利用脑—脑垂体—肝脏轴调控鱼类生长

本文综述了鱼类生长激素分泌的神经内分泌调节方面取得的研究进展,阐明脑（各种神经内分泌因子）－脑垂体（由生长激素细胞分泌的生长激素）－肝脏（肝细胞产生的类胰岛素生长因子）轴调控鱼类生长的作用,并在此基础上提出可供养鱼生产实践应用的基本途径。     

鱼类摄食和生长的神经内分泌调控途径研究进展

鱼类的生长与哺乳类相似,受脑（各种神经内分泌因子）一脑垂体（由生长激素细胞分泌的生长激素）一肝脏（肝细胞产生的类胰岛素生长因子）轴的调控,生长激素（Ｇｒｏｗｔｈ ｈｏｒ－ｍｏｎｅ,ＧＨ）和类胰岛素生长因子（Ｉｎｓｕｌｉｎ－ｌｉｋｅ ｇｒｏｗｔｈ ｆａｃｔｏｒ,ＩＧＦ）与鱼类生长发育关系十分密切,并且对鱼类的生长起主要调节作用［１～３］。而 ＧＨ的释放受到脑,特别是下丘脑合成与分泌的生长激素释放因子（ＧＲＦ）和生长激素释放抑制因子（ＳＲＩＦ）的双重调控,通过外源药物加强鱼类自身ＧＨ（内源性的）的合成与…     

鱼类内源性生长激素释放肽的研究进展

生长激素释放肽（Ghrelin）是在哺乳动物中发现的第一个生长激素促分泌素受体的内源性配体,部分鱼类的Ghrelin基因和肽链结构已经被确定。与哺乳动物相似,鱼类Ghrelin的主要分泌部位也在消化道,但在脑、肾脏、鳃、心脏等组织中也有少量分泌。鱼类的Ghrelin参与多种生理功能的调节,包括促进摄食以及调节脑垂体内多种激素的分泌,可促进脑垂体分泌LH和GH,某些鱼类Ghrelin可能具有促进脑垂体分泌PRL的功能。本文综述了近年来鱼类Ghrelin结构与生理功能研究概况,旨在为丰富鱼类内分泌生理学研究提供参考资料。[中国水产科学,2008,15（3）：516-522]     

用酶联免疫吸附受体法检测鱼类生长激素的生物活性

根据激素一受体反应的原理，结合酶联免疫吸附测定法（ＥＬＩＳＡ）和放射受体测定法（ＲＲＡ）的优点，应用我们纯化的Ａ昌鱼生长激素（ｇｃＧＨ）和大鳞大马哈鱼生长激素（ｓＧＨ）及其特异抗体，采用鱼类肝细胞膜受体制剂，首次建立了测定鱼类ＧＨ生物活性的酶联免疫吸附受体测定法（ＥＬＩＳＡ－ＲＡ）。此法检测草鱼ＧＨ的灵敏度达０．０６３￣０．１２５ｕｇ／ｍｌ，检测大马哈鱼ＧＨ与草鱼肝膜受体结合的灵敏度达０．２５ｕｇ     

鱼类生长相关激素的营养调控

<正>鱼类激素是由内分泌腺所分泌的一类具有生物活性的物质,虽然含量极低,却在鱼类整个生命活动中起重要作用。像哺乳类一样,调节鱼类生长发育的内分泌激素主要包括垂体生长激素、类胰岛素生长因子-Ⅰ和甲状腺激素。鱼类内分泌系统对营养摄入的变化非常敏感,营养状况在调控鱼类激素的合成与分泌中发挥重要作用,研究较多的有饥饿、饲料中蛋白质和碳水化合物水平等。笔者简要综述了这三种营养状况对生长内分泌激素的影响     

环境内分泌干扰物对鱼类影响的研究进展

水环境中的内分泌干扰物可导致鱼类性别特征丧失和后代不能繁殖,损伤神经、免疫和内分泌系统,引起鱼类种群生存力和资源量下降。介绍了环境内分泌干扰物的概念、种类、作用机制和危害特征,着重阐述了其对鱼类生理生化的影响,讨论了环境内分泌干扰物的降解与研究前景。     

鱼类基因分子生物学及转基因鱼研究进展↑（*）

真核基因分子克隆技术的建立，提供了从核苷酸水平了解鱼类基因结构的手段。鱼类基因的分子克隆始于八十年代初、中期对虹鳟（Ｓａｌｍｏｇａｉｒｄｎｅｒｉ）鱼精蛋白基因［５２］和美洲黄盖鲽（Ｐｓｅｎｄｏｐｌｅｕｒｏｎｅｃｔｅｓａｍｅｒｉｃａｎｕｓ）抗冻蛋白（ＡＦＰ）基因［２２］的分子克隆，随后扩展到其他极地鱼类ＡＦＰ基因，接着扩展到鱼类生长激素（ＧＨ）基因、催乳激素（ＰＲＬ）基因、生长催乳素（ｓｏｍａｔｏｌａｃｔｉｎＳＬ）基因等数十个基因。对这些控制鱼类重要生理机能的基因结构的认识，无论在理论上还是在渔业…     

