Effects of Various Amino Acids on Methionine-Induced Hyperhomocysteinemia in Rats

Rats were fed diets supplemented with 1% L-methionine with and without 2.5% various amino acids for 7 d to determine what amino acids other than glycine, serine, and cystine can suppress methionine-induced hyperhomocysteinemia. L-Glutamic acid, L-histidine, and L-arginine significantly suppressed methionine-induced enhancement of plasma homocysteine concentrations, but the mechanisms underlying the effect of these amino acids are thought not to be identical.     

Suppression of methionine-induced hyperhomocysteinemia by glycine and serine in rats

The hyperhomocysteinemia induced by a dietary addition of 1% methionine was significantly suppressed by the concurrent addition of 1% glycine or 1.4% serine to the same degree. The methionine-induced increase in the hepatic concentration of methionine metabolites was significantly suppressed by glycine and serine, but the hepatic cystathionine beta-synthase activity was not enhanced by these amino acids. When the methionine-supplemented diet was changed to the methionine plus glycine or serine diet, the plasma homocysteine concentration rapidly decreased during and after the first day. The hyperhomocysteinemia induced by an intraperitoneal injection with methionine was also suppressed by concurrent injection with glycine or serine, although the effect of serine was significantly greater than that of glycine. These results indicate that glycine and serine were effective for suppressing methionine-induced hyperhomocysteinemia: serine and its precursor glycine are considered to have elicited their effects mainly by stimulating cystathionine synthesis by supplying serine, another substrate for cystathionine synthesis.     

Effects of Sulfur-containing Amino Acids and Glycine on Plasma Cholesterol Level in Rats Fed on a High Cholesterol Diet

The effects of the addition of individual amino acids on methionine-induced hypercholesterolemia (experiment 1), and the interacting effects of dietary protein level and sulfur-containing amino acids and glycine on plasma cholesterol concentration (experiment 2) were studied in growing rats fed on a high cholesterol diet. In experiment 1, rats were fed on a 25% casein-0.75% methionine (25CM) diet containing 2.5% of individual amino acids for 2 weeks. Methionine-induced hypercholesterolemia was prevented by the concurrent addition of glycine or serine, but the other amino acids tested (alanine, threonine, leucine, phenylalanine, lysine, arginine, and glutamic acid) had no effect. Histidine rather enhanced the hypercholesterolemia. In experiment 2, rats were fed on a 10%, 25%, or 50% casein diet containing 0.75% methionine, 0.60% cystine, 0.63% taurine, 2.5% glycine, or 0.75% methionine +2.5% glycine for 3 weeks. Dietary addition of 0.75% methionine increased the plasma cholesterol concentration for the 25% and 50% casein diets, but it decreased the plasma cholesterol for the 10% casein diet. When the addition level of methionine was doubled in the 10% casein diet, the plasma cholesterol concentration was significantly higher for the 1.5% methionine-added diet than for the 0.75% methionine-added diet. Cystine and taurine lowered plasma cholesterol for all dietary casein levels. Methionine-induced hypercholesterolemia with 25% and 50% casein diets was prevented by the glycine supplementation. These data suggest that sulfur-containing amino acids and glycine are important in plasma cholesterol regulation.     

Hyperhomocysteinemia induced by guanidinoacetic acid is effectively suppressed by choline and betaine in rats

Rats were fed 25% casein (25C) diets differing in choline levels (0-0.5%) with and without 0.5% guanidinoacetic acid (GAA) or 0.75% L-methionine for 7 d to determine the effects of dietary choline level on experimental hyperhomocysteinemia. The effects of dietary choline (0.30%) and betaine (0.34%) on GAA- and methionine-induced hyperhomocysteinemia were also compared. Dietary choline suppressed hyperhomocysteinemia induced by GAA, but not by methionine, in a dose-dependent manner. GAA-induced enhancement of the plasma homocysteine concentration was suppressed by choline and betaine to the same degree, but the effects of these compounds were relatively small on methionine-induced hyperhomocysteinemia. Dietary supplementation with choline and betaine significantly increased the hepatic betaine concentration in rats fed a GAA diet, but not in rats fed a methionine diet. These results indicate that choline and betaine are effective at relatively low levels in reducing plasma homocysteine, especially under the condition of betaine deficiency without a loading of homocysteine precursor.     

