Objective：To observe the protective effect of ginkgo bilo ba extrac t (EGb 761), a free radical scavenger, on the photoreceptor cells after lighti nduced retinal damage. Methods：Seventytwo female SpragueDa wley (SD) rats we re randomly divided into 4 groups: normal control group, lightinduced retinal da m age model group, model+physiological saline group, and model+EGb 761 group, with 18 rats in each group. All of the rats except the ones in the control group were exposed to white light at (2740plusmn;120) lx for 6 hours after the dark adap tation for 24 hours to set up the lightinduced retinal damage model. Rats in m o del + physiological saline group and model+EGb 761 group were intraperitoneall y injected daily with physiological saline and 0.35% EGb 761 (100 mg/kg), respec tively 7 days before and 14 days after the light exposure. Apoptosis of photorec eptor cells was detected 4 days after light exposure; 7 and 14 days after light exposure, histopathological examination was performed and the layer number of ou ter nuclear layers (ONL) on the superior and inferior retina was counted. Results：Four days after light exposure, the apoptosis of photorecep tor cells was fou nd on ONL in model, model+ physiological saline and model+EGb 761 group, and w as obviously less in model + EGb 761 group than in model and model+physiologic al saline group. Seven days after light exposure, the layers of ONL on the super ior retina were 3 to 4 in model and model+physiological saline group, and 7 to 8 in model+EGb 761 group; the mean of the layer number of ONL in model+EGb 761 group (6.92plusmn;0.82) was less than that in normal control group (8.40plusmn;0.95) (t=-1.416, P＜0.05), but significantly more than that in model (5.96 plusmn;1.36 ) and model+physiological saline group (5.90plusmn;1.40）（t=1.024, 1.084; P＜0.05). Fourteen days after light exposure, the layers of ONL on the superior retina were 0 to 1 in model and model+physiological saline group, and 3 to 4 i n model+EGb 761 group. The mean of the layer number of ONL in model+EGb 761 group (5.5 2plusmn;1.06) was significantly more than that in model (3.44plusmn;2.15) and model + physiological saline group (3.37plusmn;1.91) (t=2.082, 2.146, P＜0.05). Conclusion：EGb 761 can partially inhibit the apoptosis of pho toreceptor cells, thus exert protective effect on photoreceptor cells.
Objective To study the response of the retinal neuronal adaptive system to changes of background illumination (BG) by measuring the oscillatory potentials (OPs) and the a- and b-waves of the electroretinogram (ERG) in different BG illuminations. Methods The a- and b-wave and the digitally filtered OPs were simultaneously recorded from Wistar Fu rats aged from 25 to 29 days during dark adaptation (DA) and during 6~8 minutes of BG illuminations at four levels increased successively by steps of two log units, i.e., ldquo;low scotopicrdquo; level of 1.43times;10-6cd/m2, ldquo;high scotopicrdquo; of 1.43times;10-4cd/m2 , ldquo;low mesopicrdquo; of 1.43times;10-2cd/m2 and ldquo;high mesopicrdquo; of 1.43times;10-2cd/m2. Full field stimulus flashes of 75 msec duration and 1.43times;10-2cd/m2intensity was delivered at an interval of 1 minute. Results Five OP wavelets were recorded in DA and during scotopic BG illuminations. The number of wavelets was reduced to three as the eyes were exposed to mesopic BG levels. However, the sum of OPs amplitudes (SOPs) increased as the BG was intensified, except at ldquo;high mesopicrdquo; level, by which a significant decrease of SOPs occurred. The amplitudes of the a-and b-waves remained unchanged at the two scotopic BG and decreased as the BG intensity increased to mesopic levels. Conclusion The response of retinal neural adaptive system of the Albino rat to changes of BG light is more sensitive and robust than the slow components of the ERG. The enhancement of the oscillatory responses at ldquo;low mesopicrdquo; illumination level suggests that using proper BG light may be conducive to reducing the variation of OPs. (Chin J Ocul Fundus Dis, 2001,17:286-288)
Objective To assess the protective effect of recombinant human erythropoietin (EPO) on human retinal pigment epithelial (RPE) cells injured by light. Methods Cultured human RPE cells were exposed to light for 12 hours, and the culture was stopped 24 hours later. The 3(4,5dimethylthiazole2y1)2,5diphenyl tetrazolium bromide (MTT) cell viability assay and annexin V flunorescein isothiocyanate/propidium iodium labeling and flow cytometry were used to assess the effects of EPO with different concentration on the cellular viability and apoptosis of human RPE cells. The protective effect and mechanism of EPO on RPE cells injured by light was detected by adding AG490. Results EPO, especially with the concentration of 40 IU/ml, obviously increased the cellular viability of RPE cells and apparently decrease the cellular apoptosis induced by light injury. After adding AG490, the effects of EPO on cellular viability and apoptosis were inhibited. Conclusion It is suggested that EPO can protect the human RPE cells from lightinduced injures, and its protective mechanism works after the combination of EPO and its receptor.