鱼类生长激素研究及应用进展

鱼类的生长和发育受体内各种激素的调节,其中生长激素对鱼类的生长起主要调控作用.同哺乳动物类似,在鱼类中,生长激素由脑垂体中的生长激素细胞分泌并通过血液运输到作用部位.现有研究发现,鱼类血液中生长激素的含量与鱼体生长速率的季节性变化有显著关系.因此,意味着如果人为增加鱼体中的生长激素含量,能够加快鱼类的生长,进而产生经济效益.生长激素在鱼体中含量很低,从脑垂体中大量获得生长激素用于渔业生产面临着生产效率低下、成本高等问题.这就限制了生长激素在生产中的大规模应用.但随着生命科学技术的发展,使得人们利用重组的鱼生长激素进行渔业生产就有了可能性.为此,本文就鱼类生长激素研究进展及其对鱼类生长发育影响的研究进行简要综述.     

双酚A和酞酸酯对鱼类的内分泌干扰效应和繁殖毒性的研究进展

环境雌激素作为一类内分泌干扰物进入人和动物体内后能干扰机体内分泌系统的正常功能,通过多种机制表现出拟天然雌激素或者抗天然雄激素的作用。双酚A（bisphenol A, BPA）和酞酸酯（也称作邻苯二甲酸酯,Phthalic Acid Esters, PAEs）是具有雌激素类活性的环境内分泌干扰物,广泛存在于水环境中,并对水生动物,特别是鱼类的安全造成潜在威胁。本文总结了目前BPA和PAEs对鱼类毒性效应的研究成果,特别是内分泌干扰作用和生殖毒性,为评估这两类环境污染物对鱼类的影响提供参考。     

NO_2~--N对鱼类毒性的研究概况

ＮＯ－２－Ｎ对鱼类毒性的研究概况ＡＳＵＲＶＥＹＯＦＲＥＳＥＡＲＣＨＯＮＴＨＥＥＦＦＥＣＴＯＦＮＩＴＲＩＴＥＴＯＸＩＣＩＴＹＯＮＦＩＳＨ王明学吴卫东（华中农业大学水产学院，武汉４３００７０）ＷａｎｇＭｉｎｇｘｕｅＷｕＷｅｉｄｏｎｇ（ＦｉｓｈｅｒｉｅｓＣ...     

基因工程在海水鱼类养殖中的应用前景

综述了鱼类基因转移的研究现状、研究方向及在海水鱼养殖中的应用前景，着重介绍了利用生长激素基因、生长激素释放因子基因、抗冻蛋白基因、金属硫蛋白基因、珠蛋白基因以及其它基因的转移培育海水鱼新产品的可能性。     

Mammalian Growth Hormone-Releasing Hormone Indirectly Stimulates Sex Steroid Production in Tilapia

Abstract.— Fish possess a growth hormone similar to mammalian growth hormone, and the presence of a growth hormone-releasing hormone-like material in the brain has been demonstrated in several teleost species. We investigated the effect of a mammalian growth hormone-releasing hormone on serum estradiol-17β and testosterone concentrations in tilapia Oreochromis mossambicus and a hybrid O. niloticus × O aureus because growth hormone has been implicated in the regulation of gonadal functions in teleosts. Three hours after injecting the releasing hormone, male and female serum testosterone concentrations significantly increased compared to controls, while serum estradiol-17β concentrations increased significantly only in females. These increases were commensurate with respective serum steroid concentrations in fish injected with gonadotropin releasing-hormone. Studies utilizing hypophysectomized fish resulted in non-detectable levels of serum sex steroids in fish treated with the growth hormone-releasing hormone; however, significant increases occurred in fish treated with human chorionic gonadotropin. Similarly, gonadal tissue incubated with growth hormone releasing hormone had non-detectable levels of sex steroids in the media, whereas gonads incubated with human chorionic gonadotropin had significant increases in sex steroid concentrations. These studies suggest that growth hormone-releasing hormone acts at the level of the pituitary. Although mammalian growth hormones have been shown to increase serum gonadotropic hormone concentrations, this study provides evidence that a mammalian growth hormone-releasing hormone has the ability to indirectly increase sex steroid levels in fish.     

