ARTICLE |
Correspondence to: José Aijón, Biología Celular, INCy L, Facultad de Medicina, Campus Unamuno, 37007 Salamanca, Spain. E-mail: rubi@usal.es
![]() |
Summary |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
This study demonstrates the peculiarities of the glial organization of the optic nerve head (ONH) of a fish, the tench (Tinca tinca), by using immunohistochemistry and electron microscopy. We employed antibodies specific for the macroglial cells: glutamine synthetase (GS), glial fibrillary acidic protein (GFAP), and S100. We also used the N518 antibody to label the new ganglion cells' axons, which are continuously added to the fish retina, and the anti-proliferating cell nuclear antigen (PCNA) antibody to specifically locate dividing cells. We demonstrate a specific regional adaptation of the GSS100-positive Müller cells' vitreal processes around the optic disc, strongly labeled with the anti-GFAP antibody. In direct contact with these Müller cells' vitreal processes, there are S100-positive astrocytes and S100-negative cells ultrastructurally identified as microglial cells. Moreover, a population of PCNA-positive cells, characterized as glioblasts, forms the limit between the retina and the optic nerve in a region homologous to the Kuhnt intermediary tissue of mammals. Finally, in the intraocular portion of the optic nerve there are differentiating oligodendrocytes arranged in rows. Both the glioblasts and the rows of developing cells could serve as a pool of glial elements for the continuous growth of the visual system.
(J Histochem Cytochem 50:12891302, 2002)
Key Words: fish, S100, glutamine synthetase, electron microscopy, PCNA
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The fish retinotectal pathway possesses some structural peculiarities that derive from its continuous development. In the retina there is a pool of neuroepithelial cells known as the peripheral growing zone (PGZ) that is continuously forming new neurons and, consequently, new retinal ganglion cell (RGC) axons are added (
The ONH possesses variations among vertebrates, because whereas some animals, such as primates, present a lamina cribrosa (
The main goal of the present study was to characterize the glial cells of the tench optic disc and the ONH intraocular portion. We describe their organization by using immunohistochemistry (IHC) and electron microscopic analyses and we look for some differences with the glial cells located in the ONH of mammals. We used anti-S100 and anti-GFAP antibodies, previously used in the visual system of teleosts, to identify glial cells (
![]() |
Materials and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
All procedures used in this work were in accordance with the guidelines of the European Communities Council Directive (86/609/EEC) and current Spanish legislation for the use and care of animals.
We employed 14 tench (Tinca tinca), 1416 cm in body length, obtained from a commercial fish hatchery (Ipescón; Salamanca, Spain). Ten of them were used for IHC analysis and the rest for the ultrastructural study. All the animals were deeply anesthetized by using an aqueous solution of 0.03% tricaine methane sulfonate (MS-222; Sigma, St Louis, MO).
For the ultrastructural analysis, the fish were perfused transcardially with 150 ml of a solution containing 2.5% glutaraldehyde, 2% paraformaldehyde, 0.05% CaCl2 in 0.1 M cacodylate buffer, 0.18 M sucrose (pH 7.4). The eyes were removed, cut into small pieces, and stored in the same solution overnight at 4C. The pieces were washed in 0.1 M cacodylate buffer, 0.18 M sucrose (pH 7.4) and postfixed with 1% OsO4 in distilled water containing 1% potassium ferricyanide for 2 hr. Before dehydration, the pieces were subjected to block staining with 1% uranyl acetate in distilled water. Dehydration was performed using a graded series of cold acetone. Epon 812 (Taab; Reading, UK) was employed as embedding resin. Semithin sections (1 µm thick) were stained with toluidine blue and ultrathin sections were mounted on formvar-coated one-hole grids, contrasted with uranyl acetate and lead citrate, and studied using a ZEISS EM-900 electron microscope. Four different antibodies were used to examine the glial population of the ONH and retina. Rabbit anti-S100 (Dako; Carpinteria, CA), previously used in teleosts to label mature astrocytes, labeled part of the Müller cell population and horizontal cells (, usually detectable in G1, S, and G2 cells (
The specimens were anesthetized and quickly decapitated. The eyes were removed and fixed for 12 hr at 4C in a solution of 95% ethanol and 40% formaldehyde (9:1). The whole eyes were then rinsed in phosphate buffer 0.1 M, pH 7.4 (PB) and soaked in 30% sucrose in PB overnight. For the single labeling with the anti-GFAP antibody and for the double labeling with GSS100, GFAPS100, and N518S100, we employed a different fixative. After decapitation the eyes were immersed in a solution of 4% paraformaldehyde in PB at 4C overnight. The eyes were then rinsed in PB and soaked in 30% sucrose in PB overnight. Then the eyes were frozen in liquid nitrogen and cut on a cryostat in 16-µm-thick nasotemporal sections. These were mounted on gelatin-coated slides.
