Objective To study on the ultrastructural characteristic of segments of photoreceptors from neonatal retinas for supporting donor retina choice of retinal transplantation． Methods Photoreceptors from neonatal calf and adult calf were analysed by scanning electron microscopy and transmission electron microscopy． Results Segments of photoreceptors from neonatal calf appeared the mushroom pattern, in which, distal end of outer segment which was ball-shaped formed the head with mushrooms appearance, and the inner segments along with some of outer segments formed the body with mushrooms appearance． Within the outer segment, plasma membranes of adjacent evaginations form a disk subsequently． The a rray of most disks were vertical to the entire length of segments, but some were parallel and slope to．Owing to the incomplete formation, some rim of disk near distal end of outer segment revealed step-shaped appearance． The distal end of outer segment displays some processes consisted of membranous discs, much vesicular material and mitochondria, much rough endoplasmic reticulum (RER) and numerous polyso mes．Segments of photoreceptor connected with outer nuclear layer via the external limiting membrane． Conclusion The typical morphol ogical structures of outer segments suggest the immature and b gowth ability of photoreceptors of the retina of neonatal calf, and therefore the competence for donor material of retinal transplantation． (Chin J Ocul Fundus Dis, 2001,227-229)
Objective To observe the relationship between the size of idiopathic macular hole (IMH) and the healing types of postoperative photoreceptor layer after vitrectomy. Methods This prospective uncontrolled study included 33 eyes of 31 consecutive patients who underwent vitrectomy for IMH. There were 9 males (9 eyes) and 22 females (22 eyes), with the mean age of (58.16±9.10) years. The mean duration of symptoms was (4.97±5.97) months. The best corrected visual acuity (BCVA) and optical coherence tomography (OCT) were measured for all patients. BCVA was measured with international standard visual acuity chart and then converted to logarithm of the minimum angle of resolution (logMAR). The mean logMAR BCVA was 1.07± 0.38. The mean intraocular pressure was (14.05±0.54) mmHg (1 mmHg=0.133 kPa). The minimum size of the macular hole (MIN), the base diameter of the macular hole (BASE), the average width of the macular hole (AWMH) and the average height of the macular hole (AHMH) were (465.19±232.84), (943.63±389.26), (704.72±292.64), (443.84±72.47) μm, respectively. According to the MIN value, the hole size were divided into small, medium and large group which had 9 eyes, 15 eyes, 9 eyes, respectively. According to the postoperative OCT characteristics, the healing types of the photoreceptor layer were divided into 0 - Ⅳ types. All patients underwent pars plana vitrectomy (25G or 27G standard three-incision) with internal limiting membrane peeling with tamponade agents. The mean follow-up was (326.42±157.17) days. The first postoperative OCT characteristics were defined as the early period. The therapy results were evaluated according to the last follow-up time point. BCVA and intraocular pressure before and after operation were compared by paired t test. The postoperative BCVA were compared with preoperative BCVA, MIN, AWMH, AHMH and follow-up using Pearson correlation analysis. Results At the last follow-up, the LogMAR BCVA was 1.52 - 1.40 in 3 eyes, 1.30 - 0.52 in 22 eyes and 0.40 - −0.07 in 8 eyes. Compared with preoperative that, the difference was statistically significant (t=−6.023, P＜0.001). The photoreceptor healing was type 0 in 10 eyes (30.3%), type Ⅰ in 4 eyes (12.1%), typeⅡ in 10 eyes (30.3%), type Ⅲ in 9 eyes (27.3%) at the early postoperative period. The photoreceptor healing was type 0 in 5 eyes (15.2%), type Ⅰ in 5 eyes (15.2%), type Ⅲ in 12 eyes (36.4 %), type Ⅳ in 11 eyes (33.3%) at the last follow-up. The preoperative size of IMH was negatively correlated to the photoreceptor healing types at early postoperative period (r=−0.590, P＜0.01) and the last follow-up (r=−0.768, P＜0.01), respectively. The correlation analysis showed that the postoperative BCVA associated with the preoperative BCVA, the stage of the macular hole, the size of the macular hole, MIN, BASE, AWMH, AHMH, the healing types of photoreceptor layer of the early and the last follow-up after surgery (r=0.500, 0.370, 0.470, 0.435, 0.533、0.505, 0.462, −0.442, −0.656, P＜0.05). There was no correlation between age, visual decreasing times and follow-up times (r=0.285, 0.234, −0.310, P＞0.05). Conclusion The preoperative sizes of IMH were associated with the postoperative healing types of photoreceptor layer.
