1. The Key Laboratory of Endemic and Ethnic Diseases of the Ministry of Education of PR China (Guizhou Medical University), Guiyang, Guizhou Province, China
2. Reproduction Centre of Luoyang Centre Hospital Affiliated to Zhengzhou University, Zhengzhou, Henan Province, China
3. Department of Pathology, Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou Province, China