Retinal Ganglion Layer Research Articles

Early-life exposure to five biodegradable plastics impairs eye development and visually-mediated behavior through disturbing hypothalamus-pituitary-thyroid (HPT) axis in zebrafish larvae

Biodegradable plastics have been commonly developed and applied as an alternative to traditional plastics, which cause environmental plastic pollution. However, biodegradable plastics still present limitations such as stringent degradation conditions and slow degradation rate, and may cause harm to the environment and organisms. Consequently, in this study, zebrafish was used to evaluate the effects of five biodegradable microplastics (MPs), polyglycolic acid (PGA), polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA) and polybutylene adipate terephthalate (PBAT) exposure on the early development, retina morphology, visually-mediated behavior, and thyroid signaling at concentrations of 1 mg/L and 100 mg/L. The results indicated that all MPs induced decreased survival rate, reduced body length, smaller eyes, and smaller heads, affecting the early development of zebrafish larvae. Moreover, the thickness of retinal layers, including inner plexiform layer (IPL), outer nuclear layer (ONL), and retinal ganglion layer (RGL) was decreased, and the expression of key genes related to eye and retinal development was abnormally altered after all MPs exposure. Exposure to PBS and PBAT led to abnormal visually-mediated behavior, indicating likely affected the visual function. All MPs could also cause thyroid system disorders, among which alterations in the thyroid hormone receptors (TRs) genes could affect the retinal development of zebrafish larvae. In summary, biodegradable MPs exhibited eye developmental toxicity and likely impaired the visual function in zebrafish larvae. This provided new evidence for revealing the effects of biodegradable plastics on aquatic organism development and environmental risks to aquatic ecosystems.

Complement propagates visual system pathology following traumatic brain injury

BackgroundTraumatic brain injury (TBI) is associated with the development of visual system disorders. Visual deficits can present with delay and worsen over time, and may be associated with an ongoing neuroinflammatory response that is known to occur after TBI. Complement system activation is strongly associated with the neuroinflammatory response after TBI, but whether it contributes to vision loss after TBI is unexplored.MethodsAcute and chronic neuroinflammatory changes within the dorsal lateral geniculate nucleus (dLGN) and retina were investigated subsequent to a moderate to severe murine unilateral controlled cortical impact. Neuroinflammatory and histopathological outcomes were interpreted in the context of behavioral and visual function data. To investigate the role of complement, cohorts were treated after TBI with the complement inhibitor, CR2-Crry.ResultsAt 3 days after TBI, complement component C3 was deposited on retinogeniculate synapses in the dLGN both ipsilateral and contralateral to the lesion, which was reduced in CR2-Crry treated animals. This was associated with microglia morphological changes in both the ipsilateral and contralateral dLGN, with a less ramified phenotype in vehicle compared to CR2-Crry treated animals. Microglia in vehicle treated animals also had a greater internalized VGlut2 + synaptic volume after TBI compared to CR2-Crry treated animals. Microglia morphological changes seen acutely persisted for at least 49 days after injury. Complement inhibition also reduced microglial synaptic internalization in the contralateral dLGN and increased the association between VGLUT2 and PSD95 puncta, indicating preservation of intact synapses. Unexpectedly, there were no changes in the thickness of the inner retina, retinal nerve fiber layer or retinal ganglion layer. Neuropathological changes in the dLGN were accompanied by reduced visual acuity at subacute and chronic time points after TBI, with improvement seen in CR2-Crry treated animals.ConclusionTBI induces complement activation within the dLGN and promotes microglial activation and synaptic internalization. Complement inhibition after TBI in a clinically relevant paradigm reduces complement activation, maintains a more surveillance-like microglia phenotype, and preserves synaptic density within the dLGN. Together, the data indicate that complement plays a key role in the development of visual deficits after TBI via complement-dependent microglial phagocytosis of synapses within the dLGN.

Investigating Nerve Fiber Layer and Retinal Ganglion Layer Cells in Patients with Essential Tremor

Investigating Nerve Fiber Layer and Retinal Ganglion Layer Cells in Patients with Essential Tremor

Neurodegeneration of the cornea and retina in patients with type 1 diabetes without clinical evidence of diabetic retinopathy.

