1. Oxford BioMedica (UK) Ltd, Oxford Science Park, Oxford OX4 4GA, United Kingdom.
2. Covance Laboratories, Madison, WI 53704.
3. Present address: Genentech, South San Francisco, CA 94080.
4. Comparative Ophthalmic Research Laboratories, University of Wisconsin-Madison School of Veterinary Medicine, Madison, WI 53792.