Neuroendocrine Control of Amphibian Metamorphosis

两个多世纪以来，两栖动物一直是胚胎学和发育研究的主要模型。我们对早期胚胎发育的了解，成功培养体外胚胎的技术，以及激素在早期发育中的作用，大多来自对两栖动物卵和蝌蚪的研究。因为两栖动物的卵是在母体外发育的，所以在实验室培养和实验操作它们相对容易。我们所了解的绝大多数关于两栖动物发育生物学的知识都直接适用于我们对人类发育的理解。尼科尔博士将研究激素在两栖动物早期发育中的作用，并将确定外部环境变量如何影响激素的产生和发育速度。他专注于促肾上腺皮质激素释放激素系统，因为这种激素的释放可能代表了一种古老的系统发育的启动者或线索。他将确定这种神经激素如何调节促甲状腺激素和促肾上腺皮质激素的分泌，这两种垂体激素已知在变态过程中起重要作用。从这些研究中获得的基本信息将有助于我们理解在人类发育过程中发生在子宫内的复杂事件。此外，考虑到最近全球两栖动物数量的下降，这些发现与生物多样性的保护直接相关。确定影响发育的环境和生理因素，以及两栖动物通过仔细、有控制的实验对这些变量作出反应的方式，将有助于设计有效的保护策略。

For over two centuries, amphibians have been primary models for embryological and developmental studies. Much of what we know about early embryonic development, the techniques for the successful culture of embryos in vitro, and the role of hormones in early development have come from studies on amphibian eggs and tadpoles. Because amphibian eggs develop outside of the mother's body, it is relatively easy to culture them in the laboratory and to experimentally manipulate them. The vast majority of what we have learned about the developmental biology of amphibians is directly applicable to our understanding of human development. Dr. Nicoll will examine the role of hormones in early development of amphibians, and will determine how external environmental variables can influence hormone production and the rate of development. He is focusing on the corticotropin-releasing hormone system since the release of this hormone may represent a phylogenetically ancient initiator or cue in development. He will determine how this neurohormone regulates the secretion of thyroid-stimulating hormone and adrenocorticotropic hormones, two pituitary hormones known to be important in the metamorphic process. The basic information gained from these studies will contribute to our understanding of the complex events which occur within the womb during human development. Moreover, given the recent global decline in amphibian populations, the findings are directly related to the conservation of biological diversity. Identification of the environmental and physiological factors which influence development, and the ways in which amphibians respond to these variables through careful, controlled experimentation will help in the design of effective conservation strategies.