The sections were rinsed three times in PBS 0.1 M, pH 7.4, with 0.2% Triton X-100 (PBSTx) before IHC processing. Endogenous peroxidase activity was blocked with 2% H2O2 in 100% methanol for 10 min. For the immunolabeling, the sections were first incubated with 2% normal horse serum in PBSTx (3 hr). Some slides were then incubated with the anti-PCNA or with the anti-GFAP monoclonal antibodies diluted at 1:500 and at 1:400, respectively, in a solution of PBSTxserum with 1% dimethylsulfoxide (DMSO) overnight in a humidity chamber. To achieve double immunolabeling of GSS100, GFAPS100, and N518S100, the same slides were incubated in the same buffered solution containing a mixture of the anti-S100 polyclonal rabbit antibody at 1:500, the anti-GS monoclonal antibody at 1:1000, the anti-GFAP antibody at 1:400, or the anti-N518 monoclonal antibody at 1:10.000 overnight in a humidity chamber.
After the latter incubations, all the slides were washed three times in PBSTx and, for the PCNA and GFAP labeling, sequentially incubated at room temperature (RT) with a biotinylated anti-mouse IgG antibody (Vector; Burlingame, CA) at a dilution of 1:200 and an avidinbiotinperoxidase complex (Vector) (1:250). Detection of both immunoreactions were carried out with a solution of 0.05% 3.3'-diaminobenzidine tetrahydrochloride (DAB) and 0.025% H2O2 in 0.1 M Tris-HCl (pH 7.5) for 10 min at RT.
The sections for the double immunolabeling with GSS100, GFAPS100, and N518S100 were incubated with a mixture of the Cy3-conjugated fluorescent anti-rabbit IgG antibody (Jackson Immunoresearch; Avondale, PA) at a dilution of 1:1000 for detection of the S100 protein, and the Cy2-conjugated fluorescent anti-mouse IgG antibody (Jackson Immunoresearch) at a dilution of 1:1000 for detection of the GS, GFAP, or the neurolin protein. Finally, some of the sections were stained with DAPI (Sigma) at a dilution of 1:10,000 in distilled water to label all the cell nuclei. They were then dehydrated and mounted in Entellan (Merck; Darmstadt, Germany).
Some of the images from light microscopy were obtained with an Olympus Apogee digital camera coupled to an Olympus AX-70 photomicroscope with the appropriate fluorescent filter settings. The Cy3 fluorescent dye was visualized with a BP 510550-nm wavelength filter, the Cy2 dye with a BP 470490 filter, and the DAPI labeling with a BP 360370 filter. The rest of the fluorescent images were obtained with a laser scanning spectral confocal microscope (Leica TCS SP2) using simultaneous excitation of fluorochromes with laser wavelengths of 488 and 543 nm and a filter-free prism spectrophotometer. Original pictures were further processed with Adobe Photoshop 5.5 software (Tucson, AZ) to obtain the optimal contrast within the same figure plate.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
We analyzed the glial organization of three different zones of the tench ONH, which is composed of the optic disc and the intraocular portion. For Zone 1, in the optic disc we studied the portion where the RGC axons coming from the NFL of the retina turn to go into the optic nerve (Fig 1A). For Zone 2, in the intraocular portion of the ONH we analyzed the interface between the retina and the optic nerve at the level of the limit with the choroid membrane (Fig 1A and Fig 7), which in mammals is denominated the Kuhnt and Jacoby intermediary tissue. For Zone 3, in the intraocular portion of the ONH, we analyzed the portion of optic nerve at the interface with the sclera, which corresponds to the lamina cribrosa in mammals. In this zone, we also studied the rows of cells located among the RGC axons (Fig 1A and Fig 7).
