Depolarizing effect of GABA in rod bipolar cells of the mouse retina

Gamma-amino butyric acid (GABA) has been characterized as inhibitory neurotransmitter through chloride mediated channels in the adult nervous system. However, using gramicidin perforated patch-clamp recordings from rod bipolar cells dissociated from retinas of adult mice, we find that GABA is capable of inducing cell depolarization. Currents mediated by GABA(A) and GABA(C) receptors were further isolated by the use of GABA receptor specific blockers. In rod bipolar cells dissociated from the mouse retina, activation of GABA(A) receptors located at the cell dendrites induces ionic currents which show a reversal potential of -33 mV. However, local activation of GABA(C) receptors located at the axon terminal induces ionic currents with a reversal potential of -60 mV. According to Nernst equation, the dendrites of rod bipolar cells of the mouse retina would have a high intracellular chloride concentration ([Cl(-)](i)) and there must be an intracellular gradient in [Cl(-)](i), being the [Cl(-)](i) more elevated in the dendrites than in the axon terminal. The depolarizing effect of GABA at the dendrites of rod bipolar cells may contribute to the lateral interaction in the mammalian retina, thereby enhancing visual discrimination of stimuli input.     

Long-term neuroretinal full-thickness transplants in a large animal model of severe retinitis pigmentosa

Background The purpose of this study was to explore neuroretinal transplantation in a large animal model of severe retinitis pigmentosa and to establish graft development, long-term survival, graft-host integration, and effects on the host retina. Methods Rhodopsin transgenic pigs, aged 6 months, received in one eye a fetal full-thickness neuroretinal sheet in the subretinal space by means of vitrectomy and retinotomy. Six months postoperatively, eyes were studied in the light microscope and with immunohistochemical markers. Full-field electroretinography (ERG) was performed at 4 and 6 months. Results Laminated grafts with well-organized photoreceptors, rod bipolar cells, and Müller cells were found in five of six eyes. Neuronal connections between graft and host retina were not seen. In the five eyes containing a graft, the number of surviving rods in the host retina was significantly higher compared with unoperated eyes. The ERG did not reveal any significant difference in b-wave amplitude between operated and control eyes, but the cone-derived response in operated eyes increased significantly from 4 to 6 months while the rod response in control eyes decreased significantly. Conclusions Fetal full-thickness neuroretina can be transplanted safely to an eye with severe retinal degeneration. In their major part, the transplants develop a normal laminated morphology and survive for at least 6 months. Graft and host retinal neurons do not form connections. Retinal function in the host is reduced initially by the surgical trauma, but the presence of a well-laminated graft counteracts this effect and rescues rods from degeneration. Supported by The Foundation Fighting Blindness (grant# C-NC02-798-0078), The Faculty of Medicine, University of Lund, The Swedish Research Council, The Princess Margaretas Foundation for Blind Children, The 2nd ONCE International Award for New Technologies for the Blind.     

Effect of exogenous administration of nerve growth factor in the retina of rats with inherited retinitis pigmentosa

NGF is implicated in retinal damage regression. To study whether this is a direct effect or an effect mediated by NGF on other endogenous biological mediators, we investigated the effect of exogenous administration of NGF in RCS rats affected by retinitis pigmentosa. We found that NGF administration exerts a rescue effect on photoreceptors in this animal model. NGF injection enhances brain-derived neurotrophic factor, beta-fibroblast growth factor, transforming growth factor-beta, vascular endothelial factor and neuropeptide-Y. This suggests that NGF has an effect on RCS rat retina, probably also through the stimulation of other biological mediators produced and released in the retina.     

视网膜色素变性患者视锥和视杆细胞多焦视网膜电图检测

目的 观察视网膜色素变性(RP)患者视锥细胞和视杆细胞的多焦视网膜电图(mfERG)特征.评估感光细胞功能.方法 选取正常受试者8例8只眼进行视杆细胞mfERG检查.分析不同刺激光亮度对P1波振幅的影响;对19例RP患者38只眼分别进行视杆和视锥细胞mfERG检查.根据局部波形信噪比判断检出率,对视锥细胞mfERG不同类型间的平均视力、P1波振幅惭度进行比较和统计学分析.同时对比分析RP患者视杆和视锥细胞mfERG在各象限P1波振幅的变化.结果 采用0.04 cd/m~2蓝色低刺激光亮度可以稳定记录正常人视杆细胞mfERG反应.RP患者视锥和视杆细胞mfERG有效波形检出率分别为65.79%和10.51%.视锥mfERG I型P1波振幅密度高于Ⅱ型,差异有统计学意义(t=5.21,P=0.0000),平均视力差异无统汁学意义(t=1.15,P=0.612).I型振幅密度与logMAR视力呈负相关(r=-0.48,P=0.04).分别比较RP患者视锥和视杆mfERG局部波形特征发现,两者在各象限的P_1振幅密度在空间上有一定的对应性.结论 RP患者黄斑区视锥细胞的反应存在多样性,视锥细胞mfERG检出率高于视杆细胞,残存视锥和视杆细胞功能在空间上有一定的对应性.     

