ENDOCRINE DISRUPTORS IN THE DEVELOPING NERVOUS SYSTEM

近年来，证据和关注都在稳步增长，合成化合物，包括杀虫剂、除草剂和工业溶剂，通过干扰内分泌敏感过程对许多物种的发展产生有害影响。大量研究表明，这些假定的内分泌干扰化合物（EDCs）会导致外周生殖器官和生殖行为异常（Gray et al ., 1992; Cooper and Kavlock, 1997; Reiter et al ., 1998）。众所周知，性腺激素对神经系统的发育有显著而广泛的影响（Dohler, 1991），神经系统的缺陷是从研究中推断出来的，研究表明生殖行为中edc依赖性异常（Gray et al, 1985; Andersen et al, 1997）。尽管有这些研究，很少有数据可以证明EDCs对神经元分化的细胞过程的潜在影响。此外，尽管数据清楚地表明，发育中的生物比成年动物对内分泌干扰更敏感，但关于EDC影响的关键时期的信息却很少。本研究的目的是确定EDCs对两栖动物非洲爪蟾（Xenopus laevis）脊椎动物脊髓神经元早期胚胎发育的不利影响的关键时期和剂量-反应关系。非洲爪蟾胚胎提供了一个高度可处理的系统，在这个系统中，神经系统形成的早期事件和突触连接的建立可以在大量动物中快速筛选，并且在体内鉴定的神经元的发育变化，以及这些相同的细胞在体外分离和维持，都有充分的记录（Brehm和Henderson, 1988; Spizter, 1994）。采用多学科方法，包括形态计量学分析、荧光显微镜、全细胞膜片钳记录和超快灌注技术，我们将确定暴露于假定的雌激素和抗雄激素EDCs是否会导致早期胚胎发育中已确定的脊髓神经元群体分化中的选择性缺陷。

In recent years, both the evidence and the concern have been steadily growing that synthetic compounds, including pesticides, herbicides, and industrial solvents, have deleterious effects on the development of a wide range of species by disrupting endocrine sensitive processes. Numerous studies indicate that these putative endocrine disrupting compounds (EDCs) induce abnormalities in peripheral reproductive organs and in reproductive behaviors (Gray et al, 1992; Cooper and Kavlock, 1997; Reiter et al, 1998). Gonadal steroids are known to have significant and widespread effects on the development of the nervous system (Dohler, 1991), and deficits in neural systems are inferred from studies demonstrating EDC-dependent abnormalities in reproductive behaviors (Gray et al, 1985; Andersen et al, 1997). In spite of these studies, little data is available documenting potential effects of EDCs on cellular processes underlying neuronal differentiation. Moreover, although data clearly suggest that developing organisms are more sensitive to endocrine disruption than adult animals, little information is available delineating critical periods for EDC effects. The goal of the present study is to determine both critical periods and dose-response relationships for putative EDCs in inducing adverse effects on the early embryonic development of vertebrate spinal neurons from the amphibian, Xenopus laevis. Xenopus embryos provide a highly tractable system in which early events underlying formation of the nervous system and establishment of synaptic connections can be screened rapidly in a large number of animals, and in which developmental changes for identified neurons in vivo, as well as these same cells dissociated and maintained in vitro, have been amply documented (Brehm and Henderson, 1988; Spizter, 1994). Using a multidisciplinary approach that includes morphometric analysis, fluorescence microscopy, whole cell patch clamp recording, and ultrafast perfusion techniques, we will determine if exposure to putative estrogenic and anti-androgenic EDCs leads to selective defects in the differentiation of identified populations of spinal cord neurons during early embryonic development.