|
|
|
|
|
|
|
The Optic Disc: Zone 1
The analysis of the semithin sections from the optic disc (Fig 1A1C), together with the GS, S100, and GFAP IHC labeling (Fig 2A, Fig 2B, Fig 3A, and Fig 3B) demonstrated that the Müller cells within this area present some variations in their morphology and arrangement compared to those that they present in the rest of the neural retina. The somata and cytoplasmic processes of the entire population of the Müller cells of the tench retina were GS positive (GS+) (Fig 2A). The GS labeling of this population at the level of the optic disc (Fig 2A and Fig 2C) demonstrated that the Müller cells' vitreal processes form a barrier at the interface between the retina and the optic nerve. At the same site, some of these long Müller cells' processes were strongly labeled with anti-S100 (Fig 2C, Fig 3A, and Fig 3B) and anti-GFAP (Fig 2B and Fig 3A).
The semithin and ultrathin sections showed that the vitreal processes of the Müller cells located around the optic disc were quite thick and were surrounded by several cell somata that were directly apposed to them (Fig 1B and Fig 1C). This is a feature that is not observed in the rest of the Müller cells of the tench retina. The ultrastructural analysis showed that the vitreal processes of the Müller cells were composed of several cytoplasmic prolongations (Fig 4B), while in the rest of the retina they were not grouped. They were not electron-dense and had many bundles of densely packed intermediate filaments, some light mitochondria, many cisternae of smooth endoplasmic reticulum, and many light vesicles adjacent to the cytoplasmic membrane (Fig 4B).
The IHC and ultrastructural analyses also permitted the characterization of the glial cell types found adjacent to the Müller cells' processes in the optic disc (Fig 1C, Fig 4A, Fig 4C, Fig 5A, and Fig 5B). Their cell bodies were arranged along the entire length of the Müller cells' vitreal processes, but most of them were located close to the inner limiting membrane (ILM) (Fig 4C). The morphological differences suggest the existence of at least two different glial types. Ultrastructurally, some of these cells had a very euchromatic kidney-shaped nucleus and contained abundant perinuclear cytoplasm, more electron-dense than the adjacent Müller cell cytoplasm. They possessed large somata from which various cytoplasmic prolongations emerged in several directions. Some of these processes divided the RGC axons into small fascicles at the level of the ONH and others ran parallel to the Müller cell processes, perpendicularly to the RGC axons in the NFL (Fig 4C). The last were joined by desmosomes and contained many bundles of intermediate filaments in the cytoplasm, typical features of astrocytes. The S100 labeling of this region also demonstrated the presence of S100-positive (S100+) mature astrocytes directly apposed to the Müller cells' arched processes (Fig 4A). This close relationship between astrocytes and Müller cells occurs only at the level of the optic disc, not in the rest of the retina. The other glial cell type found around the Müller cells' processes was S100-negative (S100-) and has been ultrastructurally characterized. They had small fusiform somata (more electron-dense than the astrocytes' somata) from which some short thin processes emerged (Fig 5A and Fig 5B). These cytoplasmic prolongations were arranged parallel to the RGC axons. Their nuclei were very heterochromatic and were surrounded by a thin rim of cytoplasm that contained free ribosomes, short and dilated cisternae of rough endoplasmic reticulum, a developed Golgi apparatus, small mitochondria, and some clear vesicles (Fig 5B). These ultrastructural characteristics are those of resident microglial cells, which are also arranged in a similar way in the NFL of the rest of the neural retina.
