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Retinal ganglion cells (RGCs) are the projection neurons of the retina, and their death promotes an irreversible blindness. Several factors were described to control their genesis during retinal development. These include Atoh7, a major orchestrator of the RGC program, and downstream targets of this transcription factor, including Pou4f factors, that in turn regulate key aspects of terminal differentiation. The absence of POU4F family genes results in defects in RGC differentiation, aberrant axonal elaboration and, ultimately, RGC death. This confirms the requirement of POU4F factors for RGC development and survival, with a crucial role in regulating RGC axon outgrowth and pathfinding. Here, we have investigated in vivo whether ectopic Pou4f2 expression in late retinal progenitor cells (late RPCs) is sufficient to induce the generation of cells with RGC properties, including long-range axon projections. We show that Pou4f2 overexpression generates RGC-like cells that share morphological and transcriptional features with RGCs that are normally generated during early development and extend axonal projections up to the brain. In conclusion, these results show that POU4F2 alone is sufficient to promote the crucial properties of projection neurons that arise from retinal progenitors outside their developmental window.

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Purpose: Stress granules (SGs) are cytoplasmic biocondensates formed in response to various cellular stressors, contributing to cell survival. Although implicated in diverse pathologies, their role in retinal degeneration (RD) remains unclear. We aimed to investigate SG formation in the retina and its induction by excessive LED light in an RD model. Methods: Rat retinas were immunohistochemically analyzed for SG markers G3BP1 and eIF3, and SGs were also visualized by RNA fluorescence in situ hybridization. Additionally, SGs were induced in primary retinal cell and eyeball cultures using sodium arsenite. Light exposure experiments used LED lamps with a color temperature of 5500 K and 200 lux intensity for short-term or two- to eight-day exposures. Results: SGs were predominantly detected in retinal ganglion cells (RGCs) and inner nuclear layer (INL) cells, with arsenite-induction verified in RGCs. SG abundance was higher in animals exposed to light for 2-8 days compared to light/dark cycle controls. RGCs consistently exhibited more SGs than INL cells, and INL cells more than outer nuclear layer (ONL) cells (Scheirer-Ray-Hare test: H = 13.2, P = 0.0103 for light condition, and H = 278.2, P < 0.00001 for retinal layer). These observations were consistent across four independent experiments, each with three animals per light condition. Conclusions: This study characterizes SGs in the mammalian retina for the first time, with increased prevalence after excessive LED light exposure. RGCs and INL cells showed heightened SG formation, suggesting a potential protective mechanism against photodamage. Further investigations are warranted to elucidate the role of SGs in shielding against light stress and their implications in retinopathies.

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Blue light reflectance (BLR) imaging offers a non-invasive, cost-effective method for evaluating retinal structures by analyzing the reflectance and absorption characteristics of the inner retinal layers. By leveraging blue light's interaction with retinal tissues, BLR enhances visualization beyond the retinal nerve fiber layer, improving detection of structures such as the outer plexiform layer and macular pigment. Its diagnostic utility has been demonstrated in distinct retinal conditions, including hyperreflectance in early macular telangiectasia, hyporeflectance in non-perfused areas indicative of ischemia, identification of pseudodrusen patterns (notably the ribbon type), and detection of peripheral retinal tears and degenerative retinoschisis in eyes with reduced retinal pigment epithelial pigmentation. Best practices for image acquisition and interpretation are discussed, emphasizing standardization to minimize variability. Common artifacts and mitigation strategies are also addressed, ensuring image reliability. BLR's clinical utility, limitations, and future research directions are highlighted, particularly its potential in automated image analysis and quantitative assessment. Different BLR acquisition methods, such as fundus photography, confocal scanning laser ophthalmoscopy, and broad line fundus imaging, are evaluated for their respective advantages and limitations. As research advances, BLR's integration into multimodal workflows is expected to improve early detection and precise monitoring of retinal diseases.