AimDiabetic retinopathy (DR) is widely considered the earliest and most common microvascular complication of diabetes. However, recent studies have shown that retinal nerve fiber layer and corneal nerve abnormalities may be present in diabetic patients without retinopathy. This preliminary study aimed to establish if structural and functional changes in the nerve fiber layer of the retina and cornea occur in patients with type 1 diabetes (T1DM) without retinopathy.MethodsTwenty patients with T1DM, without clinical evidence of retinopathy (Age: 47.0 ± 2.5 years; Duration diabetes: 27.0 ± 3 years) and 15 age-matched healthy control subjects underwent detailed medical neurological examinations. Ophthalmic examinations using Spectral Domain Optical coherence tomography (SD-OCT), Standard Automated Perimetry (SAP), Flicker Defined Form High Edge Perimetry (FDF), Corneal Confocal Microscopy (CCM) and Non-contact corneal Aesthesiometry (NCCA) were performed to quantify the structure and function of the nerves in the retina and cornea, respectively.ResultsAt the structural level, retinal nerve fiber layer thickness (RNFL) was significantly reduced in the superior nasal (p=0.001) and inferior temporal (p=0.004) sectors, in diabetic patients. Retinal ganglion layer function was reduced in the patient group when assessed using Flicker Defined Form Perimetry (FDF), but this was not significant. The function of the cornea assessed by corneal sensitivity, using a non-contact corneal aesthesiometer (NCCA), was significantly reduced (p=0.001). Structural assessment of corneal nerves using corneal confocal microscopy (CCM) showed reduction at corneal nerve fiber density (CNFD) (p=0.01), branch density (CNBD) (p=0.006) and length (CNFL) (p=0.01) in patients with diabetes. Compared to control subjects, the percentage of abnormality in patients with T1DM for RNFL was 32% while the FDF was abnormal in 61% of patients. Corneal abnormality was observed in 47% for NCCA, 28% for CNFD, and 17% for CNFL. There was no correlation between neuronal damage in the retina and cornea.ConclusionsNeuronal abnormalities were observed in both the retina and cornea of diabetic patients without evidence of retinopathy. The prevalence of structural and functional changes was higher in the retina compared to the cornea. This preliminary study suggests that structural neuronal changes may occur in parallel and correlate with functional changes. The assessment of corneal and retinal nerve structure may be clinically useful for detecting and monitoring the earliest stages of diabetic microvascular abnormalities.

Ethambutol Effect on Retinal and Optic Nerve Structural Changes in Toxic Optic Neuropathy Case: A Literature Review

Introduction: Ethambutol (EMB) is one of the first-line antituberculosis drugs that reported to cause toxic effects on the eye structure. This study aims to elucidate the histological mechanism of retinal and optic nerve damage in toxic optic neuropathy cases.
 Reference Sources: The literature search was conducted in the PUBMED and MEDLINE databases using the latest publication of the 2012-2022 series.
 Studies Selection: The observational and randomized controlled trial studies analyzing the effect of ethambutol on retinal nerve fiber layer, retinal ganglion layer, inner cell plexiform layer thickness, optic nerve tissue, best-corrected visual acuity (BCVA), color perception, visual evoked response, and patients' visual field were included.
 Data Extraction Method: Articles that met the inclusion criteria underwent a specific evaluation, whereby the main focus was the ethambutol on retinal and optic nerve tissue.
 Results: The results showed that ethambutol affects the thinning of the Retinal Nerve Fiber Layer (RNFL), decreasing the amount of Ganglion Cells and changing the optic nerve's histological function by damaging the mitochondria and axonal fiber.
 Conclusion: It was concluded that ethambutol has adverse effects on retinal and optic nerve tissue due to several mechanisms and significantly affects the patient's visual outcome.

Light controlled signaling initiated by subretinal semiconducting-polymer layer in developing-blind-retina mimics the response of the neonatal retina

Optoelectronic semiconducting polymer material interfaced with a blind-developing chick-retina (E13–E18) in subretinal configuration reveals a response to full-field flash stimulus that resembles an elicited response from natural photoreceptors in a neonatal chick retina. The response manifests as evoked-firing of action potentials and was recorded using a multi-electrode array in contact with the retinal ganglion layer. Characteristics of increasing features in the signal unfold during different retina-development stages and highlight the emerging network mediated pathways typically present in the vision process of the artificial photoreceptor interfaced retina.