大杯香菇辐射新株系各类氨基酸的遗传主成分分析

对大杯香菇辐射选育新株系的各类氨基酸总量进行了遗传主成分分析。结果表明,变异系数最大的为硫氨基酸总量,达到13．39％;其次为儿童氨基酸总量,变异系数为7．00％;其它变异系数较小分别为甜味氨基酸总量、芳香族氨基酸总量、必需氨基酸总量、支链氨基酸总量和鲜味氨基酸总量为5．69％、5．64％、5．19％、5．24％和5．06％;在相关性上,鲜味氨基酸总量与甜味氨基酸总量、支链氨基酸总量、芳香族氨基酸总量、儿童氨基酸总量和必需氨基酸总量是呈极显著和显著的正相关,甜味氨基酸总量与支链氨基酸总量、儿童氨基酸总量和芳香族氨基酸总量呈极显著和显著的正相关,硫氨基酸总量与儿童氨基酸总量呈极显著负相关,与必需氨基酸总量是呈极显著正相关;支链氨基酸总量与芳香族氨基酸总量、必需氨基酸总量是呈极显著,与儿童氨基酸总量呈显著正相关;芳香族氨基酸总量与儿童氨基酸总量和必需氨基酸总量是呈极显著和显著的正相关;主成分分析结果表明,前4个特征根在7个特征根中累计贡献率达97．14％,也就是前4个主成分对变异的贡献率达96．07％。在各类氨基酸总量指标选择上,首先对变异大的各类氨基酸总量进行选择是及其重要的。在辐射选育新株系选择时,应注意选择大杯香菇中硫氨基酸总量高的新株系。     

大菱鲆鱼皮的氨基酸分析及评价

用常规方法测定了大菱鲆鱼皮的基本营养成分,用氨基酸自动分析仪分析其氨基酸构成,并对大菱鲆鱼皮中的氨基酸组成进行了营养学评价。结果表明,大菱鲆鱼皮蛋白质含量为14.8%,脂肪含量为1.8%,氨基酸含量为27.24%,其中含量较高的是甘氨酸、丙氨酸、脯氨酸和精氨酸,占总氨基酸的59.73%;必需氨基酸、甜味氨基酸、苦味氨基酸、鲜味氨基酸和涩味氨基酸的含量分别占总氨基酸的20.81%、60.61%、30.07%、10.43%和0.01%。甜味氨基酸、苦味氨基酸、鲜味氨基酸是大菱鲆鱼皮氨基酸的主要部分,构成了大菱鲆鱼皮的主要味道,大菱鲆鱼皮是一种口感柔滑、味道鲜美的理想补强食品。     

Utilization of milk amino acids for body gain in suckling mink (Mustela vison) kits

The efficiency of utilization of milk amino acids for body gain in suckling mink kits from small (n = 3), medium (n = 6) and large litters (n = 9) was investigated by using 36 mink dams and their litters for measurements during lactation weeks 1 through 4. Measurements on each dam and litter were performed once, hence three dams per litter size each week (n = 9). Individual milk intake of kits was determined, milk samples were collected and kits were killed for determination of amino acid composition. The most abundant amino acids in milk were glutamate, leucine and aspartate making up about 40% of total amino acids. Branched chained amino acids made up slightly more than 20% and sulphur containing amino acids less than 5% of total milk amino acids. In kit bodies the sum of glutamate, aspartate and leucine made up about 32% of amino acids, branched chain amino acids about 16% and sulphur containing amino acids about 4%. The amino acid composition of both milk and bodies changed as lactation progressed with decreasing proportions of essential amino acids. The ratio between body and milk amino acids was constantly over 1 only for lysine, suggesting that it was the most limiting amino acid in mink milk. Milk amino acids were efficiently utilized during week 1, ranging from 74.7% (lysine) to 42.1% (leucine), with an average for essential amino acids of 58.4%. Tendencies for improved utilization of lysine (74.7-78.2%), phenylalanine (61.0-70.0%), histidine (62.4-68.8%), arginine (61.3-70.4%) and all essential amino acids (58.4-60.2%) from week 1 to week 2 were recorded. During weeks 3 and 4, the efficiency declined, and for all essential amino acids the average utilization was 38.1% during week 4.     

