Developmental dependence for functional eye regrowth in Xenopus laevis

Introduction：A key challenge in designing tissue repair strategies is knowing whether and how developmental mechanisms are used for successful repair of mature/adult tissues.Although it is known that developmental components are used in repair,it remains mostly unclear which ones are required and whether they act similarly as during development.This issue is further complicated by the fact that it is difficult.

Expression of nitric oxide synthase in the developing eye of Ze-brafish Danio rerio

Expression of nitric oxide synthase (NOS) in the developing eye of zebrafish was studied by NADPH-diaphorase staining technique. NOS activity was first observed in the optic primordium and the lens placode at 5-somite stage, and remained basically unchanged up to the prim-5 stage. Upon hatching, NOS activity was nearly equally detected in the gangalion cell layer and the photoreceptor layer in the developing retina. However, it began declining in the inner plexiform layer and the inner nuclear layer at this stage. NOS activity disappeared in the lens although the anterior lens epithelium was strongly stained. Two days after hatching, NOS activity was still strong in the photoreceptor layer, but decreased markedly in the gangalion cell layer, the inner plexiform layer and the inner nuclear layer with the retinal patterning. These suggested that nitric oxide (NO), the product of NOS, is not only involved in the modulation of patterning and differentiation of the retinal cells but also in the regulation of proliferation, and differentiation of the lens fibrocytes.

Myopia induced by flickering light in guinea pigs: a detailed assessment on susceptibility of different frequencies

AIM: To investigate the effectiveness and feasibility of inducing myopia in guinea pigs by flickering light (FL) stimulation with different frequencies. METHODS: Seventy 2 -week-old guinea pigs were randomly assigned to six groups: five FL groups and a control group (n =12 for each). Animals in the five FL groups were raised under 500lx illumination with a duty diurnal cycle of 50% at a flash rate of 5, 1, 0.5, 0.25 and 0.1Hz respectively. Those in the control group were reared under steady 250lx illumination. Refraction, axial length, and radius of curvature were measured before and at 2, 4, 6, 8, 10 and 12 weeks after treatment. At week 12, the eyeballs were taken out and three ocular dimensions and dry weight of sclera were measured. RESULTS: A myopic shift and axial eye length increase developed in the five FL groups. Stimulation at 0.5Hz caused greater changes in myopic shift, axial elongation, eyeball dimension, and dry weight of sclera than stimulation at other frequencies. Compared with controls, eyes in 0.5Hz group were approximately -5.5 ±1.5D more myopic with increase in horizontal, vertical, axial dimensions by 0.89 ±0.3mm, 0.69 ±0.2mm, 1.12 ±0.2mm respectively and with increase in dry weight of sclera by 0.44mg. CONCLUSION: Chronic exposure to periodic illumination at temporal frequency is attended by development of excessive ocular enlargement and myopic refractive error. Emmetropization could bedisrupted differently by frequency alteration.

Eye on Development

How to solve the refugee crisis in Africa.The refugee problem has caught the attention of the international community as the number of refugees worldwide has reached a record high.

Differentially expressed genes identified by cross-species microarray in the blind cavefish Astyanax

Changes in gene expression were examined by microarray analysis during development of the eyed surface dwelling(surface fish)and blind cave-dwelling(cavefish)forms of the teleost Astyanax mexicanus De Filippi,1853.The cross-species microarray used surface and cavefish RNA hybridized to a DNA chip prepared from a closely related species,the zebrafish Danio rerio Hamilton,1822.We identified a total of 67 differentially ex-pressed probe sets at three days post-fertilization:six upregulated and 61 downregulated in cavefish relative to surface fish.Many of these genes function either in eye development and/or maintenance,or in programmed cell death.The upregulated probe set showing the highest mean fold change was similar to the human ubiquitin specific protease 53 gene.The downregulated probe sets showing some of the highest fold changes corresponded to genes with roles in eye development,including those encoding gamma crystallins,the guanine nucleotide binding pro-teins Gnat1 and Gant2,a BarH-like homeodomain transcription factor,and rhodopsin.Downregulation of gam-ma-crystallin and rhodopsin was confirmed by in situ hybridization and immunostaining with specific antibodies.Additional downregulated genes encode molecules that inhibit or activate programmed cell death.The results suggest that cross-species microarray can be used for identifying differentially expressed genes in cavefish,that many of these genes might be involved in eye degeneration via apoptotic processes,and that more genes are downregulated than upregulated in cavefish,consistent with the predominance of morphological losses over gains during regressive evolution.