哺乳动物下丘脑-垂体-卵巢轴的研究进展

哺乳动物的下丘脑、垂体和卵巢分泌的激素在功能上相互作用,构成一个完整的神经内分泌生殖调节体系,即下丘脑垂体卵巢轴,它在生殖活动中起着主要的调节作用。下丘脑中分布的GnRH神经元可以分泌GnRH,GnRH调节垂体中促性腺激素细胞分泌促性腺激素FSH和LH,促性腺激素作用于卵巢受体,引起雌激素和孕酮分泌并影响生殖活动。从组织学角度上研究,下丘脑垂体卵巢轴中的结构,如GnRH神经元、促性腺激素细胞、卵泡随周期性变化而呈现出不同的形态结构和分泌特点。因此,对以上各种细胞的研究是探讨其所分泌激素的基础,而下丘脑垂体卵巢轴中的各种激素的研究则是了解和控制动物繁殖机能的关键。     

下丘脑-垂体-性腺轴在调控鸡产蛋性能中的核心作用

产蛋性能是蛋鸡养殖的主要指标,鸡生殖系统发育以及体内内分泌激素分泌直接影响产蛋性能,而调控生殖激素分泌的中心是下丘脑-垂体-性腺轴(HPG)。文章以HPG为主体,论述了HPG调控的生殖激素及其作用机制(促性腺激素释放激素、促性腺激素抑制激素、促卵泡素、催乳素、促黄体素、雌激素、孕酮和雄激素)、影响HPG的因素(光照和药物)及其作用机理,为HPG调节鸡产蛋性能的研究提供参考。     

体外无血清培养牛垂体细胞分泌催乳素的调节—性腺激素的作用

本实验对牛垂体混合细胞进行24小时体外无血清培养,对其分泌催乳素的功能进行了观察,并分别在培养介质中加入0、1、10、100ng/ml的孕酮、脱氢表雄酮、雄烯二酮、雌二醇和睾酮,用放射免疫测定法测定培养液介质中催乳素含量,以研究这些性腺激素和中间产物对垂体细胞分泌催乳素的影响。结果表明:孕酮对离体牛垂体细胞无血清培养条件下分泌催乳素的功能没有影响。而脱氢表雄酮、雄烯二酮、睾酮和雌激素均引起催乳素分泌量显著升高,说明这些性腺类固醇激素对牛垂体细胞离体培养分泌催乳素具有促进作用,可能是垂体前叶催乳素分泌调节的重要组成部分。     

生殖机能的环境调节——生殖神经内分泌学机理

一、前言生殖机能受下丘脑—垂体—性腺(H—P—G)轴这神经内分泌系统的控制。由下丘脑产生并释放到垂体门脉系统的促性腺激素释放激素(GnRH或LHRH)促进垂体分泌促性腺激素(GTH),进而控制性腺活动。性腺分泌的性激素又反过来影响下丘脑和垂体功能,也就是说性腺激素通过正、负反馈调节     

促性腺激素释放激素及其类似物的功能与应用

促性腺激素释放激素（gonadotropin releasing hormone，GnRH）是主要由下丘脑合成的直链十肽激素，以脉冲形式分泌进入丘脑下部垂体门脉系统到达垂体前叶，或进入神经分泌轴突末端，调控垂体促卵泡激素（follicle-stimulating hormone，FSH）、促黄体素（1uteinizing hormone，LH）的合成与分泌。它是神经、免疫和内分泌调节系统相互联系的重要信号分子，与性腺和胎盘及生殖功能密切相关。     

促性腺激素细胞的研究进展

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。     

生长激素（GH）在雌性动物生殖中的作用

生长激素(GH)是调节动物生长和发育的重要激素之一。最近研究表明，GH也能调节类固醇的生成、配子的形成、性腺分化以及促性腺激素的分泌和应答，GH在繁殖上具有重要的作用。而且．其他一些组织，如性腺、胎盘和乳房组织中也能生成GH．并且以自分泌或旁分泌方式调节由垂体GH直接调节的一些过程。     

母猪性发育及性周期过程中外周血浆LH、FSH的分泌模式

母猪的性发育和性周期受到下丘脑－垂体－卵巢轴的调节，虽然下丘脑起着主宰作用，却受到主要由卵巢和腺垂体分泌的生殖激素的影响。ＬＨ、ＦＳＨ是由腺垂体分泌的促性腺激素，在调节性发育和性周期的过程中起着重要的作用。自从激素的放免方法建立以来，已能观察到性发育和性周期中促性腺激素的动态变化。１　性发育过程中ＬＨ、ＦＳＨ的分泌胎儿是非常活跃的激素生产单位，胎儿内分泌活动对分娩产生决定性的作用。妊娠晚期胎儿体内合成大量促性腺激素，并且带到出生后，因而仔猪刚出生后血浆中ＬＨ、ＦＳＨ浓度很高。Ｐｏｎｚｉｌｉｕｓ等…     

