Retinal differentiation

A variety of disorders may lead to rapid, painless, monocular or binocular vision loss. This may include central retinal artery occlusion, acute narrow-angle glaucoma, trauma, or others. The differential diagnosis is complex and needs to be undertaken by an emergency department or ophthalmologist.9... 

Numerous studies have demonstrated that degradation products of (3-carotene exhibit deleterious effects in cellular systems (Alija et al., 2004, 2006 Hurst et al., 2005 Salerno et al., 2005 Siems et al., 2003). A mixture of (3-carotene degradation products exerts pro-apoptotic effects and cytotoxicity to human neutrophils (Salerno et al., 2005 Siems et al., 2003), and enhances the geno-toxic effects of oxidative stress in primary rat hepatocytes (Alija et al., 2004, 2006), as well as dramatically reduces mitochondrial activity in a human leukaemic cell line, K562, and RPE 28 SV4 cell line derived from stably transformed fetal human retinal pigmented epithelial cells (Hurst et al., 2005). As a result of degradation or enzymatic cleavage of (3-carotene, retinoids are formed, which are powerful modulators of cell proliferation, differentiation, and apoptosis (Blomhoff and Blomhoff, 2006). 

Dunn, KC, Aotaki-Keen, AE, Putkey, FR, and Hjelmeland, LM, 1996. ARPE-19, a human retinal pigment epithelial cell line with differentiated properties. Exp Eye Res 62, 155-169. 

Momma, Y, Nagineni, CN, Chin, MS, Srinivasan, K, Detrick, B, and Hooks, JJ, 2003. Differential expression of chemokines by human retinal pigment epithelial cells infected with cytomegalovirus. Invest Ophthalmol... 

Lampert, J. M., J. Holzschuh et al. (2003). Provitamin A conversion to retinal via the beta,beta-carotene-15,15 -oxygenase (bcox) is essential for pattern formation and differentiation during zebrafish embryogenesis. Development 130(10) 2173-2186. 

K. Hosoya, M. Tomi, S. Ohtsuki, H. Takanaga, M. Ueda, N. Yanai, M. Obinata, and T. Terasaki. Conditionally immortalized retinal capillary endothelial cell lines (TR-iBRB) expressing differentiated endothelial cell functions derived from a transgenic rat. Exp. Eye Res. 72 163-172 (2001). 

Here we have another simple chemical transformation, the oxidation of the aldehyde group in retinal to the carboxyl group of retinoic acid. Although the chemical change is simple, the physiology is profoundly different. Retinoic acid has nothing to do with vision but a lot to do with development and differentiation. Here we have yet another example of the sensitive interdependence of chemical structure and biological function. 

BRGl BRGl Zebrafish Not known Retinal cell differentiation [274]. 

Gregg, R.G., Wilier, G.B., Fadool, J.M., Dowling, J.E., and Link, B.A. (2003) Positional cloning of the young mutation identifles an essential role for the Brahma chromatin remodeling complex in mediating retinal cell differentiation. Proc. Natl. Acad. Sci. USA 100, 6535-6540. 

Diagnosis of CMV retinitis The diagnosis should be made by indirect ophthalmoscopy. Other conditions in the differential diagnosis of CMV retinitis include candidiasis, toxoplasmosis, histoplasmosis, retinal scars, and cotton wool spots, any of which may produce a retinal appearance similar to CMV. The... 

Vitamin A is essential for proper functioning of the retina, for the integrity of epithelial tissue, for growth and bone development and for reproduction. For vision the active vitamin appears to be retinal as the chromophore of both rods and cones is 11-cis-retinal which, in combination with the protein opsin, forms the photoreceptor rhodopsin. Retinoic acid is the active form associated with growth, differentiation, and transformation. Both all-trans and 9-cis retinoic acid act as a steroid hormone to affect cellular differentiation, especially for morphogenesis, reproduction and for immune responses. At... 

This suggests that adult hippocampal-derived neural progenitor and stem cells elicit limited capacity to differentiate into mature neuronal phenotypes of the retina, and that adult human retinal progenitor and stem cells may be valuable in the treatment of retinal diseases. 

