1. Morphology Laboratory, Mudanjiang Medical University, Mudanjiang, Heilongjiang 157011, P.R. China
2. School of Life Sciences, Mudanjiang Medical University, Mudanjiang, Heilongjiang 157011, P.R. China
3. Department of Extracorporeal Circulation, Mudanjiang Cardiovascular Disease Hospital, Mudanjiang, Heilongjiang 157011, P.R. China