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PURPOSE: Description of retinal phenotype by structural and functional testing, ornithine plasma levels and mutational data of OAT gene in patients with Gyrate Atrophy (GA). METHODS: Ophthalmologic examination, fundus photography (CFP), autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT), Goldmann perimetry (GP), full-field electroretinogram (ffERG) and chromatic perimetry (CP) testing were performed. Ornithine plasma levels were measured. Sanger sequencing mutational analysis of the coding exons and exon-intron junctions of the OAT gene were analyzed. RESULTS: Twelve eyes of seven Mexican patients with GA were included. CFF showed peripheric patches of chorioretinal atrophy; FAF revealed peripheric oval areas of hypoautofluorescence; SD-OCT exhibited outer retinal tubulations in 58%, cystoid macular edema in 50%, epiretinal membrane in 42%, foveoschisis and staphyloma in 17%, and hyperreflective deposits in 100% of the eyes; GP showed constricted visual fields in 100% of the eyes; ffERG revealed preserved photopic response in 17% and preserved scotopic response in 17% of the eyes; CP exposed a deficit in generalized response of rods and cones in 100% of the eyes. Mean ornithine plasma levels were 509.5 µmol/L. One patient with genetic confirmation of GA had normal ornithine plasma levels (48 µmol/L). Molecular findings in OAT gene detected two novel pathogenic variants: c.796 C > T (p.Gln266*) and c.721_722dupCC (p.Asp242ArgfsTer6). CONCLUSION: This study provides new information regarding functional and structural diagnosis in patients with GA, expands the understanding of retinal phenotype in patients with GA, reports two novel mutations and presents the first case of GA confirmed by genetic testing with normal ornithine levels.

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Diabetic retinopathy is a prevalent complication of type 2 diabetes mellitus, characterized by progressive damage to the retinal structure and function. Photobiomodulation therapy, using red or near-infrared light, has been proposed as a non-invasive intervention to mitigate retinal damage, but has been tested generally with short-term stimuli. This study aimed to evaluate the effects of prolonged photobiomodulation with deep red light on retinal structure and function in a type 2 diabetes mouse model. Transgenic LepRdb/J (db/db) mice were exposed to photobiomodulation therapy via LED devices emitting 654 nm light for 12 h daily over ten weeks and compared to untreated mice. Retinal function was evaluated by flash electroretinography, while structural changes were assessed through histology and immunohistochemistry to detect astro- and microgliosis. At 33 weeks of age, db/db mice were obese and severely diabetic, but exhibited only incipient indicators of retinal deterioration. Electroretinogram b-wave peak latencies were prolonged at intermediate flash intensities, while the outer plexiform layer displayed significantly elevated IBA1 expression. Photobiomodulation therapy prevented these two markers of early retinal deterioration but had no effect on other morphological and functional parameters. Photobiomodulation is well-tolerated and maintains potential as a complementary treatment option for diabetic retinopathy but requires further optimization of therapeutic settings and combinatory treatment approaches.

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The retina is crucial for converting light into neuronal signals for visual perception. Understanding the retina's structure, function, and development is essential for vision research. It is known that the thyroid hormone (TH) receptor type beta 2 (TRß2) is a key element in the regulation of cone differentiation in the retina, but other elements of TH signaling, such as transporters and enzyme deiodinases, have also been implicated in retinal cell development and survival. In the present study, we investigated the expression profile of genes involved in TH signaling and analyzed the impact of thyroidal status on retinal morphology, opsin expression, cell death/proliferation profile, as well as color preference behavior during the early retina development of zebrafish larvae. mRNA expression analysis on dissected whole eyes revealed that TH signaling elements gradually increase during eye development, with dio3b being the component that shows the most dramatic change. Mutations generated by CRISPR/CAS9 in the dio3b gene, but not in the thrb gene, modifies the structure of the retina. Disruption in TH level reduces the cell number of the ganglion cell layer, increases cell death, and modifies color preference, emphasizing the critical importance of precise TH regulation by its signaling elements for optimal retinal development and function.

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Explainable Artificial Intelligence (XAI) is an emerging machine learning field that has been successful in medical image analysis. Interpretable approaches are able to "unbox" the black-box decisions made by AI systems, aiding medical doctors to justify their diagnostics better. In this paper, we analyze the performance of three different XAI strategies for medical image analysis in ophthalmology. We consider a multimodal deep learning model that combines optical coherence tomography (OCT) and infrared reflectance (IR) imaging for the diagnosis of age-related macular degeneration (AMD). The classification model is able to achieve an accuracy of 0.94, performing better than other unimodal alternatives. We analyze the XAI methods in terms of their ability to identify retinal damage and ease of interpretation, concluding that grad-CAM and guided grad-CAM can be combined to have both a coarse visual justification and a fine-grained analysis of the retinal layers. We provide important insights and recommendations for practitioners on how to design automated and explainable screening tests based on the combination of two image sources.

