The identification of a hoemone secreted by the pars tuberalis cells

结节垂体部以薄细胞层的形式覆盖漏斗柄和中央隆起。尽管它存在于大量的动物物种中，但其功能意义仍然不清楚。大部分结节部由垂体这部分特有的分泌细胞组成。与哺乳动物的细胞只含有少量小的分泌颗粒相比，鸡结核paralis的特定细胞的特点是存在许多分泌颗粒，直径从90到400nm不等。鸡结核部几乎所有细胞对黄体生成素（LH）和嗜铬粒蛋白a均有免疫反应，免疫电镜采用包埋后免疫金标技术，发现结核部细胞的所有分泌颗粒中均有黄体生成素（LH）免疫反应的金颗粒。双免疫金标记证实黄体生成素和嗜铬粒蛋白A在同一分泌颗粒上均存在。关于鸡结节部的个体发育，位于中隆起附近的结节部原基在孵育8天时首先在远部外侧尖端形成。原基对糖蛋白激素共同a亚基mRNA表达强烈信号。此外，它对LH和嗜铬粒蛋白a具有免疫反应性。随着年龄的增长，结节部原基沿中隆起逐渐延伸，并在孵育14天达到凸端。原位杂交证实，结节部细胞对生命表达强烈的a亚基mRNA信号。高浓度的褪黑激素结合位点已在各种动物的结节部观察到。在1个月的长时间照相（24倍光）下，鸡结节部的特定细胞充满了增大的分泌颗粒。另一方面，在1个月的短照片（22 /暗）下，结核部特异性细胞的细胞质增大，仅显示少量小的分泌颗粒。细胞内线粒体增多，粗内质网和高尔基复合物增多，细胞活性增强。用32p标记的a亚基cDNA进行Northern blot分析发现，昼夜节律的改变显著影响鸡结节中a亚基mRNA的数量。少

The hypophyseal parts tuberalis covers both the infundibular stalk and median eminence as thin cell layers. Despite of its occurrence in large numbers of animal species, the functional significance of the pars tuberalis remains obscure. A majority of the pars tuberalis consist of secretory cells specific to this portion of the pituitary. In contrast to the cells of mammalian species that contain only a few small secretory granules, the specific cells of the chicken pars tuberalis are characterized by the presence of many secretory granules ranging from 90 to 4O0nm in diameter. Almost all cells throughout the pars tuberalis of chickens were immunoreactive for luteinizing hormone (LH) and chromogranin A.Furthermore, immunoelectron microscopy using post-embedding immunogold labeling showed that gold particles representing immunoreactivily for LH were located in all secretory granules of the pars tuberalis cells. Double immunogold labeling confirmed that LH and chromogranin A were colocali … More zed on the same secretory granules. Concerning the ontogeny of the chicken pars tuberalis, the primordium of the pars tuberalis located close to the median eminence was first formed at the lateral-apical end of the pars distalis at 8 days of incubation. The primordium expressed intense signal for common a-subunit mRNA of glycoprotein hormones. In addition, it was immunoreactive for LH and chromogranin A.The pars tuberalis primordium progressively extended along the median eminence with age and reached to the rostoral end at 14 days of incubation. It was confirmed by in situ hybridization that the pars tuberalis cells expressed intense signal for a-subunit mRNA for life. High concentrations of melatonin-binding sites have been observed in the pars tuberalis of various animal species. Under long photo periods (24 his light) for I month, the specific cells of the chicken pars tuberalis were filled with enlarged secretory granules. On the other hand, under short photo periods (22 his dark) for I months, the cytoplasm of the pars tuberalis-specific cells were enlarged in size and revealed only a few small secretory granules. Furthermore, the cells contained numerous niitochondria, increased rough endoplasmic reticulum and Golgi complexes, showing increased cell activity. Northern blot analysis with 32P-labeled a-subunit cDNA exhibited that the amounts of a-subunit mRNA in the chicken pars tuberalis were conspicuously affected by the alterations of circadian rhythms. Less