泌乳反刍动物乳腺的氨基酸代谢

 乳腺是合成乳汁的主要场所。为了提高反刍动物饲料转化效率、泌乳量和乳蛋白产量，就有必要把乳腺氨基酸代谢作为研究的基础。本文从氨基酸供应、乳腺对氨基酸的摄取、乳腺氨基酸的代谢、能量供应对乳蛋白合成的调节等4方面，对泌乳反刍动物乳腺的氨基酸代谢进行综述，为进一步深入研究乳腺代谢，调控乳产量、乳蛋白含量提供依据。     

阴外动脉灌注氨基酸对奶山羊乳腺摄取乳成分前体物的影响

 【目的】研究阴外动脉灌注不同平衡模式的氨基酸对奶山羊乳腺摄取乳成分前体物（milk components precursors,MCP）的影响规律。【方法】选用2—3周岁,体重、产奶量相近、安装有阴外动脉和腹部皮下静脉血插管的关中奶山羊3只,由阴外动脉灌注不同平衡模式的氨基酸,在灌注前后分别采集动静脉血浆,测定乳蛋白前体物（milk protein precursors,MPP）、乳脂前体物（milk fat precursors,MFP）和乳糖前体物（milk lactose precursors,MLP）的含量和乳腺对其的摄取。【结果】阴外动脉灌注不同平衡模式混合氨基酸改变了乳腺对MPP、MFP的摄取（P＜0.05）,乳腺对MLP的摄取理想模式组和平衡模式组均高于不灌注组,但理想模式组与不灌注组差异不显著（P＞0.05）,平衡模式组与不灌注组差异显著（P＜0.05）;不同氨基酸模式灌注组产奶量和乳成分明显高于对照组（P＜0.05）。【结论】阴外动脉中氨基酸的平衡改变了乳腺对乳成分前体物的摄取,有利于乳的合成。本试验条件下,阴外动脉中必需氨基酸达到理想平衡（AABI=0.972）时乳腺对MCP的摄取效果最佳。     

Acyl carrier protein: effects of acetylation and tryptic hydrolysis on function in fatty acid synthesis

Acetylation of the four lysine residues and the amino group of the terminal serine residue of Escherichia coli acyl carrier protein has no effect on the ability of this protein to function in fatty acid synthesis. Subsequent trypsin hydrolysis resulting in complete inactivation cleaves a single arginyl peptide bond, releasing the amino terminal hexapeptide from the molecule.     

Vitamin D3: induction of calcium-binding protein in embryonic chick intestine in vitro

Induction of the synthesis of calcium-binding protein in chick embryonic intestine maintained in vitro was accomplished by simply adding vitamin D(3) to the culture medium. Accompanying the induction of this protein, there was enhanced radiocalcium uptake by the intestine. These observations represent the first demonstration of an in vitro physiological effect of vitamin D(3) on the calcium absorptive mechanism of the intestine.     

Hormonal induction of increased zinc uptake in mammalian cell cultures: requirement for RNA and protein synthesis

The zinc content of HeLa S(3) cells is markedly increased after growth in medium containing adrenal glucocorticoid hormones. Studies with inhibitors indicate that the synthesis of RNA and protein is required for enhanced zinc uptake. When protein synthesis is blocked in the presence of the steroid, an intermediate, presumably messenger RNA, which specifies enhanced zinc uptake accumulates and is expressed when the inhibition of protein synthesis is removed.     

氨基酸对蛋白质翻译起始因子的调控

氨基酸既是蛋白质合成的底物又是细胞内信号传导通路的调节物。综述了蛋白质翻译起始过程、氨基酸在翻译起始Met-tRNAi结合阶段和mRNA结合阶段的调节及氨基酸调节蛋白翻译起始的信号传导机制。     

Thyroxine: effects on amino acid incorporation into protein in vivo

Treatment of rats with L-thyroxine increases the incorporation in vivo of radioactive amino acids into protein of liver, kidney, and heart, but not of spleen, testis, or brain. The distribution of the effect among the organs is the same as that observed in thyroxine stimulation of oxidative metabolism. Thus, stimulation of protein synthesis seems to be a physiological action of the thyroid hormone.     

Evaluation of the Role of Mixed Amino Acids in Nitrate Uptake and Assimilation in Leafy Radish by Using 15N-Labeled Nitrate

In this paper, the role of mixed amino acids in nitrate uptake and assimilation was evaluated in leafy radish by using ^15N labeled nitrate. The mixtures of alanine, β-alanine, aspartic acid, asparagines, glutamic acid, glutamine, and glycine were sprayed to plant leaf two or four times. The activity of the enzymes related to the process of NO3- reduction （nitrate reductase, nitrite reductase and glutamine synthetase） was affected differently depending on the application rate of mixed amino acids. Applying mixed amino acids increased the fresh weight, dry weight, and N yield. The NO3 content was reduced to 24-38%, but no significant differences were observed in amino acids and proteins. In addition, the nitrogen derived from fertilizer and the ^15N-NO3-recovery rate increased to 2-8% and 15-47%, respectively. These results strongly suggest that the positive effect of mixed amino acids on nitrate uptake and assimilation might be attributed to the regulation on NO3- uptake and assimilation, but not to the preference for amino acids as sources of reduced nitrogen.     

