title: Involvement of postnatal apoptosis on sex difference in number of cells generated during late fetal period in the sexually dimorphic nucleus of the preoptic area in rats.
abstract: Postnatal apoptosis is involved in formation of the sex difference in neuron number of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in rats. In this study, we examined the origin of neurons that die with apoptosis on the postnatal period to exhibit the sex difference in neuron number of the SDN-POA. First, we measured the number of cells that were labeled with 5-bromo-2'-deoxyuridine (BrdU) on embryonic day (ED) 17, ED18, and ED19 in the SDN-POA of rats on postnatal day (PD) 4 and PD8. The SDN-POA had many more cells labeled with BrdU on ED17 and ED18 than those on ED19. Significantly fewer cells labeled with BrdU on ED18 in the female SDN-POA from PD4 to PD8 resulted in a significant sex difference in the number at PD8. Next, combination analyses of BrdU-labeling and immunohistochemistry for single-stranded DNA (ssDNA), an apoptotic marker, were succeeded to investigate whether SDN-POA neurons generated during ED17-18 were removed by apoptosis. Many more ssDNA-immunoreactive cells that had been labeled with BrdU during ED17-18 were found in the SDN-POA of PD8 females, but few in the SDN-POA of PD8 males and PD4 females and males. These results suggest that the sex difference in the number of SDN-POA neurons generated during the late fetal period was caused by postnatal apoptosis.
authors.affiliation: Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama City, Saitama 338-8570, Japan.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Kato
authors.forename: Shizuka
authors.initials: S
authors.lastname: Nakashima
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Maekawa
authors.forename: Shinji
authors.initials: S
authors.lastname: Tsukahara
mesh_terms: D000818:Animals; D017209:Apoptosis; D002452:Cell Count; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000166:cytology; D011301:Preoptic Area / Q000166:cytology* / Q000196:embryology*; D051381:Rats; D017208:Rats, Wistar; D012727:Sex Characteristics