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Emerging evidence suggests that retinal neurodegeneration is an early event in the pathogenesis of diabetic retinopathy (DR), preceding the development of microvascular abnormalities. Here, we assessed the impact of neuroinflammation on the retina of diabetic-induced rats. For this aim we have used a two-photon microscope to image the photoreceptors (PRs) at different eccentricities in unstained retinas obtained from both control (N = 4) and pathological rats (N = 4). This technique provides high-resolution images where individual PRs can be identified. Within each image, every PR was located, and its transversal area was measured and used as an objective parameter of neuroinflammation. In control samples, the size of the PRs hardly changed with retinal eccentricity. On the opposite end, diabetic retinas presented larger PR transversal sections. The ratio of PRs suffering from neuroinflammation was not uniform across the retina. Moreover, the maximum anatomical resolving power (in cycles/deg) was also calculated. This presents a double-slope pattern (from the central retina towards the periphery) in both types of specimens, although the values for diabetic retinas were significantly lower across all retinal locations. The results show that chronic retinal inflammation due to diabetes leads to an increase in PR transversal size. These changes are not uniform and depend on the retinal location. Two-photon microscopy is a useful tool to accurately characterize and quantify PR inflammatory processes and retinal alterations.

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KIAA0586 variants have been associated with a wide range of ciliopathies, mainly Joubert syndrome (JS, OMIM #616490) and short-rib thoracic dysplasia syndrome (SRTD, OMIM #616546). However, the hypothesis that this gene is involved with hydrolethalus syndrome (HSL, OMIM #614120) and orofaciodigital syndrome IV (OMIM #258860) has already been raised. Ciliopathies' clinical features are often overlapped despite differing in phenotype severity. Besides KIAA0586, HYLS1 and KIF7 are also known for being causative of ciliopathies, indicating that all three genes may have similar or converging genomic pathways. Overall, the genotypic and phenotypic spectrum of ciliopathies becomes wider and conflicting while more and more new variants are added to this group of disorders' molecular pot. In this case report we discuss the first Brazilian individual clinically diagnosed with hydrolethalus syndrome and molecular findings that demonstrate the role of KIAA0586 as a causative gene of a group of genetic disorders. Also, recent reports on individuals with intronic and exonic variants combined leading to ciliopathies support our patient's molecular diagnosis. At the same time, we discuss variable expressivity and overlapping features in ciliopathies.

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Objetivo: Avaliar a eficácia do filtro de proteção de luz azul na proteção de retinas de ratos Wistar expostos a luz azul emitida por um aparelho fotopolimerizador LED de alta potência. Material e métodos: Nove ratos Wistar foram utilizados na pesquisa e suas estruturas oculares foram os objetos de estudo. Os animais foram distribuídos (n = 6 estruturas oculares) por grupos: GEP - exposição sobre o filtro de proteção do fotopolimerizador VALO®, GEI - exposição indireta sem filtro de proteção e GC ­ grupo controle (sem exposição), total de 18 estruturas oculares. Durante a fotoestimulação de cada animal, o olho considerado experimental foi exposto à luz indireta do LED de alta potência 3200mW/cm2 (Valo Ortho - Ultradent) por 144 segundos a uma distância de 30cm. Os animais foram expostos à luz LED três vezes ao dia para investigar se ocorreu alguma alteração inflamatória aguda na retina. Sete dias após as sessões de fotoestimulação, os animais foram anestesiados e submetidos a eutanásia. Em seguida, os olhos foram dissecados e processados histologicamente. As lâminas histológicas foram analisadas estereologicamente e histomorfometricamente para mensurar os parâmetros da retina sob investigação. Resultados: Houve aumento de 50% no volume total da retina no GEI devido ao aumento do volume das camadas de células ganglionares (CCG), camadas plexiformes internas (CPI), camadas nucleares externas (CNE) e dos prolongamentos de cone e bastonete. Não houve diferença estatisticamente significativa em termos de densidade. Porém, houve aumento médio de 15% da área nuclear das células na CNE e 49,30 na CCG no GEI. Conclusão: A exposição à luz LED emitida por um aparelho fotopolimerizador odontológico de alta potência causa danos à estrutura da retina animal e o uso do filtro de proteção é capaz de prevenir os danos causados pela exposição (AU).

