黑斑蛙光感受器计数和分类—扫描电镜研究

在扫描电镜下观察了黑斑蛙视网膜光感受器的类型、直径和密度。并用统计学方法对光感受器进行了计数。六个视网膜的光感受器计数平均为2,120,000±230,000(P<0.05)。可以见到两类视锥细胞和两类视杆细胞:单视锥,外段为锥形,最粗处直径约6微米;双视锥,由一主锥和一附锥构成,外段直径最粗处约7微米;红视杆,外段圆柱形,直径约6微米,其内段短粗,数目比绿视杆多;绿视杆,外段与红视杆极相似,但内段细长。视锥和视杆的外段上有许多小突起,这些小突起互相联系。     

崇安髭蟾视网膜的组织结构

在光镜和电镜下观察了崇安髭蟾视网膜的组织结构，着重探讨感光细胞和神经节细胞的形态，计数及分布。结果表明，其视网膜组织结构符合脊椎动物的基本模式。视我膜总厚度为１４３μｍ。感光细胞总数约２５０只，几乎全是视杆，似视锥的光感受器不超过３％。神经节细胞总数２１万，从节细胞等密度图上看出在视盘背侧沿鼻颞独有一个高密区，即视条。比较神经节细胞的密度分布及光 镜和 感光细胞形态结构及其分布，认为发髭蟾视网膜的     

RCS大鼠视网膜变性过程中二级神经元形态学变化的研究

用免疫组织化学方法研究RCS大鼠(Royal College of Surgeon's rat,RCS rat)视网膜变性过程中早、中、晚期二级神经元形态的变化。结果发现,P1MRCS大鼠各二级神经元未见明显的形态改变。P2M RCS大鼠视网膜外核层萎缩约85%,视杆双极细胞顶端树突萎缩;水平细胞的树突与轴突在外网状层的分层未见改变。P3M RCS大鼠视网膜外核层萎缩近95%,RCS大鼠视杆双极细胞顶端萌生新的神经突起;水平细胞的树突分支明显丢失,轴突在外网状层的分层发生改变,出现新生神经突起;无长突细胞的树突在内网状层的分层至变性晚期也未见改变。该研究表明RCS大鼠视网膜二级神经元形态的改变是继发性改变,是感光细胞变性后对传入缺失的一种反应,即重构反应。在进行视网膜功能救治时需要考虑重构反应带来的影响。     

人胎视网膜神经肽Y免疫反应神经元的发育

本文用免疫细胞化学ＡＢＣ法,研究１５—３８周龄人胎视网膜神经肽Ｙ免疫反应（ＮｅｕｒｏｐｅｐｔｉｄｅＹｉｍｍｕｎｏｒｅｃｔｉｖｅ,ＮＰＹ－ＩＲ）神经元（以下称ＮＰＹ－ＩＲ细胞）的发育。结果表明：①胎龄１５周视网膜中央部已出现不同类型的ＮＰＹ－ＩＲ细胞：位于黄斑及其周围外核层的为ＮＰＹ－ＩＲ视锥细胞;位于内核层最内一列的为ＮＰＹ－ＩＲ无长突细胞位于节细胞层的可能为ＮＰＹ－ＩＲ移位无长突细胞或节细胞;内核层和节细胞层的ＮＰＹ－ＩＲ细胞的突起均分布在内网层的第１亚层。②胎龄２４周后,ＮＰＹ－ＩＲ视锥细胞完全消失。③随着视网膜的发育,内核层和节细胞层的ＮＰＹ－ＩＲ细胞数量增多,突起增粗增长,胞体分布由中央部扩展到周边部,其中内核层ＮＰＹ－ＩＲ细胞的密度呈现从中央部向周边部逐渐降低的分布方式,节细胞层ＮＰＹ－ＩＲ细胞则多数集中分布在视网膜的边缘和黄斑之间,形成较高密度的环状区。     

真鲷视网膜结构及其视觉特性研究：Ⅱ视网膜光感受细胞超微结构研究

对真鲷光感受细胞的超微结构进行观察,结果表明：视杆外段膜盘为游离膜盘,视锥外段膜盘则为连续的膜结构,视锥和视杆均含有连接纤毛和辅助外段。花萼状突起起源于内段。椭体内充满线粒体,无球状小体。双锥椭圆体并生膜为六层,视锥内段无鳍状突起,视锥突触带,在明适应视网膜中数量增多,在暗适应视网中数量减少,视杆突触带在这两种适应网膜中数量不变,每一杆小球只有一个突触带,而锥小足有４－６个突触带。     

