Histological observations on ovaries of adult female red pandas(Ailurus fulgens)

Twenty-four ovaries were collected from twelve adult female red pandas died of non-reproductive system diseases at different stages of estrous cycles from 2000 to 2009.The ovaries were fixed in 10% formalin,and tissue slices were made using standard histological techniques and stained with HE.All slices were observed under optical microscopes.Results showed that(1) Primordial follicles,primary follicles and secondary follicles exist simultaneously in all ovaries of different stages of estrous cycles.Typical mature follicles and oocytes are not observed in the ovaries during the estrous stage.(2) There are more primary follicles than primordial follicles and most of primary follicles and secondary follicles are artresic in all ovaries.(3) Before follicular antrum formed,oocytes and follicles are developed synchronously,while in antral follicles,the development of follicles is faster than that of oocytes.(4) Large amounts of interstitial gland cells are observed obviously in ovaries at different estrous stages.(5) Well-developed corpus luteum is present in both the ovaries of pregnant and non-pregnant animals during diestrus period.(6) Zona peliucida is developed when oocytes are surrounded by single layer of cubical granulosa cells.Conclusions:(1) Follicular atresia occurs mainly in the primary follicle stage and only a few primary follicles can be developed to be secondary follicles.(2) Development of oocytes and follicles exhibits biphasic growth trend.(3) Ovary interstitial gland cells are well developed in all stages of the estrous cycle.(4) Durations of corpus luteum in pregnant animals are similar to those in non-pregnant animals,confirming the existence of pseudo-pregnancy of the animals.