Objective: To evaluate the the effectiveness of the blue light filter in protecting the retinas of Wistar rats exposed to the blue light emitted by a high-power LED light curing device. Materials and methods: Nine Wistar rats were used in the research, and their ocular structures were the subjects of study. The animals were divided into three groups (n = 6 ocular structures each): GEI - indirect exposure without protection filter; GEP - exposure over the protection filter of the VALO® curing and GC ­ control group (without exposure), total of 18 eye oculares. During the photostimulation of each animal, the eye considered experimental was exposed to the indirect light of the highintensity LED at 3200mW/cm² (Valo® Ortho - Ultradent) for 144 seconds at 30cm. The animals were exposed to the LED light three times a day to investigate if any acute inflammatory changes occurred in the retina. Seven days after the photostimulation sessions, the animals were anesthetized and euthanized. Subsequently, the eyes were dissected and histologically processed. The histological slides were analyzed stereologically and histomorphometrically to measure the investigated retinal parameters. Results: There was 50% increase in the total volume of the retina in the GEI due to the increased volume of ganglion cell layers (GCL), inner plexiform layers (IPL), outer nuclear layers (ONL), and the extensions of rods and cones. There was no statistically significant difference in terms of density. However, there was an average increase of 15% in the nuclear area of cells in all studied layers in the CNE and 49,30 % in the CCG in the GEI. Conclusion: Exposure to LED light emitted by a dental curing device causes damage to the animal retina structure, and the use of a protective filter can prevent damage caused by exposure (AU).

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BACKGROUND: Retinopathy of Prematurity (ROP) is a proliferative retinal vascular disease occurring in the retina of premature infants and is the main cause of childhood blindness. Nowadays anti-VEGF and retinal photocoagulation are mainstream treatments for ROP, but they develop a variety of complications. Hydrogen (H2) is widely considered as a useful neuroprotective and antioxidative therapeutic method for hypoxic-ischemic disease without toxic effects. However, whether H2 provides physiological angiogenesis promotion, neovascularization suppression and glial protection in the progression of ROP is largely unknown.This study aims to investigate the effects of H2 on retinal angiogenesis, neovascularization and neuroglial dysfunction in the retinas of oxygen-induced retinopathy (OIR) mice. METHODS: In this study, mice that were seven days old and either wild-type (WT) or Nrf2-deficient (Nrf2-/-) were exposed to 75% oxygen for 5 days and then returned to normal air conditions. Different stages of hydrogen gas (H2) inhalation were administered. Vascular obliteration, neovascularization, and blood vessel leakage were analyzed and compared. To count the number of neovascularization endothelial nuclei, routine HE staining of retinal sections was conducted. Immunohistochemistry was performed using DyLight 594 labeled GSL I-isolectin B4 (IB4), as well as primary antibodies against proliferating cell nuclear antigen (PCNA), glial fibrillary acidic protein (GFAP), and Iba-1. Western blots were used to measure the expression of NF-E2-related factor 2 (Nrf2), vascular endothelial growth factor (VEGF), Notch1, Dll4, and HIF-1α. Additionally, the expression of target genes such as NQO1, HO-1, Notch1, Hey1, Hey2, and Dll4 was measured. Human umbilical vein endothelial cells (HUVECs) treated with H2 under hypoxia were used as an in vitro model. RT-PCR was used to evaluate the mRNA expression of Nrf2, Notch/Dll4, and the target genes. The expression of reactive oxygen species (ROS) was observed using immunofluorescence staining. RESULTS: Our results indicate that 3-4% H2 does not disturb retinal physiological angiogenesis, but ameliorates vaso-obliteration and neovascularization in OIR mice. Moreover, H2 prevents the decreased density and reverses the morphologic and functional changes in retinal astrocytes caused by oxygen-induced injury. In addition, H2 inhalation reduces microglial activation, especially in the area of neovascularization in OIR mice. H2 plays a protective role in vascular regeneration by promoting Nrf2 activation and suppressing the Dll4-induced Notch signaling pathway in vivo. Also, H2 promotes the proliferation of HUVECs under hypoxia by negatively regulating the Dll4/Notch pathway and reducing ROS levels through Nrf2 pathway aligning with our findings in vivo.Moreover, the retinal oxygen-sensing mechanisms (HIF-1α/VEGF) are also involved in hydrogen-mediated retinal revascularization and neovascularization suppression. CONCLUSIONS: Collectively, our results indicate that H2 could be a promising therapeutic agent for POR treatment and that its beneficial effect in human ROP might involve the activation of the Nrf2-Notch axis as well as HIF-1α/VEGF pathways.

