1. Department of Anatomy and Cell Biology, and Department of Translational Stem Cell Biology, Research Institute , Medical University , Varna , Bulgaria
2. Fondazione Iret Tecnopolo R. Levi-Montalcini , Rome , Italy
3. Department of Pathology, Faculty of Medicine , Semmelweis University , Budapest , Hungary
4. Department of Pathology , Medical University , Varna , Bulgaria ,
5. Institute of Biochemistry and Cell Biology, Section of Neurobiology, National Research Council (CNR) , Rome , Italy
6. Department of Hygiene and Epidemiology, Faculty of Public Health , Medical University , Varna , Bulgaria
7. Department of Cardiac Surgery , St Marina University Hospital , Varna , Bulgaria