lucifer-yellow and Retinal-Detachment

To evaluate early changes in the visual response properties of Y cells in the detached feline retina.. The retinas of young adult cats were detached by injection, with a glass micropipette, of a solution of 0.004% sodium hyaluronate in a balanced salt solution between the neural retina and the retinal pigment epithelium. At 1, 3, and 7 days after detachment, the eyes were removed. The eyecup was prepared as a flat mount in a recording chamber and superfused with medium. Extracellular single-unit responses from Y cells in the retinas were recorded.. One, 3, and 7 days after retinal detachment surgery, Y cells showed clear signs of functional deterioration. At each time point, more ON center cells than OFF cells were encountered. Y cells in the detached retinas showed a statistically significant elevation in the average threshold irradiance after 1-, 3-, and 7-day detachment, respectively. The average contrast threshold recorded from cells in the normal retina was 3.6%, but it increased to 14.5%, 21.8%, and 47.5% after 1-, 3-, and 7-day detachment, respectively. Furthermore, at each time point, the capability of Y cells to process contrast information decreased significantly more because of detachment than because of luminance task performance.. Retinal detachment induced rapid functional remodeling that resulted in degenerated Y-cell function, including an elevated luminance threshold and a deteriorated contrast threshold. Detachment had a greater impact on the latter. These physiological changes after retinal detachment could be used as objective indicators of early deterioration of visual function in future studies of retinal remodeling.

Topics: Animals; Biotin; Cats; Contrast Sensitivity; Disease Models, Animal; Electrophysiology; Female; Immunoenzyme Techniques; Isoquinolines; Male; Perceptual Disorders; Photic Stimulation; Retina; Retinal Detachment; Retinal Ganglion Cells; Sensory Thresholds; Visual Perception

Mechanisms that maintain the close coupling between the formation of photoreceptor disk membranes and the displacement of disk membranes toward the pigment epithelium are poorly understood. This study was designed to determine whether the axial displacement of disk membranes requires the assembly and insertion of new disk lamellae.. Retinal detachment and treatment with cytochalasin D were employed to interrupt the normal formation of disk membranes in cultured Xenopus laevis retinas. The effect of disrupting disk initiation and assembly upon disk displacement was documented and quantified.. Isolating retinas from the retinal pigment epithelium prevented the normal morphogenesis of disks, but previously formed disks moved distally at a rate that is greater than or equal to the rate in attached retinas or in vivo. Treatment of attached retinas in eyecups with cytochalasin D blocked initiation of new disks and resulted in the formation of ectopic, disk-like membranes, but it did not stop axial displacement of previously formed disks. Rod cells in retinas that were cultured while slightly elevated from the retinal pigment epithelium sometimes formed disks of a smaller diameter than normal, even though the rate of initiation and displacement of disks was the same as in vivo.. Observations on detached retinas and or retinas treated with cytochalasin D suggest that disk displacement does not depend upon normal disk formation and that the motive mechanism does not involve filamentous actin. The formation of small diameter disks in elevated retinas suggests that disk initiation and displacement is independent of the completion of normal diameter disks.

Topics: Animals; Cytochalasin D; Fluorescent Dyes; Intracellular Membranes; Isoquinolines; Morphogenesis; Organ Culture Techniques; Retinal Detachment; Rod Cell Outer Segment; Xenopus laevis

The authors compared rod outer segment (ROS) disc membrane assembly rates in detached and attached frog retinas to determine if there was a rapid impairment of membrane assembly in response to retinal detachment. Membrane assembly was quantified in vitro by incubating retinas in medium containing Lucifer yellow, which is entrapped by nascent discs. Video microscopy was used to detect incorporation of the dye. During the first 10 hr after separation of the retina from the retinal pigment epithelium (RPE), ROS-disc membrane assembly in isolated Xenopus laevis neural retinas continued at a near normal rate, 0.81 microns/10 hr, a 13% reduction (P less than .01), compared with the 0.93 microns/10 hr observed in attached control retinas. The morphology of the OS appeared normal in most rod photoreceptors by transmission electron microscopy, although vesiculation of the most basal OS membranes was seen in a small population (25%) of rods. Approximately 90% of rod photoreceptors continued to assemble OS membranes for more than 10 hr after detachment, but by the end of 2 days, only 55% were still making new discs. The percentage of rods with normal basal OS membranes also decreased (to approximately 50%). Therefore, only 25% were assembling morphologically normal discs 2 days after detachment. In attached control regions, rod photoreceptors showed a comparatively minor response to culture conditions; assembly of morphologically normal discs continued for 2 days in about 85% and ceased in only 10%. These results indicate that the effects on disc membrane assembly of disrupting photoreceptor-RPE interaction in vitro initially are slight but become progressively severe with time.

Topics: Animals; Cell Membrane; Eye Proteins; Fluorescent Antibody Technique; Fluorescent Dyes; Image Processing, Computer-Assisted; Isoquinolines; Organ Culture Techniques; Retina; Retinal Detachment; Rod Cell Outer Segment; Rod Opsins; Video Recording; Xenopus laevis