICA E ANISOMETROPICA 1_3 V5.pdf: 3334834 bytes, checksum: f21a6dfb6b0e7fbc0eb2ef6452f3f4c0 (MD5) / Made available in DSpace on 2017-09-19T15:21:17Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) COMPARAÇÃO ENTRE O PEVP E O PERG DE CRIANÇAS COM AMBLIOPIA ESTRÁBICA E ANISOMETROPICA 1_3 V5.pdf: 3334834 bytes, checksum: f21a6dfb6b0e7fbc0eb2ef6452f3f4c0 (MD5) Previous issue date: 2017 / Universidade Federal Fluminense. Centro de Ciência Médicas / A ambliopia é uma desordem neurológica do desenvolvimento visual que se manifesta com a redução de capacidades sensoriais em ambos os olhos ou mais comumente de forma monocular, diante da total correção óptica e na ausência de anormalidades do exame clínico. Está associada ao estrabismo e a anisometropia e menos frequentemente à privação visual. As ambliopias estrábica e anisometrópicas apresentam diferenças nas suas fisiopatologias. Comparamos as respostas eletrofisiológicas das ambliopias estrábica e anisometrópicas com o eletroretinograma padrão (PERG) e o potencial evocado visual padrão (PVEP). Cinquenta e seis pacientes, 18 crianças amblíopes anisometrópicas hipermetrópicas (idade média e desviopadrão 9,7 ± 2,5); 19 crianças com ambliopia estrábica esotrópica (idade média e desvio padrão 10,3 ± 2,6) e 19 crianças emétropes normais (idade média e desvio-padrão 10,1 ± 2,2) foram divididos em três grupos. Após o exame oftalmológico de rotina, o eletroretinograma padrão (PERG) e o potencial evocação visual padrão (PVEP) foram registrados em respostas a um estímulo de padrão reverso à taxa de duas reversões/segundo. A diferença entre ambliopia anisometrópica hipermetrópica e ambliopia estrábica em relação às latências das ondas P100 / P50 / N95 (p = 0,055 / 0,855 / 0,132) e as amplitudes P100 / P50 / N95 (p = 0,980 / 0,095 / 0,045) não foi estatisticamente significante. No entanto, houve uma diferença estatística significante entre a ambliopia estrábica e os controles com relação às latências das ondas P100 / P50 / N95 (p = 0,000 / 0,006 / 0,004). Nossos achados indicam que, apesar das diferenças clínicas e fisiopatológicas entre pacientes amblíopes estrábicos esotrópicos e os pacientes com ambliopia anisometrópica hipermetrópica, não foram encontradas diferenças nas respostas de PVEP e PERG. Os componentes anormais do PVEP e PERG em crianças amblíopes podem refletir uma disfunção da retina e da via visual. / Amblyopia is a neurological disorder of visual development manifested by the reduction of sensory abilities in both eyes or more commonly monocular in the face of total optical correction and absence of clinical examination abnormalities. It is associated with strabismus and anisometropia, and less often with visual deprivation. Strabismus amblyopia and anisometropic amblyopia present clinical differences and their pathophysiology. We compared the electrophysiological responses of the strabismic and anisometropic amblyopia with the pattern electroretinogram (PERG) and the pattern visual evoked potential (PVEP). Fifty-six patients, 18 hypermetropic anisometropic amblyopic children (mean age and standard deviation 9.7 ± 2.5); 19 children with esotropic strabismus amblyopia (mean age and standard deviation 10.3 ± 2.6) and 19 normal emetopic children (mean age and standard deviation 10.1 ± 2.2) were divided into three groups. After routine ophthalmologic examination, the pattern electroretinogram (PERG) and standard visual evoked potential (PVEP) were recorded in responses to a reverse pattern stimulus at the rate of two reversions/second. The difference between hypermetropic anisometropic amblyopia and strabismus esotropic amblyopia in relation to P100 / P50 / N95 wave latencies (p = 0.055 / 0.855 / 0.132) and P100 / P50 / N95 amplitudes (p = 0.980 / 0.095 / 0.045) was not statistically significant. However, there was a statistically significant difference between strabismic amblyopia and controls with respect to P100 / P50 / N95 wave latencies (p = 0.000 / 0.006 / 0.004). Our findings indicate that, despite clinical and pathophysiological differences between esotropic strabismus-amblyopic patients and patients with hypermetropic anisometropic amblyopia, no differences in PVEP and PERG responses were found. Abnormal PVEP and PERG components in amblyopic children may reflect retinal and visual pathway dysfunction.