Infusion of amino acids decreases the hyperglycaemic effect of per- and postoperative glucose infusion: an experimental study in the rabbit

The effects on blood glucose concentration of 10% glucose with amino acid solution at low (18%) and high (25%) concentration of branched chain amino acids were studied, two days after laparotomy in fasted rabbits. During the whole study period, saline infusion was associated with normoglycaemia. Among the other infusion combinations peroperative infusion of amino acid solution high in branched chain amino acids with 10% glucose was the least hyperglycaemic. An amino acid solution low in branched chain amino acids with 10% glucose had the lowest hyperglycaemic effect 24 hours postoperatively. After 48 hours an infusion of 10% glucose produced the weakest hyperglycaemia. In preoperatively and 24 hours postoperatively 10% glucose was more hyperglycaemic than 10% glucose with the two amino acid solutions. After 24 and 48 hours, infusion of 10% glucose with amino acids high in branched chain amino acids was more hyperglycaemic than 10% glucose with amino acids low in branched chain amino acids.     

洞庭青鲫肌肉营养成分分析及营养价值评定

对2002年在湖南澧县澧水尾闾、洞庭湖区边缘化的封闭型湖泊——北民湖发现的洞庭青鲫(Carassius auratus var.dongtingking)(n=15)的含肉率和肌肉中的生化成分、比能值及氨基酸测定分析。结果表明,洞庭青鲫的含肉率为52.18%;其肌肉生化成分(鲜重百分比)为:水分78.14%,蛋白质18.63%,脂肪1.51%,灰分1.22%,比能值5.09kJ/g及E/P值27.32kJ/g。肌肉中含有17种氨基酸,总量为866.12mg/g(干重比);其中9种人体必需氨基酸含量占氨基酸总量的48.21%(盐酸水解法);支/芳值达2.81,接近人体正常所需;4种鲜味氨基酸占氨基酸总量的50.39%。根据氨基酸评分(AAS)和化学评分(CS)标准,洞庭青鲫的第一限制因子是甲硫氨酸和胱氨酸,其次是缬氨酸、苯丙氨酸和酪氨酸。即洞庭青鲫氨基酸含量与组成与彭泽鲫(C.a.var.pengze)、异育银鲫(C.a.var.allogynogeneticrp)、萍乡肉红鲫(C.a.var.pingxing red)相比,均存在差异。     

晶体氨基酸替代鱼粉蛋白对半滑舌鳎稚鱼消化酶和代谢酶活力的影响

为研究人工微颗粒饲料中晶体氨基酸替代鱼粉蛋白对半滑舌鳎（Cynoglossus semilaevis Gnther）稚鱼消化酶和代谢酶活力的影响, 以晶体氨基酸混合物分别替代0%、25%、50%、75%和100%鱼粉蛋白（0%CAA、25%CAA、50%CAA、75%CAA和100%CAA）, 在25%替代水平设计棕榈酸甘油酯包被晶体氨基酸混合物组（C-25%CAA）, 配制实验微颗粒饲料。每种微颗粒饲料随机投喂三组实验鱼初始体重（0.0940.02） g, 35日龄, 每组实验鱼放养150尾, 养殖周期28d。研究结果表明, 在不包膜条件下, 各处理组的胰蛋白酶活力随替代水平的升高显著下降（P0.05）, 且包膜处理组（C-25%CAA）与全鱼粉组无显著差异（P0.05）。肠段胰蛋白酶活力与胰段胰蛋白酶活力比值随氨基酸替代水平的升高显著下降（P0.05）, 鱼粉组显著高于75%和100%处理组（P0.05）, 但与25%处理组、包膜处理组（C-25%CAA）和50%处理组无显著差异（P0.05）。各处理组淀粉酶活力随替代水平的升高显著上升（P0.05）。亮氨酸氨肽酶（LA）和碱性磷酸酶（AP）活力（肠段与刷状缘）均随替代水平的升高显著下降（P0.05）, 包膜处理组（C-25%CAA）与全鱼粉组无显著差异（P0.05）。谷丙转氨酶（GPT/ALT）和谷草转氨酶（GOT/AST）活力随替代水平的升高显著上升（P0.05）, 50%、75%和100%处理组显著高于鱼粉组、25%处理组和包膜处理组（C-25%CAA）。研究结果显示, 饲料中晶体氨基酸显著影响了半滑舌鳎稚鱼的消化酶和代谢酶活力, 而且在25%的替代水平下, 与未包膜组相比, 包膜处理组能显著促进半滑舌鳎稚鱼消化系统的发育。       