Exploring the Neuroprotective Role of Myo/Nog Cells in a Glaucomatous Mouse

IntroductionMyo/Nog cells express MyoD, Noggin and brain‐specific angiogenesis inhibitor 1 (BAI1). They are critical for eye development and respond to injury and stress in the neonatal and adult retina. Their depletion in the embryo results in eye and retinal malformations. Myo/Nog cells increase in number and migrate to areas of injury in response to stress. Cell death in the retina increases with Myo/Nog cell depletion and decreases with their addition to the vitreous. Here we examine the effects and locations of endogenous and exogenous Myo/Nog cells in mice eyes following the induction of glaucoma.MethodsThe anterior chamber of the right eye of C57BL/6J mice was injected with magnetic microbeads and guided to the iridocorneal angle using a handheld magnet, preventing the outflow of aqueous. Intraocular pressure was measured in both eyes following microbead injection on Days 0, 4, 7, 14, D21, and 28. On D7, three of the four groups were given bilateral injections into the anterior chamber of either PBS, unsorted brain cells, or Myo/Nog cells isolated from the brain. The fourth group did not receive any follow‐up injections. Eyes were collected on D32 and labeled with an antibody to BAI1 to locate Myo/Nog cells. H&E staining was used to count living cells in the retinal ganglion layer (RGC) and measure the thickness of the nerve fiber layer and inner nuclear layer (NFL:INL).ResultsEndogenous and exogenous Myo/Nog cells increased in glaucomatous eyes around areas of stress, including the cornea, trabecular meshwork, ciliary body and retina. The highest concentration of Myo/Nog cells was present around the RGC layer and cornea. Some Myo/Nog cells had phagocytized microbeads. Glaucomatous eyes treated with Myo/Nog cells displayed a lower concentration of endogenous Myo/Nog cells when compared to PBS and mixed population treatment groups. Addition of Myo/Nog cells also decreased loss of RGC cells and increased NFL:INL thickness in glaucomatous eyes compared to the control groups.ConclusionConsistent with other types of ocular injury, Myo/Nog cells accumulate in areas of stress following damage from increased intraocular pressure. Addition of Myo/Nog cells was neuroprotective in the glaucomatous retina.

Results of the application of complex physiotherapeutic neurostimulation in optical neuropathies of various genesis

To evaluate the effectiveness of complex physiotherapeutic neuro-ophthalmostimulation in case of ON of vascular origin. The study included 60 patients (120 eyes) with a verified diagnosis of optic neuropathy of vascular origin, who were divided into 2 groups comparable in age, gender and anatomical and functional characteristics: the main group of 30 patients (60 eyes) and the control group - 30 patients (60 eyes), including 24 men and 36 women, mean age was 66.2±4.1 years, disease duration was 4.1±1.7 years. All patients underwent courses of conservative treatment with vitamins according to the available ophthalmological standards, repeating them 1-2 times a year, the last of which was six months before the present study. Physiotherapy courses and patients did not pass. 20 healthy volunteers were taken to create basic indicators of the «norm» of the applied research methods. Patients of the main group used a set of procedures: transcranial magnetic electrical stimulation, endonasal electrophoresis with the drug neuroprotector Semax 0.1%, oxybaric chamber and acupuncture. Patients in the control group were prescribed basic therapy, including taking the vitamin complex BEROCCA for 3 months. Breakpoints: before treatment and at times: 1st week, 12 weeks and 24 weeks after the course of treatment, according to the standard recommendations for international multicenter studies. The following were assessed: visual field boundaries (dilation meridians; in deg.), light sensitivity (MS, MD; in dB), indicators of the state of the retinal ganglion layer (GCS thickness, volume loss): Avg CCG (in µm), FLV, GLV (in %). When evaluating the results in patients of the main group who received complex neurostimulation, the therapeutic efficacy in a week after the end of treatment was 94%, in 12 weeks - in 88% and in 24 weeks - 83%, while in patients of the control group for all studied indicators showed only a positive trend and therapeutic efficacy did not exceed 30-42%. Under the influence of the developed neurostimulating complex, the activity of nerve cells objectively increases, leading to a significant increase in the boundaries of the field of view and light sensitivity and a decrease in global losses of the retinal ganglion complex and optic nerve.

