effects of anoxia on protein synthesis and transport in the optic system of the freshwater turtle, Trachemys scripta elegans

The effects of anoxia on retinal protein synthesis and axonal transport were investigated in the freshwater turtle, Trachemys scripta. The optic system (retina, optic nerve, optic tract, and optic tectum) of the freshwater turtle was used because, due to its linear structure, it is an ideal model to measure protein production and transport. This species of turtle is known for its ability to withstand long periods of anoxia; however, little data is available on in vivo protein synthesis in the brain on an anoxia-tolerant species. An intraocular injection of S-methionine was used to label retinal proteins during 18 hours of anoxia, and the tissues were removed and prepared for analysis using 2D gel electrophoresis. Using autoradiography the regulation of retinal proteins was compared under normoxic and anoxic conditions. In addition, labeled retinal proteins rapidly transported along the optic nerve and tract, to the tectum were also compared under these conditions. Although certain proteins were produced in lesser amounts during anoxia, the populations of proteins were the same during anoxia as they were in the control, suggesting that all proteins were still produced during anoxia. Additionally, certain proteins were produced in greater amounts during anoxia. The findings suggest that less important proteins are down-regulated in response to anoxia while those proteins that are up-regulated may serve as protective mechanisms that enable the organism to maintain neuronal connections in this system during anoxia.