性激素“抑制素”的发现及其现状

性腺以甾类激素为信息载体,通过分泌变化把性腺情况传达到丘脑下部—垂体系,来自垂体的性腺激素(促卵泡成熟激素 FSH,促黄体生成素 LH)除对激素分泌方面发挥反馈作用外,分别促使末稍靶器官显示各器官特有的生物学作用,而使生殖功能顺利进行.性腺除分泌甾类激素外还分泌水溶性蛋白质激素(抑制素),这种假说早在二十世纪二十年代即已     

促性腺释放激素（GnRH）在畜牧业上的应用

哺乳动物的生殖过程受脑下垂体内分泌器官的控制。丘脑下部神经元分泌的肽类激素LH—RH和FSH—RH调节着垂体前叶两种促性腺激素LH(促黄体素又称促间质细胞激素)和FSH(促卵泡素,又称精子生成素)的合成和分泌。 1.GnRH的作用和研究简况 LH、FSH存在于生物体是1920年Zondek和Aschhein首先提出,1931年Feoold从垂体中分离出它们的混合体,1938年Hartman和Beng确定LH为糖蛋白。此后,经过大量的工作,到1972年,几个实验室分别报告了人、猪、牛、羊的LH和FSH的结构及其特性。研究表明:LH对雌性具有促进黄体发育、成熟及合成和分泌孕酮及雌二醇的作用;对雄性作用于间质细胞,促进睾酮的生     

Effect of sodium butyric acid, sodium valerianic acid, and osmolarity on contractility of specimens of intestinal wall obtained from the cecum and spiral colon of healthy cows

OBJECTIVE: To compare the effect of various concentrations of sodium butyric acid and sodium valerianic acid, as well as various osmolarities, on contractility of ex-vivo intestinal wall specimens obtained from the cecum and spiral colon of each of several healthy cows. SAMPLE POPULATION: Full-thickness preparations of intestinal wall, dissected parallel to the longitudinal smooth muscle layers, harvested from freshly slaughtered healthy cows. PROCEDURE: Specimens of intestinal wall were incubated for 5 minutes with various concentrations of sodium butyric acid and sodium valerianic acid as well as various osmolar concentrations of NaCl, using a crossover design. Isometric contractions were induced 7 times with carbachol (CH; 5 X 10(-6) mol/L). Contractility was defined as the maximum amplitude of contraction and the amplitude of contraction 2 minutes after addition of CH. RESULTS: Repeated addition of CH did not result in a significant effect on contractility of specimens from the cecum and spiral colon. Contractility after addition of CH was not significantly affected by prior incubation with various concentrations of sodium butyric acid or sodium valerianic acid or after an increase of osmolarity. Maximum amplitude of contraction was significantly higher in specimens from the spiral colon, compared with specimens from the cecum. CONCLUSIONS: Increases in concentrations of sodium butyric acid or sodium valerianic acid and increases in osmolarity did not inhibit contractility of intestinal wall specimens from the cecum and spiral colon of a group of healthy cows.     

丁酸钠对鱼类肠道消化吸收的影响研究进展

与畜禽等动物相比,鱼类消化系统不健全,消化酶活性低,而植物性原料中常含有抗营养因子和毒性成分等,易导致肠道损伤及肠炎等疾病。丁酸等短链脂肪酸可显著改善鱼类生长性能,增强鱼体健康及抗氧化和抗应激能力。因丁酸气味不佳,影响动物适口性,丁酸钠作为丁酸的替代物,呈固态且不易挥发,易于添加使用。丁酸钠可促进肠道上皮细胞发育,改善肠道形态结构,保持肠道黏膜屏障完整,对损伤的肠道黏膜加以修复,刺激上皮细胞内mRNA和蛋白质合成,加速肠上皮细胞增殖,增加绒毛高度,促进消化吸收。丁酸钠能破坏有害菌DNA结构,蛋白质不能合成,使有害菌不能进行正常分裂,抑制肠道有害菌的生长繁殖,促进有益菌群的增殖,维持肠道菌群平衡,菌群多样性显著提高。丁酸钠可通过刺激消化酶的分泌来改善鱼类消化,降低劣质蛋白原料对肠道损伤,抑制鱼肠道细胞凋亡,减少肠道炎症发生,显著改善鱼类肠道屏障的功能。丁酸钠还可用作生长促进剂及免疫刺激剂,在低鱼粉饲料中使用可降低饲料成本,促进鱼类生长发育。因此,丁酸钠是绿色安全可替代抗生素的添加剂,同时植物蛋白适当替代鱼粉可提高经济效益。作者就丁酸钠对肠道消化吸收功能的影响进行重点阐述,以期为鱼类等水产...     

