The argyrophilic mosaic of the internal limiting membrane of the retina (original) (raw)
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Brazilian Journal of Medical and Biological Research, 2003
Different from most mammalian species, the optic nerve of the rabbit eye is initially formed inside the retina where myelination of the axons of the ganglion cells starts and vascularization occurs. Astrocytes are confined to these regions. The aforementioned nerve fibers known as medullated nerve fibers form two bundles that may be identified with the naked eye. The blood vessels run on the inner surface of these nerve fiber bundles (epivascularization) and, accordingly, the accompanying astrocytes lie mostly facing the vitreous body from which they are separated only by the inner limiting membrane of the retina. The arrangement of the astrocytes around blood vessels leads to the formation of structures known as glial tufts. Fragments (N = 3) or whole pieces (N = 3) of the medullated nerve fiber region of threemonth-old male rabbits (Orictolagus cuniculus) were fixed in glutaraldehyde followed by osmium tetroxide, and their thin sections were examined with a transmission electron microscope. Randomly located discontinuities (up to a few micrometers long) of the basement membrane of the inner limiting membrane of the retina were observed in the glial tufts. As a consequence, a direct contact between the astrocyte plasma membrane and vitreous elements was demonstrated, making possible functional interactions such as macromolecular exchanges between this glial cell type and the components of the vitreous body. Correspondence A. Haddad
Anatomy and pathology of the vitreo-retinal interface
Eye, 1992
MORPHOLOGY Macroscopic Structure Portions of this paper were originally published in Sebag J, Wendell R, DeBustros S: Disorders of the vitreo-macular inter face. In: Margo CE, Mames RN, Hamed L, eds. Diagnostic Problems in Clinical Ophthalmology. Orlando, FL: WB Saun ders (in press) and in Sebag J: Vitreous biochemistry and struc ture. In: Albert D and Jakobiec F, eds. Principles and Practice of Ophthalmology: The Harvard System. Orlando, FL: WB Saun ders (in press).
A new perspective on Bruch's membrane and the retinal pigment epithelium
British Journal of Ophthalmology, 1982
Trypsin digestion of retinal pigment epithelium is a technique that bares Bruch's membrane, to allow topographical examination by scanning electron microscopy. Twenty-five human eyes were examined. The zonula occludens of the pigment epithelium was clearly seen as a surface feature, but attachment plaques at the sides and base were not visible. The adhesion between the pigment epithelium and the basal lamina was stronger than between the basal lamina and the rest of Bruch's membrane. Surface features of the basal lamina, inner collagenous zone, elastic layer, and outer collagenous zone were seen in a way that previously required an artist's representation constructed from microscopic sections.
Cell and Tissue Research, 1991
Dissociated embryonic chicken retinal cells regenerate in rotary culture into cellular spheres that consist of subareas expressing all three nuclear layers in an inside-out sequence (rosetted vitroretinae). However, when pigmented cells from the eye margin (peripheral retinal pigment epithelium) are added to the system, the sequence of layers is identical with that of an in-situ retina (laminar vitroretinae). In order to elucidate further the lamina-stabilizing effect exerted by the retinal pigment epithelium, we have compared both systems, laying particular emphasis on the ultrastructure of the basal lamina and of Mfiller glia processes. Ultrastructurally, in both systems, an outer limiting membrane, inner segments of photoreceptors and the segregation of cell bodies into three cell layers develop properly. Synapses are detectable in a premature state, although only in the inner plexiform layer of laminar vitroretinae. Although present in both systems, radial processes of juvenile Mfiller glia cells are properly fixed at their endfeet only in laminar vitroretinae, since a basal lamina is only expressed here. Large amounts of laminin are detected immunohistochemically within the retinal pigment epithelium and along a basal stalk that reaches inside the laminar vitroretinae. We conclude that the peripheral retinal pigment epithelium is essential for the expression of a basal lamina in vitro. Moreover, the basal lamina may be responsible both for stabilizing the correct polarity of retinal layers and for the final differentiation of the Mfiller cells.