外源添加抑制剂对芦蒿吸收Cd和Pb的影响

以水生植物芦蒿为试验材料,通过人工培养液温室培养方法,研究了代谢抑制剂、P-型ATP酶抑制剂、蛋白合成抑制剂、离子通道抑制剂对芦蒿吸收Cd和Pb的影响.结果表明,代谢抑制剂(Na_3N)和P-型ATP酶抑制剂(Na_3VO_4)对芦蒿Cd和Pb的吸收均有一定的抑制作用,说明芦蒿对Cd和Pb存在主动吸收.钙离子通道抑制剂LaCl_3显著抑制芦蒿根部对Cd的吸收,而对Pb的吸收没有明显的抑制作用,说明芦蒿对Cd的吸收与钙离子通道有关;蛋白质合成抑制剂放线菌酮(CHD)对芦蒿Cd和Pb的吸收有显著的抑制作用,说明芦蒿对Cd和Pb的吸收与一些蛋白质或酶的诱导合成及其活性密切相关.     

Cytochalasin B prevents specific sorting of reaggregating embryonic cells

The effect of cytochalasin B on specific sorting during reaggregation of embryonic chick heart and neural retina cells was studied. At a dose that did not measurably affect uptake of precursors of protein and RNA synthesis, ratios of potassium to sodium ions, and nonspecific aggregation, cytochalasin B disrupted the formation of the characteristic pattern of islands of heart cells within a retinal continuum.     

精氨酸生素在猪营养中的研究与应用

在动物体内,精氨酸作为最大供氮氨基酸参与蛋白质合成,是一种功能性、限制性、条件性必需氨基酸。精氨酸也是一种促生长因子,对猪的生长发育具有重要意义。对于仔猪,体内精氨酸的不足是限制仔猪生长发育的主要因素之一。对于成年动物来说,精氨酸是非必需氨基酸,但在特殊时期是一种条件性必需氨基酸。精氨酸生素是N-乙酰谷氨酸稳定的具有活性的可食用类似物,具有调节内源性精氨酸合成的作用,促进了内源性精氨酸合成。文章就精氨酸生素的理化特性、合成方法,对精氨酸的内源性调节及其在养猪中研究与应用作以综述。     

Regulation of amino acid transport in kidney cortex of newborn rats

After incubation at 37 degrees C the subsequent uptake of alpha-aminoisobutyric acid, cycloleucine, glycine, and L-proline by newborn (as compared to adult) rat kidney cortex slices is enhanced. The effect is abolished by the presence of cycloheximide, actinomycin D, and high concentrations of the above-mentioned amino acids in the medium during the 37 degrees C incubation prior to measurement of uptake. The data suggest that there is an adaptive control mechanism which is expressed on incubation at 37 degrees C and which can regulate amino acid transport in newborn rat kidney cortex.     

温度对不同筋型小麦游离氨基酸与籽粒蛋白质含量的影响

以济南17和潍麦8号两个不同筋型小麦品种为材料,研究花后温度对小麦籽粒蛋白质和植株氨基酸含量的影响。结果表明,灌浆期高温提高了小麦籽粒蛋白质含量,两个筋型品种表现出相同的趋势;提高了小麦叶片和茎鞘中游离氨基酸含量,向籽粒中运输的氨基酸的量也增加,有利于籽粒蛋白质的合成。对黄淮海等北方强筋小麦而言,后期高温对提高籽粒蛋白质含量是有利的,但降低了弱筋小麦的品质。     

氮素调控对玉米氮素同化过程及产量的影响

氮素调控措施与作物氮素吸收利用和产量密切相关,但目前关于不同氮素调控措施对玉米主要生育期氮素同化过程的影响仍不清楚。以郑单958为试验材料,设置不施氮肥（CK）、传统施肥（CN）、氮肥+生物炭（SN）和氮肥+硝化抑制剂DMPP（DN）4个处理,分析不同氮素调控对玉米氮素同化过程中铵态氮和硝态氮含量、硝酸还原酶（NR）和谷氨酰胺合成酶（GS）活性、游离氨基酸和可溶性蛋白含量以及氮素利用率和产量的影响。结果表明：DN和SN处理较传统施肥处理均可以提高玉米植株体内硝态氮和铵态氮含量、NR和GS活性;DN和SN处理显著提高灌浆期谷氨酸、游离氨基酸和可溶性蛋白含量;DN处理成熟期籽粒的氮素积累量显著高于SN和CN处理,分别显著增加18.4%和30.0%;DN处理产量最高,SN次之,二者并无显著差异,但相较CN处理分别显著增产1 483.0和1 154.2 kg·hm^-2。两种氮素调控均促进了玉米对氮素的吸收,显著提高氮肥吸收利用率,其中硝化抑制剂处理氮肥吸收利用率最高且显著高于其他处理。综上,生物炭或硝化抑制剂配施氮肥,可以促进玉米氮素同化和转运过程,显著提高玉米产量和氮肥利用效率,综合产量、籽粒氮素积累量和氮肥吸收利用率,硝化抑制剂配施氮肥可作为淮河流域玉米高产高效的栽培措施。     

Magnesium pemoline: failure to affect in vivo synthesis of brain RNA

The effect of magnesium pemoline on the synthesis of brain RNA in vivo was studied. No significant effect either on the concentration of RNA or on the uptake of H(3)-uridine into RNA was detected.     

