Holman S D, Collado P, Skepper J N, Rice A
Department of Anatomy, University of Cambridge, United Kingdom.
J Comp Neurol. 1996 Dec 9;376(2):315-25. doi: 10.1002/(SICI)1096-9861(19961209)376:2<315::AID-CNE12>3.0.CO;2-K.
Steroid-sensitive, vocal courtship behavior is a function of a specific, hypothalamic nucleus, the sexually dimorphic area pars compacta (SDApc) in the male adult gerbil. Gender-related differences in the number of neurons in this nucleus are evident immediately after birth. By using unbiased stereological estimates of cell numbers in Nissl-stained, paraffin-wax sections of brain, we investigated the mechanisms differentiating cell number between the sexes in the SDApc on postnatal days 0, 3, 6, and 15. Cell death, identified by pyknosis, was greatest in the SDApc between days 0-3 in males, whereas in females, maximum values were reached between days 3-6. Similarly, the ratio of pyknotic to normal neurons peaked between days 0-3 in males and 3-6 in females but then declined in both sexes. Pyknotic cells were seldom seen in either sex by day 15. Morphological characteristics of apoptosis including chromatin condensation, cell fragmentation, and ingestion of apoptic bodies by macrophages were all demonstrated by transmission electron microscopy. Macrophages showed specific morphological characteristics of microglia. Cell division (mitosis) was identified in the SDApc during postnatal days 0, 3, and 6 but the numbers of mitotic figures were low, negligible on day 15, and similar between the sexes. These results demonstrate that cell death and proliferation occur simultaneously in the neonatal gerbil brain. The stereological estimates of cell death in the developing SDApc indicated a lower incidence of neuronal death occurring earlier in males than in females.
类固醇敏感的求偶鸣叫行为是成年雄性沙鼠特定下丘脑核团——性二态区致密部（SDApc）的一项功能。该核团中神经元数量的性别差异在出生后即刻就很明显。通过对尼氏染色的脑石蜡切片中的细胞数量进行无偏倚的立体学估计，我们研究了出生后第0、3、6和15天SDApc中两性细胞数量差异的机制。通过核固缩鉴定的细胞死亡在雄性出生后0 - 3天的SDApc中最为严重，而在雌性中，最大值出现在3 - 6天之间。同样，固缩神经元与正常神经元的比例在雄性0 - 3天和雌性3 - 6天达到峰值，但随后在两性中均下降。到第15天时，两性中很少见到固缩细胞。透射电子显微镜证实了凋亡的形态学特征，包括染色质浓缩、细胞碎片化以及巨噬细胞吞噬凋亡小体。巨噬细胞表现出小胶质细胞的特定形态特征。在出生后第0、3和6天的SDApc中鉴定出细胞分裂（有丝分裂），但有丝分裂图的数量很少，在第15天时可忽略不计，且两性之间相似。这些结果表明，新生沙鼠脑内细胞死亡和增殖同时发生。发育中的SDApc中细胞死亡的立体学估计表明，雄性神经元死亡的发生率低于雌性，且发生时间更早。
