对41年来激素、乳腺生长和泌乳研究综述（中）

催乳素 催乳素对乳腺的功用一直得到广泛的研究,1928年首次报道在兔乳腺叶泡发育完好的情况下注射兔垂体提取物能够立刻起动泌乳),该纯化的垂体提取物与催乳素分子相似,而且注射催乳素显著增加试验物种(尤其兔)乳腺叶泡发育,这是1958年以前的实验结果,后来研究发现对于怀孕老鼠以及牛当乳腺发育加快时血清中催乳素含量并不随之持续增加,结果似乎妊娠期催乳素不能促进乳腺发育,但是正如前文所述在没有催乳素或者     

植酸对鱼类生长的影响

植酸存在于所有粮食作物和油料作物中 ,是豆饼、菜籽饼、棉籽饼等植物蛋白饲料的抗营养的因子。印度水产科研人员测定了植酸对鲮鱼生长、蛋白质效率、饲料转换率和鱼体组成的影响。试验用露斯塔鲮鱼体长 2 .5～ 3.5ｃｍ ,水温 18～ 2 2℃。分别投喂含蛋白质 4 0 %、含热量 18.0 7ｋＪ/ ｇ、含植酸0 .5、1.0、1.5、2 .0、2 .5 %的饲料 ,日投饵率为鱼体重的 4 %、日投饵 2次。测出投喂不含植酸的对照组饲料的鱼增重 (94 .87% )、特定生长率 (1.5 8)、蛋白质效率 (2 .0 2 )和饲料转换率 (1.2 1)最高 ,而投喂植酸含量在 1%以上饲料的鱼增重和特…     

河西绒山羊血清中催乳素浓度季节性变化及其与山羊绒生长的相关性分析

选20只(公母各半)6月龄、平均体重在15.21kg±0.61kg的河西白绒山羊作为试验羊只,颈静脉采血,放射免疫法测定血清中催乳素(PRL)的浓度。结果表明:被测公、母山羊PRL平均浓度分别为817·38u/mL±269·51u/mL、778.08u/mL±187.21u/mL,性别间无明显差异(P>0.05);绒山羊血清PRL浓度呈明显的季节性变化,5月开始上升,至8月底达最高峰(1259.50u/mL±410.61u/mL);9月份则显著下降,此后呈波动性变化并维持在较低水平(613.08±55.18~780.67±127.77u/mL)。在山羊绒主要生长期(8、9、10月),山羊血清PRL平均浓度与绒毛生长速度呈负相关,说明催乳素是影响绒山羊绒毛生长的重要因素之一。     

化学引诱剂对鱼类的促生长作用

要提高水产动物的产量就得增加水产动物的饲料摄取量。这是提高鱼和甲壳类水产动物生长速度的捷径。虽然,水产动物快速繁殖的研究工作正在取得进展。但实际上,时至今日在鱼种遗传特性上仍未取得什么突破。因此,通过优化饲料配方,改善水体环境条件,增加鱼类饲料摄入量乃是提高鱼类生长速度的常用方法。工业水产养殖饲料系按配方精加工而成,营养成分充足,齐全。然而,由于种种原因,饲料却不能为鱼类以     

鱼类的补偿生长现象与启示

<正>在生长过程中,鱼类常常会受到饥饿、营养不足或者其它各种不良环境条件的胁迫,导致其生长速度下降,体重低于未受胁迫的正常个体。当胁迫消失后,在一定时间内,鱼类的生长速度加快,体重会赶上甚至超过正常个体,这表明鱼类出现了补偿生长。补偿生长现象在鱼类中普遍存在,例如,草鱼、鲫鱼、鲤鱼、鳊鱼、黄颡鱼、鲟、黄鳝、长吻鮠等淡水养殖鱼类,鲑、鳕鱼、鲽、鲆、鳎等海水养殖鱼类都具有不同程度的补偿生长能力。补偿生长的产     

催乳素基因转录调控及其在鸡中多态性与表达关系的研究

催乳素作为一种多功能多肽类激素,广泛分布在各种脊椎动物中.在鸟类中,催乳素具有调节渗透压、促进嗉囔分泌嗉囔乳、调节代谢、引起就巢、抗促性腺等功能.近年来,国内外在转录水平上对禽催乳素基因表达进行了一些研究[1,2],探讨了催乳素基因在不同的环境中mRNA的表达量以及在血液中的激素浓度,并证明了家禽就巢性与催乳素分泌量增加有关.     