The biology of salmon growth hormone: from daylight to dominance

The elucidation of the molecular structure of salmon growth hormone (GH) in the mid-1980's paved the way for a new era of endocrinological research. Establishment of homologous immuno- and receptor-assays have made studies of the secretion, tissue and plasma GH levels, GH turn-over and GH receptor concentrations possible. This overview attempts to summarize the present understanding of the biological roles of GH in salmon. Although the involvement of GH in the regulation of physiological processes throughout the salmon life history has yet to be comprehensively explored, the hormone has already been demonstrated to have several important functions. GH is a principal regulator of somatic growth in salmonids. The growth-stimulating effect of GH is probably integrated with that of insulin-like growth factor I (IGF-I), as in later vertebrates. GH stimulates protein synthesis and improves feed conversion during growth. The hormone also promotes lipid and glycogen breakdown as well as gluconeogenesis, functions which are probably of great importance during starvation when GH levels are seen to increase. During parr-smolt transformation of anadromous salmonids, circulating GH levels appear to be governed by environmental cues. Increasing springtime daylength elevates GH levels, and temperature modulates the photoperiod regulation of GH. The seawater-adapting role of GH during the parr-smolt transformation is complex. In freshwater, GH improves hypoosmoregulatory ability by stimulating branchial Na⁺,K⁺-ATPase activity and probably also acts in kidney and intestine. Following seawater entry, GH levels and turn-over increase transiently, probably to further increase seawater tolerance. Accumulating in vitro and in vivo data support the conclusion that GH is involved in the regulation of sexual maturation in salmonids although further studies are needed to establish the exact role of GH in this process. GH increases appetite but it is unclear whether the hormone effects the central nervous system directly, or acts indirectly through metabolic changes. GH increases swimming activity as well as dominant feeding behaviour and diminishes anti-predator behaviour of juvenile salmonids. The GH-induced changes of behavioural patterns imply that there exists an ecological trade-off between high growth rate and long-term survival which may explain why natural fish populations normally grow at sub-maximal rates. Current knowledge indicates that GH is an important and multi-functional hormone in salmon and a central mediator of seasonal changes in physiology and behaviour. The regulatory effects of GH are also of great applied interest as they are likely to affect both product quality in aquaculture and long-term survival of released fish.     

The Role of Somatostatins in the Regulation of Growth in Fish

Somatostatins (SS) are a structurally diverse family of peptide hormones that affect various aspects of growth, development and metabolism in vertebrates. Fish have proved to be useful models for understanding the role(s) of SS in the regulation of growth. Organismal growth is inhibited by SS and fish with impaired growth (caused by fasting or premature transfer to seawater of anadromous species) display enhanced SS production and elevated plasma levels of the hormone. Somatostatins modulate growth at the level of the pituitary through the inhibition of growth hormone (GH) synthesis and secretion. There are, however, significant structure-function relationships with regard to GH inhibition. For example, while SS-14 is a potent inhibitor of GH secretion, catfish SS-22 and salmonid SS-25 appear not to have GH secretotropic effects. Somatostatins also have extra-pituitary effects on growth. For example, SS reduce GH binding capacity and inhibit IGF-I mRNA expression in the liver. In addition, SS inhibit insulin, another factor essential to organismal growth. Finally, SS interact with a variety of reproductive and metabolic processes - actions which suggest that SS help modulate energy partitioning among biological processes.     

鱼类促性腺激素抑制激素及其受体的研究进展

促性腺激素抑制激素是2000年由日本学者首次从鹌鹑脑中分离出的一种新型下丘脑神经肽,通过其受体介导参与机体的生长、生殖以及摄食等生理过程。迄今,只在金鱼、斑马鱼、星点东方鲀、罗非鱼以及斜带石斑鱼等几种鱼中鉴定出促性腺激素抑制激素。目前,鱼类促性腺激素抑制激素的生理学功能研究相对较少,且存在争议。鱼类促性腺激素抑制激素及其受体的表达调控以及其他生理学功能仍有待进一步研究。本研究简要总结鱼类促性腺激素抑制激素及其受体的研究进展,并对促性腺激素抑制激素的生理学功能进行概括讨论,旨在加深对鱼类促性腺激素抑制激素的认识和了解,为进一步研究做铺垫。     

海水鱼类亲体必需脂肪酸营养的研究进展

脂肪酸营养特别是其中的必需脂肪酸在海水鱼类生殖调控方面具有重要的生理作用。饲料中二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)以及花生四烯酸(ARA)含量在调控海水鱼类性腺发育、排卵、孵化率及仔鱼质量等方面作用显著。本文主要从必需脂肪酸需求量、对繁殖性能影响、对机体脂肪酸存储影响及对内分泌调控作用4个方面归纳总结了海水鱼类亲体脂肪酸营养的研究概况,并重点分析探讨了在内分泌调控方面的研究进展,同时对后续的研究重点提出了一些建议。     