Objective To observe the expression of proteins in light-injured retinal pigment epithelial (RPE) cells. Methods ARPE19 cells were exposed to the cool white light at the intensity of (2200plusmn;300) Lx for 6 hours to set up the light injured model. Cellular soluble proteins was extracted and analyzed by means of twodimensional electrophoresis to find out the changes of protein map of lightinjured RPE cells. Results Cellular soluble proteins had (390plusmn;10) spots on the map, in which 11 spots had obvious difference between the light injured group and the normal control group. In the lightinjured cells, the expressio of 8 proteins increased, 1 decreased, and 2 disappeared. Conclusion Twodimensional electrophoresis can find out the difference of expression of proteins in lightinjured and normal RPE cells.
Objective To observe the expression of vascular endothelial growth factor A (VEGFA) and its receptors sFlt-1, kinase insert domain receptor (KDR) in lightinjured human retinal pigment epithelial (RPE) cells. Methods Cultured human RPE cells (8th - 12th generations) were divided into normal control group and light damage group. The cells of two groups were exposed to the 18 W cold white light (2200±300) Lux for 12 hours to induce light damage responses, but the cells of normal control group were packed by tinfoil with doubledeck high pressure disinfection. The VEGF-A, sFlt-1 and KDR mRNA and protein expressions were detected by reverse transcriptionpolymerase chain reaction (RT-PCR) and Western blot at 0, 6, 12, 24 hours after light damage. Results The VEGF-A mRNA and protein expressions in light damage group were significantly increased at 6 hours, and reached its peak at 12 hours after light damage which obviously higher than that in normal group (t=2.74, 2.93; P＜0.05), and then went down gradually. The sFlt-1 mRNA and protein expressions in light damage group reached its peak at 12 hours after light damage which obviously higher than that in normal group (t=4.32, P＜0.01), but obviously lower than that in normal group at 24 hours after light damage (t=2.41, P＜0.05). The KDR mRNA and protein expressions in light damage group were obviously higher than that in normal group at 24 hours after light damage （t=2.89, P＜0.05）,but there was no changes at 6, 12 hours after light damage (t=1.84, P＞0.05). Conclusions At 6, 12 hours after light damage, the expressions of VEGF-A and sFlt-1 increases significantly and KDR expression is stable in lightinjured RPE cells. At 24 hours after light damage, the expression of VEGF-A and sFlt-1 decreases, but KDR expression increases in light-injured RPE cells.
Objective To observe the pathological and functional changes of retinal photochemical damages exposed to green flurescent light. Methods The Sprague Dawley rats were continually exposed to green fluorescent light with an illuminancem level of (1 900plusmn;106.9) Lx for 24 hours.The changes of retinal morphology and morphometrics and flash electroretinogram were studied before light exposure and at the 6th hour,6th day and 14th day after light exposure. Results At the 6th hours after light exposure,the outer nuclear layer(ONL)of retina becoma thinner compared with that bfore light exposure.The thickness of ONL decreased by 23.91% and the inner and outer segments appeared disorderly arranged.At the 6th day after light exposure the thickness of ONL is thinner than that at the6th hour,i.e.decreased by 46.6%. At the 14th day after light exposure the thickness of ONL decreased by 42.40%.Flash electroretinogram showed that the amplitudes of a and b wave decreased continuously at the 6th hour and 6th day and unrecovered at the 14th day after light exposure. Conclusion This model might be an ideal one for research on retinal photochemical damage. (Chin J Ocul Fundus Dis,1998,14:101-103)
