The Viability of a Nonenzymatic Reductive Citric Acid Cycle – Kinetics and Thermochemistry

The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate → pyruvate → oxaloacetate → malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite–magnetite–quartz and pyrrhotite–pyrite–magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life.     

柠檬酸和抗坏血酸对蝴蝶兰叶外植体褐变发生的影响

目的:探究柠檬酸和抗坏血酸对蝴蝶兰叶片外植体褐变发生的影响以及对PPO活性变化影响的作用机理.方法:以褐变率和褐变指数为参考数据,分析柠檬酸和抗坏血酸对外植体PPO活性和PPO反应产物积累的影响以及与外植体褐变发生的关系.结果:分别用100mg/L柠檬酸共培养和50mg/L抗坏血酸浸泡处理叶片外植体,经离体培养3d,褐变率分别比对照降低94.9%和54.9%,离体培养6d,褐变指数低于对照的0.53,分别为0.46和0.36,同时PPO活性降低.结论:推测柠檬酸抑制褐变的原因是直接与酶蛋白作用,抗坏血酸则与新生醌类物质结合.     

Transient Forebrain Ischemia Impact on Lymphocyte DNA Damage, Glutamic Acid Level, and SOD Activity in Blood

Aims Brain ischemia–reperfusion injury remains incompletely understood but appears to involve a complex series of interrelated biochemical pathways caused mainly by a burst of reactive oxygen species (ROS). In the present work we studied the impact of postischemic condition in the early phase of reperfusion on plasma and blood cells. Methods Transient forebrain ischemia was induced in Wistar rats by four-vessel occlusion model. Blood samples collected during postischemic reperfusion 20, 40, 60, 90, and 120 min after ischemia were used for assessing breaks of lymphocyte DNA, fluorimetric measurement of whole blood glutamate concentration, and spectrophotometrical determination of SOD activity in plasma and blood cells. Results Our results showed the most interesting changes of all observed parameters mainly at 40 and 120 min of reperfusion, when we observed peak DNA damage of lymphocytes and highest glutamate level and total and Cu/Zn SOD activity. At those time points, Mn SOD activity was low in plasma, as well as in blood cells. On the contrary, at 60 and 90 min, all studied parameters were approximately at the level of control. Conclusion Ischemia/reperfusion injury has influence on blood cells and has at least two waves of impact on DNA damage of peripheral lymphocytes, affects activity of major antioxidant enzymes SODs, as well as blood glutamic acid level. Elevation of Mn SOD activity probably plays an important role in the processes of elimination of postischemic damage in blood cells.     

水杨酸和硝普钠对NaCl胁迫下番茄幼苗生长及生理特性的影响

以番茄品种‘秦丰保冠’为试材,采用营养液培养法,研究单独和复配施用外源水杨酸(SA)、一氧化氮(NO)供体硝普钠(SNP)对100 mmol·L-1 NaCl胁迫下番茄幼苗生长及生理特性的影响.结果显示:SA、SNP、SA+SNP处理均能显著提高盐胁迫下番茄幼苗叶片保护酶(SOD、POD、CAT)活性、脯氨酸和叶绿素含量、幼苗根系活力,并显著降低叶片电解质渗漏率及丙二醛(MDA)含量,有效减轻盐胁迫对幼苗造成的伤害,促进幼苗的生长发育,其中SA+SNP复配处理效果最好.研究表明,外源SA和SNP处理均能通过提高番茄幼苗保护酶活性和脯氨酸含量来有效缓解盐胁迫伤害,且SA+SNP复配处理在提高番茄幼苗耐盐性方面具有协同增效作用.     

J-Shaped Dose-Response Relationship for Tumor Induction by Caffeic Acid in the Rat Forestomach,Modeled by Non-Monotonic Dose Response for DNA Damage and Cell Proliferation

Dose-response relationships for chemical tumor induction can be described with stochastic carcinogenesis models by incorporation of dose-dependent parameters. We used a two-stage mutational model with clonal expansion of intermediate cells to mimic the observed U-shaped (more precisely: J-shaped) dose response for cell division in the forestomach of rats treated with caffeic acid. The question was whether biologically acceptable model parameters for the rates of mutation and cell turnover could be found to fit the experimental data, including tumor incidence in controls and at high dose. Using rates of cell turnover in proportion to the experimental labeling indices for DNA replication, model parameters could fit the tumor incidences within the 95% confidence limits of the experimental data, and the J-shape was retained quantitatively. However, when the smaller confidence limits derived from historical data on the spontaneous forestomach tumor incidence were taken into account, the original model could no longer accommodate all data and had to be expanded. For that, mutation rates were considered to be proportional to both the level of DNA damage and the rate of cell division, and both factors were allowed to be dose dependent. For the DNA damage, an increment over background was used at the higher, cytotoxic dose levels. This model improvement resulted in biologically acceptable parameters to fit all available data, demonstrating its usefulness for further analyses of hormetic dose response.     

