Phototoxicities Caused by Continuous Light Exposure Were Not Induced in Retinal Ganglion Cells Transduced by an Optogenetic Gene

The death of photoreceptor cells is induced by continuous light exposure. However, it is unclear whether light damage was induced in retinal ganglion cells with photosensitivity by transduction of optogenetic genes. In this study, we evaluated the phototoxicities of continuous light exposure on retinal ganglion cells after transduction of the optogenetic gene mVChR1 using an adeno-associated virus vector. Rats were exposed to continuous light for a week, and visually evoked potentials (VEPs) were recorded. The intensities of continuous light (500, 1000, 3000, and 5000 lx) increased substantially after VEP recordings. After the final recording of VEPs, retinal ganglion cells (RGCs) were retrogradely labeled with a fluorescein tracer, FluoroGold, and the number of retinal ganglion cells was counted under a fluorescent microscope. There was no significant reduction in the amplitudes of VEPs and the number of RGCs after exposure to any light intensity. These results indicated that RGCs were photosensitive after the transduction of optogenetic genes and did not induce any phototoxicity by continuous light exposure.

Protective roles of ketamine and xylazine against lightinduced retinal degeneration in rats

Purpose: To study the protective effects of ketamine and xylazine against light exposure-induced retinal degeneration (RD) in rats. Methods: Sprague Dawley rats were divided into three groups viz: light damage before anesthesia (LAE), light damage only (LDO), and control (CON) group which was kept in the dark for 12 - 18 h to habituate before light exposure. LDO group was exposed to light before anesthesia, while LAE group was maintained under anesthesia with ketamine and xylazine. The groups were kept for 120 min in darkness after anesthesia prior to light exposure and they were awakened prior to light damage. Functional assessment was carried out using electroretinography while morphological analysis was carried out using histology and immunochemistry techniques. Results: Ketamine-xylazine combination preserved the function of the retina and protected against light-induced RD based on retinal imaging studies and immunochemistry analysis. Xylazine and ketamine anesthesia provided protection against light-induced retinal damage, and thus reduced photoreceptor cell death. Conclusion: These results indicate that xylazine and ketamine anesthesia offer protection against lightinduced damage and photoreceptor cell death in rats, and therefore, can potentially be developed for use in humans.

Rhopalosiphum rufiabdominalis (rice root aphid).

R. rufiabdominalis is an economic pest of upland rice, particularly in Japan, but is not a pest of irrigated rice anywhere in the world (Grist and Lever, 1969). Injury to upland rice can be severe in Japan, with losses of up to 50-70% (Yano et al., 1983). Occurrence was related to the cultivars of upland rice in China, where aphids caused light damage at the seedling stage and heavy damage at the tillering stage (Ding, 1985). Generally, aphids cause more serious damage during the early growth stages (Yano et al., 1983).

A Comparative Analysis of Reactive Müller Glia Gene Expression After Light Damage and microRNA-Depleted Müller Glia—Focus on microRNAs

Müller glia (MG) are the predominant glia in the neural retina and become reactive after injury or in disease. microRNAs (miRNAs) are translational repressors that regulate a variety of processes during development and are required for MG function. However, no data is available about the MG miRNAs in reactive gliosis. Therefore, in this study, we aimed to profile miRNAs and mRNAs in reactive MG 7 days after light damage. Light damage was performed for 8 h at 10,000 lux; this leads to rapid neuronal loss and strong MG reactivity. miRNAs were profiled using the Nanostring platform, gene expression analysis was conducted via microarray. We compared the light damage dataset with the dataset of Dicer deleted MG in order to find similarities and differences. We found: (1) The vast majority of MG miRNAs declined in reactive MG 7 days after light damage. (2) Only four miRNAs increased after light damage, which included miR-124. (3) The top 10 genes found upregulated in reactive MG after light damage include Gfap, Serpina3n, Ednrb and Cxcl10. (4) The miRNA decrease in reactive MG 7 days after injury resembles the profile of Dicer-depleted MG after one month. (5) The comparison of both mRNA expression datasets (light damage and Dicer-cKO) showed 1,502 genes were expressed under both conditions, with Maff , Egr2, Gadd45b, and Atf3 as top upregulated candidates. (6) The DIANA-TarBase v.8 miRNA:RNA interaction tool showed that three miRNAs were found to be present in all networks, i.e., after light damage, and in the combined data set; these were miR-125b-5p, let-7b and let-7c. Taken together, results show there is an overlap of gene regulatory events that occur in reactive MG after light damage (direct damage of neurons) and miRNA-depleted MG (Dicer-cKO), two very different paradigms. This suggests that MG miRNAs play an important role in a ubiquitous MG stress response and manipulating these miRNAs could be a first step to attenuate gliosis.

The anti-oxidative Effect of Chrysanthemum Extract on Retinal- light Damage of Mice

Background:Apoptosis of photoreceptor cells and oxidative stress of RPE in age-related macular degeneration (AMD) could be promoted by photopic oxidative stress. In our study we are aim to study the protective effect of chrysanthemum extract on light damaged retina of mice.Methods:In vitro, ARPE-19 cells are incubated and divided into four groups: the control, the light damaged, the low and high dose-chrysanthemum extract groups. The last three groups were dropped in zero, low and high concentration of chrysanthemum extract separately before exposing to light. Cellular viability and Reactive Oxygen Species(ROS) production were measured by MTT and immunofluorescence. In vivo, C57BL/6J mice were divided into four groups as above mentioned. Low and high concentration of chrysanthemum extract were given by continuous intragastric administration before being exposed to white light. Retinal function was evaluated by electroretinogram. Optical coherence tomography and Fluorescein fundus angiography were used to observe the morphology and vessels. HE staining and TUNEL immunofluorescence for presenting morphology and apoptosis of isolated retina.Results:Viability of ARPE-19 cells decreased and ROS production increased after the light damaged. However, treatment with chrysanthemum extract, viability improved and ROS declined. After light injury, dysfunctional retina, destroyed morphology and increased apoptosis rate were observed in mice especially in RPE and photoreceptor layer. Treatment with chrysanthemum extract, retina function improved as well as structure of RPE and photoreceptor layers. Rate of apoptosis decreased via the raised concentration of anti-oxidative enzyme superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). Conclusions:Preventive administration of chrysanthemum extract reduces the oxidative-stress induced by light damage, which indicating Chrysanthemum have a potential of preventive measure for AMD.

Light intensity affects the coloration and structure of chimeric leaves of Ananas comosus var. bracteatus

Ananas comosus var. bracteatus is an important tropical ornamental plant because of its green/white chimeric leaves. The accumulation of anthocyanin makes the leaf red especially the white margin. However, the leaves lost red color in summer and winter. Light intensity is one of the most important factors affecting leaf color along the season. In order to understand the effects of light intensity on the growth and coloration of the chimeric leaves, Ananas comosus var. bracteatus was grown under full sunlight, 50% shade and 75% shade for 75 days to evaluate the content of pigments, the color parameters (value L*, a*, b*) and structural histocytology characteristics of chimeric leaves. The results showed that high irradiance was beneficial to keep the chimeric leaves red. However, prolonged exposure to high irradiance caused light damage, some of the leaves wrinkled and even burned. Shading decreased the content of anthocyanin and increased the content of chlorophyll especially in the white margin of the leaves. Numerous chloroplasts were found in the mesophyll cells of the white margin part of chimeric leaves under shading for 75 days. The increase of chlorophyll content resulted in better growth of plants. In order to balance the growth and ornamental value of the leaves, approximately 50% shade is suggested to be the optimum light irradiance condition for Ananas comosus var. bracteatus in summer.