Studies demonstrate short-wavelength cone pathway dysfunction in patients with diabetes and no clinically visible DR. Poor glycemic control, as measured by hemoglobin A1c (HbA1c), is a strong risk factor for DR. We hypothesized that raised HbA1c was associated with short-wavelength cone sensitive visual evoked potential (S-VEP) and electroretinogram (sERG) dysfunction. Forty adolescents with diabetes and 39 controls were tested using the S-VEP. Latencies to a short-wavelength stimulus were delayed in patients at low contrasts. Patient S-VEP latencies were not associated with HbA1c when controlling for age and time since diagnosis. Twenty-one adolescents with diabetes and 19 controls were tested using the sERG. Implicit times of the b-wave were delayed but not associated with HbA1c when controlling for time since diagnosis.Patient PhNR amplitudes were reduced. A one-unit increase in HbA1c was associated with a 15% sERG PhNR amplitude reduction (p=0.004). The sERG PhNR may be a potential biomarker for DR.

Studies demonstrate short-wavelength cone pathway dysfunction in patients with diabetes and no clinically visible DR. Poor glycemic control, as measured by hemoglobin A1c (HbA1c), is a strong risk factor for DR. We hypothesized that raised HbA1c was associated with short-wavelength cone sensitive visual evoked potential (S-VEP) and electroretinogram (sERG) dysfunction. Forty adolescents with diabetes and 39 controls were tested using the S-VEP. Latencies to a short-wavelength stimulus were delayed in patients at low contrasts. Patient S-VEP latencies were not associated with HbA1c when controlling for age and time since diagnosis. Twenty-one adolescents with diabetes and 19 controls were tested using the sERG. Implicit times of the b-wave were delayed but not associated with HbA1c when controlling for time since diagnosis.Patient PhNR amplitudes were reduced. A one-unit increase in HbA1c was associated with a 15% sERG PhNR amplitude reduction (p=0.004). The sERG PhNR may be a potential biomarker for DR.

No description available.

Studies demonstrate neuro-retinal damage in patients with diabetes and no clinically visible diabetic retinopathy. It is unknown which retinal regions are most vulnerable to diabetes. We hypothesized that the standard and slow-flash (sf-) multifocal electroretinogram (mfERG) and adaptive optics (AO) imaging will localize retinal regions of vulnerability. Fifty-five adolescents with diabetes and 54 controls underwent mfERG testing to isolate predominately retinal bipolar cell activity and sf-mfERG testing to isolate three oscillatory potentials (OPs) from intraretinal amacrine and interplexiform cells. Greatest mfERG delays were in the superior temporal quadrant and at 5°-10° eccentricity. Greatest sf-mfERG delays were found at different eccentricities for each OP. Twenty adolescents with diabetes and 14 controls underwent AO imaging. No significant differences in cone photoreceptor density were found; however, patients showed a trend towards reduced density in the superior nasal region. Inner retinal structures may be more susceptible to damage by diabetes than outer retinal structures.

Studies demonstrate neuro-retinal damage in patients with diabetes and no clinically visible diabetic retinopathy. It is unknown which retinal regions are most vulnerable to diabetes. We hypothesized that the standard and slow-flash (sf-) multifocal electroretinogram (mfERG) and adaptive optics (AO) imaging will localize retinal regions of vulnerability. Fifty-five adolescents with diabetes and 54 controls underwent mfERG testing to isolate predominately retinal bipolar cell activity and sf-mfERG testing to isolate three oscillatory potentials (OPs) from intraretinal amacrine and interplexiform cells. Greatest mfERG delays were in the superior temporal quadrant and at 5°-10° eccentricity. Greatest sf-mfERG delays were found at different eccentricities for each OP. Twenty adolescents with diabetes and 14 controls underwent AO imaging. No significant differences in cone photoreceptor density were found; however, patients showed a trend towards reduced density in the superior nasal region. Inner retinal structures may be more susceptible to damage by diabetes than outer retinal structures.

No description available.