Possible involvement of protein kinase C in the stimulation of amino acid transport by phorbol ester,platelet-derived growth factor and A23187 in Swiss 3T3 cells

Summary Stimulation of amino acid transport induced by phorbol-12, 13-dibutyrate, platelet-derived growth factor or A23187 was not observed in cells lacking protein kinase C. On the other hand, stimulation of transport by epidermal growth factor or insulin was not affected. These results suggested that the stimulation of amino acid transport is mediated by at least two separate pathways.This work was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, and the Ministry of Health and Welfare of Japan.     

肉仔鸡无鱼粉饲粮配方的试验研究(0—4周令)

120只肉仔鸡分为三个组。饲粮中含10％鱼粉的为对照组;饲粮中无鱼粉的为试验组。但另加0.2％的赖氨酸和0.2％的蛋氨酸。经28天试验,结果表明:无鱼粉组与含10％鱼粉的组相比较,不仅取得了同样的增重效果(p>0.05),而且饲粮成本降低,经济效益明显。     

陆地棉花粉成熟过程中特异性蛋自及单花粉电泳研究

本文对不同发育时期的花粉剥出后进行蛋白电泳，结果表明，不同发育时期的花粉其蛋白、过氧化物同工酶和酯酸都有差异，花粉在成熟过程中，伴随着过氧化物酶活性的消失和种类的减少；在花粉进行第一次细胞分裂形成营养细胞和生殖细胞之前，新的蛋白带和酯酶带的出现，尤其是近十种蛋白的大量合成提示这些蛋白在花粉成熟和以后的受精过程中可能有重要作用。对其成熟的花粉进行单花粉电泳表明，没有等位基因的分离现象，只是有约２％的花粉出现新的蛋白带，其原因有待进一步研究。     

Modulation of protein kinases and phosphoprotein phosphatases by a small acidic protein from bovine brains

Summary A small, acidic and heat-stable protein was purified from bovine brains by column chromatography on DEAE-cellulose, Bio-Gel HTP, Affi-Gel phenothiazine and Sephadex G-75. This protein stimulates megamodulin-dependent protein kinase I from brains and phosphoprotein phosphatases from either brain or yeast. However, it inhibits cyclic AMP-dependent protein kinases from skeletal muscle.Acknowledgments. This work was supported by a grant (RR-08229) from the National Institutes of Health, USA. W.N. Kuo is a recipient of a Distinguished Faculty Scholar Award from United Negro College Fund, Inc., USA.     

Interaction of mitochondrial porin with cytosolic proteins

Summary Intracellular phosphorylation is an important step in active uptake and utilization of carbohydrates. For example glucose and glycerol enter the liver, cell along the extra intracellular gradient by facilitated diffusion through specific carriers and are concentrated inside the cell by phosphorylation via hexokinase or glycerol kinase. Depending on the function of the respective tissue the uptake of carbohydrates serves different metabolic purposes. In brain and kidney medulla cells which depend on carbohydrates, glucose and glycerol are taken up according to the energy demand. However, in tissues such as muscle which synthesize glycogen or like liver which additionally produce fat from glucose, the uptake of carbohydrates has to be regulated according to the availability of glucose and glycerol. How the reversible coupling of the kinases to the outer membrane pore and the mitochondrial ATP serves to fulfil these specific requirements will be explained as well as how this regulates the carbohydrate uptake in brain according to the activity of the oxidative phosphorylation and how this allows glucose uptake in liver, and muscle to persist in the presence of high glucose 6-phosphate without activating the rate of glycolysis.     

从兔骨骼肌综合提取ALD等五种酶的研究

采用一种组合５’－ＡＭＰ亲和层析、离子交换层析、分子筛层析以及重结晶的方法，从经硫酸铵沉淀初步分离的四个兔骨骼肌酶组分中逐步分离和纯化出醛缩酶等五种医用酶。本方法提取的五种酶均具有高比活和高纯度。本方法提取成本低，操作简便，酶活回收率高，因此具有应用价值     

稻壳糟蛋白饲料的研究

本文报道利用热带假丝酵母(Candida tropicalis 2.637)以固体糟为底物,在发酵料中加入锌终浓度15ppm、钼20ppm,稀土元素0.1％,尿素2％时,30℃培养48小时后,粗蛋白含量由本底20.93％提高到36.21％。     

混合拥挤试剂对人肌肌酸激酶稳定性的影响作用研究

为了更加真实地模拟细胞内环境,在人肌肌酸激酶(HCK)的去折叠环境中同时加入了大分子拥挤试剂(葡聚糖)和小分子渗透剂(蔗糖),采用酶活性、荧光发射谱和溶液浊度检测等方法研究肌酸激酶在含有蔗糖和葡聚糖的混合拥挤环境中的稳定性,结果表明在肌酸激酶盐酸胍变性过程中,蔗糖不仅抑制肌酸激酶酶活性的丧失,还稳定肌酸激酶的构象,而葡聚糖对肌酸激酶保护能力相对较弱.对于热变性过程,相同质量浓度的蔗糖和葡聚糖能同等程度地减缓肌酸激酶活性的丧失,并抑制聚沉的产生.在葡聚糖和蔗糖同时存在的情况下,两者的保护作用可以累加,并共同维持肌酸激酶的稳定性.     

Protein oxidation and 20S proteasome-dependent proteolysis in mammalian cells

The generation of reactive oxygen species is an inevitable aspect of aerobic life. In addition to being exposed to free radicals in the environment, aerobic organisms must also deal with oxygen radicals generated as byproducts of a number of physiological mechanisms - for example, by the mitochondrial and endoplasmic reticulum electron transport chains, and by cells of the immune system. Although most organisms are equipped with several lines of defense against oxidative stress, these defensive mechanisms are not 100% effective, and oxidatively modified forms of proteins accumulate during aging, and in many pathological conditions.?Oxidatively modified proteins can form large aggregates due to covalent cross-linking or increased surface hydrophobicity. Unless repaired or removed from cells, these oxidized proteins are often toxic and can threaten cell viability. Mammalian cells exhibit only limited direct repair mechanisms, and oxidatively damaged proteins appear to undergo selective proteolysis, primarily by the major cytosolic proteinase, the proteasome. Interestingly, it appears that the 20S 'core' proteasome conducts the recognition and elimination of oxidized proteins in an ATP-independent and ubiquitin-independent pathway. Received 31 May 2001; accepted 26 June 2001