Objective To demonstrate if apoptosis is one of the mechanisms of siderotic retinopathy. Methods Autoclaved iron particles were implanted in the vitreous cavities of 32 eyes of SD rats.Glass chips were implanted in 10 control eyes.The experimental eyes were enucleated at various time intervals from days 1 to 15.Retinal degeneration was examined using the TdT-mediated,dUTP-biotin nickend labeling(TUNEL)method.Electrophoresis on agarose gel was used to detect internucleosomal DNA fragmentation.Results TUNEL-positive nuclei were observed only in the outer nuclear layer beginning on day 2.The nuclei spread throughout the outer nuclear layer by the end of day 3.No TUNEL-positive nuclei were observed in other layers throughout the experimental perios.Analysis of DNA,extracted from the retinas by electrophoresis on agarose gel,revealed a typical ladder pattern of internucleosoma DNA cleavage in the experimental eyes.ConclusionApoptosis of photoreceptors occurs at the early phase of iron-induced retinopathy in the rats.
Objective To observe the effects of Crumbs (Crb) proteins on different types of zebrafish photoreceptors. Methods The retinal cell population dynamics of adult wild-type zebrafish and Tg (RH2-2:Crb2b-sf-EX/RH2-2:GFP)pt108b transgenic zebrafish (called pt108b zebrafish for short) were evaluated by monitoring the densities of three categories of retinal photoreceptors (rod cells, UV cone cells and RGB cone cells) in different retinal regions, which were visualized by Feulgen nuclear staining histology technique. Results The wild-type zebrafish retinal photoreceptor cell densities are generally higher in the central region than the peripheral regions. Compared with wild-type zebrafish, pt108b zebrafish had much less RGB cone cells at the top of outer nuclear layer, and no RGB cone cells at the central and intermediate regions of retina. While pt108b zebrafish had normal density of UV cone cells at the top of rods and the bottom of outer limiting membrane, they had much higher density of rods. Conclusions Crb proteins may affect the zebrafish retinal cell densities of different photoreceptor types.
Cilia are hair-like protuberance on cells of the human body that play a vital role in organs generation and maintenance. Abnormalities of ciliary structure and function affect almost every system of the body, such as the brain, eyes, liver, kidney, bone, reproductive system and so on. Retinal photoreceptor cells are one of sensory neurons which convert light stimuli into neurological responses. This process, called phototransduction, takes place in the outer segments (OS) of rod and cone photoreceptors. OS are specialized sensory cilia, and disruptions in cilia genes, which are causative in a growing number of non-syndromic retinal dystrophies, such as retinitis pigmentosa, Leber’s congenital amaurosis. These syndromes are genetically heterogeneous, involving mutations in a large number of genes. They show considerable clinical and genetic overlap. At present, there are few researches on retinal ciliopathies and clinical treatment strategy. This review shows a comprehensive overview of ciliary dysfunction and visual development related diseases, which contributes to understand the characteristics of these diseases and take early intervention in clinic.
