排序方式： 共有16条查询结果，搜索用时 15 毫秒
1.
Y. Yoshiura Y.C. Sohn A. Munakata M. Kobayashi K. Aida 《Fish physiology and biochemistry》1999,21(3):201-210
A cDNA encoding the subunit of thyrotropin (TSH) was isolated from a goldfish (Carassius auratus) pituitary gland cDNA library. By comparing the sequence with other teleost TSHs, a signal peptide of 19 amino acids and a mature hormone of 131 amino acids were predicted for goldfish TSH subunits. The resulting putative mature hormone of 131 amino acids had well-conserved cysteine positions and a putative N-linked glycosylation site; homology was 51–67% with TSHs from other teleosts, 38–43% with tetrapod TSHs, but only 27 and 29% with goldfish GTH-I and -II, respectively. We also examined the effects of thyroid hormones (TH) and thiourea (TU, an inhibitor of TH production) treatments on TSH and GTH subunit gene expressions in the goldfish pituitary gland. After thyroxine (T4) treatment, circulating T4 concentration increased and TSH mRNA level decreased. Supressing the amount of circulating T4 and triiodothyronine (T3) by TU treatment increased the TSH mRNA level. Moreover, T4 replacement therapy (simultaneous treatment of both TU and T4) caused a high level of circulating T4 and a low level of circulating T3, and a decrease in the TSH mRNA level. Thus, changing levels of circulating TH exert a negative feedback on the level of TSH subunit mRNA in goldfish in vivo. On the other hand, GTH subunit mRNA levels were not affected by changes in the levels of circulating TH. 相似文献
2.
外源性卵黄蛋白对鳗鲡GTH细胞和卵母细胞超微结构的影响 总被引：1，自引：0，他引：1
外源性卵黄蛋白与鲤鱼垂体（CPG）加绒毛膜促性腺激素（HCG）混合注射（试验组）对鳗鲡具有明显的催热作用，卵巢成热系数平均为56．17±11．74％，是对照组（CPG加HCG组）的2．87倍。试验组脑垂体促性腺激素细胞（GTH细胞）中除含有数量较多的小分泌颗粒外，球状分泌颗粒增加，内质网池扩大；卵母细胞直径为450．0微米，双层滤泡膜和放射带充分发育。对照组GTH细胞的球状分泌颗粒直径和内质网扩大均小于试验组；卵母细胞直径为270．0微米。而饲养在海水中75天，未经注射催情药物的雌鳗，脑垂体GTH细胞仅有小分泌颗粒，未见球状分泌颗粒，卵母细胞的放射带正在形成，胞内开始出现脂肪油球。试验结果表明，外源性卵黄蛋白与CPG加HCG混合注射有明显协同作用，对卵母细胞成热有显著促进作用。 相似文献
3.
通过对催产和未催产的长吻鮠脑垂体中腺垂体促性腺激素分泌细胞（ＧＴＨ 细胞） 的分泌活动分析,证实了用促黄体素释放激素类似物（ＬＲＨ－ Ａ） ５０μｇｋｇ 加ＤＯＭ５ｍｇｋｇ 混合注射催产长吻鮠,能有效地促使ＧＴＨ细胞分泌促性腺激素,诱导卵母细胞成熟和排卵,催产效果显著。超微结构的进一步观察,揭示了长吻鮠脑垂体ＧＴＨ 细胞中存在两种分泌颗粒,即分泌小球,直径１２００～２０００ｎｍ ,电子密度低;分泌颗粒直径３００ ～５００ｎｍ ,电子密度高。分泌小球释放与卵母细胞的发育成熟有关,分泌颗粒的释放则与排卵相关。 相似文献
4.
济宁青山羊发情周期内促性腺激素和性激素分泌规律的研究 总被引：1，自引：0，他引：1
本试验对处于繁殖季节的济宁青山羊进行颈静脉采血,用放射免疫分析法测定了血浆内促性腺激素(FSH、LH)和性激素(E2、P)的含量。结果表明:整个发情周期中FSH、LH和E2均先后出现4个分泌峰,FSH的4个分泌峰分别晚于LH峰2 d出现。E2的分泌峰除第3个分泌峰出现在第10天之外,其余3个峰均与LH峰同时出现。P在发情周期的第5天开始逐渐升高,间情期(第7~17天)维持在一个较高的水平(P>0.05),发情前一天(第18天)骤然下降。在发情期和间情期,FSH和LH分泌方式均呈脉冲式,E2和P为波动式分泌。发情期FSH的脉冲频率较间情期低(P>0.05),而LH的脉冲频率则高于间情期(P>0.05)。 相似文献
5.
M. Kobayashi M. Amano M.H. Kim Y. Yoshiura Y.C. Sohn H. Suetake K. Aida 《Fish physiology and biochemistry》1997,17(1-6):1-8
Reproductive activities in vertebrates are regulated by an endocrine system, consisting of the brain-pituitary-gonad axis. In teleosts, gonadotropin-releasing hormone (GnRH) in the brain stimulates gonadotropin (GTH) release in the pituitary gland, but because of lack of the portal vessel, it is not known when and how much GnRH is released for the regulation of GTH release. There are multiple molecular types of GnRH in teleosts and several distinct populations of GnRH neurons in the brain. However, we do not know which types and populations of GnRH neurons regulate reproductive activities. Here we summarize our recent studies on GnRH and GTH in masu salmon Oncorhynchus masou and goldfish Carassius auratus. Immunocytochemistry showed the location and molecular types of GnRH neurons. Salmon (sGnRH) and chicken-II GnRH (cGnRH-II) neuronal fibers were widely distributed in the brain of both masu salmon and goldfish. Only sGnRH fibers were observed in the pituitary of masu salmon, whereas both sGnRH and cGnRH-II fibers were observed in the goldfish pituitary, indicating that species specific GnRH profiles are involved in the regulation of pituitary function in teleosts. A series of experiments in masu salmon and goldfish suggest that among GnRH neuron populations GnRH neurons in the ventral telencephalon and the hypothalamus regulate GTH release, and that GnRH of the terminal nerve origin is not essential to gonadal maturation and ovulation. The biological function of other GnRH neurons remains unkown. Two GTHs appear to be characteristic of teleost; however, regulation of reproduction by these GTHs is a question that remains to be elucidated. In salmonid species, it is proposed that GTH I stimulates early gonadal development, whereas GTH II acts in later stages. When GTH expression was examined in goldfish, both GTH I and II mRNA levels in the pituitary gland showed increases in accordance with gonadal development, unlike the sequential expression of GTH subunits in salmonids. The expression of these GTH subunit mRNAs were affected by water temperature, starvation, and steroid hormones in goldfish, but in what manner these two GTHs regulate gonadal development remains to be clarified. 相似文献
6.
