The specimen was divided into three parts after washing with sterilized saline, and one was ﬁxed by 2.5% glutaraldehyde solution immediately ，then coated with palladium gold for electron microscopic examination;one was fixed by 2.5% glutaraldehyde arsenate ,then embedded in Epon for transmission electron microscopy ; one was ﬁxed by 4% formalin, then embedded in parafﬁn for immunohistochemical analysis.