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.     

Fate-restricted neural progenitors in the mammalian cerebral cortex

During development of the mammalian cerebral cortex, radial glial cells (RGCs) generate layer-specific subtypes of excitatory neurons in a defined temporal sequence, in which lower-layer neurons are formed before upper-layer neurons. It has been proposed that neuronal subtype fate is determined by birthdate through progressive restriction of the neurogenic potential of a common RGC progenitor. Here, we demonstrate that the murine cerebral cortex contains RGC sublineages with distinct fate potentials. Using in vivo genetic fate mapping and in vitro clonal analysis, we identified an RGC lineage that is intrinsically specified to generate only upper-layer neurons, independently of niche and birthdate. Because upper cortical layers were expanded during primate evolution, amplification of this RGC pool may have facilitated human brain evolution.     

Decreased RNA polymerase activity in mammalian zinc deficiency

The activity of DNA-dependent RNA polymerase has been measured in liver nuclei from suckling rats nursed by zinc-deficient dams, or by controls that were either pair-fed or given free access to the diet. In the zinc-deficient pups, the activity of the enzyme did not increase; it fell after the tenth day of life.     

饲料中可利用氨基酸研究进展

综述了可利用氨基酸在饲料中的研究进展,对部分研究成果进行了评述。认为氨基酸可利用率的测定方法应从生产现场进行选择,畜禽可利用氨基酸需要量研究应成为研究重点,并对可利用氨基酸在日粮中的应用前景进行了展望。     

Hydrophobicity of amino acid residues in globular proteins

During biosynthesis, a globular protein folds into a tight particle with an interior core that is shielded from the surrounding solvent. The hydrophobic effect is thought to play a key role in mediating this process: nonpolar residues expelled from water engender a molecular interior where they can be buried. Paradoxically, results of earlier quantitative analyses have suggested that the tendency for nonpolar residues to be buried within proteins is weak. However, such analyses merely classify residues as either "exposed" or "buried." In the experiment reported in this article proteins of known structure were used to measure the average area that each residue buries upon folding. This characteristic quantity, the average area buried, is correlated with residue hydrophobicity.     

不同品种猪肌肉脂肪酸和氨基酸含量

对莆田黑猪、杜洛克、大约克3个纯种及其二元杂种杜莆(杜洛克♂×莆田黑猪♀)和大莆(大约克♂×莆田黑猪♀)背最长肌脂肪酸和氨基酸含量进行了测定与分析.杜莆的饱和脂肪酸、单不饱和脂肪酸、必需氨基酸以及鲜味氨基酸含量最高(分别为42.09%、51.14%、9.26%和7.45%),表明杜莆有效地保留了莆田黑猪肉质优良的特点;莆田黑猪与杜洛克(杜洛克♂×莆田黑猪♀)二元组合的杂交效果较好.     

猪乳中氨基酸含量的动态分析

采集杜洛克母猪分娩后1、3、5、11、15、20 d的乳汁,通过高效液相法分析氨基酸的含量变化.结果表明,随着泌乳时间的延长,猪乳中17种氨基酸的含量均呈下降趋势,各种氨基酸之间谷氨酸含量最高,而胱氨酸和蛋氨酸的含量最低.     

甘氨酸和鱼蛋白在网纹甜瓜上应用效果比较

[目的]为了提高网纹甜瓜的果实品质,筛选适宜的氨基酸类生物刺激素.[方法]测定网纹甜瓜果实膨大速率、果实产量、口感品质以及果肉养分含量等指标,运用方差分析,比较甘氨酸和鱼蛋白两种氨基酸类生物刺激素处理对品质的影响,进行综合评价.[结果]结果表明,鱼蛋白处理心糖较对照提高13.9％,边糖较对照提高19.9％.不同类型氨基酸含量也高于其他处理,品质方面占明显优势.[结论]授粉后每10d喷施浓度为1 g/L的鱼蛋白,对网纹甜瓜提质效果较好,可在网纹甜瓜生产过程中推广应用.     

Circadian rhythmicity in amino acid incorporation in Euglena gracilis

A daily rhythm of amino acid incorporation exists in nondividing cultures of Euglena kept in a light-dark cycle. This rhythmicity persists for the two cycles measured in cultures transferred to constant conditions and is therefore probably circadian in nature.     

氨基酸自动分析仪快速测定γ-氨基丁酸

用氨基酸自动分析仪30 min短程序快速测定植物产品中的γ-氨基丁酸,并与53 min标准程序的测定值进行比较,试验表明两种程序测定结果一致。用γ-氨基丁酸标准品作精密度和回收率试验,结果表明:峰位置重现性变异系数为0.17%,峰面积重现性变异系数为0.23%,回收率为97.89%~101.2%。采用两种程序测定糙米和中药材中的γ-氨基丁酸,测定结果的相对误差小于3%。该改良方法稳定、快速、准确,适于γ-氨基丁酸的测定。     

氨基酸螯合铁在母猪生产中的应用研究

以妊娠后期母猪和仔猪日粮中添加甘氨酸螯合铁为试验组,以妊娠后期母猪和仔猪日粮中添加硫酸亚铁为对照1组,以妊娠后期母猪不补铁而仔猪3日龄注射铁针制剂为对照2组,结果发现,添加甘氨酸螯合铁的母猪所产仔猪初生重比对照组提高42%～44%,仔猪28日龄内死亡率降低4 5～9个百分点,仔猪7日龄血液中铁的含量提高24 7%～89 4%,母猪初乳中铁的含量比对照组提高39%～102 6%。本试验结果表明,妊娠后期母猪日粮中添加甘氨酸螯合铁能有效预防仔猪的缺铁性贫血。