What the Photoreseptor Outer Segment Length Tells Us | Chapter 11 | Highlights on Medicine and Medical Research Vol. 13

 Novel retina morphology studies have been successfully introduced thanks to recent developments in ocular imaging technology. It's the most frequent method for displaying the Spectral domain optic coherence tomography retinal layers. On SD-OCT, the external limiting membrane (ELM), inner segment ellipsoid (ISel, previously known as the junction between the inner and outer segments (IS/OS junction)), cone outer segment tips (COST), and retinal pigment epithelium are the four hyperreflective outer retinal lines (RPE). Between IS/OS and RPE, the PROS is positioned. When calculating the PROS, Only the fovea, where the cone cells are located, is measured in length. Visual acuity and quality are intimately tied to these cells. The data was revealed in a database analysis on the issue, which indicated that ‘the difference in PROS length was not statistically significant neither for age nor for gender; females tended to have a lower PROS length than males, and PROS length was somewhat higher in the first two decades of life.' Similar investigations have also been carried out for a variety of disorders. We know that in the future, a retinal structure (PROS length) that provides so much information regarding vision and vision quality will be employed more frequently in our everyday practise.

Author (S) Details

Gamze Karataş
Department of Ophthalmology, Osmaniye State Hospital, Osmaniye, Turkey.

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Cone-Like Functional Properties of cGMP-Gated Channels in Rod-Like Retinal Photoreceptors of Nocturnal Geckoes | Chapter 7 | Recent Research Advances in Biology Vol. 4

 Nocturnal geckoes' retinas contain only scotopic photoreceptors with rod-shaped outer segments and light sensitivity close to that of retinal rods of other lower vertebrate organisms. These cells, however, are not rods, but are originally derived from cones of ancestral diurnal geckoes in cone-only retinas as a result of evolutionary pressure that forced adaptation to nocturnal behaviour. To date, several fascinating modifications of these rod-like cones have been studied; molecular biology and functional studies have reported that several phototransductive cascade proteins exhibit structural and functional properties suggesting their origin from cones rather than rods. In this paper, we examine the voltage rectification properties of photoreceptor cGMP-gated channels in three species, Gekko gecko, Tarentola mauritanica, and Hemidactylus frenatus, with whole cell voltage clamp in the detached outer segment preparation. In the physiological voltage spectrum, we show that the current-voltage properties are reminiscent of those of cGMP-gated channels from cones rather than from rods of other cold-blooded vertebrates. The sources and the importance of the examined processes are discussed. In conclusion, we provide novel, functional evidence in this paper of the existence of mechanisms in rod-shaped nocturnal gecko photoreceptors that remember their origin from ancestral cones. Recently performed in Gekko gecko, the molecular analysis of the retinal cGMP gated channel identified cone-like structural features, which agree with our observations.

Author(s) Details

Vittorio Vellani

Dipartimento di Scienze Biomediche Metabolismo e Neuroscienze, Università di Modena e Reggio Emilia, via Campi 287, 41125 Modena, Italy.

Chiara Giacomoni
Università degli Studi della Repubblica di San Marino, via Consiglio dei Sessanta 99, 47891 Dogana, Repubblica di San Marino.

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