Retina-A

Photoreceptors in the eyes convert radiation in the visible band into neural signals that reach the brain. Photoreceptors are located throughout the retina, a sensoiy membrane that covers the entire back of the... 

A new therapy involves treatment for neovascularization of the retina, a disease in which proliferation of... 

Koepcke, W., F. M. Barker et al. (1995). Canthaxanthin deposition in the retina A biostatistical evaluation of 411 patients. J. Toxicol. Cutaneous Ocular Toxicol. 14(2) 89-104. 

Schalch, W. (1992). Carotenoids in the retina-A review of their possible role in preventing or limiting damage caused by light and oxygen. EXS (Experientia Suppl. Ser.) 62 280-298. 

In horizontal cells of turtle and fish retinae, a dopamine-induced increase in intracellular cAMP levels is associated with cellular uncoupling [DeVries and Schwartz, 1989 McMahon et al., 1989] (the connexin isoform involved is not identified). Inhibition of phosphodiesterase with IBMX after stimulation of adenylate cyclase using forskolin resulted in an increase in intracellular... 

Usually used in surgery of the retina, a Silastic band can be placed into the conjunctival sac and maintained with two transcutaneous sutures. This perfectly maintains the graft to the bottom of the fonfix and prevents the development of synechia. 

The light traverses an aqueous chamber and reaches the lens, which is densely packed with proteins called crystal-lins. Adjustments in the shape of the lens focus a sharp optical image onto the retina, a thin layer of tissue that lines the back of the eye. The retina is a neural tissue with several different layers of cells. Some of these cells, the rod and cone cells, contain the visual pigments. Other cells make synaptic connections to the rods or cones and to additional neural cells that carry impulses to the brain. 

Rauen, T., Taylor, W. R., Kuhlbrodt, K., and Wiessner, M. (1998). High-affinity glutamate transporters in the rat retina A major role of the glial glutamate transporter GLAST-1 in transmitter clearance. Cell Tissue Res. 291, 19-31. 

When light first strikes the retina a photon interacts with a molecule called 11-cis-retinal, which rearranges within picoseconds to trans-retinal. (A picosecond is about the time it takes light to... 

A more serious flaw occurs because the neural wiring must poke directly through the wall of the retina to carry the nerve impulses produced by photoreceptor cells to the brain. The result is a blind spot in the retina—a region where thousands of impulse-carrying cells have pushed the sensory cells aside. 

Fig. 1. Schematic diagram of a horizontal cross-section of the eye and retina (A) and of the photoreceptor cells (B).

VKainin A (retinol) is present in many cells of the body. In the retina it is part of the rod photoreceptor pigment rhodopsin (=cis-retina] + a protein called opsin) and cone photoreceptor pigment iodopsin (= cis-retinal + a different opsin protein). When light strikes the cis-retinal part of the rhodopsin or iodopsin molecule, the "cis form changes to trans-retinal, a conformational in (he t i04 culv ti.c CIjUaU... 

Other human-health effects of ultraviolet exposure include increased risks of developing cataracts and other damage to the cornea, damage to the retina, a suppressed immune system, sunburns of exposed skin, skin allergies, and an accelerated aging of the skin. 

Shape constancy refers to an object s shape being perceived as remaining the same despite being viewed from different perspectives with different shapes being projected onto the retina. A circular shape such as a pie on a table for example, is still perceived as circular even when you sit down at the table and perceive it from the side. This is despite the fact that circles viewed from the side produce not circular but elliptical images on the retina. 

To provide a complete assessment of all these variables, the final evaluation of the safety of ophthalmic products must be made in the in vivo model using the preparation under the proposed conditions for use, following tissue compatibility with many of the techniques already discussed. Irrigating solutions of low viscosity may have limited contact, while the gel-like viscoelastic materials, which maintain the comeal dome, or the solutions and gases used as vitreous replacements to prevent retinal detachment, may have prolonged contact with delicate ocular tissues or the retina. A recent therapy involves treatment for neovascularization of the retina, a disease in which proliferation of blood vessels can lead to blindness. The treatment combines a systemic chemical that localizes... 

Hunter DD, Murphy MD, Olsson CV, Brunken WJ. 1992. S-laminin expression in adult and developing retinae A potential cue for photoreceptor morphogenesis. Neuron 8 399-413. 

Avendano J, Rodrigues MM, Hackett JJ, Gaskins R. 1980. Corpora amylacea of the optic nerve and retina A form of neuronal degeneration. Invest Ophthalmol Vis Sci 19 ... 

Transgenic mice with increased expression of vascular endothelial growth factor in the retina A new model of intraretinal and subretinal neovascularization. Am J Pathol 151 281-291,... 

Vannas-Sulonen K, Sipila I, Vannas A, Simell O, Rapola J. 1985. Gyrate atrophy of the choroid and retina. A five-year follow-up of creatinine supplementation. Ophthalmology 92 1719-1727. 

Jojich L, Pourcho RG (1996) Glutamate immunoreactivity in the cat retina a quantitative study. Vis Neurosci 75 117-133. 

Qin P, Pourcho RG (1999) Localization of AMPA-selective glutamate receptor subunits in the cat retina a light-and electron-microscopic study. Vis Neurosci 76 169-177. 

Dowhng, JE (1979) Information processing by local circuits The vertebrate retina a model system. In F.O. Schmitt and F.G. Worden (eds) The Neurosciences Fourth Study Program. Cambridge, MA MIT Press. 

Fig. 3. Schematic drawings depicting the procedure for dissection of pupal retinas, (a) Opening of the pupal case, (b) Removal of the pupal head from the case, (c) The retinae (fi) attached to the optic lobe (OL) and brain (fl) (For a detailed description see Pupal Retina").

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