prepuberty nonhuman 40 priority journal 38 article 36 rat 36 Animals 34 controlled study 34 Female 30 Rats 30 animal experiment 28 female 28 Rats, Sprague-Dawley 26 animal cell 22 animal tissue 22 Ovarian Follicle 20 Apoptosis 18 Ovary 18 apoptosis 18 protein expression 18 ovary follicle 16 Sexual Maturation 14 animal model 14 gonadotropin 14 male 14 protein bcl 2 14 Angiogenesis 12 Male 12 cell proliferation 12 chorionic gonadotropin 12 ovary follicle atresia 12