The S100 (Fig 2A, Fig 3A, and Fig 3B) and GFAP (Fig 2B) immunolabelings also demonstrated the presence of many S100+ and GFAP-positive (GFAP+) mature astrocytes in the center of the ONH that did not appear to be associated with the Müller cells' vitreal processes of the optic disc. The GFAP labeling showed that the gliofilaments of the cytoplasmic processes located in this region of the optic disc, probably from the astrocyte population located in this zone, presented a stronger labeling than the rest of the retina (Fig 2B and Fig 3A). The GFAP-S100 double immunolabeling (Fig 3A) also detected GFAP+S100+ processes in the optic disc (yellow in Fig 3A) that seemed to belong to astrocytes located close to the ILM. The N518S100 double labeling permitted the detection of some of the S100+ astrocytes from this zone of the optic disc. These were closely associated with the new RGC axons, which were N 518-positive (N518+) and ran through the most vitreal part of the NFL at the level of the optic disc (Fig 3B).
The organization of the Müller cells, astrocytes, and microglial cells in the optic disc is summarized in Fig 3E. It shows a complete view of the spatial distribution of these glial elements and their relationships with the newly formed RGC axons.
Intraocular ONH
The intraocular ONH is the region where the RGC axons have already changed their orientation by 90° and start to run parallel to the central artery of the optic nerve (Fig 1A).
Zone 2. In this zone there was a group of densely packed cells and many cytoplasmic prolongations located at the level of the choroid of the retina that constituted a real barrier between the neural retina and the optic nerve (Fig 1A and Fig 6A). The cell bodies were in close contact with the retinal layers. They were fusiform and were aligned in a sclerovitreal orientation and had a very euchromatic nucleus with the same orientation (Fig 6B). Some of these cells were labeled with the anti-PCNA antibody, indicating that they possessed the ability to proliferate (Fig 2E and Fig 2F). Moreover, these cells did not express S100 (Fig 2C, Fig 2D, and Fig 3B) or GFAP in contrast to the mature astrocytes previously shown in the optic disc (Fig 2C, Fig 2D, Fig 3A, and Fig 3B). Their ultrastructural analysis showed that the nuclear envelope had many ribosomes attached to it and the perinuclear cytoplasm contained free ribosomes, many microtubules, short cisternae of rough endoplasmic reticulum with a flocculent material, some gliofilaments, and they were joined by desmosomes (Fig 6C). These are features of immature glial cells, presumably astroblasts. The cytoplasmic processes located between the astroblasts and the RGC axons running through the optic nerve were GFAP+ (Fig 2B, Fig 3A, and Fig 6B). These processes were more electron-dense than the cytoplasm of the astroblasts and had many bundles of intermediate filaments, some pale and elongated mitochondria, and were joined by desmosomes and tight junctions (Fig 6B and Fig 6D). These features may show that the cytoplasmic processes observed in the interface between the retina and the optic nerve tissue do not belong to the adjacent astroblast but appear to emerge from the astrocytes that form the glia limitans between the meninges and the neural tissue. It is noteworthy that there was no basal membrane to separate these glial cells from the retinal cells, so they were in direct contact with them (Fig 6B). Moreover, there was no sheet of connective tissue to divide the retina from the optic nerve (Fig 6B and Fig 6D). Therefore, the limit between the intraocular portion of the optic nerve and the retina at the level of its choroid membrane is composed of astroblasts and mature astrocytes' processes.
Zone 3.
Regarding the typology of the remainder of the glial cells located in the intraocular portion of the tench ONH, we have shown in previous works (
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In this work, ultrastructural and immunohistochemical analyses have permitted the demonstration of several interesting and previously unreported peculiarities of the glial cell populations in the optic nerve head of the tench.