Reproduction Retinol and retinal are essential for normal repno duction, supporting spermatogenesis in the male and preventing fetal resorption in the female. Retinoic acid is inactive in maintain ing reproduction and in the visual cycle, but promotes growth and differentiation of epithelial cells thus, animals given vitamin A only as retinoic acid from birth are blind and sterile. 

Vitamin A Retinol Retinal Retinoic acid p-Carotene Retinol Retinal Retinoic acid FAT-SOLUBLE Maintenance of reproduction Vision Promotion of growth Differentiation and maintenance of epithelial tissues Gene expression... 

Vitamin A, as retinal, has a clearly established role in vision (Chapter 23) and apparently has a specialized function in reproduction. In vitamin A deficiency no sperm cells are formed in males, and fetal resorption occurs in females. Rats deprived of vitamin Abut fed retinoic acid become blind and sterile but otherwise appear healthy.e bb Evidently either the alcohol or the aldehyde has an essential function in reproduction, whereas bone growth and maintenance of mucous secretions requires only retinoic acid. Indeed, retinoic acid is 100 to 1000 times more active than other forms of vitamin A in these differentiation functions.1 ... 

Lentiviruses can be very effective vectors for gene therapy since they can change the expression of genes in target cells for up to 6 months. They are useful for nondividing and terminally differentiated cells including muscle cells, hepato-cytes, neurons, macrophages, retinal photoreceptors and hematopoietic stem cells. However, lentiviruses cannot enter quiescent cells in which reverse transcription is blocked. 

Intravitreal triamcinolone injection is safe and effective for cystoid macular edema caused by uveitis, diabetic maculopathy, and central retinal vein occlusion, and for pseudophakic cystoid macular edema. Potential risks include glaucoma, cataract, retinal detachment, and endophthalmitis. Infectious endophthalmitis is extremely rare when appropriate sterile technique is practised. Seven patients developed a clinical picture simulating endophthalmitis after intravitreal injection of triamcinolone (71). The authors believed that this effect was a toxic reaction to the injected material and explained that the differential diagnosis of infectious endophthalmitis in eyes that have been injected with triamcinolone under sterile conditions includes a sterile toxic endophthalmitis that requires careful monitoring, perhaps every 8-12 hours, in order to determine whether the inflammation is worsening or improving. Resolution occurs spontaneously, and in the absence of eye pain unnecessary intervention can be avoided. 

The effect of FTIs on retinal function also needs to be carefully examined. Several proteins involved in retinal signal transduction are farnesylated in vivo, presumably by FTase. These include rod cell cGMP phosphodiesterase a-subunit,108,109 rod cell transducin y-subunit,110,111 and rhodopsin kinase.112 Since the retina consists of terminally differentiated, nondividing cells, the anti-proliferative properties of FTIs should be inconsequential. Visual function could possibly be affected by alterations in the prenylation of proteins involved in retinal signal transduction, although any changes of this sort should be reversible. 

PEDF, first purified from human retinal pigment epithelial cultures as a factor that induces neuronal differentiation of cultured retinoblastoma cells (Tombran-Tink et al., 1991 Steele et al., 1993), has been recently shown to regulate normal angiogenesis in the eye (Dawson et al., 1999). PEDF is found both intracellularly and extracellularly in the fetal and early adult eye but is lost at the onset of senescence (Becerra, 1997 Araki et al., 1998). It is down-regulated by hypoxia and induced in the retina as a result of... 

Guimaraes MZ, Hokoc JN, Duvoisin R, Reis RA, De Mello FG (2001) Dopaminergic retinal cell differentiation in culture modulation by forskolin and dopamine. Eur J Neurosci 75 1931-1937. 

Retinoic acid is a metabolic product of vitamin A that supports the growth and differentiation of epithelial tissues. Retinoic acid is formed in the cytosol by the reversible oxidation of retinol to retinal, and the irreversible oxidation of retinal to retinoic acid. There is controversy as to whether retinal is oxidized by retinal dehydrogenase, which is linked to NAD+, or by retinal oxidase. 

Vitamin A is a fat-soluble vitamin. Chemically it is identical with the alcohol retinol, whereas the corresponding vitamin A aldehyd is retinal and the acid derivative of vitamin A is retinoic acid. A sufficient supply of vitamin A is required for embryonic growth and differentiation, for reproduction, including spermatogenesis, oogenesis and placental development and for vision in the developping and the adult organism. 

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