Photodynamic lipid peroxidation in the eye during the experimental induction of turkey blindness syndrome

EVALUATION OF POTENTIAL RISK FACTORS ASSOCIATED WITH CATARACT IN CAPTIVE MACARONI (EUDYPTES CHRYSOLOPHUS) AND ROCKHOPPER PENGUINS (EUDYPTES CHRYSOCOME)

Complete ophthalmic examinations were performed on 160 Macaroni penguins ( Eudyptes chrysolophus ) and 90 Rockhopper penguins ( Eudyptes chrysocome ) at eight North American zoological institutions. Cataract prevalence in the Macaroni population was 46.5% (n = 74) of penguins and 42.3% (135/319) of eyes. Cataract prevalence in the Rockhopper population was 45.5% (n = 40) of penguins and 40.6% (73/180) of eyes. The mean age of Macaroni penguins without ocular disease was 7.4 ± 5.8 yr, while that of Rockhoppers was 9.8 ± 6.4 yr. Risk factors for cataract were examined through husbandry surveys completed by each institution and by evaluation of light intensity and ultraviolet (UV) light measurements acquired in each penguin exhibit. Risk factors associated with cataract in Macaroni penguins included age, dietary smelt, hand-feeding, and fluorescent exhibit lighting. Risk factors associated with cataract in Rockhopper penguins included age, dietary capelin, increasing population density, and increasing length of minimum photoperiod. Factors associated with decreased odds of cataract in Macaroni penguins included saltwater pool, monitoring of water quality for salinity, pH, and alkalinity; use of water additives; presence of pool filtration and sterilization systems; use of metal halide lightbulbs; increasing light intensity; and UV spectrum lighting. Factors associated with decreased odds of cataract in Rockhoppers included dietary herring and krill, increasing exhibit land area, pool temperature monitoring, increasing maximum photoperiod, and increasing minimum UV light.

Solar radiation and age-related macular degeneration

Age-related macular degeneration (AMD) involves a progressive impairment of the outer layers in the center of the retina. Experimental studies have demonstrated that bright light preferentially damages precisely the region that degenerates in AMD. The evidence that solar radiation is responsible for some of the deteriorative changes that lead to AMD is examined in this review. In the primate eye, the high-energy portion of the solar spectrum is most hazardous to retinal molecules, with damaging effects increasing as photon energy rises. This action spectrum is explicable by the quantum laws which describe the interaction of radiation with matter. High-energy visible and ultraviolet photons can produce molecular damage by a photochemical mechanism. The lesion is exacerbated by oxygen, which initiates free-radical chain reactions (photodynamic effects). Melanin exerts a protective effect against damage from sunlight. In the human retina, documented lesions from solar radiation range from the acute effects of sun-gazing to injuries resulting from prolonged periods of exposure in brightly illuminated environments. The damage occurs in the same region that degenerates in AMD. A cataractous lens and ocular melanin both protect the retina against AMD, as predicted by the radiation hypothesis. Identification of an environmental factor that evidently plays a role in the etiology of AMD provides the basis for a program of preventive medicine.

Vitamin E and skeletal muscle

Vitamin E deficiency causes a myopathy in a number of animal species but the mechanism of the damage is obscure. The role of vitamin E in protecting skeletal muscle against exercise-induced damage has been investigated using both in situ and in vitro preparations. Muscles from vitamin E-deficient mice and rats were more prone than normal to damage during contractile activity; the tissue rather than the plasma level of the vitamin is probably the more important factor in this respect. Although vitamin E-deficient muscle was found to be more susceptible to peroxidative damage when stressed with iron and ascorbic acid, it was not possible to demonstrate that the damage occurring during contractile activity was mediated by free radicals.

Biochemical studies of the chicken vitreous in light-induced avian glaucoma

Changes in several macromolecular species of the vitreous are traced during post-hatching development in normal and glaucomatous avian eyes. 1. Total gel vitreous, and its hydroxyproline content, change little during development. 2. Sol vitreous increases parallel eye growth, the concentrations of hexosamine and hexuronic acid remaining constant. 3. In light-induced avian glaucoma, the sol, but not the gel, is further increased, although the hyaluronic acid components are not diluted in the pathologically enlarged eye.

Oxidative damage of retinal rod outer segment membranes and the role of vitamin E

Highly purified bovine rod outer segment membranes show loss of structural integrity under an air atmosphere. Obvious ultrastructural changes are preceded by increases in absorbance below 400 nm. These changes are inhibited by Ar or N2 atmospheres and appear to be due primarily to oxidative damage to the polyunsaturated fatty acids of the membrane lipids. Loss of polyunsaturated fatty acids, formation of malonaldehyde and fluorescent products characteristic of lipid oxidation accompany the spectral alterations. The elevated ultraviolet absorbance can largely be removed from the membranes by gentle extraction of the lipids using phospholipase C and hexane without changing the visible absorbance of rhodopsin. We have found a large seasonal variation in the endogenous level of alpha-tocopherol (vitamin E) in the bovine rod outer segment preparations. For much of the year we find that the rod outer segment membranes contain higher levels of alpha-tocopherol than have been previously reported in biological membranes. Rod outer segments which are low in endogenous tocopherol can be protected from oxygen damage by adding exogenous tocopherol. The rod outer segments are extremely susceptible to oxygen damage due to the unusually high content of polyunsaturated fatty acids in the membrane lipids. The presence of tocopherol inhibits oxygen damage but does not eliminate it. The tocopherol in the rod outer segments is consumed in air, thus complete protection from peroxidation in vitro requires an inert atmosphere as well as high levels of tocopherol. This work suggests that extensive precautions against oxidative degradation should also be employed in studies of other membrane systems where important deleterious effects of oxygen may be less obvious.