应用DiI染色晶体对人胚胎视神经发育过程的初步研究

目的：应用Dil(1,1′-dioctadecyl-3,3′,3′-tertamethylin-docarbocyanine perchlorate,一种羰花青染料)染色晶体研究人胚胎视网膜、外侧膝状体、上丘及视皮质间连接的形态学特征和动态发育过程。方法：对不同胎龄的7个胎儿眼球标本进行灌注固定后,分别于标本的视束、上丘臂和视皮质下板层植入Dil染色晶体,以标记来自视网膜和外侧膝状体的轴突。于室温下放置4-10周,等待Dil染色晶体扩散,再根据神经走向切片,通过激光共焦扫描显微镜观察并记录植入Dil染色晶体12-28周的结果。结果：植入Dil染色晶体12周时,胎儿标本的视网膜神经纤维投射已经到达外侧膝状体,但尚未出现分层现象;视网膜神经投射也已达到上丘,纤维位于上丘臂的背侧;视皮质下已出现板层结构。植入22周时视皮质下仍存在板层结构。结论：植入Dil染色晶体12周前,视网膜神经纤维投射已达到外侧膝状体和上丘,视皮质下的板层也已经形成,22周后消失。Dil染色技术能有效地用于研究胚胎期视神经的连续发育过程。     

阳离子聚合物介导的质粒EGFP基因逆行转染视网膜神经节细胞

目的 研究上丘和外侧膝状体注射阳离子聚合体/质粒复合物转染视网膜神经节细胞（RGCs）的有效性.方法 将表达增强型绿色荧光蛋白（EGFP）的重组质粒和阳离子聚合物的混合溶液分别注射于Wistar大鼠双侧上丘和外侧膝状体,注射后10 d灌注固定大鼠,取视网膜和视神经行冰冻切片,荧光显微镜下观察.结果 荧光显微镜下见视网膜内层和视神经轴突纤维中有绿色荧光表达.结论 上丘和外侧膝状体注射阳离子复合物包装的质粒可将外源性基因相对高效地转入RGCs.     

高眼压缺血-再灌注中脑组织c-fos的表达及神经营养因子对其表达的影响

目的 观察视网膜缺血再灌注损伤过程中脑组织中c-fos的变化及神经营养因子对c-fos表达的影响，探讨c-fos在脑组织不同部位的改变及可能作用机制，进而为临床实践提供依据。方法 建立眼缺血再灌注损伤动物模型，分为对照组、实验组（Ⅰ、Ⅱ、Ⅲ组）。实验Ⅰ组为缺血组（Ⅰ组），实验Ⅱ组为缺血2h＋再灌注组（I／R组），实验Ⅲ组在缺血再灌注前于右侧侧脑室注射神经营养因子（神经营养因子＋I／R组）。采用HE常规染色切片光镜下观察大鼠高眼压脑外侧膝状体、嘴侧丘、视皮质结构神经细胞变化，采用免疫组织化学染色分别测定各组大鼠中脑组织以上三个部位c-fos的变化。结果 （1）脑组织不同部位（外侧膝状体、嘴侧丘、视皮质）中c-fos在对照组、缺血组、缺血再灌注组间无统计学差异（P＞0.05）。（2）在再灌注1d组脑组织不同部位的c-fos与缺血再灌注组有显著性统计学差异（P＜0．01），其中在外侧膝状体中有明显改变。（3）在再灌注1d组与再灌注2d组间两者存在统计学差异。（4）在再灌注后5d组与2d组间c-fos无统计学差异（P＞0．05）。（5）在注射神经营养因子的实验Ⅲ组，脑组织中不同部位的c-fos与对照组无统计学差异。结论 （1）c-fos在脑外侧膝状体、嘴侧丘、视皮质参与损伤的作用。（2）在外侧膝状体中c-fos的变化在中枢调节作用中起着中介作用，c-fos可能参与引起脑组织改变。（3）神经营养因子能明显减轻损伤反应。     

