1. Section on Cellular Signaling (S.S.S.), Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510;
2. Department of Biological Science (J.T.) Florida State University, Tallahassee, Florida 32306
3. Department of Mathematics and Programs in Neuroscience and Molecular Biophysics (R.B.), Florida State University, Tallahassee, Florida 32306