泌乳调控机理与生长抑素基因疫苗的应用

本文综述了泌乳调控机制和催乳素、生长激素、生长抑素与泌乳的关系,介绍了生长抑素基因疫苗的研制与应用情况。     

奶牛泌乳调控研究进展

泌乳生理一直是人们研究的重要领域。伴随着分子生物学、生殖生物学等相关学科的发展,人们不断利用已有知识提高奶畜泌乳性能。已有不少技术进入商业应用,并已在奶业生产中取得显著效果。近年来,对生长激素(ＧＨ)、生长激素释放因子(ＧＲＦ)、甲状腺素、胎盘促乳素、促生长素抑制素(ＳＲＩＦ)等生物活性物质调控泌乳活动的研究与应用十分活跃。1　生物活性物质与泌乳调控1.1　生长激素牛生长激素(ＢＳＴ)是一种垂体前叶分泌的蛋白质激素,具有调节乳腺活动,提高泌乳量的功能。ＢＳＴ的安全性已得到承认,并在南非、捷克、俄罗斯等国认可使用,…     

奶牛泌乳启动调控激素的研究进展

哺乳动物泌乳启动都是在一系列激素的调控作用下完成的。奶牛的泌乳启动受到多种激素的共同调控,处于非妊娠期的奶牛乳腺在经过特定激素的刺激后,都会在一定程度上出现泌乳现象。本文对奶牛催乳素PRL、雌激素E、胰岛素INS、生长激素GH和孕酮P4与泌乳启动的关系进行了综述,为研究泌乳启动和奶牛产奶量等提供重要理论基础。     

动物生长轴的激素调控

1　生长轴动物生长是一个复杂的生物代谢过程 ,受基因型、激素、营养、环境等多方面的影响。这些因素对生长的影响作用都是通过直接或间接影响动物内分泌系统来实现的。人和动物的生长是由促生长激素轴来调控的 ,促生长激素轴由生长激素释放因子 (GRF)、生长激素 (GH)和胰岛素样生长因子 (IGF)构成 ,其中生长激素是调控整个机体生长的最重要的激素。生长轴是动物体内从下丘脑———垂体———靶器官的一系列激素及其受体所组成的神经内分泌系统 ,如图 1所示。注 :GRF :生长激素释放因子　SS :生长抑制激素　　GH :生长激素　IGF :胰…     

山羊生长激素基因的研究及其应用现状

动物生长激素是由垂体前叶分泌的一种蛋白类激素,由190～191个氨基酸残基组成,它是影响动物生长、泌乳、繁殖以及新陈代谢诸过程的重要因素.其作用是促进动物生长和碳水化合物代谢、葡萄糖的吸收、脂肪分解及核酸、蛋白质的合成.生长激素基因是控制生长激素分泌水平,调节动物生长发育的主效基因,文章综述了生长激素基因的结构、表达调控以及在山羊中的研究及其应用.     

利用生长轴各激素调控动物生长

动物生长受到多种激素的调控,其中生长激素能促进胰岛素样生长因子的合成,促使组织细胞的生长与分化,增加动物体蛋白合成,降低脂肪沉积,提高瘦肉率;生长抑素抑制生长激素的分泌,从而抑制动物的生长;而生长激素释放因子促进生长激素的分泌,有利于动物的生长;胰岛素样生长因子Ⅰ能促进动物的细胞分化、泌乳、繁殖以及代谢等;新近发现的Ghrelin是生长激素促分泌素受体的内源性配体,起促生长激素释放作用。通过对上述各种激素的调控可在一定程度上提高动物的生长。     

母牛施用生长激素对营养需要量的变化

具有优良遗传价值的泌乳母牛,其最显著特征之一是能够在泌乳早期为泌乳动用体能贮备。产乳量的最高遗传特征在当今乳用母牛中极为广泛,每头母牛每年产乳量多达20000磅已是普遍现象。牛生长激素(BST)的出现将产乳量迅速推向更高水平。预计在今后2年内,生长激素将在商业上使用。在广泛应用前,急待搞清的营养问题是:生长激素的施用将对泌乳母牛的营养需要量有何影响,配合日粮如何变化以确保生长激素施用的成功。     

泌乳的免疫调控研究进展

奶牛的泌乳受到以生长激素为核心的内分泌体系的调控。自２０世纪７０年代以来，随着对动物生理了解的深入和生物技术的迅速发展，在通过调控内分泌体系促进泌乳方面取得了重大成就，最典型的例子就是牛重组生长激素的应用使奶牛的产奶量平均提高了２０％。但是，直接使用外源激素至少面临两方面的问题：１）蛋白质或肽类激素不便于在动物体内长期贮存，尽管有一些缓释形式的产品出现，仍须多次重复使用；２）消费者对激素存在普遍的畏惧心理，使用外源激素容易引起部分消费者减少对奶的消费。另一种调控选择是利用免疫调控技术强化动物内分…     