丁酸对母猪繁殖性能的影响及其机制

母猪的繁殖性能直接影响着养猪业的经济效益。不可消化性碳水化合物在母猪后肠经微生物发酵可产生丁酸。研究发现，丁酸可通过调控卵泡、胚胎和乳腺的发育来提高母猪的繁殖性能。本文综述了丁酸对母猪繁殖性能的影响及其可能机制，分析了丁酸在母猪生产应用上存在的问题和未来发展方向。     

Butyric acid stimulates rumen mucosa development in the calf mainly by a reduction of apoptosis.

In ruminants the stimulation of papillar growth by butyric acid is well described but effects on mitosis and apoptosis are not known. To clarify the effect of short chain fatty acids three groups of three calves received a basic ration of 100 g hay per day for 6 weeks and additionally milk replacer. From these, two groups were fed with increasing amounts of the salts of either propionic acid (53 to 390 g) or butyric acid up to (54 to 326 g). The control group instead received an additional isocaloric amount of milk replacer. Mitosis was characterized by Ki67 immunoreactivity, apoptosis by a modified TUNEL assay and by electron microscopy. The feeding regimes led to significant differences of papillar length, increasing from 1.0 mm (controls) to 2.2 mm (propionic acid) and 4 mm (butyric acid). This enlargement was partly explained by an increased mitotic rate for the two fatty acid groups. The difference between the fatty acid groups was mainly explained by different apoptotic rates which were only one third for butyric acid compared to propionic acid (P < 0.001). In conclusion, butyric acid is a specific inhibitor of ruminal apoptosis in vivo.     

丁酸梭菌的功能性研究进展及其在畜禽生产中的应用

丁酸梭菌（Clostridium butyricum）又名丁酸梭状芽孢杆菌、酪酸梭菌,是一种产丁酸、乳酸和乙酸的厌氧异养的革兰氏阳性芽孢杆菌,具有耐高温、耐酸和耐多种抗生素等生物学特性。丁酸梭菌定植于畜禽肠道,可抑制肠道有害菌的生长,同时促进有益菌的增殖,有效提高畜禽对营养物质的消化吸收及其抵抗力,进而提高畜禽养殖经济效益。丁酸梭菌存在于土壤或健康动物的粪便中,具有绿色、无残留、安全性好,以及稳定性及耐药性强等特点,是一种具有广泛开发潜力的绿色添加剂。作者主要介绍了丁酸梭菌的特性,简述了其对畜禽肠道形态、肠道屏障、肠道菌群、免疫等方面的影响,回顾了近十年来丁酸梭菌在畜禽生产中的应用进展,并探讨了其在生产应用中的问题,以期为丁酸梭菌的进一步应用提供理论依据。     

Porcine intestinal yeast species,Kazachstania slooffiae,a new potential protein source with favourable amino acid composition for animals

There is little information about Kazachstania slooffiae which dominates among other yeasts in the pigs’ intestine. Therefore, the aims of this study were to characterise the yeast cell contents and to investigate which nitrogen sources, organic acids and alcohols may be utilised or produced by this species. The results showed that, K. slooffiae could use urea, ammonium sulphate, peptides and single amino acids and produce thereby ethanol and formic acid. However, this yeast did not metabolise amino acids, lactic, butyric, propionic and acetic acids as sole carbon source. Using a global metabolite profiling approach employing gas chromatography and high‐resolution liquid chromatography mass spectrometry, was found that the amount of peptides and dehydroascorbic acid considerably increased in the fermentation residues after yeast cultivation. It is noteworthy that the cells of K. slooffiae had higher contents of nitrogen and total amino acids (especially lysine) than the cells of nutritional yeast (Saccharomyces cerevisiae). This study indicates that due to potential production of peptides and formic acid in the intestinal tract, K. slooffiae might have an impact on the gut health. Moreover, from a nutritional standpoint, the cells of this yeast can be a good source of protein with useful amino acid composition for animal.     

