四倍体刺槐无性系K2和K3的组织培养

1997年,北京林业大学从韩国引进了具有速生和饲料用途的刺槐(Robinia pseudoacacia L.)四倍体优良无性系,目前已在全国各省区试推广.与普通刺槐相比,四倍体刺槐具有叶大、速生等优点,且较普通刺槐有更强的适应性,耐干旱、贫瘠、烟尘及盐碱能力强,成林快,是水土保持、防风固沙及退耕还林的良好树种,可作为西北地区造林的先锋树种.     

Ernst Küster

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抗大肠埃希氏菌K88ab,K88ac和K88ad特异单克隆抗体

A panel of twelve hybridoma cell lines, secreting specific antibodies to K88 adhesin antigens of enterotoxigenic Escherichia coli (ETEC) were established from eight separate fusions between mouse myeloma cell line Sp 2/0-Ag-14 and spleen cells from mice immunized with purified K88 antigens. Among the 12 monoclonal antibodies (MCA), K-A, K-35, K-11, and K-15 were K88a specific and reacted with all K88 adhesin bearing Escherichia coli strains tested, whatever K88ab, K88ac or K88ad they might be, as shown either in enzyme-linked immunosorbent assay (ELISA) or in direct agglutination test, whereas K32, K-4, and K-3 were specific for G88ab, K88ac, and K88ad respectively. The antigen patterns of 33 K88 bearing Escherichia coli strains covering 3 serotypes of K88ab, K88ac, and K88ad were analyzed by the use of these MCAs. The preliminary results showed that all Escherichia strains with the same serotype of K88 antigen shared at least one common type-specific antigenic determinant, that K88ad and K88ac strains enjoyed one common antigenic determinant that did not exist on K88ab strains, and that there were a few K88 antigenic determinants that appeared only on limited Escherichia coli strains of the same K88 serotype.     

抗大肠埃希氏菌K88ab、K88ac和K88ad特异单克隆抗体

用MCA对K88粘附素扩原结构进行分析表明：在K88ab、K88ac和K88ad三种血清到中,同一种血清型的菌株至少能表达一个共同的型特异抗原决定簇;K 88ad菌林和K88ac菌株都能稳定地表达一个K88ab菌株不县有的共同的抗原决定簇;某些抗原决定簇仅存在于同一种K88血清型的部分菌株中。     

Gut sensing of dietary K⁺ intake increases renal K⁺excretion

Dietary K(+) intake may increase renal K(+) excretion via increasing plasma [K(+)] and/or activating a mechanism independent of plasma [K(+)]. We evaluated these mechanisms during normal dietary K(+) intake. After an overnight fast, [K(+)] and renal K(+) excretion were measured in rats fed either 0% K(+) or the normal 1% K(+) diet. In a third group, rats were fed with the 0% K(+) diet, and KCl was infused to match plasma [K(+)] profile to that of the 1% K(+) diet group. The 1% K(+) feeding significantly increased renal K(+) excretion, associated with slight increases in plasma [K(+)], whereas the 0% K(+) diet decreased K(+) excretion, associated with decreases in plasma [K(+)]. In the KCl-infused 0% K(+) diet group, renal K(+) excretion was significantly less than that of the 1% K(+) group, despite matched plasma [K(+)] profiles. We also examined whether dietary K(+) alters plasma profiles of gut peptides, such as guanylin, uroguanylin, glucagon-like peptide 1, and glucose-dependent insulinotropic polypeptide, pituitary peptides, such as AVP, α-MSH, and γ-MSH, or aldosterone. Our data do not support a role for these hormones in the stimulation of renal K(+) excretion during normal K(+) intake. In conclusion, postprandial increases in renal K(+) excretion cannot be fully accounted for by changes in plasma [K(+)] and that gut sensing of dietary K(+) is an important component of the regulation of renal K(+) excretion. Our studies on gut and pituitary peptide hormones suggest that there may be previously unknown humoral factors that stimulate renal K(+) excretion during dietary K(+) intake.     

探明维生素K止血机理

探明维生素Ｋ止血机理维生素Ｋ是促凝血物质,体内维生素Ｋ缺乏可致出血。儿科医生往往给新生儿注射维生素Ｋ以防止新生儿出血。正常营养的人很少缺乏维生素Ｋ,但营养不良,肠功能紊乱者需补充维生素Ｋ。维生素Ｋ的作用机制一直未弄清。最近美国匹兹堡大学化学家保尔·道...     

eEF2K与肿瘤

真核延伸因子激酶-2(eukaryotic elongation factor 2 kinase,e EF2K)属于特殊的蛋白激酶——α-激酶小家族,并且是该家族中唯一的Ca~(2+)/Ca M依赖性蛋白激酶。e EF2K催化真核延伸因子-2(eukaryotic elongation factor 2,e EF2)的Thr56位点发生磷酸化并导致其失活,从而抑制肽链延伸过程。除了受Ca~(2+)/Ca M调控,e EF2K还受到营养、能量相关信号分子如AMPK、m TORC1等的调控。近年来研究表明,e EF2K在多种肿瘤组织及细胞中高表达,并参与肿瘤生长、细胞周期、自噬、凋亡、血管新生、侵袭转移等过程的调控。因此e EF2K可能是潜在的肿瘤治疗靶点。本文就e EF2K的结构、调控,以及与肿瘤的恶性进程、治疗及预后等关系进行综述。     

Aus dem Küstenlande

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Molecular dynamics simulation of crystalline β-cyclodextrin dodecahydrate at 293 K and 120 K

