REGULATION OF SPERM EXOCYTOSIS

精子的顶体必须经历胞吐作用，才能使卵子受精。在一个知之甚少的成熟过程中，射出的哺乳动物精子能够产生胞吐作用。这个项目的长期目标是了解顶体胞吐是如何控制的。一些不育男性的精子无法有正常的顶体胞吐，充分了解顶体胞吐是如何控制的，可能会为控制生育提供新的方法。精脂在控制精子胞吐中起着重要作用。精子必须失去胆固醇才能对顶体做出反应。胆固醇的流失会增加细胞内的pH值。实验将确定人类精子的pH值是如何控制的，这样就可以更好地了解胆固醇的影响机制。将进行结构-活性分析，以揭示胆固醇分子的哪些特征是活性所必需的。胆固醇促进磷脂有序的能力的重要性将通过测量膜探针的荧光各向异性来研究。第二种脂质，神经鞘磷脂，最近被证明参与了顶体胞吐的控制，实验将测试它是通过控制胆固醇外流还是作为信号分子的来源发挥作用。将比较新鲜射出的和输卵管的牛精子的胆固醇含量，看看精子是否会在雌性生殖道中失去胆固醇。

The acrosome of a sperm must undergo exocytosis before the sperm can fertilize an egg. Ejaculated mammalian sperm become capable of exocytosis during a poorly understood maturation process. The long-term objective of this project is to understand how acrosomal exocytosis is controlled. Sperm of some infertile men are unable to have normal acrosomal exocytosis, and a full understanding of how acrosomal exocytosis is controlled may suggest new ways to control fertility. Sperm lipids play an important role in the control of sperm exocytosis. Sperm must lose cholesterol to become acrosomally responsive. Loss of cholesterol increases the intracellular pH. Experiments will determine how human sperm pH is controlled so the mechanism of cholesterol's effect can be better understood. A structure-activity analysis will be performed to reveal what features of the cholesterol molecule are required for activity. The importance of cholesterol's ability to promote order among phospholipids will be studied by measuring fluorescence anisotropy of a membrane probe. A second lipid, sphingomyelin, has recently been shown to be involved in the control of acrosomal exocytosis, and experiments will test whether it acts by controlling cholesterol efflux or by serving as the source of signalling molecules. The cholesterol content of freshly ejaculated and oviductal bovine sperm will be compared to see if sperm lose cholesterol in the female tract.