Ocular Surface Diseases in Marine Mammals.

Marine mammal eyes are adapted for underwater and air environments by increasing the mucins in tear film and having flatter corneas and round crystalline lenses. The cornea and lens are most commonly affected by environmental imbalances. Lack of shade and excessive exposure to sunlight are significant risk factors for keratopathy in pinnipeds, and likely true in cetaceans. Natural aging is also important, as sun damage and exposure to other oxidative stressors can cause cumulative damage to the cornea over time. By diminishing UV exposure and optimizing environmental factors, surface ocular disease in marine mammals can be diminished.

Expression and characterization of the catalytic subunit of telomerase in normal and cataractous canine lens epithelial cells.

PURPOSE: To determine whether the catalytic subunit of telomerase reverse transcriptase (TERT) is regionally distributed in canine lens epithelial cells (LEC), compare TERT and the RNA subunit of telomerase (TR) mRNA expression and TERT protein expression in normal and cataractous LEC, and to evaluate whether telomerase activity is present in the cytoplasm and nucleus from normal LEC. Finally, the expression of p23 and heat shock protein 90 (hsp90), coactivators of TERT in neoplastic cells, were evaluated in normal and cataractous LEC. METHODS: TERT protein was detected by imunohistochemical staining and western immunoblotting in normal and cataractous LEC. Quantitative RT-PCR (qRT-PCR) was used to measure TERT and TR expression. Separated cytoplasmic and nuclear extracts from primary cultures of normal canine LEC were evaluated for TERT protein expression and telomerase activity. Western immunoblotting was performed on normal and cataractous LEC for p23 and hsp90, and coimmunoprecipitation was used to determine whether p23 and hsp90 were interacting with TERT in LEC. RESULTS: TERT expression in normal lens capsule whole mounts varied by region in normal LEC. All cataractous LEC demonstrated more intense TERT immunostaining in both the nucleus and cytoplasm when compared to normal LEC. Normal LEC expressed less TERT protein and less TERT and TR mRNA than cataractous LEC. Normal LEC expressed hsp90 while cataractous LEC did not; p23 was not significantly expressed in either normal or cataractous LEC. Neither hsp90 nor p23 interacted with TERT. CONCLUSIONS: The localization of TERT in normal LEC corresponded with the LEC's regional functions. There was more cytoplasmic TERT in the central region that corresponds with the need for inhibited apoptosis and for proliferative capabilities; there was more nuclear TERT in the germinal and equatorial regions corresponding with the need for proliferative capabilities. In addition, cataractous LEC demonstrated increased TERT protein and increased TERT and TR mRNA expression than normal LEC corresponding with their increased proliferative potential. However, the telomerase coactivators, p23 and hsp90, are not overexpressed and do not associate with TERT in cataractous LEC, suggesting that telomerase regulation in cataractous LEC, a somatic cell type, differs from that in neoplastic cells.