IGF—I在胃肠道中的稳定性及其对肠道生长发育的影响

IGF—I是乳中存在的一种重要的生长促进因子，特别是初乳中含量更高。人们普遍认为，母乳中的IGF—I可能对产后哺乳幼畜的生长发育起重要的调节作用，尤其是与其直接接触的胃肠道，而IGF—I在胃肠道中稳定性又是关系其功能发挥的前提条件。本文综述了IGF—I在胃肠道中的稳定性及其对肠道生长发育的影响。     

塞曼特罗(Cimaterol)对大鼠肝细胞氮代谢及6-磷酸葡萄糖脱氢酶活性的影响

利用原代肝细胞培养技术测定了塞曼特罗 (Cimaterol,CIM,1× 10 - 6 m ol)对大鼠肝细胞氮代谢和 6 -磷酸葡萄糖脱氢酶 ((G- 6 - PDH)活性的影响。结果表明 ,CIM可影响大鼠肝细胞中尿素氮的浓度 ,与对照组相比 ,CIM试验组培养液中尿素氮水平下降了 2 3.87% (P<0 .0 5 ) ,且 CIM的这种作用可被 β-受体阻断剂心得安 (PRO,1× 10 - 6 m ol)所阻断。CIM也可增加 3H-亮氨酸掺入肝细胞的量 ,与对照组相比 ,其幅度提高了 19.77% (P<0 .0 5 ) ;同样 ,PRO可抑制这种作用。CIM还具有增加大鼠肝细胞产生 IGF- 的趋势 ,但与对照组相比无明显影响 (P>0 .0 5 )。CIM对大鼠肝细胞G- 6 - PDH活性有显著影响 ,试验组肝细胞中 G- 6 - PDH活性与对照组相比下降了 4 3.36 % (P<0 .0 5 ) ;CIM引起的肝细胞 G- 6 - PDH活性下降的作用也可被 PRO所阻断。结果提示 ,CIM可通过增强大鼠肝细胞氮素的保留和蛋白质的合成 ,以及通过抑制肝细胞 G- 6 - PDH活性 ,影响脂肪代谢 ,从而调节机体的生长发育     

家禽胰岛素样生长因子-I基因与生产性能相关研究进展

胰岛素样生长因子-I是胰岛素样生长因子家族的成员,是生长激素发挥促生长作用的主要介导因子.本文介绍了家禽的IGF-I结构,阐述了当前IGF-I在组织中的表达水平、基因多态性与家禽经济性状相关的研究现状.     

Increased degradation of insulin-like growth factor-I in serum from feed-deprived steers

Severe feed restriction decreases serum insulin-like growth factor I (IGF-I) concentration in animals, and this decrease is thought to be due to reduced IGF-I production in the liver. The objective of this study was to determine whether feed deprivation also increases degradation of serum IGF-I and serum levels of IGF binding protein 3 (IGFBP-3) and acid-labile subunit (ALS), which inhibit IGF-I degradation and increase IGF-I retention in the blood by forming a ternary complex with IGF-I, in cattle. Five steers had free access to pasture, and another five were deprived of feed for 60 h. Serum concentration of IGF-I and liver abundance of IGF-I mRNA at the end of the 60-h period were 50% and 80% lower, respectively, in feed-deprived steers than in fed steers. Less ¹²⁵I-labeled IGF-I remained intact after a 45-h incubation in sera of feed-deprived steers than in sera of fed steers, suggesting that serum IGF-I is more quickly degraded in feed-deprived animals. Serum levels of IGFBP-3 and ALS were decreased by 40% and 30%, respectively, in feed-deprived steers compared with fed steers. These decreases were associated with more than 50% reductions in IGFBP-3 and ALS mRNA in the liver, the major source of serum IGFBP-3 and ALS. Taken together, these results suggest that feed deprivation reduces serum concentration of IGF-I in cattle not only by decreasing IGF-I gene expression in the liver, but also by increasing IGF-I degradation and reducing IGF-I retention in the blood through decreasing IGFBP-3 and ALS production in the liver.     

酪蛋白酶解产物对仔猪肠道黏膜IGF-I及其受体基因mRNA水平的影响

研究了酪蛋白酶解产物对新生仔猪肠道黏膜胰岛素样生长因子I（IGF-I）及其受体基因mRNA水平的影响。从五窝仔猪中选出10头仔猪，每窝选2头，分别分至酪蛋白饲喂组（对照组）和酶解酪蛋白饲喂组（试验组）。两组仔猪均以牛乳为基础日粮，并分别加入1．59，6的酪蛋白和酪蛋白酶解液取代10％体积的牛乳，人工饲喂3d后屠宰取样。试验结果表明，试验组仔猪空肠黏膜IGFI受体基因和IGFI基因mRNA水平分别显著（P〈0．05）和极显著（P〈0．01）高于对照组仔猪。说明酪蛋白酶解产物促进肠道发育可能与提高IGFI及其受体基因的mRNA水平有关。     