The GS and GFAP labelings, and also the ultrastructural analysis of the Müller cells' vitreal end-feet, showed a specific spatial arrangement of these cytoplasmic processes around the optic disc with which many cell bodies of astrocytes (S100+) and microglial cells are associated. The PCNA labeling of proliferative cells has enabled us to identify a population of glioblasts forming a glial barrier between the retina and the optic nerve at the level of the intraocular portion of the optic nerve head. Finally, we detected rows of glial cells within the optic nerve head whose ultrastructural analysis has demonstrated that most of them are composed of differentiating oligodendrocytes.
The present work adds new data to those obtained in previous works related to the glial cells located within the fish ONH. These works suggest that these cells possess a pattern of protein expression that differs from that of the rest of the optic nerve, mainly those proteins related to the glial cytoskeleton, such as GFAP (
Although the GS is present in the CNS astrocytes of vertebrates (
Ultrastructural analysis of the optic disc of tench demonstrates the presence of astrocytes and microglial cells in close relation to the Müller cell processes. This special cell grouping surrounding the Müller cells' processes is exclusive to this region and, to our knowledge, has not been described before in the ONH of vertebrates. The astrocytes that we detected in the tench ONH share their arrangement and features with the reticular astrocytes that
Because RGC axons are continually added to the optic nerve (
Previous works carried out by our group have described microglial cells in the NFL and optic disc of the tench by using specific markers for this cell type (NDPase and tomato lectin) (
In the intraocular portion of the ONH of animals that lack or present a poorly developed lamina cribrosa, as in mouse (
In the intraocular region of the ONH, at the interface between the retina and the optic nerve, we detected a group of PCNA-positive (PCNA+) proliferating cells that had not been previously described, whose ultrastructure indicates that they are probably astroblasts (
In the intraocular portion of the ONH we also detected and ultrastructurally characterized rows of glial cells. Many of these were composed of several oligodendrocytes in the process of differentiation. Because there are no antibodies to specifically detect the oligodendrocyte population in fish tissue sections, in the present work we have verified their existence taking as a reference their ultrastructural features (
![]() |
Acknowledgments |
---|
Supported by Junta de Castilla y León and F.S.E (grant numbers SA103/01, SA30/99), by the Spanish MCyT, and by DGI.
We thank Mr. G. H. Jenkins for revising the English version.
Received for publication February 8, 2002; accepted May 15, 2002.
![]() |
Literature Cited |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Anderson DR (1969) Ultrastructure of human and monkey lamina cribrosa and optic nerve head. Arch Ophthalmol 82:800-814[Medline]
Bastmeyer M, Bahr M, Stuermer CA (1993) Fish optic nerve oligodendrocytes support axonal regeneration of fish and mammalian retinal ganglion cells. Glia 8:1-11[Medline]
Bastmeyer M, Beckmann M, Schwab ME, Stuermer CA (1991) Growth of regenerating goldfish axons is inhibited by rat oligodendrocytes and CNS myelin but not but not by goldfish optic nerve tract oligodendrocyte-like cells and fish CNS myelin. J Neurosci 11:626-640[Abstract]