青光眼的中枢神经系统改变

青光眼是一组以进行性视网膜神经节细胞(RGCs)凋亡、视神经纤维层丢失为特征的神经退行性疾病.大量研究证明,青光眼患者在RGCs、视神经、视交叉、视束、外侧膝状体、视放射、大脑枕叶视皮质整个视觉通路上均出现了病理改变,青光眼是整个视觉通路在多层次、多因素损害的基础上出现的复杂综合症群.从视觉通路多级神经元水平更深入地研究青光眼视觉通路损害的特征,及时发现青光眼患者整个视觉通路的早期微小变化,重新认识疾病,开发新的临床诊治方法,早诊断、早治疗,有效延缓青光眼致盲进程,日益成为眼科学界和神经科学界关注的焦点.本文将从青光眼性中枢神经系统损害的表现、青光眼中枢神经系统损伤可能存在的机制、研究青光眼中枢神经损伤的意义几个方面就青光眼的中枢神经系统改变研究进展进行综述.     

视交叉后段视路疾病的眼部表现分析

视路是指从视网膜神经纤维层起,到大脑枕叶皮质纹状区的视觉中枢为止的整个有关视觉的神经传导的经路.     

视交叉以上视道疾病的视野改变50例分析

一眼来自视网膜鼻半侧的视神经纤维在视交叉处交叉到对侧,与来自对侧眼视网膜的颞半侧纤维会合组成视束,从此往上视道经过外侧膝状体、视放射直到视皮质;因此,视交叉以上视道的任何一段的病损,均将出现双眼在病灶的对侧半视野不同程度的缺损,     

外侧膝状体血管性损害的视野缺损

视路神经纤维有规则的空间排列,分析视路损害产生的特殊视野缺损常可对病变做出定位诊断。在诊断中最常用到的特征之一是视野缺损的相合性,即两眼视野缺损相同。视皮质损害的视野缺损的相合性最完全,视束损害其相合性最差。外侧膝状体位于视交叉后视路的前三分之一,该核前后病变产生不相合性视野缺损。在视野缺损的相合性与视路前后位置关系上,外侧膝状体血管性损害是个例外,它产生相合性视野缺损。报道5例外侧膝状体血管性损害,瞳孔对光反射均正常。例1、2表现为典型的楔形同侧偏盲,例1 CT扫描显示左后外侧丘脑缺血     

单眼剥夺大鼠视觉系统三级神经元Bcl-2表达的研究

目的　研究敏感期内和敏感期末单眼剥夺大鼠视觉系统三级神经元凋亡抑制基因Bcl 2表达规律及意义 方法　缝合 2周龄及 6周龄大鼠单侧眼睑 30d,切取视网膜中央区、外侧膝状体和视皮质 17区,行Bcl 2免疫细胞化学染色并对结果进行计算机图像分析。 结果　敏感期内剥夺眼较正常大鼠在视网膜节细胞层、同侧外侧膝状体相应输入层(A1层)和视皮质 17区(Ⅳ层)Bcl 2蛋白表达的免疫阳性神经元胞浆染色变淡(P<0 05), A1层、Ⅳ层的免疫阳性神经元数目减少(P<0 05),视网膜节细胞层免疫阳性神经元数目未见明显改变(P>0 05);敏感期末单眼剥夺大鼠视觉系统Bcl 2变化与对照组比较差异无显著性(P>0 05)。 结论　敏感期内单眼剥夺大鼠视觉系统视网膜节细胞层、外侧膝状体A1层和视皮质 17区Ⅳ层Bcl 2表达均降低,提示Bcl 2对视觉系统的作用可能是弱视发生的分子生物学基础之一。     

单眼剥夺大鼠视皮层及外侧膝状体中生长相关蛋白(GAP-43)的表达及其意义

目的研究生长相关蛋白(GAP-43)在正常大鼠与视觉剥夺性大鼠视皮层及外侧膝状体中的表达情况。方法缝合2周龄大鼠单侧眼睑30天,切取外侧膝状体和视皮质,应用免疫细胞化学SP法技术染色和计算机图像分析GAP-43在正常组和单眼视觉剥夺组大鼠外侧膝状体和视皮层的表达及变化。结果 1．GAP-43在正常大鼠视觉系统的表达主要见于外侧膝状体全层和视皮质Ⅱ-Ⅳ层神经元胞膜中,呈环状或点状棕黄色免疫阳性反应;2．在敏感期内视觉剥夺眼对侧外侧膝状体和视皮质GAP-43表达的免疫阳性神经元染色变淡(P<0．05), 且免疫阳性神经元数目减少(P<0．05)。结论单眼视觉剥夺大鼠外侧膝状体和视皮质GAP-43表达均降低,提示 GAP-43在视觉系统的作用可能是弱视发生的分子生物学基础之一。单眼剥夺性大鼠视觉系统的GAP-43表达降低可能是由于剥夺眼视觉系统神经元在发育敏感期内,长期视觉剥夺效应使其在双眼竞争突触位点时处于劣势, 表达GAP-43的能力降低。     