维生素C多聚磷酸酯对小鼠生长、淋巴细胞转化以及血清皮质酮含量的影响

目的探讨维生素C多聚磷酸酯对小鼠生长、淋巴细胞转化及血清皮质酮含量的影响以及淋巴细胞转化和血清皮质酮含量在热应激条件下的变化。方法在4组小鼠的饲料中依次添加35%的维生素C多聚磷酸酯,添加剂量分别为0(对照组)、500(实验Ⅰ组)、2500(实验Ⅱ组)和5000mg/kg(实验Ⅲ组),在(21±1)℃下饲养4周,对照组和实验Ⅱ组各取一半小鼠经(35±1)℃热应激处理24h。用特定生长率的方法测定小鼠的生长,用噻唑蓝还原法测定淋巴细胞转化,用荧光法测定血清中皮质酮的含量。结果各组间ICR小鼠的生长、淋巴细胞转化无明显差异;实验Ⅱ组的血清皮质酮含量明显低于对照组,其他组间差异无显著性。热应激后,淋巴细胞转化无明显变化;血清皮质酮含量较应激前有显著上升,但实验Ⅱ组仍显著低于对照组。结论在饲料中添加维生素C多聚磷酸酯对小鼠的特定生长率和淋巴细胞转化均无显著影响,但会降低小鼠血清皮质酮的含量。     

Molecular Cloning and Characterization of a Novel Human C4orf13 Gene, Tentatively a Member of the Sodium Bile Acid Cotransporter Family

By large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a novel human cDNA (C4orf13). This cDNA is 2706 bp in length, encoding a 340-amino-acid polypeptide that contains a typical SBF (sodium bile acid cotransporter family) domain and ten possible transmembrane segments. The putative protein C4orf13 shows high similarity with its orthologs in Mus musculus and Xenopus laevis. Human C4orf13 is mapped to chromosome 4q31.2 and contains 12 exons. RT-PCR analysis shows that human C4orf13 is widely expressed in human tissues, and the expression levels in liver and lung are relatively high, expression levels in placenta, kidney, spleen, and thymus are moderate, low levels of expression are detected in heart, prostate, and testis.The nucleotide sequence reported in this paper has been deposited to GenBank under accession number AY346324.     

柠檬酸、葡萄糖和有机质对植物磷素吸收和土壤磷素形态的影响（英）

研究了柠檬酸、葡萄糖和有机质(栎树类凋落物和三叶草茎叶)对几种栽培和野生植物磷素吸收以及高度风化老成土中磷素形态的影响。在未加入无机磷的情况下,连续加入柠檬酸溶液增加了温室盆栽大豆(Glycine max(L.)Merr.)和高梁(Sorghum bicolor)对磷素 的吸收。这表明,柠檬酸可以溶解土壤中被铁、铝氧化物固定的磷。当无机磷和柠檬酸溶液同时加入后,由于有机配位体能够阻止土壤对磷素的吸附和固定,植物对磷的吸收总量明显高于仅仅加入无机磷的对照。不论是否加入无机磷,葡萄糖均没有增加植物对磷素的吸收,但却改变了土壤中磷素的形态。该试验的结果还表明,Hedley等人提出的土壤磷素分级方法不适于有机质含量很低的酸性土壤。在另一种性质极为相似的酸性土壤中施入粉碎的栎树(Quercus spp.)凋落物和三叶草(Trifolium pratense)后,野生商陆(Phytolacca americana)吸收磷素的能力增强。通过进一步对土壤中的磷素进行化学分级,结果表明,这些有机物质可以改变土壤中磷素存在的形态。本文还就有机质分解过程中的中间产物对土壤磷素有效性的影响机理进行了探讨     