Bastmeyer M, Ott H, Leppert CA, Stuermer CA (1995) Fish E587 glycoprotein, a member of the L1 family of cell adhesion molecules, participates in axonal fasciculation and the age-related order of ganglion cell axons in the goldfish retina. J Cell Biol 130:969-976[Abstract]
Bravo R, Frank R, Blundell PA, MacdonaldBravo H (1987) Cyclin/PCNA is the auxiliary protein of DNA polymerase-delta. Nature 326:515-517[Medline]
Büssow H (1980) The astrocytes in the retina and optic nerve head of mammals: a special glia for the ganglion cell axons. Cell Tissue Res 206:367-378[Medline]
Dahl D, Crosby CJ, Sethi JS, Bignami A (1985) Glial fibrillary acidic (GFA) protein in vertebrates: immunofluorescence and immunoblotting study with monoclonal and polyclonal antibodies. J Comp Neurol 239:75-88[Medline]
Dávila JC, Guirado S, de la Calle A, MarínGirón F (1987) The intra-ocular portion of the optic nerve in the turtle Mauremys caspica. J Anat 151:189-198[Medline]
Easter SSJ, Bratton B, Scherer SS (1984) Growth-related order of the retinal fiber layer in goldfish. J Neurosci 4:2173-2190[Abstract]
Easter SSJ, Rusoff AC, Kish PE (1981) The growth and organization of the optic nerve and tract in juvenile and adult goldfish. J Neurosci 1:793-811[Abstract]
Fujita Y, Imagawa T, Uehara M (2000) Comparative study of the lamina cribrosa and the pial septa in the vertebrate optic nerve and their relationship to the myelinated axons. Tissue Cell 32:293-301[Medline]
Hernández MR (2000) The optic nerve head in glaucoma: role of astrocytes in tissue remodeling. Prog Retin Eye Res 19:297-321[Medline]
Hirata A, Kitaoka T, Ishigooka H, Ueno S (1991) Cytochemical studies of transitional area between retina and optic nerve. Acta Ophthalmol (Copenh) 69:71-75
Jimeno D, Velasco A, Lillo C, Lara JM, Aijón J (1999) Response of microglial cells after a cryolesion in the peripheral proliferative retina of tench. Brain Res 816:175-189[Medline]
Johns PR, Easter SSJ (1977) Growth of the adult goldfish eye. II. Increase in retinal cell number. J Comp Neurol 176:331-341[Medline]
Kalnins VI, Opas M, Ahmet I, Fedoroff S (1984) Astrocyte cell lineage. IV. Changes in the organization of microfilaments and adhesion patterns during astrocyte differentiation in culture. J Neurocytol 13:867-882[Medline]
Lara JM, Velasco A, Lillo C, Jimeno D, Aijón J (1998) Characterization of the glial cells in the teleost visual pathway. In Castellano B, González B, NietoSampedro M, eds. Understanding Glial Cells. Boston, Kluwer Academic Publishers, 3-18
Levine RL (1989) Organization of astrocytes in the visual pathway of the goldfish: an immunohistochemical study. J Comp Neurol 285:231-245[Medline]
Lillo C, Velasco A, Jimeno D, Lara JM, Aijón J (1998) Ultrastructural organization of the optic nerve of the tench (Cyprinidae, Teleostei). J Neurocytol 27:593-604[Medline]
Linser PJ (1985) Multiple marker analysis in the avian optic tectum reveals three classes of neuroglia and carbonic anhydrase-containing neurons. J Neurosci 5:2388-2396[Abstract]
Linser PJ (1991) Comparative immunochemistry of elasmobranch retina Müller cells and horizontal cells. J Exp Zool 5:88-96
Mack AF, Fernald RD (1995) New rods move before differentiating in adult teleost retina. Dev Biol 170:136-141[Medline]
Mack AF, Germer A, Janke C, Reichenbach A (1998) Müller (glial) cells in the teleost retina: consequences of continuous growth. Glia 22:306-313[Medline]
Maggs A, Scholes J (1986) Glial domains and nerve fiber patterns in the fish retinotectal pathway. J Neurosci 6:424-438[Abstract]
Maggs A, Scholes J (1990) Reticular astrocytes in the fish optic nerve: macroglia with epithelial characteristics form an axially repeated lacework pattern, to which nodes of Ranvier are apposed. J Neurosci 10:1600-1614[Abstract]