赖氨酸对泌乳奶牛生产性能的影响

赖氨酸是最主要的限制性氨基酸之一.奶牛小肠吸收的氨基酸对于维持生长发育、繁殖和泌乳等生命活动而言极为重要.通常反刍动物自身不能合成赖氨酸,需要通过外源补充以满足动物的需要.反刍动物小肠内的氨基酸来自瘤胃微生物蛋白和瘤胃未降解蛋白.目前常采用添加过瘤胃保护赖氨酸的方式来提高小肠代谢赖氨酸的含量,从而提高生产性能和经济效益...     

Embryonic chick intestine in organ culture: response to vitamin D 3 and its metabolites

Embryonic chick intestine maintained in organ culture responded to vitamin D(3) and its metabolites 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol by synthesis of calcium-binding protein and enchanced calcium-45 uptake. The dihydroxy metabolite was by far the most potent inducer of the protein and also acted more rapidly than vitamin D(3) to stimulate isotope uptake. Despite its lower potency, vitamin D(3) itself was effective.     

多肽和蛋白质的人工合成评述

多肽和蛋白质的人工合成,就是多个氨基酸在一定的条件下通过肽键形成多肽链。氨基酸是合成多肽和蛋白质的原料。在合成前各个氨基酸都必须经过基团保护、氨基和羧基的活化处理,然后经接肽,去除保护基,最后形成多肽链。本文对目前国内外常用的液相合成法和固相合成法的原理和步骤进行了简要的评述。     

豫芝11号种子发育过程中蛋白质及其组分的变化规律

【目的】研究芝麻种子发育过程中蛋白质及组分的变化规律,明确生长环境对种子蛋白质含量及组成的影响,为芝麻蛋白质育种及芝麻蛋白质的利用提供理论依据。【方法】选用豫芝11号芝麻品种,在周口,驻马店和南阳试验点同期播种,于盛花期一次性标记5 000朵同一天开放的花朵,在芝麻授粉第10 天开始取样,此后每5 d取样一次至芝麻成熟。测定种子生长过程中蛋白质含量及组分、蛋白质相对分子质量和氨基酸组成。【结果】芝麻种子粗蛋白质含量随着发育时间的延长逐渐增加,授粉后35 d蛋白质含量达到最大,随后处于稳定;周口试验点粗蛋白质含量显著低于南阳和驻马店试验点;球蛋白的变化规律与粗蛋白含量一致,清蛋白含量呈现出先升高后降低的趋势,成熟芝麻种子中清蛋白含量并未表现出地域差异性;授粉15 d时在凝胶谱图20、30、55 kD处出现条带,并随着种子发育延长而加深;随着芝麻种子生长发育,必需氨基酸占总氨基酸含量逐渐降低,南阳和驻马店试验点显著低于周口试验点;缬氨酸、异亮氨酸、亮氨酸和苯丙氨酸＋酪氨酸比值系数大于1。【结论】环境显著影响蛋白质含量,球蛋白含量和生长过程中芝麻清蛋白含量;不同种类蛋白质合成时间不同,芝麻蛋白相对分子质量主要集中在20-30 kD处;随着种子生长发育期的延长,芝麻种子中必需氨基酸占总氨基酸含量逐渐降低;芝麻蛋白能够很好地补充缬氨酸、异亮氨酸、亮氨酸和苯丙氨酸＋脯氨酸。     

FGF-21促进HepG2细胞摄取葡萄糖研究

肝脏是代谢的中枢性器官,在糖脂代谢中扮演重要角色。FGF-21是近年来发现的一种治疗糖尿病新型药物,研究其对肝脏糖代谢影响及机制将为FGF-21成药性提供理论依据。以Hep G2细胞为肝细胞模型,探究FGF-21对Hep G2细胞葡萄糖吸收影响及作用机制。FGF-21处理Hep G2细胞,采用葡萄糖氧化酶-过氧化物酶(GOD-POD)法检测细胞对葡萄糖摄取情况,并检查胰岛素与FGF-21协同作用,蒽酮法检测细胞内糖原含量,半定量和实时荧光定量PCR检测FGF-21对葡萄糖转运蛋白(GLUTs)m RNA表达影响。结果表明,FGF-21可促进Hep G2细胞摄取葡萄糖,与胰岛素具有一定协同作用,增加糖原合成。半定量PCR结果显示在FGF-21作用下,仅GLUT1m RNA表达有所增加。实时荧光定量PCR检测FGF-21作用时间对GLUT1 m RNA表达量影响,发现FGF-21作用6 h时GLUT1 m RNA表达量倍数增加最大。说明FGF-21可通过增加GLUT1 m RNA表达促进Hep G2细胞消耗葡萄糖,参与糖原合成。