Opportunities for agent based modeling of retinal stem cell transplantation.

Opportunities for agent based modeling of retinal stem cell transplantation.

Cyclophosphamide affects eye development and locomotion in zebrafish (Danio rerio)

Cyclophosphamide (CP) is a broad-spectrum anticancer drug and has been frequently detected in aquatic environments due to its incomplete removal by wastewater treatment facilities and slow degradation in waters. Its toxicity in fish remains largely unknown. In this study, zebrafish eggs <4 h post fertilization (hpf) were exposed to CP at the concentrations from 0.5 to 50.0 μg/L until 168 hpf, and its toxicity was evaluated by biochemical, transcriptomic, and behavioral approaches. The results showed that malformation and mortality rates increased with CP concentrations. The 7-day malformation EC50 and mortality (LC30) by CP were calculated to be 86.8 μg/L and 7.5 mg/L, respectively. Inhibited startle response (light to dark) (a minimal of 19%) and reduced swimming velocity (a minimal of 30%) were observed in the CP-exposed larvae. The thicknesses of retinal ganglion layer, inner plexiform layer, and inner nuclear layer in the retina were increased after exposure to CP. Meanwhile, exposure to CP increased karyorrhexis and karyolysis in the liver tissue. Transcriptomic analysis identified 607 differentially expressed genes (DEGs) (159 up-regulated and 448 down-regulated). A significant reduction in the transcripts of sgk1 (the FoxO pathway), jun (the MAPK pathway), and diabloa (apoptosis pathway) were observed in the CP-treated larvae. This study has demonstrated that low concentrations of CP cause malformation, reduced swimming capacity, histopathological alterations in the retina and liver tissues, and interference on transcriptional expressions of key genes associated with different pathways. The ecological risk of CP and other anticancer drugs to aquatic organisms merits future investigation.

Effects of the Topical Administration of Semaglutide on Retinal Neuroinflammation and Vascular Leakage in Experimental Diabetes.

Background: An unexpected increase in the rate of severe diabetic retinopathy was observed in the Semaglutide in Subjects with Type 2 Diabetes (SUSTAIN)-6 clinical trial. Although this effect was attributed to a rapid decrease in blood glucose levels, a direct deleterious effect of semaglutide on the retina could not be ruled out. In order to shed light on this issue, we have performed a study aimed at testing the direct effect of semaglutide administered by eye drops on retinal neuroinflammation and microvascular abnormalities using the db/db mouse model. Methods: Eye drops containing semaglutide (0.33 mg/mL; 5 μL once/daily) or vehicle (PBS; 5 μL once daily) were administered for 15 days. Results: We found that semaglutide significantly reduced glial activation, as well as the retinal expression of Nuclear factor kB (NF-κB), proinflammatory cytokines (IL-1β, IL-6, IL-18) and Intercellular Adhesion Molecule (ICAM)-1. In addition, semaglutide prevented the apoptosis of cells from the retinal ganglion layer and activated the protein kinase B (AKT) pathway. Finally, a dramatic decrease in vascular leakage was observed in db/db mice treated with semaglutide. All these findings were observed without any change in blood glucose levels and, therefore, can be directly attributed to semaglutide. Conclusions: These experimental findings point to a beneficial rather than a deleterious effect of semaglutide on the retina of subjects with diabetes.

Nuclear PKR in retinal neurons in the early stage of diabetic retinopathy in streptozotocin‑induced diabetic rats.