禽类催乳素基因的研究概况

催乳素（Prolactin,PRL）是由单基因编码23KD的多肽类激素,几乎存在于所有脊椎动物中,主要由垂体前叶嗜酸细胞分泌的,也可由各种免疫细胞、妊娠子宫蜕膜及皮肤细胞等合成和分泌。禽类催乳素前体含229个氨基酸,其中包括30个氨基酸的信号肽序列和199个氨基酸的PRL成熟蛋白.催乳素具有广泛的生理功能,它不仅具有调节生殖系统的重要作用,还具有调节体内渗透压平衡、内分泌、代谢和免疫系统,引起就巢等功能。     

鱼类的生长模型及其在营养需求研究中的应用

<正>以统计分析方法对鱼类的生长、营养需求进行研究并建立生长模型,可以得到更准确、更科学的数据。通过对鱼类生长模型的分析研究,不仅可以动态地了解鱼类的生长过程,预测鱼类的生长规律,而且在鱼类营养需求研究中的应用也非常广泛。     

A proteomic analysis of the effect of growth hormone on mammary alveolar cell-T (MAC-T) cells in the presence of lactogenic hormones

The bovine mammary alveolar cell-T (MAC-T) cell line is able to uniformly differentiate and secrete casein proteins in response to dexamethasone, insulin, and prolactin and is extensively used to study bovine mammary epithelial cell (MEC) function. Somatotropin, or growth hormone (GH), has been shown to increase milk protein synthesis both in vivo and in mammary cell models and to induce cytoskeletal rearrangement in a 3T3 fibroblast cell line and a Chinese hamster ovary cell line. To identify the nature of the effects of GH in MECs cultured with lactogenic hormones, changes in global protein expression were assessed in the MAC-T cell line with the use of two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization tandem time of flight mass spectrometry. Forty proteins were differentially expressed in response to GH (P < 0.05) and were related to metabolism, the cytoskeleton, protein folding, RNA and DNA processing, and oxidant stress. These widespread changes in protein expression are indicative of a global role of GH in overall cellular differentiation that may underlie the direct modulation of milk component synthesis in MEC models that have been described to date.     

Growth hormone and lactogenic hormones can reduce the leptin mRNA expression in bovine mammary epithelial cells

Leptin mRNA is expressed in not only adipocytes but also mammary epithelial cells and leptin protein is present in milk. Although milk leptin is thought to influence metabolism or the immune system in neonates, there is little information about the regulation of leptin expression in mammary epithelial cells. We examined the effect of growth hormone (GH) and/or lactogenic hormone complex (DIP; dexamethasone, insulin and prolactin) on leptin mRNA expression in mammary epithelial cells. We used a bovine mammary epithelial cell (BMEC) clonal line, which was established from a 26-day pregnant Holstein heifer. We confirmed that the mRNA was expressed in BMECs and the expression was significantly reduced by GH and/or DIP, when the cells were cultured on both plastic plates and cell culture inserts at days 2 and 7 after stimulation with lactogenic hormones. GH and/or DIP significantly increased level of alpha-casein mRNA in BMECs after 7 days on the cell culture inserts, but no mRNA expression was detected at day 2. GH and DIP significantly stimulated the secretion of alpha-casein from BMEC on cell culture inserts at 3.5 and 7 days. However, neither alpha-casein mRNA expression nor secretion was observed in the BMECs cultured on plastic dishes, even in the presence of GH or/and DIP. These results indicate that GH and DIP can directly reduce leptin mRNA expression in both undifferentiated and functionally differentiated bovine mammary epithelial cell.     

Analogs of growth hormone-releasing hormone induce release of growth hormone in the bovine

Biological potencies of three 29 amino acid growth hormone-releasing hormone analogs (GHRH[1-29]) were determined in the bovine and compared to synthetic human GHRH (44 amino acids; hGHRH[1-44]NH2) for their ability to increase serum growth hormone (GH) concentrations. Four prepubertal Holstein heifers (179 +/- 10 kg) received hGHRH(1-44)NH2 or analogs (D-Ala2, Nle27, Agm29 GHRH[1-29], [JG-73]; D-N-MeAla2, Nle27, Agm29 GHRH[1-29], [JG-75]; and desamino-Tyr1, D-Ala2, Nle27, Agm29 GHRH[1-29], [JG-77]) at the following doses: 0, 6.25, 25, 100 and 400 micrograms/animal. All treatment-dose combinations were administered to each heifer with at least a 1-d interval between treatments. Sixteen blood samples were collected via jugular cannulas 20 min before and up to 6 h after treatment injection. There was a linear dose-dependent GH release in response to hGHRH(1-44)NH2 and the three analogs. Growth hormone peak amplitudes for the three analogs were similar to those observed after administration of the hGHRH(1-44)NH2 (P greater than .05). However, when total area under the GH response curves for each treatment was averaged over all the doses, JG-73 stimulated greater GH release than hGHRH(1-44)NH2 (P less than .05) Heifers injected with the 400-microgram dose of hGHRH(1-44)NH2 or the three analogs showed a primary release of GH followed by a secondary release 1 h later. At all other doses, only a primary GH release was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of swine growth by porcine growth hormone