生长激素及其受体基因多态对牛泌乳性能影响的研究进展

本文以牛泌乳性能重要候选基因生长激素及生长激素受体基因为对象,揭示了泌乳性能候选基因的分子育种意义,描述了生长激素在牛生产中的应用历史及生长激素基因影响产奶量的分子机理,介绍了国内外该两种基因多态性对牛泌乳性能影响的研究以及国内外奶牛业分子育种的研究热点,最后对牦牛分子育种进行了展望。     

泌乳牛皮下注射生长激素能通过调控mRNA翻译的启动及延伸阶段增加乳蛋白的产量

目前,对控制家畜乳和乳蛋白产量的潜在分子机制研究还不是很清楚。因此,本试验以外源生长激素泌乳反应为模型,旨在研究乳腺中翻译启动及延伸阶段在乳蛋白合成中的作用。试验选用8头泌乳奶牛,4头经皮下注射商业缓释生长激素（生长激素组）,4头经皮下注射盐水（对照组）。以实时定量PCR和免疫印迹技术研究乳腺组织中雷帕霉素标靶（mTOR）关键成分mRNA转录水平和磷酸化状态。研究结果显示,生长激素处理增加了核糖体蛋白S6的磷酸化状态,提高了真核启动因子4E（eIF4E）和真核延伸因子（eEF2）的蛋白质丰度,暗示乳蛋白合成与mRNA翻译调控有关。     

Endocrine regulation of fetal and postnatal meat animal growth

Evidence is discussed which indicates that nutrient partitioning between muscle and adipose tissue can be altered by growth hormone administration in meat animals. In the limited number of studies conducted with meat animals, growth rate, feed efficiency and carcass composition were improved by growth hormone administration. When insulin was administered to normally growing swine no improvement in growth performance was observed. The mechanisms by which growth hormone affects growth performance are not clear but considerable data from rodent studies exist to indicate that many of the growth promoting effects of this hormone are due to somatomedins. However, few data are available for meat animals to indicate whether the growth promoting effects of growth hormone are mediated by somatomedins. Knowledge about the mechanisms that regulate growth hormone synthesis, secretion and biological action is accumulating. It is apparent that growth hormone administration induces an insulin-resistant state in rodents and meat animals. It is not clear whether chronic growth hormone administration in meat animals induces a growth hormone resistant state. Based on the available information, manipulation of systemic hormone concentrations and(or) tissue sensitivity to hormones involved in growth and differentiation may result in means to manipulate fetal and postnatal growth and development.     

生长激素受体介导的信号转导机制研究进展

生长激素(growth hormone,GH)对动物的生长发育具有重要的生理作用.GH与生长激素受体(growth hormone receptor,GHR)结合后才会发挥一系列的生理作用.近年来,人们对GHR结构和功能的研究取得了巨大的进展,并取得了一些重大的突破.现在已清楚了GH-GHR轴激活一些相关的信号转导通路,但并非所有的通路都依赖酪氨酸激酶.作者从以下几个方面总结了GHR作用下的信号转导机制的研究进展:GHR的结构与功能;依赖JAK2的相关信号通路;不依赖JAK2的相关信号通路;GHR信号负调控因子.阐明这些复杂机制,对进一步了解GH对动物不同的生理和病理作用具有重要意义.     

Central role of insulin in growth and development

Insulin has been shown to have an impact on both prenatal and postnatal growth. Specific mechanisms of insulin action on adipose cell function and lipid storage are well defined. Insulin probably acts in concert with other anabolic factors (i.e., growth hormone and somatomedins) to stimulate muscle protein anabolism and suppress protein catabolism (Figure 2). Insulin also plays a role in energy balance regulation by the hypothalamus, however exact mechanisms of effects on brain metabolism have not been clearly identified.     

Growth and skeletal development in the dog in relation to nutrition; a review

Summary

Longitudinal growth of the appendicular skeleton in the growth plates and the adjacent metaphyseal area includes chondrocyte differentiation, proliferation, maturation, and hypertrophy in the physis and bone (re‐)modelling in the metaphysis. The rate and extent of longitudinal growth are regulated by interactions between biomechanical factors and endogenous growth regulators, i.e., systemic endocrine factors, and local paraor autocrine factors, that act on the growth plate chondrocytes. The most important endogenous regulators of growth and skeletal development are growth hormone (GH) and insulin‐like growth factors (IGFs), and calciotropic hormones, i.e., parathyroid hormone (PTH), vitamin D (vitD), and calcitonin (CT).

The biochemistry, synthesis, secretion, target organs, and effects of these endogenous factors are reviewed, and the calcium homeostatic mechanisms, dietary intake, bone turnover, and calcium excretion are discussed. Energy, protein, and calcium are nutritional factors of great importance to (skeletal) growth. The effects of low and high dietary intake of these nutrients are discussed, especially with reference to longitudinal growth and disturbances in endochondral ossification.     