Growth Acceleration of Seawater-Adapted Female Chinook Salmon Oncorhynchus tshawytscha by Constant Infusion of Recombinant Bovine Growth-Hormone Under Ambient Summer Conditions

Seawater-adapted female chinook salmon ( Oncorhynchus tshawytscha ) in their second summer were treated with one of three doses of recombinant bovine growth-hormone (rbGH) administered in a continuous fashion by osmotic pump for approximately five weeks. Untreated fish, sham-treated fish and fish treated with the low dose of hormone (0.003 μg/g bwt/day) did not differ significantly in their growth performance over the 10 week course of the experiment. By the end of the treatment period (week 6) the mean increases in fork length and weight for these groups were 7.6% and 38.9%, respectively. A dose-dependent enhancement of growth was observed for the fish treated with the mid (0.016 μg/g bwt/day) and high (0.078 μg/g bwt/day) doses of hormone. After 6 weeks, the fish given the mid dose of rbGH had gained 9.6% in fork length and 45.3% in weight, while the fish treated with the high dose of rbGH had gained 13.9% in fork length and 52.9% in weight. A significant increase in specific growth rate was observed for these latter two groups during the treatment period while condition factor declined in response to the high dose of rbGH. This experiment indicates that chronic administration of growth-hormone to chinook salmon can result in a dose dependent elevation of growth rate. Results are discussed in relation to previous attempts to accelerate the growth of Pacific salmon with growth-hormone and the potential for using recombinant growth-hormone to improve the production characteristics of salmon being cultured in seawater.     

Correlation between dietary lipid:protein ratios and plasma growth and thyroid hormone levels in juvenile Arctic charr, Salvelinus alpinus (Linnaeus)

Sexually immature Arctic charr, Salvelinus alpinus (Linnaeus), were fed one of five isoenergetic practical diets of differing lipid:protein ratios (0.98, 0.67, 0.41, 0.26, 0.19) for an 84‐day period to examine the influence of diet composition on growth, and growth hormone (GH) and thyroid hormone physiology. All five diets supported growth at approximately the same rate, but the diet with a lipid:protein ratio of 0.98 had the lowest weight gain and highest food conversion ratios. A GH enzyme‐linked immunosorbent assay (ELISA), developed for use with oncorhynchid fishes, was validated for use with Arctic charr. Plasma GH concentrations were significantly higher in fish fed the diet with a lipid:protein ratio of 0.98, and there were significant direct and inverse correlations between plasma GH levels and dietary lipid and protein content respectively. There were no significant differences in pre‐ and post‐prandial plasma GH concentrations for any group. There were significant post‐prandial elevations of plasma triiodothyronine (T₃) and thyroxine (T₄) for fish fed the lower lipid:protein ratio diets, but there were no differences related to the diets. The results are discussed in terms of GH as a factor in the regulation of lipid and protein homeostasis in fishes.     

Muscular hypertrophy and growth‐promoting effects in juvenile pejerrey (Odontesthes bonariensis) after oral administration of recombinant homologous growth hormone obtained by a highly efficient refolding process

Growth hormone (GH) can be orally administrated to fish in order to increase growth rates. Fish growth is characterized by the hyperplasia and hypertrophy of muscle fibre throughout adult life. In this respect, GH could affect directly and indirectly (by growth and metabolic factors) the development and growth of muscle fibres. Recombinant pejerrey GH (r‐pjGH) was expressed in Escherichia coli and refolded in a highly efficient batch dilution system, obtaining 0.1 g L^?1 of hormone without protein precipitation during the refolding procedure. Orally administered hormone to pejerrey produced a 30% increase in mean weight and stimulated liver insulin‐like growth factor type I (IGF‐I) mRNA expression after 1 month of treatment. Histological analyses showed that muscle growth was generated mainly by hypertrophy of the fibres. A higher r‐pjGH dose increased muscle fibre hypertrophy but somatic growth was negatively affected probably due to a reduced capacity of generating new fibres.     

Sertoli cell proliferation and FSH signalling in African catfish, Clarias gariepinus

Sertoli cell proliferation occurs mainly during the phase of rapid spermatogonial proliferation, allowing the cyst-forming Sertoli cells to form an increasingly large space for housing the growing germ cell clone. There is no information in fish on the regulation of Sertoli cell proliferation; follicle-stimulating hormone (FSH) stimulates Sertoli cell proliferation in mammals. Increasing or decreasing FSH and FSH receptor expression experimentally in male African catfish was associated with respective changes in Sertoli cell proliferation or testis growth, suggesting that also in fish, one role of FSH may be to regulate Sertoli cell numbers.