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Cutis marmorata telangiectatica congenita is a rare congenital vascular malformation characterised by cutaneous vascular abnormalities, typically diagnosed at birth or in the early postnatal period. Although typically benign, this disease is associated with other systemic abnormalities, including rare ocular alterations, such as congenital glaucoma, cataracts and retinopathy.This manuscript describes a female infant, who presented with generalised livedo reticularis, a band of alopecia and cutaneous atrophy in the temporal region above the coronal suture. The patient was diagnosed with cutis marmorata telangiectatica congenita by a paediatrician, and an ophthalmological evaluation was requested. A funduscopy examination in both eyes showed temporal and superior retina with avascular areas with new vessels, venous dilations and shunts, and no retinal detachments. Given these findings, we performed retinal photocoagulation laser treatment with excellent results.This case report highlights the importance of early ophthalmological evaluation of children with this disease to prevent secondary complications, such as vitreous haemorrhage and tractional retinal detachment.

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PURPOSE: Diabetic retinopathy (DR) is a leading cause of preventable blindness, particularly in underserved regions where access to ophthalmic care is limited. This study presents a proof of concept for utilizing a portable handheld retinal camera with an embedded artificial intelligence (AI) platform, complemented by a synchronous remote confirmation by retina specialists, for DR screening in an underserved rural area. DESIGN: Retrospective cohort study. SUBJECTS: A total of 1115 individuals with diabetes. METHODS: A retrospective analysis of a screening initiative conducted in 4 municipalities in Northeastern Brazil, targeting the diabetic population. A portable handheld retinal camera captured macula-centered and disc-centered images, which were analyzed by the AI system. Immediate push notifications were sent out to retina specialists upon the detection of significant abnormalities, enabling synchronous verification and confirmation, with on-site patient feedback within minutes. Referral criteria were established, and all referred patients underwent a complete ophthalmic work-up and subsequent treatment. MAIN OUTCOME MEASURES: Proof-of-concept implementation success. RESULTS: Out of 2052 invited individuals, 1115 participated, with a mean age of 60.93 years and diabetes duration of 7.52 years; 66.03% were women. The screening covered 2222 eyes, revealing various retinal conditions. Referable eyes for DR were 11.84%, with an additional 13% for other conditions (diagnoses included various stages of DR, media opacity, nevus, drusen, enlarged cup-to-disc ratio, pigmentary changes, and other). Artificial intelligence performance for overall detection of referable cases (both DR and other conditions) was as follows: sensitivity 84.23% (95% confidence interval (CI), 82.63-85.84), specificity 80.79% (95% CI, 79.05-82.53). When we assessed whether AI matched any clinical diagnosis, be it referable or not, sensitivity was 85.67% (95% CI, 84.12-87.22), specificity was 98.86 (95% CI, 98.39-99.33), and area under the curve was 0.92 (95% CI, 0.91-0.94). CONCLUSIONS: The integration of a portable device, AI analysis, and synchronous medical validation has the potential to play a crucial role in preventing blindness from DR, especially in socially unequal scenarios. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

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In the animal kingdom, threat information is perceived mainly through vision. The subcortical visual pathway plays a critical role in the rapid processing of visual information-induced fear, and triggers a response. Looming-evoked behavior in rodents, mimicking response to aerial predators, allowed identify the neural circuitry underlying instinctive defensive behaviors; however, the influence of disk/background contrast on the looming-induced behavioral response has not been examined, either in rats or mice. We studied the influence of the dark disk/gray background contrast in the type of rat and mouse defensive behavior in the looming arena, and we showed that rat and mouse response as a function of disk/background contrast adjusted to a sigmoid-like relationship. Both sex and age biased the contrast-dependent response, which was dampened in rats submitted to retinal unilateral or bilateral ischemia. Moreover, using genetically manipulated mice, we showed that the three type of photoresponsive retinal cells (i.e., cones, rods, and intrinsically photoresponsive retinal ganglion cells (ipRGCs)), participate in the contrast-dependent response, following this hierarchy: cones > > rods > > > ipRGCs. The cone and rod involvement was confirmed using a mouse model of unilateral non-exudative age-related macular degeneration, which only damages canonical photoreceptors and significantly decreased the contrast sensitivity in the looming arena.