PURPOSE:The changes of expression level of rhodopsin mRNA and its relationship with the morphology in light damaged rat retinas were studied. METHODS:The changes of expresson level of rhodopsin mRNA in light damaged rat retinas and the changes on retinal morphology were observed through the technique of in situ hybridization and electron microscopy. RESULTS:The hybridization signals of rhodopsin mRNA mainly distributed in the photoreceptor layer of retina,relatively b in the inner and outer segments. As the increase of light exposure time,the expression level of rhodopsin mRNA in retinas greatly decreased before the changes on morphological injury of retina. For the same eye globe of the same rat at the same time,the hybridization signals at the upper and posterior region of the retina decreased more obviously than the lower and peripheral region of the retina. CONCLUSIONS:It was demonstrated for the first time that the expression of rhodopsin mRNA was located at the photoreceptor layer of the retina. Continuous exposure to light could greatly decrease the expression of rhodopsin mRNA and the decreases differ regionally. It might be the early signals of retinal photic injury.It is a good method to study the expression level of retina mRNA through the in situ hybridization. （Chin J Ocul Fundus Dis,1997,13: 228-210）
Purpose To evaluate the prostag landins(PG) levels and to identify the effect of dexamethasone(DXM) on PG in response to photochemical insult in rat retina. Methods The experiments were performed on 36 SD rats which were separated into two groups,control and treated groups,and the latter received daily intraperitoneal injections of DXM (1 mg/kg) for 5 consecutive days,starting 3 days before light exposure.The animals were continually exposed to green fluorescent light(510-560 nm)with an illuminance level of (1900plusmn;106.9)lx for 24 hrs.The retinal concentration of PGE 2 and 6-keto-PGF1alpha; were tested at 6hrs,1,3,7 and 14 days after light exposure. Results The PGE2 and 6-keto-PGF1alpha; levels of the control groups (37.50plusmn;2.75,48.06plusmn;4.0 4,81.90plusmn;4.89) pg/mg and (4.68plusmn;0.69,7.50plusmn;0.57,10.40plusmn;0.71) pg/mg had significantly higher values than those of the treated rats(20.60plusmn;4.28,37.36plusmn; 3.34,54.85plusmn;4.57) pg/mg and (2.50plusmn;0.59,4．68plusmn;0.81,6.87plusmn;1.10)pg/mg (Plt;0.01) after 6 hrs,1 and 3 days light exposure respectively. Conclusion By inhibition of PG synthesis,the DXM may play an ameliorative effect on retinal photochemical injury of rats. (Chin J Ocul Fundus Dis,1999,15:94-96)
Objective To observe the effect of visible light on apoptosis of cultured human retinal pigment epithelium (RPE) cells. Methods Being the light source,500lx,(2 000±500)lx and (3 400±200)lx cold white light were used. The duration of exposure was 0,6,12 and 24 hours respectively. Apoptosis was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labelling, Annexin V-flunorescein isothiocyanate/Propidium iodium labelling and flow cytometry. Results Apoptosis and necrosis were found in cultured human RPE cells which were exposed to visible light.(1)A significant increase in apoptotic and necrotic percentages was consistent with a higher light intensity.(2)Apoptosis was the main response to shorter (6 h and 12 h) exposure duration,while necrosis was more pronounced correlated to the prolongation of post-exposure culture (P＜0.05),and the longer the post-exposure period was, the more apoptotic necrosis were seen.Thirty-six hours after exposure the necrotic percentages were more pronounced (P＜0.01). Conclusions Visible light (＞500 lx) increases the proportion of apoptosis and necrosis of human RPE cells in vitro.The extent is related to exposure intensity and duration. It demonstrates that the lower intensity and the shorter duration of exposure to light are, the more pronounced apoptotic percentages are observed,otherwise necrosis. (Chin J Ocul Fundus Dis, 2002, 18: 227-230)
Purpose To observe the pathologic changes of retinal photic injury in mice. Methods A light damaged trunk was designed by ourselves.The mice were given an intermitent light exposure for 3 days,12 hours light exposure every day and 12 hours dark adaption before every exposure.Experimental animals were sacrificed on the 1st,6th,12th,18th and 30th day after light injury,and the eyes were enucleated for light and electronic microscopy observation. Results The early pathologic changes including disc membrance swelling,disorganization in outer segments,and mitochondrial swelling,spherical change in inner segments．Then the chromatin densification,liquefaction and margination,and the shrinkage of nuclear membrance were found in the nuclear layer.Finally the outer nuclear layer became thin and disappeared.The apical microvill of RPE cell disappeared and basic fold became flat in some samples. Conclusion The photoreceptor degeneration was the pathologic characteristic of retinal photic injury in mice. (Chin J Ocul Fundus Dis,1998,14:215-218)