Feline retinal ultrastructural changes induced by a high cystine diet

Cats fed a high cystine diet containing no taurine developed extreme signs of neurotoxicity and either died or had to be killed within 7 months. The presence of 0.05% taurine in the diet greatly ameliorated the neurotoxic effects of the cystine. Many developed retinal ultrastructural changes which were quite different from those previously described for cats on taurine-free diets. The most striking changes were reductions in the number of cells and extensive swelling of some remaining cells in the inner nuclear layer and in the ganglion cell layer. The most severely affected cells were amacrine cells, in contrast to photoreceptor cells in cats fed the taurine-free diet. The changes resemble those reported in other species caused by excitotoxic amino acids.