An experimental model of retinal acute photic injury was developed in Wister rats. Aninmls were exposed to white light in intensity of 20 000 lux under general anesthesia for 1 hr. Two rats were sacrificed at 24, 48hr, day 7, 14,21,28,35 after liht exposure respectively. The histopathologic study showed that the retinal acute photic injury initiated in the outer seSment characterized by disorganization and loss of the outer segment at the early stage, and then the inner segment and RPE were involved. The decrease of the thickness of the outer nuclear layer was seen in a few of our cases. Some of our samples showed recovery of the outer and inner segment from the light damage of certian degrees 2 or 3 weeks after light exposure, but others did not. One sample from 5 weeks after light exposure demonstrated that the outer nuclear layer, the outer and inner segment completely lost. Thc inflammatory responses were not observed in all of our samples inplicating that the retinal acute photic damage is a degeneration process. （Chin J Ocul Fundus Dis,1994,10:84-85）
Objective To observe the changes of electrophysio logical results in rabbits with normal and injured photoreceptor due to subretinal implantation of chip. Methods Photoreceptor damage was induced by injection with NaIO3 solution in 22 out of 30 rabbits. A chip with the diameter of 3 mm made by the array composed of 90 microelectrodes photodiode and conjoint electrode was implanted into subretinal space or choroid of the right eyes of 22 rabbits with photoreceptor and 4 normal rabbits, and the left eyes were the control. The examinations of local flash-visual evoked potential (F-VEP), local flash-electroretinogram (F-ERG), full-field F-ERG and full-filed F-VEP were measured respectively.Another 4 rabbits underwent biocular extirpation for path ological examination . Results In 22 rabbits with photo-receptor damage, the amplitude of the main wave of local ERG was obviously higher in 11 eyes with chips than that in the control ones, and was also higher in 2 eyes with chips of the 4 mormal rabbits than that in the control eyes. No wave was found in an eye with retinal hole on the surface of the chip. The repeataility of main amplitude of local-VEP and full-field F-VEP is not satisfactory; no significant changes were observed between chip-implanted eyes and the control eyes examined by full-filed F-ERG. Conclusion The implanted chip may stimulate local retina and induce electrical activities after stimulated by light. (Chin J Ocul Fundus DIs, 2006, 22: 324-327)
Photoreceptor cells are special retinal neurons with photo-transformation ability. Loss of photoreceptors in age-related macular degeneration (AMD) is secondary to RPE loss, leakage of serum components from the neovascularization and scar formation, which is one of the main mechanisms of irreversible visual impairment in patients with AMD. Many studies have shown that inflammatory environment is involved in the process of photoreceptor cell death. Aging, photooxidation injury and other factors affects the retinal microenvironment through different levels of mechanisms such as retinal pigment epithelial cells, retinal glial cells, hematogenous macrophages and inflammatory factors, which results in photoreceptor injuries and participates in the progression of AMD by drusen formation and neovascularization. This study reviews the research status and progress of inflammation and photoreceptor cell death, and provides new ideas for exploring the blinding mechanism and treatment strategies of AMD.
ObjectiveTo observe the morphological characteristics of photoreceptor necroptosis in experimental retinal detachment, and explore the mechanism. MethodsA total of 60 Sprague-Dawley male rats were included in this study. Retinal detachment were induced in the right eyes with 1% sodium hyaluronate (50 μl) injection (experimental group), while the left eyes received no treatment (control group). At 3 days after modeling, the morphological characteristics of photoreceptor cell were observed by electron microscopy. Cleaved Caspase 8 and phosphorylation receptor-interacting protein 1 (p-RIP1) were measured by Western blot and immunoprecipitation. ResultsAt 3 days after modeling, photoreceptor necroptosis showed the following morphological features: chromatin condensation, severe vacuolation, early loss of plasma membrane integrity, and many autophagosomes. Western blot showed that the protein expression of cleaved Caspase 8 were 0.78±0.03, 0.06±0.01 in experimental group and control group respectively, which was significantly different (F=4 023.21, P < 0.05). Immunoprecipitation showed that the protein expression of p-RIP1 were 0.23±0.03, 0.14±0.02 in experimental group and control group respectively, which was significantly different (F=56.44, P < 0.05). ConclusionsPhotoreceptor necroptosis showed chromatin condensation, severe vacuolation, early loss of plasma membrane integrity, and many autophagosomes. Necroptosis activation was associated with the increase of RIP1 phosphorylation.