Highly purified porcine growth hormone (pGH; USDA-B1) was administered by im injection (22 micrograms X kg body weight-1 X d-1) to rapidly growing Yorkshire barrows for 30 d. Growth hormone significantly increased growth rate (10%), feed efficiency (4%), cartilage growth and muscle mass. However, pGH did not affect carcass adipose tissue mass. Intramuscular lipid content of the longissimus was increased 50% by pGH administration. Plasma pGH concentration was elevated (7- to 11-fold) for 3 to 5 h post-injection. Chronic administration of pGH depressed pituitary GH content and concentration approximately 45%. No GH antibodies were detected in the plasma of GH-treated swine. Plasma somatomedin-C concentration was increased 55% by GH treatment 3 h post-injection. Plasma glucose and insulin concentrations were both significantly increased in GH-treated swine, suggesting that the animals had developed a state of insulin resistance. Plasma-free fatty acid concentration tended to be higher in GH-treated animals. Treatment of swine with pGH significantly decreased plasma blood urea nitrogen. Assessment of animal health during the trial and postmortem indicated that pGH administration did not have any adverse effects. In summary, treatment of young, rapidly growing swine with pGH stimulated growth performance without affecting animal health or inducing the production of GH antibodies.     

Use of growth hormone response to growth hormone-releasing hormone to determine growth potential in beef heifers.

The response of GH to GHRH at weaning is known to predict postweaning growth and body composition in beef bulls. The objective of this study was to determine whether GH response to a challenge of GHRH and plasma IGF-I can predict growth rate and body composition in the beef heifer. Growth hormone response to a challenge with two doses of GHRH was measured in 67 Angus heifers averaging 225 d of age (SD = 21) and 217 kg BW (SD = 32). Blood samples were collected at 0 and 10 min relative to an initial "clearance dose" (4.5 micrograms GHRH/100 kg BW) and again, 3 h later, relative to a challenge dose (1.5 or 4.5 micrograms GHRH/100 kg BW). Each animal received each of the two challenge doses, which were randomly assigned across 2 d of blood collection. Serum GH concentration was measured by RIA. Plasma was collected every 28 d during a 140-d growth test and assayed for IGF-I by RIA. Body weight was measured every 28 d and hip height was measured at weaning and at the end of a 140-d growth test. Average daily gain was calculated on d 140 of the growth test and body composition measurements were estimated by ultrasound 2 wk after completion of the growth test. Responses to the two GHRH challenges were dose-dependent (P < 0.05). Average daily gain tended to be related to GH response to the 1.5 micrograms GHRH/100 kg BW dose (R2 = 0.05; P = 0.06), but no relationship was observed at the 4.5 micrograms GHRH/100 kg BW dose (R2 = 0.00; P = 0.93). An inverse relationship (R2 = 0.06; P = 0.02) was observed between response to the 1.5 micrograms GHRH/100 kg BW dose and intramuscular fat percentage. Mean plasma IGF-I concentration was positively associated with ADG (R2 = 0.06; P < 0.01). Growth hormone response to GHRH is modestly related to body composition but not to ADG in weanling beef heifers and likely has limited use in evaluation of growth performance in replacement beef heifers.     

关于在鱼饵料中添加激素有关问题的探讨

近几年来,随着养鱼业的利润逐渐下降,养鱼户希望能够找到一个饵料成本相对较低的鱼饵料的心情与愿望是可以理解的,然而愿望毕竟是愿望,鱼因受品种、遗传因素、环境等限制不能达到人们的期望值。为此,有些饲料厂家为了满足这部分养鱼户的心理,也为了降低鱼饵料的生产成本,非法追求暴利,不讲职业道德,不顾人们的身体健康,不顾政府的严格限制,在鱼饵料中大量添加激素和抗生素。 添加激素的鱼饵料,前期投喂时,鱼确实较喜食,而且增速较明显,但是它给鱼的免疫、疾病等的负作用很大,其危害性有以下几个方面:     

Predicting bull growth performance and carcass composition from growth hormone response to growth hormone-releasing hormone.

