Richmond G, Sachs B D
Horm Behav. 1984 Dec;18(4):484-90. doi: 10.1016/0018-506x(84)90032-1.
The morphology and behavior of female rodents is partially masculinized as a result of residence near males in the same uterine horn (Clemens effect). Two hypothetical mechanisms have been proposed to account for this effect. In the first hypothesis ("contiguity") androgens secreted by males in utero are proposed to diffuse across the amniotic membrane, reaching adjacent fetuses. In the second hypothesis ("caudal male") androgens are transported via the cervical-to-ovarian blood flow and may diffuse directly between closely apposed uterine veins and arteries. This study was designed to test directly which of these mechanisms appears more influential in masculinizing the morphology of female rats. Pregnant Sprague-Dawley rats were decapitated early on Day 22 of gestation and pups were Caesarean delivered. Their anogenital distance and body weight were recorded, location in utero coded by means of footpad tatooing, and each litter fostered to a maternal female. Measurements were taken again when the animals were weaned. Statistical analysis revealed that the presence of one or more males caudal to a female in the uterine horn has a more critical influence on that female's morphology than contiguity per se. Such a mechanism may result in partial masculinization of dimorphic behaviors later in life.
由于与同子宫角内的雄性相邻生活，雌性啮齿动物的形态和行为会出现部分雄性化（克莱门斯效应）。人们提出了两种假说机制来解释这种效应。在第一个假说（“相邻性”）中，雄性在子宫内分泌的雄激素被认为会扩散穿过羊膜，到达相邻的胎儿。在第二个假说（“尾部雄性”）中，雄激素通过宫颈到卵巢的血流运输，可能直接在紧密相邻的子宫静脉和动脉之间扩散。本研究旨在直接测试这些机制中哪一种在使雌性大鼠形态雄性化方面似乎更具影响力。在妊娠第22天早期，将怀孕的斯普拉-道利大鼠断头，通过剖腹产取出幼崽。记录它们的肛门与生殖器之间的距离和体重，通过脚垫纹身对子宫内的位置进行编码，然后将每窝幼崽寄养给一只母鼠。当动物断奶时再次进行测量。统计分析表明，子宫角内雌性尾部存在一个或多个雄性对该雌性的形态影响比相邻性本身更为关键。这样一种机制可能导致后期生活中双态行为的部分雄性化。