视觉通路病变的视野判读要点

视觉通路的组成包括：视网膜、视神经、视交叉、视束、外侧膝状体、视放射及枕叶视觉中枢。视野检查是视觉通路疾病诊疗过程中不可或缺的重要辅助检查之一,用于早期发现视功能异常、鉴别视路疾病、了解疾病进展等。不同部位的损害可表现出不同形式的视野缺损,有些特征性的视野异常可帮助我们快速而准确地定位诊断。因此对视野检查结果的正确判读是神经眼科医师重要的基本技能之一。     

Phr1 is required for proper retinocollicular targeting of nasal-dorsal retinal ganglion cells

Precise targeting of retinal projections is required for the normal development of topographic maps in the mammalian primary visual system. During development, retinal axons project to and occupy topographically appropriate positions in the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC). Phr1 retinal mutant mice, which display mislocalization of the ipsilateral retinogeniculate projection independent of activity and ephrin-A signaling, were found to have a more global disruption of topographic specificity of retinofugal inputs. The retinocollicular projection lacks local refinement of terminal zones and multiple ectopic termination zones originate from the dorsal-nasal (DN) retinal quadrant. Similarly, in the dLGN, the inputs originating from the contralateral DN retina are poorly refined in the Phr1 mutant. These results show that Phr1 is an essential regulator of retinal ganglion cell projection during both dLGN and SC topographic map development.     

Projections of the superior colliculus to subdivisions of the inferior pulvinar in New World and Old World monkeys

Patterns of terminals labeled after WGA-HRP injections in the superior colliculus (SC) in squirrel monkeys and macaque monkeys, and after DiI application in marmosets, were related to the architecture of the pulvinar and dorsal lateral geniculate nucleus (LGN). In all studied species, the SC projects densely to two architectonic subdivisions of the inferior pulvinar, the posterior inferior pulvinar nucleus (PIp) and central medial inferior pulvinar nucleus (PIcM). These projection zones expressed substance P. Thus, sections processed for substance P reveal SC termination zones in the inferior pulvinar. The medial subdivision of the inferior pulvinar, PIm, which is known to project to visual area MT, does not receive a significant collicular input. Injections in MT of a squirrel monkey revealed no overlap between SC terminals and neurons projecting to area MT. Thus, PIm is not the significant relay station of visual input from the SC to MT. The SC also sends an input to the LGN, however, this projection is sparser than the input directed to pulvinar.     

Dendritic changes in visual pathways in glaucoma and other neurodegenerative conditions

Visual information is sent from the retina to central visual targets through the optic nerve formed of retinal ganglion cells’ (RGCs) axons. In rodents, the superior colliculus (SC) is the major site of termination of retinal axons, whilst in primates and felines, it is the lateral geniculate nucleus (LGN). Glaucoma is a progressive optic neuropathy characterized by RGC death. There is increasing evidence that neuronal changes occur both in retina and central visual targets in glaucoma and other neurodegenerative diseases such as Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS). Dendrites are fine neuronal processes which support postsynaptic contact elements and are responsible for receiving synaptic signals. The morphology of dendrites has a profound impact on integrating neuronal input to the central nervous system from peripheral targets. This review summarizes different dendritic changes that have been recorded in neurodegenerative processes including those occurring in development, ageing and diseases. The findings suggest dendritic pathology is an early sign in disease and underline the importance of synapto-dendritic structure, providing new insights into therapeutic strategies.     

