Merchant-Larios H, Taketo T
Instituto de Investigaciones Biomédicas, UNAM, Mexico D.F.
J Electron Microsc Tech. 1991 Oct;19(2):158-71. doi: 10.1002/jemt.1060190204.
Gonadal differentiation begins with the establishment of a sexually undifferentiated gonad, in which gonadal cords are formed by condensation of somatic cells and deposition of basal laminar components around the cluster of epithelial-like cells. The first event of sexual differentiation is the invasion of mesenchymal and endothelial cells into the genital ridge in the XY gonad. As a consequence of this event, the gonadal cords become conspicuous, recognized as seminiferous cords (or testis cords). Cytological differentiation of Sertoli cells follows these stromal changes. In the XX gonad, by contrast, the invasion of the mesenchyme is absent and gonadal cords remain associated with the surface epithelium. In the B6.YDOM XY ovotestis, seminiferous cords and ovarian gonadal cords are often enveloped by common basal laminae, confirming that both structures share the embryonic origin. It has been recently reported that seminiferous-like cords are formed after loss of oocytes in the rat XX ovary cultured in the presence of Müllerian inhibiting substance or after long-term culture in the basic medium alone. These results are comparable with our observation on the persistent gonadal cords in the ovary of busulphan-treated rats or W/WV mutant mice, in which oogonia are absent or scarce. Ultrastructural evidence for Sertoli cell differentiation from XX cells has been presented, so far, only in the fetal mouse ovary that has been grafted beneath the kidney capsule of adult male mice. Possible mechanism of gonadal sex determination is discussed based on these morphological studies.
性腺分化始于建立一个性别未分化的性腺，其中性腺索由体细胞凝聚以及在上皮样细胞簇周围沉积基膜成分而形成。性别分化的第一个事件是间充质细胞和内皮细胞侵入XY性腺的生殖嵴。这一事件的结果是，性腺索变得明显，被识别为生精索（或睾丸索）。支持细胞的细胞学分化跟随这些基质变化。相比之下，在XX性腺中，间充质没有侵入，性腺索仍然与表面上皮相连。在B6.YDOM XY卵睾中，生精索和卵巢性腺索通常被共同的基膜包裹，证实这两种结构具有共同的胚胎起源。最近有报道称，在存在苗勒氏管抑制物质的情况下培养的大鼠XX卵巢中卵母细胞缺失后，或仅在基础培养基中长期培养后，会形成类似生精的索。这些结果与我们对经白消安处理的大鼠或W/WV突变小鼠卵巢中持续存在的性腺索的观察结果相当，在这些动物中卵原细胞缺失或稀少。到目前为止，仅在移植到成年雄性小鼠肾被膜下的胎儿小鼠卵巢中，有从XX细胞分化为支持细胞的超微结构证据。基于这些形态学研究，讨论了性腺性别决定的可能机制。
