Rods, retinal

Kingston PA, Zufall F, Barnstable CJ (1996) Rat hippocampal neurons express genes for both rod retinal and olfactory cyclic nucleotide-gated channels novel targets for cAMP/cGMP function. Proc Natl Acad Sd USA 93 10440-5... 

The distribution of rods and cones is shown in Figure 3b centered about the fovea, the area of the retina that has the highest concentration of cones with essentially no rods and also has the best resolving capabiUty, with a resolution about one minute of arc. The fovea is nominally taken as a 5° zone, with its central 1° zone designated the foveola. There are about 40 R and 20 G cones for each B cone in the eye as a whole, whereas in the fovea there are almost no B cones. A result of this is that color perception depends on the angle of the cone of light received by the eye. The extremely complex chemistry involved in the stimulation of opsin molecules, such as the rhodopsin of the rods, and the neural connections in the retinal pathway are well covered in Reference 21. 

Fig. 1. Representative spectral sensitivities of the human retinal receptors, (-) scotopic (rod) vision, and P, y, and p cone sensitivities. The wavelengths of...

Phosducin regulates light adaptation in retinal rods... 

The retinol that is delivered to the retinas of the eyes in this manner is accumulated by rod and cone cells. In the rods (which are the better characterized of the two cell types), retinol is oxidized by a specific retinol dehydrogenase to become 2iW-trans retinal and then converted to 11-eis retinal by reti-... 

Netzhaut-. retinal, -bild, n. retinal image, -eindruck, m. retinal impression, -stabcheu, n. retinal rod, -zkpfchen, n. retinal cone. 

Pertussis toxin is produced by the bacterium Bordetella pertussis. It covalently modifies G-proteins of the G/Go family (transfer of a ADP-ribose moiety of NAD onto G-protein a-subunits). ADP-ribosylated G-proteins are arrested in their inactive state and, as a consequence, functionally uncoupled from their respective effectors. Examples for pertussis toxin-sensitive cellular responses include the hormonal inhibition of adenylyl cyclases, stimulation ofK+ channels, inhibition of Ca2+ channels and stimulation ofthe cGMP-phosphodiesterase in retinal rods. 

Photodiode arrays have been used as retinal implants [684]. These arrays of p-i-n diodes are fabricated on a thin titanium layer bonded to a glass plate. The total thickness of this flexible structure is 1.5 yum. The microphotodiode array (MPDA) is used to replace photoreceptors (rods and cones) that have become defective due to disease. 

Bleaching is reversed in the dark and the red-purple color of rhodopsin returns. This is thought to occur by the reduction of all-Pms-retinal to vitamin Ai (retinal), which diffuses from the rod into the pigment epithelium, where it is converted enzymatically to the 1 l-c isomer of vitamin At. The enzymatic isomerization is followed by diffusion back into the rod, oxidation to 11 -rfr-retinal, and combination with opsin to form rhodopsin. This process is shown schematically in Figure 12.5.[Pg.289]

The visual pigment present in rods has been termed rhodopsin and consists of 11-m-retinal, a derivative of vitamin A1( and a lipoprotein called opsin. Recent evidence(43) suggests that in native rhodopsin the retinal chromo-phore is covalently bonded to a phosphatidylethanolamine residue of the lipid portion of opsin. The structure of 1 l-cis-retinal is as follows ... 

Rat (hooded) 3 wk ad lib (W) Ocular 0.5 F (decreased retinal sensitivity, rhodopsin, and rod outer segment length) Fox and Rubinstein 1989 PbAc... 

Fox DA, Rubinstein SD. 1989. Age-related changes in retinal sensitivity, rhodopsin content and rod outer segment length in hooded rats following low-level lead exposure during development. Exp Eye Res 48 237-249. 

Ryeom, SW, Sparrow, JR, and Silverstein, RL, 1996b. CD36 participates in the phagocytosis of rod outer segments by retinal pigment epithelium. J Cell Sci 109, 387-395. 

Rhodopsin is a seven ot-helix trans-membrane protein and visual pigment of the vertebrate rod photoreceptor cells that mediate dim light vision. In this photoreceptor, retinal is the chromophore bound by opsin protein, covalently linked to Lys296 by a Schiff base linkage. Kpega et al.64 have studied NMR spectra of Schiff bases being derivatives of all-frans retinal and amino-p-cyclodextrins as a model of rhodopsin, where p-cyclodextrin plays a role of a binding pocket. On the basis of analysis of the chemical shift differences for the model compound in the presence and in the absence of adamantane carboxylate, it has been shown that the derivative of 3-amino-p-cyclodextrin forms dimer in water and retinoid is inserted into p-cyclodextrin cavity [31]. 

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