大鼠GTH细胞内PKC的改变对LH表达的影响 总被引：1，自引：1，他引：0
目的是分析大鼠分泌LH的GnRH受体后信号转导机制。将GTH细胞内PKC兴奋或抑制后,用高频GnRH脉冲刺激,再用ELISA法检测其LH分泌量,并与空白组比较。结果表明,细胞PKC活性显著影响LH的分泌。得出结论,PKC-Ca2+是GnRH脉冲刺激引起的LH分泌的GnRH受体后信号转导途径之一。 相似文献
7.
对促性腺激素释放激素(GnRH)作用机制的研究是一个重要领域。文章综述了国内外GnRH的研究进展,认为GnRH与受体(Rs)结合后,要通过一系列的信号转导,调节和控制促卵泡激素(FSH)和黄体生成素(LH)的合成和分泌。GnRH受体后信号转导途径主要是通过3大信号转导系统完成的:环磷酸腺苷(cAMP)信号转导系统、蛋白激酶C(PKC)信号转导系统和丝裂原活化蛋白激酶(MAPK)信号转导系统。cAMP信号转导通路和PKC信号转导通路都属于G蛋白偶联的信号通路,二者最后都要通过激活MAPK信号转导系统来完成调控。这为进一步研究GnRH作用机制提供了依据,同时讨论了存在的问题,并对下一步的研究方向做出展望。 相似文献
8.
哺乳类和鱼类的促性腺激素(GTH)细胞都是位于腺垂体,所分泌的激素有促卵泡激素(FSH)和促黄体素(LH),促卵泡激素可以促成卵细胞和精子的生成,而促黄体素可以促进孕酮和睾酮的产生,关于促性腺激素细胞的来源有三种假说,在所有的对促性腺激素细胞调节控制的因素中,最重要的是促性腺激素释放激素(GnRH)。文章从促性腺激素细胞的定位、功能、源泉细胞,以及对其调节控制等方面的研究进展作一综述,以期为在实践中加强对动物生殖规律的人工调控提供参考。 相似文献
9.
大鼠腺垂体细胞的体外原代培养及其GTH分泌活动的观察 总被引：4，自引：0，他引：4
本文旨在体外进行原代培养大鼠垂体细胞并观察GTH分泌活动规律;在每日观察细胞生长状态并分组检测其FSH、LH分泌水平,及做免疫组化染色实验,连续5d;结果表明,第7天时,细胞状态最佳,FSH、LH分泌水平最高,GTH的阳性率最大;所以大鼠垂体细胞体外培养生长最旺盛的时期是第7天。 相似文献
10.
M. A. Zandbergen C. A. van Branden R. W. Schulz J. Janssen-Dommerholt J. M. Ruijter H. J. Th. Goos J. Peute 《Fish physiology and biochemistry》1993,11(1-6):255-263
In an ultrastructural immunocytochemical study we investigated the development of the gonadotropic cells in the pituitary of two to six months old male African catfish in relation to testicular development. In this period, pituitary and testicular tissue samples were collected on five occasions (groups I–V). Blood samples could only be taken from the fish in groups III–V. The testicular development was divided in three stages i.e., immature (only spermatogonia, group I), early (spermatogonia and spermatocytes, groups II and III) and advanced (all germ cell stages including spermatozoa, groups IV and V) spermatogenesis. 11-Ketotestosterone blood levels were low, except for the last group. Antisera were raised against the complete catfish α,βGTH-II, as well as to the separate α- and β-subunits of catfish GTH-II. In the proximal pars distalis of immature fish, undifferentiated cells, somatotrops, putative thyrotrops (pTSH) and putative gonadotrops (pGTH) were found. In the two latter, secretory granules were labeled with anti-αGTH, but not with anti-βGTH-II. pTSH- and pGTH-cells were distinguished on the basis of the size of their secretory granules. During early spermatogenesis, two classes of putative gonadotrops could be distinguished. One type had the same immunocytochemical and ultrastructural characteristics as in immature fish; the secretory granules in the second cell type, which was more abundant, were also immunopositive for anti-βGTH-II. The mean volume of the secretory granules in these GTH-II cells was three times larger than that in the early appearing pGTH-cells. In addition, the later appearing GTH-II cells contained large inclusions, known as globules. These structures labeled with anti-αβGTH-II and with anti-βGTH-II, but not with anti-αGTH. It is assumed that the globules are involved in a differential storage and/or breakdown of the GTH-II subunits. During advanced spermatogenesis the two gonadotropic cell types could still be distinguished, but the early appearing pGTH-cell type was scarce. The present observations permit the conclusion that the early appearing cells may be GTH-I cells. However, definitive proof about their identity depends on the availability of antibodies or cDNA probes specific for GTH-I. 相似文献