阿魏酸钠联合双黄连注射液对病毒性心肌炎患者临床疗效及血清基质金属蛋白酶、锌铜水平的影响

目的:探究阿魏酸钠联合双黄连注射液对病毒性心肌炎患者临床疗效及血清基质金属蛋白酶、锌铜水平的影响。方法:选择在我院确诊为病毒性心肌炎的患者39例,随机分成实验组以及对照组。对照组18例给予阿魏酸钠治疗;实验组21例予阿魏酸钠联合双黄连注射液治疗。治疗14天后,评价和比较两组患者的临床疗效、心肌酶谱水平、血清基质金属蛋白酶水平及血清锌铜比值。结果:实验组总有效率为95.2%,显著高于对照组(72.2%),差异具统计学意义(P0.05)。与对照组比,实验组治疗后的血清、乳酸脱氢酶(LDH)水平、肌酸磷酸激酶同工酶(CK-MB)、天冬氨酸氨基转移酶(AST)、基质金属蛋白酶水平较低,血清铜锌比值较小,而左室射血分数(LVEF)水平较高,差异均具有统计学意义(P0.05)。结论:阿魏酸钠联合双黄连注射液治疗病毒性心肌炎患者能够有效提高其临床疗效,可能与其显著降低血清基质金属蛋白酶及铜锌水平有关。     

RETRACTED ARTICLE: The Influence of Sodium Hyaluronate, <Emphasis Type="SmallCaps">l</Emphasis>-Leucine and Sodium Taurocholate on the Nebulization of Aqueous Betamethasone-17-Valerate Suspensions

The purpose of this research was to evaluate the variables that are suggested to influence the adsorption of the hydrophilic hyaluronic acid (HA) onto the surface of the hydrophobic betamethasone-17-valerate (BV) particles in order to formulate a nebulizable suspension. The adsorption of HA from aqueous solutions (0.04% to 0.16%, w/v) to a fixed BV concentration (0.04%, w/v) under different experimental conditions, was investigated. The method of preparation of HA-BV suspensions involved suspending BV particles either in the hydrated HA solution (method 1) or in water followed by addition of solid HA (method 2). Other variables like the time required for the adsorption to complete and temperature at which adsorption is carried out were studied. The nebulization of the suspensions was tested via an air jet nebulizer connected to a twin stage impinger. In order to improve the nebulization behavior of the optimized suspension, l-leucine or sodium taurocholate was incorporated in increasing concentrations (0.01–0.04%, w/v). The optimized suspension, having a nebulization efficiency of 33.75%, was achieved following the adsorption of HA (0.1%, w/v) onto BV particles adopting method 2 of preparation and extending for three days at 4 °C. Incorporation of either l-leucine or sodium taurocholate significantly decreased the aggregate size of the optimized suspension and consequently caused significant increases in the nebulization efficiency to reach 46.87% and 56.25%, respectively. An erratum to this article is available at .     

DNA polymerase and thymidine kinase activities in MC-29 virus-induced transplantable hepatoma and the effect of cytostatic treatment on these activities

The activity of DNA polymerases and thymidine kinase was compared in the MC-29 leukosis virus-induced transplantable hepatoma and in the livers of rats treated with cyclophosphamide (CP), cytosine-arabinoside (ara-C) and 5-fluoro-uracil (5-FU). The specific activity of DNA polymerase was twenty times greater in the MC-29 leukosis virus-induced hepatoma, while thymidine kinase was only 3–5 times greater than in the liver.All three enzymes showed Michaelis-Menten kinetics in their substrate and template saturation curves. The template utilization of DNA polymerases from hepatoma and from liver was compared. Both had higher activities on a poly(dA) · poly(dT) template at pH 8.0, than on DNA at pH 7.5. After chromatography on a phosphocellulose column two polymerases were separated. The first peak eluted by 0.15 M KCl preferred DNA as template (polymerase α). The second eluted by 0.5 M KCl worked better on poly(dA) · poly(dT) (polymerase β). Thymidine kinase was eluted by 0.25 M KCl. Inhibition by N-ethylmaleimide (NEM) showed the polymerase α to be sensitive and the polymerase β to be resistant to the sulfhydryl blocking agent; similar to the respective enzymes of other eukaryotic cells. The specific acitivity of DNA polymerase decreased after CP treatment at 6 h and 72 h and after ara-C treatment at 72 h. The specific activities of thymidine kinase were not changed significantly in response to the drug administrations.