Retinal neuron apoptosis is a key component of diabetic retinopathy (DR), one of the most common complications of diabetes. Stress due to persistent hyperglycaemia and corresponding glucotoxicity represents one of the primary pathogenic mechanisms of diabetes and its complications. Apoptosis of retinal neurons serves a critical role in the pathogenesis of DR observed in patients with diabetes and streptozotocin (STZ)-induced diabetic rats. Retinal neuron apoptosis occurs one month after STZ injection, which is considered the early stage of DR. The molecular mechanism involved in the suppression of retinal neuron apoptosis during the early stage of DR remains unclear. RNA-dependent protein kinase (PKR) is a stress-sensitive pro-apoptotic kinase. Our previous study indicated that PKR-associated protein X, a stress-sensitive activator of PKR, is upregulated in the early stage of STZ-induced diabetes. In order to assess the role of PKR in DR prior to apoptosis of retinal neurons, immunofluorescence and western blotting were performed to investigate the cellular localization and expression of PKR in the retina in the early stage of STZ-induced diabetes in rats. PKR activity was indirectly assessed by expression levels of phosphorylated eukaryotic translation initiation factor 2α (p-eIF2-α) and the presence of apoptotic cells in the retina was investigated by TUNEL assay. The findings revealed that PKR was localized in the nucleus of retinal ganglion and inner nuclear layer cells from normal and diabetic rats. To the best of our knowledge, the present study is the first to demonstrate nuclear localization of PKR in retinal neurons. Immunofluorescence analysis demonstrated that PKR was expressed in the nuclei of retinal neurons at 3 and 6 days and its expression was decreased at 15 days after STZ treatment. In addition, p-eIF2-α expression and cellular localization followed the trend of PKR, suggesting that this pro-apoptotic kinase was active in the nuclei of retinal neurons. These findings are consistent with the hypothesis that nuclear translocation of PKR may be a mechanism to sequester active PKR, thus preventing upregulation of cytosolic signalling pathways that induce apoptosis in retinal neurons. Apoptotic cells were not detected in the retina in the early stage of DR. A model was proposed to explain the mechanism by which apoptosis of retinal neurons by PKR is suppressed in the early stage of DR. The possible role of mitochondrial RNA (mtRNA) and Alu RNA in this phenomenon is also discussed since it was demonstrated that the cellular stress due to prolonged hyperglycaemia induces the release of mtRNA and transcription of Alu RNA. Moreover, it mtRNA activates PKR, whereas Alu RNA inhibits the activation of this protein kinase.

ТОПОГРАФИЯ ГАНГЛИОЗНОГО СЛОЯ СЕТЧАТКИ И РЕТИНАЛЬНОЕ РАЗРЕШЕНИЕ У ГРЕБНЕЗУБОГО ДЕЛЬФИНА STENO BREDANENSIS (CETACEA: DELPHINIDAE)

Morphological investigation of the retinal ganglion layer in the rough-toothed dolphin Steno bredanensis was performed using the retinal wholemount technique. Mapping of the distribution density of ganglion cells revealed two areas of their concentration: in the nasal (544 cells/mm2) and temporal (594 cells/mm2) quadrants. Ganglion cell diameters ranged from 12 to 50 µm, with mean values varying from 20 to 29 µm in different areas. The obtained cell distribution density corresponded to a retinal resolution of 11’

An integrated 3D fluidic device with bubble guidance mechanism for long-term primary and secondary cell recordings on multi-electrode array platform

A 3D fluidic device (3D-FD) is designed and developed with the capability of auto bubble guidance via a helical pathway in a 3D geometry. This assembly is integrated to a multi-electrode array (MEA) to maintain secondary cell lines, primary cells and primary retinal tissue explants of chick embryos for continuous monitoring of the growth and electrophysiology recording. The ability to maintain the retinal tissue explant, extracted from day 14 (E-14) and day 21 (E-21) chick embryos in an integrated 3D-FD MEA for long duration (>100 h) and study the development is demonstrated. The enhanced duration of monitoring offered by this device is due to the controlled laminar flow and the maintenance of a stable microenvironment. The spontaneous electrical activity of the retina, including the spike recordings from the retinal ganglion layer, was monitored over a long duration. Specifically, the spiking activity in embryonic chick retinas of different days (E-14 to 21) is studied, and the presence of light-stimulated firings along with a distinct electroretinogram for E-21 mature retina provides the evidence of a stable microenvironment over a sustained period.