Amino acid regulation of insulin action in isolated adipocytes. Selective ability of amino acids to enhance both insulin sensitivity and maximal insulin responsiveness of the protein synthesis system

Using the number and concentration of amino acids in Dulbecco's modified Eagle's medium as reference (DMEM = 100%), we found that a maximally effective concentration of insulin (10 ng/ml) stimulated protein synthesis by 125% over basal rate in the presence of 50% amino acids (EC50 = 19%), but by only 48% in amino acid-free buffer. Moreover, time course experiments revealed that amino acid regulation of insulin action was very rapid (t1/2 of 9.5 min) and readily reversible (less than 30 min). This effect was specific in that basal rates of protein synthesis were unaltered by amino acids. A second effect of amino acids was to markedly enhance insulin sensitivity of the protein synthesis system in a dose-dependent manner. Thus, the half-maximally effective concentrations of insulin required to stimulate protein synthesis fell from 0.43 to 0.25 to 0.15 ng/ml in the presence of 0, 50, and 150% amino acids. Neither insulin sensitivity nor maximal insulin responsiveness of the glucose transport system was altered by amino acids, nor did amino acids affect the insulin binding capacity of cells. When we divided the 14 amino acids found in DMEM into two groups, we found that one group of 7 amino acids had little or no effect on insulin sensitivity or responsiveness, whereas the other group was fully active (a 157% increase in insulin responsiveness, ED50 of 0.21 ng/ml versus a 68% increase, ED50 of 0.51 ng/ml, with no amino acids). Isoleucine and serine together increased both insulin sensitivity and responsiveness to 60-70% of that seen with the full complement of amino acids. In conclusion: 1) amino acids modulate insulin action by enhancing maximal insulin responsiveness and insulin sensitivity of the protein synthesis system, and the regulatory site of amino acid action appears to be distal to the common signal pathway, within the insulin action-protein synthesis cascade, and 2) the effects of amino acids are specific, in that basal rates of protein synthesis are unaffected, only certain amino acids influence insulin action, and amino acids fail to alter insulin binding or the insulin-responsive glucose transport system. These studies, together with those in the companion paper, demonstrate that the pleiotropic actions of insulin on enhancing glucose uptake and protein synthesis are mediated through divergent pathways that can be independently regulated.(ABSTRACT TRUNCATED AT 400 WORDS)     

饲养中国大鲵氨基酸组成分析

实验对饲养中国大鲵氨基酸组成成分进行了比较全面的测定与分析,结果表明:饲养中国大鲵肌肉的蛋白质质量分数为164.3 g.kg-1,水解氨基酸总量为160.6 g.kg-1,各种氨基酸组成相当全面,必需氨基酸(EAA)为75.2 g.kg-1,占氨基酸总量的46.82%,符合人体需要量模式的程度相当高,为优质食物蛋白,可与做为参考蛋白的鸡蛋蛋白相媲美。研究同时发现呈味氨基酸总量70.5 g.kg-1,占氨基酸总量的43.90%,为研发味道鲜美的大鲵食品提供了有力的数据。     

Neutral amino acids in the brain: changes in response to food ingestion

Abstract— The brain levels of each of the aromatic and branched-chain amino acids change 2 h after fasting rats begin to consume either a carbohydrate-fat diet or a similar diet containing 18% or 40% protein. Carbohydrate-fat ingestion elevates the concentrations of each of the aromatic amino acids in brain, while substantially depressing those of the branched-chain amino acids. The inclusion of protein in this diet suppresses the increases in brain aromatic amino acids and attenuates the decreases in the branched-chain amino acids. The changes in the brain level of each neutral amino acid following the ingestion of any of these diets correlate extremely well with the effects of the diet on the serum neutral amino acid pattern, specifically on the serum concentration ratio of each neutral amino acid to the sum of the other neutral amino acids. The diet-induced changes in the brain level of each of the amino acids also correlate surprisingly well with the calculated rate of brain influx for each amino acid.     