Development of practical, physiologically based methods that provide an early, yet accurate, evaluation of a bull's genetic merit could benefit the beef industry. The use of GH response to a single, acute dose of GHRH was evaluated as a predictor of future growth performance and carcass characteristics of weanling bulls. Fifty-six Angus bulls averaging 229 d (SD = 27) of age were administered three doses i.v. (0, 1.5, and 4.5 microg/100 kg BW) of human GHRH (1-29) analog in a Latin square design balanced for residual effects. Blood samples were collected via jugular catheter at -60, -45, -30, -15, 0, 5, 10, 15, 30, 45, 60, 90 and 120 min relative to GHRH injection. Serum concentrations of GH were plotted over time. Response to GHRH was calculated as the area under the GH response curve (AUC-GH) using the trapezoidal approximation. Relationships between AUC-GH, weaning weight adjusted to 205 d of age (205-d WW), and direct weaning weight EPD (WWEPD) versus age-adjusted BW (BWadj), ADG, and carcass measurements from a 140-d growth performance test were evaluated using simple linear regression. A positive correlation between AUC-GH and ADG and an inverse relationship between AUC-GH and carcass fat were observed. The present study provides evidence that AUC-GH is a better predictor of future growth performance in beef bulls than 205-d WW or WWEPD values. Thus, GH response to GHRH is associated with subsequent growth and may be a useful tool for sire selection in beef production.     

Relation of growth hormone response to growth hormone-releasing hormone before weaning and postweaning growth performance in beef calves

Previously, GH response to GHRH challenge at weaning has been shown to be indicative of ADG during a standard postweaning growth performance test in Angus cattle. In this study, we tested the hypothesis that GH response to GHRH before weaning would predict postweaning ADG. Bulls with the highest and lowest GH responses to GHRH over a 3-yr period, relative to their contemporaries, were used as sires, to allow for examination of the persistence of GH response to GHRH through selection. The selected calves in this study were sired by one of four Angus bulls chosen based on their GH response to GHRH (high response, n = 2; low response, n = 2). Forty-nine Angus calves (bulls, n = 24; heifers, n = 25) were challenged with GHRH at approximately 60, 105, and 150 d of age and at weaning (219 d; SD = 25). Blood samples were taken immediately prior to and 10 min following an i.v. clearance dose of 4.5 microg of GHRH/100 kg BW and, 2 h later, immediately prior to and 10 min following a challenge dose of either 1.5 or 4.5 microg of GHRH/100 kg BW. Two hours later, the procedure was repeated, with each calf receiving the other challenge dose. Body weight was measured every 28 d and ADG was calculated over a 140-d growth performance test (heifers and bulls maintained separately). Data were log-transformed for statistical analyses. In the selected bulls and heifers, response of GH to 1.5 microg of GHRH/100 kg BW at 60 and 105 d of age was positively related (P < 0.05) to postweaning ADG. Response to 4.5 microg of GHRH/100 kg BW at 105 d of age and at weaning was positively related (P < 0.01) to postweaning ADG. Inclusion of sire in the analysis improved the relationship between GH response and ADG for calves of sires with high GH responses from R2 = 0.18 (P = 0.01) to R2 = 0.33 (P = 0.02). When the GH response to GHRH of the unselected calves at weaning was added to the data from the selected animals and analyzed, the GH response of the bulls was related to postweaning ADG (R2 = 0.09; P = 0.04). In conclusion, GH response to GHRH as early as 60 d of age is indicative of postweaning ADG in beef cattle. In addition, the relationship between GH response to GHRH and postweaning ADG is improved with selection for greater GH response to GHRH.     

Effects of growth hormone and gonadotrophin releasing hormone antagonists on ovarian follicle growth in sheep

Our objective was to determine the effects of the administration of growth hormone (GH) alone or plus teverelix, a gonadotrophin releasing hormone antagonist (GnRHa), on follicle development in sheep. Ewes were treated daily for 6 days by the intramuscular route with 15 mg of GH alone (GH group; n = 6) or combined with two subcutaneous doses of GnRHa (1.5 mg) on days 0 and 3 of GH treatment (GH/GnRHa group; n = 6); the control group (n = 6) received similar treatment with saline solution. Plasma follicle stimulating hormone levels were significantly lower in the GH/GnRHa group than in the control (P < 0.001) and GH groups (P < 0.05). The number of follicles > or =2 mm increased to reach significant differences with control (18.7 +/- 0.6) on day 4 in GH/GnRHa group (22.7 +/- 0.5, P < 0.001) and on day 5 in GH group (20.3 +/- 0.4 vs. 17.0 +/- 0.6, P < 0.05). These results indicate that GH and GnRHa may be useful for increasing the number of gonadotrophin-responsive follicles in the ovary. However, follicle function could be affected as both GH and GH/GnRHa groups showed lower plasma inhibin A concentrations than control sheep (90-110 pg/mL vs. 170-185 pg/mL, P < 0.005).