Ovarian Follicular Dynamics. A review with Emphasis on the Bovine Species. Part II: Antral Development,Exogenous Influence and Future Prospects

During an oestrous cycle, a cohort of antral follicles develops into – depending on the species – one or more ovulatory follicles. The bovine oestrous cycle is characterized by two to three such cohorts or growth waves, only the last of which will result in an ovulation. In every growth wave, several antral follicles are recruited for development. Recruited follicles are subjected to a selection process, whereby ever decreasing levels of follicle stimulating hormone (FSH) are available to the FSH dependent follicles. In the cow, a single follicle from the cohort will acquire dominance. The ability of the dominant follicle to prosper under basic FSH levels is ascribed to a transition in hormone dependency from FSH to luteinizing hormone. The exact follicle selection mechanism remains, however, to be elucidated. The beginning of this article focuses on the recruitment, selection and dominance phases in antral follicle development. Subsequently, the conditions leading to successful maturation and ovulation are discussed. The next section expounds upon the mechanisms for exogenous modulation of follicular dynamics with the aim of superovulation/superstimulation, and finally prospective future research directions are sketched.     

The role of the somatotrophic axis in the metabolism of the chicken.

As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and development of avian species. In contrast to mammals, exogenous GH administration has little, if any, potential for improving the growth rate and feed efficiency of rapidly growing broilers; it is more likely to do so in older birds. This is at least partly because of age-related changes in tissue GH-binding activity and GH-receptor mRNA expression. The effects of GH on lipid deposition depends on the age of the bird and pattern of GH administration. Pulsatile, but not continuous, GH administration to older broilers seems to reduce fat deposition. As in rats, the bioactivity of GH might also depend on the pulse-induced cyclicity in GH receptors and GH-binding proteins. In chickens, GH is also a very potent lipolytic hormone, but seems to have no diabetogenic effect, which is reported in mammalian species. Both insulin-like growth factors have apparently no growth-promoting effects in normal growing broilers, but seem to have opposite effects on fat deposition. In contrast to GH, both insulin-like growth factors have a marked hypoglycemic effect. Whether all these effects are direct effects, or are mediated by secondary mechanisms, awaits further investigations.     

Role of the somatotropic axis in the mammalian metabolism

The metabolism in mammalian is regulated by multiple levels of hormone action, with complex feedback and control mechanisms. The somatotropic axis, essentially consisting of growth hormone (GH), insulin-like growth factors (IGF-I and -II), their associated carrier proteins, and receptors, plays a key role in the control of the regulation of metabolism and physiological process. Among this axis, other hormones like insulin, leptine, glucocorticoids or thyroid hormones are involved in this mechanism by modulating GH and/or IGF-I synthesis and availability. This review summarizes the complexity of the regulation of the metabolism by the somatotropic axis using different examples such as special nutritional situations or growth promoters administration.     

动物生长激素与肉畜生产

本文综述了动物生长激素在肉畜生产中的作用、机制以及影响激素作用的因素。研究表明：生长激素能提高猪、牛、羊的日增重及饲料利用率,增加体蛋白合成,降低脂肪沉积。但生长激素作用的效果受使用的剂量、动物及日粮等因素影响。目前认为生长激素作用机制是：生长激素通过调节物质代谢, 提高蛋白质的合成速度, 抑制脂肪酶的活性,从而降低脂肪的合成。此外,生长激素还通过刺激机体产生ＩＧＦ－Ｉ（ 类胰岛素生长因子－ Ｉ） ,促进肌细胞生长。     

Control of reproductive processes by growth hormone: extra- and intracellular mechanisms

Recent data on the association between growth hormone (GH) and male and female reproductive processes, as well as the effects of GH on these processes and on some reproductive and non-reproductive disorders, and possible extra- and intracellular mediators of its action are reviewed. The available data suggest that GH is an important endocrine and autocrine/paracrine regulator of reproduction. It controls proliferation, apoptosis, growth and differentiation and the secretory and generative activities of different reproductive organs. It also regulates their response to gonadotrophin-releasing hormone (GnRH) and gonadotropins. Despite the effects of GH on the IGF/IGFBP (insulin-like growth factor binding protein) system, oxytocin, steroids, activin, gonadotropin and gonadotropin receptors, the majority of GH's actions on the reproductive processes are probably mediated not by these substances but by specific GH receptors acting through cAMP/protein kinase A, protein kinase G, tyrosine kinase-, MAP kinase and CDC2 kinase-dependent intracellular mechanisms. Although GH treatments can increase the risk of some reproductive and non-reproductive disorders, they may be useful in improving gonadal function, inducing superovulation and in embryo production.