()、纵纹腹小()和红隼视器的比较形态学研究

为了探讨猛禽视器结构与生活习性的关系,用光镜和扫描电镜观察、测量并统计了、纵纹腹小和红隼视网膜各层的厚度,三个核层的胞核层数和视细胞密度.视网膜外核层、内核层和节细胞层胞核的平均层数在依次为2.6、7.6和0.4层;在小为3.0、11.4和1.9层;红隼为1.6、14.6和1.7层.视网膜中央区视锥细胞密度(±SD)在为190 117±27 304个/mm2,小为202 122±49 542个/mm2,红隼为234 039±44 916个/mm2.视网膜周围区视杆细胞的密度在为190 422±26 595个/mm2,小为165 800±26 408个/mm2,红隼为178 015±40 165个/mm2.红隼视网膜周围区还有视锥细胞分布,其密度为22 082±9 864个/mm2.结果表明,视器的结构为夜行性特征,而小有趋于晨昏活动的特点,红隼为典型的昼行性视觉特征.3种猛禽栖息于同一生态环境内,视器的结构差异显示出其时间活动格局上的差异.     

胭脂鱼眼早期形态发生研究

采用组织学方法观察了胭脂鱼(Myxocyprinus asiaticus) 眼的发生过程, 结果显示: 胭脂鱼眼的发育经历了眼原基形成期、眼囊形成期、视杯形成期、晶体板形成期、晶体囊形成期、角膜原基形成期、角膜上皮形成期、视网膜细胞增殖期、晶状体成熟期、眼色素形成期以及眼成型期等11个时期。视网膜发育最早, 起始于眼原基的形成, 直至眼成型期分化完成, 形成了厚度不一的8层细胞, 由内向外依次为神经纤维层、神经细胞层、内网层、内核层、外网层、外核层、视杆视锥层和色素上皮层, 且发育历时最长, 约264h。晶状体的发育在视网膜之后, 始于晶体板的形成, 于出膜前期成熟, 发育历时最短, 约74h。角膜发育最晚, 始于角膜原基的形成, 出膜1 d分化为透明的成熟角膜, 发育历时约96h。出膜4 d仔鱼眼色素沉积明显, 视网膜各层分化明显, 晶状体内部完全纤维化, 眼的形态结构基本发育完全。     

脑红蛋白在家兔视网膜中的分布

目的探讨脑红蛋白(NGB)在家兔视网膜的分布特征。方法选择健康成年家兔5只,利用免疫组织化学染色SP法,观察NGB在家兔视网膜中的分布情况。结果 NGB在家兔视网膜的视神经纤维层、节细胞层、内网状层、外网状层、光感受器内节段和色素上皮层中有强阳性表达,在视网膜的内核层有弱阳性表达,在视网膜的外核层和光感受器外节段中未见有阳性表达,内界膜、外界膜和视神经中亦发现有NGB阳性表达。家兔视网膜NGB阳性表达的细胞类型主要有节细胞、双极细胞和光感受器细胞,其中节细胞的阳性表达定位于细胞质,胞核中未见表达。结论除外核层和光感受器外节段外,NGB在家兔视网膜其它各层中均有表达,提示NGB在维持视网膜氧代谢平衡中发挥着重要作用。     

鲫鱼视网膜锌离子分布的光、电镜观察

本文应用ｎｅｏ－Ｔｉｍｍ染色法,观察了鲫鱼视网膜内锌离子的分布情况以及明,暗适应条件下鲫鱼视网膜内锌离子分布的变化。结果发现,明适应条件下,外网层、部分光感受器、双极细胞、无长突细胞以及神经节细胞胞体锌离子着色明显,含锌光感受器和双极细胞的突起伸入外网层,暗适应条件下,外网层锌离子染色减弱或消失（Ｐ〈０．０１）。外核层胞体锌离子染色阴性,少数散在分布的视锥细胞呈锌离子阳性,上述资料提示,明适应条件     

Clock蛋白在甘肃鼢鼠的表达

本研究旨在探讨甘肃鼢鼠的光周期调节机制,利用免疫荧光技术观察了甘肃鼢鼠眼和脑内生物钟基因Clock蛋白的阳性表达颗粒。结果显示:甘肃鼢鼠视网膜上Clock蛋白阳表达颗粒主要在细胞膜、细胞质、神经节细胞及其树突所形成的网状结构上,在视网膜的网层、内核层、外网层、外核层及视杆视锥层均有Clock蛋白阳性表达颗粒,且网层Clock蛋白的阳性表达颗粒较核层多。视交叉上核(SCN)有Clock蛋白阳性表达颗粒。Clock蛋白在甘肃鼢鼠的表达,为其调节机体昼夜节律提供分子学基础。     

