Light Propagation through the Retina: Vertebrate Retinal Optics
Final Report Abstract
Within this project specific aspects of light guidance were studied in the vertebrate retina. In earlier studies, we could show that the typical retinal glial cells, the Müller cells, are able to transmit incoming light from their endfeet through the retina towards the photoreceptors. Thus, Müller cells act as living optical fibers. In our experiments, a light beam was directed onto the vitread side of a slice of the guinea pig retina. If the light directly hit an endfoot of a Müller cell, a small and bright light spot could be observed on the photoreceptor side of the retina. If an area apart from an endfoot was illuminated, the light spot at the photoreceptors was more diffuse, larger and less bright. Moreover, it could be observed that exact illumination of a Müller cell endfoot resulted in light transmission into a small group of closely adjacent photoreceptors. Additionally, studies on the retina of the caiman (Caiman crocodilus fuscus) were performed within this project. It could be shown that also the Müller cells of this reptile species are able to act as light cables. For the experiments, a specific setup was used with two axially aligned objectives imaging the retina from both sides to project the light onto the inner (vitread) surface and to detect the transmitted light behind the retina at the photoreceptor layer. Simultaneously, a confocal microscope obtained images of the Müller cells embedded within the vital tissue. Because of the observed light guidance by Müller cells, it can be concluded that these cells support dim light vision by increasing sensitivity to light. Moreover, the retina of the caiman was studies ultrastructurally. The following characteristics could be found: presence of a retinal tapetum, rod dominance of the retina, presence of photoreceptor cell nuclei which penetrate the outer limiting membrane, and the presence of rods with long and thick outer segments. The results suggest that the retina of the caiman is adapted to dim light and night vision.
Publications
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(2011). Müller glial cell-provided cellular light guidance through the vital guinea-pig retina. Biophysical Journal, 101(11), 2611–2619
Agte, S., S. Junek, S. Matthias, E. Ulbricht, I. Erdmann, A. Wurm, D. Schild, J. A. Käs, and A. Reichenbach
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(2012). Live cells as optical fibers in the vertebrate retina. Selected topics on optical fiber technology. Ed. by M. Yasin, H. Arof, and S. W. Harun. Rijeka: InTech, 247–270
Reichenbach, A., K. Franze, S. Agte, S. Junek, A. Wurm, J. Grosche, A. Savvinov, J. Guck, and S. N. Skatchkov
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(2014). Unidirectional photoreceptor-to-Müller glia coupling and unique K+ channel expression in Caiman retina. PLoS One, 9(5), e97155
Zayas-Santiago, A., S. Agte, Y.Rivera, J. Benedikt, E. Ulbricht, A. Karl, J. Dávila, A. Savvinov, Y. Kucheryavykh, M. Inyushin, L.A. Cubano, T. Pannicke, R.W. Veh, M. Francke, A. Verkhratsky, M.J. Eaton, A. Reichenbach, and S.N. Skatchkov
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(2017). Two different mechanosensitive calcium responses in Müller glial cells of the guinea pig retina: Differential dependence on purinergic receptor signaling. Glia, 65(1):62-74
Agte, S., T. Pannicke, E. Ulbricht, A. Reichenbach, and A. Bringmann
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(2018). Müller glial cells contribute to dim light vision in spectacled caimans (Caiman crocodiles fuscus): I. Ultrastructural indications, Exp Eye Res, 173, 160-178
Karl, A., S. Agte, A. Zayas-Santiago, F.N. Makarov, M. Francke, A. Reichenbach, S.N. Skatchkov, and A. Bringmann
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(2018). Müller glial cells contribute to dim light vision in spectacled caimans (Caiman crocodilus fuscus): II. Analysis of retinal light transmission, Exp Eye Res, 173, 91-108
Agte, S., A. Savvinov, A. Karl, E. Ulbricht, M. Francke, A. Reichenbach, A. Bringmann, and S.N. Skatchkov