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Primary congenital glaucoma is a rare disease that occurs in early birth and can lead to low vision. Evaluating affected children is challenging and there is a lack of studies regarding color vision in pediatric glaucoma patients. This cross-sectional study included 21 eyes of 13 children with primary congenital glaucoma who were assessed using the Farnsworth D-15 test to evaluate color vision discrimination and by spectral domain optical coherence tomography to measure retinal fiber layer thickness. Age, visual acuity, cup-to-disc ratio and spherical equivalent data were also collected. Global and sectional circumpapillary and macular retinal fiber layer thicknesses were measured and compared based on color vision test performance. Four eyes (19%) failed the color vision test with diffuse dyschromatopsia patterns. Only age showed statistical significance in color vision test performance. Global and sectional circumpapillary and macular retinal fiber layer thicknesses were similar between the color test outcomes dyschromatopsia and normal. While the color vision test could play a role in assessing children with primary congenital glaucoma, further studies are needed to correlate it with damage to retinal fiber layer thickness.

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PURPOSE: We aimed to evaluate retinal nerve fiber and choroidal layer alterations in adolescents with anorexia nervosa using spectral-domain optical coherence tomography. METHODS: Thirty patients with anorexia nervosa and 30 healthy adolescents aged 12-18 years were included in this study. Their age, sex, body mass index, anorexia nervosa type, disease duration, and spectral-domain optical coherence tomography data were recorded. RESULTS: Central macular thickness and retinal nerve fiber layer thickness in the temporal and inferior regions were significantly lesser in patients with anorexia than in healthy controls (p<0.05). Moreover, significant choroidal thinning around the foveal and subfoveal regions in patients with anorexia was observed (p<0.05). In addition, a statistically significant relation between the increase in disease duration and the thinning of the inferior retinal nerve fiber layer was detected (p<0.05). CONCLUSION: The retinal nerve fiber layer and choroidal layer thicknesses were lesser in patients with anorexia than in healthy controls. Screening for retinal indices might prevent the development of irreversible retinal pathologies in adolescents with anorexia nervosa. In addition, thinning of the retinal nerve fiber and choroidal layers could reflect structural or functional changes in the brain of adolescents with anorexia nervosa.

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The retina is a central nervous tissue essential to visual perception and highly susceptible to environmental damage. Lower vertebrate retinas activate intrinsic regeneration mechanisms in response to retinal injury regulated by a specialized population of progenitor cells. The mammalian retina does not have populations of progenitor/stem cells available to activate regeneration, but contains a subpopulation of differentiated cells that can be reprogrammed into retinal stem cells, the ciliary epithelium (CE) cells. Despite the regenerative potential, stem cells derived from CE exhibit limited reprogramming capacity probably associated with the expression of intrinsic regulatory mechanisms. Platelet-activating factor (PAF) is a lipid mediator widely expressed in many cells and plays an important role in stem cell proliferation and differentiation. During mammalian development, PAF receptor signaling showed important effects on retinal progenitors' cell cycle regulation and neuronal differentiation that need to be further investigated. In this study, our findings suggested a dynamic role for PAF receptor signaling in CE cells, impacting stem cell characteristics and neurosphere formation. We showed that PAF receptors and PAF-related enzymes are downregulated in retinal progenitor/stem cells derived from PE cells. Blocking PAFR activity using antagonists increased the expression of specific progenitor markers, revealing potential implications for retinal tissue development and maintenance.