Ultrastructure of the distal retina of the adult zebrafish, Danio rerio

The organization, morphological characteristics, and synaptic structure of photoreceptors in the adult zebrafish retina were studied using light and electron microscopy. Adult photoreceptors show a typical ordered tier arrangement with rods easily distinguished from cones based on outer segment (OS) morphology. Both rods and cones contain mitochondria within the inner segments (IS), including the large, electron-dense megamitochondria previously described (Kim et al.) Four major ultrastructural differences were observed between zebrafish rods and cones: (1) the membranes of cone lamellar disks showed a wider variety of relationships to the plasma membrane than those of rods, (2) cone pedicles typically had multiple synaptic ribbons, while rod spherules had 1-2 ribbons, (3) synaptic ribbons in rod spherules were ∼2 times longer than ribbons in cone pedicles, and (4) rod spherules had a more electron-dense cytoplasm than cone pedicles. Examination of photoreceptor terminals identified four synaptic relationships at cone pedicles: (1) invaginating contacts postsynaptic to cone ribbons forming dyad, triad, and quadrad synapses, (2) presumed gap junctions connecting adjacent postsynaptic processes invaginating into cone terminals, (3) basal junctions away from synaptic ribbons, and (4) gap junctions between adjacent photoreceptor terminals. More vitread and slightly farther removed from photoreceptor terminals, extracellular microtubule-like structures were identified in association with presumed horizontal cell processes in the OPL. These findings, the first to document the ultrastructure of the distal retina in adult zebrafish, indicate that zebrafish photoreceptors have many characteristics similar to other species, further supporting the use of zebrafish as a model for the vertebrate visual system.     

Correlation of rhodopsin biogenesis with ultrastructural morphogenesis in the chick retina

The developing chick retina from stages 39-45 has been examined by biochemical and electron microscope techniques. The levels of rhodopsin contained in the maturing chick retina were evaluated by detergent extraction and correlated with rod outer segment formation. It was found that the appearance of rhodopsin in significant levels preceded outer segment formation by at least 2 days, thus implying that rhodopsin is synthesized in the receptor cell inner segment and translocated to the outer limb when disk membrane biogenesis occurs. The level of rhodopsin continues to rise as the rod outer segment develops. Development of both rods and cones originates and proceeds most rapidly in the fundus or central region and proceeds toward the periphery. In general, rod outer segments were noted to develop far more rapidly than cone outer segments.     

夜行壁虎视细胞外段的更新:[~3H]亮氨酸的渗入和分布

本文报道用光镜放射自显影方法观察夜行壁虎网膜感光细胞外段的更新。当注射氚标记的亮氨酸后,这种由其祖先视锥演变来的夜行壁虎视杆(并且至今仍保留着一些形态学上属视锥的特征)其外段呈现的标记图型仍与一般的视杆细胞相似。     

Fine structure of the retina of black bass, Micropterus salmoides (Centrarchidae, Teleostei).

The structure of light- and dark-adapted retina of the black bass, Micropterus salmoides has been studied by light and electron microscopy. This retina lacks blood vessels at all levels. The optic fiber layer is divided into fascicles by the processes of Müller cells and the ganglion cell layer is represented by a single row of voluminous cells. The inner nuclear layer consists of two layers of horizontal cells and bipolar, amacrine and interplexiform cells. In the outer plexiform layer we observed the synaptic terminals of photoreceptor cells, rod spherules and cone pedicles and terminal processes of bipolar and horizontal cells. The spherules have a single synaptic ribbon and the pedicles possess multiple synaptic ribbons. Morphologically, we have identified three types of photoreceptors: rods, single cones and equal double cones which undergo retinomotor movements in response to changes in light conditions. The cones are arranged in a square mosaic whereas the rods are dispersed between the cones.     

The visual cells of the corsula mullet

The eye of Rhinomugil corsula has a duplex retina differentiated into dorsal and ventral halves, with the ventral retina 116·4 μm thicker than the dorsal retina. The rods of the ventral retina are relatively longer, with longer outer segments. The nuclei of the outer nuclear layer of the dorsal and ventral halves are in four and six to seven rows respectively. The rod outer segment bears a single incision. The mitochondria of cone and rod inner segments has a vitreal-scleral gradient. Single and double cones are present in both halves, with triple cones in the dorsal half only. The outer segments of double cones are equal and united. The single cones have two connecting cilia. The cone cells are arranged in a square mosaic with four double cones and five single cones to each unit in the dorsal half, and in a rhombic pattern in the ventral half.     