Junction-like structure appearing at apposing membranes in the double cone of chick retina
Cell and Tissue Research, 1981
No type of junction has yet been recognized between the two entities of the retinal double cone. In the present study, a junction-like structure was observed in serial sections of the double cone of the chick retina. It is recognized from the slightly outer part of the double cone to the outer limiting membrane. The apposing membranes are virtually parallel and separated by 5 to 7 nm of extracellular space. Dense material is associated on the cytoplasmic side of the opposing membranes. The structure resembles a gap junction, but there are no cross striations between the two membranes. Further experiments are required to establish this as a new type of junction. Studies in the retina of the gecko Coleonyx variegatus. I. The visual cell classification. J Ultrastruct Res 16:651-671 Dunn RF (1966 b) Studies in the retina of the gecko Coleonyx variegatus. If. The rectilinear visual cell mosaic. J Ultrastruct Res 16:672-684 Dunn RF (1966 c) Studies in the retina of the gecko Coleonyx variegatus. III. Photoreceptor cross-section area relationships. J Ultrastruct Res 16:685-692 Farquhar MG, Palade GE (1963) Junctional complexes in various epithelia. J Cell Biol 17:375-412 Hartwig HG (1968) fiber Rezeptorentypen in der Retina von Zonotrichia leucophrys gambelff. Z Zellforsch 91:411-428 Keefe JR (1971) The fine structure of the retina in the newt, Triturus virideseens.
The structure of rabbit retinal M�ller (glial) cells is adapted to the surrounding retinal layers
Anatomy and Embryology, 1989
Radial glial (Mfiller) cells of the rabbit retina were studied by various techniques including Golgi impregnation, scanning electron microscopy, horseradish peroxidase application, and staining of enzymatically isolated cells. This combination of methods produced detailed information on the specialized morphology of the Miiller cells within the different topographical regions of the retina, and of the Mfiller cell processes within the various retinal layers. As a general rule, the retinal periphery contains short thick Mfiller cells with big endfeet, whereas the thick central retina is occupied by long slender cells with small endfeet. Independent of their location within the retina, Miiller cell processes were found to be adapted to the structure of the surrounding retinal layers. Within the outer and inner nuclear layers, Mfiller cell processes (and somata) extend thin cytoplasmic "bubbles" ensheathing the neuronal somata, as do the "velate" astrocytes in the brain. In the plexiform layers, Mfiller cells extend many t-me side branches between the neuropll, comparable to the protoplasmic astrocytes of the brain. In the thick myelinated nerve fibre layer of the central retina the Mfiller cell processes are rather smooth, similar to those of fibrous astrocytes. It is concluded that the neuronal microenvironment determines the morphology of a given glial process, or even of a part of a ghal process running through a specialized neuronal compartment.
Retinal and epiretinal glia--an immunohistochemical study
British Journal of Ophthalmology, 1984
Immunohistochemical techniques were used to examine the distribution of cells containing glial fibrillary acidic protein (GFAP) in normal and pathological human specimens, including 22 globes (13 of which contained epiretinal membranes 'in situ'), 16 surgically excised epiretinal membranes, and monolayers of cells obtained from five epiretinal membranes placed in tissue culture. The astrocytic cells of normal and pathological retinae stained with the glial-cell marker, but Muller cells were GFAP-negative in normal retinae at the antisera dilutions used. Muller cells did, however, stain in retinae from glaucomatous eyes and in eyes with prolonged retinal detachment. Electron microscopy did not reveal any obvious morphological difference between the intermediate filaments of normal (GFAP-negative) and GFAP-positive Muller cells. Ten of the 13 epiretinal membranes 'in situ', all 16 excised membranes, and three of the five monolayers contained glial cells. Purely glial membranes were not associated with retinal puckering or detachment, while all membranes causing tractional complications had a prominent fibrous, non-glial component. Our findings suggest that glial cells do not contribute significantly to the contractile forces generated by epiretinal membranes. They may, however, provide a scaffold on which other cells proliferate and contract and an anchorage by means of which tangential forces are transmitted into and through the retina.