原发性视网膜色素变性合并血管闭塞的临床特点分析

目的探讨原发性视网膜色素变性(RP)合并视网膜血管闭塞患者的临床特点及预后。方法回顾性分析18例(36只眼)原发性RP合并视网膜血管闭塞患者的临床资料,包括眼底检查、荧光素眼底血管造影、吲哚氰绿血管造影、视网膜电图及视诱发电位等检查结果。对3例患者进行基因筛选。结果原发性RP合并视网膜血管闭塞患者的临床表现有视乳头萎缩、视网膜血管变细、广泛视网膜色素上皮萎缩。视网膜电图检查显示a、b波为无波型或近无波型。患者多有夜盲史。既符合原发性RP的临床表现,又具有血管闭塞的自身特征,如晚期血管可完全或近完全闭塞、视神经明显萎缩、脉络膜血管受累,最终致盲速度较原发性RP快,且无有效疗法。3例患者经基因筛查,在RHO及RLBPI两基因编码区中,未发现基因突变。结论原发性RP合并视网膜血管闭塞可能属于毯层视网膜变性范畴,血管进行性闭塞可能是其合并的临床表现。     

GABA receptors on horizontal cells in the goldfish retina

We investigated the localization of GABA(A) and GABA(C) receptors in horizontal cells (HCs) and HC axon terminals (ATs) dissociated from goldfish retina, using whole-cell patch-clamping recordings. Applications of GABA on HCs induced two groups with inward currents at the holding potential of -50 mV: One was a sustained inward current in the H1 cell, with one type of HCAT (AT1), and the other was a transient inward current in other HC soma and HCAT (AT2). Co-application of GABA with bicuculline or SR95531, GABA(A) receptor antagonists, showed a non-blocking effect in the sustained current, but a blocking effect in the transient current. The sustained current was evoked by cis-4-aminocrotonic acid (CACA), a GABA(C) receptor agonist, while the transient current was not induced by CACA, but mimicked by muscimol, a GABA(A) receptor agonist. Both the sustained and transient currents were completely blocked by picrotoxin and not mimicked by baclofen, a GABA(B) receptor agonist. Thus H1 cell and AT1 have GABA(C) receptors, while H2, H3 cells and AT2 have GABA(A) receptors.     

视网膜变性Pde6b基因突变小鼠治疗的研究进展

视网膜变性动物模型是研究人类遗传性视网膜变性疾病治疗的重要工具,目前常用于基础研究的视网膜变性动物模型包括系列视杆细胞变性小鼠(rd),如rd1小鼠、rd10小鼠和nmf137小鼠,这些模型鼠均为磷酸二酯酶β亚基(Pde6b,PDEβ)基因突变的小鼠模型,因其发病机制与人类具有某些同源性,因而已大量应用于视网膜变性疾病的基因诊断和治疗研究中.为了探索更为有效的治疗方法,就3种模型鼠的发病机制、药物治疗、神经营养治疗以及干细胞治疗方法、疗效等的研究进展进行综述.     

Genetic dissection of non-syndromic retinitis pigmentosa

Retinitis pigmentosa (RP) belongs to a group of pigmentary retinopathies. It is the most common form of inherited retinal dystrophy, characterized by progressive degradation of photoreceptors that leads to nyctalopia, and ultimately, complete vision loss. RP is distinguished by the continuous retinal degeneration that progresses from the mid-periphery to the central and peripheral retina. RP was first described and named by Franciscus Cornelius Donders in the year 1857. It is one of the leading causes of bilateral blindness in adults, with an incidence of 1 in 3000 people worldwide. In this review, we are going to focus on the genetic heterogeneity of this disease, which is provided by various inheritance patterns, numerosity of variations and inter-/intra-familial variations based upon penetrance and expressivity. Although over 90 genes have been identified in RP patients, the genetic cause of approximately 50% of RP cases remains unknown. Heterogeneity of RP makes it an extremely complicated ocular impairment. It is so complicated that it is known as “fever of unknown origin”. For prognosis and proper management of the disease, it is necessary to understand its genetic heterogeneity so that each phenotype related to the various genetic variations could be treated.     

神经营养因子治疗视网膜色素变性的研究进展

神经营养因子是能够促进神经元存活、生长、分化及维持其功能的多效性肽类因子的总称,可被作为有效的神经保护剂用于治疗多种神经变性类疾病.视网膜色素变性(RP)是以光感受器-视网膜色素上皮复合体损害为主的高度遗传异质性视网膜变性疾病,神经营养因子作为不针对致病基因的RP治疗策略,其疗效已在多种视网膜变性的动物模型中得到证实.以病毒为载体的转基因治疗和细胞包囊技术为神经营养因子提供了有效的给药途径,可使疗效明显提高.对神经营养因子在视网膜中的表达及其调节、受体分布特点、作用通路、疗效及副作用等方面的深入研究为神经营养因子的临床应用奠定了基础.     

