Institutional Repository of Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences
|Place of Conferral||北京|
2. 在生长期大菱鲆血清中，孕激素P4和DHP，雄激素T和11-KT的含量都在精原细胞增殖期较低，在精母细胞减数分裂起始阶段开始显著升高，在减数分裂结束主要细胞类型为精子细胞时显著下降。另外，P4向DHP和雄激素方向转化的关键酶 P450c17-I和P450c17-II在精原细胞增殖期显著高表达，为在减数分裂起始阶段合成高水平的DHP，T和11-KT提供条件。
4. 繁殖周期中，P4，DHP和T在血清中的含量随精巢发育显著升高，精巢退化时显著下降，P450c17-I和P450c17-II 的表达量与DHP含量具有相同的表达时序。表明在整个繁殖周期中，不断有胆固醇通过一系列转化合成P4，再通过P450c17-I和P450c17-II转化成DHP和T促进繁殖周期的进行。另外，P4和DHP含量高的雄鱼，其精子存活率也高，进一步证明高浓度P4和DHP促进精子成熟。
|Other Abstract||In teleost, sex steroid hormones are critical to reproductive endocrine, especially progestin is well known to promote spermiation. Almost all fish reared in captivity exhibit some form of reproductive dysfunction. In males turbot (Scophthalmus maximus), low quality and quantity of milt production seriously restricts the development of artificial breeding industry. To further understand the functions of progestin via its receptors during spermatogenesis in male turbot, we observed testicular development, quantified several sex steroid hormones, detected the expression of progestin receptors and the enzymes of progestin synthesis, and measured various sperm parameters from the onset of puberty to reproductive cycle. The purpose is to study the function of progestin via its functionally distinct progestin receptors on male germ cells development. Main contents and results are as follows:|
1. In this study, turbot testicular structure was characterized by the lobular type and represented a cystic type of spermatogenesis. The spermatagonial cells proliferation stage was from 6-14 months. The expression of amh of male differentiation marker gene increased significantly. The meiosis stage was from 16 to 22 mah. The expression of primary spermatocyte marker gene sycp3 and germ cell marker gene dazl increased significantly. The reproductive cycle of turbot was divided into four stages based on the proportion of different germ cells and the shape of germinal epithelium in testes. From stages III to VI, the dominant germ cells types were spermatocytes, spermatids, spermatozoa, and spermatocytes, respectively. At stage V, almost all the seminiferous lobules were filled with spermatozoa and spermatids, and a large number of discontinuous germinal epithelium appeared. At stage VI, germ cells regressed to spermatocytes. Only some seminiferous lobules still contained a small amount of spermatozoa. The number of sertoli cells increased markedly and the cyst wall had thickened.
2. In growing period, the results showed that the levels of progesterone (P4), 17α, 20β-dihydroxy-4-pregnen-3-one (DHP), testosterone (T) and 11-ketotestostrone (11-KT) were high at the initial of meiosis, and dropped significantly at spermiogenesis. In addition, the expression of enzymes of progestin and androgen synthesis P450c17 were high during the spermatagonial cells proliferation, which provides conditions for DHP, T and 11-KT synthesis.
3. The expression of nuclear progesterone receptor (pgr) was high from spermatogonial proliferation to meiosis, which was consistent with the level of DHP. While the expression of three membrane progestin receptors (mPRα，pgrmc1 and pgrmc2) did not increase significantly until late meiosis period. Hence, we speculated that DHP might play an essential role in the initiation of meiosis through pgr. And mPRα，pgrmc1 and pgrmc2 play an important role at meiosis II and spermiogenesis.
4. During reproductive cycle, serum T, P4 and DHP levels presented higher values from stage IV to V than other stages. Furthermore, the expression of P450c17-I and P450c17-II were also high from stage IV to V. The expression profiles indicated that the cholesterol transformed into P4 continuously, and then continued to transform into DHP and T via P450c17-I and P450c17-II to promote the development of reproductive cycle. In addition, the males with higher motility sperm showed higher levels of P4 and DHP comparing with those with lower motility sperm. These results indicated that P4 and DHP might induce spermiogenesis by seasonal changes.
The expression of pgr reached the peak at stage V and located in spermatid. While the expression of mPRα and pgrmc2 were higher in sperm than in testes. Futhermore, the expression of mPRα and pgrmc2 were higher in high quality sperm group than in low quality sperm group. These results indicated that progestin might exert a direct pgr-mediated effect on spermatogenesis by genomic actions and improve sperm quality depending on the abundance of membrane progestin receptors in sperm by nongenomic actions.
|丰程程. 孕激素及其受体在大菱鲆精子发生过程中的作用研究[D]. 北京. 中国科学院大学,2017.|
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