RUI: Mechanisms of Maternal-Embryonic Nutrient Transfer in Viviparous Sharks

胎生营养鱼类的胚胎生长是由母体-胚胎营养转移的结构和功能适应促进的。尽管人们对哺乳动物系统、一些爬行动物和硬骨鱼的这种转移机制了解很多，但关于鲨鱼的信息却很少。Lombardi提出，在两种具有代表性的胎生营养鲨鱼中，鉴定和研究母胚营养转移的主要细胞、发育和生理机制；犬mustus和rhizoprionodoae。我们将检查胎盘移植和胎盘旁移植的超微结构和生理学。本研究的目的是：1)描述母胚对母胚间营养转移的适应的超微结构形态；2)建立两个物种的发育序列；3)确定两种物种的养分转移效率；4)描述和量化子宫内和体外胚胎组织对蛋白质的摄取；5)分析妊娠期子宫分泌物及母体血清组成；6)评价地叶青的阑尾功能；7)鉴定、表征和比较两种动物经胎盘和胎盘旁的蛋白质转移途径。这些研究具有重要意义，因为它们首次建立了胎生营养鲨鱼母胚营养转移的形态学和生理学基础。由于高等脊椎动物中涉及母胚营养转移的许多结构也存在于鲨鱼中，因此这些研究的结果对于理解鱼类和高等脊椎动物中母胚关系的功能和起源将是不可或缺的。

Embryonic growth in viviparous matrotrophic fishes is facilitated by structural and functional adaptions for maternal-embryonic nutrient transfer. Although much is known about the mechanisms of such transfer in mammalian systems, some reptiles, and teleost fishes, very little information is available on sharks. Lombardi proposes to identify and examine the major cellular, developmental, and physiological mechanisms of maternal-embryonic nutrient transfer in two representative species of viviparous matrotrophic shark; Mustelus canis and Rhizoprionodon terraenovae. The ultrastructure and physiology of transplacental and paraplacental transfer will be examined. Objectives of this study are to: l) describe the ultrastructural morphology of both the maternal and embryonic adaptions for maternal-embryonic nutrient transfer; 2) establish a developmental series for both species; 3) determine nutrient transfer efficiencies for both species; 4) describe and quantify protein uptake by embryonic tissues in utero and in vitro; 5) analyze the composition of uterine secretions and maternal blood sera during gestation; 6)assess apendicular function in R. terraenovae; and 7) identify, characterize, and compare transplacental and paraplacental routes of protein transfer in both species. These studies are significant because they establish, for the first time, a morphological and physiological basis for maternal-embryonic nutrient transfer in viviparous matrotrophic sharks. Since many of the structures involved in maternal-embryonic nutrient transfer in higher vertebrates are also present in the sharks, the results of these studies will be integral to an understanding of the function and origin of the maternal-embryonic relationship in both the fishes and higher vertebrates.