Replication and integration of a Vibrio cholerae cryptic plasmid linked to the CTX prophage

We identified a 4.7kb cryptic plasmid in all ctxAB+ Vibrio cholerae strains we tested. An isolate of the V. cholerae classical biotype strain 0395 that harbours the cryptic plasmid at high copy number was found. Hybridization analysis demonstrated that sequences highly related or identical to this plasmid exist in all toxigenic strains of V. cholerae but were notably absent in all non-toxigenic environmental isolates that lacked the genes for toxin-co-regulated pili and the filamentous CTX prophage. Accordingly, we have named the cryptic plasmid pTLC for toxin-linked cryptic. The complete nucleotide sequence of pTLC from the high-copy-number isolate was determined. The largest open reading frame in the plasmid is predicted to encode a protein similar to the replication initiation protein (pII) of Escherichia coli F-specific filamentous phages. The nucleotide sequence of pTLC also facilitated the structural characterization of the DNA homologous to pTLC in other strains of V. cholerae. pTLC-related DNA exists in these strains as both low-copy-number, covalently closed circular DNA and tandemly duplicated, chromosomally integrated DNA. Remarkably, the chromosomally integrated form of pTLC is adjacent to the CTX prophage. The strain distribution, chromosomal location and DNA sequence of pTLC suggests that it may be a genetic element that plays some role in the biology of CTXphi, perhaps facilitating either its acquisition or its replication.     

Adducin is an in vivo substrate for protein kinase C: phosphorylation in the MARCKS-related domain inhibits activity in promoting spectrin-actin complexes and occurs in many cells, including dendritic spines of neurons

Adducin is a heteromeric protein with subunits containing a COOH-terminal myristoylated alanine-rich C kinase substrate (MARCKS)-related domain that caps and preferentially recruits spectrin to the fast-growing ends of actin filaments. The basic MARCKS-related domain, present in alpha, beta, and gamma adducin subunits, binds calmodulin and contains the major phosphorylation site for protein kinase C (PKC). This report presents the first evidence that phosphorylation of the MARCKS-related domain modifies in vitro and in vivo activities of adducin involving actin and spectrin, and we demonstrate that adducin is a prominent in vivo substrate for PKC or other phorbol 12-myristate 13-acetate (PMA)-activated kinases in multiple cell types, including neurons. PKC phosphorylation of native and recombinant adducin inhibited actin capping measured using pyrene-actin polymerization and abolished activity of adducin in recruiting spectrin to ends and sides of actin filaments. A polyclonal antibody specific to the phosphorylated state of the RTPS-serine, which is the major PKC phosphorylation site in the MARCKS-related domain, was used to evaluate phosphorylation of adducin in cells. Reactivity with phosphoadducin antibody in immunoblots increased twofold in rat hippocampal slices, eight- to ninefold in human embryonal kidney (HEK 293) cells, threefold in MDCK cells, and greater than 10-fold in human erythrocytes after treatments with PMA, but not with forskolin. Thus, the RTPS-serine of adducin is an in vivo phosphorylation site for PKC or other PMA-activated kinases but not for cAMP-dependent protein kinase in a variety of cell types. Physiological consequences of the two PKC phosphorylation sites in the MARCKS-related domain were investigated by stably transfecting MDCK cells with either wild-type or PKC-unphosphorylatable S716A/S726A mutant alpha adducin. The mutant alpha adducin was no longer concentrated at the cell membrane at sites of cell-cell contact, and instead it was distributed as a cytoplasmic punctate pattern. Moreover, the cells expressing the mutant alpha adducin exhibited increased levels of cytoplasmic spectrin, which was colocalized with the mutant alpha adducin in a punctate pattern. Immunofluorescence with the phosphoadducin-specific antibody revealed the RTPS-serine phosphorylation of adducin in postsynaptic areas in the developing rat hippocampus. High levels of the phosphoadducin were detected in the dendritic spines of cultured hippocampal neurons. Spectrin also was a component of dendritic spines, although at distinct sites from the ones containing phosphoadducin. These data demonstrate that adducin is a significant in vivo substrate for PKC or other PMA-activated kinases in a variety of cells, and that phosphorylation of adducin occurs in dendritic spines that are believed to respond to external signals by changes in morphology and reorganization of cytoskeletal structures.     