小碎斑鱼蛉幼虫资源成分分析及价值评价

针对小碎斑鱼蛉Neochauliodes sparsus(Liu et Yang)幼虫,进行了资源成分测定,分析。结果表明:小碎斑鱼蛉幼虫干物质中蛋白质、氨基酸、脂肪、糖类及灰分含量分别为67.69%、56.02%、10.4%、1.59%、7.05%,含有18种氨基酸,包括8种人体必需氨基酸,其必需氨基酸占总氨基酸含量的45.32%,必需氨基酸与非必需氨基酸含量的比值为82.89%,第一限制性氨基酸为色氨酸;此外,还含有Ca、P、Fe、Zn等多种矿物质和微量元素。在分析了小碎斑鱼蛉幼虫资源成分的基础上,对其开发利用价值进行了评价。     

Helix propagation and N-cap propensities of the amino acids measured in alanine-based peptides in 40 volume percent trifluoroethanol.

The helix propagation and N-cap propensities of the amino acids have been measured in alanine-based peptides in 40 volume percent trifluoroethanol (40% TFE) to determine if this helix-stabilizing solvent uniformly affects all amino acids. The propensities in 40% TFE are compared with revised values of the helix parameters of alanine-based peptides in water. Revision of the propensities in water is the result of redefining the capping statistical weights and evaluating the helix nucleation constant with N-capping explicitly included in the helix-coil model. The propagation propensities of all amino acids increase in 40% TFE relative to water, but the increases are highly variable. In water, all beta-branched and beta-substituted amino acids are helix breakers. In 40% TFE, the propagation propensities of the nonpolar amino acids increase greatly, leaving charged and neutral polar, beta-substituted amino acids as helix breakers. Glycine and proline are strong helix breakers in both solvents. Free energy differences for helix propagation (delta delta G) between alanine and other nonpolar amino acids are twice as large in water as predicted from side-chain conformational entropies, but delta delta G values in 40% TFE are close to those predicted from side-chain entropies. This dependence of delta delta G on the solvent points to a specific role of water in determining the relative helix propensities of the nonpolar amino acids. The N-cap propensities converge toward a common value in 40% TFE, suggesting that differential solvation by water contributes to the diversity of N-cap values shown by the amino acids.     

Promoting effect of amino acids added to a chemically defined medium on blastocyst formation and blastomere proliferation of bovine embryos cultured in vitro

This study was conducted to elucidate the role of amino acids added singly or in groups to a chemically defined culture medium in blastocyst formation and blastomere proliferation of bovine embryos. Embryos were generated by in vitro fertilization, and blastocyst formation and hatching, and blastomere number of blastocysts were subsequently monitored after the culture of embryos in synthetic oviduct fluid medium (SOFM). First, one of four non-essential amino acids (asparagine, aspartate, glutamate or serine) was added to SOFM and, compared with no addition, a significant (P <0.05) increase in blastocyst formation was found after the addition of asparagine, aspartate, or glutamate (35-42% versus 22%). Second, one of four essential amino acids (arginine, cystine, isoleucine or leucine) was added and arginine or isoleucine greatly improved blastocyst formation (30-36% versus 16%). Third, the addition of five stimulatory amino acids (aspartate, asparagine, glutamate, arginine and isoleucine) to SOFM significantly improved blastocyst formation compared with no addition (12% versus 21%) and such value was similar to that obtained after the addition of 19 amino acids consisting of MEM amino acid solutions (21-27%). However, five amino acids yielded fewer hatched blastocysts than 19 amino acids. Finally, although five amino acids yielded more cell number of blastocysts than no addition (93 versus 74 cells per blastocyst), it was lower than that from 19 amino acids (131 cells per blastocyst). In conclusion, either single or combined addition of asparagine, aspartate, glutamate, arginine and isoleucine stimulated blastocyst formation, while other amino acids might be necessary for further stimulating blastomere proliferation and blastocyst hatching.     