A soluble form of bovine rod photoreceptor phosphodiesterase has a novel 15-kDa subunit

A substantial fraction (20-30%) of the bovine rod outer segment phosphodiesterase (PDE) activity is not associated with outer segment membranes prepared with buffers of moderate ionic strength; this PDE activity appears to represent a distinct, soluble isozyme. Although this PDE isozyme can be demonstrated to be present in sealed rod outer segments, it is discarded from most standard rod outer segment preparations. A method was developed that allowed the rapid purification of the soluble rod PDE by 2600-fold, to apparent homogeneity, using a monoclonal antibody column (ROS-1a). The soluble rod PDE isozyme has a novel Mr = 15,000 subunit (delta) in addition to subunits of Mr = 88,000 (alpha sol), 84,000 (beta sol), and 11,000 (gamma sol). The delta subunit comigrates with and may be identical to the cone PDE 15-kDa subunit. The small subunits of the soluble rod PDE and the membrane-associated rod PDE were isolated by reverse-phase chromatography. The gamma sol subunit was a potent inhibitor of trypsin-activated rod PDE, inhibiting 50% of 1 pM PDE activity at a concentration of 11 pM. This concentration was similar to that observed for the gamma subunit of the membrane-associated rod PDE. The purified delta subunit did not appear to affect PDE activity; this subunit was, however, unusually difficult to keep in solution. All of the kinetic and physical properties of the soluble rod PDE tested thus far are similar to those of the membrane-associated form, except for the presence of the delta subunit, suggesting that this unique subunit could mediate the solubility of the soluble rod PDE and the cone PDE in the intact photoreceptor.     

Rhodopsin is spatially heterogeneously distributed in rod outer segment disk membranes

The visual photoreception takes place in the retina, where specialized rod and cone photoreceptor cells are located. The rod outer segments contain a stack of 500-2,000 sealed membrane disks. Rhodopsin is the visual pigment located in rod outer segment disks, it is a member of the G-protein-coupled receptor (GPCR) superfamily, an important group of membrane proteins responsible for the majority of physiological responses to stimuli such as light, hormones, peptides, etc. Alongside rhodopsin, peripherin/Rom proteins located in the disk rims are thought to be responsible for disk morphology. Here we describe the supramolecular structure of rod outer segment disk membranes and the spatial organization of rhodopsin and peripherin/Rom molecules. Using atomic force microscopy operated in physiological buffer solution, we found that rhodopsin is loosely packed in the central region of the disks, in average about 26?000 molecules covering approximately one third of the disk surface. Peripherin/Rom proteins form dense assemblies in the rim region. A protein-free lipid bilayer girdle separates the rhodopsin and peripherin/Rom domains. The described supramolecular assembly of rhodospin, peripherin/Rom and lipids in native rod outer segment disks is consistent with the functional requirements of photoreception.     

Cone cells fail to develop normally in transgenic mice showing ablation of rod photoreceptor cells

Transgenic mice were derived containing the cytotoxic dt-α gene driven by opsin promoter sequences. Mice expressing this construct showed progressive degeneration of rod photoreceptor cells commencing at birth, with obvious depletion of such cells by postnatal day 7. Ablation of rod photoreceptor cells in the transgenic retina was accompanied by the failure of developing cone cells to elaborate outer segments, although all other aspects of cone cell cytodifferentiation appeared normal. The results suggest that the 1.0-kb opsin promoter segment contains rod cell type specificity and that cone cells require maturation of rod cells to complete the late stages of their terminal differentiation and for their maintenance and cellular integrity.     

Duplex Retina in the Mesopelagic Deep-Sea Teleost Lestidiops affinis (Ege, 1930)

The eye of the deep-sea teleost Lestidiops affinis has been examined primarily by light microscopy and found to possess a duplex retina consisting of two main divisions, a pure-cone and a pure-rod region, with a narrow zone of transition, possessing both cones and rods, joining the two. The pure-cone region is located in the temporal (caudal) part of the retina subserving binocular vision in the rostral direction. It has an area temporalis retinae with particularly long and densely packed single cones arranged in a regular hexagonal mosaic. Joined (double or twin) cones have not been recognized with certainty in the pure-cone region. The pure-rod region, comprising the larger part of the retina, contains rods grouped in bundles separated by retinal pigment epithelium (RPE) processes with pigmented cores. The synaptic endings of the rods are arranged in separate clusters in the outer plexiform layer, there being apparently a separate rod pedicle cluster beneath (vitread to) each rod bundle. Structural comparisons with certain other deep-sea teleosts suggest the likely presence of a retinal tapetum in L. affinis, i.e. each single cone or rod bundle is situated in a reflecting pit formed by the RPE, with a discrete reflector apposed to the tip of each cone outer segment and the tips of the outer segments of each square-cut rod bundle.