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We report a case of acute methanol toxicity with unique optical coherence tomography findings. A 56-year-old man was referred to our ophthalmology clinic with a history of handmade vodka consumption and vision loss. On ophthalmologic examination, his vision was 20/100 in his right eye and 20/200 in his left eye. Bilateral mild optic disk hyperemia was detected on fundus examination. Because of the severity of systemic symptoms in such cases, it is very difficult to include optical coherence tomography in the ophthalmologic examination. However, we managed to perform optical coherence tomography and recorded shallow subretinal fluid and a prominent middle limiting membrane sign as acute retinal structural changes in the patient. The patient was treated with hemodialysis, intravenous ethanol, and sodium bicarbonate. On the fourth day of treatment, visual acuity improved to 20/20 in both eyes. In addition, the prominent middle limiting membrane sign and subretinal fluid disappeared. In this unusual case, retinal pigment epithelium damage and retinal ischemia may have contributed to the prominent middle limiting membrane and subretinal fluid, which are novel optical coherence tomography findings of methanol toxicity.

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K+ channel Kir7.1 expressed at the apical membrane of the retinal pigment epithelium (RPE) plays an essential role in retinal function. An isoleucine-to-threonine mutation at position 120 of the protein is responsible for blindness-causing vitreo-retinal dystrophy. We have studied the molecular mechanism of action of Kir7.1-I120T in vitro by heterologous expression and in vivo in CRISPR-generated knockin mice. Full-size Kir7.1-I120T reaches the plasma membrane but lacks any activity. Analysis of Kir7.1 and the I120T mutant in mixed transfection experiments, and that of tandem tetrameric constructs made by combining wild type (WT) and mutant protomers, leads us to conclude that they do not form heterotetramers in vitro. Homozygous I120T/I120T mice show cleft palate and tracheomalacia and do not survive beyond P0, whereas heterozygous WT/I120T develop normally. Membrane conductance of RPE cells isolated from WT/WT and heterozygous WT/I120T mice is dominated by Kir7.1 current. Using Rb+ as a charge carrier, we demonstrate that the Kir7.1 current of WT/I120T RPE cells corresponds to approximately 50% of that in cells from WT/WT animals, in direct proportion to WT gene dosage. This suggests a lack of compensatory effects or interference from the mutated allele product, an interpretation consistent with results obtained using WT/- hemizygous mouse. Electroretinography and behavioral tests also show normal vision in WT/I120T animals. The hypomorphic ion channel phenotype of heterozygous Kir7.1-I120T mutants is therefore compatible with normal development and retinal function. The lack of detrimental effect of this degree of functional deficit might explain the recessive nature of Kir7.1 mutations causing human eye disease.NEW & NOTEWORTHY Human retinal pigment epithelium K+ channel Kir7.1 is affected by generally recessive mutations leading to blindness. We investigate one such mutation, isoleucine-to-threonine at position 120, both in vitro and in vivo in knockin mice. The mutated channel is inactive and in heterozygosis gives a hypomorphic phenotype with normal retinal function. Mutant channels do not interfere with wild-type Kir7.1 channels which are expressed concomitantly without hindrance, providing an explanation for the recessive nature of the disease.

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PURPOSE: To provide a simple alternative acute ocular toxoplasmosis model with great reproducibility for experimental tests that demand monitoring of the ocular lesion. METHODS: ME49-wt and ME49-GFP tachyzoites from cell culture were used to infect male C57BL6 mice by intraperitoneal injection. B1 expression by real-time polymerase chain reaction (qPCR) assay was used to detect the presence of T. gondii in ocular tissue at the beginning of the infection. Fluorescence microscopy and histopathology analysis were carried out to assess the evolution of the acute infection up to 20 days in both eyes of infected mice. RESULTS: All mice infected with the 104 tachyzoites showed B1 expression in the retina of both eyes, in the RPE (retinal pigment epithelium), and choroid structures, after 5 days of infection. Tachyzoites of the ME49-GFP strain were easily detected by fluorescence microscopy in the retina tissue of mice after 5 days post-infection. After 20 days, mice inflammatory cell infiltrates and a disorganized morphology of the retinal laminar architecture were observed. CONCLUSION: Infection of C57BL6 mice via intraperitoneal with 104 tachyzoites of the ME49-GFP strain from cell culture is a suitable model for acute ocular toxoplasmosis. This model has great reproducibility in establishing the ocular lesion since day 5 post-infection. This model can be suitable for experimental tests of chemotherapy and the investigation of the role of the immune response on the development of uveitis.