Coated fatty acids alter virulence properties of Salmonella Typhimurium and decrease intestinal colonization of pigs

Salmonella Typhimurium infections in pigs are a major source of human foodborne salmonellosis. To reduce the number of infected pigs, acidification of feed or drinking water is a common practice. The aim of the present study was to determine whether some frequently used short- (SCFA) and medium-chain fatty acids (MCFA) are able to alter virulence gene expression and to decrease Salmonella Typhimurium colonization and shedding in pigs using well established and controlled in vitro and in vivo assays. Minimal inhibitory concentrations (MIC) of 4 SCFA (formic acid, acetic acid, propionic acid and butyric acid) and 2 MCFA (caproic and caprylic acid) were determined using 54 porcine Salmonella Typhimurium field strains. MIC values increased at increasing pH-values and were two to eight times lower for MCFA than for SCFA. Expression of virulence gene fimA was significantly lower when bacteria were grown in LB-broth supplemented with sub-MIC concentrations of caproic or caprylic acid (2 mM). Expression of hilA and invasion in porcine intestinal epithelial cells was significantly lower when bacteria were grown in LB-broth containing sub-MIC concentrations of butyric acid or propionic acid (10 mM) and caproic or caprylic acid (2 mM). When given as feed supplement to pigs experimentally infected with Salmonella Typhimurium, coated butyric acid decreased the levels of faecal shedding and intestinal colonization, but had no influence on the colonization of tonsils, spleen and liver. Uncoated fatty acids, however, did not influence fecal shedding, intestinal or tonsillar colonization in pigs. In conclusion, supplementing feed with certain coated fatty acids, such as butyric acid, may help to reduce the Salmonella load in pigs.     

甲酸对二色胡枝子青贮品质的影响

以二色胡枝子(Lespedeza bicolor Turcz.)为青贮原料,研究甲酸添加量(0、2、4、6 mL/kg鲜重)对其青贮品质的影响,以期为二色胡枝子的有效利用提供科学依据。结果表明:随甲酸添加量的增加胡枝子青贮料中pH值和氨态氮含量以及干物质损失率均呈降低趋势,而且贮料中的水溶性糖逐渐增加;添加甲酸能显著降低青贮料中NDF和ADF的含量(P<0.05);6mL/kg甲酸组对抑制青贮发酵效果最明显,有机酸产量最低;随甲酸添加量的增加,青贮料中丁酸的含量也增加,使青贮料的发酵品质有所降低。     

Modulation of post‐partum reproductive performance in dairy cows through supplementation of long‐ or short‐chain fatty acids during transition period

Thirty‐six cross‐bred cows were used to study the effect of long‐chain (flaxseed) or short‐chain (butyric acid) fatty acid supplementation on metabolic status, ovarian function and reproduction performance during transition period. Control cows received a routine feed of transition diet, while the cows in two treatment groups were supplemented with either 750‐g crushed flaxseed or 250 g butyric acid per cow per day. Ovarian activity was monitored by transrectal ultrasonography on 10th, 20th and 30th days post‐partum. Blood samples were collected by jugular venipuncture into heparinized polystyrene tubes; plasma was prepared and stored under ?20 °C until analysis. Results indicated that cows in flaxseed group were in positive energy balance as indicated by lower NEFA and Beta hydroxy Butyrate and higher glucose concentrations. Uterine involution was completed well within 30 days post‐partum in all the cows in flaxseed fed group compared to 76.9% in butyric acid supplemented and 61.5% in control groups. The size of dominant follicle and corpus luteum was significantly higher (p < 0.05) for flaxseed group compared to control group, which in turn resulted in higher concentrations of plasma progesterone. Cows fed on diets supplemented with flaxseed exhibited post‐partum heat earlier and bred sooner (p < 0.05) than control cows. It has been noticed that supplementation of flaxseed and butyric acid enhanced involution of uterus, early resumption of cyclicity and thereby early breeding. However, in view of the encouraging results obtained for flaxseed supplemented group, its organic nature and easier availability at farmer's gate, we concluded that flaxseed can be safely included in transition diet to modulate reproductive performance of dairy cattle.     

Investigations on the fermentation quality of silage from low-nitrate green forage]

In 3-year-experiments green forage from Dactylis glomerata and Festuca species, produced by differentiated cutting frequencies, was ensiled under laboratory conditions. The forage was almost without nitrate. Because of the higher content of water-soluble carbohydrates the fermentability coefficients of Festuca species were above of Dactylis glomerata. The fermentability coefficients of both plant species were inferior in the second and third cut, even if the first cut was delayed until July. Despite of similar fermentability coefficients of the two plant species silages contained different amounts of lactic and butyric acid. The portion of lactic acid amounted to 52 to 57% and 60 to 73% of total acids, the proportion of butyric acid 30 to 35% and 18 to 25% for Dactylis glomerata and Festuca species, respectively. According to the high fermentability coefficients silages free of butyric acid would be expected, however, by both species butyric acid always was formed, in some cases at high concentrations. In the contrary the amounts of ammonia, acetic acid and alcohol as well as the pH-value were almost extremely low. It can be concluded that the quality of silages produced of green forages with low nitrate cannot be assessed adequately by the current evaluation key.