Rasmussen Tina H, Jespersen Ase, Korsgaard Bodil
Institute of Biology, University of Southern Denmark, DK-5230 Odense, Denmark.
J Morphol. 2006 Sep;267(9):1032-47. doi: 10.1002/jmor.10453.
It is essential to know the timing and process of normal gonadal differentiation and development in the specific species being investigated in order to evaluate the effect of exposure to endocrine-disrupting chemicals on these processes. In the present study gonadal sex differentiation and development were investigated in embryos of a viviparous species of marine fish, the eelpout, Zoarces viviparus, during their intraovarian development (early September to January) using light and electron microscopy. In both sexes of the embryos at the time of hatching (September 20) the initially undifferentiated paired bilobed gonad contains primordial germ cells. In the female embryos, ovarian differentiation, initiated 14 days posthatch (dph), is characterized by the initial formation of the endoovarian cavity of the single ovary as well as by the presence of some early meiotic oocytes in a chromatin-nucleolus stage. By 30 dph, the endoovarian cavity has formed. By 44 dph and onward, the ovary and the oocytes grow in size and at 134 dph, just prior to birth, the majority of the oocytes are at the perinucleolar stage of primary growth and definitive follicles have formed. In the presumptive bilobed testis of the male embryos, the germ cells (spermatogonia), in contrast to the germ cells of the ovary, remain quiescent and do not enter meiosis during intraovarian development. However, other structural (somatic) changes, such as the initial formation of the sperm duct (30 dph), the presence of blood vessels in the stromal areas of the testis (30 dph), and the appearance of developing testicular lobules (102 dph), indicate testicular differentiation. Ultrastructually, the features of the primordial germ cells, oogonia, and spermatogonia are similar, including nuage, mitochondria, endoplasmic reticulum, and Golgi complexes.
为了评估接触内分泌干扰化学物质对这些过程的影响，了解所研究特定物种正常性腺分化和发育的时间及过程至关重要。在本研究中，利用光学显微镜和电子显微镜，对一种胎生海洋鱼类——绵鳚（Zoarces viviparus）胚胎在卵巢内发育期间（9月初至1月）的性腺性别分化和发育进行了研究。在孵化时（9月20日），雌雄胚胎最初未分化的成对双叶性腺中均含有原始生殖细胞。在雌性胚胎中，孵化后14天（dph）开始卵巢分化，其特征是单个卵巢的卵巢内腔初步形成，以及存在一些处于染色质 - 核仁阶段的早期减数分裂卵母细胞。到30 dph时，卵巢内腔已形成。到44 dph及以后，卵巢和卵母细胞体积增大，在出生前的134 dph时，大多数卵母细胞处于初级生长的核仁周围阶段，并且已形成成熟卵泡。在雄性胚胎的假定双叶睾丸中，与卵巢的生殖细胞不同，生殖细胞（精原细胞）在卵巢内发育期间保持静止，不进入减数分裂。然而，其他结构（体细胞）变化，如输精管的初步形成（30 dph）、睾丸基质区域血管的出现（30 dph）以及发育中的睾丸小叶的出现（102 dph），表明睾丸分化。在超微结构上，原始生殖细胞、卵原细胞和精原细胞的特征相似，包括基质、线粒体、内质网和高尔基体复合物。