Functional and structural analysis of the visual system in the rhesus monkey model of optic nerve head ischemia

PURPOSE: A redistribution of neurochemicals has been identified in the visual cortex of monkeys with laser-induced glaucoma. Examined were functional, structural, and neurochemical changes to the retina, optic nerve, and central visual system in a nonhuman primate model of optic nerve head (ONH) ischemia caused by sustained unilateral administration of endothelin (ET)-1 to the optic nerve. METHOD: ET-1 or sham control solution was delivered by osmotic minipump to the retrolaminar region of one optic nerve of rhesus monkeys (Macaca mulatta) for 1.5 years. ONH topography and blood flow velocity were serially studied with scanning laser tomography and laser Doppler flowmetry, respectively. Retinal and cortical electrophysiologic measurements from pattern-derived stimuli were obtained quarterly. Immunohistochemistry was used to identify the distribution of calbindin (CB) and c-Fos labeled neurons in the visual cortex areas V1 and V2, and lateral geniculate nucleus (LGN). Retinal ganglion cell counts and optic nerve axon density were determined by light microscopy. RESULTS: No significant changes in retinal and ONH morphology, ONH blood flow velocity, and retinal and cortical pattern-derived functional activity were detected. Measurement of CB-positive cell density in V1 and V2 showed a significant decrease in CB labeling to the contralateral side of the ET-1-treated eye (P < 0.04). CB-positive cells were present in the magnocellular layers of the LGN with no differences noticed between the ET-1- and sham-treated eyes. c-Fos-labeled neurons were found in striate area V1 and extrastriateV2 of both groups. No c-Fos labeling was observed in the LGN. CONCLUSIONS: Administering ET-1 to the orbital optic nerve alters neuronal metabolic activity in the visual cortex in rhesus monkeys. Metabolic activity reductions in the visual cortex precede the ability to detect functional and structural alterations in the retina, ONH, and visual cortex in this animal model.     

The physiological basis of wavelength discrimination: evidence from dichoptic and Ganzfeld viewing

It has been suggested that human wavelength discrimination depends on the peripheral visual system outputting a signal which already indicates the difference between the two test wavelengths. In the present paper an alternative mechanism whereby wavelength discrimination is carried out by the visual cortex and not by the retina or the LGN is suggested. Wavelength discrimination was first tested under dichoptic viewing so that discrimination could, most likely, be performed by the visual cortex. Since performance was normal it is concluded that the visual cortex is capable of fine, normal level of wavelength discrimination. When the task was performed under ganzfeld viewing (alternating wavelengths) so that the LGN would output only the difference between the two wavelengths, discrimination was poor and sometimes, absent. This indicates that it is unlikely that wavelength discrimination is complete at the LGN level.     

The squirrel as a rodent model of the human visual system

Over the last 50 years, studies of receptive fields in the early mammalian visual system have identified many classes of response properties in brain areas such as retina, lateral geniculate nucleus (LGN), and primary visual cortex (V1). Recently, there has been significant interest in understanding the cellular and network mechanisms that underlie these visual responses and their functional architecture. Small mammals like rodents offer many advantages for such studies, because they are appropriate for a wide variety of experimental techniques. However, the traditional rodent models, mice and rats, do not rely heavily on vision and have small visual brain areas. Squirrels are highly visual rodents that may be excellent model preparations for understanding mechanisms of function and disease in the human visual system. They use vision for navigating in their environment, predator avoidance, and foraging for food. Visual brain areas such as LGN, V1, superior colliculus, and pulvinar are particularly large and well elaborated in the squirrel, and the squirrel has several extrastriate cortical areas lateral to V1. Unlike many mammals, most squirrel species are diurnal with cone-dominated retinas, similar to the primate fovea, and have excellent dichromatic color vision that is mediated by green and blue cones. Owing to their larger size, squirrels are physiologically more robust than mice and rats under anesthesia, and some hibernating species are particularly tolerant of hypoxia that occurs during procedures such as brain slicing. Finally, many basic anatomical and physiological properties in the early visual system of squirrel have now been described, permitting investigations of cellular mechanisms. In this article, we review four decades of anatomical, behavioral, and physiological studies in squirrel and make comparisons with other species.     

