E.P. Stankova - Post-graduate Student, Department of Human and Animal Physiology, Yaroslavl State University, Yaroslavl, Russia. E-mail: stankova-katia@yandex.ru I.U. Myshkin - Dr.Sc. (Biol.), Professor, Department of Human and Animal Physiology, Yaroslavl State University, Yaroslavl, Russia. E-mail: myshkin@uniyar.ac.ru