Retinal regeneration

Ramsden CM, Powner MB, Carr AJ, Smart MJ, da Cruz L, Coffey PJ (2013) Stem cells in retinal regeneration past, present and future. Development 140 2576-2585. 

Promotes hair fol- Notch inhibitor licle growth blocks retinal regeneration... 

Moreover, efficient rhodopsin regeneration may precede enzymatic reduction of all-fran.v-retinal to all-trans-retinol in the aged retina (Figure 15.2c) (Schadel et al., 2003). Upon rhodopsin regeneration, all-trans-retinal is released from the exit site of the protein into the lipid membrane (Figure 15.2c) (Schadel et al., 2003). From here the removal of all-tnms-retinal to the outer leaflet of the disc membrane is dependent on activity of ATP-binding cassette trasporter A4 (ABCA4) present in the rim of photoreceptor disc, known also as ABCR protein. 

Bleached rhodopsin must be regenerated to maintain normal vision. Regeneration occurs by several mechanisms. The major pathway occurs in the retinal pigmented... 

In these spectra, the protein has been regenerated with retinal specifically 13 C labeled at positions 11,12 and 13, and in each case the retinal resonance exhibits a sharp centerband at the isotropic chemical shift and is flanked by rotational sidebands. Other lines in the spectrum are the natural-abundance 13C resonances of the protein carbonyls ca 175 ppm) and aliphatic carbons (0-100 ppm). Contributions from the Ammonyx-LO detergent in these spectra are seen in the different intensities in the 0-100 ppm region. Ammonyx-LO does not exhibit NMR resonances above 100 ppm. Spectra of the 9-cis pigment isorhodopsin are similar. Table 38 summarizes the isotropic chemical shifts from the solid-state NMR spectra of rhodopsin regenerated with retinal13 C labeled at each position along... 

For vision to continue, c/s-retinal must be regenerated. The /rans-retinal is reduced to /rans-retinol (i.e. the aldehyde is converted to alcohol) and is isomerised to c/s-retinal this is oxidised to c/s-retinol (see Figure 15.9(b)). Two different cells are involved the oxidation of retinal to retinol occurs in the photoreceptor cell. The retinol is then released and is taken up by the adjacent epithelial cell where it is isomerised to c/s-retinol and then reduced to... 

The release of all-tram-retinal from opsin takes sev-eral minutes and is too slow to be an obligatory step in visual perception. It appears to be a step in the regeneration of the active form of rhodopsin. The all-tram-retinal leaves the rod cell and is isomerized back to the 11-cm form before it returns. 

Another study45 used the 2H 7jz anisotropy of CD3 groups in 6-5-civ-retinoic acid, in 6-5-frans-retinoic acid (Fig. 16a) and in the membrane protein bacteriorhodopsin regenerated with CD3-labelled retinal (Fig. 16b) to examine the motion of the CD3 groups. It was found that for both forms of retinoic acid, a three-site hopping model fitted the experimental data, but with the difference that the activation energy for the cis isomer was 14.5 1 kJmol-1 whereas for the... 

Rhodopsin can be regenerated in vitro by adding 1 l-c -retinal to bleached rod outer segment membranes (ROS) in suspension or in a suitable detergent. The requirements for efficient regeneration are the following ... 

In cultured mouse retinal ganglion cells, lithium supported the survival and regeneration of axons (23). This led the authors to the very speculative suggestion that lithium might be useful in treating conditions such as glaucoma, optic neuritis, and other neuron loss disorders. 

Huang X, Wu DY, Chen G, Manji H, Chen DF. Support of retinal ganglion cell survival and axon regeneration by lithium through a Bcl-2-dependent mechanism. Invest Ophthalmol Vis Sci 2003 44(l) 347-54. 

When a solution of rhodopsin, having at 500 m u, is illuminated, separation of the protein and the retinal occurs. The product, purple at the beginning, turns pale. Regeneration of the rhodopsine can be carried out by bringing its two components into contact in the dark. Examination of the UV spectrum after bleaching the rhodopsine shows that the generated retinal possesses the trans structure, which has to be isomerized before combination with the protein can again occur. 

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