MonzónMayor M, Yanes C, James JL, Sturrock RR (1990a) An ultrastructural study of the development of astrocytes in the midbrain of the lizard. J Anat 170:33-41[Medline]
MonzónMayor M, Yanes C, James JL, Sturrock RR (1990b) An ultrastructural study of the development of oligodendrocytes in the midbrain of the lizard. J Anat 170:43-49[Medline]
Mori S, Leblond CP (1970) Electron microscopic identification of three classes of oligodendrocytes and a preliminary study of their proliferative activity in the corpus callosum of young rats. J Comp Neurol 139:1-28[Medline]
Morrison JC, Jerdan JA, L'Hernault NL, Quigley HA (1988) The extracellular matrix composition of the monkey optic nerve head. Invest Ophthalmol Vis Sci 29:1141-1150[Abstract]
Müller H (1952) Bau und Wachstum der Netzhaut des Guppy (Lebistes reticulatus). Zool Jb 275324
Navascués J, Moujahid A, Quesada A, Cuadros MA (1994) Microglia in the avian retina: immunocytochemical demonstration in the adult quail. J Comp Neurol 350:171-186[Medline]
Negishi K, Stell WK, Teranishi T, Karkhanis A, OwusuYaw V, Takasaki Y (1991) Induction of proliferating cell nuclear antigen (PCNA)-immunoreactive cells in goldfish retina following intravitreal injection with 6-hydroxydopamine. Cell Mol Neurobiol 11:639-659[Medline]
Nona SN, Duncan A, Stafford CA, Maggs A, Jeserich G, CronlyDillon JR (1992) Myelination of regenerated axons in goldfish optic nerve by Schwann cells. J Neurocytol 21:391-401[Medline]
Nona SN, Shehab SA, Stafford CA, CronlyDillon JR (1989) Glial fibrillary acidic protein (GFAP) from goldfish: its localisation in visual pathway. Glia 2:189-200[Medline]
Norenberg MD, MartinezHernandez A (1979) Fine structural localization of glutamine synthetase in astrocytes of rat brain. Brain Res 161:303-310[Medline]
Ogden TE (1978) Nerve fiber layer astrocytes of the primate retina: morphology, distribution, and density. Invest Ophthalmol Vis Sci 17:499-510[Abstract]
Okinami S, Ohkuma M, Tsukahara I (1976) Kuhnt intermediary tissue as a barrier between the optic nerve and retina. Graefes Arch Klin Exp Ophthalmol 201:57-67
Ott H, Bastmeyer M, Stuermer CA (1998) Neurolin, the goldfish homolog of DM-GRASP, is involved in retinal axon pathfinding to the optic disk. J Neurosci 18:3363-3372
Peters A, Palay SL, Webster HD (1991) The Fine Structure of the Nervous System. Neurons and Their Supporting Cells. 3rd ed New York, Oxford University Press
Peterson RE, Fadool JM, McClintock J, Linser PJ (2001) Müller cell differentiation in the zebrafish neural retina: evidence of distinct early and late stages in cell maturation. J Comp Neurol 429:530-540[Medline]
Petrausch B, Jung M, Leppert CA, Stuermer CAO (2000) Lesion-induced regulation of netrin receptors and modification of netrin-1 expression in the retina of fish and grafted rats. Mol Cell Neurosci 16:350-364[Medline]
Prada FA, Espinar A, Chmielewski CE, Dorado ME, GenisGalvez JM (1989) Regional adaptation of Müller cells in the chick retina. A Golgi and electron microscopical study. Histol Histopathol 4:309-315[Medline]
Radius RL, Gonzales M (1981) Anatomy of the lamina cribrosa in human eyes. Arch Ophthalmol 99:2159-2162[Abstract]
Raff MC, Abney ER, Miller RH (1984) Two glial cell lineages diverge prenatally in rat optic nerve. Dev Biol 106:53-60[Medline]
Raymond PA, Hitchcock PF (2000) How the neural retina regenerates. In Fini ME, ed, Results and Problems in Cell Differentiation. Vertebrate Eye Development, 31, pp. Berlin, Springer-Verlag, 197217
Reichenbach A, Robinson SR (1995) Ependymoglia and ependymoglia-like cells. In Kettenmann H, Ransom BR, eds. Neuroglia. Oxford, Oxford University Press, 58-84