Bone spicule pigment formation in retinitis pigmentosa: insights from a mouse model

Background

Bone spicule pigments (BSP) are a hallmark of retinitis pigmentosa (RP). In this study, we examined the process of BSP formation in the rhodopsin knockout (rho ^-/- ) mouse, a murine model for human RP.

Methods

In rho ^-/- mice from 2 to 16 months of age, representing the range from early to late stages of degeneration, retinal sections and whole mounts were examined morphologically by light and electron microscopy. The results were compared to scanning laser ophthalmoscopy of BSP degeneration in human RP.

Results

After the loss of all photoreceptor cells in rho-/- mice, the outer retina successively degenerated, leading to approximation and finally a direct contact of inner retinal vessels and the retinal pigment epithelium (RPE). We could show that it was the event of proximity of retinal vessel and RPE that triggered migration of RPE cells along the contacting vessels towards the inner retina. Ultrastructurally, these mislocalized RPE cells partially sealed the vessels by tight junction linkage and deposited extracellular matrix perivascularly. Also, the vascular endothelium developed fenestrations similar to the RPE-choroid interface. In whole mounts, the pigmented cell clusters outlining retinal capillaries correlated well with BSPs in human RP. The structure of the inner retina remained well preserved, even in late stages.

Conclusions

The Rho ^-/- mouse is the first animal model that depicts all major pathological changes, even in the late stages of RP. Using the rho ^-/- mouse model we were able to analyze the complete dynamic process of BSP formation. Therefore we conclude that: (1) In rho ^-/- retinas, BSPs only form in areas devoid of photoreceptors; (2) Direct contact between inner retinal vessels and RPE appears to be a major trigger for migration of RPE cells; (3) The distribution of the RPE cells in BSPs reflects the vascular network at the time of formation. The similarity of the disease process between mouse and human and the possibility to study all consecutive steps of the course of the disease makes the rho ^-/- mouse valuable for further insights in the dynamics of BSP formation in human RP.     

Synaptic vesicle dynamics in mouse rod bipolar cells

To better understand synaptic signaling at the mammalian rod bipolar cell terminal and pave the way for applying genetic approaches to the study of visual information processing in the mammalian retina, synaptic vesicle dynamics and intraterminal calcium were monitored in terminals of acutely isolated mouse rod bipolar cells and the number of ribbon-style active zones quantified. We identified a releasable pool, corresponding to a maximum of 7 s. The presence of a smaller, rapidly releasing pool and a small, fast component of refilling was also suggested. Following calcium channel closure, membrane surface area was restored to baseline with a time constant that ranged from 2 to 21 s depending on the magnitude of the preceding Ca2+ transient. In addition, a brief, calcium-dependent delay often preceded the start of onset of membrane recovery. Thus, several aspects of synaptic vesicle dynamics appear to be conserved between rod-dominant bipolar cells of fish and mammalian rod bipolar cells. A major difference is that the number of vesicles available for release is significantly smaller in the mouse rod bipolar cell, both as a function of the total number per neuron and on a per active zone basis.     

Exclusion of the apoE gene in autosomal dominant retinitis pigmentosa

Our purpose was to search for mutations in the apolipoprotein E (apoE) gene and to evaluate the role of apoE polymorphisms in the occurrence of autosomal dominant retinitis pigmentosa (ADRP). The ApoE gene coding sequence was analyzed in 51 unrelated patients affected with ADRP. A screening for mutations by SSCP and an analysis of the apoE polymorphisms were performed using PCR and restriction enzymatic digestion. No abnormal patterns of migration were observed by SSCP analysis. No significant statistical difference was seen between our ADRP population and the French general population for apoE allele frequency. From these results we report that the apoE gene does not seems to be involved in our ADRP population.     

视网膜色素变性的分子遗传学研究进展与基因治疗

视网膜色素变性(RP)是遗传性致盲眼病,其患病率约为1／3500。该病目前尚无有效的预防和治愈方法。本文综述了RP分子遗传学的最新进展,着重对诊断和预后有价值的基因突变进行了总结,并归纳了RP基因治疗的新动向。（中华眼科杂志,2005,41：188-192)     

Pattern-reversal electroretinograms and visual evoked potentials in retinitis pigmentosa

