1. Department for Neurobiology and Immunology; Institute for Biological Research; 29 Novembra 142 11000 Belgrade Yugoslavia
2. N. N. Koltzov Institute for Developmental Biology of Russian Academy of Sciences; Vavilova Street 26 Moscow 117808 Russia
3. Laboratory for Molecular Biology and Endocrinology; Vinca Institute for Nuclear Science; P.O.B. 522 11000 Belgrade Yugoslavia