Retinal tissue

Although spectrophotometric detection is generally acceptable, electrochemical detection seems to be more appropriate for the analysis of -agonists, due to the presence on the aromatic part of their molecule of oxidizable hydroxyl and amino groups. This method of detection has been applied in the determination of clenbuterol residues in bovine retinal tissue with sufficient sensitivity for this tissue (478). 

Grey A, Chaurand P, Caprioli R, Schey K (2009) MALDI imaging mass spectrometry of integral membrane protein from ocular lens and retinal tissue. J Proteome Res 8 3278-3283. 

When cataracts necessitate lens removal to restore vision, the kinetics between aqueous and vitreous humor change. A major barrier to molecular transport is removed, and more rapid exchange can occur between aqueous and vitreous contents and various ocular components. In one experimental study the concentration of a topically applied anti-inflammatory agent, flurbiprofen, was increased in retinal tissues, vitreous humor, and choroid after lens removal. 

Choroidal neovascularization associated with age-related macular degeneration is difficult to treat with conventional laser procedures because normal retinal tissues can be destroyed, which results in loss of central vision. Photodynamic therapy offers the opportimity to selectively eradicate neovascular membranes while producing minimal damage to normal retinal and choroidal tissues. 

Lin, L.A. Tomlinson, J.A. Satzger, R.D. Detection ol clenbuterol in bovine retinal tissue by high performanceg liquid-chromatography with electrochemical J. Chromatogr. 1997, 762, 275 -280. 

The retinal pool of 11 -cis-retinal is clearly critical for photon detection and visual signal transduction. There are two key aspects regarding this that are important to consider the precursor(s) from which 11 -cis-retinal derived, and, bioconversion of isomerized trans-retinal back to 11-cis-retinal that can recombine with opsin to re-form rhodopsin. The latter aspect is obligatory for restoration of the dark state, regenerating a photosensitive receptor capable of undergoing another cycle of photon detection and signal transduction. Considered together, these events represent the retinoid cycle in the visual process (22). The entire process of re-isomerization and formation of a new rhodopsin molecule occurs in two different retinal tissues and involves several enzymatic steps that are described below (see Fig. 7.14). 

Some other recent contributions to the carbohydrate metabolism in fish may also be mentioned the description of the occurrence in fish muscle of the K-activated pyruvic phosphopherase already described in mammalian muscle (Boyer, 1953), the observation of the glycolytic activity of the swim bladder gland (Strittmatter, Ball, and Cooper, 1952), the study of the respiration and glycolysis of the retinal tissues of fishes (De Vincentiis, 1952). 

Futterman S, Stevens-Andrews J. The fatty acid composition of human retinal vitamin A ester and the lipids of human retinal tissue. Invest Ophthalmol Vis Sci 1964 3 441 44. 

Laser-Targeted Drug Delivery to Retinal Tissues... 

While systemic delivery of medications does not have associated surgical risks, it may be difficult to achieve adequate intraocular penetration without causing systemic side effects. To minimize systemic toxicity and increase retinal tissue drug levels, local delivery methods to treat and prevent PVR have been investigated. 

Retina. Phototoxic damage can occur in retinal pigment epithelial tissues, the choroid, and the rod outer segments, which contain the photoreceptors. If the damage is not extensive, repair mechanisms are present to allow for recovery of retinal tissues. However, extensive phototoxic damage to the retina can lead to permanent blindness (Glickman, 2002 Dayhaw-Barker, 2002 Dayhaw-Barker and Barker, 1986 Ham et al., 1982). 

We ve seen already that inactivating mutations in both RB alleles lead to childhood retinoblastoma, a relatively rare type of cancer. However, loss of RB gene function also is found in more common cancers that arise later In life (e.g., carcinomas of lung, breast, and bladder). These tissues, unlike retinal tissue, most likely produce other proteins whose function is redundant with that of Rb, and thus loss of Rb is not so critical. Several proteins are known that are related in structure and probably function to Rb. In addition to inactivating mutations, Rb function can be eliminated by the binding of an inhibitory protein, designated E7, that is encoded by human papillomavirus (HPV), another nasty viral trick to create virus-producing tissue. 

Chida, M., Suzhd, K., Nokanishi-Ueda, T. et al.. In vitro testing of antioxidants and biochemical endpoints in bovine retinal tissue, Ophtalmic Res., 31,407-415,1999. 

Berko-Flint, Y., Levkowitz, G. Vardimon, L. (1994). Involvement of c-jun in the control of glucocorticoid receptor transcriptional activity during development of chicken retinal tissue Eur. J. Mol. Biol, 13, 646-54. 

Schulze E. and Neuhoff V. (1983) Uptake, autoradiography and release of taurine and homotaurine from retinal tissue Int, /. Neurosci 18, 253-268... 

The polymer used is mostly PCL. It has been found that PCL is well tolerated by the retinal tissue and can deliver bioactive agents without eliciting inflammatory response or complications. PCL can elute a steroid for a period of at least 4 weeks without eliciting inflammatory response or complications (61). 

Our second example is a direct application of Dalton s law. Oxygen gas is essential for our survival, so it is hard to beheve that an excess of oxygen could be harmful. Nevertheless, the toxicity of too much oxygen is well established. For example, newhom infants placed in oxygen tents often sustain damage to the retinal tissue, which can cause partial or total bhndness. 

---