OBJECTIVE: To analyze pattern electroretinograms (PERGs) and pattern visual evoked potentials (PVEPs) in retinitis pigmentosa (RP) patients. METHODS: PERGs and PVEPs were recorded in 106 eyes of 53 RP patients. A RETIport system was used for stimulation and recording. RESULTS: Reproducible PERGs were found in 17 (32%) of the patients, from only one eye in 4 of the 17 patients. We failed to record a normal PERG in any patient. All 53 patients gave reproducible PVEPs. The patients could be divided into three groups according to the waveform of the response. In the first group (n = 17), all patients produced PVEPs with a characteristic, triphasic shape, but with smaller amplitudes. In the second group (n = 16), the PVEPs displayed doubled P100 peaks, with components separated by about 50 ms. The recordings in the third group (n = 20) were broad in shape and characterized by a greatly increased N70-N170 latency difference and decreased amplitudes. CONCLUSIONS: In the population of RP patients, different types of PVEP waveform alterations can be observed. The appearance of both the responses with decreased amplitude and those with broad, doubled P100 waves might reflect differences in central retinal degeneration. The significance and pathological background of these PVEP alterations need further investigations.     

Retinal neovascularization induced by mutant Vldlr gene inhibited in an inherited retinitis pigmentosa mouse model: an in-vivo study

Fungal keratitis (FK) is a refractory disease that poses a serious threat to vision, with common risk factors like eye trauma, contact lens wearing, topical corticosteroids and antibiotic abuse. Nowadays, topical and systemic anti-fungal drugs and ocular surgeries are still the main therapeutic modalities. However, the pathogenesis of FK, especially the immunologic mechanism within it, has not yet been deeply clarified. A better understanding of the pathogenesis of FK is imperative for more effective therapies and prognosis. Meanwhile, the immune protection strategies are also urgently required to manage FK. This review highlights recent advances in the immunologic mechanism in the pathogenesis of FK, in hope of providing valuable reference information for more effective anti-fungal treatment.     

Abnormalities in rod photoreceptors, amacrine cells, and horizontal cells in human retinas with retinitis pigmentosa

PURPOSE: To evaluate changes in the rods and amacrine cells and horizontal cells in human retinas with retinitis pigmentosa. METHODS: Seven retinas from patient donors with retinitis pigmentosa and 14 age- and postmortem-matched normal human retinas were processed for immunocytochemistry and confocal microscopy. The following cell-specific antibodies were used: anti-rhodopsin (rods), anti-gamma-aminobutyric acid (amacrine cells), anticalbindin (cones and horizontal cells), anti-glial fibrillary acidic protein (astrocytes and reactive Müller cells), and anti-synaptophysin and anti-SV2 (synaptic vesicles). RESULTS: In retinal regions with significant photoreceptor loss, the rods, gamma-aminobutyric acid-positive amacrine cells, and calbindin-positive horizontal cells had undergone neurite sprouting. The rod, amacrine and horizontal cell neurites were associated with the surfaces of glial fibrillary acidic protein-immunoreactive Müller cells. Most rod neurites that projected into the inner retina contacted the somata of gamma-aminobutyric acid-positive amacrine cells. CONCLUSIONS: Rods, amacrine and horizontal cells undergo neurite sprouting in human retinas with retinitis pigmentosa. These changes in the retinal neurons may contribute to the electroretinographic abnormalities and progressive decline in vision noted by patients with retinitis pigmentosa. These alterations may also complicate strategies for treatment of retinitis pigmentosa.     

Ambient hypoxia reverses retinal vascular attenuation in a transgenic mouse model of autosomal dominant retinitis pigmentosa

PURPOSE: Loss of retinal capillaries is an inherent component of late stage autosomal dominant retinitis pigmentosa (ADRP). This study examined the hypothetical role of tissue hyperoxia in this vascular attenuation process and tested the potential of ambient hypoxia to reverse it. METHODS: Transgenic mice expressing a mutant opsin gene with a 3-bp deletion of isoleucine at codon 255/256 were used. This model is characterized by early onset of a rapidly progressing retinal degeneration that by postnatal day (P)20 results in the loss of all but one row of photoreceptor nuclei. At P20 some mice were placed in 12% oxygen until they were euthanatized at P26. The remainder were maintained in normoxia and killed at the same age. Retinas were dissected, stained for ADPase, and flat-mounted. RESULTS: Deep plexus capillary density was significantly different in normoxic normals versus transgenics at 20 days of age (P: 相似文献   

视网膜色素变性发病机制及治疗进展

视网膜色素变性（retintis pigmentosa,RP）是指以进行性感光细胞及色素上皮功能丧失为共同表现的遗传性、退行性的疾病,RP是主要的致盲性眼病。其遗传方式包括X连锁遗传、常染色体隐性或者显性遗传,也有散发。临床表现为典型的三联征:骨细胞样色素沉着、视网膜血管缩窄和视盘蜡样苍白。RP具有高度的基因异质性(多个突变位点引起同一疾病）及表型异质性。本文对RP的发病机制和治疗方法进行简要综述。