Effects of branched chain alpha-ketoacids on the metabolism of isolated rat liver cells. I. Regulation of branched chain alpha-ketoacid metabolism.

alpha-Ketoisocaproate (ketoleucine) is shown to be metabolized to ketone bodies rapidly by isolated rat liver cells. Acetoacetate is the major end product and maximum rates were observed with 2 mM substrate. Studies with 2-tetradecylglycidic acid (an inhibitor of long chain fatty acid oxidation) showed that ketogenesis from alpha-ketoisocaproate and from endogenous fatty acids were additive. With alpha-ketoisocaproate present as soole substrate at 2 mM, leucine production was less than 10% of alpha-ketoisocaproate uptake and only 30% of the acetyl coenzyme A generated was oxidized in the citric acid cycle. Metabolism of alpha-ketoisocaproate was inhibited by fatty acids, alpha-ketoisovalerate, alpha-keto-beta-methylvalerate, and pyruvate. Oxidation of acetyl-CoA generated from alpha-ketoisocaproate was suppressed by oleate and by pyruvate, but was enhanced by lactate. Metabolism between the different branched chain alpha-ketoacids was mutually competitive. When alpha-ketoisocaproate (2 mM) was added in the presence of high pyruvate concentrations (4.4 mM), flux through pyruvate dehydrogenase was decreased, and the proportion of total pyruvate dehydrogenase in the active form (PDHa) also fell. With lactate as substrate, PDHa was only 25% of total activity and was little affected by addition of alpha-ketoisocaproate. These data suggest that enhanced oxidation of acetyl-CoA from alpha-ketoisocaproate by lactate addition is caused by a low activity of pyruvate dehydrogenase combined with increased flux through the citric acid cycle in response to the energy requirements for gluconeogenesis. However, acetyl-CoA generation from pyruvate is apparently insufficiently inhibited by alpha-ketoisocaproate to cause a diversion of acetyl-CoA formed during alpha-ketoisocaproate metabolism from ketone body formation to oxidation in the citric acid cycle. Measurements of the cell contents of CoASH, acetyl-CoA, acid-soluble acyl-CoA, and acid-insoluble fatty acyl-CoA indicated that when the branched chain alpha-ketoacids were added as sole substrate, their oxidation was limited at a step distal to the branched chain alpha-ketoacid dehydrogenase. Acid-soluble acyl-CoA derivatives were depleted after oleate addition in the presence of alpha-ketoisocaproate, suggesting an inhibition of the branched chain alpha-ketoacid dehydrogenase by the elevation of the mitochondrial NADH/NAD+ ratio observed during fatty acid oxidation. This effect was not observed in the presence of oleate and 2-tetradecylglycidic acid.     

序贯抽样技术——用于褐稻虱的防治和研究

褐稻虱Nilaparavata lugens(stal)在亚洲造成广泛的灾害。近十余年来,我国南方稻区普遍遭受褐稻虱连年为害,不少稻田后期出现块状穿顶(hopper burn),甚至倒伏,严重影响粮食产量。 在水稻害虫综合防治中,当前仍主要依靠化学农药,划分防治对象田是合理使用农药,减少农药对生态环境的不良影响的重要手断之一。为了准确划清防治对象田,有效的抽样技     

西藏缩栉蚤属一新种（蚤目：角叶蚤科）

1978年在西藏自大耳鼠兔Ochotona macrotis采到缩栉蚤属一新种,定名为西藏缩栉蚤Brevictenidia xizangensis sp.nov.。     

Red-edge excitation fluorescence measurements of several two-tryptophan-containing proteins.

The dependence of the fluorescence emission maximum of the tryptophan residues in several two-tryptophan-containing proteins (horse liver alcohol dehydrogenase, yeast 3-phosphoglycerate kinase, Staphylococcus aureus metalloprotease and bee venom phospholipase A2) on the excitation wavelengths has been studied. Using fluorescence-resolved spectroscopy, we have dissected the contributions of particular tryptophan residues located in different parts of the protein molecule. The results demonstrate that dipolar structural relaxation can occur in the environment of tryptophan residues buried within protein molecules. The observed spectral shifts upon red-edge excitation of these residues can depend on temperature or ligand binding, as demonstrated in case of metalloprotease and alcohol dehydrogenase. No spectral shifts upon red-edge excitation have been observed for tryptophan residues totally exposed to the rapidly relaxing aqueous solvent.     

