Zamboni L, Upadhyay S
Am J Anat. 1982 Nov;165(3):339-56. doi: 10.1002/aja.1001650309.
In this study, which was performed on 52 sheep fetuses aged 24 to 85 days, we examined the relationship between testicular development and the "giant" mesonephric nephron, a peculiar structure consisting of a large glomerulus and multiple tubules. The development of the testis occurred in two phases. The preparatory phase began at day 24 of gestation, evolved simultaneously with the involution of the glomerulus of the giant nephron, and was characterized by mobilization of the glomerular cells and by their colonization of the genital ridge. By day 31, a prominent mass of migrating mesonephric cells had developed; it extended uninterrupted from the giant glomerulus into the gonad where the mesonephric cells associated with the germinal cells forming the cellular template from which the testicular cords later became assembled. At complete involution of the glomerulus (day 52), the migratory mass implanted on the tubules of the giant nephron, which thus became continuous with the gonad. During the organizational phase, which began at day 29 with the formation of the tunica albuginea, the various components of this continuum became progressively organized along a testis-to-mesonephros direction into seminiferous cords, tubuli recti, the cords of the rete testis, and the ductules efferentes. These observations show that, in the sheep, the precursors of the Sertoli cells are mesonephric in origin, and that the genital tract proximal to the epididymis differentiates from a single mesonephric nephron.
在这项对52只年龄在24至85天的绵羊胎儿进行的研究中，我们研究了睾丸发育与“巨大”中肾单位之间的关系，“巨大”中肾单位是一种由大肾小球和多个肾小管组成的特殊结构。睾丸的发育分两个阶段进行。准备阶段始于妊娠第24天，与巨大肾单位肾小球的退化同时发生，其特征是肾小球细胞的动员及其在生殖嵴的定植。到第31天，形成了一个突出的迁移中肾细胞团；它从巨大肾小球不间断地延伸到性腺，在那里中肾细胞与生殖细胞相关联，形成细胞模板，随后睾丸索从中组装而成。在肾小球完全退化时（第52天），迁移团植入巨大肾单位的肾小管，从而使肾小管与性腺相连。在组织阶段，从第29天白膜形成开始，这个连续体的各个组成部分沿着从睾丸到中肾的方向逐渐组织成生精小管、直精小管、睾丸网索和输出小管。这些观察结果表明，在绵羊中，支持细胞的前体起源于中肾，附睾近端的生殖道由单个中肾单位分化而来。