Preventive and therapeutic effects of Keluoxin Capsules on early diabetic retinopathy in db/db mice

The aim of this paper was to investigate the preventive effects of Keluoxin Capsules(KLX) on diabetic retinopathy in db/db mice. One hundred male db/db diabetic mice(45-55 g, 8 weeks) were randomly divided into 5 groups(model, KLX low dose, KLX middle dose, KLX high dose, Dobesilate) and 20 male C57 BL/KsJdb~(+/+) were taken as control group. Body weight and fasting blood-glucose were detected every week. Mice were administrated with saline(control and model group), KLX(780, 1 560, 3 120 mg·kg~(-1)·d~(-1), ig), Dobesilate(195 mg·kg~(-1)·d~(-1), ig) for 20 weeks, respectively. At the end of the administration, optical coherence tomography, fundus fluorescein angiography and electroretinogram of the retina were measured. The eyeball was extirpated and retina was isolated to make paraffin section, followed by HE staining and glial fibrillary acidic protein(GFAP) immunohistochemistry. The results indicated that KLX has no obvious effect on body weight and fasting blood level in db/db mice. However, KLX could significantly regulate the thickness of retinal ganglion layer and inner plexiform layer. KLX was able to remarkably reduce the quantity of diabetic microvessel. Meanwhile, KLX could notably improve retinal function. Moreover, KLX could observably modulate the cell arrangement and edema in each layer. There was no markable difference in retina according to the immunochemistry assay. In the present study, KLX exert marked preventive effects on diabetic retinopathy in db/db mice, which provided an experimental evidence for clinical use.

Combination of circulating microRNAs as indicators of specific targets of retinal toxicity in rats

Circulating miR-96-5p, -124-3p, and 183-5p have been reported as safety biomarkers for retinal toxicity. In the present research, 5 serum microRNAs (miRNAs), which are highly specific to and abundant in the retina, including the 3 miRNAs previously mentioned, were assessed in 3 different models of retinal toxicity. Distinct types of retinal lesions were induced in rats by a single dose of N-methyl-N-nitrosourea (MNU: 10, 30, and 50 mg/kg, i.p.), N-methyl-d-aspartate (NMDA: 200 nmol/eye, intravitreal injection), or sodium iodate (NaIO3: 30 mg/kg, i.v.). Time-course change of serum miRNAs was evaluated by RT-PCR for up to 1 week after administration. Ophthalmologic and histologic examinations and electroretinogram recording were also performed. MNU at 50 mg/kg induced photoreceptor cell death, with elevation in serum miR-96-5p, -124-3p, and -183-5p levels. NMDA induced retinal ganglion and inner nuclear layer cell death, with elevation in serum miR-124-3p. In both models, serum miRNA elevations occurred in parallel with the onset of neuroretinal cell death and retinal dysfunction. NaIO3 induced retinal pigment epithelial cell death without changes in neuroretinal cell or serum miRNAs.In the present research, circulating miR-124-3p was elevated in a case of retinal ganglion and inner nuclear layer cell death as well as photoreceptor cell death. Our data suggest that different patterns of circulating miRNA elevations correspond to death of a specific neuroretinal cell. A miRNA panel consisting of miR-96-5p, -124-3p, and -183-5p may be used as a biomarker to detect neuroretinal cell death and identify the specific target cell.

Experimental study of the protective effects of SYVN1 against diabetic retinopathy

Genetic factors play an important role in the pathogenesis of diabetic retinopathy (DR). While many studies have focused on genes that increase susceptibility to DR, herein, we aimed to explore genes that confer DR resistance. Previously, we identified Hmg CoA reductase degradation protein 1 (SYVN1) as a putative DR protective gene via gene expression analysis. Transgenic mice overexpressing SYVN1 and wild-type (WT) mice with streptozotocin-induced diabetes were used in this experiment. Retinal damage and vascular leakage were investigated 6 months after induction of diabetes by histopathological and retinal cell apoptosis analyses and by retinal perfusion of fluorescein isothiocyanate-conjugated dextran. Compared with diabetic WT mice, diabetic SYVN1 mice had significantly more cells and reduced apoptosis in the retinal ganglion layer. Retinal vascular leakage was significantly lower in diabetic SYVN1 mice than in diabetic WT mice. The expression levels of endoplasmic reticulum (ER) stress-related, pro-inflammatory, and pro-angiogenic genes were also analyzed. Lower expression levels were observed in diabetic SYVN1 mice than in WT controls, suggesting that SYVN1 may play an important role in inhibiting ER stress, chronic inflammation, and vascular overgrowth associated with DR. Thus, these results strongly supported our hypothesis that SYVN1 confers DR resistance.