虎纹蛙的含肉率及蛙肉和蛙皮氨基酸组成分析

测定了8只人工养殖虎纹蛙的含肉率及氨基酸组成。结果表明,虎纹蛙的含肉率平均为35．27％;蛙肉和蛙皮干物质中水解氨基酸总量分别为71．740％和79．084％,其中必需氨基酸分别为22．95％和15．88％,分别占氨基酸总量的32．00％和20．08％;游离氨基酸中6种呈味氨基酸含量丰富,分别占游离氨基酸总量的45．50％和60．40％;蛙肉和蛙皮限制氨基酸均为缬氨酸,必需氨基酸指数分别为43.83和27．66。认为虎纹蛙是一种营养价值和养殖价值都较高的品种。     

Amino acid vs. nucleotide characters: challenging preconceived notions

The 567-terminal analysis of atpB, rbcL, and 18S rDNA was used as an empirical example to test the use of amino acid vs. nucleotide characters for protein-coding genes at deeper taxonomic levels. Nucleotides for atpB and rbcL had 6.5 times the amount of possible synapomorphy as amino acids. Based on parsimony analyses with unordered character states, nucleotides outperformed amino acids for all three measures of phylogenetic signal used (resolution, branch support, and congruence with independent evidence). The nucleotide tree was much more resolved than the amino acid tree, for both large and small clades. Nearly twice the percentage of well-supported clades resolved in the 18S rDNA tree were resolved using nucleotides (91.8%) relative to amino acids (49.2%). The well-supported clades resolved by both character types were much better supported by nucleotides (98.7% vs. 83.8% average jackknife support). The faster evolving nucleotides with a smaller average character-state space outperformed the slower evolving amino acids with a larger average character-state space. Nucleotides outperformed amino acids even with 90% of the terminals deleted. The lack of resolution on the amino acid trees appears to be caused by a lack of congruence among the amino acids, not a lack of replacement substitutions.     

黄粉虫蛹的营养成分分析

采用现代分析技术手段对黄粉虫Tenebrio molitor（L．）蛹的营养成分进行分析,结果表明：其蛋白质、粗脂肪、碳水化合物及灰分含量分别为鲜重的16．8％、7．6％、1．2％、1．4％,其氨基酸和胆固醇含量分别为18.7mg／g和0．4mg／g;含有7种人体必需氨基酸,其必需氨基酸占总氨基酸含量的44．40％,必需氨基酸与非必需氨基酸含量的比值为79.8％,第一限制性氨基酸为含硫氨基酸,即蛋氨酸和胱氨酸;同时,其不饱和脂肪酸与必需脂肪酸分别占总脂肪的73．9％和24．1％,特别是油酸和亚油酸含量较高,分别达49．8％和23．4％：另外,该昆虫还含有K、Ca、Mg、Fe、Zn、Cu、Mn等多种矿物质和微量元素。     

白斑狗鱼含肉率及其营养价值的分析

测定了6尾白斑狗鱼(Esox lucius)的含肉率和营养成分,并与部分淡水优质经济鱼类进行了比较.结果表明:白斑狗鱼含肉率为64.8%,粗蛋白含量和脂肪含量分别为19.1%和1.4%,17种氨基酸总量为17.38%,其中7种必需氨基酸总量为8.14%,鲜味氨基酸总量为6.36%.必需氨基酸总量占氨基酸总量的45.73%,低于鸡蛋蛋白模式,但明显高于WHO/FAO模式.必需氨基酸指数为76.35,根据化学评分计算结果,得出第一限制性氨基酸为缬氨酸,第二限制性氨基酸为蛋氨酸,第三限制性氨基酸为异亮氨酸.结果提示,白斑狗鱼是一种营养价值较高的鱼类.