银纹夜蛾的核型多角体病毒病

银纹夜蛾(Plusia agnata Staudinger)幼虫是大豆主要食叶害虫。在泰安地区,历年约占大豆害虫总发生量的70％以上;除大豆外,还为害甘蓝、白菜、棉麻等作物。 1979年6月,发现室内饲养的银纹夜蛾幼虫有倒挂死亡的虫体,经鉴定是一种核型多角体病毒病,现将其实验结果报道如下。     

温度对干旱、盐胁迫下两种黄芪属种子萌发和幼苗生长的影响

为探讨温度对干旱、盐胁迫下黄芪属种子萌发和幼苗生长特性的影响,以黄芪属蒙古黄芪和扁茎黄芪2种种子为研究对象,纯净水处理为对照组,NaCl、PEG处理为实验组,设置4个渗透势水平(0、-0.1、-0.3、-0.5 MPa),置于5种不同的温度(10、15、20、25、30 ℃)下,每日观察并记录两种种子萌发和幼苗生长情况。结果表明：旱盐胁迫下蒙古黄芪和扁茎黄芪种子萌发最适宜的温度分别为25和20 ℃左右;蒙古黄芪耐高温不耐低温,而扁茎黄芪恰恰相反;但25和20 ℃均适宜两种幼苗生长,包括胚根、胚轴和子叶的生长。蒙古黄芪各处理组(除未发芽的种子)的平均发芽时间都比扁茎黄芪长;NaCl胁迫程度的增加使得两种种子的最终发芽率降低,但蒙古黄芪的耐盐性高于扁茎黄芪;随着PEG胁迫程度的增加,二者的发芽均受到抑制,甚至会出现完全不萌发,但扁茎黄芪的耐旱性高于蒙古黄芪;在相同的渗透势时,尤其是-0.5 MPa,PEG比NaCl对两种种子的影响大;交互胁迫作用下,随着渗透势的增加两种幼苗的鲜重、干重以及胚根、胚轴、子叶的长和宽变化较大;利用Design Expert软件预测发现：温度25 ℃、NaCl渗透势为-0.1 MPa,温度24 ℃、PEG渗透势为-0.04 MPa的处理是蒙古黄芪种子萌发和幼苗生长达到最优化的组合;而扁茎黄芪最优化的组合则为23 ℃下NaCl渗透势为-0.07 MPa的处理,20 ℃下PEG渗透势为-0.13 MPa的处理。     

The elucidation of the effect of ammonium chloride on pyruvate distribution and pyruvate dehydrogenase interconversion in isolated rat hepatocytes

The distribution of pyruvate between cell compartments measured in isolated hepatocytes in the presence of lactate was in agreement with delta pH across plasma and mitochondrial membranes. In isolated liver mitochondria NH4Cl decreased the transmembrane potential (delta psi) by about 14 mV, whereas no change of delta pH was observed. In the presence of lactate or alanine NH4Cl increased the mitochondrial pyruvate concentration presumably due to the inhibition of the flux through pyruvate carboxylase. In the presence of lactate or alanine changes in the amount of the active form of pyruvate dehydrogenase (PDHa) were correlated with the mitochondrial pyruvate concentration, NH4Cl increased the amount of PDHa by lowering the mitochondrial ATP/ADP and NADH/NAD+ ratios.     

Radiation protection of mice with hypoxic gas mixtures after administration of anti-hypoxic agents

It is shown that such substances as gutimine, antizol and mexamine increases the resistance of animals to short-term breathing of gas mixtures containing 6 and 5% oxygen. Even if some of them decrease the degree of radioprotective effect of hypoxia, they afford the possibility to safe use of breathing mixtures with lower oxygen content than endured by intact animals, with the resulting increase in radioprotection. Thus the antihypoxic substances can be tested during hypoxiradiotherapy of human tumors.     

大鼠尾壳核衰老变化定量分析：Ⅱ.多巴胺（DA）系统

本实验结果表明:衰老大鼠(26—27月龄)尾壳核多巴胺(DA)神经末梢膨体较成年组(3—4月龄)明显减少,而单个膨体内DA含量较成年组显著增多,提示纹状体DA系统在衰老过程中可能具有一定的代偿机制。本文对其意义进行了讨论。     

Cell sheet technology: a promising strategy in regenerative medicine

Regenerative medicine is a burgeoning field that is important to combat challenging diseases and functional impairments. Compared with traditional cell therapies with evident shortcomings (e.g., cell suspension injection or tissue engineering with scaffolds), scaffold-free cell sheet technology enables transplanted cells to be grafted and fully maintain their viability on target sites. Clinical and experimental studies have advanced the application of cell sheet technology to numerous tissues and organs (e.g., liver, cornea and bone). However, previous reviews have failed to discuss vital aspects of this rapidly developing technology, and many new challenges are gradually emerging. This review aims to provide a comprehensive introduction to cell sheet technology from cell selection to the ultimate applications of cell sheets, and challenges and future visions are also described.