1. de Duve Institute; Université Catholique de Louvain; Brussels B-1200 Belgium
2. Life Science Research Centre; Faculty of Science; University of Ostrava; Ostrava 710 00 Czech Republic
3. Biology Centre; Institute of Parasitology; Czech Academy of Sciences; České Budějovice (Budweis) 370 05 Czech Republic
4. A.A. Kharkevich Institute for Information Transmission Problems; Russian Academy of Sciences; Moscow 127 051 Russia
5. Faculty of Science; Institute of Environmental Technologies; University of Ostrava; Ostrava 710 00 Czech Republic
6. Faculty of Science; University of South Bohemia; České Budějovice (Budweis) 370 05 Czech Republic
7. Canadian Institute for Advanced Research; Toronto ON M5G 1Z8 Canada