Formation of Ecdysteroid Hormones in Crustaceans

两种激素控制着生长、蜕皮和再生的周期， 节肢动物（昆虫和甲壳类）。 在甲壳类动物中， 激素是蜕皮激素，化学上是一种类固醇， 循环 蜕皮激素由体内的腺体（Y器官）分泌 腔 Y器官的分泌依次由第二个 激素，蜕皮抑制激素（MIH），化学上是一种蛋白质 并由大脑中的专门神经细胞分泌。 该系统 类似于人类和其他脊椎动物（肾上腺 皮质、卵巢和睾丸）分泌类固醇激素， 由脑垂体分泌的蛋白质激素控制 然而，在这方面， 甲壳类系统在细胞结构和新陈代谢方面比较简单。 为 因此，该系统被用作研究 细胞如何吸收胆固醇的细节（胆固醇的普遍前体） 类固醇激素）和处理它的激素合成，以及如何神经 激素控制这些事件。 这个项目的重点是揭示 胆固醇进入Y器官细胞的机制， 研究发现，胆固醇被呈递给细胞， 密度脂蛋白（HDL）。 细胞上HDL的特异性受体 表面，复合物如何在细胞中分解以及如何和在哪里分解 游离胆固醇被加工成激素将被检查。 随后的研究将探索MIH如何改变细胞功能， 或者停止激素的合成 在这方面，甲壳类动物似乎 在动物中是独一无二的;这个模型的一个理论上重要的方面 脑激素（MIH）负调节，而在所有 在其它已知的系统中，相应的激素是刺激性的。 技术将包括使用放射性示踪剂，电子 显微镜、超离心和高压液体 层析 这项研究包括神经生物学、内分泌学和 发展生物学在解决协调 身体功能。 结果应最终应用于临床 类固醇内分泌学、生殖医学 生理学、腺体病理学和动脉粥样硬化（由 胆固醇代谢缺陷）。 此外，获得的知识将增加 了解节肢动物蜕皮/生长周期， 这一过程主导了这一丰富的，经济上的存在， 重要的动物群。

Two hormones control the cycles of growth, molting and regeneration in arthropod animals (insects and crustaceans). In crustaceans, one of the hormones is ecdycsone, chemically a steroid, that directly controls the cycles. Ecdysone is secreted by glands (Y-organs) in the body cavity. Secretion by the Y-organs is controlled in turn by the second hormone, molt-inhibiting hormone (MIH) which is chemically a protein and is secreted by specialized nerve cells in the brain. This system is analogous to that in the human and other vertebrates (adrenal cortex, ovary and testis) that secrete steroid hormones and that are governed by protein hormones from the brain/pituitary gland. However, the crustacean system is simpler in cell structure and metabolism. For this reason, the system is being used as a model for studying the details of how cells take up cholesterol (the universal precursor of steroid hormones) and process it for hormone synthesis, and how neural hormones control these events. The focus of this project is to uncover the mechanism by which cholesterol enters Y-organ cells in light of findings that cholesterol is presented to the cells bound up in high- density lipo-protein (HDL). Specific receptors for HDL on the cell surface, how the complex is broken down in the cell and how and where the freed cholesterol is processed into hormone will be examined. Attendant studies will explore how MIH modifies cell function to slow or stop hormone biosynthesis. In this regard, crustaceans appear to be unique among animals; a theoretically significant aspect of this model is that the brain hormone (MIH) regulates negatively, whereas in all other known systems the corresponding hormone is stimulatory. Techniques will include use of radioactive tracers, the electron microscope, the ultracentrifuge and high-pressure liquid chromatography. This research embraces the fields of neurobiology, endocrinology and developmental biology in addressing basic questions on coordination of bodily functions. Results should have eventual application of clinical medicine in the areas of steroid endocrinology, reproductive physiology, pathologies of glands and atherosclerosis (arising from defects in cholesterol metabolism). Also, knowledge gained will add to understanding the arthropod molting/growth cycle, a developmental process that dominates the existance of this abundant, economically important group of animals.