新疆东昆仑地区金矿成矿地质条件及找矿方向初探

东昆仑地区是昆仑巨型成矿带中２个重要的成矿区之一，从大地构造背景、沉积建造、岩浆活动等成矿地质条件的分析入手，对东昆仑地区的求勉雷克成矿远景区、鸭子泉成矿远景区、库木巴彦成矿远景区和石雪尖成矿远景区的金矿成矿条件进行了初步的探讨，指出了找矿方向。     

Biochemical genetic studies on wild populations of the Vicia amoena complex (tribe Vicieae: Fabaceae)

A 45-year-old human immunodeficiency virus (HIV)-infected patient has suffered for a period of 4 years from recurrent and, later on, persistent oral pseudomembranous candidosis. The Candida isolates proved to be resistant to azole derivates in vitro and in vivo. Treatment with amphotericin B parenterally was successful in February 1996, but had to be stopped when chemotherapy for lymphoma was started. In August 1996, the patient showed a shift from the pseudomembranous to the erythematous type of oral candidosis; antiretroviral combination therapy including the HIV protease inhibitor saquinavir had been started 4 months previously. In July 1997, the patient was still suffering from a persistent oral candidosis of the erythematous type.     

供热外网采用直埋式保温管的讨论

从工程投资,施工及保温材料的技术性能的分析入手,认为采用硬脂聚氨酯泡沫塑料保温的直埋管道比地沟管更具有优越性。     

Thermodynamic model for MnO-containing slags and gas-slag-metal equilibrium in ferromanganese smelting

The thermodynamics of MnO-containing slags was reviewed, and the properties of such slags were correlated by application of the cell model. This model, together with a previously developed unified interaction parameter model for the metal phase, was used to simulate the gas-slag-metal conditions in the hearth of a ferromanganese submerged arc furnace. The calculated slag and metal compositions and distribution of Mn, Si, and K between slag, metal, and fume were compared with plant data and satisfactory agreement was obtained. A steady recirculation of potassium inside the furnace was also predicted. For a potassium percentage in the raw materials of 0.63 pct, the amount of the recirculating potassium was about 160 kg per metric ton of ferromanganese. Due to the recirculation, the average potassium content in the solid mix coming down to the hearth could be as high as 7 pct.     

A general class of sliding surface for sliding mode control

In the conventional sliding mode control, the relative degree of the chosen sliding surface is usually one. This paper addresses a general class of sliding surface whose relative degree is no longer restricted to one. We show that when the relative degree is more than two, it is inevitable that there will exist a limit cycle for the nonlinear sign function. And for the case of relative degree two the system possesses poor phase margin. However, these disadvantages can be remedied remarkably by smoothing out the control nonlinearity in a suitable boundary layer with a saturation function that ensures asymptotic stability of the overall system     

PC／ABS合金的研制及其在汽车上的应用

对ＰＣ／ＡＢＳ合金开发和研制及其在汽车上的应用作了评述。介绍了上海杰事公司在该领域的进展。     

钨精矿、锡石矿中铌和钽的5—Br－PADAP分光光度法的测定

用２－（５－溴－２吡啶偶氮）－５－二乙氨基苯酚（５－Ｂｒ－ＰＡＤＡＰ）为显色剂，采用多波长分光光度法测定钨精矿、难溶锡石矿中的铌、袒，方法快速、准确、灵敏度高，相对标准偏差≤０．０２１（ｎ＝１６）．     

钇、钪分离工艺的新进展

本文简要介绍中国科学院长春应用化学研究所近年来在钇、钪分离工艺研究方面的新进展。