Prenatal disruption of binocular interactions creates novel lamination in the cat's lateral geniculate nucleus

The elimination of retinogeniculate afferents from one eye on embryonic day 44 (E44) has pronounced effects on the formation of the cellular laminae in the cat lateral geniculate nucleus (LGN). Only two laminae form: a dorsal, "magnocellular" layer, and a ventral, "parvocellular" layer. Soma size measurements and previously reported patterns of termination of retinogeniculate axons suggest that the dorsal lamina is a coalescence of the normal A-laminae and the dorsal, magnocellular division of layer C, while the ventral layer is a composite of the parvocellular sublamina of layer C and the remaining C-laminae. This is a novel pattern of lamination in the LGN that differs from that found in the normal nucleus, not only in that there are now only two cell layers rather than the normal five, but also in that the interlaminar zone occurs in an abnormal location. This result is markedly different from that observed in other species where interlaminar zones present after early monocular enucleation are a subset of the ones which would normally be present. We suggest that, in the absence of ongoing binocular interactions, interactions between functionally distinct retinal ganglion cell classes from the remaining eye may direct the formation of cell laminae in the LGN, even when such interactions are not normally operative.     

Restoration of visual responses following transplantation of intact retinal sheets in rd mice

PURPOSE: To correlate the functional outcomes with histologic findings following transplantation of fetal retinal sheets in rd mice, and to investigate the mechanisms of visual function restoration. METHODS: Twenty-one postnatal day 31-38 rd/rd (C3H/HeJ) mice were transplanted in one eye with retinal sheets (1.0 x 0.4 mm) obtained from embryonic day (E) 17 enhanced-green-fluorescent protein (eGFP) mice. Five mice underwent sham surgery without insertion of tissue. Four to five weeks after transplantation, visual responses to a light flash were recorded across the superior colliculus (SC) in seven eyes of seven transplanted mice that had clear corneas and lenses, and in all five sham surgery mice. Following the SC recording, the eyes were enucleated and processed for immunohistochemistry and examined using confocal microscopy. RESULTS: In three out of the seven eyes (43%), positive responses were recorded in the SC in an area topographically corresponding to the placement of the transplant in the host retina. No responses were recorded in the untreated eyes of 5-week-old and 9-week-old rd/rd mice, and in the 9-week-old sham surgery mice. In contrast, visual responses were recorded over the entire SC in normal eyes. The response onset latencies of the 3 transplanted mice with responses were similar to those of normal control mice. The organization of the graft did not appear to correlate as expected with the electrophysiology results, as eyes with well-organized, laminated grafts showed no response whereas the three light-responsive eyes had rosetted or disorganized grafts. All three light-responsive eyes demonstrated much higher levels of recoverin immunoreactivity in the host retina overlying the graft compared with untreated age-matched rd/rd mice. CONCLUSION: Restoration of the SC visual response does not appear to depend on a well-organized transplant in the rd mouse. Increased recoverin-staining in the host retina in light-responsive animals suggested that host cone rescue was the likely mechanism of vision restoration in this transplant model.     

Increased serotonin in the developing superior colliculus affects receptive-field size of retinotectal afferents but not that of postsynaptic neurons

Administration of a single subcutaneous dose of 5,7-dihydroxytryptamine (5,7-DHT) to newborn hamsters results in a significant increase in the density of serotoninergic (5-HT) fibers in the superficial layers of the superior colliculus (SC) and marked abnormalities in the uncrossed retinotectal projection when these animals reach adulthood (Rhoades et al., 1993). The present study was undertaken to determine whether elevation of 5-HT in the developing SC altered the visual representation in SC. Multi-unit recordings from SC cells demonstrated that the overall organization of the visual map in the superficial SC laminae was normal and that the receptive-field sizes for unit clusters were unchanged in the 5,7-DHT-treated animals. However, when a combination of CNQX and MK-801 was directly applied to the SC to block postsynaptic activity, the receptive fields of unit clusters (presumably retinotectal axon terminals) in the 5,7-DHT treated animals were significantly larger than those in the normally reared hamsters. These results are consistent with the conclusions that elevation of 5-HT levels in the developing SC reduces the postnatal refinement of the crossed retinotectal axons, and that mechanisms operating within the SC may act to maintain normal sizes for the receptive fields of its constituent neurons.