Reichenbach A, Wohlrab F (1986) Morphometric parameters of Müller (glial) cells dependent on their topographic localization in the nonmyelinated part of the rabbit retina. A consideration of functional aspects of radial glia. J Neurocytol 15:451-459[Medline]
Riepe RE, Norenburg MD (1977) Müller cell localisation of glutamine synthetase in rat retina. Nature 268:654-655[Medline]
Schnitzer J (1985) Distribution and immunoreactivity of glia in the retina of the rabbit. J Comp Neurol 240:128-142[Medline]
Scholes J (1991) The design of the optic nerve in fish. Vis Neurosci 7:129-139[Medline]
Schuck J, Gerhardt H, Wolburg H (2000) The peripapillary glia of the optic nerve head in the chicken retina. Anat Rec 259:263-275[Medline]
Skoff RP, Price DL, Stocks A (1976) Electron microscopic autoradiographic studies of gliogenesis in rat optic nerve. II. Time of origin. J Comp Neurol 169:313-334[Medline]
Springer AD, Mednick AS (1986) Retinotopic and chronotopic organization of goldfish retinal ganglion cell axons throughout the optic nerve. J Comp Neurol 247:221-232[Medline]
Stensaas LJ (1977) The ultrastructure of astrocytes, oligodendrocytes, and microglia in the optic nerve of urodele amphibians (A. punctatum, T. pyrrhogaster, T. viridescens). J Neurocytol 6:269-286[Medline]
Stone J, Dreher Z (1987) Relationship between astrocytes, ganglion cells and vasculature of the retina. J Comp Neurol 255:35-49[Medline]
Stuermer CA, Bastmeyer M (2000) The retinal axon's pathfinding to the optic disk. Prog Neurobiol 62:197-214[Medline]
Trimmer PA, Reier PJ, Oh TH, Eng LF (1982) An ultrastructural and immunocytochemical study of astrocytic differentiation in vitro: changes in the composition and distribution of the cellular cytoskeleton. J Neuroimmunol 2:235-260[Medline]
Triviño A, Ramírez JM, Salazar JJ, Ramírez AI, GarcíaSánchez J (1996) Immunohistochemical study of human optic nerve head astroglia. Vis Res 36:2015-2028[Medline]
Uga S (1974) Some structural features of the retinal Müllerian cells in the juxta-optic nerve region. Exp Eye Res 19:105-115[Medline]
Uga S, Ikui H, Kono T (1974) Electron microscope study on astrocytes in the human retina. Nippon Ganka Gakkai Zasshi 78:681-685[Medline]
Vecino E, Velasco A, Caminos E, Aijón J (1997) Distribution of S100 immunoreactivity in the retina and optic nerve head of the teleost Tinca tinca L. Microsc Res Tech 36:17-25[Medline]
Velasco A, Briñón JG, Caminos E, Lara JM, Aijón J (1997) S-100-positive glial cells are involved in the regeneration of the visual pathway of teleosts. Brain Res Bull 43:327-336[Medline]
Velasco A, Cid E, Ciudad J, Orfao A, Aijón J, Lara JM (2001) Temperature induces variations in the retinal cell proliferation rate in a cyprinid. Brain Res 913:190-194[Medline]
Velasco A, Jimeno D, Lillo C, Caminos E, Lara JM, Aijón J (1999) Enzyme histochemical identification of microglial cells in the retina of a fish (Tinca tinca). Neurosci Lett 263:101-104[Medline]
Watanabe T, Raff MC (1988) Retinal astrocytes are immigrants from the optic nerve. Nature 332:834-837[Medline]
Wolburg H (1978) Growth and myelination of goldfish optic nerve fibers after retina regeneration and nerve crush. Z Naturforsch 33:988-996. [C]
Wolburg H (1981) Myelination and remyelination in the regenerating visual system of the goldfish. Exp Brain Res 43:199-206[Medline]
Wolburg H, Buerle C (1993) Astrocytes in the lamina cribrosa of the rat optic nerve: are their morphological peculiarities involved in an altered blood-brain barrier? J Hirnforsch 34:445-459[Medline]
Ye H, Hernández MR (1995) Heterogeneity of astrocytes in human optic nerve head. J Comp Neurol 362:441-452[Medline]