Organotypic culture of neural retina as a research model of neurodegeneration of ganglion cells

Organotypic models deserve special attention among the large variety of methods of vertebrate retina cultivation. The purpose of this study was to make a detailed qualitative and quantitative characterization of a model employing roller organotypic cultivation of the neural retina of rat eye posterior segment, with special attention to morphological and functional characteristics of retinal ganglion cells. The study included morphological analysis of retina histological preparations as well as estimation of RNA synthesis and evaluation of neuron survival by the Brachet and TUNEL methods, respectively. Retina has been shown to display normal morphofunctional characteristics for the first 12 h of cultivation. After 24 h, a substantial number of ganglion cells underwent pyknosis and stopped RNA synthesis. Almost all the cells of the retinal ganglion layer became apoptotic by 3-4 days in vitro. In the course of cultivation, neural retina is detached from the underlying layers of the posterior eye segment and undergoes significant cytoarchitectonic changes. The causes of ganglion cell death during organotypic cultivation of eye posterior segment are discussed. This method can serve as a suitable model for the screening of new retinoprotectors and for research on ganglion cell death resulting from retina degenerative diseases, e.g. glaucoma.

Optical Coherence Tomography Study of Experimental Anterior Ischemic Optic Neuropathy and Histologic Confirmation

The optic nerve is part of the central nervous system, and interruption of this pathway due to ischemia typically results in optic atrophy and loss of retinal ganglion cells. In this study, we assessed in vivo retinal changes following murine anterior ischemic optic neuropathy (AION) by using spectral-domain optical coherence tomography (SD-OCT) and compared these anatomic measurements to that of histology. We induced ischemia at the optic disc via laser-activated photochemical thrombosis, performed serial SD-OCT and manual segmentation of the retinal layers to measure the ganglion cell complex (GCC) and total retinal thickness, and correlated these measurements with that of histology. There was impaired perfusion and leakage at the optic disc on fluorescein angiography immediately after AION and severe swelling and distortion of the peripapillary retina on day-1. We used SD-OCT to quantify the changes in retinal thickness following experimental AION, which revealed significant thickening of the GCC on day-1 after ischemia followed by gradual thinning that plateaued by week-3. Thickness of the peripapillary sensory retina was also increased on day-1 and thinned chronically. This pattern of acute retinal swelling and chronic thinning on SD-OCT correlated well with changes seen in histology and corresponded to loss of retinal ganglion layer cells after ischemia. This was a serial SD-OCT quantification of acute and chronic changes following experimental AION, which revealed changes in the GCC similar to that of human AION, but over a time frame of weeks rather than months.

Comparative Study of Visual Pathways in Owls (Aves: Strigiformes)

Although they are usually regarded as nocturnal, owls exhibit a wide range of activity patterns, from strictly nocturnal, to crepuscular or cathemeral, to diurnal. Several studies have shown that these differences in the activity pattern are reflected in differences in eye morphology and retinal organization. Despite the evidence that differences in activity pattern among owl species are reflected in the peripheral visual system, there has been no attempt to correlate these differences with changes in the visual regions in the brain. In this study, we compare the relative size of nuclei in the main visual pathways in nine species of owl that exhibit a wide range of activity patterns. We found marked differences in the relative size of all visual structures among the species studied, both in the tectofugal and the thalamofugal pathway, as well in other retinorecipient nuclei, including the nucleus lentiformis mesencephali, the nucleus of the basal optic root and the nucleus geniculatus lateralis, pars ventralis. We show that the barn owl (Tyto alba), a species widely used in the study of the integration of visual and auditory processing, has reduced visual pathways compared to strigid owls. Our results also suggest there could be a trade-off between the relative size of visual pathways and auditory pathways, similar to that reported in mammals. Finally, our results show that although there is no relationship between activity pattern and the relative size of either the tectofugal or the thalamofugal pathway, there is a positive correlation between the relative size of both visual pathways and the relative number of cells in the retinal ganglion layer.