1. Division of Gastroenterology, University Hospital “Heart and Brain”, Zdrave Str. 1, 8000 Burgas, Bulgaria
2. Department of Genetics, Faculty of Biology, Sofia University “St. Kliment Ohridski”, 8 Dragan Tzankov Str., 1164 Sofia, Bulgaria
3. Medical Faculty, Sofia University St. Kliment Ohridski, 1 Kozyak Str, 1407 Sofia, Bulgaria
4. Department of Pharmacology and Toxicology, Faculty of Pharmacy, Medical University of Sofia, ul. Dunav 2, 1000 Sofia, Bulgaria