Molecular dynamics (MD) simulations for crystalline -cyclodextrin dodecahydrate (-CD) at two different temperatures, 293 K and 120 K, have been performed using the GROMOS program package. The calculated structural properties are compared to those obtained from neutron diffraction studies of this system at the quoted temperatures. The simulation was carried out over a period of 20 ps on four unit cells containing 8 -CD molecules and 96 water molecules, whereby all atoms were allowed to move.At room temperature, the experimental positions of the (non-hydrogen) glucose atoms are reproduced within 0.034 nm, a value which is smaller than the experimental (0.041 nm) or simulated (0.049 nm) overall root mean square (rms) positional fluctuation. The corresponding numbers for the low temperature study are 0.046 nm, 0.019 nm and 0.022 nm. At both temperatures the experimentally observed degree of anisotropy of the atomic motions is also found in the simulations.The comparison of a variety of structural properties leads to the conclusion that the molecular model and force field used are able to simulate the cyclodextrin system very well. Experimentally observed differences in properties as a function of number of glucose units in the CD molecule (-CD, 6 versus -CD, 7) and as a function of temperature are qualitatively reproduced by the simulations.     

人类疱疹病毒8型K1和K15基因致病机制的研究进展

人类疱疹病毒8型K1和K15是HHV-8基因组所特有的基因,K1和K15基因结构的独特性决定了其在疾病的致病机制中发挥着一定的作用;近年来有关K1和K15基因致病机制的研究较多,本文结合近几年的文献将时K1和K15基因致病机制做一综述.     

K27泛素化修饰研究进展

泛素化修饰作为最普遍存在的翻译后修饰形式之一,介导了生物体内蛋白质稳态调控等功能。泛素分子的7个赖氨酸和N端甲硫氨酸可以继续被泛素分子修饰,进而形成8种类型的泛素链。其中,K48和K63泛素链由于丰度高且功能研究相对清楚被称为经典泛素链,而其他6种泛素链被称为非经典泛素链。在非经典泛素链中,K27泛素链是在泛素分子的Lys27 (K27)位点上继续发生泛素化形成的,具有紧密的空间结构。近些年,K27泛素链在固有免疫、蛋白稳态和DNA损伤修复等方面的功能逐渐被报道,但K27泛素链的合成、修剪过程及其下游招募特定蛋白质的分子调控机制还所知甚少。文中结合实验室研究,综述了K27泛素链结构特征、结合方式和生物学功能,为未来K27泛素链结构和生物学功能的深入研究提供参考。     

实验药物K11777抗击血吸虫病

有一种实验药物证明可抗击血吸虫病.血吸虫病是遍及热带地区的一种瘟疫,可感染几百万人.小鼠试验提示,该药物很可能作为当前所用的抗击血吸虫病的单一疗法的补充.血吸虫是血的吸虫或扁虫,在血吸虫水传播幼虫时期通过皮肤感染人.幼虫穿过循环系统而最后定居于肝脏,在肝脏它们以血为食,并发育成为成虫.雌虫然后产卵,受感染的人将部分卵从粪中排出,这可能造成血吸虫的播散,其余的卵则寄居于肝脏和其他组织,它激发免疫反应,引起腹痛、发烧和以血吸虫为特征的不适.旧金山加州大学的科学家在几年前曾发现一种药物,称为K11777,其杀死引起恰加斯病…     

烤烟烟叶中N,K营养及N,K平衡的初步研究

研究了滇中地区烤烟中部叶片旺长期（移栽后６０－６５ｄ）Ｎ、Ｋ营养及Ｎ、Ｋ平衡。结果表明：⑴烟叶一般Ｎ含量为２．５％－４％,Ｋ含量为１％－３％,Ｎ／Ｋ比为２．５－３．５。⑵烟叶Ｎ含量＞４％,就有Ｎ过剩的症状产生。⑶烟叶Ｎ含量＜２．５％,Ｋ含量＜１％,就表现出Ｎ、Ｋ缺乏症状。⑷烟叶Ｎ／Ｋ比失调,过高或过低,都会影响烟株正常生长。     

Does sumoylation control K2P1/TWIK1 background K+ channels?

A novel model for the regulation of cell excitability has recently been proposed. It originates from the observation that the background K(+) channel K2P1 (TWIK1) may be silenced by sumoylation in Xenopus oocytes and that inactivation of the putative sumoylation site (mutation K274E) gives rise to robust current expression in transfected COS-7 cells. Here, we show that only the mutation K274E, and not K274R, is associated with an increase of K2P1 current density, suggesting a charge effect of K274E. Furthermore, we failed to observe any band shift by western blot analysis that would confirm an eventual sumoylation of K2P1 in COS-7 cells and oocytes.     

Is the K permeability of the resting membrane controlled by the excitable K channel?

To test whether or not the potassium permeability of the resting membrane is controlled by the excitable K channels (delayed rectifier), we examined changes in the Na and K permeability ratio, PNa/PK, of the squid axon before and after the excitable K channels were blocked. The blockage of the K channels was accomplished by three independent methods: internal application of tetraethylammonium, internal application of 4-aminopyridine plus Cs, and prolong internal perfusion of NaF solution. The permeability ratio was determined using two different methods: the conventional electrophysiological method and a new method based on the measurements of the hyperpolarizing effect of Na removal. We found that blocking the K channels did not cause a proportional decrease in the K permeability of the resting membrane, suggesting that the semipermeable property of the resting membrane is not determined by the excitable K channels.     

大鼠消化道内的K物质

本工作应用K物质的特异性放射免疫测定和免疫组织化学方法,研究了K物质在大鼠胃肠道内的分布、生化特点和功能。结果表明K物质样免疫活性物质广泛存在于大鼠胃肠道内,空肠含量最高,食道含量最低。K物质主要分布于胃肠道的肌间神经丛神经元内,它可促进大鼠消化道离体平滑肌收缩。外周和中枢注射K物质可抑制大鼠胃酸分泌。