日粮蛋白含量及家系对黄颡鱼幼鱼生长性能和肝脏IGF-I mRNA表达水平的影响

采用2×2实验设计,研究不同家系种质(G♂×S♀、S♂×S♀)和日粮蛋白含量(37%、40%)对黄颡鱼幼鱼生长性能及肝脏IGF-I m RNA表达水平的影响及其交互作用。各试验组设3个平行,养殖60 d。分析结果显示:日粮蛋白含量、家系两因素对末重、增重率、特定生长率及IGF-I m RNA的相对表达量等指标均影响显著(P0.05),两因素在对上述指标的影响上均不存在交互作用。P40/(G♂×S♀)获得最大末重、增重率和IGF-I基因表达量。结果表明黄颡鱼幼鱼可通过种质筛选和日粮蛋白营养调节达到更好的养殖效果,G♂×S♀家系在高蛋白日粮投喂下,获得最佳生长性能。     

不同品种牛IGF-I基因5'调控区序列的多态性分析

采用PCR-SSCP方法,检测134头牛IGF-I基因5'调控区的多态性.结果表明,在外显子1上游510 bp处检测到1个C→T的碱基突变,有2个等位基因和3种基因型.统计结果发现,在夏洛莱牛和草原红牛群体中等位基因A占优势,但是在利木赞牛群体中却是等位基因B占优势,西门塔尔牛群体中2种等位基因的比例相对平均.AB基因型在4个群体中均为优势基因型.夏洛莱牛、西门塔尔牛、利木赞牛群体均处于Hardy-Weinberg平衡状态(P>0.05),而草原红牛群体处于非平衡状态(P<0.05).为今后对牛的肉质性状研究打下分子生物学基础.     

Sequence Variations in the Bovine IGF-I and IGFBP3 Genes and Their Association with Growth and Development Traits in Chinese Beef Cattle

The objective of this study was to determine the genotype effects of the bovine insulin-like growth factor I (IGF-I) and its binding protein 3 (IGFBP3) genes on growth and development traits in beef cows,including 130 Chinese Simmental,42 Nanyang,and 47 Luxi Yellow cattle.Sequence variations in the bovine IGF-I and IGFBP3 genes were investigated by single strand conformation polymorphism (SSCP).SSCPs were detected in 6 fragments,which is the 5'-flanking region,the 2nd exon,the 5th exon,and the 5th intron of the IGF-I gene,and the 2nd exon,the 3rd exon of the IGFBP3 gene.Two polymorphisms,an A-to-G transition in the 2nd exon of the IGF-I gene and a T-to-C transition in the 2nd exon of IGFBP3 gene were detected in 3 breeds.The allele frequencies of 2 polymorphisms were 0.0411 (A),0.9589 (B),and 0.7237 (A),0.2763 (B),respectively.These 2 loci were analyzed to associate with body weight,height at withers,body length,heart girth,rump width,and beef production index (BPI) at 0,6,12,24,and 36-month old.The 1GFBP3 locus was shown to be associated with rump width,heart girth at 24-month and 36-month.Animals with BB genotype had higher rump width (24.86±0.47) cm at 24-month and (27.50±0.63) cm at 36-month.The heart girth was highest for the individuals with BB genotype (171.33±1.84) cm and higher than those with AB genotype (166.68±1.13) cm (P＜0.05) at 36-month.     

大口黑鲈IGF-I基因内含子1、3和4序列多态性研究

根据大口黑鲈IGF-I基因的cDNA序列设计引物,克隆IGF-I基因内含子核苷酸序列,采用PCR产物直接测序方法,在中国养殖群体和美国野生群体中筛选IGF-I基因内含子上的多态位点.应用RFLP、CRS-RFLP和SSCP技术建立多态位点的检测方法,同时比较分析其中4个多态位点在两个群体中基因频率分布.结果表明:(1)IGF-I基因内含子1、3和4序列长分别为1 317 bp、712 bp和1 941 bp;(2)在3个内含子上共发现7个多态位点,其中在内含子1的208和1070位为G-A突变;内含子3的第40个碱基为一个 "A" 的插入-缺失突变,第307位为C-T突变,683位是G-A突变;内含子4上的696碱基处有一个20 bp的插入-缺失突变,在1 563位为G-A突变,表明大口黑鲈IGF-I基因序列上存在较多的SNPs;(3)内含子1上SNP G1070A的A等位基因能为Hind III限制性内切酶识别,采用RFLP技术分型.根据内含子1上SNP G208A侧翼序列,设计错配引物,使错配碱基和A等位基因共同形成Taq I酶切位点,建立CRS-RFLP检测方法.内含子4上SNP G1563A采用SSCP检测方法,同时对内含子4上的插入-缺失突变进行PAGE电泳分型.试验结果显示,RFLP、CRS-RFLP和SSCP三种SNP检测方法简单易行,适于在水产动物SNP标记研究中推广应用;(4)在中国养殖群体中,只有内含子1上的SNP G1070A具有多态性,其它3个多态位点只在美国野生群体中存在多态,证实中国养殖群体的遗传多样性相对较低.